[China Aluminum Network] 6063 aluminum alloy melting process and precautions
one. Basic features of Al-Mg-Si alloys:
The chemical composition of 6063 aluminum alloy in the GB/T5237-93 standard is 0.2-0.6% of silicon, 0.45-0.9% of magnesium, iron higher limit of 0.35%, the remaining impurity elements ( Cu, Mn, Zr, Cr, etc.) are all less than 0.1%. This is a very wide range of ingredients and it has a great deal of choice.
6063 aluminum alloy belongs to the aluminum-magnesium-silicon series heat-treatable aluminum alloy. In the ternary system consisting of AL-Mg-Si, there is no ternary compound, only two binary compounds Mg2Si and Mg2Al3, with alpha (Al) Pseudo-binary cross section of Mg2Si is the boundary, forming two ternary systems, α(Al)-Mg2Si-(Si) and α(Al)-Mg2Si-Mg2Al3.
In the Al-Mg-Si alloy, the main strengthening phase is Mg2Si. When the alloy is quenched, the more Mg2Si solid-dissolved in the matrix, the higher the strength of the alloy after aging, and vice versa, as shown in Figure 2. In the pseudo-binary phase diagram of α(Al)-Mg2Si, the eutectic temperature is 595°C, the greater solubility of Mg2Si is 1.85%, and it is 1.05% at 500°C. It can be seen that the temperature of Mg2Si is The solubility of Al in the solid solution, the higher the quenching temperature, the higher the intensity after aging, conversely, the lower the quenching temperature, the lower the strength after aging. Some aluminum profiles factory production of the chemical composition of qualified parts, strength can not meet the requirements, the reason is that the aluminum heating temperature is not enough or outside the internal cooling, resulting in profile quenching temperature is too low.
In the Al-Mg-Si alloy series, the weight ratio of magnesium to silicon in the strengthening phase Mg2Si is 1.73. If there is an excess of magnesium in the alloy (ie, Mg:Si>1.73), magnesium will reduce the solid solubility of Mg2Si in aluminum. , thereby reducing the strengthening effect of Mg2Si in the alloy. If there is excess silicon in the alloy, ie, Mg:Si<1.73, then the solid solubility of Mg2Si in the aluminum is not affected by silicon. Therefore, in order to obtain a higher strength alloy, Mg:Si<1. 73.
two. Alloy composition selection 1. Alloy Element Content Selection There is a wide range of 6063 alloy compositions. In addition to considering the mechanical properties and processing properties, the specific ingredients must also consider the surface treatment properties, ie, how the profile should be surface treated and what surface it needs to obtain. For example, to produce abrasives, Mg/Si should be smaller, generally in the range of Mg/Si=1-1.3. This is because there is more relative surplus of Si, which is favorable for the profile to get a sand-like surface; Bright materials, coloring materials, and electrophoretic paints are used, and Mg/Si is preferably in the range of 1.5-1.7. This is because there is less excess silicon, and the profile has good corrosion resistance and easy to obtain a bright surface.
In addition, the extrusion temperature of aluminum extrusions is generally about 480°C. Therefore, the total amount of alloying elements magnesium and silicon should be about 1.0%, because at 500°C, the solid solubility of Mg2Si in aluminum is only 1.05%. The excessively high content of alloying elements will cause Mg2Si to not dissolve into the matrix during quenching, and there will be more Mg2Si phase dissolved. These Mg2Si alloys have little effect on the strength of the alloy, which will affect the surface treatment properties of the profiles and the oxidation of the profiles. Coloring (or painting) causes trouble.
2. Impact of Impurity Elements 1 Iron and iron are the main impurity elements in aluminum alloys. In the 6063 alloy, the national standard specifies that it is not more than 0.35. If a primary industrial aluminum ingot is used in production, the general iron content can be controlled at 0. Below 25, but if in order to reduce production costs, the large amount of recycled scrap aluminum or aluminum, iron is easy to exceed the standard. Fe exists in aluminum in two forms, one is an acicular (or platelet) structure of β phase (Al9Fe2Si2), one is a granular structure of α phase (Al12Fe3Si), different phase structure, the aluminum alloy There are different effects, the β-phase structure of the sheet structure is much more destructive than the α-phase of the granular structure, β-phase can make the aluminum surface rough, mechanical properties, corrosion resistance become worse, the oxidation of the profile surface blue, shiny When it falls, it will not be purely shaded. Therefore, the iron content must be controlled.