Stainless steel is a delayed cracked steel, which is low in the thermal conductivity of ordinary carbon steel, high expansion coefficient, slow heat transfer, and is extremely expanded and expanded. Based on this nature, stainless steel sheets are soldered ...
Stainless steel is a delayed cracked steel, which is low in the thermal conductivity of ordinary carbon steel, high expansion coefficient, slow heat transfer, and is extremely expanded and expanded. Based on this nature, there may be many problems in the process of welding, such as hanketing, air holes, unfused cracks, etc.
Then you know why stainless steel sheets do cracks during welding? Today, crazy metal small packs and everyone simply share. Cracks of stainless steel sheets can be divided into cold cracks, thermal cracks and reheat cracks in different temperatures and times thereof.
1. Hot cracks refers to the thermal cracks produced by weld and thermal influence zone metal cooling to the vicinity of the solid phase line during welding.
Preventive measures: Strictly control the sulfur content of stainless steel sheet and weld material, phosphorus content, etc. Or disperse segregation; use alkaline welding materials to reduce impurity content in welds, improve segregation.
2. Cold cracks refer to the welded joints to cool to lower temperatures (that is, the austenite starts to transition to the martensite temperature below the temperature below the martensite). Preventive measures: Use a low hydrogen type welding material, which is soldered in accordance with the provisions; preparation of oil, moisture on the welds, reducing the hydrogen content in weld; select reasonable welding process parameters and thermal input, reducing the hardening of weld The hydrogen-hydrogen treatment immediately afterward welding, so that hydrogen is overflowing from the welded joint. Refold crack refers to the crack produced by heating (eliminating the stress heat treatment or other heating process) in a certain temperature range.
3. Preventive measures: Under the premise of satisfying design requirements, select low-intensity welding materials, so that the weld intensity is lower than stainless steel sheet, stress in the weld, avoid cracking in the thermal influence zone; minimize welding residual stress and stress Concentrate; control welded welding heat input, reasonably select preheating and heat treatment temperature, and avoid the sensitive area as much as possible. Stainless steel sheets generally take preheated to weld, and should pay attention to the surrounding environment during welding, and make adjustments in time. If you need non-destructive testing, it is generally subject to 44 hours after welding.
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