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CENTRIFUGAL CASTING

The principle of this casting process is that the mold the rotates fairly rapidly while the molten metal is poured into it. This casting process is also referred to as liquid fording because of the poured metal being worked while the mold rotates. Due to the rotation of the mold centrifugal forces are being developed, which direct the incoming liquid metal to the inner surface of the mold with considerable intensity, where solidification occurs. This method of casting produces a product of greater accuracy and superior physical properties as compared with that produces by gravity sand casting.1 Centrifugal casting is especially appropriate for products of symmetrical shape, such as cast-iron pipes, sleeves, and entirely metallic, semi-permanent (made of metal and lined with refractory material), or of sand. If sand molds are used, they arc usually placed in a metallic container or housing adapted for spinning.

Production of sound cylindrical castings depends upon correct spinning speeds. These have been well determined after considerable research and development. Excessive spinning speeds produce high stresses m the casting, making it unsuitable for practical purposes, while

gravity sand casting - литье без применения давления

slow speeds prevent the molten it unsuitable for practical purposes, wile slow speeds prevent the molten metal from adhering to the inside surface of the mold. Speeds vary in accordance with the metal being cast, the size of the casting and other factors a shop producing a large variety of work by centrifugal casting requires mechanical equipment suitable for speeds ranging from 50 to 3,000 revolutions per minute. The machines are either mechanically or hydraulically driven, hydraulic operation being preferred because of (he smooth operation and the capacity for infinite speed variation it provides.

 

 

Exercise 22. Read the text and find the definition of the following terms:

centrifugal casting, b) symmetrical shape product ; c) container.

 

Exercise 23. Look through the text attentively and name the problems dealt with.

Exercise 24. Write out all special terms from the text and give their Russian equivalents.

Exercise 25. Define which of these statements is right or wrong, using the phrase:

a) it is right; b) it is wrong

1. The casting process is referred to liquid forging processes.

2. Centrifugal casting is not appropriate for products of symmetrical shape.

3. Production of sound cylindrical castings does not depend upon correct spinning speeds.

4. Excessive spinning speeds produce nigh stresses in the casting.

5.

Exercise 26. Look through text В again and express the main points of it in 3 sentences.

Exercise 27. Speak on the following:

1. the principle of centrifugal casting;

2. molds in centrifugal casting ;

3. spinning speeds ;

4. mechanical equipment for centrifugal casting ;

Exercise 28. Summarizing the information of TEXT A and TEXT В write an abstract using the key- patterns.


Date: 2016-03-03; view: 1059


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