Nippon Kokan Kabushiki Kaisha

Kobe Steel, Ltd.

Koshiro Tsukada

Makoto Yamada

Itaru Watanabe

Haruo Suzuki

Tomokazu Godai

Hiroaki Tsukamoto

Masatoshi Nakagaki

Isao Aida

Mutsuro Araki

Toshio Takano

Bunshiro Sakai

A method of manufacturing pressure vessel steel having high strength and high toughness comprising the steps of heating steel to a temperature higher than 1200.degree. C., said steel containing from 0.03 to 0.12 wt. % C, 0.10 to 0.8 wt. % Si, 0.45 to 1.00 wt. % Mn, 0.80 to 3.50 wt. % Cr, 0.10 to 1.60 wt. % Mo, 0.10 to 0.53 wt. % Ni, 0.010 to 0.040 wt. % soluble aluminum, at least one of 0.05 to 0.40 wt. % V and 0.02 to 0.20 wt. % Nb, less than 0.010 wt. % Ti, 0.0002 to 0.0010 wt. % B, and less than 0.004 wt. % N, the balance of iron and impurities, the N and Ti satisfying the following equation

Method of manufacturing pressure vessel steel with high strength and

A method of manufacturing a thick, high-strength steel pipe for low temperature service comprising the steps of forming into tubular shape a steel plate having a thickness of over 12 mm and a specific composition, of which the C.sub.eq value is adjusted to less than 0.50, when the Mn content is less than 1.0 % whereas the C.sub.eq value is adjusted to less than 0.45 when the Mn content is over 1.0 % and less than 2.0 %, and nextly of welding said tube form at high speeds and high efficiency by the process of single electrode or multiple electrode large-current gas-shielded arc welding with one pass per electrode on each side of the seam at a specific condition, each electrode preferably consisting of a solid wire essentially containing less than 0.3 % Ti with or without the addition of less than 0.01 % B, and said steel pipe having, in its as-welded condition, mechanical properties such that the yield point of the base metal portion is over 60,000 psi and the weld zone has a maximum hardness of less than Hv10-280 and a Charpy test absorbed energy of over 7 Kg.m at -10.degree. F. Even when the C.sub.eq value of said steel plate is less than 0.65, a thick, high-strength steel pipe for low temperature service having equal mechanical properties to the above mentioned pipe may be manufactured, after welding, by subjecting the welded pipe to a post heat treatment in which the welded pipe is held at a temperature between 500.degree. and 700.degree. C for less than 1 hour.

Method of manufacturing thick, high-strength steel pipe for low

Growing community of inventors

Fukuyama, Japan

Koshiro Tsukada