Ferrous & Non-Ferrous Metals

1. Ferrous & Non-Ferrous Metals Engineering Chemistry (17CY1001) Department of Chemistry K L University

6. Fabrication of Steel

7. Low Carbon Steels • Steels with less than 0.3% Carbon. • Ductile, Malleable, High toughness and Non hardenable by using heat treatment. • Due to high toughness these are used for producing nails, rivets, gears etc. • Due to its cheap cost it is used for making form tools and also wood working tools. • Steels having carbon percentage 0.15 to 0.30 are preferred to use in construction of structures, buildings

8. Medium Carbon Steels • Steels with 0.3% to 0.6% carbon. • These steels have all the intermediate properties of both the low carbon steels and high carbon steels. i.e. Not as hard as high carbon steels and not as ductile as that of low carbon steels. • Little wear resistance and also have relatively high hot hardness. • Applications: Automobiles: manufacturing of axles, lock washers, springs, wheels spokes, crank pins, cylinder liners etc., & tires of a railway wagon. • These steels are used for making form dies. • Wires can also be drawn from these steels

9. High Carbon Steels/Tool Steels • Steels With 0.6 to 2% of Carbon. • Due to high hardness and wear resistance = Tool steels. • High hardness, Brittleness, High wear resistance and Low toughness. • Hardness can be improved by heat treatment • Applications: • Forging dies, Hammers clips, vice jaws, drills and many other machine shop components • In automobiles for the manufacture of balls and races for ball bearings

10. Alloy Steels • ALLOY STEELS: Alloy steel is any type of steel to which one (or) more elements besides carbon are intentionally added to produce a desired physical property (or) characteristic ,for specific applications (or) end products. • The common allowing elements are C, Cu ,S, Mn, P, Cr, Ni, Si, V, B,Mo etc., • The most common alloys are: Mn, Ni, Cr, Mo, V, B &Si and less common are Al, Co, Cu, W, Zr.

11. Alloy steels: High alloy steel & low alloy steels • High alloy steel: >8% (other than C & Fe) • Low allot steel: < 8% (other than C & Fe) • Significance: • To attain greater hardness, durability, corrosion-resistance and toughness as compared to carbon steel.

12. General effects of alloying elements • Ni - Increase toughnes, response to heat treatment - Provides special electric & magnetic properties Cr - Provides stainless steel property, corrosion resistance Widely used in tool steels & in electric plates • Mn- Response to heat treatment • W - Retention of hardness & toughness at high temperature used in tools, values, magnets • Si - High electrical resistance & magnetic permeability used in electrical machinery • Cu - Improves atmospheric corrosion resistance

13. Tool Steels • Tool steels (with 0.7%-1.4% of C) refers to a variety of carbon & alloy steels are particularly well-suited to be made into tools. • Their suitability comes from their distinctive hardness , resistance to abrasion , their ability to hold a cutting edge &/or their resistance to deformation at elevated temperatures (red hardness). • These are machinable & grindable • Cheapest tool steels are high carbon steels contains 0.5% -1.55 carbon.

14. CAST IRON • The product of the blast furnace i.e., pig iron is unsuitable for castings as it contains impurities in high percentage. To render for desired purpose it is refined in the furnace known as cupola. The refined product is termed as cast iron. Cast iron may be classified as follows: • Grey Cast Iron(6-10% Graphite+ Fe ): D.C. Motors • White cast Iron(94% Fe+ 0.5% Graphite C + 3.5% Combined C): rim of car wheel or railway brake blocks • Nodular Cast Iron(3.8% C + 3.2% Si + Fe): machine parts • Malleable Cast Iron(Processed (at 950oc)White Cast Iron): brake pedals, tractor springs, hangers and washing machine parts.

15. NON FERROUS METALS • Aluminium:The important ore of Al is Bauxite (Al2O3.2H2O). Bauxite contain 40-60% alumina. • Extraction Methods: • 1. Bayer’s process. • 2. Electrolytic refining. • Alloys: Casting Aluminium alloys: • Major alloying elements: Cu, Si, Zn, Mg, Ni & Fe. Al – Cu alloys: good machining properties after heat treatment, but have high contraction on solidification By the addition of 12% Si decreases contraction. Al-Si alloys have high fluidity and are used for casting intricate designs. • Ductility of Al-Si alloys is increased by adding trace amount of Sodium or Calcium. • Al- Mg alloys shows good mechanical properties after heat treatment and have good corrosion resistance

16. Applications of Al & It’s alloys • Aluminium in Building: windows and doors: curtain walls, frames, shutters, false windows, insect screens, solar panels, roofing, etc. • Aluminium in Transport: railways, aeronautics and cars etc., • Aluminium in Production engineering:Printing machines, textile machines, woodworking machines, office equipment and computers, scientific instruments. • Aluminium in Electronics: it is cheaper than Cu.overhead electricity distribution lines almost all based on aluminium cables. • Aluminium in the Household: ladders, shower screens, furnishing, lighting fixtures, furniture components, equipment for sports and leisure.

17. Alloys of copper Brass & Bronze • Brass: Copper and Zinc • α- Brass: 35% Zn; Highly ductile, (cold worked: • 70/30: Cu/Zn –Cartridge Brass: both ductility and strength • β- Brass: 35%-46.6% Zn; Harder materials (hot worked) • 60/40: Cu/Zn- Muntz metal • γ- Brass: Above 50.5% Zn; • Season Cracking: Stresses are produced due to which they suddenly crack in service. This is known as ‘season cracking’ and the defect is removed by heating around 30000C.

18. Properties • Admiral Brass: 1% Sn to 70/30 brass: resistant to see water corrosion • Naval Brass:1% Sn to 60/40 brass: Marine and engineering castings. • Leaded brass: 3% Pb to 60/40 brass: improves its machining property. • German Silver = Cu + Ni = Nickel Silver: good mechanical and corrosion resistance

19. Bronze= Cu + Sn • Bronzes are harder and stronger than the brasses. • As tin content increases up to 20% the tensile strength increases. • Bell Metal: Alloy of copper with 20% of tin. • Wrought bronze: “Sn” is less than 8%: cold worked. • Gun metal: zinc + Bronze = Gun metal (88%Cu,10% Sn and 2% Zn) • Properties: very good casting properties, well defined structure during solidification, anti-friction properties and are used for making bearings. • Gun metal is harder than bronze.

20. Applications • Generators, transformers,motors, bus bars and cables etc., Electrical wiring and contacts for PCs, TVs and mobile phones. Copper's naturally antimicrobial properties can be exploited in hygienic surfaces for hospitals and healthcare facilities.

21. PHASE EQUILIBRIUM Components Independent chemical species which comprise the system: These could be: Elements, Ions, Compounds E.g. Au-Cu system : Components → Au, CuIce-water system : Component → H2O H2O – C2H5OH : Components → 2 NaCl- H2O : Components → 2 N2 – O2 : Components → 2 Al2O3 – Cr2O3 system : Components → Al2O3, Cr2O3 Note that components need not be only elements It is the smallest (least) number of independent chemical constituents by means of which the composition of each phase present in the particular system can be expressed, either directly by formula or in the form of a chemical equation This is important to note that components need not be just elements!!

22. PHASE EQUILIBRIUM Components When no reaction takes place, The number of constituents = the number of components Pure water: a one-component system water Mixture of ethanol and water: a two-component system ethanol water

23. PHASE EQUILIBRIUM Components When a reaction takes place, CaCO3(s)  CaO(s) + CO2(g) Phase 1 Phase 2 Phase 3 a two-component system CaO CO2 CaO + CO2  CaCO3 The number of constituents the number of components

24. PHASE EQUILIBRIUM Components COMPONENTS CHOSEN ARE CaCO3(s) and CaO(s) CaCO3(s) = CaCO3(s) + 0 CaO(s) CaO(s) = 0 CaCO3(s) + CaO(s) CO2(g) = CaCO3(s) - CaO(s)

25. PHASE EQUILIBRIUM Components COMPONENTS CHOSEN ARE CaO(s) and CO2(g) CaCO3(s) =CaO(s) + CO2(g) CaO(s) = CaO(s) + 0 CO2(g) CO2(g) = 0 CaO(s) + CO2(g)

26. PHASE EQUILIBRIUM Components COMPONENTS CHOSEN ARE CaCO3(s) and CO2(g) CaCO3(s) =CaCO3(s) + 0 CO2(g) CaO(s) = CaCO3(s) - CO2(g) CO2(g) = CO2(g) + 0 CaCO3(s)

27. PHASE EQUILIBRIUM Components Counting components How many components are present in a system in which ammonium chloride undergoes thermal decomposition? NH4Cl(s)  NH3(g) + HCl(g) Phase 1 Phase 2 three constituents two-component a one-component system additional NH3 or HCl NH4Cl NH4Cl  NH3 + HCl

28. PHASE EQUILIBRIUM P V = RT Degrees of Freedom CONSTANT Any two variables are sufficient to define the system completely and the third variable gets defined automatically. P and V P and T V and T System is said to possess two degree of freedom A mixture of two gases, e.g. CO2 and O2? DOF Degree of freedom or Variance (f): the number of intensive variables that can be changed independently without disturbing the number of phases in equilibrium.

29. PHASE EQUILIBRIUM The GIBB’S PHASE RULE • The phase rule connects the Degrees of Freedom, the number of Components in a system and the number of Phases present in a system via a simple equation. • To understand the phase rule one must understand the variables in the system along with the degrees of freedom. For a system in equilibrium F = C  P + 2 F – Degrees of FreedomC – Number of ComponentsP – Number of Phases The phase rule or F  C + P = 2 The Phase rule is best understood by considering examples from actual phase diagrams as shown in some of the coming slides

30. PHASE EQUILIBRIUM Phase diagram Map demarcating regions of stability of various phases. or Map that gives relationship between phases in equilibrium in a system as a function of T, P and composition (the restricted form of the definition sometime considered in materials textbooks) Phase transformation Phase Transformation is the change of one phase into another. E.g.: ► Water → Ice ► - Fe (BCC) → - Fe (FCC)► Ferromagnetic phase → Paramagnetic phase (based on a property)

31. PHASE EQUILIBRIUM Understanding A way of understanding the Gibbs Phase Rule: The degrees of freedom can be thought of as the difference between what you (can) control and what the system controls P  F = C + 2 What the system controls Degrees of Freedom = What you can control  System decided how many phases to produce given the conditions Can control the no. of components added and P & T

32. Variation of the number of degrees of freedom with number of components and number of phases. C = 2 2 components C = 3 3 components

33. Phase Diagram of Water How many components do you have? We have only one component which is H2O. In the one-phase regions, one can vary either the temperature, or the pressure, or both (within limits) without crossing a phase line. We say that in these regions: f = c – p + 2 = 1 – 1 + 2 = 2 degrees of freedom.

34. Phase Diagram of Water Along a phase line we have two phases in equilibrium with each other, so on a phase line the number of phases is 2. If we want to stay on a phase line, we can't change the temperature and pressure independently. We say that along a phase line: f = c – p + 2 = 1 – 2 + 2 = 1 degree of freedom.

35. Phase Diagram of Water At the triple point there are three phases in equilibrium, but there is only one point on the diagram where we can have three phases in equilibrium with each other. We say that at the triple point: f = c – p + 2 = 1 – 3 + 2 = 0 degrees of freedom.

36. Phase Rule Reminder: Gibbs Phase Rule F = C – P + 2 • degrees of Freedom = Components– Phases +2 Gibbs Phase Rule

38. Simple Eutectic (Lead-Silver System)