Steel

UNIT - II

Chapter - 4 (G)

STEEL SECTIONS

 

STEEL SECTIONS

 

1. FERROUS METALS - IRON AND STEEL

Ferrous Metals are iron based metals for all varieties of irons and steels. It is worth mentioning that steel was first produced in India as early as 3000 BC. King Gupta 1 in 310 AD erected the Iron Pillar located at Mehrauli in Delhi. It has not yet been affected by the weathering actions of Nature. It is a metallurgical feat unparalleled elsewhere...!

Based on the Carbon content in iron, the iron is classified into three types. They are:

1. Cast Iron

Iron ores are Magnetite, Hematite, Limonite, Siderite and Pyrite. Pig Iron is an impure iron obtained by smelting iron ores in a blast furnace. Pig iron is combined with Carbon, Silicon, Manganese, Sulphur and Phosphorous. Cast iron is manufactured by re-melting pig iron in a Cupola Furnace. Cast iron contains Carbon 1.5% to 4%. It resists compressive stresses only.

2. Wrought Iron:

It contains Carbon less than 0.15%. It resists tensile stresses only.

3. Steel

Steel is an alloy of Iron and Carbon Steel contains Carbon 0.15% to 1.5%. Thus, steel forms an intermediate stage between cast iron and wrought iron. In steel, carbon does not exist in free graphite state, but in chemical combination with iron.

Various grades of steel are manufactured by refining pig iron using Cementation Process, Bessemer Process, Open Hearth Process and Electric Smelting Process. Refining is done by the removal of unwanted Carbon, Silicon, Sulphur and Phosphorous from pig iron. Ferro-manganese is added to produce steel of required quality.

Ingots: The molten steel after refining in the above process is poured into moulds. The output will be in blocks called Ingots of square or rectangular shape. Steel

Sections: The steel ingot is taken to a Blooming Mill. The blooming mill produces desired sections of shapes such as Round/Square Bars, Angles, Channels, I/T/H Sections, Plates, Sheets, etc.

 

2. CLASSIFICATION OF STEEL

1. Low Carbon Steel or Mild Steel: It contains Carbon between 0.10% and 0.25%.

2. Medium Carbon Steel or Medium Hard Steel: It contains Carbon 0.25% to 0.60%.

3. High Carbon Steel or Hard Steel: It contains Carbon between 0.60% and 1.5%.

 

3. PROPERTIES AND USES OF STEEL

1. Properties of Low Carbon Steel or Mild Steel

1. Structure: Mild steel has fibrous structure.

2. Ductility: It is very ductile and malleable.

3. High Strengths: It has high compressive, tensile and shear strengths.

4. Toughness and Elastic Property: It is tougher and more elastic than wrought iron.

5. Magnetization: It can be readily magnetized permanently.

6. It can be readily welded, forged or riveted.

7. It is not affected by salt water.

Uses of Low Carbon Steel or Mild Steel

(i) R.C.C. Works: Mild steel is used in R.C.C. construction works.

(ii) It is used in the manufacture of angles, plates, steel sections, sheet metal, wires, tubes, etc.

(iii) It is used to manufacture tools, machine parts, tubes, electrical industries, etc.

2. Properties of Medium Carbon Steel or Medium Hard Steel

1. Higher Strengths: It has higher compressive, tensile and shear strengths than Mild Steel.

2. Tough and Hard: It is tougher and harder than Mild Steel.

3. It can be hardened to certain extent. .

4. It cannot be easily forged or welded.

5. It can withstand shocks and vibrations.

Uses of Medium Carbon Steel or Medium Hard Steel

(i) Structural Steel: It is used as structural steel for construction works.

(ii) It is also used to manufacture hammers, springs, press dies, rails, etc.

3. Properties of High Carbon Steel or Hard Steel

1. Structure: High carbon steel has granular structure.

2. Hard and Tough: It is very hard and tougher than other types of carbon steels.

3. It is possible to magnetize permanently.

4. Very High Strengths: It has very high compressive, tensile and shear strengths than other Carbon Steels.

5. It can be easily tempered and hardened.

6. It can withstand shocks and vibrations.

Uses of High Carbon Steel or Hard Steel

(i) It is used to manufacture plates, stone mason's tools, etc..

(ii) It is used to manufacture wood working tools such as chisels, sledge hammers, drills, etc.