Papers by Keyword: Twin Roll Caster

Abstract: Clad strip consisting of 5182 aluminum alloy and other aluminum alloys could be cast using a twin roll caster equipped with a scraper. This twin roll caster could carry out the strip casting and the bonding of the strips. The equipment, that was developed to prevent the contact between the bonding surface of the strip and oxidizing environment, was adopted. The developed equipment was a scraper. The 5182 strip could be bonded to other aluminum alloy strips by the effect of the scraper. Aluminum alloys for casting has poor formability, especially, bending ability is poor. The clad strip consisting of A356 casting aluminum alloy and 3003 wrought aluminum alloy was cast. 180 degree bending test was carried out on this clad strip. In the condition that the 3003 strip was outer side and A356 strip was inner side, the crack did not occur at the outer 3003 strip. In the deep drawing test or the clad strip, LDR (Limiting Drawing Ratio) was 1.8. These results mean that the casting aluminum alloy has ability to be used for the sheet forming, if the casting aluminum alloy is cladded with the wrought aluminum alloy.

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: A vertical type tandem twin roll caster equipped with a scraper for the clad strip was invented. This roll caster could cast three layers clad strip which base strip had lower melting point than that of the overlay strips. The base strip was cast by an upper twin roll caster and the overlay strips were cast by a lower twin roll caster. The scrapers were attached to the lower twin roll caster, and were innovated to cast this type of three layers of clad strip. Solidification layers those became the overlay strips were pulled from between the scraper and the roll. The melt of the alloy which was as same as the base strip was poured between the scraper and the base strip. This melt connect the overlay strip and the base strip. The base strip was not re-melted. The scraper enabled that the solidification layer of the overlay strip contact to the melt of the base strip without mixing of the melt of the base and overlay strip. In this way, the sound three layers clad strip which base strip had lower melting point than that of the overlay strip could be cast by the vertical type tandem twin roll caster equipped with a scraper.

Abstract: A tandem-type roll caster that can cast a three-layered clad strip was developed by mounting one twin roll caster on another twin roll caster. In this caster, the base strip is cast by the upper twin roll caster, and the overlay strips are cast by the lower caster. The three strips are metallurgically bonded by the lower caster. This study investigated three aspects of this caster. First, the clad ratio could be controlled by the solidification lengths of strips from the upper and lower twin roll casters, and a clad ratio of 1:8:1 was attained. Second, although it is known that fabrication of clad strips from Al-Mg alloy and other Al alloys is very difficult, the clad strip with the Al-Mg alloy as the base strip or the overlay strip could be cast. Finally, by adding scrapers, the caster could cast the clad strip with a base strip having a lower melting point than the overlay strip. Element strips of the clad strip are made by many processes, such as direct chill (DC) casting, scraping of the ingot surface, heat treatment, hot rolling, and cold rolling. Typically, surface treatment and hot rolling are used to clad the strips. Since many processes are required, clad strips require consume much energy. Therefore, producing clad strips is expensive. A vertical-type tandem twin roll caster was developed to cast clad strips. This caster has the advantages of process saving and energy saving, and so can fabricate economical clad strips. In the fabrication of clad strips, control of the clad ratio is very important. In the brazing sheet for automobile radiators, the base strip is made from AA3003 and the overlay strips are made from AA4045, and the clad ratio is usually 1:8:1. In the present study, a clad strip with a clad ratio of 1:8:1 was attained. The cladding by hot rolling of Al-Mg and other aluminum alloys, which is considered to be a very difficult process, was also investigated. Clad strips with either a base strip or an overlay strip of an Al-Mg alloy were cast by the roll caster. Although the cladding was not easy, the Al-Mg alloy could be cast into the clad strip. In addition, a clad strip with a base strip having a lower melting point than that of the overlay strip was investigated. Such cladding cannot be cast by the vertical-type tandem twin roll caster as mentioned above because the base strip is re-melted from the heat of the overlay strips. In the present study, a scraper was developed and adopted to cast a clad strip with a base having a lower melting point than that of the overlay strips. This type of clad strip could be cast because the scrapers prevented the re-melting of the base strip. In this paper, these three aspects of fabrication are reported.

Abstract: High speed roll casting of AA5182 aluminum alloy was tried using a vertical type high speed twin roll caster equipped with mild-steel rolls. Parting material was not used and speed was 80m/min. AA5182 strip, which thickness was 2.1mm, could be cast continuously. However, porosity occurred at center area at the thickness direction of the strip of the as-cast strip. Si was added to original AA5182 to improve the porosity at 0.2, 0.4, 0.6, 0.8 and 1.0 mass%. The porosity was improved as the content of the Si increased. The elongation resulting from the tension test was the best when 0.2mass%Si was added. The clack on the surface was improved by the increase of the Si content. Roll casting ability was improved by the Si, too.

Abstract: A vertical type high speed twin roll caster can be cast an aluminum alloy strip directly from a melt at high casting speed. However defects of the cast strip occurred at faster roll speed, which includes small cracks on the cast strip and unsoundness thickness distribution. They are related to contact condition of roll surface and melt. In the present study, a grooved roll was used to eliminate the defects and adopted in terms of the cost saving. We experimented using several grooved rolls with different patterns. When the groove width was 0.45mm; depth 0.2mm; pitch 0.1mm and 1.0mm, stable casting was possible. The shape of bulge was formed on the cast strip surface by the grooved roll. As a result of color check, we found that the grooved roll eliminate the small cracks. We stopped the rotated roll during the casting to observe the contact condition between the melt and the roll, and confirmed how the bulge was formed. The as-cast strip with the bulge was able to cold rolling.

Abstract: Roll caster to cast a three layers clad strip was invented and effect of casting conditions on the clad strip was investigated. Two vertical type twin roll casters were set at vertically tandem position to cast three layers clad strip. Roll speed, roll load (separating force), melt temperature and elements of the aluminum alloy were chosen as the experimental conditions to be investigated. The roll load (separating force) and elements of aluminum alloy were important factors to cast sound clad strip. The clad strip could be cast at the speeds up to 40m/min. Interface between the strips were clear and elements of each strip did not diffuse to other strip. The clad strip was not peeled off at the interfaces by continuous bending. Strips were strictly connected at the interfaces.

Abstract: Roll casting of the model alloy of recycled AA5182 aluminum alloy was investigated. Fe up to 0.6% was added to the AA5182 to make the model alloys of recycled AA5182. Increase of 0.6% of Fe means that the recycle was three times operated. A vertical type high speed twin roll caster was used. Some devices were operated on the twin roll caster to increase the cooling rate in order to make impurity fine. The roll speed could be increased up to 80m/min. The roll-castability did not become worse by the addition of the Fe. The LDR (limiting Drawing Ratio) was 1.9 when the Fe addition was 0.6. The deterioration of the mechanical properties by the addition of impurity Fe was very small.

Abstract: Casting of a wire inserted strip was investigated using a downward melt drag twin roll caster. A nozzle was mounted to each roll. The wire was inserted between the lower and upper strip. Effect of use of two nozzles on the insertion of the wire was investigated. The insertion of the wire by the two nozzles was easier than one nozzle. The surfaces of the wire inserted strip cast using two nozzles was more sound than that cast using one nozzle. The position of the wire at thickness direction was almost center. When different aluminum alloys were poured from an upper nozzle and from a lower nozzle, a wire inserted clad strip could be cast.

Abstract: Effect of Si content of Al-Si matrix on roll cast wire inserted strip was investigated in this paper. 99.5%Al, Al-4%Si , Al-12%Si and Al-18%Si were used as matrix. Slit depth of the nozzle, superheat of melt, wire-diameter and roll speed was chosen as the casting parameters, too. Addition of the Si was useful to prevent the reaction between the matrix and the wire. A downward melt drag twin roll caster could cast the wire inserted strip of the Al-Si matrix of which Si content was ranging up to18%. Composite strip, which matrix was hyper eutectic Al-18%Si, could be cast at the speeds up to 20m/min. The gap between the wire and matrix became thin when the superheat was high. When the slit depth of the nozzle was too shallow, the wire could not be inserted in the strip. The thickness of the wire inserted strip became thinner as the roll speed became higher.