scholarly journals Exploratory Study of Sensitization in Cryogenically Cooled Ferritic Stainless Steel Welds

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
M. O. H. Amuda ◽  
S. Mridha
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Heat Affected Zone ◽  
Cryogenic Liquid ◽  
Cryogenic Cooling ◽  
Martensite Content ◽  
Steel Grades ◽  
Single Grain ◽  
Steel Welds ◽  
Aisi 430

Enhanced cooling via forced convection using cryogenic liquid is an option for controlling grain growth in the heat affected zone (HAZ) of ferritic stainless steel welds which improves joint strength. However, this technique seems to alter the martensite distribution in the high-temperature heat affected zone (HTHAZ) which is a critical constituent in rating the susceptibility to sensitization in ferritic stainless steel grades; any such information is not available in the literature. Thus, it is imperative to establish the influence of cryogenic cooling on sensitization dynamics in the HTHAZ. This paper discusses the influence of cryogenic cooling on sensitization in an AISI 430 ferritic stainless steel weld. It is established that cryogenic cooling increases the cooling rate in the HTHAZ and reduces the martensite volume percent by an average of 20%. This reduction in martensite content in the HTHAZ increases the level of ditched structure in cryogenically cooled welds and yields more ferrite-martensite ditched grain boundaries than in conventional welds. Although the cryotreated welds exhibit greater ditched boundary, the structure is still classified as nonsensitized, since no single grain boundary is completely surrounded by ditches.

Parametric Study of Carbide Precipitation in 16wt% Chromium Ferritic Stainless Steel (FSS) Welds

2012 ◽  
Vol 445 ◽  
pp. 723-728
Author(s):  
M.O.H. Amuda ◽  
S. Mridha
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Flow Rate ◽  
Cryogenic Liquid ◽  
Carbide Precipitation ◽  
Cryogenic Cooling ◽  
Grain Structure ◽  
Martensite Content ◽  
Electrolytic Etching ◽  
Single Grain

Other than grain coarsening, the loss of corrosion resistance in ferritic stainless steel (FSS) welds due to intergranular precipitation of chromium carbides restricts the use of the alloy for structural application. The use of cryogenic cooling offers dual opportunities for the control of weld geometry and grain structure in FSS. This results in improved mechanical properties but the effect on carbide precipitation was not investigated. In this paper, the effect of heat flux, welding speed and flow rate of cryogenic liquid on carbide precipitation in 16% chromium FSS welds are discussed. The use of cryogenic cooling reduces the size of the sensitized zone but this is not significantly affected by the flow rate of the cryogenic fluid. Compared to the conventional welding, the cryogenic cooling increases the cooling rate and reduces the martensite content in the high temperature heat affected zone (HTHAZ) by about 20%. This results in wider ditched-structure in welds made with flow rates lower than 0.052L/min. Cryogenic cooling produces more ditched weld microstructure revealed by electrolytic etching in oxalic acid; however, the structure is acceptable since no single grain boundary is completely surrounded by ditches.

scholarly journals Influence of Nb Content on Sensitization and Pitting Corrosion of Welded AISI 430 Ferritic Stainless Steel

2019 ◽  
Vol 24 ◽  
Author(s):  
Caroline Nazaré Gonçalves ◽  
Gabriel Mendes de Almeida Carvalho ◽  
Jordânio Samuel Siqueira ◽  
Reny Ângela Renzetti
Keyword(s):  
Stainless Steel ◽  
Weld Metal ◽  
Ferritic Stainless Steel ◽  
Pitting Corrosion ◽  
Heat Affected Zone ◽  
Electrochemical Techniques ◽  
Welding Process ◽  
Pitting Potential ◽  
Degree Of Sensitization ◽  
Aisi 430

Abstract In this work, the effect of Nb addition on sensitization and pitting corrosion of welded AISI 430 ferritic stainless steel subjected to autogenous GTAW was investigated by microstructural characterization and electrochemical techniques. The three distinct regions of welding process, weld metal, heat affected zone and base metal of AISI 430 steel with and without Nb were evaluated. The degree of sensitization was measured by double loop electrochemical potentiodynamic reactivation and pitting corrosion was studied by potentiostatic polarization test. The microstructural analyses reported martensite network in the weld metal and heat affected zone of AISI 430 non stabilized. The electrochemical studies revealed that the highest degree of sensitization and the lowest pitting potential are in the weld metal of AISI 430 without Nb.

Influences of Grain Refining Conditions on Sensitization in 16 wt% Chromium Ferritic Stainless Steel Welds

2012 ◽  
Vol 576 ◽  
pp. 496-499
Author(s):  
M.O.H. Amuda ◽  
S. Mridha
Keyword(s):  
Stainless Steel ◽  
Oxalic Acid ◽  
Ferritic Stainless Steel ◽  
Cryogenic Cooling ◽  
Inert Gas ◽  
Grain Refining ◽  
Powder Addition ◽  
Titanium Powders ◽  
Steel Welds ◽  
Metal Powder Addition

The paper discusses sensitization characteristics in medium chromium Ferritic Stainless Steel (FSS) welds processed at two different grain refining conditions namely metal powder addition and cryogenic cooling. Tungsten Inert Gas (TIG) torch welded samples were exposed to 10% oxalic acid electrolytic etch for evaluation of sensitization. Empirical analysis indicated that, though both the grain refining conditions reduced the sensitization width relative to the conventional weld, the width was virtually nil with cryogenic cooling suggesting the elimination or reduction of sensitization. Similarly, the microstructure of cryogenically cooled welds showed no ditched grain boundary but aluminum powder treated welds revealed extensive ditching and none in titanium treated welds while knifeline attack was observed in welds treated with the mixture of aluminum and titanium powders.

Effect of Energy Input on Microstructure and Hardness of TIG Welded AISI 430-Ferritic Stainless Steel

2011 ◽  
Vol 264-265 ◽  
pp. 390-396 ◽  
Author(s):  
M.O.H. Amuda ◽  
S. Mridha
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Heat Input ◽  
Energy Input ◽  
Microstructural Characterization ◽  
Input Rate ◽  
Thin Sections ◽  
Steel Grades ◽  
Aisi 430

Studies on the weldability of ferritic stainless steel grades suggests that low heat input rate and better heat transfer dynamics are appropriate for the control of grain size and microstructural feature in thin sections. However, the optimal welding conditions to achieve combination of such characteristics are yet to be established. In the present investigation, AISI 430 ferritic stainless steel is TIG welded using energy input between 0.205 and 2.05kj/mm and characterized in terms of microstructure and hardness. The microstructural characterization of the welds with varying heat input rates suggests the presence of interdendritic martensite in the fusion zone and grain boundary martensite in the HAZ in conjunction with some intermetallics in varying proportion. The hardness values across the welds indicate that grain growth and the presence of intermetallics are minimized when welded with increased heat input rates that permits transformation within the dual phase regions. The study provided a new insight into the contribution of heat input rate in the production of unwanted weld microstructural features and assisted in the design of methods and techniques for tailoring weld microstructures with optimum properties.

Continuous drive friction welding studies on AISI 430 ferritic stainless steel

2003 ◽  
Vol 8 (3) ◽  
pp. 184-193 ◽  
Author(s):  
V. V. Satyanarayana ◽  
G. Madhusudhan Reddy ◽  
T. Mohandas ◽  
G. Venkata Rao
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Friction Welding ◽  
Aisi 430
Sign in / Sign up

Export Citation Format

Share Document