Effect Of Tempering Imperature On Hardness Of D2 Tool Steel

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Figure 7: Effect of tempering temperature on hardness of D2 tool steel at 970, 980,990, and 1000oC austenitizing temperatures.
At tempering temperature range of 200oC- 250oC, for the rise of 25% (50oC) of tempering temperature, the hardness decreases from 69Rc to 67Rc (2.89%). At tempering temperature range of 250oC- 300oC, for rise of 20% (50oC) of tempering temperature, the hardness decreases from 67Rc to 65Rc (2.98%). Thus the rate of decrease in hardness varies between nominal value of 2.81% to 2.98%.

2.1.7 S. Prabhu, B. K. Vinayagam studied Modeling the machining parameters of AISI D2 tool steel material with multi wall carbon nano tube in electrical discharge machining process using response surface methodology-dec-2011 This work investigates the machining characteristics of American Iron and Steel Institute (AISI) …show more content…

WEAR TESTING OF D2 TOOL STEEL UNDER HARDENING, SINGLE TEMPERING (HT)
3.1 HARDENING

The first step in the heat treatment of AISI D2 tool steel was hardening. The purpose of hardening was to harden steel to increase the wear resistance, cutting ability. Hardening of AISI D2 tool steel was done at a temperature of 1020°C [6] for 1 Hour. Harden AISI D2 tool steel followed air cooling which provides great benefit of minimizing distortion and dimensional changes [6]

3.2 TEMPERING
The process which consists of heating the hardened components to a temperature between 100°C and 700°C, holding at this temperature for specific period and cooling to room temperature, usually by air is called as „tempering‟.
Purpose of tempering is as follows
1. To relieve the internal stresses developed due to rapid cooling of steels after hardening process and due to volume changes occurring in the austenite to martensite transformation, to reduce brittleness,
2. To reduce hardness and to increase ductility and toughness,
3. To eliminate retained austenite [7].

Table No-1 working condition of HT
Sr. No. Normal Load FN (Kg, N) Velocity V

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