Through-thickness fracture of a Ti-V-N plate steel

The effects of microstructure on through-thickness fracture properties of a Ti-V-N plate steel have been determined directly by through-thickness tensile tests and indirectly by studying delamination fractures in longitudinal tensile and Charpy tests. The initiation of ductile fracture is primarily controlled by inclusions, but overall ductility is influenced by microstructure such that the tensile fracture strain is higher for ferrite-pearlite microstructures than for ferrite-bainite or ferrite-martensite. The cleavage fracture stress is lower for steels which have been rolled belowAr ₃ and contain deformed ferrite than for steels finish rolled aboveAr ₃. Measurements of true stress and true strain for fracture initiation qualitatively fit a model which assumes cleavage fracture occurs at a critical stress, ductile rupture at a critical strain, and a transition fracture mode comprising ductile initiation followed by cleavage. Formerly Visiting Research Fellow, Metals Technology Laboratories, CANMET, Ottawa, ON, Canada Formerly Research Scientist, Metals Technology Laboratories, CANMET     

Effects of thermomechanical processing on the microstructure and mechanical properties of a Ti-V-N steel

Based on studies of austenite deformation behavior and continuous-cooling-transformation behavior of a Ti-V microalloyed steel by cam plastometer and quench-deformation dilatometer, respectively, plate rolling schedules were designed to produce (i) recrystallized austenite, (ii) unrecrystallized austenite, (iii) deformed ferrite + unrecrystallized austenite. The effects of austenite condition and cooling rate on the final microstructure and mechanical properties were investigated. To rationalize the variation in final ferrite grain size with different thermomechanical processing schedules, it is necessary to consider the kinetics of ferrite grain growth in addition to the density of ferrite nucleation sites. The benefit of dilatometer studies in determining the optimum deformation schedule and cooling rate for a given steel is domonstrated. A wide range of tensile and impact properties results from the different microstructures studied. Yield strength is increased by increasing the amount of deformed ferrite, bainite, or martensite, and by decreasing the ferrite grain size. Impact toughness is most strongly influenced by ferrite grain size and occurrence of rolling plane delaminations. B. Dogan, Formerly with CANMET, Ottawa, Canada,     

Evaluation of the fracture toughness of hot-rolled low-alloy Ti-V plate steel

The effects of varying finish rolling temperature (FRT) and cooling rate on the mechanical properties of hot rolled plates of an experimental low-alloy Ti-V steel were studied. Fracture toughness was evaluated for various types of specimens at slow and high deformation rates. However, the transition temperatures determined by the various tests do not always correlate. Therefore, it is recommended that fracture toughness be evaluated by both static and dynamic testing. Following a low cooling rate, the best plate properties are obtained at the lowest FRT in the austenite-ferrite range, although occurrence of delaminations at this temperature may be detrimental for specific applications. Higher cooling rates produce higher strength but lower toughness than lower cooling rates in plates with the same FRT.     

锁定钢板治疗桡骨远端C型骨折的案例研究

目的:研究锁定钢板治疗桡骨远端C型骨折的效果.方法:均采用掌侧入路,T型锁定板固定,严重骨质缺损者予以植骨,术后不予外固定,加强腕关节功能锻炼.结果:5～20个月骨折均愈合,骨折平均愈合时间为8周,术后内固定特无松动或断裂.结论:锁定钢板治疗桡骨远端C型骨折具有固定牢靠,腕关节活动恢复好等优点.     

运用锁骨钩钢板治疗锁骨远端骨折

目的:观察锁骨钩钢板内固定治疗肩锁关节脱位临床疗效.方法:对应用锁骨钩钢板内固定治疗肩锁关节脱位的23例病人资料进行回顾性分析.结果:45例患者得到随访,41例疗效良好,其中4例出现与锁骨钩钢板直接相关的并发症有肩痛、脱钩.结论:锁骨钩钢板内固定治疗肩锁关节脱位能取得满意的疗效,但正确手术和内固定置入及合理功能锻炼是手术成功的关键.     

The microstructure and fracture of a carburized steel

The case microstructure and fracture of a coarse-grained 8620 steel carburized to 1 pet surface carbon are quite sensitive to austenitizing conditions. Reheating martensitic speci-mens below theA _cm produces in the case a refined austenitic grain size, a very fine mar-tensite, spherical carbide particles and a minimum of retained austenite and microcrack-ing. Overload fracture through the latter microstructure is transgranular and scanning electron microscopy shows both microvoid coalescence around thecarbide particles and an apparent fine cleavage in other areas. As-carburized specimens and specimens re-austenitized above theA _cm developed a case microstructure characterized by a coarse austenitic grain structure in which plate martensite with microcracks developed on cool-ing within a large amount of retained austenite. The overload fracture through this mi-crostructure followed a predominately intergranular path and effectively by-passed the retained austenite and microcracked martensite. Auger electron analysis showed that C and P were present on the intergranular fracture surfaces at concentrations above bulk, an observation consistent with literature reports of P segregation during austenitizing. This paper is based on a presentation made at a symposium on “Carburizing and Nitriding: Fundamentals, Processes and Properties” held at the Cincinnati Meeting of The Metallurgical Society of AIME, November 11 and 12, 1975 under the sponsorship of the Heat Treatment Committee.     

胶粘钢板在钢筋砼结构补强中的应用

通过模拟加荷试验方法，鉴定了其结构的可靠性，并为采用胶粘钢板法加固钢筋砼梁板结构提供了可靠的依据。叙述了胶粘钢板法加固砼梁板结构的操作工艺。     

加压钢板内固定治疗胫骨平台骨折80例临床分析

目的:探讨加压钢板内固定治疗胫骨平台骨折的方法及临床疗效.方法:将我院2009年1月至2010年1月收治的120例胫骨平台骨折患者分为观察组80例和对照组40例,观察组采用加压钢板治疗,对照组采用解剖钢板治疗,采用HSS评分比较两组患者的手术疗效.结果:两组的优良率分别为87.9%、81.5%,无显著性差异,P>0.05.但观察组的术中出血量、骨折愈合及石膏固定时间要显著优于对照组,P<0.05.结论:加压固定钢板治疗胫骨平台骨折效果较好,其出血量少,骨折愈合及石膏固定时间短,值得临床推广.     

Hot ductility and fracture mechanisms of a C-Mn-Nb-Al steel

Hot-ductility tests of a C-Mn-Nb-Al steel were performed in a tensile machine at different strain rates of 1×10⁻⁴, 3×10⁻⁴, 1×10⁻³, and 3×10⁻³ s⁻¹ and at temperatures of 650 °C, 710 °C, 770 °C, 840 °C, 900 °C, 960 °C, and 1020 °C, which are close to the continuous casting conditions of steel. Fracture surfaces were examined using a scanning electron microscope. It was found that low strain rates and coarse austenitic grains decrease hot ductility. At all test temperatures, when the strain rate decreases, the hot ductility also decreases because the void growth mechanism predominates over void nucleation, giving time for nucleated cracks to grow. This leads, finally, to the catastrophic failure. The minimum hot ductility was found at 900 °C for all strain rates, and the fracture was intergranular. Fractographic evidence showed that the voids formed during the deformation surrounded the austenite grains, indicating that the deformation was concentrated in ferrite bands located in the same places when the testing temperature was in the two-phase field.     

镀层钢板镀前处理工艺的改进

镀层钢板的镀前处理主要有碱洗和酸洗两道工序，它们是整个电镀工艺过程中相当重要的一环，任何不当的工艺条件和操作都影响到后面的电镀作业，造成有缺陷的甚至是不合格的产品．现对中粤马口铁工业有限公司的镀前处理工艺作一简单的介绍，并对该公司的镀前处理工艺提出改进意见．     

Quality of low-carbon steel rolled plate

Donetsk Scientific-Research Institute of Metallurgy (DonNIIchermet). Kommunarsk Metallurgical Plant. Translated from Metallurg, No. 9, pp 35–36, September, 1988.     

Through-thickness texture gradients in cold-rolled aluminum

The through-thickness texture variations in ∼40 pct cold-rolled polycrystalline aluminum were studied using X-ray diffraction and the electron backscattering pattern (EBSP) technique. The influence of the roll-gap geometry and of sequences of small and intermediate draughts on the development of deformation textures in multipass rolling was considered. It was found that similar textures were formed near the surface and in the central layers of all specimens, while, in the intermediate layers of different plates, different textures were observed. Small draughts gave rise to the shear texture in the intermediate layers, while no pronounced shear texture was revealed anywhere through the thickness of plates rolled with intermediate draughts. It was found that small-draught rolling only has a pronounced effect on the texture if it accounts for a significant strain in the rolling schedule. It was found, furthermore, that nonuniformity of the initial recrystallization texture may be retained in the texture after ∼40 pct rolling.     

含钛微合金钢的高温热塑性及断裂机理

运用Gleeble 1500热模拟机对600~1350℃温度范围内SS400B钢加入钛后的高温力学性能进行测试,对断口形貌及低倍组织进行扫描电镜观察,研究其断裂机理及影响因素.利用热力学软件Factsage对不同钛含量条件下第二相粒子的析出情况进行计算分析.结果表明,在实验温度范围内测试试样的断面收缩率均超过了45%;在高温区生成的铝钛氧化物可作为塑坑的形核核心,促进延性断裂的发生;同时由于铝钛氧化物、氮化钛的生成,降低了对钢塑性有害的氮化铝生成;沿晶铁素体和沿晶渗碳体的生成恶化钢的塑性,促进沿晶脆性断裂的发生.     

Review of accelerated cooling of steel plate

Abstract

The cooling of steel plates after the completion of rolling, while a universal requirement, was historically accomplished using "home-made" systems contrived by individual mills. In recent times, commercial solutions suitable for general application have evolved. This article reviews the development of such systems and explains the metallurgical and operational factors that dictate their design. It has a particular focus on MULPIC® technology and its uses.