Preparation work before nitriding 310S stainless steel pipe and how to deal with pores caused by welding

Preparation work before nitriding 310S stainless steel pipe and how to deal with pores caused by welding
The following preparations should be made before nitriding the 310S stainless steel pipe workpiece:
(1) The preparation drawings and process documents of 310S stainless steel pipes should be correct and complete.
(2) Before operating 310s stainless steel pipes, workers should learn more about the technical conditions and requirements for nitriding.
Preparation of workpiece
1) The original state and processing method of the 310S stainless steel pipe workpiece must comply with the provisions of the process documents.
2) The type of preliminary heat treatment of 310S stainless steel pipe workpieces must comply with the provisions of the process documents. The preparatory heat treatment before nitriding is mainly tempering and normalizing. Generally, 310s stainless steel pipe structural steel should be quenched and tempered before nitriding to obtain the tempered troostite structure.
The tempering and tempering temperature of 310S stainless steel pipe is usually 20-40°C higher than the nitriding temperature, and the holding time should not be too long. When quenching, tempering and quenching 38CrMoA1 steel, it should be ensured that the austenite on the surface of the workpiece is transformed into martensite, and no massive iron wires are allowed to exist within 5mm of the surface after quenching and tempering. Generally, after quenching and tempering of nitrided steel, the amount of free iron wire within 5mm of the surface layer shall not exceed 5%, and the tempered structure or pearlite structure containing granular bainite or upper bainite is not allowed.
Causes and preventive measures of pores produced during welding of 310s stainless steel pipes
Porosity refers to the cavity formed when the bubbles in the molten pool fail to escape during solidification during welding.
Reasons for pores in manual welding of 310s stainless steel pipes: poor welding rod or moisture; moisture, oil or rust in the weldment; too fast welding speed; too strong current; unsuitable arc length; large thickness of the weldment and excessive cooling of the metal.
Preventive measures: Use appropriate welding rods for 310s stainless steel pipes and pay attention to drying; clean the welded part before welding 310s stainless steel pipes; reduce the welding speed to make the internal gas escape easily; use the appropriate current recommended by the manufacturer for 310s stainless steel pipes; adjust the appropriate arc length ; Carry out appropriate preheating work.
310S stainless steel pipe billet casting technical requirements
When casting 310S stainless steel pipe blanks, ensure the uniformity of the structure, reduce segregation and prevent excessive concentration of non-metallic inclusions; use the optimal casting temperature to increase the critical reduction; ensure the heating temperature of the leather before perforation to reduce the reduction before the top. , improve the quality of hot tools. Hot-rolled 310S stainless steel pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, straight steel pipes and other steel pipes. In addition to general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, straight steel pipes and other steel pipes, cold-rolled (drawn) 310S stainless steel pipes also include carbon thin-walled steel pipes, alloy Thin-walled steel pipes, stainless steel thin-walled steel pipes, special-shaped steel pipes. The outer diameter of hot-rolled 310S stainless steel pipes is generally larger than 32mm, and the wall thickness is 2.5-75mm. The outer diameter of cold-rolled 310S stainless steel pipes can be up to 6mm, and the wall thickness can be up to 0.25mm. The outer diameter of thin-walled pipes can be up to 5mm, and the wall thickness is less than 0.25mm. Cold rolling has higher dimensional accuracy than hot rolling.
310S stainless steel pipe welding precautions
310S stainless steel pipe welding wire uses H1Cr26Ni21.
The electrode used for welding 310S stainless steel pipes is A407.
When using 310S stainless steel pipe welding materials, pay attention to the isolation from carbon steel. It is best to clean the welding wire with acetone before use. The welding rod is baked as required. When welding, pay attention to the interlayer temperature not being too high.