ABSTRACT

ABSTRACT Recent price fluctuations of raw materials such as chromium and nickel have led to the development of stainless steel grades containing less nickel, which are known as lean duplex stainless steels. A research project has been initiated involving stainless steel manufacturers and end-users in order to study the weldability and properties of such grades. Investigations have been carried out on three lean duplex grades: UNS S32101, UNS S32202 and UNS S32304. Test pieces have been welded using several arc welding processes: Gas Tungsten Arc Welding (GTAW), Gas Metal Arc Welding (GMAW) using solid and cored wires, plasma, Submerged Arc Welding (SAW) and Shielded Metal Arc Welding (SMAW) and two plate thicknesses, 5 and 12 mm. These welded test pieces were then used for characterization work including metallographic examinations (in order to check weld quality and to measure the ferrite content), mechanical testing (hardness measurements, tensile and impact tests) and pitting corrosion on welded joints. The influence of gas shielding upon ferrite content and pitting corrosion behaviour was also studied. Pitting corrosion of welded joints has been evaluated in terms of critical pitting temperature (CPT) using a modified ASTM(1) G1501 test method. CPT and pits location, as well as mechanical testing results have been related to ferrite content and chemical analysis of both base metal and fusion zone. INTRODUCTION Recently, the price of nickel has shown considerable variability and an increase seems to be inevitable in the long term. So, it is predictable that the cost of austenitic stainless steels will grow too. It is well-known that it is possible to reduce the cost of steels by replacing nickel with manganese and nitrogen, which are the two basic elements of low cost austenitic steels (AISI 200 series). However these steels are less resistant to stress corrosion cracking or pitting corrosion, particularly in media with high content of chlorides.

Keywords:
metals & mining, Production Chemistry, H2S management, Corrosion Inhibition, materials and corrosion, riser corrosion, Publication Division, flowline corrosion, oilfield chemistry, well integrity
Subjects:
Production Chemistry, Metallurgy and Biology, Pipelines, Flowlines and Risers, Materials and corrosion, Well Integrity, Subsurface corrosion (tubing, casing, completion equipment, conductor), Corrosion inhibition and management (including H2S and CO2)
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2012. NACE International
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