Titanium alloys are widely used in high-end manufacturing fields such as aviation and aerospace due to their unique physical and chemical properties. However, the poor thermal conductivity, high chemical activity, and small deformation coefficient of titanium alloys lead to problems such as rapid tool wear, large processing deformation, and difficult chip removal during the thread processing. The processing quality and efficiency are significantly limited by the material characteristics. This paper focuses on the thread processing problem of titanium alloy pipe joints and explains it from the aspects of tool selection and process optimization.
Optimization Strategies For Titanium Alloy Thread Processing Tools
1. Application Of Serrated Taps
Serrated taps remove teeth at intervals, forming staggered cutting edges, which enables the workpiece to have single-sided contact with the tap, reducing friction and torque, and effectively preventing the tap from getting stuck or damaged. Its advantages include:
• Increased cutting thickness: The single tooth cutting thickness is doubled, and the cutting force is more evenly distributed;
• Improved chip removal performance: The chip thickness increases, the friction force decreases, and chip removal is more smooth;
• Enhanced durability: The adhesion between the tap and the chip decreases, and the tool life is prolonged;
• Design considerations: The number of teeth grooves should be an odd number to balance the force on the tooth edges.
2. Combination Of High-speed Steel Taps And Hard Alloy Taps
• High-speed steel taps: High toughness and strong resistance to deformation, suitable for initial tapping;
• Hard alloy taps: Good wear resistance and high precision, used for hole correction;
• Combined process: First rough processing with high-speed steel taps, then fine processing with hard alloy taps, balancing efficiency and quality.
3. Research And Development Of New Tool Materials
With the advancement of materials science, new tools such as coated tools (e.g. TiAlN coating) and ceramic tools are gradually applied to titanium alloy processing. In the future, they are expected to further break through the limitations of tool life and processing accuracy.
Optimization Of The Processing Technology For Titanium Alloy Pipe Joint Threads
1. Optimization Of Thread Bottom Hole Design
• Increase in bottom hole diameter: Reduces cutting force and processing heat, but the size needs to be adjusted according to the thread contact rate and the number of threads;
• Expansion of thread inner diameter: Reduces tooth height, reduces processing difficulty, while ensuring connection strength;
• Preferential use of machine tool for tapping: Using machine tool tapping can stably control the processing pressure and prevent the tap from breaking.
2. Control Of Cutting Parameters
• Cutting speed: Controlled at 200-300mm/min, preventing the softening of materials and the wear of tools caused by high temperatures;
• Tool geometric parameters:
• Forward angle: Increasing the forward angle can enhance the strength of the cutting edge and extend the tool life;
• Rear angle: Increasing the rear angle is beneficial for chip removal, reducing the friction between the chip and the tool;
• Deep hole tapping strategy: Reduce the number of chip retention slots to increase the chip retention space and prevent chip blockage.
3. Cooling And Lubrication Technology
• Cooling liquid selection: Recommended mixtures of oil acid, sulfided oil and kerosene or F43 cutting oil, which have both lubrication and cooling functions;
• Optimization of cooling method: Open cooling channels on the cutting edge of the tap to ensure that the cooling liquid reaches the cutting area directly;
• Retracting slot design: Extend the length of the thread tail stop and set a retraction slot to prevent the bottom of the tap from chipping.