Stainless steel elbow 1

The passivation process of stainless steel elbows can be divided into two types, namely wet and dry methods. It can be further divided into many types.
Stainless steel elbows are widely used in industries such as petrochemicals, instrumentation, and food due to their excellent corrosion resistance. For professional pipe fittings manufacturers, the quality and output of stainless steel elbows, as a high value-added product, will directly affect the efficiency of the enterprise. At present, various domestic pipe fittings manufacturers use radial cold pressing production technology when processing stainless steel elbows. This technology is mainly adopted due to the high elongation rate and thermal brittleness of stainless steel pipe fittings.
The passivation effect of stainless steel stamping elbows depends not only on the passivation process, but also on the material of the stainless steel stamping elbow itself. Specific influencing factors include the elements contained in the stainless steel stamping elbow, the metallographic structure of the stainless steel, and the processing state of the stainless steel. Among the constituent elements, chromium and nickel are highly passivating elements, while iron has slightly weaker passivity. Therefore, the higher the content of chromium and nickel, the stronger the passivity of stainless steel. Austenitic and ferritic stainless steel stamping elbows have a relatively uniform structure and good passivity. Martensitic stainless steel is strengthened by heat treatment, and its metallographic structure is multiphase, so its passivity is not strong. The passivation of the smooth surface of stainless steel stamped elbows after mechanical processing is good, while the rough surface of workpieces obtained by casting, sandblasting, etc. is not conducive to passivation.
The plates used for stainless steel stamping elbows in the 1960s and 1970s were mainly A3 and 16Mn produced by manufacturers such as Ansteel. As the pipe diameter increased and the conveying pressure increased, the strength of the pipe fitting plates could not meet the requirements. After the 1980s, various oil welded pipe fittings factories began to use pipeline steel plates produced according to American API standards. Due to the immature technology of domestic stainless steel stamping elbow plate production plants at that time, imported plates were mainly used.
Any stainless steel stamped elbow parts that do not require electroplating or other coatings generally need to undergo passivation treatment (including acid washing to remove black skin, polishing, etc.) before they can be used as finished products or assembled into components. Passivation can improve the thermodynamic stability of stainless steel stamping elbows in environmental media, prevent local corrosion of stainless steel stamping elbows, provide sufficient cleanliness on the surface of stainless steel stamping elbows, and eliminate thermal processing oxides on the surface of stainless steel stamping elbows.
Stainless steel elbows are mainly made of stainless steel, and the chemical composition contained in stainless steel will keep the surface of the stainless steel elbow from corrosion and rust for a long time. When cleaning, we also need to pay attention to the following two aspects:
1、 According to the requirements and surface condition of the workpiece, alkaline cleaning, water-soluble cleaning agents, chlorine solvent sandblasting, shot blasting and other methods are used for cleaning;
2、 Cleaning stainless steel elbows generally does not involve acid washing.
Proper cleaning of stainless steel elbows can improve their safety performance and extend their service life.
Welding rods should be kept dry during use. Titanium calcium type should be dried at 150 ℃ for 1 hour, and low hydrogen type should be dried at 200-250 ℃ for 1 hour (repeated drying is not allowed, otherwise the coating is prone to cracking and peeling), to prevent the coating of the welding rod from sticking to oil and other dirt, so as not to increase the carbon content of the weld and affect the quality of the welded part. During elbow welding, repeated heating can precipitate carbides, reducing corrosion resistance and mechanical properties. After welding, it has a high degree of hardening and is prone to cracking. If the same type of welding rod is used for welding, preheating at 300 ℃ or above and slow cooling treatment at around 700 ℃ after welding must be carried out. If the welded parts cannot undergo post weld heat treatment, chromium nickel stainless steel welding rods should be used.