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在Gleeble-3500热模拟试验机上,利用应力松弛试验研究了钛微合金化IF钢奥氏体区第二相粒子析出行为。试验结果表明:因第二相粒子析出钉轧位错与晶界,应力松弛曲线呈现出3个阶段的特征。试验钢的析出-时间-温度曲线呈现出典型的“C”曲线形状,最快析出鼻子点温度约为900℃,在此温度下,第二相粒子析出开始时间与结束时间分别为10与160 s;随着等温弛豫时间的延长,第二相粒子析出数量逐渐增加,当弛豫时间超过析出结束时间后,析出物数量将不再增加而尺寸增加。试验用Ti-IF钢主要观察到Ti N、Ti4C2S2、Ti C 3种析出物,Ti4C2S2与Ti C沉淀物的形状和尺寸相差不多,无法从形状和大小上来区分,易于沿奥氏体晶界或亚晶界析出,奥氏体亚晶的尺寸大约分布在0.1~0.4μm。900℃应变诱导析出物数量较800℃多,该结果与试验钢PPT曲线析出鼻子点温度900℃是相符的。对于Ti-IF钢,其热轧工艺过程应有利于C,N化物的析出和聚集长大,最终形成粗大、稀疏的第二相粒子,因此宜采用“三低一高”快速大压下的热轧工艺制度,以提高Ti-IF钢的深冲性能。
On the Gleeble-3500 thermal simulator, the stress relaxation test was used to study the precipitation behavior of second phase particles in the austenite region of titanium microalloyed IF steel. The experimental results show that the stress relaxation curves show three stages of characteristics due to the second phase particles precipitating pinning dislocation and grain boundaries. The precipitation-time-temperature curve of the test steel shows a typical “C” curve shape, and the temperature of the fastest precipitation nose is about 900 ° C. At this temperature, the onset time and the end time of the precipitation of the second phase particles are respectively 10 And 160 s, respectively. With the extension of the isothermal relaxation time, the amount of second phase particles precipitated gradually increased. When the relaxation time exceeded the end of precipitation, the amount of precipitates would no longer increase but increased in size. The Ti-Ti, IF, Ti4C2S2 and TiC precipitates were mainly observed in the Ti-IF steels tested. The shapes and sizes of the Ti4C2S2 and TiC precipitates were similar and could not be distinguished from the shape and size, Subgrain boundary precipitation, austenite sub-size distribution of about 0.1 ~ 0.4μm. The number of strain-induced precipitates at 900 ° C was more than 800 ° C, which was in agreement with the temperature of 900 ° C at the nose point of the PPT curve of the test steel. For Ti-IF steel, the hot-rolling process should be conducive to the precipitation of C, N compounds and aggregation and growth, the final formation of coarse, sparse second-phase particles, it is appropriate to adopt Under the hot-rolled process system to improve the deep-Ti-IF steel performance.