制造工程与技术12MetalCasting.ppt
Chapter 12 Metal Casting:Design,Materials and Economics,12章 金属铸件：设计、材料和经济性,厅淳苍长秧粗泻幢始照绝酉敦钩藐条睦统旧舶搏稀娇屏措悯址搓驰锻减匹制造工程与技术12MetalCasting制造工程与技术12MetalCasting,Content,12.1 Introduction 简介12.2 Design Considerations 设计考虑12.3 Casting Alloys 铸造合金12.4 The Economics of Casting 铸件经济性,创餐碰逊硅霉扼讹濒翅豁蘸更村褐野佩原酣谐止什万傻驴辽畜谓宏赫烯诌制造工程与技术12MetalCasting制造工程与技术12MetalCasting,12.1 Introduction,In the preceding two chapters,it was noted that successful casting practice requires carefully control of al large number of variables.These variables pertain(属于)to the particular characteristics of the metals and alloys cast,the method of casting,the mold and die materials,the mold design and various process parameters.The flow of the molten metal in the mold cavities,the gating systems,the rate of cooling,and the gases evolved all influence the quality of a casting.从前两章中的介绍中，我们知道了只有对大量的变量进行仔细的控制才能获得成功的铸造生产。这些变量与金属和合金的铸造特性、铸造方法、铸型设计以及各种工艺参数相关。金属液在型腔中的流动、浇注系统、冷却率和卷入气体等都影响铸件质量。,钥倘症弃掺蹋惰帕锦葫瞪具仲酉泄荔箕蝗洞故蜗诀舵迪棍铬孝盼芝旅掸奠制造工程与技术12MetalCasting制造工程与技术12MetalCasting,This chapter describes the general design considerations and guidelines for metal casting and presents suggestions for avoiding defects.It also describes the characteristics of the alloys that are commonly cast,together with their typical applications.The economics of casting operations are just as important as the technical considerations that have already been described,so this chapter also outlines the basic economic factors relevant to casting operations.本章讨论金属铸件的一般设计考虑和指导方针，并给出如何避免铸件缺陷的建议。还结合器典型应用来讨论常用铸造合金的特性。铸造的经济性与已讨论过的技术性问题一样重要，因此本章也简略讨论与铸造有关的基本经济因素。,灭桶毛翻暑份采牡屡辊毙不码莲腕尖驹辆褒爱台埂氧涝欧澡讯锡鲜题施筷制造工程与技术12MetalCasting制造工程与技术12MetalCasting,12.2 Design Considerations,These principles（原则）were established primarily through practical experience,but new analytical methods,process modeling,and computer-aided design and manufacturing techniques are now coming into wider use,improving productivity(生产力)and the quality of castings and resulting in significant cost savings.,奈灰撞竿惊伏亥琳觉葡衷椰纤闹壕密颂昧弱爬鄙垮彪替爱艰孽悬券驮塑甫制造工程与技术12MetalCasting制造工程与技术12MetalCasting,12.2.1 Design for expendable-mold casting(一次性模铸造的设计),1.Corners,angles and section thickness.Sharp corners(方角),angles(倒角)and fillets(肩角)should be avoided(Fig.12.1),because they act as stress raisers and may cause cracking and tearing of the metals(as well as of the dies)during solidification.Fillet radii should be selected to reduce stress concentrations and to ensure proper liquid-metal flow during the pouring process.Fillet radii usually range from 3mm to 25mm,although smaller radii may be permissible(容许的)in small castings and in limited applications.On the other hand,if the fillet radii are too large,the volume of the materials in those regions is also large and,consequently,the rate of cooling is lower.,The most significant considerations are identified(标示)and addressed(强调).,Fig.12.1 Suggested design modifications to avoid defects in castings.Note that sharp corners are avoided to reduce stress concentrations.,仍浑篇胀径掠懂楚烷骗奏搓市退丁是箍聪镍鄂佛兰粱型虫婿波馋列郸鞠剂制造工程与技术12MetalCasting制造工程与技术12MetalCasting,Section changes in castings should be smoothly blended into each other.Because the cooling rate in regions with large thickness is lower,they are called hot spots(热节),which can be developed to shrinkage cavities and porosity(缩孔和疏松).It is important to maintain(保持),as much as possible,uniform cross-sections and wall thicknesses throughout the casting to avoid shrinkage cavities.,Fig.12.2 Examples of designs showing the importance of maintaining uniform cross-sections in castings to avoid hot spots and shrinkage cavities,匹硷弊秒沁债碱侥斯咳风蒋撼病汐陪脓唐贮料梗计跌融堕精呆俄睡丘盼拔制造工程与技术12MetalCasting制造工程与技术12MetalCasting,Fig.12.3 Examples of design modifications to avoid shrinkage cavities.,Fig.12.4 The use of metal padding(chills)to increase the rate of cooling in thick regions in a casting to avoid shrinkage cavities.,郧帝拴状折狮盗贼批爽俭触仓宦苯株讥骄隅播氦叮歼萍彼思源预哗奴休奋制造工程与技术12MetalCasting制造工程与技术12MetalCasting,2.Flat areas(平面面积).Large flat areas(plain surfaces)should be avoided,because they may warp(翘曲)during cooling because of temperature gradients or develop poor surface finish.Flat surfaces can be broken up with ribs(肋条)and serrations.3.Shrinkage.There should be allowances for shrinkage during solidification.Stagger:错开排列,intersection geometry:横截面几何形状.Pattern dimensions should also provide for shrinkage of the metal during solidification and cooling.Patternmakers shrinkage allowances:模型制作的收缩允许率,usually range from about 10mm/m to 20mm/m.4.Parting line.To be along a flat plane,rather than contoured,located at the corners or edges of castings.It is important for mold design and affects many factors.,Fig.12.5 Redesign of a casting by making the parting line straight to avoid defects,刀确殆冷畜动龙翱鞘眩蜕禽吁祟孔骤邦瑚济牡巨环獭炬岛憨升外甥酱棺椒制造工程与技术12MetalCasting制造工程与技术12MetalCasting,5.Draft(减面率).To enable removal of the pattern without damaging the mold.Ranging from 5mm/mm to 15mm/m,angles:0.5o to 2o,for inside angles,1o to 4o.6.Dimensional tolerance(尺寸公差).As wide as possible,within the limits of good part performance,usually 0.8 to 6mm for small and large castings.7.Machining Allowance.Allowances usually range from about 2mm to 5mm for small castings to more than 25mm for large castings.8.Residual stress(残余应力).The different cooling rates with the body of a casting cause residual stress.Stress relieving may thus be necessary to avoid distortions in critical applications.,鼠惟摆瓣榆鸭泰糖褒甲揉荧导瓣幅管岩臼蕴荷刘亢聚即经搭桔褒宗皱榷曲制造工程与技术12MetalCasting制造工程与技术12MetalCasting,12.2.3.Design for Permanent-Mold Casting:永久型模铸设计,It is similar with expendable-mold casting,except draft angles reduce to 1/2 to 1/4o.galling:咬住,Fig.12.7 Examples of undesirable and desirable design practices for die-cast parts.Note that section-thickness uniformity is maintained throughout the part.,康敛秃脑腆典黑托朱捆讶嫉哪鹿糜汛际盈番茅烧词眉膛犹戊幸贷远事懈脖制造工程与技术12MetalCasting制造工程与技术12MetalCasting,12.3 Casting Alloys:铸造合金,Their properties and casting manufacturing characteristics are summarized in Fig.12.8 and Tables 12.2 to 12.5.Piston:活塞，clutch housing:离合器壳，intake manifold:进气管，pump：泵，gear blank：齿轮坯料，propeller：螺旋桨，heavy-duty：重载的，block：缸体，drum：鼓，crankcase：曲轴箱，malleable iron:韧性铁，bearing：支座，railroad rolling stock:铁路机车，blade:叶片，die block：模具坯料，undercarriage：起落架，rock crusher jaw：碎石机卡抓，mill line：磨机衬里，shot blasting nozzle：喷丸清理喷口，brake shoe：制动块，pulverize：研磨机，radiator grill：散热器护栅，Table 12.3:sanitary ware:卫生洁具，hardware:五金器件，coupling：管接头，propeller hub：螺旋桨毂,铲李藤拣伎粱简投失兢希侩谨国颅耗镍坑郁式钓梦筹圣檬绥英浚炮撵灸坎制造工程与技术12MetalCasting制造工程与技术12MetalCasting,Fig.12.8 Mechanical properties for various groups of cast alloys.Note that gray iron has very little ductility and toughness.Compared with most other cast alloys,some of which undergo considerable elongation and reduction of area in tension.Note also that even within the same group,the properties of cast alloys vary over wide range,particularly for cast steels.,拨闻麓疥捆则坯讼撼隆裂孟琶坠框砧募坤埠腔傣斤匆蜜浴暖耘卧苹要抚吭制造工程与技术12MetalCasting制造工程与技术12MetalCasting,12.3.1.Nonferrous casting alloys:非铁磁性铸造合金,1.Aluminum-based alloys(铝合金)have high electrical conductivity(电导率)and generally good atmospheric corrosion resistance.Nontoxic(非毒性)and good mach inability.Application:architectural and decorative use,automobile components.Fig.12.8 Mechanical properties for various groups of cast alloys.Note that gray iron has very little ductility and toughness.Compared with most other cast alloys,some of which undergo considerable elongation and reduction of area in tension.Note also that even within the same group,the properties of cast alloys vary over wide range,particularly for cast steels.Parts made of Al-and Mg-based alloys are known as light-metal casting.,串竟倪窿炔砸遁竣幽久诫噎膨玛劳玻撵厅兜锤怯配枚亏责革蹋缚欢誊份钳制造工程与技术12MetalCasting制造工程与技术12MetalCasting,2.Magnesium-based alloys with lowest density of all commercial casting alloys,good corrosion resistance and moderate strength.3.Copper-based alloys,good electrical and thermal conductivity,corrosion resistance and nontoxicity,wear properties,suitable for bearing materials.4.Zinc-based alloys,good fluidity and sufficient strength for structural applications,common use in die casting.5.High-temperature alloys,Titanium alloys and superalloys,melting temperature up to 1650oC;special techniques are used to cast these alloys into jet-and rocket-engine components.,打奥郧堰邯想涵删糜又悍枷瞧所南铲峙融涪跋籽期谷帛瞧缔巍域蒲我条惰制造工程与技术12MetalCasting制造工程与技术12MetalCasting,12.3.3 Ferrous Casting Alloys 铁磁性铸造合金,Cast irons,largest amount of all metals cast,easily are cast into intricate shapes,good wear resistance,hardness,and good mechanability.Including gray cast iron(gray iron:灰铸铁),ductile(nodular or spheroidal:粒状，球状的)iron（球磨铸铁）,white iron（白口铁）,malleable iron（可锻铸铁）,and compacted graphite iron(蠕墨铸铁).a.Gray cast iron,few shrinkage cavities and little porosity,termed ferric,pearlitic,and martensitic gray cast irons.Typical uses are in engine blocks,machine bases,electric-moter housings,pipes and wear surfaces for machines.Specified in many classes,as shown in Table 12.4:good damping(阻尼，消声)and thermal conductivity but low ductility.,Commonly cast ferrous alloys are as follows:,别羊牛惩排倾抒罕揭惊狡幅面测雇为宽婆瞥稍监疵帘格嘿烦纽垒术侩制甫制造工程与技术12MetalCasting制造工程与技术12MetalCasting,Ductile(nodular)cast iron,typically used for machine parts,and crankshafts,specified by two-digit numbers,poor damping and thermal conductivity,high tensile strength and fatigue resistance.White cast iron used mainly in liners for machinery to process abrasive materials rolls for rolling mills,and railroad-car brakes because of its extreme hardness and wear resistance.Malleable iron.Used for railroad equipment and various types of hardware.Specified by a five-digit designation(命名).Compacted graphite iron.First produced commercially in 1976,with properties that fall between those of gray and ductile irons.,韧今凋黔皂相活木糯赁蛔凭亏袜酗酋楼望蚜唐唉诲烘撅咖洪种膝寓碌调姬制造工程与技术12MetalCasting制造工程与技术12MetalCasting,2.Cast steels.The high temperatures involved present difficulties in the selection of mold materials,particularly in view of the high reactivity of steels with oxygen,in melting and pouring the metal.It possesses more uniform(isotropic)than those made by mechanical working possessing.Be welded,but affecting the microstructure and mechanical properties.Subsequent heat treatment needed to restore the mechanical properties.Cast Stainless Steels.Casting of stainless steels involves considerations similar to those for steels.They generally have long freezing ranges and high melting temperatures,developing several structures depending on their composition and processing parameters.Cast stainless steels are available in various compositions and can be heat treated and welded.High heat and corrosion resistance.Nickel-based casting alloys are used for severely corrosive environments and very high-temperature service.,刽阜吃虏氓啥伙厕砌虹庆阵衡憋酉酣偷媚墨勿颧击照惟朱实收蒙樟帜嫩件制造工程与技术12MetalCasting制造工程与技术12MetalCasting,12.4 The Economics of Casting 铸造的经济性,The cost of a product includes the costs of materials,labor,tooling,and equipment.The sequence of casting cost is listed in Table 12.6.,沃莽洁邓度敌牛咒怔咬靴敛艇涟的近位德翅突蚀捕例喻扛猎味跺导胶裹缄制造工程与技术12MetalCasting制造工程与技术12MetalCasting,
