Visual method for brightness level of polished stainless steel:
Level 1: white oxide film on the surface, no brightness;
Level 2: Slightly bright, can not see the outline;
Level 3: Brightness is good and outline can be seen;
Level 4: The surface is bright, and the contour can be seen more clearly (equivalent to the surface quality of electrochemical polishing);
Level 5: Mirror-like bright.
Note for stainless steel polishing:
Grinding with sandpaper or belt during the grinding operation basically belongs to the polishing cutting operation, leaving very fine lines on the surface of the steel plate. I have had trouble using alumina as an abrasive, partly because of pressure problems. Any abrasive parts of the equipment, such as abrasive belts and wheels, must not be used on other non-stainless steel materials before use. Because this will contaminate the stainless steel surface. In order to ensure the consistency of surface processing, new grinding wheels or belts should first be tested on wastes of the same composition for comparison with samples.
Basic procedures for mechanical polishing:
In order to obtain a high-quality polishing effect, the most important thing is to have high-quality polishing tools and auxiliary products such as whetstone, sandpaper and diamond grinding, polishing paste and so on.
The choice of polishing program depends on the surface condition after the previous processing, such as machining, EDM, grinding and so on. The general process of mechanical polishing is as follows:
(1) Rough throw
After milling, EDM, grinding and other processes, the surface can be polished with a rotating surface polisher or an ultrasonic grinder at a speed of 35 000-40 000 rpm. A common method is to remove the white electric spark layer by using wheels with a diameter of 3mm and a diameter of WA # 400. This is followed by manual whetstone grinding, with strips of whetstone plus kerosene as a lubricant or coolant. The general usage order is # 180 ~ # 240 ~ # 320 ~ # 400 ~ # 600 ~ # 800 ~ # 1000. Many mold makers choose to start with # 400 to save time.
(2) Semi-fine polishing
Semi-precision polishing mainly uses sandpaper and kerosene. The number of the sandpaper is: # 400 ~ # 600 ~ # 800 ~ # 1000 ~ # 1200 ~ # 1500. In fact, # 1500 sandpaper is only suitable for hardened mold steel (above 52HRC), not for pre-hardened steel, because it may cause burns on the surface of pre-hardened steel.
(3) Fine polishing
Diamond polishing paste is mainly used for fine polishing. If you use a polishing cloth wheel to mix diamond abrasive powder or abrasive paste for grinding, the usual grinding sequence is 9 μm (# 1800) to 6 μm (# 3000) to 3 μm (# 8000). The 9 μm diamond abrasive paste and polishing cloth wheel can be used to remove hairline marks from # 1200 and # 1500 sandpaper. Followed by polishing with sticky felt and diamond abrasive paste, the order is 1 μm (# 14000) ~ 1/2 μm (# 60000) ~ 1/4 μm (# 100000). The polishing process with an accuracy of more than 1 μm (including 1 μm) can be performed in a clean polishing room in the mold processing workshop. For more precise polishing, an absolutely clean space is required. Dust, smoke, dandruff and drool are all possible high-precision polished surfaces that can be scrapped for hours.