Color Metallography of Characteristic Microstructure in High-Speed Twin-Roll Cast Al–Mn–Si Alloy Strip Using Weck’s Reagent

Nguyen, Thai Ha; Song, Ram; Harada, Yoshio; Kumai, Shinji

doi:10.2320/matertrans.l-m2020856

Cited by 10 publications

(15 citation statements)

References 17 publications

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“…This reagent causes regions rich in the alloying element to become bright, and regions rich in Al to become dark. 7) A band zone existed in the center of the thickness direction; this is characteristic of high-speed roll casting. 7) There was a tendency for the band zone to form under high-speed roll casting at smaller roll loads than for the CHTRCA.…”

Section: Band Zone In Cast Strip At Roll Bitementioning

confidence: 99%

“…7) A band zone existed in the center of the thickness direction; this is characteristic of high-speed roll casting. 7) There was a tendency for the band zone to form under high-speed roll casting at smaller roll loads than for the CHTRCA. The band zone formed up to the roll bite.…”

Section: Band Zone In Cast Strip At Roll Bitementioning

confidence: 99%

“…Specimens attained by the roll-stop were etched by Weck's reagent. 7) The chemical composition was 4 g KMnO 4 , 1 g NaOH, and 100 mL distilled water.…”

Section: Surface and Microstructure Observationsmentioning

confidence: 99%

“…In AlSi strips cast using a VHSTRC at a normal roll load, a band zone exists in the center of the thickness direction. 7,8) Globular crystals are formed in the band zone in the AlSi alloy. The reason for the existence of this band zone in AlSi and AlMg strips cast using very small roll loads has not yet been clarified.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Casting Conditions on Surface Defect and Segregation of Strips Cast by a High-Speed Twin-Roll Caster

Yamazaki

Haga

2023

Mater. Trans.

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In this study, the effects of the roll load and superheating on the appearance of surface defects in AlMg and AlSi alloy strips cast using a high-speed twin-roll caster were investigated. The band zone that existed in the center of the thickness direction was investigated. The alloy compositions were Al4.8%Mg and AlSi with Si contents of 1, 2, 3 and 11%. The diameter and width of the copper roll in the twin-roll caster were 300 and 50 mm, respectively. The superheating temperature of the molten metal was 5 and 50°C, and the roll load was varied from 2 to 88 N/mm. A roll speed of 30 m/min was utilized. The existence of surface cracks was investigated by penetrant inspection and bending test. The amount of surface cracking in the AlMg alloy was affected by the roll load, and the number of surface cracks decreased with decreasing roll load. Surface cracks occurred more easily in the Al4.8%Mg alloy than in the AlSi alloys. The degree of cracking could not be reduced by cold-rolling. In the AlSi alloys, the ripple marks were affected by the Si content, degree of superheating of the molten metal and the roll load. In the Al3%Si alloy, ripple marks were produced, and worsened as the roll load and the superheating of the molten metal were increased. A specimen for observation of the microstructure near the roll bite was obtained by performing a roll-stop during casting, and observed using Weck's reagent. A band zone was found to exist. The band zone in AlSi consisted of globular crystals, and that in AlMg consisted of equiaxed dendrites and Mg-rich areas.

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Section: Band Zone In Cast Strip At Roll Bitementioning

confidence: 99%

Section: Band Zone In Cast Strip At Roll Bitementioning

confidence: 99%

“…Specimens attained by the roll-stop were etched by Weck's reagent. 7) The chemical composition was 4 g KMnO 4 , 1 g NaOH, and 100 mL distilled water.…”

Section: Surface and Microstructure Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Casting Conditions on Surface Defect and Segregation of Strips Cast by a High-Speed Twin-Roll Caster

Yamazaki

Haga

2023

Mater. Trans.

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“…The occurrence mechanism of surface cracks in the strip cast using the VHSTRC was precisely investigated by Kumai and Hrada. 4,5) It was reported that solution-rich liquid, which existed between the dendrites and at the grain boundary in the center area in the thickness direction, was squeezed by solidification shrinkage to the strip surface. The brittle ¢-Al 3 Mg 2 solidified, and cracking occurred at ¢-Al 3 Mg 2 .…”

Section: Introductionmentioning

confidence: 99%

Reduction of Surface Crack by Modified Molten Metal Pouring Method on Al–Mg Alloy Strips Produced by Twin-Roll Casting

Yamazaki,

Haga

2024

Mater. Trans.

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In this study, cracks formed on the surface of Al-Mg alloy strips cast using a high-speed unequal-diameter twin-roll caster were observed. In addition, the effects of the roll load and the molten metal pouring method on the crack were investigated. Four types of Al-Mg alloys (AC7A, AC7B, Al-3%Mg, and Al-7%Mg) were cast into strips at roll speed of 30 m/min. The crack size decreased with decreasing roll load, and when the roll load was 4 N/mm, no cracks formed. However, the strips did not completely solidify under this low load, and conveyance was difficult due to the insufficient strength of as-cast strips. To reduce the load in the inner area along the width direction of the strips, the thickness of the solidification layer in this area was made shorter than that at the edges by modifying the molten metal pouring method. In the modified pouring method, the molten metal was poured onto the roll using a launder placed against the roll at a small angle. With this method, the edges completely solidified and had enough strength for conveyance. Moreover, cracking substantially improved, and when the distance between the edge of the molten metal pool and the pouring point was set, crack formation was almost completely eliminated. The band region at the center in the thickness direction of the strips was widened using the proposed pouring method. The tensile strength and limiting drawing ratio of strips cast using the proposed pouring method were both greater than those of the strips cast using the conventional pouring method.

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Effect of Large Particles in Central Band of Al–4%Mn–1%Si High-Speed Twin-Roll Cast Strip on Elongation of Cold-Rolled and Annealed Sheets

et al. 2022

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Mn-containing (2 and 4 mass%) AlMn-based alloys were fabricated by high-speed twin-roll casting (HSTRC). Al4 mass%Mn 1 mass%Si strips contained coarse particles in the central band of the cast strips. Microstructure and chemical analyses revealed that the particles were primarily Al 6 (MnFe) and ¢-Al(MnFe)Si. These particles formed during the solidification process of the residual liquid, which slowly cooled after the strip exited the roll gap during HSTRC. However, blowing compressed air onto the strip surface as it exited the roll gap rapidly cooled the residual liquid, reducing the number and size of large particles in the central band region. The cold-rolled and annealed sheets fabricated from the strips exhibited a refined and homogenous microstructure. Consequently, both the strength and elongation of the sheets were improved.

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Color Metallography of Characteristic Microstructure in High-Speed Twin-Roll Cast Al–Mn–Si Alloy Strip Using Weck’s Reagent

Cited by 10 publications

References 17 publications

Effect of Casting Conditions on Surface Defect and Segregation of Strips Cast by a High-Speed Twin-Roll Caster

Effect of Casting Conditions on Surface Defect and Segregation of Strips Cast by a High-Speed Twin-Roll Caster

Reduction of Surface Crack by Modified Molten Metal Pouring Method on Al–Mg Alloy Strips Produced by Twin-Roll Casting

Effect of Large Particles in Central Band of Al–4%Mn–1%Si High-Speed Twin-Roll Cast Strip on Elongation of Cold-Rolled and Annealed Sheets

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