20CrMo合金钢生产过程中非金属夹杂物的演变 |
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作者姓名: | 王伟健 罗艳 张立峰 任英 |
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作者单位: | 1.北京科技大学冶金与生态工程学院,北京 100083 |
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基金项目: | 国家自然科学基金资助项目(U1860206,51725402) |
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摘 要: | 为了进一步研究20CrMo合金钢在生产过程中夹杂物的演变机理,实现对钢中非金属夹杂物的合理控制,保证生产顺行,提高产品力学性能,针对“BOF→LF→RH→钙处理→连铸→热轧”工序生产20CrMo合金钢全流程中非金属夹杂物的演变规律进行了研究。在LF精炼及RH精炼加钙前钢中非金属夹杂物含有70%以上的Al2O3。钙处理后,由于过量的钙加入到钢液中,夹杂物中CaS质量分数迅速增加至59%,Al2O3质量分数降低至21%。在连铸过程中由于二次氧化的发生,夹杂物转变为CaO?Al2O3,其中含有50%的Al2O3、39%的CaO和10%的CaS,并且夹杂物平均尺寸增加。在钢的冷却和凝固过程中,CaO质量分数降低至5%,CaS质量分数增加至57%,钢中夹杂物转变为Al2O3?CaO?CaS的复合夹杂物,同时含有少量大尺寸的CaO?Al2O3夹杂物。在钢的轧制过程中,夹杂物中CaO含量进一步降低,CaS含量增加,夹杂物平均尺寸增加,形成了CaO?Al2O3与CaS黏结型的复合夹杂物与Al2O3?CaS复合夹杂物。对CaO-Al2O3与CaS黏结型的复合夹杂物的形成原因进行了讨论。
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关 键 词: | 合金钢 钙处理 夹杂物 二次氧化 凝固 |
收稿时间: | 2020-12-17 |
Evolution of nonmetallic inclusions during production of 20CrMo alloy steel |
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Authors: | WANG Wei-jian LUO Yan ZHANG Li-feng REN Ying |
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Affiliation: | 1.School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China2.State Key Laboratory of Metastable Materials Science and Technology, School of Mechanical Engineering, Yanshan University, Qinhuangdao 066004, China |
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Abstract: | 20CrMo alloy steel is commonly used to produce high-pressure pipes, gears, automobile parts, etc., and there are stringent requirements for its yield strength, tensile strength, and impact energy. In the actual production process, the existence of nonmetallic inclusions has an important impact on the properties of 20CrMo steel; therefore, studying the evolution of inclusions in the process is necessary. To further examine the evolutionary mechanism of inclusions in the overall production process, the evolution of nonmetallic inclusions in a 20CrMo alloy steel produced via the route of “Basic oxygen furnace (BOF)→Ladle furnace refining (LF)→ Vacuum cycle degassing process (RH)→ calcium treatment→ Continuous casting (CC)→ hot rolling” was studied. This process ensured a smooth production process and improved the mechanical properties of the products. Al2O3 was the main inclusions in the steel during LF and RH refining, which was up to 70%. After calcium treatment, CaS in inclusions increased to 59% and Al2O3 decreased to 21% due to the excessive mixing of calcium into the molten steel. Due to reoxidation during continuous casting, inclusions were transformed to CaO–Al2O3, with 50% Al2O3, 39% CaO, and 10% CaS. And the average diameter of inclusions also increased, which was detrimental to the mechanical properties of the steel. After cooling and solidification of the steel, CaO decreased to 5% and CaS increased to 57%. Inclusions in the steel were transformed into Al2O3–CaO–CaS, and a small amount of large-sized CaO–Al2O3 was also observed. During the rolling process of steel, the CaO content in inclusions further decreased while the CaS content and the diameter of inclusions increased. Moreover, two types of inclusions were observed in the hot-rolled plate, one being Al2O3–CaS compound inclusions, whose size was relatively small, and the other being CaO–Al2O3–CaS compound inclusions. Reasons for the formation of compound inclusions consisting of CaO–Al2O3 and CaS were also discussed. |
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