A study of the interface reaction mechanism between molten aluminum and ferrous die materials.

摘要

One of the main concerns in the aluminum die casting industry is the problem of die soldering. Die soldering is when aluminum sticks to the surface of the die material, mostly H-13 tool steel, and remains there after ejection of the cast part. In recent times, this defect has posed a major concern because of the notable decrease in productivity and efficiency of casting operations. Due to the high affinity that aluminum has for iron, a vigorous physio-chemical reaction occurs at the die/molten metal interface when aluminum melt comes in direct contact with the ferrous die. This reaction results in the immediate formation of a series of iron-aluminum-silicon intermetallic compounds over the die surface and eventually the cast metal sticks to this intermetallic layer.; The aim of this work is to illustrate and quantify the effect of the various die casting parameters, which enhance die soldering, and subsequently alleviate or mitigate the defect. The primary objective was to establish the mechanism of die soldering and other aluminum/ferrous die interface reactions.; Two sets of experimental work was carried out—L-9 Taguchi Matrix, L-16 Taguchi matrix. These experiments quantified the effect of various critical casting parameters that influenced the molten aluminum/ferrous die interface reactions. In addition critical diffusion couple experiments between aluminum 380 alloy and H-13 tool steel was carried out to establish the reaction mechanisms between the two.; Based on the analysis of the results from the above-mentioned set of experiments, a mechanism for the molten aluminum/ferrous die interface reactions was presented. The interaction is a diffusion controlled process consisting of six stages. Stage I is the erosion of the die material by the aluminum melt to form pits on the surface. In Stage II, binary iron-aluminum intermetallic compounds grow on these pits. Stages II through VI deals with the different stages of development of these intermetallic phase layers due to the diffusion of iron atoms from the die surface into the aluminum melt, and the subsequent soldering of aluminum alloy on these layers of intermetallic compounds, respectively. Subsequently, recommendations were put forth to alleviate the reaction between aluminum and ferrous die.