Mechanism of heat treatment temperature on microstructure and properties in deposited metal of 1000 MPa grade high strength steel

1000 MPa high strength steel deposited metal is prepared by wire submerged arc welding. The effect of post-weld heat treatment temperature (500 ~ 620 ℃) on the microstructural evolution in deposited metal of 1000 MPa grade high strength steels has been investigated using microanalytical methods such as SEM, EBSD, XRD and TEM. Evaluate their mechanical properties by tensile and impact tests. The results show that with the increase of heat treatment temperature, 1000MPa grade high-strength steel deposited metal tensile strength and yield strength of heat-treated state than the AW first increase and then reduce. The heat-treated state deposited metal toughness is lower than the AW. The strength and toughness matching effect of 1000 MPa grade high strength steel deposited metal is good at 540 ℃ heat treatment, the tensile strength is 1030 MPa, the yield strength is 970 MPa, and the impact toughness is 58 J at −40 ℃. 1000 MPa grade high strength steel fused metal in 500 ~ 620 ℃ heat treatment process in the M/A group element A gradually decomposed into carbides and ferrite. During heat treatment at 620 ℃, reverse austenite is generated and retained to room temperature. Carbide for dislocations has a pinning effect, but with the increase of heat treatment temperature carbide on the dislocation of the pinning effect is weakened, dislocations through the slip and climb constantly reduced. Deposited metal precipitation of carbide on the dislocation pinning effect is stronger than the softening effect of dislocation slip, the deposited metal strength, carbides on the dislocation pinning effect is weaker than the softening effect of dislocation slip when the matrix microstructure softens, the deposited metal strength is reduced. The precipitated carbide leads to dislocation plugging, and the stress concentration area becomes the crack source, which makes the toughness of the heat-treated deposited metal lower than the AW.