Connect pieces of metal welding — a familiar technology. However good when you need to merge the two into one piece of the same material, but what happens when metals are different and, as they say, non-weldable? Scientists at the Institute of Theoretical and Applied Mechanics. SAChristianovich RAS exactly know the answer to that question.
— All the usual methods of welding, which is now based on a very simple principle: there is a metal, it is heated, it melts and mixes, entering into a chemical reaction. The result is a permanent connection — says deputy director of ITAM SB RAS, Doctor of Physical and Mathematical Sciences Anatoly Mitrofanovich Orishich — but there is one feature that, unfortunately, negatively affect the quality of any classical weld: it is not particularly strong. Incidentally, this applies to any material of the cast steel which after the process necessarily anything treated to enhance strength characteristics. The fact is that during the casting formed dendridnye large structure, ie, the metal is collected coarse crystals, poor connections between them, and it becomes brittle. In the weld taking place the same things, but you can not handle it, which affects the strength. No wonder on a pipe or, for example, gas pipelines seam almost two times thicker than the base metal, you ought to make it stronger.
If the ship is used in the construction of welding, the aircraft is still riveting. One hundred years ago the seas were floating vessels with rivets, to recall the same "Titanic," but as people have learned to combine pieces of steel welded, and the extra weight of its hardening in this case, does not play a big role, and the technology used. As for the "iron bird", here it is not necessary to increase the mass. Despite the fact that in today’s aircraft about 30 million rivets, do not give up on them because of the qualities needed in the operation.
— Go to weld in aviation — The cutting — exclaims Anatoly Orishich. — The Germans called this transition the same revolution as during the Second World War, a change in the metal timber vehicles. It is very important to the combination of low weight and high strength. Here comes the problem: we need the item with a weight of titanium, but with the characteristics of stainless steel.
In fact, to connect welding titanium and steel is quite possible — but not for long. Blow on the knee — design and smashed on the weld. This is nesvarivaemost metals: it is associated with a complex physical phenomenon, which is called the emergence of intermetallic compounds — chemical compounds whose crystals are very fragile. So constituted in nature, and change it, alas, can not. Therefore, we must look for a workaround by which and went Siberian scientists. His name — laser welding.
— In contrast to classical methods, it has a unique feature — a dagger penetration, — says Anatoly Orishich. — The fact that the material when subjected to a very important role is played by the power density. Laser — a unique source in many ways, but here he can focus at a point of application of force is so great that there where it shines, the material is forced out. Therefore, when laser welding is formed in the literal sense saucepan. Inside it there is no substance, and a wall — of the molten metal. In a saucepan, you can cook any soup — smiling scientist — that is, to create any song. We added there nanoparticles special ceramics, which are mixed with the material to melt and become the centers of crystallization. As a result, instead of long dendrites formed small, and this leads to the fact that strength is increased significantly.
So, thanks to the three components — the laser radiation, the formation with the help of tanks and nanoparticles — the researchers were able to do what no one has ever done before: a strong connection, in fact, the three metals: titanium, steel, and copper, which is a pure thing is soft, but when intermetallic small droplets smeared inside her, finds strength.
— First, we applied the technology of homogeneous materials thus tried weld two pieces of titanium — commented Anatoly Orishich — and we succeeded seam strength is the same as that of the base metal. Incidentally, this is done the first time. Then — he grins — we have decided to "swing at our William Shakespeare," and connect weldable. This, as you can see, too, turned out. So with the help of our way, we can create any song, and this way, by the way, we have patented.
The task pursued by the scientists of today, is divided into two parts, just as the name of ITAM SB RAS: first, to study the fundamental properties of the resulting weld — a composite material. It is planned to do with the help of colleagues from the Institute of Strength Physics and Materials Science SB RAS (Tomsk) and the Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences (Ekaterinburg). Second, there is a question, and the introduction of new technology.
— In June of this year, our Director of Academician Vasily Fomin go to the conference, which will take place at the All-Russian Institute of Aviation Materials, Moscow. They are interested in our designs, and have agreed that we will begin its certification. After all, we do not have the right to come to the Novosibirsk Plant. Chkalov and say cook! Need of the committee — says Anatoly Orishich plans.
However, even now in the framework of the technological platform "Photonics" ITAM SB RAS has established contacts with shipbuilding companies of St. Petersburg, who praised the technology of welding non-weldable metals. It turns out that the problem is on such a scale that is not just floating or flying, but any of us who travel by car: there is also a connection problem in one part of iron and copper, which is now being decided by the bolts, but who knows …