This paper will debunk the age-old theory that the smaller the vacuum furnace, the faster it will quench supposition. Our study compared the cooling rates of two vacuum high pressure gas quenching furnaces - a large 10-bar vacuum furnace equipped with a 600 HP blower motor to a smaller 10-bar vacuum furnace equipped with a 300 HP motor. In comparing the critical cooling temperatures for H13 in the 1850°F to 1300°F range, the furnace that is almost three times larger in volume (110 cubic feet versus a 40 cubic feet of hot zone) cooled the same workload almost identically to its smaller counterpart. These tests prove a very important fact - that the gas flow or velocity is more meaningful than pressure (bar) when it relates to cooling rates.

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