Introduction about alloy steels

1. STAINLESS STEEL
(ALLOY STEELS)
1. STAINLESS STEELS
2. TOOL STEELS
3. HSLA STEELS
4. MARAGING STEELS

2. Stainless steel
• Its an alloy of iron, chromium and other
elements that resist corrosion from many
environments
• This is also known as corrosion resistant steel
or chromium- bearing steels

3. COMPOSITION
• 12 % --------CHROMIUM is the main
element.
• Which form a protective layer(chromium
oxide) against oxidation and avoid rust or
corrosion.
• To increase resistance we add other elements
like Cu, Ni, Si, Mn

4. Types
on the basis of main constituent of the
Microstructure
• Austenitic Stainless Steel
• Ferritic Stainless Steel
• Martensitic Stainless steel

5. IMPORTANT NOTE
• Alloying elements in steel can be either austenite
stabilizers or ferrite stabilizers
– AUSTENITE STABILIZERS:
• Enhance Retention of Austenite as steel when cooled
• Ni, Mn, Co (cobalt), Cu (copper)
– FERRITE STABILIZERS:
• Prevent transformation of steel to austenite up on heating.
• Cr, W, Mo, V, Si
• Stabilizers are used to increase the resistance property
in this steel.

6. 1. Austenitic Stainless Steel
• It’s a most widely used steel, having austenite
structure retained at room temperature

7. Composition percentages
• C ------0.03 – 0.15%
• Si ------ 1 – 2 %
• Ni ------ 3.5 – 22 %
• Mn ---- 2 – 10 %
• Cr ------ 16 – 26 %
• Mo and Ti in some cases we used.

8. • This steel contains both chromium and nickel. And
having carbon less than 0.15 %
• The less percentage of carbon minimize the formation
of chromium carbide
• Carbides are formed during slow cooling from high
temperature.
• For this lead to weld decay in welding.
• For avoiding Weld decay we add austenite stabilizers
like titanium or nobium in small amounts to this
austenitic stainless steel.

9. PROPERTIES
• High Corrosion resistance
• Good strength and scale resistance
at high temperature.
• Non – Magnetic
• Good ductility
• Very tough and can be welded, forged or Rolled

10. APPLICATIONS
• Engine parts in Air – Crafts
• As a heat exchanger ----in chemical industry
• As a parts like tank in ---- Food processing industry
• As a house hold items --- cooking utensils
• Dairy industry ------------ milk cans
• Transport ------------- trailers and railway cars.

11. Images for Austenitic Stainless Steel

12. 2. Ferritic Stainless steels
• Ferritic stainless steel contains between 12 and 25%
of chromium and less than 0.1% carbon
• Here we cannot heat up to austenitic temperature
(723 ͦC) level ---- so there is no chance of formation
of martensitic structure by quenching it from high
temperature.
• It cannot used for heat treatment process. But
strenghtened by work hardening

13. Composition
• C- 0.08 – 0.10%
• Mn – 1 – 1.5 %
• Si – 1%
• Cr – 12 – 25%

14. PROPERTIES
• Having Magnetic property
• Having good ductility
• Having good strength
• Having good toughness & resistance to corrosion
• It can be welded, forged, rolled and Machined

15. Applications
• As a lining --------- in petrolium industry
• As a heating element ----- in furnace
• And in interior decorative works, screws , fittings and
oil burner parts.

16. 3. Martensitic Stainless steels
• Here the steel is heated up to austenite temperature
and cooled by quenching for obtaining martensite
structure.
• This contains 12-25% chromium and carbon
contents from 0.1 – 1.5%

17. Composition
• 12 --- 25 % of chromium
• C – 0.1 – 1.5%
• Mn --- 1 %
• Si --- 1 %

18. PROPERTIES
• Good hardness , ductility and thermal
conductivity.
• Good toughness and corrosion resistance

19. APPLICATIONS
• Used in pumps , valve parts, rules and taes,
• Turbine blades and surgical instruments.

20. TOOL STEEL
.

21. DEFINITION
• These are the steels used to make tools and
dies for cutting, forming and shaping
• Other words, Metals designed to provide wear
resistance and toughness combined with high
strength
• They are basically high carbon alloys.

22. PROPERTIES
• High toughness
• Good wear resistance
• Very good machinability
• Resistance to de- carburisation
• High strength

23. CLASSIFICATION OF TOOL
STEELS
• Cold work tool steels
• Shock resistance
• Hot work
• High speed
• Plastic mould
• Special purpose
.

24. COMPOSITION
• For high speed steel Super high speed steel
• 18 % tungsten 20 % tungsten
• 1 % vanadium 2 % vanadium
• 4 % chromium 4 % Cr
12 % cobalt