Duplex stainless steel has the characteristics of austenitic and ferritic stainless steel, has good mechanical properties and corrosion resistance, and is mainly used in petroleum, chemical, construction, shipbuilding and other industries. Carbon is one of the most effective and economical elements to improve the strength of the alloy, but so far, there are few studies on the structure and properties of high-carbon duplex stainless steel. Therefore, taking high-carbon duplex stainless steel 20Cr25Ni11Mo3CuWV as the research object, after different solution and aging treatment, The change of precipitated phase in the steel structure and its effect on the hardness of the alloy. It provides an effective basis and guidance for the further research and application of these alloys in industrial production.

Dual-phase stainless steel was smelted by medium frequency induction furnace and cast into round ingot in sand mold. The ingot is forged into a 10mm thick plate, and then hot rolled into a 5mm thickness plate, and the sample of 50mm×50mm is taken on the plate for test. The solution temperature is 1050, 1150 and 1250℃ respectively, and the holding time is 20min. The morphology and composition of the phase were analyzed by JSM-6610LV scanning electron microscope and accompanying energy spectrometer. The phase analysis of the alloy samples was carried out by D/max-2500pc-X X-ray diffractometer, and the Cu target 2θ range was 25° ~ 95°. The Rockwell hardness of the sample was measured by HR-150D Rockwell hardness tester.

The results show that the residual particles of the two-phase stainless steel after solid solution treatment are chromium carbide, which can not be completely dissolved when the solid solution temperature reaches 1250℃. With the increase of solution temperature, the content of ferrite increases, and the hardness of alloy is the lowest at 1150℃ (25.8HRC). After solution treatment at 1150℃ and aging treatment at different temperatures, two peaks of hardness will appear, corresponding to 450℃ (38.1HRC) and 700℃ (52.9HRC) respectively. The former is due to the amplitude-modulated decomposition in the ferritic phase, which precipitates chromium-rich and iron-rich phases with a coherent relationship, while the latter is mainly due to the eutectoid transformation in the ferritic phase, which continuously and uniformly precipitates a large number of σ phases.