Increasing the hardness of ShKh15 steel in its products

The methods of reaching a high hardness, which is the main characteristic determining the service resistance of rolling tools (sheet mill rolls, cogging-down rolls, the mandrels of cold-rolling tube mills, etc.), in low-alloy hypereutectoid steels are theoretically grounded. The “ultrahigh hardness” effect is shown to be achieved when the structure of a steel is preliminarily prepared and a disperse ferrite-cementite mixture forms in it. This structure is achieved upon special-purpose quenching followed by medium tempering. As a result of such a nonstandard heat treatment, carbide particles become an order of magnitude smaller than the secondary carbides that form upon conventional annealing. The steel grades to be subjected to the additional treatment are listed, and specific technological procedures that provide an increase in the hardness of quenched hypereutectoid steels are described. As a result, a hardness of 68–69 HRC is reached in experimental samples of commercial ShKh15 steel.     

Analysis of the annealing kinetics of ShKh15 steel sludge waste

Conclusions In ShKh15 steel powder particles internal stresses are relieved during heating to a temperature at which they sinter to porous sponge. The processes taking place during the reduction annealing of sludges are described by an equation of chemical kinetics. The energies of activation for the sintering of filing and roll-forming sludge particles are practically identical and equal to 30 kJ/mole. ShKh15 steel sludge waste can be processed to give powder with a density ranging from 0.5 to 1.0 g/cm³.1.0% C-1.5% Cr ball-bearing grade — Publisher.Translated from Poroshkovaya Metallurgiya, No. 3(303), pp. 16–20, March, 1988.The authors are grateful to I. V. Uvara for the determination of the specific surfaces of powders.     

Nonmetallic inclusions in electric furnace steel ShKh15SG-V bars

The mechanisms of formation and the methods of controlling nonmetallic inclusions (NIs) in bearing steel are considered. The number and composition of NIs in electric furnace ShKh15SG-V steel bars made using various versions of heat and out-of-furnace treatment are studied by fractional gas analysis and number estimation according to State Standard GOST 801-79. A high calcium content is found to result in large globular NI numbers in the bars. Fractional gas analysis is shown to correctly determine the oxide inclusion content in steel.     

Nonmetallic inclusions in ShKh15 steel powder and solid compacts

Conclusions To obtain metal which is comparatively free from endogenic nonmetallic inclusions, it is necessary to refine it more thoroughly in the furnace or subject it to treatment outside the furnace, in the ladle (argon blasting, vacuum treatment, treatment with synthetic slags). Contamination by exogenic inclusions can be reduced by preventing slag from reaching the atomization zone, protecting the particle surfaces against oxidation during atomization, and careful preparation of lined guides.1.0% C-1.5% Cr ball-bearing steel-Publisher.Translated from Poroshkovaya Metallurgiya, No. 10(298), pp. 17–19, October, 1987.     

Evolution of the structure of a quenched 30KhN3T steel single crystal during cold plastic deformation

A sequence of the structural transformations occurring in a quenched single crystal (pseudo-single crystal) of medium-carbon structural 30KhN3T steel during cold plastic deformation by rolling with a reduction of 20, 40, 60, 80, and 86% is studied by metallography and electron microscopy. It is shown that the quenched steel single crystal can be deformed by rolling at reductions that are unattainable for quenched polycrystalline steels of the same chemical composition. It is established that the laws of the structural transformations occurring during cold deformation of the pseudo-single crystal have specific features characteristic of both single crystals and polycrystals.     

Estimation of plastic deformation in the technologies of bulk cold deformation

A technique for determining the degree of reduction upon forming by cold bulk shaping has been proposed. The technique is based on a comparison of the measurement data on the hardness of a cold-worked metal with that of the same metal subjected to a compression test at a certain strain intensity. The technique has been tested in technological operations of reduction and thread rolling.     

Preparation and properties of P/M ShKh15 steel from machining waste

1% C-1.5% Cr ball-bearing grade — Publisher.     

SIMS study on hydrogen behaviour of 18Ni maraging steel during plastic deformation

In this paper, hydrogen behaviour in high dislocation material during plastic deformation was studied by means of SIMS. Experimental results show that hydrogen release rate increases with the increase of stress during elastic deformation stage; the hydrogen release rate increases dramatically at the very beginning of plastic deformation, and reaches the maximum in the vicinity of yield point, then it decreases with further increases of strain. The calculated hydrogen diffusivity is 10^?13 cm²/s, which is 3 to 4 orders of magnitude lower than that of undeformed ones. Hydrogen egress in high vacuum was also discussed.     

Assessment of the effectiveness of compaction of ShKh15 steel powders by hot extrusion

Conclusions Hot extrusion enables high-density steel to be obtained from an ShKh15 powder at a reduction = 2.15 (degree of deformation 33%). The strength of P/M ShKh15 steel after extrusion and annealing lies in the range 720–780 MPa, and thus surpasses the strength of the same steel produced by casting (650–700 MPa), while the ductility characteristics of the two steels are comparable.Translated from Poroshkoyaya Metallurgiya, No. 1(289), pp. 25–28, January, 1987.A 1.0% C-1. 5% Cr ball-bearing stell grade — Publisher.Deceased.