Vol 58, No 7-8 (2016)

High-strength cast iron of grade VCh50 with globular graphite is studied after isothermal quenching in the bainitic and martensitic ranges. The mechanical properties of the iron and the hardness of its structural components are determined. The fine structure of the iron with bainitic and martensitic matrix is studied. The effect of the tempering temperature after the isothermal quenching on the hardness and structure of the iron is estimated.

The mechanical properties and the structure of forming rolls from cast irons of different compositions are studied. A novel iron including a copper additive that lowers its chilling and raises the homogeneity of the structure is suggested for the roll cores. The use of such iron should raise the reliability of the rolls in operation.

The effect of the parameters of thermal-rate treatment of melt on the iron-containing phases in alloy Al – 15% Si – 2.7% Fe is considered. The structure and mechanical properties of the alloy are determined after a thermal-rate treatment conducted at different temperatures of the melt, different pouring temperatures, and different holds at the pouring temperature. The optimum variants of thermal-rate treatment of melt for alloy Al – 15% Si – 2.7% Fe are chosen.

The effect of heat treatment on the structure and physical and mechanical properties of flat specimens cut from a massive billet from steel 15Kh2MFA with an austenitic facing on one side is studied. The hardness and the microhardness of the specimens are determined. Acoustic and x-ray studies are performed. The causes of residual stresses giving rise to deformation and formation of cracks in the faced steel are established. Ways to solve the problem are suggested.

Mechanical properties and characteristics of the structure of welded joints of screw piles are studied. It is shown that cast tips from steel 25L do not meet the performance specifications for operation in the Northern climatic zone. Quality welded joints of screw piles can be obtained by semiautomatic welding in an environment of CO₂ with Sv-08G2S welding wire.

Prismatic sensors of two standard sizes are used to determine the heat-transfer coefficients of high-pressure nitrogen at different turbine rotor speeds of a SECO/WARWICK 10.0VPT-4020/24N vacuum furnace. The adequacy of the values obtained is estimated.

A Cu₄₉Zr₅₁ intermetallic is used as a base for synthesizing metallic glasses and composites with glass matrixes [(Cu₄₉Zr₅₁)_{100 – x}Al_x, where x = 0, 2, 4, 6, 8, 10 and 12 at.%]. The introduction of aluminum raises the microhardness and the ultimate compressive strength. In addition, the suppression of formation of crystalline phase upon the introduction of 8 at.% Al provides a glass-like structure in alloy (Cu₄₉Zr₅₁)₉₂Al₈. The formation of the glass-like structure is discussed within the concept of competitive nucleation of different intermetallics.

Methods and problems of determination of the structure of steels from phase diagrams are considered. Expediency of transition to methods of mathematical modeling is shown. Amethod of mathematical modeling of the structure of high-alloy steels with the use of the Potak – Sagalevich diagram is suggested.

The effect of superheating of melt on structure formation in hypereutectic alloy Al – 1.2 at.% Co is studied under the conditions of rapid cooling. It is shown that any superheating of the melt yields a double-phase structure in ribbons, which is represented by an aluminum solid solution partially supersaturated with cobalt and cobalt aluminides. Annealing changes the morphology of the cobalt aluminides. The solid solution decomposes at about 350°C.

The possibility of application of a nonstandard deformation process by the method of hydroextrusion (HE) to commercial high-strength magnesium alloys MA14 and MA22 is studied and proved. It is shown that specific modes of HE deformation raise the level of the strength properties of the alloys by 25 – 50% as compared to the standard deformation process.

A study of commercial tubes from steel ShKh15 produced in a chamber furnace is performed for investigating the active annealing process. The causes of inappropriate heating and cooling of tubes in a charge are determined. The annealing mode is shown to mismatch the required temperature regime, which elevates rejection. Recommendations for eliminating the determined drawbacks, raising the quality of the annealed tubes and the output of the chamber furnaces are developed.

The hardness and the structure of the heat-affected zone (HAZ) under welding of tube steels of strength category K60 – K70 are studied. The steels are treated by regimes imitating the thermal cycles of different welding processes applied to tubes starting with manual arc welding and ending with energy-intensive automatic submerged-arc welding. The welding modes causing maximum decrease in the hardness of HAZ regions are determined. The conditions preventing softening under one-pass and multipass welding of high-strength steels are presented.

The effect of carbonitriding of nickel-free die steel 5Kh2GF in a highly active environment based on amorphous carbon and potassium ferricyanide is studied. The temperature of the carbonitriding process is varied within 800 – 900°C, and the duration is varied from 3 to 8 h. The structure and the hardness of the steel are determined. The wear resistance of the steel after the carbonitriding increases by a factor of 4 – 6.

The structure and the wear resistance of commercial-purity titanium subjected to plasma nitriding followed by chemical deposition of a Ni – B coating are studied.

Processes of induction heat treatment of steel articles are studied with the help of ELTA and 2DELTA software for electrothermal analysis. A novel process of combined hardening of extra heavy balanced drill pipes is studied as an example. The results of the computations are confirmed by experimental data.

The crystallization behavior of phases in alloys of the Co – Sn – Bi system is studied by the methods of differential thermal (DTA), x-ray phase (XRP) and x-ray diffraction (XRD) analyses and hardness measurement. The projection of the liquidus surface is plotted. The boundaries of layering, the development of the monovariant processes, and the coordinates of the nonvariant equilibrium compositions are determined. Compositions of (Co₃Sn₂)_{1 – x}Bi_x solid solutions suitable for the production of antifriction materials are suggested.