How to polish stainless steel sheet metal, before we understand this problem, let’s first understand why we need to polish stainless steel sheet metal?
One: There are two main reasons why stainless steel materials need to be polished:
The first reason is aesthetics. Using a stainless steel machine to polish stainless steel can improve the gloss of the stainless steel surface, which makes the metal texture of stainless steel stronger and gives people a favorite appearance. Compared with many metal products, stainless steel The metallic luster makes consumers feel more like it, and the metallic characteristics of stainless steel also make consumers more willing to choose. Reflected in life, there are mobile phone shells, stainless steel tableware, stainless steel doors and windows…
In addition to processing the luster shape of the stainless steel surface, in fact, stainless steel polishing has another purpose. The reason why stainless steel is not easy to rust is because this metal is an alloy and is a new type of metal that is made by fusion of multiple metals in proportion. The molecular structure of this metal is not active, so it is not easy to chemically react with the air, but it does not mean that stainless steel will not rust 100%, which depends on the method and location of use.
After using a stainless steel polishing machine to polish the stainless steel, a protective film will be formed on the surface of the stainless steel. This protective film can better isolate the chemical reaction of active molecules such as water and air, and can make the molecular structure of the stainless steel. It is firmer and does not easily undergo chemical reactions, so that the stainless steel characteristics can be better maintained. Therefore, the stainless steel must be polished to make the service life longer.
Two: several methods of polishing stainless steel sheet metal
1. Grinding before welding
Grinding range: 15-50mm on both sides of all welds.
Operation method: When grinding long welds, use an angle grinder or a straight shank grinder equipped with a stainless steel bowl brush to grind along the direction of the weld; for welds that require laser tracking and automatic welding, only a straight shank grinder can be used for grinding; When welding accessories on the surface of workpieces with relatively large welding accessories, use a thousand blades to polish the welding surface or polish and polish the products that require deburring before welding.
Technical requirements: polish the metallic luster, ensure that there is no oxide film in the welding area, the polishing pattern is parallel and uniform with the welding seam direction, and the polishing depth does not exceed 0.2mm.
2. Polishing of weld reinforcement
Grinding range: 25-50mm area on each side of the weld.
Operation method: When the angle grinder is working, it should be parallel to the surface to be polished, so that the welding seam’s residual height is removed; when the welding seam is recessed, the standard is not to damage the base material.
It is strictly forbidden to polish the surface with the inclined shovel at the end of the thousand blades.
Technical requirements: the polished surface must be smooth; the base material shall not be damaged, and the removal of the base material shall not exceed 0.2mm as the standard; the polished part of the surface
The surface texture requirements are consistent. Irregular grinding is strictly prohibited along the direction of the weld.
3. Remove surface scratches
Polishing range: Take a rectangular frame to cover the scratched area.
Operation method: Use a polishing tool to polish in a certain direction, not exceeding the rectangular frame.
Technical requirements: the polished surface must be smooth; the base material shall not be damaged, and the removal of the base material shall not exceed 0.2mm as the standard; the polished part of the surface
The surface texture requirements are consistent, the large parts and the oven body have the same horizontal drawing direction, and the small parts are in the same drawing direction; irregular grinding is strictly prohibited.
4. Grinding of machining allowance
Grinding range: 40-50mm on each side of the machining allowance.
Operation method: Grind along the direction of the vertical rib to be processed, and use an angle grinder in the space that the angle grinder can use; use a straight grinder for the space that can not be used by the angle grinder; the method and the grinding of the weld reinforcement same.
Technical requirements: the polished surface must be smooth; the base material should not be damaged, and the removal of the base material should not exceed 0.2mm as the standard; the surface texture of the polished part must be the same.
5. Use emery cloth wheel for polishing
Scope of polishing: polishing the edges and corners of small spaces such as wire holes or polishing some parts that require polishing.
Operation method: Use a straight grinder equipped with an emery cloth wheel to polish the edges and corners.
Technical requirements: The surface to be polished must be smooth, and the standard should be visually consistent with the drawing requirements, and no sharp edges or corners to the touch; no damage to the base material, and the removal of the base material should not exceed 0.2mm as the standard.
Three: Brightness grade after polishing of stainless steel Visual inspection method to grade the brightness of the surface of the polished parts:
Level 1: White oxide film on the surface, no brightness;
Level 2: Slightly bright, can’t see the outline;
Level 3: The brightness is good, and the outline can be seen;
Level 4: The surface is bright, and the outline can be seen clearly (equivalent to the surface quality of electrochemical polishing);
Level 5: Bright as a mirror.
Precautions for stainless steel polishing
Grinding with sandpaper or belt in the grinding operation is basically a polishing and cutting operation, leaving very fine lines on the surface of the steel plate. There have been troubles when using alumina as an abrasive, partly due to pressure issues. Any abrasive parts of the equipment, such as abrasive belts and grinding wheels, must not be used for 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 be tried on waste materials with the same composition first, so that the same products can be compared. To
Basic procedure of mechanical polishing
1. To obtain high-quality polishing effect,
2. The most important thing is to have high-quality polishing tools and auxiliary products such as whetstone, sandpaper and diamond lapping paste.
The choice of polishing procedure depends on the surface condition after pre-processing, such as machining, EDM, grinding and so on. The general process of mechanical polishing is as follows:
(1) Rough throwing
After milling, electric spark, grinding and other processes, the surface can be polished by a rotating surface polisher or an ultrasonic grinder with a speed of 35 000-40 000 rpm. The commonly used method is to remove the white electric spark layer by using wheels with a diameter of Φ 3mm and WA # 400. Then there is manual whetstone grinding, and the strips of whetstone are added with kerosene as a lubricant or coolant. The general order of use is #180 ~ #240 ~ #320 ~ #400 ~ #600 ~ #800 ~ #1000. Many mold manufacturers choose to start with #400 in order to save time.
(2) Semi-precision throwing
Semi-precision polishing mainly uses sandpaper and kerosene. The number of sandpaper is: #400 ~ #600~ #800 ~ #1000 ~ #1200 ~ #1500. In fact, #1500 sandpaper only uses die steel suitable for hardening (above 52HRC), not pre-hardened steel, because it may cause burns on the surface of pre-hardened steel parts.
(3) Fine throwing
Diamond polishing paste is mainly used for fine polishing. If the polishing cloth wheel is mixed with diamond abrasive powder or abrasive paste for grinding, the usual grinding order is 9 μ m (#1800) ~ 6 μ m (#3000) ~ 3 μ m (#8000 ). 9 μm diamond abrasive paste and polishing cloth wheel can be used to remove hair-like wear marks left by #1200 and #1500 sandpaper. Then use sticky felt and diamond paste for polishing, the order is 1 μ m (#14000) ~ 1/2 μ m (#60000) ~ 1/4 μ m (#100000). The polishing process with an accuracy requirement of 1 μm or more (including 1 μm) can be carried out in a clean polishing room in the mold processing workshop. For more precise polishing, an absolutely clean space is necessary. Dust, smoke, dandruff and saliva can all scrap the high-precision polished surface obtained after hours of work.