CHAPTER 14 - C HAPTER 14 1 Tempering softens metal 2...

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1. Tempering softens metal. 2. Tempering is the process of reheating metal immediately after quenching for the purpose of increasing ductility or relieving stress. During the tempering process, the metal is heated to a temperature below its lower transformation temperature .This process is also called drawing or drawing back. 3. The tempering also referred to the tendency of tempering to “draw back” the hardness in steel. 4. The purpose of tempering is to increase ductility and reduce internal stress. 5. Ductility is the property normally improved by tempering. 6. Tempering is not desirable for all applications .When hardness is important, tempering may become a problem (when the internal stress not relief is tempering not desirable). 7. The standard range in temperature use for tempering metal is between 300 0 F and 1200 0 F in a furnace. 8. A bout hour is a typical wait after a sample has been quenched before beginning tempering. 9. After the material quenched, it is not transformed into other metallurgy structures by tempering. 10. – General quenching and tempering: when the material is quickly reheated to a tempering temperature between 500 0 F and 1000 0 F, the steel reaches the tempering temperature for several hours and is then quenched back to room temperature. The resulting structure is known as tempered martensite. – Martempering: when the steel is quenched, it is cooled rapidly at first. However, it is held at about 500 0 F to 600 0 F for a short period of time .As a result, the effects of the quench are less drastic when the steel finally crosses the martensitic transformation region. 11. The special quenching method produces 100% bainite is austempering.
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CHAPTER 14 - C HAPTER 14 1 Tempering softens metal 2...

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