子午线轮胎用帘线钢非金属夹杂物的研究进展

随着汽车轻量化的发展,子午线轮胎用帘线钢对夹杂物的要求越趋严格。根据钢帘线用盘条对夹杂物的要求,综述了国内外帘线钢冶炼工艺和目前关于帘线钢中夹杂物的研究进展,并对未来需关注的夹杂物控制方向提出观点。随着90级极高强度级帘线钢将成为主流产品,富含Al_2O_3类夹杂物和钛夹杂物依旧是控制的重难点所在。除了进一步加强冶炼过程中夹杂物塑性化控制外,对于轧制和拉拔等各个环节中夹杂物的性质行为都应予以重视,从而更好地实现全过程控制。     

帘线钢凝固过程夹杂物生成热力学及工业实践

 非金属夹杂物是影响帘线钢拉拔性能的重要因素之一,为了研究帘线钢中夹杂物的生成及转变机理,使用ASPEX自动扫描电镜观察分析了帘线钢工业生产过程中不同碱度条件下从钢液到铸坯中非金属夹杂物的转变现象,并使用FactSage7.0热力学计算软件对非金属夹杂物的转变机理进行了讨论。在高碱度条件下,钢液中非金属夹杂物主要类型为低熔点的CaO-SiO₂-Al₂O₃-MnO,铸坯中非金属夹杂物的CaO和MnO含量有所降低,同时SiO₂含量有所增加。在低碱度炉次中,钢液中非金属夹杂物主要为较高熔点的SiO₂-MnO-CaO类型,Al₂O₃含量较低。连铸坯中非金属夹杂物的SiO₂含量与钢液相比有所增加,同时MnO含量降低。热力学计算结果表明,帘线钢凝固和冷却过程中的非金属夹杂物转变由夹杂物自身的相转变和析出、非金属夹杂物和钢液间的化学反应以及溶解氧和钢基体化学成分的反应3方面原因造成。热力学计算结果较好地解释了帘线钢工业生产中钢液和铸坯中非金属夹杂物成分和形貌的转变,为帘线钢中非金属夹杂物的控制提供参考。     

含锆氧化镁耐火材料对帘线钢中夹杂物的影响

通过实验研究了含锆氧化镁耐火材料对帘线钢中夹杂物成分的影响,并采用熔点测试和热力学计算考察了ZrO_2对帘线钢中夹杂物熔点的影响规律.研究发现MgO耐火材料能使帘线钢中夹杂物的MgO含量上升.耐火材料中微量的ZrO_2也会对钢中的夹杂物产生较大的影响.ZrO_2使帘线钢中SiO_2-MnO-Al_2O_3系夹杂物和SiO_2-CaO-Al_2O_3系夹杂物熔点显著升高,使夹杂物塑性变差.在帘线钢的生产过程中,应该避免使用含锆的耐火材料.     

帘线钢轧制和拉拔过程中夹杂物变形能力的研究

对帘线钢热轧过程夹杂物变形能力及其影响因素进行了分析,并对帘线钢冷拉拔过程中夹杂物变形能力的影响因素进行了探讨。研究发现帘线钢热轧过程夹杂物的变形能力随夹杂物中Al_2O_3和(MgO+Al_2O_3)含量的增加呈现出先增加后降低的变化趋势。整体上看夹杂物热轧变形指数与夹杂物的固相线温度成反比,即随着夹杂物熔点的降低,夹杂物热轧过程中的变形能力增强。同时采用杨氏模量来评估帘线钢冷拉拔过程中夹杂物的变形能力。研究认为冷拔过程夹杂物变形能力与杨氏模量成反比,为了降低夹杂物引起的断丝率,应将帘线钢夹杂物控制到低杨氏模量区域,即SiO_2含量高且Al_2O_3含量极低的区域。     

帘线钢中非金属夹杂物控制技术

为了满足高强度钢帘线的生产要求,必须降低钢中不变形非金属夹杂物的尺寸和数量。本文对帘线钢中氧化物夹杂物控制机理进行了总结,并对国内几家著名钢厂控制帘线钢夹杂物的措施进行了分析。     

帘线钢脱氧过程中非金属夹杂物生成热力学

帘线钢要求良好的拉拔性能,而影响其拉拔性能的主要因素之一是钢中非金属夹杂物。钢中非金属夹杂物的主要来源为钢液的脱氧反应,为了更好地控制帘线钢中非金属夹杂物,必须对其脱氧热力学有深刻认识。然而,目前教科书中纯铁液脱氧热力学不能指导工业生产实践,且当前实际钢液的脱氧热力学没有系统化,需要进行深入研究。对帘线钢成分条件下的脱氧热力学进行了计算,并与纯铁液条件下的脱氧平衡曲线进行了对比分析,发现帘线钢成分条件和纯铁液条件下的脱氧平衡曲线差异明显。由于帘线钢实际生产过程中不可避免地存在多种合金元素,相比于纯铁液条件,帘线钢成分条件下的脱氧平衡曲线能够更加准确地指导帘线钢实际生产过程中的脱氧和非金属夹杂物的控制。     

帘线钢小方坯夹杂物的控制

阐述了帘线钢对夹杂物的要求,及夹杂物对盘条性能的影响。针对本钢北营炼钢厂小方坯连铸机生产的帘线钢出现的夹杂物断丝的问题,通过检测分析得出其主要夹杂物为钛夹杂、铝夹杂、铝镁复合夹杂、氧化钾及氧化钠等。从夹杂物的产生机理入手,通过对钛来源进行控制、炼钢全流程控氮降低氮化钛析出,精炼渣系调整及铝含量控制避免纯Al2O3析出,精炼过程碱度的调整和萤石量降低避免耐材侵蚀MgO析出,连铸液面自动控制改进避免卷渣后钾钠氧化物夹杂带入,工艺优化后再未出现钛夹杂超标以及夹杂物引起的断丝率超标问题。     

帘线钢中氧化物夹杂塑性化控制技术研究

为将帘线钢中氧化物夹杂转变为低熔点塑性夹杂物,在实验室开展了夹杂物组成、钢液成分和顶渣组成之间的关系研究,基于研究结果提出了工业生产中实现钢中夹杂物塑性化控制的技术方案,并进行了精炼工艺技术对钢中夹杂物塑性化影响的工业试验,夹杂物成分位于低熔点液相区,实现了夹杂物塑性化控制。制丝过程将Ф1.25 mm的粗丝拉为Ф0.2 mm帘线,2 000 m试验拉拔的全部生产过程未出现断丝,且盘条中夹杂物数量也降低到3个/mm2。工业生产中制丝过程的断丝率为0.47次/t。     

帘线钢钢中夹杂物塑性化控制技术

介绍了武钢通过超低[0]冶炼、钢中[Als]控制以及非金属夹杂物的形貌和成分控制等关键工艺技术,对转炉出钢、吹氩、LF精炼、连铸等不同工艺阶段钢液、炉渣、夹杂物的组成变化的分析研究,攻克高纯净帘线钢钢中夹杂物塑性化控制技术,满足了高附加值硬线产品的要求.     

碱金属氧化物对帘线钢中夹杂物的影响

帘线钢主要用于制作轮胎骨架和切割硅片的线锯，其中主流切割钢丝的直径已经达到了47μm。夹杂物的大小、变形能力对帘线钢拉拔过程中的断丝率极为关键。为了提高帘线钢中夹杂物的变形能力，通过向钢液中添加碱金属氧化物以变质钢中夹杂物，从而获得塑性良好的低熔点夹杂物。向帘线钢中分别添加了吨钢质量分数为0.3%、0.5%、1.0%的Na₂CO₃、K₂CO₃、B₂O₃,共冶炼了9炉钢，对产品取样并用扫描电镜观察夹杂物形貌和统计成分。FactSage(FactPS+FToxid数据库)相图计算和试验结果表明，随着帘线钢中Na₂CO₃加入量的增加，夹杂物中铝含量逐渐降低，当Na₂CO₃加入吨钢质量分数为0.5%时，钢中绝大部分夹杂物落在低熔点区域；随着帘线钢中K₂CO₃加入量的增加，夹杂物中硅含量逐渐降低，当K₂CO     

钢包初始状态对帘线钢夹杂物的影响

运用Aspex Explorer扫描电镜对比了3种不同初始状态钢包冶炼条件下的帘线钢盘条中夹杂物成分、变形性能以及数量密度等,指出不同初始状态的钢包对帘线钢精炼渣成分和成品[Al]含量的影响。结果表明,同等条件下,分别使用冶炼过Si、Al-Si以及Al脱氧钢的钢包冶炼帘线钢时,精炼渣碱度、渣中Al_2O_3含量和成品[Al]含量均呈上升趋势,对应精炼渣碱度分别为0.95、1.1、1.4,渣中Al_2O_3质量分数分别为7.0%、11.0%、15.0%,成品[Al]的质量分数分别为7×10~(-6)、13×10~(-6)、16×10~(-6)。采用冶炼过Al、Al-Si脱氧钢的钢包冶炼的帘线钢盘条夹杂物数量密度分别为0.96、1.20个/mm~2,夹杂物中Al_2O_3平均质量分数分别为25.9%、31.8%,夹杂物塑性差,轧制后长宽比平均值分别为5.6、5.1。采用冶炼过Si脱氧钢的钢包冶炼的帘线钢盘条中夹杂物数量密度为0.79个/mm~2,夹杂物中Al_2O_3平均质量分数为15.0%,为塑性夹杂物,轧制后长宽比均值为11.3。实验证明,冶炼帘线钢不宜使用初态为Al脱氧或者Al-Si脱氧的钢包。     

Research progress on non- metallic inclusion in tire cord steel for radial tire

With the development of automobile lightweight, the requirements of steel cord for radial tire on inclusions are becoming more stringent. According to the demands of steel cord wire rod on inclusions, the smelting technology at home and abroad and the research progress on the inclusions in the steel cord at present were summarized, and some views on the control direction in future were put forward. With the 90 grade ultra high strength tire cord steel becoming the mainstream product, the Al2O3- rich type inclusion and titanium inclusion remains a difficult point of control. In addition to further strengthening the plasticity control of the inclusions in the process of smelting, the attention also should be paid on the properties and behaviors of the inclusions in each link such as rolling and drawing process, so as to better realize the whole- process control.     

帘线钢中氮含量对TiN析出的影响

 研究了攀钢新钢钒公司生产帘线钢72A过程中钢中氮含量变化对钢中TiN夹杂析出的影响。研究发现,随着钢中氮含量的升高,钢中析出的TiN夹杂数量变多,尺寸变大。热力学研究表明,在帘线钢中TiN一般只能在固相区形成,考虑元素偏析对凝固前沿元素富集的影响,凝固过程中TiN能在固液两相区析出。在帘线钢生产过程中,为了控制钢中TiN的析出,除了控制钛含量,控制钢中氮含量及氮偏析更加重要。理论计算结果表明,当钢中钛的质量分数控制在0.0003%~0.0005%区间时,将钢中氮的质量分数控制在0.0017%~0.0029%区间内能显著降低乃至杜绝帘线钢中TiN的析出。攀钢将帘线钢中钛、氮的质量分数分别控制在0.0005%以下和0.002%以下,显著减少了钢中TiN的析出,个别炉次中没有发现尺寸大于2μm的TiN夹杂。     

State of the Art in the Control of Inclusions in Tire Cord Steels ‐ a Review

The control of inclusions in tire cord steels and techniques used in the production process are extensively reviewed. Inclusion and segregation requirements for the tire cord steel are discussed. The deformability of an inclusion is significantly affected by its Al₂O₃ content. Inclusions containing 20% Al₂O₃ has best deformability. The undeformable inclusions can be avoided by controlling the dissolved aluminum in the steel. Low basicity slags favour the generation of deformable inclusions. When the basicity R (=CaO/SiO₂) = 0.8‐1.5, the dissolved aluminum in the steel should be 1‐5ppm to achieve 20% Al₂O₃ in inclusions. With R=1.0‐1.4, in order to control [Al] in the range of 1‐5ppm, the slag should contain approximately 8% Al₂O₃. The technologies to control inclusions in tire cord steels are reviewed including steel deoxidizer choice, steel refining method, slag carry over from BOF to the ladle, ladle stirring practice, control of nitrogen pickup and caster curvature. Control methods to decrease the central segregation in the tire cord steel are briefly reviewed, such as electromagnetic stirring during continuous casting.     

CaO-MgO-SiO2-Al2O3类夹杂物塑性化对帘线钢加工断丝率的影响

通过分析70 t转炉流程和180 t转炉流程生产的LX72A帘线钢合股断丝率,得出中心偏析相同的条件下,当钢中脆性夹杂物比例由90.7%降至20.5%,也就是塑性夹杂物的比例由9.3%提高79.5%时,平均盘条断丝率由4.20次/t降至2.56次/t。通过采用碱度1.05不含MgO的LF精炼渣,控制钢中Als含量≤0.001%,氧含量≤22×10^-6,可有效地降低钢中脆性夹杂物含量,降低盘条断丝率。     

Influence of the pressure in the vacuum unit’s working chamber on the content of hydrogen and nonmetallic inclusions in steel

In electrosmelting shop 2 at Belarussian Metallurgical Plant, the removal of hydrogen from steel is studied as a function of the residual pressure in the working chamber of the RH vacuum unit. The influence of the pressure on the quantity and composition of the nonmetallic inclusions in cord steel is also investigated.     

钙处理对20CrMnTiH齿轮钢中非金属夹杂物的影响

铝脱氧齿轮钢中易生成大量的高熔点Al₂O₃类夹杂物,容易导致水口结瘤及钢材性能恶化,目前较常采用钙处理将钢中高熔点的Al₂O₃类夹杂物改性为低熔点的钙铝酸盐类夹杂物。合理的钙处理可以减轻水口结瘤并提高连铸过程钢液的可浇性,工业试验研究了喂钙前钢液中T.Ca含量、喂钙速度、喂钙量、净空高度及渣厚等参数对齿轮钢中钙收得率的影响,并在1.5 m·s?1的喂钙速度条件下研究了不同喂钙量对钙处理过程中齿轮钢中非金属夹杂物改性的影响。研究结果表明,当喂钙前钢液中T.Ca的质量分数小于10×10?6,喂钙速度为1.5 m·s?1,适当降低喂钙量和净空高度和渣厚,钢液中钙收得率均高于20%。当钢液中T.Ca的质量分数高于17×10?6时,钢中生成大量高熔点CaS型夹杂物,三元相图中夹杂物的平均质量分数远离液相区。随着齿轮钢中T.Ca含量的增加,夹杂物的平均尺寸和数密度逐渐增加。热力学计算结果与工业试验钙处理对钢中非金属夹杂物改性效果具有较好的一致性。      

Nonmetallic inclusions in vacuum-treated austenitic stainless steel

The nonmetallic phase in 08X18H10T and 03X18H10 vacuum-treated austenitic stainless steel is investigated by means of a scanning electron microscope. The composition of the nonmetallic inclusions in cast samples of metal from the casting ladle, the vacuum unit, and the continuous-casting machine and samples of cold-rolled sheet (thickness 1.2 mm) is studied. In 08X18H10T steel samples from the tundish of the continuous-casting machine, the nonmetallic phase consists mainly of titanium-nitride aggregations, the crystals of which contain oxides of aluminum and titanium; a few of the nonmetallic inclusions are small globules with a titanium-oxide shell. In cold-rolled sheet, the nonmetallic inclusions are distributed over the whole cross section and consist of small (5–6 μm) crystals of titanium nitrides. Cast samples of 03X18H10 austenitic titanium-free steel are relatively free of nonmetallic inclusions. The nonmetallic phase consists mainly of small inclusions of alumocalcium silicate. In cold-rolled sheet (thickness 1.2 mm), the nonmetallic phase consists of a few very small globules (2–3 μm). The results are compared with the composition of the nonmetallic phase in analogous steel with no vacuum treatment.     

Precipitation and Solid Solution of Titanium Carbonitride Inclusions in Hypereutectoid Tire Cord Steel

The properties of titanium carbonitride Ti(C_xN_(1-x))inclusions precipitated during solidification of tire cord steels and the thermodynamic conditions for their decomposition and solid solution during billet heating were investigated using a thermodynamics method.The solid solution of Ti(C_xN_(1-x))inclusions during high-temperature heating was also studied experimentally.The results revealed that:(1)the higher the content of carbon in the tire cord steel is,the greater the value of xin the Ti(C_xN_(1-x))inclusions is;(2)the higher the content of carbon in the tire cord steel is,the earlier the Ti(C_xN_(1-x))inclusions precipitated during the solidification process and the lower the solidification front temperature is during precipitation;(3)when an 82 Asteel sample was heated to 1 087℃,the Ti(C_xN_(1-x))inclusions possess the thermodynamic conditions of decomposition and solid solution;and(4)when 82 Asamples were heated to 1 150 and 1 250 ℃,the total number of Ti(C_xN_(1-x))inclusions larger than 5 μm in diameter decreased by55.0% and 70.3%,respectively.In addition,although smaller inclusions with diameter less than 2 μm continued to decompose when the sample was heated at 1 250℃for 2 hand then cooled to 1 000℃in the furnace,the number of inclusions larger than 5 μm in diameter increased.