ASTM A53 A283 A106 A179 A210 galvanized steel pipe

  Galvanized steel pipes are divided into cold-galvanized steel pipes and hot-dip galvanized steel pipes. Cold-galvanized steel pipes have been banned, and the latter is also advocated by the state to be used temporarily. In the 1960s and 1970s, developed countries in the world began to develop new types of pipes and gradually banned galvanized pipes. Four ministries and commissions including the Ministry of Construction of China also issued a document clarifying that galvanized pipes have been banned as water supply pipes since 2000. Galvanized pipes are rarely used for cold water pipes in newly built communities, and galvanized pipes are used for hot water pipes in some communities. Hot-dip galvanized steel pipes are widely used in fire fighting, electric power and highways. Hot-dip galvanized steel pipes are widely used in manufacturing industries such as construction, machinery, coal mines, chemicals, electric power, railway vehicles, automobile industry, highways, bridges, containers, sports facilities, agricultural machinery, petroleum machinery, prospecting machinery, greenhouse construction and other manufacturing industries. Galvanized steel pipes are welded steel pipes with hot-dip galvanized or electro-galvanized layers on the surface. Galvanizing can increase the corrosion resistance of the steel pipe and prolong its service life. Galvanized pipe has a wide range of uses. In addition to line pipes for conveying water, gas, oil and other general low-pressure fluids, it is also used as oil well pipes and oil pipes in the petroleum industry, especially offshore oilfields, as well as oil heaters and condensate for chemical coking equipment. Pipes for coolers, coal-distilled wash oil exchangers, pipe piles for trestle bridges, pipes for support frames of mine tunnels, etc. The hot-dip galvanized pipe is to make the molten metal and the iron matrix react to produce an alloy layer, so that the matrix and the coating are combined. Hot-dip galvanizing is to pickle the steel pipe first. In order to remove the iron oxide on the surface of the steel pipe, after the pickling, it is cleaned in a tank of ammonium chloride or zinc chloride aqueous solution or a mixed aqueous solution of ammonium chloride and zinc chloride, and then sent to In the hot dip plating tank. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. The matrix of the hot-dip galvanized steel pipe undergoes a complex physical and chemical reaction with the molten plating solution to form a corrosion-resistant zinc-iron alloy layer with a compact structure. The alloy layer is integrated with the pure zinc layer and the steel pipe matrix, so its corrosion resistance is strong. Cold galvanized pipe is electro-galvanized, and the amount of galvanization is very small, only 10-50g/m2, and its corrosion resistance is much different than that of hot-dip galvanized pipe. Most of the regular galvanized pipe manufacturers do not use electro-galvanized (cold plating) in order to ensure the quality. Only those small enterprises with small scale and outdated equipment use electro-galvanization, and of course their prices are relatively cheaper. The Ministry of Construction has officially announced that cold-galvanized pipes with outdated technology should be eliminated, and cold-galvanized pipes are not allowed to be used as water and gas pipes. The galvanized layer of cold galvanized steel pipe is an electroplated layer, and the zinc layer is layered independently from the steel pipe matrix. The zinc layer is thin, and the zinc layer simply adheres to the steel pipe substrate and is easy to fall off. Therefore, its corrosion resistance is poor. In newly-built houses, it is forbidden to use cold galvanized steel pipes as water supply pipes. Weight factor Nominal wall thickness (mm): 2.0, 2.5, 2.8, 3.2, 3.5, 3.8, 4.0, 4.5. Coefficient parameter (c): 1.064, 1.051, 1.045, 1.040, 1.036, 1.034, 1.032, 1.028. Note: The mechanical properties of steel is an important index to ensure the final use performance (mechanical properties) of the steel, and it depends on the chemical composition of the steel and the heat treatment system. In the steel pipe standard, according to different application requirements, tensile properties (tensile strength, yield strength or yield point, elongation), hardness and toughness indexes are specified, as well as high and low temperature properties required by users. Steel grades: Q215A; Q215B; Q235A; Q235B. Test pressure value/Mpa: D10.2-168.3mm is 3Mpa; D177.8-323.9mm is 5Mpa. The use of galvanized pipes. The iron pipes used for gas and heating are also galvanized pipes. Galvanized pipes are used as water pipes. After a few years of use, a large amount of rust and dirt will be generated in the pipes. The yellow water flowing out not only pollutes the sanitary ware, but also contains uneven inner walls. The breeding of bacteria and rust cause high levels of heavy metals in the water, which seriously endangers human health. Production steps The process flow is: black tube-alkaline washing-water washing-pickling-water rinsing-soaking aid-drying-hot dip galvanizing-external blowing-internal blowing-air cooling-water cooling -Passivation-water rinsing-inspection-weighing-storage. skills requirement 1. Brand and chemical composition The grade and chemical composition of the steel for galvanized steel pipes should comply with the grade and chemical composition of the steel for black pipes as specified in GB/T3091. 2. Manufacturing method The manufacturing method of the black pipe (furnace welding or electric welding) is selected by the manufacturer. Hot-dip galvanizing is used for galvanizing. 3. Thread and pipe joints (A) For galvanized steel pipes delivered with threads, the threads should be machined after galvanizing. The thread should comply with YB 822 regulations. (B) Steel pipe joints should comply with YB 238; malleable cast iron pipe joints should comply with YB 230. 4. Mechanical properties The mechanical properties of steel pipes before galvanizing should meet the requirements of GB 3091. 5. The uniformity of the galvanized layer Galvanized steel pipe should be tested for the uniformity of the galvanized layer. The steel pipe sample shall not turn red (copper-plated color) after being immersed in copper sulfate solution for 5 consecutive times. 6. Cold bend test The galvanized steel pipe with a nominal diameter of not more than 50mm should be subjected to a cold bend test. The bending angle is 90°, and the bending radius is 8 times the outer diameter. There is no filler during the test, and the weld of the sample should be placed on the outside or upper part of the bending direction. After the test, there should be no cracks and peeling of the zinc layer on the sample. 7. Water pressure test The water pressure test should be carried out in the clarinet. Eddy current flaw detection can also be used instead of the water pressure test. The test pressure or the size of the comparison sample for eddy current testing shall meet the requirements of GB 3092. The mechanical properties of steel is an important index to ensure the final use performance (mechanical properties) of the steel. Mechanical properties ① Tensile strength (σb): The maximum force (Fb) that the sample bears when it breaks during the tensile process, divided by the stress (σ) obtained by the original cross-sectional area (So) of the sample, is called the resistance Tensile strength (σb), the unit is N/mm2 (MPa). It represents the maximum ability of a metal material to resist damage under tensile force. In the formula: Fb-the maximum force that the sample bears when it is broken, N (Newton); So-the original cross-sectional area of ​​the sample, mm2. ②Yield point (σs): For a metal material with a yield phenomenon, the stress at which the sample can continue to elong without increasing the force during the stretching process is called the yield point. If the force drops, the upper and lower yield points should be distinguished. The unit of yield point is N/mm2 (MPa). Upper Yield Point (σsu): The maximum stress before the specimen yields and the force drops for the first time; Lower Yield Point (σsl): The minimum stress in the yield stage when the initial transient effect is not taken into account. Where: Fs--yield force (constant) during the tensile process of the sample, N (Newton) So--the original cross-sectional area of ​​the sample, mm2. ③ Elongation after break: (σ) In the tensile test, the percentage of the length of the gauge length increased by the specimen after it is broken to the original gauge length is called the elongation. Expressed by σ, the unit is %. In the formula: L1-the gauge length of the specimen after breaking, in mm; L0-the original gauge length of the specimen, in mm. ④ Reduction of area: (ψ) In the tensile test, the percentage of the maximum reduction of the cross-sectional area at the reduced diameter of the sample after the sample is broken to the original cross-sectional area is called the reduction of area. Expressed in ψ, the unit is %. In the formula: S0-the original cross-sectional area of ​​the sample, mm2; S1-the minimum cross-sectional area at the reduced diameter of the sample after it is broken, mm2. ⑤Hardness index: The ability of metal materials to resist the indentation of hard objects on the surface is called hardness. According to different test methods and scope of application, hardness can be divided into Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, micro hardness and high temperature hardness. There are three commonly used pipes: Brinell, Rockwell, and Vickers hardness. Brinell Hardness (HB): Use a steel ball or cemented carbide ball of a certain diameter to press into the surface of the sample with the specified test force (F), remove the test force after the specified holding time, and measure the indentation diameter on the surface of the sample (L). The Brinell hardness value is the quotient obtained by dividing the test force by the spherical surface area of ​​the indentation. Expressed in HBS (steel ball), the unit is N/mm2 (MPa).  

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Because the hot-dip galvanized seamless steel pipe is hot-dip galvanized, the amount of galvanized is very high. The average thickness of galvanized layer is more than 65 microns, and its corrosion resistance is much different from that of hot-dip galvanized pipe. Regular galvanized pipe manufacturers are allowed to use cold galvanized pipes as water and gas pipes. The galvanized layer of cold galvanized steel pipe is an electroplating layer, and the zinc layer is separated from the steel pipe substrate. The zinc layer is thin, and the zinc layer is simply attached to the steel pipe matrix, which is easy to fall off. Therefore, its corrosion resistance is poor. In new houses, it is forbidden to use cold galvanized steel pipes as water supply steel pipes. After pickling, API seamless steel pipes are cleaned in ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution tank. In order to ensure quality, electro galvanizing (cold plating) is mostly not used. Only those small enterprises with small scale and old equipment use electro galvanizing, of course, their price is relatively cheap. The Ministry of construction has officially eliminated the backward cold galvanized pipe, which will not be electro galvanized in the future. It is to make the molten metal react with the iron matrix to produce an alloy layer, so as to combine the matrix and the coating. Hot dip galvanizing is to pickle the steel pipe first, in order to remove the iron oxide on the surface of the steel pipe, and then send it to the hot dip galvanizing tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. 1. Medium plate unit: it mainly produces wide and thick plates for the production of longitudinal submerged arc welded pipes. The longitudinal submerged arc welded pipes are of reliable quality and are widely used in the main line of oil and gas high-pressure transmission. Steckel Mill: Steckel mill includes a reciprocating roughing mill and a 4-high reciprocating finishing mill. Two hot coil mills are installed on the conveyor lines on both sides of the finishing mill. The output roller table usually includes a laminar cooling system and a coiling station. On the steckel mill, the thermomechanical history of the whole length of stainless steel stamping elbow pipe fittings changes significantly, especially in the production of micro stainless steel stamping elbow pipe fittings, which will strongly affect the recrystallization degree, grain growth and precipitation on the finishing mill, and lead to drastic changes in the final microstructure and properties of the whole length of stainless steel stamping elbow pipe fittings Semi continuous mill: including 1 Steckel mill and 5 finishing mills. On a semi continuous rolling mill, the hot rolling of pipe fittings in finishing passes is essentially constant from one end to the other. The time between passes on the finishing mill is usually less than 3S. CSP continuous casting and rolling: for low carbon manganese steel containing niobium, vanadium and titanium composite Microalloying on CSP production line, appropriate controlled rolling, controlled cooling and coiling processes can ensure that the mechanical properties and microstructure of pipe fittings meet the technical requirements of modern X60 stainless steel stamping elbow and the development trend of modern stainless steel stamping elbow pipe fittings. China's CSP continuous casting and rolling production line has developed X60 stainless steel stamping elbow fittings, while other CSP manufacturers in the United States and abroad have developed and produced high-grade stainless steel stamping elbow fittings X60, X65 and even X70. The process feature is that there is central segregation in continuous casting thin slab. The elimination of central segregation in continuous casting thin slab by galvanized seamless steel pipe is the key technical problem to further improve the quality of stainless steel stamping elbow fittings. The plates used for stainless steel stamping elbow mainly used A3 and 16Mn produced by Angang and other manufacturers in the 1960s and 1970s. With the increase of pipe diameter and transmission pressure, The strength of pipe fitting plate can not meet the requirements. After the 1980s, all petroleum welded pipe parts factories began to use pipeline steel plates produced according to American API standards. At that time, due to the immature technology of domestic stainless steel stamping elbow plate manufacturers, imported plates were mainly used.

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