【作者】 黄永建；

【导师】 刘才；

【作者基本信息】 燕山大学 ， 机械设计及理论， 2010， 博士

【摘要】 大棒材产品的内部缺陷是导致最终产品质量不合格的主要原因,心部孔洞及裂纹等孔隙性缺陷是大棒材缺陷的主要形式。大棒材产品心部孔隙性缺陷是大棒材轧制生产过程中经常遇到的问题,严重地影响了产品的质量。本文系统地分析了棒材心部孔隙性缺陷产生的原因,对冶炼工艺钢中氢含量的控制技术及轧制工艺进行了理论及实验研究。首次引入相对密度来间接表征轧件内部呈弥散分布的孔隙性缺陷,利用体积可压缩刚塑性有限元法模拟轧制过程中棒材心部相对密度变化情况。针对生产现场的实际情况,建立了大棒材轧制有限元模拟热力耦合仿真模型,通过对现场轧制过程测试数据的分析,验证所建立模型的可靠性。采用控制变量法,揭示了温度、密度、压下量、轧制速度、摩擦等工艺参数对心部孔隙性缺陷压实效果的影响规律及提高压实效果的力学机理,为轧制工艺的制定及改进提供了理论依据。提出了石钢对炼钢VD真空精炼炉(简称VD炉)的控制方法与工艺,确定了真空时间、真空吹氩强度以及炉渣厚度等因素对氢含量的影响,为轧制大棒材提供高质量的坯料。为分析初始坯料中允许存在(后继可以通过轧制压合)的最大孔隙性缺陷尺寸,对一定轧制工艺下所能压合的棒材心部孔隙性缺陷的极限尺寸进行了模拟研究,为生产中坯料质量的判定提供了依据。根据石钢现场实际情况,对现有轧制工艺进行优化,模拟结果分析表明采用优化工艺生产的大棒材心部质量得到明显改善。根据优化工艺对石钢原有工艺进行改进,生产实践表明,采用优化工艺后,大棒材孔隙性缺陷得到了有效控制,验证了所用方法的实用性和可靠性。更多还原

【Abstract】 With rapid development of computer technology and increasingly drastic market The internal defect of big bar is the main reason to cause quality problems of end-products. Porous defects like holes at core and cracks are the main defect forms of big bar. The porous defect at core of big bar is a problem very frequently occurred during production, which influences products quality seriously.In this paper, the reason to cause porous defects at core of bar is analysed systematically, and the theoretical and experimental research on control of hydrogen content in the molten steel and rolling process are carried out.The relative density is introduced firstly as indirect token of discrete distributed porous defects in the inner of bar, and volume compressible rigid-plastic finite element method is used to simulate the change of relative density at core of bar.The finite element simulation thermal-dynamic coupling model is established aiming at the actual situation of plant site, and the reliability of the model is verified through the analysis of data measured during rolling process.The rule of influence caused by process parameters, such as temperature, density, reduction, rolling speed, friction, etc., to pressing effect of porous defects at core of bar and thermaldynamics mechanism to improve pressing effect are revealed via the experimental simulation through changing parameter values, which provides theoretical basis for setting rolling process and optimization.The analysis on control of VD refining furnace is performed, and the influence of vacuum time, argon-blowing intensity and slag thickness to hydrogen content is discussed, and the control process of hydrogen content for vacuum treatment in Shigang is defined consequently, and finally high quality bloom is supplied for rolling of big bar.The utmost dimension of porous defects at bar core that can be pressed under certain rolling process is researched by simulation in order to analyse max.porous defects allowed for rolling stock but later can be pressed through rolling, and provide basis for judgement of stock quality. The optimization to existing rolling process is made according to actual situation of plant site in Shigang, and the simulation result shows that the quality of bar core is improved obviously. The existing rolling process is improved on the basis of the optimized process, and the production practice indicates that the porous defect of big bar is effectively controlled, and the practicality and reliability of improved process are verified as right solution.更多还原