Asymmetric three-roller sheet-bending systems in steel-pipe production

Various attachments are used to produce components of particular configurations from metal sheet. In particular, sheet-bending roller systems may be classified in terms of the number of rollers (two, three, or four); the type of drive (mechanical, pneumatic, electromechanical, hydraulic); and the roller configuration (symmetric, asymmetric). Three-roller systems are used for the production of cylindrical, oval, and conical components by bending the metal sheet. They may be employed to manufacture pipes, channels, airways, shells, barrels, and sheathes. The operation of three-roller sheet-bending systems is based on the rotation of rollers in opposite directions, so that the sheet is captured and bent to the specified radius. To facilitate sheet supply and the release of the products bent into closed circles, the three-roller sheet-bending systems are combined with a removable front shaft applying a pressure that may be adjusted. In the three-roller systems, the diameter of the upper roller is about 1.5 times that of the lower rollers. In shaping, the rollers perform reversible motion. The upper roller may be raised and lowered to regulate the diameter of the circle produced. In this approach, extremely small sheet sections remain flat. This problem is eliminated by bending the ends of the sheet in a press or in a roller mill. In the present work, a mathematical method is proposed for determining the forces and torques in cold flexure of thick steel sheet on three-roller sheet-bending systems. The calculations permit the determination of the reaction of the roller supports, the residual stress in the wall of the steel sheet, the proportion of the plastic deformation over the sheet thickness, and the relative deformation of longitudinal surface fibers of the sheet in flexure as a function of the roller radius, the roller spacing, the reduction of the sheet by the upper roller, the sheet thickness, the Young’s modulus, the yield point, and the strengthening modulus of the steel sheet. The results may be used at metallurgical and manufacturing plants in the production of large-diameter steel pipe for major pipelines.     

Simplified calculation of the bending torques of steel sheet and the roller reaction in a straightening machine

In the straightening of steel sheet, it is necessary to calculate the optimal reduction of the steel blank by the working rollers of the straightening machine so that the sheet produced has the minimum residual stress and curvature. In the simulation of sheet straightening in multiroller machines, the curvature and bending torques of the steel sheet at contact points with the working rollers are first calculated and then the straightening forces are determined. In straightening steel sheet, it is important to calculate the forces in the multiroller straightening machine. Such calculations are based on determination of the reaction of the roller bearings and the forces at the upper and lower working-roller cassettes in straightening. With insufficient bending torque, it is impossible to eliminate harmful residual stress and surface defects in the sheet. Extreme roller torques and forces at the roller cassettes often lead to defects of the sheet, fracture of the working and supporting rollers, and failure of the straightening machine. In the present work, an approximate method is proposed for calculation of the optimal cold-straightening parameters of the steel sheet in a multiroller machine. The calculations permit determination of the curvature of the neutral plane in the sheet on straightening, the residual curvature of the sheet after straightening, the bending torque and the reaction of the working-roller bearings, the residual stress in the sheet, the penetration of the plastic deformation into the depth of the steel sheet, and the relative deformation of the longitudinal surface fibers of the sheet on straightening as a function of the radius of the working rollers, the distance between the rollers of the straightening machine, the reduction of the sheet by the upper rollers, the sheet thickness, and its properties (Young’s modulus, yield point, and strengthening modulus). The results may be widely used at manufacturing and metallurgical plants.     

Preliminary straightening of thick steel sheet in a seven-roller machine

A mathematical model is proposed for determining the forces and torques in the preliminary cold straightening of thick steel sheet in a seven-roller machine. On that basis, the bearing reaction of the working rollers, the residual stress in the wall of the steel sheet, the proportion of plastic strain over the sheet thickness, and the relative strain of longitudinal surface fibers of the sheet in straightening may be determined as a function of the working-roller radius, the spacing between rollers of the straightening machine, the reduction of the sheet by the upper rollers, and the sheet thickness, as well as the Young’s modulus, yield point, and strengthening modulus of the sheet. The results may be used at manufacturing and metallurgical plants.     

3D surface microtopography of cold-rolled and galvanized strip

The switch from 2D filtration to 3D filtration of surface microtopography is described. Important new surface parameters in the metallurgical industry are considered. The use of 3D parameters reveals new aspects of working-roller wear and the development of roughness at the surface of cold-rolled and galvanized auto-industry steel sheet and permits comparison of the surface roughness of coated and uncoated sheet. On that basis, the development of roughness on auto-industry steel sheet in temper rolling may be reassessed; the surface texturing of the rollers may be further improved; and the quantity of rolled metal obtained from a single pair of working rollers may be considerably increased.     

钨粉颗粒级配对氧化铝陶瓷金属化方阻的影响

选取3种平均粒径分别为0.2、0.5和1μm的钨粉,将任意2种钨粉按一定的质量比混合后与氧化铝陶瓷共烧,得到氧化铝陶瓷的金属化层,研究钨粉颗粒级配对氧化铝陶瓷金属化方阻的影响。结果表明,钨金属化层的方阻与其烧结致密化程度直接相关,钨金属化层越致密,其表面方阻越低。单独使用其中1种粒度的钨粉与氧化铝陶瓷共烧时,金属化方阻较高。将0.5μm和1μm钨粉混合能显著降低方阻,当两者质量比为45:55时得到的金属化方阻最小(12.10 m/□)。混合钨粉的累积分布曲线符合Dinger-Funk粉体堆积公式,分布模数n越接近0.37,其烧结致密化程度越高,金属化方阻越低。     

Geometry of steel sheet in a seven-roller straightening machine

A method of determining the parameters of preliminary cold straightening of steel sheet on a seven-roller machine is proposed. The calculations permit the determination of the shape and curvature of the sheet’s central plane during and after straightening, as a function of the radius and spacing of the rollers, the reduction of the sheet by the upper rollers, the sheet thickness, and also the Young’s modulus, yield point, and hardening modulus of the steel. The results may be used at steel plants in the production of broad sheet and thick-walled pipe for pipelines.     

Effect of purity and processing procedure on the mechanical properties of beryllium sheet

The purpose of this research was to assess what improvements might be obtained in the bend ductility of beryllium sheet by starting with high purity commercial powder and consolidating it into sheet by techniques that minimized deformation and texturing. Sound sheet was achieved with reduction ratios from 2∶1 to 12∶1 at temperatures from 700° to 1050°C by forging, upsetting and compression rolling. Compression rolling is accomplished by successively changing the rolling direction by 30 deg after each pass so that no preferred rolling direction was developed. It was found that as the plastic bend ductility increased (up to 4 pct) the yield strength decreased. The higher bend ductilities corresponded to lower reduction ratios, lower degrees of preferred orientation and a larger subgrain size as determined by transmission electron microscopy. Sheet prepared by commercial rolling practices from the less pure commercial powder exhibited similar behavior. The ductile-to-brittle transition temperature for bending decreased with improved purity and reduced texture.     

Si-Mn系超高强度热成形淬火钢板的点焊性能

 采用不同的点焊工艺参数对研发的1700MPa级Si-Mn系热成形淬火钢板与低碳钢板DC04进行异种材料之间点焊,并对焊接接头的拉伸性能、显微硬度分布及微观组织特征等进行了分析。结果表明,焊接电流对点焊接头熔核直径和抗剪强度具有显著的影响,而焊接时间的影响相对较小。超高强度钢板侧的热影响区存在两个明显的软化区和硬化区,即在靠近母材处存在一个硬度明显低于母材的软化区,其组织为回火马氏体;在靠近熔核处存在一个硬度明显高于母材的硬化区,其组织为细小的马氏体。点焊接头熔核部位为柱状粗大马氏体组织,其硬度明显低于超高强度钢板母材且远高于低碳钢板母材。低碳钢板热影响区低的硬度和明显粗化的铁素体组织,使得点焊接头单向拉伸时均从低碳钢板的热影响区一侧破断。     

On measuring the elastic and damping constants of orthotropic sheet materials

Many common sheet materials, ranging from natural materials such as wood to modern composites, possess approximately orthotropic symmetry. Within the approximations of thin-plate bending theory, the linear vibrational properties of such sheets are governed by four elastic constants and four damping constants (at any given frequency). A simple procedure is presented whereby all four elastic constants may be determined, quickly and with reasonable accuracy, from measurements of the resonant frequencies of low-frequency modes of thin rectangular plates with free edges. Also, at least three of the four damping constants may be determined by measuring the damping factors of the same modes—it turns out that the fourth damping constant does not usually have sufficient influence on the low-frequency modes for a reliable value to be found by this approach. The procedure is illustrated with measurements on a range of different sheet materials: wooden plates cut at different angles from the solid timber, plywood, and two very different fibre-reinforced composites. The discussion of these experimental results suggests that this simple procedure could form a valuable part of any programme of quality control, material selection or non-destructive testing involving orthotropic sheet materials.     

Fe-6.5%Si钢极薄带的试制

 为了研究Fe-6.5%Si钢极薄带的制备工艺,并获得良好的产品磁性能,以薄带铸轧试验机制备的6.5%Si钢铸带为原料,分别采用一次温轧法、二次温轧法和基于应变诱导无序(DID)原理的高硅钢室温冷轧3种工艺制备出厚度为0.1 mm的Fe-6.5%Si钢。分析结果显示,一次温轧法退火后以高强度γ织构为主,由于压下率达到90%,形变储能高,晶粒尺寸最大,铁损最低,同时磁感也最低;二次温轧的退火板除了γ织构外,还有较强的η织构,故其磁感值高于一次温轧法,该方法得到的6.5%Si钢薄带综合磁性能最优,但生产成本高,效率低;基于DID原理,对6.5%Si钢热轧板在温度为300～450 ℃、压下率为45%～65%的条件下进行温轧,实现了6.5%Si钢软化,随后可将6.5%Si钢室温冷轧至0.1 mm,此时温轧板和冷轧板内部有序相消失,基体变成无序态;室温冷轧板退火后晶粒更细,铁损略有升高。此外,室温冷轧可促进{111}<112>形变晶粒在冷轧剪切带中形核形成有利织构,因此磁感值得到更大提升;采用DID原理进行室温冷轧,效率较高,后续可通过优化退火工艺使其进一步降低铁损,该方法为薄带铸轧工艺批量生产磁性能优异的6.5%Si钢极薄带提供技术参考。     

双辊铸轧Cr12钢的热处理工艺对深冲性和抗皱性的影响

将双辊铸轧Cr12钢薄板于1 000℃固溶,再采用炉冷和水淬两种方式冷却至室温,分别获得了多边形铁素体和板条马氏体两种组织,再经过相同冷轧和退火工艺,得到了两种成品板.经拉伸试验测定,水淬板的深冲性和抗皱性均强于炉冷板.组织分析发现:热处理后,水淬板内马氏体板块明显细小于炉冷板内铁素体晶粒;冷轧后,水淬板内板块间界演变...     

Placental implantation on the amniotic sheet: effect on pregnancy outcome

PURPOSE: To assess pregnancy outcome in patients with amniotic sheets and to determine whether outcome is affected by placental implantation on the amniotic sheet. MATERIALS AND METHODS: Sonograms obtained during the 2nd and 3rd trimesters were reviewed in 157 patients with amniotic sheets to confirm the presence of an amniotic sheet and to determine the relationship of the placenta to the amniotic sheet. The cesarean section rate, gestational age at birth, birth weight, birth weight percentile, and Apgar score 1 minute after birth were recorded in patients in whom the postnatal follow-up data were available. Data were compared with overall data obtained at the authors' institution during the same period. RESULTS: The placenta appeared implanted on the amniotic sheet in 41 (26.1%) of the 157 patients. In the 120 patients with amniotic sheets and follow-up data, the cesarean section rate was 32.5% compared with 21.5% overall. The mean gestational age at birth was slightly lower than that overall (38.2 vs 39.0 weeks, P < .001), but the birth weight percentile was similar (48.6% vs 50.0%, P = .58). No statistically significant differences were found in postnatal follow-up data between pregnancies with placental implantation on and in those without implantation on the amniotic sheet. CONCLUSION: Pregnancy outcome is similar in patients with and in those without placental implantation on the amniotic sheet.     

The Bauschinger effect and the formation of microalloyed-steel properties in pipe manufacture

The Bauschinger effect is investigated on samples of microalloyed pipe steel. Tests are conducted with one and several extension-compression cycles on a Gleeble-3800 system, at room temperature and elevated temperatures. The influence of temperature on the final sheet properties is considered in conditions of small alternating deformation, so as to simulate the straightening of hot-rolled sheet. The successive influence of each cycle on the final properties of the metal is demonstrated. The strength of the final strip may be modified by 150 MPa, depending on the selected straightening temperature.     

Design Considerations of Carbon Fiber Anchors

Carbon fiber-reinforced polymer (CFRP) sheets can be used to strengthen existing reinforced concrete members. However, debonding (separation of the CFRP sheet from the concrete surface) may occur at less than 50% of CFRP sheet’s tensile capacity, implying that half of the CFRP material is ineffective in increasing the strength of a concrete member. The use of carbon fiber anchors can increase the amount of tension carried in the CFRP sheets. Forty specimens were tested to develop initial design parameters of carbon fiber anchors. Tests showed that by providing anchors with a total cross-sectional area at least two times greater than that of the longitudinal sheet, it was possible to fracture the CFRP sheets. The best results were obtained using a greater number of smaller anchors. Further, surface preparation is unimportant when the CFRP sheets were well anchored and a 1:4 transition slope can manage any offsets in surface level. The general anchor design was then implemented on a series of long beams and demonstrated that the full CFRP sheet tensile capacity can be realized without incurring limitations due to debonding.     

钛铝异质自冲铆接头疲劳性能及失效机理

对纯钛(TA1)和铝锂合金(AL1420)异质单搭自冲铆接头进行静力学实验和疲劳实验研究,通过三参数经验公式采用S-N曲线拟合法绘制接头的S-N曲线,分析接头的疲劳性能;采用扫描电子显微镜对接头疲劳断口进行观测,研究接头的微观疲劳失效机理.结果表明:接头的静力学性能与疲劳性能不具有一致性,TA1-AL1420(TA)接头静力学性能更优,但其疲劳性能比AL1420-TA1(AT)接头差;TA接头疲劳失效形式为下板断裂,疲劳裂纹萌生于靠近铆钉脚处的板材区域,随后沿着板宽方向扩展,最终导致下板完全断裂.AT接头在短寿命区因铆钉断裂失效,铆钉的断口属于脆性疲劳断裂;在中长寿命区出现铆钉断裂和下板断裂的混合失效形式,疲劳裂纹从下板一端萌生,沿着板宽向另一端方向扩展,导致下板断裂失效.      

Production of thick 10XCHДΦ steel sheet of optimized composition for the construction industry

On the basis of newly developed steel, thick sheet for the construction industry may be produced, by smelting and casting, hot rolling, and subsequent heat treatment. In the oxygen-converter shop at OAO Magnitogorskii Metallurgicheskii Kombinat (MMK), a 370-t melt of steel is produced as a trial run. The metal is cast to slabs (thickness 300 mm), which are rolled on a 5000 mill to sheet (thickness 22–50 mm). A production technology for thick vanadium-steel sheet on the 5000 mill is developed: rolling with subsequent heat treatment (quenching + tempering); or controlled rolling with subsequent accelerated cooling to ensure the required strength class 390 and impact strength (KCU_?60, KCV_?20, KCA₂₀). The structure of the cast 10XCHДΦ steel sheet is investigated. Control tests of sheets used in the manufacture of metal structures for the Kazan football stadium confirm the high quality of the sheet.     

Analysis of the influence of the hot-rolling material on galvanized product

Hot-rolled galvanized steel sheet is made from hot-rolled pickled sheet by continuous hot-dip galvanizing process.Without the cold-rolling process,it greatly reduces the operating costs and saves investment for shorter process and lower energy consumption.The economic advantage is obvious.The characteristics of high-yield and low cost will greatly enhance the competitiveness of enterprises in the market.There are big differences between the substrates of hot-rolled galvanized steel sheet and cold-rolled galvanized steel sheet in surface roughness,chemical elements,and surface defects.These factors directly affect on the quality of galvanized sheet.Pickling process is used to remove the oxide layer which is formed on the surfaces of hot-rolled steel sheet.The surfaces must be thoroughly cleaned for the oxide layer will seriously affect the adhesion of galvanized coating.Residual impurities,Carbon concentrating and other problems must not be caused during pickling as well.Therefore,the quality of galvanizing depends on the quality of pickled sheet surfaces.Experimental methods such as AES,XPS,SEM,OM are employed during the research for detailed analysis on the effects of hot-rolled plates and hot pickling plates on the quality of hot-rolled galvanized products.     

The Formation of Edge Cracks during Rolling of Metal Sheet

Many metals tend to develop edge cracks during hot and cold rolling. Edge cracks need to be removed by a trimming operation, and they may cause rupture of the sheet in the rolling mill. Hence, there is a strong motivation to understand the mechanisms of edge crack formation and to develop predictive tools for controlling the phenomenon. The present work explores the applicability of damage mechanics models to this problem. In conjunction with a plausible failure criterion the Gologanu‐Leblond model, which is based on non‐spherical ductile void growth, is able to predict edge cracking and the characteristic zigzag damage pattern on the edge of the rolled sheet. The experimental determination of the model parameters remains a challenging task, since the stress and strain history at the edge of a rolled sheet is substantially different from the situation in a tensile test, and also from that in other conventional laboratory tests.     

Surface-crack formation in the manufacture of microalloyed steel pipe

Deform-3D software is used to model surface-crack formation in the rolling of thick sheet on a 5000 mill. The calculations show that the temperature field and stress state are relatively uniform over the width of the sheet, except at the edges. The minimum temperature of the surface layers of metal hardly depends on the sheet thickness and the relative reduction per pass. The Cockroft–Latham criterion is used to analyze the probability of steel failure in rolling. Analysis shows that metal failure may occur at points where ferrite appears, especially at the instant that the metal leaves the deformation region. Considerable tensile stress acts at those points.     

Modeling hydrogen entry and exit in metals exposed to multiple charging processes

A model is presented to evaluate hydrogen entry or exit in metals exposed to an aqueous environment. The model may be used to analyze data obtained from hydrogen permeation experiments through metal membranes. The model takes advantage of the ideal behavior predicted from the Nernst Equation and Sievert’s Law. It provides a single parameter,κ, to quantify the deviation from Sievert/Nernstian behavior. It is sufficiently general to allow arbitrary chemical potentials of hydrogen on both sides of a sheet, in addition to an arbitrary initial hydrogen distribution within a metal sheet. Simulated permeation curves are presented to show the influence of the model parameters upon permeation behavior. The model is applied to solution agitation during permeation of a low-carbon steel sheet as an illustration. By curve-fitting the model to experimental data, the diffusivity, surface solubilities, andκ on both sides of a metal sheet may be obtained for a given electrochemical charging condition. When compared to other popular models, the model presented by this article fit the experimental data well. The parameters obtained by the model may be used to characterize a given charging process. As such, the effect of one or more processes may be evaluated by using the model to calculate hydrogen distributions in a metal sheet.