1. Steels and Cast Irons Applications and Metallurgy Metallurgy for the Non-metallurgist

2. Learning Objectives After completing this lesson, students will be able to: o Describe steel o List some of the properties of steel and explain how they are different from those of other materials o Tell how steel is produced o Describe cast irons o Tell how cast iron differs from steel

3. Introduction: Steels and Cast Irons Steel as an engineering material Production of steel and steel shapes Some mechanical properties/microstructures Production of cast irons Microstructures of cast irons

4. Steels Enormous variety, compositions & micros Plain carbon, low alloy, alloy, specialty Range from ELC to 2 % C, plus Si, Mn, Al, S Plastic for forming, elastic for use Modulus: 30 million PSI Properties largely dictated by amount and distribution of Fe 3 C; heat treatment Up to 600+KSI BCC: ductile to brittle transition

5. Elasticity Steel is Elastic σ = Eε Elastic Limit—maximum stress steel can withstand without permanent deformation Elastic Modulus is not appreciably affected by carbon content, amount of alloying elements or processing variables

6. Stress-strain diagram plotted from tensile test results. (Upper curves show other possible variations.)

7. Strength Plasticity—elongation due to load Effect of Composition—effects the shape of the stress-strain curve High carbon steels resist deformation and are more elastic

8. Hardness of Steel

9. Approximate relationship between hardness and tensile strength for steel

10. Impact Resistance Charpy V-notch Impact Test Ductile to Brittle Fracture Transition

11. Effect of carbon content on notch toughness

12. Effect of microstructure on notch toughness

13. Fatigue Resistance

14. Effect of shot peening on fatigue behavior

17. Flow diagram showing the principal processes involved in converting raw steel into mill product forms (excluding coated products)

18. Cast Iron Contain more than 2% carbon Types of Cast Iron o White Iron o Gray Iron o Ductile Iron o Malleable Iron

19. Schematic illustration of the mechanical deforming action that occurs during hot rolling

20. Types of graphite flakes in gray iron (AFS-ASTM)

21. Structure of as-cast white iron

22. Gray cast iron, as-cast. Structure is Type A graphite flakes (dark) in a matrix of pearlite (gray lamellar structure of ferrite and pearlite).

23. Typical ductile (nodular) iron as-cast. Spheroidal nodules of graphite (dark) surrounded by an envelope (bull’s-eye) of ferrite (white) in a pearlite (gray) matrix. With slower cooling, the ferrite envelope would be larger until eventually the entire matrix would be ferrite.

24. Ferritic malleable iron two-stage annealed by holding 4 h at 954 °C (1750 °F), cooling to 704 °C (1300 °F) in 6 h, air cooling. Type III graphite (temper carbon) nodules in a matrix of granular ferrite; small gray particles are MnS

25. Typical stress-strain curves for three classes of gray iron in tension

26. Effect of section diameter on tensile strength at center of cast specimen for five classes of gray iron

27. Tensile properties of ductile iron vs. hardness

28. Stress-strain curve for as-cast ductile iron used for crankshafts

29. Effect of composition and microstructure on Charpy V-notch impact behavior of ductile iron

30. Fatigue properties of ductile iron (a) ferritic and (b) pearlitic

31. Rubber wheel abrasion test results

32. Wear of grinding balls

33. Relation between gouging wear and carbon content for various types of steel and cast iron

34. Melting and Casting

35. Sectional view of conventional cupola

36. Sectional view of a coreless induction furnace. (Arrows in crucible show direction of stirring action.)

37. Design of a bottom-pour ladle used for pouring large steel castings

38. Typical teapot-type ladle used for pouring small to medium-size castings

39. Summary Both steels and irons show wide range of compositions and properties Anisotropy from working or from cast structure Small alloy additions have dramatic effects Heat treatments applicable to both