热压成形技术对汽车高强度钢性能影响机械专业英语文献翻译.doc

Influence of Hot Press Forming Techniques on Properties of Vehicle High Strength SteelsCHANG Ying, MENG Zhaohuan, YING Liang, LI Xiaodong , MA Ning, HU Ping( Scho ol of Automotive Engineering , State Key Laboratory of Structural Analysis for Industrial Equipment,Dalian University of Technology , Dalian 116024, Liaoning, China)Abstract: Based on the combination of materials science and mechanicalengineering ,hotpress forming process of the vehicle high strength steels was analyzed. The hot forming processinclud -ed: heating alloy srapidly to austenite micr ostructures, stamping and cooling timely,maintaining pressur eand quenching . The results showed that most of austenite micr ostructure w as changed into uniform mar tensite by the hot press form ing while the samples were heatedat 900 。

C and quenched. The optimal tensile strength and yield streng th were up to 1530 MPa and 1000 MPa, respectively, and the shape deformation reached about 23% . And springback defect did not happ -en in the samples.Key words: high streng th steel; lightw eight ; hot forming ; martensiteAs an effective economical energy measure, the lightw eight dev elo pment dir ection of automo -bile has become one of the most important research subjects in the automotive industry. There are three major ways to achieve automobile light weight : optimizing vehicle frames and struc- tures; making vehicle bodyor f rame of new and alternativ ematerials to reduce the vehicle mass ( The high and ultra high strength steel can be used as alternative materials because of its thinner thickness) ; adopting advanced manufacturing techniques for the sake of automobile light wei- ght , such as thickness-gradient high strength steel (HSS) or metal based compound plates by con -tinuous pressing or hot press forming [ 1] . Although HSS has been applied in some domestic top grade vehicles, the key producing technologies have always been dominated by foreign compan- ies, such as Acelor Company, so as to raise the product cost obviously. By domestic self-designed hot press forming techniques and water-cooling mould, the automo bile HSS can be produced to subst itute foreign vehicle parts.In general, with the enhancement of steel blank，s mechanical strength, its formability is worsened dramatically. It is difficult to apply the traditional cold stamping technolog y into the f ield of pressing HSS. Thus, the hot stamping technology of martensit icsteel blank is applied as a new technology , which combines metal thermoplast ic forming metho d and water-cooling mould quenching principle. In this paper, boro n steel blank was formed and water-cooling mould was quenched simultane ously during the process of hot stamping . Comparedwith original automobile pearlite steel[ 2] , the automobile HSS obtained by advanced hot press forming technique can reduce about 30% of the total vehicle mass and achieve complex g eomet ries, high security and mechanical st reng th. The r easo n is that austenite microst ructure with optimal plast icity and ductility can be obtained by hot press forming at high temperature[ 3- 5] , and the HSS with both excellent mechanical properties and light weight will be obtainedafter being formed and quenched[ 6- 8] . The application of hot-formed thinner HSS plates will becoman important measure to realize vehicle light weight.1 Experimental SetupIn order to form HSS at high temperature, and to avoid cracks and springback, the sam -ples need rapid heating and transform completely into stabl eaustenite microst ructure. And then, samples are pressed and cooled in self-made water-cooling mould.For the obtained HS -S sample, its shape-freezing character or no spring back defect is an obvious advantage, and most of microst ructure in the sample is martensite. The thickness of sample is 1.6 mm, and the main elements of HSS in this experiment are show n in Table 1.Table 1 Main elements of material in the experimen22MnB5CMnCrSiBPSAlMinimum0.2201.2000.1100.0020.002--0.020Maximum0.2501.4000.2000.0050.0050.0200.0050.050Actual ex perimental procedure included: 1) set different heat t reatment temper atures in ther ange of750 to 1 000℃; 2) put the sample into the heat treated furnace to be heated for 4 min at a certain temperature; 3) remove it by mechanical hand and put it into the hot forming moulds to be pressed quickly ;4) simultaneously, it was water-cooled at about 30℃/s in the mound. The mechanical properties of sample were analyzed by tensile test system and the microstructure appear ance was analyzed by metal lographic analysis device.The shape and size of test sample are show n in Fig. 1.Fig 1 The shape and size of specimen2 Results and DiscussionMechanical propert ies of HSS ( boron steels)with different thicknesses ( 1.0mm, 1.6mm, 2.0mm,2.5 mm, 3.0 mm and 4.0 mm, respectively) were checked (GBT 16865-1997 was consulted, and samples were selected along 。