How is the mirror polishing finish done on stainless steel?

polishing stainless steel

Stainless steel mirror polishing is a surface treatment of stainless steel tubes. It is a finish that is smooth enough to provide a reflective surface. After polishing stainless steel tubes by many different processes, the mirror quality of stainless steel obtained is usually 6K or better.

The common stainless-steel mirror surface is divided into 6K, 8K, and 10K according to the degree of its mirror effect after processing. The reason because of which it is called “stainless steel mirror tube” is that it has a high degree of surface polishing and is as bright and reflective as a mirror.

So, how is the stainless steel polished to form a mirror tube?

The working principle of the stainless-steel round tube polishing machine is to use a high-speed rotating polishing wheel combined with a rotating guide wheel to make the round tube automatically move forward while using the polishing wheel to rub the surface of the circular tube and achieve the polishing effect.

By adjusting the feed amount of the grinding head, one can choose the amount of the polishing effect, and thus, the ideal polishing effect can be achieved by adjusting the feed amount for the workpiece. Various polishing wheels are used, the commonly used include grinding wheels, hemp wheels, cloth wheels, nylon wheels, and wool wheels, etc. The polished round tube surface gives off a mirror effect, and the polishing quality is higher than other polishing processes.

The mirror finish is achieved by mechanically treating the surface with a series of gradually refined abrasive materials. At this stage, the deep scratches must be removed because any surface defects on the final product are very noticeable. After this, the final process involves polishing the surface for 5-10 minutes to form a mirror-like, highly reflective mirror surface.

How to get a mirror effect on a stainless-steel tube? Here we shall take a look!

SANDING
The primary purpose of grinding the welded parts of stainless steel is to remove the solder joints to reach a workpiece with a surface roughness of R10um and prepare to glowing surface.
Generally, there are three processes for grinding the parts: rough grinding, semi-finishing, and finishing, the details of whom are as follows:

  1. First, the workpiece (transferred from the previous step to the polishing process) is visually inspected to see the depth of the weld and find if there are any leaks in the weld, the depth of the weld is uneven, the deviation from the joint is too large, there is any local depression, the butt is uneven or if there is a deeper stroke in the surface. If any of the above defects are present, the articles with defects that cannot be repaired during the polishing process, such as spots, bumps, severe deformation, etc. should be returned to the previous process for repair. If there are no such defects, the polishing process should be continued.

 

  1. For rough sanding, use a 600 # abrasive belt to grind the workpiece back and forth on three sides. The goal of this process is to eliminate the welding points that have been left by the workpiece welding and other welding points that have occurred in the previous process to reach the weld angle. Basically, after the initial molding, no significant scratches or bulges remain on the horizontal and vertical planes. After this step, the roughness of the workpiece surface should reach R0.8mm. One must pay attention to the inclination angle of the belt machine and control the pressure of the belt machine on the workpiece during the polishing process. In general, it is more suitable to form a straight line with the surface tossed!

 

  1. In semi-precision sanding, 800 # sand belt is used to grind the three sides of the workpiece, mainly to correct the seams that might appear in the previous process, and to further finely grind the print marks produced after roughing. Grinding of the marks left in the previous process must be done repeatedly until there are no scratches on the surface of the workpiece, and it becomes bright. The surface roughness in this step should be R0.4mm. One should be careful not to create new scratches and abrasions during this process, as such defects cannot be repaired in subsequent processes.

 

  1. In fine sanding, a 1000 # abrasive belt is mainly used to correct the fine lines that appear in the previous step. The polishing method is the same as described above. The goal to be achieved in this process is that the connection between the ground and the unground parts of the workpiece mainly goes away, and the surface of the workpiece becomes brighter.

 

POLISHING
A high-speed motor is used to drive the hair wheel and is used in conjunction with wax to mimic previous polishing methods. The primary purpose of this step is to mirror polish the workpiece after the last level without further grinding. During the operation of this step, one should be careful not to wipe the polishing wax on the cover film on the surface of the workpiece. One must also take care not to damage the cover film.

The wool wheels available in the market are divided into thick wheels and fine wheels. The selection of the wool wheel is very important. By using the wool wheel with very rough wool, the sanding marks appear easily. In actual production, a thin wool wheel is generally used. During the grinding process, wax must be supplied continuously. Otherwise, there will be smoke from the wool wheel due to excessive temperature, which will cause severe wear to the wool wheel and damage to stainless steel.

 

In the last step of mirror polishing, clean cotton cloth is used to rub the surface of the workpiece after passing it from the previous steps to wipe it clean. The goal of this step is to make the surface of the tube free of welding marks and further polish the already waxed and polished tube to achieve a mirror effect.
The mirror finish on stainless steel enhances its appearance and consistency, making its cleaning easier. It also masks the after-effects of welding and hides surface damage, if any.
The benefit of the mirror finish is that it also improves corrosion resistance. Further, mirror finish eliminates crevices, where corrosive particles deposit themselves.

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