Research On Titanium Alloy Thread Processing Technology

In many fields such as aerospace and chemical industry, titanium alloys have been widely used because of their excellent properties. However, the unique processing characteristics of titanium alloy have brought certain challenges to its thread processing. In-depth exploration of the processing characteristics of titanium alloy, tool selection and pipe joint thread processing technology is of great significance to improve the quality of titanium alloy thread processing and improve production efficiency.

1. Processing Characteristics And Characteristics Of Titanium Alloy

1) Low Thermal Conductivity

Titanium alloy has poor thermal conductivity, which directly leads to poor heat dissipation. During thread processing operations, it is difficult to effectively diverge and cool the heat, and the temperature of the processing site rises rapidly. After processing, due to the accumulation of heat, the material has a large amount of rebound, which can easily deform, affecting the machining accuracy and part quality. At the same time, the high temperature environment has a serious impact on the processing tool, and the wear of the tool edge is aggravated, which greatly reduces the service life of the tool and increases the processing cost.

2) Small Deformation Coefficient

The small deformation coefficient of titanium alloy is characteristic, which makes the cutting force distribution of the tool during the processing process uneven, and the tool loss increases. During the cutting process of the tool, the force per unit area is increased, which leads to faster tool wear and requires more frequent tool replacement, which affects the continuity and efficiency of production.

3) High Chemical Activity

Titanium alloy has strong chemical activity, and it is easy to react chemically with other metal materials under the condition of high temperature during processing. This reaction will cause the adhesion between the tool and the tap and the processed material, resulting in the phenomenon of “biting the knife”. Biting the knife” will not only cause damage to the tool, affect the normal progress of processing, but also reduce the surface quality of thread processing and increase the difficulty of subsequent processing.

4) Excellent Overall Performance

In order to enhance the strength of titanium metal elements, alloying elements are added to pure titanium to form titanium alloys. Titanium alloys are mainly divided into three types: titanium alloys represented by TA, titanium alloys represented by TB, and +titanium alloys represented by TC. Among them, +titanium alloy is a duplex alloy and is widely used. It is an important titanium alloy raw material in the aviation industry. Titanium alloy has many good metal properties: high strength, low density, but far stronger than many alloy steels; good heat resistance, heat resistance is hundreds of times higher than aluminum alloy, with good thermal stability; excellent low temperature performance, can still maintain good performance under ultra-low temperature conditions; strong corrosion resistance, strong resistance to acids, alkalis, moisture, chlorides, etc.; However, its chemical activity is large, it can react with oxygen, nitrogen, carbon and other chemical elements in the air, and its thermal conductivity is low, and its thermal conductivity is much lower than that of iron, aluminum and other metals.

Tests by Baoji Titanium Industry Research Institute have shown that there are certain differences in the performance indicators of titanium alloys with different composition proportions, which further highlights the importance of in-depth understanding of the processing characteristics of titanium alloys.

2. Selection Of Thread Processing Tools For Titanium Alloy

1) The Advantages Of Wrong-Tooth Taps

Titanium alloy thread processing mostly uses wrong-tooth taps for tapping operations. The design of the wrong-tooth taps is unique, and the knife teeth of the taps are removed one at each interval, and they are arranged in staggered patterns. This structure enables the processed parts and the taps to have only one-sided contact, which effectively reduces the friction between each other and reduces the torque generated by the friction. In this way, the tap can be effectively prevented from being stuck or damaged, thereby improving the quality of thread processing.

When using wrong-tooth taps, the cutting thickness is doubled and the depth is greater than the cold-work hardened layer. Although the increase in cutting thickness will lead to an increase in the cutting force of the tap teeth, it is more advantageous for cutting chip removal, the friction force is reduced, and the adhesion of the tap and the chips is reduced, thereby improving the durability and thread accuracy of the tap. In terms of the design of the wrong-tooth tap, the number of completed cogs should be odd, which can reduce the force on the tooth edge and extend the service life of the tap. In the threading of titanium alloy materials, the use of wrong-tooth taps can maintain the stability of tapping and improve the threading accuracy.

2) The Cooperation Between High-Speed Steel Wire Taps And Cemented Carbide Taps

For the threading of titanium alloy materials, it is recommended to use high-speed steel wire cones. The high-speed steel wire cone has the characteristics of high toughness, deformation resistance and good wear resistance. In the tapping process, a high-speed steel wire cone can be used for preliminary tapping to complete most of the cutting work. After the initial tapping, the screw hole is corrected with a cemented carbide tap. Cemented carbide taps have high hardness and strong wear resistance, which can further ensure the accuracy and quality of the thread. With the continuous deepening of tool material research, it is expected that tap materials that are more suitable for titanium alloy thread processing will appear in the future.

3. Processing Technology Of Titanium Alloy Pipe Joint Thread

1) Treatment Of Threaded Bottom Holes

Increasing the threaded bottom hole can effectively reduce the cutting force and heat generated during processing. Due to the large strength of titanium alloy pipes, when increasing the diameter of the threaded bottom hole, it is necessary to fully consider the requirements for the thread contact rate and the specific number of thread heads. Under the premise of ensuring the threaded connection performance, the amount of increase in the diameter of the bottom hole is reasonably determined. From the perspective of processing technology, appropriately increasing the thread inner diameter requirements can reduce the thread tooth height. Appropriately increase the thread diameter, which is particularly suitable for tapping special materials such as titanium alloys. Although this will reduce the thread contact rate, the thread connection is still stable and reliable due to the increase in thread length.

2) Selection Of Machine Tool Tapping Process

In order to prevent the tap from breaking due to excessive pressure during processing, the processing technology of machine tapping can be selected. The tapping of the machine tool has the advantages of high stability and accurate pressure control, which can ensure uniform tap force during the tapping process and reduce the risk of tap breaking. Through the precise control of the machine tool, the quality and consistency of thread processing can be improved, and the high-precision requirements of titanium alloy pipe joint threads can be met.

Titanium alloy thread processing needs to fully consider its unique processing characteristics, and reasonably choose processing tools and processing techniques. Through the use of wrong-tooth taps, high-speed steel wire taps and cemented carbide taps in combination, as well as the optimization of thread bottom hole processing and the use of machine tool tapping technology and other measures, the quality and efficiency of titanium alloy thread processing can be effectively improved, and it provides a strong guarantee for the wide application of titanium alloy in various fields.