SURFACING OF DETAILS OF MINING EQUIPMENT BY POWDER WIRES OF C – Si – Mn – Mo – V – B AND C – Si – Mn – Cr – Mo – V SYSTEMS

Abstract

A new composition of the powder wires based on the C – Si – Mn – Mo – V – B and C – Si – Mn – Cr – Mo – V doping systems represented by steels 40GMFR and 40Kh3G2MF was developed. The influence of alloying elements in the composition of C – Si – Mn – Mo – V – B and C – Si – Mn – Cr – Mo – V powder wires on the size of the martensite needles was studied, as well as the primary austenite grain size and the contamination of the weld layer with non-metallic inclusions. The infl uence of the structure on the strength and durability of the deposited metal was defi ned. It is shown that an increase in the content of carbon and alloying elements, in particular chromium, in the composition of the welded steel contributes to the formation of a structure with a medium-carbon fi ne-grained martensite and a small volume fraction of δ-ferrite. It provides reduction in size of the primary austenite grain and decrease in the contamination degree of the deposited layer with non-metallic inclusions. The established improvement in the structure aff ects the hardness increase up to 22 % and the decrease in the abrasion rate of the deposited layer up to 34 %. The chemical composition of samples welded with a fl ux-cored wire of C – Si – Mn – Mo – V – B system is characterized by a lower content of carbon and alloying elements compared to a 40Kh3G2MF steel, which causes the formation of low-carbon martensite in the structure after surfacing. It was established that a signifi cant increase in the content of carbon, manganese, chromium, vanadium and molybdenum in 40GMFR welded steel provides a structure with fine needle and medium needle martensite, reduces the size of the primary austenite grain and the contamination level of the deposited layer with non-metallic inclusions, in particular, non-deformed silicates. Changes in the micro structure are accompanied by an increase in hardness up to 16 % and a decrease in the attrition rate of the deposited layer up to 20 %. As a result of a comparative analysis of the two studied systems of powdered wires, it was found that it is more eff ective to use C – Si – Mn – Cr – Mo – V wire for surfacing mining equipment, since the content and ratio of alloying elements in steel of type 40Kh3G2MF contributes to obtaining a dispersed martensitic structure with an insignifi cant volume fraction of δ-ferrite, which provides high hardness and wear-resistance of the deposited layer.