提高渗碳淬火齿轮硬度的后处理工艺

研究了20Cr2Ni4A钢渗碳淬火齿轮在低温回火后硬度较低时进行后冷处理和后低温回火处理对表面硬度、有效硬化层深度及心部硬度的影响。结果表明,20Cr2Ni4A钢在渗碳淬火低温回火后的残留奥氏体稳定化现象并不明显,此时进行冷处理仍能提高工件硬度,而当残留奥氏体较多时具有低温回火二次硬化现象,提高低温回火温度也能提高表面硬度。据此可采用后冷处理和后低温回火工艺提高硬度,代替常规的重新高温回火+渗碳淬火+低温回火的返工工艺。后冷处理温度可根据Mf点确定,对于渗碳后高温回火并重新加热淬火和低温回火工艺,Ms和Mf点不能按常规方法计算,可根据残留奥氏体含量进行估算。     

Cr-W-Mo-V中合金钢的淬火硬度计算及其回火硬度特性

研究了4种不同成分的Cr-W-Mo-V中合金钢的淬火硬度、回火硬度变化和组织结构转变.在淬火基体成分计算的基础上提出了该钢淬火硬度与某一淬火温度下奥氏体基体化学成分关系的近似计算公式.此类钢均具有较高的抗回火性,随着Cr、W、Mo、V含量的增加,不同类型碳化物的沉淀强化可使回火硬度出现低温二次硬化区或平台区,甚至高温二次硬化区.讨论表明,上述淬火硬度计算公式隐含着洛氏硬度测定和马氏体强化机理的对应关系,对其它钢种也适用.     

某型智能柴油机凸轮轴热处理工艺的开发

某型智能柴油机凸轮轴长径比大,热处理技术要求高,生产难度大。为了解决该难点,利用多用炉、真空回火炉、井式渗碳炉、深冷箱、井式回火炉、校直机等设备从技术难点分析、试验摸索等方面进行了研究,认为该凸轮轴通过清洗→防渗→烘干→预热→循环渗碳→高温回火→校直→真空去应力→机加工→淬火→深冷处理→回火等工艺流程,可以生产出硬度高、显微组织好、力学性能高、热处理畸变可控的产品。需要指出的是,多用炉高低碳势多次循环渗碳比传统二段渗碳优势明显,如渗碳速度快、碳化物形态好、硬度高、硬度梯度平缓、渗碳时间短、生产效率高等。采用上述热处理工艺方案,最终加工的样件完全满足用户要求。     

Relation Between Parameters of Cavitation Resistance and Structure of Steels

The cavitation resistance of steels with different initial structure and hardness (05Kh13, Kh18N10T, St 3, VNS17, 07Kh14AG12M, 12Kh13N3G5, 30Kh13, 03N18K8M5T, 30Kh10G10, 95Kh18, 150Kh12M) is studied. Laws of variation of parameters of cavitation resistance are determined as a function of the level of ultimate hardening of the cavitation-affected surface in the final stage of the incubation period under microimpact loading of the studied steels.__________Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 15 – 19, January, 2005.     

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.     

Method to Predict Tempering of Steels Under Non-isothermal Conditions

A common way of representing the tempering responses of steels is with a “tempering parameter” that includes the effect of temperature and time on hardness after hardening. Such functions, usually in graphical form, are available for many steels and have been applied for isothermal tempering. In this article, we demonstrate that the method can be extended to non-isothermal conditions. Controlled heating experiments were done on three grades in order to verify the method.     

Structure and Properties of Low-Alloy High-Nitrogen Martensitic Steels

Special features of structure formation and mechanical properties of low-alloy martensitic steels with superequilibrium content of nitrogen and low content of carbon are considered. Experimental data on the effect of the temperature of heating for hardening and tempering on the structure, strength, and ductility of these steels are presented. The advantages and disadvantages of the introduction of nitrogen into low-alloy martensitic steels instead of carbon are discussed. It is shown that steel 10Kh3A combines high strength with high ductility. This steel is considered as a material for heavily loaded parts and nonwelded structures instead of high-strength steels alloyed with Ni, Mo, V and other expensive and scarce elements.     

Cr-Mo等离子表面冶金高速钢及其性能研究

介绍了在Q235钢表面进行Cr-Mo等离子合金化及渗碳、淬回火和深冷处理而获得表面高性能强化层的技术方法。结果表明，经深冷处理的试样表面硬度达到1600HV，明显高于未经过深冷处理的合金层表面硬度。摩擦磨损实验表明，经不同深冷处理试样的滑动摩擦系数基本相同，但与未经深冷处理的试样相比，摩擦系数降低大约15％。     

提高20Cr2Ni4A钢齿轮渗碳淬火硬度的试验研究

针对20Cr2Ni4A钢制造的中大型齿轮在不允许冷处理的条件下渗碳淬火硬度偏低的问题,通过对渗碳淬火碳势、中间高温回火工艺、淬火温度的优化,在不冷处理的情况下使齿轮硬度提高了2 HRC以上至58~61 HRC,显微组织良好,达到了预期目的。试验发现,该材料渗碳后经过高温回火再重新加热淬火时,为了提高表面及次表面硬度,渗碳扩散碳势、渗碳降温保温阶段碳势和淬火碳势在碳化物不超标的前提下要尽量提高;反复试验与检测证明,中间高温回火也会导致渗碳层一定深度内碳含量的降低,从而影响渗碳淬火硬度,故高温回火时不仅要注意回火不足更要防止过回火,高温回火次数过多时间过长,淬火后硬度不升反降。     

钨钼钇共渗强化层的回火硬度及红硬性

利用双层辉光等离子渗金属技术,在Q235钢表面分别进行钨钼钇共渗与钨钼共渗,形成均匀致密合金扩散层;共渗后,将两种试样分别在960℃、980℃、1020℃下进行8h渗碳及淬火,并在200℃低温回火1h。之后将两者在1 020℃渗碳及淬火,并分别进行200～700℃回火。采用显微硬度仪检测其表面硬度,采用光学显微镜、SEM及EDS分别对渗层进行金相组织及成分分析。结果表明:其回火特征与冶金高速钢类似,在500℃时出现"二次硬化"现象,回火硬度达到峰值,且前者高于后者。将经过1 020℃渗碳淬火后的两种试样在600℃下保温1h后空冷,重复4次后,前者与后者的表面硬度最大值分别达到750 HV0.05、650HV0.05。     

Low-carbon manganese carburizing steels

Conclusions High-manganese low-carbon steels may be a new and promising class of carburizing steels. They do not contain expensive elements or those in short supply, are simple in production, and possess high strength properties and sufficient plasticity of the core. The obtaining in the case of metastable austenite which becomes harder during service opens new possibilities for increasing the life of machine parts.The principle of obtaining metastable austenite in the case may be broadened with the use of other methods of chemicothermal treatment such as nitriding, chromizing, etc. Subsequent treatment (hardening, tempering, plastic deformation) must be directed toward regulating the quantity of austenite, the degree of its hardening, and its stability in relation to the specific part service conditions.Zhdanov Metallurgical Institute. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 32–35, March, 1985.     

8620H钢拨叉的热处理

8620H钢拨叉单件质量1.05kg,需进行碳氮共渗和淬火、回火处理,达到表面硬度680~800HV0.3、心部硬度30~45HRC和至550HV0.3的有效硬化层深度0.1~0.3mm。采用UBG渗碳炉对拨叉进行了3次碳氮共渗及淬火和低温回火工艺试验,通过适当缩短碳氮共渗时间、降低淬火温度、调整淬火油温及其搅拌烈度,最终达到了拨叉的质量要求要求。     

Effect of Initial Microstructure of Tool Steels on the Thickness and Hardness of Layers Obtained by Nitrocarburizing

The effect of preliminary heat treatment on the microstructure and kinetics of formation of the hardened layer in the process of subsequent nitrocarburizing of steels A681 (ASTM), Kh12M (GOST), Kh12FS (GOST), 6437E (AMS), and X46Cr13 (BS) is studied. Preliminary treatment of two kinds, i.e., annealing and quenching with tempering, is considered. The thermochemical processes are performed in a solid carburizer (powder) at 500°C for 4 h. The thickness, hardness, microstructure, and phase composition of the resulting layers are determined.     

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.     

Nb对H13钢组织及冲击性能的影响

采用OM、SEM、EDS、相分析、硬度测试和冲击性能试验等分析手段,对比研究Nb含量为0、0.067%和0.270%(质量分数)的H13试验钢淬回火后的组织及力学性能。结果表明,加入Nb后试验钢淬火硬度有所下降;淬火温度提高后,含Nb试验钢的晶粒尺寸小于0Nb试验钢,但含Nb试验钢中存在部分未溶碳化物;3种试验钢回火后的二次硬化峰均出现在510 ℃。经1050 ℃淬火、不同温度回火后,0.067Nb试验钢的冲击吸收能量高于0Nb试验钢。0.27Nb试验钢受到大尺寸碳化物的影响,淬火温度在1080 ℃以下时,冲击吸收能量不及另两种试验钢。     

Improving the stability of a cold-worked tool

Conclusions The recommended heat-treatment regime—quenching in the melt of a salt mixture and tempering at 380–400°C for 2 h—tends to produce an optimal combination of hardness, strength, and ductility, and ensures higher operational stability of punches formed from steels Kh12M and Kh12F1 as compared with those treated in accordance with the technology of series production. The annual saving generated from the implementation of this heat treatment is 12,000 rubles.Klimovsk Machine-Building Plant. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 24–26, August, 1991.     

Analysis of alloying systems of clad stamping tools for cold deformation of metal (review)

Two alloying systems of stamping tools (with intermetallic and carbide hardening) are analysed. Analysis shows the high characteristics of the metal with different alloying systems. The heat resistance of the 100Kh4M5F2(Zr) alloy is not inferior to the R18 high-speed tool steel, and the hardness equals 58–62 HRC as a result of carbide hardening. The relative wear resistance of the 8Kh4GSV2M5F2T alloy was (ε = 2.65), impact toughness (0.28 MJ/m²) and hardness (55 HRC). The highest wear resistance was recorded for the K15M15N5Kh3B2 alloy with the following properties after heat treatment: impact toughness (0.1 MJ/m²) and hardness (39 HRC). The wear resistance is 2–2.5 times higher than that of the R18 high-speed tool steel and 6–6.5 times higher than that of Cr12 and Cr12Mo steels.     

Low-temperature thermomechanical treatment of chromium steels

Conclusions Low-temperature thermomechanical treatment considerably improves the mechanical properties of 1Kh12NVMFA and VNS-6 steels.Low-temperature thermomechanical treatment followed by tempering at secondary hardness temperatures produces a particularly favorable combination of properties.Low-temperature thermomechanical treatment increases not only the resistance to rupture but also the resilience.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 4, pp. 32–35, April, 1963     

Effect of hardening conditions on mechanical properties of high speed steels

Abstract

Hardness and toughness are the main properties determining wear resistance and performance of high speed steel tools. The objective of the present paper was to study the effect of hardening conditions on the toughness of high speed steels, mainly concerning the hardening temperature and cooling rate during quenching. Several conditions were simulated in laboratory and industrial heat treatment furnaces and toughness was evaluated through the static bend test. Under the same tempering condition, the higher the hardening temperature, the higher the attained hardness. The results also point out a compromise situation between hardness and toughness, until 1200°C hardening temperature is reached; for temperatures over this value, the loss in toughness become more accentuated, without a considerable increase in hardness. The present paper also describes the mechanical properties of M2 high speed steel heat treated to lower hardness, necessary in some cold work tooling applications. In this case, hardening at lower temperatures and tempering close to the peak hardness has shown the best results. And lastly, regarding cooling conditions during nitrogen hardening in a vacuum furnace, the results point out that low quenching pressures might reduce the cooling rate and decreases material toughness, but the differences are very small for pressures between 6 and 9 bar.     

20CrMnTi钢花键轴开裂失效分析

经渗碳、淬火和回火处理的20CrMnTi钢花键轴在使用中其轴肩的根部开裂。对开裂的花键轴进行了宏观、微观分析和硬度测试。结果表明,花键轴的显微组织没有达到要求,导致韧性降低;轴肩根部不是圆角而是直角,造成应力集中,最终导致花键轴开裂失效。