宣钢SWRCH35K冷镦钢的质量研究
摘要
为了研究宣钢SWRCH35K冷镦钢的质量问题,通过现场系统取样和试验检测等方法,观察了钢中大型夹杂物,显微夹杂物的形貌,并用扫描电镜对钢中夹杂物做进一步分析,研究了冶炼过程中各个环节的夹杂物类型、数量、分布以及T[O]、N的变化规律;分析了冷镦样和盘条样的表面质量、金相组织、夹杂物等影响冷镦性能的因素,得出冷镦盘条开裂的原因。
研究表明:铸坯的T[O]平均为41×10-6;铸坯N平均值为68.67×10-6;大型夹杂物平均值为105.33mg/10kg,以硅酸盐类的复合夹杂物为主;LF处理后显微夹杂物的含量较处理前有很大减少,说明精炼去除夹杂物效果较好;中间包中的显微夹杂物的数量较LF处理后有所增加,首先,原因为中间包覆盖剂只有碳化稻壳,碳化稻壳有良好的绝热保温作用,但不能防止二次氧化和吸附夹杂物;其次,长水口没有采用氩封而吸入空气;铸坯中的夹杂物中含有Ti、Zn、Na、Ka等元素是来自结晶器保护渣,说明结晶器存在卷渣现象;各个工序显微夹杂物的变化规律与T[O]的变化规律基本一致;冷镦开裂的原因主要是由于盘条表面存在折叠;盘条的金相组织为铁素体+珠光体,铁素体呈块状,铁素体占30%~50%,未发现贝氏体和魏氏体组织;盘条的晶粒度普遍较高,达到9.0~10.0级,会导致抗拉强度提高,冷镦性能变差。虽然没有发现夹杂物直接导致冷镦开裂的现象,但是,较高含量的夹杂物将限制冷镦性能进一步提高。发现钢的夹杂物中含有氯元素,并分析了氯元素的来源和对冶炼的影响。
To research the quality of SWRCH35K cold-heading steel in Xunhua Iron and Steel Co.Ltd, the macro-inclusions and micro-inclusions are observed by the means of on-site systemic sampling and testing detection. Inclusions are further analysed by SEM/EDS. The amount, dimension, distribution, and contents variation of T[O] and N are studied during the production process. To investigate the cracking reasons, the effects such as inclusions, surface quality, metallographlic structure of cold-heading samples and wire rod samples are studied.
It is found that: The contents of T[O] and N in billet are 41×10-6 and 68.67×10-6 in average; The macro-inclusion is 105.33mg/10kg, It is mainly multiplicity of silicate; the amount of micro-inclusion is reduced dramatically after LF process. The results show that: The refining of LF is effective on removing inclusions and the amount of inclusions is higer in the tudish than that after LF process. The reason is that: first, the carbonized rice-hull has only adiabatic function but can not prevent reoxidation and absorbing inclusions in the tudish; secondary, the extended nozzle without argon gas seal absorbs air. The elements of Ti, Zn, Na, and Ka in billet come from the mould flux. It indicates that the entrapment is in mould; the amount variation of micro-inclusion is consistent with the content of T[O] in every site; the surface fold of wire rod is the main reason of crack and the metallographic structure is made up of ferrite and perlite. The ferrite content is about 30%~50% in the lumpish shape and no bainite no marstensite are found in the wire rod. The grain size of wire rod is about 9.0~10.0. This will make the tensile strength increase, and impair the cold-heading performance. Although the inclusion is not the cracking reason, the high level amount of inclusions will restrict the improving of cold-heading performance. Chelorine is found in the inclusion of steel. Chelorine’s source and effect on the smelt precess are analysed.
研究表明:铸坯的T[O]平均为41×10-6;铸坯N平均值为68.67×10-6;大型夹杂物平均值为105.33mg/10kg,以硅酸盐类的复合夹杂物为主;LF处理后显微夹杂物的含量较处理前有很大减少,说明精炼去除夹杂物效果较好;中间包中的显微夹杂物的数量较LF处理后有所增加,首先,原因为中间包覆盖剂只有碳化稻壳,碳化稻壳有良好的绝热保温作用,但不能防止二次氧化和吸附夹杂物;其次,长水口没有采用氩封而吸入空气;铸坯中的夹杂物中含有Ti、Zn、Na、Ka等元素是来自结晶器保护渣,说明结晶器存在卷渣现象;各个工序显微夹杂物的变化规律与T[O]的变化规律基本一致;冷镦开裂的原因主要是由于盘条表面存在折叠;盘条的金相组织为铁素体+珠光体,铁素体呈块状,铁素体占30%~50%,未发现贝氏体和魏氏体组织;盘条的晶粒度普遍较高,达到9.0~10.0级,会导致抗拉强度提高,冷镦性能变差。虽然没有发现夹杂物直接导致冷镦开裂的现象,但是,较高含量的夹杂物将限制冷镦性能进一步提高。发现钢的夹杂物中含有氯元素,并分析了氯元素的来源和对冶炼的影响。
To research the quality of SWRCH35K cold-heading steel in Xunhua Iron and Steel Co.Ltd, the macro-inclusions and micro-inclusions are observed by the means of on-site systemic sampling and testing detection. Inclusions are further analysed by SEM/EDS. The amount, dimension, distribution, and contents variation of T[O] and N are studied during the production process. To investigate the cracking reasons, the effects such as inclusions, surface quality, metallographlic structure of cold-heading samples and wire rod samples are studied.
It is found that: The contents of T[O] and N in billet are 41×10-6 and 68.67×10-6 in average; The macro-inclusion is 105.33mg/10kg, It is mainly multiplicity of silicate; the amount of micro-inclusion is reduced dramatically after LF process. The results show that: The refining of LF is effective on removing inclusions and the amount of inclusions is higer in the tudish than that after LF process. The reason is that: first, the carbonized rice-hull has only adiabatic function but can not prevent reoxidation and absorbing inclusions in the tudish; secondary, the extended nozzle without argon gas seal absorbs air. The elements of Ti, Zn, Na, and Ka in billet come from the mould flux. It indicates that the entrapment is in mould; the amount variation of micro-inclusion is consistent with the content of T[O] in every site; the surface fold of wire rod is the main reason of crack and the metallographic structure is made up of ferrite and perlite. The ferrite content is about 30%~50% in the lumpish shape and no bainite no marstensite are found in the wire rod. The grain size of wire rod is about 9.0~10.0. This will make the tensile strength increase, and impair the cold-heading performance. Although the inclusion is not the cracking reason, the high level amount of inclusions will restrict the improving of cold-heading performance. Chelorine is found in the inclusion of steel. Chelorine’s source and effect on the smelt precess are analysed.
引文
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[2]项程云.合金结构钢[M].北京:冶金工业出版社,2000:313.
[3]林慧国.袖珍世界钢号手册[M].第二版.北京:机械工业出版社, 1998.
[4]殷瑞钰.钢的质量现代进展[M].北京:冶金工业出版社,1995:622-623.
[5]颜根发,陈亮,殷朝海.自攻螺钉专用冷镦钢的开发[J].钢铁,1997,32(7):12-14.
[6] COOK W T, WILLIAMS R G, ALBISTON J N. Cold forging for high strength lower cost steel fasteners[J]. Iron-making and Steel-making, 1995, (22): 117-118.
[7] ERNST WALPER, HEMAN KOHLER. High-tensile bolts without heat treatment[J]. Steel Research, 1993, (8): 437-440.
[8] GILLES PIERSON. Improvements and developments in the cold heading field[J].Wire journal International, 1986, (11): 51-55.
[9] FRANCISCO B, MACEDO D S. Dual-phase steel for 8.8 strength class fasteners[J].Wire journal International, 1993, (9): 70-73.
[10]长古川,丰文,松岛义武.冷镦用钢的要求及发展[J].国外技术,1998,(11):34.
[11]孙维,王开忠.低碳低硅高铝冷镦钢小方坯连铸工艺研究[J].炼钢,2005,21(4):34.
[12]傅余东.喂线技术与钢中铝含量的控制[J].湖南冶金,2002,(4):34.
[13]赵岳龙.湘钢含铝冷镦钢的开发[J].湖南冶金,2004,(4):36.
[14]汤伟,杨琦云. SWRCH18A冷镦钢生产实践[J].湖南冶金,2005,(4):21.
[15]刘振成,候基林,姜德刚. SWRM12盘条钢试制[J].炼钢,2004,20(2):15.
[16]周建男,袁长波,姜世全.冷镦钢性能试验研究[J].冶金标准化与质量,2005,43(2):19.
[17]李义长. ML35冷镦用圆钢的工艺研究[J].四川冶金,2005,27(6):14.
[18]陈钢,王金平,王国平.连铸铝镇静钢冷镦钢方坯生产实践[C].第十二届全国炼钢学术会议论文集,北京:2002:70-73.
[19]马志军,赵贤平,踞艳军,等. SWRCH35K盘条冷镦开裂原因探讨[J].河南冶金,2005,13(5):24.
[20]申景霞,何庆文,倪有来,等.高强度标准件用ML35钢的开发[J].山东冶金,1997,19(2):36.
[21]缪新德,钱刚,邹文喜,等.连铸ML35的开发[J].炼钢,1999,15(6):38.
[22]张春燕,陈嘉华,吉学军. SWRCH22A冷镦钢线材拉拔断裂分析[J].金属制品,2004,30(1):35.
[23] GILLES RIGANT,SERGE TASSUN. New steel grades for cold heading quality[J]. Wire journal international, 1988, (2): 34 -42.
[24] RICARDO MACEDODOS,SANTOS,DELMAR BARROS,etc. Development of a low carbon steel wire rod through continuous casting and controlled cooling After rolling[J]. Wire journal internatio-nal, 1992, (1): 65-70.
[25]刘学华,茆勇,宋超,等. BOF—LF—CC工艺生产冷镦钢纯净度的研究[J].钢铁,2005,40(2):27.
[26]陈奇明.低碳冷镦钢的冶炼控制[J].湘钢科技,2003,(2):3.
[27]曹同友,刘万善.武钢三炼钢厂工序过程磷的控制[J].钢铁研究,2002,(1):6-7.
[28] Emi T.炼钢与钢水精炼系统的理论与操作经验[C].第二阶段届全国炼钢学术会议境外专家论文集,攀枝花:中国金属学会炼钢分会,1994:7-15.
[29]左腾秀树.高纯净钢的铁水预处理技术和转炉技术[J].世界钢铁,1996(8) :1-4.
[30]蔡开科.钢洁净度的控制[C].第十届全国炼钢年会论文集,中国郑州:1998:70-76.
[31]小川兼宏.熔炼高纯净钢的渣精炼技术[J].世界钢铁,1996,(8):28-41.
[32]李伟,张寿禄,郝旭明.采用渣精炼提高连铸含硼冷镦钢洁净度的实践[J].太钢科技, 2005,(2):6.
[33]王丽萍,李晓星,于广石.冷镦钢线材生产工艺控制及其表面缺陷的分析[J].首钢科技,2002,(4):20.
[34] Dieter. Improvement of castability and quality of continuously cast steel[J].ISIJ International, 2000, (1): 31.
[35] KOO Y S,KANG T,LEE I R. Thermal cycle model of ladel for steel temperature control in melt and its application[C]. Steelmaking Conference Proceedings, Tokyo: 1989: 415-420.
[36] CHAKRABORTY S, DUKELOW D A. Correlation of steel cleanliness with operating parameters through total oxygen studies[C]. Steelmaking Conference Proceedings,. Dallas: AIME: 1993: 487-496.
[37] BRINKMEYER L,MELVILLE S D. Factor affecting cleanliness of continuously cast steel[J]. Iron and Steelmaking, 1995, 6, (22): 502-507.
[38] MCPHERSON N A. The effect of tundish design on the quality of continuously cast steel slabs[J]. MPT. 1986, (3): 40-51.
[39] GATELLIER C, OLETTE M. Kinetics of high temperature[J]. Metallurgy, 1979, (79): 377-386.
[40]张彩军.管线钢显微夹杂物行为研究[D].北京:北京科技大学,2003.
[41] MITTEILUNG A S. Deoxidation and desulphurization by blowing of calcium compounds into molten steel and its effects on the mechanical properities of heaby plates[J]. Stahl U.Eisen, 1974, (11): 74-485.
[42]汤曙光.洁净钢精炼实践[J].炼钢,2003,19,(5):10-14.
[43] KIEDSSLING R. Non-metallic inclusion in steel[M]. London: Met Soc, 1978: 11-62.
[44] STOUVENOT F, GAYE H. Secondry steelmaking slag treatment for inclusions control in semi-killed steels[C]. Electric Furnace Conference Proceedings, 1994, (52): 423-428.
[45] NISHI S. Melting of Clean Maraging Steel by Vacuum Induction Method[R], R & D Kobe Steel Report, 1989, 39 (1): 73.
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