In the manufacturing process of heat exchangers, the welding of heat exchanger titanium tubes is widely used in various types of heat exchange equipment due to their excellent corrosion resistance, high strength, and good thermal stability. However, titanium tube welding is difficult and requires extremely high process and operation. After long-term practice and continuous exploration, we have summarized a set of effective titanium tube welding methods, which will be described in detail below.
Welding characteristics of titanium
Titanium has extremely excellent fluidity in the molten state, and its fluidity is higher than that of other metals except silver. This characteristic makes the molten droplet very easy to flow when the titanium tube is welded in all positions. If it is not effectively controlled, it will cause uneven thickness of the weld, which seriously affects the welding quality and appearance of the weld. Therefore, in the welding process, targeted process measures must be taken to deal with this characteristic.
Arc initiation and welding direction control
Arc initiation position selection
When welding in all positions, the selection of the arc initiation position is crucial. It is recommended to initiate the arc at one o'clock on the titanium tube. This position has been verified in practice to provide a relatively stable starting condition for subsequent welding operations, which is conducive to controlling the flow direction of the molten droplet and the stability of the welding arc.
Welding direction and arc extinguishing operation
After arcing, welding is carried out in a counterclockwise direction until 11 o'clock. When welding is close to the 11 o'clock position, high-frequency arc extinguishing technology is required. Increasing the arc extinguishing frequency can effectively control the flow speed of the molten droplet and avoid weld quality problems caused by too fast flow of the molten droplet. Through high-frequency arc extinguishing, the molten droplet can be solidified in a smaller range to ensure the uniformity and appearance quality of the weld.
Key points of arc extinguishing operation
Determination of arc extinguishing position
When the welding of heat exchanger titanium tubes reaches the appropriate position to prepare for arc extinguishing, the arc extinguishing point should be 4-6mm beyond the arc ignition point. This distance is set to ensure that the end of the weld can be filled and fused and to avoid defects such as unfused and pores at the end of the weld due to premature arc extinguishing.
Arc extinguishing with a copper rod
During the arc extinguishing process, it should be carried out on the copper rod. Pure copper rods have the characteristic of fast heat absorption. When the arc is extinguished on the copper rod, the copper rod can quickly absorb the heat generated by the arc, reduce the temperature at the end of the weld, and avoid the formation of arc pits. Arc pits not only affect the appearance quality of the weld but may also become the origin of defects such as cracks, seriously affecting the safety of the heat exchanger.
Welding equipment and auxiliary measures
Selection of large nozzle water-cooled welding guns
In titanium tube welding, the selection of large nozzle water-cooled welding guns is one of the key factors to ensure welding quality. The large nozzle can provide a wider range of protective gas coverage, effectively preventing the titanium tube from reacting with oxygen, nitrogen, etc. in the air during welding, and avoiding defects such as pores and oxidation. At the same time, the water-cooled design can cool the welding gun in time, extend the service life of the welding gun, and ensure the stability of the welding process.
Use pure copper rods to accelerate cooling
In addition to using copper rods when the arc is extinguished, during the welding of heat exchanger titanium tubes, pure copper rods can also be placed close to the weld in time to accelerate the cooling rate of the weld by using its fast heat absorption characteristics. Rapid cooling can make the titanium tube quickly form a stable organizational structure after welding, reduce residual stress, and improve the mechanical properties and corrosion resistance of the weld.
Effects of process measures and operating methods
By adopting the above process measures and operating methods, significant results have been achieved in the welding of heat exchanger titanium tubes. The welded titanium tube has stable weld quality, good appearance, and no defects such as pores, cracks, and unfused welds. These high-quality welds ensure the overall welding quality of the heat exchanger and improve the reliability and service life of the heat exchanger. At the same time, due to the reduction of welding defects, the rework rate is reduced, and the production efficiency is improved, bringing significant economic benefits to the enterprise.
