Papers by Keyword: Twin Roll Caster

Abstract: The temperature of a strip cast using a vertical type high-speed twin-roll caster was measured by inserting a k-type thermocouple into the strip. The effects of the roll speed and roll load on the cooling rate and temperature at the roll gap were investigated using two aluminum alloys: A383 and Al–4.8%Mg. The thickness of the thermocouple was 0.1 mm, and the sampling time was 0.01 s. The cooling rate increased and the temperature at the roll bite decreased with decreasing roll speed and increasing roll load. The positions of the liquidus and solidus lines were measured, and the reduction of the thickness of the strip was inferred from the roll gap at the solidus line.

Abstract: Effect of casting conditions on ripple mark and surface crack of as-cast Al-4.7%Mg strip was investigated. A vertical type high speed twin roll caster was used. A casting speed was 30 m/min. Casting conditions were tip-shape of a back-dam plate, gap between a roll and the back dam plate and texture on the roll-surface. The texture on the roll-surface was useful to reduce the ripple mark. In bending test conducted to investigate surface crack of as-cast strip, the texture on the roll surface was effective to the reduce the crack. The position of the crack was not coin side with the position of the ripple mark. This result shows that there is no correlation between the ripple mark and the ductility or the strength of as-cast strip. Small roll load was effective to reduce the crack and degree of the ripple mark. Effect of the roll load on the ripple mark was discussed including solidification delay and seepage of Magnesium.

Abstract: The aluminum alloy Al–5%Mg–2%Si, the chemical content of which is close to that of the Magsimal-59 aluminum alloy commonly for die casting, was successfully cast into strips using a vertical high-speed twin-roll caster at a speed of 30 m/min. This means that Al–5%Mg–2%Si is suitable for the high-speed twin roll-casting. The as-cast Al–5%Mg–2%Si strip was then successfully cold-rolled to a thickness of 0.7 mm. Tension and cup tests were conducted on the cold-rolled annealed strips. The tensile stress was 205 MPa and the elongation was 20% for a thickness of 1 mm. The limiting drawing ratio was 2.0 at a 0.7 mm thickness. The present results demonstrates that Al–5%Mg–2%Si can be used for die casting and sheet forming. This means that use of this alloy for both sheet forming and die casting could eliminate the need for the separation of wrought aluminum alloys from cast aluminum prior to processing at recycling plants.

Abstract: This study investigated the crystallization position and formation mechanism of globular crystals at the center area in the thickness direction of aluminum alloy strips cast by a high-speed twin roll caster. Twin roll casters for single strips and clad strips were used, as well as twin roll casters equipped with a cooling slope. The globular crystals were formed from dividing arms of dendrites of the solidified layer facing the center area at the roll gap. The arms of isolated dendrite also divided. No globular crystals were formed at the interfaces of clad strips with different solidification temperatures because of the temperature gradient at the interface which inhibited division of the dendrite arms. It was demonstrated that globular crystals at the center area of the thickness direction were formed by dendrite-arm-dividing at the roll gap by the strip casting clad strip. Experiments by semisolid-strip casting with the cooling slope showed that globular crystals in the molten metal existed in the solidification layers.

Abstract: This study shows that the latent heat of the aluminum alloy in an overlay strip is the key factor affecting the bonding quality of clad strips fabricated by a vertical-type tandem twin-roll caster. Three-layer clad strips, for which the base strip was 3003 aluminum alloy and the overlay strip was Al-1%Si, Al-2%Si, Al-11%Si (4045), Al-2%Mg, and Al-4.5%Mg (5182), respectively, were cast. The 4045 overlay strip bonded to the base strip. However, overlay strips made of the other alloys did not bond to the base strip. The latent heat of Si is much higher than that of Al, which in turn is higher than that of Mg. Therefore, the latent heat of the 4045 alloy was higher than that of the other alloys. The high latent heat of the 4045 alloy allowed it to heat the base strip to a temperature at which bonding was possible.

Abstract: The effect of the base strip temperature on the bonding between base strip and overlay strips in a three-layer clad strip cast by a vertical-type tandem twin roll caster was investigated. The base strip was 3003 aluminum alloy and the overlay strip was 4045 aluminum alloy. The bonding was investigated for base strip temperatures ranging from 200 °C to 550 °C. The bonding condition was investigated by cold-rolling, bending-to-failure test and tensile shear test. The shear stress increased with the base strip temperature. Sound bonding was achieved at base strip temperatures higher than 450 °C. The results of this study indicated that the second caster is not required to be set below the first roll caster.

Abstract: This paper shows improvements made to a vertical type tandem twin roll caster and the appropriate casting conditions necessary to cast three-layer clad strips, the base strip of which has a lower solidification temperature than the overlay strip. In experiments, 4045 aluminum alloy was used for the base strip and 3003 aluminum alloy was used for the overlay strips. The roll speed was 30 m/min. By connecting the overlay strips to the base strip one at a time and cooling the base strip to between 450 and 530°C after applying the first overlay strip, a sound three-layer clad strip – defined as one in which the interfaces between strips are clear and do not separate during bending-to-failure tests – could be cast. The tensile shear testing between the base and second overlay strip was improved as the base-strip temperature was increased to 450^-530°C range.

Abstract: An unequal diameter twin-roll caster equipped with a channel scraper is proposed to improve center-line segregation. A semisolid metal layer was made by the channel scraper on the upper side of the strip and solidified by an upper roll. The twin-roll caster cast a strip of 5182 with equiaxed grain and without center-line segregation at a speed of 30 m/min and a unit roll load of 104 N/mm. The tensile stress and elongation after cold rolling and annealing were 294 MPa and 28%, respectively.

Abstract: Casting of clad strip consisting of Al-30vol%SiC_p and 1070 aluminum alloy, and clad strip consisting of AM60 magnesium alloy and AZ121 magnesium alloy was carried out in an oxidizing atmosphere by two types of twin roll casters. One was the vertical type twin roll caster equipped with a scraper and the other was the melt drag type vertical type twin roll caster, both operating at a speed of 30 m/min and a roll load of 0.2 kN/mm. The clad strip of the aluminum alloys could be cast by both twin roll casters. The clad strip of the magnesium alloys could be cast only by the vertical caster equipped with a scraper. The clad strips were bonded strongly at the interface in spite of the high roll speed and the low roll load.

Abstract: Casting of an Mg alloy clad strip was attempted with a twin roll caster equipped with a scraper in an oxidizing atmosphere. The base strip was AM60 and the overlay strip was AZ121. The AM60 strip was cast with a roll, and the upper side of the strip was scribed by the scraper. The molten AZ121 was poured on the scribed AM60 strip. The scribed surface of AM60 contacted the molten metal of AZ121 without exposure to the atmosphere. Therefore, the scribed surface was not oxidized. Most of the AZ121 strip was solidified by the other roll. The casting speed was 30 m/min. The roll load was 0.05 kN/mm. The roll speed was very high and the roll load was very small. However, the strips were bonded, and they did not peel with bending until breaking. The interface between the two strips was clear. When AM60 was on the outer side, the results of the V-bending test and the Erichsen test were better. These results mean that the ductility of AZ121 was improved by cladding with AM60.