Stainless steel comes in several common finishes.It’s important to know what these common finishes are and why they’re important.The latest innovations in abrasive technology can reduce process steps to deliver the desired finish, including the sought-after surface gloss.
Stainless steel can be difficult to work with, but the finished product offers one of the best looks and makes all the work worth it.It is generally accepted that using a finer grit in a sanding sequence can remove previous scratch patterns and improve the finish, but there are many overall steps to be aware of when using many grit sequences to achieve the desired finish.
Stainless steel comes in several common finishes.It’s important to know what these common finishes are and why they’re important.The latest innovations in abrasive technology can reduce process steps to deliver the desired finish, including the sought-after surface gloss.
The Specialty Steel Industry of North America (SSINA) describes industry standards and where products use different finish numbers.
No. 1 is done.This surface treatment is made by rolling (hot rolling) stainless steel that has been heated before rolling.Very little finishing is required, which is why it is considered rough.Common products with No. 1s are air heaters, annealing boxes, boiler baffles, various furnace components, and gas turbines, to name a few.
No. 2B is complete.This bright, cold-rolled surface is like a cloudy mirror and requires no finishing steps.Parts with a 2B finish include universal pans, chemical plant equipment, cutlery, paper mill equipment and plumbing fixtures.
Also in category 2 is the 2D finish.This finish is a uniform, matte silver grey for thinner coils, the thickness of which has been reduced by a cold rolling minimal finishing process as it is often used with a factory finish.Pickling or descaling is required after heat treatment to remove chromium.Pickling can be the final production step for this surface treatment.When a painted finish is required, the 2D finish is preferred as the substrate as it provides excellent paint adhesion.
Polish No. 3 is characterized by short, relatively thick, parallel polishing lines.It is obtained by mechanical polishing with progressively finer abrasives or by passing coils through special rollers that press patterns into the surface, simulating the appearance of mechanical wear.It is a moderately reflective finish.
For mechanical polishing, a 50 or 80 grit is usually used initially, and a 100 or 120 grit is usually used for the final polish.Surface roughness typically has an average roughness (Ra) of 40 microinches or less.If the manufacturer requires fusion welds or other finishing, the resulting polishing line is usually longer than what the manufacturer or tumbler polishes.The most common in brewery equipment, food processing equipment, kitchen equipment, and scientific instruments is the No. 3 finish.
No. 4 finish is the most common and is used in the appliance and food industries.Its appearance is characterized by short parallel polished lines extending evenly along the length of the coil.It is obtained by mechanically polishing finish No. 3 with progressively finer abrasives.Depending on the application requirements, the final finish can be anywhere between 120 and 320 grit.Higher grit produces finer polished lines and more reflective finishes.
Surface roughness is typically Ra 25 µin.or less.This finish is widely used in restaurant and kitchen equipment, storefronts, food processing and dairy equipment.As with Finish No. 3, if the operator needs to fuse welds or perform other finishing touches, the resulting polished line is usually longer than the line on the product polished by the manufacturer or roll polisher.Other areas where Finish 4 is found include road tank trailers, hospital surfaces and equipment, instrumentation or control panels, and water dispensers.
Polish No. 3 is characterized by short, relatively thick, parallel polishing lines.It is obtained by mechanical polishing with progressively finer abrasives or by passing coils through special rollers that press patterns into the surface, simulating the appearance of mechanical wear.It is a moderately reflective finish.
Finish No. 7 is highly reflective and has a mirror-like appearance.Polished to 320 grit and polished No. 7 finish can often be found in column caps, decorative trim and wall panels.
There have been significant advances in abrasives used to achieve these surface finishes, helping manufacturers produce more parts safely, quickly and cost-effectively.New minerals, stronger fibers and antifouling resin systems help optimize the finishing process.
These abrasives provide fast cuts, long life, and reduce the number of steps needed to get the job done.For example, a flap with microcracks in ceramic particles extends its life at a slow rate and provides a consistent finish.
In addition, technologies similar to aggregate abrasives have particles that bond together to cut faster and provide a better finish.It requires fewer steps and less abrasive inventory to do the job, and most operators see greater efficiency and cost savings.
Michael Radaelli is Product Manager at Norton|Saint-Gobain Abrasives, 1 New Bond St., Worcester, MA 01606, 508-795-5000, michael.a.radaelli@saint-gobain.com, www.nortonabrasives.com.
Manufacturers are challenged to complete the corners and radii of stainless steel parts.To blend hard-to-reach welds and forming areas, it has a five-step process that requires a grinding wheel, a square pad of several grits, and a uniform grinding wheel.
First, operators use a grinding wheel to make deep scratches on these stainless steel components.Grinding wheels are generally stiffer and less forgiving, putting the operator at a disadvantage in the beginning.The grinding step was time-consuming and still left scratches that had to be removed by three additional pad finishing steps of different grain sizes.This step is followed by the use of uniform wheels to achieve the desired surface finish.
By changing the grinding wheel to a ceramic lobe wheel, the operator was able to finish polishing in the first step.Keeping the same grit sequence as in the second step, the operator replaced the square pads with a flap wheel, improving time and finish.
Removing the 80-grit square pad and replacing it with a non-woven mandrel with agglomerated particles followed by a 220-grit non-woven mandrel allows the operator to produce the desired sheen and overall finish and eliminates the need for The last step is the original process (use the unity wheel to close the step).
Thanks to improvements in flapper wheels and nonwoven technology, the number of steps has been reduced from five to four, reducing completion time by 40%, saving labor and product costs.
There have been significant advances in abrasives used to achieve these surface finishes, helping manufacturers produce more parts safely, quickly and cost-effectively.
WELDER, formerly Practical Welding Today, showcases the real people who make the products we use and work with every day.This magazine has served the welding community in North America for over 20 years.
Now with full access to the digital edition of The FABRICATOR, easy access to valuable industry resources.
The digital edition of The Tube & Pipe Journal is now fully accessible, providing easy access to valuable industry resources.
Enjoy full access to the digital edition of STAMPING Journal, which provides the latest technological advancements, best practices and industry news for the metal stamping market.
Now with full access to the digital edition of The Fabricator en Español, easy access to valuable industry resources.