奥氏体逆相变工艺对低碳中锰钢组织性能匹配性的影响

Effect of Austenite Reverted Transformation Process on Match of Microstructure and Mechanical Properties of Low-Carbon Medium-Manganese Steel

采用扫描电子显微镜、X射线衍射仪、电子背散射衍射和透射电子显微镜研究了低碳中锰钢在不同奥氏体逆相变(austenite reverted transformation,ART)处理过程中的组织演变以及影响性能的主要机制。结果表明:为避免奥氏体的不均匀长大和粗化,轧制前铸坯加热温度应控制在1200℃及以下。随着ART温度的升高,试验钢中逆转变奥氏体(reverted austenite,RA)含量逐渐增加,屈服强度逐渐下降,-60℃冲击韧性先升高后下降,但仍保持在150 J以上。低温ART处理后,RA含量较少,Mn主要以(Fe,Mn)_(3)C型短杆状碳化物的形式存在,具有较强的析出强化效果;高温ART处理后,Mn富集于RA中,少量RA长大明显,导致更强的相变诱导塑性效应和塑性提升,但对抑制低温下的裂纹扩展不利。

Microstructural evolution and dominant mechanism whereby the mechanical properties of low-carbon medium-manganese steel were affected during different austenite reverted transformation(ART)processes was investigated by using scanning electron microscope,X-ray diffractometer,electron backscattered diffraction,and transmission electron microscope.The results showed that(a)in order to avoid the hetogenious growth and coarsening of austenite,the heating temperature of slab before rolling need to be controlled at or below 1200℃;(b)With the increase in ART temperature,the content of reverted austenite(RA)increased,the yield strength gradually decreased,and the impact toughness at-60℃raised at first and then decreased,but still kept above 150 J;(c)after ART-treating at lower temperature,the content of RA decreased,and Mn mainly existed in the form of short rod-like(Fe,Mn)_(3)C carbides that had greater precipitation strengthening effect;(d)after ART-treating at higher temperature,Mn was enriched in RA,and a small amount of RA grew obviously,resulting in stronger transformation induced plasticity effect and improvement in plasticity,but being detrimental to inhibiting crack propagation at lower temperature.