Determination of residual stress by X-ray diffraction in a weld cordon

1

Determination of residual stress by X-ray diffraction

in a weld cordon

H. Nezzari¹, L. Chekour¹, H. Berkane¹, S. Boudrahem², A. Djermoune²

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.

berkanehayat@gmail.com; chekourl@umc.edu.dz;

Abstract

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 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.

Keywords:Welding, residual stress, X-ray diffraction, microscopy.

Résumé

Dans cette étude, notre principal objectif est la mise en œuvre de la méthode de détermination des contraintes résiduelles par diffraction de rayon X et de l’appliquer au cas d’un cordon de la soudure. Les procédés de soudage induisent des modifications de la microstructure et des 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 électrode enrobées en acier doux. La morphologie des échantillons à été caractérisée par microscopie optique et 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.

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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.

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.1. Microstructure of the three zones of the raw sample : a) B.M , b) H.A.Z, c) F.Z

Fig.2.Microstructure of the three zones of the sample annealed - 650 ° C: a) B.M, b) H.A.Z, c) F.Z

2

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.

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.1. Microstructure of the three zones of the raw sample : a) B.M , b) H.A.Z, c) F.Z

Fig.2.Microstructure of the three zones of the sample annealed - 650 ° C: a) B.M, b) H.A.Z, c) F.Z

2

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.

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.1. Microstructure of the three zones of the raw sample : a) B.M , b) H.A.Z, c) F.Z

Fig.2.Microstructure of the three zones of the sample annealed - 650 ° C: a) B.M, b) H.A.Z, c) F.Z

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3.2. Microhardness

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.

Fig.3. Superposition of the profiles of microhardness of the three transverse positions of the crude: a) samples and, b) annealed at 650 ° C.

Fig.4. Superposition of the profiles of microhardness of the three longitudinal positions of the crude a) samples and, b) annealed at 650°C.

3.3. Analysis of residual stresses

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.

1,0 1,5 2,0 2,5 3,0

170 175 180 185 190 195 200 205 210 215 220 225 230 235 240

Microhardnes (Hv)

Distance(mm) ATZ BM

FZ

1,0 1,5 2,0 2,5 3,0

170 175 180 185 190 195 200 205 210 215 220 225 230 235 240

Microhardnes (Hv)

Distance(mm) BM

HAZ FZ

5 10 15 20 25

170 180 190 200 210 220 230 240

Microdureté(Hv)

Distance(mm) center

supérior inferior

5 10 15 20 25

170 180 190 200 210 220 230 240

Microhardnes (Hv)

Distance(mm) inferior

center superior

4 Fig.5. diffraction spectra X-ray samples: A) gross:

(a) B.M, (b) H.A.Z, (c) F.Z , B) Annealing

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).

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 long piece of life in its operation

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Références Bibliographiques

[1] H. Granjon. Bases métallurgiques de soudage, publications de soudage et de ses applications 1995.

Sofiane Belhenini, Thèse, « Analyse numérique des contraintes résiduelles dans les structures assemblées par soudage, cas des pipelines en acier a haut grade », Université Djilali Liabes (Sidi- Bel-Abbes, Algerie) - Magister (Génie mécanique) 2009 . [2] R.C. Cochrane, P. R. Kirkwood «The effect of oxygen on weld metal microstructure», Proceedings, trends in steels and consumables for welding, the welding institute, London (1978).

These christian bonnet ;le soudage metallurgie et produits ; air liquide /ctas 2001

[3] C. Blais, G. l’esperance , G.M. Evans.« Characterization of inclusions found in c–mn steel welds Containing titanium », science and technology of welding and joining, 1999, vol. 4, no.

3, p. 143-150.

These christian bonnet ;le soudage metallurgie et produits ;air liquide /ctas 2001

[4] C. Bonnet. « relation structure - resilience dans les soudures d’aciers doux et faiblement allies Brutes de solidification », soudage et techniques connexes, juillet - aout 1980, p 6.

These christian bonnet ;le soudage metallurgie et produits ;air liquide /ctas 2001

[5] G.M. Evans., N. Bailey. metallurgy of basic weld metal, abington publishing, 1997.

[6] L. Devillers.,D Kaplan., B. Marandet ., A. Ribes., P.V.Riboud . « the effect of low level of some Elements on the toughness of submerged-arc welded cmn steel welds », proceedings, the effects of residual,impurity and micro-alloying elements on weldability and weld properties, the welding institute, london, 15-17 november 1983, paper 1. These christian bonnet ;le soudage metallurgie et produits ;air liquide /ctas 2001.

[7] N. Cavallo. Contribution a la validation experimentale de modeles decrivant la zat lors d’une operation de soudage, these de doctorat,insa,avril1998

[8] Anne-sophie bilat, Ecole nationale supérieure des mines de paris, 2007 Estimation du risque de rupture fragile de soudures de pipelines en aciers a haut grade Caracterisation et modelisation.

[9] R. Bourgeois. Memothech, Génie des matériaux, édition éducative 2001 Métallurgie, zaoui moussa , influence des traitements thermiques sur la Rupture fragile des constructions soudees, cas des ,

Thèse pour l’obtention du diplome de docteur en sciences en genie mecanique.

[10] M. Drui., A.Henni, M Heugel., C. Martin., C. Simon c. Les differents procedes manuels de soudage, leurs risques et leur prevention ; 2003 www.ast67.org tig mig

[11] Les fiches conseils : la soudure au gaz. La soudure a l’arc.

Www.mr-bricolage.fr

40 60 80 100 120 140

100 200 300 400 500 600 700

Fe(211) Fe(002) Fe(001)

Intensity(u-a)

2 (°)

BM FZ HAZ

Fe_ Fe_

40 60 80 100 120 140

100 200 300 400 500 600 700 800 900 1000

Fe_{}

Fe

Fe

Intensity (u-a)

2^ (°)

FZ BM HAZ

Fe_{}

Fe

0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8 2,0 2,2

-440 -420 -400 -380 -360 -340 -320 -300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100

stress residuel (MPa)

Distance(Cm)

non recuit recuit (HAZ)

(BM)

1

2

3 (FZ)