Remote Fibre Laser Welding of Advanced High Strength Martensitic Steel

Prijanovič, Urban; Tonkovič, Marica Prijanovič; Trdan, Uroš; Pleterski, M.; Jezeršek, Matija; Klobčar, Damjan

doi:10.3390/met10040533

Cited by 11 publications

(9 citation statements)

References 18 publications

(55 reference statements)

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“…Martensitic steel is always facing difficulties in conventional fusion welding due to the high heat input. In addition to the easy formation of solidification cracking, the formation of brittle, coarse martensite in the fusion zone and the softening in the heat affected zone (HAZ) [1][2][3] result in a weak weld joint. Recently, the application of friction stir welding (FSW) to martensitic steels has been paid attention to in consideration of the advantages of low heat input and severe plastic deformation during welding [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Suppression of softening in heat affected zone by Mo addition in friction stir welded martensitic steel

Ushioda

Fujii

2022

Science and Technology of Welding and Joining

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The drastic softening in the heat affected zone (HAZ) of friction stir welded 0.2C-2Si-3Mn martensitic steel occurred due to the martensite tempering in the subcritical temperature range just below A 1 temperature in HAZ. It was revealed that the softening in the subcritical HAZ was successfully suppressed by Mo addition. The optimum condition was found to be 3 wt-% Mo addition with the solution temperature of 1120°C, where densely distributed nanometer-sized Mo 2 C were confirmed by transmission electron microscopy and atom probe tomography in the subcritical HAZ. These fine Mo 2 C precipitates gave rise to an increase in the hardness of approximately 110 HV compared with a no-Mo-added sample, which was in good agreement with the predicted precipitation strengthening value based on the Ashby-Orowan model.

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Section: Introductionmentioning

confidence: 99%

Suppression of softening in heat affected zone by Mo addition in friction stir welded martensitic steel

Ushioda

Fujii

2022

Science and Technology of Welding and Joining

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“…High strength DP steel, with an ultimate tensile strength about 980 MPa (DP980), is composed of ferrite matrix along with a relatively high volume fraction of martensite, ranging from 45 to 55 pct. Softening (reduction of hardness with respect to the base metal) in the sub-critical heat-affected zone (SC-HAZ) due to martensite tempering in DP steels has been widely reported when subjected to different welding processes such as resistance spot welding (RSW) [2][3][4][5][6], laser beam welding (LBW) [7][8][9][10][11][12], and gas metal arc welding (GMAW) [13][14][15][16][17][18][19][20][21]. Softening occurring at the SC-HAZ of welded DP steels is predominantly attributed to the tempering of martensite without major influence from the ferrite matrix [22].…”

Section: Introductionmentioning

confidence: 99%

On the Measurability and Predictability of HAZ Softening in GMAW of Automotive DP980 Steel

Martínez-González

López-Baltazar

Alvarado-Hernández

et al. 2022

Metals

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Dual Phase (DP) steel, composed of a ferrite matrix with dispersed islands of martensite, has become popular in auto-body car construction due to its outstanding mechanical properties (i.e., high strength and good ductility). DP steel softens at the sub-critical heat-affected zone (SC-HAZ) when subjected to welding thermal cycles, owing to the tempering of the martensite phase. In this work, DP980 steel was subjected to varied thermal cycles: (a) furnace-tempering treatment, (b) gas metal arc welding (GMAW), and (c) resistance spot welding (RSW), in order to characterize the tempering of martensite below the Ac1 critical temperature and at the sub-critical heat-affected zone (SC-HAZ) in the case of the welded specimens. The coarsening stage of cementite phase was characterized through microstructure observations and hardness measurements. As expected, the comparative results indicated an advanced stage of the martensite tempering in the furnace heat-treated specimens, followed by the GMAW and the RSW specimens. Further, developed softening kinetic models have been suitably employed and adjusted in order to predict the extent of softening along the SC-HAZ of the GMAW specimen. Finally, as the advanced stage of cementite coarsening is due to the influence of the arc welded thermal cycle, a reasonable estimation of the hardness profile was obtained, particularly for tempering temperatures above 400 °C.

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“…For instance, Reference [ 17 ] presents the results of Docol 1200 M martensitic steel welding. In this study, the very thick sheets were joined in a lap joint configuration.…”

Section: Introductionmentioning

confidence: 99%

High Martensitic Steel after Welding with Micro-Jet Cooling in Microstructural and Mechanical Investigations

et al. 2021

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Modern means of transport will play a significant role in the smart city. In the automotive industry, high-strength steels such as Docol are employed more often. This kind of material is relatively not very well weldable. The main reason is related to the Heat Affect Zone, the region in which cracks occur. Another disadvantage is connected with differences in values of ultimate strength of parent and weld material. The differences can be diminished using the correct welding process, which employs nickel and molybdenum electrode wires at much lower sulfur content. The weld metal deposit contains mainly martensite and bainite with coarse ferrite, while the parent material contains mainly martensite and rather fine ferrite. New technology, micro-jet cooling after the joining process enables to obtain the microstructure of weld metal deposit at acceptable parameters. Welding with micro-jet cooling could be treated as a very promising welding Docol steels process with high industrial application. Results of non-destructive inspections on macro samples corresponded with further destructive test results (tensile strength, hardness, fatigue, metallographic structure analyses). This article aims to verify fatigue behavior of Docol 1200 M steel after welding supported by the cooling using the micro-jet technique. For the first time, micro-jet cooling was used to weld this kind of steel to check the mechanical properties of the joint, especially to determine the fatigue limit. This study is formulated as follows: investigating fatigue resistance of the Docol 1200 M weld manufactured at the cooling process with micro-jets. The joints were produced in the MAG (Metal Active Gas) technology modified by micro-jet cooling. The results collected in the fatigue test were processed in the form of the Wöhler’s S–N diagram following the fatigue limit of the weld examined. All data have indicated the possibility of obtaining a new method of welded joints with high fatigue limit minimum of 480 MPa. It could be important to achieve a tensile strength of 700 MPa while maintaining the best relative elongation at the level of the base material.

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Remote Fibre Laser Welding of Advanced High Strength Martensitic Steel

Cited by 11 publications

References 18 publications

Suppression of softening in heat affected zone by Mo addition in friction stir welded martensitic steel

Suppression of softening in heat affected zone by Mo addition in friction stir welded martensitic steel

On the Measurability and Predictability of HAZ Softening in GMAW of Automotive DP980 Steel

High Martensitic Steel after Welding with Micro-Jet Cooling in Microstructural and Mechanical Investigations

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