Mg对2.25Cr1Mo钢热处理显微组织与力学性能的影响

Effect of trace Mg addition on microstructure and mechanical properties in 2.25Cr1Mo steel

为揭示Mg在低合金钢中的微合金化效果,以2.25Cr1Mo钢为研究对象,利用真空感应炉、450型双辊可逆轧机制备不同Mg含量的15 mm板材,采用OM、TEM等手段分析热处理后显微组织,以及原奥氏体晶粒特征,并对其力学性能进行了测定。研究结果表明:Mg加入2.25Cr1Mo钢中可细化其原奥氏体晶粒,增加热处理组织中多边形铁素体体积分数。2.25Cr1Mo钢全氧含量在0.0003%的低含量条件下,Mg会偏聚在碳化物中,诱使碳化物尺寸降低,数量增多,增强碳化物对奥氏体晶粒长大的钉扎作用,进而达到细化原奥氏体晶粒的效果。经0.005%Mg处理后,2.25Cr1Mo钢冲击韧性稍有提升,而显微硬度变化并不明显。Mg处理后使得钢中铁素体分数出现一定范围内的增加是改善其冲击韧性的重要原因。

In order to reveal the function of Mg micro-alloying in low micro-alloyed steel,the2.25Cr1Mo with 15 mm thick steel plates containing different Mg content were prepared with vacuum induction furnace and rolled with double-stick reversible rolling mill.The characteristics of heat-treated microstructure,primary austenite grain,and mechanical properties were investigated with TEM,OM and so on.The results show that after adding Mg for the heat-treated microstructure,the primary austenite grain size is refined and the ferrite volume fraction is increased.When the total oxygen content of2.25Cr1Mo steel is 0.0003%,Mg will segregate in the carbides,thereby reducing the size of carbides and increasing the amount of these compounds,which increases the pinning effect on austenite grain growth,and then refines the original austenite grain.After adding 0.005%Mg,the impact toughness of2.25Cr1Mo steel is slightly improved,but the microhardness change is not obvious.The increase of ferrite content in steel after Mg treatment contribute to improving its impact toughness.