链轮用40Cr钢温挤压精密成型热力模拟试验

Thermal simulation of warm extrusion of a 40Cr steel used for chain wheel

利用Gleeble3800型热力模拟试验机对40Cr试样进行热压缩试验,得到不同温度和应变速率下的应力-应变曲线。用XRD、SEM和OM对热压缩后试样表面物相和金相形貌进行表征,分析了不同温度和不同应变速率下,热压缩对试样表面组织性能的影响。结果表明:变形抗力与应变速率成正比,与试验温度成反比,残留奥氏体含量同样遵循此规律;650℃时表面以片状珠光体为主,750℃时表面组织以马氏体和贝氏体为主,随着温度升高,材料表面出现轻微氧化;在650℃时可获得约350 MPa的平均残余应力,且在同一温度下,应变速率的提高有利于提高表面残余应力,这将有利于提高材料的抗疲劳性能。

Hot compression tests of 40 Cr steel were carried out on a Gleeble3800 thermal mechanical simulator,and the stress-strain curves of the steel deformed at different temperatures and strain rates were analyzed. The phases and microstructure of the sample surface after hot compression were characterized by XRD,SEM and OM. The sample surface microstructure and its mechanical properties were discussed. The results show that the deformation resistance and the content of residual austenite are proportional to strain rate and inversely proportional to test temperature. The main microstructure of the sample surface deformed at 650 ℃ is lamellar pearlite,and the main microstructure of the deformed sample surface at 750 ℃ consists of martensite and bainite. With the increase of temperature,the surface of the material is slightly oxidized. The average residual stress of the sample deformed at 650 ℃ is about 350 MPa,and the increasing of strain rate can enhance the surface residual compressive stress,which is beneficial to improving the fatigue resistance of the material.