OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 4 2024 earth metals. Rare earth metals play an important role in the manufacture of high-tech products, such as electronics, batteries and renewable energy equipment [2–5]. Increasing the mineral extraction requires active improvement of both equipment and machinery, as well as extraction tools. Rotary-percussive drilling is a combined type of drilling that combines rock cutting with the application of percussive loads. In this type of drilling, the rock cutting tool is subjected to torque, static feed force and impacts of a certain frequency and force. In some geological conditions, rotary-percussive drilling turns out to be more productive than rotary and percussive drilling separately. This explains its wide application in various mining operations [6, 7]. Effi cient rock destruction during rotary-percussive drilling with carbide bits is achieved by an optimal selection of the carbide composition, the tool size, the geometry of cutters, its location along the bit face, the well-organised fl ushing system and properly calculated parameters of the drilling mode [8–10]. In pin drills, hard alloys are used as the material for the cutting teeth, usually tungsten-cobalt alloys VK6 (94 %W; 6 % Co) and VK8 (92 %W; 8 % Co). These carbide materials have proven to be reliable and relatively inexpensive to use. Bits of such type can be exploited in the rocks up to the ninth category of drillability [11]. Bit wear resistance in operation depends on geological and technical drilling conditions: hardness, abrasiveness, fracture density, discontinuity of rocks; rotation speed, diameter of the bit and axial load; a depth and curvature of the borehole, serviceability of the drilling machine [12–15]. However, the hardness and bending strength of carbide cutters, as well as the quality of manufacturing and the assembly of the pin bit, are of decisive importance. A signifi cant share of such tools is produced in European countries and has a high cost. Within the framework of the AlmalykMMC JSC enterprise (Uzbekistan), rock-cutting bits are produced at a signifi cantly lower cost. At the same time, the resistance and durability of such bits are lower than those of European analogues. The purpose of this work is to increase the durability of drill bit teeth by improving the manufacturing technology of this tool Research Methodology This work was carried out in three stages. At the fi rst stage, an analysis of the causes of the destruction of the bits manufactured by Almalyk Mining and Metallurgical Company JSC was carried out. At the second stage, based on the results obtained, the technology of bit teeth manufacturing was changed, and the samples, obtained by the new technology, were investigated. At the third stage, the comparative testing of bit samples manufactured using the improved technology and European analogues of the Atlas Copco company (Sweden) were carried out. The research work was performed on the basis of the Scientifi c and Production Association for the production of rare metals and hard alloys of the Almalyk Mining and Metallurgical Company JSC (NPO AGMK). The research was focused on the development of the technology to manufacture the KNSh 40×25 mm type drill bits with seven inserted pins-tooths that are similar to Atlas Copco drill bits (Sweden). Prototype bits were manufactured using tungsten-cobalt alloy carbide teeth. The teeth were produced at NPO AGMK. Structural studies were carried out, using a Carl Zeiss Axio Observer Z1m light microscope and a Carl Zeiss EVO 50 XVP scanning electron microscope (Jena, Germany). The phase composition was studied using an ARL X’TRA X-ray diff ractometer (Thermo Fisher Scientifi c, Waltham, MA, USA) in the CuKα radiation. For metallographic analysis of the bit tooth surface, the visual-optical method was employed, using a Carl Zeiss Axio Observer A1m microscope.
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