Steel alloy for a low-alloy steel for producing high-strength seamless steel tubing
View Patent ↗The invention relates to a steel alloy for a low alloy steel for producing high-tensile, weldable, hot-rolled seamless steel tubing, in particular construction tubing. The chemical composition (in % by mass) is: 0.15-0.18% C; 0.20-0.40% Si; 1.40-1.60% Mn; max. 0.05% P; max. 0.01% S; >0.50-0.90% Cr; >0.50-0.80% Mo; >0.10-0.15% V; 0.60-1.00% W; 0.0130-0.0220% N; the remainder is made up of iron with production-related impurities; with the optional addition of one or more elements selected from Al, Ni, Nb, Ti, with the proviso that the relationship V/N has a value of between 4 and 12 and the Ni content of the steel is not more than 0.40%.
1. A steel alloy for a low-alloy steel for producing high-strength, weldable, hot-rolled seamless steel tubing, comprising in mass-%:
0.15-0.18% C,
0.20-0.40% Si,
1.40-1.60% Mn,
max. 0.05% P,
max. 0.01% S,
>0.50-0.90% Cr,
>0.50-0.80% Mo,
>0.10-0.15% V,
0.60-1.00% W,
0.0130-0.0220% N,
one or more elements selected from Al, Ni, Nb, and Ti with a concentration of max. 0.03% Al, max. 0.40% Ni, max. 0.04% Nb, and max, 0.04% Ti, remainder iron with melt-related impurities, wherein a total content of added Cr, Mo and W is at least 1.6%, a ratio V/N has a value of 4 to 12 and a nickel content of the steel is not more than 0.40%.
2. The steel alloy of the claim 1 , wherein W has a concentration of 0.7-0.9%.
3. The steel alloy of claim 1 wherein the steel alloy has a yield strength of more than 960 MPa.
4. A high-strength weldable seamless steel tubing produced by hot-rolling with subsequent hardening and tempering, comprising a steel having the following alloy composition in mass-%:
0.15-0.18% C,
0.20-0.40% Si,
1.40-1.60% Mn,
max. 0.05% P,
max. 0.01% S,
>0.50-0.90% Cr,
>0.50-0.80% Mo,
>0.10-0.15% V,
0.60-1.00% W,
0.0130-0.0220% N, with
4≦V/N≦12,
one or more elements selected from Al, Ni, Nb, and Ti, with a total content of added Cr, Mo and W of at least 1.6%, a nickel concentration of not more than 0.40%,
remainder iron with melt-related impurities.
5. The tubing of claim 4 , wherein the one or more elements have the following concentration:
max. 0.03% Al,
max. 0.40% Ni,
max. 0.04% Nb,
max. 0.04% Ti.
6. The steel alloy of the claim 4 , wherein W has a concentration of 0.7-0.9%.