Flux-Cored Wire Composition for Weld Metal Toughness

The patent applies parameter changes by strictly controlling the chemical composition parameters of the flux-cored wire, specifically limiting Nb content to 0.015% or less and V content to 0.021% or less. This parameter control transforms the rutile material to have minimal impurity content, thereby resolving the contradiction between maintaining good welding activity and achieving excellent low-temperature toughness after PWHT.

The patent applies local quality by creating a localized improvement in the rutile material quality. Instead of using conventional rutile with high impurity content, the patent specifies a particular grade of rutile with controlled Nb and V levels, thereby achieving both good welding performance and excellent post-PWHT toughness in the specific application context.

The patent applies parameter changes by optimizing multiple chemical composition parameters simultaneously. It specifies C content of 0.02-0.10%, Si of 0.10-1.00%, Mn of 1.00-3.00%, Ni of 0.10-3.00%, B of 0.002-0.015%, Mg of 0.10-0.80%, and controlled Nb of 0.015% or less and V of 0.021% or less. This multi-parameter optimization ensures both high strength and excellent low-temperature toughness after PWHT, avoiding the strength loss associated with using titanium oxide alone.

The patent applies composite materials by combining multiple alloying elements in specific proportions. The flux composition includes C, Si, Mn, Ni, B, Mg, and controlled amounts of Nb and V, creating a composite chemical system that provides both strength and toughness. This composite approach prevents the strength deterioration that occurs when using titanium oxide with very low impurity content alone.