Apart from the factors such as coating variety, coating quality and construction condition, the surface treatment of elbow has an effect on the service life of the coating, which accounts for about 50%. Now let's see how to prevent rust after elbow processing. The first thing is to use wire brush to polish the steel surface. Adding these factors to elbow processing can remove loose or warped oxide scales, rust and welding. Slag and so on. Rust removal of hand tools can reach Sa2 level, power things can reach Sa3 level. If the steel surface is adhered to strong oxide scale, the result of rust removal of things can not be considered. Deep spraying rust removal of anchor lines which can not meet the requirements of anticorrosion construction is driven by high-power motor to twist the spraying blade at high speed, so that abrasives such as steel sand, steel shot, iron wire segment and minerals can advance to the outside surface of elbow pipe under centrifugal force effect. Jet disposal can not only thoroughly remove rust, oxides and dirt, but also achieve the required average roughness of elbow under the effect of ferocious impact and friction of abrasives.
Chemical and electrolytic methods are commonly used for acid pickling treatment. Chemical acid pickling is only used for elbow anticorrosion. It can remove oxide scales, rust and old coatings. Sometimes it can be used as reprocessing after sandblasting and rust removal. Chemical cleaning can make the appearance reach the necessary cleanliness and roughness, but its anchor lines are shallow and easy to pollute the situation.
First of all, steel brushes and other things are used to polish the appearance of steel, and these can remove loose or tilted oxide scales, rust, welding slag and so on. Rust removal of hand tools can reach Sa2 level, power things can reach Sa3 level. If the steel surface is adhered to solid iron oxide scale, the results of rust removal of things are not considered, and the depth of anchor lines required for anti-corrosion construction can not be reached.
http://www.xysteelpipe.com/info/How-to-Prevent-Elbow-Rust-1492-1.htm
2019年8月27日星期二
2019年8月26日星期一
What is the shape of the welded square pipe
There are two main methods for forming welded square tubes: solid bending and hollow bending.
1. solid bending
It means that the bending is compacted, and the inner and outer rollers and the inner and outer walls of the tube blank are biaxially compacted during the solid bending.
1) The advantage of solid bending is that the rebound is small, the forming is accurate, and as long as the roll type is accurate, the R formed at the inner corner is more accurate.
2) The disadvantage of solid bending is the stretching/thinning effect. First, the solid bend causes the bend to be stretched, and the stretch effect shortens the longitudinal length of the bend line. Second, the metal at the bend bend becomes thinner due to stretching.
2. hollow bending
The hollow bend is formed by the unidirectional contact between the outer roller and the outer wall of the tube blank to form a bending moment to bend the strip. The hollow bend causes the bending line to compress, and the compression effect causes the bending line to longitudinally elongate, and the metal at the bend is thickened. This is the compression/thickening effect of the empty bend.
1) The advantage of the empty bend is that the side length can be bent when the solid bend cannot be performed, for example, the upper side/side side of the square tube is synchronously bent and finished. The hollow bend can also bend the internal angle of R < 0.2t without causing the tube wall to break.
2) The disadvantage of the empty bend is that when the upper side/side side is synchronized, the forming force easily exceeds the critical point due to the simultaneous pressure of the upper roll and the lower roll, causing the edge to be unstable and concave, and also affecting the stable operation of the unit, and molding quality. This is also a different feature of the rectangular.
1. solid bending
It means that the bending is compacted, and the inner and outer rollers and the inner and outer walls of the tube blank are biaxially compacted during the solid bending.
1) The advantage of solid bending is that the rebound is small, the forming is accurate, and as long as the roll type is accurate, the R formed at the inner corner is more accurate.
2) The disadvantage of solid bending is the stretching/thinning effect. First, the solid bend causes the bend to be stretched, and the stretch effect shortens the longitudinal length of the bend line. Second, the metal at the bend bend becomes thinner due to stretching.
2. hollow bending
The hollow bend is formed by the unidirectional contact between the outer roller and the outer wall of the tube blank to form a bending moment to bend the strip. The hollow bend causes the bending line to compress, and the compression effect causes the bending line to longitudinally elongate, and the metal at the bend is thickened. This is the compression/thickening effect of the empty bend.
1) The advantage of the empty bend is that the side length can be bent when the solid bend cannot be performed, for example, the upper side/side side of the square tube is synchronously bent and finished. The hollow bend can also bend the internal angle of R < 0.2t without causing the tube wall to break.
2) The disadvantage of the empty bend is that when the upper side/side side is synchronized, the forming force easily exceeds the critical point due to the simultaneous pressure of the upper roll and the lower roll, causing the edge to be unstable and concave, and also affecting the stable operation of the unit, and molding quality. This is also a different feature of the rectangular.
Magnetism of carbon steel tube
Residual magnetism causes and impact on quality of welding
When the gas pipeline construction and repair welding operations, sometimes magnetic blow phenomena affect the welding process. Forming a magnetic blow is the result of the presence of residual magnetism in the pipe metal. Typically, the magnetic induction and magnetic remanence divided into two processes. Magnetic induction in plants often produce tube links, such as: metal smelting, using electromagnetic crane for loading and unloading, pipe parked or garaged in a strong magnetic field, the magnetization is completed nondestructive inspection method, the pipe is placed close to power lines and so strong. Processes often produce magnetic welding operations during the assembly and the use of a magnetic holder, fixture and took DC welding pipes, such as: prolonged contact is connected to a DC power supply electric wire, bare wire segment or short-circuit pipe welding clamp and so on.
When welding with magnetic steel, often difficult to see the arc ignition, combustion undermine the stability of the arc, the arc of the deviation, the liquid metal and slag melt the spill from the weld pool in a magnetic field. In order to stabilize the welding process and improve the quality of the welded joint, the steel is magnetized to demagnetized before welding. It should be noted, to be welded steel pipe is difficult to achieve full demagnetization. Therefore, when the remanence is insufficient to affect the quality of welding, it allows welding.
Magnetic elimination of carbon steel pipe process
1 to determine the size and direction of the pipe left field;
2 Select the degaussing method, system diagrams and technical means;
3 butt welded steel pipe or at the degaussing degaussing with the selected method;
4 After checking the amount of residual magnetism after degaussing, to see if it meets the requirements.
When the gas pipeline construction and repair welding operations, sometimes magnetic blow phenomena affect the welding process. Forming a magnetic blow is the result of the presence of residual magnetism in the pipe metal. Typically, the magnetic induction and magnetic remanence divided into two processes. Magnetic induction in plants often produce tube links, such as: metal smelting, using electromagnetic crane for loading and unloading, pipe parked or garaged in a strong magnetic field, the magnetization is completed nondestructive inspection method, the pipe is placed close to power lines and so strong. Processes often produce magnetic welding operations during the assembly and the use of a magnetic holder, fixture and took DC welding pipes, such as: prolonged contact is connected to a DC power supply electric wire, bare wire segment or short-circuit pipe welding clamp and so on.
When welding with magnetic steel, often difficult to see the arc ignition, combustion undermine the stability of the arc, the arc of the deviation, the liquid metal and slag melt the spill from the weld pool in a magnetic field. In order to stabilize the welding process and improve the quality of the welded joint, the steel is magnetized to demagnetized before welding. It should be noted, to be welded steel pipe is difficult to achieve full demagnetization. Therefore, when the remanence is insufficient to affect the quality of welding, it allows welding.
Magnetic elimination of carbon steel pipe process
1 to determine the size and direction of the pipe left field;
2 Select the degaussing method, system diagrams and technical means;
3 butt welded steel pipe or at the degaussing degaussing with the selected method;
4 After checking the amount of residual magnetism after degaussing, to see if it meets the requirements.
High quality stainless steel pipe
All the fluids in the world reach their destination thanks to the creation of pipe systems, which must be adapted to the characteristics of the fluid in question such as corrosion. Stainless steel tubes are currently the best option, due to their great resistance to different fluids, which implies greater durability, less money and time.
Without a doubt, iron is one of the most economical metals in the world, but it oxidizes easily in the presence of the simplest elements: water and air. Currently, alloys between metal, copper, chromium and even nickel have been created, to name a few examples, which are more resistant, lasting longer in not corroding under fluid or climatic conditions.
Stainless steel is an alloy with chromium, which does not deteriorate to a greater extent with the presence of oxygen. This material in everything related to pipe networks is very useful because it is not easily damaged, since it has an affinity with oxygen, causing fewer replacements, even if required for a long time.
Pipe systems are seen both at home and in large industries. They are primarily responsible for the distribution of both liquid and gaseous fluids: water, solvents, air, natural gas and many others. The magnitude of the flow and its pressure help to define the characteristics that said tubes must have in order to function efficiently and effectively.
It should be noted that in addition to the tubes themselves, which although it is true that they are essential, a series of accessories such as valves and Schedule are also needed, being responsible for regulating the flow, preventing leaks and having a pipe system ideal.
Currently, everything related to pipe is made with stainless steel and in particular cases even special alloys are used.
Without a doubt, iron is one of the most economical metals in the world, but it oxidizes easily in the presence of the simplest elements: water and air. Currently, alloys between metal, copper, chromium and even nickel have been created, to name a few examples, which are more resistant, lasting longer in not corroding under fluid or climatic conditions.
Stainless steel is an alloy with chromium, which does not deteriorate to a greater extent with the presence of oxygen. This material in everything related to pipe networks is very useful because it is not easily damaged, since it has an affinity with oxygen, causing fewer replacements, even if required for a long time.
Pipe systems are seen both at home and in large industries. They are primarily responsible for the distribution of both liquid and gaseous fluids: water, solvents, air, natural gas and many others. The magnitude of the flow and its pressure help to define the characteristics that said tubes must have in order to function efficiently and effectively.
It should be noted that in addition to the tubes themselves, which although it is true that they are essential, a series of accessories such as valves and Schedule are also needed, being responsible for regulating the flow, preventing leaks and having a pipe system ideal.
Currently, everything related to pipe is made with stainless steel and in particular cases even special alloys are used.
Application of Boiler Tubes
The boiler tube is a type of seamless tube. The manufacturing method is the same as that of the seamless pipe, but there are strict requirements for the steel used in the manufacture of the steel pipe. According to the use of high and low temperature is divided into two types of general boiler tubes and high pressure boiler tubes.
The mechanical properties of the boiler tube are important indicators to ensure the final performance of the steel (mechanical properties), which depends on the chemical composition of the steel and the heat treatment system. In the steel pipe standard, according to different use requirements, tensile properties (tensile strength, yield strength or yield point, elongation), hardness and toughness index, as well as high and low temperature properties required by users are specified.
1. The general boiler tube use temperature is below 450 °C, and the domestic tube is mainly made of 10 or 20 carbon steel hot rolled tube or cold drawn tube.
2. High-pressure boiler tubes are often subjected to high temperature and high pressure conditions, and the tubes will oxidize and corrode under the action of high temperature flue gas and water vapor. Steel pipes are required to have high durability, high corrosion resistance and good structural stability.
Use of boiler tubes
1. General boiler tubes are mainly used to manufacture water-cooled wall pipes, boiling water pipes, superheated steam pipes, superheated steam pipes for locomotive boilers, large and small smoke pipes and arch brick pipes.
2. High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, air ducts, main steam tubes, etc. for high-pressure and ultra-high pressure boilers. The supply and demand trend of the high-pressure boiler tube industry is generally stable, but the supply and demand situation of each specific sub-sector will be further differentiated. Insiders pointed out that the most critical link is the use and promotion of new energy-saving insulation 20g high-pressure boiler tube equipment.
New energy-saving 20g high-pressure boiler tube products are gradually increasing in the market, for example, green environmental protection coatings, energy-saving and water-saving sanitary ware products, environmentally-friendly stone materials, environmentally-friendly external cement foam insulation boards, etc., energy-saving and environmental protection products in the vast market of 20g high-pressure boiler tube industry The prospects are optimistic.
http://www.xysteelpipe.com/info/Application-of-Boiler-Tubes-1490-1.htm
The mechanical properties of the boiler tube are important indicators to ensure the final performance of the steel (mechanical properties), which depends on the chemical composition of the steel and the heat treatment system. In the steel pipe standard, according to different use requirements, tensile properties (tensile strength, yield strength or yield point, elongation), hardness and toughness index, as well as high and low temperature properties required by users are specified.
1. The general boiler tube use temperature is below 450 °C, and the domestic tube is mainly made of 10 or 20 carbon steel hot rolled tube or cold drawn tube.
2. High-pressure boiler tubes are often subjected to high temperature and high pressure conditions, and the tubes will oxidize and corrode under the action of high temperature flue gas and water vapor. Steel pipes are required to have high durability, high corrosion resistance and good structural stability.
Use of boiler tubes
1. General boiler tubes are mainly used to manufacture water-cooled wall pipes, boiling water pipes, superheated steam pipes, superheated steam pipes for locomotive boilers, large and small smoke pipes and arch brick pipes.
2. High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, air ducts, main steam tubes, etc. for high-pressure and ultra-high pressure boilers. The supply and demand trend of the high-pressure boiler tube industry is generally stable, but the supply and demand situation of each specific sub-sector will be further differentiated. Insiders pointed out that the most critical link is the use and promotion of new energy-saving insulation 20g high-pressure boiler tube equipment.
New energy-saving 20g high-pressure boiler tube products are gradually increasing in the market, for example, green environmental protection coatings, energy-saving and water-saving sanitary ware products, environmentally-friendly stone materials, environmentally-friendly external cement foam insulation boards, etc., energy-saving and environmental protection products in the vast market of 20g high-pressure boiler tube industry The prospects are optimistic.
http://www.xysteelpipe.com/info/Application-of-Boiler-Tubes-1490-1.htm
2019年8月15日星期四
High frequency resistance welded steel pipe set
High frequecy resistance welded pipe mill usually consists of flow forming, high frequency welding, extrusion, cooling, sizing, flying saw cutting units, the front end unit with accumulator looper, the rear end of unit with a steel fram plipping, electrical prat of the main high frequency generator, DC generator exictation and instrument control devices and other components. Taking our OD 165mm frequency welded pipe units as an example, the main technical parameters are as follows:
3.1 Finished Pipe:
Tube outer diameter: φ111 ~ 165mm
Square tube: 50 × 50 ~ 125 × 125mm
Rectangular tube: 90 × 50 ~ 160 × 60 ~ 180 × 80mm
Finished wall thickness: 2 ~ 6mm
3.2 Forming speed: 20 to 70 m / min
3.3 High Frequency Sensor:
Thermal power: 600KW
Output frequency: 200 ~ 250KHz
Power supply: Three-phase 380V 50Hz
Cooling: Water-cooled
3.1 Finished Pipe:
Tube outer diameter: φ111 ~ 165mm
Square tube: 50 × 50 ~ 125 × 125mm
Rectangular tube: 90 × 50 ~ 160 × 60 ~ 180 × 80mm
Finished wall thickness: 2 ~ 6mm
3.2 Forming speed: 20 to 70 m / min
3.3 High Frequency Sensor:
Thermal power: 600KW
Output frequency: 200 ~ 250KHz
Power supply: Three-phase 380V 50Hz
Cooling: Water-cooled
Welding process of ERW steel pipe
Welding technology controls the production and quality of ERW steel pipe. Below are the technical control methods we applied to ensure the high quality and efficiency of ERW steel pipe production.
1. Weld Gap Control
2. Welding Temperature Control
3. Pressing Force Control
4. Frequency Induction Loop Position Control
5. Impedance Check and Replacement
6. Burr Remove
Now, we apply our OD 32mm & WT 2mm welding process as an example, the parameters are as below:
Strip Size: 2 × 98mm in diameter to expand the bandwidth by adding a small amount of profiling allowance
Steel Material: Q235A
Input field voltage: 150V excitation current: 1.5A Frequency: 50Hz
DC output voltage: 11.5kV DC Current: 4A Frequency: 120000Hz
Welding speed: 50 m / min
Parameter adjustment: the timely adjustment of output voltage and welding speed according to the welding line energy change. After the fixed parameters generally do not adjust.
1. Weld Gap Control
2. Welding Temperature Control
3. Pressing Force Control
4. Frequency Induction Loop Position Control
5. Impedance Check and Replacement
6. Burr Remove
Now, we apply our OD 32mm & WT 2mm welding process as an example, the parameters are as below:
Strip Size: 2 × 98mm in diameter to expand the bandwidth by adding a small amount of profiling allowance
Steel Material: Q235A
Input field voltage: 150V excitation current: 1.5A Frequency: 50Hz
DC output voltage: 11.5kV DC Current: 4A Frequency: 120000Hz
Welding speed: 50 m / min
Parameter adjustment: the timely adjustment of output voltage and welding speed according to the welding line energy change. After the fixed parameters generally do not adjust.
Technical Requirement for Welded Steel Pipe
According to the API/ASTM stadnards, there are many technical requirements for producing welded steel pipe.
The nominal pipe diammeter ranges from 6-150mm, nominal wall thickness ranges from 2.0-6.0mm and the length of the pipe is usually from 4 to 10. The pipe surface shoule be smooth, no collapse, no cracks, no delamination, and no lap welding defects exist. The wall thickness is not allowed to over the deviation, no scratches, no weld dislocation, no burns and scarring and other minor defects.
Welded steel pipe should perform mechanical test, flattening test and flaring test to achieve the standard requirements. 2.5 Mpa internal pressure test is allowed to keep over 1 minue without leakage. It allows use eddy current testing method instead of the hydrostatic test. After the eddy current testing, welded steel pipe will be cut to a predetermined length by flying saw and then flip-off from the assembly line. Then both ends of the pipe should be flat head chamfering, painting, marking and hexagonal packing before delivery.
The nominal pipe diammeter ranges from 6-150mm, nominal wall thickness ranges from 2.0-6.0mm and the length of the pipe is usually from 4 to 10. The pipe surface shoule be smooth, no collapse, no cracks, no delamination, and no lap welding defects exist. The wall thickness is not allowed to over the deviation, no scratches, no weld dislocation, no burns and scarring and other minor defects.
Welded steel pipe should perform mechanical test, flattening test and flaring test to achieve the standard requirements. 2.5 Mpa internal pressure test is allowed to keep over 1 minue without leakage. It allows use eddy current testing method instead of the hydrostatic test. After the eddy current testing, welded steel pipe will be cut to a predetermined length by flying saw and then flip-off from the assembly line. Then both ends of the pipe should be flat head chamfering, painting, marking and hexagonal packing before delivery.
Chromium determines the corrosion resistance of 304 stainless steel tubes
The so-called corrosion resistance is actually anti-oxidation. As long as it is a steel product, it will react with oxygen in the atmosphere. Once it happens, it will expand continuously, and finally it will not be able to use the entire product, but we can avoid it by processing. In the case of the occurrence of the general situation, the corrosion resistance of the 304 stainless steel pipe is mainly coated with anti-oxidation metals such as zinc, nickel and chromium to form an anti-oxidation protective film on the surface.
Among the anti-oxidation metals, chromium is able to determine the corrosion resistance of the final 304 stainless steel tube. Generally, when the amount of chromium is increased to 10% or more, the corrosion resistance and oxidation resistance of the steel will be greatly increased. And thanks to the use of chrome, the 304 stainless steel tube emits natural light, making the entire surface look more beautiful and generous. However, if this layer of anti-oxidation protective film is damaged, the 304 stainless steel tube will still rust.
Among the anti-oxidation metals, chromium is able to determine the corrosion resistance of the final 304 stainless steel tube. Generally, when the amount of chromium is increased to 10% or more, the corrosion resistance and oxidation resistance of the steel will be greatly increased. And thanks to the use of chrome, the 304 stainless steel tube emits natural light, making the entire surface look more beautiful and generous. However, if this layer of anti-oxidation protective film is damaged, the 304 stainless steel tube will still rust.
Concrete analysis of the production process steps of spiral tubes
Spiral tube production process steps
(1) The spiral pipe raw material is a ribbon coil, a welding wire, and a flux. Strict physical and chemical testing is required prior to input.
(2) The steel head and the tail are butt jointed, and single or double-line submerged arc welding is adopted. After the steel pipe is rolled, automatic submerged arc welding is adopted.
(3) Before the forming, the strip is smoothed, trimmed, planed, surface cleaned and pre-bent.
(4) The electric contact pressure gauge is used to control the cylinder pressure on both sides of the conveyor to ensure the smooth conveying of the conveyor belt.
(5) The spiral tube is formed by external control or internal control roll forming.
(6) Weld control device is used to ensure that the weld meets the welding requirements, strictly control the pipe diameter, the misalignment and the weld gap.
(7) Both internal and external welding are performed by single or double wire submerged arc welding of American Lincoln welding machines to obtain stable welding specifications.
(8) The welds are all online continuous ultrasonic automatic injury detection to ensure non-destructive testing of 100% spiral welds. If there is a defect, the alarm will automatically alarm and spray, and the production worker can adjust the process parameters at any time to eliminate the defects.
(9) The spiral tube is cut into a single piece by an air plasma cutting machine.
(10) After cutting into a single steel pipe, each batch of steel pipes shall undergo a strict inspection system to check the mechanical properties, chemical composition, fusion state, surface quality and non-destructive testing of the steel pipe to ensure the pipe making process. After that, it can be officially put into production.
(11) The weld part with the continuous acoustic flaw detection mark, after manual ultrasonic and X-ray inspection, if it is defective, it will pass the non-destructive test again after the repair, until the defect is confirmed.
(12) The butt weld pipe of the strip and the butt joint that intersects the spiral weld are inspected by X-ray television or film.
(13) A hydrostatic test was performed on each of the spiral tubes, and the pressure was radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. Automatically print and record test parameters. The tube ends are machined to precisely control the end face perpendicularity, groove angle and blunt edge.
http://www.xysteelpipe.com/info/Concrete-analysis-of-the-production-process-steps-of-spiral-tubes-1482-1.htm
(1) The spiral pipe raw material is a ribbon coil, a welding wire, and a flux. Strict physical and chemical testing is required prior to input.
(2) The steel head and the tail are butt jointed, and single or double-line submerged arc welding is adopted. After the steel pipe is rolled, automatic submerged arc welding is adopted.
(3) Before the forming, the strip is smoothed, trimmed, planed, surface cleaned and pre-bent.
(4) The electric contact pressure gauge is used to control the cylinder pressure on both sides of the conveyor to ensure the smooth conveying of the conveyor belt.
(5) The spiral tube is formed by external control or internal control roll forming.
(6) Weld control device is used to ensure that the weld meets the welding requirements, strictly control the pipe diameter, the misalignment and the weld gap.
(7) Both internal and external welding are performed by single or double wire submerged arc welding of American Lincoln welding machines to obtain stable welding specifications.
(8) The welds are all online continuous ultrasonic automatic injury detection to ensure non-destructive testing of 100% spiral welds. If there is a defect, the alarm will automatically alarm and spray, and the production worker can adjust the process parameters at any time to eliminate the defects.
(9) The spiral tube is cut into a single piece by an air plasma cutting machine.
(10) After cutting into a single steel pipe, each batch of steel pipes shall undergo a strict inspection system to check the mechanical properties, chemical composition, fusion state, surface quality and non-destructive testing of the steel pipe to ensure the pipe making process. After that, it can be officially put into production.
(11) The weld part with the continuous acoustic flaw detection mark, after manual ultrasonic and X-ray inspection, if it is defective, it will pass the non-destructive test again after the repair, until the defect is confirmed.
(12) The butt weld pipe of the strip and the butt joint that intersects the spiral weld are inspected by X-ray television or film.
(13) A hydrostatic test was performed on each of the spiral tubes, and the pressure was radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. Automatically print and record test parameters. The tube ends are machined to precisely control the end face perpendicularity, groove angle and blunt edge.
http://www.xysteelpipe.com/info/Concrete-analysis-of-the-production-process-steps-of-spiral-tubes-1482-1.htm
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