A method for preparing super duplex stainless steel valves for offshore platforms by controlled precipitation

Abstract

The invention discloses a method for preparing a super duplex stainless steel valve for an ocean platform through a controlled precipitation method. The method comprises the steps that the super duplex stainless steel valve is prepared from the following chemical components, by percentage content: less than or equal to 0.03% of C, 0.5-0.8% of Si, 26-28% of Cr, 1.0-1.5% of Mn, 7-8% of Ni, 3.5-4.0%of Mo, 0.4-0.6% of N, 0.8-1.5% of Al, 0.025-0.035% of Nb, and the balance Fe; and smelting and casting are carried out, specifically, after a cast ingot is completely solidified and cooled, and a riser is removed, the cast ingot is heated to 1160-1200 DEG C, heat preservation is carried out for 1-2 hours, a vacuum pressurized gas quenching technology is adopted, and the proportion of precipitatedphases is controlled through a controlled cooling technology. According to the method, the proportion is scientific, the process is reasonable, under the condition that the proportion of the two phases of austenite and ferrite are guaranteed to be accurately controlled, through the chemical components, the austenitizing temperature, controlled cooling and other precipitation kinetic principles, the vacuum pressurized nitrogen gas quenching method and the staged controlled cooling technology are adopted, so that the proportion of the precipitated phases is controlled within 0.5%, and thereforethe mechanical property can be improved, and meanwhile, through the balance control over the proportion of the two phases in steel, the steel can have high pitting corrosion resistance and crevice corrosion resistance.

Description

Technical field [0001] The invention relates to a method for preparing a super duplex stainless steel valve for an ocean platform by a controlled precipitation method. Background technique [0002] In recent years, my country has established many seawater desalination devices, looking for water resources from seawater, and achieved good results. Among the seawater desalination projects that have been completed in my country, nearly 80% of the installed capacity is constructed by introducing foreign technologies. Reverse osmosis membranes, energy recovery and high-pressure pumps are listed as the three major technologies in the reverse osmosis desalination system. Most of its core technologies and patents are mastered by the United States, Germany, Japan and other countries, especially large-tonnage desalination energy recovery devices and high-pressure valves are completely dependent on imports, resulting in high desalination costs. [0003] In seawater desalination projects, valv...

AI Technical Summary

Problems solved by technology

This patent adopts solution and quenching treatment, and the solution treatment time is 6-8 hours. This method reduces the content of precious element nickel in duplex stainless steel, increases the content of chromium and other elements, and increases the B, Te and Nb elements make stainless steel products still have excellent resistance to stress corrosion cracking and pitting corrosion under the influence of aging heat treatment, and the corrosion resistance is improved, but it is not ideal, especially for large seawater desalination equipment Valves, etc. are in harsh corrosive environments, and have high requirements for pitting corrosion resistance and crevice corrosion performance

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