2. 3 Sand Casting 2．3 砂型铸造：
Casting is used to make metal products of almost any desired shape by the pouring of molten metal into a reshaped hollow mold. As the metal freezes, the mold is removed. This technique was learned thousands of years ago when it was discovered that damp sand could be packed by hand into almost any shape.
铸造通过将熔融金属液浇入成型空腔以生产几乎任何所需形状的金属制品。当金属凝固后，铸型被移走，这项技术在几千年前当人们发现湿砂能够用手制作成任何形状时就已经被掌握。
Generally speaking, clean, fine sand is placed in a wooden or steel box and packed around a preformed wooden pattern or actual object. When the pattern is removed, its imprint remains in the sand. Molten metal is then poured into the hollow mold. Castings made from sand molds have a rough surface. They must be cleaned, trimmed and, at times, machined. Sand molds must be repacked after each casting to obtain additional parts. Therefore, the casting of many pieces using sand molds requires much time and labor.
总体上说，干净的细砂放于一个木制盒或钢盒子里，在一个预成型的木模或实物周围压紧，当模型移走后，它的轮廓留在砂上，然后液态金属浇入空腔中，砂型铸件表面很粗糙，他们必须清理、修型，有时还需要进行机加工，砂型在每次铸造后必须重新制作以得到其他的零件，所以，许多零件的砂型铸造需要大量的人力和时间。
2. 4 Permanent Mould Casting 2．4 金属型铸造
The mould material is selected on the consideration of the pouring temperature, size of the casting and frequency of the casting cycle. They determine the total heat to be borne by the die. Fine grained grey cast iron is the most generally used die material. Alloy cast iron, C20 steel and alloy steel (H11 and H14) are also used for very large volumes and large parts. Graphite mould may be used for small volume production
from aluminum and magnesium. The die life is less for higher melting temperature alloys such as copper or grey cast iron.
铸型材料是在考虑浇注温度、铸件尺寸和铸件循环使用频率方面的基础上进行选择的，它们决定了金属模所能承受的所有热量，有细密纹理的灰铁是最经常使用的模具材料，合金铸铁、C20钢和合金钢也被用于大体积和大件产品中，石墨型可用于小体积的铝件和镁件生产，对于高熔点合金，比如铜和灰铁，模具的寿命会减少。
For making any hollow portions, cores are also used in permanent mould casting. The cores can be made out of metal, or sand. When sand cores are used, the process is called semi-permanent moulding. The metallic core cannot be complex with under-cuts and the like. Also, the metallic core is to be withdrawn immediately after solidification, otherwise, its extraction becomes difficult because of shrinkage. For complicated shapes, collapsible metal cores (multiple-piece cores) are sometimes used in permanent moulds. Their use is not extensive because of the fact that it is difficult to securely position the core as a single piece as also due to the dimensional variations that are likely to occur. Hence, with collapsible cores, the designer has to provide coarse tolerance on these dimensions.
在金属型铸造中，生产所有带空腔型件也要使用芯子，芯子可用金属和砂制作。使用砂芯是的工艺称作半金属造型，金属芯在侧凹之类上不能太过复杂，另外，金属芯在凝固后要尽快取出，否则取出将会因为收缩变得困难。对于复杂形状，金属模中有时要使用分瓣金属芯（组合芯）。它们没有被广泛使用是因为难以有效的将芯子作为单独的一部分放置，还有就是经常出现尺寸的变化。因此，用组合芯，设计者必须在这些尺寸上提供大概的公差。
第五章：金属工艺的基本设计
Chapter 5 Basic Design of Metal Processes 第五章：金属工艺的基本设计
5.3.1 Patternmaking 5.3.1模样制作
The pattern is a physical model of the casting used to make the mold. 模样是用于制作铸型的铸件物理模型
The mold is made by packing some readily formed aggregate material, such as molding sand, around the pattern. When the pattern is withdrawn, its imprint provides the mold cavity, which is ultimately filled with metal to become the casting.
铸型是通过将一些易变形的聚合体材料紧实得到的，像型砂，包围在模样周围。当模样取出后，它的轮廓提供了最终浇满液态金属形成铸件的型腔。 If the casting is to be hollow, as in the case of pipe fittings, additional patterns, referred to as cores, are used to form these cavities. As has been defined earlier, a pattern is a replica of object to be made by the casting process, with some modification. The main modifications are:
如果铸件是中空的，比如在管件装配的条件下，其他模样像芯子将用于形成这些空腔。就像前面所定义的，模样是铸造所生产的实物经过某些改变后的复制品，主要的改变有：
(a) the addition of pattern allowances, (b) the provision of core prints,
(c) the elimination of fine details which cannot be obtained by casting and hence are to be obtained by further process. (a)增加模样的余量； (b)提供芯头；
(c)对于精密铸件，不能通过铸造得到的部分，要通过进一步的工艺来完成。
5.3.1.2 Core prints 5.3.1.2 芯撑
For all those casting where coring is required, provision should be made to support the core inside the mould cavity. One of the methods that is universally followed is to provide core prints where possible. In Fig 5.22 is shown an example of the provision of core prints. The size of the core prints to be provided is to be
estimated based on the specific casting.
Fig.5.22 Typical job, its pattern and the mould cavity
对所有需要芯子的铸件，应该采取措施来支撑型腔中的芯子，其中的一个普遍使用的方法是在可能的地方使用芯撑，在图5.22展示了一个芯撑使用的例子，所提供的芯撑的尺寸将在精确的铸件的基础上进行估算。 5.3.2Moulding Materials 5.3.2 造型材料
A large variety of materials are used in foundries for manufacturing moulds and cores. They are:
Moulding sand,
System sand (backing sand), Rebounded sand, Facing sand, Parting sand, Core sand.
在铸造中，许多种材料被用于生产铸型及芯子。它们包括：
型砂 背砂
加粘土回用砂 面砂 分型砂
5.3.2.1 The properties of moulding sand 5.3.2.1 型砂性能
The choice of moulding materials is based on their processing properties. The properties that are generally required in moulding materials are:
造型材料的选择是基于它们的工艺性能，通常造型材料要求的性能包括： Refractoriness: it is the ability of the moulding material to withstand the high temperatures of the molten metal so that it dose not cause fusion.
耐火度：造型材料承受熔融液态金属的高温而不会熔解的能力。 Green strength: The moulding sand that contains moisture is termed as green sand. The green sand should have enough strength so that the constructed retains its shape.
湿强度：包含湿气的型砂通常术称为湿型砂，湿型砂应该有足够的强度以保持所构造的形状。
Dry strength: When the moisture in the moulding sand is completely expelled, it is called dry sand. When molten metal is poured into a mould, the sand around the mould cavity is quickly converted into dry sand as the moisture in the sand immediately evaporates due to the heat in the molten metal. At this stage, it should retain the mould cavity and at the same time withstand the metallostatic forces.
干强度：当型砂中的湿气都被排出的时候，其被称为干砂。当熔融金属浇入型中，型腔周围的型砂由于液态金属中的散热，湿气快速蒸发而迅速转变成干砂，此时，它应该保持型腔同时承受金属静力学的作用力。
Hot strength: After all the moisture is eliminated, the sand would reach a high temperature when the metal in the mould is still in the liquid state. The strength of the sand that is required to hold the shape of the mould cavity then is called hot strength.
热强度：所有的湿气消除以后，当铸型中的金属仍处于液态时砂子就会达到一个高温。砂子要求保持型腔形状的强度就被称作热强度。
Permeability: During the solidification of a casting, large mounts of gases are to be expelled from the mould. The gases are those which have been absorbed by the metal in the furnace, air absorbed from the atmosphere and steam and other gases that are generated by the moulding and core sands. If the gases are not allowed to escape from the mould, they would be trapped inside the casting and cause defects. The moulding