Analyze the embrittlement of stainless steel welded joint

The phenomenon of decreasing impact toughness is called embrittlement when the weld seam of stainless steel is heated at high temperature for a period of time.

475 ℃ brittleness. When heated at 350℃ ~ 500℃, the plasticity and toughness of the dual-phase weld metal containing more ferritic phase (more than 15% ~ 20%) will be significantly reduced, that is, the property embrittlement. Due to the fastest embrittlement at 475℃, it is called “brittleness at 475℃”. The more ferrite, the more embrittlement. Embrittlement welds at 475℃ have been produced and can be eliminated by 900℃ quenching.

σ embrittlement. The long-term use of welded stainless steel joints at 375 ° c to 875℃produces an Fe-Cr intermetallic compound called the sigma phase. At 60HRC or more, there is a sharp decline in the impact toughness of the weld. This is called “sigma embrittlement”. It is generally considered that the sigma is derived from the ferrite, and when the ferritic mass is over 5%, it is very quickly formed. Therefore, for stainless steel materials used at high temperatures, the ferrite content must be controlled to prevent the appearance of sigma. In order to eliminate the generated noise and restore the toughness of the welded joints, the welded joints can be heated to 1000℃ – 1050℃ and then cooled down rapidly.

The fuse wire is brittle. Stainless steel welding in the long-term use of high temperature, along the weld fusion line several grains, will occur brittle phenomenon, this phenomenon is called the fusion line brittle. Adding MO element to steel can improve the ability of resisting brittle fracture.

Post time: Jul-11-2019