INFLUENCE OF THERMAL TREATMENTS ON SENSITIZATION IN Cr-Mn-Cu AUSTENITIC STAINLESS STEEL WELDS

  • M. O.H. Amuda
  • Lawal, T. F., Enumah, K.S. Ezeonu, L. L., Onitiri, M.A.
Keywords: Austenitic Stainless Steel, Chromium Back-diffusion, Chromium Carbide Precipitation, Pre-weld Thermal Treatment, Post-weld Thermal Treatment

Abstract

In an earlier work, Cr-Mn-Cu austenitic stainless steel was established to be susceptible to chromium carbide precipitation in the as-welded condition in the heat input range 207-302 J/mm due to the formation of sensitized structure. Whereas, literature indicate that pre or post-weld thermal treatment has been effective in minimizing carbide precipitation in stainless steel welds; such has not been reported for the welds of the new Cr-Mn-Cu austenitic stainless steel variety. Thus, in this work, sensitization behaviour in Cr-Mn-Cu austenitic stainless steel welds subjected to either pre weld or post-weld thermal treatment was investigated. Pre-weld thermal treatment was conducted with oxy-acetylene flame torch to pre-heat temperatures of 180, 220, 260, 300 and 3500C, respectively for 30 min each and then welded at a heat input of 293 J/mm. Post-weld thermal treatment was conducted on welded coupons at a fixed temperature of 650oC for varying times of 30, 60., 120, 180 and 240 min, respectively. Microstructural characterisation using 10% oxalic acid etch established that post-weld thermal treatment could not prevent the occurrence of sensitization irrespective of the treatment time. On the other hand, pre-weld heat treatment of Cr-Mn-Cu austenitic stainless steel was only effective for eliminating sensitization at preheat temperature around 300oC and above. The work further showed that the mechanism of chromium back diffusion known to be responsible for the effectiveness of post-weld thermal treatment in the control of carbide precipitation in other grades of stainless steel is not applicable to Cr-Mn-Cu austenitic stainless steel grade.

Author Biographies

M. O.H. Amuda

Materials Development and Processing Research Group, Department of Metallurgical and Materials Engineering, University of Lagos, 101017

 Department of Mechanical Engineering, University of Lagos, Nigeria, 101017

 

Lawal, T. F., Enumah, K.S. Ezeonu, L. L., Onitiri, M.A.

Materials Development and Processing Research Group, Department of Metallurgical and Materials Engineering, University of Lagos, 101017

Department of Mechanical Engineering, University of Lagos, Nigeria, 101017

 

Published
2019-05-17
How to Cite
Amuda, M. O., & Ezeonu, L. L., Onitiri, M.A., L. T. F. E. K. (2019). INFLUENCE OF THERMAL TREATMENTS ON SENSITIZATION IN Cr-Mn-Cu AUSTENITIC STAINLESS STEEL WELDS. UNILAG Journal of Medicine, Science and Technology, 6(2), 91-106. Retrieved from http://ujmst.unilag.edu.ng/article/view/397