Journal of Korea Foundry Society (한국주조공학회지)

Korea Foundry Society (한국주조공학회)
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Effect of Scrap Addition Ratio on Tensile and Solidification Cracking Properties of AC4A Aluminum Casting Alloy

AC4A 알루미늄 합금의 인장 및 응고균열 특성에 미치는 스크랩 첨가 비율의 영향

  • Oh, Seung-Hwan (Department of Metallurgical Eng., Pukyong National Graduate School) ;
  • Kim, Heon-Joo (Department of Metallurgical Eng., Pukyong National Univ.)
  • 오승환 (부경대학교 대학원 금속공학과) ;
  • 김헌주 (부경대학교 공과대학 금속공학과)
  • Received : 2020.03.16
  • Accepted : 2020.05.19
  • Published : 2020.06.30
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Abstract

The effect of an aluminum scrap addition ratio on the tensile and solidification cracking properties of the AC4A aluminum alloy in the as-cast state and heat-treated state were investigated in this study. Generally, the expected problem of using scrap in aluminum casting is an increase of hydrogen and Fe element inside the aluminum melt. Another issue is an oxide film which has a weak interface with the molten aluminum and acts as potent nucleation sites for internal porosity and crack initiation. Solidification cracking is one of the critical defects that must be resolved to produce high quality castings. A conventional evaluation method for solidification cracking is a relative and qualitative analysis method which does not provide quantitative data on the thermal stress in the solidification process. Therefore, a newly designed solidification cracking test apparatus was used in this study, and the device can provide quantitative data. As a result, after conducting experiments with different scrap addition ratios (0%, 20%, 35%, 50%), the tensile strengths and elongations in the as-cast state were 214, 187.7, 182.1 and 170.4MPa and 4.6%, 3.4%, 3.1% and 2.3%, respectively. In the case of the T6 heat-treated state, the tensile strengths and elongations were 314.9, 294.6, 293.1 and 271.1MPa and 5.4%, 4.6%, 3.8% and 3.1%, respectively. The strength of the solidification cracking was 3.1, 2.4, 2.2and 1.6MPa as the scrap addition ratio increases.

Keywords

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