1. Atmospheric corrosion resistance of ferrite wear-resistant plate
Because ferrite wear-resistant plates have good resistance to atmospheric corrosion, they have recently been used as roofs and curtain walls of buildings. However, the atmospheric environment in areas close to the sea is particularly harsh, especially the suspended particles in the air from seawater, which are quite corrosive substances. Therefore, high-chromium ferrite wear-resistant plates used in these environments have been developed. Wear-resistant plates that resist atmospheric corrosion contain high chromium and molybdenum, with small amounts of niobium and titanium added. This steel type actually contains 22% chromium and 1.2% molybdenum. Sufficient chromium and molybdenum are essential to improve the pitting corrosion resistance of the wear-resistant plate. As the number of cyclic corrosion test cycles increases, the rusted area of type 304 and 316 austenitic wear-resistant plates increases significantly. On the contrary, for ferrite wear-resistant plates such as type 444 and R&D steels, the rust area increases slightly during the first 600 test cycles, and after a longer test cycle, the rust area is in a saturated state. The research and development steel type (22Cr-1.2Mo-Nb, Ti) shows the characteristics of having the smallest rust area in any test cycle.
2. Intergranular corrosion resistance of ferrite wear-resistant plate
Type 410L or 409 wear-resistant plate is used as a material for automobile exhaust emission control systems due to its good corrosion resistance, formability and heat resistance. In recent years, the design temperature of automobile exhaust has increased. This is because the increase in automobile exhaust temperature can improve the conversion efficiency of the catalytic converter and reduce the emissions of harmful gases such as NOx, SOx and hydrocarbons (HC). However, an increase in temperature may lead to worse corrosion conditions for the material. For example, chromium carbide will produce deposits on the muffler at exhaust temperatures, that is, at temperatures of 400 to 500°C, it will lead to chromium depletion in the grain boundaries and intergranular corrosion. Since the weld area is particularly sensitive to intergranular corrosion, it is necessary to improve the corrosion resistance of ferrite wear-resistant plates containing 12% Cr. Another way to solve this problem is to develop new ferritic wear plates. One example is the addition of niobium to steel containing 12% Cr. These steels are widely used in automobile exhaust systems as intergranular corrosion-resistant materials, such as front ducts, center pipes and mufflers. It is well known that reducing the carbon and nitrogen content in steel is quite effective in preventing intergranular corrosion. In this way, adding niobium and titanium to steel can further improve its resistance to intergranular corrosion.
3. Formability of iron cable body wear-resistant plate
The uses of ferrite wear-resistant plates are so wide, and the properties of ferrite wear-resistant plates required for each use are different. However, the formability of ferritic wear-resistant plates is worse than austenitic wear-resistant plates such as 304 steel. Although the γ value of ferrite wear-resistant plate, that is, the deep drawability index, changes in a wide range of 1.0 to 2.0, the n value, that is, the ductility index is limited, about 0.2, which is 0.4 to 0.4 than that of austenitic wear-resistant plate. 0.65 low. For draw-formed products, it is difficult to replace austenitic wear-resistant plates with ferrite wear-resistant plates. If you want to replace them, you must change the design of the product and design it into a draw-formed shape.
4. Toughness of ferrite wear-resistant plate
Many studies have been conducted on the effects of titanium and niobium on pressure formability, with the focus mainly on the average γ value. The conclusion is that appropriate amounts of these elements can effectively improve pressure formability. However, excessive addition of these elements can also have harmful effects. For example, as the titanium and niobium content increases, the transformation temperature of longitudinal cracks also increases. Even if ferritic wear-resistant plates have good average γ values, the ductile-to-brittle transition temperature may cause damage to deep drawability. Since transformation temperature is one of the decisive factors for formability, deformation may be difficult to proceed at higher transformation temperatures.
