Roller grooving in ball-rolling mills. Part 1

In ball rolling, the metal is deformed in rollers with helical grooves. Accordingly, the deformation zone may be dividing into the shaping section, where the blank is captured and rolled and the ball is formed, and the finishing section, where the ball is smoothed, its final dimensions are attained, and the links between balls are severed. For normal rolling, the shaping section is calibrated. In the present work, the roller grooving for a spherical blank is calculated, when the ball diameter is 125 mm. The initial data for grooving of the ball mill are presented.     

Capture of an H-beam blank by the rollers in the reduction stand of a 1300 universal beam mill

The capture conditions for an H-beam blank by the grooved rollers in the 1300 reduction stand of a universal beam mill at Nizhny Tagil metallurgical works are considered. The stress–strain state of the metal in the deformation regions on rolling the beam in the roller grooves of the reduction stand is investigated. The calculation results are presented as the distribution of the contact normal and tangential stress in the deformation regions as the H-beam blank is captured by the rollers. The normal tensile stress in the wall of the Hbeam blank is no more than 52 MPa. In the deformation regions of the crosspieces and at their junction with the wall, the normal contact stress is compressive. That indicates a stress state favorable in terms of H-beam quality, with high compressive stress. A method is developed for calculating the dynamic loads in the drive line of the 1300 reduction stand, with allowance for the gaps in the spindle joints.     

Heat treatment of rollers in the ShPS 30-80 ball-rolling mill at JSC DMPZ

In the production of steel rollers, surface decarburization may occur in the course of heating before quenching. Means of more effective protection against such decarburization are considered in the case of the 35X CA steel barrel of wrapped rollers for the ShPS 30-80 ball-rolling mill. A technological protocol for the heat treatment of the rollers is developed. It is shown that protection by means of nitrogen + a carburizing agent + a muffle increases the likelihood of the desired outcome (no decarburized surface layer and hardness no less than 45 HRC) by 31.9% in comparison with protection by means of Barier protective compound + a carburizing agent + a muffle. On average, 450–470 t of grinding balls (diameter 40 mm; hardness groups III and IV) may be rolled in a complete run (to regrinding) on rollers heat-treated by the proposed protocol.     

热轧带钢局部硬度对冷轧带钢板形的影响

考虑轧件材质横向差异对冷轧带钢板形的影响,采用末架轧机出口带材横向厚度分布和板形作为验证模型精度的指标,定量研究了热轧来料局部硬度对冷轧带钢板厚和前张应力分布的影响程度及规律,通过与现场实测数据的对比,证明该模型提高了轧后板形的计算精度。研究结果显示,局部硬度对冷轧带材的张应力分布影响显著,附加张应力与硬度峰高度成正比,给出了冷连轧过程中轧后带材附加厚度和附加张应力与热轧来料局部硬度的关系。     

不锈钢/碳钢耐蚀海水带肋钢筋轧制复合工艺

摘要：海洋工程用带肋钢筋要求有耐氯离子腐蚀能力，但选用双相不锈钢生产成本过高，不锈钢 碳钢轧制复合钢筋则可兼顾耐蚀性和低成本。覆层采用2205不锈钢，基材为低合金钢20MnSi，用有限元方法模拟钢筋的热轧复合过程，分析轧制过程尤其是成品孔中轧件的变形规律。有限元仿真发现，矩形组合坯料无孔型轧制时，其角部复合困难，而成品孔轧制时，钢筋横肋根部的应变最大，覆层在此位置减薄显著，应选择合适的复合坯覆层厚度。在实验室采用焊接、真空处理和热轧方法制备了直径为16mm的复合钢筋，屈服强度为485MPa，抗拉强度为701MPa，断后伸长率约为37.1%，复合界面剪切强度为317.5MPa。复合钢筋呈良好的冶金结合，Fe和Cr的扩散层厚度约为40μm。该工艺生产的复合带肋钢筋成本较不锈钢降低50%以上。     

Improving the quality of steel grinding balls

The development of steel-ball production within the Commonwealth of Independent States over the last 50 years is analyzed. Three periods are identified and characterized. The factors responsible for poor ball quality are discussed. The requirements for the production of high-quality balls with hardness up to HRC 65 are outlined, in terms of the chemical composition of the steel, the equipment required, and the production technology. Significant increase in ball quality requires the creation of specialized rolling systems. The fundamental principles to be adopted in creating such systems are reviewed.     

Multi-Wedge Cross Rolling of Balls

The multi-wedge cross rolling process of forming balls is described. The process tool for rolling 8 balls with a diameter of 35 mm is presented. The course of the rolling process, distributions of forming forces as well as maps of effective strain and temperature in the obtained balls are presented by finite element modeling (FEM). Experimental tests of simultaneous forming of 4 balls with a diameter of 22 mm conducted in laboratory conditions at Lublin University of Technology have proved that the balls obtained in multi-wedge cross rolling are of good quality and can therefore be used in both ball mills and rolling bearings.     

薄板坯连铸连轧低合金耐磨钢磨料磨损特性

 研制了30CrMo,50CrV4两种牌号的薄板坯连铸连轧低合金耐磨钢板,对试验钢板进行淬火和低温回火热处理,并且与传统热轧工艺生产的热轧态的45,16Mn,Q235钢对比进行低应力磨料磨损试验,研究其磨损特性。结果表明,淬火低温回火态薄板坯连铸连轧30CrMo,50CrV4钢的相对耐磨性都达到了热轧Q235钢的1.6倍以上。在低应力磨料磨损下,显微切削机制为主要磨损机制,淬火回火态薄板坯连铸连轧低合金耐磨钢具有高硬度因而具有较好的耐磨性能,并在试验钢板硬度高于450HBW以后相对耐磨性明显提高。对比两种牌号的薄板坯连铸连轧低合金耐磨钢的显微组织、硬度、韧性及耐磨性能,30CrMo钢的综合性能较好。50CrV4钢耐磨性能较好,但其冲击韧性较低。     

Optimization of groove configurations

Billet of square or rectangular cross section is rolled in grooves on bar mills. The degree of reduction and the shape of the grooves determine the stress state of the metal in the deformation region and the energy consumption in rolling. The tensile stress at the bar surface depends on the longitudinal and transverse deformation. Under the action of the tensile stress, the integrity of the metal surface may be disrupted. For each steel, there is a limiting strain beyond which the bar surface disintegrates. The ratio of the current strain to its limiting value determines the degree to which the metal’s reserve of plasticity has been depleted; that, in turn, characterizes the probability of defect formation at the metal surface. The optimal groove configuration may be selected by simulation of the rolling conditions and assessment of the metal’s plasticity and the energy consumption.     

高速线材轧制断丝原因分析与控制

针对小规格高速线材生产中出现的颈缩、断丝等现象,分析了生产中辊缝、张力、温度、辊环、导卫等轧制工艺参数设定与调整不当,电气和设备故障,结疤、缩孔、夹杂群等轧件的内外部缺陷等影响因素。讨论了张力设置、高温强度、小断面断丝和断丝受力分析等关键问题,指出机架间张力增大、轧件断面积减小和材料的强度极限降低是产生断丝的根本原因。...     

轧制变形对93WNiCu合金微观结构和力学性能的影响

选用93WNiCu高比重合金,采用冷轧的方法对其进行轧制变形处理,变形量分别为5%、10%、15%、20%,通过对变形前后材料内部组织结构的观测,分析了材料内部轧制变形机理,并对变形前后的材料进行力学性能测试,对比分析轧制变形对93WNiCu合金性能的影响。结果表明:93WNiCu合金材料经过轧制变形后内部钨颗粒呈条带状,粘结相均匀分布在钨颗粒之间;轧制变形可有效地提高合金的抗拉强度,20%变形量的轧制变形就可使材料的室温抗拉强度由烧结态的900 MPa提高到1 270 MPa,延伸率由7.6%降低到4%;通过金相以及拉伸断口显微观测,分析了93WNiCu轧制变形强化机理。     

Modelling floorplate pattern generation

Abstract

The rolling of floorplate is considered as a combined process of reduction and extrusion. The reduction from the incoming plate thickness to the outgoing plate thickness is combined with extrusion of material into grooves cut into the rolls to produce a raised pattern on one side of the base plate. The average rolling pressure is predicted and used to determine an extrusion ratio and hence a pattern height. The theoretical model is based upon mass flow conservation, a simplified form of rolling pressure calculation, and a linear fit to known relationships between extrusion ratios and pressures. Comparisons with results obtained from dimension measurements of rolled floorplate are presented.     

Plasma hardening of cast-iron rollers for channel production on a 450 mill at OAO EVRAZ ZSMK

The microstructure and microhardness of the hardened surface layers of cast-iron rollers are investigated. Plasma hardening of the grooves in a 450 mill is proposed. Industrial tests show that this approach extends roller life.     

Kinetics of static strain aging after temper rolling of low carbon steel

Abstract

In this study, static strain aging behaviour of cold rolled steel strips was considered with emphasis on the distribution of residual hydrostatic stress developed during temper rolling. In order to assess residual stress distribution produced by the temper rolling, a three-dimensional model was first employed. Then, samples were rolled at a reduction of 4% under single and double pass rolling programmes and the kinetics of static strain aging phenomenon as well as the required activation energies were then evaluated using hardness and tensile tests on the deformed samples. Considering the predicted residual hydrostatic stress distribution, it was found that tensile hydrostatic stresses promote the kinetics of the static strain aging process and alter the activation energy required for the phenomenon. In addition, it was revealed that different positions of the rolled steel show different aging behaviour owing to non-uniform distribution of residual stresses after temper rolling.     

Flexural Forces of the Working Rollers and the Broadening of Thin Steel Strip in Hot Rolling

On the basis of the Jourdain variational principle for a rigid–plastic body and the kinematically permissible velocity field, a model of the free expansion in the hot rolling of thin sheet is developed. The functional used in the variational equation is the total power of the internal resistances, the slipping-friction forces, the shear forces, and the front and rear tension. The Ritz method is used in solving the Jourdain variational equation for rolling with tension. The Jourdain variational equation is converted to a system of uniform equations, with a derivative of a variable parameter on the left side of each. The variable parameters are the exponent of the kinematic condition; the total broadening in the plastic-deformation region; and the expansion in its neutral cross section. The mathematical model developed for the broadening of hot-rolled strip may be used to investigate the distribution of broadening along the plastic-deformation region as a function of the parameters of the rolling process and the strip. To verify the model of free expansion, experiments are conducted on a two-roller laboratory cold-rolling mill. Lead samples are rolled. Their measured broadening matches the theoretical values to within 10%. The cold rolling of lead samples simulates hot rolling. Theoretical analysis of the influence of tension on the free expansion is consistent with practical results in the literature. The nonuniform tensile stress seen in the input and output cross sections of the deformation region when tension is applied gives rise to additional powers in the balance equation, with consequent decrease in the broadening. The resulting nonuniformity of the tensile stress may be used to regulate the broadening in thin-sheet rolling. In turn, the nonuniformity of the tensile stress over the strip width may be increased or decreased by means of the flexural forces of the working rollers in the mill. A method of regulating the broadening of the strip in hot rolling by means of the flexural forces of the working rollers is outlined in the present work.     

Using rollers with increased barrel length in four-high mills

Increase in barrel length of the working rollers from 3100 to 3400 mm is proposed in the 3000 mill, without change in barrel length of the supporting rollers (2980 mm) or in the structure of the cell. Calculations of the pressure between the rollers and the transverse thickness variation of the rolled metal when the barrel length of the working rollers is 3100 and 3400 mm shows that the maximum pressure between the rollers is increased by 6–8% for 3400-mm working rollers with rolled sheet of maximum width 3200 mm; the rolled material is concave. To obtain a convex cross section, the depth of the bevel of the edges of the supportingroller barrel is doubled. Increasing the length of the working rollers in the 3000 mill at PAO Mariupol’skii Metkombinat im. Il’icha permits the production of commercial sheet with a width up to 3000 mm.     

Formation of surface microtopography in the temper rolling of auto-industry steel sheet

A model is proposed for the formation of the surface microtopography in the temper rolling of cold-rolled steel sheet as function of the microtopography of the blank and the working rollers. In the model, temper rolling is treated as a linear system with several inputs and a single output. The results of simulation are compared with experimental data, and the model proves adequate.     

连铸坯轧重轨的压缩比及帽形孔和切深孔的应力场分析

对某厂所使用的重轨孔型自切深孔以后的轧件压缩比进行了分析，对帽形孔和切深孔中沿轧件横断面上的应力场分布进行了弹塑性有限元计算机模拟。结果表明，用连铸坯取代初轧坯，如果坯形和孔形不进行相应的改变，轧件轨头和轨底的压缩比小，难以确保重轨的质量。现有的孔型，沿轧件的横断面上，局部位置存在着较大的拉应力。使用初轧坯，这种拉应力对产品质量的影响不大。但对于连铸坯，如果坯形和孔型均与初轧坯相同，轧件有产生内部缺陷的条件。     

冷轧工作辊回火工艺与硬度的回归计算

介绍冷轧工作辊经50／250Hz双频感应淬火后低温回火工艺与硬度的关系，揭示了二者之间的规律，并用回归方程计算方法阐明回火工艺与硬度之间存在强负线性相关关系。     

热轧带钢纵向亮带产生原因分析

根据热轧带钢表面出现的纵向亮带特征及发生规律,结合热轧生产过程工艺特点,分析了其产生的主要原因是带钢与卷取张力辊的局部接触,在张力辊压力、张力辊与卷筒间的张力共同作用,使接触区域的带钢发生塑性变形造成的。并提出了消除缺陷的措施。