The high temperature transformation of high speed steel

Low tempered hardnesses on high speed steels which had been hardened in vacuum or atmosphere furnaces and gas quenched led to a search for a reaction occurring above 1400°F and probably initiated as a result of the slower cooling rate of the gas quench. A standard TTT evaluation was carried out on Ml, M2 high carbon, M3, and M7 high speed steels, quenching from conventional hardening temperatures, into salt baths maintained at 2000° to 1500°F. Examination of these specimens indicated the presence of a reaction occurring at all temperatures investigated but having its maximum rate at 1700° to 1800°F. The reaction involved precipitation of an MoC/Mo₂C carbide at grain boundaries and within the grains, with the amount of precipitate increasing with time. The precipitation of MoC/Mo₂C is directly related to the loss in tempered hardness and apparently causes this effect by 1) reducing precipitation hardening on tempering, 2) drastically lowering retained austenite contents, and 3) reducing as-quenched hardnesses.     

MgO对高碱度高铝烧结矿的影响

 随着钢铁企业高铝铁矿粉使用比例的提高,带来了高炉炉渣黏度增大、渣铁分离困难等一系列问题。采用烧结杯试验,研究了MgO含量增加对高碱度高铝烧结矿经济技术指标、冷强度和冶金性能的影响,采用Nova400 NanoSEM型场发射扫描电子显微镜分析了烧结矿微观结构。试验结果表明,高碱度高铝烧结矿中MgO质量分数从1.72%提高到2.49%时,垂直烧结速度降低4.38 mm/min,利用系数降低0.51 t/(m2·h),低温还原粉化指数增加6.7%;当烧结矿中MgO质量分数为2.11%时,转鼓指数和还原度最高,分别达到61.93%和86.39%;Mg2+主要固溶在磁铁矿晶格中并替代Fe2+,替代的质量分数最高达3.64%,生成的含镁磁铁矿抑制烧结矿降温过程中由Fe₃O₄→Fe₂O₃氧化过程的相变,减少了二次赤铁矿的生成,有利于改善烧结矿的低温还原粉化性能。研究结果可以为改善高碱度高铝烧结矿性能和提高炉渣流动性提供理论指导和参考依据。     

Smoking: high hazards in high school

BACKGROUND: Young people in school are at an impressionable age, peer pressures are intense, and the probability that they will pick up a high-risk behavior, such as smoking, is high. The key to reduction of smoking among adults is to target our prevention efforts at young adults and teens. OBJECTIVE: To study the prevalence and trend of smoking among young adults and teens and to formulate guidelines on smoking reduction to guide those who counsel young people. STUDY DESIGN: The study design is cross sectional. METHODS: This study is based on the data from the Oklahoma Behavioral Risk Factor Surveillance System and the National Youth Risk Behavioral Surveillance System - the two systems that monitor the prevalence of behaviors that most influence health. RESULTS: The prevalence of smoking among young adults (age 18-24) in Oklahoma is high at more than 21%. The disturbing feature is that it is higher among young females than among young males. The prevalence of smoking among young adults is the highest among high school dropouts and is more than 38%. It is lower among high school graduates (about 28%) and lowest among college graduates (about 18%). The percentage of smoking among students who classify themselves as current smokers rises from 23% to 30% as the students progress from grade 9 to 12 and the percentage of frequent smokers increases from 8% to 16%. CONCLUSIONS: Guidelines suggested for counselors are: 1. Along with smoking, look for comorbid behaviors such as alcohol use, drug abuse, and high-risk sexual behavior. 2. Ask whether the student has easy access to free cigarette samples. 3. Check whether the teen is trying to lose weight; suggest appropriate methods for losing weight if smoking is being used for losing weight. 4. Target health education efforts early in a student's school career starting in elementary school, but concentrate especially at the 8th or 9th grade level to have maximum preventive impact.     

高碳钢高温力学性能研究

在Gleeble-2000动态热模拟试验机上采用凝固法研究了高碳钢的高温力学性能.测定了tZD(零塑性温度)、tZS(零强度温度).在4×10-4/s应变速率条件下,所测钢种在熔点到750 ℃范围存在两个脆性温度区域,即熔点到1 300 ℃的第Ⅰ脆性温度区域和750～925 ℃的第Ⅲ脆性温度区域.在第Ⅲ脆性温度区域,γ单相AIN、NbN等氮化物在γ晶界的析出和在γ α两相区先共析α相呈网膜状,在γ晶界的析出是造成钢脆化的主要原因.通过控制钢中氮、铝含量,以及采用合理的冷却方式可以提高钢种的内在质量.     

高综合性能亚共晶高铬铸铁的烧结制备

以气雾化粉末为原料,采用液相烧结(LPS)制备亚共晶高铬铸铁(HCCIs),系统研究烧结工艺参数对致密化行为、显微组织演变和力学性能的影响规律。研究结果表明,采用LPS可以获得相对致密度达99%以上的制品,但合适的烧结温度范围很窄;XRD分析表明烧结亚共晶高铬铸铁由M7C3型碳化物、马氏体和奥氏体构成;金相分析显示烧结样晶粒细小,碳化物为一次晶杆状,且分布均匀。随烧结温度升高和保温时间延长,晶粒和碳化物均逐步粗化,其中温度的影响更加显著;而强度和冲击韧性则呈现先升高后降低的变化规律。优化的烧结工艺下高铬铸铁的力学性能为：硬度HRC65,抗弯强度1199 MPa,冲击韧性4.6 J/cm2。并提出了一个烧结高铬铸铁中碳化物形态演变的生长模型。     

Demanganisation of high manganese pig iron to produce high manganese slag

Abstract

Pig iron with a high manganese content makes further processing to steel using converter technology difficult and unprofitable. In the present study, external demanganisation of high manganese pig iron before the oxygen converter process has been investigated. Pilot plant experimental heats were designed and carried out to optimise the demanganisation process, to produce hot metal adequate for the conventional LD converter, and high manganese slag suitable for the production of silicomanganese. Various high manganese pig irons with different [Si]/[Mn] contents were treated by injection of various oxidisers at varying temperatures, slag basicities and injection rates. The optimum conditions for the demanganisation process have been attained by injection of an oxygen gas–manganese ore mixture at the injection rate of 6.8 L min^-1kg^-1 into molten high manganese pig iron with a [Si]/[Mn] ratio of 0.3 at an initial temperature of 1350°C and slag basicity of 0.3–0.4.     

Microstructure characteristics of spray-formed high vanadium and cobalt high speed steel

The microstructure of high vanadium and cobalt high speed steel(high-V/Co HSS) and the morphology of its carbides were analyzed by optical microscope(OM),scanning electron microscope(SEM),electron probe microanalysis(EPMA),X-ray power diffraction(XRD),atomic force microscopy(AFM) and single phase erosion(SPE).The results suggest that the as-sprayed high-V/Co HSS has fine equiaxed grains(about 20 μm in size),which were homogeneously distributed.The carbides have two classical morphologies:one is fine particles(about 2 μm in size) distributed along the grain boundaries and the other is needle-like one,distributed on the grain boundaries.There are MC carbides,M2C carbides,M6C carbides and Cr2WC2 carbides in the as-sprayed high-V/Co HSS samples,however,in the as-cast high-V/Co HSS,there are MC carbides and Cr2WC2 carbides only.The SPE results show that there are two types of MC carbides in the as-sprayed HSS:the sphere one and the particle-like one.The former is about 2 μm in size and the latter is less than 1 μm,dispersed inside the grains,quite different from the MC carbides in the as-cast HSS.According to the AFM results,the skeleton-like M6C carbides of the as-sprayed high-V/Co HSS are embedded in the matrix along the grain boundaries.It is found that there are sharp membrane pieces on the carbides.Some small bamboo-shoot-like MC carbides grow from the matrix and are dispersed inside the grain.Those larger MC carbides are spherical particles embedded at the grain boundary junctions.     

Recent developments of the high strength and high ductility nanostructured materials

This talk will summarize the recent work related to a kind of new nanomaterials produced by the SMAT (surface mechanical attrition treatment).The concept of surface nanocrystallization of materials will be presented.In terms of the grain refinement mechanism induced by plastic deformation,a novel surface mechanical attrition(SMA) technique was developed for synthesizing a nanostructured surface layer on metallic materials in order to upgrade the overall properties and performance.The grain refinement mechanism of the surface layer during the SMA treatment will be analyzed in terms of the nanostructure observations in several typical materials.Very high yield stress(5 times of the base material) on the surface layer of the material obtained by the SMAT has been observed.The effect of surface nanostructures on the mechanical behavior and on the failure mechanism of metallic material shows the possibility to develop a new strength gradient composite using co-rolling and nitriding.The role of residual stress induced during the treatment will be investigated and discussed.The developed materials are also porosity free materials which can be used as reference material for the local mechanical behavior investigation technique such as the nanoindentation.A general concept for obtaining high strength and high ductility nanostructured materials will be presented.The exceptional high strength and high ductility steels have developed.The simulation of the mechanisms for improving ductility of high strength nanostructured materials will be presented.The potential applications for the land transportation vehicles(car,bus,train) and wind energy have been investigated.Some examples of concept design for the integration of the advanced nanostructured steels will be presented.     

浅谈优质高蛋白大豆高产栽培技术措施

针对勃利县大豆生产情况和对高蛋白大豆的需求,提出采用连片种植、选择种植高蛋白大豆新品种、深松秋整地、种子处理、测土配方施肥、加强田间管理和大豆标准化"垄三"栽培技术等措施.     

宝钢3号高炉高煤比条件下的高利用系数生产研究

宝钢3号高炉通过技术创新和开发,不断完善操作技术水平,改善原燃料条件,1999年在维持煤比200kg/t以上的同时,实现年均利用系数2．303,2000年高炉利用系数再创新高,月均最高达到2．145,宝钢高煤比高利用系数冶炼技术达到世界领水平。     

高密度高强度高精度粉末冶金同步器齿毂生产工艺探讨

粉末冶金零件在汽车上的应用越来越广泛。粉末冶金同步器齿毂是汽车零部件中难度较大的一类。高密度高强度高精度粉末冶金同步器齿毂的生产工艺研究是中国现阶段的主要研究方向之一。长期的生产工艺研究表明,先进的生产工艺是粉末冶金同步器齿毂大批量国产化的关键。     

电渣重熔用五元高氟渣高温挥发机制

 为探究高温过程电渣组元挥发机理,以电渣重熔用高氟渣CaF2 CaO SiO2 Al2O3 MgO五元渣系为基础研究炉渣高温挥发机制,通过FactSage理论计算、热重及高温质谱检测,结合1 000～1 500 ℃高温焙烧试验以及XRF检测与SEM物相观察,对炉渣加热过程成分及物相变化进行了研究。结果表明,温度为550～800 ℃时,CaF2与SiO2反应生成SiF4气体;温度为800～1 200 ℃时,CaF2与MgO反应生成MgF2气体,同时与少量Al2O3反应生成AlF3气体;温度为1 200～1 500 ℃时,挥发分主要为CaF2及少量AlF3。在高温区(1 000～1 400 ℃),晶体主要为二铝酸钙和和少量枪晶石;当温度达到1 500 ℃,晶体主要为枪晶石结构,为探究高温过程电渣组元挥发机理以及电渣制备工艺的优化提供参考。     

高性能管线钢高温延塑性对比研究

用Gleeble-1500热/力模拟机测试了X60、X65、X70钢铸坯的高温延塑性,并进行对比研究.通过扫描电镜、金相显微镜对断口形貌及组织进行分析,得出主要结论:高温脆性区(T1～1 300℃)钢的延塑性主要受碳含量多少的影响,相比较X70的塑性较好;高温高塑性区(1 100～1 300℃)由于试验应变速率小于10-2/s时,该区域不存在脆化,3个钢种塑性均很好;在塑性槽高温端(900～1 100℃),由于低熔点硫化物等析出,弱化晶界,另外动态再结晶发生温度的不同,导致两个钢种塑性的明显差别;塑性槽两相区(700～900℃)先共析铁素体的出现是3个钢种塑性很低的共同原因,MnS和钛可以促进铁素体在晶内和晶界同时生成,750℃以下,3个钢种延塑性均有所提高,X65塑性恢复较快.     

一种高铬的铁镍基高温合金物理化学相分析

采用物理化学相分析方法研究了高铬的铁镍基高温合金时效后碳化物和金属间化合物的析出行为,通过实验确定了铁镍基高温合金中析出相的萃取方法、相分离方法、钢中析出相的类型和含量、γ′相的粒度分布。研究结果表明,铁镍基高温合金中析出相为γ′、NbC、TiC、Laves和σ,随着时效时间的增加,NbC和TiC相含量变化不大,Laves相和γ′含量略有增加,σ相含量增加比较明显,γ′相的粒度随时效时间明显增加,σ相含量的增加和γ′相颗粒的增大是造成合金高温屈服强度下降的主要原因。研究结果对高铬的铁镍基高温合金成分的控制、生产工艺的选择和热处理制度的合理制定具有指导意义。     

弹丸高速冲击条件下高强度钢板抗弹性能

摘要：为了研究弹丸高速冲击条件下不同洁净度的40CrNi2Mo钢板的抗弹性能，利用12.7mm穿甲燃烧弹对抗拉强度分别为800和1200MPa级的钢板进行抗弹性能测试。通过观察不同强度钢板出现的损伤形貌，评定背面强度极限，分析了穿甲机制。结果表明：抗拉强度为800MPa级的钢板在弹丸冲击过程中以塑性扩孔方式侵彻，抗弹性能随着强度升高而提高，与洁净度关系不大。抗拉强度为1200MPa级的钢板，弹丸冲击过程中因钢板较低的绝热剪切临界失稳应变而出现绝热剪切；由于塑韧性较低，低洁净度钢板阻止绝热剪切引发裂纹扩展的能力较弱，因此形成与绝热剪切相关的裂纹，导致抗弹性能降低；高洁净度钢板抗弹性能相对较高，因背面出现剪切裂纹而失效，此裂纹与绝热剪切无关。     

高强耐磨稀土高锰黄铜的组织与性能

设计一种用于制造同步器齿环的CuZnMnAlSiFeCeB复杂黄铜合金,利用水平连铸,热挤压和快速水冷的工艺制备合金型材.利用金相显微镜和扫描电镜以及能谱分析的手段研究合金的铸态组织,挤压态组织. 合金铸态组织均匀,无气孔和夹杂等缺陷. 挤压淬火态合金组织为β+少量α+均匀分布强化相. 合金挤压淬火后的性能为抗拉强度783 MPa,断后伸长率5.89 %.      

高碳钢转炉冶炼过程高拉碳工艺研究

针对东北特钢集团北满特殊钢有限责任公司普遍采用的炉后增碳法转炉冶炼高碳低磷钢工艺存在的诸多问题,在理论分析和工业试验的基础上,通过造渣模式、化渣脱磷工艺、氧枪枪位及终点控制等工艺技术的系统优化,克服了恶劣原料条件的影响,研究开发了适用于北满特钢的高碳钢转炉冶炼高拉碳工艺,使终点碳质量分数由0.12%提高到0.29%,脱氧剂消耗平均降低了0.21 kg/t,增碳剂消耗平均降低了2.16 kg/t,吨钢成本降低了30.76元,高碳钢综合合格率提高了3.5%。     

高化学耗氧量、高浊度废水絮凝研究

研究了一种化学耗氧量、浊度很高的废水絮凝过程。首先,对不同的絮凝剂进行筛选。以COD、浊度为指标,选出最佳絮凝剂;然后,对选定的絮凝剂,在不同的因素下进行试验,找出最佳试验条件,各种因素分别为：絮凝剂的加入量、pH、搅拌速度、沉降时间。以不同的絮凝剂采处理废水,试验结果表明,Al2（SO4）,絮凝效果最好。采用单因素对Al2（SO4）,絮凝废水进行优化试验,结果表明,絮凝剂加入量与料液比值为0．85g／L、pH为7、搅拌速度为130r／min、沉降时间为80min．絮凝效果最好。     

高供氧压力下高马赫数氧枪数值模拟

  以北方某钢厂100 t转炉为原型，建立顶吹转炉炉内流场的三维数学模型，采用Fluent软件研究了不同高马赫数氧气射流与熔池钢液速度流场分布之间的依赖关系。研究发现，高马赫数氧枪在Ma（马赫数）为2.0～2.3时，曲线平稳，为最佳供氧压力。在提高供氧压力的同时，氧气射流的最大速度、熔池钢液面的冲击直径及冲击深度也随之增加。模拟结果显示，氧气射流在设计工况氧压小于1.0 MPa时，射流之间相互干扰作用最弱；氧气射流在设计工况氧压力大于1.0 MPa后，冲击直径与冲击深度增幅较小。基于上述研究，在实际生产中应用了高马赫数氧枪后，并结合变枪变压操作工艺，可以改善熔池底部钢液流动状况、稳定转炉吹炼过程、控制炉渣喷溅。