The rough gear quenching after cause analysis

by:Hengyang Furnace     2021-01-09
Organization's massive after carburizing, quenching, tempering gear banded structure of raw materials is relatively serious, banded structure level are at level 3 above. Tissue defects, banded structure belongs to a kind of material is as raw materials organization segregation, in the process of forging and rolling elongated. Due to the uneven material composition and organization, uneven when heated to high temperature of the grain grew up, resulting in the organization's massive phenomenon. Therefore must be from the source to control raw material, put an end to composition segregation seriously, organization, coarse grains of material into production. So when the raw material incoming inspection, must strengthen the control of the process of test, to avoid the unqualified raw materials circulation under the production process. Intermediate process of heat treatment process also has a great influence, in the products once appear the phenomenon of organization is bulky, also can bring organization and performance degradation. When first hot working forging, too hot heating materials organization bulky. Next higher heating temperature, can form the stabilization of overheating bulky organization, this organization has transmissibility, normal heat treatment method is difficult to eliminate. Finish forging temperature is low, the organization is difficult to reply recrystallization, will be formed in the formation of fibrous tissue and banded structure, appear even bainite and martensite non-equilibrium organization, organization, make the post heat treatment uneven grain growth, also will cause the coarse grains. Must also be a deformation control forging process, in order to avoid the critical deformation within the scope of the thick grain structure formation. Strengthen the quality control of intermediate hot working process, all hot working procedures from product circulation, ensure material organization keep grain size. Especially in forging temperature control, must control the forging process of forging and finish forging temperature. Forging heating of forging temperature, general control in 950 ~ 1 050. C, finish forging temperature control in 850 ~ 950 ℃. Hot working normalizing treatment after forging process, the heating temperature is too high and likely to cause a group phenomenon. And after normalizing treatment, cooling rates too fast, easy to form the stable organization, such as westergren body, granular bainite and martensite and austenite transformation product, the presence of these organizations, also can cause massive group of transmissibility. To strengthen the operation technology of normalizing treatment at the same time, the purpose of normalizing treatment is to uniform organization, refine the grain, late for carburizing and quenching tempering treatment for organization and properties of security.
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