Influence of Carbon Content on Strain Hardening Behaviour of Sintered Plain Carbon Steel Preforms

 Complete experimental investigation on the instantaneous strain hardening behaviour of powder metallurgy (P/M) preforms of pure iron, Fe-0.35%C, Fe-0.75%C and Fe-1.1%C was carried out. The strain hardening behaviour of the above-mentioned P/M sintered steel preforms with aspect ratio of 0.4 under triaxial stress state condition was determined by cold upsetting under nil/no and graphite lubricant conditions. The instantaneous strain hardening value (ni), strength coefficient (Ki), and the stress as a function of strain and densification were obtained and analyzed. Furthermore, a relation was obtained from a semi-log plot of stress against relative density and analyzed to study the hardening behaviour owing to densification as stress was a function of induced strain as well as densification in the P/M materials.     

中碳钢的高温力学行为

借助Gleeble1500热模拟试验机,测试了45钢自凝固点至600℃温温度范围内的强度和塑性变化规律,并就加热方式、应变速率、冷却速度等因素对凝固温度区、奥氏体区和γ→α相变区的强度和塑性的影响进行了研究,还对3个区形成裂纹的机理进行了初步探讨。     

Hot Deformation and Dynamic Recrystallization Behaviour of Medium Carbon Steel in Austenite Region

The hot deformation behaviour of a 0.47%C (JIS‐S45C) steel in the stable austenite region was systematically investigated under various deformation conditions to collect fundamental data on its high‐temperature deformation and microstructure evolution. The medium carbon steel showed dynamic recrystallization in a wide range of temperatures (850°C～1150°C) and strain rates (10^‐3 s^‐1～100 s^‐1) in the stable austenite region. The dynamically recrystallized grain size was monotonically decreasing with increasing steady state stress. The minimum grain size obtained through dynamic recrystallization was 8.3 μm when the S45C specimen was deformed at 850°C and 1 s^‐1. The stress‐strain relationships were formularized based on a phenomenological model. The stress‐strain curves estimated by the obtained equation were in good agreement with the experimental results.     

Mild Oxidative Wear Behaviour of Plain Carbon Dual‐Phase Steel

In order to explore the tribological potential of the dual phase (DP) steel as wear resistant material, the wear and friction characteristics of this steel, which consists of hard martensite island embedded in a ductile ferrite matrix, were investigated and compared with those observed in plain carbon normalized (N) steel with the same composition of 0.2 wt pct carbon. Dry sliding wear tests were carried out using a pin‐on‐disk wear testing machine at normal loads of 21.3, 28.5, 35.7 and 42.6 N and at a constant sliding velocity of 1.20 m/s. The analysis of surface and wear debris of the tested specimens showed that wear mechanism was mainly mild oxidative. The friction and wear rate of the DP steel and N steel were explained with respect to microstructure and the wear mechanism.     

The Influence of Rapid Annealing Cycles on the Recrystallisation Behaviour of Cold Rolled Ultra Low Carbon and Low Carbon Steel

For ultra low carbon (ULC) and low carbon steel (LC), the influence of heating rate, annealing temperature, and holding time on the recrystallisation behaviour and the resulting grain size was investigated. For ULC smallest grain sizes of about 9 μm were obtained at the lowest heating rate whereas for LC significant smaller grain sizes of about 5 μm were determined at the highest heating rate. Furthermore, the evolution of the grain size distribution with varying heating rate, annealing temperature, and holding time was studied in dependence of the rolling and normal direction. The state of the as‐hot rolled microstructure as well as the precipitation state exert a strong influence on the development of the recrystallised microstructure along the different directions for both steel grades. The inherent prolonged microstructure due to the cold rolling process is still obvious just after recrystallisation. With ongoing annealing and grain growth, the aspect ratio approaches the equiaxed state. This change proceeds faster for the ULC steel grade. With increasing annealing temperature, the bimodal character of the grain size distribution disappears and the distribution becomes more homogeneous.     

包钢天诚线材漩流井缺陷改造

漩流井运行发现,立式水泵故障率高,备件费用昂贵,考虑到维修方便,降低成本,将立式水泵改造为卧式水泵,并将漩流井溜渣缝及切线的缺陷进行了改造.     

钢帘线用高碳钢(82B)氧化物夹杂控制热力学

用热力学方法预测了高碳帘线钢 (82B)中强脱氧元素的含量与各阶段脱氧产物组成之间的关系。指出在合金化阶段当钢中w ([Al]) <3× 10 - 6 时 ,一次脱氧产物为具有良好变形能力的锰铝榴石 ,相应的一次脱氧产物析出量小于 10 %。钢液在冷却和凝固阶段析出的脱氧产物组成决定于钢液中钙和铝的相对含量 ,控制钢液中w ([Al]) <3.5× 10 - 6 就可避免析出Al2 O3。这时的二、三次脱氧产物组成随钢液中钙含量的高低可分别为假硅灰石、钙斜长石或莫来石。     

超低碳贝氏体钢(ULCB)和耐候钢 09CuPCrNi 的耐蚀性

通过周期性浸润腐蚀试验测定了ULCB钢(%:0.05C、1.61Mn、0.51Cu、0.17Cr、0.26Ni)和耐候钢09CuPCrNi(%:0.09C、0.35Mn、0.09P、0.31Cu、0.45Cr、0.31Ni)14 mm板的耐腐蚀性能,并用偏光显微镜,X-射线衍射仪和能谱仪等研究了耐蚀机理.结果表明,ULCB钢的耐腐蚀性能优于09CuPCrNi钢;发现两种钢均存在由α-FeOOH,β-FeOOH和Fe3O4组成致密的内锈层、由α-,β-FeOOH和Fe3O4组成的疏松外锈层;Cu和Cr合金元素在锈层和锈层-钢基体界面均存在富集现象.     

稀土在低硫钢中的作用规律

研究了稀土对低硫（Ｓ〈０．００５％）钢性能和组织的影响，研究结果表明，稀土元素的加入可大大改善钢的冲击韧性，而不影响钢的组织类型，但可使钢中铁素体数量增加，珠洮体数量减少，晶粒度级别略有提高。     

软水对碳钢和紫铜腐蚀的影响因素

稳定的冷却水水质对高炉长寿有着至关重要的作用。设计正交试验研究高炉用软水水质指标温度、pH、电导率对碳钢和紫铜腐蚀的影响,并对其影响规律进行分析。对碳钢而言,pH、电导率不具有显著性,而温度具有显著性,温度是引起碳钢腐蚀的主要因素。对紫铜而言,温度、pH、电导率都不具有显著性,软水对紫铜几乎不腐蚀。     

本钢RH生产超低碳钢的实践

根据RH真空脱碳机理,结合本钢冶炼超低碳钢的生产实践,分析了脱碳时间和钢包等因素对钢水碳含量的影响,确定了超低碳钢的冶炼操作工艺以及降低钢液增碳的措施。     

中碳硫系易切削钢LF(VD)精炼实践

中碳硫系易切削钢1141(%:0.37～0.45C、1.20～1.65Mn、0.06～0.12S)和1144(%:0.40～0.48C、1.35～1.65Mn、0.24～0.33S)由65 t Consteel电弧炉-LF(VD)-(150～200)mm×(150～200)mm CC流程生产。LF精炼时喂Al线,控制[Al]0.02%～0.05%,精炼渣CaO/SiO₂ 2.62～3.02,使精炼中后期渣中硫化物容量达到饱和,在VD处理时吹氩200～250 L/min,≥15 min,使1141钢[S]在VD前后分别为0.11%～0.12%和0.10%～0.12%,1144钢[S]VD前后分别为0.30%～0.33%和0.29%～0.30%,稳定了VD处理前后钢中的硫含量。     

预应变量对超低碳烘烤硬化(ULC-BH)钢硬化性能的影响

测定了ULC-BH钢1 mm退火冷轧钢板(/%:0.002C,0.008Si,0.60Mn,0.043P,0.009S,0.031Al,0.071Ti)经2%~10%预应变,170℃20 min烘烤后的烘烤硬化(BH)值,通过内耗实验获得不同应变时效下的内耗谱线,利用X射线衍射技术测定位错密度,研究了Cottrell气团对ULC-BH钢烘烤硬化性能的影响。结果表明,随预应变量增加,ULC-BH钢的BH值增大;随预应变量增加,Snoek峰逐渐降低,而SKK峰逐渐升高;经2%、6%和10%预应变,位错密度增大,分别为3.9×10¹⁰/cm~2,8.4×10¹⁰/cm²和6.8×10¹¹/cm²,相应的Cottrell气团密度逐渐减小。     

Behaviour of Hydrogen in Industrial Scale Steel Melts

The behaviour of hydrogen during controlled industrial scale secondary steel making process has been examined in a variety of low alloy steels, sensitive to hydrogen flaking. The study examines the role played by the moisture in input raw materials such as the ferro-alloys, type of carbon additive and fluxes in enhancing the hydrogen content in the ladle furnace. Post alloying, the influence of vacuum degassing parameters such as the vacuum level, vacuum holding time, Ar flow rate, type of porous plug used, slag chemistry and the steel grade was examined. The vacuum degassing process was analysed using a kinetic model, which could justify the trends seen in the vacuum level, holding time and Ar gas flow rate. Finally, the hydrogen pick-up post vacuum degassing through slag cover and the casting tundish was found to be influenced by parameters such as the quality of the tundish spray mass, and casting sequence. The influence of steel grade in hydrogen removal was also examined.     

Austenite Grain Coarsening Behaviour in a Medium Carbon Si‐Cr Spring Steel with and without Vanadium

The austenite grain coarsening behaviour in a medium carbon Si‐Cr spring steel with and without vanadium was investigated by the thermal etching method. This method is efficient when the austenitization temperature is not lower than 900 °C. The average grain sizes on the surfaces of the samples determined by thermal etching vary little from those in the bulk as revealed by chemical etching. The austenite grain coarsening behaviour of the steel with vanadium can be classified in three temperature regimes. Below a critical temperature the vanadium addition is effective to impede grain growth and fine grains are observed. The austenite grain size was significantly smaller than in the steel without vanadium. In a medium temperature regime the steel with vanadium exhibits a bimodal grain size distribution. Above the dissolution temperature of vanadium carbides normal grain growth is observed. An equation was set up to predict the grain coarsening behaviour in the steel without vanadium. The results show how the austenite grain size, which is very important for the toughness and ductility of the spring steels, can be controlled by microalloying with vanadium.     

非调质N80（F—N80）油井管用钢的开发

对42MnMo7油井管失效形式分析,提出了非调质（F－N80）成分设计方案,通过工业性试验,寻找出F－N80成分范围及轧制方案。     

Hot Deformation Behaviour of Low Alloy Steel

Hot deformation of a continuously cast low alloyed steel is studied by means of hot compression and tensile tests by using a Gleeble® 1500 machine after austenitization in a wide range of strain rates and between 720–800 °C. The flow data are evaluated to obtain the strain rate sensitivity and the processing maps. A new calculation method is used, yielding on the instability parameter defined as κ_J which correlates well with the microstructural changes. The strain rate sensitivity does not predict any instability but all the others instability parameters do, including the new κ_J. Flow instability appears at high temperatures and low strain rates where pores are formed at the austenitic grain boundaries, causing a decay of ductility in the tensile test. During hot deformation more ferrite is formed than corresponding heat treatments without deformation. In these conditions, the deformation is concentrated in the softer ferrite phase. The deformation induced ferrite deforms by dynamic recovery forming new grains as revealed by metallography and is correlated with low coefficients of power dissipation. The sinh type constitutive equation represents the flow data well with a stress exponent n = 4.1 and an apparent activation energy Q = 218 kJ/mol.     

Reduction Behaviour of BOF Slags by Carbon in Iron

Experiments were carried out in a system with BOF slags from industrial operations in order to optimize the conditions of recycling BOF slags produced in the steelmaking process. Reduction reactions of FeO and P₂O₅ proceeded steadily and the FeO reduction rate was almost identical to that of P₂O₅. The reduction reaction of FeO and P₂O₅ in BOF slag at the slag/gas interface is the rate‐controlling step. The reaction rates of FeO and P₂O₅ by dissolved carbon in molten iron are of first order with respect to their respective concentrations. The reduction reactions of FeO and P₂O₅ by dissolved carbon in iron are much closer to the equilibrium state compared with the reduction by solid carbon. It is necessary to control the portion of phosphorus vaporization during reduction treatment in order to obtain efficient operational conditions for BOF slag reduction.     

RE-Carbide in High Carbon Steel

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