Stainless steel seamless pipe of metal and oxygen react in the atmosphere, in the appearance will form an oxide film. However, the oxidation of the iron oxide formed on the ordinary carbon steel pipe continuously causes the corrosion to be enlarged, and as a result, the pores are formed. If stainless steel seamless tube is damaged, we can use paint or oxidation-resistant metal such as zinc, nickel and chromium plating to cover the appearance of carbon steel, but, this maintenance is a layer of maintenance film, if the maintenance layer is damaged, the steel will corrosion. The corrosion resistance of stainless steel depends on the chromium, chromium is a part of steel composition, chrome on steel combined treatment, will change the appearance of the oxide type similar to pure chromium metal surface oxide. This tightly adhered chromium-rich oxide maintains the appearance and avoids further oxidation.
Heat treatment process includes heating, insulation, cooling, etc. This is done in order to reduce the deformation of the metal forming process hardening and other deficiencies, so that the deformation of the pipe after processing to restore the performance, to improve its performance.
Now the most common heat treatment tools include electric furnace and reverberatory furnace; common control mode is automatic temperature control mode.
Different stainless steel seamless pipe fittings on the heat treatment requirements are different, and not all deformation of the tools must be heat-treated, usually the final temperature of low-carbon steel pipe fittings is not less than 723 ℃, then you can not heat treatment, if lower than this temperature or the temperature above 1000 degrees celsius should be heat treatment.
2018年9月28日星期五
The Damaged Form of LSAW Steel Pipe Surface
LSAW steel pipe is formed by the surface layer of very thin and strong stability of fine chromium-rich oxide film (protective film), to prevent the continued infiltration of oxygen atoms, to oxidation, and access to anti-corrosion ability. If there is some reason, this film was the constant destruction, air or liquid oxygen or metal atoms will continue to penetrate the iron atom out from the constant analysis of the formation of loose iron oxide, metal surface corrosion will be constantly . This surface film in the form of a lot of damage, more common in everyday life are summarized as follows:
1. LSAW steel pipe surface deposit product with other metals containing dust particles or heterogeneous metal fixtures in the humid air, and stainless steel fixtures between the condensate, the two together into a micro-battery, causing the electric chemical reactions, protective film is damaged, call it that electrochemical corrosion.
2. Straight pipe surface adhesion organic juice (such as vegetables, soup, sputum, etc.), oxygen in the water case, constitutes organic acids, organic acids long is the corrosion of metal surfaces.
3. LSAW steel pipe surface adhesion with acid, alkali, salts (such as a wall decoration lye, lime splash), causing localized corrosion.
4. In a polluted air (which contain a large number of sulfide, carbon dioxide, nitrogen oxide atmosphere), the case of condensed water to form sulfuric acid, nitric acid, acetic acid solution point, cause chemical corrosion.
1. LSAW steel pipe surface deposit product with other metals containing dust particles or heterogeneous metal fixtures in the humid air, and stainless steel fixtures between the condensate, the two together into a micro-battery, causing the electric chemical reactions, protective film is damaged, call it that electrochemical corrosion.
2. Straight pipe surface adhesion organic juice (such as vegetables, soup, sputum, etc.), oxygen in the water case, constitutes organic acids, organic acids long is the corrosion of metal surfaces.
3. LSAW steel pipe surface adhesion with acid, alkali, salts (such as a wall decoration lye, lime splash), causing localized corrosion.
4. In a polluted air (which contain a large number of sulfide, carbon dioxide, nitrogen oxide atmosphere), the case of condensed water to form sulfuric acid, nitric acid, acetic acid solution point, cause chemical corrosion.
Function of stainless steel tube
Stainless steel pipe materials are various. There are a number of different types of stainless steel pipes classified by the ratio of strength and weight. Architects can choose all kinds of stainless steel pipes according to the building structure requirements. In order to help you have a better understanding of the stainless steel pipe function, this passage will divide the functions of stainless steel pipe into five categories. Now, we will explain them one by one. The first category we are going to mention about stainless steel pipe function is in water supply and drainage system. We all know that heat makes objects expand and cold makes it contract.
Because the temperatures of a year are changing according to different seasons, the intensity of the pipes used in water supply and drainage system should be excellent. Stainless steel pipes rightly meet the requirements. The second category we are going to talk about the stainless steel pipe function is in hydraulic system. The pipes used to convey oil, gas or stream should be corrosion resistance. Sometimes, the fluid is rusty. Or the gases are flammable or combustible. So plastic pipes or ordinary pipes are not suitable for conveying these objects. The function of stainless steel pipes is to protect the safety.
The third category we are going to deal with the stainless steel pipe function is in city heat supply. Stainless steel pipes can support reciprocating motion at axial direction. Thus, it is the ideal material for city heat supply. Besides, stainless steel pipes can be used in various pipe networks of heat addition. The fourth category we are going to mention of the stainless steel pipe function is in chemical engineering. Such as API steel pipe. In pipe laying projects, stainless steel pipes can help the process of cold and heat compensating action proceed. The fifth category we are going to talk about the stainless steel pipe function is pipe installation. The stainless steel pipes are widely used in the building of power station, oil field, chemical industry and so on. Sometimes, they are used as conveying pipes. Other time it is used as decorations. Because the stainless steel pipes are shiny and beautiful, they are widely used various areas.
Because the temperatures of a year are changing according to different seasons, the intensity of the pipes used in water supply and drainage system should be excellent. Stainless steel pipes rightly meet the requirements. The second category we are going to talk about the stainless steel pipe function is in hydraulic system. The pipes used to convey oil, gas or stream should be corrosion resistance. Sometimes, the fluid is rusty. Or the gases are flammable or combustible. So plastic pipes or ordinary pipes are not suitable for conveying these objects. The function of stainless steel pipes is to protect the safety.
The third category we are going to deal with the stainless steel pipe function is in city heat supply. Stainless steel pipes can support reciprocating motion at axial direction. Thus, it is the ideal material for city heat supply. Besides, stainless steel pipes can be used in various pipe networks of heat addition. The fourth category we are going to mention of the stainless steel pipe function is in chemical engineering. Such as API steel pipe. In pipe laying projects, stainless steel pipes can help the process of cold and heat compensating action proceed. The fifth category we are going to talk about the stainless steel pipe function is pipe installation. The stainless steel pipes are widely used in the building of power station, oil field, chemical industry and so on. Sometimes, they are used as conveying pipes. Other time it is used as decorations. Because the stainless steel pipes are shiny and beautiful, they are widely used various areas.
Large diameter seamless steel pipe cutting method
Large diameter seamless steel pipe is over 1000MM, which is made from steel ingot or solid tube, and then processed by hot rolling or cold rolling. Sometimes, the seamless steel pipes is long or short while using. Short seamless steel pipes can be welded, long seamless steel pipes can be cut off. Here are three methods of cutting large diameter seamless steel pipes to proper length to meet industry needs.
1. By saw machine
Saw machine can make neat section which is convenient for welding. The disadvantage is low efficiency.
2. By gas cutting
Though gas cutting is fast, the disadvantage is presented notched surface which is not good for construction.
3. By cnc cutting machine
By cnc cutting machine, seamless steel pipes manufacturers will not save a lot cost but also can obtain smooth section of seamless steel pipe which has not much difference from cutting by saw machine.
1. By saw machine
Saw machine can make neat section which is convenient for welding. The disadvantage is low efficiency.
2. By gas cutting
Though gas cutting is fast, the disadvantage is presented notched surface which is not good for construction.
3. By cnc cutting machine
By cnc cutting machine, seamless steel pipes manufacturers will not save a lot cost but also can obtain smooth section of seamless steel pipe which has not much difference from cutting by saw machine.
What is Low Carbon Steel Pipe
Low carbon steel pipe known as mild steel pipe and carbon content from 0.10% to 0.30% in low-carbon steel is easy to accept all kinds of processing such as forging, welding and cutting, commonly used in the manufacturing chain, rivets, bolts, axis. The carbon content of less than 0.25% carbon steel, because of its low intensity, low hardness and soft, it is also known as mild steel pipes. It includes the majority of ordinary carbon steel pipe and part of high-quality carbon structural steel, mostly used in engineering structures without heat treatment, and some by carburizing and other heat treatment is used for wear-resistant mechanical parts.
Low carbon steel pipe annealed structure of ferrite and pearlite, the lower its strength and hardness, good ductility and toughness. Therefore, the cold good form ability and can use methods such as crimping, bending, stamping, cold forming. This structural steel pipe has good weld ability. Low carbon content of low carbon steel hardness is low, the poor machinability of normalizing treatment can improve machinability. Low-carbon steel pipes have a greater tendency of aging, both quench aging and the tendency to deformation aging tendencies. When the steel from high temperature and rapid cooling, the ferrite scratch carbon, nitrogen supersaturation at room temperature can slow the formation of iron carbonitride material, and thus improve the strength and hardness of the steel pipe, reduce the ductility and toughness of this phenomenon known as the quench aging. Low carbon steel quenching and air cooling will produce aging. Low-carbon steel large number of dislocations generated by deformation, the elastic interaction from the carbon and nitrogen atoms with dislocations in the ferrite, carbon, nitrogen atoms gather around the dislocations Line. This carbon, nitrogen atom and the dislocation line combination that old Coriolis air mass (Ke lop air mass). It will make the strength and hardness of the steel to improve the ductility and toughness decreased, a phenomenon known as the deformation aging. Deformation than the quench aging on the ductility and toughness of low carbon steel pipe greater harm evident in the tensile curve of the low-carbon steel and lower yield point.
Low carbon steel pipe annealed structure of ferrite and pearlite, the lower its strength and hardness, good ductility and toughness. Therefore, the cold good form ability and can use methods such as crimping, bending, stamping, cold forming. This structural steel pipe has good weld ability. Low carbon content of low carbon steel hardness is low, the poor machinability of normalizing treatment can improve machinability. Low-carbon steel pipes have a greater tendency of aging, both quench aging and the tendency to deformation aging tendencies. When the steel from high temperature and rapid cooling, the ferrite scratch carbon, nitrogen supersaturation at room temperature can slow the formation of iron carbonitride material, and thus improve the strength and hardness of the steel pipe, reduce the ductility and toughness of this phenomenon known as the quench aging. Low carbon steel quenching and air cooling will produce aging. Low-carbon steel large number of dislocations generated by deformation, the elastic interaction from the carbon and nitrogen atoms with dislocations in the ferrite, carbon, nitrogen atoms gather around the dislocations Line. This carbon, nitrogen atom and the dislocation line combination that old Coriolis air mass (Ke lop air mass). It will make the strength and hardness of the steel to improve the ductility and toughness decreased, a phenomenon known as the deformation aging. Deformation than the quench aging on the ductility and toughness of low carbon steel pipe greater harm evident in the tensile curve of the low-carbon steel and lower yield point.
2018年9月12日星期三
ASTM A270 Sanitary Stainless Tube Manufacturing Processes
ASTM A270 sanitary (hygienic) stainless steel tubing is the standard specification for the welded seamless, and heavily cold worked welded austenitic and ferritic stainless steel sanitary tubing. It includes the stainless steel tube types in seamless and welded ERW, EFW. ASTM A270 sanitary tubing intended applied in the diary and food industry, bio processing equipment, and having special surface finish. ASTM A270 sanitary stainless steel pipe shall be noted below points during manufacturing processes:
1) Seamless steel pipe should not contains any kind of welding processing.
2) Welded steel pipe applied in automatic welding processing, but should not use metal materials as filler.
3) Heavily cold worked (HCW) tubes shall be manufactured by cold working of not less than 35% reduction of thickness of both wall and weld to a welded pipe prior to the final anneal. Filler materials shall be noted added during welding process. The weld shall be 100% radio graphically inspected in accordance with ASME boiler and pressure vessel standards specification.
4) Sanitary pipe could be furnished with hot finished or cold finished at Manufacture’s option.
Hot-treatment methods for ASTM A270 stainless tube
All materials should supply after hot-treatment. Except the for duplex stainless steel materials S31803, S32003, S320205, S32750, N08926 and N08367, in these cases it shall consist of heating the material to a minimum temperature of 1900 ℉ (1040 ℃) and quenching in water or rapid cooling by other means.
1) Seamless steel pipe should not contains any kind of welding processing.
2) Welded steel pipe applied in automatic welding processing, but should not use metal materials as filler.
3) Heavily cold worked (HCW) tubes shall be manufactured by cold working of not less than 35% reduction of thickness of both wall and weld to a welded pipe prior to the final anneal. Filler materials shall be noted added during welding process. The weld shall be 100% radio graphically inspected in accordance with ASME boiler and pressure vessel standards specification.
4) Sanitary pipe could be furnished with hot finished or cold finished at Manufacture’s option.
Hot-treatment methods for ASTM A270 stainless tube
All materials should supply after hot-treatment. Except the for duplex stainless steel materials S31803, S32003, S320205, S32750, N08926 and N08367, in these cases it shall consist of heating the material to a minimum temperature of 1900 ℉ (1040 ℃) and quenching in water or rapid cooling by other means.
Preventive measures for cold treatment of seamless steel tube
A steel pipe made of a single piece of metal and having no seams on its surface is called a seamless steel pipe. Seamless steel pipes are mainly used as petroleum geological drilling pipes, cracking pipes for petrochemicals, boiler tubes, bearing tubes, and high-precision structural steel tubes for automobiles, tractors, and aviation.
Cold treatment method of seamless steel pipe may affect the performance of the seamless steel pipe, so we need to do some preventive measures when carrying out the seamless steel pipe cold treatment. The following small series introduces the preventive measures for the cold treatment of seamless steel pipe in detail:
(1) The seamless steel pipe is placed in boiling water for 30-60 minutes before quenching after quenching, which can eliminate 15%-25% quenching internal stress and stabilize the retained austenite, and then carry out conventional cold treatment at -60 °C. Or cryogenic treatment at -120 °C, the lower the temperature, the more the retained austenite transforms into martensite, but it is impossible to complete the conversion. Experiments show that about 2%-5% retained austenite remains, press It is necessary to retain a small amount of retained austenite to relax the stress and play a buffering role. Because the retained austenite is soft and tough, it can partially absorb the martensite sharp expansion energy and alleviate the phase transformation stress;
(2) After the cold treatment is completed, the seamless steel pipe is taken out and heated in hot water to eliminate 40%-60% cold treatment stress. After heating to room temperature, it should be tempered in time, the cold treatment stress is further eliminated, cold crack formation is avoided, and stable microstructure performance is obtained. Ensure that the seamless steel pipe products are not distorted during storage and use.
http://www.xysteelpipe.com/info/Preventive-measures-for-cold-treatment-of-seamless-steel-tube-1277-1.htm
Cold treatment method of seamless steel pipe may affect the performance of the seamless steel pipe, so we need to do some preventive measures when carrying out the seamless steel pipe cold treatment. The following small series introduces the preventive measures for the cold treatment of seamless steel pipe in detail:
(1) The seamless steel pipe is placed in boiling water for 30-60 minutes before quenching after quenching, which can eliminate 15%-25% quenching internal stress and stabilize the retained austenite, and then carry out conventional cold treatment at -60 °C. Or cryogenic treatment at -120 °C, the lower the temperature, the more the retained austenite transforms into martensite, but it is impossible to complete the conversion. Experiments show that about 2%-5% retained austenite remains, press It is necessary to retain a small amount of retained austenite to relax the stress and play a buffering role. Because the retained austenite is soft and tough, it can partially absorb the martensite sharp expansion energy and alleviate the phase transformation stress;
(2) After the cold treatment is completed, the seamless steel pipe is taken out and heated in hot water to eliminate 40%-60% cold treatment stress. After heating to room temperature, it should be tempered in time, the cold treatment stress is further eliminated, cold crack formation is avoided, and stable microstructure performance is obtained. Ensure that the seamless steel pipe products are not distorted during storage and use.
http://www.xysteelpipe.com/info/Preventive-measures-for-cold-treatment-of-seamless-steel-tube-1277-1.htm
2018年9月11日星期二
Standards and Size of Boiler Pipe
Boiler steel pipes includes medium pressure boiler pipe and high pressure boiler pipe, it is often manufactured in seamless procedures, welded steel pipe is not applicable. It has been widely used at heat exchanger pipe and tubing services, tube exchanger bundle, high pressure boiler, economizer, super heater, petrochemical industry pipes, etc.
Boiler pipe materials and standards
Standards and material for steel pipe is available at carbon, alloy, and stainless steel material.
Carbon steel: ASTM/ASME A/SA 106, ASTM A179, ASTM A192, ASTM/ASME A/SA 210, ASTM A333 Gr 1, 6,7 to Gr 9,
Alloy steel: ASTM/ASME A/SA 213 T1, T2, T5, T9, T11, T12, T22, T91, T92; ASTM A335 P1, P2, P5, P9, P11, P12, P22, P91, P92
Stainless Steel: ASTM A268, ASTM A213, TP304/L, TP316/L, 310S,309S,317,317L,321,321H, and duplex stainless steel material etc.
Common Sizes: OD from 6mm to 1240mm, thickness from 1mm to 50mm
Types: Straight boiler pipe, and U boiler steel pipe for tube exchanger bundle.
These standards specify the classification, size, shape, weight and allowable deviation, technical requirements, inspection and test, packaging, marking and quality certificate of seamless steel tubes for boiler.
Boiler Pipe Size
Boiler pipe size range complied with the different ASTM standard required. Like ASTM A106 or ASTM 179, 192 etc. But most of the boiler pipe size is small, outer diameter usually less than 1 1/2” (1/4”, 1/2”, 3/4”, 1” and 1 1/2”). Then 2”, 2 1/2”, 3” and maximum to 4”.
Boiler pipe materials and standards
Standards and material for steel pipe is available at carbon, alloy, and stainless steel material.
Carbon steel: ASTM/ASME A/SA 106, ASTM A179, ASTM A192, ASTM/ASME A/SA 210, ASTM A333 Gr 1, 6,7 to Gr 9,
Alloy steel: ASTM/ASME A/SA 213 T1, T2, T5, T9, T11, T12, T22, T91, T92; ASTM A335 P1, P2, P5, P9, P11, P12, P22, P91, P92
Stainless Steel: ASTM A268, ASTM A213, TP304/L, TP316/L, 310S,309S,317,317L,321,321H, and duplex stainless steel material etc.
Common Sizes: OD from 6mm to 1240mm, thickness from 1mm to 50mm
Types: Straight boiler pipe, and U boiler steel pipe for tube exchanger bundle.
These standards specify the classification, size, shape, weight and allowable deviation, technical requirements, inspection and test, packaging, marking and quality certificate of seamless steel tubes for boiler.
Boiler Pipe Size
Boiler pipe size range complied with the different ASTM standard required. Like ASTM A106 or ASTM 179, 192 etc. But most of the boiler pipe size is small, outer diameter usually less than 1 1/2” (1/4”, 1/2”, 3/4”, 1” and 1 1/2”). Then 2”, 2 1/2”, 3” and maximum to 4”.
Method of bonding carbon steel pipe to CRA material
Solid CRA lined pipes or CRA clad (cladding) pipes are known to be corrosion-resistant that consists of an inner pipe which is also corrosion-resistant and a carbon steel outer pipe which can withstand external and internal pressure. There are various applications of pipes made from CRA material and include subsea pipelines for conveying sour gas and oil, saltwater pipelines, water reinjection systems, process pipes in the chemical industry, salt water pipes and much more.
These CRA lined and clad steel pipes are majorly used as: water injection pipelines, interfield pipelines, riser pipelines, flow-lines
In bonding the CRA material to carbon steel pipe, there are two methods:
1.Metallurgical bond (for CRA Clad (caldding) pipes) – Cladding of plates (metallurgical bond between 2 different metals) is carried out by various operations such as coextrusion, hot rolling, explosive bonding or weld overlay. The major problem with metallurgical bonding is the high costs which is created by the limited number of suppliers due to the complex and demanding manufacturing process of metallurgical bonding the plates.
2.Mechanical bond (for CRA lined pipes) – Mechanical bonding the CRA pipe and the backing steel pipe by using spring back variation which can be achieved by means of Hydroforming or full-length pipe expander.
These CRA lined and clad steel pipes are majorly used as: water injection pipelines, interfield pipelines, riser pipelines, flow-lines
In bonding the CRA material to carbon steel pipe, there are two methods:
1.Metallurgical bond (for CRA Clad (caldding) pipes) – Cladding of plates (metallurgical bond between 2 different metals) is carried out by various operations such as coextrusion, hot rolling, explosive bonding or weld overlay. The major problem with metallurgical bonding is the high costs which is created by the limited number of suppliers due to the complex and demanding manufacturing process of metallurgical bonding the plates.
2.Mechanical bond (for CRA lined pipes) – Mechanical bonding the CRA pipe and the backing steel pipe by using spring back variation which can be achieved by means of Hydroforming or full-length pipe expander.
Treatment Technology of Stainless Steel Seamless Pipes
Stainless steel seamless pipes treatment technology refers to the processing of achieving uniform silver, and has a metallic luster. This is generally referred to the production of large stainless steel seamless pipes. Because large stainless steel seamless pipe is manufactured through stamping, folding and welding process, the surface of workpiece has oil, rust, macular, which is neither beautiful, and easy to rust, reducing its stainless steel quality and value.
To make stainless steel seamless pipes achieve the standard, the surface must be finished. After forming matte treatment, that can achieve beautiful appearance, but also improve its anti-corrosion and anti-discoloration performance. After the above method, the corrosion resistance of stainless steel seamless pipes can be increased by 2 to 3 times.
Stainless steel seamless pipes does not rust due to the existence of chromium, nickel components, and then through the matt treatment, not only can eliminate the matrix impurities and iron-rich layer, but also can make chromium on the surface, forming a complete purification film, play a better anti-corrosion effect. According to the complexity of stainless steel seamless pipes and user requirements, we can choose different processing technology, such as mechanical polishing, chemical polishing, electro chemical polishing and other methods to achieve specular gloss.
To make stainless steel seamless pipes achieve the standard, the surface must be finished. After forming matte treatment, that can achieve beautiful appearance, but also improve its anti-corrosion and anti-discoloration performance. After the above method, the corrosion resistance of stainless steel seamless pipes can be increased by 2 to 3 times.
Stainless steel seamless pipes does not rust due to the existence of chromium, nickel components, and then through the matt treatment, not only can eliminate the matrix impurities and iron-rich layer, but also can make chromium on the surface, forming a complete purification film, play a better anti-corrosion effect. According to the complexity of stainless steel seamless pipes and user requirements, we can choose different processing technology, such as mechanical polishing, chemical polishing, electro chemical polishing and other methods to achieve specular gloss.
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