碾环是指通过专用设备碾环机生产不同直径的环形零件，主要用来生产汽车轮毂、火车车轮等轮形零件。特种锻造包括辊锻、楔横轧、径向锻造、液态模锻等锻造方式，这些方式都比较适用于生产特殊形状的零件。Rollerringreferstotheproductionofcircularpartswithdifferentdiametersthroughtherollerringmachineofspecialequipment,whichismainlyusedtoproducewheelhub,trainwheelandotherwheelshapedparts.Specialforgingsincluderollforging,crosswedgerolling,radialforging,liquidforgingandsoon.Thesemethodsaresuitableforproducingpartswithspecialshape.自由锻造所用的工具简单，加工方法通用性强，生产准备周期短，因而应用较为广泛。自由锻分为手工锻造和机器锻造两种。手工锻造只能生产小型锻件，生产率也较低。Thetoolusedforfreeforgingissimple,theversatileandtheproductionperiodisshort,soitiswidelyused.Freeforgingisdividedintotwokinds:manualforgingandmachineManualforgingcanonlyproduce***allforgings,andtheproductivityislow.镦粗主要有以下形式：完全镦粗。完全镦粗是将坯料竖直放在砧面上，在上砧的锤击下，使坯料产生高度减小，横截面积增大的塑性变形。Upsettingmainlyincludesthefollowingforms:Fullupsetting.Completeupsettingistoplacetheblankverticallyontheanvilsurface,hammeringontheanvil,sothattheheightoftheblankdecreases,thecross-sectionalareaincreasesplasticdeformation.)