Alloy steels

Introduction about alloy steels

1. STAINLESS STEEL (ALLOY STEELS) STAINLESS STEELS TOOL STEELS HSLA STEELS 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