高频红外吸收法测定铁矿石中硫

采用高频红外吸收法,以线状氧化铜为主要助熔剂,对铁矿石中硫进行测定,通过对样品的处理、空白实验、比较水平和分析时间的确定,助熔剂及助熔剂的加入程序,称样量的选择和试验,从而获得了最佳测试条件,并对检测精密度和准确度进行了验证,结果令人满意,具有较高的使用价值。     

高频红外吸收法快速测定硫精矿中高含量硫

采用硫铁矿标准样品绘制硫的校准曲线,并用内控管理样品对曲线进行校准,建立了快速测定硫精矿中高含量硫的高频红外吸收法。对样品的粒度、称样量、燃烧时间和助熔剂的选择进行了研究。结果表明,以约0.400 g铁屑和约1.500 g钨粒作为助熔剂,0.100 0 g样品在高频感应条件下燃烧45 s,然后在选定的仪器工作参数下测定,硫的测定结果与空气燃烧中和滴定法的测定结果相符。对一硫精矿样品进行精密度试验,硫的11次测定结果的相对标准偏差(RSD)为0.39% 。方法可以用于硫精矿中质量分数为40%～50%硫的快速测定。     

高频燃烧—红外吸收法测定金属铬中硫含量

采用高频燃烧一红外吸收法对金属铬中硫含量进行测定。确定了称样量为0.5g,高频燃烧功率为80%,助熔剂的选择及配比为纯铁0.5 g＋钨锡混合助熔剂（4：1）1.2g;比较级水平为1%,分析时间为45s。该方法用于金属铬标样（GSBH 42006-92）分析,所得结果同标准值一致,标准偏差为0.00033%。     

用HCS-140A高频红外碳硫仪测定煤中硫含量

介绍了采用高频红外碳硫仪测定煤中硫含量的方法,通过选择合适称样量、助熔剂及合理的加入顺序,可以获得令人满意的试验结果.     

铁精矿高硫分析方法的改进

采用CS-206高频红外碳硫分析仪对铁精矿中高硫(0.5≥%)进行测定,对助熔剂种类、加入量、比例、称样量、试样的加入顺序等条件进行试验,选择出测定铁精矿中高硫的最佳条件,此法上限为3.50%。     

高频红外碳硫仪法测铬铁合金中的碳硫

研究了,刚高频红外碳硫仪测中碳铬铁、低碳铬铁合金中碳硫含量的方法,对空白值的扣除、试样加入量、助熔剂的选择及其配比、助熔剂的加入方式以及粉尘的影响进行了试验,确定了最佳分析条件,陔办法快速准确、相对标准偏差小,能够满足生产需要。     

高频感应红外吸收法测定钨精矿中硫量

本方法采用高频感应红外吸收法测定钨精矿中硫含量。经实验确定了测定硫量的最佳分析条件:板极电流150 mA;加热时间25 s;称样量0.1～0.3 g;助熔剂的用量及加入顺序为1.0 g锡粒+0.1 g试样+1.5 g钨粒+0.5 g铁屑。该方法通过标准样品的回收实验、不同方法的对照实验、精密度实验以及实际试样的分析,证明该方法操作简单快捷,回收率达到96.90%～99.77%,相对标准偏差为0.69%～0.85%。     

异标校正红外吸收法测定特性材料保护渣中碳硫含量

利用高频红外吸收法测定了特性材料保护渣中碳硫元素含量,同时采用钢标、铁合金、钢渣等异标相结合方式绘制工作曲线并进行校正。通过对坩埚预处理、仪器参数设置、选择最佳样品称样量和助熔剂等一系列手段,最终确定称样量在0.050 0±0.000 1 g范围内,助熔剂选择“纯铁+钨粒+锡粒”,过原点且扣空白的方式进行基础曲线校正。该分析方法准确度和精密度高,解决了特性材料保护渣无国标样品检测的难题,保证了张宣科技特性材料物料进厂检测的需求。     

高频燃烧红外吸收法测定高锰不锈钢中痕量硫的助熔剂选择及其作用机理研究

针对高频燃烧红外吸收法测定高锰不锈钢中痕量硫的结果严重偏低现象,以Cr18Ni5Mn10Mo3和GH139高锰不锈钢为试验样品,考察助熔剂的种类、配比、加入顺序及称样量对测定的影响。同时,借助热分析仪对助熔剂的高温氧化行为进行了分析,探讨了助熔剂的作用机理,为助熔剂的选择提供了理论依据。试验结果表明,Cr18Ni5Mn10Mo3和GH139不锈钢的最佳助熔剂用量及样品加入顺序分别为0.5 g纯铁+0.25 g样品+0.5 g锡+2.5 g钨和0.5 g锡+0.7 g纯铁+0.20 g样品+0.5 g三氧化钼和五氧化二钒的混合物(m(MoO₃)∶m(V₂O₅)) +1.5 g钨。用本方法测定了2个高锰不锈钢标准样品中的硫量,测定值与认定值相符,测定结果的相对标准偏差分别为7.2%和4.5%（n=6）。     

高频红外法快速测定金属锑中微量硫

应用高频红外碳硫仪 ,建立了金属锑中微量硫测定方法 ,本文对选择适当的测定条件如助熔剂、分析时间和称样量等进行了较为详细的探讨 ,在最佳条件下测定 ,取得了满意的测定效果。     

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.     

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.     

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。     

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。     

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。     

含Nb高强钢高温凝固特性与物性参数的计算

以Ueshima的正六边形凝固模型为基础,通过有限差分法建立了钢凝固过程中两相区溶质微观偏析模型,分析了含Nb高强钢溶质元素对其凝固偏析的影响,并通过理论计算分析了连铸条件下含Nb高强钢的高温物性参数。分析表明,在碳含量低于包晶点时,P、S、Nb和Ti元素偏析程度随着碳含量的增加而降低;碳含量高于包晶点时,元素偏析趋势相反。定量计算了固定成分下含Nb钢高温物性参数的值,由于Fe不同相的高物性参数并不一致,可以看出一个准确的相组成对高温物性参数的确定十分重要。     

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.     

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.     

CNS tumours in south-western Finland: high location, high incidence

The Department of Paediatrics at the University Central Hospital of Turku, Finland has 130,000 children under 17 y of age within its catchment area. We collected all 103 cases of newly diagnosed CNS tumours from the 15-y period of 1981-95. The incidence was 5.3:100,000, a figure twofold those usually presented. During the period 1981-85 the incidence was lower (4) than during the subsequent 5-y periods (5.7 and 6.2). There were no statistical differences between the incidences of the supra- vs infratentorial brain tumours. Optic glioma was unusually common (17%, CI 13.9-20%).