国内外热作模具钢的研究进展

介绍了国内外传统和新型热锻、热挤压和压铸用热作模具,以及特殊用途热作模具的钢种和特点;热作模具钢热处理和表面处理技术的研究进展。提高模具钢纯净度、均匀和细化组织,用计算机模拟技术开发热作模具钢新钢种是目前提高热作模具钢寿命的重要方法。     

Development and application of a new hot-work die steel for hot stamping

A new hot-work die steel for hot stamping was developed, and used the die for mass production. The produced die showed good performance owing to its high heat conductivity and wear-resistant characteristics. Two different benchmarking hot-work die steels were investigated, and then compared in terms of their impact ductility,temper characteristics, heat conductivity, and thermal stability. The result of the high-temperature friction wear test indicated that oxidative wear was the main mode in high temperature. On the basis of the comparison and test results, the alloying composition of the new hot-work die steel was especially designed. The new die steel showed good performance with good wear-resistant quality, as well as temper hardness and heat conductivity of HRC 50 and34.3 W/(m·K), respectively. Furthermore,without surface plasma nitriding, the die made of the new steel had no obvious galling with 6142 strokes. After surface plasma nitriding, the die completed 40000 strokes with good surface. The die life is expected to exceed 200000 strokes.     

The strength and ductility of continuouslycast steels above 800°C

The tensile strength and ductility of continuously cast steels have been determined for temperatures above 800°C. The results show that the maximum stress decreases progressively until close to the melting temperature, then drops to zero. The maximum stress is essentially independent of residual and solute concentrations, cast structure and prior heat treatment. Above 1250°C the steels are ductile to near the melting temperature. Below 1250°C the ductility decreases, the amount of decrease, and the temperature range over which the change occurs depending on composition, cast structure and heat treatment. The ductility decreases at higher temperatures with high sulfur and phosphorus levels in the steel. Increasing sulfur from 0.010 to 0.025 pct in laboratory cast steels markedly decreases the ductility. Small grain size also tends to reduce ductility. Preheating the steel to near its melting point prior to testing markedly reduces the ductility below 1250°C in most steels. It is postulated that this is due to local remelting of solute rich pockets of material which extend along the grain boundaries. The extended material is brittle at lower temperatures reducing the ductility of the steel.     

A new generation of economical automotive steel

To meet the demands of the auto industry, facilitate import substitution, and improve the global competitiveness of Russian products, there is a pressing need for new high-quality economical steels with excellent stamping properties, strength, and corrosion resistance. Between 2001 and 2011, intensive research permitted the development of high-technology production processes for a new generation of automotive steels; these technologies have no counterparts around the world. A fundamentally new approach was adopted: the required structure and properties of the metal are obtained by regulating the deposition of nonmetallic excess phases, the state of the solid solution, the grain boundaries, and the types of impurities at all stages of production. On the basis of extensive research, including more than 1000 trial melts, production technologies for more than 30 grades of automotive steel that match—and in many respects outperform— their foreign counterparts have been introduced at OAO MMK and OAO Severstal’.     

稀土La对5CrNiMo模具钢力学性能的影响

研究了加入稀土La后5CrNiMo钢的强度、硬度、冲击韧性变化;并在相同热处理工艺条件下,与不添加稀土La的5CrNiMo钢进行对比.结果表明:稀土La加入量在适当的范围内可显著提高钢的强度、硬度和冲击韧性;当稀土La质量分数为0.033%时,5CrNiMo钢可获得最好的综合力学性能.     

Heat treatment for improvement in lower temperature mechanical properties of 0.40 pct C-Cr-Mo ultrahigh strength steel

In the previous paper, it was reported that isothermal heat treatment of a commercial Japanese 0.40 pct C-Ni-Cr-Mo ultrahigh strength steel (AISI 4340 type) at 593 K for a short time followed by water quenching, in which a mixed structure of 25 vol pct lower bainite and 75 vol pct martensite is produced, results in the improvement of low temperature mechanical properties (287 to 123 K). The purpose of this paper is to study whether above new heat treatment will still be effective in commercial practice for improving low temperature mechanical properties of the ultrahigh strength steel when applied to a commercial Japanese 0.40 pct C-Cr-Mo ultrahigh strength steel which is economical because it lacks the expensive nickel component (AISI 4140 type). At and above 203 K this new heat treatment, as compared with the conventional 1133 K direct water quenching treatment, significantly improved the strength, tensile ductility, and notch toughness of the 0.40 pct C-Cr-Mo ultrahigh strength steel. At and above 203 K the new heat treatment also produced superior fracture ductility and notch toughness results at similar strength levels as compared to those obtained by usingγ α′ repetitive heat treatment for the same steel. However, the new heat treatment remarkably decreased fracture ductility and notch toughness of the 0.40 pct C-Cr-Mo ultrahigh strength steel below 203 K, and thus no significant improvement in the mechanical properties was noticeable as compared with the properties produced by the conventional 1133 K direct water quenching treatment and theγ α′ repetitive heat treatment. This contrasts with the fact that the new heat treatment, as compared with the conventional 1133 K direct water quenching treatment and theγ α′ repetitive heat treatment, dramatically improved the notch toughness of the 0.40 pct C-Ni-Cr-Mo ultrahigh strength steel, providing a better combination of strength and ductility throughout the 287 to 123 K temperature range. The difference in the observed mechanical properties between the above two ultrahigh strength steels is discussed on the basis of the effect of nickel content, fracture profile, and so forth.     

Steel with a nitride phase for hot forging and pressing tools

Nitride hardening effectively increases the high-temperature strength and wear resistance of die steels, without loss of ductility. In comparison with 5XHM(Л) steel, with moderate high-temperature strength, 5XHMAΦ(Л) steel for large forging and pressing tools of hammer type matches the high-temperature strength and matches or exceeds the ductility. In terms of its basic operational properties, 3X5MAΦЛ steel outstrips practically all steel with moderate and elevated high-temperature strength and is universally effective as a replacement.     

国内外易切削钢的现状和研究进展

易切削钢比普通碳素钢有较好的切削性能和更好的产品表面光洁度。随着自动化加工工业和汽车工业的发展,易切削钢的使用量不断增加。目前,国外普遍采用电弧炉二次精炼连铸流程生产易切削钢。工业化国家切削钢已形成标准化系列产品,并伴随连铸技术的广泛采用,使易切削钢具有均匀的切削性能。现有易切削钢种为易切削碳钢、渗碳钢、调质钢和不锈钢,并不断将易切削钢扩展到诸如模具钢、高锰钢、耐热钢、高工钢等钢类。在分析国内外易切削钢发展的基础上,讨论了易切削钢生产工艺、钢种的发展方向。     

异步轧制TWIP钢的力学性能和微观组织

 利用金相显微镜、X射线衍射仪和透射电子显微镜对异步轧制及热处理TWIP钢的力学性能与微观组织进行了研究。结果表明,TWIP钢经500℃异步轧制后强度显著提高,而塑性降低,这是位错与孪晶共同作用的结果。轧制后的热处理降低了位错密度以及变形孪晶数量,导致强度降低,伸长率升高。经600℃和700℃退火后,TWIP钢表现出良好的强度和塑性综合性能。因此,异步轧制后热处理是获得具有优良综合力学性能TWIP钢的可行途径。     

Delta ferritic heat-resistant chromium-molybdenum steels with improved rupture strength

Nine experimental delta-ferritic steels have been examined as potential low expansion heat-resistant steels for use in fossil fuel power generation, nuclear power generation, nuclear process heat plants and coal gasification plants. The steels contain 10 to 14 pct Cr and 2 to 6 pct Mo, with additions of columbium, titanium, vanadium, aluminum and boron. Room-temperature tensile properties and oxidation resistance of all steels were determined. Selected steels were aged for 1000 h at 760 °C (1400 °F) and subjected to elevated temperature tensile tests at the aging temperature. Creep-rupture properties of selected steels were determined at 760 and 815 °C (1400 and 1500 °F). Extensive metallographic and phase identification studies were conducted. Of the two steels tested for creep-rupture strength, the 10Cr-6Mo-0.5Cb steel, with good room-temperature ductility, has rupture strength exceeding that of martensitic 12Cr-1Mo-V steel. The 14Cr-3Mo-0.5Cb-lTi-2Al steel exhibits an even higher rupture strength, but has only marginal ductility at room temperature.     

Main Trends in the Growth of Converter Steelmaking at the Company Severstal'

The development plan of the company Severstal' places special emphasis on the introduction of new machinery and equipment and the development of technologies that make it possible to produce new grades of steel and high-quality products while also lowering production costs. In the last five years, the company has given particular attention to mastering the production of the following types of steels: steels with a strength rating of up to X80 for making pipes used in critical applications; ship plate; IF steels for automobile construction; high-strength steels and electrical steels. The company has thus stressed improvements in the following areas in order to achieve this goal: improve the indices of converter steelmaking; optimize the technologies used for out-of-furnace treatments of steel; improve the continuous casting of steel.     

稀土在低硫16Mn钢中的作用

长条状的MnS夹杂对钢的横向韧塑性极为不利。喷吹Si—Ca或加入RE,通过脱硫和变质硫化物的作用,都可显著地消除其危害。喷吹Si—Ca变质硫化物的程度与钢中Ca/S有关。喷吹Si—Ca后加入少量RE,有利于控制MnS完全变质,此时钢中所需的RE/S可明显低于3。在大幅度脱硫的基础上加入少量RE,是使钢材韧塑性获得稳定大幅度提高的一条有效途径。     

高热强性热作模具钢SDH3的研究

根据热作模具钢的服役条件,基于成分均匀设计方法设计出一种高硅低钼型热作模具钢SDH3钢(专利钢),并与H13钢进行了室温冲击韧性、回火稳定性和热疲劳性能的对比试验研究,结果表明:热处理后,两种钢冲击韧性相当;620℃下保温22 h后,SDH3钢的硬度值大于35 HRC,比H13钢高4 HRC左右;SDH3钢具有比H13钢更优良的抗热疲劳性能。     

Effect of Microalloying Additions on the Microstructure and Mechanical Properties of Low Carbon Steel

Low carbon steels are characterized by good weldability,formability and fracture toughness properties.However,the low strength levels of these steel grades limit their wide applications.On the other hand,increasing the strength by increasing the carbon content and alloying elements deteriorates the other properties.In this study,the microalloying technique was used to examine the possibility of attaining low carbon steels with good combination of strength,ductility and impact properties.A low carbon steel microalloyed with single addition of vanadium and another one microalloyed with combined addition of vanadium and titanium were used in this investigation and their properties were compared with non-microalloyed low carbon steel having the same base composition.Furthermore,other two nonmicroalloyed and V-microalloyed steels with higher carbon,silicon and manganese contents were also investigated to reveal the effect of base composition.Tensile,hardness,room and zero temperature Charpy V-notch impact tests were conducted to evaluate the variations in the mechanical properties of low carbon hot forged steel containing vanadium and combinations of vanadium and titanium.In addition,the microstructures of the different investigated steels were observed using both optical microscope and scanning electron microscope.Furthermore,the hardness of the ferrite phase was also determined using micro-hardness technique.The results showed improvement of the mechanical properties of the investigated steels by both single V-and combined V + Ti-microadditions.Tensile,hardness and impact tests results indicated that good combinations of strength,ductility and impact properties can be achieved by V-microalloying addition.Steel with combination of V and Ti microaddition has much higher hardness,yield strength,ultimate tensile strength and impact energy at both room and zero temperatures compared with non-microalloyed and single Vmicroalloyed steels.Higher C,Si and Mn contents result in increasing the strength accompanied with decrea     

鞍钢1780机组汽车大梁板A420L、A510L的研制与开发

介绍了鞍钢1780机组新型含铌汽车大梁板（A420L、A510L）的生产工艺与组织性能。试验研究了A510L钢的高温塑性以及控冷控轧对钢组织和性能的影响,测定了汽车大梁板成形性参数。试验证明,鞍钢1780机组生产的汽车大梁板（A420L、A510L）具有良好的强韧性配合,优良的成形性能及较高的尺寸精度,可以满足汽车实际生产工艺的要求。     

汽车用微合金化非调质钢的进展

与淬回火调质钢比较,空冷非调质钢不但能降低成本,而且可避免热处理所引起的零件变形,减少机械性能的偏差。介绍了空冷铁素体-珠光体高韧性非调质钢、贝氏体和马氏体非调质钢的进展以及当前国内非调质钢的生产和应用。     

Investigation of modern fabricated pattern welded Damascus steel

Work on modern fabricated pattern welded Damascus steel by two of the best Russian bladesmiths was investigated. The main mechanical properties were measured, macro and microstructure were examined, and EDAX, mass-spectroscopy, and fractography tests were performed. The effect of heat treatment on both macrostructure and hardness was studied. It was shown that mechanical properties of pattern welded Damascus steel was on a level with standard tool plain carbon and low alloyed steels.     

New approach to predict the long-term creep behaviour and evolution of precipitate back-stress of 9–12% chromium steels

Modern advanced 9–12 % Cr steels are complex alloys with excellent creep strength even at high temperatures up to 620°C. The mechanical properties of these steels are significantly influenced by the presence and stability of various precipitate populations. Numerous secondary phases grow, coarsen and, sometimes, dissolve again during heat treatment and service, which leads to a varying obstacle effect of these precipitates on dislocation movement. In this work, the experimentally observed creep rupture strength of an modified 9–12% Cr steel developed in the European COST Group is compared to the calculated maximal obstacle effect (Orowan stress) caused by the precipitates present in these steels for different heat treatment conditions. It is shown that the differences in creep rupture strength caused by different heat treatments disappear after long time service. This observation is discussed on the basis of the calculated evolution of the precipitate microstructure. The concept of boosting long-term creep rupture strength by maximizing the initial creep strength with optimum quality heat treatment parameters for precipitation strengthening is critically assessed.     

高端装备用轴承钢冶金质量性能现状及未来发展方向

针对滚动轴承特点、轴承钢类型以及国内外轴承钢差距,本文对国内外高端装备用轴承需求、国内外轴承钢品种、轴承钢生产装备与冶金质量、轴承钢热处理技术以及轴承钢质量性能评价技术等发展现状进行了综述,指出了国内外高端装备用轴承钢在冶炼流程的超纯净控制、新型热处理技术和新型轴承钢研发对提升轴承长寿命的巨大作用,提出了未来基于夹杂物...     

高疲劳寿命轴承钢洁净度现状及研究进展

对比了国内外高疲劳寿命轴承钢主要杂质元素、主要夹杂物特征等冶金性能的差异，并对比了不同冶金质量下，轴承钢的疲劳性能及诱发疲劳断裂的因素，总结了国产轴承钢洁净度现状及与国外优质轴承钢的差距。在此基础上，围绕高疲劳寿命轴承钢，以进一步提高国产轴承钢质量为目的，分析梳理了国产轴承钢冶炼技术及夹杂物控制方法的发展轨迹，探讨了国产轴承钢进一步提高疲劳寿命及质量的发展方向。