1, Answer the following questions

1. What is the shortest distance between raw material and a fin­ ished part?

2. Is the casting process widely used nowadays? 3- What does the melting process begin with?

4. Does the simplicity of casting make it the lowest cost method?

5. Are forging, stamping, welding required in the casting process?

6. In what case is a plate usually cast?

7. When are rolling and shearing processes used?

8. Where are castings used?

9. How do castings range in size (function, cost)?

10. Is the casting process always necessary when metalworking is done?

2. Find out which sentences correspond to the contents of the text

1. The casting process is not finding many new applications be­cause it is the most expensive process.

1. Casting is low-cost method because of its simplicity.

2. There are great limitations in size of castings.

3. Metalworking can't be done without casting.

4. All metal processes begin with pouring metal into a mould.

3. Match the words on the left with their definitions on the right

1) mould a) a method of causing fusion between

two pieces of metal

2) advantage b) measurable extent of length, breadth,

thickness, area, volume

3) welding c) the passing of a solid body into the

liquid state

4) billet d) a set of elements forming a cavity,

into which molten metal is poured to form a casting

5. dimension e) better position, superiority

6. melting f) small metal bar

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4. Render the following

A casting is the shortest distance between raw material and a fin­ished part. Casting the metal into the shape desired without further working is one of the important methods of producing metal parts. The simplicity of this method makes it the lower cost way of producing metal parts. In many cases the choice of the method depends upon the shape itself. For example, metal sheets must be rolled. Complex shapes, on the other hand, would be too expensive produced by any other method than casting. Generally, many considerations should be taken into choosing the most economical and reliable method. Modern metallurgists and casting engineers do all their best to raise the levels of quality and reliability of the casting.

5. Translate at sight

Есть разные способы производства металлических изделий. Литье - один из них. Изделия, полученные этим способом, назы­ваются отливками. Во многих случаях простота процесса литья делает его самым дешевым способом получения металлических изделий. В литье не требуется таких операций, как сварка, воло­чение, штамповка, прокатка и другие.

Отливки по величине колеблются от нескольких унций до сотен тонн и более, по стоимости от десяти центов до десяти дол­ларов за фунт. Отливки используются в различных целях.

Units

SAND MOULDING AND SAND MIXTURES

By far the most widely and the most flexible moulding process is sand moulding. It is used for producing castings in almost all castable metals and in those sizes ranging from a few ounces to more than a hundred tons.

When using the term «sand casting», we refer to the fact that the moulds, which will contain the molten metal, are made of silica sand. This material is used perhaps more universally than any other mould

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material, primarily because of its refractoriness, its simple supply and its low cost. Good foundry sand is found in a variety of locations, the most common being the Ottava District and the Albany District.

A foundry-man combines these sand binders, which range all the way from volcanic clays to organic starches made from corn, wheat and tapica. A typical list of binders might be that of bentonite, fire clay, corn flour, linseed oil, synthetic resins, sodium silicate, pitch, and sea coal. Each binder and each sand is very accurately designed for a specific function in the construction of the mould. For instance, as metal enters a mould it is very much like a piston moving in a cylinder. Entrapped air ahead of the piston or ahead of the metal must be cleared to allow a mould to fill in all the detail. Thus, the sand mixture must have an ability to allow the air and gas to move out of the mould through the sand itself. This property known as permeability is de­signed into the mould material. It is measured in terms of centimetres of air passing through the sand each second.

The sands themselves are selected according to the principle of particular size and shape, and particle distribution to promote proper permeability. Binder selection is based on the strength the binder ivill develop, when mixed with sand, and on relative length of time that will retain its strength, when to hot metal.

Typical compression strength vary from as little as one pound per square inch for oil-sand mixtures before baking to greater than 400 pounds per square inch for a pitch and clay sand when completely baked.

Exercises