Factors to be considered in the selection of the h

Factors to be considered in the selection of stainless steel

when selecting stainless steel in a corrosive environment, in addition to a detailed understanding of the specific service conditions of stainless steel, the main factors to be considered include: corrosion resistance, strength, toughness and physical properties of stainless steel, processing, formability, resources, price and difficulty in obtaining

corrosion resistance corrosion resistance includes rust resistance and resistance to acid, alkali, salt and other corrosive media, as well as oxidation resistance, vulcanization, chlorination, fluorination and other properties at high temperature. Since different stainless steels are mainly selected to solve various corrosion problems encountered in practical projects, how to resist corrosion of stainless steel in corrosive environment is the first thing that material selection personnel need to consider. Corrosion is the damage caused by chemical or electrochemical action between metal and medium, and corrosion resistance refers to the ability of stainless steel to resist the corrosion damage of medium. Therefore, when corrosion resistance is involved in material selection, the following points should be paid attention to

1. The standard of corrosion resistance is artificially determined. We should recognize it, use it, and not be bound by it. We should determine the specific standard of corrosion resistance according to the specific use requirements. At present, the corrosion resistance of stainless steel mostly adopts grade 10 standard. Which grade should be selected as the corrosion resistance requirements, we should consider the characteristics of the equipment, and the characteristics (thickness, size) that bulotai adhesive can be processed as a single component system. Requirements for service life, product quality (such as impurities, color, purity), etc. Generally speaking, level 1-3 standards can be selected for equipment, instruments and components that require bright and clean mirrors or precise dimensions in the process of use; For the equipment that requires close cooperation, long-term non leakage or long-term use limit, the components are selected as grade 2-5. For the equipment that does not require high maintenance convenience or does not require long service life, the components can be selected as grade 4-7. Except for special exceptions, stainless steel with an annual corrosion rate of more than 1mm under service conditions is generally not selected. It should be pointed out that the grade 10 standard is not applicable to local corrosion

2 the research team is actively designing and developing a 5kW level high-power aluminum air battery system for backup power supply of communication base stations and range extenders of electric vehicles. Corrosion resistance is relative and conditional. It is often said that stainless steel has rust resistance. Corrosion resistance refers to that under certain conditions (medium, concentration, temperature, impurities, pressure, flow rate, etc.). Up to now, there is no stainless steel in any corrosive environment. The stainless steel GB, ISO and ASTM Test Specifications for corrosion resistance can be arbitrarily selected and set. Therefore, the material selection personnel must choose according to the specific use conditions. After the stainless steel brand is selected, the use department should also use it correctly according to the characteristics of the selected stainless steel, That is, reasonable material selection and correct use can achieve the purpose of rust resistance or corrosion resistance

3. when selecting stainless steel, we should consider not only its general corrosion resistance, but also its local corrosion resistance. In some aqueous media and chemical media, the latter should be paid more attention to, because the material selection personnel generally pay more attention to it, which will also provide inexhaustible development power for the extruder industry. The general corrosion resistance of stainless steel, while under service conditions, they have local corrosion, For example, the sensitivity of stress corrosion and pitting corrosion is less considered; Local corrosion of stainless steel often occurs in corrosive environments with good general corrosion resistance. Local corrosion often leads to sudden damage of stainless steel equipment and components, and its harm 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, which are often quite different from the actual medium environment. In order to obtain the corrosion resistance data closer to the actual service conditions, the corrosion test of the actual medium or the coupon test under the field conditions should be carried out in the laboratory, and the test of the simulation device should be carried out when necessary

under some service conditions, this situation will also be encountered. When the working medium or the industrial products produced, even if there is a trace of some or some metal ions in this stainless steel, it will affect the quality of industrial products in the chemical process (including gloss, color, purity, etc.). This situation is most common in nuclear fuel pharmaceutical and pigment industries. At this time, stainless steel without certain elements is often selected or the corrosion resistance grade of the selected stainless steel is appropriately improved, so as to reduce the metal ions to the allowable limit

5. If the components of stainless steel equipment fail due to corrosion, the causes of corrosion damage should be analyzed, and measures should be taken after finding out the causes, rather than throwing them away. (end)