Grinding balls. Specific gravity of steel

At previous article we talked about the kinds of mills and grinding media. We have found that the most effective and widely used grinding media are grinding balls

Production of grinding balls is regulated by DSTU 8538: 2015 (DSTU 3499-97). Grinding steel balls for ball mills are made of carbon steel and / or stainless steel. Table 1 shows the specific gravity of carbon and alloy steel. The specific gravity of metal is a physical quantity defined as the ratio of the weight of metal to the volume it occupies.

Table 1. Specific gravity of carbon and alloy steel

Grinding balls characterized by high hardness, resistance to abrasion. Surface of balls responds poorly to splitting and practically don’t crumble.

Grinding balls usually classified into five groups of hardness:

• The first group includes balls with normal hardness.
• The second group includes grinding balls with increased hardness.
• The third group includes balls of high hardness.
• The fourth group consists of grinding balls of high hardness with enhanced depth of hardenability.
• The fifth group includes balls with especially high hardness with enhanced depth of hardenability.

Grinding balls with normal and high hardness usually used for grinding relatively soft materials. These include, for example, ore, coal, etc. Grinding balls with high hardness used for grinding a variety of metals that came in unsuitability. Balls of the fourth group and the fifth group of hardness are used for grinding solid materials, alloys and products.

Due to the method of rolling balls is identical to a high-temperature thermomechanical processing (VTMO) – austenite deformed in area of its thermodynamic stability and then subjected to hardening on martensite followed by tempering – that significantly increasing the mechanical properties of the steel.