由于热变形形成纤维***，会使金属的力学性能出现异向性，即纵向力学性能指标中的A，Z，Ak比横向相应的指标大得多，两个方向上的强度Rm。Re差别不大。Duetotheformationoffibrousmicrostructurebythermaldeformation,themechanicalpropertiesofmetalswillbedifferent.Thatis,A,ZandAkinlongitudinalmechanicalpropertiesaremuchlargerthanthoseitransversedirection,andthestrengthintwodirectiisRm.Reisnotverydifferent.随着电动机的发明，十九世纪末出现了以电为动力的机械压力机和空气锤，并获得迅速发展。第二次以来，七十五万千牛的模锻水压机、一千五百千焦的对六万千牛的板料冲压压力机、十六万千牛的热模锻压力机等重型锻压机械，和一些自动冷镦机相继问世，形成了门类齐全的锻造机械体系。自由锻造是靠人工操作来控制锻件的形状和尺寸的，所以锻件精度低，加工余量大，劳动强度大，生产率也不高，因此它主要应用于单件、小批量生产。Withtheinventionofmotor,themechanicalpressandairhammerpoweredbyelectricityappearedattheendofnineteenthCentury,anddevelopedrapidly.SincetheSecondWorldWar,theforgingwaterpress,onethousandandfivehundredthousandchar,thepunchingpressofLiuWanqiancattle,thehotforgingpressofsixteenthousandthousandcattle,andsomeautomaticcoldheadingmachinesh***ecomeoutinsuccession,formingacompletesystemofforgingmachinery.锻造工艺过程一般由以下工序组成，即选取钢坯下料、加热、成形、锻后冷却。锻造的工艺方法有自由锻、模锻和胎膜锻。生产时，按锻件质量的大小，生产批量的多少选择不同的锻造方法。Theforgingprocessisgenerallyofthefollowingprocesses,namely,theselectionofhighqualitybillets,heating,formingandcoolingafterforging.Theforgingprocessincludesfreeforging,dieforgingandfetalmembraneforging.Whenmanufacturing,accordingtothesizeofforgingsandthenumberofproductionbatches,differentforgingmethodsarechosen.自由锻造的设备分为锻锤和液压机两大类。生产中使用的锻锤有空气锤和蒸汽-空气锤，有些厂还使用结构简单，***少的弹簧锤、夹板锤、杠杆锤和钢丝锤等。Theequipmentoffreeforgingcanbedividedintotwocategories:forginghammerandhydraulicpress.Theforginghammersusedinproductionareairhammerandsteam-airhammer.Somefactoriesalsousespringhammer,splinthammer,leverhammerandsteelwirehammerwithsimplestructureandlowinvestment.)