SA508-3钢初始晶粒度对热变形后微观组织的作用规律

Effect of initial grain size on microstructure evolution for SA508-3 steel after hot deformation

为研究初始晶粒度对SA508-3钢热变形后微观组织的作用规律,将Φ10mm×15mm圆柱形试样置于电阻加热炉中加热并保温不同时间,以获得不同的初始晶粒度。运用面积法测得保温0min、30min和60min后的微观组织晶粒尺寸分别为650μm、950μm和1200μm。设计并进行了楔形试样高温镦粗实验,研究了SA508-3钢不同初始晶粒度在热变形过程中的动态再结晶体积分数和动态再结晶晶粒尺寸的演化规律。结果表明,当楔形试样压下率为50%时,不同初始晶粒尺寸对发生完全动态再结晶的临界应变有较大影响,初始晶粒尺寸越大,发生完全动态再结晶的临界应变越大。当动态再结晶完全发生时,3种不同初始晶粒尺寸对应的热变形后平均晶粒尺寸分别约为70μm、73μm和75μm。表明当变形量超过临界应变促使发生完全动态再结晶时,初始晶粒尺寸基本不影响热变形后的晶粒尺寸。

The effect of initial grain size on microstructure evolution was studied for SA508-3steel after hot deformation.The cylindrical specimens ofΦ10mm×15mm were heated and held for 0min,30 min and 60 min,respectively.Then three initial grain sizes with 650μm,950μm and 1 200μm were obtained respectively by using area method.Based on the hot upsetting experiments,the dynamic recrystallization volume fraction and average grain size for different initial grain sizes were investigated.The experimental results show that different initial grain sizes have great influence on the dynamic recrystallization process when the reduction rate of wedge-shaped specimen is 50%,and the critical strain of dynamic recrystallization increases with the initial grain size increases.When the dynamic recrystallization is completely finished,the average grain size after hot deformation is 70μm,73μm and 75μm respectively corresponding to three different initial grain sizes,which indicates that the initial grain size has little significant influence on the grain sizes of the deformed material.