Evaluation of stamping lubricants using the deep drawing test

This paper presents a practical methodology that uses the deep drawing test and finite element (FE) analysis to evaluate stamping lubricants under near production conditions. In stamping operations good lubrication helps to reduce wrinkling, premature fracture, and localized thinning. Furthermore, lubrication also reduces tool wear in large-volume production. Determination of reliable friction data associated with a given lubrication system is also important for successful process design and simulation by FE analysis. In this study, five stamping lubricants (four dry film lubes and one wet lube) were evaluated using the deep drawing test. The performance of the lubricants were evaluated based on: (a) maximum punch force measured, (b) the maximum applicable blank holder force (BHF), (c) the draw-in length, (d) the perimeter of flange after test, (e) the change of surface roughness, and (f) the inspection of surface topography. The coefficient of friction for each lubricant tested was determined through the FE-based inverse analysis by matching the predicted and measured values of the load-stroke curve and the draw-in length. This study showed that one of the tested lubricants was most effective, regardless of test speed and the magnitude of BHF. The methodology used was shown to be effective in evaluating various lubricants for sheet metal forming and accurately differentiating their performances.     

Evaluation of stamping lubricants in forming advanced high strength steels (AHSS) using deep drawing and ironing tests

In forming AHSS, the lubricant must reduce the friction between die and sheet as well as the effect of heat generated from deformation and friction, especially in forming at high stroking rates. In this study, the effectiveness of stamping lubricants was evaluated by using the deep drawing and ironing tests. Various stamping lubricants were tested in forming of DP590 GA round cup samples. In these tests, the performance of lubricants was ranked via evaluation criteria that include punch force and the geometry of tested specimens. Deep drawing tests were conducted at two different blank holder forces, BHF (30 and 70 ton) at a constant ram speed (70 mm/s). The ironing tests were conducted to evaluate the performance of lubricants at higher tool–workpiece interface pressure than that is present in deep drawing. Polymer-based thin film lubricants with pressure additives (e.g. Lubricants A and B) were more effective than other lubricants as shown by the force (e.g. maximum punch force and applicable BHF without cup fracture) and geometry indicators (e.g. draw-in length, flange perimeter and sidewall thinning).The pressure and temperature distributions at the die–sheet interface were predicted by FE simulation of deep drawing and ironing tests. As expected, the value of interface pressure and temperature were maximum at the die corner radius.     

Optimization of ironing processes by means of DOE and FEA

The range of possible applications of ironing processes reaches from the production of cylindrical pressure tanks, shock absorber pipes, battery and beverage cans to the production of flacons for the cosmetics industry. One goal of the finite element analyses of ironing processes is to gain knowledge about process limits regarding maximized forming capacity and optimized surface quality. The ironing process is characterized by parameters like friction, geometry of the ironing ring and anisotropic material behavior. Due to the high complexity of this process, it is complicated to detect these effects on the basis of experimental investigations only. Therefore, one of the aims of this study is to identify relevant process parameters by means of systematic numerical analyses. The design of experiments was utilized to create a model of the ironing process. By means of this model it was possible to reduce the punch load and to minimize the tensile stresses in the first stage of the analyzed ironing process.     

变薄拉深过程的数值模拟

利用上限元法对变薄拉深过程进行了数值模拟。在考虑加工硬化的基础上分析了凹模、芯轴与制件之间的摩擦因子以及变形比对变薄拉深工艺过程的影响。     

Analysis of the ironing of a BJ-type constant velocity joint outer race with the upper bound element method

A constant velocity joint outer race is an important load-supporting part in cars, which transmits torque between the transmission gear box and the driving wheel. The outer race is difficult to be forged because its shape is very complicated and its required precision is high. There is no mature technology, especially no cold and warm forging process, to produce this component in China. In order to meet the demands of Chinese automobile industry, the Science Committee of China approved a project named “Development of Constant Velocity Joint Outer Race with Cold and Warm Forging Technology” in 1995. It is one of the key projects in the ninth five-period of China, and is in the charge of Beijing Mechanical and Electrical Research Institute.The key of forging the outer race is how to implement its ironing. This paper analyzes the cold and warm forming of the ironing process of the outer race, in order to offer a theoretical basis for die designing and the choice of press, with the upper bound method. The paper deduces the general equations for computing the forming force and punch pressure for the problem of the ironing of the outer race. In order to testify these equations, this paper computes the numerical solution of the ironing force of the outer race of a Santana car.     

Development of simulation code for calculating residual stress distribution in D-I cans produced by both-sided ironing process

A code of FEM for an elastic and plastic material has been developed to calculate a residual stress distribution in D-I can by both-sided ironing. It is possible for the code to simulate a forming process of deep drawing from a sheet to a can, an ironing process of both-sided of the can wall, and a deformation of the whole of the can under perfect unloading when the can is removed from an equipment of deep drawing and ironing. From these simulations, quite different and contrary distributions of residual stress are obtained according to mutual positions of dies for the ironing, which are considered to expand the wall of can as an ellipsoidal shape or shrink it to a hyperbolic shape.     

干式与湿式清洗机在大型冲压线上的应用对比

干式清洗机是大型冲压线线首用于清洗汽车外覆盖件板坯料的一种新型的清洁设备。本文介绍了该设备原理、国内外应用情况以及与传统的湿式清洗机的性能特点、实际工程应用的对比分析。分析表明干式清洗机在清洗效果、性能和经济性上较传统的湿式清洗机有明显优势。     

Lubricity of volatile lubricants in sheet metal rolling

A series of experiments is carried out by using a rolling type tribometer to investigate the lubricity of the volatile lubricants at high speed forming. The roll material is the die steel alloy SKD11, and the workpiece material is the mild steel SPCE with a rough surface and the aluminum alloy A3004 with a smooth surface. Experimental results show that the friction coefficient decreases with increasing working velocity for both SPCE and A3004, in any lubricant. With an increase of reduction in thickness, the friction coefficient decreases for SPCE, but increases for A3004. Some volatile lubricants have the same lubricity as the generally used mineral oil with low-viscosity by judging from the value of friction coefficient, the surface appearance of rolled workpiece and the roll surface damage.     

Evaluation of coefficients of friction in hot stamping by hot flat drawing test

The coefficient of friction in hot stamping was measured using a tribosimulator. Simulative experiments were carried out using SPHC steel and 22MnB5 steel under dry conditions. The coefficient of friction of 22MnB5 steel was higher than that of SPHC steel. The obtained coefficients of friction were effective for use in numerical simulations by finite element analysis. The obtained coefficients of friction under lubricated conditions for both steels were lower than those under dry conditions. It could be understood that the use of lubricants is effective for decreasing of the stamping load and die wear.     

Thermal behavior of aluminum-coated 22MnB5 in hot stamping under dry and lubricated conditions

The hot stamping of aluminum-coated 22MnB5 has usually been conducted under dry condition, for which the forming load is high since the coefficient of friction is over 0.5. In order to decrease the forming load, the authors previously proposed the use of a lubricant to decrease so that the coefficient of friction from over 0.5 to 0.3. However, it is necessary to understand the heat transfer property in hot stamping under lubricated condition. The purpose of this paper is to examine the heat transfer property of aluminum-coated 22MnB5 in hot stamping under dry and lubricated conditions. In this study, the die and specimen temperatures were measured during compression and compression-sliding tests under dry and lubricated conditions using the hot flat drawing test simulator. In the compression test, the die and specimen temperatures measured under dry and lubricated conditions were the same. On the other hand, in the compression-sliding test up to a sliding distance of 70 mm, the die temperature under lubricated condition was lower than that under dry condition, and it was found that the heat transfer under lubricated condition is superior to that under dry condition. Consequently, there is a difference between the specimen temperatures under dry and lubricated conditions. However, from the results of the tensile test, there is no difference between the tensile strengths under dry and lubricated conditions.     

一种新型热冲压模具钢的高温摩擦磨损性能

将开发的新型热冲压模具钢作为试验钢,常用的热作模具钢H13作为对照钢,采用Bruker UMT-3型高温摩擦磨损设备,同时对试验钢和H13钢分别在400、500、600和700℃进行高温摩擦磨损试验。针对摩擦因数和磨损率两方面的试验结果,从微观角度、磨损机理、化学成分和碳化物类型等方面进行了分析和探讨。研究表明：试验钢的高温摩擦磨损性能优于H13钢,温度是影响热冲压模具钢摩擦磨损性能的重要因素,具体体现在氧化层厚度和基体硬度两方面。试验钢的磨损机制主要以氧化磨损和粘着磨损为主,而H13钢同时存在氧化磨损、粘着磨损和磨粒磨损。     

Evaluation of high‐temperature corrosion life using temperature gradient corrosion test with thermal cycle component in waste combustion environments

In energy conversion facilities such as boilers and pyrolysis reactors that burn waste, fossil fuel, biomass and other materials, many corrosion factors, such as gas temperature and fluctuations in gas temperature, the condition of deposits, and gas composition, influence the high‐temperature corrosion rate of materials in a complex manner. In order to evaluate the corrosion behavior and corrosion life time of materials rapidly and accurately, a temperature gradient corrosion test (TGT) was developed and applied to waste incineration environments. The TGT with thermal cycle was carried out without corrosive deposits in order to investigate the basic effect of gas temperature and fluctuation on corrosion behavior, especially in terms of the stability of protective oxide layers. As a result, it was clarified that gas temperature enhances the environmental factors such as the deposition rate of ash and penetration of corrosive species, while thermal cycle mainly enhances material factors such as the breakdown of protective scales. Furthermore, three application case studies of TGTs for corrosion life estimation were carried out with a comparison between TGT and field corrosion data. From these studies, a good correspondence of corrosion rates between TGTs and field tests was obtained. This correspondence of corrosion rate was explained by the breakdown of the protective oxide layer and the penetration of corrosive species in a corrosion front. The reproducibility and applicability of TGTs in the evaluation of the corrosion life time of materials were clarified based on the consideration of various corrosion mechanisms.     

防撞梁热冲压成形温度场研究

通过热冲压成形试验,研究防撞梁热冲压过程中的温度变化情况。结果表明,防撞梁坯料从炉子转移至模具过程中,出炉时降温速率为25 ℃/s,成形前降温速率为10 ℃/s。初始成形淬火1 s内,温度下降剧烈,冷却速度可达到200 ℃/s以上,成形淬火后5 s内,基本完成马氏体相变,平均淬火速度达到108.5 ℃/s以上,远远超过马氏体临界淬火速度。     

Lubrication using porous surface layer for cold drawing of steel wire

As a lubricant for steel cold working, metal soap on zinc phosphate coating is widely used. However the lubrication causes hazardous wastes, and hence an alternative system is demanded. The authors proposed to utilize porous layer on workpiece surface as a reservoir of liquid lubricant. In this study, 0.64%C steel wires were oxidized at 923 K under air and chemically reduced by pure hydrogen to form porous surface layer with pores 1–2 μm in diameter. In cold drawing with machine oil, the friction coefficient on the porous surface was 0.06, while that on normal surface was 0.11. The lubrication mechanism with porous surface is discussed.     

Evaluation of new cold forging lubricants without zinc phosphate precoat

Zinc phosphate coatings plus metal soap lubrication system is required in nearly all steel cold forging operations. However, the chemical byproducts of this lubricant system are difficult to dispose of and have a negative environmental impact. In order to replace zinc phosphate based lubricants partially or completely, candidate lubricants were sought from lubricant manufacturers worldwide. The performance evaluation of these lubricants was conducted using the double cup backward extrusion test developed at the Engineering Research Center for Net Shape Manufacturing (ERC/NSM). With the use of the commercial FEM code DEFORM, friction factor calibration curves, i.e. cup height ratio vs. punch stroke, were established for different friction factor values. By matching the cup height ratio and the punch stroke from experiment to that obtained from FE simulations, the friction factor of the lubricants was determined. Three lubricants; namely, MEC Homat, Daido AquaLub, and MCI Z-Coat, were found to perform comparable to or better than zinc phosphate.     

利用SolidWorks 2001求解冲模压力中心

在模具设计过程中,冲模压力中心通常采用解析法或作图法求解,但这些方法计算繁琐,效率低,易出错。本文介绍一种利用SolidWorks软件在设计过程中直接求解冲模压力中心的方法,快速直接,简单方便,精度较高。     

翼子板前保险杠处冲压工艺分析

翼子板前保险杠处由于翻边面太深导致翻边起皱及外观圆角不顺等缺陷,影响零件的成形质量,通过实际案例介绍了2种常见的翼子板与前保险杠的搭接结构,并通过Auto Form软件对前期工艺方案进行成形性分析,找出最优的工艺方案,后期实际模具再验证方案的可行性,减少模具开发时间,为后续零件设计及工艺设计提供指导。