高碳钢板的组织控制

为了降低环形齿轮，驱动装置等汽车零件的成本，研究了高碳钢板显微组织对其加工性和淬透性的影响，通过最佳的一次冷轧及退火，再将渗碳体细化至超微细晶粒的短时热处理后，可获得高的淬透性；依靠二次冷轧和退火，使铁素体晶粒充分长大和降低硬度，从而改善了钢的成形性。     

硫化铜对超低碳钢板的沉淀硬化

开发了用于汽车的高强度冷轧硬化钢板。在过去的10年中,对超低碳钢（ELC）和无间隙原子钢（IF）主要强化方法是用硅、锰、磷及微合金元素,如铌和钛的沉淀硬化进行固溶强化。当钢用大量固溶元素如硅和锰强化时,由于氧化而使钢的表面质量恶化。另外,磷加入到ELC钢和IF钢中,由于降低晶界强度而出现脆化敏感性,使钢的性能不能满足要求。本文提出采用Cu2S弥散分布沉淀强化超低碳硬化钢代替用硅、锰、铌及钛的固溶强化和沉淀强化。铜硫化物与体心立方的α-Fe有（001）Cu2S//（001）α-Fe和[001]Cu2s//[001]α-Fe晶格取向关系。     

1.2085模具钢锻制大模块时成分偏析对预硬化硬度的影响

抚钢研制的1.2085模具钢在锻制大模块时预硬化硬度超出要求范围。通过对此钢种进行酸浸试验、硬度检验、成分分析、热处理试验等,研究了1.2085模具钢宏观成分偏析对预硬化硬度的影响。结果表明:宏观成分偏析主要是C及S元素,且C偏析影响预硬化硬度,正偏析部位硬度高,负偏析部位硬度低;钢锭尺寸愈大,影响愈明显,热处理亦无法消除这种影响。     

等离子钨钼镝合金层的强化工艺及抗回火性能

利用双层辉光等离子渗金属技术和固体渗碳法在Q235钢表面获得与冶金高速钢成分相当的等离子钨钼镝合金层,并对合金层进行不同温度的淬火和回火作为复合强化热处理,得到硬度和抗回火性都较高的合金强化层。采用场发射扫描电镜(附带能谱仪)和显微硬度计研究不同热处理工艺对等离子钨钼镝合金强化层的显微组织,硬度和抗回火性能的影响,结果表明,等离子钨钼镝合金层的最优强化热处理工艺为1050℃淬火+550℃回火,所得强化层中碳化物呈颗粒状弥散分布,且数量最多,尺寸最小(≤1μm),未经回火的表面硬度为1144HV_(0.05),在550℃回火出现二次硬化,表面硬度达到1153 HV0.05。     

热处理对亚微细硬质合金的强化效应

本文以亚微细硬质合金(平均粒径≈0.8 μm)G0811的热处理作为研究对象,通过对热处理前后合金物理机械性能的对比,发现经热处理后合金的磁性能变化不大,但是合金硬度和断裂韧性呈现出一定的上升趋势;通过对材料的XRD分析,发现在适当的热处理条件下合金的粘结相得到了有效强化,同时WC晶粒度也有一定程度细化.     

超高强度钢：向高性能、低成本方向发展

根据钢中合金含量，将超高强度钢分为低合金超高强度钢、中合金超高强度钢和高合金超高强度钢。据合结钢的物理冶金学特点可以将超高强度钢分为低合金超高强度钢、二次硬化超高强度钢和马氏体时效钢。     

合金元素对奥氏体热模具钢时效硬化及力学性能的影响

本文对Fe-Ni-Mn-Cr奥氏体热模具钢的时效硬化特性及力学性能进行了探讨。结果表明:在钢中加入少量的铌元素后,在相同的热处理工艺条件下,将使试验钢的最大时效硬度值减小。增加钢中Mn/Ni比可以提高最大时效硬度值,但使试验钢的室温和高温塑性下降     

无钴二次硬化超高强度钢合金设计

利用人工神经网络对Ｆｅ－９．５Ｎｉ－Ｃｒ－Ｍｏ－Ｃ合金基本成分进行了优化,并在此基础上引入其他强化途径,开发了一种力学性能与９Ｎｉ－５Ｃｏ钢基本相当的无钴二次硬化超高强度钢。     

高Co—Ni二次硬化马氏体钢中合金元素对相变的影响

利用“固体与分子经验电子理论”（ＥＥＴ）分析了高Ｃｏ－Ｎｉ二次硬化马氏体钢中几种主要合金元素在不同状态下的价电子结构，认为Ｃｏ、Ｎｉ在奥氏体中与Ｃ相互作用较强，它们能降低Ｃ的扩散能力，推迟马氏体相变。在马氏体回火过程中，Ｃｏ 和Ｎｉ溶入渗碳体形成的合金渗碳体，在较高的温度下分解，使固溶于基体中的Ｍｏ 与位错充分结合。在渗碳体分解后，Ｍｏ 与Ｃ形成富Ｃ、Ｍｏ的溶质簇，或以Ｍ２Ｃ的形式析出，在基体内弥散分布，形成二次硬化。     

弥散硬化型无磁模具钢的组织与性能

通过合金元素及热处理工艺的变化，对弥散硬化型无磁模具钢的组织与性能进行了研究，从而开发出一种成本较低的无磁模具钢，经１１８０℃固溶，７００℃时效后，硬度可达４８，相对磁导率＝１．００５６，而吨材料成本则比目前国内通用的７Ｍｎ１５Ｃｒ２Ａｌ３Ｖ２ＷＭｏ钢下降数千元，耐磨性提高约３８％。     

The Investigation for Development on Precipitation Phases in 25Co15Ni11Cr2MoE Steel during Tempering

The evolution law of precipitated alloy carbides and reverted austenite in a high Co-Ni secondary hardening ultra-high strength 25Co15Ni11Cr2MoE steel tempered at 300??~ 660?? after quenched has been studied by means of transmission electron microscopy (TEM) and X ray diffraction (XRD) in this paper. The results show that the precipitate order of alloy carbides with the increasing of tempering temperature from 300?? to 600?? in experimental steel is: dispersed ??-carbides?? lamellar alloy cementites?? dispersed M2C carbides?? coarse M23C6 carbides. When the experimental steel tempering at 495??, fine M2C carbides precipitated on the lath martensite matrix. Meanwhile, coarse lamellar alloy cementites that precipitated during the early tempering stage has all dissolved, and reverted austenite precipitated at the boundaries of lath martensite and grows up into thin-film sharp along the lath boundaries. When the tempering temperature rose to 530??, the content of reverted austenite continues to increase, but the morphology of reverted austenite changed from thin-film to strip or block. When the tempering temperature rose to 530??, the content of reverted austenite in the steel reaches maximum value.     

PCBN刀具高速精密切削W-Ni-Fe合金的性能研究

采用PCBN刀具对W-Ni-Fe合金进行高速精密切削试验,通过观测PCBN刀具前、后刀面的磨损形貌,分析了刀具的失效磨损机理;从CBN含量、刀具参数以及已加工表面粗糙度方面研究了PCBN刀具加工W-Ni-Fe合金的切削性能。结果表明,CBN含量高且刀尖圆弧半径大的PCBN刀具具有更长的使用寿命,在高速、低进给、小切深条件下可获得良好的表面质量。SEM和EDS分析结果表明,PCBN刀具高速精密切削W-Ni-Fe合金的磨损机理为粘结磨损、扩散磨损、局部剥落、氧化磨损以及崩刃磨损等多重磨损机理共同作用的结果。     

Influence of Initial Microstructure on Warm Deformation Processability and Microstructure of an Ultrahigh Carbon Steel

Various isothermal compression tests are carried out on an ultrahigh carbon steel(1.2% C in mass percent), initially quenched or spheroidized,using a Gleeble-3500system.The true stress is observed to decrease with increasing temperature and decreasing strain rate.The true stress of the initially quenched steel is lower than that of the initially spheroidized steel at high deformation temperature(700℃)and low deformation strain rate(0.001s-1).The value of the deformation activation energy(Q)of the initially quenched steel(331.56kJ/mol)is higher than that of the initially spheroidized steel(297.94kJ/mol).The initially quenched steel has lower efficiency of power dissipation and better processability than the initially spheroidized steel.The warm compression promotes the fragmentation and the spheroidization of lamellar cementites in the initially quenched steel.The fragmentation of lamellar cementites is the spheroidizing mechanism of the cementites in the initially quenched steel.Results of transmission electron microscope investigation showed that fine grains with high angle boundaries are obtained by deformation of the initially quenched steel.     

Effect of cementite morphology on pearlitic wire drawing deformation

A comparative study was conducted on the effects of lamellar cementites and globular cementites on the cold drawing process and the mechanical properties of pearlitic wire steel, with the help of metallographic microscope, scanning electron microscope, transmission electron microscope, tensile tester and hardness tester. The lamellar cementites showed the deformation capacity to some extent during the cold drawing process. As the drawing strain increased, the pearlitic wire with globular cementites evolved into the fibrous form gradually and no obvious defects were found in the microstructure. The globular cementites turned to the drawing direction without any deformation of itself during the deformation process. And micro- cracks occurred in the cementite/ferrite interface due to stress concentration caused by pinning dislocations in spherical cementites. The strength and hardness of both pearlitic wires gradually increased as the drawing strain rose. And the pearlitic wire with lamellar cementites had a higher drawing hardening rate. The ferrite <110> texture formed in both pearlitic wires during the cold drawing process. Compared with the globular pearlite, the pearlitic wire with lamellar cementites had higher ferrite <110> texture intensity. And the difference of their ferrite <110> texture intensity became bigger and bigger as the drawing strain increased.     

Cutting performance and microstructure of high speed steels: Contributions of matrix strengthening and undissolved carbides

While it is accepted that both the hot strength of the matrix and the amount of undissolved carbides are important for the cutting performance of high speed steels, the relative weights of their contributions are unknown. In this work, they are separately identified and a model is presented that provides a quantitative prediction of tool life (solely in uninterrupted cutting) on the basis of microstructural and compositional data over a wide range of alloy compositions and cutting speeds. The model seems to describe the individual contributions to tool life well enough to serve as a guide in alloy development. The model has been developed using 13 different steels, spanning the entire range of customary compositions. It is based on the following parameters: volume fractions and compositions of undissolved carbides; precipitates formed during tempering (secondary hardening) and during operation (tertiary precipitates); and, finally, residual solute in the matrix. Tool life is modeled as a linear combination of contributions from the undissolved carbides and from the precipitate population, including a contribution due to the action of Co, and with an additional term due to solute strengthening of the matrix. The weight factors are determined by multiple linear regression analysis. They reflect the relative importance of each contributing factor, and their dependence on cutting speed can be interpreted in terms of the change in operative wear mechanism with tool temperature.     

Effects of austenitizing temperature on the kinetics of bainite reaction at constant austenite grain size in FeC and FeNiC alloys

The influence of austenitizing temperature on a subsequent diffusional transformation has been investigated. The overall bainite transformation rate in a slightly hypo-eutectoid Fe-7.6Ni-0.48C alloy is increased by a double austenitizing treatment. Optical microscope observations have revealed that this acceleration of bainite transformation is caused mostly by the acceleration of nucleation rate at austenite grain boundaries. Intergranular fracture surface observations have shown that a second austenitizing treatment enhances cementite precipitation on grain boundaries. It is considered that the enrichment of sulfur at grain boundaries by a second austenitizing treatment enhances the precipitation of cementite during the subsequent cooling to the transformation temperature. When the second austenitizing temperature is 750°C or below, disc shaped Fe-rich FeS precipitates are formed together with the cementites. The initial stage of bainite transformation has shown that the cementites and Fe-rich FeS precipitates act as preferential nucleation sites for bainite. The precipitation of cementite and Fe-rich FeS by a double austenitizing treatment is also observed in a Ni free Fe-0.61C alloy.     

Effect of Nitrogen and Niobium on the Structure and Secondary Hardening of Super Hard High Speed Tool Steel

High‐speed steels have been used mostly for multi‐point cutting tools and for plastic working tools. High speed steels are ferrous based alloys of the Fe‐C‐X multi‐component system where X represents a group of alloying elements comprising mainly Cr, W or Mo, V, and Co. The properties of these steels can be improved by modifying their chemical composition or the technology of their production. One of the new trends in modifying the tool steels chemical composition consists in the addition of niobium and nitrogen. In this work, the effects of niobium and nitrogen on morphology of carbides and secondary hardening temperature of investigated high speed tool steels were studied. This experimental work shows that, the conventional ingots have many types of carbides of different shapes and sizes precipitate on the boundary together with thick needle like carbides. On the contrary, for nitrogen steel, the nitrogen alloying leads to form dense, fine and well distributed microstructure. While, on the case of niobium alloying, single carbide (MC), and different types of eutectic carbides were precipitated which have a major effect on the secondary hardening temperature.     

高强度焊管去毛刺硬质合金刀具的研制

去毛刺刀是清除焊管内外焊缝毛利的专用硬质合金刀具,其几何精度、合金的内在质量和性能指标均有较高的要求。本文介绍了为引进焊管机组生产线配套而研制的硬质合金去毛刺刀具,该合金通过采用强化球磨、添加组元等有效的工艺控制手段,使所研制的合金具有细晶粒组织和良好的高温使用性能,取代了进口产品,具有显著的经济效益和社会效益。     

Tensile Deformation Behavior of Fe-Mn-Al-C Low Density Steels

Room temperature tensile tests of Fe-Mn-Al-C low density steels with four different chemical compositions were conducted to clarify the dominant deformation mechanisms.Parameters like product of strength and elongation,as well as specific strength and curves of stress-strain relations were calculated.The microstructures and tensile fracture morphologies were observed by optical microscope,scanning electron microscope and transmission electron microscope.The tensile behavior of low density steel was correlated to the microstructural evolution during plastic deformation,and the effects of elements,cooling process and heat treatment temperature on the mechanical properties of the steels were analyzed.The results show that the tensile strength of steels with different cooling modes is more than 1 000 MPa.The highest tensile strength of 28Mn-12Al alloy reached 1 230 MPa,with corresponding specific strength of 189.16 MPa·cm~3·g~(-1),while the specific strength of 28Mn-10 Al alloy was 178.98 MPa·cm~3·g~(-1),and the excellent product of strength and elongation of 28Mn-8Al alloy was over 69.2 GPa·%.A large number of ferrite reduced the ductility and strain hardening rate of the alloy,while the existence of κ carbides may improve the strength but weaken the plasticity.Some fine κ carbides appeared in the water-quenched specimen,while coarse κ carbides were observed in the air-cooled specimen.High temperature heat treatment improved the decomposition kinetics of γ phase and the diffusion rate of carbon,thus speeded up the precipitation of fine κ carbides.The dominant deformation mechanism of low density steel was planar glide,including shear-band-induced plasticity and microbandinduced plasticity.     

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