The Effect Of The Hot Deformation Behavior On 20 And 10B21 Steel Austenite Grain Morphology

Also known as wire rod,drawing mainly for the billets, but also can be directly used as building materials and processed into machine parts.The intrinsic quality of rod is to ensure consistency in the performance of the key organizations.On the surface quality of wire rod,iron oxide composition and thickness of skin,the depth of decarburization layer and so on,have strict requirements.In recent years the development increasingly demand of industrial fasteners for high-performance hot-rolled rod. And the domestic wire rod exist a variety of defects such as the handle, folding, cracking, delamination, mixed grain and so on. Therefore the cause of mixed grain is signifigant to improve the performance of hot-rolled coil.In this paper, the specimen is from domestic iron and steel enterprise where produced 20 and 10B21 hot-rolled wire rod. By the examination of the austenite grain size with different heat treatment, use Gleeble-2000 thermal simulation machine to test two steel under different hot conditions. Make sure the extent of mixed grain and conditions when mixed grain occurred more serious. The main results obtained are as follows:1 10B21 steel,the degree of mixed grain size increases with the cooling rate raises when single-pass deform and increase slowly when multi-pass deform.20 steel,the degree of mixed grain size decreases with the cooling rate raises. The grain size of two types steel enhance when deformation temperature increase. Under the same conditions (deformation temperature,deformation,cooling rate), the average grain size of 10B21 steel is smaller than 20 steel.2 Multi-pass accumulation of deformation, small homogeneous grains only can be got when pass deformation at more than 15%,and mixed structure will be got when the deformation is less than the amount.10B21 steel pass deformation of 10% and 12% will increase mixed grain size when slower cooling rate after deformation. In addition to deformation 8% of 20 steel, The remaining deformation when speed up the cooling rate (4℃/s) will help reduce the occurrence of the phenomenon of mixed grain size after the multi-pass deformation.3 Single-pass deformation, the amount of deformation have significant effects on the 20 steel and little with deformation temperature. When 70% of the amount deformation, Deformed austenite grain of the remaining deformation are uniform in addition to 1050℃, and the average grain size is about 5. The deformation amount of 30% for the mixed grain size is the most serious with the temperature of 950℃and 1000℃.4 10B21 steel, single-pass deformation, the deformation of 10% and 70%, the small grain is got at every deformation temperature,other deformation will be mixed. Deformation appears to increase the temperature of mixed grain to high temperature to promote. At 850℃and 1050℃temperature deformation, no matter the size of deformation, have access to a small uniform grain size. Reduce the cooling rate after deformation in favor of mixed grain size of 10B21 steel to eliminate.