METHOD AND DEVICE FOR COOLING IN HEAT TREATMENT OF METAL

摘要

PURPOSE:To enable cooling which has the initial cooling rate satisfying a desired heat treatment and is thereafter slow with less quenching strain and crack by using a gas-liquid mixture formed by dispersing fine foam of gas into liquid as a cooling medium. CONSTITUTION:An air-water mixture is put into an inside vessel 2 of a cooling vessel 1 having a double construction and liquid such as water or oil is put into an outside vessel 3. The temp. of said liquid is controlled by a heater 4 to maintain the temp. of the above-mentioned mixture or to control the temp. thereof. The above-described mixture is subjected to flow rate control by a throttle valve 7 from a device 5 for forming said mixture and is admitted into the vessel 2 in the circumferential tangential direction along the inside wall of the lower part thereof so as to be distributed uniformly in the tank 2. The mixture is then discharged from an overflow port 8. The air foam is thus uniformly dispersed at the horizontal section of the vessel 2 and at the same time the floating of the air foam is limited. The quasi-static state of the cooling liquid in the vessel is obtd. with the decreased amt. of the mixture to be introduced. The inflow rate is conversely increased by the valve 7 or turning flow is formed in the vessel 2 by a stirrer 9 to make the cooling liquid more positively convectional.