摘要
为了增加材料抗氧化性能,用于汽车排气系统的一类奥氏体耐热不锈钢含有1.5%以上的硅元素,AOD采用硅铁进行脱氧后生成直径大于50μm的硅酸盐夹杂物,由于钢液合金成分含量高,黏度较大,大颗粒硅酸盐夹杂物不能通过LF底吹气体搅拌方法去除,残留在铸坯中经过轧制变形后被拉长,导致排气系统用奥氏体耐热不锈钢冷轧板内夹杂物级别超过2.0级,严重影响了产品的抗高温疲劳与蠕变性能,降低了产品使用寿命。针对汽车排气系统用耐热不锈钢冷轧薄板夹杂物的较高要求,从基本热力学理论出发,根据实际冶炼过程及钢液成分计算出冶炼过程中SiO_(2)、Al_(2)O_(3)和MgO·Al_(2)O_(3)夹杂物生成的热力学条件及钙变性高熔点MgO·Al_(2)O_(3)夹杂物的热力学基础,根据热力学结果调整LF精炼工艺,得到如下结论,当钢液中铝质量分数大于0.003%时,钢液内夹杂物以Al_(2)O_(3)为主,并且极易生成MgO·Al_(2)O_(3)夹杂物;钙可以将高熔点MgO·Al_(2)O_(3)夹杂物变性成低熔点复合夹杂物,1 500℃时,钢液中铝质量分数为0.04%时,开始变性MgO·Al_(2)O_(3)夹杂物的临界钙质量分数为0.000 4%;实际生产中,将大尺寸硅酸盐夹杂物改质成小尺寸塑性夹杂物工艺为,吨钢加入0.1 kg铝丸、1.5 kg铝粉,反应一段时间后吨钢喂钙线3 m。经过LF冶炼工艺调整后生产的汽车排气系统用奥氏体耐热钢冷轧薄板全氧质量分数小于0.002 5%,夹杂物级别小于1.0级。
In order to increase the oxidation resistance of the material,a kind of austenitic heat-resistant stainless steel used in the automobile exhaust system contains more than 1.5%Si element.The silicate inclusions with diame-ter larger than 50μm were formed by ferrosilicon deoxidation during AOD process.Due to the high alloy composi-tion,the viscosity of the molten steel is high,therefore,the large particle silicate inclusions cannot be removed by LF bottom blowing gas stirring method.The inclusions in continuously cast strands was deformed greatly during rolling process,and the grade was exceeding level 2.0in the austenitic heat-resistant stainless steel cold rolled plate for the exhaust system,which seriously affects the high temperature fatigue and creep resistance of the product and reduces the service life of the product.Aiming at the higher requirements of inclusions in heat-resistant stainless steel cold rolled sheet for automobile exhaust system,starting from the basic thermodynamic theory,according to the actual smelting process and the composition of molten steel,the thermodynamic conditions for the formation of SiO_(2),Al_(2)O_(3)and MgO·Al_(2)O_(3)inclusions in the smelting process and the thermodynamic basis of Ca modified high melting point MgO·Al_(2)O_(3)inclusions were calculated.LF refining process were improved according to the thermo-dynamic results,and the following conclusions were obtained.When the mass percent of Al in molten steel is more than 0.003%,the inclusions in molten steel are mainly Al_(2)O_(3),and MgO·Al_(2)O_(3)inclusions are easily formed.Ca can modify high melting point MgO·Al_(2)O_(3)inclusions into low melting point composite inclusions.At 1500℃,when the mass percent of Al in molten steel is 0.04%,the critical mass percent of Ca that begins to modify MgO·Al_(2)O_(3)inclusions is 0.0004%.In actual LF refining production process,the technology of modifying large-size sili-cate inclusions into small-size plastic inclusions is adding 0.1kg aluminum shot and 1.5kg aluminum po
作者
庄迎
李国平
ZHUANG Ying;LI Guo-ping(State Key Laboratory of Advanced Stainless Steel Materials,Taiyuan Iron and Steel(Group)Co.,Ltd.,Taiyuan 030003,Shanxi,China;Technology Center,Shanxi Taiyuan Stainless Steel Co.,Ltd.,Taiyuan 030003,Shanxi,China)
出处
《钢铁》
CAS
CSCD
北大核心
2023年第3期151-157,共7页
Iron and Steel
基金
山西省关键核心技术和共性技术研发攻关专项资助项目(20201102017)。
关键词
排气系统
耐热不锈钢
夹杂物
热力学计算
成分控制
exhaust system
heat resistant stainless steel
inclusion
thermodynamic calculation
composition con-trolling
