Lay a sheet of cheap steel, it is more thin sheet of stainless expensive. Explosion! — And this is a dual-layer structural material. The blast plating welded to the base and is now made of this material can make a mountain body chemical, which is made of pure stainless steel would have cost twenty times more expensive.
Explosion welding is young, it has not yet solved widely used. And it would be good to do so double-layer pipe. They need almost all branches of engineering. But convenient, secure and high-performance manufacturing method yet.
VS Sapelkin now working in the patent office of one of the suburban companies, and recently worked as a designer. Then I came up with fellow new way to connect parts with metal inserts swelling.
I tried this way and make a two-layer pipe. The brass steel pipe inserted in it — from a metal blank, swellable upon saturation with hydrogen, and the assembly placed in a furnace with a hydrogen atmosphere. Billets increased in diameter, and so pressed the copper pipe to the steel casing, they are welded to each other.
Steel pipe has a small diameter, and the copper walls of the race, so the task was lite. I wondered how long it takes for the swelling, such as blanks with a diameter of two hundred millimeters — it turned out that dozens.
Then, maybe a sandwich tube inserted into a simple steel bar so that when it is heated and expanded as it should be pressed to the inner tube to the outer? Sapelkin made a simple calculation, and made sure that nothing happens. Billets will increase in diameter so small that even the tolerance for the manufacture of pipes does not override.
And why not take plain water? Froze, it can even thick pipe break. Sapelkin said application of negative temperatures with unnatural deformation of metals in general (but inventor P. Radchenko flared tube ice and very successfully. Almost all metals in the cooling reduces the ductility, so that they are not in the distribution of cooling and heating is necessary.
Thermal expansion of the different materials are widely used in the art, such as thermal relays, and in any case it is always taken into account their properties and physical characteristics tend to indicate the coefficient of linear expansion. And here is the property of some metals and materials increase in volume during solidification somehow overlooked. For example, in the last Polytechnic dictionary on this property — even a word, but in the famous guide metalworker, which brought up a generation of designers and engineers, is mentioned once in passing. For example gallium about that when they melt crystallization increase in volume, and about the same properties of silicon somehow glossed over.
That among these «abnormal» Sapelkin materials and found suitable for your business, and when he found — invented a method of producing bimetallic tubes is not required for its implementation no press equipment, as without it, you can get inside the preform pressure of tens of thousands of atmospheres. As extenders can use silicon (melting point of about one thousand four hundred degrees Celsius, in the crystallization amount increases almost ten percent), germanium (melts at about nine hundred thirty degrees and increases in volume during solidification five percent), gallium, melted at thirty degrees and increases its volume almost four per cent, as well as various alloys based on these elements. It is important that the yield strength of the material of the inner pipe was lower than the specific pressure on her from the crystallizing melt. For example, copper-clad steel pipe can, in the assembly bay bismuth (melting point of about two hundred and seventy degrees Celsius). For less ductile metal clad, naturally, you need to fill to take material with greater capacity and expansion.
To test the method Sapelkin taken stainless steel tube dvadtsatimillimetrovogo diameter of three mm wall, inserted into it with a small gap zirconium tube millimeter wall drowned assembly with the ends of the flanges, poured into the silicon melt, pumped from the gap the air to not interfere with compound and left to cool at room temperature. Everything turned out as planned. Once again the silicon melt and poured it out of the inner tube, it was firmly attached to naruzhnoy.- There was something like a vacuum diffusion welding.
Unfortunately, the inventor can not verify its way in large and thick-walled pipes (the company where he works, manufacturing, pipe is not involved), but believes that no restrictions on diameter or length. Since the deformation of the inner tube with a new process occurs with heating, for I plating can be used such brittle metals such as titanium, molybdenum, tungsten, Sapelkin also believed that the production of two-layer tubes may be without difficulty automatically, for example the melt removed from the finished tube can It is sent to the next workpiece.
Of course, the creation of the production line will require technological research and study, but it seems to us that it is worth to do such experts on nuclear energy, zirconium and stainless steel tubes in vogue.