在实验室条件下向GCr15轴承钢中添加Ni?Mg合金进行镁合金化，研究了镁对液析碳化物的影响规律，用电感耦合等离子体原子发射光谱仪分析了钢中的镁含量，用光学显微镜统计了随机选取的100个视场中的液析碳化物出现的数量、最大尺寸及其平均值。结果表明，通过NiMg合金化，Mg能较顺利加入钢液中，在钢中的平均收率为9.20%。液析碳化物数量、最大尺寸、平均最大尺寸均随镁含量提高先减少后增加，镁含量为16?10?6(wt)时效果最佳。未添加镁时，液析碳化物呈大块状析出，加镁后仍以块状为主，但尺寸更细小。微量镁细化液析碳化物的主要原因在于，镁原子向晶界或相界偏聚，阻碍C和Cr等元素扩散，抑制液析碳化物长大；同时添加镁形成的大量细小MgS?MnS可诱导碳化物析出，使碳化物弥散化，也起到细化液析碳化物的效果。
关键词：
轴承钢; 镁; 液析碳化物; 凝固; 偏聚
Eutectic carbides are very harmful to bearing steel, which is easy to cause stress concentration and lead to premature failure of bearing. Reducing the number of eutectic carbides and refining the size of carbide is one of the key factors to improve the fatigue life of bearing steel. Therefore, the effect of magnesium on the carbide was studied systematically by adding Ni?Mg alloy to GCr15 bearing steel. The magnesium content in steel was analyzed by ICP-OES method. The number, maximum size and average maximum size of the eutectic carbide in the 100 randomly selected field of view were counted by the optical microscope. The eutectic carbide was observed by SEM. The results showed that magnesium could be added to molten steel and the average yield of magnesium in steel was 9.20%. The number, maximum size and average maximum size of the eutectic carbide decreased first and then increased with the increase of magnesium content in the GCr15 steel. The refinement effect of magnesium on the eutectic carbide was best when the magnesium content in GCr15 bearing steel was 16?10?6(wt). The eutectic carbide precipitated in the large and lump shape in the steel without magnesium. When magnesium was added to the steel, carbides were still lumpy, but smaller in size. The main reason for the refinement of the eutectic carbide by trace magnesium was that the diffusion of magnesium atoms to the grain boundary or the phase boundary hindered the diffusion of C and Cr elements, so that the formation and growth of eutectic carbide was inhibited. At the same time, a large number of fine MgS?MnS could induce the precipitation of eutectic carbides, which led to the dispersion of carbides and make the carbide finer.
[1] Du Gang, Li Jing,Wang Zhong-Bing. Control of Carbide Precipitation During Electroslag Remelting-Continuous Rapid Solidification of GCr15 Steel[J].Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science，2017，48（6）: 2873-2890.
[2] Qi Yong-feng,Li Jing, Shi Cheng-bin et al. Effect of directional solidification of electroslag remelting on the microstructure and primary carbides in an austenitic hot-work die steel[J]. Journal of Materials Processing Technology,2017,249(11): 32-38.
[3] 贺宝，李晶史，成斌，等. 电渣重熔过程冷却强度对含镁H13钢中碳化物的影响[J].工程科学学报，2016，38（12）：1720-1727.
[4] 陈锟. 控制Cr5钢冷轧辊坯质量的锻造变形工艺研究[D]，2011，11,上海大学.
[5] 于瑞芝，刘洪波. 加热温度与时间对MC5 轧辊钢液析碳化物溶解扩散的影响[J].特钢技术，2013，19（2）：31-34,51.
[6] 常立忠， 施晓芳， 从俊强，等. 结晶器旋转对电渣重熔钢锭中元素分布的影响[J].过程工程学报，2014,14（2）:266-272.
[7] L. Z. Chang, X. F. Shi, J. Q. Cong et al. Effects of relative motion between consumable electrodes and mould on solidification structure of electroslag ingots during electroslag remelting process[J]. Ironmaking and steelmaking, 2014,41（8）：611-617.
[8] 龚伟，姜周华， 战东平，等. 轴承钢中镁的行为热力学分析[J]. 过程工程学报，2009,9（S1）:117-121.
[9] 王昊，李晶，王亮亮. 镁对H13模具钢中夹杂物变性的影响[J]. 中国科技论文，2014,9（2）：175-177.
[10] 王德永，徐周，屈天鹏. 镁处理对低碳微合金钢中夹杂物和凝固组织的影响[J].炼钢，2017,33（5）：12-18.
[11] 王承，龚伟，姜周华，等.镁对冷作模具钢碳化物及热塑性的影响[J].工程科学学报,2016,38(04):501-506.
[12] 刘军，陆青林，李铮，等.轴承钢中微量镁改善碳化物作用机理研究[J].钢铁研究学报,2011,23(05):39-44.
[13] 李勇勇,王亮亮,宁博. Mg对退火后H13模具钢力学性能的影响[J].南方金属,2013(02):48-53.
[14] Shuqi Wang, Qichuan Jiang, Yuguang Zhao et al. Cast Cr12MoV die steel with granular carbide modified by Re-Mg compound[J]. Journal of Materials Science Letters,1996,15(3): 256-257
[15] Li.J.,Shi.C.B.,Wang.L.L.,et al. Effect of trace magnesium on carbide improvement in H13 steel[J]. Canadian Metallurgical Quarterly, 2016, 55(3): 321-327.
[16] Ge. H.L., Youdelis. W.V., Chen. G.L. Effect of interfacial segregation of magnesium on high carbon (18%Cr) cast steel, [J]. Materials Science and Technology,1989,5(12): 1207-1211.
[17] 郑万，吴振华，李光强，等. Ti--Mg 复合脱氧和硫含量对钢中夹杂物特征及MnS析出行为的影响[J].工程科学学报，2015，37（3）：292-300.
[18] 刘艳华,赵德忠. 轴承钢碳化物液析缺陷的控制工艺探讨[J].金属世界，2012,2：45，49.
[19] 左毅,米振莉，李志超. 加热工艺对轴承钢连铸坯液析碳化物溶解行为的影响[J].材料热处理学报，2016，37（2）：146-137.
[20] 孔祥华，刘建尊，刘在龙，等．高温变形处理对GCr15 轴承钢液析碳化物的影响[J].热处理学报，2014，35(7): 173-176．
[21] 钟顺思，王昌生． 轴承钢[M]． 北京: 冶金工业出版社，2000.
[22] 胡赓祥等. 材料科学基础[M]. 上海：上海交通大学出版社，2001.
[23] Chen Guoliang，Ge Honglin. Computer simulation of grain boundary segregation behavior and mechanisms of strengthening of Mg in Ni-based superalloys[J].Journal of University of Science and Technology Beijing,1995，2(02): 84-91.
[24] Mclean D. Grain Boundaries in metals[M]. London,Oxford Universeristy Press,1957.
