high speed steel, heat resisting steel, silicon steel, spring steel and stainless steel etc.

 

Give the composition, properties and uses of the following alloy steels: high speed steel, heat resisting steel, silicon steel, spring steel and stainless steel etc.

A. High Speed Steel:

High Speed Steel:

1. High speed steels are widely used for cutting of metals where hardness must be retained at elevated temperatures.
2. These steels are obtained by alloying 18 % tungsten, 4 % chromium and 1% vanadium with a carbon content of 0.6 to 0.7 %. This alloy is termed as 18:4:1 while an increase of vanadium to 2 % produces 18: 4:2 steels. 
3. In addition to heat resistance high speed steels have the desirable properties of high hardness, high compressive strength and outstanding wear resistance.

Uses: This steel is used for high-speed cutting tools.

B. Heat Resisting Steel :

Heat Resisting Steel :

1. Steels which must be resistance to creep at high temperatures must contain molybdenum. Silicon and chromium impart resistance to oxidation and scaling.
2. Steels which are satisfactory upto about 700°C operating temperature are C 0.15 %, Si = 0.5 to 20 %, Mn = 0.5 % maximum, Ni = none, Cr= 1.0 to 6%, Mo = 0.5%

Uses: These are used in valves of internal combustion engines in rolled or in forged condition. For higher temperature upto 1000 °C, steels containing upto 22 % nickel and 26% chromium are used.

C. Silicon Steel:

Silicon Steel:

1. Improves the electrical properties of steel.
2. Silicon imparts fatigue strength and resistance to steel.
3. Steel containing silicon is more ductile than plain carbon steel.
4. Steel containing 3 to 5% silicon has very low magnetic hysteresis.

Uses:

• i. Steel with Mn = 1%, Si = 2%, C = 0.4 to 0.6 % has very high elastic limit and is used for springs.
• ii. With Cr 5 to 7 %, Si = 2 to 4 %, C = 0.4 to 0.5 % steel retain its hardness and resistance to oxidation even at red heat. Such steels are used for internal combustion engines.
• iii. 13% silicon content steel has very high corrosion resistance so it is used in chemical industries.

D. Stainless Steel :

Stainless Steel 

a. Plain Chromium and High Chromium Low Nickel Steel:

1. Out of this group the former has C = 0.8%, Cr = 12 to 20 % and latter has C=0.1 to 0.2 %, Cr= 12 to 20 % and Ni = 2%.
2. These steels can be heat-treated.

Uses: For dies, valves and cutlery.

b. Chromium-Nickel Steel:

1. These steels are non-magnetic and cannot be hardened.
2. They have varieties due to varying contents of chromium and nickel respectively e.g., small quantity of copper, tungsten and molybdenum is also added to these steels.
3. They have high resistance to corrosion and may be cold or hot worked, pressed welded, brazed or soldered.
4. These steels are poor conductors of heat and electricity. 

Uses: It is used in making utensils.