Surface Cracks in Wire Rod Rolling

Surface defects in wire rod and bar rolling are common and well‐known to mill people. Nowadays, surface defects are not accepted on high‐alloyed steel wire rods. The steel making, casting and rolling processes give rise to defects. Also, the final handling of the wire and bar can destroy the surface. In this work, artificial V‐shaped cracks in the longitudinal direction were investigated for different reduction series. The false round‐oval series are known as a series for high quality steels and are usually better than square–oval series. Experiments confirmed that in the false round‐oval sequences a surface crack in the groove bottom may open up during rolling at the same time as its depth is reduced, which is a beneficial situation. Surface cracks found at 45° to the rolling direction, at groove “corners” and on free surfaces will be closed or reduced in depth. The closing of cracks is detrimental since the cracks usually hide rolled‐in oxides beneath the bar surface. The experiments showed that for the subsequent oval–false round sequence the visible crack at the groove bottom will be closed and become shallower. The cracks at 45° and on the free sides will also be closed, but deeper causing a serious surface defect. An FE‐analysis was carried out, explaining the experimental results. Flat oval grooves are better than round ovals and false rounds are superior to square for opening and decreasing the depth of a longitudinal crack. It is difficult to eliminate a surface defect constituting a closed crack.     

棒线材轧制的上限法解

应用上限法建立了棒线材轧制的三维运动许可速度场，并通过对变形功率求最小值确定最佳的变形过程，该解析方法可用于求解平辊和凸凹型辊的二辊、三辊及多辊轧制过程的轧制力，轧制力矩和宽屏率等参数。其结果与刚一塑性有限元法计算结果进行了比较，其中力能参数与有限元法计算结果吻合较好，而且求解过程较刚一塑性有限元法更简便、灵活。     

Flexibility and Utilization of Roll Pass Sequences in some Swedish Wire Rod Mills

A computer program has been developed to calculate the working range for series of two‐symmetrical grooves including oval, round, false round, square and diamond shapes. Eight different pass designs are compared. The geometry of rolling or entry bar height over roll radius is in the range 0.09‐0.26 for squares, 0.10‐0.23 for false round and 0.06‐0.21 for ovals. Square‐oval and round‐oval have similar flexibility, but in the round‐oval sequence, the flexibility can be extended by opening up the gaps and run the rounds as false rounds. In the square‐oval sequence the flexibility can be improved by making the squares with larger corner radii but the reduction capability will be reduced. The false round‐oval sequence has the best flexibility and the working range can be extended by making “flatter” ovals. Improvement of the roll pass design in Fagersta Stainless AB has made it possible to roll wire rod with higher flexibility and better quality.     

77MnCr钢丝笔尖状断口形态的分析

某预应力钢丝生产厂在使用Φ12.5 mm的77MnCr盘条生产Φ7.0 mm的螺旋肋预应力钢丝时,常在拉拔过程中发生断线的现象.针对该问题,利用光学显微镜、扫描电镜和能谱仪对77MnCr盘条在冷拉拔过程中产生笔尖状断口的断裂试样进行了系统检测和分析.检验结果表明,试样中心部位存在的“V”形裂纹是造成盘条在拉拔过程中产生断裂的裂纹源.经分析得出V形裂纹的形成与盘条心部存在的网状渗碳体有关,而网状渗碳体的产生与连铸坯中心偏析,尤其是碳偏析和盘条轧制过程中的冷却速度有着十分紧密的关系.     

高线粗中轧轧辊轧槽磨损规律浅析

轧辊槽面状况直接影响高速线材盘条表面质量,对粗中轧不同机架轧辊孔型磨损进行了大量测量,结果显示,无论是椭圆孔型还是圆孔型,孔型磨损都呈现极大不均匀性,槽底磨损量最大;沿轧制方向,磨损量逐渐增加,且椭圆孔型磨损量增加幅度高于圆孔型;单机架磨损量随吨位呈正相关关系。这些基本规律,有助于轧机操作人员适时地进行辊缝调整,更容易地控制料形。     

棒线材节能减排低成本轧制技术的发展

在市场需求的强力拉动、棒线材研究成果的科技引领、产能过剩导致激烈竞争的形势下,中国棒材的生产技术向着节能减排、降低成本的方向快速发展,取得了显著的进步。典型的棒线材节能减排低成本轧制技术包括低成本高性能产品开发技术、免加热直接轧制技术、多线切分轧制技术、低温轧制技术、无孔型轧制技术、无头轧制技术等。对中国棒线材节能减排轧制技术今后发展提出了建议。     

棒线材低温轧制技术发展

介绍了国内外棒线材低温轧制技术的发展情况.叙述了低温轧制的节能效果、低温轧制过程的温度控制、低温轧制对成品质量及轧机负荷的影响.为国内在棒线材生产中进一步应用低温轧制工艺提供了有益的参考.     

3D FE Analysis of Thermal Behavior of Billet in Rod and Wire Hot Continuous Rolling Process

 An FE model was developed to study thermal behavior during the rod and wire hot continuous rolling process. The FE code MSCMarc was used in the simulation using implicit static arithmetic. The whole rolling process of 30 passes was separated and simulated with several continuous 3D elastic plastic FE models. A rigid pushing body and a data transfer technique were introduced into this model. The on line experiments were conducted on 304 stainless steel and GCr15 steel hot continuous rolling process to prove the results of simulation by implicit static FEM. The results show that the temperature results of finite element simulations are in good agreement with experiments, which indicate that the FE model developed in this study is effective and efficient.     

Finite Element Modelling and Laboratory Simulation of High Speed Wire Rod Rolling in 3‐Roll Stands

Modern wire rod rolling is characterized by high finish rolling speed and requirements on close tolerances and well defined mechanical properties of the rolled product. In some senses the technological development has run in advance of the scientific knowledge of the phenomena involved in the process. Thus at present no laboratory mill is in operation for rolling speeds above 40 m/s. The modern technologies on thermomechanical rolling and sizing give certain phenomena difficult to handle for the mills, and especially finish rolling at low reductions and temperatures performed in three‐roll units sometimes give surprises on grain size distribution and allied properties of the wire rod. Traditional plastic analysis has proven not to be sufficient to analyse the processes involved in high speed rolling of close tolerance wire rod with well‐defined properties. Simulations by means of the Finite Element Method on the other hand have proven to be a powerful tool for this kind of analysis, even if the initial difficulties in creating a suitable model require certain care. Also the calculation capacity must be sufficient for making relevant three‐dimensional thermomechanically coupled studies. The high speed rolling of wire rod can be simulated under full‐scale conditions, and with correct boundary condition in the high‐speed laboratory wire rod mill at Örebro University. By utilizing both conventional two‐high stands and three‐roll units it has been possible to design a laboratory rolling mill for any rolling condition that can occur in wire rod mills. Rolling speeds up to 80 m/s can be combined with thermomechanical rolling in any interesting temperature range, and with total flexibility of reductions. Further, fundamental studies of high‐speed deformations can be performed in full‐scale and with correct frictional conditions and geometries. Thanks to the flexibility in layout and combinations with other equipment in the laboratory also other processes can be simulated.     

我国线材生产的现状和对今后发展的看法

对我国目前线材生产的产量和装备进行了统计和研究，得出线材产量已达总钢材量的２０．１％，已建成投产了一大批世界最高水平的线材轧机。根据这些现状，提出了对线材生产在今后数年内和今后长远发展两步走的意见。在第二步和长远发展的意见中，提出了一些具体开发线材车间主要设备的项目及其开发方向，可为发展线材生产技术作参考。     

高线无孔型轧制技术的开发与应用

无孔型轧制是一项可以优化线棒材生产的先进技术。本文依托新兴铸管盘螺生产机组开展了无孔型轧制工业试验和研究,具体介绍新兴铸管股份公司在高线车间粗中轧1-12^#轧机上采用了无孔型轧制工艺并介绍了其工艺特点,通过制定合理的轧制工艺参数正确的使用轧辊、导卫,解决开发中发现的问题,并分析了高线无孔型轧制技术带来的效益。实践证明,无孔型轧制技术开发成功后,可优化轧制工序,能达到统一坯料、去除氧化铁皮、节约生产时间、降低轧辊和导卫消耗、降低劳动强度和减少固定资产投入等目的。无孔型轧制技术具有广阔的发展应用前景,技术价值和经济价值较大,特别适合小型材生产的老线改造和新线建设。     

天铁集团棒线厂45~#硬线盘条研发

天铁棒线厂为增加线材产品的新品种,研发出45#硬线盘条。对研发过程中存在的脱碳、晶粒粗大、混晶现象等缺陷的原因进行分析,改进了原生产工艺方案,采用新方案轧制,消除了原工艺生产过程中的几种缺陷,成功生产出了符合国标要求的45#硬线盘条,满足了市场对硬线钢的需求,提高了经济效益。     

不锈钢软接触电磁连铸的工业试验

 通过分析碳钢和不锈钢材质的电阻率差异性,以及304不锈钢软接触电磁连铸的中试试验结果,证实了不锈钢软接触电磁连铸的可行性。进而,在商业级规模铸机上分别开发了不锈钢圆坯和方坯软接触电磁连铸系统,进行了不同钢种、不同保护渣条件下的相关工业生产试验。结果表明,不锈钢圆坯和方坯软接触电磁连铸在不超过150 kW的电源输出功率条件下,均能获得较佳的振痕去除效果,改善铸坯表面质量。对获得的铸坯进行免修磨轧制成[?]8 mm线材,并经过固溶热处理以及酸洗等工序,使线材成品的综合成材率提高3%以上。多次生产试验采用不间断连浇方式,期间,软接触电磁连铸设备系统生产稳定可靠,未发现液面异常波动以及铸坯低倍组织卷渣等缺陷,使软接触电磁连铸技术向商业化生产运营迈出了关键一步。最后,讨论了软接触电磁连铸技术拓展至不锈钢板坯断面的可行性。     

First results of process‐studies to enhance the ductility of ferritic steels containing chromium mass contents of more than 8%

Otherwise their drawback is the tendency towards cold brittleness expressed by their low impact energy values. They obtain the high range of ductility only at termperatures higher than room temperature. It was found that this low ductility at room temperature is caused by a high‐temperature embrittlement besides the well‐known low‐temperature 475°C embrittlement. The high‐temperature embrittlement is provoked by submicroscopic precipitates but can be remedied by a special annealing treatment. The results with enhanced ductility of the ferritic microstructure are confirmed under manufacturing conditions for semifinished products such as slabs, billets, bars, wire rod and strips, depending on alloying contents of mainly chromium and aluminium. In the field of near‐net‐shape casting, first results also confirm the same beneficial effect. Using the heat‐content of the casting and rolling for the annealing process, moreover, results in lower process costs.     

高线无孔型轧制难点分析及解决措施

石横高线通过对无孔型轧制生产过程中的难点分析,采用合理料型设计、改进导卫、增设刻痕装置和方法设计、轧辊水冷装置改型等,解决了无孔型轧制过程中的咬入难、轧制稳定性差、轧制缺陷、轧辊冷却难度大等诸多技术难题,成功实现无孔型轧制技术在高线生产线的稳定生产,成材率由98.55%提高到98.81%,轧辊消耗由0.254 kg/t降低到0.10 kg/t,年降低工艺更换时间11460 min.     

新日铁先进棒线材生产工艺

记述了新日铁最先进的棒线材生产工艺和新产品发展现状。介绍了热轧棒线材生产用高效无扭线材轧机,指出降低成本、提高生产率和保护环境是主要发展方向。     

高速线材无孔型轧制技术的研究与应用

介绍了酒钢炼轧厂高线工序粗轧轧机开发无孔型轧制技术的实践。根据高线工艺特点,对轧辊辊型、无孔型专用导卫、轧制工艺参数进行了优化设计。投入使用后,轧辊寿命提高2.5倍以上,轧机负荷下降7.5%,节能效果明显,产品质量进一步得到提高。实践结果表明,无孔型轧制在节能、降耗、提高生产率等方面具有显著效果。     

变质处理高碳高速钢导板的研究

导板是线材轧机的关键备件，要求有优良的耐磨性，抗断裂性，抗粘钢性和热冲击抗力，常用高镍镍钢导板和高铬铸铁导板满足不了上述要求，使用寿命短，更换频繁，降低了轧机作业率，增大了工人劳动强度，高速钢具有硬度高，红硬性好和耐磨性好等特点，但铸造高速钢脆性大，通过调整高速钢成分和采用RE－Mg-Ti复合变质处理，可改变共晶碳化物的形态和分布，使高速钢冲击韧性大幅度提高，变质处理高速钢导板使用中不粘钢，不断裂，耐磨性明显优于普通导板。     

气保焊接用钢WER80S—G盘条的研制

采用先进的延迟冷却工艺在高速线材生产线上开发出550MPa级低硫、高韧性气保焊接用WER80S-G盘条,盘条ω（S）不高于0．005％。焊丝富Ar熔敷金属冲击功-30℃KV2平均达到170J以上,远高于设计要求。对比分析2种不同微量元素总量的盘条（焊丝）熔敷金属韧性以及2种不同保温罩状态设置轧制工艺时盘条金相组织的差异,据此优化WER80S-G盘条（焊丝）化学成分及轧制工艺条件,盘条具有F＋B组织,避免了淬硬组织,拉拔性能优良。     

南通钢厂改建设计方案浅议

根据最近几年我国建筑钢材，特殊钢材紧俏情况，在宝钢集团内部，拟将南通钢厂改建成能生产优质棒材，螺纹钢筋，线材和特殊钢材的基地。在南通钢厂的改建设计中，采用国内外先进技术，新工艺和新装备。对现有炼钢车间和即将新建的轧钢车间的改建设计作了概要介绍和探讨。