Development and application of wear-resistant plate for seawater desalination plant
1. Wear plate for seawater desalination device
The metal materials used in a multistage flash desalination device that can efficiently desalinate seawater in large quantities are shown in Table 1. According to the salt concentration and temperature conditions of seawater desalination process, the wear-resistant plates with different corrosion resistance are combined. In the Austenitic system wear plate, 316L with high pitting resistance is used, and in the parts with high salt concentration and serious corrosion environment, biphase wear plate is used. The characteristics of the dual-phase wear-resistant plate are that, from the point of view of metal composition, its resistance to stress corrosion cracks caused by chloride ions is stronger than that of the Austenitic system wear-resistant plate, but its corrosion resistance varies with the addition amount of effective corrosion resistant alloys such as Ni and Mo. Compared with the dual-phase wear-resistant plate standard ASTMS31803(22%Cr-5%Ni-3%Mo), the steel grade such as S32101(21%Cr-1.5%Ni-N) with fewer alloying elements is called low-alloy dual-phase steel.
2. Development and characteristics of wear-resistant plate
The advent of low alloy biphase steel with minimal addition of precious metals such as Ni and Mo has further expanded the application range of biphase wear-resistant plates. Low alloy duplex steel has three advantages: (1) The corrosion resistance is the same as that of ordinary Austenitic wear-resistant plates used in medium salt environment; ② The alloy cost is low, the price change is small; (3) The yield strength is about twice that of the same Austenitic steel, so the low-alloy biphase steel can be expanded as an economic biphase steel to replace the ordinary Austenitic wear-resistant plate. However, in the past, the low alloy duplex steel represented by S32101 has the problem of poor corrosion resistance and toughness during high line energy welding, so it is difficult to apply the submerged arc welding method to the efficient welding of structural parts. The main chemical composition of the wear-resistant plate is 21%Cr-2%Ni-N, which solves the welding problem by balancing the composition ratio, and can be applied to large-line energy welding.
According to the comparison of corrosion resistance of wear-resistant steel plate, other biphase steel and Austenitic system steel in artificial seawater CCT test, the wear-resistant plate has the same pitting resistance as TY304. In addition, in terms of stress corrosion cracking resistance, due to the mixed structure and high strength of dual-phase steel, its stress corrosion cracking resistance is better than TY304.
3, the application of seawater desalination equipment
According to the characteristics of the wear-resistant plate, its properties as a material for desalination plants were evaluated, and the result was that it could be used in the largest desalination plant in Qatar. A total of 3200t dual-phase wear-resistant plate is used in the desalination device, of which 700t is wear-resistant plate. Because it can greatly improve welding operability, it can replace S32101. In the future, wear-resistant plates can be expanded to large-scale desalination plants in the Middle East.
4. Applications in other industries
Wear-resistant plates have begun to be widely used in other industries. The Japanese shipbuilding industry has used a large number of wear-resistant plates in the manufacture of offshore tankers, replacing TY304 and coated carbon steel plates, which not only ensures corrosion resistance, but also has good processability and weldability, and can also simplify maintenance in navigation. In the future, wear-resistant plates can be expanded to ocean-going oil tankers. In addition, wear-resistant plates can also be used in reservoir gates and water treatment equipment. Due to the Great East Japan earthquake and tsunami, the infrastructure of the northeast coast of Japan has been seriously damaged, and many floodgates and water treatment equipment need to be maintained and rebuilt in the medium and long term.
Nippon Steel has applied for technical registration of high-strength low-alloy dual-phase steel to the New Technology Intelligence Agency of the Japanese Ministry of Land, Infrastructure and Transport to accelerate its application in the construction of public infrastructure projects such as gates, reservoirs and dike facilities with new technologies.
5. Summary
Since the wear-resistant plate has the same advantages of corrosion resistance and high strength as TY304 in a low-carbon environment, it is estimated that it can not only be applied to energy equipment in the future, but also can be widely used in other industries. In the construction industry, wear-resistant plates have the advantages of lightweight and maintenance-free, so it can replace the structural parts and accessories that used to use galvanized steel. Because the elastic-plastic properties corresponding to tensile stress are closer to carbon steel than ordinary austenite, it can be expanded as a structural part in the future. Recently, wear-resistant plates have been used instead of galvanized steel for large solar brackets. In addition to the characteristics of maintenance-free wear plate, it also has the advantages of lightweight and cost reduction, which is the biggest reason for its adoption.
