INFLUENCE OF THE PROCESSES OF GAS-FLUX TREATMENT OF THE MELT ON THE STRUCTURE AND PROPERTIES OF THE ALUMINUM ALLOYS

Processy litʹâ, 2019, Tom 136, №4, p.3-10

Abstract

Received 01.07.2019

UDK 669.715:621.791.048:622.765

It is presented the results of the researches on influence of the methods gas-flux treatment liquid metal on the efficiency of refining, physical and mechanical characteristics and structure of the aluminum alloys. It is shown that at the treatment of the alloy by the gas-flux mediums emerging bubbles of the gas by diameter 0,5−3 mm entrain oxide inclusions and carry them on melt surface. In spite of all the oxides with size of 30−80 mm are removed by flotation. For removing more small (< 30 mm) solid particles the liquid metal necessary to pass through filters of fine cleaning. The treatment of alloy AK7 it is carried out the melt flux (35 % NaCl, 25 % KCl, 30 % NaF, 10 % Na3AlF6) in the number of 0,5 % from metal mass. For gas-flux treatment in the metal it is batched mechanically the melting flux in the number of 0,3 % from alloy mass and then the bath is blowed by cold or plasma jet of argon. The alloy without flux also is processed by plasma jet with vapors of mentioned flux. It is defined that after usual fluxing from the melt it is removed to 50 % oxides and small (~ 22 %) amount of hydrogen. After fluxing of the melt average grain size in the casts decreases on 35 % (from 2,6 to 1,7 mm). Strength σвof the cast metal increases in all this by ~ 10 %, plasticity (δ) − by 48 %, in comparison with initial. The treatment of liquid metal without flux by velosity jet of cold argon is allowed to decrease the content of hydrogen in alloy by 55 %, oxide inclusions > 30 %. After blowing by cold argon before fluxing melt hydrogen concentration and oxides in alloy decreases by 64 and 56 % respectively. The grain size in the cast metal decreases by 2 times and it strength σв increases on 18 %, relative elongation − on 60 %. The most effectively alloys is refined from hydrogen and oxides during the depth treatment their by plasma. After blowing by plasma jet the before fluxing melt it is removed 77 % of hydrogen and 62 % of oxides from the alloys. The mean size of grain in the castings desminishes by 58 % (from 2,6 to 1,1 mm). Strength σв increases by 25 %, relative elongation by 70 %. The blowing the metal by plasma jet with vapors of the flux it allowed reduce hydrogen concentration in cast products by 83 %, oxides − up 74 %. After such treatment of the melt the grain size in the cast metal decreases in 4,3 times (from 2,6 to 0,6 mm), strength σ_в increases to 30 %, relative elongation increases more than 4 times.