Low-temperature cyaniding of cylinder block sleeves

Conclusions We recommend the following heat treatment for the cylinder sleeves of certain tractor and automobile engines; it ensures a high wear resistance and does not induce warping: a) annealing for stress relief, with heating at 75–100 deg/h to 580–600°C, soaking, cooling at the rate of 40–50 deg/h to 200°C; final machining, including honing; b) gas cyaniding 6 h at 560–580°C in a medium of 70% carburizing gas and 30% ammonia.Bauman MVTU, Moscow Automobile Plant. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 60–62, July, 1967.     

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.     

Heat treatment of two-layer plates of St. 3 steel cladded with high-chromium stainless steels 0Kh17T and Kh25T

Conclusion The optimal heat treatment for bimetals, guaranteeing the mechanical properties specified in GOST 10885-64 and the possibility of shearing and cold straightening, was a multistage treatment consisting of heating to 830–850°C, soaking 20–30 min, slow cooling to a temperature below Ac₁, and quenching in water. This treatment can be replaced by a double heat treatment consisting of normalization at 830–850°C followed by quenching in water from 650–700°C.TsNIIChERMET, Chelyabinsk Metallurgical Plant. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 68–70, April, 1968.     

Extreme diffusional activity in steel in a state of transformation

Conclusions The pretransformation state in steel is characterized by an increased diffusional activity of the iron atoms. The temperature range of this state may be utilized for plastic deformation and heat treatment in steels. The diffusional mobility of the atoms and the plasticity of the steel in the pretransformation state (at 700–720 and 780–800°C for carbon and high speed steel, respectively) are approximately the same as those at 1100–1200°C.Utilization of the pretransformation state for technological purposes permits economies in the use of energy, due to the decreased process temperatures.The narrower temperature interval for commercial processing (±3–5°C) should not be an obstacle to its use in practice, since presently existing equipment permits temperature regulation with an accuracy up to ±1°C.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 13–15, July, 1990.     

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.     

Increasing the relaxation resistance of heat resistant Ni−Cr alloys by conditioning

Conclusions The effect of repeated loading (conditioning) in the first period of relaxation on the relaxation resistance of heat resistant Ni–Cr alloys depends on the working temperature. At 750–800°C the effectiveness of this treatment is adequate for practical use (although it is smaller than at 700–725°C). At temperatures up to 850°C conditioning cannot prevent the intensive relaxation weakiening that is characteristic of Ni–Cr alloys at this temperature.Central Scientific-Research Institute of Ferrous Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 53–57, October, 1972.     

Carburization of 310 stainless steel exposed at 800-1100 °C in 2%CH4/H2 gas mixture

Carburization of 310 stainless steel has been investigated after cyclic exposures at high temperatures 800-1100 °C in a 2%CH₄/H₂ carburizing gas mixture for 500 h duration. A thermodynamic analysis indicates that 1000 °C is an approximate boundary temperature, below which the environment should result in mixed oxidizing/carburizing behavior, while above this temperature reducing/carburizing behavior should occur. The experimental results agree well with the thermodynamic analysis. Below 1000 °C, 310SS suffered external carburization, oxidation, and internal carburization. In excess of 1000 °C, extensive external carburization occurred and internal Cr-carbides disappeared. Cr segregation is proposed to interpret the effect of temperature on the continuity of an external scale layer and carburization behavior.     

Recommended heat treatment for case hardened parts made of 18KhNVA steel

Conclusions The optimum heat treatment conditions for case hardened 18KhNVA steel resulting in a stable hardness HRC>60 are quenching from 780–800°C in oil or air and subsequent treatment at –70°C for 20–30 min followed by tempering for 2 h at 150–160°C.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, p. 47, June, 1964     

Improving the strength properties of steels by vanadium nitride case-hardening

Conclusions To attain an effective increase of the strength properties of steels 40AF and 45AF, it is necessary to lay down rules for the content of vanadium within the limits 0.08–0.12%, of nitrogen 0.012–0.018%, of residual aluminum not more than 0.015%, normalizing and hardening temperature within the limits 940–960°C, tempering temperature 570–600°C.Foundry Institute (IPL), Academy of Sciences of the Ukrainian Production Association ZIL. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 55–58, April, 1984     

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.     

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.     

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.     

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.     

Low-temperature heat treatment of high-strength cast iron articles

Conclusion For cast components of high-strength cast iron containing 2.9–3.7% C and 3.5–4.7% Si, instead of the normally used high-temperature heat treatment (920–950°C), it is possible to recommend low-temperature heat treatment (normalizing or spheroidizing anneal at 725°C), which provides the required set of mechanical properties and good workability.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 63–64, September, 1985.     

High-temperature oxidation and spalling behavior of incoloy 825

Incoloy-825-sheet specimens were exposed to four different atmospheres; steam, synthetic air, CO₂, and CO₂ diluted with argon. The duration of exposure was varied from 2 min to 100 hr in the temperature range of 600–1300°C. A comparison of the results in these four atmospheres showed the maximum weight gain in specimens exposed under steam, while the minumum value was obtained in specimens subjected to diluted CO₂. The alloy obeyed similar reaction kinetics while exposed to all the atmospheres under consideration. The overall domination of parabolic rates was observed at 800–1000°C. For still higher temperatures, a transition from the parabolic to the cubic rate law was observed. Thermal cycling did not show any appreciable effects on the reaction kinetics of the alloy when specimens were cycled between test temperatures and 500°C, and finally cooled to ambient temperature.     

Effect of Carbon on the Long-Term Oxidation Behavior of Fe3Al Iron Aluminides

Electroslag, remelted-iron aluminides having the compositions: (1) Fe–16Al–0.05C, (2) Fe–16Al–0.14C, (3) Fe–16Al–0.5C, and (4) Fe–16Al–1.0C were investigated to understand the effect of carbon on their oxidation behavior in the temperature range 700–1000°C. The oxidation behavior of these aluminides was compared with that of 310 SS, a reference alloy used in the study. Regardless of carbon content, the iron aluminides exhibit marginally higher oxidation tendency than that of 310 SS at 700°C. However, between 800 and 1000°C, they exhibit better oxidation resistance than 310 SS. Although the oxidation resistance of aluminides at 1000°C is better than that of 310 SS, they suffer severe spallation during long-term exposure and C exacerbates this effect. Examination of the early stages of oxidation of the alloys at 800 and 900°C shows that they do not gain a corresponding weight as they do for a temperature rise from 700 to 800°C. A further rise to 1000°C leads to a marginal inversion in the oxidation tendency of the alloys. Based on the literature, this inversion is attributed to the possible dissolution and/or change in compo- sition of Fe₃AlC_0.69 carbide phase with temperature.     

The oxidation resistance of a sputtered,microcrystalline TiAl-intermetallic-compound film

The oxidation behavior of a cast TiAl intermetallic compound and its sputtered microcrystalline film was investigated at 700–900°C in static air. At 700°C, both the cast alloy and its sputtered microcrystalline film exhibited excellent oxidation resistance. No scale spallation was observed. However, at 800–900°C, the oxidation kinetics for the cast TiAl alloy followed approximately a linear rate law, which indicates that it has poor oxidation resistance over this temperature range. The poor oxidation resistance of TiAl was due to the formation of an Al₂O₃+TiO₂ scale which spalled extensively during cooling. Nevertheless, the sputtered, TiAl-microcrystalline film exhibited very good oxidation resistance. The oxidation kinetics followed approximately the parabolic rate law at all temperatures. Although the composition of the scales was the same as that of scales formed on the cast alloy, the scales formed on the sputtered microcrystalline-TiAl film are adherent strongly to the substrate. No scale spallation was found at 700–850°C, while a small amount of spallation was observed only at 900°C. This indicates that microcrystallization can improve the oxidation resistance of the TiAl alloy.     

Heat treatment of cast aluminum alloys obtained by application of regulated pressure during crystallization

conclusion For castings of AK8 alloy obtained by application of regulated pressure during crystallization, we recommend the following heat treatment conditions: homogenization at 460–470°C for 8 h, quenching from 505–510°C, aging at 150–170°C for 3.5–4h. After treatment according to this procedure, a hardness of 72–74 HRB is achieved for the alloy.Vladimir Polytechnical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 36–39, October 1992.