PROFESSIONAL POLISHING SERVICES LTD
SPRING 2021
St ain less St eel Polish in g What does it do? There are many reasons why the surface finish of stainless steel products is important. It is often a critical element in the design of a product and has a strong visual appeal to the consumer. A properly specified finish can also help with cleanliness of the product and can also assist surface corrosion resistance. The smoother the surface the less likely the product is to attract deposits of dirt which can dull the finish without proper cleaning. In sanitary applications this is invaluable. With fabricated products such as vessels for the nuclear, pharmaceutical and food and drink industries the finish is paramount as it is a critical design and technical feature that combats against cross-contamination. Even if the finish is not seen when the fabrication is complete it is still an essential design element. The substrate is very important to the end result as certain products, such as hot rolled plate, are more likely to exhibit inherent defects, and this is something that should be taken into account when specifying the finish for your project.
SHEET
Stainless steel sheet is usually either a 2B (Cold Rolled) substrate or it is Bright Annealed (2R). ?Sheet?tends to refer to 3mm and thinner, although 2B is commonly available up to 6mm thick. This tends to be referred to as Cold Rolled Plate. Grained Finishes are popular and with a wide variety to choose from they are suitable for many applications. They have a unidirectional grain produced with either an aluminium oxide abrasive, a silicon carbide abrasive or a ?scotchbrite?type media. All of these finishes conform to BS EN 10088-2; previously BS 1449 Part 2, and each has its own surface measurement commonly achieved which can be certified. An ?Ra?finish is the universally recognised and most used parameter or surface roughness. It is the arithmetic mean of the departures of the profile from a ?mean?or ?centreline?and is displayed in microns (µm).
Often the specification is not that of Ra but of grit. The abrasive grit is bonded to either paper or cloth and, for example, a 240 grit has an average particle scale of .0028 in inches (or a micron scale of 58.5). However specifying by ?Ra?or Grit does not guarantee a match from different suppliers.
The abrasive media is made up of minerals and they perform differently on the material. Most are synthetically produced grit types in aluminium oxide, silicon carbide, zirconia alumina and ceramic aluminium oxide. Obviously the actual 'work' is done by the grit/grain and so choosing the correct media is very important.
ABRASIVEPOLISHING The following information explains just what a ?Dull Polish?actually is and how the finish is produced. * Abrasives are mineral particles that are bonded to either cloth or paper. * The abrasive is applied to the stainless steel surface? usually through mechanical means? with both pressure and speed at optimum levels to ensure a uniform finish is produced.
* The hardness of the contact roll is also a factor in the final finish. * The contact roll applies the pressure to the abrasive which then makes contact with the stainless steel surface.
PLATE Extensive pre-grinding is done on Hot Rolled Plate to removed the majority of surface defects.
Hot Rolled Plate usually exhibits defects that are usually removed or reduced during the cold rolling process. Pitting, laminations and scale are all common defects and are not always removed by surface finishing. Dull and Satin polishes, as well as Ra measured finishes are available on this material but the overall quality of the end product does depend on the substrate supplied. The larger the plate then the possibility that there will be some de-coiling ripple in the substrate as well.
REFLECTIVE There are many different names to describe a ?Bright Polish' when produced on sheets; Bright, Mirror, UltraBright to name a few! The industry accepts that there tends to be a standard bright / mirror finish and then an UltraBright?which is more reflective, and then specific finishes for different industries such as Marine. Bright finishes can be good, bad or indifferent but all of them depend on the quality of the substrate provided to be polished. Most standard bright / mirror finishes do not remove any surface substrate and so any defects that are inherent in the material in it?s mill condition will probably still be there when it has been bright polished. Pre-grinding is only a suitable process for Hot Rolled material and this will leave some grain marks under the reflective finish. On Stainless Steel sheet Bright Annealed material is the best substrate to produce a reflective finish and this yields a deep colour that has good clarity and tone. However the majority of material that is bright or mirror polished is from 2B and this occasionally has surface defects such as pitting and laminations? most usually in the thicker gauges.
SAMPLEPACKS
MEASURE&CERTIFY Often Customers require certification for the polished finish. All grained finishes that request certification are measured and a certificate produced showing the readings taken. Bright finishes are measured by a Gloss meter although an Ra value can also be taken. Rather than measuring the centre line average of the grain pattern in the surface a gloss metre bounces a beam of light at a 60 degree angle onto the surface. This beam of light bounces back and the reflectivity is measured by the unit depending on the amount of light that is returned. The measurements are shown in ?Gloss Units?or as a percentage of 100. We can also take photographs or videos of material being measured after polishing and send these to you so you have visual evidence as well as certification. As well as measuring in RA we can also provide measurements in RZ if required.
Contact us for your Sample Pack Tel
0121 555 6569
Email Admin@professionalpolishing.co.uk
www.professionalpolishing.co.uk
CIRCLE Circle polishing is ideal for applications where something decorative is needed without a high degree of reflectviity. The pattern is ideal for high traffic areas as it can disguise small scratches and scuffs. With state of the art equipment we offer a traditional 50mm diameter circle pattern onto flat sheet as well as more intricate finishes. With multiple lines producing from 1 metre to 2 metres wide we are proud of our investment in this section and have won and retained many prestigious contracts with the UK and mainland Europe as well as producing circle polished sheets in 10mtr lengths of a project in USA.
www.professionalpolishing.co.uk
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