电炉用渣钢(铁)生产HRB400钢工艺实践

介绍了攀枝花钢城集团瑞钢工业有限公司以冶金渣二次资源渣钢、渣铁为原料,采用"EBT电炉+LF精炼+小方坯连铸"流程生产HRB400钢工艺实践。通过对EBT电炉、LF精炼、连铸工艺参数的合理控制,能够批量生产出符合GB1499.2—2007要求的HRB400钢,实现了二次资源的有效利用。     

超低温LNG储罐用钢的炼钢生产实践

介绍了超低温LNG储罐用钢的炼钢生产实践。采用转炉双渣、双联低温冶炼脱磷技术实现了转炉终点磷含量≤0.002 0%;钢水扒渣与LF脱硫实现了硫含量≤0.001 0%;RH真空度≤200 Pa,循环时间30 min,使钢中氮、氢含量分别控制在0.003 0%和0.000 1%以下;采用连铸全程保护浇铸工艺、铸坯高温矫直工艺以及铸坯缓冷工艺,抑制了铸坯表面和皮下裂纹的产生。     

淮钢80t BOF-90t LF-RH-CC流程开发特殊钢的生产实践

通过转炉采用高拉碳操作,控制出钢[P]≤0.012%,终渣碱度2.8～3.5;双挡渣工艺,LF精炼渣碱度≥4,(TFe+MnO)≤1.0%;应用低铝洁净钢精炼技术和含钡洁净钢生产技术专利;RH-MFB真空处理,连铸全程保护浇铸及二冷技术优化等措施,淮钢开发了127个特钢新产品,总氧含量(T[O]):轴承钢≤10×10-6,60Si2CrVAT弹簧钢≤12×10-6,CM490锚链钢≤15×10-6,37Mn5油井管坯钢≤18×10-6,SAE1022A冷镦钢和15CrMoG高压锅炉管坯钢≤20×10-6。     

直上钢水渣洗工艺的应用实践

针对不经过LF处理的45号钢在连铸坯中出现的夹杂缺陷，采用渣洗工艺，在出钢时随钢流加入渣洗料，从而起到净化钢液的作用。采用渣洗工艺后，基本上解决了45号钢连铸坯的夹杂缺陷。     

转炉合成渣洗工艺对45钢纯净度的影响

主要研究了转炉出钢合成渣洗工艺对45钢纯净度的影响。结果表明：采用合成渣洗工艺后,铸坯中的全氧质量分数有所降低,比未合成渣洗的铸坯全氧质量分数降低2588%;采用合成渣洗工艺后,铸坯中大颗粒夹杂物含量平均由966 mg/10 kg减少为512 mg/10 kg,平均减小了4700%。     

连铸漏钢原因分析

通过对某厂连铸漏钢时结晶器内残留坯壳的剖析和工艺分析,查明漏钢的原因是结晶器内卷渣造成局部坯壳过薄,该处坯壳在拉出结晶器后被撕裂所致.采用预熔性保护渣并改善工艺操作后避免了漏钢事故的发生.     

优化10PCuRE炼钢工艺消除铸坯表面纵裂纹

10PCuRE钢是一种C含量较低、P含量很高的稀土钢种,浇铸时难度大,板坯容易产生裂纹和夹杂等缺陷。针对10PCuRE连铸坯表面纵裂缝问题,对原10PCuRE钢冶炼工艺进行了优化,加强了出钢过程的钢液脱氧,并用合成渣技术和强化吹氩搅拌,以改善钢包中的渣—金反应;结晶器中使用专用稀土保护渣以在浇铸过程中有效地防止钢液的二次氧化,较好地润滑初始凝固坯壳和结晶器内模壁,降低表面热裂纹的倾向。应用优化后的冶炼工艺后,钢中氧含量和硫含量得到控制,稀土利用率提高,连铸坯表面纵裂缝消失,铸坯角部裂纹和内部裂纹问题大大改善,并且成品钢成分、晶粒组织、夹杂物的级别均得到了很好的改善。     

冷轧辊电渣钢用合金钢连铸坯的研发

冷轧辊电渣钢用合金钢连铸坯属于高碳高铬含钼高合金钢种,是集冶炼、连铸、缓冷处理为一体的高技术含量和高附加值的产品。河钢邯钢研发了采用转炉—精炼—连铸—铸坯缓冷工艺的冷轧辊电渣钢用合金钢连铸坯。采用转炉前期脱磷及钢包顶渣改质的超低磷洁净钢控制技术,基于"恒拉速"提高连浇炉数,通过增加喷铁粉装置及铸坯余热硬度控制法,高碳高合金铸坯质量完全满足使用要求。     

BOF-BCC流程生产高品质汽车齿轮钢实践

结合攀钢转炉-LF-RH-大方坯连铸工艺装备条件,针对高品质汽车用齿轮钢的质量要求,重点开展了精炼渣开发、钢包渣组成控制、脱氧工艺、钙处理及成分精度控制等相关技术研究。试验结果表明:采用该工艺可生产w(T[O])≤10×10-6,夹杂物种类、形态和尺寸得到有效控制的高品质汽车用齿轮钢。     

碳脱氧在钢包顶渣改质中的应用

 为了进一步降低夹杂物缺陷并提高产品质量,基于碳脱氧进行了钢包顶渣改质的研究。冷轧产品的生产工艺为铁水预处理→转炉→RH精炼→连铸,为减少钢中夹杂物质量分数,需要进行钢包顶渣改质,同时降低钢包顶渣TFe质量分数。采用粒碳部分替代铝渣球的方法进行基于碳脱氧工艺的钢包顶渣改质,试验结果表明,顶渣改质效果良好,在顶渣TFe质量分数、中间包钢水游离氧明显降低的同时铸坯中Al₂O₃夹杂物得到优化;“30 kg粒渣+铝渣球”工艺降低生产成本5.16元/t(钢)。     

不锈钢连铸坯表面缺陷与对策

针对不锈钢中镍、铬、钛等合金元素的作用,分析了不锈钢的组成、凝固特征、高温热性能、力学性能与普碳钢的差异以及不锈钢连铸坯表面凹陷、裂纹、夹渣等表面缺陷产生的机理.重点阐述了钢水洁净度、浇铸温度、保护渣性能、结晶器振动以及液面控制等连铸工艺对表面质量的影响.结合0Cr18Ni9、2Cr13以及钛不锈钢实际生产情况,提出解决铸坯表面凹陷、裂纹、夹渣及不易除掉的深振痕等缺陷的措施与对策.     

钢球用钢Φ380mm连铸圆坯表面裂纹原因分析及工艺改进

对Φ380mm高碳钢球钢连铸圆坯轧成钢材出现的表面裂纹进行了统计分析结果表明:抛丸检查后的连铸圆坯表面存在纵向裂纹,主要原因是钢液在结晶器中凝固时冷却不均产生的。通过将结晶器铜管锥度由0.45%/m调整为0.63%/m,1300℃保护渣粘度由0.60 Pa·s降到0.50 Pa·s,1300℃保护渣熔速由36s调整到49s,二冷比水量由0.30L/kg降到0.25L/kg,二冷段四面冷却改为八面冷却等措施,有效降低了大规格钢球钢铸坯及轧材的表面纵裂纹,轧材表面探伤合格率提高到95%以上。     

石钢中碳高锰钢连铸坯表面纵裂纹成因及控制

通过对石钢公司大方坯连铸机生产现场的调查、跟踪、试验、取样和统计,认为以40Mn2H(K)为代表中碳高锰钢铸坯表面纵裂纹的主要原因是二冷制度控制不当、保护渣性能不良、钢水过热度高,制定了相应措施,进行工业试验。试验结果表明,中包钢水的过热度控制在15~30℃、二冷水各区分配比由33∶42∶25调整为32∶40∶28、保护渣渣耗量提高到0.5 kg/t、液渣层厚度提高到10 mm左右,能有效减轻中碳高锰钢的表面纵裂纹。     

316H不锈钢铁素体的形成与控制

 为了提高316H不锈钢中厚板在钠冷快堆高温、强中子辐射环境下的质量稳定性,要求其残余铁素体面积分数不大于1%,而316H不锈钢中厚板的残余铁素体面积分数在常规工艺下为2%~8%。为了满足该要求,首先根据相图分析优化了316H不锈钢中C、Cr、Ni、Mo、N等元素含量,将其铬镍当量比控制到1.3以下,使其平衡态组织下铁素体面积分数小于7%。此外,根据相变过程,在凝固初期应快速冷却使钢水快速通过δ相区,尽可能少析出δ铁素体;在钢水快速通过δ相区后,应减缓冷却速度,使析出的铁素体尽可能多地通过包晶反应和高温扩散转变为奥氏体。因此,为了在316H连铸过程中实现这一目标,将钢水过热度从(45±5) ℃降低到(35±5)℃,铁素体面积分数最高由15%以上降低至10%附近;结晶器冷却水强度由2 700 L/min提高至3 000 L/min可以继续使铁素体面积分数从10%降至7%;最后再将二冷水比水量由0.75 L/kg降低至0.55 L/kg,整个连铸坯断面铁素体面积分数可全部降低至7%以下。通过连铸生产过热度、结晶器冷却强度、二冷水配水量3个工艺参数分步骤调整后得到的较低铁素体含量,连铸坯轧制成的钢板依然不能满足技术要求,需要将铸坯进行均质化处理,通过不同保温温度与保温时间的交叉试验,获得了最佳的均质化工艺,即1 250 ℃保温24 h,基本消除铸坯内残余铁素体组织,实现了残余铁素体面积分数不大于0.1%的316H中厚板的高效生产。     

Improvement of Castability and Surface Quality of Continuously Cast TWIP Slabs by Molten Mold Flux Feeding Technology

An innovative continuous casting process named POCAST (POSCO’s advanced CASting Technology) was developed based on molten mold flux feeding technology to improve both the productivity and the surface quality of cast slabs. In this process, molten mold flux is fed into the casting mold to enhance the thermal insulation of the meniscus and, hence, the lubrication between the solidifying steel shell and the copper mold. Enhancement of both the castability and the surface quality of high-aluminum advanced high-strength steel (AHSS) slabs is one of the most important advantages when the new process has been applied into the commercial continuous casting process. A trial cast of TWIP steel has been carried out using a 10-ton scale pilot caster and 100-ton scale and 250-ton scale commercial casters. The amount of mold flux consumption was more than 0.2 kg/m² in the new process, which is much larger than that in the conventional powder casting. Trial TWIP castings at both the pilot and the plant caster showed stable mold performances such as mold heat transfer. Also, cast slabs showed periodic/sound oscillation marks and little defects. The successful casting of TWIP steel has been attributed to the following characteristics of POCAST: dilution of the reactant by increasing the slag pool depth, enlargement of channel for slag film infiltration at meniscus by elimination of the slag bear, and decrease of apparent viscosity of the mold slag at meniscus by increasing the slag temperature.     

莱钢近终形异型坯铝脱氧工艺的研究与应用

莱钢针对供异型坯连铸机钢水采用硅、锰脱氧存在脱氧效果差、炉渣流动性差、炉渣碱度低及精炼造渣困难等一系列问题。利用铝脱氧剂脱氧快、脱氧效率高的特点,提高异型坯钢水的脱氧效率和钢水质量;优化精炼渣系功能,采用夹杂物全流程控制技术,提高钢水纯净度;优化精炼钙化处理效果,加强对夹杂物进行变性处理,提高钢水可浇性;强化连铸机铝脱氧钢水的无氧化浇注技术,解决水口结瘤问题。该措施确保了异型坯连铸机铝脱氧工艺生产的顺行,提高了铸坯质量,降低了生产成本。     

Parameter optimization for continuous casting of low carbon steel based on big data mining

As to the surface defects in hot rolled coils, based on the neural network prediction model in big data mining, a new method (prediction model method, PMM) for optimizing continuous casting process parameters was proposed. The multi sample continuous variation chart of the possibility of surface defects in each continuous casting parameter can be obtained by the PMM method. And based on it, corresponding influence law, key process parameters and critical values can also be obtained. The results show that among the parameters of argon blowing, the protective argon flow has the most obvious effect on the surface defects of low carbon steel hot rolled coils and has a negative correlation. The optimal argon blowing flow for the stopper rod and the nozzle position are 3.0L/min and 1.8L/min, respectively. Among the heat flow parameters of the mold, the influence of the water flow on the inner arc side is the most obvious, and the best range of water temperature difference on each surface is 7-9℃, the best water inlet temperature is about 35℃. At the same time, the possibility of surface defects increases significantly with the increase of the casting speed, the width of the slab, and the increase of the casting length, but it gradually decreases with the increase of the weight of the molten steel in the tundish. The casting speed, slab width, protective argon flow and mold cooling water flow are the key process parameters that affect the formation of surface defects in hot rolled coils. And the possibility of defect occurrence is the most sensitive to the fluctuation of the total cooling water flow of the crystallizer, and its critical lower limit is 8700L/min.     

Three-dimensional analysis of molten steel flow in slab continuous casting mould with rotated ports in submerged entry nozzle

Abstract

The purpose of this study is to develop a three-dimensional (3D) analysis system capable of analysing the flow field of molten steel in the slab continuous casting mould with rotated ports in the submerged entry nozzle. The ultimate goal is to obtain the optimal design for the entry ports of the submerged nozzle, which can introduce favourable flow patterns to remove non-metallic inclusions and avoid entrapment of molten slag and casting powder to produce steel slab of high cleanliness. In this study, a computational fluid dynamics technique, Sola-Surf, is employed to conduct the 3D fluid flow analysis. The technique has the capability of treating fluid flow problems with a free surface that slightly vibrates. The slightly vibrating free surface presents fairly accurately the behaviour of the molten slag–casting powder layer in the continuous casting mould. The developed simulation system is then tested on a slab continuous casting mould to analyse the fluid flow behaviour of molten steel under various nozzle designs. The design conditions include submerged depth of the nozzle, tilted angle of the nozzle port, and rotated angle of the nozzle port. The results of the simulations show that of the various design factors rotation of the nozzle entry ports has the greatest effect on the flow pattern. It can prolong the residence time of the molten steel and stabilise the molten slag–casting powder layer, which is very favourable for obtaining continuous casting slag of high cleanliness.     

基于大数据挖掘的低碳钢连铸工艺参数优化

摘要：针对热轧卷表面缺陷，基于大数据挖掘技术中的神经网络预测模型，提出了一种优化连铸工艺参数的新方法(prediction model method，简称PMM)。PMM方法可以得到各连铸参数对表面缺陷发生可能性的多样本连续变化图，并以此得到对应影响规律、关键工艺参数及临界值。结果表明，吹氩参数中，保护氩气流量对低碳钢热轧卷表面缺陷影响最为明显且呈负相关关系，塞棒与水口位置的最佳吹氩流量分别为3.0和1.8L/min。结晶器热流参数中，内弧侧水流量影响最明显，各面水温差最佳范围为7~9℃，最佳进水温度在35℃附近。同时，表面缺陷发生可能性随拉速提高、板坯宽度、浇铸长度增加而增加明显，但随中间包钢水质量增加而逐渐降低。此外，对比发现浇铸速度、板坯宽度、保护氩气流量与结晶器冷却水流量等参数是影响热轧卷表面缺陷形成的关键连铸工艺参数，且缺陷发生可能性对结晶器冷却水总流量的波动最为灵敏，其临界下限值为8700L/min。