High nitrogen steel powder for near net shape products

This study has been performed to relate the powder properties to the process parameters of the plasma-rotating-electrode-process (Prep). A regression equation for average powder diameter was acquired from the experimental data as . A model is developed to describe the nitrogen pick-up by the Prep. On the basis of this model an expression for nitrogen content of the powder produced is deduced as: The powder has a solidification structure of austenitic dendrites. The CrN precipitates, the amount of which is dependent upon the nitrogen content, can be found in the interdendritic areas. During the solution annealing the Cr₂N precipitation reaction occurs in both of the inter- and intradendrite.     

Modern processes of production of thin sheets and strips by continuous casting

The history of the development of producing thin sheets and strips by continuous casting methods is considered. The mechanism of this sheet formation during casting of steel in a two-roll continuous caster is described. The advantages of this process over the corresponding traditional technologies are discussed.     

The influence of alloy composition on the as-cast grain structure in near net shape low-density steels

Low-density steels are considered an attractive potential replacement for conventional steel in industries such as the automotive sector. However, there are several issues that need to be overcome before they become commercially useful grades. A significant constraint is in their processability, for example, a large as-cast grain size means these steels are prone to hot cracking. This paper explores how compositional variations affect the as-cast grain size in 12 low-density steels cast at solidification rates representative of near net shape casting. It is shown that while mushy zone width is a good indicator of the cast grain size, using a mushy zone width from liquidus to 85% solidified fraction gives a better correlation. It was found that the as-cast grain size of a 7?wt-% Al steel can be reduced from 736 to 244?µm through the addition of 1.5?wt-% Si which acts to increase the mushy zone width by 19°C.     

带钢热连轧非对称因素对板形的影响

为研究某2250 mm热连轧生产中非对称因素对轧件非对称板形(如楔形和单边浪)的影响,利用基于影响函数法的辊系变形模型、张应力模型和简化的轧制压力横向分布模型相结合的方法,建立了集轧机和轧件为一体的非对称板形计算模型.研究结果表明:来料楔形对轧件楔形的影响明显超过其对轧件平坦度的影响;上游机架和下游机架刚度非对称分别主要影响轧件楔形和平坦度;40℃以内的轧件温度不对称分布对轧件平坦度影响较小,对出口楔形的影响可以忽略;轧件跑偏对楔形和平坦度均有显著影响.根据板形良好条件确定了各非对称参数的允许范围.     

论连铸设备在连铸生产中的地位和作用

本文对连铸设备对提高连铸生产效率、质量和效益的作用，连铸设备组成与连铸设备管理中几个主要问题，连铸装备水平的优化与提高，连铸工艺与设备的结合，抓好连铸设备人员培训等问题进行了论述。     

连续退火炉内双锥度辊辊形参数对带钢跑偏的影响

针对连续退火炉实际生产过程中的跑偏问题,运用ABAQUS有限元软件建立炉辊-带钢动态仿真模型,定量计算了连续退火炉内双锥度辊辊形参数对带钢跑偏的影响,并分析了带钢的横向压应力以及产生的瓢曲变形．计算结果显示双锥度辊辊形对炉内带钢跑偏有明显的抑制作用,且随着锥度段总辊径变化量、辊径变化量比值和张力的增加,以及平直段长度的减少,带钢的跑偏量逐渐减少,最大横向压应力逐渐增大,使带钢发生瓢曲变形的概率增加．根据以上计算结果,建立带钢跑偏量的计算模型,并结合瓢曲变形理论,为进一步对加热段双锥度炉辊辊形和张力设定的优化提供了依据．     

带钢横向厚度控制不均对退火板形的影响分析

带钢横向厚度控制不均,会使带钢在退火过程中产生横向温度差异和横向张应力分布差异,而横向温度和横向张应力分布存在差异会使带钢横向各位置处产生纵向延伸不均,进而导致退火带钢板形不良。以实际生产过程中带钢横向厚度控制不均的典型现象为切入点,分析带钢横向厚度不均对退火板形的影响,对分析和改进退火板形有一定的指导意义。     

双锥度辊辊形参数对带钢瓢曲变形的影响

根据连续退火生产实际情况,运用MARC有限元软件,定量计算了连退炉内双锥度辊辊形参数对带钢瓢曲的影响.模拟发现在双锥度辊锥肩处,带钢张应力和横向应力发生突变,并且带钢横向压应力和等效应力都具有最大值,此处最先发生瓢曲变形,这与现场观测到的带钢瓢曲出现的位置完全吻合.随着总锥度和锥度比的增大,以及平直段长度和直径的减少,带钢发生瓢曲变形的概率都会增加.其中平直段长度对带钢发生瓢曲变形的影响最大,总锥度和锥度比其次,平直段直径的影响最小.     

Steel flow and inclusion separation in continuous casting tundishes

A model for the calculation of flow patterns and inclusion separation in continuous casting tundishes is described. Velocity and turbulence fields for the liquid steel are calculated, assuming three-dimensional, turbulent steady-state flow. A transport equation for particles is solved, which takes into account buoyancy, convection und turbulent dispersion. Particle concentration fields and the percentage of removed particles are calculated as a function of particle rise velocity. The influence of increased tundish width and height and of dams and weirs on the rate of inclusion separation is investigated for a slab caster tundish. Non-dimensional representations and approximation expressions are discussed and used to compare the computed removal rates to measured values from literature.     

炼钢—连铸区段生产调度与计算机仿真

炼钢-连铸区段的生产调度包括炉次计划、浇次计划的生成和时间、设备的分配,以及针对各种扰动的动态调整.根据钢种和规格的限制,提出了最优炉次计划模型,并采用禁忌搜索算法进行求解;根据炉次计划和连铸机连浇限制,生成浇次计划;根据炉机匹配和等待时间最小原则,生成静态调度甘特图,并对仿真过程中出现的出钢延迟提出了动态调度的策略和算法.仿真结果表明,基于模型的动态调度策略能够有效地解决出钢延迟问题.     

日本新日铁自主创新的连铸技术

介绍了新日铁自主创新的6项连铸技术,重点有:中间包等离子加热、多模式电磁搅拌、铸坯面压下、复合钢板坯连铸、超厚钢板新型连铸机和薄带铸轧等。分析认为,目前新日铁的传统连铸技术领先于世界,下一步发展目标是薄带连铸技术的推广与普及。指出学习和借鉴新日铁自主创新的连铸技术,对低成本制造顶级钢铁产品会有一定的促进作用。     

The shape of bubbles rising near the nozzle exit in molten metal baths

A previously developed multineedle electroresistivity probe was used to investigate the shape of bubbles generated at the exit of a central single-hole bottom nozzle in molten Wood’s metal and mercury baths. This probe is capable of detecting the vertical cross section of rising bubbles. The shape of bubbles just after the detachment from the nozzle exit was correlated as a function of a modified Reynolds number and a modified Weber number. Furthermore, the relations between the shape of bubbles and the radial distributions of bubble characteristics specified by gas holdup, bubble frequency, etc. were derived. As a result, it is possible to predict the shape of the bubbles by measuring the bubble characteristics with a conventional two-needle electroresistivity probe.     

莱钢连铸20CrMnTiH钢非金属夹杂物研究

利用大样电解法、LEO-1450型能谱分析仪和NEOPHOT-32型金相显微镜对连铸生产的20CrMnTiH钢中非金属夹杂物的种类、含量、来源、形状、尺寸及分布等进行了研究。结果表明,精炼前夹杂物数量多,颗粒较大,类型主要为硅钙、硅锰酸盐等;中间包中主要为硅酸盐类型的球形和玻璃状夹杂物;铸坯中主要为硅铝酸盐球形夹杂物。经LF精炼后,非金属夹杂物去除率可达99％以上。     

珠钢CSP连铸的生产实践

本文介绍珠钢CSP连铸投产一年多的生产实践,描述连铸主要设备及特点,对连铸工艺进行介绍及总结,特别是对于连铸开浇失败和漏钢,提出一些对策和措施。     

热等静压近净成形数值模拟的研究进展

热等静压近净成形工艺具有材料利用率高、坯料组织均匀性好的突出优势,是镍基粉末高温合金、粉末钛合金等复杂形状部件的重要成形工艺。介绍了热等静压近净成形的工艺特点和生产流程、热等静压近净成形技术在国内外的发展和应用以及粉末热等静压致密化的微观模型和宏观模型,通过对比分析不同模型的热等静压数值模拟和试验验证结果,总结了不同模型的优缺点,分析了影响数值模拟准确性的因素。     

结晶器专家系统在凌钢连铸的应用

介绍了凌源钢铁集团股份有限公司转炉炼钢厂连铸机上安装的连铸结晶器专家系统.实际运行表明:该系统运行效果良好,既能有效防止粘结漏钢事故发生,又能帮助观测结晶器工艺参数的异常状况,优化保护渣以及其他连铸操作方案,减少了纵裂和粘结发生率.     

热态铸余渣返生产可行性分析

铸余渣综合利用是钢铁企业节能减排的重要方法.在分析铸余渣资源属性的基础上,结合炼钢工艺流程,研究了铸余渣返生产的工艺路径和关键技术,重点讨论了返生产过程中由于温降而产生的粘罐和铸余渣与铁水混兑时的喷爆问题,提出了通过调整钢水碳含量解决钢水粘罐问题的技术措施和通过实验室研究解决喷爆的思路.同时结合现场生产管理调度,分析了铸余渣返生产后的炼钢工艺优化方向,为铸余渣的资源化利用提供了依据.     

梅钢连铸生产中的增氮控制

氮在钢中通常是一种有害元素,钢中氮含量高会严重影响钢的高温强度和高温塑性,降低钢的深冲性能。在连铸环节,保护浇铸不当会导致钢水增氮。基于连铸生产的实绩,介绍了梅钢连铸生产中对钢水增氮的控制,通过分析钢水连铸过程中的增氮机理,调查梅钢连铸当前的增氮现状,查找出了连铸增氮的主要影响因素,并对连铸工序的生产工艺、设备、耐材等方面实施了改进,有效减少了连铸的增氮保留,减少了改钢损失,为高质量要求钢种的生产创造了条件。