What Are The Different Grades Of Carbide?

In the metal processing and manufacturing industry, cemented carbide is almost an indispensable material. From turning tools and milling cutters to drill bits and mold components, it has become a “frequent guest” in the processing field due to its high hardness, wear resistance and excellent cutting performance. However, if we delve into practical applications, a common problem will be discovered: Why are some hard alloy cutting tools suitable for steel while others are more suitable for cast iron or stainless steel? And how should the grade systems (grades) marked by different manufacturers be understood?

Choosing the right grade of cemented carbide is no small matter. It directly determines the lifespan of the cutting tool, the quality of the machined surface and the overall production cost. If the wrong choice is made, problems such as premature wear of the cutting tool, chipping, and low processing efficiency may occur. However, if the right choice is made, it can significantly enhance production efficiency. Next, we will take you through a systematic understanding of hard alloy grades from the perspectives of their significance, classification methods, comparison tables, and application scenarios.

Why Is The Grade Of Cemented Carbide Important?

Hard alloy is a material mainly composed of tungsten carbide (WC), which is made by adding metal binders (such as cobalt and nickel) and through powder metallurgy process. It combines the advantages of hardness and toughness and is a commonly used basic material for cutting tools, wear-resistant parts and molds.

However, cemented carbide is not a single material. The performance of materials will vary significantly depending on the formula and microstructure. For example:

• An increase in cobalt content → leads to an improvement in toughness but a decrease in hardness, making it more suitable for intermittent cutting.
• A higher proportion of tungsten carbide → increased hardness, better wear resistance, but possibly more brittle.
• Finer grains → achieving a good balance between hardness and toughness.

These differences determine the performance of the cutting tools during processing. If a grade with higher toughness is selected when processing cast iron, the cutting tool may have insufficient wear resistance and fail quickly. Conversely, if a grade with very high hardness is chosen when cutting steel, chipping may occur due to the lack of toughness.

Therefore, understanding and mastering the grades of cemented carbide can not only help select the appropriate cutting tools, but also reduce tool costs, decrease the frequency of tool changes, and ensure the processing quality of workpieces.

Basic Classification of Cemented Carbide Grades

To better understand the performance of different grades, we can classify them from several perspectives.

1. According to the proportion of ingredients

• WC-Co (tungsten cobalt type) : This is the most common combination and has a wide range of applications. Cobalt, as a binder, can provide certain toughness and is suitable for general cutting and wear-resistant parts.
• WC-TiC-Co (tungsten titanium cobalt type) : With titanium carbides added, it can enhance performance at high temperatures and is particularly suitable for steel part processing.
• Fine-grained cemented carbide: By controlling the grain size, it can balance hardness and toughness, and is often used in high-precision and high-speed cutting.

2. Balance hardness and toughness

• High hardness grade: Strong wear resistance, long tool life, but insufficient toughness, not suitable for working conditions with significant impact.
• General grade: It strikes a balance between hardness and toughness, meeting the requirements of most applications.
• High toughness grade: Strong impact resistance, particularly suitable for intermittent cutting or rough machining.

3. Classified by international standards (ISO series)

To facilitate global application, ISO classifies cemented carbide grades into six major categories:

• Class P: Mainly used for steel cutting, emphasizing toughness.
• Class M: Suitable for stainless steel, resistant to adhesion and high-temperature deformation.
• Class K: Suitable for cast iron, high hardness grade, and outstanding wear resistance.
• Class N: For non-ferrous metals such as aluminum and copper, the requirements are smoothness and anti-adhesion.
• Class S: Used for heat-resistant alloys and titanium alloys, emphasizing high-temperature resistance.
• Class H: Suitable for hardened steel, super-hard grade, suitable for quenched steel and high-hardness materials.

This classification method has become an industry standard and serves as the most intuitive basis for tool selection.

Comparison of Hard Alloy Blade Grades

One of the most concerning issues for users in actual processing is: Where exactly do the performance differences of different grades of blades lie? For a more intuitive understanding, it can be presented through a comparison table:

ISO Category	Main Characteristics	Suitable Materials	Recommended Applications
P Series	High toughness, good impact resistance	Steel	Continuous cutting, light interrupted cutting
M Series	Anti-adhesion, stable performance	Stainless steel	Machining materials prone to built-up edge
K Series	High hardness, excellent wear resistance	Cast iron	High-speed cutting, large cutting depth
N Series	Good surface finish, anti-chip adhesion	Non-ferrous metals (aluminum, copper)	High-speed machining, parts requiring fine surface quality
S Series	Heat-resistant, wear-resistant at high temperatures	Heat-resistant alloys, titanium alloys	Aerospace parts machining
H Series	Ultra-hard, excellent wear resistance	Hardened steel, hard materials	Precision machining of molds or hardened components

For instance, in the production of automotive parts, cast iron parts account for a relatively high proportion, and K series cutting tools are usually chosen. In the processing of aviation components, heat-resistant alloys and titanium alloys are more common, and the S series grades can better demonstrate their advantages.

Common Cemented Carbide Grades and Applications

In addition to comparing from the perspective of performance, different grades also have clear application scenarios in actual processing:

• Steel parts processing (Class P) : Emphasizes toughness and impact resistance, suitable for common processes such as turning and milling.
• Stainless steel processing (Class M) : It can resist the high temperature and adhesion phenomenon generated during the cutting process, ensuring the tool life.
• Cast iron processing (Class K) : High hardness, strong wear resistance, capable of withstanding the friction caused by high-speed cutting.
• Non-ferrous metals (Class N) : They have high requirements for surface finish, and the cutting tools are not prone to chip adhesion. They are often used in aviation aluminum parts or mold aluminum alloys.
• Heat-resistant alloys (Class S) : They can maintain cutting performance at high temperatures and are suitable for aero engine components.
• Hardened steel (Class H) : It is used for quenched steel or high-hardness workpieces and is widely applied in the mold industry with high processing accuracy.

These application differences are precisely where the value of grade classification lies.

How to Choose the Right Grade of Cemented Carbide?

When faced with a variety of grades, it is advisable to follow these steps when making a choice:

1. Clarify the material of the workpiece: Is it steel, stainless steel, cast iron, or non-ferrous metals such as aluminum and copper? Different materials correspond to different ISO classifications.
2. Consider the cutting method: Continuous cutting is more suitable for grades with high hardness, while intermittent cutting requires more toughness.
3. Set processing goals: Is it to pursue efficiency or surface quality? Different goals will result in different grades of cutting tools being selected.
4. Evaluating cost and lifespan: Sometimes, grades with higher performance are more expensive, but the tool change frequency is lower, and the overall cost actually decreases.
5. Seek professional advice: If you are still unsure, you can refer to the suggestions of tool suppliers, who often offer more precise recommendations.

By screening step by step in this way, the most suitable grade can be found, avoiding the losses caused by blind selection.

Final Thoughts

The classification of carbide grades is not a complex and hard-to-understand professional symbol, but a clear logical system. By understanding its classification method, comparing the performance of different grades, and combining with actual processing requirements, one can find the suitable cutting tool more quickly.

For enterprises, the correct selection of grades not only extends the service life of cutting tools but also significantly enhances processing efficiency and reduces overall production costs. Whether it is steel, stainless steel or high-temperature alloys, as long as the characteristics of the grades are fully understood, the maximum value of the cutting tools can be brought into play.

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