In the past few years the development of supermartensitic stainless steels for flow-line materials has been fast. Recently the demand for weldable 13%Cr with larger outside diameter such as 18", 20" and 24” has increased greatly. Considering such a requirement, a new production route for big size pipes with OD over 16” was developed.

A girth weld on 20" pipe was produced with GTAW procedure utilizing duplex and superduplex filler wire. No post welding heat treatment was applied. The mechanical properties of both the base material and welded joints met the target requirements.

Corrosion qualification was aimed to determine the Sulfide Stress Cracking (SSC) resistance of weldable supermartensitic steel to be used as flow-line in slightly sour oil and gas wells.

SSC resistance of the welded joints was excellent in 5% NaCl solution with 0.004 MPa of H2S partial pressure at pH 4.5. The influence of chloride concentration (NaCl 5÷25%), hydrogen sulfide partial pressure (1÷10 kPa) and pH (3.5÷5, was assessed as well.

Resistance to general corrosion was good confirming the suitability of 20” weldable 13%Cr steel at elevated concentration of CO2 and even in slightly sour environment.

Subject
Materials, Piping, Autoclaves, Sour environments, Welding, Girth welds, Acidity, Welded joints, Sodium chloride solution, Steel, Corrosion resistance, Sulfide stress cracking, Stress corrosion cracking
Keywords:
Supermartensitic steels, flow-line, slightly sour, Gas Tungsten Arc Welding (GTAW), toughness, Sulfide Stress Corrosion (SSC), Uniform corrosion
© 2001 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2001
Association for Materials Protection and Performance (AMPP)
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