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Welding thermal cycles of joints made of S1100QL steel by saw and hybrid plasma-mag processes

Sajek A.

Advances in Materials Science

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2020

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Vol. 20, nr 4(66)

75--86

EN

The aim of this article is to validate the method of conducting a multipoint temperature measurement in the area of welded joints as a tool for quality assessment of the joints in question. In order to establish a relationship between temperature readout at a given point, the value of heat input and the distance of the point form the weld axis, preliminary tests have been conducted on a set of padding welds. Correlation of measurement data analysis showed the high 0.99 level. In the second stage of the study, temperatures of joints welded with two different methods have been measured: the HPAW (Hybrid Plasma – Arc Welding) and classic SAW (Submerged Arc Welding) method. The obtained temperature curves reflect the intensity of heat input in a given welding process. When compared to thermal effects on metallographic specimens, the shapes of the curves show a potential for quality assessment of joints in production conditions. Estimating thermal effects with classic analytical methods proves imprecise with respect to advanced high-power welding processes. Monitoring temperature will allow to assess the quality of joints in the course of welding, which may be a remarkable factor in terms of limiting the HAZ (heat affected zone) tempering of joints made from MART steels (advanced high strength martensitic steel) – a phenomenon that exceedingly decreases the strength of the joints. The method for quality assessment of welded joints presented in this paper allows to extend the analysis of welding thermal conditions.

2

Comparative evaluation of various experimental and numerical simulation methods for determination of t8/5 cooling times in HPAW process weldments

Sajek A., Nowacki J.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 2

583--591

EN

The aim of this article is to provide a quantitative comparison and efficiency verification of the methods of estimating t8/5 cooling time in the process of HPAW of S960QL steel. The measurements of t8/5 welding time were conducted at the face of weld with the use of thermoelectric, pyrometric and thermovision methods. A FEM model of the joint was made, and welding simulation was done. The results of the calculations were then confronted with experimental data, and measuring methods were evaluated. Differences in the results of t8/5 time measurements were determined for the analysed methods and arranged according to the precision of results presented; the applicability of FEM for predicting the value of t8/5 time was investigated. The usability of temperature measuring methods for determining cooling time was determined, the weaknesses of non-contact measurement in terms of diversification of cooling time in a section of a welded joint were shown, and the advantages of numerical method were demonstrated. It was established that joining experimental methods for measuring cooling time of a joint with FEM analysis allows to obtain a desired resolution of prediction. In this way, the technology for hybrid welding of advanced high-strength steels can be designed more efficiently.

3

Numerical simulation the thermal cycle of the PAW-MAG hybrid welding of advanced high strength steels

Nowacki J., Sajek A.

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2016

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Vol. 60, No. 6

13--19

PL

Zbadano możliwość wyznaczania czasu t8/5 za pomocą metody elementów skończonych. Badaniom poddano modelowe złącze spawane metodą hybrydową PAW-MAG ulepszanych cieplnie stali AHSS S960QL. Porównano czas t8/5 dla charakterystycznych stref złącza przy stałej ilości wprowadzonego ciepła. Dostrzeżono istotne różnice w szybkości stygnięcia wynikające ze zróżnicowanej geometrii złącza i niesymetrycznej dystrybucji ciepła. Zdefiniowano możliwości metody elementów skończonych z zastosowaniem modelowania przestrzennego w badaniu historii cieplnej dowolnego obszaru złącza spawanego. W wyniku porównania analizowanego sposobu określania czasu t8/5 z tradycyjnymi metodami pomiarowymi i analitycznymi wykazano znacząca przewagę MES polegającą na dokładnej i całościowej indukcji cyklu w całym przekroju złącza w przeciwieństwie do eksperymentalnych metod stykowych i bezstykowych, które uśredniają pomiar na jego powierzchni lub tylko w osi spoiny. W aspekcie różnic w czasie t8/5 sięgających 1,5 s w obszarze złącza i bardzo wąskiego zakresu tolerancji wartości czasu stygnięcia stali AHSS ulepszanej cieplnie, uznano metodę elementów skończonych z zastosowaniem modelowania przestrzennego za niezbędne narzędzie do projektowania złączy spawanych stali AHSS.

EN

The research described in the article was concerned with the possibility of determining time t8/5 using the Finite Element Method. The research-related tests involved a joint made of AHSS S960QL using the PAW-MAG method. Values of time t8/5 were compared in relation to characteristic zones of the joint and constant heat input values. Differences in cooling rates related to the diversified geometry of a joint and the asymmetric distribution of heat proved significant. The research involved the identification of possibilities offered by the Finite Element Method involving space modelling in the examination of the thermal history of any welded joint area. The comparison of the analysed manner of determining time t8/5 with traditional measurement and analytical methods revealed the significant advantage of the FEM consisting in the accurate and complete induction of a cycle in the entire cross-section of the joint in contrast with experimental contact and non-contact methods averaging the measurement on the joint surface or only in the weld axis. In view of differences related to time t8/5 reaching 1.5 seconds in the joint area and the very narrow range of the tolerance concerning the value of the cooling time of AHSS, the Finite Element Method involving the use of space modelling was recognised as a necessary tool when designing welded joints made of Advanced High Strength Steels.