Method for metal treating

A method for metal treating including: a surface cleaning step, to clean the surface of a metal; a cooling processing step, to place the metal in an ultra-cooling equipment processing tank, and then continue for a cooling time to make the inside temperature of the ultra-cooling equipment processing tank is cooled down to -150 degrees Celsius ~ -196 degrees Celsius, where the cooling time is 6 to 12 hours; a temperature holding processing step, the temperature in the processing tank of the ultra-cold equipment is controlled to maintain a temperature of -150 degrees Celsius ~ 196 degrees Celsius, wherein the temperature holding time is 10 to 25 hours; and a warming processing step, the temperature in the processing tank of the ultra-cooling equipment is returned to a room temperature, wherein the warming time is 10 to 25 hours. The present invention can refine the crystal grain size of the metal workpiece, increase the overall hardness, reduce the surface roughness of each area of the metal, and improve the usi