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This article discusses key issues regarding the prospects for the development of high-strength wearresistant steels. It is noted that Russian steelmakers have long been producing a large number of steels that have very similar strength characteristics. A generalized criterion which the authors developed and which makes it possible to rank steels by wear resistance without having to conduct wear tests might serve a reliable guide in selecting high-strength steels for different service conditions.

Problems are examined in updating machines and equipment in various branches of engineering from the viewpoints of the designer, the metallurgist, and the tribologist. Convincing conclusions are drawn on the metallurgical and tribological aspects in technical renewal. The organizational aspect is also considered.

This paper investigates the mechanical properties, local plastic deformation, and character of failure of D5KhN2MFASh and 16KhN3MASh steels after different heat treatments. The chemical analyses of these steels are shown in a table. An analysis of the geometry of type T drill bit roller cutter teeth of different diameters showed that the relative area of the tough core of the roller cutters in the most dangerous (from the point of view of failure) cross section for 93-151 mm diam. bits is 0.38-0.45. Taking into consideration the higher strength properties of D5KhN2MFASh steel, higher wear resistance and life of drill bits (type T) with roller cutters of this steel may be expected in comparison with the wear resistance of drill bits with standard roller cutters produced of 16KhN3MASh steel.

The authors verify the dependence of the wear resistance of steels on their hardness in testing steels used for the manufacture of components working in friction on an abrasive: D5KhN2MFASH, 45, U8, 30Kh13, and 14KhN3MA. After quenching, all the steels were tempered at 100, 200, 300, 400, 500, and 600/sup 0/. Tests on the heat treated specimens revealed the relationship between fracture load and hardness. Advantages of the proposed method are discussed.

This article describes a drilling tool that has been designed in the form of a block of unified pneumatic-percussion mechanisms equipped with rock-breaking elements and placed on a single body with the possibility of free axial movement of the percussion mechanisms in the body of the drilling tool guarantees identical (constant, depending only on air pressure) force of each strike on the face. The power of the drilling tool and the drilling efficiency are determined by the air supply pressure. The rock-breaking elements on the peripheral crown set at an angle to the face maintain the required hole diameter as the components fall constantly on the surface being broken even when they are wearing away. The drill bit is fitted with low wedge-shaped drilling tips with an advancing edge for drilling shallow holes using light mobile drilling units.

The presence of hard abrasive particles in the impact zone between parts of machines is the reason for their intensiveabrasive-impact wear. No attempt to analytically account for the features of the interaction of hard abrasive particles with the wear surface during impact has been made, even though such information is needed to develop methods for calculating the rate of abrasive-impact wear of equipment parts. This paper examines a method of calculating the depth of penetration of hard abrasive particles into the surface layer. The experimental values of penetration depth are less than the theoretical values for reasons which are discussed.

The influence of the mechanical properties of steels on their wear resistance under conditions of rolling friction has been studied. The purpose includes investigation of the basic rules of fatigue wear of D7KhFNSh and D5KhN2MFASh steels in rolling friction applicable to the rolling bearing balls of drill bits. For comparison, specimens of 55SM5FA steel were also studied. The results of a test of a ring and three balls of the same material are shown. The relationship of the wear resistance of steels to hardness, energy content, and the index shown which is a criterion of fatigue strength, is presented.

The authors state that an analysis of the mechanical properties and wear resistance of the experimental steels makes it possible to recommend them for use in various branches of machine building. In petroleum machine building this steel may be recommended for the production of parts of the drive chains of drilling units in place of 30KhN3A, 12KhN3A, and 50KhFA steels. This is also a basis for expecting a definite effect from the use of such steels in the mining industry and in construction. The paper reports on studies of experimental steels based on the premise that an analysis of the designs and operating conditions of rapidly wearing parts of well-drilling equipment has shown that the primary reason for their unsatisfactory life span is the low mechanical properties of the steels used.