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Influence of the base metal grain size and heat input on decarburization in single pass SAW and multi pass SMAW welded joints of dissimilar ferritic steels

Nimko M. O., Skulskyi V. Yu.

Journal of Achievements in Materials and Manufacturing Engineering

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2023

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Vol. 119, nr 1

14--26

EN

Purpose This paper aims to assess a separate influence of heat input and base metal grain size on microstructural evolution in the weld adjacent zone of bainitic steels with 1.5…2.0% Cr, welded or overlayed with consumables with 9% Cr after post-weld heat treatment. Design/methodology/approach Analysis of the width of decarburised layer on microphotographs of welded or overlayed specimens after tempering at 750°C. Specimens were made by using different welding approaches: single-pass welding, multi-pass welding and overlaying. Findings It is shown that with an increase of the heat input energy, the width of the resulting decarbonised layer decreases linearly; the increase of the base metal grain size leads to a decrease in the layer width after tempering at 750°C. The microhardness testing showed the average hardness in the decarburised layer of 15Kh2M2FBS steel was 161 HV0.1 (minimum – 154 HV0.1), while the average hardness in the rest of the heat-affected zone was 192 HV0.1. Research limitations/implications Future research may include comparing the creep rupture strength of the weldments made with different welding parameters or base metal grain size to assess the influence of these factors on creep rupture strength. Practical implications Results permit to achieve minimisation of the rate of carbon diffusion in the weld-adjacent area of the heat-affected zone by means of variation of welded parameters and base metal grain size. Originality/value An influence of high-diffusivity paths (grain boundaries) on carbon diffusion in the heat-affected zone of dissimilar weldments was confirmed experimentally; the correlation between base metal grain size/welding parameters and the rate of the diffusion during high-temperature exposure was found.

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Influence of welding parameters on decarburization in heat affected zone of dissimilar weldments after post weld heat treatment

Nimko M.O.

Archives of Materials Science and Engineering

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2021

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Vol. 112, nr 1

23--31

EN

Purpose: This paper aims to assess an influence of thermal welding parameters on microstructural evolution in the weld adjacent zone of P91 steel, overlayed by austenitic consumables, after post weld heat treatment. Design/methodology/approach: Analysis of the width of decarburized layer on microphotographs of overlayed specimens after tempering 750°C, 7 and 18 hours. Specimens were made by using different heat input and preheating temperature parameters. Findings: It is shown that with increase of the heat input energy, the width of the resulting decarbonized layer decreases linearly; the effect of heating temperature on the layer width is parabolic with a minimum at a temperature of ~195°C. Research limitations/implications: Future research may include comparison of the creep rupture strength of the weldments, made with different welding parameters, to assess the influence of kinetics of decarburization and variation of the parameters on creep rupture strength. Practical implications: Results permit to achieve minimization of rate of carbon diffusion in the weld adjacent zone of the HAZ by means of variation of welded parameters. Originality/value: Experimentally was confirmed a role of high-diffusivity paths (grain boundaries) on carbon diffusion in the HAZ of dissimilar weldments; found correlation between welding parameters and the rate of the diffusion during high temperature exposure.

3

Wpływ kształtu narzędzia w procesie zgrzewania FSW na właściwości złączy stopów aluminium 5083 i 7075

Kalemba-Rec I.

Inżynieria Materiałowa

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2015

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Vol. 36, nr 5

338--342

PL

W pracy określono wpływ kształtu narzędzia zgrzewającego na właściwości mechaniczne doczołowych złączy stopów aluminium 5083-H111 i 7075- T651 wykonanych metodą zgrzewania tarciowego z mieszaniem materiału (Friction Stir Welding — FSW). Do wykonania złączy zastosowano dwa różne narzędzia. Oba narzędzia składały się ze spiralnego wieńca opory i trzpienia: stożkowego, gwintowanego lub typu Triflute. Właściwości mechaniczne złączy określono na podstawie pomiarów twardości i próby rozciągania. Wyniki tych badań porównano z obserwacjami mikrostruktury wykonanymi za pomocą mikroskopii świetlnej i skaningowej mikroskopii elektronowej. Przeprowadzone badania wykazały, że dobór odpowiednich parametrów procesu FSW (prędkości zgrzewania i prędkości obrotowej narzędzia) pozwala na uzyskanie trwałego złącza stopów 5083-H111 i 7075-T651, pozbawionego wad i nieciągłości, charakteryzującego się bardzo dobrymi właściwościami mechanicznymi, bez względu na zastosowane narzędzie zgrzewające. Jednak kształt narzędzia (trzpienia) ma istotny wpływ na wymieszanie materiałów i mikrostrukturę w strefie mieszania, a zatem i na własności złącza. Za pomocą narzędzia z trzpieniem typu Triflute uzyskano szerszy obszar zgrzeiny o dokładniejszym wymieszaniu materiałów (obecność w mikrostrukturze pasm o pośrednim składzie chemicznym pomiędzy składem stopu 5083 a 7075) niż w przypadku użycia trzpienia stożkowego. Wytrzymałość na rozciąganie złącza uzyskanego narzędziem Triflute jest o 90 MPa większa niż w przypadku zastosowania narzędzia stożkowego.

EN

The influence of shape of FSW tool on mechanical properties of friction stir welded 5083-H111 and 7075-T651 aluminium alloys has been investigated. Two different tools have been used to weld the joints. Both tools consisted of a spiral shoulder and a pin: tapered with thread or Triflute. The mechanical properties of welds were determined by hardness measurements and tensile tests. The mechanical characterization was supplemented by microstructural examination using light microscopy and scanning electron microscopy. The results indicate that the choice of right FSW parameters (welding velocity and tool rotation speed) allows to obtain a defect-free joint between 5083-H111 and 7075-T651 alloys, which was characterized by good mechanical properties irrespective of the applied FSW tool. But the pin shape have the effect on mixing of materials and microstructure in the stirred zone as well as on weld properties. In case of Triflute pin the weld area was wider with more accurate mixing of materials (presence of microstructural bands, which the chemical composition was intermediate between 5083 and 7075 alloys) than using the tapered pin. Tensile strength of weld obtaining by Triflute pin was higher (about 90 MPa) than for weld produced by the tapered pin.

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Corrosion resistance of dissimilar austenite and duplex steels welded joints

Łabanowski J.

Advances in Materials Science

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2007

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Vol. 7, nr 2(12)

121-128

EN

This paper describes influence of welding conditions on structure and corrosion resistance of dissimilar stainless steels welded joints. Butt joints between duplex 2205 and austenitic 316L steels were performed with the use of submerged arc welding method. The plates 15 mm in thickness were welded with beat input in the range of 1.15 - 3.2 kJ/mm using duplex steel filter metal.. Microstructure examinations and corrosion tests were carried out. ASTM G48 pitting corrosion tests and slow strain rate tests were performed. It was shown that place of the lowest resistance to stress corrosion cracking is beat affected zone at duplex steel side of dissimilar joins. That phenomenon was connected with undesirable structure of that zone consisted of coarse ferrite grains and acicular austenite precipitates.