方矩形管连续辊弯成型金属的流动规律

 为了研究方矩形管辊弯成型时金属的流动规律,结合某厂实际生产工艺,建立了方矩形管辊弯成型的三维弹塑性非线性有限元模型,基于该模型得到的仿真结果与现场轧制结果基本一致,通过对仿真结果的分析分别得到了方矩形管辊弯成型时长边、角部、短边和纵向上的内、中、外层的金属流动规律。研究结果表明：在厚度方向稳定段处,从外层到内层的金属流动规律是不一致的,长边处的不一致性要比短边处明显;在纵向上前、中、后段处,外层上的金属流动规律存在较大的差异,前段与后段的外、内层上的金属流动规律是相反的。分析结果为预测最终成型尺寸精度与辊弯成形工艺参数的制定提供了理论依据。     

Forming evaluation of complex tube hydroformed components

Abstract

Currently, the main feedstock of tubular blank material for tube hydroforming is derived from slit steel coil, which has been roll formed and electric resistance welded (ERW). From ERW tubular blank, a number of intermediate processing stages such as prebending and preforming may be necessary to achieve the final formed component. The end result is a component that may have experienced a complex strain path history. The traditional forming limit (strain) curve (FLC) is inherently affected by non-linear strain paths; hence, a suitable alternative forming limit criterion has been studied and is proposed for complex tube hydroforming processes. The criterion proposed is the forming limit stress curve (FLSC), which is theoretically independent of strain path and prestrain history. The methods used to generate the FLC and FLSC for tubular blanks are described, and prebending is used as an example to demonstrate how complex tubular component forming operations, and subsequent formability, may be evaluated through use of the FLSC.     

Tailored Profiles Made of Tailor Rolled Strips by Roll Forming – Part 2 of 2

The main scope of the presented work is to demonstrate the potential of load optimized tubes with a varying thickness distribution in circumferential direction produced by roll forming. As initial material a so called Tailor Rolled Strip (TRS) sheet metal coil produced by Strip Profile Rolling (SPR) method was used instead of plain sheet. The TRS sheet metal is manufactured in a continuously working process by rolling one or more groves in transverse direction into the sheet metal coil. In this paper, the secondary forming of the TRS sheet metal to TRS tubes is investigated by means of FE‐simulations and roll forming experiments. To simulate the manufacturing process of the TRS tube by FEM, an integrated consideration of the process is necessary because of the large local strain hardening in the groves of the initial SPR sheet metal. In experimental roll forming operations welded tubes could be manufactured successfully. The geometrical and material properties of these tubes are analyzed. The reprocessing of TRS tubes by hydroforming is investigated by means of tube bursting tests. It has been found that an additional annealing process is necessary to achieve deformations in the grooved area during the hydroforming process.     

钢管三辊冷斜轧的轧辊辊型设计

根据钢管冷斜轧过程的变形特点，建立了辊型设计系统。把辊型设计的结果作为初始参数，由刚塑性有限元分析成型过程，将速度场、应变和应力反馈到辊型设计系统，调整辊型设计的初始参数，绘制出适应钢管冷斜轧工艺要求辊型图。     

成形工艺对冷弯方管残余应力及焊接微观组织的影响简

 冷弯方管成形有“直接成方”和“圆成方”两种方式。为了研究成形工艺对于产品的不同影响,以规格为100mm×100mm×6mm,材料为Q235的两种成形工艺的方管为研究对象,采用钻孔法对方管各个部位的残余应力进行了测量,并观测了焊缝处的显微组织。研究结果表明,不同成形工艺对纵向残余应力的分布影响较大,焊缝处的残余应力最大。“圆成方”过程中施加较大的焊接压力使得其焊接热影响区宽度小于“直接成方”工艺条件下焊接热影响区的宽度,且抑制了奥氏体晶粒长大,冷却后获得较为细小均匀的晶粒。     

方矩形管端部成型机制

 利用非线性有限元方法,结合实际生产中方矩形管辊压成形过程,建立了有限元仿真模型。基于该模型对7机架实际辊压成型过程进行了模拟运算,得到了成形过程中稳定段处节点位移矢量、应力和应变的分布情况。通过对仿真计算结果的分析,得到管头端面上在角部和边部的过渡区存在着“位移中性面”,在端面上角部和边部的中心处伴有明显的金属“外翻”和“内翻”的情况,仿真结果与现场轧制结果相符。     

The PQF pass parametric design system of heavy calibre seamless tube

According to the characteristics of PQF continuous rolling pass,the relationship between spread coefficient,wall thickness coefficient and elongation are analyzed.The section shape of tube in each stand outlet,the efficient working radius and the rotational speed of each roll are obtained,therefore,the pass parametric design is completed.A thermal-mechanical coupled model of continuous rolling tube’ s forming process is established by the three-dimensional elasto-plastic finite element method,the section shape and area of tube in each stand outlet are forecasted,which is used to modify the pass.The rolling force of each roller is predict too,which provides a guidance for pass design.In addition,a visual software of PQF pass parametric design system on heavy calibre seamless tube is generated with Visual Basic.The forming dimension of tube and the rolling force of each roller are successfully obtained,by simulating the forming process of a certain series heavy calibre seamless tube.This system posses practical utilization value.By using this system,the development cycle of new product can be shortened,the reliability of pass design can be improved,and the energy consumption of rolling mill and production cost can be decreased.     

六斜辊管材矫直过程精度解析

摘要：以管材六斜辊矫直过程为研究对象,推导了管材经一次反弯后,弹复曲率及残余曲率的演变过程。根据管材旋转一圈弯曲2次,计算了管材全流程矫直微元段的反弯次数;借助三次样条函数,以管材与矫直辊接触点为特征点,拟合出了管材在辊系中的弯曲形态。基于所获得的函数,可以获得任意位置处的弯曲曲率;对某一微梁段的反弯弹复过程进行循环迭代,计算出管材微梁段的最终残余曲率,进而得到最终的管材矫后的直线度精度。通过与现场矫直数据对比,证明该模型能够可靠地预测六斜辊矫直精度,为科学合理的设定矫直参数奠定了理论基础。     

Peter Groche

Tube hydroforming (THF) is a relatively new but established technology among metal tube forming processes. It is the technology of forming closed sections, hollow parts with different cross‐sections by applying an internal hydraulic pressure and sometimes additional axial compressive loads to force a tubular blank to conform to the shape of a given die cavity. Material properties have a significant influence on the process stability. Often roll‐formed, non‐heat treated tubular materials made of steel with longitudinally oriented welding lines are used in tube hydroforming. Different production processes involve a change of the material properties from the initial flat sheet to the hydroformable tube. Testing methods such as tensile tests and conventional forming limit diagrams do not accurately reflect the state of stress and strain conditions seen in the tubular blank during the hydroforming process. Thus, inaccuracies in FEA predictions and design failures occur. Test methods were developed to characterize the relevant geometrical and mechanical properties of tubular semi‐finished products.     

Tailored Profiles Made of Tailor Rolled Strips by Roll Forming – Part 1 of 2

To fully exploit the potential of sheet and profiles, various technologies to produce tailored blanks and profiles have been developed [1,2]. In earlier work [3] it has been shown that Strip Profile Rolling (SPR) can be used to produce metal strips with a predefined thickness distribution across the width of the strip. Building upon this knowledge, in two subsequent papers the extended goal of the project is presented. Therein is demonstrated that Strip Profile Rolling can be applied very effectively using a combination of roll forming (part 1) as well as further processing by roll forming (see part 2) to allow for the production of profiles with varying wall thickness in their cross section. To achieve the goal of part 1, a numerical model describing SPR was developed and used to study the influencing process parameters on spread and bulge formation. As a result of this parametric study, an optimized roll design and rolling sequence was developed to produce a demonstrator strip on a 12 stand roll forming mill manufactured by the company Dreistern [4]. Starting with a conventional strip out of DC01 steel (width 170 mm, thickness 2.5 mm), 29 rolling passes were necessary to achieve the desired geometry (width 186 mm, thickness 2.5 mm with a longitudinal groove being 64 mm wide where the thickness is reduced to 1.5 mm). In the second part of the process chain the coils produced by Strip Profile Rolling were successfully roll formed into a circular tube of 60 mm.     

Zr-4薄壁管矫直过程VRM20/30矫直机矫直辊角度的调整

探讨了工业生产过程中采用VRM20/30矫直机对Zr-4合金薄壁管矫直时矫直辊的调整方法,并分析研究了矫直辊角度的变化对管材的性能影响。实验证明:矫直辊角度的调整不仅影响管材的表面质量和直线度,而且对管材氢化物取向因子起着非常关键的作用;适当的矫直辊角度能很好的解决管材头尾翘起的问题,获得良好的管材表面和直线度,同时,确保管材的氢化物取向因子控制在理想的范围内。     

Numerical Simulation and Sensitivity Analysis of Parameters for Multistand Roll Forming of Channel Section With Outer Edge

 Cold roll forming is a high production but complex metal forming process under the conditions of coupled effects with multi factor. A new booting finite element method (FEM) model using the updated Lagrangian (UL) method for multistand roll forming process is developed and validated. Compared with most of the literatures related to roll forming simulation, the new model can take the roll rotation into account and is well suited for simulating multistand roll forming. Based on the model, the process of a channel section with outer edge formed with twelve passes is simulated and the sensitivity analysis of parameters is conducted with orthogonal design combined FEM model. It is found that the multistand roll forming process can be efficiently analyzed by the new booting model, and sensitivity analysis shows that the yield strength plays an important role in controlling the quality of the products.     

内螺纹铜管成形工艺研究

阐述了内螺纹铜管成形的两种生产工艺：拉拔旋压成形法和铜带滚压成形焊接法。对两种工艺的优劣进行了研究分析，并指出了应用前景。     

天钢连铸板坯中心裂纹的成因分析

针对天钢炼钢厂在连铸生产中出现的中心裂纹,结合VAI动态辊缝模拟软件、铸坯凝固过程应变理论及天钢炼钢厂的生产实践,分析了产生铸坯中心裂纹的影响因素.在设备方面,辊缝超差,特别是凝固末端辊缝超差是造成中心线裂纹的主要原因.在工艺方面,铸坯在冷却过程中,由钢水成分、浇注温度以及拉速变化引起的相变降低了钢的高温塑性.在外力作用下,坯壳承受的应力之和超过了钢的允许强度和应力时,铸坯就会产生裂纹.     

冷弯型钢成型过程的实验研究

冷弯成型变形复杂,实验研究是冷弯成型研究中不可缺少的一部分,采用电阻应变片测量法和网格法对冷弯成型过程进行研究,并以直缝焊管为例,对带材的变形及弹复等进行综合测试,获得了许多有价值的实验数据,有助于工厂改进工艺,生产出高质量的产品。     

圆管二次辊弯成形过程中的大变形有限元法模拟

应用弹塑性三维大变形有限元理论，同时考虑材料和几何双重非线性，基于Ｐｒａｎｄｔｌ－Ｒｅｕｓｓ流动规律和Ｍｉｓｓ屈服准则，并采用Ｕｐｄａｔｅｄ－Ｌａｒｇｒａｎｇｉａｎ增量叠加法分析了不同压下量成形过程中金属由非稳态到稳态的流动规律，然后通过有限元程序实现了计算机模拟。模拟结果为ＣＡＤ（计算机辅助设计）及ＣＡＭ（计算机辅助制造提供了重要理论依据，同时还可以指导实际生产过程，对提高产品的质量和经济效益有     

三辊连轧管(PQF)的计算机仿真

针对影响连轧管产品质量的几大关键因素进行了三维弹塑性大变形有限元分析，建立了相应的各种分析模型，以动态图形形式的模拟了变形过程与壁厚变化规律，为产品工艺设计提供科学依据。     

辊弯成型工艺、理论及CAE技术研究进展与展望

辊弯成型是一种未完全掌握的工艺,近年来,得到了显著的发展。从成型工艺技术、成型理论及成型ＣＡＥ技术等方面综合论述和分析了国内外辊弯成型研究的现状和发展趋势     

冷弯成型数值模拟与孔型CAD集成系统

建立了冷弯成型有限条数值模拟与孔型CAD集成系统,以轧辊孔型CAD设计的结果作为数值模拟系统的初始参数,由数值模拟系统分析成型过程,将位移、应变和应力等分析结果反馈到孔型CAD系统,修改初始孔型设计,绘制轧辊图。以槽钢为例,进行了孔型设计、成型过程数值模拟以及轧辊设计,分析结果与实际生产相结合,轧辊图被工厂所采用。     

二辊斜轧穿孔时圆管坯的变形与应力分布及其发展

为了分析二辊斜轧穿孔时圆管坏中心金属的断裂机制,确立穿孔变形的工艺实质,用MARC／Autoforge软件研究了圆管坏斜轧时的应力、应变场及其发展。进一步证实了沿圆管坯横截面直径上的变形强度确实呈W形分布。同时还发现变形强度以W形分布形态出现不是必然的,还存在U形分布形态,这与穿孔变形工具和轧机调整参数有关。在大多数情况下,二辊斜轧圆管坯变形的发展过程是：与轧辊接触的局部区域发生变形,变形随轧件的螺旋前进,先出现U形分布形态,最后出现W形分布形态。