Metal Finishing and Buffing of Steel & Stainless Steel

Steel and Stainless Steel:  Steel is an iron based alloy that is often combined with small amounts of carbon and other alloys to stabilize the metal structure to enhance its strength, machining and forming properties.  The hard structure of steel requires aggressive buffing to achieve a high luster.  Because carbon steel is prone to oxidation and corrosion it is most often plated after buffing to retain the luster and bright aesthetic quality.

When chromium is added to iron based alloy it produces a tough corrosion resistant metal called stainless steel. When other alloys like nickel and molybdenum are added it produces grades of stainless that not only have great wear and corrosion properties but often can be buffed to a beautiful, high luster. 

Before steel or stainless steel can be buffed to a high luster it usually needs to have scratches, forming marks and tool lines removed and smoothed out. Often a steel part can have a surface roughness of 100 to 150 µ inch after a normal bending, forming or press operation.  This roughness, usually measured in Ra, needs to be reduced by polishing to about 10 to 12 µ inch before it should be buffed.  This is most often accomplished by polishing with a progressively finer series of abrasive belts or flap wheels.

The high temperature and pressure of aggressive tangential buffing is common for steel and stainless buffing applications.  Heat does not bother steel and stainless since they have very high melt points (2500 to 2700 °F)  These parts normally need 9,000 to 10,000 surface feet per minute (SFPM) in the initial cut buff operations to be effective and efficient.  In addition it will often use a sisal or combination cloth & sisal bias buff with a steel cut compound to smooth the part.  This is then followed up with a cut & color operation using either a dip treated buff or a mill treated cotton buff to provide a good shine to the metal part.  The buffing step can reduce the surface roughness to a surface roughness Ra of <1 µ inch.

For stainless steel or in critical high luster applications a final color buff operation is the final step.  This uses a regular or loose weave cotton buff along with a high color compound using a color grain like red oxide mixed with a fine grade of alumina.  When this is combined with a color stroke it can produce a beautiful, high luster that brings out the natural luster of the metal.