Why does the steel ball break?

author: Changzhou Feige Steel Ball Co., Ltd

2020-08-17

The reason why the steel ball is round is due to physical changes. The round steel bars and square steel bars, which are neat or irregular, are heated and are shaped by free forging by the die when they reach a certain set temperature.

But when we use steel balls as grinding media, we will find that some steel balls are broken. Is this just because the quality of the steel balls is not good? Changzhou Feige Steel Ball Manufacturing Co., Ltd. will explain why.

We need to clarify why the steel ball is broken. A fundamental problem that steel balls will break is internal stress:

To put it simply, internal stress is a measure of the degree of deformation, strength, impact toughness, and other physical quantities related to the failure of the object; in layman's terms, internal stress is the internal pressure.

The steel ball cannot be used immediately after forging, but should be left unused first. This is to eliminate the internal stress of the forging, which is due to the uneven internal structure of the newly forged steel ball, tightness and looseness.

If the workpiece that has just been forged is immediately taken to a lathe for processing, the finished work is measured with a dial indicator and caliper, and the dimensional accuracy fully meets the requirements of the drawing, but after a short period of time, the dimensional accuracy is unqualified. Where is the problem? The internal stress of the forging has not been completely eliminated, causing the deformation of the workpiece.

The solution is to do not rush to process, throw the workpiece aside, and wait for its internal stress to be completely eliminated, the internal structure is uniform, loose and compact, and then to process, the size of the processed workpiece will not change. Eliminate internal stress from forgings or steel balls

Now that we talk about internal stress, we might as well extend it and share with you four methods for relieving internal stress in steel balls:

Different Tempering Methods for Steel Balls and Their Characteristics

When it comes to enhancing the mechanical properties of steel balls, tempering is a critical process that follows quenching. The purpose of tempering is to relieve stresses induced during the quenching process and to adjust the hardness, strength, and toughness of the steel balls. Here are some of the most common tempering methods used in the industry:

A. Tempering Heating Method

This method involves heating the steel balls using different types of furnaces before cooling them down. The furnaces used can be electric, gas, or oil-fired furnaces:

Electric Furnace: Electric furnaces are known for their uniform heating and precise temperature control. They are ideal for applications where consistency is crucial. The heating process is usually faster and cleaner compared to other methods.

Gas Furnace: Gas furnaces are typically used for larger batches of steel balls. They offer good temperature uniformity across the batch and are suitable for operations where fuel costs are a consideration.
Oil Furnace: Oil furnaces are another option for tempering, though they may require more maintenance due to the nature of oil combustion. They are useful in situations where electric or gas furnaces are not readily available or economically viable.

After heating, the steel balls are cooled either by air or water, depending on the desired properties. This method is versatile and can be adapted to various production scales and requirements.

B. Residual Temperature Tempering Method

In this method, the forged steel balls are subjected to a period of heat preservation followed by natural cooling. This process leverages the residual heat generated during the forging process itself. The steps involved are:

Heat Preservation: After forging, the steel balls are kept at a high temperature for a specified duration to allow the residual heat to penetrate thoroughly.
Natural Cooling: Once the heat preservation phase is complete, the steel balls are allowed to cool naturally. This method is energy-efficient as it utilizes the heat already present in the material without the need for additional heating sources.

This method is particularly useful in scenarios where energy conservation is a priority or when rapid cooling could introduce unwanted stresses into the material.

C. Impact Method

The impact method involves using mechanical forces to temper the steel balls. Two common approaches include the use of a ball segment separator and the barrel impact method:

Ball Segment Separator: In this method, the steel balls are separated and subjected to impacts that help relieve internal stresses. This method is effective in achieving uniform properties across the surface of the steel balls.
Barrel Impact Method: Here, the steel balls are placed inside a rotating drum or barrel where they collide with each other repeatedly. The collisions act as a form of tempering, helping to distribute the stresses more evenly and improve the overall durability of the steel balls.

Both methods are beneficial for imparting additional strength and toughness to the steel balls, making them suitable for applications that require high impact resistance.

D. Natural Failure Method

The natural failure method refers to allowing the steel balls to remain in a natural state without any additional processing after initial manufacturing. This method is sometimes referred to as stress relief tempering. The idea is to let the internal stresses of the material dissipate naturally over time:

Stress Relief: After the initial heat treatment, the steel balls are left undisturbed in a controlled environment where they can gradually release any residual stresses.
Natural State: This process does not involve any active manipulation, such as heating or mechanical impact. Instead, it relies on the inherent properties of the material to reach a state of equilibrium.

This method is particularly relevant when the steel balls are part of a larger assembly or when immediate post-processing is not feasible.

If you need to purchase large quantities of steel balls, please contact Changzhou Feige Steel Ball Manufacturing Co., Ltd. We have a large amount of stock available for sale, and we also accept customers' special customization requirements.