Al-containing austenitic stainless steel for supercritical fluid gas cooled reactor cladding and preparation method of Al-containing austenitic stainless steel

The invention discloses Al-containing type 20Cr25NiNb austenitic stainless steel for a supercritical fluid gas cooled reactor cladding and a preparation method of the Al-containing type 20Cr25NiNb austenitic stainless steel. The Al-containing type 20Cr25NiNb austenitic stainless steel comprises the following components in percentage by mass: 19-22% of Cr, 25-27% of Ni, 0.02-0.06% of C, 0.3-1.0% of Nb, 0.2-0.4% of Si, 1.8-2.5% of Mo, 2-4% of Al, less than or equal to 0.008% of P, less than or equal to 0.003% of O and the balance of Fe. Preferably, 0.005 to 0.008 percent of B and 0.16 to 0.27 percent of V are added; al is added to generate an aluminum oxide film between chromium oxide and a metal matrix, so that the corrosion resistance of stainless steel in a high-temperature supercritical fluid environment is improved; the mass percent of Ni is greater than that of Cr, so that an austenite FCC structure is obtained, and the creep resistance of the alloy in a high-temperature supercritical fluid is greatly imp