Characterisation of welding consumables and weld metal

Chris Knee, Johan Börjesson and Kamellia Dalaei

Global R&D Filler MetalsLindholmsallén 9

402 77 Göteborg, SverigeChristopher.knee@esab.se

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ESAB products

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Welding consumables • Submerged Arc Welding (SAW) powders

• Shielded metal Arc welding covered electrodes

• Flux Cored Wires (FCW)

• The Filler Metal wire (often copper coated)

Many consumables contain a lot of inorganic components Act as slag builders to protect / clean the cooling weld metal and some active alloying

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T in the plasma arc > 8,000 °C

Things happen quickly, heat up in ~10 seconds, cool down to RT in ~5 minute

Base metal, heat affected zone and weld metal (often multiple weld passes).

Arc welding

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We are interested in characterising a range of materials:

1) Inorganic oxides / carbonates – (Raw materials for electrode covers / SAW fluxes )

2) Multicomponent SAW fluxes and electrode covers

3) Slags – mainly Mg-silicate / CaF2 type

4) Oxidation states – Mn oxides / Cr 3+ vs. Cr 6+

5) Plasma arc – physics and chemistry

6) Steels, nickel and aluminum based alloys

7) Phase transformation (austenite to ferrite) / element segregation

8) Evolving microstructure / inclusions

9) Retained austenite

10) Hydrogen in weld metal / heat affected zone

11) Residual stress

All, except investigation of Plasma, could potentially be helped by Synchrotron and/or neutron

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1) Quantification of Fe and Mn alloys in SAW welding fluxes

2) Residual stresses in welded joints / fatigue behaviour

3) Quantification of inclusions / precipitates in weld metal

Some examples..

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1) Submerged Arc Welding fluxes – phase identification and quantification

Waterglasssilicate added toDry powder mix

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SEM cross section of welding flux grains

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CaF2 MgOAl2O3SiO

1 mm

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Quantitative analysis of SAW flux – Rietveld analysis of XRD data

Position [°2θ] (Copper (Cu))

10 20 30 40 50 60 70

Counts

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10000

20000

16-1277-1_309FW1

Wollastonite 1A 13.1 %

Fluorite 18.8 %

Periclase 25.1 %

Rutile 0.4 %

Mullite 13.2 %

Corundum (Cr-doped) 19.1 %

Hausmannite 0.7 %

Zircon 2.5 %

Quartz low 1.0 %

Iron Titanium (2/1) 0.0 %

Forsterite, ferroan 2.8 %

Monticellite 1.2 %

Cristobalite low 2.0 %

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Challenge 1 - Can we use neutron diffraction data to identify / quantify these Fe-Mn alloys (Approx. ~ 0.5 - 1 wt. %) more accurately?

To what extent do they react / oxidise??

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2) Residual strains and fatigue durability of welded joints

As partners with

University West, Department of Engineering Science, Welding Technology Division

Motivation - Development of new filler metals with low transformation temperatures (LTT) may be able to reduce residual strains / improve fatigue properties

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Residual strains and fatigue durability of welded joints (T joints neutron diffraction)

As partners with Volvo andUniversity West, Department of Engineering Science,

Welding Technology Division

Data collected on SALSA, ILL 14

Residual strains and fatigue durability of welded joints (Butt joints neutron diffraction)

As partners with Cambridge University

Data collected on ENGIN-X, ISIS

Multi-pass welds

Challenge 2 - In-situ measurements of residual stresses during welding / reheating / under load? 15

3) Inclusions / Precipitates

• Important parameters that often governs the mechanical properties.

• Local variations within a weld metal due to reheating.

• Characterisation of composition, crystallographic phase, size, shape and number density. Has generally small volume fraction.

• Both qualitatively and quantitative analysis from well defined volume is desirable.

• Current techniques are SEM-EDS and TEM-ED.

200nm

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Challenge 3 - Could neutron / synchrotron diffraction be used to characterize small inclusions and precipitates in an iron-based matrix?

- If so, what is the lower volume fraction limit of the inclusions/precipitates?

Potential: A technique that offers better statistics (compared to TEM) and the possibility of in-situ measurements.

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Summary

• Overview of areas of potential interest was given.

• 3 specific examples were highlighted with current challenges.

Interested in learning more………

i) New instruments, sample environment, access routes etc..

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