| 摘要 |
FIELD: metallurgy. ^ SUBSTANCE: steel consists in wt %: C: from 0.12 to 0.27, Si: from 0.05 to 0.40 and Mn: from 0.8 to 2.0, the rest is Fe and impurities of Ca, P and S. Contents of Ca are 0.001 % or less, P 0.02 or less and S: 0.01 or less. Steel additionally contains at least one element chosen from Cr: 1 % or less, Mo: 1 % or less, Ti: 0.04% or less, Nb: 0.04 % or less and V: 0.1 % or less. Maximal diametre of non-metallic inclusions present in at least in zone running from internal surface of steel tube to depth of 20 mcm is 20 mcm or less. ^ EFFECT: disclosed steel tube is not subjected to fatigue destruction and possesses increased fatigue life and high reliability due to high strength and high limit of internal pressure. ^ 2 cl, 2 tbl, 1 ex |
