Social progress leads the development in various engineering projects. No matter the house building, boat industry or airplane construction, lots of bosses shall adopt convenient equipment for work. And thus, scaffolding products from frame scaffolding to a scaffolding base jack, should be taken safety into account.
There is safety instruction for it, and each of us need to keep in mind for safety.
First of all, before the erection of multi-pole scaffold, we should set the construction plan and the construction form shall be determined according to the plane form, size, and height and construction technology of the building.
Second, same kind of raw material for the scaffolding is necessary. Steel scaffold joints should be fastened with fasteners, not with lead wire binding.
What’s more, the pole of steel tube scaffold shall be placed vertically on the metal base, and then we should set a thick board placed below according to our installation requirement.
In addition, the adjacent joints of the vertical bar should stagger. A small bar must be set at the node of the pole. The bar at the node cannot be removed before the scaffold is removed.
Safety would be on the top list when we use scaffolding for engineering projects. Thus, be prepared for each detail is necessary.
2019年12月26日星期四
Analysis of seamless steel tube cutting problems
What should be paid attention to after the seamless steel tube is cut? What should be paid attention to during the heat treatment? The following seamless steel tube manufacturers will introduce you in detail:
1. Attention to cutting of seamless steel tube
After the seamless steel pipe is straightened, the initial inspection of soot blowing is performed to determine the length of the cut head and tail. The purpose of seamless steel tube cutting is to remove the ends with cracks, knots, scars, tears and uneven wall thickness to obtain the required fixed-size seamless steel tube. In addition, the defects that are unqualified and difficult to salvage after inspection are removed, as shown in the figure. Breaks, internal scarring, severe uneven wall thickness, etc. Generally the former is cut off on the working line, while the latter is cut off-line.
2. Control of heat preservation time during seamless steel tube heat treatment
The heat preservation time of the seamless steel tube during heat treatment should ensure that the steel pipe in the furnace can be completely burned through, make its temperature uniform, and complete the due structural transformation, so as to obtain uniform structure and performance. Generally increasing the heating temperature can shorten the holding time appropriately. When performing low temperature annealing (including softening, stress relief and recrystallization annealing),the closer the annealing temperature is to the lower critical point A1, the faster the recovery of the seamless steel pipe and the more complete the effect of eliminating work hardening, so the holding time can also be appropriately shortened.
http://www.xysteelpipe.com/info/Analysis-of-seamless-steel-tube-cutting-problems-1585-1.htm
1. Attention to cutting of seamless steel tube
After the seamless steel pipe is straightened, the initial inspection of soot blowing is performed to determine the length of the cut head and tail. The purpose of seamless steel tube cutting is to remove the ends with cracks, knots, scars, tears and uneven wall thickness to obtain the required fixed-size seamless steel tube. In addition, the defects that are unqualified and difficult to salvage after inspection are removed, as shown in the figure. Breaks, internal scarring, severe uneven wall thickness, etc. Generally the former is cut off on the working line, while the latter is cut off-line.
2. Control of heat preservation time during seamless steel tube heat treatment
The heat preservation time of the seamless steel tube during heat treatment should ensure that the steel pipe in the furnace can be completely burned through, make its temperature uniform, and complete the due structural transformation, so as to obtain uniform structure and performance. Generally increasing the heating temperature can shorten the holding time appropriately. When performing low temperature annealing (including softening, stress relief and recrystallization annealing),the closer the annealing temperature is to the lower critical point A1, the faster the recovery of the seamless steel pipe and the more complete the effect of eliminating work hardening, so the holding time can also be appropriately shortened.
http://www.xysteelpipe.com/info/Analysis-of-seamless-steel-tube-cutting-problems-1585-1.htm
2019年12月25日星期三
Three properties of 20cr seamless steel tube
(I) Chemical stability of 20cr seamless steel pipe
Refers to the general term for the corrosion resistance and oxidation resistance of 20cr seamless steel pipe materials. The chemical stability of the material at high temperatures is called thermal stability.
(II) the oxidation resistance of 20cr seamless steel pipe
The ability of 20cr seamless steel pipe to resist oxidation at room temperature or high temperature, the oxidation process is actually a form of chemical corrosion. It can directly use the amount of heavy loss after the surface of the pipe is corroded within a certain period of time, which is expressed by the speed of metal weight loss.
(III) the corrosion resistance of 20cr seamless steel pipe
The ability of a material to resist the corrosive effects of surrounding media. The corrosion resistance of metals is related to many factors, such as the chemical composition of metals, processing properties, heat treatment conditions, microstructure, and media and temperature. Chemical corrosion is the result of direct chemical interaction between metals and surrounding media. It includes two forms of gas corrosion and metal corrosion in non-electrolyte. Its characteristics are: no current is generated during the corrosion process; and corrosion products are deposited on the surface of the 20cr seamless steel pipe. To understand the corrosion resistance of 20cr seamless steel pipes, we should first grasp the following points:
(1) General corrosion: This kind of corrosion is evenly distributed on the entire inner and outer surfaces, which continuously reduces the cross-section, and finally causes the force parts to be destroyed.
(2) Pitting corrosion: The corrosion is concentrated in a small area of the surface of the 20Cr seamless steel pipe, and it develops rapidly to the deep, and finally penetrates the metal, which is a relatively harmful corrosion damage.
(3) Corrosion fatigue: refers to the damage caused by the material in the corrosive medium under the action of alternating stress.
(4) Corrosion rate: The depth of material that a metal material corrodes in a unit time is called the corrosion rate.
(5) Electrochemical corrosion: The corrosion caused by the action of 20cr seamless steel pipe when it comes into contact with electrolyte solutions such as acid, alkali and salt is called electrochemical corrosion. Its characteristic is that current is generated during the corrosion process, and its corrosion products (rust) are not covered on the metal surface as the anode, but at a certain distance from the anode metal.
(6) Intergranular corrosion: Corrosion takes place inside the metal along the edges of the grains, usually does not cause any change in the shape of the metal, and often causes sudden damage to equipment or machinery.
(7) Stress corrosion: refers to the damage caused by metals in corrosive media under the effect of static stress. The damage caused by this corrosive medium is also a type of transgranular corrosion.
(8) Corrosion rate: The weight loss of 20cr seamless steel pipe material per unit area after corrosion in a unit time is called the corrosion rate.
Refers to the general term for the corrosion resistance and oxidation resistance of 20cr seamless steel pipe materials. The chemical stability of the material at high temperatures is called thermal stability.
(II) the oxidation resistance of 20cr seamless steel pipe
The ability of 20cr seamless steel pipe to resist oxidation at room temperature or high temperature, the oxidation process is actually a form of chemical corrosion. It can directly use the amount of heavy loss after the surface of the pipe is corroded within a certain period of time, which is expressed by the speed of metal weight loss.
(III) the corrosion resistance of 20cr seamless steel pipe
The ability of a material to resist the corrosive effects of surrounding media. The corrosion resistance of metals is related to many factors, such as the chemical composition of metals, processing properties, heat treatment conditions, microstructure, and media and temperature. Chemical corrosion is the result of direct chemical interaction between metals and surrounding media. It includes two forms of gas corrosion and metal corrosion in non-electrolyte. Its characteristics are: no current is generated during the corrosion process; and corrosion products are deposited on the surface of the 20cr seamless steel pipe. To understand the corrosion resistance of 20cr seamless steel pipes, we should first grasp the following points:
(1) General corrosion: This kind of corrosion is evenly distributed on the entire inner and outer surfaces, which continuously reduces the cross-section, and finally causes the force parts to be destroyed.
(2) Pitting corrosion: The corrosion is concentrated in a small area of the surface of the 20Cr seamless steel pipe, and it develops rapidly to the deep, and finally penetrates the metal, which is a relatively harmful corrosion damage.
(3) Corrosion fatigue: refers to the damage caused by the material in the corrosive medium under the action of alternating stress.
(4) Corrosion rate: The depth of material that a metal material corrodes in a unit time is called the corrosion rate.
(5) Electrochemical corrosion: The corrosion caused by the action of 20cr seamless steel pipe when it comes into contact with electrolyte solutions such as acid, alkali and salt is called electrochemical corrosion. Its characteristic is that current is generated during the corrosion process, and its corrosion products (rust) are not covered on the metal surface as the anode, but at a certain distance from the anode metal.
(6) Intergranular corrosion: Corrosion takes place inside the metal along the edges of the grains, usually does not cause any change in the shape of the metal, and often causes sudden damage to equipment or machinery.
(7) Stress corrosion: refers to the damage caused by metals in corrosive media under the effect of static stress. The damage caused by this corrosive medium is also a type of transgranular corrosion.
(8) Corrosion rate: The weight loss of 20cr seamless steel pipe material per unit area after corrosion in a unit time is called the corrosion rate.
How to prevent rust of seamless steel tube
Choosing the right warehouse for seamless steel pipes
(1) The warehouses where seamless steel pipes are kept should be selected in a clean and well-drained place away from factories and mines that produce harmful gases or dust. Remove weeds and all debris on the site and keep steel pipes clean.
(2) Do not stack in the warehouse with materials that are corrosive to steel pipes such as acids, alkalis, salts, and cement. Different types of steel pipes should be stacked separately to prevent confusion and prevent contact corrosion.
(3) Some small steel pipes, thin steel plates, steel strips, silicon steel sheets, small-caliber or thin-walled steel pipes, various cold-rolled, cold-drawn steel pipes, and high-priced and easily corroded metal products can be stored in the warehouse.
(4) Treasury should be selected according to geographical conditions. Generally, general closed warehouses are used, that is, warehouses with roofs and walls, tight doors and windows, and ventilation facilities.
(5) Treasury requires ventilation in sunny days, and close moisture-proof in rainy days, and often maintain a suitable storage environment.
Common methods to prevent rusting of seamless steel pipes are:
(1) Composition alloy to change the internal structure of iron. For example, chromium, nickel and other metals are added to ordinary steel to make stainless steel, which greatly increases the rust resistance of steel products.
(2) Covering the surface of iron products is a common and important method to prevent iron products from rusting. According to the composition of the protective layer, it can be divided into the following types:
a. Apply mineral oil, paint or fired enamel, spray plastic on the surface of iron products. For example: cars and buckets are often painted with paint; machines are often coated with mineral oil.
b. On the surface of steel, use a method such as zinc, tin, chromium, nickel, etc. These metal surfaces can form a dense oxide film to prevent iron products from contacting water and air and rust.
c. A dense and stable oxide film is formed on the surface of iron products by chemical methods to prevent iron products from rusting.
(3) Keeping the surface of iron products clean and dry is also a good way to prevent iron products from rusting.
(1) The warehouses where seamless steel pipes are kept should be selected in a clean and well-drained place away from factories and mines that produce harmful gases or dust. Remove weeds and all debris on the site and keep steel pipes clean.
(2) Do not stack in the warehouse with materials that are corrosive to steel pipes such as acids, alkalis, salts, and cement. Different types of steel pipes should be stacked separately to prevent confusion and prevent contact corrosion.
(3) Some small steel pipes, thin steel plates, steel strips, silicon steel sheets, small-caliber or thin-walled steel pipes, various cold-rolled, cold-drawn steel pipes, and high-priced and easily corroded metal products can be stored in the warehouse.
(4) Treasury should be selected according to geographical conditions. Generally, general closed warehouses are used, that is, warehouses with roofs and walls, tight doors and windows, and ventilation facilities.
(5) Treasury requires ventilation in sunny days, and close moisture-proof in rainy days, and often maintain a suitable storage environment.
Common methods to prevent rusting of seamless steel pipes are:
(1) Composition alloy to change the internal structure of iron. For example, chromium, nickel and other metals are added to ordinary steel to make stainless steel, which greatly increases the rust resistance of steel products.
(2) Covering the surface of iron products is a common and important method to prevent iron products from rusting. According to the composition of the protective layer, it can be divided into the following types:
a. Apply mineral oil, paint or fired enamel, spray plastic on the surface of iron products. For example: cars and buckets are often painted with paint; machines are often coated with mineral oil.
b. On the surface of steel, use a method such as zinc, tin, chromium, nickel, etc. These metal surfaces can form a dense oxide film to prevent iron products from contacting water and air and rust.
c. A dense and stable oxide film is formed on the surface of iron products by chemical methods to prevent iron products from rusting.
(3) Keeping the surface of iron products clean and dry is also a good way to prevent iron products from rusting.
Method for avoiding wear of spiral steel pipe
1. Spiral steel tube packaging should prevent slackness and damage during normal loading, unloading, transportation and storage.
2. It is assumed that the purchaser has special requirements for the packaging materials and packaging methods of spiral steel pipes, which shall be specified in the contract; if not specified, the packaging materials and packaging methods shall be selected by the supplier.
3. Packaging information should conform to relevant rules. It is assumed that no packaging information is required, and it should be suitable for the intended use to prevent waste and environmental pollution.
4. Assume that the customer requires that the spiral steel pipe should not have damage such as bumps on the appearance, and can consider selecting maintenance equipment between spiral steel pipes. Maintenance equipment can use rubber, straw rope, fiber cloth, plastic, pipe caps, etc.
5, thin-wall spiral steel pipe because of the thick wall and thin can choose the method of pipe internal support or pipe maintenance. The material of the bracket and the outer frame is selected from the steel material with the spiral steel pipe material.
6, the national rules spiral steel pipe in bulk. It is assumed that customers can consider bundling as appropriate, but the caliber must be between 159MM and 500MM. The bundled materials are packed and fastened with steel belts, and each lane should be twisted into at least two strands, and added appropriately according to the outer diameter and weight of the spiral steel pipe to prevent the occurrence of looseness.
7. Fixed-length spiral steel pipes cannot be bundled.
8. If both ends of the spiral steel pipe are provided with threaded buckles, they shall be protected by thread maintainers. Apply lubricating oil or rust preventive to the threads. Spiral steel pipe is broken at both ends, and a mouthpiece protector can be added at both ends according to requirements.
9. It is assumed that when the spiral steel pipe is put into a container, the container is lined with soft, moisture-proof equipment such as textile cloth and straw mat. In order to spin the spiral steel pipe in the container, a protective support can be welded on the bundle or the outside of the spiral steel pipe.
http://www.xysteelpipe.com/info/Method-for-avoiding-wear-of-spiral-steel-pipe-1584-1.htm
2. It is assumed that the purchaser has special requirements for the packaging materials and packaging methods of spiral steel pipes, which shall be specified in the contract; if not specified, the packaging materials and packaging methods shall be selected by the supplier.
3. Packaging information should conform to relevant rules. It is assumed that no packaging information is required, and it should be suitable for the intended use to prevent waste and environmental pollution.
4. Assume that the customer requires that the spiral steel pipe should not have damage such as bumps on the appearance, and can consider selecting maintenance equipment between spiral steel pipes. Maintenance equipment can use rubber, straw rope, fiber cloth, plastic, pipe caps, etc.
5, thin-wall spiral steel pipe because of the thick wall and thin can choose the method of pipe internal support or pipe maintenance. The material of the bracket and the outer frame is selected from the steel material with the spiral steel pipe material.
6, the national rules spiral steel pipe in bulk. It is assumed that customers can consider bundling as appropriate, but the caliber must be between 159MM and 500MM. The bundled materials are packed and fastened with steel belts, and each lane should be twisted into at least two strands, and added appropriately according to the outer diameter and weight of the spiral steel pipe to prevent the occurrence of looseness.
7. Fixed-length spiral steel pipes cannot be bundled.
8. If both ends of the spiral steel pipe are provided with threaded buckles, they shall be protected by thread maintainers. Apply lubricating oil or rust preventive to the threads. Spiral steel pipe is broken at both ends, and a mouthpiece protector can be added at both ends according to requirements.
9. It is assumed that when the spiral steel pipe is put into a container, the container is lined with soft, moisture-proof equipment such as textile cloth and straw mat. In order to spin the spiral steel pipe in the container, a protective support can be welded on the bundle or the outside of the spiral steel pipe.
http://www.xysteelpipe.com/info/Method-for-avoiding-wear-of-spiral-steel-pipe-1584-1.htm
2019年12月15日星期日
Carbon Steel Alloy-ASTM A53
ASTM A53 is a carbon steel alloy,used as structural steel or for low-pressure plumbing.The alloy specifications are set by ASTM international,in specifications ASTM A53/A53M.
A53 pipe comes in three types and two grades,A53 Type F,which is longitudinally furnace butt welded or continuous welded(Grade A only),A53 Type E，which is longitudinally electric resistance welded(Grades A and B)，and A53 Type S,which is seamless pipe,produced by hot working,and possibly cold finishing,the steel(Grade A and B).ASTM A53 pipe is sized according to the nominal pipe size(NPS)system.It is commonly available with national pipe thread ends or with plain cut ends.It can be used for steam,water,and air conveyance.It is also weldable and can be used in structural application,although ASTM A500 tube,which is available in the same NPS
Sizes,is sometime preferred.
This is a standard set by the standards organization ASTM international,a voluntary standards development organizations that sets technical standards for materials,products,systems,and service.
A53 pipe comes in three types and two grades,A53 Type F,which is longitudinally furnace butt welded or continuous welded(Grade A only),A53 Type E，which is longitudinally electric resistance welded(Grades A and B)，and A53 Type S,which is seamless pipe,produced by hot working,and possibly cold finishing,the steel(Grade A and B).ASTM A53 pipe is sized according to the nominal pipe size(NPS)system.It is commonly available with national pipe thread ends or with plain cut ends.It can be used for steam,water,and air conveyance.It is also weldable and can be used in structural application,although ASTM A500 tube,which is available in the same NPS
Sizes,is sometime preferred.
This is a standard set by the standards organization ASTM international,a voluntary standards development organizations that sets technical standards for materials,products,systems,and service.
Why do stainless steel fittings need solution treatment?
Austenitic stainless steel is softened by solution treatment. Generally, the stainless steel pipe is heated to about 950 to 1150 ° C for a period of time, so that carbides and various alloy elements are completely and uniformly dissolved in austenite, and then quenched and cooled quickly. Carbon and other alloying elements are too late to precipitate and a pure austenite structure is obtained, which is called a solution treatment.
Solution treatment has three effects.
1. Due to the different rolling temperature and cooling rate of each section of the hot-rolled wire rod, the structure is inconsistent. Therefore, it is particularly important for the raw materials to make the structure and composition of the stainless steel pipe uniform.
At high temperatures, the atomic activity is enhanced, the polymer phase is dissolved, and the chemical composition tends to be uniform. After cooling, a uniform single-phase structure is obtained.
2. Eliminate work hardening to promote continuous cold work.
After the solution treatment, the deformed crystal lattice is restored, the elongated and fractured grains are recrystallized, the internal stress is eliminated, the tensile strength of the stainless steel pipe is reduced, and the elongation is increased.
3. Repair the inherent corrosion resistance of stainless steel pipe fittings.
Due to carbide precipitation caused by cold working, lattice defects lead to reduced corrosion resistance of stainless steel pipe fittings. After solution treatment, the corrosion resistance of stainless steel pipe fittings is restored to a better state.
The three elements of solution treatment of stainless steel pipe fittings are temperature, holding time and cooling rate. The solution temperature is mainly determined by the chemical composition.
In general, for grades with multiple alloying elements and high contents, the solution temperature should be increased accordingly. In particular, steels with high Mn, Mo, Ni, and Si content can only be softened by increasing the solution temperature and sufficiently dissolving.
However, in stable steels such as 1Cr18Ni9Ti, when the solid solution temperature is high, the carbides of the stabilizing element are sufficiently dissolved in austenite, and then precipitated at the grain boundaries in the form of Cr23C6 during subsequent cooling, causing intergranular corrosion.
In order to prevent decomposition or solid solution of the carbides (TiC and Nbc) of the stabilizing element, a lower limit solid solution temperature is usually used.
As the saying goes, stainless steel pipe is not easy to rust. In fact, part of the stainless steel pipe contains both stainless steel and acid resistance (corrosion resistance). The rust and corrosion resistance of stainless steel pipe fittings is caused by the formation of a chromium-rich oxide film (passivation film) on the surface. Stainless steel tubing and corrosion resistance are relative.
The experimental results show that the corrosion resistance of steel in weak media such as atmosphere and water and the oxidation medium such as nitric acid will increase with the increase of chromium water content in steel, and it is proportional to the corrosion resistance of stainless steel pipe fittings.
When the chromium content reaches a certain percentage, the corrosion resistance of stainless steel pipe fittings changes suddenly, that is, from rust to non-rust, and from corrosion to corrosion resistance.
Solution treatment has three effects.
1. Due to the different rolling temperature and cooling rate of each section of the hot-rolled wire rod, the structure is inconsistent. Therefore, it is particularly important for the raw materials to make the structure and composition of the stainless steel pipe uniform.
At high temperatures, the atomic activity is enhanced, the polymer phase is dissolved, and the chemical composition tends to be uniform. After cooling, a uniform single-phase structure is obtained.
2. Eliminate work hardening to promote continuous cold work.
After the solution treatment, the deformed crystal lattice is restored, the elongated and fractured grains are recrystallized, the internal stress is eliminated, the tensile strength of the stainless steel pipe is reduced, and the elongation is increased.
3. Repair the inherent corrosion resistance of stainless steel pipe fittings.
Due to carbide precipitation caused by cold working, lattice defects lead to reduced corrosion resistance of stainless steel pipe fittings. After solution treatment, the corrosion resistance of stainless steel pipe fittings is restored to a better state.
The three elements of solution treatment of stainless steel pipe fittings are temperature, holding time and cooling rate. The solution temperature is mainly determined by the chemical composition.
In general, for grades with multiple alloying elements and high contents, the solution temperature should be increased accordingly. In particular, steels with high Mn, Mo, Ni, and Si content can only be softened by increasing the solution temperature and sufficiently dissolving.
However, in stable steels such as 1Cr18Ni9Ti, when the solid solution temperature is high, the carbides of the stabilizing element are sufficiently dissolved in austenite, and then precipitated at the grain boundaries in the form of Cr23C6 during subsequent cooling, causing intergranular corrosion.
In order to prevent decomposition or solid solution of the carbides (TiC and Nbc) of the stabilizing element, a lower limit solid solution temperature is usually used.
As the saying goes, stainless steel pipe is not easy to rust. In fact, part of the stainless steel pipe contains both stainless steel and acid resistance (corrosion resistance). The rust and corrosion resistance of stainless steel pipe fittings is caused by the formation of a chromium-rich oxide film (passivation film) on the surface. Stainless steel tubing and corrosion resistance are relative.
The experimental results show that the corrosion resistance of steel in weak media such as atmosphere and water and the oxidation medium such as nitric acid will increase with the increase of chromium water content in steel, and it is proportional to the corrosion resistance of stainless steel pipe fittings.
When the chromium content reaches a certain percentage, the corrosion resistance of stainless steel pipe fittings changes suddenly, that is, from rust to non-rust, and from corrosion to corrosion resistance.
Advantages of natural gas 3pe anticorrosive steel pipe
Natural gas 3pe anti-corrosion steel pipe This three-layer coating system combines the excellent properties of single-layer epoxy and polyethylene coatings. Natural gas 3pe anti-corrosion steel pipe meets the requirements of operating temperature (90 ° C) and improves the resistance of the coating system. Cathode peeling and adhesion strength, three-layer structure polyethylene anticorrosive coating has excellent mechanical protection and adhesion properties.
It can withstand the stress caused by the movement of the soil caused by vibration and temperature changes, and can resist the impact stress of sharp stones on the pipe surface. The resistance of the water supply polyethylene anticorrosive coating in the community is high, which will greatly reduce the installation and maintenance costs of the cathodic protection system. The current density of the cathodic protection of the three-layer structure polyethylene anticorrosive coating pipeline is less than 10 μA * m2.
Epoxy resin powder has high adhesion, peeling properties, chemical barrier properties and oxygen resistance. The polymer coating and the epoxy resin bottom layer have good chemical adhesion, and the natural gas 3PE anticorrosive steel pipe can resist the shear force caused by soil movement and temperature change. High-density poly surface coating has a good barrier effect against moisture, can protect the epoxy resin bottom layer and polymer coating, has strong resistance to mechanical damage, peeling, and low cathodic protection current, and has a wide temperature range (from 5 to 0 8 zero ° C).
The combination of three-layer structure polyethylene anticorrosive coating is characterized by the combination and enhancement of the three coatings. The three-layer coating has strong chemical adhesion. The performance and characteristics of each layer make the three-layer coating complement each other. This three-layer anti-corrosion coating is integrated into a three-in-one form, and makes the overall chemical and mechanical properties reach a good degree. It combines the good adhesion properties of epoxy resin, chemical resistance and mechanical properties of polyethylene coating Strength and protection.
Natural gas 3pe anti-corrosion steel pipe is widely used in anti-corrosion projects of metal pipelines such as gas, oil, and water. Steel pipe is preheated. The steel pipe treated with fine dust should be preheated before epoxy powder coating. The natural gas 3pe anticorrosive steel pipe is heated by a KGPS-750uw constant power intermediate frequency machine. The preheating temperature must meet the requirements of the environment. The temperature required for oxygen powder coatings, but the maximum temperature must not exceed 275 ° C.
It can withstand the stress caused by the movement of the soil caused by vibration and temperature changes, and can resist the impact stress of sharp stones on the pipe surface. The resistance of the water supply polyethylene anticorrosive coating in the community is high, which will greatly reduce the installation and maintenance costs of the cathodic protection system. The current density of the cathodic protection of the three-layer structure polyethylene anticorrosive coating pipeline is less than 10 μA * m2.
Epoxy resin powder has high adhesion, peeling properties, chemical barrier properties and oxygen resistance. The polymer coating and the epoxy resin bottom layer have good chemical adhesion, and the natural gas 3PE anticorrosive steel pipe can resist the shear force caused by soil movement and temperature change. High-density poly surface coating has a good barrier effect against moisture, can protect the epoxy resin bottom layer and polymer coating, has strong resistance to mechanical damage, peeling, and low cathodic protection current, and has a wide temperature range (from 5 to 0 8 zero ° C).
The combination of three-layer structure polyethylene anticorrosive coating is characterized by the combination and enhancement of the three coatings. The three-layer coating has strong chemical adhesion. The performance and characteristics of each layer make the three-layer coating complement each other. This three-layer anti-corrosion coating is integrated into a three-in-one form, and makes the overall chemical and mechanical properties reach a good degree. It combines the good adhesion properties of epoxy resin, chemical resistance and mechanical properties of polyethylene coating Strength and protection.
Natural gas 3pe anti-corrosion steel pipe is widely used in anti-corrosion projects of metal pipelines such as gas, oil, and water. Steel pipe is preheated. The steel pipe treated with fine dust should be preheated before epoxy powder coating. The natural gas 3pe anticorrosive steel pipe is heated by a KGPS-750uw constant power intermediate frequency machine. The preheating temperature must meet the requirements of the environment. The temperature required for oxygen powder coatings, but the maximum temperature must not exceed 275 ° C.
Several methods of connection of anticorrosive steel pipe are introduced
Generally speaking, because the cost of anticorrosive steel pipes is relatively low, the connection method of anticorrosive spiral steel pipes is welding. Due to the limitation of construction period, construction conditions, geographical environment and other factors, some projects will also use other connection methods, such as screw connection, flange connection, socket connection, slot connection and so on.
1. Flange connection anticorrosive steel pipe generally has the advantages of fast speed, convenient construction, simple tools, etc., but it cannot meet most engineering requirements in terms of safety and tightness. Generally, low-pressure pipes are suitable for this connection, such as sludge pipes.
2. Grooved anticorrosive steel pipe: Also known as clamp connection technology, it has become the first technology to connect liquid and gas pipelines. Although this technology developed later in China than abroad, it was quickly accepted by the domestic market due to its advanced technology. The application of grooved pipe connection technology makes the complicated pipe connection process simple, fast and convenient. Pipe connection technology is a big step forward. Grooved connectors include two products:
1) rigid joints, flexible joints, mechanical tees and grooved flanges;
2) Elbows, tees, crosses, reducers, blind plates, spiral welded pipes, etc. The grooved connecting pipe fittings for connection and sealing are mainly composed of three parts: a sealing rubber ring, a clamp and a locking bolt. The rubber seal ring on the inner layer is placed outside the connecting pipe and coincides with the pre-rolling groove. Then tighten the clamp on the outside of the rubber ring, and then tighten with two bolts. Due to the special sealing structure design of the rubber sealing ring and the clamp, the groove connection has a good sealing performance. As the fluid pressure in the pipeline increases, its sealing performance also improves accordingly.
The trench connection makes the pipeline connection easy to operate, conducive to construction safety, good system stability, convenient maintenance, saving time and labor, and good economic benefits. When using a clamp connection, although the price of a single piece of the clamp is higher, the overall benefit of the entire pipe network installation is higher than the flange connection.
3. As a kind of advanced anti-corrosion steel pipe connection method, the clamp pipe fittings can be exposed or concealed, that is, steel joints or flexible joints. Therefore, it has broad application prospects. Suitable for firefighting water supply system, air-conditioning hot and cold water system, water supply system, petrochemical pipeline system, thermoelectric military pipeline system, sewage treatment pipeline system, etc.
1. Flange connection anticorrosive steel pipe generally has the advantages of fast speed, convenient construction, simple tools, etc., but it cannot meet most engineering requirements in terms of safety and tightness. Generally, low-pressure pipes are suitable for this connection, such as sludge pipes.
2. Grooved anticorrosive steel pipe: Also known as clamp connection technology, it has become the first technology to connect liquid and gas pipelines. Although this technology developed later in China than abroad, it was quickly accepted by the domestic market due to its advanced technology. The application of grooved pipe connection technology makes the complicated pipe connection process simple, fast and convenient. Pipe connection technology is a big step forward. Grooved connectors include two products:
1) rigid joints, flexible joints, mechanical tees and grooved flanges;
2) Elbows, tees, crosses, reducers, blind plates, spiral welded pipes, etc. The grooved connecting pipe fittings for connection and sealing are mainly composed of three parts: a sealing rubber ring, a clamp and a locking bolt. The rubber seal ring on the inner layer is placed outside the connecting pipe and coincides with the pre-rolling groove. Then tighten the clamp on the outside of the rubber ring, and then tighten with two bolts. Due to the special sealing structure design of the rubber sealing ring and the clamp, the groove connection has a good sealing performance. As the fluid pressure in the pipeline increases, its sealing performance also improves accordingly.
The trench connection makes the pipeline connection easy to operate, conducive to construction safety, good system stability, convenient maintenance, saving time and labor, and good economic benefits. When using a clamp connection, although the price of a single piece of the clamp is higher, the overall benefit of the entire pipe network installation is higher than the flange connection.
3. As a kind of advanced anti-corrosion steel pipe connection method, the clamp pipe fittings can be exposed or concealed, that is, steel joints or flexible joints. Therefore, it has broad application prospects. Suitable for firefighting water supply system, air-conditioning hot and cold water system, water supply system, petrochemical pipeline system, thermoelectric military pipeline system, sewage treatment pipeline system, etc.
2019年12月12日星期四
What are the factors that affect the performance of large flanges?
Annealing temperature (annealing temperature is the temperature parameter when the primer and template are separated. When 50% of the primers and complementary sequences are double-stranded DNA molecules, the annealing temperature is an important factor affecting the specificity of PCR.
Ideally, the annealing temperature is low enough to ensure efficient annealing of homologous primers, and high enough to reduce non-specific separations. A reasonable annealing temperature range is 55 to 70 ° C. The annealing temperature is generally 5 ° C lower than the primer TM.
Can we reach normal temperature? Large flanges generally adopt solution heat treatment, commonly known as "annealing", and the temperature range is 1040 ~ 1120 ℃. You can also check the annealing furnace and find that the large flange fittings in the annealing zone should be incandescent, but not soften and sag.
Secondly, the tightness of the furnace body (furnace shell is welded by steel plate and section steel, and trolley is welded by steel section and steel plate). Through the soft contact sand sealing mechanism with the furnace lining, the trolley can reduce heat radiation and convection loss, and effectively ensure the tightness of the furnace body. The bright annealing furnace should be closed and isolated from the outside air. As long as an exhaust port is opened (for igniting the discharged hydrogen), the hydrogen is used as a maintenance gas. This inspection method can clean the gaps between the joints of the annealing furnace with soapy water to see if it can run away. The easiest outflow center is the center of the inlet and outlet tubes of the annealing furnace. This type of central seal is particularly prone to wear and should be inspected and replaced frequently.
Secondly, maintenance pressure, in order to avoid slight leakage, the furnace maintenance gas should adhere to a certain positive pressure, if it is hydrogen maintenance gas, generally requires more than 20kbar. Annealing atmosphere: Generally, pure hydrogen is used as the annealing atmosphere, and the purity of the atmosphere is greater than 99.99%. If the other part of the atmosphere is an inert gas, the purity can be reduced, but it must not contain excessive oxygen and water vapor.
Ideally, the annealing temperature is low enough to ensure efficient annealing of homologous primers, and high enough to reduce non-specific separations. A reasonable annealing temperature range is 55 to 70 ° C. The annealing temperature is generally 5 ° C lower than the primer TM.
Can we reach normal temperature? Large flanges generally adopt solution heat treatment, commonly known as "annealing", and the temperature range is 1040 ~ 1120 ℃. You can also check the annealing furnace and find that the large flange fittings in the annealing zone should be incandescent, but not soften and sag.
Secondly, the tightness of the furnace body (furnace shell is welded by steel plate and section steel, and trolley is welded by steel section and steel plate). Through the soft contact sand sealing mechanism with the furnace lining, the trolley can reduce heat radiation and convection loss, and effectively ensure the tightness of the furnace body. The bright annealing furnace should be closed and isolated from the outside air. As long as an exhaust port is opened (for igniting the discharged hydrogen), the hydrogen is used as a maintenance gas. This inspection method can clean the gaps between the joints of the annealing furnace with soapy water to see if it can run away. The easiest outflow center is the center of the inlet and outlet tubes of the annealing furnace. This type of central seal is particularly prone to wear and should be inspected and replaced frequently.
Secondly, maintenance pressure, in order to avoid slight leakage, the furnace maintenance gas should adhere to a certain positive pressure, if it is hydrogen maintenance gas, generally requires more than 20kbar. Annealing atmosphere: Generally, pure hydrogen is used as the annealing atmosphere, and the purity of the atmosphere is greater than 99.99%. If the other part of the atmosphere is an inert gas, the purity can be reduced, but it must not contain excessive oxygen and water vapor.
2019年12月2日星期一
Boiler tube formation
Boiler pipe forming: ① fin tube ② serpentine tube ③ reaming welding
Industrial boilers occupy a very important position in the modern energy industry, is a major industrial power or production equipment. In order to improve the thermal efficiency of the boiler, using a steel pipe manufacturing boilers, increasing heating area. Thus, in the medium and low pressure boiler or high pressure boiler works, boiler pipe accounts for a great part, about 30% to 60% of boiler steel, used as boiler engineering stave pipes, economizer tubes, heat exchanger tubes convection tubes, superheater tubes, etc., used in locomotive boiler opium pipe, small pipe and so on.
Boiler tubes need take for a variety of molding in the boiler manufacture and installation process ; for example stave pipe in pipe welding corresponding sides made of slats or finned-tube, also known as "fin tubes." The tube heat exchanger tubes often need to be processed into a certain shape, like snake collectively "serpentine"; welding locomotive boiler header tubes, both ends need to be processed after reaming. Therefore, in order to detect boiler tube pipe processing technology performance, except for routine physical and chemical properties of the test, but still need to make the appropriate technology test.
The purpose of the test is to detect plasticity situation of boiler pipes in the process. Process test generally includes: upset test, bending test, necking test, flaring test, curling test and flattening test and so on.
Industrial boilers occupy a very important position in the modern energy industry, is a major industrial power or production equipment. In order to improve the thermal efficiency of the boiler, using a steel pipe manufacturing boilers, increasing heating area. Thus, in the medium and low pressure boiler or high pressure boiler works, boiler pipe accounts for a great part, about 30% to 60% of boiler steel, used as boiler engineering stave pipes, economizer tubes, heat exchanger tubes convection tubes, superheater tubes, etc., used in locomotive boiler opium pipe, small pipe and so on.
Boiler tubes need take for a variety of molding in the boiler manufacture and installation process ; for example stave pipe in pipe welding corresponding sides made of slats or finned-tube, also known as "fin tubes." The tube heat exchanger tubes often need to be processed into a certain shape, like snake collectively "serpentine"; welding locomotive boiler header tubes, both ends need to be processed after reaming. Therefore, in order to detect boiler tube pipe processing technology performance, except for routine physical and chemical properties of the test, but still need to make the appropriate technology test.
The purpose of the test is to detect plasticity situation of boiler pipes in the process. Process test generally includes: upset test, bending test, necking test, flaring test, curling test and flattening test and so on.
The difference between carbon steel and alloy steel
Carbon steel is also known as the iron-carbon alloy containing less than 2% carbon WC. Generally also contain small amounts of silicon, manganese, sulfur, phosphorus and carbon steel, in addition to carbon use can be divided into carbon steel and carbon structural steel, carbon tool steel, and ease of cutting structural steel three categories. Carbon structural steel is divided into building structural steel and machinery manufacturing structural steel two kinds. According to the carbon steel, carbon content can be divided into low-carbon steel (WC ≤ 0.25%), medium carbon steel (WC0.25% - 0.6%) phosphorus, sulfur content and high-carbon steel (WC> 6%) can be divided into ordinary carbon steel (containing phosphorus, sulfur higher), high-quality carbon steel (containing phosphorus, low sulfur) and high quality steel (phosphorus, sulfur less), generally, the higher carbon content, the higher the hardness, higher strength but lower ductility.
Alloy steel refers to steel in addition to silicon and manganese as an alloying element or a deoxidizing element, but also contain other alloying elements (such as chromium, nickel, molybdenum, vanadium, titanium, copper, tungsten, aluminum, cobalt, niobium, zirconium, and other elementsetc.), and some also contain certain non-metallic elements (such as boron, nitrogen, etc.) of the steel. How much of the content of alloying elements in steel, can be divided into low-alloy steel, alloy steel and high-alloy steel.
Alloy steel refers to steel in addition to silicon and manganese as an alloying element or a deoxidizing element, but also contain other alloying elements (such as chromium, nickel, molybdenum, vanadium, titanium, copper, tungsten, aluminum, cobalt, niobium, zirconium, and other elementsetc.), and some also contain certain non-metallic elements (such as boron, nitrogen, etc.) of the steel. How much of the content of alloying elements in steel, can be divided into low-alloy steel, alloy steel and high-alloy steel.
Cold drawn steel pipe is passivated by pickling
The appearance of the cold drawn steel pipe will form a dense oxide film, to prevent the concentrated sulfuric acid or nitric acid to further react with the phenomenon called passivation. An active metal or an alloy, wherein the chemical activity is greatly reduced, and a noble metal state phenomenon, called passivation.
Metal generated by the role of the medium due to corrosion products, which has a dense structure, the formation of a layer of film (often invisible tightly covered in the outer of the metal, then change the state of the metal on the outer significantly to the positive direction, so that the electrode potential of the metal transitions become passive corrosion such as FeFe + + when the specification potential transition to +0.51 V-0.44V passivation shows precious metals corrosion performance, this film is called passivation film cold drawn steel pipe chromate solution with Miles hung metal appearance generated trivalent or hexavalent chromium layer, called passivation, Yiming chromium used for the disposal of aluminum, magnesium and their alloys can also form on the steel chromium layer, but rarely used alone, often phosphide and supporting the use of, to close the porosity of the phosphate layer, the phosphating layer bare steel passivation, to inhibit the corrosive effect of the remaining phosphating accelerator, to further increase the protective capacity cold drawn steel pipe passivation Usually using potassium dichromate solution (2 to 4 grams / liter, and sometimes 1 to 2 g of phosphoric acid was added) 80-90 degrees Celsius dip Tut 2-3 minutes to remove.
Metal generated by the role of the medium due to corrosion products, which has a dense structure, the formation of a layer of film (often invisible tightly covered in the outer of the metal, then change the state of the metal on the outer significantly to the positive direction, so that the electrode potential of the metal transitions become passive corrosion such as FeFe + + when the specification potential transition to +0.51 V-0.44V passivation shows precious metals corrosion performance, this film is called passivation film cold drawn steel pipe chromate solution with Miles hung metal appearance generated trivalent or hexavalent chromium layer, called passivation, Yiming chromium used for the disposal of aluminum, magnesium and their alloys can also form on the steel chromium layer, but rarely used alone, often phosphide and supporting the use of, to close the porosity of the phosphate layer, the phosphating layer bare steel passivation, to inhibit the corrosive effect of the remaining phosphating accelerator, to further increase the protective capacity cold drawn steel pipe passivation Usually using potassium dichromate solution (2 to 4 grams / liter, and sometimes 1 to 2 g of phosphoric acid was added) 80-90 degrees Celsius dip Tut 2-3 minutes to remove.
Annealing process of seamless steel tube
Annealing process of seamless steel pipe:
1. Fully annealed. It is used to refine the coarse and superheated structure with poor mechanical properties in medium and low carbon steels after casting, forging and welding. The workpiece is heated to a temperature between 30 and 50 ° C above the temperature at which ferrite is completely transformed into austenite, and is held for a period of time, and then slowly cooled with the furnace. During the cooling process, the austenite is transformed again, which can make the steel structure fine .
2. Spheroidizing annealing. Used to reduce the high hardness of tool steel and bearing steel after forging. The workpiece is heated to a temperature between 20 and 40 ° C above the temperature at which the steel begins to form austenite, and is slowly cooled after the heat preservation. During the cooling process, the lamellar cementite in pearlite becomes spherical, thereby reducing the hardness.
3. Isothermal annealing. Used to reduce the high hardness of some alloy structural steels with higher nickel and chromium content for cutting. Generally, it is first cooled to the most unstable temperature of austenite at a relatively rapid rate, and after holding for an appropriate time, the austenite is transformed into toustenite or sorbite, and the hardness can be reduced.
4. Recrystallization annealing. It is used to eliminate the hardening phenomenon (increased hardness and decreased plasticity) of metal wires and sheets during cold drawing and cold rolling. The heating temperature is generally 50 to 150 ° C below the temperature at which the steel begins to form austenite. Only in this way can the work hardening effect be softened.
5. Graphitizing annealing. Used to make cast iron containing a large amount of cementite into malleable cast iron with good plasticity. The technical operation is to heat the casting to about 950 ° C, and then cool it properly after holding for a certain period of time to decompose the cementite to form flocculent graphite.
6. Diffusion annealing. Used to homogenize the chemical composition of alloy castings and improve their performance. The method is to heat the casting to the highest possible temperature without melting, and keep it warm for a long time, and then slowly cool after the various elements in the alloy tend to be uniformly distributed.
7. Stress relief annealing. Used to eliminate the internal stress of steel castings and weldments.
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1. Fully annealed. It is used to refine the coarse and superheated structure with poor mechanical properties in medium and low carbon steels after casting, forging and welding. The workpiece is heated to a temperature between 30 and 50 ° C above the temperature at which ferrite is completely transformed into austenite, and is held for a period of time, and then slowly cooled with the furnace. During the cooling process, the austenite is transformed again, which can make the steel structure fine .
2. Spheroidizing annealing. Used to reduce the high hardness of tool steel and bearing steel after forging. The workpiece is heated to a temperature between 20 and 40 ° C above the temperature at which the steel begins to form austenite, and is slowly cooled after the heat preservation. During the cooling process, the lamellar cementite in pearlite becomes spherical, thereby reducing the hardness.
3. Isothermal annealing. Used to reduce the high hardness of some alloy structural steels with higher nickel and chromium content for cutting. Generally, it is first cooled to the most unstable temperature of austenite at a relatively rapid rate, and after holding for an appropriate time, the austenite is transformed into toustenite or sorbite, and the hardness can be reduced.
4. Recrystallization annealing. It is used to eliminate the hardening phenomenon (increased hardness and decreased plasticity) of metal wires and sheets during cold drawing and cold rolling. The heating temperature is generally 50 to 150 ° C below the temperature at which the steel begins to form austenite. Only in this way can the work hardening effect be softened.
5. Graphitizing annealing. Used to make cast iron containing a large amount of cementite into malleable cast iron with good plasticity. The technical operation is to heat the casting to about 950 ° C, and then cool it properly after holding for a certain period of time to decompose the cementite to form flocculent graphite.
6. Diffusion annealing. Used to homogenize the chemical composition of alloy castings and improve their performance. The method is to heat the casting to the highest possible temperature without melting, and keep it warm for a long time, and then slowly cool after the various elements in the alloy tend to be uniformly distributed.
7. Stress relief annealing. Used to eliminate the internal stress of steel castings and weldments.
For more information, please feel free to follow our website, thank you for your support.
http://www.xysteelpipe.com/info/Annealing-process-of-seamless-steel-tube-1566-1.htm
Galvanized steel pipe welding
The galvanized steel pipe is characterized by its excellent benefits such as corrosion resistance, long life, low initial cost and maintenance costs, has been wieldy used in outdoor and indoor, marine and underground applications
Galvanized steel pipe is a 20um thick zinc coating on the outside of the low carbon steel pipe. The melting point of zinc is at 419°C and the boiling point is around 908° ℃. In welding, zinc is melted on the surface of the molten pool or at the root of the weld. Since zinc has a relatively high solid solubility in iron, the zinc liquid will deeply erode the weld metal along the grain boundary, forming "liquid metal embrittlement". At the same time, zinc and iron can form an intermetallic brittle compound, which reduces the plasticity of the weld metal and leads to cracks under the action of tensile stress.
When welding galvanized steel, the surface of groove and the edge of the zinc layer under the action of arc heat, oxidation, melting and evaporation of white smoke and steam easily lead to weld porosity. ZnO formed by oxidation has a high melting point, above 1800°C. If the parameters are too small in the welding process, ZnO slag inclusion will be caused. Meanwhile, as Zn becomes a deoxidizer, FeO-MnO or Feo-Mno-Sio2 oxide slag inclusion with low melting point will be generated. It must be noted that the white dust of zinc volatilization is harmful to human body and the galvanized layer at welding must be polished off.
Step 1: Polishing
The galvanized layer must be polished off at the welding part, otherwise will occur bubbles, trachoma, false welding and other defects, which leads to brittle welding seam and rigidity decreases.
Step 2: Weld groove
The preparation of galvanized steel before welding is similar to the general low carbon steel, it is necessary to pay attention to the groove size and galvanized layer. The groove size is generally 60~65° and there is a certain gap, generally 1.5~2.5mm; In order to reduce the penetration of zinc into the weld, the galvanized layer in the groove can be removed before welding and then welded. In practical welding, the groove is generally concentrated and no blunt edge is left. Two-layer welding reduces the possibility of incomplete welding. The welding rod should be selected according to the base material of galvanized steel tube. Generally speaking, J422 is an ideal choice.
Step 3: Welding
In the first layer of multilayer welding weld, try to melt the zinc layer and make it vaporized, evaporation, this can greatly reduce the zinc liquid remained in the weld. The same method is used for fillet welds. First move the electrode tail forward about 5~7mm, and then return to the original position to continue welding after melting the zinc layer. If the choice of short slag electrode such as J427, there will be a very small bite edge tendency; Back and forth input electrode can get the welding quality without defects.
Galvanized steel pipe is a 20um thick zinc coating on the outside of the low carbon steel pipe. The melting point of zinc is at 419°C and the boiling point is around 908° ℃. In welding, zinc is melted on the surface of the molten pool or at the root of the weld. Since zinc has a relatively high solid solubility in iron, the zinc liquid will deeply erode the weld metal along the grain boundary, forming "liquid metal embrittlement". At the same time, zinc and iron can form an intermetallic brittle compound, which reduces the plasticity of the weld metal and leads to cracks under the action of tensile stress.
When welding galvanized steel, the surface of groove and the edge of the zinc layer under the action of arc heat, oxidation, melting and evaporation of white smoke and steam easily lead to weld porosity. ZnO formed by oxidation has a high melting point, above 1800°C. If the parameters are too small in the welding process, ZnO slag inclusion will be caused. Meanwhile, as Zn becomes a deoxidizer, FeO-MnO or Feo-Mno-Sio2 oxide slag inclusion with low melting point will be generated. It must be noted that the white dust of zinc volatilization is harmful to human body and the galvanized layer at welding must be polished off.
Step 1: Polishing
The galvanized layer must be polished off at the welding part, otherwise will occur bubbles, trachoma, false welding and other defects, which leads to brittle welding seam and rigidity decreases.
Step 2: Weld groove
The preparation of galvanized steel before welding is similar to the general low carbon steel, it is necessary to pay attention to the groove size and galvanized layer. The groove size is generally 60~65° and there is a certain gap, generally 1.5~2.5mm; In order to reduce the penetration of zinc into the weld, the galvanized layer in the groove can be removed before welding and then welded. In practical welding, the groove is generally concentrated and no blunt edge is left. Two-layer welding reduces the possibility of incomplete welding. The welding rod should be selected according to the base material of galvanized steel tube. Generally speaking, J422 is an ideal choice.
Step 3: Welding
In the first layer of multilayer welding weld, try to melt the zinc layer and make it vaporized, evaporation, this can greatly reduce the zinc liquid remained in the weld. The same method is used for fillet welds. First move the electrode tail forward about 5~7mm, and then return to the original position to continue welding after melting the zinc layer. If the choice of short slag electrode such as J427, there will be a very small bite edge tendency; Back and forth input electrode can get the welding quality without defects.
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