Material Flow Control and Optimization in High‐Pressure Sheet Metal Forming by Active‐Elastic Tools

High‐pressure forming of metal sheets is an innovative forming technology for the production of complex components and offers high potentials to improve the properties and qualities of sheet metal parts. This report describes investigations of a newly developed active‐elastic tool system referred to as ACTEC system. Unlike the use of a comparable semi‐rigid tool system, the ACTEC system shows improvements with respect to the material flow in the flange area and reduced sheet thinning in critical corner regions of the workpiece. In addition, the clamping forces respectively sealing forces necessary to avoid leakage in the tool system during the forming process can be reduced. Moreover, the specific design of the ACTEC‐system as well as current experimental examinations are presented and discussed.     

High‐Pressure Sheet Metal Forming of Large Scale Structures from Sheets with Optimised Thickness Distribution

In order to manufacture components optimised in regard to lightweight construction, the use of innovative forming processes like high‐pressure sheet metal forming (HBU) in combination with the use of tailor rolled blanks (TRB) as innovative semi‐finished materials is a promising solution. To realise a sufficient forming process reliability, at first, investigations on the seal system were carried out. Hereby, a non‐adjustable as well as a new adjustable seal system have been investigated and qualified as sufficient solutions for this process depending on thickness ratio and thickness gradient within the TRB. One typical workpiece geometry which offers a promising lightweight potential and which can be manufactured from TRB with the HBU‐process is the class of body structures. Therefore, an idealised large scale structure has been designed and investigated in theoretical (numerical) and experimental research. The research work has shown that this large scale structure can be manufactured sufficiently by the HBU of TRB.     

Increase of Process Stability of Sheet Metal Hydroforming due to Feed Back Control

Sheet metal hydroforming of single sheets is a deep drawing process. In contrast to deep drawing with rigid tools, an active fluid medium performs the forming operation. The process is chiefly influenced by the control of the clamping force against the increasing fluid pressure. Although the optimum force‐pressure progression is close to the sealing line, it is initially unknown and dependent on different system parameters. To perform the process at the ideal curve, the system parameters need to be detected online and led back to the feed back control unit. An optical system is used for the detection of the sealing state. The detection system is a CCD‐camera system that allows for the continuous recording of occurring leakages. Acquired data permit the application of different strategies to control the forming process along the sealing line. This paper provides an overview of this developed technology, advantages and problems with regard to the process stability and performance, the parts quality, and recent results comparing control strategies.     

Properties of Large‐Scale Structure Workpieces in High‐Pressure Sheet Metal Forming of Tailor Rolled Blanks

In order to manufacture components optimised in regard to lightweight construction, the use of innovative forming processes like high‐pressure sheet metal forming (HBU) in combination with the use of tailor rolled blanks (TRB) as innovative semi‐finished material is a promising solution. Fundamental investigations on the HBU of TRB have been carried out in a joint research project at the Institute of Forming Technology and Lightweight Construction (IUL), University of Dortmund, and the Institute of Metal Forming (IBF), RWTH Aachen. The experiments performed with cylindrical parts have provided basic knowledge on the sheet material flow and resulting part properties. To achieve sufficient process reliability, a non‐adjustable as well as an adjustable seal system have been tested and proved to be suitable solutions, depending on thickness ratio and thickness gradient within the TRB. In order to demonstrate the lightweight potential of this process chain, a forming tool for an automotive body structure has been designed and tested. The experiments have shown that this large‐scale structure can well be manufactured in the HBU process from a TRB.     

金属材料可锻性准则在大锻件生产中的应用

莱芜钢铁总厂锻压厂１９９６年生产大锻件８５００ｔ。在２５００ｔ水压机大锻件生产中应用金属材料可锻性准则制定了加热及锻造工艺规范并用于生产实践，提高钢锭利用率１．６２％，降低废品率０．５％￣０．８６，获经济效益９１．８８万元／ａ，锻件产品质量稳步提高。     

Investigation of Elongation at Fracture in a High Speed Sheet Metal Forming Process

This paper investigates the dynamic elongation at fracture of conventional steels, advanced high strength steels and nonferrous metals, such as aluminium and magnesium alloys. Dynamic tensile tests were carried out using a high speed material testing machine at various strain rates ranging from 0.001/s to 200/s. The results show that the elongation at fracture of sheet metals does not simply decrease with the increase of the strain rate. The elongation of SPCC, SPRC450R, TRIP600 and AZ31 decreases when the tests are carried out under the quasi‐static state at the strain rate of 0.1/s, but increases again when the tests are carried out at the strain rate of 0.1/s up to the strain rate of 200/s. Furthermore, DP600 and AA7003‐T7 show the tendency that the tensile elongation increases as the strain rate increases. This tendency is related to the microstructure and forming history of the sheet metal. It is concluded that localized strain rate hardening in the necking region induces the enlargement of the necking region and thus the increased elongation. This phenomenon is worth being considered to predict the fracture of sheet metal products in high speed sheet metal forming.     

钢铁生产流程中物流对能耗和铁耗的影响

提出了钢铁生产流程的基准物流图,分析了偏离基准物流图的各股物流对吨材能耗和吨材铁耗的影响。以唐钢年均生产数据为例,分析了钢铁生产流程的物流对能耗和铁耗的影响。向中间工序输入废钢,可同时使吨材能耗和吨材铁耗降低;流程中途向外界输出含铁物料,可同时使吨材能耗和吨材铁耗上升;含铁物料在某一工序内部循环,或在工序之间循环,不影响吨材铁耗,但会使吨材能耗上升。