In 1978, Swiss Dr. Leeb proposed a brand-new hardness test method. Under the action of elastic force, an impact body of speci- fied quality was used to impact the surface of the sample at a certain speed, and the rebound speed of the punch at 1mm from the surface of the sample The hardness value is calculated by the ratio of the electromagnetic principle to the impact speed. Calculated formula as follows: HL=1000×VB/ VA