Modification of oxide inclusions in calcium-treated Al-killed high sulphur steels

A study has been carried out to understand the modification of alumina inclusions in Al-killed high sulphur steel with calcium treatment. For calcium treatment to be effective, a general practice is to desulphurise the steel to prevent the formation of solid CaS inclusions that are harmful to steel quality and final properties. To avoid this additional desulphurising step, the authors developed a new approach of calcium treatment of steel at an industrial scale. This approach involves treating the liquid steel with calcium treatment at low aluminium levels which enables formation of liquid calcium aluminate inclusions (C12A7) in the melt and then adding remaining amount of required aluminium. Based on this principle, Al-S diagram has been developed and calcium treatment has been modified accordingly. The inclusion transformation and morphology were studied using scanning electron microscope /energy dispersive spectroscopy analysis and. activity of CaS was calculated.     

高强度汽车渗碳齿轮钢的发展及应用

渗碳齿轮钢是汽车用主要结构钢之一,国内主要汽车生产厂家的高强度齿轮钢材料一直使用不同国家多个牌号的渗碳钢。随着技术和应用的发展有必要开发新品种的高强度齿轮钢。分析了高强度汽车渗碳齿轮钢在国内外的发展及应用现状,并根据我国合金材料的特点展望了其发展趋势。     

Characteristics of aluminium metal foam for automotive applications

Closed cell aluminium foam has been examined with respect to crash protection systems, stiff and strong light weight structures and sound absorbing panels / enclosures for use in automotive systems. Monotonic compression tests revealed that the crash box made from aluminium foam-filled steel tube showed twice the energy absorption compared to empty crash box. Flexural studies on foam-filled thin walled aluminium extruded section showed higher resistance to bending (7.5 kN) against empty Al-section (5.8 kN). Differences in the mechanisms of deformation between foam filled sections and their empty counterparts were studied in compression and bend loading conditions. Acoustic behaviour was evaluated in the as-received foam and in foams post processed to increase cell interconnectivity. High sound absorption coefficients were observed in most conditions. The optimum combination of high sound absorption coefficient and frequency range occurred in a crushed foam with good cell interconnectivity.     

Microstructure and properties of hot‐rolled high strength multiphase steels for automotive application

Effects of alloying with combinations of the elements Mo, Cr and B on the bainite transformation behaviour and microstructure of hot‐rolled high strength sheet steels microalloyed with mass contents of Ti and Nb, 0.05 or 0.15 % C and 1.5 % Mn have been studied. The relationships between microstructures formed in the steels coiled at various temperatures and their mechanical properties have been investigated. The 0.15 % C microalloyed steel alloyed with Mo,Cr and B with a complex bainitic microstructure was found to have distinctive high performance behaviour combining continuous yielding, high tensile strength and plasticity after coiling in a wide temperature region. The strain hardening of the micro‐constituents typical for the investigated steels has been analysed to have a better understanding of the mechanical properties of complex phase microstructures in low alloy ferrous alloys. It was found that bainitic ferrite with austenitemartensite islands as a second phase leads to high strength and adequate elongation. The features of the bainite formation in the Mo, Cr and B alloyed CMn steel microalloyed with Ti and Nb during slow cooling from temperatures between 650 and 550 °C was studied by dilatometry.     

Wear resistant sintered aluminium parts for automotive applications

Abstract

The automotive industry's focus on weight saving has increased interest in optimised process routes and alloy compositions for light alloy PM components. Conventional pressing, sintering and sizing of aluminium alloys containing about 16%Si has been applied to produce components with high wear resistance and mechanical strength. CISIZE^®, a novel continuous isostatic pressure sintering process, combined with sizing, produces aluminium alloys with finely dispersed Si particles having excellent ductility. Combining parts obtained by these two process routes can give interesting tribological systems. Complete sintered aluminium cam phaser systems, including the sprocket wheel, are being produced in series using this approach, which also shows promise for automotive parts such as oil pumps and rotors.     

汽车排气系统用不锈钢及焊管制造技术

铁素体不锈钢具有良好的耐氧化性、低的热膨胀系数、高的抗腐蚀性能以及更为经济的成本,使得铁素体不锈钢更多地用于汽车排气系统零部件。欧美及日本汽车全部使用不锈钢材料特别是铁素体不锈钢用于排气系统零部件制造以满足汽车轻量化及严格的尾气排放要求。其中,汽车排气系统中60%以上零件为管件。介绍了汽车排气系统的构成、常用不锈钢品种及各部件的性能要求,并阐述了汽车用不锈钢焊管的主要焊接加工方式。     

宝钢汽车排气系统用铁素体不锈钢产品开发

最近几年,随着对全球环境问题的关注,各国都对汽车尾气排放要求给予高度重视以减低对环境的危害。随着汽车燃油的经济性和汽车尾气排放的等级化要求不断提高,排放标准变得更为严厉。因铁素体不锈钢具有良好的耐氧化性、低的热膨胀系数、高的抗腐蚀性能及更为经济的成本,铁素体不锈钢更多用于汽车排气系统零部件。欧美及日本汽车几乎全部使用超纯铁素体不锈钢用于排气系统零部件制造以满足汽车轻量化及严格的尾气排放要求。介绍了汽车排气系统的构成、各部件的性能要求及宝钢汽车用不锈钢的产品开发。     

Some aspects of behaviour of calcium in silicon killed steels

Abstract

Irregular flow can occur randomly in a casting sequence and mostly occurs in Si-Mn killed high C steels. Irregular flow increases reoxidation, mould level fluctuations and slag entrainment, all of which cause deterioration of the surface quality of the billets. The effect of calcium on irregular flow in billet casting of Si-Mn killed steels is discussed based on experience at two Corus steelplants, Scunthorpe and IJmuiden. Some theoretical aspects of calcium treatment are also discussed.     

大型工业铝合金型材的挤压生产工艺与关键技术（续）

在德国 VAW公司装备有 72 MN油压传动的卧式挤压机 ,该机配备有 50 0、 560 mm圆挤压筒和675mm× 2 30 mm和 675mm× 2 80 mm扁挤压筒 ,亦可生产不同合金、不同厚度规格、宽度可达 650 mm、长度可达 30 m的车辆用大型型材。这两台挤压机的前面都配有铸锭感应加热炉 ,机后则配有自动出料台 ,精密气淬火装置、牵引机、精密中断锯、拉伸矫直机、辊式矫直机和长度为 30 m以上的人工时效炉等辅助设备。为了满足大型化、薄壁化、高精化和现代化的要求 ,在生产线除采用 PLC控制外 ,所有的工艺参数 (挤压温度、挤压速度、变形程度、铸锭规格、…     

Application and failure evaluation of ferritic stainless steels for automotive exhaust systems

In recent years,with attention paid to global environmental problems,there have been requirements for continuous improvement of automobile fuel economy and exhaust gas purification rate.The properties of the ferritic stainless steels(FSS) used to make automobile parts have been improved.This paper introduces the construction of automotive exhaust systems and describes their main failure behaviors and corrosion evaluation procedures.     

Delayed fracture of tensile strength 980 MPa grade steels for automotive applications

Three different types of tensile strength( TS) 980 MPa grade advanced high-strength steels used in automotive applications,namely,980 MS( martensite steel),980DP( dual phase) and 980QP( quenching and partitioning) steels were examined. The delayed fracture resistance of the steels was evaluated using a U-bend test,slowstrain rate test( SSRT) and a constant load tensile test. The results indicated that all the steels could pass the300h HCl solution immersion test and none of the U-bend specimens was fractured in the test. However,the steels exhibited different susceptibilities to delayed fracture under SSRT and the constant load tensile tests. 980 DP exhibited the highest resistance to delayed fracture among all the samples,while 980 MS was found to be the most susceptible to delayed fracture.     

用先进的温模压制工艺生产高密度汽车零件

高密度压制工艺(温模压制)扩大了粉末冶金零件的应用范围。鉴于一次压制/一次烧结(1P/1S)所达到的密度已超过了7.3 g/cm~3,这种成本可行的零件生产方法,往往是最新高密度汽车零件应用采用的方法。达到较高零件密度的关键的第一步是改进润滑剂与预混合工艺,以将润滑剂的含量减小到预混合粉重量的0.25%。本文详述了新润滑剂系统,能够使润滑剂含量减低到预混合粉重量的0.25%,并使生坯密度高达7.5 g/cm~3左右。除了生坯密度高外,生坯强度也达到了30 MPa左右;并能将压制与生坯零件后续处理时开裂的可能性减小到最小程度。虽然还不能用于所有类型的零件,但在Cloyes Gear已证明,这种新的粉末预混合粉,对于生产汽车的气门机构零件是成功的。将详述开发工作的情况和得到的生产体验,并讨论其优点与局限性。     

Design of steels for high speed machining

Abstract

Historical analysis of metal cutting shows that metal removal rates have been increasing in the course of the century, predicated by the advancement in tool materials but the steel design has lagged behind. This paper examines the mechanisms of chip formation and tool wear as a function of cutting speed in metal cutting. Chemical wear is identified as the dominant mechanism of tool wear at high cutting speeds caused by temperature rise due to shear localisation in the primary and secondary shear zones of chip. Shear localisation in the primary shear zone is shown to be influenced by both microstructural parameters, i.e. matrix hardening and second phase particles, and metal cutting variables, i.e. cutting speed (strain rate) and feed (pressure). Shear localisation in the secondary shear zone is caused by the tribological conditions of seizure at the tool/chip interface. Chemical crater wear is caused by the dissolution of tool into the workpiece (chip) by diffusion mechanism and can be prevented by suppressing the tribological condition of seizure. The design of steel for high speed machining is based on engineering glassy oxide inclusions in steel, which are designed to form a viscous layer in situ at the tool/chip interface at high cutting speeds. The viscous layer lubricates the tool/chip interface and prevents the occurrence of seizure, thereby suppressing chemical crater wear. In comparison with the large volume fraction of inclusions required for promoting ductile fracture at low cutting speeds, the amount of inclusions required for lubricating the tool/chip interface is very small and is in the range that is typical of clean steel. Thermodynamic modelling is shown to be a powerful tool to engineer glassy oxide inclusions in steel     

Development of microalloyed steels for high temperature carburizing

The potential for use of microalloy additions to suppress abnormal austenite grain growth and produce steels with enhanced bending fatigue resistance after high temperature vacuum carburizing was investigated in a series of Ti-modified SAE 8620 steels with w(niobium) additions up to 0.1%.Results are considered from a series of papers at the Advanced Steel Processing and Products Research Center on the effects of Nb content,heating rate, rolling history,and processing temperature on the evolution of austenite grain structures in carburizing steels. Emphasis is placed on understanding the effects of alloying and processing on each stage in the annealing process including the as received laboratory rolled conditions,during the onset of carburizing after annealing at different heating rates,and after annealing for various times at carburizing temperatures up to 1 100℃.Heating rate to the carburizing temperature was shown to be an influential variable and suppression of abnormal grain growth was dependent on the development of a critical distribution of fine NbC precipitates,stable at the austenitizing temperature.The importance to industrial carburizing practice of heating rate effects on precipitates and austenite grain size evolution are discussed and correlated to selected data on fatigue performance.     

烧结硬化粉末冶金钢在高性能零件中的应用

粉末冶金烧结硬化是一种经济有效的生产高强度零件工艺过程。但是,其后续机加工相对困难和昂贵,因此尺寸公差控制也是烧结硬化过程中关注的重要目标。本文基于MPIF标准制备了多种烧结硬化材料,并对比了它们在同等压制压力下的测试试棒以及同等密度下工业粉末冶金零件上的强度、延伸率及尺寸稳定性表现。结果表明在工业生产条件下,所有材料都得到了有效烧结硬化并表现出了优秀的尺寸稳定性。在工业零件生产中,Cr M作为一种预合金无铜添加的经济有效的烧结硬化材料,由于它的高淬透性,在0.5%C(质量分数)添加时,表现出高的尺寸稳定性及极佳的性能。