Influence of roll speed difference on microstructure, texture and mechanical properties of 7075 aluminum plates produced via combined continuous casting and rolling process

The influences of the dissimilarity in the roll speeds on the microstructure, texture and mechanical properties of 7075 aluminum plates produced via combined continuous casting and rolling(CCCR) process were investigated. Several experiments were conducted with three different upper/lower roll rotational speed ratios(ω/ω0, ω is the upper roll rotational speed and ω0 is the lower roll rotational speed), namely 1:1, 1:1.2 and 1:1.4. It was found that the greatest dissimilarity in the roll speed(ω/ω0=1:1.4) improved the yield strength and ultimate tensile strength of 7075 Al plate in the rolling direction by 41.5% and 21.9%, respectively. Moreover, at a roll speed ratio of ω/ω0=1:1.4, the average grain size was decreased by 36% whereas the mean hardness of the transverse cross-section of the finally rolled plate was increased by about 9.2%. Texture studies also revealed that the more the difference in the roll speeds was, the greater the isotropy and the hardness of the final product were. Nevertheless, conducting CCCR operation with different roll speeds resulted in about 6% reduction in the elongation of the deformed plate.

Microstructure evolution and mechanical properties of Cu-0.36Be-0.46Co alloy fabricated by heating-cooling combined mold horizontal continuous casting during cold rolling

Cu-0.36 wt.%Be-0.46 wt.%Co alloy plate with 300 mm in width and 10 mm in thickness prepared by heating-cooling combined mold(HCCM) horizontal continuous casting was cold rolled. Microstructure evolution and mechanical properties of the alloy as well as its deformation mechanism were investigated. The results showed that the as-cast alloy plate had columnar grains along the length direction, good surface quality and elongation of 35%, which was directly large-reduction cold rolled without surface treatment, and the accumulative cold rolling reduction reached 98%. When the reduction was small(20%), numerous dislocations and dislocation cells formed, and the deformation mechanism was dislocation slip. When the reduction was 40%, deformation twins appeared, and interactions between twins and dislocation cells induced strip-like dislocation cells. When the reduction exceeded 60%, shear bands formed and apparent crystal rotation in the micro-region happened. Further increasing the reduction, the amount of the shear bands rose and they interacted with each other, which refined the grains apparently. The tensile strength and hardness increased from 353 MPa and HV 119 of the as-cast alloy to 625 MPa and HV 208 with 95% reduction, respectively, and the elongation reduced from 35% to 7.6%. A process of HCCM horizontal continuous casting-cold rolling can work as a novel compact method to fabricate Cu-Be alloy sheet.

Slab Storage Calculation Method for Continuous Casting-Hot Rolling

Based on load-oriented manufacturing control theory,different combining modes and slab storage calculation method for continuous casting and hot rolling were discussed.The buffer capacity index of continuous casting-rolling was introduced,and the reasonable slab storage under different combining modes was calculated with buffer capacity index of 120.00 hfor CCR,79.20 hfor HCR,19.68 hfor DHCR and 3.84 hfor DR.Thin slab is 1.20 h,and the strip is zero.Theory gist was provided for steel enterprise to decrease storage.

The future of the twin-roll strip casting and rolling process

Twin-roll strip casting and rolling is a typical near-net-shape steel manufacturing process.The twin-roll strip casting and rolling of low-carbon steel strips has made a number of breakthroughs and achieved significant results during the past 20 years.Baosteel has been paying close attention to the development of this technology and set up a research and development project focused on its industrialization in 2001.The Ningbosteel-Baosteel strip casting industrialization demo project(NBS),which was launched in 2016,marks the strip-casting technology(registered as Baostrip) developed by Baosteel as having reached an advanced international level after 15 years of effort.This paper summarizes the results obtained in the industrialized demonstration plant and considers the future development of strip casting and rolling.

Simulation of microstructures in solidification of aluminum twin-roll casting

Based on the research on the solidification of twin-roll continuous casting aluminum thin strip, the analytical model of heterogeneous nucleation, the growth kinetics of tip （KGT） and columnar dendrite transformation to equiaxed dendrite （CET） of twin-roll continuous casting aluminum thin strip solidification was established by means of the principle of metal solidification and modem computer emulational technology. Meantime, based on the cellular automaton, the emulational model of twin-roll continuous casting aluminum thin strip, solidification was established. The foundation for the emulational simulation of twin-roll casting thin strip solidification structure was laid. Meanwhile, the mathematical simulation feasibility was confirmed by using the solidification process of twin-roll continuous casting aluminum thin strip.

Numerical simulation of the temperature fields of stainless steel with different roller parameters during twin-roll strip casting

The temperature field of stainless steel during twin-roll strip casting was simulated by experiment and a finite element （FE） model. By comparing the measured result with the simulated values, it is found that they fit close to each other, which indicates this FE model is effective. Based on this model, the effects of roll gap （t） and roll radius （R） on solidification were simulated. The simulated results give the relationship between t or R and the position of the freezing point. The larger the t is and the smaller the R is, the closer the position of the freezing point is to the exit.

Experimental research on electromagnetic continuous casting high-speed steel composite roll

A high speed steel composite roll billet was fabricated, which is regular in shape, smooth in surface, slight in trace, compact in internal structure, free of slag inclusion, shrinkage cavity, cracks and other flaws, and good in macro quality of junction surface using a vertical continuous casting machine. The interface zone microstructure of bimetallic in billet of high speed steel composite roll was analyzed by metallurgical microscope(OM), X-ray diffractmeter(XRD), scanning electron microscopy(SEM) and energy-dispersive X-ray analysis(EDS). The results indicate that the microstructure of roll billet is composed of chilled solidified layer, dendrite zone, interfacial zone of bimetal and core material zone. The microstructure of outer shell material is composed of martensite + bainite + residual austenite + some small labyrinth-shape, small-short lath-shape, or dollop-shape eutectic carbides. The microstructure of core material is slice-shape pearlite and a little ferrite along boundary of cells. The interface region microstructure of bimetallic composite roll consists of diffusion region, chilled solidified layer and columnar grain region.

Effect of twin-roll casting parameters on microstructure and mechanical properties of AA5083-H321 sheet

Thepurpose of the present paper is to study the mechanical propertiesand microstructureof the twin-roll cast and cold rolled AA5083 aluminum alloy sheet in strain-hardened H321 temper. To reach this goal, first, a sound surface slab of 8.90 mm thick and 1260 mm wide was cast by a 15°; tilt back twin roll caster at a casting speed of 490 mm/min. After homogenization at 520 ℃, the product was cold rolled to two thicknesses of 6.30 mm and 3.85 mm with an intermediate annealing at 370 ℃ and final stabilization at 180 ℃. Opticalmicroscopyand scanning electron microscopy （SEM） investigations of the as-cast state depicted the segregation of intermetallic particles mainly in grain boundaries which wasthe cause of grain removal observed in the fracture surface of tensile test samples. In addition, mechanical properties indicated an increase in total elongation after homogenization heat treatment dueto the elimination of the grain boundary segregations. Finally, it was observed that the properties of the 3.85 mmthick sheet were consistent with the H321 temper requirements according to ASTM B 290M standard due to applying sufficient cold reduction during cold rolling stage.

PHYSICAL SIMULATION OF CONTINUOUS ROLL CASTING PROCESS

A series of simulating experimental studies on the rheological behavior and its influential factors of aluminum alloy in continuous roll-casting process have been explored in this paper with a Gleeble-1500 Thermal-Mechanical Simulation Tester and a set of special clamp system. Relevant rheological rules in the process of coupling transient solidification and continuous deformation of roll-casting conditions are obtained. Experimental results indicate that four different characteristic stages exist in the whole rheological process, and relative constitutive models suitable for the given conditions of continuous roll casting process have been established through multivariable linear regression analysis of the experimental data.

Preparation of AZ31 magnesium alloy strips using vertical twin-roll caster

A newly developed technology for manufacturing magnesium alloy strip,vertical twin-roll strip casting,has been described.This manufacturing process is easy to be facilitated in an economical way to manufacture wrought magnesium alloy strips. As an example,AZ31 magnesium alloy was used to investigate the appropriate manufacturing conditions for vertical twin-roll strip casting by varying the temperatures of the molten materials and rolling speeds.The effects of manufacturing conditions on forming quality were clarified in terms of roll speeds and casting temperature.In addition,microscopic observation and X-ray diffraction of the as-cast strips were performed.It has been determined that AZ31 alloy strip of 1-3 mm in thickness can be produced at a speed of 30 m/min by a vertical twin-roll caster.The microstructure of as-cast strip only containsα-phase(Mg)and no other phase,and the twin-roll casting process can effectively refine the grain size.The fine equiaxed grain of as-cast strips is beneficial to the plastic deformation of the strips,and it is also suitable for direct cold-rolling with a maximum cold-rolling reduction of 40%.

Rheological behavior of continuous roll casting process of aluminum alloy

The rheological behavior of aluminum alloy and its influencing factors in physical simulation of continuous roll casting process were studied by using a Gleeble-1500 thermal-mechanical simulation tester with a set of special clamp system. The relationships between the flow stress and the strain rate in the deformation process of simulating roll casting experiment were obtained. The results show that four different characteristic stages exist in the temperature range of the whole rheological process. The first occurs when the temperature is higher than 600 ℃, which belongs to the creep deformation stage; the second occurs when the temperature lies in the range of 500600 ℃, and it can be regarded as the high temperature and low stress level deformation stage; the third occurs when the temperature decreases to the range of 300500 ℃, it is considered to be the middle stress level deformation stage; the last occurs when the temperature is less than 300 ℃ and the strain rate is less than 1.00 s -1, it belongs to middle stress level deformation stage. But when the strain rate is larger than 1.00 s -1,it belongs to the high stress level deformation stage. And the relative constitutive models suitable for the four different stages of continuous roll casting process were established through multivariate linear regression analysis of the experimental data.

Numerical simulation of continuous roll-casting process of aluminum alloy

In order to improve the strip quality of continuous roll-casting process (CRP) of aluminum alloy, the investigations of the flow behavior within the metal pool, the heat transfer condition between roll and strip, the pouring temperature of molten alloy, the roll-casting speed and the control of the position of solidification final point are important. The finite volume method was applied to the analysis of the continuous roll-casting process. A two-dimensional incompressible non-Newtonian fluid flow with heat transfer was considered, which was described by the continuity equation, the Navier-Stokes equation and the energy equation. With this mathematical model, the flow patterns, temperature fields and solid fraction distributions in the metal pool between two rolls were simulated. From the calculated results, the effects of technical parameters to the position of solidification final point are obtained. The simulated results show that the roll-casting speed and pouring temperature have an enormous effect on the temperature distribution and the position of solidification final point.

EFFECTS OF ELECTROMAGNETIC FIELD ON CASTING-ROLLING STRIP BREAKDOWNS

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Establishment of mathematical moment model in twin casting rolling rolls

In continuous casting rolling process, the deformed body is different from the hot rolling strip. The metal in casting rolling zone is first assumed to be viscous fluid and the mathematical model of casting rolling force is established, then the calculating formula for casting rolling torque is derived. In addition, considering the effects of deforming cone and appendant torque of rotary junctions sealing ring, the calculating model which accords with casting rolling condition is found out. Theoretical formula is proved by experiment.

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 are discussed:continuous casting-direct rolling(CC-DR) process of hot-rolled strip:thermomechanical control process(TMCP)of heavy plates:in—line heat treating pro- cess of rails:direct lead patenting(DLP)process of wire rods;and fully integrated processing line(FIPL)of cold-rolled strip.

Evolution of inclusions in a pipeline steel during continuous casting and hot rolling process

Industrial trials were performed to study the evolution of inclusions in a pipeline steel during the continuous casting and hot rolling process.The main composition of inclusions changed from Al_(2)O_(3)-CaO in the liquid steel to Al_(2)O_(3)-CaO-CaS in the slab,and then to Al_(2)O_(3)-CaS in the rolled plate.Corresponding area fractions of inclusions increased from 47.0×10^(-6) to 76.7×10^(-6),and to 144.3×10^(-6).It was explained by thermodynamic calculations that the thermodynamic equilibrium between inclusions and the steel varied with the temperature.Element contents of Al,Ca,Mg,S,and O in the steel decreased during the solidification and cooling process.Due to the difference in the cooling rate,the transformation ratio of CaS increased from 61% at the slab surface to 95% in the slab center.It was also affected by the size of inclusions as smaller inclusions provided better kinetic conditions.Critical diameters of inclusions for the composition transformation were calculated.For the hot rolling process,the average aspect ratio of inclusions increased from 1.4 in the slab to 2.8 in the rolled plate.During the hot rolling process,a part of inclusions was crushed into small particles of CaS phase and Al_(2)O_(3)-CaO-MgO cores,leading to a decrease in CaS content of inclusions.

AZ31B镁合金连续铸轧板材搅拌摩擦搭焊接头组织研究

对AZ31B镁合金连续铸轧板材进行搅拌头逆时针与顺时针相结合的二道搅拌摩擦搭接焊。经对其搭接接头横截面的焊缝宏观及不同部位微观组织对比来分析二道搅拌摩擦焊对焊接接头塑性组织及成形的影响。结果表明:焊核区等轴晶粒组织特别细小、均匀;过渡区晶粒组织大小起伏较大,略大于焊核,较小于母材组织;前进侧界面迁移呈现大弧度卷起,比较突兀与焊核隔断,形成钩状缺陷,而后退侧界面迁移线缓缓渗入中部焊核区,渐渐消失于焊核组织内;前进侧迁移线的成形特点相比于孔洞隧道缺陷,成为整个焊接接头最薄弱部分;前进侧界面迁移线边的组织融合影响了对焊接头的成形;二道搅拌摩擦搭接两次搅拌头旋转方向同为逆时针时,能得到表面良好、组织熔合紧密、强度较高接头;当搭接接头上板为后退侧时,与上板为前进侧相比,搭接接头能够承受更大剪切力。

双辊铸轧工艺制备连续碳纤维增强铝基复合材料的研究

连续碳纤维增强铝基(CCF/Al)复合材料具有高比强度、低密度、良好的传热性以及低热膨胀系数等诸多优良的特性,在航空材料、汽车制造、电子设备和工业生产等领域均具有广阔的应用前景。对连续碳纤维表面涂层的制备方法进行了讨论,并总结了近年来CCF/Al复合材料的主要制备工艺、重要研究成果以及存在的问题;重点阐述了采用双辊铸轧工艺制备CCF/Al复合材料的研究结果,具体包括搭建的实验设备、改性后碳纤维的性能、所制备复合材料的组织结构及强化机理;讨论了该工艺目前存在的主要问题,并对其发展前景进行了展望。

蜂窝铝箔产业化应用研究

通过研究热轧、连续铸轧和连铸连轧加工铝板带坯料的特点,介绍了3003合金蜂窝铝箔生产工艺及控制要点。结果表明,连铸连轧3003合金3.5 mm蜂窝箔坯料,不仅可以减少2个压延道次,而且通过工艺参数调整,可获得成品力学性能优良的蜂窝铝箔产品。

连铸连轧铜杆生产线SCR法和Contirod法浅析

本文首先对当前主流的两种连铸连轧铜杆生产工艺进行简要阐述,其次对两款设备的不同之处进行较为详细的介绍,最后从多个方面阐述不同工艺对能耗指标和铜杆产品质量的影响。