Unequal Diameter Twin Roll Caster Research Articles

Reduction of Elongation Anisotropy of Roll-Cast Strips by Cold Rolling and Annealing

Roll-cast strips are usually cold-rolled and annealed before forming. The elongation of these strips is known to be different between the casting and lateral directions after thinning by cold rolling. Whether cold rolling is the main factor determining the anisotropy of the elongation is not clear. Likewise, it is not clear whether the elongation anisotropy can be reduced by conventional cold rolling. Roll-cast strips have centerline segregation, forming a so-called band area. The relationship between the anisotropy of the elongation and these defects is not clear. A strip cast using an unequal-diameter twin-roll caster also has a band area but a strip cast using a single-roll caster equipped with a scraper has no centerline segregation or band area. Strips made this way were cold-rolled in the casting and lateral directions, and tensile testing was conducted on the cold-rolled and annealed strips. In this study, the ability of conventional cold rolling and one-time annealing to reduce the elongation anisotropy of a cast strip was clarified. Moreover, the influence of the band area and Fe impurities on the elongation anisotropy was determined.

Inline Hot Rolling of Al-5%Mg Strip Cast Using an Unequal Diameter Twin-Roll Caster.

One advantage of twin-roll casting for aluminum alloys is that hot rolling can be omitted, thus shortening the process. The effect of inline hot rolling on the anisotropy of the mechanical properties, especially the elongation, of the roll-cast strip has not been investigated. In a high-speed twin-roll caster, inline hot rolling forms the metal shape before the temperature of the cast strip decreases below the temperature needed for hot rolling. In this study, inline hot rolling of Al-5%Mg strips cast using an unequal diameter twin-roll caster was performed to validate the technique and evaluate its ability to reduce surface cracking and improve the elongation anisotropy. A rolling speed of 30 m/min was used, and the effects of temperature and thickness reduction during inline hot rolling on the surface and mechanical properties were investigated. Inline hot rolling was found to effectively reduce the formation of surface cracks and the anisotropy of the mechanical properties.

Sheet Forming of Roll Cast Aluminum Alloy for Die Casting

This study explored the capability of sheet forming of JIS ADC12 aluminum alloy, commonly used for die casting. Despite the poor ductility of ADC12, we attempted to improve this property by applying rapid solidification through an unequal diameter twin roll caster. A strip with a thickness of 3.7 mm was cast at a speed of 20 m/min. The as-cast strip was then cold rolled and annealed to investigate its sheet-formability by deep drawing, three-roll bending and V-bending. This research also investigated the elements of ADC12 that contribute to poor ductility, with a focus on the impact of Mg, Cu, Fe, and Zn during the deep drawing process.

Reduction of Surface Cracking for Al-4.6%Mg Strips Cast Surface Using an Unequal-Diameter Twin-Roll Caster by Back-Dam Plate with Lip

Cracks occur on the surface of Al-Mg strips cast using a high-speed twin-roll caster. Surface cracking of the as-cast strip decreases with decreasing roll load. However, the difficulty of roll casting increases as the roll load is decreased because the strip becomes brittle and is easily broken because the strip is not completely solidified. In the present study, an unequal-diameter twin-roll caster, which is capable of high-speed casting, was used with a lip attached to a back-dam plate in an attempt to decrease surface cracking without deceasing the roll load. The thickness of the solidified layer was found to decrease as the length of the solidified region decreased. The thickness of the solidified layer at the center of the width direction of a strip on the lower roll decreased by shortening the solidification length by a lip attached to a back dam-plate. The solidified layer at the edges was thicker than that inside the cast strip. The thickness of semisolid metal inside the cast strip increased more than that at the edges of the roll bite. The roll load at the width of the lip decreased. The effect of the lip length on surface cracks was investigated.

Twin-Roll Casting of Al-4.8%Mg Alloy with Added Fe

Fe (0.2, 0.4, 0.6, and 0.8 %) was added to roll-cast Al-4.8%Mg alloy to create a model of recycled Al-4.8%Mg and its effect was investigated. An unequal-diameter twin-roll caster was used. The roll speed was 20 m/min. An as-cast strip was cold-rolled down to 1 mm and annealed. Its mechanical properties were then evaluated. The surface condition of the as-cast strip was not influenced by the Fe content. The thickness of the as-cast strip decreased with increasing Fe content. The tensile strength and 0.2% proof stress increased with Fe content up to 0.4%Fe and then decreased. When 0.8% Fe was added to Al-4.8%Mg, the tensile strength and 0.2% proof stress became higher than those for Al-Mg. Elongation and the limiting drawing ratio gradually decreased with increasing Fe content. When 0.8% Fe was added, elongation in the lateral direction was 19.6% and the limiting drawing ratio was 1.7.

High Speed Roll Caster for Aluminum Alloy

Two types of high-speed twin-roll casters and a single-roll caster equipped with a scraper were proposed. One of the twin-roll casters is a vertical-type high-speed twin-roll caster, and the other twin-roll caster is an unequal-diameter twin-roll caster. The vertical-type high-speed twin-roll caster can cast strip at speeds of up to 120 m/min. The unequal-diameter twin-roll caster casts strip at speeds up to 60 m/min. The unequal-diameter twin-roll caster is superior to the vertical-type high-speed twin-roll caster at the point of conveyance of the cast strip. A single-roll caster equipped with a scraper can cast strip without center-line segregation at speeds of up to 40 m/min. The use of a copper alloy roll and the non-use of a parting material enable high-speed roll casting. Since the roll loads of these casters are smaller than 0.1 kN/mm, soft copper alloy roll can be used. The strip does not stick to the roll without the parting material because of the use of the copper alloy roll with high thermal conductivity and the small roll load. The cooling rate near the surface is higher than 2000 °C/s.

Reduction of Surface Cracks at Al-Mg Alloy Strip Surface Cast by Unequal Diameter Twin Roll Caster

Al-Mg alloy strips were cast by an unequal-diameter twin-roll caster. It was found that cracks formed on the surface at grain boundaries. The grains near the surface were small in size, which likely contributed to crack formation. The use of a molten metal pouring method to increase the grain size near the surface is proposed to reduce cracks. In the previous method, molten metal is poured into a pool, which is on the lower roll surrounded by side-dam plates, a back-dam plate, and the upper roll. In this study, molten metal was directly poured onto the roll surface at a shallow angle using a launder. When the angle was smaller than 20°, cracks did not form. With the proposed method, the heat transfers between the molten metal and the roll surface decreased, as determined from the grain size and strip thickness. The cracks on the strip surface were color-checked and visually inspected.

The effect of inline rolling on Al-Mg alloy strip cast by the unequal diameter twin roll caster

The effect of inline rolling on Al-Mg alloy strip cast by the unequal diameter twin roll caster

Study of aluminum alloy strip cast by an unequal diameter twin roll caster.

Study of aluminum alloy strip cast by an unequal diameter twin roll caster.

Mechanical property of AC4CH aluminum alloy strip cast by an unequal diameter twin roll caster

Mechanical property of AC4CH aluminum alloy strip cast by an unequal diameter twin roll caster

Roll Casting of Al-40%Sn-1%Cu Strip

Strip casting of Al-40%Sn-1%Cu, which is an aluminum alloy used for sliding bearings, was attempted using an unequal diameter twin roll caster. The conditions required to cast sound strips, including the roll speed, molten temperature, roll load, solidification length, melt head, and use of an upper plate, were investigated. The roll load required to make a stable strip surface was 0.01 kN/mm, and the porosity was minimum when the solidification time was less than 0.6 s. The solidification time was controlled by the roll speed and the solidification length. The casting temperature must be set below 670°C to properly solidify the molten metal, and the metal microstructure became finer as the melt head decreased.

Property of aluminium alloy strip cast by an unequal diameter twin roll caster

Property of aluminium alloy strip cast by an unequal diameter twin roll caster

Roll Casting of 400 mm Width Al-40%Sn-1%Cu Clad Strip

A 400 mm width of clad strip consisting of Al-40%Sn-1%Cu and 1070 aluminum alloy could be cast directly from molten metals at a speed of 10 m/min by an unequal diameter twin roll caster equipped with a scraper. An interface clearly existed between the two strips of the clad strip. As-cast clad strip could be cold rolled down to 1 mm without peeling at the interface. The as-cast clad strip could also be bent in the full contact condition without peeling at the interface.

Casting of aluminum alloy clad strip by an unequal diameter twin-roll caster equipped with a scraper

A single-roll caster equipped with two scrapers and an unequal-diameter twin-roll caster equipped with two scrapers are proposed for casting clad strip without centerline porosity or segregation. Although usually found in roll cast 5182 strip, no centerline porosity or segregation occurred in the 5182 strip, which was the overlay clad strip cast by both types of roll casters. The interface between the 5182 strips and the 3003 base strip was clear. The two strips consisting of layers of the clad strip were bonded strongly at the interface. Both roll casters could cast the clad strip at 30 m/min. This casting speed is much higher than that for the conventional twin-roll caster for aluminum alloys.

Casting of aluminum alloy strip by an unequal diameter twin roll caster equipped with a scraper

Casting of aluminum alloy strip by an unequal diameter twin roll caster equipped with a scraper

異径双ロールキャスターによる半凝固温度範囲が広いAl合金板の鋳造

異径双ロールキャスターによる半凝固温度範囲が広いAl合金板の鋳造

異径双ロールキャスターによるすべり軸受材料板の鋳造に関する研究

異径双ロールキャスターによるすべり軸受材料板の鋳造に関する研究

Strip Casting of Al-25%Si Alloy

Strip casting of Al-25%Si strip was tried using an unequal diameter twin roll caster. The diameter of the lower roll (large roll) was 1000mm and the diameter of the upper roll (small roll) was 250mm. Roll material was mild steel. The sound strip could be cast at the speeds ranging from 8 m/min to 12 m/min. The strip did not stick to the roll without the parting material. The primary Si, which existed at centre area of the thickness direction, was larger than that which existed at other area. The size of the primary Si was smaller than 0.2 mm. Eutectic Si was smaller 5μm. The as-cast strip was ranging from 2mm to 3mm thick and its width was 100mm. The as-cast strip could be hot rolled down to 1mm. The hot rolled strip was cold rolled. The primary Si became smaller and the pore occurred around the primary Si after the rolling.

Effect of Some Factors on Fabrication of Clad Strip by a Roll Caster

A vertical tandem positioned twin roll caster and an unequal diameter twin roll caster were used in this study. Factors which affected the connecting of the strips in the fabrication using a roll caster were investigated. They were influences of oxide film, roll-load (separating force) and temperature of a strip. In the clad-strip casting by the roll caster, the connecting could be operated before the oxide film became firmly. Mn was useful element to prevent the oxidation. The roll-load could break the oxide film existed on the strip surface. Prevention of the occurrence of the oxide film was important to make strip connecting condition firm. In the casting of the clad strip using an unequal diameter twin roll caster, strips did not contact to the atomosphere before connecting.

Strip Casting of 6061 and Recycled 6061 Alloy by an Unequal Diameter Twin Roll Caster

A 6061 aluminium alloy and an alloy with increased Fe content, representing recycled 6061 aluminium alloy were cast into strips at speed of 30m/min by an unequal diameter twin roll caster. The Fe content of 6061 aluminium alloy and the model of recycled 6061 aluminium alloy was 0.36 mass% and 0.59 mass%, respectively. Ripple marks, which are typical surface defect of roll cast strips, did not occur on the surface of both as-cast strips. Fe content did not influence the surface condition of the roll-cast-strip. The as-cast strip was cold rolled down to 1 mm, T4 heat treatment was conducted, and then subjected to180 degrees bending test. The result of 180 degrees bending test shows that roll cast 6061 aluminium alloy and 6061 aluminium alloy with increased Fe as recycled had bending ability as same as that of roll-cast 6022 aluminium alloy. In the strip cast by the twin roll caster of the present study, increased Fe content did not influence on the result of the180 degrees bending test.