How to improve the machinability of OT4 titanium sheet?

As a supplier of OT4 titanium sheet, I understand the challenges and importance of improving its machinability. OT4 titanium sheet is widely used in various industries due to its excellent corrosion resistance, high strength-to-weight ratio, and good biocompatibility. However, its low thermal conductivity, high chemical reactivity, and strong work hardening tendency often make machining difficult. In this blog, I will share some practical methods to enhance the machinability of OT4 titanium sheet based on my experience and industry knowledge.

Understanding the Characteristics of OT4 Titanium Sheet

Before discussing how to improve machinability, it is crucial to understand the unique properties of OT4 titanium sheet. OT4 is a titanium alloy that contains a small amount of aluminum and other elements. It has high strength and good plasticity at room temperature, but its machinability is affected by several factors.

• Low Thermal Conductivity: Titanium has a relatively low thermal conductivity compared to other metals. During machining, heat generated at the cutting edge cannot be dissipated quickly, leading to high cutting temperatures. These high temperatures can cause tool wear, thermal damage to the workpiece, and even change the material's microstructure.
• High Chemical Reactivity: Titanium is highly reactive with oxygen, nitrogen, and other elements at high temperatures. This reactivity can result in the formation of hard compounds on the tool surface, which increases friction and tool wear.
• Strong Work Hardening Tendency: OT4 titanium sheet has a strong work hardening tendency, which means that the material becomes harder and more difficult to cut as it is deformed during machining. This can lead to increased cutting forces, poor surface finish, and reduced tool life.

Selecting the Right Cutting Tools

The choice of cutting tools is critical for improving the machinability of OT4 titanium sheet. Here are some key considerations when selecting cutting tools:

• Tool Material: Carbide tools are commonly used for machining titanium alloys due to their high hardness, wear resistance, and heat resistance. Coated carbide tools, such as those coated with titanium nitride (TiN), titanium carbonitride (TiCN), or aluminum oxide (Al₂O₃), can further improve tool performance by reducing friction and wear. Cubic boron nitride (CBN) tools are also suitable for high-speed machining of titanium alloys, especially for finishing operations, as they have excellent hardness and thermal stability.
• Tool Geometry: The geometry of the cutting tool has a significant impact on cutting performance. Tools with a sharp cutting edge, large rake angle, and appropriate relief angle can reduce cutting forces and improve chip formation. For example, a positive rake angle can help to reduce the cutting force and improve chip flow, while a large relief angle can prevent the tool from rubbing against the workpiece and reduce heat generation.

Optimizing Cutting Parameters

Proper selection of cutting parameters is essential for achieving good machinability of OT4 titanium sheet. The main cutting parameters include cutting speed, feed rate, and depth of cut.

• Cutting Speed: The cutting speed should be carefully selected to balance between productivity and tool life. Generally, a lower cutting speed is recommended for machining titanium alloys to avoid excessive heat generation. However, too low a cutting speed can also lead to increased tool wear due to the long contact time between the tool and the workpiece. A typical cutting speed for machining OT4 titanium sheet with carbide tools ranges from 30 to 60 m/min.
• Feed Rate: The feed rate determines the amount of material removed per revolution of the tool. A higher feed rate can increase productivity, but it also increases cutting forces and tool wear. A suitable feed rate for machining OT4 titanium sheet is usually in the range of 0.05 to 0.2 mm/r.
• Depth of Cut: The depth of cut should be selected based on the tool's strength, the workpiece's geometry, and the desired surface finish. A larger depth of cut can reduce the number of passes required for machining, but it also increases cutting forces and heat generation. A common depth of cut for machining OT4 titanium sheet is between 0.5 and 2 mm.

Using Coolants and Lubricants

Coolants and lubricants play a vital role in improving the machinability of OT4 titanium sheet. They can help to reduce cutting temperatures, flush away chips, and prevent the formation of built-up edge on the tool surface.

• Coolant Type: Water-based coolants are commonly used for machining titanium alloys due to their good cooling and lubricating properties. They can effectively reduce cutting temperatures and prevent thermal damage to the workpiece and the tool. Synthetic coolants, which are formulated with special additives, can provide better lubrication and corrosion protection.
• Coolant Application: The coolant should be applied directly to the cutting zone to ensure effective cooling and lubrication. High-pressure coolant systems can be used to improve chip evacuation and reduce cutting temperatures. In some cases, minimum quantity lubrication (MQL) systems can also be used, which apply a small amount of lubricant in the form of a fine mist to the cutting zone.

Improving Workpiece Preparation

Proper workpiece preparation can also contribute to improved machinability of OT4 titanium sheet. Here are some tips for workpiece preparation:

• Annealing: Annealing the OT4 titanium sheet before machining can help to reduce its hardness and improve its machinability. Annealing can also relieve internal stresses in the material, which can prevent distortion during machining.
• Surface Finish: A smooth surface finish on the workpiece can reduce friction and improve chip flow during machining. Therefore, it is recommended to perform surface grinding or polishing on the OT4 titanium sheet before machining.

Conclusion

Improving the machinability of OT4 titanium sheet requires a comprehensive approach that includes selecting the right cutting tools, optimizing cutting parameters, using coolants and lubricants, and improving workpiece preparation. By following these methods, we can reduce tool wear, improve surface finish, and increase productivity in the machining of OT4 titanium sheet.

If you are interested in purchasing high-quality OT4 titanium sheet or have any questions about its machinability, please feel free to contact us for further discussion. We also offer other titanium sheet products, such as Gr 4 Titanium Sheet, Gr 12 Titanium Sheet, and Gr 5 Titanium Sheet. Our team of experts is always ready to provide you with the best solutions and support.

References

• Boothroyd, G., & Knight, W. A. (2006). Fundamentals of machining and machine tools. CRC Press.
• Trent, E. M., & Wright, P. K. (2000). Metal cutting. Butterworth-Heinemann.
• Kalpakjian, S., & Schmid, S. R. (2010). Manufacturing engineering and technology. Pearson Prentice Hall.