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Carburzing and Different Types of Carburzing
- 1. Seminar On CARBURIZING Melwin D’mello M.E(Welding Engineering) Centre for Materials Joining & Research (CEMAJOR), Department of Manufacturing Engineering, ANNAMALAI UNIVERSITY Presented by
- 2. CONTENTS • Introduction • Typesof Carburizing • Advantages/Disadvantages • Applications • Conclusion
- 3. INTRODUCTION • It isa heat treatment process. • Increasing Carbon on the surface of iron or steel followed by heat treatment. • Absorbs Carbon liberated when the metal is heated in the presence of Carbon bearing materials. • Carbon bearing materials can be Charcoal, Carbon Monoxide or Carbon gases.
- 4. HARDENING AGENTS •Carbon MonoxideGas •Sodium Cyanide •Barium Carbonate •Hardwood Charcoal
- 5. EFFECTING FACTORS • LongerCarburizing time and higher temperatures lead to greater diffusion of carbon into the metal/alloy. • Rapid Cooling/Quenching results transformation of austenite to martensite. • While core remains soft and tough as a ferritic or pearlitic microstructure.
- 6. WHY CARBURIZING IS USED? Itis used to increase • Ductility • Toughness • Hardness • Strength It is also used to relieve internal stresses.
- 7. TYPES OF CARBURIZING • GasCarburizing • Vacuum Carburizing • Pack Carburizing • Liquid Carburizing
- 8. GAS CARBURIZING Process Description: •Main carburizing agent can be either Methane, Propane, Natural Gas or any other Carbon carrying gas. • Work pieces are heated with carbon carrying gas. • Then held for period of time at specific temperature between 800°C - 950°C. • After that quench the sample.
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- 10. VACUUM CARBURIZING • Itis done under very low pressure. • Sample is heated in vacuum above transformation temperature. • Then exposed to carbon carrying gas or mixture under partial pressure. • Temperature Range: 800°C to 1100°C • Pressure Range: 1 to 20 torrs
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- 12. PACK CARBURIZING • Sampleis packed in a steel container & sample is completely surrounded by granules of charcoal. • Then heated in a furnace for 12 to 72 hours at 900°C. • Due to high temperature, carbon diffuses into the surface of sample.
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- 14. LIQUID CARBURIZING • Sampleis placed in molten cyanide’s bath so that carbon will diffuse into the sample. • Diffusion of carbon into sample is greater than nitrogen. • Low temperature salt bath contains 20% cyanide & operate between 1550°F to 1650°F. • High temperature salt bath contains 10% cyanide & operate between 1650°F to 1750°F.
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- 17. GAS CARBURIZING Advantages: • SurfaceCarbon contents & case depth can be controlled accurately. • It is much cleaner and more efficient method. Dis Advantages: • Furnace & gas generator are expensive. • Handling of fire hazards & toxic gases is difficult.
- 18. VACUUM CARBURIZING Advantages: • Absenceof inter-granular oxidation. • The process is safe & simple to operate & easy to operate. Dis Advantages: • Higher initial equipment cost. • Formation of soot & tar due to pressure and Hydrogen gas introduced.
- 19. PACK CARBURIZING Advantages: • Itis simple method and less capital investment. • No atmosphere control furnace is required. Dis Advantages: • Carburizing time is very long. • Difficult to control surface carbon & case depth.
- 20. LIQUID CARBURIZING Advantages: • Freedomfrom oxidation & soot problems. • A rapid rate of penetration. Dis Advantages: • Proper composition is necessary to obtain uniform case depth. • Parts must be washed after doing the process.
- 21. CHANGES Mechanical Changes: • Increasesurface hardness • Increase wear resistance • Increase Fatigue strength • Increase Tensile Strength
- 22. CHANGES Physical Changes: • Graingrowth may occur. • Changes in Volume may occur. Chemical Changes: • Increased surface carbon content.
- 23. APPLICATIONS • Gear teethprofiles • Crane wheels • Crane cable drum • Support bracket for agricultural tractor • Machines worm steels • Hydraulic clutch
- 24. APPLICATIONS • Fly wheels •Ball bearings • Gear wheels & pinion blanks • Railway wheels • Crankshaft • Shackles of lock • Bevel Gears
- 25. CONCLUSION • The mechanicalproperties of the steels strongly influence by carburizing. • Carbon plays important role in increasing the toughness, hardness and other mechanical properties of steels. • Gas Carburizing is used for large parts, liquid carburizing is used for medium & pack carburizing is used for small parts usually.
- 26. REFERENCES • A Textbook of “MATERIAL SCIENCE AND ENGINEERING” By O P Khanna : 2013 Edition
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