Steel tube is used as a structural element in buildings, bridges and other structures, and in a wide variety of manufactured products. It's produced in round, square and rectangular shapes in a broad range of sizes and gauges.
Rectangular tubing has many benefits: aesthetic appeal, high strength-to-weight ratios, uniform strength, cost effectiveness and recyclability.
The advantages for designers, specifies, fabricators and end users are outlined on the
Rectangular tubing has greater strength-to-weight ratios. So, with Rectangular tubing you need less steel, by weight, to do the job. And less weight equals less cost
Excellent compression and support characteristics and superior resistance make Rectangular tubes particularly well suited to all types of column applications
Rectangular steel tube is made from steel, one of the world’s most recyclable and recycled materials
Torsional strength makes steel rectangular tube an excellent choice for bear resistant and consistent.
Rectangular tube is fire resistant and does not warp, twist, split, swell or shrink. It resists dry rot and mildew, termites and carpenter ants. For increased fire resistance, the exterior of the product may be sprayed with a fire retardant material. The interior can be filled with concrete. Tube rectangular can be readily bent, formed, punched, and drilled. New and improved methods to fasten Rectangular tubing to itself or to other materials are making its use simpler and fabrication faster.
2019年7月31日星期三
Precision seamless steel tube extrusion process
Precision seamless steel tubes with conventional technology for the furnace + ESR -> forging or forging billet and rolling way. Product shape round bar, square flat and forgings. Then steam turbine plant for further processing, but the processing process more special shape, metal utilization after processing about 30%. To squeeze mode after production, will have the following advantages:
1, Precision seamless steel tubes in the best state of stress in the hot extrusion process, reducing the product of internal defects.
2, Easy to implement diverse cross-sectional shape, adapt more variety, small batch production.
3, In each direction of performance uniformity.
The main way to produce extrusion process: EAF + ESR -> forging or rolling cogging -> induction heating -> Extrusion -> annealing.
Extrusion and forging, rolling approach is the difference between:
1, Precision seamless extrusion heating temperatures than forging, rolling production is higher 30-60 ℃;
2, Deformation, high speed (deformed steel requires only 2-4S).
3, Multi-step, high metal consumption.
1, Precision seamless steel tubes in the best state of stress in the hot extrusion process, reducing the product of internal defects.
2, Easy to implement diverse cross-sectional shape, adapt more variety, small batch production.
3, In each direction of performance uniformity.
The main way to produce extrusion process: EAF + ESR -> forging or rolling cogging -> induction heating -> Extrusion -> annealing.
Extrusion and forging, rolling approach is the difference between:
1, Precision seamless extrusion heating temperatures than forging, rolling production is higher 30-60 ℃;
2, Deformation, high speed (deformed steel requires only 2-4S).
3, Multi-step, high metal consumption.
2019年7月30日星期二
Martensite: Definition, Transformation & Microstructure
Martensite can be divided into lath martensite and lamellar martensite. When the austenite carbon content is less than 0.20%, the quenched martensite is lath-like. When the austenite has a carbon content of more than 1.0%, it is in the form of a sheet.
Bainite has various histological forms and can be roughly classified into granular bainite, upper bainite and lower bainite according to its metallographic structure.
The first stage of tempering (≤250 ° C): decomposition of quenched martensite;
The second stage of tempering (200-300 ° C): the transformation of retained austenite;
The third stage of tempering (250-400 ° C): the transformation of carbide type;
The fourth stage of tempering (≥400 °C): spheroidization, coarsening of ferrite, recovery and recrystallization of ferrite.
According to the tempering temperature and the corresponding tissue change, the microstructure transformation process of the quenched steel during tempering can be divided into four stages:
1. Tempered martensite - The quenched steel is tempered at 150-250 ° C to form a tempered martensite structure.
2. Tempered tortite - After tempering at 350-450 °C, the quenched steel forms a tempered tortite structure.
3. Tempered Sorbite - After quenching at 500-650 °C, the quenched steel forms a tempered sorbite.
4. Tempered pearlite - quenched steel in the temperature range of 650 ° C - A1 after a long time tempering, that is, the formation of tempered pearlite structure.
Bainite has various histological forms and can be roughly classified into granular bainite, upper bainite and lower bainite according to its metallographic structure.
The first stage of tempering (≤250 ° C): decomposition of quenched martensite;
The second stage of tempering (200-300 ° C): the transformation of retained austenite;
The third stage of tempering (250-400 ° C): the transformation of carbide type;
The fourth stage of tempering (≥400 °C): spheroidization, coarsening of ferrite, recovery and recrystallization of ferrite.
According to the tempering temperature and the corresponding tissue change, the microstructure transformation process of the quenched steel during tempering can be divided into four stages:
1. Tempered martensite - The quenched steel is tempered at 150-250 ° C to form a tempered martensite structure.
2. Tempered tortite - After tempering at 350-450 °C, the quenched steel forms a tempered tortite structure.
3. Tempered Sorbite - After quenching at 500-650 °C, the quenched steel forms a tempered sorbite.
4. Tempered pearlite - quenched steel in the temperature range of 650 ° C - A1 after a long time tempering, that is, the formation of tempered pearlite structure.
Welding gap of welded pipe
The strip steel is sent to the welded pipe unit, and the strip is rolled by a plurality of rolls, and the strip is gradually rolled up to form a circular tube blank having an open gap, and the pressing amount of the pressing roll is adjusted to control the weld gap to be 1 to 3 mm. And make the ends of the solder joints flush. If the gap is too large, the proximity effect is reduced, the eddy current is insufficient, and the weld intergranular joint is poor to cause unmelting or cracking. If the gap is too small, the proximity effect is increased, the welding heat is too large, and the weld is burnt; or the weld is pressed and rolled to form a deep pit, which affects the surface quality of the weld.
1, Welding temperature control
The welding temperature is mainly affected by the high-frequency eddy current thermal power. According to the relevant formula, the high-frequency eddy current thermal power is mainly affected by the current frequency. The eddy current thermal power is proportional to the square of the current excitation frequency; and the current excitation frequency is affected by the excitation voltage. Current and capacitance, inductance.
2, The control of the pressing force
After the two edges of the tube are heated to the soldering temperature, under the extrusion of the pressing roller, common metal crystal grains are mutually infiltrated and crystallized, and finally a firm weld seam is formed. If the pressing force is too small, the number of common crystals formed will be small, the strength of the weld metal will decrease, and cracking will occur after the force is applied; if the pressing force is too large, the molten metal will be extruded out of the weld, not only will it be lowered. The weld strength, but also a large number of internal and external burrs, and even caused by welding seams and other defects.
3. Regulation of the position of the high frequency induction coil
The high frequency induction coil should be as close as possible to the position of the squeeze roller. If the induction coil is far away from the squeeze roller, the effective heating time is longer, the heat affected zone is wider, and the weld strength is decreased; otherwise, the weld edge is insufficiently heated, and the extrusion is poorly formed.
4. The resistor is one or a set of special magnetic rods for the welded pipe.
The cross-sectional area of the resistor is usually not less than 70% of the cross-sectional area of the inner diameter of the steel pipe. The function is to form an electromagnetic induction circuit between the induction ring and the edge of the tube blank and the magnetic rod to genera
te a proximity effect. The eddy current is concentrated in the tube blank weld. Near the edge, the edge of the tube blank is heated to the soldering temperature. The resistor is dragged in the tube blank with a wire, and its center position should be relatively fixed near the center of the squeeze roller. When starting up, due to the rapid movement of the tube blank, the resistor is greatly damaged by the friction of the inner wall of the tube blank and needs to be replaced frequently.
5. After the weld is welded and extruded, it will produce a weld bead and need to be removed.
The cleaning method is to fix the tool on the frame and smooth the welding bead by the rapid movement of the welded pipe. The burrs inside the welded pipe are generally not removed.
1, Welding temperature control
The welding temperature is mainly affected by the high-frequency eddy current thermal power. According to the relevant formula, the high-frequency eddy current thermal power is mainly affected by the current frequency. The eddy current thermal power is proportional to the square of the current excitation frequency; and the current excitation frequency is affected by the excitation voltage. Current and capacitance, inductance.
2, The control of the pressing force
After the two edges of the tube are heated to the soldering temperature, under the extrusion of the pressing roller, common metal crystal grains are mutually infiltrated and crystallized, and finally a firm weld seam is formed. If the pressing force is too small, the number of common crystals formed will be small, the strength of the weld metal will decrease, and cracking will occur after the force is applied; if the pressing force is too large, the molten metal will be extruded out of the weld, not only will it be lowered. The weld strength, but also a large number of internal and external burrs, and even caused by welding seams and other defects.
3. Regulation of the position of the high frequency induction coil
The high frequency induction coil should be as close as possible to the position of the squeeze roller. If the induction coil is far away from the squeeze roller, the effective heating time is longer, the heat affected zone is wider, and the weld strength is decreased; otherwise, the weld edge is insufficiently heated, and the extrusion is poorly formed.
4. The resistor is one or a set of special magnetic rods for the welded pipe.
The cross-sectional area of the resistor is usually not less than 70% of the cross-sectional area of the inner diameter of the steel pipe. The function is to form an electromagnetic induction circuit between the induction ring and the edge of the tube blank and the magnetic rod to genera
te a proximity effect. The eddy current is concentrated in the tube blank weld. Near the edge, the edge of the tube blank is heated to the soldering temperature. The resistor is dragged in the tube blank with a wire, and its center position should be relatively fixed near the center of the squeeze roller. When starting up, due to the rapid movement of the tube blank, the resistor is greatly damaged by the friction of the inner wall of the tube blank and needs to be replaced frequently.
5. After the weld is welded and extruded, it will produce a weld bead and need to be removed.
The cleaning method is to fix the tool on the frame and smooth the welding bead by the rapid movement of the welded pipe. The burrs inside the welded pipe are generally not removed.
Factors affecting the transformation rate of austenite
1, The effect of heating temperature
As the heating temperature increases, the nucleation rate, the growth rate, and the atomic diffusion capacity of austenite increase the formation rate of austenite.
2, The impact of heating speed
As the heating rate increases, the various stages of the austenite formation process move to a higher temperature range. The faster the heating rate, the greater the superheat of the pearlite, the shorter the incubation period of the transition, and the longer the time required for the transformation. short.
3. The influence of the chemical composition of steel
The effect of carbon content of steel
When the carbon content in the steel increases, the total interface of the ferrite and the cementite increases, and the carbon diffusion capacity increases. At the same time, the higher the carbon concentration in the austenite, the faster the diffusion rate of the atom, the austenite The greater the probability of nucleation of the body.
Effect of alloying elements in steel
The alloying elements in steel do not change the general course of austenitization during steel heating, but the alloying elements have a great influence on the nucleation, growth, dissolution of carbides, and austenite homogenization of austenite. .
4. The influence of the original structure of steel
The finer the original structure of the steel, the greater the dispersion of carbides, the smaller the interlamellar spacing of ferrite and cementite, and the more the phase interface, the faster the austenite formation.
http://www.xysteelpipe.com/info/Factors-affecting-the-transformation-rate-of-austenite-1470-1.htm
As the heating temperature increases, the nucleation rate, the growth rate, and the atomic diffusion capacity of austenite increase the formation rate of austenite.
2, The impact of heating speed
As the heating rate increases, the various stages of the austenite formation process move to a higher temperature range. The faster the heating rate, the greater the superheat of the pearlite, the shorter the incubation period of the transition, and the longer the time required for the transformation. short.
3. The influence of the chemical composition of steel
The effect of carbon content of steel
When the carbon content in the steel increases, the total interface of the ferrite and the cementite increases, and the carbon diffusion capacity increases. At the same time, the higher the carbon concentration in the austenite, the faster the diffusion rate of the atom, the austenite The greater the probability of nucleation of the body.
Effect of alloying elements in steel
The alloying elements in steel do not change the general course of austenitization during steel heating, but the alloying elements have a great influence on the nucleation, growth, dissolution of carbides, and austenite homogenization of austenite. .
4. The influence of the original structure of steel
The finer the original structure of the steel, the greater the dispersion of carbides, the smaller the interlamellar spacing of ferrite and cementite, and the more the phase interface, the faster the austenite formation.
http://www.xysteelpipe.com/info/Factors-affecting-the-transformation-rate-of-austenite-1470-1.htm
2019年7月22日星期一
Five Different Heat Treatment Technique
Heat treatment is the process of heating and cooling metals to achieve desired physical and mechanical properties through modification of their crystalline structure. The temperature, length of time, and rate of cooling after heat treatment will all impact properties dramatically. The most common reasons to heat treat include increasing strenght or hardness, increasing toughness, improving ductility and maximizing corrosion resistance.
1. Annealing
Annealing is a rather generalized term. Annealing consists of heating a metal to a specific temperature and then cooling at a rate that will produce a refined microstructure. The rate of colling is generally slow. Annealing is most often used to soften a metal for cold working, to improve machinability, or to enhance properties like electrical conductivity.
2. Normalizing
Normalizing is a technique used to provide uniformity in grain size and composition throughout an alloy. The term is often used for ferrous alloys that have been austenitized and then cooled in open air. Normalizing not only produces pearlite, but also bainited sometimes martensite, which gives harder and stronger steel , but with less ductility for the same composition than full annealing.
3. Stress relieving
Stress relieving is a technique to remove or reduce the internal stresses created in a metal. These stresses may be caused in a number of ways, ranging from cold working to non-uniform cooling. Stress relieving is usually accomplished by heating a metal below the lower critical temperature and then cooling uniformly.
4.Quenching
Quenching is a process of cooling a metal at a rapid rate. This is most often done to produce a martensite transformation. In ferrous alloys, this will often produce a harder metal, while non-ferrous alloys will usually become softer than normal.
5. Tempering
Untempered martensitic steel, while very hard, is too brittle to be useful for most applications. A method for alleviation this problem is called tempering. Most applications require that quenched part be tempered. Tempering consists of heating steel below the lower critical temperature, (often from 400 to 1105° F or 205 to 595°C, depending on the desired results), to impart some toughness. Higher tempering temperatures are sometimes used to impart further ductility, although some yield strength is lost.
1. Annealing
Annealing is a rather generalized term. Annealing consists of heating a metal to a specific temperature and then cooling at a rate that will produce a refined microstructure. The rate of colling is generally slow. Annealing is most often used to soften a metal for cold working, to improve machinability, or to enhance properties like electrical conductivity.
2. Normalizing
Normalizing is a technique used to provide uniformity in grain size and composition throughout an alloy. The term is often used for ferrous alloys that have been austenitized and then cooled in open air. Normalizing not only produces pearlite, but also bainited sometimes martensite, which gives harder and stronger steel , but with less ductility for the same composition than full annealing.
3. Stress relieving
Stress relieving is a technique to remove or reduce the internal stresses created in a metal. These stresses may be caused in a number of ways, ranging from cold working to non-uniform cooling. Stress relieving is usually accomplished by heating a metal below the lower critical temperature and then cooling uniformly.
4.Quenching
Quenching is a process of cooling a metal at a rapid rate. This is most often done to produce a martensite transformation. In ferrous alloys, this will often produce a harder metal, while non-ferrous alloys will usually become softer than normal.
5. Tempering
Untempered martensitic steel, while very hard, is too brittle to be useful for most applications. A method for alleviation this problem is called tempering. Most applications require that quenched part be tempered. Tempering consists of heating steel below the lower critical temperature, (often from 400 to 1105° F or 205 to 595°C, depending on the desired results), to impart some toughness. Higher tempering temperatures are sometimes used to impart further ductility, although some yield strength is lost.
Seamless steel tube deformation production process
There are three main deformation processes throughout hot rolled seamless steel pipe production methods.
1. Perforating.
Perforation methods are common rotary piercing and pressure perfortion. In addition, we can use centrifugal casting, continuous casting with electroslag re-melting and other methods to obtain a hollow shell and to eliminate the perforation step.
2. Rolling.
On the extension machine, the pipe billit will roll thin capillary and become close to extending the original pipe wall thickness. The common type of rolling methods including continuous rolling, rolling cycle, automatic rolling tube, top tube, three roll rolllin, two roll rolling etc.
3. Finishing.
The main process for pipe finishing are sizing and reducing. The goal is to achieve improved accuracy of the pipe thickness, improve the surface quality, improve pipe roundness and expand the product specifications.
1. Perforating.
Perforation methods are common rotary piercing and pressure perfortion. In addition, we can use centrifugal casting, continuous casting with electroslag re-melting and other methods to obtain a hollow shell and to eliminate the perforation step.
2. Rolling.
On the extension machine, the pipe billit will roll thin capillary and become close to extending the original pipe wall thickness. The common type of rolling methods including continuous rolling, rolling cycle, automatic rolling tube, top tube, three roll rolllin, two roll rolling etc.
3. Finishing.
The main process for pipe finishing are sizing and reducing. The goal is to achieve improved accuracy of the pipe thickness, improve the surface quality, improve pipe roundness and expand the product specifications.
Ordinary seamless steel tube standard
1. General purpose seamless steel pipe ASTM A53 GR.B, steel number: SA53 B, specification: 1/4′′-28′′, 13.7-711.2mm
2. Seamless steel pipe for high temperature operation ASTM A106 GR.B, steel number: SA106B, specification: 1/4′′-28′′, 13.7-711.2mm
3. Line pipe API SPEC 5L, steel number: B, X42, X46, X52, specifications: 1/4"-28", 13.7-711.2mm
4.ASTM A106/A53/API 5L GR.B, steel number: B, specification: 1/4"-28", 13.7-711.2mm
5. Seamless low carbon steel pipe ASTM A179 for heat exchangers and condensers, size: 3/4′′, 1′′
6.-40°C-101°C seamless steel pipe ASTM A333 for low temperature operation, steel number: GR.A, GR.1, GR.6, GR.7, GR.3, specification: 1/4′′-28′′, 13.7-711.2mm
7. German standard DIN2448/1629 seamless steel pipe, steel number: St37, St44, St52, specifications: 1/4"-28", 13.7-711.2mm
8. Heat-resistant steel seamless steel pipe (heat-strength pipe) DIN17175-1979, steel number: carbon structural steel St35.8-St45.8/I, St35.8-St45.8/III, alloy structural steel 15Mo3, 13CrMo44 , 10CrMo910, specifications: 1/4"-28", 13.7-711.2mm
9. Structural seamless steel pipe GB/T8162-1999, steel number: 10#, 20#, 35#, 45#, 16Mn (Q345), specification: 6-720×1-70mm
10. Seamless steel pipe for conveying fluid GB/T8163-1999, steel number: 10#, 20#, 16Mn (Q345), specification: 6-720×1-70mm
11. Low and medium pressure boiler tube GB3087-1999, steel number: 10#, 20#, specification: 6-720×1-70mm
12. High pressure boiler tube GB5310-1995, steel number: 20G, specification: 6-720×1-70mm
2. Seamless steel pipe for high temperature operation ASTM A106 GR.B, steel number: SA106B, specification: 1/4′′-28′′, 13.7-711.2mm
3. Line pipe API SPEC 5L, steel number: B, X42, X46, X52, specifications: 1/4"-28", 13.7-711.2mm
4.ASTM A106/A53/API 5L GR.B, steel number: B, specification: 1/4"-28", 13.7-711.2mm
5. Seamless low carbon steel pipe ASTM A179 for heat exchangers and condensers, size: 3/4′′, 1′′
6.-40°C-101°C seamless steel pipe ASTM A333 for low temperature operation, steel number: GR.A, GR.1, GR.6, GR.7, GR.3, specification: 1/4′′-28′′, 13.7-711.2mm
7. German standard DIN2448/1629 seamless steel pipe, steel number: St37, St44, St52, specifications: 1/4"-28", 13.7-711.2mm
8. Heat-resistant steel seamless steel pipe (heat-strength pipe) DIN17175-1979, steel number: carbon structural steel St35.8-St45.8/I, St35.8-St45.8/III, alloy structural steel 15Mo3, 13CrMo44 , 10CrMo910, specifications: 1/4"-28", 13.7-711.2mm
9. Structural seamless steel pipe GB/T8162-1999, steel number: 10#, 20#, 35#, 45#, 16Mn (Q345), specification: 6-720×1-70mm
10. Seamless steel pipe for conveying fluid GB/T8163-1999, steel number: 10#, 20#, 16Mn (Q345), specification: 6-720×1-70mm
11. Low and medium pressure boiler tube GB3087-1999, steel number: 10#, 20#, specification: 6-720×1-70mm
12. High pressure boiler tube GB5310-1995, steel number: 20G, specification: 6-720×1-70mm
High Strength Corrosion Resistant and Environmentally Friendly Anticorrosive Coating
High strength corrosion resistant and environmentally friendly anticorrosive coating - IPN8710 coatings are specially designed for the distribution of water distribution pipes.
Cold drawn (rolled) seamless steel pipe. Cold drawn (rolled) tubes are divided into two types: round tubes and shaped tubes.
a. Process flow overview Hot rolling (extrusion seamless steel pipe): round billet → heating → perforation → three-roll cross-rolling, continuous rolling or extrusion → pipe removal → sizing (or reducing diameter) → cooling → blank tube → straightening → hydraulic test (or flaw detection) → marking → Storage.
b. Cold drawn (rolled) seamless steel pipe: round tube billet → heating → perforation → head → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → blank tube → heat treatment → straightening → Hydraulic test (inspection) → mark → storage.
First, Spiral steel pipe, straight seam steel pipe and seamless steel pipe are used as base material for processing anti-corrosion steel pipe. The types of anti-corrosion processing are as follows:
1. Oil and gas are treated with 3pe steel pipe anti-corrosion and two-layer polyethylene (2PE) steel pipe.
2. FBE anti-corrosion steel pipe for oil and gas (single-layer sintered epoxy powder anti-corrosion) steel pipe, 2FBE (double-layer melting epoxy powder anti-corrosion) steel pipe. standard: SY/T0315-97
3, water supply pipeline cement mortar lining steel pipe internal corrosion protection. Standard: CECS10:89
4. Epoxy coal tar pitch glass cloth steel pipe anti-corrosion. Standard: GB50268-97
5, water supply pipeline IPN8710 polymer non-toxic paint steel pipe anti-corrosion.
6, sales of epoxy coal bitumen anti-corrosion coatings, IPN8710 coatings, chlorinated rubber anti-corrosion coatings, polyurethane anti-corrosion coatings, and other anti-corrosion coatings.
7, high-density polyethylene polyurethane foam insulation steel pipe.
Second, the biggest advantage of IPN8710 coating is that it has good durability. The film after curing of epoxy resin is tough and water resistant, the coating film is non-toxic, and it has no pollution to water. Strong adhesion, good adhesion between paint film and paint film. It has excellent rust and
water resistance and uses excellent anti-rust materials to ensure its anti-rust properties. It has good mechanical strength, tough film, abrasion resistance and impact resistance. High solid content and thick coating film. Curing to film at room temperature. No large baking equipment is required. It
is widely used in the inner wall coating of water supply equipment such as drinking water tanks, water pipes, water tanks and water towers, and in the cargo tanks of sugar and grain. It can also be used as a swimming pool, a power plant cooling tower, and an inner wall coating for fuel oil, gasoline metal,
and concrete.
Third, PN8710 anti-corrosion coating technical indicators and storage methods
Applicable period: 8 hours
Thinner and dosage: special thinner, ≤ 5%
Coating method: brush, roller or spray coating interval: the shortest 4 hours, the longest 3 days .
Film thickness: wet film: 200μm dry film: theoretical dosage
Surface treatment: remove oil stains, dust, welding slag, and oxidized into loose rust on the
Surface of the anti-corrosion parts to keep the surface dry and free of dirt.
Matching primer: IPN8710 anti-corrosion primer, IPN8710-4 thick paste anti-corrosion primer.
Storage period: 12 months
Fourth, secondly understand the precautions of IPN8710 anti-corrosion coating: the product should be stored in a cool, ventilated and dry place, isolated from the fire source, away from heat.
This product is a thick paste type paint, which can be applied thickly without sag. It can be brushed without adding thinner after opening the barrel.
After the coating period is too long, it will precipitate slightly and should be stirred before use.
After the paint is prepared, it will be matured for 20 minutes in the summer and 1.5-2 hours after the winter ripening. It is usually used up within 8 hours, otherwise the viscosity will thicken and it is not easy to construct.
After the primer is dry, the topcoat can be applied. The interval at room temperature should not exceed two days. Otherwise, the interlayer bonding will be affected. The time gap between the coatings of each layer is also better.
Cold drawn (rolled) seamless steel pipe. Cold drawn (rolled) tubes are divided into two types: round tubes and shaped tubes.
a. Process flow overview Hot rolling (extrusion seamless steel pipe): round billet → heating → perforation → three-roll cross-rolling, continuous rolling or extrusion → pipe removal → sizing (or reducing diameter) → cooling → blank tube → straightening → hydraulic test (or flaw detection) → marking → Storage.
b. Cold drawn (rolled) seamless steel pipe: round tube billet → heating → perforation → head → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → blank tube → heat treatment → straightening → Hydraulic test (inspection) → mark → storage.
First, Spiral steel pipe, straight seam steel pipe and seamless steel pipe are used as base material for processing anti-corrosion steel pipe. The types of anti-corrosion processing are as follows:
1. Oil and gas are treated with 3pe steel pipe anti-corrosion and two-layer polyethylene (2PE) steel pipe.
2. FBE anti-corrosion steel pipe for oil and gas (single-layer sintered epoxy powder anti-corrosion) steel pipe, 2FBE (double-layer melting epoxy powder anti-corrosion) steel pipe. standard: SY/T0315-97
3, water supply pipeline cement mortar lining steel pipe internal corrosion protection. Standard: CECS10:89
4. Epoxy coal tar pitch glass cloth steel pipe anti-corrosion. Standard: GB50268-97
5, water supply pipeline IPN8710 polymer non-toxic paint steel pipe anti-corrosion.
6, sales of epoxy coal bitumen anti-corrosion coatings, IPN8710 coatings, chlorinated rubber anti-corrosion coatings, polyurethane anti-corrosion coatings, and other anti-corrosion coatings.
7, high-density polyethylene polyurethane foam insulation steel pipe.
Second, the biggest advantage of IPN8710 coating is that it has good durability. The film after curing of epoxy resin is tough and water resistant, the coating film is non-toxic, and it has no pollution to water. Strong adhesion, good adhesion between paint film and paint film. It has excellent rust and
water resistance and uses excellent anti-rust materials to ensure its anti-rust properties. It has good mechanical strength, tough film, abrasion resistance and impact resistance. High solid content and thick coating film. Curing to film at room temperature. No large baking equipment is required. It
is widely used in the inner wall coating of water supply equipment such as drinking water tanks, water pipes, water tanks and water towers, and in the cargo tanks of sugar and grain. It can also be used as a swimming pool, a power plant cooling tower, and an inner wall coating for fuel oil, gasoline metal,
and concrete.
Third, PN8710 anti-corrosion coating technical indicators and storage methods
Applicable period: 8 hours
Thinner and dosage: special thinner, ≤ 5%
Coating method: brush, roller or spray coating interval: the shortest 4 hours, the longest 3 days .
Film thickness: wet film: 200μm dry film: theoretical dosage
Surface treatment: remove oil stains, dust, welding slag, and oxidized into loose rust on the
Surface of the anti-corrosion parts to keep the surface dry and free of dirt.
Matching primer: IPN8710 anti-corrosion primer, IPN8710-4 thick paste anti-corrosion primer.
Storage period: 12 months
Fourth, secondly understand the precautions of IPN8710 anti-corrosion coating: the product should be stored in a cool, ventilated and dry place, isolated from the fire source, away from heat.
This product is a thick paste type paint, which can be applied thickly without sag. It can be brushed without adding thinner after opening the barrel.
After the coating period is too long, it will precipitate slightly and should be stirred before use.
After the paint is prepared, it will be matured for 20 minutes in the summer and 1.5-2 hours after the winter ripening. It is usually used up within 8 hours, otherwise the viscosity will thicken and it is not easy to construct.
After the primer is dry, the topcoat can be applied. The interval at room temperature should not exceed two days. Otherwise, the interlayer bonding will be affected. The time gap between the coatings of each layer is also better.
Analysis of influencing factors of weld impact toughness of ERW steel pipe
How to improve the impact toughness of ERW steel pipe welds is a major problem in the technology of pipe making. On the basis of mass production practices, various factors affecting the impact toughness of ERW straight seam resistance welded steel pipe welds were analyzed. It is pointed out that in order to further improve the impact toughness of welds and meet the high toughness requirements of long-distance pipelines for ERW steel pipes, it is necessary to start with the control of the quality of raw material coils, combined with the pipe-making process, and strengthen the quality control of forming, welding and on-line heat treatment after welding.
1 ERW steel pipe weld joint toughness characteristics
The welding process of ERW steel pipe uses the principle of skin effect produced by high-frequency current to heat the edge of the hot rolled plate to the molten state, and then it is welded by the mechanical extrusion method. A white fusion line appears at the center of the weld seam of the steel pipe produced by this process, and the heat affected zone on both sides of the fusion line will generate a metal flow line extending from the middle to the inner and outer surfaces. As the ERW steel pipe uses the base metal as the welding material, the performance of the weld seam is greatly related to the performance of the base metal. In ordinary materials, there is little difference in the absorbed energy value of the Charpy impact test between the weld and the base metal. On the contrary, there is a big difference in high-toughness materials. The weld joints are significantly inferior to the parent metal in terms of impact toughness, but they are significantly better than those of common materials. It can be seen that the impact toughness of the center of the weld of the ERW steel pipe, even if the use of high toughness materials, although the toughness of the weld is improved, but can not completely improve the impact toughness of the weld center.
2 Influence factors of weld impact toughness
The main factors affecting the impact toughness of welds are:
(1) Physical and chemical properties of raw materials
(2) Grain size and non-metallic inclusions of raw materials
(3) Heat treatment conditions of welds
(4) Forming conditions
(5) Welding conditions
http://www.xysteelpipe.com/info/Analysis-of-influencing-factors-of-weld-impact-toughness-of-ERW-steel-pipe-1462-1.htm
1 ERW steel pipe weld joint toughness characteristics
The welding process of ERW steel pipe uses the principle of skin effect produced by high-frequency current to heat the edge of the hot rolled plate to the molten state, and then it is welded by the mechanical extrusion method. A white fusion line appears at the center of the weld seam of the steel pipe produced by this process, and the heat affected zone on both sides of the fusion line will generate a metal flow line extending from the middle to the inner and outer surfaces. As the ERW steel pipe uses the base metal as the welding material, the performance of the weld seam is greatly related to the performance of the base metal. In ordinary materials, there is little difference in the absorbed energy value of the Charpy impact test between the weld and the base metal. On the contrary, there is a big difference in high-toughness materials. The weld joints are significantly inferior to the parent metal in terms of impact toughness, but they are significantly better than those of common materials. It can be seen that the impact toughness of the center of the weld of the ERW steel pipe, even if the use of high toughness materials, although the toughness of the weld is improved, but can not completely improve the impact toughness of the weld center.
2 Influence factors of weld impact toughness
The main factors affecting the impact toughness of welds are:
(1) Physical and chemical properties of raw materials
(2) Grain size and non-metallic inclusions of raw materials
(3) Heat treatment conditions of welds
(4) Forming conditions
(5) Welding conditions
http://www.xysteelpipe.com/info/Analysis-of-influencing-factors-of-weld-impact-toughness-of-ERW-steel-pipe-1462-1.htm
2019年7月12日星期五
What is the performance index analysis of square pipe?
What is the performance index analysis of square pipe?
1. Plasticity
Plasticity refers to the ability of a metal material to undergo plastic deformation (permanent deformation) without damage under load.
2. Hardness
Hardness is a measure of the hardness of a metal material. At present, the most commonly used method for measuring hardness in production is the indentation hardness method, which presses the surface of the metal material to be tested under a certain load with a certain geometry of the indenter, and determines the hardness value according to the degree of being pressed.
Commonly used methods are Brinell hardness (HB), Rockwell hardness (HRA, HRB, HRC) and Vickers hardness (HV).
3. Fatigue
The strength, plasticity, and hardness discussed above are all indicators of the mechanical properties of the metal under static load. In fact, many machine parts work under cyclic loading, under which conditions parts can fatigue.
4. Impact toughness
The load acting on the machine at a large speed is called the impact load, and the ability of the metal to resist damage under the impact load is called impact toughness.
5. Strength
Strength refers to the property of a metal material against damage (excessive plastic deformation or fracture) under static load. Since the action mode of the load is tensile, compression, bending, shearing, etc., the strength is also divided into tensile strength, compressive strength, bending strength, shear strength and the like. There is often a certain relationship between various strengths, and tensile strength is generally used as the most basic strength indicator.
1. Plasticity
Plasticity refers to the ability of a metal material to undergo plastic deformation (permanent deformation) without damage under load.
2. Hardness
Hardness is a measure of the hardness of a metal material. At present, the most commonly used method for measuring hardness in production is the indentation hardness method, which presses the surface of the metal material to be tested under a certain load with a certain geometry of the indenter, and determines the hardness value according to the degree of being pressed.
Commonly used methods are Brinell hardness (HB), Rockwell hardness (HRA, HRB, HRC) and Vickers hardness (HV).
3. Fatigue
The strength, plasticity, and hardness discussed above are all indicators of the mechanical properties of the metal under static load. In fact, many machine parts work under cyclic loading, under which conditions parts can fatigue.
4. Impact toughness
The load acting on the machine at a large speed is called the impact load, and the ability of the metal to resist damage under the impact load is called impact toughness.
5. Strength
Strength refers to the property of a metal material against damage (excessive plastic deformation or fracture) under static load. Since the action mode of the load is tensile, compression, bending, shearing, etc., the strength is also divided into tensile strength, compressive strength, bending strength, shear strength and the like. There is often a certain relationship between various strengths, and tensile strength is generally used as the most basic strength indicator.
2019年7月11日星期四
How to distinguish seamless steel pipe from welded steel pipe
The difference between a seamless tube and a conventional welded tube is that the main differences between the two types of tubes are only apparent. There is a general understanding of the difference between a seamless tube and a common welded tube. Seamless pipes and ordinary welded pipes are mainly formed by different molding processes. Ordinary steel pipes, such as tap water pipes, are generally welded by bending the flat plates, and a weld seam can be found on the above; the coarser diameter is generally a spiral weld.
The seamless steel pipe is generally formed by laminating molten steel in a molten state through a circular slit and then being subjected to a stretching process, so that there is no weld, the strength of the pipe is naturally higher, the industrial value is also increased, and the price is also slightly higher. For ordinary welded pipes. Seamless pipes and ordinary welded pipes are greatly improved in performance, especially in pressure bearing capacity, and are often used in high-voltage equipment. Such as the piping connection of hydraulic equipment. The weld seam of ordinary steel pipe is its weak link, and the weld quality is also the main factor affecting its overall performance. People who have lived in the north generally have experienced the experience that the water pipes or heating pipes are frozen in the winter. The places where the explosions are usually welded. Welded pipes are not as strong as seamless steel pipes. By comparing the above two points, it is easy to distinguish between the seamless pipe and the ordinary welded pipe when purchasing the pipe.
Although the price of ordinary welded pipe is very cheap, its service life is quite short, especially in the northern region, so it is recommended to purchase a cost-effective seamless pipe for long-term industrial use.
http://www.xysteelpipe.com/info/How-to-distinguish-seamless-steel-pipe-from-welded-steel-pipe-1454-1.htm
The seamless steel pipe is generally formed by laminating molten steel in a molten state through a circular slit and then being subjected to a stretching process, so that there is no weld, the strength of the pipe is naturally higher, the industrial value is also increased, and the price is also slightly higher. For ordinary welded pipes. Seamless pipes and ordinary welded pipes are greatly improved in performance, especially in pressure bearing capacity, and are often used in high-voltage equipment. Such as the piping connection of hydraulic equipment. The weld seam of ordinary steel pipe is its weak link, and the weld quality is also the main factor affecting its overall performance. People who have lived in the north generally have experienced the experience that the water pipes or heating pipes are frozen in the winter. The places where the explosions are usually welded. Welded pipes are not as strong as seamless steel pipes. By comparing the above two points, it is easy to distinguish between the seamless pipe and the ordinary welded pipe when purchasing the pipe.
Although the price of ordinary welded pipe is very cheap, its service life is quite short, especially in the northern region, so it is recommended to purchase a cost-effective seamless pipe for long-term industrial use.
http://www.xysteelpipe.com/info/How-to-distinguish-seamless-steel-pipe-from-welded-steel-pipe-1454-1.htm
Usage of Hollow Structural Sections
HSS (hollow structural sections) refers to a metal profile that is hollow and tubular. This hollow structural tube (or HSS) is used as a structural element in buildings, bridges and other structures, and in a wide variety of manufactured products. It's produced in round, square and rectangular shapes in a broad range of sizes and gauges.
According to EN10219, EN10225, API and ASTM standards, in a wide range of geometries and wall thickness in HFW, HSAW and LSAW production, suitable for very demanding highly-stressed steel structures such as:
1. Road and Pedestrian Bridges
2. Roofs, Hangars and various Superstructures widely used in airports, stadiums, shopping malls etc.
3. Long-span and slender steel structures
4. Cranes, booms and masts
5. Earth-moving, agricultural & machinery equipment frameworks
6. Road, railway-car and trailer frames
7. Lighting and traffic-poles, road-sign frameworks
8. Jacket foundations for offshore OG & wind power
9. Offshore platform top-sides
10. Jack-up rig frameworks
11. Pile foundations
According to EN10219, EN10225, API and ASTM standards, in a wide range of geometries and wall thickness in HFW, HSAW and LSAW production, suitable for very demanding highly-stressed steel structures such as:
1. Road and Pedestrian Bridges
2. Roofs, Hangars and various Superstructures widely used in airports, stadiums, shopping malls etc.
3. Long-span and slender steel structures
4. Cranes, booms and masts
5. Earth-moving, agricultural & machinery equipment frameworks
6. Road, railway-car and trailer frames
7. Lighting and traffic-poles, road-sign frameworks
8. Jacket foundations for offshore OG & wind power
9. Offshore platform top-sides
10. Jack-up rig frameworks
11. Pile foundations
Spiral welded pipe anti-corrosion technology
The individual quality spiral welded pipe is relatively large, so it is necessary to be placed outdoors. However, this will be difficult to avoid the sun and rain, the rust has been plagued spiral welded pipe storage time and conditions. We need to conduct a comprehensive answer on rust knowledge of spiral welded pipe.
The main method is to use steel wire to brush the surface grinding, cleaning and preheating the spiral welded pipe can remove or loose or tilt of the oxide scale, rust and welding slag. Hand tool rust can reach Sa2 level, power tools rust can be achieved Sa3 level, if attached to a solid steel sruface oxide skin, tools rust effect is not ideal which can not reach the anchor pattern depth of anti-corrosion construction requirements.
Pickling by solvent or emulsion can clean low pressure liquid delivery pipe surface. It can achieve the removal of oil, grease, dust, lubricants and similar organic matter, but it can not remove the steel surface rust, scale, welding flux etc.
General chemical and electrolytic picking are two ways to do, pipeline corrosion using only chemical pickling can descaling, rust, old coatings, and sometimes used as a sand-blasting after reprocessing. Although chemical cleaning the surface can reach a certain cleanliness and roughness, the anchor pattern shallow, and easy to pollute the environment stacking spiral welded pipe.
When the rational use of means to clean rusty pipe and fittings, we guarantee long service in production, creating more production efficiency.
The main method is to use steel wire to brush the surface grinding, cleaning and preheating the spiral welded pipe can remove or loose or tilt of the oxide scale, rust and welding slag. Hand tool rust can reach Sa2 level, power tools rust can be achieved Sa3 level, if attached to a solid steel sruface oxide skin, tools rust effect is not ideal which can not reach the anchor pattern depth of anti-corrosion construction requirements.
Pickling by solvent or emulsion can clean low pressure liquid delivery pipe surface. It can achieve the removal of oil, grease, dust, lubricants and similar organic matter, but it can not remove the steel surface rust, scale, welding flux etc.
General chemical and electrolytic picking are two ways to do, pipeline corrosion using only chemical pickling can descaling, rust, old coatings, and sometimes used as a sand-blasting after reprocessing. Although chemical cleaning the surface can reach a certain cleanliness and roughness, the anchor pattern shallow, and easy to pollute the environment stacking spiral welded pipe.
When the rational use of means to clean rusty pipe and fittings, we guarantee long service in production, creating more production efficiency.
2019年7月10日星期三
Professional Skills of Straight Seam Double Submerged Arc Welded Steel Pipe
Professional skills of straight seam double submerged arc welded steel pipe(lsaw steel pipe) are following below:
1, Double submerged arc welding method in a new invention in 1940, in front of it and the manual welding the same place that it still uses residue protection, but this is not the dregs electrode coating. Straight seam double submerged arc welding and manual welding the same place that it still uses residue protection, but this is not the dregs electrode coating, specifically melting out of the flux. Flux The flux system consists of a funnel filled through a pipeline to be welded to the front.
2. The second difference is the use of electrode using wire, because wire can be continuously sent; electrodes, we burn a welding electrode must have a head gave threw it, and the operation had to stop, and then change the electrode welding.
3. In this way, the first advantage is fully automated; second advantage, which is under the submerged arc welding, so its heat exchange and protection of relatively strong performance, high quality weld out; third advantage, since the automatic submerged arc welding arc buried under welding flux, so it can use high-current, high welding efficiency, the recent progress of our country natural gas pipeline project.
4, Later changed to the wire, with the wire feed unit and wire spool is continuously sent to the wire, the welding wire is continuously fed, igniting an arc in the meltable particulate flux covering, welding wire, part of the melting and evaporation of the base metal and solder forms a cavity, the arc is stabilized combustion cavity inside, so call it submerged arc welding. Arc is buried in the inside of the cavity.
5, The pipe is a high-strength steel, such pipelines in the factory inside the first preformed section, and then get on the site, in the field of welding, the welding process such pipelines in factory production is the use of submerged arc welding, now buried welding has developed into, a double wire submerged arc welding, as well as multi-wire submerged arc welding, to further improve efficiency.
1, Double submerged arc welding method in a new invention in 1940, in front of it and the manual welding the same place that it still uses residue protection, but this is not the dregs electrode coating. Straight seam double submerged arc welding and manual welding the same place that it still uses residue protection, but this is not the dregs electrode coating, specifically melting out of the flux. Flux The flux system consists of a funnel filled through a pipeline to be welded to the front.
2. The second difference is the use of electrode using wire, because wire can be continuously sent; electrodes, we burn a welding electrode must have a head gave threw it, and the operation had to stop, and then change the electrode welding.
3. In this way, the first advantage is fully automated; second advantage, which is under the submerged arc welding, so its heat exchange and protection of relatively strong performance, high quality weld out; third advantage, since the automatic submerged arc welding arc buried under welding flux, so it can use high-current, high welding efficiency, the recent progress of our country natural gas pipeline project.
4, Later changed to the wire, with the wire feed unit and wire spool is continuously sent to the wire, the welding wire is continuously fed, igniting an arc in the meltable particulate flux covering, welding wire, part of the melting and evaporation of the base metal and solder forms a cavity, the arc is stabilized combustion cavity inside, so call it submerged arc welding. Arc is buried in the inside of the cavity.
5, The pipe is a high-strength steel, such pipelines in the factory inside the first preformed section, and then get on the site, in the field of welding, the welding process such pipelines in factory production is the use of submerged arc welding, now buried welding has developed into, a double wire submerged arc welding, as well as multi-wire submerged arc welding, to further improve efficiency.
2019年7月3日星期三
Seamless steel tube rolling
The raw material is rolled seamless round tube, tube embryos to go through a cutting machine cutting a length of about 1 meter blank, and by conveyor belt to the furnace heating. The billet is fed into the furnace is heated to a temperature of about 1200 degrees Celsius. The fuel is hydrogen or acetylene. Furnace temperature control is the key issue. After a round tube came out to go through the pressure punching machine wear air. Generally more common punch is tapered roller punching machine, punching machine such high production efficiency, product quality, perforated expanding capacity, can be worn a variety of steels. After perforation, round tube has been three-roll rolling, rolling or extrusion. To post extrusion detached sizing. Sizing high-speed rotary cone drill bit through the perforated steel embryo formed steel. Pipe inner diameter is determined by the outer diameter sizing mill drill length.
Pipe by sizing after entering the cooling tower through spray cooling pipe after cooling, will be straightening. After straightening the steel conveyor belt to the metal detection machine (or pressure test) for internal testing. If the thick-walled seamless internal cracks, bubbles and other issues, will be detected. After the selection of steel but also through strict quality control manual. After the steel quality inspection, using spray paint on number, size, production batch number. By a crane into the warehouse.
Pipe by sizing after entering the cooling tower through spray cooling pipe after cooling, will be straightening. After straightening the steel conveyor belt to the metal detection machine (or pressure test) for internal testing. If the thick-walled seamless internal cracks, bubbles and other issues, will be detected. After the selection of steel but also through strict quality control manual. After the steel quality inspection, using spray paint on number, size, production batch number. By a crane into the warehouse.
Effect of nitrogen on corrosion resistance of stainless steel
1. Influence on the microstructure of stainless steel
The effect of nitrogen on stainless steel is very strong. The nitrogen element in the stainless steel matrix can replace part of the nickel element, reduce the ferrite content in the stainless steel, help stabilize the austenite, reduce the precipitation of harmful intermetallic phases, and even eliminate the martensite transformation during cold working.
2. Influence on mechanical properties of stainless steel
The effect of nitrogen on the mechanical properties of the matrix in stainless steel is mainly reflected in two aspects. First of all, nitrogen can significantly increase the strength of stainless steel, and will not reduce the plastic toughness of stainless steel. This is a good study of the direction of high strength and toughness of stainless steel. Secondly, the nitrogen element can also enhance the creep resistance, fatigue resistance and wear resistance of the stainless steel.
3. Influence on corrosion resistance of stainless steel
Nitrogen is also beneficial for increasing the corrosion resistance of stainless steel. Mainly to improve the resistance to intergranular corrosion, pitting corrosion, crevice corrosion. The mechanism of nitrogen resistance to pitting corrosion and crevice corrosion of stainless steel is mainly acid consumption theory. Nitrogen forms NH4+, lowers pH value, prevents anode dissolution and slows local acidification, which can inhibit the autocatalytic process of pitting corrosion. Secondly, the enrichment of interfacial nitrogen, the enrichment of nitrogen in the passivation film of the metal interface near the metal side, will affect the repassivation kinetics, promote the rapid re-passivation of the stainless steel surface, and thus play a role in suppressing pitting corrosion. In addition, nitrogen and other elements can work synergistically. Nitrogen can inhibit the over-passivation and dissolution of elements such as chromium and molybdenum, and can produce a stronger surface layer in the local corrosion process of the stainless steel plate surface, and improve the corrosion resistance of the stainless steel plate surface.
Nitrogen plays an indispensable role in the stability and corrosion resistance of stainless steel, and since nitrogen is cheaper than alloying elements such as nickel and chromium, the future development space in the field of stainless steel should have unlimited potential.
http://www.xysteelpipe.com/info/Effect-of-nitrogen-on-corrosion-resistance-of-stainless-steel-1447-1.htm
The effect of nitrogen on stainless steel is very strong. The nitrogen element in the stainless steel matrix can replace part of the nickel element, reduce the ferrite content in the stainless steel, help stabilize the austenite, reduce the precipitation of harmful intermetallic phases, and even eliminate the martensite transformation during cold working.
2. Influence on mechanical properties of stainless steel
The effect of nitrogen on the mechanical properties of the matrix in stainless steel is mainly reflected in two aspects. First of all, nitrogen can significantly increase the strength of stainless steel, and will not reduce the plastic toughness of stainless steel. This is a good study of the direction of high strength and toughness of stainless steel. Secondly, the nitrogen element can also enhance the creep resistance, fatigue resistance and wear resistance of the stainless steel.
3. Influence on corrosion resistance of stainless steel
Nitrogen is also beneficial for increasing the corrosion resistance of stainless steel. Mainly to improve the resistance to intergranular corrosion, pitting corrosion, crevice corrosion. The mechanism of nitrogen resistance to pitting corrosion and crevice corrosion of stainless steel is mainly acid consumption theory. Nitrogen forms NH4+, lowers pH value, prevents anode dissolution and slows local acidification, which can inhibit the autocatalytic process of pitting corrosion. Secondly, the enrichment of interfacial nitrogen, the enrichment of nitrogen in the passivation film of the metal interface near the metal side, will affect the repassivation kinetics, promote the rapid re-passivation of the stainless steel surface, and thus play a role in suppressing pitting corrosion. In addition, nitrogen and other elements can work synergistically. Nitrogen can inhibit the over-passivation and dissolution of elements such as chromium and molybdenum, and can produce a stronger surface layer in the local corrosion process of the stainless steel plate surface, and improve the corrosion resistance of the stainless steel plate surface.
Nitrogen plays an indispensable role in the stability and corrosion resistance of stainless steel, and since nitrogen is cheaper than alloying elements such as nickel and chromium, the future development space in the field of stainless steel should have unlimited potential.
http://www.xysteelpipe.com/info/Effect-of-nitrogen-on-corrosion-resistance-of-stainless-steel-1447-1.htm
2019年7月2日星期二
Welding process of straight seam welded pipe
Longitudinal straight seam welded pipe butt weld joint cross-sectional shape, depending on the thickness of the body to be welded before welding groove and then type two sides. When welding thick steel plate, for penetration in contact at the edges out of various shapes of the groove, so that more easily into the welding rod or wire. Groove patterns are one-sided welding the welding groove and the sides of the groove. When you select groove type, in addition to outside should be considered to ensure penetration welding convenient, less filler metal Chi, small welding deformation and beveling of Longitudinal low cost factor.
Linker connecting the two is in the welding Longitudinal seam formed called weld. Both sides of the weld in the welding welding heat effect will be, but the organization and performance vary, this area is known as the heat affected zone. Welding due to the workpiece material welding materials, Longitudinal welding current so different, after welding may occur in the weld and heat affected zone of overheating, embrittlement, hardening or softening, but also the weldment performance degradation, deterioration of weldability. This need to adjust the welding conditions, before welding weldment interface preheating, post-weld heat when and weld heat treatment can improve the quality of welding weldment quality.
Longitudinal is of two or more homogeneous or heterogeneous material through a combination of diffusion and the question of the atom or molecule is integrally connected to the process, prompting the question of atoms and molecules produce binding and diffusion method is to heat or pressure, or simultaneously heated and pressurized.
In addition, a local weld foot rapid heating and cooling process, the weld zone due to the binding body and four weeks of the workpiece can not freely expand and contract in the weldment after cooling will produce welding stress and deformation. Important product after welding is required to eliminate welding stress, welding distortion correction.
Linker connecting the two is in the welding Longitudinal seam formed called weld. Both sides of the weld in the welding welding heat effect will be, but the organization and performance vary, this area is known as the heat affected zone. Welding due to the workpiece material welding materials, Longitudinal welding current so different, after welding may occur in the weld and heat affected zone of overheating, embrittlement, hardening or softening, but also the weldment performance degradation, deterioration of weldability. This need to adjust the welding conditions, before welding weldment interface preheating, post-weld heat when and weld heat treatment can improve the quality of welding weldment quality.
Longitudinal is of two or more homogeneous or heterogeneous material through a combination of diffusion and the question of the atom or molecule is integrally connected to the process, prompting the question of atoms and molecules produce binding and diffusion method is to heat or pressure, or simultaneously heated and pressurized.
In addition, a local weld foot rapid heating and cooling process, the weld zone due to the binding body and four weeks of the workpiece can not freely expand and contract in the weldment after cooling will produce welding stress and deformation. Important product after welding is required to eliminate welding stress, welding distortion correction.
Disadvantages of galvanized low carbon steel
Disadvantages of galvanized mild steel has following aspects:
On the surface of hot dip galvanized steel rice distribution classes of small dots, called zinc particles is customary. Defective zinc particles can be divided into two: one is up and down the strip surface adhesion lot of granular, strip local increase in the thickness of the zinc layer, causing the surface rough, unsightly and harmful use of known zinc particles. There are two forms, one of the larger particles of zinc tablets, the main ingredient is iron - zinc compound, which is the end of slag.
When coated galvanized steel edge is much higher than the middle of coating thickness, edge thickness is produced.
When the air knife nozzle clogging occurs locally when in a position corresponding to the strip will produce thick zinc layer is formed with marks.
In the middle of the strip edge or rendered bright stripes or the presence of dendritic conchoidal crystal crystalline zinc this particular often make local zinc layer projections, it is called zinc projections. Strip out from uncoiler to galvanized defects between coiler, strip and a mechanical relative movement generated.
On the surface of hot dip galvanized steel rice distribution classes of small dots, called zinc particles is customary. Defective zinc particles can be divided into two: one is up and down the strip surface adhesion lot of granular, strip local increase in the thickness of the zinc layer, causing the surface rough, unsightly and harmful use of known zinc particles. There are two forms, one of the larger particles of zinc tablets, the main ingredient is iron - zinc compound, which is the end of slag.
When coated galvanized steel edge is much higher than the middle of coating thickness, edge thickness is produced.
When the air knife nozzle clogging occurs locally when in a position corresponding to the strip will produce thick zinc layer is formed with marks.
In the middle of the strip edge or rendered bright stripes or the presence of dendritic conchoidal crystal crystalline zinc this particular often make local zinc layer projections, it is called zinc projections. Strip out from uncoiler to galvanized defects between coiler, strip and a mechanical relative movement generated.
Pipeline inspection of welded steel pipe
Welded steel pipe at the factory to go through rigorous testing to ensure the quality of welded compliance standards and user requirements. Pipe inspection items generally include: appearance quality factory inspection project, straightness, dimensions, and other types of weld quality inspection items (flattening, flaring, bending, etc.). Welded pipe surface quality and straightness inspection by a full-time quality inspector confirmed finishing process pipe segment using visual way, the implementation of the detection test dimensions available random sampling method, and the weld quality inspection shall be made on special equipment by root on line. This article focuses on online testing of the weld. At present, about our national standards, testing methods available weld pipe hydrostatic testing, ultrasonic testing, eddy current testing in any way.
Hydrostatic test is the most common, the most direct and reliable weld line inspection
Measured way, in a variety of hydraulic test machine. When the pressure test, through the first low-pressure water, filled the whole steel pipe to make the air side by side, and then to test pressure specified by the pressurized way, and to stabilize the prescribed time, when there is no pipe welds and around wet, spray, leakage or permanent deformation is considered qualified.
When the metal by an alternating magnetic field is induced metal surface
Eddy currents; when the presence of the metal surface defects, since the impedance increases, the eddy current value becomes smaller; and when no defect of a metallic material, the value of the stable vortex; size of the power according to the eddy current loss, can be characterized metals whether the surface defects.
Ultrasonic wave propagation in the process, will have a reflection on the media surface.
If there is a crack pipe welds, weld, false welding, lap welding defects such as acoustic impedance will change significantly, so that ultrasonic generating different reflection, through a dedicated instrument will be identified to achieve the purpose of flaw detection. The main steel tube ultrasonic flaw detection are: rotating the probe, steel straight forward; probe fixed, steel rotating forward; steel rotating probe straight forward three forms, in the production of different pipe diameter in both applications.
Hydrostatic test is the most common, the most direct and reliable weld line inspection
Measured way, in a variety of hydraulic test machine. When the pressure test, through the first low-pressure water, filled the whole steel pipe to make the air side by side, and then to test pressure specified by the pressurized way, and to stabilize the prescribed time, when there is no pipe welds and around wet, spray, leakage or permanent deformation is considered qualified.
When the metal by an alternating magnetic field is induced metal surface
Eddy currents; when the presence of the metal surface defects, since the impedance increases, the eddy current value becomes smaller; and when no defect of a metallic material, the value of the stable vortex; size of the power according to the eddy current loss, can be characterized metals whether the surface defects.
Ultrasonic wave propagation in the process, will have a reflection on the media surface.
If there is a crack pipe welds, weld, false welding, lap welding defects such as acoustic impedance will change significantly, so that ultrasonic generating different reflection, through a dedicated instrument will be identified to achieve the purpose of flaw detection. The main steel tube ultrasonic flaw detection are: rotating the probe, steel straight forward; probe fixed, steel rotating forward; steel rotating probe straight forward three forms, in the production of different pipe diameter in both applications.
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