LOW ALLOY HEAT-RESISTANT STEEL AND STEEL PIPE

To provide a low alloy heat-resistant steel which contains W and B, in which material cost is reduced, and which has a high tensile strength and toughness, as well as a steel pipe formed therefrom.SOLUTION: There is provided a low alloy heat-resistant steel comprising, predetermined chemical components, with the balance consisting of Fe and impurities, in which a total amount of Ni, Co and Cu satisfies the following expression (1), and an amount of W, analyzed as an electrolytic extraction residue, satisfies the following expression (2): 0.03≤[%Ni]+[%Co]+[%Cu]≤0.80...(1), -10×[%B]+0.07≤[%W]ER≤10×[%B]+0.18...(2), wherein in expressions (1) and (2), [%Ni], [%Co], [%Cu] and [%B] represent amounts of Ni, Co, Cu and B, in % by mass, contained in the steel, respectively; and [%W]ER represents an amount of W, analyzed as the electrolytic extraction residue, in % by mass. There is also provided a steel pipe formed from the above-described low alloy heat-resistant steel.SELECTED DRAWING: None 【課題】Ｗ及びＢを含有すると共に材料コストを抑制し、高い引張強さと靭性を有する低合金耐熱鋼及び鋼管を提供する。【解決手段】所定の化学成分を有し、Ｎｉ、Ｃｏ及びＣｕの合計量が（１）式を満足し、かつ電解抽出残渣として分析されるＷ量が（２）式を満たし、残部がＦｅ及び不純物からなる低合金耐熱鋼及び該低合金耐熱鋼により成形された鋼管。０．０３≦［％Ｎｉ］＋［％Ｃｏ］＋［％Ｃｕ］≦０．８０ （１）−１０×［％Ｂ］＋０．０７≦［％Ｗ］ＥＲ≦１０×［％Ｂ］＋０．１８ （２）式中、［％Ｎｉ］、［％Ｃｏ］、［％Ｃｕ］、及び［％Ｂ］は、それぞれ鋼に含まれるＮｉ、Ｃｏ、Ｃｕ、及びＢの質量％を意味し、［％Ｗ］ＥＲは、電解抽出残渣として分析されるＷの質量％を意味する。【選択図】なし