steel pipe

　　Austenitic stainless steel welded pipes are softened by solution treatment.-Generally, stainless steel pipes are heated to about 950 to 1150 ° C and held for a period of time, so that carbides and various alloy elements are fully and uniformly dissolved in austenite, and then quickly quenched Water cooling, carbon and other gold elements are too late to precipitate, and a pure austenite structure is obtained, which is called solid solution treatment. There are three effects of the solution treatment. 　　(1) Make the structure and composition of stainless steel welded pipe uniform, which is especially important for raw materials, because the rolling temperature and cooling rate of each section of hot-rolled wire are not the same, resulting in inconsistent microstructure. At high temperatures, atomic activity intensifies, phases dissolve, chemical composition tends to be uniform, and a uniform single-phase structure is obtained after rapid cooling. 　　(2) Eliminate work hardening to...

Cold galvanized steel pipe has been banned by the state. The reason for the ban is that the cold galvanized steel pipe cannot meet the requirements in the production process and cannot achieve the effect it should have in its range of use. Cold galvanizing is electrogalvanizing, and the amount of galvanizing is very small, only 10-50g / m2, and its own corrosion resistance is much worse than that of hot-dip galvanizing pipe. In order to ensure quality, regular galvanized pipe manufacturers do not use galvanized (cold plating). Only small companies with small and obsolete equipment use electrogalvanizing, of course, their prices are relatively cheaper. Hot dip galvanized steel: It can be clearly seen from the production process that the hot-dip galvanized steel pipe reacts the molten metal with the iron substrate to generate an alloy layer, thereby combining the substrate and the plating layer. Hot-dip galvanizing is to pickle the steel pipe first. In order to remove ...

　　a. Pickling passivated seamless steel tube dipping method. Stainless steel pipelines, elbows, small parts, etc. are most suitable for this method, and the processing effect is the best. Because the treatment part can be fully immersed in the pickling passivation solution, the surface of the pickled passivation seamless tube is completely reacted, and the passivation film is dense and uniform. This method is suitable for continuous batch operation, but needs to be replenished with new solution as the reaction concentration of the solution decreases. The disadvantage is that due to the limitation of the shape and capacity of the acid tank, it is not suitable for large-capacity equipment and pipelines that are too long and wide in shape; long-term use will reduce the effect due to solution volatilization and other reasons. Special sites, acid pools and heating equipment are required. 　　b. Pickling passivated seamless steel tube plaster method. Stainless steel pickling passivation past...

　　ERW straight seam welded pipe, also known as "resistance welded straight seam welded pipe", ERW straight seam welded pipe is mainly divided into two forms: ERW AC welded steel pipe and ERW DC welded steel pipe. ERW straight seam welded pipes are further divided into low frequency welding, intermediate frequency welding, ultra intermediate frequency welding and high frequency welding according to different frequencies. High-frequency welding is mainly used for the production of thin-walled steel pipes or ordinary thick-walled steel pipes. High-frequency welding is divided into contact welding and induction welding. 　　The straight seam high-frequency welded steel pipe has advanced forming technology, reliable quality, good welding position, stable welding parameters, fast welding speed, high output, and the equipment and technology of the entire production line are currently at the international first-class level. 　　Features: 　　(1) During the forming process of high-fre...

　　1. In order to prevent inter-eye corrosion due to the heating of the flange cover, the welding current should not be too large, about 20% less than carbon steel electrodes, the arc should not be too long, and the interlayer should be cooled quickly. 　　2. The electrode should be kept dry during use. The titanium-calcium type should be dried at 150 ° C for 1 hour, and the low-a hydrogen type should be dried at 200-250 ° C for 1 hour. The coating of the electrode sticks with oil and other dirt, so as not to increase the carbon content of the weld and affect the quality of the weldment. 　　3. When welding stainless steel flange pipe fittings, carbides are precipitated by repeated heating, which reduces corrosion resistance and mechanical properties. 　　4. The chrome stainless steel flange pipe fittings have large hardened American standard flanges after welding and are prone to cracks. If the same type of chromium stainless steel electrode (G202, G207) is used for welding, it must b...