scholarly journals A New Approach to the Study of Multi-Pass Welds–Microstructure and Properties of Welded 20-mm-Thick Superduplex Stainless Steel

2019 ◽  
Vol 9 (6) ◽  
pp. 1050 ◽  
Author(s):  
Maria Valiente Bermejo ◽  
Kjell Hurtig ◽  
Daniel Eyzop ◽  
Leif Karlsson
Keyword(s):  
Stainless Steel ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Secondary Phases ◽  
Σ Phase ◽  
Flux Cored Arc Welding ◽  
Welding Sequence ◽  
Superduplex Stainless Steel ◽  
Secondary Austenite ◽  
The Impact

Type 2507 superduplex stainless steel 20 mm in thickness was multi-pass-welded with Gas Metal Arc Welding (GMAW) and Flux-Cored Arc Welding (FCAW) processes. Recommended and higher arc energies and inter-pass temperatures were used. Thermal cycles were monitored using a recently developed procedure involving the successive instrumentation of the multi-pass welds, pass by pass, by addition of thermocouples in each weld pass. The repeatability of temperature measurements and survival rate of more than 90% of thermocouples confirmed the reliability of the procedure. Reheating by subsequent passes caused a progressive increase in the austenite content of the weld metal. The as-deposited GMAW passes with higher-than-recommended arc energy showed the lowest presence of nitrides. Therefore, the cooling rate—and not the time exposed at the critical temperature range—seems to be the key factor for nitride formation. The welding sequence layout also plays an important role in the distribution of secondary phases. A larger amount and concentration of secondary austenite and σ-phase was found for a larger number of subsequent passes in the immediate vicinity of a specific weld pass. The impact toughness exceeded requirements for all welds. Differences in absorbed energies were related to the amount of micro-inclusions found with the FCAW weld showing the lowest absorbed energies and highest amount of micro-inclusions. Pitting corrosion preferentially initiated in locations with secondary austenite and σ-phase. However, in the absence of these secondary phases, the HAZ containing nitrides was the weakest location where pitting initiated. The results of this work have implications on practical welding for superduplex stainless steels: the current recommendations on maximum arc energy should be revised for large thickness weldments, and the importance of the welding sequence layout on the formation of secondary phases should be considered.

Effect of Post-Weld Heat Treatment on Hardness in Superduplex Stainless Steel ASTM A890/A890M - Grade 6A

2020 ◽  
Vol 1012 ◽  
pp. 296-301
Author(s):  
Clélia Ribeiro de Oliveira ◽  
Eloá Lopes Maia ◽  
Solange T. da Fonseca ◽  
Marcelo Martins ◽  
Julián Arnaldo Ávila Díaz ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Arc Welding ◽  
Treatment Condition ◽  
Heat Treatment Condition ◽  
Shielded Metal Arc Welding ◽  
Metal Arc Welding ◽  
Superduplex Stainless Steel ◽  
Secondary Austenite ◽  
Welding Processes

Superduplex stainless steel alloy exhibit high mechanical and corrosion resistance, which main industrial application is in the petrochemical industry. The manufacture and maintenance of such equipment usually involve welding processes, followed by post-welded heat treatment and it often becomes impossible to apply heat treatments. Thereby, the purpose of this work is to verify the effect of a post-welded heat treatment on shielded metal arc welding in steel grade ASTM A890/A890M - grade 6A. The microstructure in the as-welded condition consisted of austenite, secondary austenite, and ferrite phases and, the post-welded heat treatment condition exhibited only austenite and ferrite. The hardness in the melt zone reached values of 300 HV after welding and, the value was reduced to 260 HV in the post-welded heat treatment condition.

Hexavalent Chromium Exposure Levels Resulting from Shipyard Welding

1998 ◽  
Vol 14 (04) ◽  
pp. 246-254
Author(s):  
Bhaskar Kura ◽  
Praveen Mookoni
Keyword(s):  
Hexavalent Chromium ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Task Group ◽  
Health Administration ◽  
Metal Arc Welding ◽  
Flux Cored Arc Welding ◽  
Exposure Levels ◽  
The Impact ◽  
Welding Processes

The Occupational Safety and Health Administration is expected to reduce permissible exposure limits of hexavalent chromium from 100 ng/m3between 5 to 0.5 fig/m3. A Navy Industry Task Group study revealed that the impact of proposed regulations on the shipbuilding industry is significant. The estimated cost of compliance by the Navy facilities could be as much as $46 Million/year besides a one-time cost of about $22 Million. Also, the task group estimated that the cost of $9 Million. This paper presents the results of a study undertaken at the University of New Orleans in support of the Navy/Industry Task Group efforts. The study included assessments of Cr(VI) exposure levels for two specific welding processes and three welding scenarios. Airborne particulate matter was collected using personal samplers for two specific welding processes, Gas Metal Arc Welding and Flux-Cored Arc Welding. Two base metals, HY100 and DH36, were considered for Flux-Cored Arc Welding and one base metal, HY100, was considered for Gas Metal Arc Welding. The samples were analyzed for Cr(VI) using OSHA Method 215. Based on the data generated, it can be concluded that Gas Metal Arc Welding and Flux-Cored Arc Welding on HY100 steel result in 8-hr. worker exposures less than 0.5 fig/m3 in a laboratory type setting, though the same levels of exposure may be difficult to be achieved in the field. Flux-Cored Arc Welding on DH36 resulted in exposure above 0.5 ng/m3, again in laboratory type setting.

scholarly journals The Effect of Welding Conditions on Mechanical Properties of Superduplex Stainless Steel Welded Joints

2014 ◽  
Vol 14 (1) ◽  
pp. 14-23 ◽  
Author(s):  
A. Świerczyńska ◽  
J. Łabanowski ◽  
D. Fydrych
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Heat Affected Zone ◽  
Welded Joints ◽  
Arc Welding ◽  
Submerged Arc Welding ◽  
Flux Cored Arc Welding ◽  
Superduplex Stainless Steel ◽  
Zone Microstructure ◽  
Submerged Arc

ABSTRACT The tests results of superduplex stainless steel welded joints made with a different heat input, using automatic submerged arc welding (SAW) and semi-automatic flux-cored arc welding (FCAW) have been presented. Metallographic examinations, the measurements of the ferrite content, the width of the heat affected zone (HAZ) and the hardness of the welds in characteristic areas have been performed. Significant differences in the amount of ferrite in the weld metal and in the heat affected zone microstructure of joints were found.

scholarly journals Strength Enhancement of Superduplex Stainless Steel Using Thermomechanical Processing

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1094
Author(s):  
M. A. Lakhdari ◽  
F. Krajcarz ◽  
J. D. Mithieux ◽  
H. P. Van Landeghem ◽  
M. Veron
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Thermomechanical Processing ◽  
Tensile Tests ◽  
Image Correlation ◽  
Strength Enhancement ◽  
Industrial Material ◽  
Superduplex Stainless Steel ◽  
The Impact ◽  
Strength Improvement

The impact of microstructure evolution on mechanical properties in superduplex stainless steel UNS S32750 (EN 1.4410) was investigated. To this end, different thermomechanical treatments were carried out in order to obtain clearly distinct duplex microstructures. Optical microscopy and scanning electron microscopy, together with texture measurements, were used to characterize the morphology and the preferred orientations of ferrite and austenite in all microstructures. Additionally, the mechanical properties were assessed by tensile tests with digital image correlation. Phase morphology was not found to significantly affect the mechanical properties and neither were phase volume fractions within 13% of the 50/50 ratio. Austenite texture was the same combined Goss/Brass texture regardless of thermomechanical processing, while ferrite texture was mainly described by α-fiber orientations. Ferrite texture and average phase spacing were found to have a notable effect on mechanical properties. One of the original microstructures of superduplex stainless steel obtained here shows a strength improvement by the order of 120 MPa over the industrial material.

Sign in / Sign up

Export Citation Format

Share Document