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高碳钢82A断面180 mm × 240 mm矩形坯轻压下试验中,铸坯心部碳元素产生了负偏析现象.将轻压下工艺与负偏析形成条件相结合,对中心负偏析形成机理进行了探讨.结果表明,轻压下消除了枝晶间富集溶质钢液向铸坯中心流动通道,铸坯中心受枝晶间富集溶质液体流动影响较小;凝固过程中心负偏析产生条件为vr/R<-0.042 2,即液相流动速度vr和凝固速度R方向相反为形成中心负偏析的必要而非充分条件;轻压下易满足该条件并在此基础上提出了2种形成机理,即轻压下挤压作用导致心部钢液流动速度方向的改变或者脱落枝晶在铸坯心部先形核凝固导致凝固速度方向的改变都可能导致中心负偏析的形成. 相似文献
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Dynamic Soft Reduction for Continuously Cast Rail Bloom 总被引:2,自引:0,他引:2
Center porosity and centerline segregation in continuously cast bloom can be minimized by the well known method of dynamic soft reduction. Metallurgical results of soft reduction previously employed in continuous bloom casting for heavy rail steel in Panzhihua Iron and Steel Group were not fully achieved because of the improper soft reduction process. Therefore, experiments for optimizing the process parameters of soft reduction for bloom were carried out. The results show that the proportion of the center porosity, which is less than 10, increases from 2841% to 9981%, while the proportion of the centerline segregation class increases from 4091% to 100%, and the proportion of the central cavity increases from 9205% to 100%, whereas the center carbon segregation index decreases from 117 to 105. The internal quality and the mechanical performance of the rails produced from continuously cast blooms meet the requirement of high speed tracks of 350 km/h. 相似文献
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铸坯在连铸生产过程中很容易产生中心偏析和中心疏松缺陷,其质量对后续的轧材产生直接的影响。随着近年来人们的不断摸索研究,在连铸方面开发了许多改善铸坯质量的新技术,其中最为行之有效的一种便是轻压下技术。为此综述了轻压下技术的基本原理,对其各项工艺参数进行了理论分析选择,并对该技术在国内外企业的应用和发展方向做了一定的阐述和讨论。 相似文献
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The dynamic soft reduction technology for 360mm×450mm bloom casting and its application results at PISCO (Panzhihua Iron &; Steel Co.) were presented. In order to analyze the influence of the soft reduction on internal defects of bloom, such as center porosity and central segregation, experiment for contrasting process with or without soft reduction for bloom was investigated. The operation shows that after applying the soft reduction of bloom alloy steel, the ratio of center porosity whose defect level is below 1.0 increased from 66.67% to 85.71%, ratio of central segregation whose defect level is below 1.0 increased from 94.44% to 100%, ratio of central shrinkage cavity which is free increased from 88.89% to 96.42%, and central segregation index of carbon decreased from mean value of 1.15 to 1.05. These results have provided important technology supports for PISCO to optimize the steel product structure, and to improve the production of high quality, property, and value added products. 相似文献
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针对生产中出现的厚规格Q345B板材厚度中心分层缺陷进行了调查分析,结果表明:板材中心分层是由于连铸坯中较为严重的中心疏松在后期轧制过程中未能轧合所致。进一步对Q345B连铸坯轻压下工艺调查发现,实际凝固终点位置比模型计算值靠后,且凝固末端扇形段压下率低,不足以补偿其凝固收缩,从而形成较为严重的中心疏松缺陷。在调查分析基础上,通过将该规格连铸坯轻压下区间后延并加大轻压下量,增加了凝固末端压下率,降低了连铸坯中心疏松和中心偏析程度,从而彻底解决了板材中心分层问题。 相似文献
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对首秦2号板坯连铸机轻压下工艺进行了细致的研究。通过连铸坯射钉试验对首秦2号连铸机二级冷却模型进行了校验;通过不同轻压下率试验条件下连铸坯中心偏析的程度确定了合理的、能够有效改善连铸坯中心偏析的轻压下率;通过连铸坯厚度方向不同部位碳硫元素的分析对轻压下工艺改善前后连铸坯中心偏析度进行了对比。结果表明:首秦2号连铸机二级冷却模型能够准确反映连铸坯凝固末端的位置。在拉速为0.70m/min的连铸工艺条件下,320mm厚连铸坯轻压下段为第9和第10段,合理的轻压下率应该保持在0.85~1.0mm/m之间。采用合理的轻压下工艺后,连铸坯中心偏析得到了明显改善,满足了首秦高品质中厚板对连铸坯内部质量的严格要求。 相似文献
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探讨了单对辊凝固末端大压下对连铸板坯内部质量的影响。研究中,分析检测了不同拉速条件下Q345D连铸坯低倍组织特征,并对铸坯中心疏松进行了定量测量。结果表明,采用大压下能够有效改善连铸坯的内部质量。拉速为0.70 m/min时,大压下15 mm相比轻压下时铸坯在宽度1/2位置、1/4位置处的中心疏松体积均明显降低。轻压下时铸坯宽度1/2、1/4位置处的中心疏松体积分别为1.73×10-7、2.68×10-7 cm3/g;大压下15 mm时铸坯宽度1/2、1/4位置处的中心疏松体积分别为5.33×10-8、-1.84×10-8cm3/g。轻压下、大压下15 mm时连铸坯中心碳偏析均较轻,但后者相对稍重,最大值分别为1.176、1.282;轻压下与大压下条件下,铸坯宽度1/4位置中心碳偏析均高于宽度1/2位置。特别地,大压下15 mm时,铸坯宽度1/2位置、1/4位置处,连铸坯中心靠外弧侧出现负偏析,最大负偏析值为0.916。 相似文献
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There are significant effects of process parameters on internal qualities of bloom,and these process parameters are as follows:position and reduction amount,reduction distribution,reduction rate,and so on.Developing a control model is the key to apply soft reduction technology successfully.As the research object,360 mm×450 mm bloom caster in PISCO (Panzhihua Iron and Steel Co.) has been studied,and the research method for control model of dynamic soft reduction has been proposed.On the basis of solidification and heat transfer model,the position of soft reduction and reduction distribution of each frame are determined according to the bloom temperature distribution and solid fraction in bloom center calculated.Production practice shows that the ratio of center porosity which is less than or equal to 1.0,increased to 97.27%,ratio of central segregation which is less than or equal to 0.5,increased to 80.91%,and ratio of central carbon segregation index which is more than or equal to 1.10,decreased to 4% with the applying model of dynamic soft reduction. 相似文献
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轻压下技术在高碳钢方坯连铸中的应用 总被引:4,自引:0,他引:4
台湾中钢、韩国浦项等5家钢厂在高碳钢方坯连铸中采用轻压技术之后,铸坯中碳和其它元素的中心偏析程度明显降低,缩孔和中心疏松缺陷也大大减少。从这些厂家的应用效果还可以看出,普通的轻压下技术,即机械轻压下技术用于小方坯连铸似乎存在一定的局限性,而热轻压下技术则为小方坯连铸提供了一种新的选择。 相似文献
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凝固末端轻压下技术在连铸中的应用 总被引:6,自引:0,他引:6
文章阐述了凝固末端轻压下技术的原理,介绍了这种技术的几种不同方式,并对其主要工艺参数轻压下的位置、压下率、总压下量、压下速率和拉速等等的确定进行了讨论和分析。对比了一些厂家使用末端轻压下技术的效果。末端轻压下技术对减少中心偏析很有效,对提高产品质量、生产高附加值产品有重要意义。 相似文献