The impurity elements of 5000 series aluminum alloy mainly include Fe, Si, Cu, Zn and so on. Fe, Mn and Cr can form insoluble compounds, thereby weakening the role of Mn and Cr in the alloy. When more hard and brittle compounds are formed in the ingot structure, processing cracks are likely to occur. In addition, Fe also reduces the corrosion resistance of this series of alloys, so the Fe content is generally controlled below 0.4%. For welding wire materials, Fe is best limited to below 0.2%.
Impurity Elements of 5000 Series
Si is a harmful impurity (except LF3 alloy). Si and Mg form the Mg2Si phase. The excessive Mg content reduces the solubility of the Mg2Si phase in the melt, so not only does it have little strengthening effect, but also reduces the plasticity of the alloy. During rolling, Si has more side effects than Fe, so the content of Si should generally be limited to less than 0.5%.
The 5A03 alloy contains 0.5% to 0.8% Si, which can reduce the tendency of welding cracks and improve the welding performance of the alloy. A small amount of Cu is detrimental to the corrosion resistance of the alloy, so the Cu content is generally limited to less than 0.2%, and some alloys have stricter requirements. When the Zn content is less than 0.2%, it has no obvious impact on the mechanical properties and corrosion resistance of the alloy. Adding a small amount of Zn to the high Mg alloy can increase the tensile strength by 10-20Mpa. Therefore, the impurity Zn in the alloy should be limited to 0.2% the following.
In addition, the trace impurity Na in 5000 series aluminum alloy can strongly damage the hot deformation performance of the alloy, and the appearance of sodium brittleness, which is more prominent in high Mg alloys. The way to eliminate sodium brittleness is to make the free Na enriched and at the grain boundary into a compound. The flux chlorination method can be used to produce sodium chloride and be removed with the slag, or the method of adding a trace of lead can be used. AdTech aluminum casting flux can remove the micro-scale of impurity elements of 5000 series aluminum alloy in the furnace.