Tungsten Carbide Rolls are vital tools in the modern metal processing industry and are widely used in the rolling process of metals such as steel, aluminum, and copper. Its unique hardness, wear resistance, and high temperature stability make carbide rolls perform well in heavy-load working environments. However, what is the hardness of carbide rolls? This is a very important question, which is related to the service life, processing efficiency, and economic benefits of the rolls.

This article will discuss in detail the hardness index of industrial carbide rolls, the factors affecting hardness, the hardness test method, and the effect of hardness on the performance of carbide rolls.

What does the hardness of carbide rolls mean?

Hardness is a measure of the material's ability to resist local plastic deformation (such as indentation, scratches, etc.), usually expressed as an indentation hardness value. The hardness of carbide rolls is usually measured by microhardness or Brinell hardness (HB), Rockwell hardness (HRB) and other standards.

For industrial carbide rollers, hardness is not just a static value, it has an important impact on the wear resistance, corrosion resistance, thermal stability and other properties of the roller. Therefore, hardness is often one of the most critical technical indicators when selecting suitable carbide materials and their application areas.

What is the hardness range of industrial carbide rollers?

The hardness of carbide rollers is usually closely related to the alloy composition used. Carbide rollers are mainly composed of elements such as tungsten, carbon and cobalt, and different alloy formulas will affect their hardness. Specifically, the hardness of carbide rollers is usually between 55-80 HRC (Rockwell hardness C scale).

● Tungsten-cobalt alloy rollers: This type of carbide roller has a common hardness range of 60-75 HRC. When the tungsten content is high, the hardness will be higher, and the cobalt component plays a lubricating and toughness role. Therefore, the higher the proportion of cobalt, the lower the hardness. Generally speaking, the higher the proportion of tungsten, the better the hardness and wear resistance, but the corresponding brittleness may also increase.

● Tungsten-carbon alloy roller: This alloy has a high hardness, usually between 70-80 HRC, and is suitable for applications that require extremely high wear resistance and high hardness. When the tungsten content is high, the hardness is significantly improved, but the toughness is relatively poor.

● Nickel-tungsten alloy roller: The hardness of nickel-tungsten alloy rollers is generally between 55-70 HRC, with good corrosion resistance, suitable for special working conditions.

It should be noted that the hardness of cemented carbide rollers is one of the important indicators affecting their working performance, but too high hardness may also lead to increased brittleness, so it is necessary to find a suitable balance between hardness, toughness and wear resistance.

What factors affect the hardness of cemented carbide rollers?

The hardness of cemented carbide rollers is not a fixed value, but is affected by multiple factors. The following are the main factors affecting the hardness of cemented carbide rollers:

1. Alloy composition

The hardness of cemented carbide is closely related to the type and content of the elements it contains. The main components of the alloy are usually tungsten, cobalt, carbon, etc. Tungsten has extremely high hardness and wear resistance, while cobalt mainly acts as a binder to improve the toughness of the alloy.

● Tungsten content: The higher the tungsten content, the higher the hardness of the cemented carbide, but the toughness will be relatively reduced. Cemented carbide rollers with higher tungsten content usually have stronger wear resistance, but may be more prone to cracking or breaking under high impact loads.

● Cobalt content: Cobalt is an important binder for cemented carbide, which mainly plays a role in increasing the toughness of the alloy, improving processing performance and improving thermal stability. The higher the cobalt content, the better the toughness of the alloy, but the hardness is relatively low. The cobalt content is generally controlled between 5% and 30%, and the specific proportion will be adjusted according to different usage requirements.

● Carbon content: The carbon content also affects the hardness and wear resistance of cemented carbide. Generally, when the carbon content in cemented carbide is higher, the hardness will increase, but this may also cause the brittleness of the alloy to increase, so the carbon content needs to be controlled according to the specific application.

2. Sintering temperature and time

The sintering process of cemented carbide is a key link that affects its hardness. During the high-temperature sintering process, the bonding between powders and the degree of densification of the structure are crucial to the improvement of hardness.

● Sintering temperature: The sintering temperature is usually between 1400℃ and 1600℃. Too high or too low temperature will affect the density of cemented carbide, and then affect the hardness. If the sintering temperature is too high, excessive grain growth may occur inside the alloy, resulting in a decrease in hardness; while if the sintering temperature is too low, the alloy may not be completely sintered, resulting in pores and loose structure, thus affecting hardness and durability.

● Sintering time: The length of sintering time will also affect the density and hardness of cemented carbide. Too long or too short a time may lead to unstable performance of the alloy, so the appropriate sintering time must be selected according to the composition and requirements of the alloy.

3. Powder metallurgy process

In the manufacturing process of cemented carbide rollers, powder metallurgy technology plays a decisive role. Powder metallurgy process includes multiple links such as preparation, mixing, pressing, and sintering of alloy powders, which have an important influence on the hardness and structure of the alloy.

● Particle size of alloy powder: The particle size of the powder has a significant effect on the hardness of cemented carbide. Generally speaking, finer powder particles are conducive to the densification of the alloy, thereby improving its hardness. Coarse particles may cause the internal structure of the alloy to loosen, affecting the hardness.

● Powder uniformity: Powder uniformity is also one of the factors affecting the hardness of cemented carbide. If the components in the powder are unevenly distributed, inconsistent performance may occur after sintering, resulting in reduced hardness.

4. Post-treatment process of alloy

After sintering, cemented carbide rollers usually need to undergo a series of post-treatment processes, such as heat treatment, surface hardening, coating, etc., to further improve their hardness and wear resistance.

● Heat treatment: By controlling the heating and cooling rates, heat treatment can significantly improve the hardness of cemented carbide. For example, after proper quenching treatment, the surface hardness of cemented carbide rollers can be greatly improved.

● Coating treatment: Some cemented carbide rollers will form a hardened coating (such as TiN, CrN coating) on the surface through coating technology to improve their surface hardness and wear resistance. This treatment can significantly extend the service life of cemented carbide rollers, especially in high temperature and high speed working environments.

What are the test methods for the hardness of cemented carbide rollers?

The hardness test of cemented carbide rollers is a very important step in the manufacturing process. Common hardness test methods include microhardness test, Brinell hardness test, Vickers hardness test, Rockwell hardness test, etc. The following are several common test methods:

1. Microhardness test (HV)

The microhardness test is mainly used to measure the hardness of a small area on the surface of cemented carbide materials. By applying a certain load, the diamond pyramid indenter leaves an indentation on the surface of the material, and then the diagonal length of the indentation is measured through a microscope to calculate the hardness value. Microhardness test is suitable for high hardness materials such as cemented carbide.

2. Rockwell hardness test (HRC)

The Rockwell hardness test is the most widely used hardness test method, especially for the test of cemented carbide rollers. By applying a certain pressure to the surface of the cemented carbide roller, the depth of the indentation is measured to obtain the hardness value. The Rockwell hardness C scale (HRC) is usually used to measure the hardness of cemented carbide rollers. The test process is fast and the results are intuitive.

3. Brinell Hardness Test (HB)

The Brinell hardness test determines the hardness by applying a certain pressure on the surface of the carbide roller with a steel ball of a certain diameter and measuring the diameter of the indentation. Brinell hardness is suitable for testing softer materials. Although it is not commonly used for testing carbide rollers, this method is also used in some fields.

The impact of carbide roller hardness on performance

The hardness of carbide rollers is directly related to their performance, especially wear resistance and working life. The higher the hardness, the stronger the wear resistance of the carbide roller, and it can maintain a lower wear rate for a longer time under high-speed and heavy-load working conditions. Therefore, hardness is one of the key indicators to measure the quality of carbide rollers.

However, the higher the hardness, the better. Excessive hardness may increase the brittleness of the alloy, thereby affecting its impact and seismic resistance. In practical applications, a balance needs to be achieved between hardness, toughness and wear resistance to ensure the good performance of carbide rollers under complex working conditions.

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