Seamless steel pipe for line pipe plus a approach for its manufacture

The environment of use with the illustrated risers and stream line is severe, and it is mentioned to reach a temperature of 177?? C. and an inside strain of 1400 atmospheres. Thus, metal pipes employed for risers and movement lines ought to be in a position towithstand this kind of a serious atmosphere of use. Moreover, a riser is subjected to bending tension on account of waves, so it should also be capable to stand up to such exterior influences.

Accordingly, metal pipes having a higher energy and high toughness are wanted for risers and circulation lines. Moreover, to be able to make sure higher reliability, seamless steel pipes are used as an alternative to welded steel pipes. For welded steel pipes,tactics for production metal pipes obtaining a strength exceeding X80 quality have currently been unveiled. For example, Patent Document one (JP H09-41074 A1) discloses a metal which exceeds X100 quality (a yield energy of no less than 689 MPa) specified inAPI standards. A welded metal pipe is formed by 1st manufacturing a steel plate, forming the metal plate into a tubular form, and welding it to kind a steel pipe. As a way to impart crucial attributes for example energy and toughness whenmanufacturing a metal plate, the microstructure is controlled by making use of thermomechanical heat treatment for the metal plate during rolling thereof. Patent Document one also carries out thermomechanical heat therapy, whenever a steel plate is becoming hotrolled, this kind of that its microstructure is controlled so as to contain strain-induced ferrite, therefore attain the attributes of the steel pipe right after welding. Thus, the technique disclosed in Patent Document 1 can only be realized by a rollingprocess to get a steel plate to which thermomechanical warmth treatment can effortlessly be used by controlled rolling. Therefore, this method may be utilized to some welded steel pipe but not to a seamless steel pipe.

Assuming that seamless metal pipes are involved, in recent times, seamless metal pipes of X80 grade have been developed. It really is tough to use to seamless metal pipes the above-described approach utilizing thermomechanical warmth therapy whichwas created for welded metal pipes, so basically it can be necessary to acquire preferred homes by heat therapy immediately after pipe development. A method for producing a seamless steel pipe of X80 grade (a generate power of no less than 551 MPa) is disclosedin Patent Document two (JP 2001-288532 A1), for example. However, as unveiled within the examples of Patent Document two, the technique in that document is validated only having a thin-walled seamless metal pipe (wall thickness of 11.1 mm) which basically hasgood hardenability by quenching. Therefore, even if the approach unveiled therein is used, when producing a thick-walled seamless steel pipe (wall thickness of around 40-50 mm) truly employed for risers and movement lines, the cooling price at thetime of quenching of the pipe gets to be gradual, especially at the central portion thereof because of its thickness, and there exists the trouble that a adequate energy and toughness can't be obtained. This can be since the cooling rate is slow, and with aconventional alloy design, it can be difficult to acquire a uniform microstructure and there exists a high chance of the brittle phase creating.

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