Coating external circulation air cooling device and air cooling method

The invention discloses a coating external circulation air cooling device and an air cooling method, and belongs to the technical field of metal hot working cooling, and the coating external circulation air cooling device comprises an air cooling cavity, a pipeline, a vacuum system, a gas transmission system, a heat exchanger, a refrigeration device and a fan system. According to the invention, the air cooling cavity is vacuumized, the inert gas is injected, the temperature of the cooling gas is reduced to below zero, and the inert gas is cyclically refrigerated for use, so that the effects of preventing oxidation, accelerating the cooling speed and saving the cost can be achieved; when materials are taken out after cooling is finished, the heat exchanger is independently isolated to avoid gas interaction, water vapor in air cannot enter the heat exchanger, frosting caused by too low temperature and the influence of the water vapor on the next working step are avoided, and meanwhile the service life of the he