轴承钢中D类夹杂物的形成与控制
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摘要
轴承钢对钢中非金属夹杂物,尤其是对D类夹杂物的要求非常严格.为了分析国内某钢厂GCr15轴承钢棒材试样探伤不合的D类夹杂物形成原因并提出有效控制措施,采用ASPEX自动扫描电镜对GCr15轴承钢生产工艺优化前后全流程夹杂物的演变进行观察.研究结果表明,原工艺下轴承钢中D类钙铝酸盐夹杂物生成的主要原因包括两个方面,一是精炼渣碱度过高导致渣中Ca O活度很大;二是在真空脱气(VD)精炼过程中,强烈搅拌给钢-渣反应提供了良好的动力学条件.本文从精炼渣碱度和VD真空度两方面对轴承钢生产工艺进行了优化.优化后能够在保持高洁净度情况下,使钢中夹杂物由钙铝酸盐类转变为镁铝尖晶石类,减少了轴承钢中D类夹杂物的生成.
There are strict requirements for non-metallic inclusions in bearing steel,especially for Type-D inclusions. To analyze the formation mechanism of Type-D inclusions in high-frequency detection defects of GCr15 bearing steel bar sample in domestic steel plant and give the effective controlling measure,the inclusion evolution in bearing steel production process before and after optimization was investigated by ASPEX automatic scanning electron microscope. The results show that,the main formation mechanism of calcium aluminate Type-D inclusions present in the original process includes two aspects: one is the high basicity of refining slag,resulting in the high Ca O activity in slag. The other is the strong stirring in vacuum degassing(VD) process,providing good kinetic conditions for slag-steel reactions. The bearing steel production process is optimized from the basicity of refining slag and the vacuum degree of VD process. After optimization,the inclusions change from calcium aluminate to spinel type,and the formation of Type-D inclusions in bearing steel is reduced. Meanwhile,the high cleanliness of bearing steel is maintained.
There are strict requirements for non-metallic inclusions in bearing steel,especially for Type-D inclusions. To analyze the formation mechanism of Type-D inclusions in high-frequency detection defects of GCr15 bearing steel bar sample in domestic steel plant and give the effective controlling measure,the inclusion evolution in bearing steel production process before and after optimization was investigated by ASPEX automatic scanning electron microscope. The results show that,the main formation mechanism of calcium aluminate Type-D inclusions present in the original process includes two aspects: one is the high basicity of refining slag,resulting in the high Ca O activity in slag. The other is the strong stirring in vacuum degassing(VD) process,providing good kinetic conditions for slag-steel reactions. The bearing steel production process is optimized from the basicity of refining slag and the vacuum degree of VD process. After optimization,the inclusions change from calcium aluminate to spinel type,and the formation of Type-D inclusions in bearing steel is reduced. Meanwhile,the high cleanliness of bearing steel is maintained.
引文
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[10] Liu C Y,Huang F X,Wang X H. The effect of refining slag and refractory on inclusion transformation in extra low oxygen steels.Metall Mater Trans B,2016,47(2):999
[11] Chen P J,Zhu C Y,Li G Q,et al. Effect of sulphur concentration on precipitation behaviors of MnS-containing inclusions in GCr15 bearing steels after LF refining. ISIJ Int,2017,57(6):1019
[12] Li J X. Analysis and Control of Inclusions in GCr15 Bearing Steel[Dissertation]. Chongqin:Chongqing University,2016(李敬想. GCr15轴承钢夹杂物分析与控制研究[学位论文].重庆:重庆大学,2016)
[13] Huang F X,Zhang L F,Zhang Y,et al. Kinetic modeling for the dissolution of Mg O lining refractory in Al-killed seels. Metall Mater Trans B,2017,48(4):2195
[14] Shen P,Zhang L F,Zhou H,et al. Wettability between Fe--Al alloy and sintered Mg O. Ceram Int,2017,43(10):7646
[2] Ha H Y,Park C J,Kwon H S. Effects of non-metallic inclusions on the initiation of pitting corrosion in 11%Cr ferritic stainless steel examined by micro-droplet cell. Corros Sci,2007,49(3):1266
[3] Oguma N,Lian B,Sakai T,et al. Long life fatigue fracture induced by interior inclusions for high carbon chromium bearing steels under rotating bending. J ASTM Int,2010,7(9):1
[4] Murakami Y. Metal fatigue:effects of small defects and nonmetallic inclusions. Chromatographia,2002,70(7):1197
[5] American Society for Testing Materials Committee. Effect of Steel Manufacturing Process on the Quality of Bearing Steels. Ed by Hoo J J C. Philadelphia:American Society for Testing Materials,1988
[6] Ma W J,Bao Y P,Wang M,et al. Influence of slag composition on bearing steel cleanness. Ironmaking Steelmaking,2014,41(1):26
[7] Yoon B H,Heo K H,Kim J S,et al. Improvement of steel cleanliness by controlling slag composition. Ironmaking Steelmaking,2013,29(3):215
[8] Duan J H,Zhang L F,Yang W,et al. Ds inclusion control in GCr15 bearing steel//Chinese Ladle Refining Conference and Steel Quality and Inclusion Control Annual Meeting. Quzhou,2017:300(段加恒,张立峰,杨文,等. GCr15轴承钢中Ds类夹杂物控制//2017年全国炉外精炼年会暨第17届钢质量与非金属夹杂物控制学术年会论文集.衢州,2017:300)
[9] Sakata K. Technology for production of austenite type clean stainless steel. ISIJ Int,2006,46(12):1795
[10] Liu C Y,Huang F X,Wang X H. The effect of refining slag and refractory on inclusion transformation in extra low oxygen steels.Metall Mater Trans B,2016,47(2):999
[11] Chen P J,Zhu C Y,Li G Q,et al. Effect of sulphur concentration on precipitation behaviors of MnS-containing inclusions in GCr15 bearing steels after LF refining. ISIJ Int,2017,57(6):1019
[12] Li J X. Analysis and Control of Inclusions in GCr15 Bearing Steel[Dissertation]. Chongqin:Chongqing University,2016(李敬想. GCr15轴承钢夹杂物分析与控制研究[学位论文].重庆:重庆大学,2016)
[13] Huang F X,Zhang L F,Zhang Y,et al. Kinetic modeling for the dissolution of Mg O lining refractory in Al-killed seels. Metall Mater Trans B,2017,48(4):2195
[14] Shen P,Zhang L F,Zhou H,et al. Wettability between Fe--Al alloy and sintered Mg O. Ceram Int,2017,43(10):7646