The ex-factory hardness and polishing of P20 are higher than those of 45 steel and Cr 12. It can be known that 45 steel and Cr 12 sparks are medium carbon steel and alloy steel. Look at the appearance of Cr 12. Generally, cutting 45# by sawing machine is mostly gas cutting Cr 12. When drilling, the spark Cr 12 is a dark red spark at the spark root of high carbon and high chromium steel, and the explosion is short and large. The more carbon in carbon steel, the more sparks.

A, you can use a grinder to strike a light, 45#, and the spark is floating and big; Cr 12, the spark is dark red, small and few, and does not float.

B. Knock with an iron block with moderate hardness. The bigger the trace, the softer the material. Cr 12 is an alloy tool steel, which is relatively hard; 45# is high-quality structural carbon steel, which is relatively soft. Or you can beat it with a file.