The effect of cold working and annealing practice on earing in 3104 Al alloy sheet

A study was conducted with a 3104 Al alloy on the effect on earing of five annealing and cold-rolling practices preceeding a final cold reduction of 88%. Included in these were the effect of slow heating (15°C/h) to the annealing temperature of 332°C, which simulated batch annealing; and the effect of rapid heating (about 140°C/min), which simulated strip annealing. The annealing time was 2 h. The starting condition was hot-rolled material; some of the practices involved an intermediate cold reduction of 35%.

The tensile mechanical properties were independent of the test direction for the final 88% cold-rolled material for all practices. The yield and tensile strengths were slightly lower for practices involving the intermediate 35% cold rolling. These practices also had markedly higher 45° earing. The rapid heating rate gave a finer annealed grain size, but the heating rate had no effect (other steps of the processing being the same) on the earing behavior.

The primary particle density of the annealed condition that preceded the final 88% cold rolling did not correlate with the earing. It appears that the finer microstructural features produced after the 35% cold rolling and annealing are responsible for the high earing observed.     

Recent Developments in the Continuous Processing of Steels

This paper reviews recent developments in the contin-uous processing of steels in Japan.The following items arediscussed:continuous casting-direct rolling(CC-DR)process of hot-rolled strip:thermomechanical controlprocess(TMCP)of heavy plates:in—line heat treating pro-cess of rails:direct lead patenting(DLP)process of wirerods;and fully integrated processing line(FIPL)ofcold-rolled strip.     

样品取向对轧制钢板拉伸性能的影响

分别对不同厚度、不同取向(α=0°,45°,90°)的SPCC冷轧钢板、SPHC热轧钢板、SUS304冷轧不锈钢板和SUS304热轧不锈钢板进行了拉伸试验,研究了取向因素对轧制钢板拉伸性能的影响,并分别探讨了钢板厚度、轧制状态和钢板材料等因素引起的拉伸性能各向异性程度的差异。结果表明:样品取向对轧制钢板的拉伸性能有明显影响,轧制方向的抗拉强度和断后伸长率较高,而屈服强度的变化规律则较为复杂;钢板厚度、轧制状态、钢板材料等因素对轧制钢板拉伸性能的各向异性都有不同程度的影响。     

Thin-slab casting: New possibilities

Changes in the IT industry are known to proceed at a scorching pace. In sharp contrast, the rate of development in the steel industry is generally slow. Nonetheless, the unpact of recenr technical development on the steel industry has been quite significant. The production chain from iron ore to final rolled steel is a long one and the shortening of this length has long been the endeanvour of scientists and engineers. The initial development came in the form of speeding up the process of steelmaking by reducing the slow open-hearth process (8 h tap-to-tap time with the 45 min tap-to-tap time of the Basic Oxygen Furnace (BOF) process. Significant development thereafter have been in the process of continuous production of billets and blooms from liquid steel thereby doing away with the large blooming mills needed for rolling ingots. For a fairly long time after the stabilition of continuous casting, hot rolling involved reheating thick (200–250mm) slabs and reducing them in a hot strip mill. The advent of thin-slab casters has made even these large hot strip mills redundant. The new installations produce thin slabs (50–70mm) that are directly nil led hin strip without the need of an intermediate furnace for raising the stock temperature; the so-called cunnel furnace prior to the rolling stands serving only to equalise stock temperatures. Additionally, what started as a step for reducing investment in hot rolling has in fact, given new opportunity for direct hot rolling of thickneses that were, for long, considered to be feasible only through the cold-rolling route. This article discusses the slow but steady encroachment of hot-rolled sheets into the domain of strip thicknesses hitherto produced by cold rolling and tries to show how the development of thin-slab casters has allowed this process to be accelerated. A techno-economic analysis of thin-slab casting: been presented along with the benefits that arise when a thin-slab caster is linked to the blast furnace and basic oxygen route of steel making.     

Lattice rotation and stability of 22.5° ND rotated cube orientation in cold rolled polycrystalline AA 5182 aluminum alloy

AA 5182 aluminum alloy with a strong cube texture was cold rolled to different reductions at an angle of 22.5° to the prior rolling direction. The texture evolution at this new rolling direction was investigated by X-ray diffraction. The rotation paths and stability of the 22.5° ND rotated cube orientation were determined based on the variation in the three-dimensional orientation distribution function (ODF) with rolling reduction. The results show that most of the grains with the 22.5° ND rotated cube orientation are directly rotated to the β fiber along different rotation paths, but there are a few grains moving through the cube orientation to the β fiber. The {0 0 1}<1 1 0> oriented grains possess the lowest stability during rolling, and the stability increases as the initial orientation changes from the {0 0 1}<1 1 0> orientation to the {0 0 1}<1 0 0> orientation along the ₁ axis.     

Application of the Metallurgically Oriented Simulation System “TKS‐StripCam” to Predict the Properties of Hot Strip Steels from the Rolling Conditions

Basis for all colculations of steel properties using metallurgical modelling is the fact that the mechanical properties are determined unambiguously by the microstructure and the chemical composition of the hot strip. Therefore it is the task of metallurgical modelling to describe the metallurgical processes which are involved in the evolution of microstructure during the rolling and cooling of hot strip as precise as possible. From the calculated microstructural parameters of the finished product in final algorithms the mechanical properties are predicted. For the production of hot strip in a hot rolling mill at TKS such a simulation system has been developed and named TKS‐StripCam. It is based mainly on semi‐physical models adapted to results from laboratory measurements. Using production parameters such as rolling schedule or as cooling conditions as well as the chemical composition as input parameters TKS‐StripCam allows one to the calculate the microstructure and to derive from this e.g. yield strength, tensile strength, elongation to fracture with sufficient precision. The principles of TKS‐StripCam will be presented. Some applications of this metallurgical simulation system with offline use in the office and online use in a hot rolling mill will be demonstrated.     

Age Hardening Behavior of Wrought Al-Mg-Sc Alloy

Ageing of Al-6Mg alloy doped with varying concentration of scandium ranging from 0.2 wt% to 0.6 wt% has been carried out. Cold-rolled alloy samples are isochronally aged for 60 minutes at different temperatures. The cast and hot-rolled samples are also aged isochronally for 90 minutes at different temperatures up to 450°C. Isothermal ageing of cold-rolled samples is conducted at various temperatures for different periods of time ranging from 30 to 480 minutes. Hardness values of the differently processed alloys have been measured to understand the ageing behavior of Al-6Mg alloy with scandium addition. The hot-rolled alloys after ageing do not show any hardening response due to ageing. Ageing of cold-rolled alloys envisaged precipitation of Al₃Sc which is not noted to be dislocation induced. The kinetics of precipitation of Al₃Sc in Al-6Mg-Sc alloys are found to be controlled by the diffusion of scandium in aluminum.     

Streamline strip element method for analysis of the three‐dimensional stresses and deformations of strip rolling

This paper puts forward a new method—the streamline strip element method (SSEM) for simulating the three‐dimensional stresses and deformations of strip rolling process. The rolling deformation zone is divided into a number of streamline strip elements along metal flow traces, and the streamline strip elements are mapped onto the corresponding rectangle strip elements for computation. The longitudinal distribution model of the metal lateral displacement is constructed to be a quartic plus cubic curve. The three‐dimensional deformations and stresses of the deformation zone are formulated. For the cold strip rolling on a 300 mm wide four‐high mill, the computed results of the transverse distributions of the rolling pressure and the front and back tension stresses are close to the experimental ones. For the cold strip rolling on a 1850 mm wide six‐high CVC mill, the computed results of the transverse distributions of the front tension stress are also close to the experimental ones. This proves that the streamline strip element is a reliable engineering–computation method, and of great importance to developing the mathematical model of the shape control of strip rolling. Copyright © 2001 John Wiley & Sons, Ltd.     

Static strain ageing behaviour of dual phase steels

In this work an investigation was conducted into the cold deformation ageing susceptibility of a carbon steel and a microalloyed steel, both with dual phase micro-structure. Ageing experiments after different prestrains were carried out at temperatures ranging from 25 to 250 °C. It was found that yield strength (YS) and tensile strength (UTS) of the steels with different dual phase micro-structures exhibit maximum values at ageing temperature of 100 °C after different prestrains. It is assumed that the first rise is based on the formation of solute atom atmospheres around dislocations and the further strengthening in the second step is caused by the low-temperature carbide precipitation in ferrite. When the ageing temperature increased to 150, 200 or 250 °C, YS decreased due to tempering effect in martensite. It was also found that the ageing of the microalloyed steel occurred more slowly than that of the carbon steel. The slow occurrence of ageing was clearly observed at temperatures of 100, 150, 200 and 250 °C and was attributed to the chemical composition of the steels.     

Influence of hydrostatic pressure on the mechanical behavior and properties of unidirectional, laminated, graphite-fiber/epoxy-matrix thick composites

This paper reviews and gives new insight into earlier work by the author and his co-workers on the experimental investigation of the influence of superimposed hydrostatic pressure on the mechanical behavior and properties of the epoxy used for the matrix and unidirectionally laminated, graphite-fiber/ epoxy-matrix thick composites. The direction of the fibers was, respectively, 0°, 45° and 90° for the compressive test samples and 0°, 45° -45° and 90° for the shear samples.

Hydrostatic pressure induces very significant, often dramatic changes in the compressive and shear stress/ strain behavior of composites, and consequently in the elastic, yielding, deformation and fracture properties. The range of pressures covered for the compressive experiments was 1 bar to 4 kbar, and for the shear tests 1 bar to 6 kbar. The shear modulus (G) of the epoxy increased bilinearly with pressure, with the break, or the discontinuity point, occurring at 2 kbar. The compressive elastic modulus (E) and the shear modulus (G) of the composites increase in the same manner as for the epoxy. The break, which is located at 2 kbar, represents a pressure at which physical changes in the molecular motion of the matrix epoxy occur. That is, segmental motion of molecules between the cross-links is frozen in by 2 kbar pressure. This pressure is known as the secondary glass transition pressure of the epoxy at room temperature. Alternatively, the sub-zero secondary glass transition temperature of the epoxy is shifted to ambient temperature by 2 kbar pressure. The increase in the moduli may also be given a mechanical interpretation. The elastic or shear modulus of an isotropic, elastic material due to small compressive or shear deformations, respectively, superimposed on a finite volume deformation, which is caused by hydrostatic pressure, increases with pressure. Such an increase in E or G has been predicted using finite deformation theory of elasticity.

The normally brittle epoxy develops yielding when the superimposed hydrostatic pressure exceeds 2 kbar. The shear yield stress (1% off-set) of the epoxy increases linearly with pressure above 2 kbar. This kind of yielding behavior can be predicted by a pressure-dependent yield criterion. The compressive yield strength of the 45° and 90° composites increases bilinearly with pressure, and the shear yield strength of the 0°, 45° and 90° composites also increases bilinearly with pressure. This bilinear behavior is also due to the secondary glass transition pressure of the matrix epoxy, being located at 2 kbar. The fracture strength of the composites also increases with pressure linearly and the greatest increase occurs in the 45° composite in compression and in the −45° composite in shear. The fracture modes of the composites undergo changes with increasing hydrostatic pressure. For instance, the 0° composite undergoes a brittle-ductile transition under shear stress, while no such transition appears to set in under compressive stress. The fracture mode of the 45° composite changes from matrix failure at lower pressures to fiber failure at high pressures under shear stress.     

径-轴向辗环机轴向轧制机构结构分析

采用三维造型软件SolidWorks建立了某型号径-轴向辗环机轴向轧制机构的实体模型。以有限元软件ANSYS为分析平台,通过合理处理接触、约束和载荷等边界条件,建立了有限元分析模型,对轴向轧制机构进行了三维弹性接触分析,得到了轴向轧制机构及主要部件的等效应力、位移变形、等效应变。对变形角进行了定义,提出了求解变形角的方法。计算结果表明,变形角为0.041°时,各部件的最大等效应力均小于屈服极限,轴向轧制机构刚度符合设计要求,各部件满足强度要求。     

带钢表面黑斑缺陷分析

采用扫描电镜及能谱等手段对热轧带钢和冷轧带钢表面产生黑斑的原因进行了分析。结果表明:酸洗热轧带钢表面黑斑主要是氧化铁,冷轧带钢表面黑斑主要是热轧带钢氧化铁经退火后被还原产生的还原铁。     

Ti超低碳烘烤硬化钢铁素体区轧制试验研究

实验室进行了Ti处理超低碳烘烤硬化钢的常规奥氏体区热轧和铁素体区润滑轧制以及冷轧、连续退火试验,结果表明与常规奥氏体区轧制相比,铁素体区润滑轧制能够提升超低碳烘烤硬化钢板的深冲性能,在伸长率相当的情况下退火后钢板的屈服强度和烘烤硬化BH值均略有所下降.EBSD微观取向分析表明,铁素体区润滑轧制退火钢板中的<111>//ND纤维织构稍强,两种情况下退火板中晶粒间取向都是以大角度晶界为主.     

Effect of packaging and storage on the stability of carbamazepine tablets

The effect of packaging and storage on carbamazepine (CBZ) tablets was examined using Tegretol® and Tegral, dispensed in strip seals, and Finlepsin®, dispensed in bottles. Tegretol and Tegral tablets were stored in their original strips at 40°C, 50°C, and 60°C for 6 months, 3 months, and 1 month, respectively, at 75% relative humidity (RH). Also, tablets were removed from their strips, placed in bottles, and exposed daily to 97% RH at 40°C for 5 min for 30 days. Finlepsin tablets were exposed to 97% RH at 25°C or 40°C for 1 month by removing bottle caps daily for 5 min. Dissolution was used to assess in vitro tablet performance, and high-performance liquid chromatography (HPLC) was used to evaluate the chemical stability of CBZ. Results show that Tegretol tablets were not affected by the tested stress conditions. Tegral tablets, stored in their strips at 50°C or 60°C and 75% RH, showed increased disintegration and dissolution. The effect of 40°C/75% RH for 6 months was similar to 1-month storage at 40°C/97% RH; the tablets hardened and dissolved less than fresh Tegral tablets. Removal of Tegral tablets from their original strips resulted in only 7% dissolved in 60 min. For Finlepsin, the effect of 97% RH at 40°C was more profound than 97% RH at 25°C, but both conditions caused a decrease in dissolution, the extent of which was dependent on tablet position in the bottle. Stressed CBZ tablets, however, showed no change in the chemical stability of CBZ under all tested conditions.     

A novel etchant for revealing the prior austenite grain boundaries and matrix information in high alloy steels

To observe the prior austenite grain (PAG) boundaries in high-alloy steels, a novel etchant composed of oxalic acid, hydrogen peroxide, sodium bisulfite, and water has been developed. Etching with this system successfully revealed both the grain boundaries and the deformation bands within grains in high Co–Ni martensitic alloy steels. The carbon content of the alloys used in the test program varied from 0.23% to 0.35%, the cobalt content was in the range 9–13%, and the nickel content was in the range 8–11%. The specimens were austenitized at temperatures in the range 900–1200 °C. The rolling temperatures ranged from 700 °C to 1000 °C. The grain sizes in these alloys and those containing titanium were clearly revealed by optical microscopy following application of the new etchant.     

异步轧制对硅钢极薄带三次再结晶的影响

分别采用同步和异步轧制将成品工业取向硅钢板冷轧到0.045～0.10mm,然后在纯氢气热处理炉中进行三次再结晶高温退火,研究轧制工艺参数对取向硅钢极薄带织构和磁性能的影响,探索异步轧制对硅钢极薄带三次再结晶行为影响机理.结果表明,采用异步轧制取向硅钢极薄带的磁性能优于同步轧制的;硅钢极薄带厚度愈薄,磁性能愈好,三次再结晶发展得越完善.     

六辊轧机扭振动态建模及与板带钢质量关系研究

考虑轧机扭振与辊系沿轴向动态特性和板带材质量的关系,基于连续体动力学建立了六辊轧机扭振动力学模型,包括轧机辊系等效模型和辊身与辊径过渡部分等效模型。根据轧制速度与轧辊角速度的关系,建立了板带钢前后张力、轧制力等参数与辊系扭振的关系模型。基于所建模型对某六辊轧机施加位移激励模拟扭振情况,仿真分析了轧机辊系和板带钢在扭振激励下的三维动态响应。仿真结果表明,轧辊角位移和角速度沿辊身长度方向波动较小;轧辊扭振使轧制压力、前张应力和后张应力横向分布发生不同程度的波动,扭振对前张应力分布影响较大,即对板带钢板形产生影响,且传动侧的波动幅值大于操作侧。     

Genesis of High Hardness in Hot-Rolled Coils of Cold Reducers’ Grade Steels

A significant quantity of cold-reducible hot-rolled (HR) coils is produced every year. These are basically low-carbon steels; however, the quality of HR coils with respect to cold reducibility had not been entirely satisfactory. The hardness of HR coil was generally higher (≥65 HR_B) than desirable for attaining satisfactory cold reducibility. A systematic study was, therefore, undertaken with the objective to control the hardness to ≤55 HR_B by modifying the existing chemistry, finish rolling temperature (FRT), and the coiling temperature (CT). To find the optimum conditions for lower hardness, trial rolling of slabs of cold reducers’ grade of selected chemistry was conducted under varied conditions. An assessment of hardness across the width and of the microstructure was carried out. The evolution of microstructure in the HR band at different locations from the edge of the strip and the genesis for the resulting hardness profile across the width of the HR coil were examined in detail. The influence of grain size on hardness was also analyzed. The paper outlines the role of finish rolling temperature, coiling temperature, chemistry, and grain size in restricting the hardness to values below 55 HR_B.     

An elastic–plastic thermal stress analysis of aluminum metal–matrix composite beams

In this study, an elastic–plastic thermal stress analysis is carried out on steel fiber-reinforced aluminum metal–matrix composite beams. Temperature is chosen to vary linearly. It is zero and T₀ at the upper and lower surfaces, respectively. The beam is fixed by two rigid planes at the ends. The solution is performed at 0°, 30°, 45°, 60° and 90° orientation angles. The plastic region is expanded at the lower side of the beam. It is found that the intensity of the residual stress component of σ_x and the equivalent plastic strain are maximum at lower surface of the beam. The residual stress is found to be greatest for the 0° orientation angle. In addition, the intensity of the equivalent plastic strain is the greatest for the same angle.     

CSP生产SPHC板材的冷轧退火工艺优化

对酒钢CSP生产的SPHC热轧钢进行了冷轧退火及相关试验。研究表明,当冷轧压下量为70％,退火温度为700℃时,可以得到良好的织构和优异的冲压性能。