热轧板坯头部翘曲的热力耦合仿真

根据某热轧厂R1轧机的轧制过程工艺参数,建立板坯在轧制过程中的三维动态非对称轧制的有限元模型,分析热轧板坯在轧制过程中头部翘曲的产生机理。通过仿真,分别探究轧辊辊径差、轧制线中心高度及板坯上下表面温差对轧件头部翘曲的单作用的影响规律,板坯头部翘曲的翘曲量随着非对称轧制条件程度的增加而增大。根据实际生产情况对R1轧机的轧制过程进行热力耦合仿真,综合考虑轧辊辊径差、轧制线中心高度和板坯上下表面温度差3个因素对板坯头部翘曲共同作用的影响,由仿真结果得到了有利于生产的"雪橇"式头部弯曲的轧制规程,从而对实际生产予以指导。     

Prediction of spread in hot flat rolling under variable geometry conditions

Geometric deformation of steel blanks having a smoothly varying rectangular cross section under hot flat rolling was experimentally investigated. Specimens of different initial geometries were used. The experimental results were then utilized to develop mathematical expressions which represent the variant nature of the deformation process. These expressions were incorporated in El-Kalay and Sparling’s conventional steady-state spread formula. The resulting empirical formula related spread to the relevant process variables under the unsteady-state rolling conditions. The application of this formula is the process planning for manufacturing of a class of industrial components by rolling—whose distinct feature is the gradual change of cross-sectional size along the length.     

带钢轧制负荷的研究

本文在研究C Mn钢带钢热连轧再结晶软化程度的基础上 ,揭示其对实质应变及轧机负荷的影响 ,与传统的计算轧制压力方法相比 ,考虑奥氏体再结晶软化不充分的影响后预报和实测符合更好 ;对带钢热连轧的轧制压力计算 ,中轧阶段选用Sims式、精轧阶段采用才利柯夫式 ,对发生完全再结晶软化的道次偏差不大 ,但若发生部分再结晶 ,所得结果明显偏低     

Dynamic explicit FE modeling of hot ring rolling process

1Introduction Ring rolling is an advanced process typically used to manufacture parts with revolved geometries.It makes use of rotating rolls to press a ring continuously and locally,causing the wall thickness of the ring to reduce,the diameter to expand …     

A study of pore closure and welding in hot rolling process

The design of processing conditions to eliminate porosity in steel during hot rolling has become more critical with the advent of continuously cast feed stock. To predict appropriate process parameters, experiments were performed in which holes were drilled in steel slabs, at different depth below the surface perpendicular to the rolling direction. After hot rolling, the state of the deformed holes was examined by optical microscopy. The fracture surfaces of tensile specimens notched in the plane of the closed holes were examined under a scanning electron microscope to investigate the bonding ( welding ) between the surfaces of the closed holes because this bonding is the most important factor indetermining the transverse mechanical properties of the rolled product. The deformation of such holes in the roll gap was modelled as an clastic / plastic plane strain problem using the FE software ABAQUS to investigate the strain and stress around holes and to analyze the conditions required to promote pore closure and welding between the closed surfaces.

Experiment results showed that the rate of pore closure was affected by the parameters of rolling process and the position of holes relative to the rolling contact surfaces. FE simulation of pore closure showed a good agreement with experimental results and showed that a certain level of hydrostatic pressure resulted in the closure of pore and that the holding period of the pressure in the compressive state determined the degree of welding of surface of pores; shear is favourable to this welding.     

环件热辗扩成形有限元建模仿真研究进展

环件热辗扩成形问题是多场、多因素耦合作用下集三维连续渐变、非稳态及非对称等特点于一体的高度非线性问题,采用有限元建模仿真方法研究与发展该技术对实现无缝环形构件的高质量、低成本及短周期制造具有重要意义.分别从宏观和微观尺度评述环件热辗扩成形有限元建模仿真的国内外研究现状、存在的问题与发展趋势,进而指明其发展方向如下:大型、复杂环件径、轴双向热辗扩成形全过程自适应建模的仿真方法与关键技术;环件热辗扩成形过程宏观与微观有限元建模仿真无缝集成技术;适用于以环件热辗扩为代表的连续局部塑性成形过程的材料本构模型和组织演变模型以及相应稳健而高效的有限元算法、本构积分算法与组织演变仿真方法;考虑模具的变形、传热及主要失效形式的环件热辗扩成形过程建模仿真技术.     

Application of mathematical modeling in two-stage rolling of hot rolled wire rods

The no-recrystallization temperature (T_nr) is an important parameter in the design of two-stage rolling schedule to obtain finer grain size. T_nr was obtained both by continuous cooling compression testing and tension-compression testing. However, due to the limitations of experimental installation, both compressing testing and tension-compression testing have a scaling down of practical pass strain and strain rate in rolling mill. The mathematical model that calculates mean flow stress (MFS) can eliminate these limitations and the pass strain and strain applied in mathematical model are approximately equal to the mean value of that in wire-rod rolling mill. Therefore, mathematical calculation is a new method to determine T_nr and the predicted T_nr is similar to experimental results. Due to the high strain rate and short interpass time at the finishing strain of wire rods mills, mathematical modeling is also an effective method to simulate microstructure-evolution in wire rods rolling. An expert system was established to study the microstructure evolution in two-stage rolling through the obtained dynamic recrystallization (DRX) model combined with metadynamic recrystallization (MRX) and static recrystallization (SRX) model in literature. In the present work, it is simplified that the complete metadynamic recrystallization (MRX) is achieved when strain for deformation exceeds critical strain ɛ_c. It was found that strain accumulation played an important role in finishing rolling. The recrystallization behavior during finishing rolling stage was repeated by static and dynamic model. The predicted austenite grain size and mean flow stress at each pass are expected to provide guidance for appropriate rolling schedule design.     

Fuzzy logic modeling and control of steel rod quenching after hot rolling

Reinforced concrete rod produced by European Community countries must comply with standards that establish minimum strength and tensile properties along with other technological and geometrical characteristics; however, possible variability within the assigned limits is not specified. Consequently, a number of manufacturing methods are now used, with the result that over time the mechanical properties of these products vary widely. Increased competition has led to the development of new procedures incorporating both process and quality control. One example is a process based on the heat treatment undergone by the metal bars leaving the final stand of the rolling mill train. In this way, the mechanical and technological properties can be graduated, thereby enhancing strength (particularly yield point) without altering the deformability of the material. This procedure does away with the need to alter the chemical composition of the steel used to manufacture the rods. Process adjustment still relies on the experience of the production manager, however. This paper examines the possibility of applying fuzzy logic computer techniques to the heat treatment process in order to render it more rational and independent of operator unreliability.     

Comparative study on hot rolling of Cu-Cr and Cu-Cr-CNT nanocomposites

Cu-1%Cr (mass fraction) and Cu-1%Cr-5% carbon nanotube (CNT) (mass fraction) nanocomposite powders were produced by mechanical alloying and consolidated by hot pressing. Then, nanocomposites were hot-rolled by the order of 50% reduction at 650 °C. The structure and microstructure were investigated by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Relative density, microhardness, thermal stability, electrical and wear properties were evaluated. Compared to the Cu-Cr sample, the relative density of Cu-Cr-CNT sample is greatly improved from 75% to near full density of 98% by hot rolling. Although electrical conductivity and microhardness increase in both Cu-Cr and Cu-Cr-CNT nanocomposites after hot rolling, the effect of hot rolling on the enhancement is more prominent in the presence of CNTs. The microhardness and electrical conductivity of hot-rolled Cu-Cr-CNT nanocomposite approach HV 175 and 68% (IACS), respectively. Also, hot rolling is more effective on thermal stability improvement of Cu-Cr-CNT nanocomposite compared to Cu-Cr composite. However, after hot rolling, both the friction coefficient and wear loss of the Cu-Cr sample display higher reduction than those of Cu-Cr-CNT nanocomposite owing to different wear mechanisms. After hot rolling, friction coefficient and wear loss of Cu-Cr sample display variation of 25% and 62%, respectively.     

热轧润滑的效果——热轧润滑技术讲座（二）

介绍了热轧润滑技术在国内外热连轧机上的应用效果,即可明显减少辊耗,降低轧制力,轧制力矩,提高作业率,因而经济效益非常明显;同时提出进一步改善热轧润滑效果需要重视的问题。     

热连轧生产线轧制节奏的提速优化

介绍了某热连轧厂通过优化加热炉的步进梁与装、出钢机的逻辑关系,以及优化运输区的1#回转台与1#步进梁、快链的逻辑关系,打通了整条生产线的前后咽喉,使生产节奏得到大幅提高,小时产量从19.0提高到21.8块。     

首钢迁钢2 160 mm热卷箱开卷跑偏问题分析与控制

针对首钢股份有限公司迁安钢铁公司2 160 mm热轧生产线热卷箱在使用过程中经常出现开卷跑偏的问题进行了系统分析, 发现开卷跑偏受侧导板控制、弯曲辊、夹送辊精度等多种因素影响。通过优化侧导板控制, 提高关键设备精度, 有效提高了卷形质量, 避免了热卷箱开卷跑偏的问题。     

新一代热轧强力地下卷取机

西门子奥钢联公司推出了新一代的热轧地下卷取机,命名为四辊强力卷取机。与传统热轧地下卷取机相比,四辊强力卷取机配备有四个助卷辊,用于卷取厚规格、高强度钢板,其关键技术是通过夹送辊和1#助卷辊,将进入卷取机内的带头事先进行预弯曲。卷取的钢板厚度为1.2～25.4mm,宽度可达到2800 mm。     

汽车B柱热成形试验与热力耦合仿真

热成形技术作为改善高强度钢板成形性及提高机械性能的先进制造技术,可在保证汽车被动安全性的前提下实现车身轻量化,具有重要的工业应用价值。本文基于典型汽车B柱热成形产品建立热力耦合有限元模型,对B柱热成形及淬火过程进行了数值模拟分析并与试验结果进行对比,从成形零件厚度分布、温度场及微观组织性能方面对其进行研究。结果表明:B柱产品中部拐角处厚度增加较大,尾部两侧成形壁厚减薄趋势较大,但都满足成形性要求;B柱降温速率大于27℃/s,可保证马氏体转变;成形后B柱的硬度可达450HV以上,抗拉强度可达1600MPa,微观组织为均匀的马氏体。成形后B柱各项性能均满足热成形技术规范要求。     

Measurements of friction in cold flat rolling

The effect of reduction, rolling speed and material properties on the variation of interfacial frictional and normal stresses in the roll gap during cold flat rolling is studied. The results confirm the conclusions of earlier research, emphasizing the dependence of the coefficient of friction, and hence the interfacial shear stress, on the process parameters. Preliminary experiments, using mineral oil with 1% oleic acid as lubricant, show the possible existence of hydrodynamic lubrication, at least over part of the contact area. The validity of the data is substantiated by comparing the roll separating forces, measured by transducers located under the bottom workroll, to those obtained by integrating the measured roll pressure distribution over the arc of contact. The comparison is found to be favorable, indicating that in spite of its shortcomings, the embedded pin technique gives reliable measurements.     

弹簧扁钢半连续轧制工艺技术

为了满足汽车工业的需要，兴澄钢铁有限公司在建成的具有90年代国内先进水平的中型半连轧生产线上，通过严格控制加热工艺、轧制工艺、改进孔型设计，使之成为我国弹簧扁钢的重要生产基地。     

热轧润滑油中的添加剂及热轧润滑在我国的发展——热轧润滑技术讲座(四)

介绍了热轧润滑油中各种添加剂的成分和功能，以及对其性能的要求，同时分析了热轧润滑在中国的发展前景。     

热轧带钢生产中的板形控制

针对带钢生产中出现的板形问题进行了分析,得出板形主要与轧件温度、辊缝设置、轧辊辊型等因素有关,进而提出了预防措施:不断进行轧辊辊型优化、确保轧机调整精度及保证带钢良好的运行环境。     

AM50镁合金多道次热轧中动态再结晶过程的有限元模拟及实验研究

通过开发用于组织模拟的用户程序,采用有限元软件DEFORM-3D模拟AM50镁合金多道次热轧过程中的组织转变,并通过与实验结果的对比分析证明该用户程序模拟多道次轧制的可行性。结果表明：多道次热轧有助于镁板的晶粒细化及均匀再结晶组织的获得,精轧前的板坯温度对终轧后的晶粒尺寸影响很大,但对晶粒尺寸的分布情况影响不明显。开发的用户程序亦可应用于其他类型多道次热变形过程的模拟研究。     

Nb+Ti-IF钢铁素体区热轧工艺试验研究

通过Nb Ti IF钢在1700mm机组上进行的铁素体区热轧试验,表明在现有设备能力条件下,此钢完全可进行铁素体区轧制,若在较高温度(720℃)下卷取,则钢卷中部的伸长率将能达到53%。