There are several modes of processing stainless steel, which help not only to improve its quality characteristics, but also significantly improve its appearance. In addition, the processing of such a metal surface allows you to bring operational performance to the desired performance.
Grinding material
Thanks to various methods of processing stainless steel, it is often used not only for the manufacture of parts or structural elements, but also for decoration. In order to improve the appearance, as well as achieve the required level of surface roughness, a method such as grinding and polishing is used. Quite often, these two methods are combined into one, and it is called saturation. This processing method received its name due to the fact that the surface of such steel after completion of work begins to resemble satin or satin fabric.
Processing of stainless steel welds, for example, begins with the fact that it is necessary to bring the surface to small marks. For this, a grinder with a circle of a petal type is used.
Why grinding
In addition to grinding stainless steel to improve the appearance of the metal, it can also help eliminate surface defects. If you cannot completely eliminate them, then using this method you can make them almost invisible. As for the methods of execution, the operation can be performed both manually and with the help of special equipment that works from an electric or pneumatic drive. There are several most common devices that are used to implement this method of processing stainless steel:
- tape pneumatic file;
- drum-belt grinding machine;
- other devices that may use sanding belt.
As for the implementation of such an operation at home, the manual method is most often used here. For this, usually use either sanding sheets, or devices, which are called grinding. In industrial enterprises, saturation, of course, is carried out using a variety of special equipment.
It is worth adding that the processing of stainless steel seams, sheets and other things begins with the use of a grinding wheel with a grain size of 180. After that, you must still use two wheels - 320 and 600. To complete the work, you must also process the alloy with a felt wheel.
Manual processing
In the event that the processing of the stainless steel after welding is carried out manually, it is necessary to adhere to the following sequence of work:
- Since the surface was previously welded, it is first necessary to remove the burns.
- The surface of the stainless alloy, which will be the first to undergo such processing, must be separated by aluminum tape. It is laid in 2 or 3 layers.
- The part that is not sealed with such a tape should be processed using reciprocating movements. However, it must be remembered that it is not necessary to put too much pressure on the polish.
- After the required surface quality is achieved, the aluminum tape is glued to the area that was previously processed, and the freed coating is ground.
Grinding on machines
It is worth noting that it is possible to perform stainless steel turning. That is, grinding can be performed on turning equipment. In this case, special grinding wheels are installed on such devices. It is also worth noting that this operation can be performed on the machine both in production and at home, if such an assembly is available. It is important to note here that even the simplest turning equipment will allow such an operation to be performed efficiently.
As for the operation in manual mode, it is not always advisable to use polishing, and therefore sanding sheets are sometimes used. In this case, it is very important to select them correctly according to grain size. In order not to be mistaken, they usually use draft parts for selection.
Description of etching
Another effective method of machining stainless steel after welding is pickling. This technological operation will help to cope with surface defects that arise just because of welding, due to heat treatment of the alloy, due to metal processing by plastic deformation. Another advantage of using the etching method as a treatment is the ability to get rid of the discoloration color on the surface of the material. Also, this procedure will update the passive protective coating layer, which protects the stainless steel from the adverse effects of elevated temperatures.
Operation
To carry out the operation on an industrial scale, acid for processing stainless steel or molten alkaline media is used. In the event that the acid medium is used for etching, the process proceeds in two successive stages. At the first stage, the alloy is treated with a sulfuric acid solution, at the second stage, a solution is used, the basis of which is nitric acid.
In the event that alkaline acid is used for pickling, the steel is placed in a solution of caustic soda. This solution is able to completely remove the oxide film from the metal surface without damaging its structure.
As for the implementation of such an operation at home, the use of acid or alkaline agents is excluded. For this, special etching pastes were invented. Their feature is that they have a jelly-like consistency. It is necessary to use such pastes with extreme caution, since in addition to nitric and hydrofluoric acid, the composition also includes hydrochloric acid and chloride, and these substances pose a threat to human health.
Paste application
It is possible to apply etching paste only on that surface which was previously well cleaned, and also fat-free. To achieve the desired effect, you just need to rinse the part with warm water, and then rinse with any detergent. After applying the paste, you must leave it on the surface of the metal. The exposure time is from 10 to 60 minutes. After the desired time, the paste is washed off with ordinary running water. To apply this composition, you will have to use either an acid-resistant brush or a special plastic spatula. It is worth adding that if the area of the metal is large enough, then for the application you can use the etching spray, which is sprayed using equipment for spraying. To date, there are several manufacturers of pickling pastes that are best known. These companies include SAROX TS-K 2000, Avesta BlueOne and Stain Clean (ESAB).
Several other processing methods
There are several other processing methods that are used less frequently, but are still sometimes used. One such method is chromium plating. The use of this processing mode allows you to achieve such qualities as:
- improved appearance;
- increased resistance to mechanical stress;
- a strong increase in corrosion resistance.
The disadvantage of this method is that it can only be performed under production conditions. The operation is quite complicated, and therefore requires a qualified specialist to carry it out. In addition, special consumables are needed. For these reasons, performing chromium plating at home will not work.
However, in home workshops, you can successfully perform another operation, which is called bluing. It will help give the surface an attractive appearance. This procedure can be performed in three different ways. The first method is the use of acid solutions, the second method is accompanied by the use of alkali, the last option is the use of heat.
Turning Application
Turning stainless steel is also currently possible. However, there are several problems. Parameters such as tensile strength and hardness are almost the same for stainless steel and carbon steel. However, there is a big difference in the microstructure of the material, and therefore some problems arise.
For example, if the method of cutting stainless steel is used, then it will first elastically deform, after which it is easy to process, and then the hardening stage begins. At this stage, cutting metal will only work if much more effort is applied. The difference lies in the fact that high-alloy steel, like stainless steel, undergoes all these stages much more noticeably than ordinary. There are several main problems that stand out with this processing method.
The first problem is significant strain hardening. The second problem is the need to remove chips. The third problem is the wear of the working tool. There is another problem that stands out quite strongly among heat-resistant grades of stainless alloys. The problem is the high viscosity coefficient. Because of this, the chips do not crumble, but are constantly twisted into a long spiral.
Cutting tools
Due to the fact that steel is capable of strong self-hardening, it is necessary to develop special types of edges for the cutting tool. In addition, special alloys must be used to make such special tools. Today there are two types of special tools.
The first type is a cutting device that has a chemically deposited coating. The second type has a physically deposited coating on the cutting edge of the alloy cutting tool.