YG80钎尾寿命试验及破坏原因初探

YG80钎层是重型凿岩机极易损坏的重要另件．在四种材料（45Cr，42CrMo，30CrNi2MoVA，45CrNiWVA）及不同热处理方法制造的16根钎尾，进行矿山工业试验的基础上．对它们的使用寿命及失效形式进行分析，找出影响钎尾寿命的因素及其规律．试验中对各钎尾材料的渗碳层深度、淬火硬度、纯凿岩时间、总进尺深度、岩石硬度等数据作了详细的记录．为理论分析、应用和选择提供了可靠的原始数据．为今后选择针尾材料、确定合理结构、改进冷热加工工艺、提高钎尾寿命提供一定可靠的参考依据．     

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。     

先进汽车钢扁平材和长形材的研发进展

汽车的高性能、轻量化和高安全发展需要先进钢铁材料作为基础。汽车上应用和制造过程所涉及的钢材品种繁多：铝镇静钢、IF钢、BH钢、IS钢、CMn钢、HSLA钢、DP钢、CP钢、马氏体钢、TRIP钢、TWIP钢、奥氏体不锈钢、热成形马氏体钢、碳结钢、优碳钢、齿轮钢、螺栓钢、弹簧钢、轴承钢、调质合结钢、非调质钢、气阀钢、铁素体不锈钢、耐热合金、粉末冶金钢、热作模具钢、     

鞍钢150吨转炉扩大品种提高质量的技术措施

近几年来,鞍钢150t转炉生产的品种不断扩大。现已生产了九十四种碳素钢和低合金钢(锰钢、加稀土钢、锰钒钛钢、锰钼钒氮钢和铬钼钒钢等),包括结构钢、汽车用钢、锅炉用钢、石油管钢、压力容器钢、铁路用钢、塘瓷用钢、桥梁用钢、船舶用钢、氧气瓶钢、电工钢和供出口用钢等。其中,重深冲08镇冷轧汽车板钢、内圈网汽车轮网钢、65Y三角股钢绳钢先后被评为国家金牌产品;16MnR、16MnL、HG、16Mnq、J55、DZ_2、20gu等被评为部级优质产品。实践证明,转炉钢的     

轻质钢的研究进展(一)——富Al无间隙原子钢和铁素体轻质钢

轻质钢是在超低碳钢或C-Mn钢基础上添加Al元素而形成的Fe-Al或Fe-Mn-Al-C合金钢。简要介绍了Al元素对钢的密度、相组织构成和基体碳化物形成的影响,并依据合金成分和相组织构成将轻质钢大致分为单一铁素体钢(多为富Al无间隙原子钢,即Al-IF钢)、铁素体钢(多为δ-TRIP钢)、铁素体—奥氏体双相钢和奥氏体钢四类。重点阐述了Al-IF钢和δ-TRIP钢的微观组织特征、力学性能和强韧化机制,为进一步研究开发上述种类轻质钢提供参考。     

电炉虹吸出钢法的研究和应用

改电炉钢、渣混出的出钢方式为虹吸出钢。具体主要是:出钢口由水平改成30°倾斜;出钢过程中始终保持钢液面高于出钢孔内一端一定距离;通过改变炉坡角度来扩大熔池容积;出钢口大小和位置通过留渣量和留钢量来选取最佳值;出钢操作分始出钢、主出钢和终出钢3个阶段等技术。改后可实现无渣出钢,留钢、留渣操作,达到优化工艺,缩短冶炼时间、降低成本和提高产品质量的目的。     

首钢热轧酸洗先进高强钢的开发与进展

介绍了首钢热轧酸洗先进高强钢的开发与进展。根据客户的使用要求,结合生产设备,首钢研发了双相钢、高扩孔钢、复相钢、相变诱导塑性钢等系列高强钢。分析了双相钢、高扩孔钢、复相钢以及相变诱导塑性钢等产品的化学成分和力学性能,并利用金相显微镜和扫描电镜等手段对微观组织特征进行了描述。首钢热轧酸洗先进高强钢因出色的力学性能已经在汽车控制臂和纵梁等零件上得到广泛应用,未来将在乘用车减重和安全等方面发挥更大作用。     

日本钢铁材料研究的进展

一、绪言钢铁材料可分为纯铁、钢和铸铁三类,在日本国将钢分为普通钢和特殊钢。特殊钢又按其用途和性能分为结构钢、高强度钢、弹簧钢、工具钢、轴承钢、不锈钢及耐热钢等。不论哪一类钢,日本的研制和技术进步都非常显著。本文仅以高强度钢、不锈钢和耐热钢三类为中心,同时考虑与炼钢、轧钢和热处理等生产工艺的关系,介绍该三类钢的研制现状和动向。二、高强度钢     

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。     

基于ADAMS T型电梯导轨钢叠钢装置设计及仿真

叠钢操作是T型电梯导轨钢自动码垛系统的关键一环。针对T型导轨钢自动码垛系统的工艺要求,将叠钢操作分解为挡钢、抬钢和推钢这三个环节,设计了叠钢装置的基本结构。通过机构学分析,建立了摆杆位移与液压缸伸缩量的理论模型,为装置的参数设计提供了理论参考。运用ADAMS软件对叠钢过程进行了仿真,得到不同型号导轨钢叠钢过程的驱动力、位移和速度等参数,为装置的结构优化及控制参数设置提供了参考依据。仿真结果表明,所设计的叠钢装置能够实现不同型号导轨钢的叠钢操作。     

An improved calculation of the transformation of steels

For the calculation of the transformation of steels during continuous cooling a new method is proposed. For isothermal transformation the temperature dependence of 1% and 99% transformation of austenite is described by a function which can well be fitted to measured values. This function allows an extrapolation beyond the measured values giving good agreement between calculated and measured TTT-diagrams. For continuous cooling it is possible to calculate the transformation below M_s. The agreement between calculated and measured values of the volume fractions of different microstructural constituents at room temperature after continuous cooling is good.     

Q&P钢在冷却过程中铁素体的相变规律

 为了研究冷却过程中Q&P钢(quenching and partition steel)铁素体的相变规律,在热膨胀仪上以846 ℃均热200 s为冷却的初始条件,检测了成分(质量分数)为0.2%C、1.25%Si、2.0%Mn的Q&P钢在不同冷却速率下铁素体的相变热膨胀数据,应用杠杆定律将数据处理为相变规律与温度的关系,通过光学显微镜检测热处理后金相中的铁素体相体积分数和铁素体晶粒尺寸,得出了饱和位置形核条件下铁素体的形核率,基于混合控制模型得出了铁素体相变的相界迁移速率。结合相变开始温度,利用混合控制模型计算了相变结束温度和铁素体晶粒尺寸在相变过程中的演变规律,铁素体晶粒尺寸计算值与实测值吻合程度较高,相变结束温度的计算值与实测值的误差在±15 ℃以内,所获得的铁素体相变规律可以用于控制Q&P钢在冷却过程中的铁素体相变体积分数。     

空冷状态下金属相变温度的实测判定

 实测了空冷条件下金属的温度,分析了相变潜热释放引起的温降速度变化规律,并通过冷却速度曲线畸变特征点对实际工况下的金属相变开始温度和结束温度以及相变持续时间进行了判定。结果表明：该判定方法能够准确判断非恒速缓慢冷却时金属的相变特征点,解决了热模拟CCT曲线在实际应用中的局限性,是一种适合于实际生产应用的相变特征点的数值判定方法。     

Modeling of Incubation Time for Austenite to Ferrite Phase Transformation

 The giant stress-impedance (GSI) effect in as-cast and DC current annealed Co71.8Fe4.9Nb0.8Si7.5B15 amorphous glass-covered wires is presented. The SI ratio of the as-cast sample exhibits negative GSI effect. For the sample annealed by 60 mA DC current, the SI ratio first increases with applied tensile stress, then decreases with the applied tensile stress. The maximum ΔZ/Z ratio of 304% is obtained. Frequency dependence in the range from 1 to 110 MHz of the GSI effect is investigated. Experimental results show that the real part R and the imaginary part X of impedance play an important role at high frequency and low frequency, respectively. At 1 MHz, the maximum ΔX/X of 1 448% is obtained. At 110 MHz, the maximum ΔR/R ratio of 648% is obtained.     

TRIP780钢贝氏体区等温转变的规律

采用 DIL805L 型淬火膨胀仪测定了 C-Si-Mn 系 TRIP780钢贝氏体区等温转变曲线。依据膨胀量-时间曲线,计算出相变过程中的组织转变率,分别统计不同工艺下的转变率以及对应的时间关系。研究了 TRIP 钢在等温转变时的相变规律。结果表明：加热温度相同时,贝氏体转变速率随着等温温度的升高而提高,但总转变率降低;在等温温度相同时,加热温度越高,转变率也相应增大。在贝氏体等温转变图上,转变终了线为 C 形,即存在一个鼻尖,对应于最短的转变时间。     

86CrMoV7钢的过冷奥氏体转变

利用Ｆｏｒｍａｓｔｅｒ－Ｆ全自动膨胀仪测定８６ＣｒＭｏＶ７钢的过冷奥氏体等温转变曲线（ＴＴＴ图）中续冷却转变曲线（ＣＣＴ图）,结果表明：在ＴＴＴ图中存在珠光体、贝氏体、马工体转变,珠光体、贝氏体转变都呈“Ｃ”型,有两个鼻点,球光体的“鼻点”温度为６２５℃,孕育期为５０ｓ,贝氏体转变的“鼻点”温度为４００℃,孕育期为１２６ｓ。在ＣＣＴ图中,只存在珠光体和马氏体转变。     

A Conversional Model for Austenite Formation in Hypereutectoid Steels

An on-heating conversional model has been proposed to calculate the volume fraction of austenite in hypereutectoid steels from dilation strain. The transformation strain equation for austenite formation from ferrite and cementite was developed with lattice parameters modified to include alloying element effects. The conversional model was verified by comparing calculations with experimentally measured transformation temperatures and constituent volume fractions in the transformation temperature range for various heating rates. A continuous heating transformation (CHT) diagram was produced from model results.     

Continuous Cooling Transformation Behavior and Kinetic Models of Transformations for an Ultra-Low Carbon Bainitic Steel

 The aim was to investigate transformation behavior and transformation kinetics of an ultra-low carbon bainitic steel during continuous cooling. Continuous cooling transformation (CCT) curves of tested steel were measured by thermal dilatometer and metallographic structures at room temperature were observed by optical microscope. Then transformation kinetic equation of austenite to ferrite as well as austenite to bainite was established by analyzing the relationship of lnln［1/(1-f)］ and lnt in the kinetic equation on the basis of processed experimental data. Finally, the measured and calculated kinetic behaviors of the steel during continuous cooling were compared and growth patterns of transformed ferrite and bainite were analyzed. Results showed that calculated result was in reasonable agreement with the experimental data. It could be concluded that the growth modes of transformed ferrite and bainite were mainly one dimension as the Avrami exponents were between 1 and 2.     

NiTi and NiTi-TiC composites: Part 1. transformation and thermal cycling behavior

The transformation behavior of titanium-rich NiTi containing 0 vol pet, 10 vol pct, and 20 vol pct equiaxed TiC particles was studied by differential scanning calorimetry. The thermoelastic phase transformation of the unreinforced matrix exhibits multiple steps. Upon multiple transformation cycles, the rhombohedral phase (R phase) appears and all transformation temperatures decrease. The TiC particles inhibit the R phase and also lower some of the transformation temperatures. These effects can be explained by the internal misfit stresses resulting from both thermal expansion and transformation mismatch between matrix and reinforcement. The measured transformation enthalpy of bulk and reinforced NiTi is discussed in light of a thermodynamical model, taking into account the elastic energy stored upon cycling. The model indicates that a significant fraction of the matrix is stabilized and thus does not contribute to the transformation enthalpy. Formerly Postdoctoral Fellow, Department of Materials Science and Engineering, Massachusetts Institute of Technology.