Abstract

Microstructure development is examined for a specialized spot weld that is used as a solid-state closure process for austenitic stainless steel tubing, referred to as pinch welding. In order to elucidate the microstructural evolution of the weld, a series of test welds were made at nominal conditions using tubing and production like components. These pinch welds normally terminate after twelve cycles of a 60 Hz AC weld process. In this study, production tubes were welded from one to twelve cycles and the microstructure and weld variables after each individual weld cycle number were characterized using radiography and optical metallography. Two electrochemical etchants were used to highlight different microstructural features. The study revealed that: (1) this type pinch weld is largely complete after about six cycles of 60 Hz AC current, half the weld time utilized; (2) the resistance, deformation, and closure length approach “steady-state” conditions after six cycles; and (3) both oxalic and nitric acid electrolytic etchants are useful for highlighting specific microstructural attributes of type 304 L stainless steel. Finally, two distinct microstructural regions can be identified for these welds: the edge of the weld, which is driven by concentrated deformation, recrystallization, and grain growth, and the center region, which is more typical of forge welding and micro-asperity breakdown followed by diffusion and grain-growth.

References

1.
Kianersi
,
D.
,
Mostafaei
,
A.
, and
Amadeh
,
A. A.
,
2014
, “
Resistance Spot Welding Joints of AISI 316 L Austenitic Stainless Steel Sheets: Phase Transformations, Mechanical Properties and Microstructure Characterizations
,”
Mater. Des.
,
61
, pp.
251
263
.10.1016/j.matdes.2014.04.075
2.
Karcı
,
F.
,
Kac
,
R.
, and
Gündüz
,
S.
,
2009
, “
The Effect of Process Parameter on the Properties of Spot Welded Cold Deformed AISI304 Grade Austenitic Stainless Steel
,”
J. Mater. Process. Technol.
,
209
(
8
), pp.
4011
4019
.10.1016/j.jmatprotec.2008.09.030
3.
Moshayedi
,
H.
, and
Sattari-Far
,
I.
,
2012
, “
Numerical and Experimental Study of Nugget Size Growth in Resistance Spot Welding of Austenitic Stainless Steels
,”
J. Mater. Process. Technol.
,
212
(
2
), pp.
347
354
.10.1016/j.jmatprotec.2011.09.004
4.
Korinko
,
P. S.
, and
Arnold
,
K. F.
,
2006
, “
Optimization Study for Fill Stem Manufacturing and Pinch Weld Processing
,” Report No.
WSRC-TR-2006-00158
.https://digital.library.unt.edu/ark:/67531/metadc879335/
5.
Korinko
,
P. S.
, and
Maxwell
,
D. N.
,
2008
, “
Fill Stem Manufacturing Changes and Pinch Weld Qualifications
,” Report No.
WSRC-STI-2008-00098
.https://digital.library.unt.edu/ark:/67531/metadc894887/
6.
Korinko
,
P. S.
, and
Maxwell
,
D. N.
,
2008
, “
Pinch Weld Testing to Support Change in Manufacturing Oil at the KCP
,” Report No.
WSRC-STI-2006-00041
.10.2172/927599
7.
Korinko
,
P. S.
,
2005
, “Evaluation
of Internal Brushing on Pinch Weld Quality
,” Report No.
WSRC-TR-2005-00436
.10.2172/891768
8.
Korinko
,
P. S.
,
2005
, “
Effect of Scratches on Pinch Weld Quality
,” Report No.
WSRC-TR-2005-00435
.10.2172/890203
9.
Korinko
,
P. S.
, and
Howard
,
S. R.
,
2005
, “
Evaluation of Constant Current Weld Control on Pinch Welds
,” Report No.
WSRC-TR-2005-00434
.10.2172/891866
10.
Korinko
,
P. S.
,
2005
, “
Comparison of Air and Deuterium on Pinch Weld Bond Appearance
,” Report No.
WSRC-TR-00433
.10.2172/891766
11.
Bowers
,
J. A.
, and
Korinko
,
P. S.
,
2003
, “
Exploration of Summary Data Sheets of Pinch Weld Experiments and Draft Neural Network Models Forecasting Weld Closure Length
,” Report No. WSRC-TR-2003-00455.
12.
Hartman
,
D. A.
,
Korinko
,
P. S.
,
Tolk
,
N. R.
,
Malene
,
S. H.
,
Smith
,
M. G.
,
Cola
,
M. J.
,
Dave'
,
V. R.
,
Miller
,
J. P.
, and
King
,
W. H.
,
2005
, “
In-Process Monitoring of Pinch Welding: An Investigation Into a Bond Quality Metric
,”
Seventh International Conference on Trends in Welding Research
, Pine Mountain, GA, May 16–20, pp.
839
848
.
13.
Korinko
,
P. S.
,
Pechersky
,
M. J.
,
Zeha
,
D. L.
,
McKinney
,
G. J.
,
Reister
,
L.
,
Blau
,
P.
, and
Lara-Curzio
,
E.
,
2002
, “
Characterization of Confined Pinch Welds in Type 304 L Stainless Steel
,”
Sixth International Conference on Trends in Welding Research
, Callaway Gardens Resort, Pine Mountain, GA, Apr. 15–19, pp. 804–809.https://digital.library.unt.edu/ark:/67531/metadc734434/m2/1/high_res_d/799673.pdf
14.
Necker
,
C. T.
,
Marchi
,
A. N.
, and
Smith
,
M. G.
,
2008
, “
Multi-Cycle Pinch Welding of 304 L Tubes: Inhomogenieties in Deformation and Recrystallization Textures and Microstructures
,” Applications of Texture Analysis, Ceramic Transactions Series, ACerS.10.1002/9780470444214.ch53
15.
Porter
,
D. A.
, and
Easterling
,
K. E.
,
1981
,
Phase Transformations in Metals and Alloys
,
Van Nostrand Reinhold
, Berkshire, Wokingham,
UK
.
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