The different materials have distinct differences in the cutting fluid. Choosing the wrong cutting oil is not just a matter of making do, but leading to more losses.
Aluminium alloys:
They are vulnerable to adhesion, corrosion, and discoloration.
Main questions: the materials are soft and prone to sticking to the tool, which compromises the surface finish.
Requirements: using the cutting fluids only for aluminium cutting oils (pH 8.0-8.5). The cutting fluid for aluminium should contain aluminium corrosion inhibitors to prevent discoloration or white spotting. The semi-synthetic fluids are superior to fully synthetic ones.
Common mistake: using cutting fluid for steel that leads to surface staining.
Stainless steel:
It’s vulnerable to hardness, heating, and cold welding.
Main questions: stainless steel has a poor thermal conductivity and strong work-hardening tendencies. If the cutting zone’s temperature is over 600 ℃, the common cutting fluid can not form a useful lubricant film.
Requirements: it should use extreme-pressure (EP) type cutting fluids, which contain sulfur, chlorine, or phosphorus additives. Or using high oil content emulsions or semi-synthetic fluids. The high flow flushing is more effective than simply increasing concentration.
Common mistake: using cheap cutting fluids to save cost, resulting in workpiece rust and frequently change cutting fluids. Therefore, the comprehensive cost is higher.
Copper alloys:
They are vulnerable to discoloration and spotting
Requirements: the cutting fluid must be free of active sulfur and have a low oil or fully synthetic formulation. After operating, the copper alloys should be cleaned or coated with anti-rust oils.
All in all, there is no universal cutting fluid. Aluminum alloys require low pH and corrosion inhibition; stainless steel requires EP additives and high flow rates; cast iron requires fully synthetic fluids with high chip-settling capabilities; copper alloys require sulfur-free, low-residue formulas. At a minimum, use two categories of fluid: one for aluminum and another for steel. Insisting on a "one-size-fits-all" solution saves money on procurement but leads to losses in tooling, yield rates, and fluid sump longevity.
