Stainless steel clad steel plate is a steel plate made of ordinary steel plate by exploding, rolling, surfacing, and other processes, and combining stainless steel and ordinary steel plate. It has the characteristics of two different steel types at the same time. Steel has the advantages of low price and good rigidity and is widely used in medical, petroleum, and chemical pressure vessels.
The influencing factors of intergranular corrosion of stainless steel are relatively complex. According to the intergranular corrosion mechanism, the main influencing factors include C and Cr content, stability elements, heating temperature, etc. According to the actual situation, representative factors are selected for analysis, and then appropriate materials are selected.
1. C content
C is a key element for the sensitization of stainless steel, and its content has a significant impact on intergranular corrosion. When the C content is more than 0.03 percent , the stainless steel is in a supersaturated state. The higher the C content, the faster the carbon atom precipitation rate, and the more chromium carbide is formed at the grain boundary, which leads to an accelerated corrosion rate and intergranular corrosion of the material. tend to increase.
2. Stability elements
Elements such as Ti have a stronger bonding ability with C than Cr and can form stable carbides after bonding, which can avoid the formation of Cr-depleted areas in austenite. These elements are called stabilizers.
3. Heating temperature
When the heating temperature is less than 450 degree or greater than 850 degree , 18-8 austenitic stainless steel will not produce intergranular corrosion. Because when the temperature is less than 450 degree , Cr23C6 will not be produced in the steel. When the temperature is greater than 850 degree , due to the enhanced diffusivity, the Cr element diffuses to the grain boundary and combines with C, so a Cr-depleted zone will not be formed at the grain boundary.
The cladding of the stainless steel clad steel plate should have good corrosion resistance, and the low-cost base layer should be able to meet the strength requirements of the equipment. Whether the stainless steel plate is heat treated is determined according to the use requirements of the equipment, and the characteristics of the medium should be fully considered in the design of equipment with intergranular corrosion tendency. For austenitic stainless steel clad steel plates, generally, hot working or heat treatment should be avoided within the sensitization temperature range. If it cannot be avoided, ultra-low carbon materials should be selected or stabilizing elements should be added.
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