ANALYSIS OF THE CAUSES OF THE SUDDEN DESTRUCTION OF THREE-CONE DRILL BITS WITH BUILT-IN ROCK-DESTRUCTION EQUIPMENT
Tricone drill bits with plug-in rock-cutting equipment are intended for the construction of wells in hard rocks. To the operational performance of bits, stringent requirements for wear resistance and crack resistance of bit steel, structural strength of parts of bits, and especially cones, are put forward. The scientific work involves a comprehensive analysis of the causes of the sudden failure of the rock-cutting tool, research of all factors affecting the performance and durability, and the options for selecting materials and rolled products for the manufacture of roller cone bits are proposed. A general analysis of the destruction of the cutters of spent tricone drill bits, as well as metallographic studies of the heat of steel, have been carried out. The materials from which bits are made have been investigated for the content of chemical elements and the determination of the physicomechanical properties of these steels. It is established that the causes of sudden failures of bits through the brittle destruction of cones are the inconsistency of smelting steel requirements for strength, ductility and technological – quenching. It has been found that the average value of the percentage of chemical elements in the body of the tested cone does not go beyond the limits of tolerance. By analyzing the physicomechanical and technological indicators of the studied steel smelting, increased values of strength and quenching have been established, and the ductility and impact toughness values have been reduced. The analysis of the chemical composition of steel melting did not reveal a significant dispersion of the percentage of chemical elements. Segregations and similar effects were not detected. It is established that such technical conditions allow too wide dispersion and optional value of non-metallic inclusions, and also do not regulate the presence of harmful impurities, which dramatically increase the quenching, hardness and other indicators that worsen the performance of cones. It is proposed to abandon the use of existing rolled stock and to develop and introduce a more reasonable regulatory document according to which rolled steel should be supplied for the manufacture of parts of tricone drilling bits.
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