Influencing factors of wrinkle defects of tailor rolled blank for square box in drawing process

Tailor rolled blank(TRB) is inclined to wrinkle during the forming process because of the nonuniformity of blank thicknesses and mechanical properties. The wrinkle defect of TRB square box in deep drawing was studied by numerical simulation and stamping experiment. The mechanism for the wrinkle defect of TRB square box was discussed, and effects of blank size, thickness transition zone length and position, and blank thickness on the wrinkle defect of TRB were analyzed by taking thickness strain as an evaluating indicator. Finally, the measures restricting the wrinkle defects were presented. The results indicate that the spots inclined to wrinkle for TRB square box are the flange on the thinner side, the flange on the thicker side, and the flange in the thickness transition zone. The smaller the blank size and the thickness transition zone length are, the harder TRB is to wrinkle. Greater or smaller thickness difference can both restrain the wrinkle phenomenon, and thickness transition zone center offset from the blank center may lead to the occurrence of wrinkle.     

一种Si-Mn系超高强度钢板的热冲压成形试验研究

 采用弯曲件热冲压成形试验研究了板料加热温度、保温时间及移送时间等工艺参数对一种Si-Mn系超高强度钢板热成形零件的力学性能及微观组织的影响规律。结果表明,通过控制热成形工艺参数,在所设计的模具上可实现Si-Mn系超高强度钢板热成形零件的有效淬火,在合适的工艺参数下,可获得细小均匀的马氏体组织,从而获得抗拉强度1700MPa以上,伸长率10%以上的性能,达到原始板料抗拉强度的3倍左右,并明显高于传统的Mn-B系超高强度钢板。     

轿车零件应变分析与FLD选材预测

对ＣＡ７２００红旗矫车主要零件使用的钢板进行了冲压级别分类,采用网格法测定了零件冲压后的应变值并绘制了零件应变图和成形极限图（ＦＬＤ）。用有限元模拟分析（ＦＦＡ）确定出油底壳零件变形的危险部位,计算了危险部位的成形安全裕度,并对零件优化选材进行了性能预测。     

Material Flow Control in High Pressure Sheet Metal Forming of Large Area Parts with Complex Geometry Details

Working media based forming processes show advantages compared to the conventional deep drawing in the range of sheet metal parts with complex geometry details. By High Pressure Sheet Metal Forming (HBU), complex parts can be formed with reduced tool costs, fewer process steps, and improved part properties, particularly by the use of high strength steels. In order to use these advantages to full capacity, the material flow into the area of the geometry details needs to be optimised. The key element for the material flow control is a multi‐point blank holder. In combination with flange draw‐in sensors, a closed loop flange draw‐in control can be built up which guarantees a reproducible material flow and, consequently, defined part properties. Furthermore, a favourable pre‐distribution of sheet metal material can be reached which leads to a widening of the process limits. Considering a large area sheet metal part with a complex door handle element as example, strategies for the material flow control will be discussed in this paper. The conclusions are based on FE‐simulations as well as experimental findings.     

镀铝08Al冷轧薄板冲裂原因分析

针对０８Ａｌ薄板镀Ａｌ后在冲压成形过程中开裂原因，进行化学成分，宏观缺陷及为口特征、金相检验等分析，认为造成此冲压件冲裂的直接原因一是冲压模具在使用磨损，破坏正常成形；二是先镀后冲的工艺程序所造成的冷轧镀Ａｌ薄板冲压开裂．     

Numerical analysis of the formability of an aluminum 2024 alloy sheet and its laminates with steel sheets

A criterion for ductile fracture is applied to the formability prediction of an aluminum 2024 alloy sheet and its laminated composite sheets. Axisymmetric deep-drawing processes of the 2024 sheet and the laminates clad by mild steel sheets are simulated by the finite-element method. From the calculated distributions and histories of stress and strain, the fracture initiation site and the forming limit are predicted by means of the ductile fracture criterion. The predictions so obtained are compared with experimental observations. The results show that the fracture initiation in the 2024 sheet with no appearance of necking is successfully predicted by the present numerical approach. Furthermore, it is found that the formability of the 2024 sheet is improved by sandwiching it with the mild steel sheets.     

Finite element analysis of formability of a few kinds of special steel sheets

Deep drawing processes of various special steel sheets are simulated by the rigid-plastic finite element method. To predict the forming limit a criterion for ductile fracture is applied. From the histories of stress and strain in each element calculated by the finite element simulation, the fracture initiation site and the critical stroke are predicted by means of the ductile fracture criterion. The predictions so obtained are compared with experimental observations. The results show that the finite element analysis combined with the ductile fracture criterion is useful to predict the forming limit in a wide range of sheet steels.     

A New Forming Strategy to Realise Parts Designed for Deep‐drawing by Incremental CNC Sheet Forming

The work detailed in this paper focuses on a new forming strategy for the CNC incremental sheet forming (ISF) process that is appropriate to form steep flanges, e.g. for parts designed for deep‐drawing. When parts are designed for deep‐drawing, they usually contain steep or rectangular side walls that cannot be manufactured using the standard ISF strategies. Unlike prior approaches to obtain steep flanges through ISF, the present method achieves a rough approximation to the final part already in the preforming stage. This can be accomplished without excessive sheet thinning due to sheet bending and stretching at this stage. As a consequence, additional material can be used for the finishing stages, thus yielding a final part with largely reduced thinning. After basic studies on a simple benchmark problem, the new bending/stretching strategy is tested with an industrially applied part that is usually produced by deep‐drawing. Finally, the ISF workpiece is evaluated against the deep‐drawn component with respect to sheet thickness and geometric accuracy.     

圆锥形零件冲压成形皱曲和破裂三极限的预报与控制

根据变形区“多余三角形材料皱曲模型”和防皱曲压边力分别导出外皱曲极限预报与控制判据和内皱曲极限预报与控制判据,以及防外皱曲压边装置的选择判据和防内皱曲压边装置的选择判据。依据破裂模型和拉深变形力导出破裂极限的预报与控制判据,最后给出了圆锥形零件冲压成形皱曲和破裂三极限的预报与控制判据和图形。依据选定的压边力可计算出拉深变形力。实验验证和对比结果证明,将上述判据用于圆锥形零件冲压成形皱曲和破裂三极限的预报与控制是相当准确的     

深拉型搪瓷内胆用热轧钢带开发及应用

热水器搪瓷内胆结构由三段式升级为二段式,内胆毛坯的成形方式由卷圆成形+冲压成形方式转变成深拉成形方式,相应的钢板也必须满足深拉成形要求。由于搪瓷内胆结构的变化,对钢板提出了更高的要求,在保障涂搪性能的基础上还需更好的深拉性能。宝钢运用钢厂工业数据与试验设计(DOE)工具,建立钢种设计优化模型,开发出了深拉型搪瓷内胆专用热轧钢板。经工业大生产验证,深拉件报废比例可以控制在千分之四以内,涂搪性能优良。     

Fracture morphologies of a hot stamped steel and comparisons with several sheet metals

Hot stamping has been widely used in car industry to produce safety components.Most existing researches focused on the stamping and quenching process,but less on the mechanical properties of stamped parts.The fracture behaviors of hot stamped boron steel B1500 HS have been studied,and other four commonly used sheet metals with different strengths,including Q235,TRIP780,QP980 and MS1300,were also introduced for comparison.Both uniaxial tests and mechanical trimming tests were performed,and the fracture surfaces under different stress states were observed and discussed.The SEM observations showed that the fracture models are closely related to the stress states,i.e.,the tensile surfaces have ductile rupture characters while the trimming surfaces have brittle rupture characters.Compared with other steels,the quenched boron steel has smaller dimple size accompanied by shear planes in the tensile surface,and has smaller burnish zone in the trimming surface,and its cutting surface with‘S'like shape is also very different with others.Furthermore,two fitted empirical models were derived to describe the quantitative correlations between the average dimple diameter and the steel strength and between the percentage of burnish zone and the steel strength.     

东汽EQ153柴油车油底壳应变分析与选材预测

用ＳＰＣＥＮ和０８Ａｌ两种薄板材料坟东汽ＥＱ１５３柴油车油度壳，用应自动测试系统（ＡＳＡＭＥ）对成形后的应变进行分析。作出成形极奶图，确定了危险部位；评价了两种钢板的成形效果，对优化选材进行预测，指出了应变硬化指数ｎ为０．２１的钢板是冲压该油底壳的最佳网板。     

热成形工艺参数对AC1500HS钢板性能的影响

以鞍钢热成形用钢ACl500HS为研究对象．采用热模拟试验机测定了ACl500HS的CCT曲线并模拟了热成形工艺,确定了ACl500HS钢热成形工艺参数：对钢板进行热成形汽车零件试制,结果表明,该钢热成形性良好,零件尺寸精度达到要求。抗拉强度达到1500MPa以上,满足汽车零件装车要求。     

Experimental Characterization of Heat Transfer Coefficients During Hot Forming Die Quenching of Boron Steel

The heat transfer coefficient (HTC) between the sheet metal and the cold tool is required to predict the final microstructure and mechanical properties of parts manufactured via hot forming die quenching. Temperature data obtained from hot stamping experiments conducted on boron steel blanks were processed using an inverse heat conduction algorithm to calculate heat fluxes and temperatures at the blank/die interface. The effect of the thermocouple response time on the calculated heat flux was compensated by minimizing the heat imbalance between the blank and the die. Peak HTCs obtained at the end of the stamping phase match steady-state model predictions. At higher blank temperatures, the time-dependent deformation of contact asperities is associated with a transient regime in which calculated HTCs are a function of the initial stamping temperature.     

CSP热轧及冷轧工艺对深冲板组织和性能的影响

以某钢厂CSP工艺生产的SPHE热轧板为研究对象,在实验室条件下,研究了CSP卷取温度对SPHE冷轧深冲板组织和性能的影响。研究结果表明,CSP工艺生产的SPHE热轧板的卷取温度应控制在560-565℃;冷轧工艺相同时,基于CSP工艺生产的SPHE深冲板的退火温度越高,再结晶进行越充分,晶粒尺寸越大,对性能越有利,尤其是560-565℃卷取的SPHE板在700℃退火时已可以获得很好的深冲性能。     

A general approach for predicting the drawing fracture load and limit drawing ratio of an axisymmetric drawing process

Based on Hill’s theory of plasticity and the Swift diffuse instability criterion, new theoretical models are proposed for predicting the drawing fracture load and limit drawing ratio (LDR) of an axisymmetric cup drawing. These models take into account the influence of triaxial stress state, anisotropy, strain hardening, bending, and tool geometry. By introducing both conventional and modified Hollomon’s equations, the influences of these variables on the constitutive relation of sheet steels are also analyzed. It is shown that the theoretical predictions of the drawing fracture load are in good agreement with experimental results for a wide range of sheet steels currently used in the automotive industry. Specific tool geometries are found to decrease the drawing fracture load and the LDR, because of increased triaxial stress states and bending effects at the critical section of the workpiece. The optimum punch-profile radius is found to be between 5.0 and 7.0 times the thickness of the sheet. Additionally, the role of both the anisotropy and strain-hardening properties of the sheet steels in determining the drawing fracture load and the LDR are, subsequently, discussed.     

铍板材深冲压成形异形件探讨

冲压成形是金属板材加工异形件的最基本方式。金属材质不同,冲压成形异形件的难易程度不同,主要影响因素是冲压成形性能和冲压成形极限。文章结合铍板材的冲压成形性能和冲压成形极限,对铍板材冲压成形异形件的难易性作了探讨。     

热轧深冲钢板的分析和应用

在对比冷轧深冲钢的基础上,分析了工业试制的热轧深冲钢板的组织和性能。研究结果表明：该钢的碳含量较低,相应的金相组织和晶粒度合适;厚度大于２ｍｍ的钢板未经冷轧和退火处理可达到与冷轧深冲钢弧相当的成型性能,是代替冷轧深冲钢板冲压汽车零件的理想材料。该钢生产工艺简单,质量稳定,具有明显的经济效益和社会效益。     

A calculation method for determining the limit of flange wrinkling in the deep-drawing of cylindrical steel shells without blankholding

Flange wrinkling in deep drawing of cylindrical cups without a blankholder restricts the depth of the cup. In addition to the blank and tool geometries, the material properties determine the maximum reduction attained. Geckeler, Senior and Kawai have developed theories for calculating the critical hoop stress in the flange and the number of waves formed. In the present work a calculation method for predicting the limiting drawing ratio in drawing without blankholding on the basis of the theories mentioned above and the material properties is developed. By comparing the experimental and calculated values, it is shown that the limiting drawing ratio can be determined theoretically.     

HC340LA钢冲压“桔皮”缺陷成因及措施

分析了340 MPa级冷轧低合金高强度钢“桔皮”缺陷钢板和正常钢板的微观组织结构和力学性能。结果表明,缺陷钢板的应力-应变曲线屈服点伸长率达到了3.73%,屈服延伸过大导致了所冲压的前风窗横梁连接板表面产生“桔皮”缺陷。在实验室采用对钢板预拉伸的方法模拟钢板工业化生产的平整与拉伸矫直工艺,随着预拉伸量的增加,试验样屈服平台的长度减少,当预拉伸量超过1.8%时,试验样的屈服平台消失。微观组织进一步分析显示,退火温度高导致钢板晶粒粗大和晶粒取向异常是冲压钢板 “桔皮”缺陷产生的根源。在连续退火工艺环节中合理控制平整和拉伸矫直工艺可以消除或者缩短试验钢屈服平台长度,并避免冲压件表面“桔皮”缺陷发生。