Lesson 6

Read the text: The Blast Furnace

Ferrous metals are alloys of iron with carbon; these alloys may contain also some other elements such as silicon (Si), phosphorus (P), etc., but carbon is the most important of all elements present in ferrous alloys.

Ferrous metals are used in industry in two general forms: cast iron and steel. These two ferrous alloys are usually produced from pig iron and they have different carbon content. Steel is iron containing from 0.05 to 1.7 per cent carbon, while pig iron is an alloy of iron and carbon with the carbon content more than 2.0 per cent. Pure iron is not used in industry because it is too soft.

The furnace that is used for separating iron from the other elements combined with it in the iron ore is called a blast furnace. It is called so because a blast of hot air is forced into it, while producing the pig iron. This is a vertical furnace from 50 to 100 feet high and from 10 to 20 feet in diameter. The walls of this furnace are made of refractory bricks, which can stand great heat.

The largest parts of the blast furnace are the shaft and the hearth. The charging mechanism is in the shaft top; through this charging mechanism the iron ore, coke, and flux are charged into the blast furnace. The blast of hot air forced into the hearth through tuyers, special holes in the top part of the hearth. These tuyers are cooled with water while working. The pig iron flows out of the furnace through the tap which is a special hole in the wall of the hearth near the hearth bottom. The slag, which is lighter than the pig iron, flows out through another hole made in the wall of the furnace higher than the tap. This hole is called the slag hole.

For separating iron from the impurities the iron ore must be melted. The ore melts at a very high temperature that is why the temperature inside the blast furnace is held about 2,500 degrees Fahrenheit. This great heat is produced by the coke burning in the blast of hot air. The air is heated in special stoves which are called hot-blast stoves. In these stoves the blast furnace gases are burned to produce heat and to heat the air.

A blast furnace may hold about 1,000 tons of iron ore, coke, and fluxes.

1. Match the left part with the right:

1. The slag flows down	a) to the temperature about 1000 degrees Fahrenheit in special hot-blast stoves.
2. The air which is forced into the blast furnace is usually heated up	b) which are called hot-blast stoves.
3. The pig iron flows out of the hearth through the tap	c) to the hearth.
4. The air is heated in special stoves	d) and the slag through the slag hole.

2. Complete the sentences with the suggested words: blast, tuyer, hole, top part; hearth

The________of hot air is forced into the________through________, special ________in the _______ of the hearth.