Geometry of steel sheet in a seven-roller straightening machine

A method of determining the parameters of preliminary cold straightening of steel sheet on a seven-roller machine is proposed. The calculations permit the determination of the shape and curvature of the sheet’s central plane during and after straightening, as a function of the radius and spacing of the rollers, the reduction of the sheet by the upper rollers, the sheet thickness, and also the Young’s modulus, yield point, and hardening modulus of the steel. The results may be used at steel plants in the production of broad sheet and thick-walled pipe for pipelines.     

Simplified calculation of the bending torques of steel sheet and the roller reaction in a straightening machine

In the straightening of steel sheet, it is necessary to calculate the optimal reduction of the steel blank by the working rollers of the straightening machine so that the sheet produced has the minimum residual stress and curvature. In the simulation of sheet straightening in multiroller machines, the curvature and bending torques of the steel sheet at contact points with the working rollers are first calculated and then the straightening forces are determined. In straightening steel sheet, it is important to calculate the forces in the multiroller straightening machine. Such calculations are based on determination of the reaction of the roller bearings and the forces at the upper and lower working-roller cassettes in straightening. With insufficient bending torque, it is impossible to eliminate harmful residual stress and surface defects in the sheet. Extreme roller torques and forces at the roller cassettes often lead to defects of the sheet, fracture of the working and supporting rollers, and failure of the straightening machine. In the present work, an approximate method is proposed for calculation of the optimal cold-straightening parameters of the steel sheet in a multiroller machine. The calculations permit determination of the curvature of the neutral plane in the sheet on straightening, the residual curvature of the sheet after straightening, the bending torque and the reaction of the working-roller bearings, the residual stress in the sheet, the penetration of the plastic deformation into the depth of the steel sheet, and the relative deformation of the longitudinal surface fibers of the sheet on straightening as a function of the radius of the working rollers, the distance between the rollers of the straightening machine, the reduction of the sheet by the upper rollers, the sheet thickness, and its properties (Young’s modulus, yield point, and strengthening modulus). The results may be widely used at manufacturing and metallurgical plants.     

Asymmetric three-roller sheet-bending systems in steel-pipe production

Various attachments are used to produce components of particular configurations from metal sheet. In particular, sheet-bending roller systems may be classified in terms of the number of rollers (two, three, or four); the type of drive (mechanical, pneumatic, electromechanical, hydraulic); and the roller configuration (symmetric, asymmetric). Three-roller systems are used for the production of cylindrical, oval, and conical components by bending the metal sheet. They may be employed to manufacture pipes, channels, airways, shells, barrels, and sheathes. The operation of three-roller sheet-bending systems is based on the rotation of rollers in opposite directions, so that the sheet is captured and bent to the specified radius. To facilitate sheet supply and the release of the products bent into closed circles, the three-roller sheet-bending systems are combined with a removable front shaft applying a pressure that may be adjusted. In the three-roller systems, the diameter of the upper roller is about 1.5 times that of the lower rollers. In shaping, the rollers perform reversible motion. The upper roller may be raised and lowered to regulate the diameter of the circle produced. In this approach, extremely small sheet sections remain flat. This problem is eliminated by bending the ends of the sheet in a press or in a roller mill. In the present work, a mathematical method is proposed for determining the forces and torques in cold flexure of thick steel sheet on three-roller sheet-bending systems. The calculations permit the determination of the reaction of the roller supports, the residual stress in the wall of the steel sheet, the proportion of the plastic deformation over the sheet thickness, and the relative deformation of longitudinal surface fibers of the sheet in flexure as a function of the roller radius, the roller spacing, the reduction of the sheet by the upper roller, the sheet thickness, the Young’s modulus, the yield point, and the strengthening modulus of the steel sheet. The results may be used at metallurgical and manufacturing plants in the production of large-diameter steel pipe for major pipelines.     

首秦公司冷矫直机工艺优化及应用

为解决原有矫直模式单独依靠钢板厚度来判断的问题,在现有各缺陷矫直模型的基础上,根据实际生产特点进一步对厚度和变辊原则进行优化。结合屈服强度对厚度进行细化,将矫直模式的判断量（钢板期望塑性变形率）由原设计的3降为2,优化冷矫直机九/五矫直模式,改变了以前固定的矫直模式,实现了矫直模式的动态调整。使矫直模式根据钢板强度和厚度的变化来确定,缺陷钢板经过矫直后板形良好,完全满足标准要求。     

9～12 mm板材矫直原理与控制

由于传统矫直方法错误以及宽度、温度、钢种等因素的变化,导致9～11 mm薄规格钢板不能有效矫直,或者矫直后出现上冷床切边、分段后弯曲,成本升高,一直是板材部宽板线矫直机的一大难题.文章具体论述了如何利用矫直机使钢板产生塑性变型和弯曲变型,以及改变矫直机中心线,达到矫直边浪薄板且不反瓢的方法.     

镀锡板开平线矫直机插入量对板形控制的影响

基于镀锡板开平线矫直机结构形式,分析了矫直机结构特点及带材矫直机理。通过建立开平线矫直机有限元仿真模型,研究带材矫直过程的变形机理,分析各矫直辊组插入量对板形质量的影响。结合带材矫直过程仿真分析规律,建立了不同规格开平线矫直机插入量参数优化表,并针对不同来料板形制定矫直参数。参数优化后,带材浪形及翘曲缺陷基本消除,实现了镀锡板开平后板形质量的大幅提升,取得了良好的实用效果。     

3D surface microtopography of cold-rolled and galvanized strip

The switch from 2D filtration to 3D filtration of surface microtopography is described. Important new surface parameters in the metallurgical industry are considered. The use of 3D parameters reveals new aspects of working-roller wear and the development of roughness at the surface of cold-rolled and galvanized auto-industry steel sheet and permits comparison of the surface roughness of coated and uncoated sheet. On that basis, the development of roughness on auto-industry steel sheet in temper rolling may be reassessed; the surface texturing of the rollers may be further improved; and the quantity of rolled metal obtained from a single pair of working rollers may be considerably increased.     

Continuous bending and straightening technology of Q345c slab based on high-temperature creep deformation

A new continuous bending and straightening casting curve with the aim of full using of high-temperature creep deformation was proposed.The curvature of bending and straightening segment varies as sine law with arc length.The basic arc segment is shortened significantly so that the length of bending and straightening area can be extended and the time of creep behavior can be increased.The distance from solidifying front in the slab was calculated at 1 200°C by finite element method.The maximum strain rate of new casting curve at different locations inside the slab is 6.39×10~(-5) s~(-1) during the bending segment and it tends to be 3.70×10-5 s~(-1) in the straightening segment.The minimum creep strain rate is 7.45×10~(-5) s~(-1)when the stress is 14 MPa at 1 200°C.The strain rate of new casting machine can be less than the minimum creep strain rate.Thus,there is only creep deformation and no plastic deformation in the bending and straightening process of steel continuous casting.Deformation of slabs depending on creep behavior only comes true.It is helpful for the design of the new casting machine and improvement of old casting machine depending on high temperature creep property.     

Prediction of Maximum Section Flattening of Thin-walled Circular Steel Tube in Continuous Rotary Straightening Process

Cross-sectional ovalization of thin-walled circular steel tube because of large plastic bending,also known as the Brazier effect,usually occurs during the initial stage of tube′s continuous rotary straightening process.The amount of ovalization,defined as maximal cross section flattening,is an important technical parameter in tube′s straightening process to control tube′s bending deformation and prevent buckling.However,for the lack of special analytical model,the maximal section flattening was determined in accordance with the specified charts developed by experienced operators on the basis of experimental data;thus,it was inevitable that the localized buckling might occur during some actual straightening operations.New normal strain component formulas were derived based on the thin shell theory.Then,strain energy of thin-walled tube(per unit length)was obtained using the elastic-plastic theory.A rational model for predicting the maximal section flattening of the thin-walled circular steel tube under its straightening process was presented by the principle of minimum potential energy.The new model was validated by experiments and numerical simulations.The results show that the new model agrees well with the experiments and the numerical simulations with error of less than 10%.This new model was expected to find its potential application in thin-walled steel tube straightening machine design.     

Operation of an extension and bending machine in scale removal from hot-rolled strip

Statistical analysis of the operation of an extension and bending machine in scale removal from hot-rolled strip provides the basis for a construction of a mathematical model by logit regression, in which the tensile energy of the strip in the standard range is related to a controllable characteristic—the total overlap of the working rollers in the machine with natural variation in strip thickness and width. The model may be used to maintain stable operation of the extension and bending machine with regulation of the drive’s load over a specified range. Prospectively, it may be used to determine the rational overlap of the machine’s working rollers with modification of the extension and bending mechanism or the cross section and properties of the machined strip.     

Elastoplastic Flexure of Round Steel Beams. 1. Springback Coefficient

Round steel beams are widely used in metallurgy, manufacturing, and construction. It is often irreplaceable in the production of machines and mechanical equipment on account of its excellent corrosion resistance and remarkable strength. Cylindrical springs for road and railroad vehicles are manufactured from round beams by means of special bending machines. Round beams also serve as blanks in the production of seamless pipe for the oil and gas industry. Stepped round beams are used as rollers in rolling and straightening mills. Steel rebar is manufactured from round beams of similar size. Outside Russia, the main producers of continuous-casting machines for the production of round billet are SMS Demag (Germany), Danieli (Italy), SMS Concast (Switzerland), and Siemens VAI (Austria). Russian producers include AO Chusovskii Metallurgicheskii Zavod, PAO Chelyabinskii Metallurgicheskii Kombinat, AO Volzhskii Trunbnyi Zavod, OAO Nizhneserginskii Metizno-Metallurgicheskii Zavod, AO Chepetskii Mekhanicheskii Zavod, PAO Severskii Trubnyi Zavod, and PAO Taganrogskii Metallurgicheskii Zavod. In the manufacture of parts from round beams and their use, they often experience elastic or elastoplastic flexure or complex torsion and flexure. In the present work, we propose an analytical method of calculating the residual curvature of round steel beams in elastoplastic flexure. In the calculations, the residual curvature of the round beam after flexure and the bending moments of the beam cross section in flexure are determined as a function of the beam radius, the Young’s modulus, the yield point, and the hardening modulus of the steel. The results may be widely used at manufacturing and metallurgical plants.     

钢高温蠕变特性对连铸坯矫直变形的影响

 为使连铸坯在矫直过程中能够充分利用钢的高温蠕变特性,避免产生内部矫直裂纹,对铸坯矫直及机型曲线进行了研究。首先,在Gleeble-3800热模拟试验机上对Q345C连铸坯进行热塑性和高温蠕变试验,确定了Q345C钢的热物性参数和最小蠕变应变速率方程;其次,根据钢的高温蠕变特性,针对目前使用的某连铸机设计了新机型曲线;最后,采用热力耦合数值模拟的方法,计算了距离铸坯内弧侧表面38.3 mm处中心点的温度分布和应变速率。通过蠕变矫直机型应变速率和蠕变速率的对比表明,蠕变矫直机型曲线可以充分利用钢的高温蠕变变形进行矫直,蠕变变形量占总矫直变形量的比例达到88.6%,因此可降低铸坯内部矫直裂纹产生的可能性,有利于提高铸坯质量。     

φ15～70mm液压管材矫直机机架工作状态有限元研究

φ15 ～ 70mm液压管材矫直机为十二辊矫直机,采用有限元方法分析矫直过程中机架受力变形情况.研究建立了矫直机机架的三维模型,用最大理论矫直力作为工作载荷,对机架的形变进行有限元仿真分析研究.得出了机架的各单元、节点的变形值及应力值,找到了机架的应力和位移分布规律,并据此提出了机架的改进措施,为保证矫直精度打下基础.     

The Bauschinger effect and the formation of microalloyed-steel properties in pipe manufacture

The Bauschinger effect is investigated on samples of microalloyed pipe steel. Tests are conducted with one and several extension-compression cycles on a Gleeble-3800 system, at room temperature and elevated temperatures. The influence of temperature on the final sheet properties is considered in conditions of small alternating deformation, so as to simulate the straightening of hot-rolled sheet. The successive influence of each cycle on the final properties of the metal is demonstrated. The strength of the final strip may be modified by 150 MPa, depending on the selected straightening temperature.     

18－8型不锈微型工字钢的矫直与设备参数

１８－８型不锈微型工字钢因断面小和两个方向尺寸的相对接近而产生严重的双向弯曲，加之该材料的高强化系数（η＝０．２５），使普通的单向弯曲矫直方法很难保证矫直精度，故确定采用立辊组与水平辊组联合的双向辊式弯曲矫直新方案。文中同时推荐了带微张力的拉伸弯曲矫直新工艺。     

九辊高强度钼材料热板矫直机技术分析

以一台满足矫直高温、高强度钼板材料的九辊矫直机为例,对矫直大厚度规格范围的热态、高强钼板矫直机进行了完整的技术分析,包括辊系布置方式、矫直主要力能参数、矫直机结构特点。     

金属薄板滚压冲裁过程数值模拟及模具参数

研究了在没有压下辊的情况下滚压冲裁过程的运动学特性,据此提出了通孔滚压冲裁模具的设计方案.在此基础上,利用ABAQUS有限元软件进行了基于Shear Failure韧性断裂准则和任意拉格朗日一欧拉自适应网格技术的45号钢薄板滚压冲裁过程有限元仿真,分析了主要参数对断面质量的影响.仿真结果表明:方形孔滚压冲裁时,前后刃口依次经历板带弯曲、凸模压入、裂纹产生和发展、断裂和凸模拔出五个阶段;滚压冲裁断面的主要质量缺陷包括断面垂直度、毛刺、塌角、压痕等;影响滚压冲裁断面质量的主要因素包括侧隙、凸模高度、辊子半径等.减小标称侧隙和凸模高度、增大辊子半径均会使断面质量提高,其中又以对断面垂直度和毛刺高度的影响更为明显.对于45号钢一类的碳钢,后刃口标称侧隙以板厚的5%-10%为宜,前刃口标称侧隙可以更小:辊子半径应以大于板厚的100-150倍为宜;在保证板材完全断裂的前提下,应使凸模高度尽量减小.      

辊式水平矫直对重轨断面尺寸的影响分析

 采用ANSYS/LS DYNA软件模拟了八辊复合矫直机水平矫直60 kg/m重轨过程,计算了矫直前后轨头宽度、轨底宽度和轨高的变化,并对60 kg/m重轨实际矫直前后的断面尺寸进行了测量。矫直后轨头宽度增加量在0.1~0.5 mm范围内所占比例约为82.9%,轨底宽度增加量在0.1~0.4 mm范围内所占比例约为68.6%,轨高减小量在0.2~0.6 mm范围内所占比例约为71.4%。模拟结果和实测断面尺寸的变化量基本吻合。矫直辊压下量和重轨弯曲度的减少,可以降低矫直对重轨断面尺寸的影响。     

Q345钢中厚板热矫直变形抗力与弹性模量数学模型的研究

根据中厚板矫直力的理论公式和Q345钢22～40mm板500～630℃矫直的生产实测数据,以变形抗力和弹性模量数学模型中的待定系数为优化变量,以矫直力计算误差最小为目标函数,采用单纯形法对待定系数进行优化计算,建立了Q345钢中厚板矫直过程变形抗力和弹性模量数学模型,得出Q345钢中厚板在500～630℃矫直过程随温度(T)提高,变形抗力(σs)降低:σs=-1080.1+4.8547 T-0.0048115 T~2;随温度(T)提高,弹性模量(E)先增加后减少:E= (-6.4807×10~5) +2576.5 T-2.3875 T~2。结果表明,矫直力的计算值和测量值的相对误差小于5%。     

Influence of alternating cold flexure on the properties of low-alloy pipe steel (strength class K56–K65)

In laboratory conditions, the cold straightening of thick (17.5 mm) low-carbon low-alloy steel sheet (yield point no less than 550 N/mm²) is simulated by alternating flexure. The influence of the number of cycles and the strain in alternating flexure on the strength of the steel is studied. For industrial production on the 5000 mill at OAO Vyksunskii Metallurgicheskii Zavod (VMZ), the influence of the cold-rolling conditions on the yield point and strength of thick (15–23 mm) steel sheet (strength class K56–K65) is demonstrated.