铸态T/P91耐热合金钢热加工图与热挤压工艺

Hot processing map and hot extrusion of as-cast heat-resistance T/P91 alloy steel

利用热力模拟实验研究铸态耐热合金钢T/P91材料在热加工温度范围900～1200℃、应变速率范围0.01～5 s-1、变形量60%、70%下的真应力-应变曲线,并建立铸态T/P91合金钢的热变形本构方程;利用DMM动态材料模型计算出铸态T/P91合金钢在热变形中的耗散因子和流变失稳判据,绘制出热加工图。结果表明,热加工图预测的安全区晶粒组织均匀、组织易出现失稳开裂和组织粗大的缺陷,T/P91合金钢的热加工要避免高温低应变;利用DEFROM-3D软件通过数值模拟研究挤压工艺参数对挤压过程动态再结晶的影响,制定工艺参数为：挤压温度1500～1200℃,挤压比9,挤压速度26～36 mm/s。

Hot compression experiments of cast heat-resistance T / P91 steel were conducted by thermo-mechanical simulation on a Gleeble-3500 simulator under strain rate ranged from 0. 01 s-1to 5 s-1at temperature ranged from 900 ℃ to 1200 ℃ with deformation of 60% and70%. True stress-strain curves of the as-cast T / P91 steel were obtained and hot deformation constitutive equation was established.Utilizing dynamic material model,the dissipation factor and the flow instability criterion were calculated and the hot processing maps of the T / P91 steel were obtained. The results show that the grains under the safe areas which are predicted by the hot processing map are uniform in size,on the contrary,the structure with defects of instability cracking and coarse grains prevails in the unstable region,so,the hot processing of the T / P91 steel should be avoided conducting under the conditions of high deformation temperature and lower deformation rate. In addition,the numerical simulations for the effect of the extrusion parameters on dynamic recrystallization by DEFROM-3D software give the extrusion parameters as follows： the extrusion temperature is 1500-1200 ℃,the extrusion ratio is 9 and the extrusion speed is 26-36 mm / s,respectively.