【作者】 王哲；

【导师】 战东平；

【作者基本信息】 东北大学 ， 冶金工程（专业学位）， 2019， 硕士

【摘要】 随着人们对能源与环保问题的日益关注,发展节能、环保、低成本的非调质钢代替能耗高、周期长的调制钢生产汽车曲轴成为发展汽车用钢的必然趋势。典型的非调质曲轴用钢,主要有以下优点:采用微合金化技术提高了钢材的强度;非调质钢省去了调质热处理,节能效果显著;通过对钢中硫化物的控制,使得钢材具有良好的加工性能。但受其化学成分的影响,在生产此类品种时冶炼难度较大,制约了此类钢的低成本生产,其冶金难点主要有:钢中硫质量分数的稳定控制、连铸可浇性差极易造成水口结瘤、连铸坯表面及皮下裂纹倾向严重。作者在抚顺特殊钢股份有限公司生产非调质曲轴用钢时,采用EAF-LF-VD-CC的短流程生产工艺路线,生产过程容易出现硫元素收得率不稳定、连铸钢液可浇性差、轧材表面缺陷多、铸坯皮下裂纹倾向严重的问题。本文通过此类品种对冶炼工艺的研究,得出如下结论:在冶炼过程中使用硫磺包芯线,硫元素收得率较好,钢液温降低,利于的稳定控制钢中硫的质量分数:通过示踪剂标定,抚钢生产易切削非调质钢时,钢材出现的大尺寸B类粗系夹杂物是由精炼过程中卷渣引起的,通过降低钢包渣量、控制软吹操作,可减少钢材中出现大尺寸B类粗系夹杂物的机率;通过降低电炉终点氧质量分数、强化脱氧、优化精炼顶渣渣量、真空后软吹技术、减少钢液二次氧化技术能够有效提高钢液的纯净度,可有效解决易切削非调质钢连铸过程絮水口问题,絮流率降低至3%以内;易切削非调质钢铸坯表面质量较差,使用易切削钢专用保护渣以及控制稳定液渣层厚度,可改善铸坯质量,钢材黑皮一次通过率可由67%稳定上升至85%;采用弧形连铸机生产含硫易切削钢时,选择圆角半径为8 mm的结晶器铜管、降低结晶器水流量至2100 L/min、改善二冷水冷却强度的均匀性,同时保证铸机对弧精度,可有效将连铸坯皮下裂纹发生率控制在7%以下,且皮下裂纹长度<5 mm。更多还原

【Abstract】 With the increasing concern about energy and environmental protection issues,the development of energy-saving,environmentally-friendly,low-cost non-tempered steel instead of high-energy,long-cycle modulated steel to produce automotive crankshafts has become an inevitable trend in the development of automotive steel.The typical nontempered crankshaft steel has the following advantages:the use of microalloying technology improves the strength of the steel;the non-tempered steel eliminates the quenching and tempering heat treatment,and the energy saving effect is remarkable;by controlling the sulfide in the steel,Steel has good processing properties.However,due to its chemical composition,it is difficult to smelt in the production of such varieties,which restricts the low-cost production of such steels.The metallurgical difficulties include:stable control of sulfur mass fraction in steel,and poor castability of continuous casting.It is easy to cause nodulation of the nozzle,and the surface of the continuous casting blank and the subcutaneous crack tend to be serious.When the company produces non-tempered crankshaft steel in Fushun Special Steel Co.,Ltd.,it adopts the short process production route of EAF-LF-VD-CC.The production process is prone to unstable sulfur yield and continuous casting of molten steel.Poorness,many defects on the surface of the rolled material,and the tendency of the submerged crack of the cast blank to be serious.In this paper,through the study of such varieties on the smelting process,the following conclusions are drawn:In the smelting process,the sulfur core-containing wire is used,the sulfur element yield is good,and the molten steel temperature is lowered,which is favorable for stably controlling the mass fraction of sulfur in the steel;Through tracer calibration,when Fugang produces free-cutting non-quenched and tempered steel,the large-sized B-type coarse inclusions appearing in the steel are caused by the slag-crushing during the refining process.By reducing the amount of ladle slag and controlling the soft blowing operation,Reduce the chance of large-sized B-type coarse inclusions in steel;By reducing the oxygen content of the end point of the electric furnace,strengthening the deoxidation,optimizing the amount of refining top slag,soft blowing after vacuum,and reducing the secondary oxidation of molten steel,the purity of the molten steel can be effectively improved,and the non-tempered steel joint can be effectively solved.The problem of flocculation in the casting process,the floc flow rate is reduced to less than 3%;The surface quality of the free-cutting non-quenched and tempered steel slab is poor.The special slag for free cutting steel and the thickness of the stable slag layer can be used to improve the quality of the slab.The pass rate of the black skin of the steel can be steadily increased from 67%to 85%.When using a curved continuous casting machine to produce sulfur-containing freecutting steel,choose a crystallizer copper tube with a fillet radius of 8 mm,reduce the crystallizer water flow to 2100 L/min,improve the uniformity of the cooling energy of the second cold water,and ensure the casting.Machine-to-arc precision can effectively control the incidence of subcutaneous cracks in continuous casting blanks to within 7%and subcutaneous crack lengths<5 mm.更多还原