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As with C-Mn steels, fillet welds in stainless steels can display low fatigue strengths. Therefore, possible ways of improving their fatigue performance were investigated, by choice of welding process or the application of a post-weld improvement technique.
Three types of fillet welded specimen were made from three stainless steels, namely 10 mm thick 304L austenitic and higher strength S31803 duplex and 3 mm thick highstrength Cr-Mn austenitic steel. One aim was to show that the higher strength steels gained more benefit from an improvement technique. The basic test series were MAG welded, but TIG and powder plasma arc welds (PPAW) were included to investigate possible improved fatigue performance from these welding processes. In addition, four weld toe improvement techniques were applied, namely weld profile improvement by grinding or re-melting the weld toe with a TIG or plasma torch (TIG or plasma dressing) and the introduction of compressive residual stress by ultrasonic impact treatment (UIT).
The specimens were fatigue tested axially at R = 0.1 or under high tensile mean stress conditions. Most tests were performed in air under constant amplitude loading, but toe ground and plasma dressed specimens were also tested in 3 % NaCl solution, while some TIG dressed and UIT specimens were tested under variable amplitude loading. Many testing conditions were selected specifically to investigate features of actual service operation that might reduce the benefit of an improvement technique. The TIG and PPA welds did not produce better fatigue performance than MAG welds. However, all the improvement techniques were beneficial, the improvement increasing with decrease in applied stress range. The basic level of improvement in fatigue strength in air for R = 0.1 was 30 %.

Additional information

Authors: MADDOX S J, TWI Ltd., Cambridge (GB);HOPKIN G R, TWI Ltd., Cambridge (GB);HOLY A, TWI Ltd., Cambridge (GB);MOURA BRANCO C A, InstitutoSuperior Tecnico, Lisbon (PT);INFANTE V, InstitutoSuperior Tecnico, Lisbon (PT);BAPTISTA R, InstitutoSuperior Tecnico, Lisbon (PT);SCHUBERTH S, ThyssenKrupp Nirosta, Düsseldorf (DE);SONSINO C M, Fraunhofer Institute for Structural Durability, Darmstadt (DE);KÜPPERS M, Fraunhofer Institute for Structural Durability, Darmstadt (DE);MARQUIS G, Lappeenranta University of Technology, Lappeenranta (FI);LIHAVAINEN V-M, Lappeenranta University of Technology, Lappeenranta (FI);GALES A, TNO Institute of Industrial Technology, Eindhoven (NL);DEN HERDER A J, TNO Institute of Industrial Technology, Eindhoven (NL);LONT M A, TNO Institute of Industrial Technology, Eindhoven (NL)
Bibliographic Reference: EUR 22809 EN (2007), 190 pp. Euro: 25
Availability: Katalogue Number: KI-NA-22809-EN-S The paper version can be ordered online and the PDF version downloaded at:
ISBN: ISBN: 978-92-79-05259-0
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