Die steels for high-speed automatic hot die forging machines

Conclusions Steel 3Kh3M3F produced by ESR has the best combination of strength, hardness, and toughness, and also resistance to crazing. The life of punches made of this steel was double that of standard steel 3Kh2V8F and considerably higher than that of steels with a higher carbon content (0.4–0.5%).The life of 3Kh3M3F punches (ESR) was three to four thousand bearing races higher than that of the same steel melted in an open furnace.These data lead us to recommend that punches for high-speed water-cooled presses be manufactured from steel 3Kh3M3F (ESR) with the following chemical composition: 0.26–0.34% C, 2.8–3.3% Cr, 2.5–2.9% Mo, 0.40–0.60% V (ChMTU-1-963-70).The following heat treatment is recommended: preliminary heating in an electric furnace at 500–510°, salt bath at 850–860°, and salt bath at 1040±10°. The parts should be quenched in oil with a temperature of 120–150°. The first tempering after quenching should be conducted in a salt bath at 600° for 2 h, with cooling in air. The second tempering should be conducted in a salt bath at 560° for 2 h, with cooling in air. The hardness of the parts after heat treatment is HRC 49–51.All-Union Scientific-Research Institute of the Bearing Industry. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 20–25, November, 1973.     

Effect of heat treatment on corrosion cracking of high-strength steels

Conclusion The susceptibility of steel to corrosion cracking depends to a large extent on the tempering temperature. With increasing tempering temperatures the susceptibility of oil-quenched steels decreases. At the tempering temperature at which preferential martensite decomposition occurs in former austenite grain boundaries one observes an increase of the susceptibility to corrosion cracking. For steels 30Kh-GSA, 30KhGSNA, and 25Kh2GNTA this increased susceptibility occurs on tempering at 250°C, for steel ÉI643 at 400°C, and for steel D at 450–500°C.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 45–48, February, 1968.     

Effect of heat treatment on cyclic-wear resistance of steel shot

Conclusions After heat treatment consisting of heating in a protective atmosphere to (780–830)±20°C depending on the shot size, water-quenching, and medium-temperature tempering at 360±20°, the cyclic wear resistance of the steel shot increases from 30–50 cycles (in the as-cast condition) to 450–500 cycles. The shot microstructure changes from coarse martensite to a mixture of troostite and fine martensite.Kommunarskii Metallurgical Works. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 60–61, August, 1986.     

Effect of tempering at subcritical temperatures on the fracture strength of medium carbon structural steel

A special pretransformation state in steels is of considerable interest and importance for practical application.Difficulties arising from the necessity for precise temperature regulation have already been overcome incontemporary heating equipment. In this article certain features of this pretransformation state are explainedor confirmed, and the utility of its application in heat treatment is described.Bardin Central Scientific Research Institute for Steel Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 10–13, August, 1992.     

Instrument for measuring and controlling the carbon potential of products of incomplete combustion in fluidized beds

Conclusion The instrument permits continuous measurement of the carbon potential of the atmosphere resulting from incomplete combustion of hydrocarbons in a fluidized bed. The accuracy of the measurements is ±0.02% C and the limits of measurement are 0.1–1.0% C. The operating range of the instrument is from 830 to 1000°C. It can be used as a primary instrument for automatic control of the carbon potential by changing the fuel-air ratio.Urals Polytechnical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 28–31, November, 1971.     

Oxidation of Low-Carbon,Low-Silicon Mild Steel at 450–900°C Under Conditions Relevant to Hot-Strip Processing

The oxidation behavior of a low-carbon, low-silicon mild steel was investigated in ambient air at 450–900°C to simulate steel strip oxidation during finishing hot rolling and coiling. Oxide scales developed at 880–900°C for a very short time (12 sec) had a structure similar to that formed on pure iron, but with a greater thickness ratio between the magnetite and wüstite layers. However, the scale structure after oxidation for a longer period (200 sec) at 900°C deviated significantly from that reported for pure iron. This difference was attributed to the loss of scale–steel adhesion at some locations. Oxide scales formed in the range of 580–700°C after oxidation for more than 2 hr also differed from those reported for pure iron. The scale structures were irregular, comprising mainly hematite and magnetite with no or very little wüstite, while the thickness ratio of these two layers differed considerably at different locations. The scale formed at 450–560°C was relatively uniform with a two-layered (hematite and magnetite) structure; however, the thickness ratio of these two scale layers varied for different oxidation temperatures and different oxidation durations. It was also found that limited oxygen supply (zero air flow) improved the scale–steel adhesion, and substantially reduced the relative thickness of the hematite layer. Continuous-cooling experiments proved that significant growth of the hematite layer, as well as the entire scale layer, may occur if the steel is cooled slowly through the temperature range 600–660°C, and even more significantly through the range 660–720°C.     

Nature of the red-shortness of steel

Conclusions The red-shortness of steel is caused by sulfide and oxysulfide nonmetallic inclusions, the types of which are determined by the composition of the steel. The melting points of the inclusions are FeS–FeO 980°C, (Fe, Mn)S–FeO 1120°C, (Fe–Mn)S–FeS 1050°C, (Fe, Mn, Cr)S–(Fe, Mn)S 1190°C, and (Fe, Mn, Cr)S–FeO 1250°C. At lower temperatures the eutectic inclusions are plastic but the development of their deformation and failure is determined by the temperature and degree of plasticity of the surrounding steel matrix, which determine the critical parameters of fracture development.Dnepropetrovsk Metallurgical Institute. Moscow Institute of Steel and Alloys. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 11–15, October, 1984.     

Effect of heat treatment on the properties of deformed alloy 36N

Iron-nickel alloy 36N (Invar) is widely used in industry as a material having an anomalously low and almost constant thermal coefficient of linear expansion (TCLE) in the temperature range of 20 – 100°C. This value of the coefficient is attained after heat treatment of the deformed semifinished product by the regime of quenching from 830°C in water, tempering at 315°C for I h, and aging at 95°C for 48 h. The minimum value of the TCLE is provided by the quenching operation, whereas the tempering and aging prevent growth of the TCLE during long-term operation of Invar. The use of such heat treatment for rods and wire of alloy 36N guarantees a TCLE of at most 1.5 × 10^–6 °C^–1. It is known that the value of the TCLE and the level of the mechanical properties of Invar can be changed by changing the temperature and deformation regime of its treatment. The aim of the present work is to determine an optimum regime of heat treatment of the alloy after drawing that would ensure, without a finishing treatment, a TCLE not exceeding 1.0 × 10^–6 °C^–1 in the temperature range 20 – 100°C.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 31 – 32, April, 1996.     

Strength and plasticity of steel VNS-17 at low temperatures

Conclusions In the hot-rolled condition steel VNS-17 has a fairly high plasticity and is not sensitive to sharp notches at testing temperatures from room temperature to –253°C. After welding with or without filler wire steel VNS-17 can be used at temperatures down to –196°. In the presence of a sharp notch the strength of welded joints at –253 and –269° is higher than at room temperature.Physicotechnical Institute of Low Temperatures of the Academy of Sciences, Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 7–9, March, 1971.     

Effect of alloying elements on the structure of cast hypereutectoid steels after heat treatment

Conclusions In selecting a treatment schedule providing uniform distribution of carbides in cast hypoeutectic steels for rolls it is necessary to take account of the fact that the cementite network along grain boundaries dissolves in the temperature range 850–950°C. In steel with a low content of carbide-forming elements eutectic cementite does not dissolve at these temperatures. As the heating temperature is increased from 850 to 1100°C intense surface graphitizing commences, which points to the possibility of forming graphite inclusions with bulk heat treatment. With an increase in the content of chromium and molybdenum in steel the graphitizing process is suppressed, and carbon is bonded into stable carbides. In such a steel eutectic carbides dissolve at 1050–1100°C. Preparation of a structure with uniform carbide distribution during heat treatment is only possible in steels containing about 2% Cr and not less than 0.3% Mo.Ukrainian Research Institute of Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 62–64, August, 1987.     

Reasons for the suppression of temper brittleness in steels with rapid electric tempering

The phenomenon of first-order temper brittleness, which is defined by a reduction in impact strength, by an increase in the ductile-brittle transition temperature, and by an increase in the proportion of the brittle component in a fracture, is observed in steels after tempering in the range 350–500°C. For steels inclined toward temper brittleness, it is recommended that during traditional heat treatment low-temperature (200–250 °C) and high-temperature (550–600°C) tempering is used which may not always provide the optimum combination of strength and ductility properties. Features are considered in the present work for the effect of rapid tempering on the properties of steel 30KhGSA.Institute for Metal Physics, Ukrainian Academy of Sciences, Kiev. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 15–17, February, 1994.     

Cooling capacity of molten salts and alkalis containing water

Conclusions The method of cooling molten salts and alkalis in austempering and martempering by adding water to the bath at any temperature, which was developed and put into operation at the Gor'kovskii Metallurgical Plant, guarantees: 1) a constant temperature of the bath within limits of ±5°C; 2) constant amount of water in the bath, which increases the cooling capacity four to five times; 3) prevention of "aging" and elimination of the necessity of renewing the molten salts; 4) the use of austempering and martempering for tools, machine parts, rolled steel (including railroad rails) in place of ordinary oil-quenching to martensite with subsequent tempering.Gor'kovskii Metallurgical Plant. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 58–62, November, 1967.     

The internal-nitriding behavior of 310 stainless steel with and without Al and Ti additions

The internal-nitriding behavior in ammonia-hydrogen atmospheres of type-310 stainless steel and 310 to which either 2 wt.% Ti or 3 wt.% Al were added was studied over the range of 550–950°C. An Fe-24Cr binary alloy was included to assess the role of a BCC crystal structure vs the FCC crystal structure of 310 stainless steel. The BCC alloy exhibited the most rapid kinetics as expected. X-ray diffraction showed only the presence of CrN in all the alloys up to 735°C. At 850°C and above, both CrN and Cr₂N were detected. The nonformation of TiN and AlN at lower temperatures is attributed to nucleation problems. Precipitates were extremely fine (unresolvable even at 20,000×) at 563°C and became much coarser with increasing temperature. The precipitate density, size, and shape varied across the internal-nitriding zone at the higher temperatures. External scaling was noted at 850°C and above, however, it was not a continuous film. The activation energy of internal nitriding from 563–735°C ranged from 3.8 kcal/mol for 310+2Ti to 18.2 kcal/mol for 310+3Al; from 850–950°C, the activation energy ranged from 44 (310+2Ti) to 56.6 kcal/mol (310+3Al). Microhardness profiles show that an intermediate zone exists between the nitride case and the base metal. The origin of this zone is discussed.     

Heat Treatment of Cast Carburizing High-Speed Steel Alloyed with Ti, Nb, and V

Special features of the structure and phase composition of cast carburizing high-speed steel of the ferrite-carbide class and the laws of their variation in the process of the carburizing hold and subsequent heat treatment are described. The temperature of heating for quenching was varied within 1180 – 1220°C, and the tempering temperature was varied within 560 – 640°C using the hardness and heat resistance as criteria. The results of mechanical tests of heat treated steels are analyzed.     

Effect of boron on ductility of austenitic Cr−Ni−Mn steel with nitrogen

Conclusions Microalloying of Cr–Ni–Mn steel with boron in amounts of 0.002–0.005% (nominal) increased the ductility at 900–1100° by 100–125%, making it insusceptible to hot shortness. This improves the deformability of the ingots and slabs. With an increase of the boron concentration from 0.005 to 0.10% the ductility of the steel is greatly impaired at temperatures above 1100°.In view of the susceptibility of the steel to overheating at temperatures above 1260°, the optimal temperature for heating the ingots is 1240–1260° on condition that they be held in the range of 1200–1220° in the first stage of heating.I. P. Bardin Central Scientific-Research Institute of Ferrous Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 67–69, August, 1975.     

Heat treatment of steel castings in a chamber furnace

Conclusions Forced heating permits even heating of the entire load, the temperature differential at the end of heating amounting to 20–25°C. The heat transfer conditions are greatly improved and the heating time is shortened 40%.West Siberian Metallurgical Plant. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 75–77, October, 1969.