微量稀土元素对低碳钢相变温度的影响

Effect of Trace Rare Earth Elements on Transformation Temperature of Low Carbon Steel

通过测量不含稀土元素、含微量(总含量小于20×10-6)稀土元素两组实验钢相变点Ac1和Ac3,对比研究了微量稀土元素对低碳钢相变点的影响。选取两组不同合金成分体系实验钢作为研究对象,分别采用赛特拉姆分析仪和Formastor-FⅡ型全自动相变仪测量其相变点,探索微量稀土元素对低碳钢相变点的影响规律。利用光学显微镜观察两组实验钢原始奥氏体晶粒尺寸变化情况,利用冲击实验机进行-40℃低温冲击韧性检测,分析相变点的变化趋势。实验结果表明,微量稀土元素对低碳微合金本质细晶粒钢的Ac1点影响不大,但对普通碳锰钢影响较大,使其Ac1点约提高19℃;微量稀土元素的加入,使两种合金体系实验钢的Ac3均升高了20℃左右;金相观察表明,加入稀土的实验钢原始奥氏体晶粒尺寸均有不同程度细化,进一步证明了微量稀土元素对Ac3相变点的影响规律。-40℃低温冲击结果也显示,细化晶粒后的稀土钢具有更好的冲击韧性,约提高50 J~100 J。研究结果为企业开发低成本、高强度、高韧性稀土钢的变形工艺、热处理工艺提供了参考依据。

The influence of trace rare earth elements on the transformation point of low carbon steel was studied by measuring the transformation point Ac1 and Ac3 of two groups of experimental steels,which contain no rare earth elements and trace rare earth elements(the total content is less than 20×10-6).Two groups of experimental steels with different alloy composition system were selected as the research objects,and their transformation points were measured by setram analyzer and formastor-f full-automatic transformation instrument respectively to explore the effect of trace rare earth elements on transformation points of low carbon steel.The change of original austenite grain size of two groups of experimental steels was observed by optical microscope,and the impact toughness at-40℃was tested by impact tester,and the change trend of transformation point was analyzed.The experimental results show that the trace rare earth elements have little effect on the AC1 point of the low carbon microalloyed fine grain steel,but have a great effect on the common carbon manganese steel and increase the Ac1 point by about 19℃;the trace rare earth elements increase the Ac3 of the two alloy system experimental steels by about 20℃;the metallographic observation shows that the original austenite grain size of the test steel with rare earth elements was refined.The results of low temperature impact at 40℃also show that the RE steel with refined grains has better impact toughness.The research results provide a reference for enterprises to develop the deformation process and heat treatment process of low cost,high strength and high toughness rare earth steel.