When selecting stainless steel in a corrosive environment, in addition to a detailed understanding of the specific conditions for the use of stainless steel,steel bar factory the main factors to be considered are: corrosion resistance, strength, toughness and physical properties of stainless steel, processing, Formability, resources, price and difficulty.
1. The standard of corrosion resistance is artificially determined. It must be recognized, used, and not subject to it. It is necessary to determine the specific standard of corrosion resistance according to the specific use requirements.
For the corrosion resistance of stainless steel, the level 10 standard is adopted. Which one is selected as the corrosion resistance requirement, the equipment, the characteristics of the part (thin thickness, size) should be considered. The service life is long, the product quality (such as impurities, color) Requirements for purity, etc., generally speaking, for equipment instruments and components that require smooth mirrors or precise dimensions during use, you can choose Class 1~3 standards; closely match requirements, long-term leak-free or require long-term equipment The parts are selected from 2 to 5 grades. For equipments that are not required for high maintenance or require a long service life, the components can be used in grades 4-7. With special exceptions, the annual corrosion rate of stainless steel under the conditions of use is more than 1 mm. More than not to use, it is necessary to point out that the 10th level standard is not applicable for local corrosion.
2. Corrosion resistance is relative, conditional, often said stainless steel rust, corrosion resistance refers to relative to rust and non-corrosion, refers to under certain conditions (medium, Concentration, temperature, impurities, pressure, flow rate, etc.). Up to now, there is no stainless steel with corrosion resistance and corrosion resistance in any corrosive environment. Therefore, the selection of materials must be selected according to the specific conditions of use. After the stainless steel grade is selected, the use department should also use it correctly for the characteristics of the selected stainless steel, that is, the rational selection and correct use can achieve the purpose of stainless or corrosion resistance.
3. The choice of stainless steel should consider its resistance to general corrosion and its resistance to local corrosion. In some aqueous media and chemical media, the latter needs more attention. This is because the selection of materials is generally more Pay attention to the general corrosion resistance of stainless steel, and under the conditions of use, they are less sensitive to local corrosion, such as stress corrosion pitting corrosion; local corrosion of stainless steel is mostly resistant to general corrosion. Occurred in a good corrosive environment, local corrosion often leads to the sudden destruction of stainless steel equipment and components, and its harmfulness is far greater than general corrosion.
4. When applying the corrosion resistance data of stainless steel in various manuals, it should be noted that many of the data are only the test results in some experiments, and often have a large difference with the actual media environment, in order to obtain closer to the actual use conditions. Corrosion resistance data, generally should be carried out in the laboratory in the actual medium corrosion test or on-site conditions of the coupon test, if necessary, the simulation device test.
Under some conditions of use, this is also the case. In the working medium or industrial products produced, even if it contains a trace amount of metal ions in some or some of the stainless steel, it will affect the chemical process. The quality of industrial products (including gloss, color, purity, etc.). This situation is most common in industries such as nuclear fuel pharmaceuticals and pigments. In this case, stainless steel containing no element is often used or the selected stainless steel is appropriately selected. Corrosion resistance grade to reduce metal ions to the allowable limit.
Stainless steel equipment, if the parts fail due to corrosion, the analysis of the causes of corrosion damage should be carried out, and the measures should be taken after the cause is identified, and should not be thrown away. It is recommended that the purchase of stainless iron products should be reputable. Manufacturer’s products, do not be cheap, beware of being fooled.