超声振动下Q235钢奥氏体再结晶模型的适用性试验研究

超声振动改变碳素钢热变形条件,从而影响形变后微观组织。通过仿真和试验分析了超声振动条件下两组常用碳素钢奥氏体再结晶模型的适用性。结果表明:Q235圆柱试样1150℃加热5 min完成奥氏体化后,超声振动形变处理试样内奥氏体再结晶平均晶粒尺寸更接近C. M. Sellars模型的计算结果。试样950℃加热完成奥氏体化,800～700℃温度区间超声振动形变处理,因试样表层不具备发生铁素体动态再结晶温度条件,距表层50μm深度范围内,超声振动剧烈形变导致组织纳米化;而试样内部超声振动造成了高Z值条件,铁素体动态再结晶晶粒明显细化。

Experimental research on applicability of austenite recrystallization model of Q235 steel under ultrasonic vibration

Ultrasonic vibration can greatly affect the thermal conditions of plain carbon steel during hot deformation,and therefore,determine the final microstructure in the deformed steel. The applicability of two commonly used austenite recrystallization models of he plain carbon steel Q235 under ultrasonic vibration condition were investigated by means of FEM simulation and experiments. The results show that the average grain size of austenite recrystallization in the Q235 cylindrical specimen, when heated at 1150 ℃ for 5 min to complete austenitization and then undertaken hot upsetting with ultrasonic vibration,is closer to that of the C. M. Sellars model. Severe ultrasonic vibration deformation results in nanocrystallization within a depth of 50 μm from the surface of specimen,because the surface of the specimen austenitized at 950 ℃ and compressed with ultrasonic vibration at 800 ℃ to 700 ℃ does not have the temperature condition for ferrite dynamic recrystallization. Ultrasonic vibration cause the increase of the Z parameter inside the specimen, so the ferritic dynamic recrystallized grains are refined compared to the normalized microstructure.