Determination of residual stress by X

Determination of
residual stress
by X-ray diffraction
in a weld cordon
Dans cette étude, notre principal objectif est la mise en
H. Nezzari 1, L. Chekour1, H. Berkane1, S. Boudrahem2,
résiduelles par diffraction de rayon X et de l’appliquer au
A. Djermoune2
cas d’un cordon de la soudure. Les procédés de soudage
Keywords: Welding, residual stress, X-ray diffraction,
microscopy.
Résumé
œuvre de la méthode de détermination des contraintes
induisent des modifications de la microstructure et des
1) Département de Physique, Laboratoire « Microstructure et
Défauts dans les Matériaux (LMDM », Université Frères
Mentouri Constantine 1, Algérie.
2) Département de physique, laboratoire «Génie des Procédés »,
Université Abderrahmane Mira, Bejaia, Algérie.
contraintes et déformations résiduelles qu'il est autant
difficile qu'important de maîtriser. Pour étudier ce
phénomène de soudage, deux pièces peu alliées et à faible
taux de carbone, ont été soudées à l’arc électrique avec
[email protected]; [email protected];
électrode enrobées en acier doux. La morphologie des
Abstract
échantillons à été caractérisée par microscopie optique et
In this study, the implementation of the method for
determining residual stresses by X-ray diffraction and
apply it to the case of a bead of solder. Welding
processes induce changes in the microstructure and
residual deformations and stresses that it is so difficult
to control that important To study this phenomenon
of welding two pieces and low alloy low carbon, were
welded to the electrical arc with coated electrode of
mild steel. The morphology of the samples was
characterized by optical and electron microscopy,
showing the significant change in the microstructure
in the different area of the cord. The hardness profiles
obtained show that the hardness is stable (200 Hv) in
the base metal and increases in the cord (230 Hv). In
this work, the X-ray diffraction was used to analyze
the residual stresses. The results of measurements on
the crude sample show that the constraints are all
compression, with a higher level in the side region to
the cord and in the base metal. The relief annealed at
650 ° C relaxes the constraints to a lower level while
électronique et montrent le changement sensible de la
microstructure dans les différentes zone du cordon. Les
profils de dureté réalisés montrent que la dureté est stable
(200 Hv) dans le métal de base et augmente
dans le
cordon (230 Hv). Dans ce travail, la diffraction des RX a
été utilisée pour analyser les contraintes résiduelles. Les
résultats des mesures faites sur l’échantillon brut montrent
que les contraintes sont toutes de compression, avec un
niveau plus élevé dans la zone latérale au cordon et dans
le métal de base. Le recuit de détente à 650 °C relaxe les
contraintes à un niveau plus bas tout en restant
compressives. Ces résultats
montrent que la soudure
présente des caractéristiques mécaniques et structurales
intéressantes, vu la présente de contraintes résiduelles de
compression, l’absence de défauts de structure et de
fissures. Ce qui favorise la bonne tenue et une longue
durée de vie de la pièce dans son fonctionnement.
Mots clés : Soudage, contraintes résiduelles, diffraction
de rayon X, microscopie.
remaining compressive. These results show that the
present solder interesting mechanical and structural
characteristics, having regard to the present of
residual
compressive
stresses,
the
absence
of
structural defects and cracks. Which promotes good
performance and long life of the part in its operation.
1
1. Introduction
The many applications of welding and the wide
variety of processes used result
not only of the diversity of the types of materials to
be assembled and the multiplicity of requirements
imposed on service buildings, but also the search of
ever greater 'higher profitability.
Welding operations of steels are accompanied by
metallurgical and mechanical thermal phenomena.
These phenomena induce deformations and residual
stresses. The nature and distribution of these
stresses can have serious consequences during the
commissioning of the welded parts.
2. Experemental method
To study the phenomena induced by the arc
welding using two samples, one plain and the other
annealed at 650 ° C. The weld was made using the
electric arc and a mild steel electrode with cellulose
coating. It is performed by the inside and outside in
several passes. The crude sample is cut on a welded
cylindrical channel (02 assembled tubes) and
having a portion of the weld joint. The direction of
the cut is perpendicular to the weld seam.
Fig.1. Microstructure of the three zones of the raw sample : a)
B.M , b) H.A.Z, c) F.Z
3. Results and Discussion
L’étude microstructurale vise à décrire les
différents types de microstructures que nous avons
observées dans notre matériau.
Figure1 shows the microstructure of the three zones
of the raw sample: a) B.M, b) H.A.Z, c) F.Z
Figure 2 shows the microstructure of the three
zones of the sample annealed at 650 °C: a) B.M, b)
H.A.Z, c) F.Z. It can be seen that:
The existence of three specific areas: a) B.M
coarse, b) H.A.Z to larger grains, c) F.Z fine grains.
Effect of heat treatment, scope and distribution of
perlite and ferrite islands.
Fig.2.Microstructure of the three zones of the sample annealed 650 ° C: a) B.M, b) H.A.Z, c) F.Z
2
3.2. Microhardness
240
235
230
225
ATZ
BM
FZ
Microhardnes (Hv)
220
215
205
195
Microdureté(Hv)
190
180
170
240
5
10
inferior
center
superior
230
15
Distance(mm)
20
25
220
210
200
175
170
1,0
1,5
2,0
Distance(mm)
2,5
3,0
15
Distance(mm)
20
25
3.3. Analysis of residual stresses
BM
HAZ
FZ
220
215
210
205
200
195
190
185
180
175
170
1,0
10
Fig.4. Superposition of the profiles of microhardness of the
three longitudinal positions of the crude a) samples and, b)
annealed at 650°C.
180
Microhardnes (Hv)
200
5
185
225
210
170
190
230
220
180
200
235
center
supérior
inferior
230
190
210
240
240
Microhardnes (Hv)
Figure 3 shows the Superposition of the profiles of
microhardness of the three transverse positions of
the crude: a) samples and, b) annealed at 650 °C.
Figure 4 shows the Superposition of the profiles of
microhardness of the three longitudinal positions of
the crude a) samples and, b) annealed at 650 °C
Microhardness (195Hv) is constant in the base
metal. It decreases slightly (180 Hv) at the zone
(HAZ) and then increases (220 Hv) substantially at
the area of the level (ZF) for the raw sample and
Hardness is basically stable around the average
value of 200HV. And this, in different zones and
positions of the sample annealed at 650 °C.
1,5
2,0
Distance(mm)
2,5
3,0
Fig.3. Superposition of the profiles of microhardness of the three
transverse positions of the crude: a) samples and, b) annealed at
650 ° C.
Figure 5 Shows the XRD patterns of A) gross: (a)
B.M, (b) H.A.Z, (c) F.Z. B) annealing.
It can be seen the different lines (001) (002) (211)
(220) and (310) sign the presence of Fe phase in
the three areas (BM, HAZ, FZ) of crude and
annealed samples.
Figure 6 shows the Evolution of residual stress
generated by the welding arc process before and
after annealing at 650 ° C
It can be seen that: The values of residual stress
found at each region are compressive. With,
however, a lesser degree in the area FZ. thermal
annealing treatments relaxes residual stresses.
3
600
500
Intensity(u-a)
BM
FZ
HAZ
Fe(211)
Fe(002)
Fe(001)
700
Fe
Residual stresses are determined by XRD of
compression, with a higher level in the side region
to the cord and in the base metal. The relief
annealed at 650 ° C relaxes the constraints to a
lower level while remaining compressive.
These results show that the present solder
interesting mechanical and structural characteristics
due to the presence of compressive residual
stresses, the absence of structural defects and
cracks. Which promotes good performance and a
Fe
400
300
200
100
40
1000
60
80
2 (°)
100
120
140
long piece of life in its operation?
FZ
BM
HAZ
Fe
900
Références Bibliographiques
Intensity (u-a)
800
700
600
Fe
500
Fe
Fe
Fe 

400
300
200
100
40
60
80
100
120
140
2 (°)
stress residuel (MPa)
Fig.5. diffraction spectra X-ray samples: A) gross:
(a) B.M, (b) H.A.Z, (c) F.Z , B) Annealing
non recuit
recuit
-100
-120
-140
-160
-180
-200
-220
-240
-260
-280
-300
-320
-340
-360
-380
-400
-420
-440
(FZ)
(HAZ)
(BM)
1
2
3
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
1,8
2,0
2,2
Distance(Cm)
Fig.6. Evolution of residual stress generated by the welding arc
process before and after annealing at 650 °C.
4. Conclusion
In this work, we became interested in the study of a
weld arc.
Microscopy shows the significant change in the
microstructure in the different zones of the cord.
The hardness profiles obtained show that the
hardness is stable (200 Hv) in the base metal
decreases in the HAZ and increases slightly in the
FZ cord (230 Hv).
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