Why 7075 material is easy to oxidize during CNC precision machining

There are many materials commonly used in machining, such as stainless steel, aluminum alloy, carbon steel, etc., among which the most common should be aluminum alloy. 6061 and 7075 grades are the most common in the Aluminum alloy materials. The 7075 aluminum alloy is oftenly used  in CNC precision in the processing industry, and it is very easy to oxidize in the machining process, which brings a lot of troubles to the factories of cnc precision machining.

First of all, let’s take a look at the properties of 7075 material, the physical and chemical composition of 7 series aluminum. 

Physical properties of 7075 aluminum alloy: 

tensile strength: 524Mpa 0.2% 

yield strength: 455Mpa 

elongation: 11% 

elastic modulus E ：71GPa 

Hardness: 150HB 

Density: 2.81g/cm^3 

Tensile strength σb (MPa): ≥560 

Elongation stress σp0.2 (MPa): ≥495 

Elongation δ5 (%): ≥6

7075 Aluminum alloy is a kind of Cold-treated forging alloy has high strength, far better than mild steel. The 7075 aluminum alloy has a compact structure, strong corrosion resistance, good mechanical properties and anode reaction.

In the cnc precision machining, a layer of natural protective film of aluminum oxide on the surface of 7075 material is precision processed in CNC.

After being damaged, the magnesium element in the material easily reacts with the air, causing the surface to corrode and rust. After the surface is rusted, the 7075 material is also extremely difficult during the surface treatment process. It is easy to ablate and white spots on the surface. Therefore, during the oxidation process, do not take it out frequently to check the thickness of the film. Pay attention to controlling the current. If it is too big, it will cause ablation, and if it is too small, it will not react. After the film thickness is reached, the color will be heavier.