Formation of the microstructure and properties of heat-hardenable steels of the 15G2MFTR type in isoscleric tempering

An optimur set of properties in heat-hardenable high-strength weldable steels of the 15G2MFTR type is attained after quenching and tempering at 650–680°C for I h. The tempering operation (to a specified level of strength) can be intensified by a certain increase in the heating temperature, thereby decreasing the hold time, which makes the heat treatment less expensive. This work concerns the possibility of replacing the standard tempering regime for steels 15G2MFTR and 15G2KhNMFTR by an accelerated tempering at a higher temperature.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 6 – 9, June, 1996.     

Tendency of steels 10KhSND and 09G2S towards brittle failure

Conclusions The tendency towards brittle failure of low-alloy steels type 10KhSND and 09G2S at low temperatures depends on the supply condition. The highest resistance to brittle failure occurs for steel after temper hardening, i.e., quenching and high-temperature tempering. A changeover into a brittle condition for temper hardened steels of the test melts commences at –60°C, and for hot-rolled steels it commences at –40°C."Kompozit." Scientific-Production Organization. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 14–16, May, 1993.     

Tungstenless high-speed steels 12M5F3SYu and 11M3F3SBTs

Conclusion Both investigated steels are characterized by reduced red hardness in the temperature range not causing fusion; this does not ensure the required resistance of the tools.Increasing the holding time at the hardening temperature by a factor of 1.2–1.5 does not help increase hardness and red hardness.Combined tempering at three different temperatures (350+570+550°C) has no advantages over ordinary threefold tempering at 560°C.Both investigated steels are characterized by good mechanical properties which practically do not depend on the hardening temperature in the range 1170–1190°C. Good mechanical properties are ensured with grain sizes up to No. 6.On the basis of metallographic investigations and cutting tests it was established that the experimental steels are not equivalent to steel R6M5.Production Association "Kirovskii Zavod." Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 6–8, August, 1988.     

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     

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.     

Reversible temper brittleness in heat treatment of large forgings

Conclusion The results of the investigation of the kinetics of temper brittleness of steels with a view to the structural state and the theoretical data on the real distribution of characteristics of resistance to brittle and ductile failure over the cross section of parts make it possible to devise rationally alloyed steels and regimes of high tempering ensuring the required complex of properties and improved operational reliability.TsNIIM, Sverdlovsk. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 16–20, April, 1990.     

复合金化低碳SiMn3型贝氏体钢的组织与性能研究

研究了符合我国资源特点的复合金化低碳SiMn3型贝氏体钢在不同热处理状态下的组织与性能。结果表明：该类钢空冷获得粒状贝氏体并具有良好的强韧性;空冷后中低温回火具有最佳强韧性组合;空冷后高温回火产生回火脆性。     

Combined thermal and mechanical treatment of molybdenum steels 15M and 12Mkh

Summary Steel 12MKh has a somewhat greater rupture strength than steel 15M, after the same treatment.Steel 15M has the worst combination of mechanical properties after strain hardening followed by heating for 90 minutes at 250°C (480°F).The treatments which pipes of these steels undergo in fabrication do not lower their properties to an extent to make these treatments unacceptable.As a result of the treatment during fabrication and erection, these steels acquire very high rupture strengths at 480°C (895°F) and suffer comparatively little loss of elongation at rupture.It is recommended that the final heat treatment of the steels should be tempering, or normalizing and tempering. This will stabilize the structure and properties and improve the plasticity under creep-rupture conditions.     

The destructive mechanisms in high-strength steels under the effect of impurities

An increase in the strength of the existing high-strength medium-carbon steels is accompanied by a decrease in their ductility and plasticity, which reduces the reliability of structures from these materials and limits the possibility of decreasing the mass of aircraft parts and raising their efficiency. A way to improve the ductility parameters of steels consists of decreasing the content of impurities in them. In order to correctly ascertain the admissible content of impurities and estimate their effect on the properties of steels, we should study the mechanism of the influence of impurities on the destruction processes in high-strength medium-carbon steels. It is a common practice to associate the effect of impurities with the reversible temper brittleness.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 15–19, January, 1995.     

Heat treatment of corrosion resistant chromium-molybdenum steels

Conclusions Quenched chromium-molybdenum steels retain their strength almost intact after tempering at temperatures up to 500°C. Only at temperatures above 500°C does the metal begin to lose its strength This loss of strength is due to the precipitation and coagulation of the carbide phase from the martensite.Central Scientific Research Institute of Ferrous Metallurgy Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 49–51, May, 1964     

High-strength structural steels with a structure of low-carbon bainite subjected to thermomechanical treatment

Conclusions The development of TMT for low-pearlite and pearlite-free steels has led to the development of steels containing 0.06% C, 1.8% Mn, 0.3% Mo, and 0.05–0.09% Nb. Depending on the type of TMT, the most important parameters of which are the final rolling temperature and the total deformation at temperatures below 900°, the transformation occurs partially or completely in the intermediate region. The high dislocation density of the bainite has a substantial effect on the increase of the yield strength.Large rolling reductions at temperatures below 870° favor the formation of ferrite nuclei. The polygonal ferrite formed in this case has a characteristic grain size of grade 13–14.Rolling under laboratory conditions showed that by selecting the conditions of TMT one can control the mechanical properties of the steel. A guaranteed yield strength of 70 kgf/mm² and transition temperature T₅₀=–25° can be obtained on plates 13 mm thick, while after rolling under other conditions the ductile-brittle transition temperature is –125° and the yield strength 45 kgf/mm². Numerous production tests indicate that a yield strength of at least 50 kgf/mm² in the hot rolled condition can be obtained for plates 20 mm thick. In rolling mills permitting substantial reduction at low temperatures these values can be improved. For example, a yield strength of 56 kgf/mm² and transition temperature of –60° can be obtained for plates 30 mm thick. The steel has substantial reserves of strength due to precipitation hardening, which amount to 8–12 kgf/mm² after tempering at 600–625°. The weldability of the steel is good due to its low carbon content.Stahl und Eisen,93, No. 22, 1041 (1973).Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 11–18, December, 1975.     

Temper brittleness of cast steel

Conclusions Cast alloy steels of the Cromansil type are susceptible to reversible temper brittleness. Brittleness at these temperatures can be prevented by alloying with molybdenum or tungsten.Reversible temper brittleness in cast steels can be completely prevented only by alloying with additional elements and martempering.Institute of Casting Problems. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 21–22, November, 1966.     

回火温度对不同淬火处理0.6C超级贝氏体钢组织及性能的影响

分析了不同回火温度下等温盐浴和淬火-配分-回火(Q-P-T)工艺处理0.6C超级贝氏体钢的微观组织和力学性能。结果表明:经230 ℃×10 h+320 ℃×7 h两步法等温淬火处理后,试样在360~500 ℃温度区间出现明显的第二类回火脆性,而Q-P-T试样回火脆性温度区间为450~470 ℃,经Q-P-T工艺处理后,回火脆性温度区间明显变窄,试样力学性能全面提高。利用SEM、TEM、XRD等手段对显微组织进行表征,揭示了Q-P-T试样优于等温处理的两个主要因素:经Q-P-T工艺处理后,微观组织更为细化,随着亚晶界的增多,组织稳定性进一步增强,碳化物晶界偏聚受到阻碍,难以连接成网状,故经Q-P-T工艺处理后试样第二类回火脆性区间极大缩小;经Q-P-T工艺处理后薄膜状残留奥氏体含量增大,奥氏体更为稳定,有利于减弱第二类回火脆性的影响。     

Evaluation of temper softening behavior of Fe–C binary martensitic steels by nanoindentation

The temper softening behavior of Fe–C binary martensite with various carbon contents was considered by evaluating the matrix strength through nanoindentation. The tempering temperature dependence of conventional micro-Vickers hardness shows a “hump” around 673 K, while the matrix strength obtained by nanoindentation simply decreases with tempering temperature.     

两相区淬火+回火对600 MPa级低合金高强钢组织与性能的影响

对某600 MPa级低合金高强钢采用了淬火+回火的热处理方式,研究了不同回火温度以及不同淬火温度对其组织性能的影响。结果表明,随着回火温度的升高,屈服强度、抗拉强度以及屈强比都呈下降趋势,伸长率逐渐上升,在620 ℃以上回火时出现第二类回火脆性,导致冲击性能急剧降低;在淬火温度达到820 ℃后得到的两相区淬火组织为铁素体+粒状贝氏体,有利于阻止裂纹的扩展,确保有较高的冲击性能。     

淬火钢的高温快速回火工艺

采用高温快速回火方法,对40Cr钢及45、T10钢进行了高于Ac1以上温度的高温回火试验,并与传统回火工艺进行了比较,建立了高温回火时间与传统回火温度的对应关系.试验结果表明用高温快速回火后,其组织和力学性能与传统工艺回火后的基本相同,且所用的回火时间可以大大缩短,并可以避免回火脆性.     

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.     

Temper brittleness of structural manganese steel microalloyed with V, Mo, B

The effect of V, Mo, and B on the development of reversible temper brittleness in manganese steels having various contents of phosphorus is investigated. Special features of the embrittlement mechanism in tempering the steel at 500–550°C are described. Recommendations are given for expedient alloying and regimes of heat treatment of high-strength weldable steels. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 12, pp. 25–28, December, 1998.