摘要
为了研究硼铬微合金钢的脆性断裂失效机理,以工厂履带拖拉机支重轮的中心轴脆性断裂为研究背景,通过对中心轴断口的观察以及不同位置的组织和晶粒度的对比,得出了硼铬微合金钢的断裂失效机理。利用FactSage和Thermo-Calc软件对TiN夹杂物的析出机理和控制进行理论计算。结果表明,钛合金的不完全溶解和钛、氮元素质量分数的不合理控制,导致大量的大尺寸硬质TiN夹杂物在凝固过程中析出,使得钛元素的加入没有起到很好地细化晶粒的效果,中心区域的铁素体+奥氏体组织的晶粒度过于粗大。大尺寸TiN夹杂物作为裂纹源和心部粗大的晶粒导致了硼铬微合金钢的脆性断裂失效。热力学计算表明,TiN夹杂物在凝固过程中形成,低钛低氮和钛、氮质量分数的合理搭配可以有效推迟TiN夹杂物的析出,降低其尺寸。较小的夹杂物尺寸和细小的晶粒均可以有效增强材料抵抗裂纹扩展的能力。
In order to identify the fracture failure of B-Cr microalloyed steel,the brittle fracture of track roller during the operation of tracking tractor was taken as the research background.The fracture failure of TiN inclusion on B-Cr microalloyed steel was studied by observing the fracture surface of the central axis and comparing the microstructure and grain size at different positions.The FactSage and Thermo-Calc software were used to calculate the formation and control mechanism of TiN inclusion.The results were as follows.Due to the incomplete dissolution of Ti alloy and irrational control of Ti and N mass fraction in the molten steel,lots of large-size TiN inclusions were formed during the solidification of B-Cr micro-alloyed steel.The addition of Ti element did not play agood role in refining grain,resulting in the large grain size in the center,and further reducing the impact property of B-Cr microalloyed steel.Large-size TiN inclusion acted as the crack origin and the large grain size led to the brittle fracture of B-Cr microalloyed steel.Thermodynamic calculation showed that the TiN inclusion formed during the solidification process and the precipitation temperature of TiN can be effectively delayed with low Ti and N mass fraction in molten steel.Small inclusion size and fine grain size can effectively enhance the crack resistance of the material.
作者
黄宇
成国光
杨洪根
代卫星
李世健
HUANG Yu;CHENG Guo-guang;YANG Hong-gen;DAI Wei-xing;LI Shi-jian(State Key Laboratory of Advanced Metallurgy,University of Science and Techonlogy Beijing,Beijing 100083,China;Technology Center,Kunshan Track Co.,Ltd.,Suzhou 215313,Jiangsu,China)
出处
《中国冶金》
CAS
北大核心
2019年第1期38-44,共7页
China Metallurgy
基金
国家自然科学基金资助项目(51874034
51674024)
