Study on the Directional Solidification Process of an Aluminum Alloy Bar in Multishell Mold Being Gradually Immersed in Water.

Jiwu Wang,Yongyi Hu,Lele Zheng,Jinwu Kang

doi:10.3390/ma13092197

Jiwu Wang, Yongyi Hu + Show 2 more

Open Access

https://doi.org/10.3390/ma13092197

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Journal: Materials	Publication Date: May 11, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: Beijing Jiaotong University, Tsinghua University

Abstract

A multishell mold structure and water-immersion cooling method (MSMWI) is proposed for the directional solidification of castings. A four-layer-shell sand mold was designed for a bar with diameter of 40 mm. As the aluminum melt was poured, the multishell mold was gradually immersed in water, and the water level drove the advancement of the solidification front from bottom to top. The multishell mold was helpful for the heat insulation of its upper part, and its bottom was chilled by the water. Therefore, directional solidification of the bar was vertically realized. The water-cooled solidification process of the bar was 5.8 times faster than that by air natural cooling (MSMNC), and the temperature gradient was increased by 78 times. The secondary dendrite arm spacing (SDAS) and eutectic silicon were significantly refined. Its tensile strength, elongation, and hardness were increased by 56%, 185%, and 62.6%, respectively.

Highlights

Casting cooling efficiency and quality control have always been the focus of casting research.Rapid solidification (RS) has been used to prepare metals, alloys, or metal glasses, which is a typical melt-quenching technique that can be classified into three categories: (i) spinning, (ii) droplet, and (iii) surface melting [1,2,3]
[24].mold during the casting process, the air gaps served as insulation layers, which reduces the heat transfer from casting to mold andmethod thatare from mold to
The multishell mold could be poured into the mold from the top with the cover removed, the mold was cooled in a water tank with the gradual rise of water level

Summary

Introduction

Rapid solidification (RS) has been used to prepare metals, alloys, or metal glasses, which is a typical melt-quenching technique that can be classified into three categories: (i) spinning, (ii) droplet, and (iii) surface melting [1,2,3]. Metal dies were popularly used to replace traditional sand molds for higher cooling rates. Water-cooling and oil-heating channels are always arranged in the dies for high-pressure die casting [4,5]. During the making of billets, direct-chill (DC) casting was adopted to improve the cooling rate by bottom chill and water spray [6]. To further improve the cooling rate for large billets, intercooling was realized by inserting an in-mold cooler in replacement of the core rod into the melt sump [7]. The billet could be cooled from the center and surface positions.

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Results

Conclusion