Instructions on how to identify stainless steel
|Instructions on how to identify stainless steel|
Instructions on how to identify stainless steel
Stainless steel, has qualities inherent only in this type of steel. It is possible to distinguish it from its "brethren" by subjecting it to some tests. This can be done by placing the steel in a saline solution. You can resort to more complex methods by using physical calculations.
To do this, you will need table salt and water.
Since, based on the name, "stainless steel" is resistant to rust, it is necessary to check it from this point of view. It is necessary to make a concentrated solution of table salt in water and place a stainless steel product in it. On the next day, you can evaluate the result. Stainless steel can be food grade and non-food grade. You can distinguish them using a spectrograph.
How to weld stainless steel:
Welding is a process of inseparable connection of parts by establishing interatomic bonds between them during heating or plastic deformation. As a rule, welding is used to connect various metals and their alloys. When welding stainless steel parts, it is necessary to take into account the differences in the physical properties of "stainless steel" from the properties of carbon steel. What are the ways of welding "stainless steel"? Stainless steel is distinguished from carbon rolled steel by its high resistivity, lower melting point and thermal conductivity, and a greater percentage of thermal expansion. There are several ways to weld stainless steel. With a material thickness of more than 1.5 mm, manual arc welding with a tungsten electrode in an inert gas is usually used. High productivity is achieved when welding thin sheets of stainless steel, as well as stainless pipes. But for welding sheets of "stainless steel" with a thickness of 0.8 – 1.5 mm, pulsed arc welding with a melting electrode in an inert gas is suitable, as well as arc welding with jet transfer of metal. Plasma welding is increasingly being used. For thick stainless metal, submerged arc welding is performed, and for thinner sheets, spot and roller welding is performed. After welding, subsequent processing of the welds is required. A porous oxide layer forms on the surface of the joint obtained by welding, which significantly weakens the resistance of the weld to corrosion. Various methods are used for the subsequent processing of welds. One of these methods of processing welds is considered etching. With proper application, etching can eliminate the harmful oxide layer, as well as the area with a reduced chromium content. Depending on the specific conditions, etching is performed by immersion, application to the surface or coating of products with paste. Most often, mixed acid is used in combination with water. The etching time of stainless steel depends on the concentration of acids, the thickness of the scale, the temperature regime and the grade of stainless steel. Another stage of processing when welding "stainless steel" is bringing the degree of roughness of the weld to the corresponding indicator of the base material. And this is achieved by grinding and polishing after etching. Such treatment usually enhances the resistance of the structure to corrosion.
Stainless steel is one of the most popular among all types of steel. The advantages of stainless steel are high corrosion resistance, smoothness of the surface, hygiene, durability, manufacturability, practicality. To weld stainless steel, you will need certain qualifications for working with welding machines in order for this process to take place quickly, efficiently and without harm to anyone. Weld stainless steel using a welding machine and a rectifier, but not a simple one, but a rectifier with a choke. The usual one will not work absolutely, because with it the process will be more difficult and turn into a continuous torment, so spare your nerves and take what you need. Also, special electrodes, preferably of good quality, will be needed for welding stainless steel, otherwise the whole process will be spoiled. These may also be black electrodes, but in this case, problems with seams may arise. It is better to cook stainless steel with argon. If you don't have the equipment for this option, then proceed to step 2. Perform welding in a heated state at a temperature of approximately 2000 ° C, carefully making sure that the heating of stainless steel during welding is minimal. If we compare, then a more acceptable result is obtained with electric arc welding than with gas welding. After the work done, heat the joint to 7200-7800 ° C and then cool it very quickly. If you don't have the equipment for this option, then go to step 3. Step 3. Cook stainless steel at high speed and very fast cooling, which can most often be done by using cooling or copper linings and linings for the weld. Previously, the product should be subjected to "hardening" 1050-1150 ° C followed by instant cooling. If you do not have the equipment for this option, then proceed to step 4. Preheat the stainless steel before welding to 2500-3500 ° C. This will avoid the appearance of cracks and rupture of welded joints. Use austenitic steel as electrodes, thanks to which a viscous weld is formed. The main thing is to do everything carefully, calmly and evenly, and then the probability of errors and failures during welding will be minimal.
A smooth mirror surface of a stainless pipe or sheet can be obtained not only in the factory, it is quite possible to polish stainless steel at home. This process is necessary to give a spectacular look to homemade work, to clean welding seams or to neutralize scratches on the surface.
To do this, you will need:
• - angle grinder (grinder);
•- grinding wheels of various grain sizes;
•- sandpaper or stone;
•- felt or felt circles;
•- polishing paste.
First, it is necessary to perform a rough cleaning of the surface, remove metal deposits from the welds. To do this, use a fiber-based circle. If the surface is smooth enough, skip this step. In order to remove the risks from the grain, take a felt or felt circle and evenly apply carpentry glue on it. Then carefully walk it over the abrasive crumbs. Abrasive crumbs can be obtained from sandpaper or stone by rubbing them against each other. Sand the stainless steel surface several more times, each time reducing the size of the abrasive by half. Do not forget to wash the stainless steel surface after each grinding. Check, the surface after grinding should be completely smooth. Make sure that all rough roughness is eliminated, otherwise after polishing these areas will have to be sanded again. Take a clean felt or felt circle and a polishing paste. It is important to choose the right polishing paste, because different types of paste are suitable for different brands of stainless steel. Try to find a diamond paste, the grain of which corresponds to your metal, in extreme cases, a regular polishing paste or GOI will do. Start the finishing polishing of stainless steel, consistently removing visible risks. Gradually, after a while, you will see that the surface becomes smoother and smoother, this is due to the fact that under the influence of high temperature, the surface of the part melts and spreads. Try not to overheat the part, some metals may change color from this.