| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength thick-walled electro-resistance-welded steel tube excelling in sour-proof property of an electro-resistance-welded part, causing no hydrogen-induced cracking to the electro-resistance-welded part in an HIC test of NACE regulations regardless of the presence/absence of Ti content. <P>SOLUTION: The individual equivalent circle diameters of oxides 1 in the electro-resistance-welded part are 20 μm or less, and the equivalent circle diameter of a cluster 2 which is a mass of a plurality of oxides 1 gathering at the nearest interval of 100 μm or less is 300 μm or less. A steel composition contains, by mass, 0.01-0.15% C, 0.005-0.9% Si, 0.2-1.3% Mn, at most 0.01% P, at most 0.01% S, and at most 0.1% Al with a remaining portion consisting of Fe and inevitable impurities. <P>COPYRIGHT: (C)2013,JPO&INPIT |
