In all the main reasons that lead to the failure of aluminum alloy die-casting die, the problem of welding on the die surface has been gradually concerned. “Welding” is a term used in the die casting industry. It refers to the reaction between the die and the die casting alloy.

　　Complex Fe-Al intermetallic compound phases are formed on the mold surface once welding occurs, which causes defects on the casting surface during the next die casting cycle. Hard intermetallic phases can also build up on the mould surface, so production must be interrupted and the weld product removed by polishing, which can lead to longer production times and a waste of labour, but also reduce the die life.

　　Usually according to the different forms of welding, “Welding” can be divided into two kinds.

　　The first type of welding is called“Impact welding”, which occurs at the entrance or Ingate of the mold facing the cavity. These areas are generally subjected to the violent impact of molten metal flow when filling, the surface temperature is higher, the pressure is greater, and the protective layer is extremely easy to destroy, when die-casting alloy scours continuously, the mold protective layer fails and the metal matrix is exposed. The alloy reacts with the matrix material to form complex intermetallic compound phases. The cracking and shedding of the intermetallic compound in die casting will not only lead to the quality defect of the casting, but also take away the base material and expose the fresh surface, serious will lead to mold surface corrosion and mold material melting loss. Therefore, it is necessary to remove and repair the damaged surface early in the welding process.

　　In all the main reasons that lead to the failure of aluminum alloy die-casting die, the problem of welding on the die surface has been gradually concerned. “Welding” is a term used in the die casting industry. It refers to the reaction between the die and the die casting alloy.

　　Complex Fe-Al intermetallic compound phases are formed on the mold surface once welding occurs, which causes defects on the casting surface during the next die casting cycle. Hard intermetallic phases can also build up on the mould surface, so production must be interrupted and the weld product removed by polishing, which can lead to longer production times and a waste of labour, but also reduce the die life.

　　Usually according to the different forms of welding, “Welding” can be divided into two kinds.

　　The first type of welding is called“Impact welding”, which occurs at the entrance or Ingate of the mold facing the cavity. These areas are generally subjected to the violent impact of molten metal flow when filling, the surface temperature is higher, the pressure is greater, and the protective layer is extremely easy to destroy, when die-casting alloy scours continuously, the mold protective layer fails and the metal matrix is exposed. The alloy reacts with the matrix material to form complex intermetallic compound phases. The cracking and shedding of the intermetallic compound in die casting will not only lead to the quality defect of the casting, but also take away the base material and expose the fresh surface, serious will lead to mold surface corrosion and mold material melting loss. Therefore, it is necessary to remove and repair the damaged surface early in the welding process.

　　The second type of welding is called“Deposition welding”, that is, the location of the welding back to the gate or away from the gate. These areas are usually inaccessible to surface treatments or mold lubricants. Therefore, their surface state, temperature distribution, pressure conditions and other places are different.

　　Die-casting alloys usually reach these areas at lower temperatures, and their fluidity becomes poor, easy to first solidification, hot semi-solid alloy and mold surface contact time is longer, in addition, the surface state of the mould itself is not very good, so it is easy to form FeAl intermetallic compounds. In the repeated die casting cycles, the intermetallic compounds will gradually deposit in these areas with poor fluidity, finally, serious welding is formed, which affects die casting production.

　　Although different types of welds occur in different areas of aluminum alloy die casting dies, the welds have some common features-that is, the welds on the die surface are generally silver-white.

　　The composition of the weld layer is usually complex Fe-Al intermetallic compound, and it is difficult to analyze because of the thin intermetallic compound.

　　But foreign researcher Z. W. Chen and D. T. Using X-ray diffraction, Fraser et al analyzed the intermetallic compound structure formed by dipping H13 steel into molten Al-11Si-3Cu die-casting aluminum alloy, the welding layer is composed of the intermetallic compound αbcc-(FeSiAlCrMnCu) in the complex layer, the hexagonal αh-(Fe2SiAl8) intermetallic compound in the outer compact layer and the intermetallic compound η-Fe2Al5 in the inner compact layer. The morphology of Fe-Al interface observed by the authors is similar to that obtained by dipping H13 steel into ADC12 die-casting aluminum alloy.

　　At present, the quantity of intermetallic compound is very small, the welding surface layer is very thin, and the analysis method is limited. The Quantitative analysis of the intermetallic compounds will be the focus of the researchers' work in the future.

　　The second type of welding is called“Deposition welding”, that is, the location of the welding back to the gate or away from the gate. These areas are usually inaccessible to surface treatments or mold lubricants. Therefore, their surface state, temperature distribution, pressure conditions and other places are different.

　　Die-casting alloys usually reach these areas at lower temperatures, and their fluidity becomes poor, easy to first solidification, hot semi-solid alloy and mold surface contact time is longer, in addition, the surface state of the mould itself is not very good, so it is easy to form FeAl intermetallic compounds. In the repeated die casting cycles, the intermetallic compounds will gradually deposit in these areas with poor fluidity, finally, serious welding is formed, which affects die casting production.

　　Although different types of welds occur in different areas of aluminum alloy die casting dies, the welds have some common features-that is, the welds on the die surface are generally silver-white.

　　The composition of the weld layer is usually complex Fe-Al intermetallic compound, and it is difficult to analyze because of the thin intermetallic compound.

　　But foreign researcher Z. W. Chen and D. T. Using X-ray diffraction, Fraser et al analyzed the intermetallic compound structure formed by dipping H13 steel into molten Al-11Si-3Cu die-casting aluminum alloy, the welding layer is composed of the intermetallic compound αbcc-(FeSiAlCrMnCu) in the complex layer, the hexagonal αh-(Fe2SiAl8) intermetallic compound in the outer compact layer and the intermetallic compound η-Fe2Al5 in the inner compact layer. The morphology of Fe-Al interface observed by the authors is similar to that obtained by dipping H13 steel into ADC12 die-casting aluminum alloy.

　　At present, the quantity of intermetallic compound is very small, the welding surface layer is very thin, and the analysis method is limited. The Quantitative analysis of the intermetallic compounds will be the focus of the researchers' work in the future.