Use friction heat to seal or shape the tube
Using frictional heat to seal or form pipes is a highly efficient and energy-efficient process. The principle is to use the heat generated by mechanical friction to locally plasticize the pipe. Then, using a mold or external force, forming effects such as sealing, bending, and reducing the pipe diameter are achieved. Compared with traditional welding or flame forming, this process offers advantages such as a smaller heat-affected zone, higher joint strength, and no smoke or dust pollution. It is widely used in pipe manufacturing for the automotive, aerospace, and home appliance industries. For example, in the sealing of automotive air conditioning ducts, frictional heat sealing technology can achieve 100% sealing at the interface, far exceeding the 95% pass rate of traditional welding processes, significantly improving product reliability.
The core of the friction heat sealing process lies in the precise control of friction parameters, primarily friction pressure, friction speed, and friction time. Friction pressure must be set based on the strength and wall thickness of the tube material. Excessive pressure can cause excessive deformation or even rupture, while too little pressure will not generate sufficient heat. The friction speed directly affects the rate of heat generation and is typically adjusted within a range of 500-2000 r/min. For high-melting-point materials such as stainless steel, higher friction speeds are required. The friction time determines the amount of heat accumulated, ensuring that the tube ends reach their plastic temperature without overheating. A refrigeration equipment manufacturer, while processing copper tube seals, experimentally determined a parameter combination of 0.5 MPa friction pressure, 1200 r/min friction speed, and 3 seconds friction time. This combination resulted in a tensile strength at the seal exceeding 90% of the parent material, meeting the requirements for high-pressure operating conditions.
In the tube forming process, the application of frictional heat can significantly reduce the material’s resistance to deformation and improve forming accuracy. Taking tube bending as an example, the traditional cold bending process easily causes wrinkling on the inside of the tube and cracking on the outside. However, after using frictional heat to locally heat the bending part, the plasticity of the material is significantly improved, and a large curvature radius can be achieved under the action of a small external force. Frictional heat forming can also be used for processes such as tube reduction and expansion. The friction between the mold and the tube generates heat, which softens the processed part, and then precise forming is achieved through the constraint of the mold cavity. When processing the reduction of titanium alloy catheters, an aviation company uses frictional heat forming technology to control the dimensional tolerance of the reduction part within ±0.02mm, and there is no obvious stress concentration phenomenon, meeting the stringent requirements of aerospace products.
The design of equipment and molds is the basis for ensuring the quality of friction heat processing. Friction heat processing equipment usually consists of a drive system, a pressurizing system, a temperature control system and a mold. The drive system provides the speed and torque required for friction, the pressurizing system realizes precise control of the friction pressure, and the temperature control system monitors the temperature of the processing area in real time through infrared temperature measurement and other methods to ensure that it is within a reasonable range. The mold material must have the characteristics of high temperature resistance and wear resistance. For the processing of high-strength materials such as stainless steel, the mold can be made of high-speed steel or cemented carbide; for soft materials such as copper and aluminum, alloy tool steel can meet the requirements. In order to improve the efficiency of friction heat bending, an automobile parts factory optimized the design of the mold and opened a guide groove on the friction contact surface, which not only enhanced the uniformity of heat dissipation, but also reduced mold wear and extended the mold life by 50%.
The development trend of friction heat processing technology is characterized by intelligentization and integration. With the application of industrial robots and CNC technology, friction heat processing can be automated. Sensors collect real-time parameters such as temperature and pressure, and the control system automatically adjusts process parameters to ensure consistent processing quality. For example, after a home appliance company introduced a robot-assisted friction heat sealing production line, production efficiency increased by three times and product consistency was significantly improved. Simultaneously, the integration of friction heat processing with other forming processes has become a research hotspot. For example, combining friction heat forming with welding technology enables the integrated processing of pipe fittings, reducing process flow. Furthermore, friction heat processing techniques for high-strength and high-hardness materials are constantly being refined. The development of new mold materials and the optimization of friction parameters have expanded the application scope of this technology. It is foreseeable that with continued technological advancement, friction heat pipe sealing or forming technology will play a significant role in more fields, providing strong support for the green and efficient development of the machinery manufacturing industry.
