Fundamental manufacturing processes

Casting

The foundry process used in 2000 B.C. is very same to that used today. True or False? (Para.1)

Basically foundry processes include :a:_________________________________b:_________________________________c:_________________________________d:_________________________________

making moldspreparing and melting the metalpouring the metal into the moldscleaning the castings

How do you understand the sentence “The product of the foundry is a casting, which may vary from a fraction of a kilogram to several hundred tons.”?(para.2)

Casting

Foundry processes consist of making molds, preparing and melting the metal, pouring the metal into the molds, and cleaning the castings.

铸造工艺包括制模、备料、金属熔炼、金属液浇注入模及铸件清理等过程。

Casting

What metals are frequently cast? And what metal is most outstanding for its suitability for casting? Why?(para.3)

Casting is a widely used method of producing ____________________.

Translate the sentence “Since molten materials will readily take the shape of the container into which they are poured, it is nearly as easy to cast fairly complex shapes as to produce simple forms.” (para.4)

Intricate metal products

Terms(para.5-6)

cast iron 铸铁

cupola 化铁炉；冲天炉

foundry 铸造厂；铸造车间

pig iron 生铁

ladle 铸勺；铸桶；浇注桶

cupola

The cast iron flows into ladles from

which it is poured into the molds.

An introduction to casting

Metal Casting is one of the oldest materials shaping methods known. Casting means pouring molten metal into a mold with a cavity of the shape to be made, and allowing it to solidify. When solidified, the desired metal object is taken out from the mold either by breaking the mold or taking the mold apart. The solidified object is called the casting. By this process, intricate parts can be given strength and rigidity frequently not obtainable by any other manufacturing process.  The mold, into which the metal is poured, is made of some heat resisting material. Sand is most often used as it resists the high temperature of the molten metal. Permanent molds of metal can also be used to cast products. Casting is a 6000 year old process.

sand molds

sand molds

Metal mold

A metal mold consists of two hollow parts, which should be joined for pouring the metal into it. The inside of this mold is covered with carbon or graphite so that the metal could not be stick to the wall of the form. When the metal has solidified, these hollow parts are disjoined and the casting is taken out.

Casting

A relatively wide range of nonferrous alloys can be die-cast.

Casting

Die casting is a cost-effective method to mass-produce lightweight metallic parts for household and industrial use. Die casting is a metal forming method to manufacture metallic components by injecting molten metal alloys into a mold, or "die" at high pressure. Die casting is used to rapidly create metallic parts that require little post-manufacturing machining.Die cast parts are generally fabricated from metallic alloys that have relatively low melting point. This protects the die from cracking due to excess heat. Typical die-casting alloys include aluminum, zinc, magnesium, and copper.

Casting

As the casting temperature increases, alloy and other special steels in the best treated condition are required to resist the erosion and heat checking of die surfaces.( 当铸造温度上升时，需要最佳条件下处理过的合金钢和其他特种钢来抵抗腐蚀及防止模具表面的热裂纹。）

Review:

1 casting processes consist of_______,_______,______,___

Making molds, preparing and melting the metal, pouring the metal into the molds, and cleaning the castings.

Review:

2 What metal is outstanding for its suitability for casting and used far more than all the others?

3 what is a cupola?

Cupola is the special melting furnace for re-melting pig iron to produce cast iron.

4 Why is the inside of metal mold covered with carbon or graphite ?

Permanent mold casting 永久型铸造或硬模铸造Here, the two halves of the mold are made of metal, usually cast iron, steel, or refractory alloys. The cavity, including the runners and gating system are machined into the mold halves. For hollow parts, either permanent cores (made of metal) or sand-bonded ones may be used, depending on whether the core can be extracted from the part without damage after casting. The surface of the mold is coated with clay or other hard refractory material __ this improves the life of the mold. Before molding, the surface is covered with a spray of graphite or silica, which acts as a lubricant. This has two purposes ___ it improves the flow of the liquid metal, and it allows the cast part to be withdrawn from the mold more easily. Also, it produces very good tolerance and surface finish. It is commonly used for producing pistons used in car engines, gear blanks, cylinder heads, and other parts made of low melting point metals, e.g. copper, bronze, aluminum, magnesium, etc.

Useful Words

refractory alloys 耐热合金 runners 流道

gating system 浇注系统 extract 拔出

lubricant 润滑剂 tolerance 公差

surface finish 表面光洁度 pistons 活塞

gear blanks 齿轮毛坯 cylinder head 汽缸盖

Permanent mold casting 永久型铸造或硬模铸造Here, the two halves of the mold are made of metal, usually cast iron, steel, or refractory alloys. The cavity, including the runners and gating system are machined into the mold halves. For hollow parts, either permanent cores (made of metal) or sand-bonded ones may be used, depending on whether the core can be extracted from the part without damage after casting. The surface of the mold is coated with clay or other hard refractory material __ this improves the life of the mold. Before molding, the surface is covered with a spray of graphite or silica, which acts as a lubricant. This has two purposes ___ it improves the flow of the liquid metal, and it allows the cast part to be withdrawn from the mold more easily. Also, it produces very good tolerance and surface finish. It is commonly used for producing pistons used in car engines, gear blanks, cylinder heads, and other parts made of low melting point metals, e.g. copper, bronze, aluminum, magnesium, etc.

Tolerance 公差The unwanted but acceptable deviation from a desired dimension. Increasingly accurate dimensions require tighter tolerances.

Surface finish

deterioration of the surface finish

The degree of smoothness of a part's surface after it has been manufactured. Surface finish is the result of the surface roughness, waviness, and flaws remaining on the part.

Review:

5 Translation Practice:我们每天使用的大量金属零件都是通过铸造制成的，铸造有许多优点：a. 铸造可以制造具有复杂几何结构的零件b. 铸造可以用来制造尺寸大小不等的零件c. 铸造没有浪费的、很经济；用于每一次铸造多余的金属都可以重新熔化再使用。d. 铸造后的金属在任何方向上都具有相同的机械特性。

Review

5 A large number of metal components we use every day are made by casting. It has a lot of advantages as follows:a.Casting can produce very complex geometry parts.b.It can be used to make small to very large size parts.c.It is economical, with very little wastage: the extra metal in each casting can be re-melted and re-used.d.Cast metal has the same mechanical properties along any direction.

Lesson 7 Die Life and Die Failure( 模具寿命和失效）

Dies may have to be replaced for a number of reasons, such as changes in dimensions due to wear or plastic deformation, deterioration of the surface finish, breakdown of lubrication, and cracking or breakage.

模具可能因为种种 原因而不得不进行更换，例如由于磨损或发生塑性变形导致尺寸的变化，表面光洁度的破坏，润滑故障及裂纹。

Elastic/Plastic Deformation

When a sufficient load is applied to a metal, it will cause the material to change shape. This change in shape is called deformation. A temporary shape change that is self-reversing after the force is removed, so that the object returns to its original shape, is called elastic deformation. In other words, elastic deformation is a change in shape of a material at low stress that is recoverable after the stress is removed. This type of deformation involves stretching of the bonds, but the atoms do not slip past each other. When the stress is sufficient to permanently deform the metal, it is called plastic deformation. Plastic deformation involves the breaking of a limited number of atomic bonds by the movement of dislocations.

Impression-die drop forging

Impression-die forging is also called closed-die forging. In impression-die work metal is placed in a die, which is attached to the anvil( 铁砧） . The hammer is then dropped on the workpiece, causing the metal to flow and fill the die cavities. Depending on the size and complexity of the part the hammer may be dropped multiple times in quick succession. Excess metal is squeezed out of the die cavities, forming what is referred to as flash. The flash cools more rapidly than the rest of the material; this cool metal is stronger than the metal in the die so it helps prevent more flash from forming. After forging the flash is removed.

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