高品质2Cr13不锈钢关键冶金技术研究

发布时间：2018-07-09 12:33

本文选题：不锈钢 + VOD　；参考：《北京科技大学》2017年博士论文

【摘要】：2Cr13不锈钢是一种具有良好抗腐蚀性以及机械性能的马氏体不锈钢,因此被广泛的应用于航天航空、海洋环境、机械零件以及医疗器械等领域。并且随着我国镍矿储量的下降,镍资源对外依存度的提高,不含镍元素的2Cr13不锈钢将具有低生产成本优势。而国内关于不锈钢的研究多集中在热处理、铸坯质量控制以及合金元素对2Crl3性能的影响方面,对于2Cr13不锈钢洁净钢生产关注较少。为满足高端产品对不锈钢性能的要求,亟需从洁净钢生产角度对2Crl3进行研究,进而达到生产高品质2Crl3不锈钢的目的。本文以国内某厂EF+VOD工艺流程为背景开展研究,通过对各工艺环节调研分析发现不锈钢生产过程中主要存在脱氧后全氧含量高、夹杂物变性控制效果差、精炼后期二次氧化以及现有生产工艺流程易产生含铬固废的问题。因此以下将通过理论分析与工业试验相结合的方法对不锈钢真空搅拌铝脱氧平衡、精炼渣钢渣反应、钢包底吹搅拌、不锈钢钙处理以及氧化性炉渣脱碳反应等不锈洁净钢冶炼关键工艺进行研究。为改善不锈钢脱氧后钢液全氧含量高以及精炼后期出现二次氧化的现象,首先对不锈钢真空搅拌脱氧过程中A1-O平衡、精炼后酸溶铝控制及精炼渣成分对二次氧化的影响等方面进行研究。研究结果表明钢中活度氧含量由炉渣成分及钢中酸溶铝含量共同控制,炉渣碱度在3-5,钢中铝含量大于0.015wt%时可使活度氧含量小于0.0006wt%。另外,由于钢渣间Si-O平衡,提高钢液中Si含量将提高炉渣SiO_2含量,所以为形成高碱度炉渣应在造渣前降低钢液Si含量。采用高碱度低Al_2O_3炉渣并在后续精炼过程中提高Si含量可防止由还原炉渣SiO_2产生的酸溶铝降低。为改善钢液搅拌条件,将中心吹氩钢包改为1/2R吹氩偏心钢包,钢包静吹氩流量控制在2.1 m~3/h-3.6 m~3/h,真空搅拌流量可控制在7.2 m~3/h,静吹时间保持在15分钟以上为减少不锈钢脱氧后产生的Al_2O_3夹杂物以及控制改善夹杂物熔点,对不锈钢钙处理过程进行了研究。研究结果表明为减少炉渣的二次氧化以及对喂入钙线的烧损,渣中FeO摩尔分数应控制到0.0012以下,钢液中酸溶铝含量应大于0.01wt%。当钢液钙含量控制在0.0019wt%-0.0035wt%时,可以将钢中Al_2O_3及镁铝尖晶石夹杂物转变为钙铝酸盐夹杂。并且通过使用CaO、Al_2O_3及CaS三组元活度得到CaS在不同成分的钙铝酸盐上析出曲线,进一步解释CaS夹杂物的析出机理。为减少不锈钢现有工艺中含铬固废的排放以及提高铬在钢厂中的利用率,本文开展了使用氧化性不锈钢炉渣进行不锈钢真空脱碳的研究。研究结果表明不锈钢渣钢反应后高温物相组成为高温熔渣相与FeCr_2O_4相。通过钢渣间的热力学反应平衡计算了不同成分的炉渣及高温析出相参与脱碳反应后钢液的碳含量,并且确定氧化炉渣脱碳能力(Fe_2O_3) (FeO)Cr_2O_3 (s)＞ FeCr2O4 (s) (Cr_2O_3)。同时计算结果表明脱碳反应受到炉内真空度影响明显。最后为验证真空氧化炉渣脱碳生产2Crl3不锈钢的可行性进行了真空感应炉氧化渣脱碳实验。实验结果表明,氧化炉渣脱碳反应后炉渣中Cr_2O_3和Fe203平均为5.7wt%和3.9wt%,渣中Cr、Fe氧化物含量明显低于电炉及VOD各工位炉渣中Cr203和Fe203含量,达到减少电炉生产过程中产生含铬固废的目的,并且相较于VOD吹氧脱碳工艺,可有效减少脱氧剂加入量,最终改善钢液洁净度水平。在基于双膜理论建立氧化炉渣脱碳反应动力学方程后,计算脱碳速率常数及传质系数。实验中脱碳反应速率常数为0.00087-0.0022s-1,碳的总传质系数为8.8×10-6-2.1×10-5cm/s,但是脱碳反应后钢液终点碳含量受传质影响明显,采用钢包底吹氩气等手段提高钢液中碳的传质将有利于超低碳钢的生产。
[Abstract]:2Cr13 stainless steel is a martensitic stainless steel with good corrosion resistance and mechanical properties, so it is widely used in the fields of aerospace, marine environment, mechanical parts and medical instruments. And with the decline of the nickel ore reserves in China, the increase of the dependence of nickel resources on external dependence and the low nickel content of the 2Cr13 stainless steel will be low. The domestic research on stainless steel is mainly focused on heat treatment, casting quality control and the effect of alloy elements on the performance of 2Crl3. It is less concerned about the production of 2Cr13 stainless steel. In order to meet the requirements of the performance of stainless steel for high-end products, it is urgent to study the 2Crl3 from the angle of clean steel production. To produce high quality 2Crl3 stainless steel, this paper studies the EF+VOD process of a domestic factory. Through the investigation and analysis of various process links, it is found that the main oxygen content in the process of the production of stainless steel is high, the control effect of inclusion denaturation is poor, the two oxidation in the later stage of refining and the production process are easy to produce. In order to improve the deoxidation of stainless steel, the key technology of stainless steel vacuum stirred aluminum deoxidation balance, refining slag steel slag reaction, ladle bottom blowing agitation, stainless steel calcium treatment and oxidizing slag decarbonization reaction are studied by the combination of theoretical analysis and industrial test. The phenomenon of high total oxygen content in molten steel and two oxidation in the later stage of refining is studied. First, the A1-O balance in the process of stainless steel vacuum deoxidization, the effect of acid soluble aluminum control and the composition of refining slag on the two oxidation after refining are studied. The results show that the activity oxygen content in steel is controlled by the composition of slag and the content of acid soluble aluminum in steel. When the slag basicity is 3-5 and the slag basicity is 3-5, the activity oxygen content is less than 0.0006wt%. when the aluminum content of steel is greater than 0.015wt%. Because of the balance between the steel slag and the Si content in the molten steel, the SiO_2 content of the slag will be increased. Therefore, the Si content of the steel should be reduced before the slag formation for the formation of high basicity slag. The low Al_2O_3 slag with high alkalinity and low Al_2O_3 slag should be used in the subsequent refining process. The increase of Si content can prevent the reduction of acid soluble aluminum produced by the reduction slag SiO_2. In order to improve the mixing condition of steel liquid, the central argon blowing ladle is changed to 1/2R argon blowing eccentricity ladle, the static blowing rate of steel bag is controlled at 2.1 m~3/h-3.6 m~3/h, the vacuum stirring flow can be controlled at 7.2 m~3/h and the static blowing time is over 15 minutes to reduce the deoxidization of stainless steel. The Al_2O_3 inclusion and the control of the melting point of inclusions have been controlled to improve the melting point of the inclusions. The results show that the FeO mole fraction in the slag should be controlled to less than 0.0012 to reduce the two oxidation of the slag and to the burning loss of the calcium wire. The content of the acid soluble aluminum in the molten steel should be greater than 0.01wt%. when the content of the molten steel is controlled by 0. At 19wt%-0.0035wt%, the inclusion of Al_2O_3 and magnesia aluminum spinel inclusions can be transformed into calcium aluminate inclusions. The precipitation curve of CaS on different components of calcium aluminate can be obtained by using CaO, Al_2O_3 and CaS three component activity. The precipitation mechanism of CaS inclusions is further explained. To reduce the emission of chromium containing solid waste in the existing stainless steel process. As well as improving the utilization rate of chromium in the steel plant, the study on the vacuum decarburization of stainless steel with oxidizing stainless steel slag has been carried out in this paper. The results show that the high temperature phase group becomes the phase of the high temperature slag and the FeCr_2O_4 phase after the reaction of the stainless steel slag steel. The carbon content of the molten steel was involved and the decarburization capacity (Fe_2O_3) (FeO) Cr_2O_3 (s) > FeCr2O4 (s) (Cr_2O_3) of the oxidizing slag was determined. The results showed that the decarburization reaction was affected by the vacuum degree in the furnace. Finally, the vacuum induction furnace was tested to verify the feasibility of the vacuum oxidation furnace slag decarbonization for the production of 2Crl3 stainless steel. The experimental results show that the average Cr_2O_3 and Fe203 in the slag after the decarbonization reaction of the oxidation slag are 5.7wt% and 3.9wt%, and the content of Cr and Fe oxides in the slag is obviously lower than the Cr203 and Fe203 content in the furnace slag of the electric furnace and VOD, to reduce the chromium containing solid waste in the production process of the electric furnace and to compare with the VOD oxygen decarburization. Art can effectively reduce the amount of deoxidizing agent and finally improve the level of cleanliness of molten steel. The decarburization rate constant and mass transfer coefficient are calculated after the kinetic equation of decarbonization based on the double film theory. The rate constant of decarburization reaction is 0.00087-0.0022s-1, the total mass transfer coefficient of carbon is 8.8 x 10-6-2.1 x 10-5cm/s, but decarburization is reversed. The final carbon content of the molten steel should be affected obviously by mass transfer. The use of ladle bottom argon blowing to increase the mass transfer of carbon in the molten steel will be beneficial to the production of ultra low carbon steel.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TF764.1

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