Metal handling

The molten metal is tapped from the furnace into a pouring ladle. It is poured from the ladle into the mould. Three common types of ladles may be named.

Larger ladles are usually composed of a metal shell lined with refractories capable of withstanding temperatures up to 3100 °F. Smaller ladles may be either refractory lined, or precast, and preshaped crucible made of either bonded graphite or silicon carbide. The ladles should be preheated to a bright red colour (about 1500 °F) before use. This helps to avoid loss of temperature between the furnace and the mould. Also, it is highly desirable to ensure dryness of the ladle so that hydrogen and oxygen from the water vapour will not become dissolved in the molten metal.

Lip Pouring. As the name implies, metal is poured over the lip of the ladle. Slag is held back by an internal skimmer or trapped in a runner box on the mould.

Teapot Pouring. Metal leaves the ladle through the bottom side and emerges through the «teapot» spout. In this way slag on top of the metal is held back while clean metal enters the mould.

Bottom Pouring. Metal leaves the ladle through the nozzle in the bottom. A stopper plug controls the rate of pouring. All slag re­mains on the top of the metal, and as the metal level in the ladle drops, the slag drops with it. Clean metal enters the mould

Exercises

1. Answer the following questions

1. What is the molten metal tapped from the furnace into?

2. How many types of ladles are there?

3. What are larger ladles usually composed of?

4. What may smaller ladles consist of?

5. What temperature should the ladles be preheated to before use?

6. Why should they be preheated to this temperature?

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7. Is it desirable to ensure the dryness of the ladle? 8- What types of pouring do you know?

9. How is metal poured in

1. lip pouring

2. teapot pouring

3. bottom pouring

10. How is slag held back in

1. lip pouring

2. teapot pouring

3. bottom pouring

1. bottom

2. ladle

3. nozzle

4. skimmer

5)spout

6) stopper, plug

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

1. a large spoon with a long handle for transferring liquid (for pour­ing it into the mould)

2. a plug of refractory material used for stopping the tapping hole in a furnace

3. a trough made of steel plate and lined with a refractory material attached to the furnace shell un­der the tap or slag hole

4. the replaceable bottom of a bottom

pour ladle, a vessel in which the molten metal is collected and rocked in order to ensure a uniform composition and temperature

5. a tool for striking off the slag from the surface of a metal bath

6. a shaped piece of a refractory ma-

terial., in the form of a ring , fitted in the bottom of a bottom-pour ladle

3. Look up in the Polytechnical or Metallurgical dictionaries to find some other types of pouring metal in addition to those given ** the text. Give their definitions.

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4. Find out which sentences do not correspond to the con­tents of the text