Arcelormittal Wire France

Thyssenkrupp Steel Ag

Xavier Perroud

Sylvain Foissey

Christophe Bertout

A process for the manufacture of a profiled wire of hydrogen-embrittlement-resistant, low-alloy carbon steel for flexible pipelines for the offshore oil and gas operations sector is provided. The process includes providing a low-alloy carbon steel wire rod having a composition including, expressed in percentages by weight of the total mass 0.75&#x3c;C %&#x3c;0.95; 0.30&#x3c;Mn %&#x3c;0.85; Cr&#x2266;0.4%; V&#x2266;0.16%; and Si&#x2266;1.40%, the rest being iron and the inevitable impurities from smelting of the metal in the liquid state. The process further includes hot-rolling the wire rod in an austenitic region above 900&#xb0; C., cooling the wire rod to ambient temperature, subjecting the wire rod to isothermal quenching to obtain a homogeneous pearlitic microstructure, subjecting the wire rod to an operation of cold mechanical transformation, carried out with a global work-hardening ratio of from approximately 50 to 80%, to give the wire rod a diameter of from approximately 5 to 30 mm and subjecting the drawn wire to a short-duration recovery heat treatment carried out below an Ac1 temperature of the steel.

Process for manufacturing a profiled steel wire

A profiled wire, of NACE grade, made of low-alloy carbon steel intended to be used in the offshore oil exploitation sector is provided. The profiled wire includes the following chemical composition, expressed in percentages by weight of the total mass: 0.75&#x3c;% C&#x3c;0.95; 0.30&#x3c;% Mn&#x3c;0.85; Cr&#x2266;0.4%; V&#x2266;0.16%; Si&#x2266;1.40% and preferably &#x2267;0.15%; and optionally no more than 0.06% Al, no more than 0.1% Ni and no more than 0.1% Cu, the balance being iron and the inevitable impurities arising from smelting the metal in the liquid state. The steel is obtained, from hot-rolled rod stock cooled down to room temperature, and then having a diameter of about 5 to 30 mm, by subjecting this starting rod firstly to a thermomechanical treatment comprising two successive steps carried out in order, namely an isothermal quench, giving it a homogeneous perlitic microstructure, followed by a mechanical transformation operation carried out cold with an overall degree of work-hardening (or reduction ratio) of between 50 and 80% at most, so as to give the wire its definitive shape, and in that the profiled wire thus obtained is then subjected to a restoration heat treatment of short duration carried out below Ac1 (preferably between 410 and 710&#xb0; C.), giving it the desired final mechanical properties.

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Mollon, France

Xavier Perroud