In aviation, shipbuilding, mechanical engineering, and in some other industries, expensive materials such as titanium are used to make complex and critical assemblies. It is good not only for its low weight, but also for the fact that this metal is not exposed to corrosion processes. Let's take a closer look at what titanium is. Welding of titanium is a rather interesting topic for discussion, and this will be discussed.
A bit of general information
It’s rare to take and use a piece of titanium just like that. Often it is pre-processed. It should be understood that it is usually subjected to welding. But since this metal is a hard-to-work metal, specialists are faced with the problem of material destruction at a temperature of 400 degrees Celsius under the influence of water vapor, oxygen, and nitrogen. The process itself is quite complicated, since it is necessary to observe a large number of technological rules, and indeed not any type of welding is suitable for processing this metal. In any case, today we have learned to process titanium. Titanium welding is carried out by several methods:
- electron beam;
- arc flux;
- argon.
Currently, all methods are popular, but argon welding is most widely used for several reasons, which we will talk about a little later.
Titanium and its alloys
This metal in nature is quite common. Many say that it is not enough, but it depends on what to compare. In any case, the amount of titanium in the earth's crust is greater than copper or lead. This is a very strong metal. In its pure form, its strength reaches 337 MPa, and in the alloy about 1,250 MPa. The melting point of titanium is 1668 degrees Celsius.
At normal temperatures, it is resistant to corrosion and works in aggressive environments. Nevertheless, when the temperature reaches 400 degrees Celsius, its operational properties drop sharply. It enters into a violent reaction with nitrogen, begins to be oxidized by oxygen and water vapor, which greatly limits its scope. It is noteworthy that the material is not at all prone to the formation of hot cracks during welding, but its grain becomes larger, which affects the technical characteristics of the metal and the quality of the weld. Basically, we figured out a bit what titanium is. Welding of titanium is another interesting thing. Let's talk about this.
Technological features of welding
At present, it cannot be said that titanium is a rarity in a particular product. A lot of manufacturers from a wide variety of industries work with it. But you must understand that titanium is an active chemical element. This suggests that the use of conventional welding is unacceptable. This is due to the fact that contaminants in the form of carbides and nitrides fall in the process, which reduce the operational properties of the material.
Therefore, the main condition for welding is complete isolation from the environment. These include: oxygen, nitrogen, hydrogen and others. In addition, welding should be performed at relatively high speeds. With prolonged heating, the grains in the crystal lattice expand, which significantly increases brittleness. In any case, welding of titanium, the technology of which will be discussed in more detail below, is a complex and responsible process. Well, now let's move on.
Argon welding of titanium
The argon type of welding of this metal is most popular among specialists all over the world. This is due to the fact that fluxes and electrodes are not used here, therefore, more subtle and complex welding works are performed. In addition, the argon method for producing welded joints refers to high-quality types of welding. Subject to technology, a high-quality seam is obtained.
One cannot but say about the universality of argon welding. It lies in the fact that there is the possibility of processing both large structures and small parts. The seam is equally high quality. In addition, argon welding of titanium is also good because it can be operated at low current, and this allows welding of material with a thickness of 0.5 mm or more. Argon allows you to restore parts that have lost their original volumes.
Welding of titanium and its alloys: technology
Work must be carried out by a qualified technician with appropriate equipment. In addition, this process is multi-stage. All stages must go in a strictly established sequence and performed in accordance with the standards.
The first stage is preparatory. At this stage, it is necessary to clean the surface of the metal. It is extremely important to remove the oxide film. Edges are usually machined by oxy-fuel cutting. The part or workpiece is treated with fluorine and acid (hydrochloric). At the same time, a constant temperature of 60 degrees Celsius should be maintained. Here it is extremely important to protect the metal being treated from reaction with atmospheric air from both the outside and the back. For this, copper or steel gaskets are suitable, which must be applied to the seam. In addition to gaskets, the use of protective visors and special nozzles is permissible.
During welding
The process runs on direct current. A special tungsten electrode is installed in the burner. When the metal comes into contact with an electric arc, a weld pool is formed. The temperature in it often reaches 6 thousand degrees Celsius.
Under the pressure of the welding arc, molten titanium is somewhat pushed back. It turns out that the burner burns in the recess. This can be considered an advantage, since the penetration ability is significantly improved. In addition, argon is constantly pumped, which provides reliable protection against exposure to oxygen, nitrogen and other harmful impurities.
Something else
About the same way titanium is processed. Cold welding involves the use of filler wire only if the thickness of the metal exceeds 1.5 mm. If the thickness reaches 10-15 mm, then welding is performed by a submerged arc in one pass. If the work was carried out in compliance with the technology, then the seam will not need to be processed from toxins. It will be smooth and high quality. Such compounds are characterized by high tightness and durability.
Arc and electron beam welding
Submerged arc welding has appeared relatively recently. The method is based on the isolation of the material from the external environment with special fluxes. The flux is a kind of paste. Most often, ANT-A of various modifications is used. A feature of the method is that it was possible to achieve a better structure of the crystal lattice than when welding in an inert medium. Therefore, it is preferable to treat titanium in this way. Welding titanium by this method does not impair the performance of the part.
Electron beam welding has a large number of disadvantages. But there is one significant plus, which is the complete protection of the metal from the environment. This allows you to get a very high-quality crystal lattice. Moreover, the process proceeds at high speed, which significantly reduces the energy intensity of the work performed. There is also electroslag welding, which today has not received proper distribution. Its peculiarity lies in the fact that the process uses electrodes of the same material as the surface being welded.
Conclusion
Now you have a general idea of what welding is. Titanium, for which invertor welding is widely used, has unique technical characteristics. That is why it is used where steel or other metals are not suitable. But the high cost of equipment for welding, the energy intensity of the process, as well as many other negative factors do not contribute to the development of the use of this metal. Nevertheless, some companies are constantly trying to do as much as possible so that it is easier and easier to get a high-quality seam. For example, the leader in sales of additives is the company "Elf Filling" - "Titan". Cold welding with the help of this company is becoming not so difficult and lengthy. Of course, a beginner still can not cope with such a task, but it will be much easier for a specialist to do his job. In principle, this is all that can be said about welding a metal such as titanium.