Toshio Haga

Roll Casting of Clad Strip

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.

Effect of Si on AA5182 Strip Cast by a High Speed Twin Roll Caster

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.

Single Roll Caster Equipped with a Scraper

A scraper was developed and attached to the single roll caster in order to improve the free solidified surface of as-cast strip cast. Semisolid metal on the free solidified surface was flattened by the scraper and the surface became flat. The AA5182 aluminum alloy could be cast at speeds up to 40m/min. Thickness was about 3mm. Pressure of the unit width of the scraper was ranging from 0.1N/mm to 1.0N/mm, and these pressure was enough to make the free solidified surface flat. Center line segregation did not occur as the strip was solidified from single side at the strip cast by the single roll caster. Roll-cast strip could be cold rolled down to 1mm. There was not difference between the roll contact surface and the free solidified surface of the strip after cold rolling judging by a visual examination. Result of tension test of the roll cast and cold rolled strip was as same as that of D.C. cast and rolled strip. Deep drawing test was operated at the conditions both of the roll contact surface and the free solidified surface were outer side. LDR (limited drawing ratio) was same at both conditions and they were 1.8. Thickness of the strip was controlled by the roll speed, solidification length (length of the melt pool) and pressure of the scraper. The single roll caster is simpler than a twin roll caster. Rigidity for rolling was not required for the single roll caster. Cost of the roll is half comparing a twin roll caster. The equipment cost of the single roll caster is more economy than that of the twin roll caster.

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.

Solidification Heat Transfer Analysis of AZ91D Cast Strip by Using a Horizontal Twin Roll Caster

This study was investigated about Solidification heat transfer analysis of AZ91D cast strip by using a horizontal twin roll caster. Density of magnesium alloy is the lightest within all of the practicable metal, and AZ91D magnesium alloy have high specific strength. So, magnesium alloy was expected to apply for transport machines. Twin roll caster is able to cast low cost magnesium strip. The heat transfer coefficient between the molten magnesium alloy and copper roll is important to cast magnesium strip. The present study investigated the heat transfer coefficient and distribution of temperature during casting by the two dimensional heat transfer solidification analysis. We investigated about the effect of heat transfer coefficient between roll velocity and roll gap. AZ91D cast by twin roll caster at 16 m/min. the caster using copper roll, and roll size was φ 300 mm. roll gap was 3 mm. This experimental condition was able to cast AZ91D strip cast, and this study of twin roll caster of optimum K value was 36.5.

Casting of aluminum alloy strip by a single-roll caster equipped with a scraper

A SRCES(Single-Roll Caster Equipped with a Scraper)was devised in order to improve the free-solidified surface. A scraper contacted to the free-solidified surface at the constant force. The some amount of semisolid metal on the solid layer was removed and the surface condition becomes flat. The melt pool was mounted on the top of the roll. Therefore, the scraper was easily operated. In our study, aluminum alloy strip was cast by the SRCES. The scraped surface condition of the cast strip was investigated. The as-cast strip could be cold-rolled and the roughness of the free-solidified surface was reduced. There was no difference between the free-solidified surface and roll-contact surface after cold-rolling. The cross-section of the as-cast strip was observed. The porosity of the free-solidified surface was less than the porosity at center area of the strip cast by a TRC(Twin-Roll Caster). The mechanical properties of the cast strip were investigated by deep-drawing test and tensile test. As a result of deep-drawing test, there was no difference between the free-solidified surface and the roll-contact surface after cold-rolling. As a result of tensile test, mechanical properties of cold-rolled strips were similar to the strip cast by the D.C.casting. These result shows that the free-solidified surface could be improved up to the roll-contact surface by the scraper and cold-rolling. (Received September 20, 2011 Accepted January 12, 2012)

Roll Casting of Aluminum Alloy Strip by a Single Roll Caster Equipped with a Scraper

A single roll caster equipped with a scraper was devised to cast the strip with sound free solidified surface. A property of this single caster is equipment of the scraper. Semisolid metal on the free solidified surface was scribed by a scraper and the surface became flat. Center line segregation did not occur as the strip was solidified from single side. The AA5182 aluminum alloy could be cast at speeds up to 40m/min. Thickness was about 3mm. Pressure of the unit width from the scraper was ranging from 0.1N/mm to 1.0N/mm, and these pressure was enough to make the free solidified surface flat. Roll cast strip could be cold rolled down to 1mm. There was not difference between roll contact surface and the free solidified surface after cold rolling by a visual examination. Result of tension test of the roll cast strip was as same as that of D.C. cast and rolled strip. Deep drawing test was operated at the conditions both of the roll contact surface and the free solidified surface was outside. LDR (limited drawing ratio) was same at both conditions and they were 1.8. Thickness of the strip was controlled by the roll speed, solidification length (length of the melt pool) and pressure of the scraper. The single roll caster is simpler than a twin roll caster. Rigidity for rolling was not needed for the single roll caster. Cost of the roll is half comparing a twin roll caster. The equipment cost of the single roll caster is more economy than that of the twin roll caster.

Roll Casting of Recycled AA5182

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.