金属成型基础

1、1Lecture 1 Fundamentals ofMetal FormingCourse Hour: 3Basic requirements: Recalling the principles and concepts of the course “Metal forming: mechanics and principles” Acquainting with classification of forming processes, Acquainting with temperature in metal working, hot working, cold working, strai

2、n rate effects, metallurgical structure, hydrostatic pressure, workability, residual stresses; acquainting with friction and lubrication in metal forming processes mechanics of metal workingEmphasis: classification of forming processes and temperature in metal working, Temperature in metal working,

3、friction and lubrication in metal forming processesDifficulties: Mechanics of metal working, Residual stressHome work: Read the textbook from pages 287-2972Metal ForminglPlastic Deformation to Change ShapelNo Volume ChangelStresses YieldlGood Forming Properties Low Yield Strength High Ductility Elev

4、ated temperature, low strain rate and lubrication can Help3Bulk forming Characterized by significant deformations and massive shape changes Bulk refers to workparts with relatively low surface area-to-volume ratios Starting work shapes include cylindrical billets and rectangular barsRolling4ForgingE

5、xtrusion5DrawingSheet Metal6Bulk DeformationlSignificant DeformationslMassive Shape Changes (w/o Waste)l“Blacksmith”lWork in Plastic Region Flow StressYf= KnFlow Stress Curve* during compression, determine instantaneous force from Yf* max force is often all that is required, typically at end of stro

6、ke* force analysis may be based on average stresses and strains7Cold WorkinglAdvantagesBetter Accuracy, Closer Tolerances; Better Surface Finish; Increased Strength and HardnesslDisadvantagesHigher Forces, Power; Limited Deformation; Annealing May Be RequiredWarm WorkinglBelow Recrystallization Temp

7、.lAdvantages Over Cold WorkingLower Forces and power; More Intricate Geometries; Reduced Annealing Requirements8Hot WorkinglAbove Recrystallization Temp. (0.5Tm)l AdvantagesSubstantially Lower Force, Power NeededSignificant Deformations Possiblen Approaches ZeroNo Work Hardening (Strengthening)Isotr

8、opic PropertiesExtended Material ApplicationslDisadvantagesNo StrengtheningLower AccuracyLots of Heat Energy RequiredSevere Surface OxidationPoor Surface FinishHigher Tool Wear9Temperature & Strain RateFig 20.5We will mostly assume that strain rate is negligible at room temperature!(high values

9、- 1000 s-1)Strain rate equation:C = strength constantm = strain-rate coefficienthv 10Friction* undesirable* retards metal flow (residual stresses & defects)* increases force and power requirements* wears tooling* high temperature stickLubricants* reduce frictional effects* remove heat and materi

10、al* lengthen tool life* may react chemically with tool or work* concerns about toxicity, flammability. (mineral oils, emulsions, oils, graphite, glass)11lMetal forming products of our country产品名称 尺 寸 范 围 金属材料产品 的外形特征 基本塑性 加工方法板材0 . 3 8 0 5 0 0 2 5 0 0 1 0 0 0 10000mm长度一定，较短，块状或片状平辊轧制带材0.1220600mm厚度较薄，长度大，卷状平辊轧制条材 宽度较窄，长度一定平辊或型辊轧制箔材0.0050.15101200mm厚度很薄、长度大，卷状平辊轧制管材14200.150断面圆环形中空，直条状挤压、拉拔、轧制棒材50300mm断面圆