Flux-cored welding strip and welding flux used in combination for submerged arc welding of duplex stainless steel, and preparation methods and use thereof

A flux-cored welding strip and a welding flux used in combination for submerged arc welding of a duplex stainless steel, wherein

• the flux-cored welding strip is composed of a stainless steel shell and a flux core powder, the flux core powder consisting of the following components:
• in percentages by mass, ferrochrome nitride:
• 0.70% to 1.0%, a chromium powder:
• 26% to 27%, a nickel powder:
• 4.5% to 5.5%, a molybdenum powder:
• 3.7% to 4.2%, a manganese powder:
• 2.55% to 2.65%, a copper powder:
• 1.45% to 1.55%, a ferrosilicon powder:
• 1.1% to 1.2%, a tungsten powder:
• 1.0% to 1.15%, a niobium powder:
• 0.25% to 0.35%, an aluminum powder:
• 0.35% to 0.55%, a rhenium powder:
• 0.35% to 0.40%, a lanthanum powder:
• 0.1% to 0.15%, and a balance being an iron powder;
• and
• the welding flux consists of the following components:
• in percentages by mass, bauxite:
• 20% to 25%, a clay:
• 5% to 10%, a zircon sand:
• 10% to 15%, a magnesite clinker:
• 10% to 15%, fluorite:
• 25% to 30%, an alloying agent:
• 1.5% to 2%, and a balance being chromium oxide green.