帘线钢盘条索氏体片层间距控制生产实践

对帘线钢盘条索氏体片层间距控制进行了理论分析和生产实践研究。根据理论分析确定了控制索氏体片层间距所需的盘条相变过程的转变温度;通过测定帘线钢的相变过程连续冷却曲线,确定了盘条吐丝后冷却速度。在生产实践中采用了增加风机风量的方法,增加了盘条相变过程的冷却速度,保证了盘条相变温度,使盘条索氏体片层间距得到了有效控制。     

控制冷却对SWRH82B-1V高碳钢盘条组织和性能的影响

用Gleeble-2000热模拟机测定了V微合金化SWRH82B-1V钢(%:0.79C、0.23Si、0.63Mn、0.18Cr、0.05V、0.004 ON)热变形奥氏体连续冷却转变(CCT)曲线,并研究了冷却速度(1～15℃/s)对钢中索氏体和马氏体面积分数和HV硬度值的影响。通过改变斯泰摩尔生产线的冷却风量模式研究了冷却风量对SWRH82B-1V钢Φ12.5 mm盘条组织和力学性能的影响。结果表明,盘条吐丝温度880℃50%风量冷却可使该钢中索氏体组织≥90%,马氏体组织≤0.05%,盘条抗拉强度≥1130 MPa,断面收缩率≥30%。     

φ5.35mm-2100MPa桥梁用锌铝钢丝的工艺与组织性能

 为了制备更高强度级别的桥梁缆索用热镀锌铝钢丝，通过对高碳钢盘条的成分设计、低损伤拉拔技术以及热浸镀锌铝等工艺过程的优化，成功试制出?5.35 mm-2 100 MPa级桥梁缆索用热镀锌铝钢丝。设计的SWRS92Si盘条主要成分为（质量分数）：C 0.90%～0.95%，Si 0.8%～1.1%，Cr 0.20%～0.30%。试制结果表明，?13 mm-SWRS92Si盘条经铅浴处理后，珠光体层片平均尺寸从120下降至90 nm，盘条强度上升约260 MPa。经冷拉拔与热镀锌铝后，层片宽度约40 nm的珠光体层片未明显球化，可制备出2 100 MPa级直径5.35 mm的桥梁缆索用热镀锌铝钢丝。钢丝的平均抗拉强度为2 128 MPa，平均断后伸长率为5.4%，扭转圈数平均值为22圈，断口均为平断口，镀层较均匀致密；其他性能指标均优于交通部标准JT/T 1104—2016《桥梁用热镀锌铝合金钢丝》中的要求。     

超高强度钢绞线用盘条现状及发展

随着钢铁冶金技术与拉拔工艺技术的进步,钢绞线向着超高强度级别发展,具有广阔的市场前景。讨论了钢绞线用盘条的大小方坯制造流程、冷却方式,讨论了微合金元素的作用,网状碳化物、马氏体组织的形成条件与控制措施,以及超高强度钢绞线及盘条的发展方向。在线水浴韧化处理技术凭借着绿色环保、生产效率高等优点,有着广阔的应用前景。兴澄特钢利用在线水浴韧化处理技术已成功开发2300 MPa级超高强度钢绞线用盘条。     

吐丝温度对ER50-6盘条性能的影响

结合天钢现有装备特点,设计出三种不同吐丝温度下的控冷工艺,研究焊接用钢ER50-6盘条的力学性能及微观组织演变规律,以提高盘条的微观组织均匀性和力学性能。研究结果表明,ER50-6盘条吐丝温度为850℃,冷却速度控制在1℃/s以内时,ER50-6盘条具有均匀的铁素体和珠光体组织,可以避免产生贝氏体组织,力学性能适中,有利于后续的拉拔加工。     

82B盘条控冷工艺优化研究

通过热膨胀试验测定了82B试验钢的临界转变温度并绘制静态CCT曲线;研究了冷却制度对82B盘条金相组织的影响。结果表明:冷却相变时大的过冷度,可以减小片层间距,提高索氏体化率,得到强度和伸长率更好的盘条。因此须增加相变前的冷速(不低于8℃/s),控制相变过程中温度的稳定(560～640℃),控制相变后冷速不进入马氏体转变区间。经过工艺调整,盘条的索氏体化率从88%提高到90%以上,珠光体片间距控制在150 nm以下。     

大规格82B轧后强冷工艺研究与应用

高碳钢盘条冷却速度控制,主要是通过两个方面影响其金相组织、力学性能:一是控制水冷箱水量水压,达到穿水冷却后的吐丝温度;二是通过风机风量大小控制辊道上的冷却速度,从而减少铁素体组织、提高索氏体化率。通过轧后强冷+相变后缓冷工艺,使索氏体组织片层间距减小,盘条的强度和塑性大大增加。     

Φ7.0mm 2000MPa级桥梁缆索用热镀锌铝合金钢丝的研制

通过对高碳高硅盘条的合金化成分设计、离线索氏体化处理、低损伤拉拔技术和热浸镀锌铝等工艺过程的优化,成功试制出Φ7.0mm 2000MPa桥梁缆索用热镀锌铝钢丝,钢丝的性能指标均符合桥梁缆索用热镀锌铝钢丝的要求。     

桥梁缆索热镀钢丝的应力腐蚀性能研究

作为大跨度桥梁的主要承载材料,桥梁缆索用热镀钢丝应具有良好的力学性能和抗应力腐蚀性能。钢丝强度不断提升,应力腐蚀敏感性也不断增加。热镀钢丝的抗应力腐蚀性能已成为影响高强度钢丝应用的关键参数之一。采用FIP试验和电化学方法,研究了强度等级和表面质量对热镀钢丝应力腐蚀敏感性的影响,并分析了应力腐蚀断口形貌。结果表明,1860 MPa级和2060 MPa级桥梁缆索用热镀钢丝的应力腐蚀断裂时间相当,但2060 MPa级钢丝的应力腐蚀时间更加离散;钢丝表面越粗糙,应力腐蚀敏感性越强;2060 MPa级钢丝表面采用800目砂纸打磨后,应力腐蚀断裂时间明显缩短。应力腐蚀断口形貌分为裂纹源区、裂纹扩展区和瞬断区,裂纹主要起源于表面。在现有成分体系和生产工艺条件下,2060 MPa级桥梁缆索用热镀钢丝应力腐蚀性能尚能满足应用要求,但更高强度钢丝的应力腐蚀性能有待于深入研究。     

高档制绳用盘条的生产工艺开发

为了优化产品结构,应对市场激烈竞争,天钢研制并开发了高档制绳用盘条。系统的阐述了高档制绳用盘条工艺开发的情况,采用低温精轧结合先快冷后慢冷的冷却工艺,较好的解决了盘条索氏体化率低、异常组织、性能波动大的问题。产品综合力学性能优良,索氏体化率高,表面质量、夹杂物控制良好,满足了用户制作高档钢丝绳的要求。     

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。     

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.     

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%).     

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.     

Tubeless superimposed high frequency jet ventilation in high grade laryngeal stenoses

Massive stenosis of the larynx may present a potentially life-threatening situation for the patient, requiring immediate measures to ensure a patient's airway. The aim of this prospective study was to evaluate potential benefits of Superimposed High Frequency Jet Ventilation (SHFJV) in patients requiring microlaryngeal surgery due to massive stenosis of the larynx. Patients and methods: 23 patients (age range 1.5 to 90 years) with laryngeal stenosis grade 2 and 3 according to the Cotton scale were ventilated using SHFJV. The duration of the SHFJV was 12 to 116 minutes. SHFJV was performed using a Bronchotron Respirator via a jet-laryngoscope. Results: Arterial blood gases demonstrated paO2 between 71 and 295 mmHg and paCO2 of 28 to 81 mmHg. The mean FiO2 applied was 61.75 +/- 19.26. The airway pressure was measured at the tip of the jet-laryngoscope and was between 6 and 15 mmHg, and PEEP was 1 to 5 mmHg. In 13 patients a CO2 laser was utilised during surgery. Discussion: In all patients SHFJV was performed without problems. Since the ventilation is delivered above any possible stenosis the danger of barotrauma is minimised. The surgeon obtains optimal visibility of the larynx and is not obstructed in the surgical procedure. SHFJV enables both the surgeon and the anesthetist to perform their respective duties and therefore increases the safety of the patient in the management of such a difficult problem as massive stenosis of the larynx.