We offer polished stainless steel tubing and pipe with a wide range sizes in welded type, stainless steel grades include 201, 304/304L, 316/316L and other stainless steels, tubing forms have round tubing, square tubing and rectangular tubing.
Stainless Steel Grades
There are a variety of stainless steel grades for polished tubing, they are also food grade stainless steels, exhibiting high strength and excellent corrosion resistance, common grades include 304, 304L and 316L.
|TP 304||0.08||2||0.045||0.03||1||18 – 20||8 – 11|
|TP 304L||0.035||2||0.045||0.03||1||18 – 20||8 – 13|
|TP 316L||0.035||2||0.045||0.03||1||16 – 18||10 – 14||2 – 3|
Advantages of Polished Tubing
Polished finishing makes welding seam integrity with base metal after heat treatment, and have a visible bright surface, furthermore, it can make a uniform and smooth surface, and easy to clean, no dark scale on tubing surface, polished tubing have a low Ra value in roughness, it is a value adding service.
- Improve surface finish and “RA” Value
- Reduce product adhesion
- Improve surface cleanability and form a reflective surface
- Improve aesthetic appeal
- Remove scales and oxidation
- Prevent corrosion
ASTM A270 and 3A Polished Tubing
Stainless Steel Welded Tubing is usually polished conforming to ASTM A270 and 3A standard, this polished tubing undergoes multiple passes through the polishing heads to remove any unwanted residue on nterior and exterior surface。
This tubing undergoes a rigorous quality inspection, including destructive and non-destructive examination, at the mill prior to shipment.
There are several polishing equipment to use, either outside surface ir inside surface, we have capacity to offer sanitary and food grade standard for special applications.
Stainless Steel Polished Grits
- 120 grit
- 180 grit
- 320 grit
- 400 grit
- 600 grit
- 800 grit
Ra refers to roughness average, which is the measure of roughness of a surface and measured in micrometers (μm), Ra value is to describe Average scratch depth of tubing surface, the lower the Ra value, the smoother and more polished the surface, we provide minimum Ra value is 0.05 μm, “Ra,” or surface roughness, is confirmed using microscopic and profilometry testing.
Polished Tubing Sizes
- 1 1/2″
- 2 1/2″
Polished Tubing Applications
Stainless steel polished tube is wide used in food processing, bear, beverage, drinking water, it is also used for construction purpose, like handrail required a bright surface, polishing inside surface for stainless steel sanity tubing conforming to ASTM A270 specification。
- Food, Beverage, and Dairy
- Kitchen equipment
Mechanical Polishing is a process to grind surface of metal using abrasive belt and mechanical tools at multi stages so as to achieve desired smooth surface and roughness value, meanwhile, it alters the microstructure of surface.
Stainless steel tubing is polished mechanically to pass through a set of abrasive wheels and tapes with polishing machine, with polishing paste to improve polishing efficiency, finally this process makes desired polishing level using different grinding belt to remove surface layer。
There are Dry and Wet mechanical polishing for selecting, wet style is a better option。
Electropolishing is a process that uses a metal workpiece as an anode and performs electrolysis in a suitable electrolyte to selectively remove its rough surface and improve the surface finish, it is also called Electrochemical or anodic polishing.
During electropolishing, current flows on the surface of the metal product as the anode, which will form an oxide film, a salt film or an oxygen adsorption layer on the surface, so that the metal dissolution rate of the anode drops sharply, that is, in a passive state. But this passivation film layer may be dissolved in the electrolyte, and the anode is reactivated. At a certain current density, metal passivation and metal dissolution proceed alternately.
The electrolyte usually uses phosphoric acid as the main component, and it also needs to add certain oxidants (such as sulfuric acid, chromic anhydride, etc。)。 Without electricity, the electrolyte should have no significant corrosive effect on the metal being polished。 It also requires that the electrolyte has a high solubility for the anode dissolution product and is easily removed。 In addition, the electrolyte is required to have good stability, low cost and low toxicity。 If necessary, a small amount of organic substances (such as glycerin, methyl cellulose, etc。) can be added to the electrolyte as a corrosion inhibitor。 Use perchloric acid-acetic acid electrolyte for electropolishing to obtain a high-finish surface。
After being energized, a polarized film is formed on the surface of the polished metal, allowing metal ions to diffuse through this thin flag. The current density of microscopic and macroscopic bumps or rough spots on the surface and the burr area is greater than the rest of the surface, and it dissolves at a faster rate to achieve the purpose of leveling and deburring. By prolonging the polishing time, increasing the polishing temperature and current density, a bright surface can be obtained.
Mechanical Polishing vs. Electropolishing
Mechanical Polishing and Electropolishing are main methods to polish stainless steel tubing, mechanical polishing performs well for general industries, when higher polishing level is required, like in the pharmaceutical and semiconductor industries, Electropolishing has its advantages.
- Improve Cleanability
- Enhance Durability
- Improve Sterility
- Increase Corrosion Resistance
Mechanically polished surfaces retain the basic alloy composition with only slight depletion of the other alloy elements, whereas electropolished surfaces contain essentially only chromium and iron, and no stress resided.