辊子错位对铸坯鼓肚变形的影响

 由于加工、安装、变形与磨损等原因,连铸机辊列中的辊子会偏离设计位置而产生错位,这对铸坯鼓肚变形产生较大影响。基于高温铸坯黏弹塑性本构方程,建立两辊间距内的铸坯坯壳动态鼓肚数学模型,并利用模型计算试验铸机的铸坯坯壳鼓肚曲线,依照实测数据验证了模型的有效性。根据奥钢联工业连铸机的设备及工艺参数,计算铸机不同扇形段内铸坯坯壳在不同辊子错位量情况下的鼓肚变形,并讨论在辊子发生错位的情况下辊间距对铸坯坯壳固液交界面处最大应变的影响,并给出铸机辊间距的确定方法。     

铸坯鼓肚对辊列的影响

在实际生产过程中，连铸机扇形段下线维修很大程度上是因为辊列支撑轴承的失效两造成辊子塌或辊子不转，我厂1600mm直弧型连锊机扇形段采用的是二分节辊的辊列排布方式，在使用过程中，长辊支撑轴承失效率是短辊的三倍，为此，就浇注过程中的铸坯鼓肚的存在及其存在形态进行了论证，并通过受力分析对理想状态下铸坯对辊列的载荷和发生锊坯鼓肚时铸坯对辊列的载荷做了分析和对比，论证了二分节辊辊列排布受铸坯鼓肚的影响较大，而新型辊采用的三分节辊辊列排布形式可以减小铸坯鼓肚对辊列的影响，同时就二分节辊辊列的日常维护和线下维任提出相关建议。     

大圆坯连铸带液芯矫直过程的应力、应变有限元模拟

应用Marc有限元软件对圆坯连铸的连续矫直变形过程进行模拟.以马鞍山钢铁公司大圆坯连铸机为原型,考虑铸坯与辊子的接触状态,建立了圆坯矫直变形模型;模拟分析了大圆坯连铸带液芯矫直过程中坯壳的应力、应变,得到了铸坯在矫直过程中的变形规律,可为铸机矫直工艺及设备设计提供参考依据,从而进一步优化铸坯的矫直变形,以提高圆坯的内部质量和表面质量.     

液心连铸坯矫直内裂分析

本文给出了液心铸坯矫直和考虑“鼓肚”时矫直应变的综合计算式。此式阐明了铸坯矫直内弧内裂与工艺设备参数的关系,并对两种铸机半径进行了具体计算分析。     

中冶连铸大方坯及扁坯辊列设计程序开发与应用

中冶连铸自主开发了大方坯、扁坯辊列设计程序。大方坯、扁坯辊列程序设计中一个重要指标是夹持段长度,由鼓肚量决定,而不像板坯有鼓肚计算的一维弹性梁的经验公式,大方坯、扁坯鼓肚量的计算是一个难点。据此,开发了三维蠕变有限元鼓肚计算模型,可以计算鼓肚细节,并且考虑蠕变的影响。在此基础上,整合了几何、温度场和鼓肚程序,实现自动化计算目标,并对输出结果进行标准化。以本模型为平台,对中冶连铸现有的大方坯和扁坯铸机进行了计算,确定了夹持段标准,形成了辊列设计工具。依据此工具,给出了目前常用的断面不同拉速(即产能)对应的夹持段长度建议,供铸机设计或者改造使用。     

连铸坯弯曲矫直时的变形行为

 连铸机的弯曲矫直曲线的确定属于铸机辊列设计的重要内容之一。通过对不同的弯曲矫直方法的比较分析,提出了关于铸坯弯曲矫直原理的一些新的看法,指出确定铸机的弯曲矫直曲线时应综合考虑铸坯的变形速率、剪切力和矫直反力3个因素。同时对目前铸机设计中广泛使用的连续矫直曲线进行了分析,理论推理并结合实例验证了该曲线的正确性,并对该曲线下铸坯的变形规律和力学特征进行了分析和讨论,从理论上说明了该曲线的合理性。     

扁坯窄面鼓肚变形的分析和避免措施

扁坯由于厚度较薄,理论上一般不会出现窄面鼓肚的问题,但是实际生产中这种情况时有发生。本文通过研究分析,发现当铸坯宽面夹持辊间距过大引起铸坯鼓肚后,鼓肚的铸坯通过下一对宽面夹持辊时,由于坯壳角部的扭转变形会造成铸坯窄面出现明显的鼓肚。高碳钢连铸过程中,当二次冷却比水量不合适时,也有可能导致铸坯的窄面鼓肚,同时产生三角区、中间裂纹。通过分析两个钢厂出现的问题,给出了相应的解决方法,可以为同类连铸机的设计、维护起到一定的参考作用。     

连铸机二冷配水对铸坯鼓肚的改善

部分生产165 mm×280 mm、165 mm×240 mm的R6和R8连铸机,没有二冷夹持段,在提高拉速后铸坯易出现鼓肚现象。通过分析和试验,得出调整和适当增加窄边水量,明显改善了铸坯的鼓肚。通过推导出的坯壳角部最大受力公式,调整凝固系数K值,可防止铸坯各边的变形,以改善铸坯鼓肚现象。     

连铸板坯的鼓肚应变速率

本文建立了新的连铸板坯鼓肚变形的计算模型，与原有的模型相比，该模型更接近于坯壳变形的实际情况，并且还可求出坯壳应变速率的值，结合钢的临界应变与应变速率的关系，可为确定连铸机的辊距提供更为科学的理论依据。     

两种冷却方式下铸坯变形问题的讨论

根据梅山炼钢厂板坯连铸机的特点，通过对在喷水和气雾两种冷却方式下铸坯矫直变形和鼓肚变形的讨论，认为喷水冷却更适合。     

Comparison of different caster designs based on bulging,bending and misalignment strains in solidifying strand

Abstract

If the strain level in the solidifying strand is more than the critical strain limit, cracking occurs. This strain depends strongly on the caster design and the process parameters. In the present work, an attempt has been made to show the effect of various caster designs and process parameters on the bulging and bending strain in the continuously solidifying strand. For simplicity an analytical tool is chosen for the strain prediction. As the solidifying front is the most critical, strain is calculated on the solidifying front and therefore, the use of the hard box approach near the edges is not considered. Three different caster designs are considered for the comparison and the effects of casting speed, radius of the machine and roll pitch on the strains are studied. It is found that the misalignment strain is quite significant. The strong dependence of strain level on the rolls not in contact with the solidifying strand and the misalignment has highlighted the importance of good machine maintenance. A comparison between the prediction from the soft and the hard box approaches for bending/unbending strain is carried out and it is found that the soft box approach is more conservative for strain prediction.     

广钢新转炉连铸机五辊拉矫机矫直原理探讨

多点矫直技术和连续矫直技术已经在连铸设备得到广泛的应用。本文对广钢新转炉连铸机五辊拉矫机矫直原理进行了初步探讨。     

Analytical model for continuous caster profile optimisation

Abstract

As a partial solution of the differential equation of the continuous caster pass line, the analytical relationship between the basic radius and the lengths of the radial and unbending zones was derived. Choosing rationally the length of the unbending zone at a given unbending strain rate, it is possible to reduce the height of a high productivity caster and the ferrostatic pressure within the strand shape to eliminate internal cracking. The software developed allows the temperature, stress, and strain distribution in the strand shell to be determined and, for assumed allowable strains due to bulging and unbending, the caster profile and the positioning of support and unbending rollers to be optimised. For the case of a continuous caster with a vertical mould, the same technique for its profile optimisation was proposed.     

连铸坯三角区裂纹的形成研究及解决措施

研究了连铸板坯三角区裂纹的形成机理，分析了二次冷却、钢种化学成分、铸机状况、工艺操作等因素的影响，提出防止三角区裂纹产生的措施。     

莱钢特钢厂小方坯合金钢连铸机改造

莱钢特钢厂小方坯合金钢连铸机采用无氧化全保护浇注系统、快速更换定径水口专利技术、渐进矫直技术,实现了合理的炉机匹配,连铸机作业率达到90%,连铸坯合格率达到99%以上,满足了生产高温无缺陷连铸坯的需要。     

提高方圆坯铸机连浇炉数的工艺及装备技术

 攀钢钒提钒炼钢厂2009年10月中旬投产的方圆坯连铸机单中间包连浇炉数较低,影响了炼钢生产组织。分析了浇注铝镇静钢水口堵塞原因,通过研究脱氧工艺、夹杂物变性处理工艺及优化二冷喷嘴结构与布置方式、改进拉矫设备及工艺,改善了钢水可浇性,提高了铸机拉速,铝镇静钢因水口堵塞造成的流次断浇率由投产初期的12.9%降至2.0%以下,单中间包连浇炉数由投产初期的4～5炉提高到7～10炉,硅镇静钢单中间包连浇炉数由6～9炉提高到8～14炉,从而保证了方圆坯铸机生产顺行,降低了生产成本。     

Adhere to the direction of detailization in CC technology and equipment

Since the excessive capacity in steelmaking and continuous casting at present,and the limited development margin of CC technology and equipment in scale,the further development must be made in a profound and detailized way.This paper enumerates the items of CC technology and equipment,which need to be detailized from several aspects such as roll arrangement design,equipment design and production operation,and it points out that detailization is the future direction of CC technology and equipment.The items in roll arrangement design include eliminating periodic meniscus fluctuation by adjusting space between rolls reasonably;taking special measures to avoid dangerous regions of casting speed,in order to reduce the center porosity and centerline crack of slab;optimizing the major radius and the length of outer arc of caster before straightening point to avoid dangerous region of casting speed.The items in equipment design include choosing a suitable structure of support and guiding roll according to the concrete conditions of caster;according to bulging shape of slab,thinking more about restriction of shell to bulging force, discussing the force on rollers,optimizing split roll to support slab;safety factor should be considered together with calculation method of the bearing nominal static load.The items in aspects of continuous casting operation include the delicacy division and the function-positioning of operation modes for CC machine due to the consideration of dynamic soft reduction;monitoring and controlling system of CC machine must be further detailized to improve the stability of production operation and slab quality.In addition to the three aspects mentioned above,this article points out many other items also,such as homogenization of secondary cooling of slab,quality control of surface and internal of slab,and so on.This article emphasizes,some key technologies need to be researched also,and all these researches will never stop.     

Study on the Design of the Soft Reduction Unit of High‐Speed Billet Casters

The production of continuously cast products that display very low centre segregation and thus more homogeneous properties is an important objective, particularly for high‐speed continuous casting of billets, in meeting increasingly stringent quality requirements. In addition to the well known methods of reducing macro‐segregation in continuous casting, inline deformation of the partially solidified strand, already used successfully in slab and bloom casting, offers an alternative for producing material with low segregation level. The present report considers the feasibility and effectiveness of mechanical soft reduction for the continuous casting of billets. The structural design of the soft reduction unit as a stand or segmental construction was investigated, as well as the influence of varying roll diameters. A strand of the existing billet caster S4 was modified for this purpose and soft reduction tests were conducted on spring steel grade 54SiCr6 at casting speeds between 3.30 and 3.60 m/min. The conclusions drawn from the test results as regards roll diameter, required reduction rate and necessary reduction force formed the basis for designing the soft reduction unit of the new billet caster SO that went in operation in March 2004.     

电磁出钢装置中填装料对固-液界面位置的影响

 在电磁出钢系统中 ,为了提高感应加热效果以实现快速出钢 ,需将固-液界面控制在感应线圈的有效加热区内。设计了模拟钢包上水口处固-液界面测量装置,考察了上水口内在高中低碳钢的出钢温度分别为1550、1600、1620℃时,铁碳合金颗粒的成分、形状、大小对固-液界面的影响规律。结果表明：使用铸铁填装料比使用铸钢填装料时固-液界面的下移量要大,并且成分的影响随着钢液温度的升高有增大的趋势;规则球形颗粒比不规则的砂形颗粒对固-液界面位置影响要大,而且固-液界面的下移量随着填装料粒径的增大而增大;选用粒径为2.0mm的铸铁颗粒作为填充料,当出钢温度为1600和1620℃时,固-液界面位置能够进入有效加热区;当出钢温度为1550℃时,使用粒径为4.0mm的铸铁颗粒做填充料时,固-液界面位置也能够进入有效加热区。