One of the methods for increasing the complexity of chromium steel properties of martensitic class AISI 420 is the use of an optimal heat treatment mode. The steel of martensitic class AISI 420 has high resistance in atmospheric conditions (except for the sea atmosphere), in the river, and tap water. It is widely used in power engineering, in cracking units with a long service life at temperatures up to 500 °C, for furnace parts. Additionally, it is used in the following fields: the production of turbine blades, working in conditions of high temperatures and parts of increased plasticity, subject to shock loads, for products exposed to atmospheric precipitation, solutions of organic salts and other slightly aggressive environments; production of fasteners; production of parts for compressor machines operating with inert gas; production of parts operating at low temperatures in corrosive environments; production of parts for aviation purposes. It is shown that the optimal mode of heat treatment for a maximum hardness of 40 HRC is quenching at a temperature of 980 °C with cooling in oil and tempering at a temperature of 200 °C with air cooling. With an increase in the tempering temperature from 200 °C to 450–500°C, the impact strength does not change much. Tempering at higher temperatures leads to the intense weakening of the steel. Simultaneously, a decrease in the impact strength is observed, the minimum value is reached at a tempering temperature of 550 °C. With an increase in the tempering temperature to 700 °C, the impact toughness increases, but the steel’s hardness sharply decreases at such temperatures. Keywords: hardening, tempering, hardness, toughness, mechanical properties, chromium carbide.
Problem statement. The problem of influence of capillary-porous structure, characterized by the presence of a spatial lattice of micropores, capillaries and various defects on the strength and stability of concrete polymer, is considered. Purpose of the article. Estimation of porosity determination methods (total volume and size distribution of pores) as a structural characteristic of concrete polymer components, aggregates and fillers. Conclusion. The drop in strength of furan compositions is mainly determined by the pore formation as a result of the accumulated wetted aggregates from the particles of the dispersed filler. The results of the experiments show that with increasing the dispersion of the filler there is a decrease in the volume of the binder under the condition of constant ratio p / n, which is explained by the increase in pore formation, which is increased due to lack of polymer and the manifestation of the effect of air trapping. The complete impregnation of the mineral components creates a polymer distribution over the entire volume and forms a continuous and evenly distributed lattice of the polymer and its porous space. Accordingly, the polymer concrete is compacted and contact is formed between the matrix and the polymer.
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