The Quality Analysis of the SCM435 Cold Forging Steel and Technical Research on Rolling Process

SCM435 cold heading steel is the main raw material for the production of Advanced fasteners fastener industry . The chemical composition of the products on the rod , the surface quality and the performance of cold heading higher . The SCM435 hot-rolled wire production that often appear cold upsetting surface cracking phenomenon , and the production did not raise the hardness requirements remained after抽测SCM435 cold heading steel hot-rolled wire rod surface hardness (superscript th) -325 . The topics for cold heading steel SCM435 site production , to take appropriate measures to reduce the hardness of the SCM435 cold heading steel hot-rolled wire rod , and practiced and worked out a set of rolling process is suitable for the production line . The main contents and conclusions of the study include the following aspects : ( 1 ) from the SCM435 the CCT curve test results within 1-10 ℃ / s cooling rate will be the formation of bainite , when the cooling rate is less than 1 ° C / s appear ferrite and pearlite , by slow rolling , cold cooling rate as much as possible in the relatively slow cooling of the rollers of the transport line of the insulation cover intrinsic phase change . Therefore, to ensure that the cooling rate of the cooling transport line roller transport line should be to reduce the the SCM435 hardness of key . ( 2 ) stainless steel long products cooling transportation line roller cooling conveyor line 21M insulation cover design , due to the cooling rate is too fast , resulting in the SCM435 hardness value can not achieve the desired level . Through the design and application of the fourth paragraph of the roller conveyor insulation cover , the effect is obvious. (3) The test results show that : the finish rolling temperature and low temperature silking , and wire insulation cover travel speed slow help to reduce the surface hardness . By slow cooling after rolling , as far as possible in the complete phase-change cooling insulation cover internal transport line roller conveyor slower cooling rate . To reduce SCM435 hot cold heading steel wire hardness , spit temperature controlled at 800-850 ℃, and the slow cooling process after silking effect , its hardness from the original down to HB270 HB310 .