Effect of heat input on the mechanical properties of welded joints in high-strength steels

Pirinen, Markku; Martikainen, Yu.; Layus, Pavel; Karkhin, Victor A.; Ivanov, S. Yu.

doi:10.1080/09507116.2015.1036531

Cited by 21 publications

(16 citation statements)

References 12 publications

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“…7(b) that the higher the Δt 8/5 in the weld metal, the lower the microhardness measure in the HAZ and WM. Therefore, probably the main factor for the microhardness reduction in the HAZ and WM was the heat input increase, as the results presented by [17], [20], [22], and [23].…”

Section: Microhardness and Cooling Rates (δT 8/5 )mentioning

confidence: 82%

“…The cooling time between 800 °C and 500 °C is often used in welding. The reason is that the cooling rate of the welded joint is very important to determine its microstructure and mechanical properties [2], [18], [19], especially in HAZ [20]. The local microstructure and the properties of any point along the weld bead are determined by the thermal cycle undergone at the point in question, with the peak temperature decreasing as distance from the weld bead center line increases [18], [21].…”

Section: Microhardness and Cooling Rates (δT 8/5 )mentioning

confidence: 99%

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Bending Strength of Welded Joints in TMCP Steel Square Tubular Profiles “T” Connexions

Dalcin

Machado²,

Gonzalez³

et al. 2016

IJET

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The use of DOMEX 700 MC TM steel weldments is still little explored, due to some concern of the validity of the rules imposed by several standards and Codes for this class of steel. This material has low ductility and consequently the relation between tensile strength and yield strength is significantly lower than ordinary structural steels. For this reason, the instability phenomena are more critical than the instability phenomena of ordinary structural steels. Therefore, the aim of this study was to obtain detailed data on the mechanical efficiency of joints welded by GMAW. Six different heat inputs were used on square tubular profiles of TMCP steel. The tubular profiles were placed as a column/beam weldment with transverse and longitudinal welds positioned in relation to the loading axis. Twelve welded structures were instrumented with extensometer and tested in simple bending. Comparing the obtained data, it was verified that longitudinal welded joints presented higher bending strength than transversal welded joints. In the case of longitudinal joints, two weld beads were subjected to bending efforts, and in the case of transverse joints, only one weld bead resisted bending forces.

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Section: Microhardness and Cooling Rates (δT 8/5 )mentioning

confidence: 82%

Section: Microhardness and Cooling Rates (δT 8/5 )mentioning

confidence: 99%

Bending Strength of Welded Joints in TMCP Steel Square Tubular Profiles “T” Connexions

Dalcin

Machado²,

Gonzalez³

et al. 2016

IJET

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“…Effect of the welds have not been taken into account in temperature distribution analysis. Based on the mechanical studies [18][19] welding process has multiple effect on the connection properties. However, Franssen [16] proved that in context of heat distribution a model without the weld offers an acceptable prediction.…”

Section: Experimental Observationmentioning

confidence: 99%

10.11: Fire design of rectangular hollow section joints

et al. 2017

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The component method is a design approach for the characterization of the mechanical properties of structural joints and it is referred to in Eurocode 3 Part 1-8. Eurocode design rules for open sections are already based on the component method. The design rules for joints between tubular hollow sections are still based on simple theoretical mechanical models validated against experimental test results. However, there are research activities in progress to extend the application of the component method also to hollow section joints in the next revision of Eurocode. The fire design of steel joints is carried out in accordance with Eurocode 3 Part 2. Eurocode gives only a guidance on how the temperature of the joint components can be assessed based on the local values of thermal resistance of the joint's fire protection. The method is not sufficient for the component method and Tampere University of Technology is currently carrying out experimental fire research to better understand the temperature distributions in the vicinity of the joint. The aim of the research is to develop experimental methods to determine steel temperatures at the actual joint component, spring, locations and to transfer this information into the joint design approach based on the component method. This paper introduces an experimental research demonstrating the actual temperature distributions within the joint area and highlights the differences between the failure modes and the design criteria at normal temperature design and fire design of a joint.

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“…However, they seemed to not consider the effect of the microstructural gradient and the impact of different microhardness in the various HAZ regions. As a result, researchers studied the tensile properties of undermatch welds of QT HSS RQT701 for different heat inputs [23]. It was observed that an increase in the heat input values produces a coarsening of the microstructure of the weld metal (WM) and the HAZ.…”

Section: Introductionmentioning

confidence: 99%

Numerical and Experimental Investigation of the Heat Input Effect on the Mechanical Properties and Microstructure of Dissimilar Weld Joints of 690-MPa QT and TMCP Steel

Bayock

Kah

Layus

et al. 2019

Metals

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The study evaluates numerically and experimentally the effect of welding heat input parameters on the microstructure and hardness of the heat-affected zone (HAZ) of quenched and tempered (QT) and thermo-mechanically controlled process (TMCP) 690-MPa high-strength steel. Numerical analyses and experimental comparisons were applied using three heat input values (10, 14, and 17 kJ/cm) in order to predict the thermal fields during welding. Experimental analysis was carried out of the microstructure and microhardness behavior in different HAZ areas. The numerical values indicate that the maximum respective values of temperature measured in QT steel and TMCP steel were about 1300 and 1200 °C for a heat input of 10 kJ/cm, 1400 and 1300 °C for a heat input of 14 kJ/cm, and 1600 and 1450 °C for a heat input of 17 kJ/cm. The cooling times resulted, for a heat input of 10 kJ/cm, in numerical t8/5 (14.5 s) and experimental (18.84 s) increases in hardness in the coarse-grain heat-affected zone (CGHAZ) of the QT steel (317 HV0.1), due to the formation of bainite and lath martensite structures with grain growth. Decreased hardness in the CGHAZ of TMCP steel (240 HV0.1) was caused by primary recrystallization of the microstructure and the formation of more equilibrium products of austenite decomposition. Increasing the heat input (14 to 17 kJ/cm) led to numerical t8/5 (29 s) and experimental (36 s) decreases in hardness in the CGHAZ of QT steel (270 HV0.1) due to the full austenite (thermal weld cycle), and maintained the relative value of TMCP steel (235 HV0.1).

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Effect of heat input on the mechanical properties of welded joints in high-strength steels

Cited by 21 publications

References 12 publications

Bending Strength of Welded Joints in TMCP Steel Square Tubular Profiles “T” Connexions

Bending Strength of Welded Joints in TMCP Steel Square Tubular Profiles “T” Connexions

10.11: Fire design of rectangular hollow section joints

Numerical and Experimental Investigation of the Heat Input Effect on the Mechanical Properties and Microstructure of Dissimilar Weld Joints of 690-MPa QT and TMCP Steel

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