铸造翻译终稿(5)

Fig. 5.29 Chill

在铸件中，经常使用冷铁以达到逐层凝固或者避免收缩孔洞。冷铁本质上讲，是大的吸热源。无论何时，为厚重铸件的一部分提供一个冷铁是不可能的，冷铁与其紧密接触，如图5.29所示，从而冷铁从厚大质量部分中快速的吸收了更多热量，使得冷却速度和薄壁部分的相当。从而，阻止了缩孔的形成。但是使用冷铁意味着更高的冷却速度，它也会在和冷铁交叉区趋于形成麻点，如果这个区域需要进一步的机械加工，就会导致问题的出现。 5.3.5 Melting Practice 5.3.5 熔炼操作

The preparation of molten metal for casting is referred to simply as melting. Melting is usually done in a specifically designated area of the foundry, and the molten metal is transferred to the pouring area where the molds are filled. After moulding, melting is the major factor which controls the quality of the casting. There are a number of methods available for melting foundry alloys such as pit furnace, open hearth furnace, rotary furnace, cupola furnace, etc. The choice of the furnace depends on the cupola in its various forms is extensively used basically because of its lower initial cost and lower melting cost.

铸造中熔融金属液的准备阶段通常被称为熔炼，熔炼通常在一个专门设计的车间区域内完成，然后熔融金属转移到铸型充满的浇注区域内。造型结束后，熔炼就成为控制铸件质量的主要因素。有很多有效的方法熔炼铸造合金比如：坑式炉、 开式炉、 旋转炉、冲天炉等，炉子的选择取决于多种形式冲天炉的广泛应用，主要是因为低的原始成本和低的熔炼成本。

5.3.6 cleaning 5.3.6 清理

Cleaning refers to all operations necessary to the removal of sand, scale, and excess metal from the casting. The casting is separated from the mold and transported to the cleaning department. Burned-on sand and scale are removed to be improved the surface appearance of the casting. Excess metal, in the form of fins, wires, parting line fins, and gates, is removed. Castings may be upgraded by welding or other procedures. Inspection of the casting for defects and general quality is performed

清理涉及到所有为清除砂子、 鳞屑状物和铸件多余的上金属，铸件从铸型中分离出来然后输送到清理工位，清理烧结的砂子和鳞屑状物以改善铸件的表面形貌。多余的金属，以飞翅、线状物、分型线飞翅和浇口的形式清理掉。铸件可以通过焊接或其他步骤进一步成型，再进行铸件的缺陷和质量检测。 5.3.7 Other processes 5.3.7 其他工艺

Before shipment, further processing such as heat-treatment, surface treatment, additional inspection, or machining may be performed as required by the customer's specifications.

在运输之前，进一步的工艺比如热处理、 表面处理、附加检测，或机加工也要根据消费者的需要进行操作。

Chapter 6 Advanced Technologies of Metals 第六章：金属的先进技术 6.2 Casting Processes 6.2 铸造工艺方法 6.2.1 Shell Moulding 6.2.1 壳模法

It is a process in which, the sand mixed with a thermosetting resin allowed to come into contact with a heated metallic pattern plate, so that a thin and strong shell of mould is formed around the pattern. Then the shell is removed from the pattern and the cope and drag are removed together and kept in a flask with the necessary back up material and molten metal is poured into the mould.

在这种造型工艺中，将砂子和热固性树脂混合并将其与加热的金属模型表面紧密接触，，从而围绕着模型形成了一个薄且坚固的铸型壳层。然后将壳层与模型分离，并将上下型同时移出放入到有必需的填背材料的砂箱中，随即将熔融的金属浇入到铸型中。

Generally, dry and fine sand (90 to 140 GFN) which is completely free of the clay is used for preparing the shell moulding sand. The grain size to be chosen depends on the surface finish desired on the casting. Too fine a grain size requires large amount of resin which makes the mould expensive.

通常，完全没有粘土成分的干的细砂（90-140目）用于做壳型造型砂，颗粒尺寸的选择取决于铸件所要求的表面光洁度，太细的颗粒尺寸需要大量的树脂进而使造型成本提高。

the synthetic resins used in shell moulding are essentially thermosetting resins, which get hardened irreversibly by heat. The resins most widely used, are the phenol formaldehyde resins. Combined with sand, they have very high strength and resistance to heat. The phenolic resins used in shell moulding usually are of the two-stage type, that is, the resin has excess phenol and acts like a thermoplastic material. During coating with the sand the resin is combined with a catalyst such as hexa-methylene-tetramine (hexa) in a proportion of about 14 to 16% so as to develop the thermosetting characteristics. 壳型造型中使用的人造树脂实质上就是热固性树脂，热量导致它不可逆硬化，应用最广泛的树脂是酚醛树脂。与砂子相结合时，它们有很高的强度和耐热性。壳型造型中使用的酚醛树脂通常属于两级类型式，即树脂有过量的酚醛时会在使用中体现热塑材料的性质，在对砂进行覆膜的过程中，树脂中会加入一种催化剂比如以14%-16%的比例加入六甲撑四胺以产生热固性。

Additives may sometimes be added into the sand mixture to improve the surface

finish and avoid thermal cracking during pouring. Some of the additives used are coal dust, pulverised slag, manganese dioxide, calcium carbonate, ammonium borofluoride and magnesium silicofluoride. Some lubricants such as calcium stearate and zinc stearate may also be added to the resin sand mixture to improve the flowability of the sand and permit easy release of the shell from the pattern.

砂混合物中有时会加入附加物以改善表面光洁度和浇注过程中的热裂。附加物中一些是煤粉、粉状渣滓、二氧化锰、碳酸钙、胺基氟硼酸盐和镁基氟硅酸盐。一些润滑剂比如硬脂酸钙和硬脂酸锆也可以加入到树脂砂中来改善型砂流动性和壳型与模型容易脱离。

The first step in preparing the shell mould is the preparation of sand mixture in such a way that each of the sand grain is thoroughly coated with resin. To achieve this, first the sand, hexa and additives which are all dry, are mixed inside a Mueller for a period 1 min. Then the liquid is added and mixing is continued for another 3min. To this cold or warm air is introduced into the Mueller and the mixing is continued till all the liquid is removed from the mixture and coating of the grains is achieved to the desired degree.

准备壳型的第一步是以一种将砂粒完全覆盖树脂的砂混合物的准备，为了达到这个要求，首先是将干的砂子、六甲撑四胺和附加物在缪勒中混合一分钟。然后加入到液体中并继续混合三分钟，向缪勒中导入冷的或者热的空气，继续混砂知道液体从混合物中析出，沙粒覆盖到所需要的程度。

The metallic pattern plate is heated to a temperature of 200 to 350 oC depending on the type of the pattern. It is very essential that the pattern plate is uniformly heated so that the temperature variation across the whole pattern is within 25 to 40 oC depending on the size of the pattern. A silicone release agent is sprayed on the pattern and the metal plate. The heated pattern is securely fixed to a dump box, as shown in Fig. 6.7 (a), wherein the coated sand in an amount larger than required to form the shell of necessary thickness is already filled in.

Fig. 6.7 Shell moulding procedure

取决于模型的类别金属型板被加热到200-350度不等。型板能够均匀加热以使整个模型温度变化在25-40度范围内。在模型和金属板涂一层聚硅酮脱模剂，加热的铸型不可见的固定在翻斗中，如图6.7（a）中所示，腹膜砂以一种大于所需形成壳型厚度的量填入到其中。

然后旋转翻斗，如图6.7（b）所示以使覆膜砂落到加热板上。模型的热量熔化相邻树脂，从而使得型砂混合物黏附在模型上。

When a desired thickness of shell is achieved, the dump box is rotated backwards by 180 so that the excess sand falls back into the box, leaving the formed shell intact with the pattern as in Fig. 6.7 (d). The average shell thickness achieved depends on the temperature of the pattern and the time the coated sand remains in contact with the heated pattern. The actual shell thicknesses required depends on the pouring metal temperature and the casting complexity. This may normally be achieved by trial and error method.

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