MOSCOW, October 4The cause of the formation of defects in the process of explosion welding was investigated by scientists from Volga State Technical University. According to them, the data obtained for the first time in the world will improve the technology for creating bimetallic composites, which are in demand in the nuclear industry, shipbuilding and other areas. The results were published in the International Journal of Heat and Mass Transfer.
Bimetals are two-component composites that combine the high strength of the base layer and the special properties of the additional layer, for example, wear resistance or resistance to aggressive environments. Bimetals are used in the production of nuclear and petrochemical equipment, in shipbuilding, the space industry and other industries, scientists said.
According to them, explosion welding is widely used to produce bimetals, which is the most effective and often the only way to join many metals, such as steel and titanium.
The process of such welding involves the collision of two metal plates at a certain angle, one of which accelerates to several hundred meters per second due to the detonation of a special charge. As the scientists explained, the materials set in millionths of a second.
Existing methods of explosion welding, according to experts, regularly lead to the formation of defects. The problem is that during a supersonic collision, the air in the gap between the plates heats up to several thousand degrees. Because of this, the plates are melted before impact, which reduces the strength of the composite.
Scientists from the Volgograd State Technical University (Volgograd State Technical University) were able for the first time in the world to establish the dependence of such “premature” heating on the speed of detonation of the explosive, the angle of impact and other parameters of explosion welding.
According to the researchers, the results obtained will make it possible to improve import-substituting technology for the production of bimetals, achieving a complete absence of defects, and this is fundamentally important for a number of industries.
“At the point of impact, enormous pressures develop, at which metals begin to behave like a viscous liquid. At the same time, cumulation, wave formation and plastic deformation of materials also occur. We were able to trace and describe all the relationships in this extremely intense and fast process,” said the associate professor Department of «Equipment and Welding Technology» Volgograd State Technical University Svyatoslav Khaustov.
Measuring temperatures under such conditions is a very difficult task, for which Volga State Technical University scientists used mathematical modeling, as well as precision recording equipment and special thermal sensors they developed, a fraction of a millimeter thick.
«With the help of our original sensors, it was possible to establish the exact values of heat flows from the area of shock-compressed air in the gap between the plates to their surfaces, as well as to determine the main physical characteristics of this area,” Khaustov noted.
In the future, the research team intends to develop ways to replace the air environment between plates on inert gases, such as argon or helium. In the future, according to scientists, this will eliminate or minimize defects when welding large plates with an area of up to tens of square meters.
VolGTU is a participant in the state support program for universities of the Russian Federation «Priority-2030» of the national project «Science and Universities».