Nippon Steel Corporation

Hideto Kawano

Tatsuo Yokoi

Osamu Yoshida

Kensuke Nagai

Shinya Sakamoto

Takaaki Fukushi

Tetsuo Ishitsuka

Shunichi Kobayashi

Takashi Tsusue

Shuji Iwamoto

Toshiyuki Ogata

Kenzo Tashima

An as-rolled type K55 electric resistance welded oil well pipe includes, in terms of % by mass, 0.30 to 0.50% of C, 0.05 to 0.40% of Si, 0.50 to 1.20% of Mn, 0 to 0.030% of P, 0 to 0.020% of S, 0.002 to 0.080% of Al, 0 to 0.0080% of N, 0 to 0.30% of Cu, 0 to 0.30% of Ni, 0 to 0.30% of Cr, 0 to 0.10% of Mo, 0 to 0.10% of V, 0 to 0.050% of Nb, 0 to 0.030% of Ti, 0 to 0.0100% of Ca, and the balance being Fe and impurities. In the pipe, a metallographic structure at a position of &#xbc; of a pipe thickness in an L cross-section at a base metal 90&#xb0; position is a ferrite-pearlite structure in which prior &#x3b3;-grains are flattened, includes grain boundary ferrite and intragranular ferrite, and has a rate of a total area of the grain boundary ferrite and the intragranular ferrite, of 10 to 30%.

As-rolled type K55 electric resistance welded oil well pipe and hot-rolled steel sheet

Electric resistance welded steel pipe securing the high strength and high toughness demanded from oil well pipe in recent years. The metal structure in a region having a width of 0.5 mm in both the thickness directions from a reference point, when using a point defined as a point &#xbc; of the thickness in the thickness direction from the surface in the base material part of the steel as the reference point, consists of polygonal ferrite: 10 area % or less and a balance: bainitic ferrite. The thickness is 15 mm or more.

High strength electric resistance welded steel pipe and method for producing high strength electric resistance welded steel pipe

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Tokyo, Japan

Hideto Kawano