1. Chemical composition. At present, the chemical components commonly are used b2b3 40Cr 42CrMo, etc. The chemical composition is described in the attached table.Usually chemical composition is tested by spectrometer, with fast speed and small error.

 2、Hardness index. Generally speaking, hardness is refers to the surface hardness of grinding steel ball, which is generally described by HRC (Rockwell hardness) and HB (Brinell hardness). The hardness of steel ball is around on HRC60, and it will be break if it is high (once fall with two halves, peeling, slag, etc.). Professional customers will ask about the core and volume hardness. The core is refers to the hardness at the center of the steel ball. Generally, the hardness of the grinding steel ball is in gradient distribution from the surface to the core, that is, the surface hardness of the steel ball is higher and the core hardness is lower. If professional customers are need to report then understand the hardness gradient distribution of steel balls with different materials and diameters. Generally, the hardness is measured by Rockwell hardness tester.

 3、Crushing rate. If the heat treatment process of grinding steel ball is not well controlled, the hardness will be too high, and the non tempering will lead to the stress accumulation and other reasons, which will lead to the situation that one drop in two and one half, peeling and slag dropping during the use process, which will affect the normal use. This is one of the important indicators of steel ball quality. Generally, it is agreed that the crushing rate is less than 1%, that is, the crushing rate of 100t steel ball shall not be more than 1t, otherwise it will be judged as unqualified. Actually the broken rate of forging ball is much lower than that of casting ball.

 4、Out of round rate. Out of round is refers to the phenomenon that the ball becomes ellipse in the use process, which affects the grinding effect. Generally,this indicator is not reflected in the contract.
    
 5、Impact value. Impact is refers to taking out the core bar of the steel ball according to the requirements and testing it with impact tester. The higher of the impact value, the less likely of ball to break, and the better the quality. Generally, the impact value of forging ball is greater than 12j /cm² , and that of casting ball is greater than 3

 6、The latest executive standard of forging ball is Yb / t091-2019