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Flame Hardening

Flame Hardening

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Flame Hardening

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  1. ENMAT101A Engineering Materials and ProcessesAssociate Degree of Applied Engineering (Renewable Energy Technologies)Lecture 14 – The surface hardening of steels Flame Hardening

  2. The surface hardening of steels EMMAT101A Engineering Materials and Processes

  3. The surface hardening of steels Note: This lecture closely follows text (Higgins Ch14) EMMAT101A Engineering Materials and Processes

  4. Principles of hardening (Higgins 14.1) READ HIGGINS 14.1 Many metal components require a hard outer skin and tougher inner core. E.g. Machine elements like shafts, bearings, gears, cams etc. There are two ways to achieve this; 1. Use low-carbon steel (tough) and add carbon to the outer skin. 2. Use carbon steel and heat only the surface before quenching. EMMAT101A Engineering Materials and Processes

  5. Case-hardening (Higgins 14.2) 1. Use low-carbon steel (tough) and add carbon to the outer skin. Higgins EMMAT101A Engineering Materials and Processes

  6. Case-hardening (Higgins 14.2) READ HIGGINS 14.2 14.2.1 Carburising in solid media: (pack carburising) Higgins EMMAT101A Engineering Materials and Processes

  7. Case-hardening (Higgins 14.2) READ HIGGINS 14.2 14.2.2 Carburising in liquid media (cyanide) Higgins EMMAT101A Engineering Materials and Processes

  8. Case-hardening (Higgins 14.2) READ HIGGINS 14.2 14.2.3 Carburising by gaseous media Higgins EMMAT101A Engineering Materials and Processes

  9. Heat-treatment after carburising (Higgins 14.3) READ HIGGINS 14.3 Refining the core Refining the case Higgins EMMAT101A Engineering Materials and Processes

  10. Case-hardening steels (Higgins 14.4) READ HIGGINS 14.4 Higgins EMMAT101A Engineering Materials and Processes

  11. VIDEO: Crystals and Grain Structure 1. What is a grain? BBC (1973) 2. Recrystallisation Part 3: Heat Treatment • Steel grains are too small to be visible - need a microscope approx 250 times magnification. • Ferrite: Light coloured. Made of iron. Gives ductility to the steel • Pearlite: darker coloured. Layers of Iron + Iron Carbide. Hardness and strength to the steel. • 100% Pearlite: 0.83%C. Recrystallisation temperature 723C. Eutectic alloy. • Normalising - cooled in air, grain size reduced and more uniform shape, toughness increased  due to smaller grains • Quenching - increases hardness. Not enough time for pearlite to form, so a needle like structure forms - martensite. Very hard and brittle. • Tempering - (after quenching) restores toughness. Modifies the martensite needles with small flakes of carbon. This gives keeps most hardness, adds toughness. • 0.1%C steel (Mild Steel). Recrystallisation 900C. Not enough carbon to produce martensite. EMMAT101A Engineering Materials and Processes

  12. Nitriding (Higgins 14.5) • READ HIGGINS 14.5 • Requires Steel with alloys that form carbides with N • Lower temperature for diffusion (500oC for 40 to 100 hours) Higgins EMMAT101A Engineering Materials and Processes

  13. Nitriding (Higgins 14.5) READ HIGGINS 14.5 Higgins EMMAT101A Engineering Materials and Processes

  14. Nitriding (Higgins 14.5) READ HIGGINS 14.5 14.5.1 Heat treatment 14.5.2 Advantages and disadvantages of nitriding 14.5.3 Carbonitriding EMMAT101A Engineering Materials and Processes

  15. Ion Nitriding (Higgins 14.6) READ HIGGINS 14.6 Plasma nitriding and ion implantation. EMMAT101A Engineering Materials and Processes

  16. Flame-hardening (Higgins 14.7) READ HIGGINS 14.7 Localised heating/quenching Higgins EMMAT101A Engineering Materials and Processes

  17. Induction-hardening (Higgins 14.8) READ HIGGINS 14.8 Powerful, high frequency current induces eddy currents in the surface of the component, heating it locally. Higher frequencies heat to a shallower depth (skin effect). Induction Heating http://www.automotive-business-review.com EMMAT101A Engineering Materials and Processes

  18. Summary (Higgins 14.9) Higgins EMMAT101A Engineering Materials and Processes

  19. Video: Heat Treatment: BBC: 1981 Heat treatment [videorecording] / producer Brian Davies. Video: Discusses the use of heat which changes the properties of metals. Outlines different techniques including hardening, tempering, annealing, normalising as well as a non-heat process, cold-working. Recommended viewing: All EMMAT101A Engineering Materials and Processes

  20. Online Resources. Teach yourself phase diagrams Handout http://www-g.eng.cam.ac.uk/mmg/teaching/phasediagrams/i2a.html Heat Treatment: BBC: Heat treatment [videorecording] / producer Brian Davies. [B.B.C.], 1981. Video: Discusses the use of heat which changes the properties of metals. Outlines different techniques including hardening, tempering, annealing, normalising as well as a non-heat process, cold-working. Wikipedia: EMMAT101A Engineering Materials and Processes

  21. GLOSSARY • Carburising • Plasma Ion • Nitriding • Pack carburising • Cyanide hardening • Gas-carburising • Flame hardening • Induction hardening • Carbonitriding EMMAT101A Engineering Materials and Processes

  22. QUESTIONS Moodle XML: Some questions in 10105 Steel • Define all the glossary terms. • Describe why a part would need a hard skin and a soft core. • Use a table to summarise the advantages and disadvantages of the three carburising methods as shown in the video: Pack carburising, cyanide and plasma. • List advantages and disadvantages of nitriding EMMAT101A Engineering Materials and Processes