If the forging process is not reasonable, forging defects may occur, including surface defects, internal defects or unqualified performance, which will affect the processing quality of subsequent processes, and some seriously affect the performance of forging, reduce the service life of finished products, and even endanger safety.The influence of forging structure on the structure and performance after final heat treatment is mainly shown in the following aspects.
(1) can not improve the structure defects: austenite and ferrite heat-resistant stainless steel, high temperature alloy, aluminum alloy, magnesium alloy in the process of heating and cooling, there is no isomorphic transformation of materials, as well as some copper alloy and titanium alloy, in the forging process of the structure defects with heat treatment method can not improve.
(2) the microstructure defects can be improved: in general overheating coarse grain and widmanstatten structure in structural steel forgings, hypereutectoid steel and bearing steel caused by improper cooling slightly carbide network such as heat treatment after forging, forging eventually still satisfied with the organization and performance can be obtained after heat treatment.
(3) the normal heat treatment is difficult to eliminate the structure defects: such as low-power coarse crystal, 9Cr18 stainless steel, H13 twin carbide, such as high temperature normalizing, repeated normalizing, low temperature decomposition, high temperature diffusion annealing measures to be improved.
(4) with the general heat treatment process can not eliminate the defects of the structure: serious stone fracture and edge surface fracture, overburning, ferritic belt in stainless steel, laijinsi alloy tool steel carbide network and belt, so that the final heat treatment after the performance of the forging decreased, even unqualified.
(5) the structural defects that will be further developed in the final heat treatment: for example, the coarse crystal structure in the forging of alloy structural steel, if it is not improved in the heat treatment after forging, it will often lead to the thickness of martensite needle and the disqualification of performance after carbon, nitrogen and quenching;The thick band carbide in high speed steel often causes cracking during quenching.
(6) if the heating is not appropriate, such as the heating temperature is too high and the heating time is too long, will cause decarburization, overheating, overheating and other defects.
(7) during the cooling process after forging, if the process is not appropriate, it may cause cooling cracks, white spots, etc., cracking in the heat treatment process.