含氮半高速钢冷轧辊材料回火组织转变研究

Study on microstructure transformation of semi-high speed steel cold roll material containing nitrogen during tempering process

合金多元化是提高轧辊性能的重要方式,氮合金化是强化方式之一。针对半高速钢冷轧辊材料组织转变的研究集中在回火二次硬化阶段,缺乏对含氮半高速钢材料的回火组织转变研究。本文根据回火过程中硬度与组织随回火温度变化的关系,将回火过程划分为四个阶段,并对每个阶段组织的转变行为进行了分析,结果表明:含氮半高速钢冷轧辊材料淬火后基体组织为以位错马氏体为主的混合组织,未溶碳化物相包括富铬和铁的M7C3碳化物和富钒并含氮的M(C,N)碳氮化物。整个回火处理过程中,一次M(C,N)和M7C3保持较强的稳定性;随着回火温度的升高,含氮半高速钢材料微观组织会发生一系列变化;在回火温度逐步提高的过程中,伴随着微观组织的转变和碳化物的析出、溶解等现象,在一定程度上影响了材料的硬度、力学性能和使用性能。

Nitrogen alloying is one of the most popular processes in alloy diversity,which is used to improve the property of semi-high speed steel roll.The researches,on the microstructure transformation of semi-high speed steel cold roll,focused on secondary hardening tempering process,and lack of the analysis of nitrogen alloying behavior.In this paper,the tempering processes of semi-high speed roll was divided to four stages,according to the variations of hardness and microstructure with the tempering temperature,and the microstructure transform of each stages was analyzed.The results reveals that the microstructure of cold roll material of nitrogen-containing semi-high speed steel after quenching are consists of dislocation martensite,undissolved carbide phases including M7C3 carbide rich in chromium and iron and M(C,N)rich in vanadium and containing nitrogen.In the whole tempering aging process,M(C,N)and M7C3 maintain strong stability.While the transformation of microstructure and the precipitation and dissolution of carbides will occur accompany with the increase of tempering temperature,which may influence the hardness,mechanical properties and serviceability of semi-high speed steel cold roll material containing nitrogen.