Chapter3 Foundry processes-Sand casting铸造工艺.ppt
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1、Chapter3 Foundry processes-Sand casting铸造工艺过程,3.1Overview 概述 铸造casting是指熔炼金属、制造铸型,并将熔融金属浇入铸型,凝固后获得一定形状、尺寸和性能的金属零件或毛柸的液态成形liquid state shaped方法。 铸造(casting)功用Function: 制造形状复杂或大型的工件、 制造承受静载荷及压应力的机械零件 如:床身Bed、 机座base support (saddle) 箱体case(box),1、铸造特点The feature of foundry processes (1)适应性强 flexibilit
2、y (2)成本较低low cost (3)铸件的组织性能较差 Casting performance is poor (4)工序较多working process more,2、铸造的分类The classification of casting 铸造 砂型铸造sand casting 手工砂型铸造-单件、小批及大 型复杂铸件的生产One-piece, small batch and large-scale complex casting production 机器砂型铸造:成批、大量生产Batch, mass production 特种铸造special casting process:不同
3、于砂型铸造 的所有铸造方法,,金属型铸造The metal mold casting (Permanent ) 特种铸造 压力铸造 Die casting 离心铸造 Centrifugal casting 熔模铸造 Investment casting,铸铁的种类Types of Cast irons 铸铁的特点:优良的铸造性Excellent castability 减震性damping 切削加工性working quality 熔炼简单Melting simple 成本低廉Low cost 根据铸铁中的碳C的存在形式分为: 白口铸铁White cast iron- 断口成白色,硬而脆 灰铸
4、铁Gray cast iron: C以片状石墨形式存在, 断口呈灰色,机械制造应用最多的,代号100最小抗拉强度 可锻铸铁Malleable cast iron:白口铸铁经石墨化退火而成。,牌号黑心可锻铸铁 珠光体可锻铸铁 可锻铸铁是不可锻的。,球墨铸铁Ductile cast iron石墨成球状,提高强度和韧度,用来制造受力复杂,力学性能要求高的零件,如曲轴,凸轮轴等。牌号:3 蠕墨铸铁Vermicular cast iron RuT420,砂型铸造Sand casting: 当形成铸型的原材料主要为型砂,且液态金属完全靠重力充满整个铸型型腔时,称为砂型铸造。 特种铸造Special cas
5、ting process 凡是不同于砂型铸造的所有铸造方法统称为特种铸造,金属性铸造、压力铸造、离心铸造、熔模铸造。,3.2 砂型铸造Sand casting,砂型铸造的工艺过程Sand casting process 图3-1,制造砂型和制造型芯两道工序对铸件的质量和铸造的生产率影响最大。 砂型Sand mold(铸型)结构如图3-2所示 组成:型砂mould sand 型腔Mold cavity 型芯Mold core 浇注系统Gating system 冒口riser raiz,Figure 3-2 Sand mold structure 1.Cold iron;2. Mold cavi
6、ty;3.Riser; 4. air channel; 5. vent hole出气孔;6.Gating system7. op half ;.Bottom half .Mold core; 10.Parting surface,Key Words,铸造casting 液态成形liquid state shaped, 适应性 flexibility .fleksbiliti 工序working procedure (process) 砂型铸造sand casting 特种铸造special casting process,金属型铸造The metal mold casting 压力铸造 Die
7、 casting 离心铸造 Centrifugal sentrifjugl casting 熔模铸造 Investment investmnt casting,Introduction To Material Processing New Words,Riser raiz冒口 Optimizeptimaizv. 使.完美,乐观,使.完善v.优化 Proposeprpuzv. 计划,打算,向.提议 Stuffstfn. 材料,原料,东西v. 填满,塞满 Environmentinvairnmntn. 环境 Associatesuieitn. 同伴,伙伴v. 联合,联想adj. 副的,Exploi
8、tiksplitn. 功绩,勋绩v. 开发,利用,开拓 Incorporateink:preitadj. 合并的,公司组织的,具体化的v. 合并,组成公司,具体表现 Phenomenonfinminnn. 现象 Consolidationkn.slideinn. 巩固,团结,合并 Bondingbndin. 结合(粘接,粘结料,屏蔽接地,键,联系)v. 结合 Brazingn. 铜焊(钎焊,钎焊,钎接),Solderingsldri软焊, 锡焊, 低温焊接, 热焊接, 软钎焊 Notably ntbli adv. 显著地(著名地, 值得注意地, 格外, 特别是),Numerous proces
9、ses and operation can be involved in the manufacture of products and components, and many of them are associated with the production of a desired shape. These shape-producing processes are often grouped into four basic “families,” as indicated in Figure 13-1. Casting,Introduction To Material Process
10、ing,processes exploit the fluidity of a liquid as it flows, assumes the shape of a prepared container, and solidifies upon cooling. The material removal processes produce a desired shape by removing segments from an initially oversized piece. While these processes have often been referred to as,Mach
11、ining, that term is generally used to describe the mechanical cutting of materials. The more general term material removal is used to incorporate material removal by all means, including chemical, thermal,and,physical processes. Deformation processes exploit the ductility of certain materials, most
12、notably metals, and produce the desired shape by mechanically moving or rearranging the solid through a phenomenon known as plasticity. Consolidation processes,Introduction To Material Processing,Materials processing is the science and technology by which a material is converted into a useful shape
13、with a structure and properties that are optimized for the proposed service environment. A less technical definition of materials processing might be “all that is done to convert stuff into things.”,Put pieces together, and include welding, brazing, soldering, adhesive bonding,and mechanical fastene
14、rs. Power metallurgy is the manufacture of a desired shape from particulate material and involves aspects of casting, forming, and consolidation.,Assignment,What are the four families of shape-production processes?,Chapter3 Foundry processes-Sand casting 铸造工艺-砂型铸造,3.2.1造型材料Making mould materials 制造铸
15、型用的材料-造型材料 砂型铸造所用材料主要有型砂和芯砂 1、型砂和芯砂应具备的性能The properties of molding sand and core sand (1)可塑性-Plasticity 型砂在外力作用下可塑造成形,当外力消除后仍能保持已成形的形状的性能称为可塑性。型砂的可塑性好,易于成形,就能获得型腔清晰的铸型,从而保证铸件具有精确的轮廓尺寸。,(2)强度Strength 型砂承受外力作用而不 易破坏的性能称为强度。铸型必须具备足够的强度,才能在浇注时承受金属溶液的冲击和压力,不致发生毁坏,如冲砂、塌箱等,可防止铸件产生夹砂、砂眼等缺陷。 (3)耐火性Fire resis
16、tance(Refractoriness) 型砂在高温液态金属作用下不软化、不烧结或熔化的性能称为耐火性。 耐火性差后果:铸件表面粘砂,增加清理和切削加工的困难,严重时还会使铸件报废。,(4)透气性 Air Permeability型砂在紧实后能使气体通过的能力称为透气性。 气体的来源:浇注时砂型中会产生大量气体,金属溶液内部也会析出气体。 透气性差影响:部分气体就会留在铸件中形成气孔。 (5)退让性Collapsibility型砂冷却收缩时,其体积可以被压缩的性能称为退让性。 退让性差的影响:铸件收缩困难,铸件会产生较大的内应力,甚至会引起铸件的变形和开裂。 此外,型砂和芯砂还要求有好的流动
17、性、溃散性、 不粘模性、耐用性和低的吸湿性。,2、型砂和芯砂的组成The structure of mold sand and core sand 型砂和芯砂主要由砂和粘结剂binder组成。砂的主要成分是石英( ),并含有少量杂质。高质量的铸造用砂要求石英含量高,杂质少,砂粒均匀且呈圆形。 粘结剂:普通粘土clay klei和膨润土bentonite两种 。 为了使他们发挥粘结作用,需加入适量的水。对于要求较高的芯砂,可采用特殊的粘结剂,如桐油或树脂等。,在型砂和芯砂中,有时还要加入一些附加物。例如,在型砂中加入少量的煤粉,能防止粘砂缺陷,使铸件表面光滑;在型砂和芯砂中加入木屑,可提高退让性
18、减少铸件内应力,防止铸件的变形和开裂。,3.2.2模样和芯盒Pattern and core-box,模样和芯盒是造型和制芯的模具,模样用来形成铸件外部形状,芯盒用来制造型芯,以形成铸件内部形状在单件、小批生产中,广泛用木材来制造模样和芯盒,在大量生产中,常用铸造铝合金、塑料来制造模样和芯盒。,一般地说,模样的外形与铸件的外形相适应,芯盒的内腔形状与铸件的内腔形状相适应,但不能完全按照零件的形状和尺寸来制造模样和芯盒在形状上,铸件和零件的差别在于有无起模斜度、铸造圆角,零件上尺寸较小的孔在铸件上不铸出等;在尺寸上, 零件尺寸+加工余量(孔的加工余量为负值)铸件尺寸 铸件尺寸+收缩量=模样尺寸
19、模样尺寸铸件尺寸零件尺寸,图35c、d所示的是轴承支架铸件和模样、芯盒的关系生产中首先根据零件图,考虑模祥和芯盒制造的工艺因素,绘制出铸造工艺图,再制造模样和芯盒模样和芯盒的制作主要考虑如下工艺因素。,1、分型面Parting line(surface) 分型面是指上型与下型之间的结合面在铸造工艺图上,分型面用细直线条和箭头表示,并注明上、下”宇样,如图35b所示。分型面决定了铸件在铸型中的位置,直接关系到模样的结构、芯盒数量、铸造工艺和铸件质量等合理选择分型面是一个重要而复杂的问题,总的原则是起模要方便,并有利于保证铸件质量。,2、加工余量Machining allowance 铸件的加工余
20、量是指在切削加工时从铸件上切去的金属层因此,制造模样和芯盒时,应在铸件需要加工的表面上,留出加工余量加工余量的大小主要取决于造型方法、铸件大小和铸件材料等因素。一般铸铁件的加工余量为26mm在单件、小批生产时,铸件上小于 30 mm的孔通常不铸出,而在切削加工时直接进行钻孔加工。,3、起模斜度Pattern draft (Stripping gradient) 为了起模方便,凡垂直于分型面的壁上应有一定的斜度如果零件图上没有结构斜度,则在制造模样时应作出起模斜度。起模斜度的大小主要取决于模样的种类、壁的高度和位置等。木模样的起模斜度通常在 之间选取,壁高时取下限,反之取上限。,4、铸造圆角Cu
21、rving of castings 铸造圆角是指铸件两表面交接处应做成的圆弧过渡,如图35b所示这样,造型时不易损坏铸型,并且能提高转角处的力学性能,避免产生缩孔和裂纹等缺陷。铸造园角半径一般为310 mm,具体数值可查有关手册。,5、收缩率Shrinkage ratio 铸件在冷却时要产生收缩,因此,模样的外形尺寸要比铸件大,其数值取决于铸件材料的线收缩率例如,灰铸铁为1%,铸钢为2,非铁金属为15,6、芯头 Core print (core mark ) 为了在铸型中安放型芯,在模样中要做出相应的凸起部分,成为心头。如图3-5c所示。,Key Words,模样Pattern 芯盒core
22、芯头 Core print 起模斜度Pattern draft 铸造圆角Curving of castings 收缩率Shrinkage ratio 粘结剂Binder baind 粘结剂Sticker stik,Sand casting New words,Versatile v:stail adj. 多才多艺的,多方面的,通用的, Granular grnjul adj. 由小粒而成的,粒状的 Refractory rifrktriadj. 不听话的,执拗的,难治疗的 Silica silik矽土 Zircon z:kn n. 锆石 Olivine .livi:nn. 橄榄石,黄绿,Chr
23、omite krumaitn. 铬铁矿,亚铬酸盐 Clay klei n. 粘土,泥土 Grain greinn. 谷物,谷类,颗粒,细粒,纹理 Span spnn. 跨度,跨距,范围v. 持续,贯穿,跨越 Sprue spru:直浇口 Runner横浇道,Sand casting,Sand casting is by far the most common and possibly the most versatile of the casting processes. Granular refractory material (such as silica(硅石), zircon(锆石),
24、olivine(橄榄石), or chromite(亚铬酸盐)is mixed with small amounts of other materials, such as clay and water, and is then packed around a pattern that has the shape of the desired casting. Because the grains can pack into thin sections and can be economically used in large quantities, products spanning a w
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