How to Choose the Right Cemented Carbide Inserts?

As a experienced toolmaker in the cemented carbide industry for many years, I am delighted to share some insights on selecting cemented carbide inserts. This is a common question many newcomers often ask. I am now putting it all together here in one go, hoping to help more friends. If you think my writing is useful, please feel free to share it elsewhere to help more people. After reading, you will have a new understanding of how to choose cemented inserts. let us begin :

What is Cemented Carbide?

To understand cemented carbide inserts, you first need to know what cemented carbide is. Cemented carbide, also known as tungsten carbide or carbide, is a composite material made by powder metallurgy from tungsten carbide (WC) and a binding metal (such as cobalt or nickel). Simply put, it is an extremely hard, wear-resistant material widely used in various high-strength and high-precision machining applications.

Advantages of Cemented Carbide

1. High Hardness and Wear Resistance: The hardness of cemented carbide is several times that of steel, allowing it to maintain a sharp cutting edge when machining high-hardness materials. This means that by using cemented carbide inserts, you can significantly reduce wear and extend the tool’s service life.

2. Excellent High-Temperature Performance: During high-speed cutting, the temperature can rise rapidly. Cemented carbide can maintain its mechanical properties in high-temperature environments and won’t soften or deform like other materials. This makes cemented carbide inserts especially suitable for high-speed and efficient machining operations.

3. High Precision and Stability: The high hardness and rigidity of cemented carbide mean it undergoes minimal deformation during machining, allowing for very high machining accuracy. This is particularly important for machining parts that require high precision.

4. Wide Applicability: Cemented carbide can be used to machine various materials, including steel, non-ferrous metals, wood, and stone. It finds wide application in industries such as mechanical manufacturing, aerospace, and automotive.

Disadvantages of Cemented Carbide

1. High Brittleness: Although cemented carbide is very hard, its toughness is relatively low. This means that in machining environments, especially those with impact or vibration, cemented carbide inserts are prone to chipping or breaking.

2. High Cost: The manufacturing process for cemented carbide is complex, and the material itself is expensive. Therefore, cemented carbide inserts are usually pricier than ordinary tool steel inserts.

3. High Machining Difficulty: Due to the high hardness of cemented carbide, special grinding and coating techniques are required for forming machining, which increases production difficulty and cost.

4. High Requirements for Machining Conditions: To fully utilize the performance of cemented carbide inserts, precise machine tools and reasonable cutting parameters are usually required, which places higher demands on the machining environment and equipment.

How to Choose Suitable Cemented Carbide Inserts

Understanding the advantages and disadvantages of cemented carbide inserts is critical when navigating a market filled with various brands and models. Here are some key considerations:

1. Determine the Machining Material

When selecting cemented carbide inserts, the first step is to determine the material you will be machining, which influences the choice of hardness, coating, and geometry of the insert.

• Steel (including carbon steel and low alloy steel):

  • Insert Type: Choose inserts with high hardness and wear resistance, also requiring certain toughness to prevent chipping.
  • Recommended Coating: TiAlN (Titanium Aluminum Nitride) coating and PVD (Physical Vapor Deposition) coated inserts provide good heat resistance and wear resistance.
  • Geometry: Square or rhombic inserts are common, offering stable cutting performance.

• Cast Iron:

  • Insert Type: High hardness and wear resistance are needed since cast iron is hard and brittle.
  • Recommended Coating: TiCN (Titanium Carbonitride) and CVD (Chemical Vapor Deposition) coated inserts enhance wear resistance and impact resistance.
  • Geometry: Square or round inserts are usually selected, suitable for rough and finish machining.

• Aluminum alloy:

  • Insert Type: Aluminum alloys are softer and have high adhesion, requiring inserts with high sharpness and lower hardness.
  • Recommended Coating: DLC (Diamond-Like Carbon) and uncoated inserts are effective in preventing aluminum adhesion.
  • Geometry: Triangular or round inserts are commonly used to reduce cutting resistance and improve surface quality.

• Stainless Steel:

  • Insert Type: Stainless steel has high strength and is prone to work hardening, needing inserts with high hardness and wear resistance while maintaining good toughness to prevent breaking.
  • Recommended Coating: TiAlN and AlTiN (Aluminum Titanium Nitride) coated inserts provide excellent oxidation resistance and wear resistance.
  • Geometry: Square or round inserts are suitable for both rough and finish machining of stainless steel.

• High-Temperature Alloys (such as titanium and nickel-based alloys):

  • Insert Type: These materials are difficult to machine, requiring inserts with extremely high hardness and wear resistance, as well as high thermal stability.
  • Recommended Coating: AlCrN (Aluminum Chromium Nitride) and SiAlON (Silicon Aluminum Oxynitride) ceramic coated inserts offer exceptional heat resistance.
  • Geometry: Square or larger angle inserts are commonly used to enhance cutting efficiency and tool life.

2. Balance Between Hardness and Toughness

Hardness and toughness are two crucial performance parameters. High hardness usually means better wear resistance, while high toughness means the insert is less likely to break. Choose hardness and toughness based on machining conditions:

• Workpiece Material:

  • Hard Materials (e.g., high hardness steel, high-temperature alloys): Select high hardness inserts to ensure the insert maintains cutting performance under high pressure and high temperature.
  • Soft Materials (e.g., aluminum alloys, copper alloys): Select high toughness inserts to prevent inserts from breaking due to material adhesion during cutting.

• Cutting Method:

  • Rough Machining: Requires inserts to withstand large cutting forces and impacts, thus needing a balance of hardness and toughness.
  • Finish Machining: Requires inserts to provide high surface quality, thus preferring high hardness inserts.

• Cutting Parameters:

  • High-Speed Cutting (HSC): Requires high hardness inserts to withstand high temperatures and pressures from high-speed cutting.
  • Low-Speed Cutting: High toughness inserts are suitable to prevent damage due to vibrations and impacts at low speeds.

3. Coating Types

Coating on cemented carbide inserts significantly enhances tool performance and lifespan. Different coating technologies and materials can substantially improve wear resistance, heat resistance, and oxidation resistance of inserts.

• TiN (Titanium Nitride) Coating: Suitable for high-speed cutting of steel, stainless steel, and cast iron.
• TiAlN (Titanium Aluminum Nitride) Coating: Suitable for high-speed cutting of high hardness steel, stainless steel, and high-temperature alloys.
• AlTiN (Aluminum Titanium Nitride) Coating: Suitable for high-speed cutting of hard materials and high-temperature alloys.
• TiCN (Titanium Carbonitride) Coating: Suitable for medium-speed cutting of steel, cast iron, and stainless steel.
• DLC (Diamond-Like Carbon) Coating: Suitable for cutting aluminum alloys, copper alloys, and non-ferrous metals.
• CrN (Chromium Nitride) Coating: Suitable for cutting plastics and rubber.

4. Insert Geometry

The geometry of inserts significantly impacts cutting performance, machining quality, and tool life. Different geometries are suitable for different machining scenarios and materials.

• Square Inserts: Suitable for rough and semi-finish machining.
• Rhombic Inserts: Suitable for finish and semi-finish machining.
• Triangular Inserts: Suitable for rough and semi-finish machining.
• Round Inserts: Suitable for rough machining, especially effective in cast iron and stainless steel.
• Negative Rake Rhombic Inserts: Suitable for rough machining of high hardness materials, high feed rate, and large depth of cut.
• Positive Rake Rhombic Inserts: Suitable for finish machining and light materials like aluminum and non-ferrous metals.

5. Common Insert Grades and Applications

Insert grades refer to the material composition and performance classification of inserts. Different grades have varying hardness, toughness, and wear resistance.

• P Grade (for steel): Suitable for rough and finish machining of steel.
• M Grade (for stainless steel): Suitable for semi-finish and finish machining of stainless steel.
• K Grade (for cast iron): Suitable for rough machining of gray cast iron and ductile iron.
• N Grade (for non-ferrous metals): Suitable for machining aluminum alloys, copper alloys, and plastics.
• S Grade (for high-temperature alloys): Suitable for rough and finish machining of nickel-based and titanium alloys.
• H Grade (for hardened steel): Suitable for finish machining of hardened steel and high hardness materials.

International Standard Models

International standard models of cemented carbide inserts are based on their shape, size, clamping method, and other characteristics. These standardized naming systems make the selection and application of inserts more convenient.

• ISO Standard Insert Models: ISO standard models generally consist of a series of letters and numbers, such as CCMT 09T304.
• ANSI Standard Insert Models: ANSI standard models also consist of a series of letters and numbers, such as VNMG 332.

Manufacturer-Specific Coding Rules

Different cemented carbide insert manufacturers often add specific grades or codes based on their own coding rules. These codes not only help in product identification but also help users understand the material, application, and performance of the inserts.

• ISO Standard Codes: Many manufacturers adopt the coding system defined by the International Organization for Standardization (ISO).
• Manufacturer-Specific Grades: For example, some manufacturers might use codes like “WNMG080408-MF”.
• Brand-Specific Grades:
  • Sandvik: Might use “GC4225″ to denote specific material and coating inserts.
  • Kennametal: Might use “KC725M” to denote specific application inserts.
  • Seco: Might use “TP2501″ to denote specific cemented carbide material and coating combinations.

Understanding these codes and grades can help you more accurately choose inserts suitable for specific machining tasks. From different manufacturers’ product catalogs, you can find detailed explanations of the codes, which will greatly simplify the selection process. Of course, the quickest way is to consult the sales representatives of the insert manufacturers and ask them to recommend suitable inserts based on your needs.