Papers by Keyword: Strip Casting

Abstract: A vertical type twin roll caster with two side dams was used to cast aluminium alloy strip with a thickness of about 5mm at speed higher than 10m/min. The characteristics of the twin roll caster with two side dams are as follows: The diameter of the copper roll is 500mm, the width of the copper roll is 110mm and the thickness of the copper roll sleeve is 25mm.The maximum casting speed is up to 60m/min. Using the vertical type twin roll caster, a 4.5mm thickness of 6111 strip could be cast at a speed of 30m/min. The microstructure of the as-cast strip was equiaxed and spherical, not columnar. The mechanical properties of the strip casted from the vertical type twin roll caster were almost as same as that of the strip made from the conventional cast ingot.

Abstract: The microstructure and texture evolution of the as-cast and hot rolled grain-oriented silicon steel strips was investigated, and the precipitation of the inhibitors of the hot rolled strips was clarified. The results showed that the microstructure of the as-cast strip was characterized by coarse columnar grains with strong {001}<0vw> fiber texture. The microstructure of hot rolled strips was composed of ferrite and pearlite and the microstructure was gradually refined with increasing hot rolling reduction. In the hot rolled strips, α and γ fiber textures were enhanced at the expense of initial {001}<0vw> fiber texture and Goss texture was generated in the surface and sub-surface layer with increasing hot rolling reduction. Besides, a great number of dispersed MnS particles with the size of 20-30nm were observed in the hot rolled strips. These MnS particles could act as the effective inhibitors during the second recrystallization annealing of the grain-oriented silicon steel.

Abstract: A Fe-3wt% Si strip was produced using a vertical type twin-roll casting process. Sub-grains with an inhomogeneous distribution through the thickness direction were firstly observed in the as-cast strip. It was found that the surface layer was characterized by columnar grains containing lineage sub-grains, the subsurface layer was dominated by numerous polygonal sub-grains inside columnar grains or fine equiaxed grains, and the center layer was composed of coarse equiaxed grains without sub-grains. In addition, the sub-grain boundaries provided additional nucleation sites for precipitates and the nanoscale MnS particles were successfully obtained. Moreover, the average size of MnS precipitates in the surface layer was smaller than that in the subsurface layer. The inhomogeneous distributions of sub-grains and precipitates can be attributed to the large temperature gradient through the thickness direction during the strip casting process.

Abstract: A Fe-1.3% Si non-oriented silicon steel strip was produced by twin-roll strip casting process, and subsequently treated with cold rolling and annealing. The effect of heating rates on the recrystallization and precipitation behavior of second phase particles (AlN and MnS) was investigated by MMS-200 thermal mechanical simulator. It was found that the recrystallization area fraction decreased obviously with the increase of heating rate. At the heating rate of 5 °C/s, the recrystallization rate gradually decreased with the extension of holding time, but it increased at the rapid heating rates. The particle’s sizes mainly concentrated in 50~200 nm at the heating rate of 5 °C/s during annealing. The number of particles under 50nm increased gradually and the number of precipitates between 50~400 nm reduced significantly when the heating rate was increased to 50~300 °C/s. The results indicated that the rapid heating rate could refine the size of precipitates and decrease the number of particles above 50nm.

Abstract: In the production of aluminum alloy strips for packaging industry twin roll strip casting technique is now being extensively employed. The twin roll caster has advantage of the energy saving, low cost equipment and rapid solidification. The present research aimed to investigate the microstructure and hardness of twin roll strip cast aluminum alloys strips by varying the speed of roller cast. Al-Mg-Si ingot was melt in an induction furnace. Once it melted, the liquid was poured into a crucible attached to a twin roller cast to maintain the liquid temperature at 700°C. Molten alloy was poured in the gap between the copper rollers to produce the strips. The rotational speed of the cast rolls was varied from 60-30 rpm. During this process, the melt solidified to form strips. A specimen of 50 mm length cut from the cast strips was subjected to physical and mechanical characterization. Variation in hardness and microstructure of the produced trip were discussed.

Abstract: Continuous metal matrix composite strip casting (MMCS-ing) composed of six 0.3-mm diameter annealed bare copper wires in a eutectic SnPb matrix was manufactured by a two-roll melt dragged processing (TRMD-ing) method at a rate of 0.3 m/s. The wires were dragged through a semisolid pool with a fibre contact time of approximately 0.2 s. The required gap between rolls to thixoforge the semisolid material around the wire filaments was approximately 1.4 mm. A successful continuous composite strip casting was achieved with a notably good degree of wire alignment. No cracks were observed at the copper wire/matrix interface. However, regions of porosity occurred in the matrix; their possible formation mechanisms are discussed. The solidification structure of the matrix was analysed, and the analysis results indicated the formation of small globular grains measuring approximately 3 μm in diameter. The specimens were evaluated for their tensile properties and compared with the rule of mixtures. The surface fracture analysis indicated a good matrix/fibre union. MMCS-ing is an economically viable process and has significant advantages over other metal matrix composite (MMC) fabrication methods.

Abstract: Twin roll casting is an innovative route to produce thin metal strip directly from the melt. In this paper, solidification characteristics in roll strip cast aluminum alloys is described. Al-Mg-Si alloy was melted in a crucible and poured to stainless steel roller. The roll was connected to a driving motor which the rotation speed can vary from 10 rpm to 100 rpm. During this process, the melt was solidified to form a strip. A specimen of 50mm was cut from the cast strips. The strip was characterized for the thickness, hardness and microstructure. Variation in hardness, microstructure of the produced trip is explained as a comparison to normal casting.

Abstract: Al-11%Si (-0.44%Fe-0.16%Cu-0.14%Mg) was cast into the strip using a vertical type high speed twin roll caster at speed of 60m/min. Cooling rate of the strip was ranging from 2000^OC/s at surface to 1000^OC/s at center of thickness. The eutectic Si was smaller than 2μm. The homogenization, cold rolling down to 1mm, and annealing were carried out before the tension test, 180 degrees bending test and deep drawing test. Tensile stress was 192MPa, 0.2%proof stress was 84MPa, and elongation was 23.8%. Roll cast Al-11%Si had excellent elongation. The specimen was not broken by the 180 degree bending. LDR (Limiting Drawing Ratio) of the deep drawing test was 1.8. The ductility was drastically improved by the high speed twin roll caster. These results show that roll cast Al-11%Si has ability to be used for sheet forming. Moreover, Fe was increased up to 1.0% as the model of recycled alloy. The elongation was 15.9% and LDR was 1.7 in the condition that Fe content was 1.0%. Al-Si-Fe intermetallic became fine by the effect of rapid solidification. As the result, deterioration of the ductility was improved.

Abstract: An Fe-3wt% Si as-cast strip was produced by twin-roll strip casting process. The as-cast strip was hot rolled at 1150°C by one pass of 20% reduction and coiled at 550°C. The tensile test was carried out and the elongation was measured. The microstructure and texture of the coiled strip and the fracture surface morphology of the tensile samples were characterized. It is found that the microstructure of the as-cast strip was characterized by columnar ferrite grains with pronounced {001}<0vw> fiber texture and martensite. The microstructure of coiled strip consisted of ferrite grains and pearlite, and the texture was mainly characterized by {001}<0vw> fiber texture. The necking was absent during the tensile test and the elongation of coiled strip was as low as 12%. The fracture surfaces of the tensile samples mainly exhibited cleavage fracture mode with coarse cleavage facets and some ligaments.

Abstract: Steels with manganese contents of more than 20% offer a new and favourable combination of material properties like high strength and high ductility. These extraordinary mechanical properties are based on the TWIP effect, which depends on the Stacking Fault Energy (SFE). But there are still problems in the conventional production of high-manganese steels, which prevents their widespread use. Both in casting and subsequent hot rolling difficulties occur, with the consequence that the production is very expensive. One alternative production process of high-manganese steels is strip casting, which basic feasibility was shown in earlier work. Strip casting allows the casting and rolling of hot strip in one combined process. In this way hot strip with a thickness of less than 3 mm could be produced. Characteristic for the strip cast material is the as-cast structure with a fine dendritic structure, which shows pronounced microsegregations with a short wavelength. The pronounced microsegregations can have an impact on the local chemical composition and thus on the dominating forming mechanisms that occur. In this work therefore the microsegregations of strip cast material are investigated by means of electron probe microanalysis (EPMA) measurement. Besides the local element distribution, also the presence and composition of non-metallic inclusions are analysed. Especially oxides from the casting process and sulfides from the raw material are expected. Furthermore, different annealing processes for the elimination of the dendritic as-cast structure are examined. In these experiments the temperatures were varied in the range from 900 to 1150°C at annealing times from several minutes to a few hours.