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Notes: Conclusions 1. The initial crystallographically ordered structure produced after martensite or bainite transformation is retained during subsequent heating up to the temperature at which there is formation of grains with high-angle boundaries, detected in the fracture. 2. Numerous intragranular interfaces obtained after initial martensite quenching, on which the dense carbide chains are predominantly found, prevent further disorientation of the austenite forming through advancement of the diffusion front deep into the ferrite plate absorbed by it. Further disorientation of the low-angle austenite plates, produced until the formation of independent grains with high-angle boundaries, is delayed until a higher heating temperature at which there is dissolution of the bulk of the carbide particles deposited on the ferrite (former martensite) plate boundaries. 3. As the amount of molybdenum in the steel is increased, given the same amount of carbon, there is sharp increase in the resistance of carbide particles to dissolution in austenite, on account of the increased molybdenum in them. There is a corresponding increase in the temperature difference between Ac3 and the temperature at which the carbide particles dissolve and grains detectable in the fracture are formed. 4. In steel with an initial crystallographically ordered structure, the heating rate has a substantial effect on the temperature at which there is absorption of the ferrite plates and carbide particle chains creating suitable conditions for the formation of polyhedral grains. The heating rate affects the composition of the ferrite and carbides as well as their size, shape, arrangement, and conditions for dissolving carbides, and, therefore, also influences the effectiveness of phase recrystallization through nonuniform grain growth during slow heating. 5. Dissolution of carbides and formation of austenite grains in initially quenched steels is completed at higher temperatures than in annealed steels through slowing down of the diffusion processes under the influence of intragranular interfaces. 6. The arbitrary process of austenite grain formation occurring in initially quenched steel after the carbide particles have dissolved at temperatures considerably above Ac3 leads to a reduction in the free surface energy of the system.

Notes: Conclusions 1. Austenitization of white iron primary cementite crystals in contact with ferrite commences at the interphase boundary. Austenite is formed as a result of withdrawal of carbon atoms from cementite into ferrite. 2. Grains of austenite phase forming in cementite create lamellar clusters oriented along the direction of cementite crystal layer surfaces. 3. The type of pseudopearlite structure depends on the withdrawal direction for carbon atoms.

Notes: Conclusions 1. The partial coefficients of the thermal expansion of the majority of carbides in tool steels are lower than those of the ferrite. 2. The thermal expansion coefficients of the phases depend on their composition. As the content of atoms of high-melting metals increases in the carbide, its thermal expansion coefficient increases to a smaller degree on heating.

Notes: Conclusions As the result of hydrostatic extrusion, the ultimate strength of steel 20 increases from 40 kg/mm2 in the original condition to 74 kg/mm2 with 70% deformation. The reduction of the ductility is explained by cold working of the ferrite matrix and the oriented arrangement of pearlite colonies in the structure.

Notes: Abstract The physicochemical processes entailed in carburization are distinguished by their complexity and instability. When such treatment is to be carried out under industrial conditions, it requires operative information on the distribution of the diffusing element across the metallic layer that is being saturated. This information is particularly important in automated technological processes. Timely correction of the technological parameters of carburization helps attain a stabler level of the strength properties of the treated components. The article suggests a method of checking the distribution of carbon across the carburized layer in steel by measurement of the thermo-emf. It presents the results of investigations of the steels 12KhN3A, 20Kh2N4A, 18KhGT after different kinds of heat treatment. The accuracy of determining the carbon content of the layer is not poorer than 0.08%.