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The effect of heat treatment parameters (the temperature of 850 – 930°C and the cooling rate of 1 – 20 K/min) on the microstructure and mechanical properties of carbon steel with 1.95 wt.% C is studied. The temperatures of the phase transformations in the steel are determined. X-ray diffractometry is performed. A heat treatment mode preventing the formation of ledeburite in the structure of the steel and promoting a uniform distribution of carbide particles in the matrix is suggested.

The structure and mechanical properties of an ultrahigh-carbon steel modified with amorphous ferrosilicon with a low melting point are studied. The methods of x-ray diffraction, optical and scanning electron microscopy are used to study the effect of the amorphous modifier on the structure of eutectic ledeburite in the cast steel. Tests for tensile strength and impact toughness are conducted. It is shown that the mechanical properties increase as a result of the modification without subsequent heat treatment.

The possibilities and special features of formation of two-phase austenite-carbide structure in decomposition of supersaturated austenite are studied. The effect of alloying is considered for manganese steels, cast irons, and chilled nickel-molybdenum high-strength cast iron with globular graphite.

The possibility is demonstrated of improving the microstructure of cast high-speed steel R6M5-Sh by use of thermal cycling treatment (TCT) as an intermediate production operation between preliminary isothermal annealing and final hardening with triple tempering. As a result of TCT there is a reduction in the amount of ledeburite eutectic, size of the carbide network, carbide inhomogeneity, and a change in carbide size and composition. Rational treatment regimes are determined.

Fracture mechanisms are considered for high-speed steels of ledeburite (R6M5) and hypereutectoid (11M5F) classes. It is shown that formation of critical length cracks for hypereutectoid steels occurs as a result of not only elastic, but also significant plastic strain, and therefore work for crack generation is significantly greater for steel 11M5F than for R6M5. A relationship is established between strain and work for failure with static bending on one hand, and impact strength on the other.

Eutectic polyhedration of the diagram is presented and special features of structure formation in high-manganese irons are analyzed. It is shown that eutectics of two kinds (alloyed ledeburite and a eutectic based on M7C3 carbides), which are in peritectic equilibrium with the melt, can be formed and be accompanied by a special austenite-carbide component having a pearlite-like structure. The quasi-eutectic and the M7C3-bearing eutectic in heat-treated high-manganese irons have a special morphology with composite arrangement of carbides in austenite. It is shown that additional alloying of manganese irons with silicon might be a promising direction. Silicon stabilizes the M7C3 carbide in its competition with cementite and ensures the possibility of fabricating austenitic mottles with such carbide. Mottles alloyed with manganese and silicon and having globular graphite, M7C3 carbides and metastable austenitic matrix are characterized by high wear resistance, good antifriction properties, and a combination of high mechanical properties.

The effect of spinodal austenite-carbide layering on formation of groups in liquid iron and stability of its microheterogeneous structure are considered.

1. Eutectic graphite of different morphologies is observed in cast hypoeutectic iron depending on the cooling rate. After hardening at atmospheric pressure we distinguished rosette, “twisted” flake, and point graphite, and after hardening under pressure we observed pseudoeutectic and fine-flake graphite. 2. Pressure promotes considerable deceleration of segregation of graphite independently of the cooling rate. The appearance of cementite and needle ledeburite in the structure of hypoeutectic cast iron under the action of pressure is connected with superposition of the stable and metastable transformation ranges and a change in the thermodynamic equilibrium between graphite and cementite in the metal. 3. Pressure applied to the hardening casting increases the proportion of bound carbon that segregates in the form of compact graphite inclusions in graphitization annealing, thus promoting an increase in the mechanical properties of the metal.

Special features of plastic deformation and fracture of excess cementite segregated under the conditions of high-temperature carbon supersaturation of steel are studied by the methods of light and scanning electron microscopy. It is shown that regularly oriented flakes of excess cementite with a lamellar structure are formed within the former austenite grains. The cementite flakes oriented along the, rolling plane fracture by a brittle mechanism forming numerous fragments. The behavior of free cementite under the conditions of cold rolling depends on the orientation of the flakes in the specimen. The mutual shift of the layers allows coarse cementite formations to deform under the action of compressive stresses without cracking.

Carbon fibers and textiles based on them are being used increasingly to reinforce composites. In this article we report the results of inetallographic research on the surface layers formed by passing an electric current through a hardened steel part and a fabric or felt made of a carbon-fiber material on its surface.

The most technologically advanced material for valve seats of internal-combustion engines are the phosphorus-alloyed cast irons strengthened by a reinforcing phase consisting of the phosphide eutectic and cementite, the ratio between which depends on the Cr to P ratio, the technology of the modification, and the cooling rate of the castings. The optimum structure of the cast iron for valve seats, which produces a combination of good machinability and high wear resistance is the troostomartensitic or troostosorbitic matrix with a network of the FE5-type phosphide eutectic (with cementite lamellae), and clusters of graphite combined with fine- and medium-size flakes with less than 5% of the structurally free graphite. The optimum combination of wear resistance, machinability, and strength of the valve seats is attained at the ratio Cr/P=3–4 and modification by 0.5–0.8% ferrosilicon. The wear of the phosphorous-containing cast iron with a troostomartensitic or troostosorbitic matrix is determined by the amount of the cementite in the ledeburite and, when its content is small or it is absent, by the type of the phosphide eutectic. A phosphorus-containing cast iron of the type of 360S3KhGMD has been suggested which has gone into production. It has the composition: 3.5–3.8% C, 2.5–3.0% Si, 0.7–1.0% Mn, 0.9–1.2% Cr, 0.9–1.2% Mo, 0.3–0.6% P, 0.7–1.2% Cu, and up to 0.1% S.

1. With accelerated heating up to the melting temperature during heat treatment for cast iron IChKh12M a composite structure is retained: a skeleton of primary ledeburite carbides included in a matrix of variable structure. 2. Use of accelerated austenitizing causes formation of a nonuniform solid solution of austenite in the cast iron matrix. Variation of the heating temperature and cooling rate makes it possible to change within wide limits the structure of the matrix and cast iron properties. An increase in heating temperature followed by slow cooling changes the cast iron matrix structure from pearlite-bainite to bainite-martensite. After quenching there is formation of a martensite-austenite structure. 3. Accelerated heating shifts the temperature of phase transitions for cast iron into a higher temperature region compared with furnace heating. On the basis of this an optimum heat treatment schedule was developed for cast iron IChKh12M which makes it possible to obtain high abrasive wear resistance. Heat treatment with heating for hardening in molten salts or electric heating is recommended for articles of cast iron IChKh12M which operate under abrasive wear conditions.

1. After electron beam treatment of the cast iron guides with an electron energy of E=1.5 MeV the structure of the surface layers consists of α- and γ-phases with a content in the latter of up to 1% C and also clusters ordered according to type Fe4C formed in the transition zone. In contrast to the original condition up to 10% austenite is observed in the transition zone of the iron. A ledeburite eutectic is formed in the surface and the transition zone to the base metal consists of fine crystalline martensite with areas of residual austenite, partially dissolved graphite inclusions, and ferrite grains. The fine crystalline martensite and the remaining ferrite grains are bordered with a troostite border. 2. Electron beam treatment with fusion of the surface of guides with gray iron with a ferrite matrix causes strengthening of them to a depth of up to 0.6 mm. 3. Production tests of the guides on the 250–2 mill in hot rolling of 8–10 mm wire in Western Siberia Metallurgical Combine showed an increase in their service life of 2 to 5.6 times.

White cast iron powder rapidly quenched from the liquid condition with presence of the same phases and structural components differs markedly in structure from normally cast white iron.

1. The level of crack resistance of cast hypereutectoid steels is determined by the size of the inclusions of eutectic cementite which depends solely on the amount of carbon contained in the steel. Alloying with 0.86–1.72% Cr, 0.9–1.32% Ni and 0.16–0.3% Mo does not affect the amount of eutectic cementite, and has practically no effect on the level of crack resistance when the steel contains 0.90–1.00% C; it decreases somwhat when the carbon concentration increases to 1.80–1.90%. 2. Heat treatment (quenching in air from 920°C, tempering at 550°C) raises the level of crack resistance of chrome-molybdenum and chrome-nickel-molybdenum steels. The effect manifests itself the more strongly, the higher the degree of alloying of the steel with carbide forming elements is (with 0.9–1% C). 3. The optimal combination of hardness and dynamic crack resistance after heat treatment of specimens is attained in hypereutecoid alloy steels when the carbon content is slightly higher than the eutectoid concentration. This has to do with the complete dissolution of excess cementite and the formation of special globular carbides. The same combination of properties can be ensured in steels with higher carbon content by raising the degree of alloying of the steel with carbide forming elements.

When cast irons containing ledeburitic cementite are heated, the peripheral regions of the inclusions are decarburized as a result of the diffusion of carbon to the surrounding metal, and the chemical composition of the carbide M3C deviates from stoichiometric. This is manifested by the formation of microrelief on the surface of the inclusion of ledeburitic cementite, in which the layered structure within a single monocrystal of cementite has practically a single preferred direction. The development of microrelief and the formation of baikovite have much in common.

1. Manganese lowers the solubility of carbon in the melt, while austenite raises the eutectic equilibrium temperature and shifts the eutectic point toward lower carbon concentrations. 2. With a high manganese concentration in cast iron the shift of the eutectic point leads to a sharp change in the ratio of phases and their composition. The amount of cementite is insufficient for the formation of a dense matrix, and it is possible for the eutectic to grow as a conglomerate of phases with a predominance of austenite. 3. By refining of the conglomerate structure (by increasing the solidification rate, e.g.) in combination with heat treatment it is possible to isolate carbide inclusions in the austenite matrix from each other, which provides a combination of mechanical properties unusual for cast iron (strength, ductility, and toughness). 4. Under conditions of nonequilibrium eutectic solidification the austenite in manganese cast irons is highly supersaturated with carbon and manganese. The decomposition of supersaturated austenite at high temperatures leads to formation of a pearlite-like component consisting of platelets of cementite containing manganese and interlayers of austenite. At low temperatures (during tempering after quenching, e.g.) this austenite ages, with a precipitation hardening effect.

1. The retained austenite in quenched steel R9M4K8 has a smaller lattice constant, which increases during tempering. This is evidently due to elastic compression of the austenite lattice during the martensitic transformation and the subsequent reduction of elastic deformation of austenite during tempering resulting from stress relaxation. 2. No stable cementite is observed in quenched steel R9M4K8. It appears after tempering for 1 h at 350–600°. This may indicate a substantial change in the properties of carbides of the cementite type formed in the presence of high-carbon martensite and austenite in the elastically compressed condition. The higher strength and toughness of quenched steel R9M4K8 in comparison with other high-speed steels are evidently due to the absence of cementite. 3. Intermetallic phases of the Laves type are observed in the steel in all structural conditions. 4. Special carbides of the MC (VC) and M2C (Mo2C) types are precipitated during tempering of steel R9M4K8. Highly dispersed M6C carbides are observed after tempering at temperatures above 650°, and thus M6C is a weakening phase. 5. After the optimal heat treatment (quenching from 1220°, austenite grain size grade 10–11, triple tempering at 560° for 1 h), ensuring the maximum hardness, strength, and toughness of steel R9M4K8, the structure consists of highly alloyed (∼7.3% alloying elements) twin-dislocation martensite, excess carbides (not dissloved during quenching) of the M6C and MC types, intermetallic phase of the Laves type (∼8.7%), and dispersed special carbides of the MC and M2C types with a size of order 50 A and M3C in the form of platelets with a length of 1000–5000 A and thickness 100–700 A (∼5.0% in all).

1. In analyzing the deformation curves of cast irons with a ledeburite eutectic based on vanadium supersaturated and chromium alloyed cementite and of normal white irons a difference including oscillation of the flow stress was observed. 2. In addition to relaxation stresses in the matrix the character of the yield curves is determined by the phase transformations in the alloyed cementite occurring during deformation. 3. Plastification of the cementite as the result of the carbide transformation causes an increase in the total plasticity of the iron. The level of plasticity obtained makes it possible to work chrome-vanadium iron by rolling on reduction mills. 4. As economically alloyed cast irons with a plasticity imparted by the carbide transformation (PICT-irons) for production of rolled bars hypoeutectic while irons containing less than 5% carbide-forming elements may be recommended. 5. A method for production of rolled bars of white irons was developed. 6. Work rolls of wrought cast iron were produced and introduced on a 20-roll cold rolling mill. Their life was three and more times longer than of those produced from 9KhFSh steel.

1. The pearlitic transformation of austenite is a two-stage process: the first stage is associated with the formation of the phase that controls the growth of the pearlite column — cementite; the formation of ferrite and a thickening of the cementite plates occur in the second stage. Both stages are separate in time. 2. The formation of upper bainite consisting of a cementite skeleton and ferrite envelope, the latter forming by diffusionless means from decarbonized austenite, occurs within a narrow temperature interval (500–400°C). 3. Acicular (lower) bainite forms below 400°C via segregation of disperse cementite inclusions with their subsequent envelopment by martensite. The martensite is decarbonized by means of diffusion, transforming into ferrite. 4. At temperatures below 240°C, the occurrence of the diffusionless transformation of austenite of initial composition is possible in eutectoid steel. The martensite that forms during sufficient isothermal holding may decompose in accordance with two mechanisms: with the segregation of cementite (the formation of lower bainite), and with the segregation of e-carbides inaccordance with the mechanism of spinoidal stratification (the formation of temper martensite). 5. All of the transformations that we have enumerated are reflected in diagrams of the isothermal decomposition of austenite, which have been constructed schematically for eutectoid, subeutectoid, and transeutectoid steels. A second region of pearlitic transformation, which expands with increasing carbon content in the steel, is located on these diagrams between the curves of the upper and lower bainite.

1. After austenization at 1150°C and quenching in oil, precipitation of clusters enriched in Cr and C occurs in the austenite of high-chromium ledeburitic steel. With tempering temperature increasing up to 300°C the number of clusters increases, and at the same time they start to transform into alloyed cementite (Cr, Fe)3C. The transformation proceeds at temperatures above 400°C. At that time the cementite particles grow and their number decreases. During a single tempering at 520°C, the particles become almost-completely dissolved in the austenite. 2. The processes of particle precipitation in austenite influence its mechanical properties. Increasing the number of particles in austenite at tempering temperatures up to 300°C increases the microhardness and the fracture toughness. Fracture toughness decreases with increase of size and distance between the particles. 3. Variation of the number of clusters and cementite particles with tempering temperature is the main reason for the thermal stability of residual austenite in the steel studied. Cementite instability, and its dissolution in austenite at 520°C, causes the secondary transformation into martensite during the cooling process.

1. The flame produced by burning propane—butane and acetylene in oxygen is stable, has a high carburizing capacity, and is suitable for high-temperature carburizing. 2. The structure of the flame depends on the ratio of acetylene and propane—butane, and the ratio of oxygen and the gas mixture. The heating and carburizing capacity of the flame increases with the percentage of acetylene in the mixture. 3. During carburizing with a gas—oxygen flame the gaseous phase has the highest carburizing potential, not attainable with other methods of carburizing, which leads to formation of a case beginning from the surface of the ledeburite zone. 4. The process of flame carburizing is divided into two time periods — a short first period characterized by a high rate of carburizing and a second period of relatively slow carburizing. 5. The carbon concentration in the case can be controlled by changing the carburizing capacity of the flame.

1. As the solidus temperature is approached the fracture of high-carbon carbide steels occurs due to the solution of carbides, saturation of the solid solution with carbon, and the formation of carcks in sections rich in carbon. Internal oxidation of the boundaries was not observed. 2. Overheating of alloy steels with 1.2–2% C above the temperature at which the boundaries melt can be corrected by cooling the overheated ingots 10–50° below the maximum permissible temperature. After holding at this temperature, the structure is more suitable for deformation, and the plasticity is restored and even improved.

1. With quenching of white synthetic cast irons (Fe−C and Fe−C−Cr) from temperatures up to 1000°C the cementite lattice is distorted, the volume of the unit cell decreases, the carbon content decreases, and the microhardness increases considerably. The phenomenon is reversible, and the observed effects of the hardening of cementite are removed by high-temperature tempering. 2. The fact that the results contradict earlier results can be explained by the completing processes — the effect of hardening of the carbide phase and the initial stages of graphitization occurring at high temperatures, particularly in commercial cast irons containing silicon. 3. The investigation confirmed Baikov's assumption that cementite is a phase of variable composition. With increasing temperatures cementite approaches austenite in its carbon concentration and the chains of octahedral cells of the iron sublattice.

1. Cementite is enriched with manganese during graphitization annealing of white cast iron. 2. The change in the manganese content of cementite had no effect on the microhardness and is not accompanied by phase reconstruction. 3. The graphitization process during annealing of cast iron results from the dissociation of cementite directly, without formation of any intermediate carbide.

The use of high rates of heating makes it difficult to dissolve the excess cementite in U12 steel. Complete solution of cementite and saturation of austenite with carbon can be attained only by soaking at high temperatures.