Hardening characteristics of CO2 laser welds in advanced high strength steel

Han, Tae-Kyo; Park, Bong-Gyu; Kang, Chung Gil

doi:10.1007/s12540-012-3014-2

Cited by 23 publications

(14 citation statements)

References 12 publications

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“…Although a wide WM and HAZ were generated under lower-welding-speed conditions because of the relatively high heat input, the average hardness within the WM and minimum hardness within the HAZ, which determines the HAZ failure, were almost constant regardless of the heat input ( Figure 3). These results are in good agreement with the study of Han et al [7]. The hardness profiles were determined by the thermal history and chemical composition of the BM.…”

Section: Laser Weld Characteristics Under Various Welding Conditionssupporting

confidence: 92%

“…Laser welding enables a low heat input during welding and the hardness of the WM can be increased similarly to that of a water-quenched specimen [7]. As shown in Figure 3, the average hardness within the WM and the minimum hardness of the HAZ were maintained, even for different welding speeds and resultant heat inputs.…”

Section: Estimation Of Hardness With Carbon Equivalentmentioning

confidence: 93%

“…When welding a conventional mild steel, the weld metal (WM) and heat-affected zone (HAZ) are subjected to a high cooling rate during the solidification and their microstructures become harder than those of the base material (BM). For the case of high-strength steel containing martensite, the strength difference between the WM and BM was reduced, even though the WM can almost become fully hardened by laser welding [7]. Because the martensite fraction within the BM increases, the strength of BM becomes higher.…”

Section: Introductionmentioning

confidence: 99%

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Tensile–Shear Fracture Behavior Prediction of High-Strength Steel Laser Overlap Welds

Kang

Jeon

Han

et al. 2018

Metals

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Abstract:A wider interface bead width is required for laser overlap welding by increasing the strength of the base material (BM) because the strength difference between the weld metal (WM) and the BM decreases. An insufficient interface bead width leads to interface fracturing rather than to the fracture of the BM and heat-affected zone (HAZ) during a tensile-shear test. An analytic model was developed to predict the tensile-shear fracture location without destructive testing. The model estimated the hardness of the WM and HAZ by using information such as the chemical composition and tensile strength of the BM provided by the steel makers. The strength of the weldments was calculated from the estimated hardness. The developed model considered overlap weldments with similar and dissimilar material combinations of various steel grades from 590 to 1500 MPa. The critical interface bead width for avoiding interface fracturing was suggested with an accuracy higher than 90%. Under all the experimental conditions, a bead width that was only 5% larger than the calculated value could prevent the fracture of the interface.

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Section: Laser Weld Characteristics Under Various Welding Conditionssupporting

confidence: 92%

Section: Estimation Of Hardness With Carbon Equivalentmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Tensile–Shear Fracture Behavior Prediction of High-Strength Steel Laser Overlap Welds

Kang

Jeon

Han

et al. 2018

Metals

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“…After consulting present paper 19) (Thermal conductivity 30.0 W/m/K, Density 7 860 kg/m 3 , heat efficiency 50% and specific heat capacity 680 J/kgK) and the data in Tables 1 and 2, the t9/4 was calculated to be about 1.3 s, much faster than the critical speed of martensitic transformation of 22MnB5 steel. 20) As a result, the microstructure of the WZ fully contained martensite with a lathy morphology, as can be seen in Fig.…”

Section: Microstructurementioning

confidence: 99%

Retraction: Microstructure and Properties of Fiber Laser Welded Joints of Ultrahigh-strength Steel 22MnB5 and its Dissimilar Combination with Q235 Steel

Jia

Yang

et al. 2014

ISIJ Int.

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This paper is to analyze the microstructure, microhardness, tensile and fatigue properties of the welded joints performed by a fiber laser on the 22MnB5 and Q235 steels in similar and dissimilar combinations. The result shows that the weld zone (WZ) consisted of lathy martensite, and the heat affected zone (HAZ) of 22MnB5 could be divided into 3 parts: quenched zone, incomplete quenched zone and the tempered zone which didn't appear in the Q235 HAZ. The WZ had the highest hardness, while the HAZ was very narrow with a very fast drop in hardness. A soft zone existed in the HAZ of 22MnB5, and it was absent on the Q235 side. With the welding speed increasing, the martensite in the WZ became thinner and shorter, and the width of HAZ decreased. All the tensile and fatigue specimens of the similar 22MnB5 welded joints were broken in the HAZ. The base metal (BM) had a higher fatigue life than the similar 22MnB5 welded joints. The fatigue fracture contained 3 parts: crack initiation region which occurred from the specimen surface, crack propagation region and the final fast fracture region.

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“…Han et al [35] examined the laser weldability of thin high strength steel sheets using a high-energy density beam and high welding speeds of 4-10 m/min. They found that the maximum hardness of the FZ did not vary with the welding speed, and it was similar to that of the water-quenched specimen.…”

Section: Effect Of Heat Input On Mechanical Propertiesmentioning

confidence: 99%

Effects of Phase Evolution on Mechanical Properties of Laser-Welded Ferritic Fe-Al-Mn-C Steel

Kang

Kim

Han

et al. 2017

Metals

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Abstract:In the present study, the evolution of microstructure in laser-welded joints of ferrite-based dual-phase Fe-Al-Mn-C steel sheets was analyzed and its effect on the mechanical properties of the joints was investigated. Laser welding was performed using different powers and welding speeds to attain different heat inputs. Electron backscatter diffraction (EBSD) examinations and hardness measurements were used to characterize the microstructure of the welds. The tensile properties were found to depend on the heat input, but joint strength exceeding that of the base metal (BM) were obtained at low heat inputs. However, the fracture location shifted from the base metal to the heat-affected zone (HAZ) as the heat input was increased. The HAZ consisted of a mixture of austenite, ferrite and martensite, and its width increased with increasing the heat input. It was supposed that the incompatibility between the ferrite, austenite and martensite phases led to early void formation and fracturing of the phase interfaces in the wide HAZ.

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Hardening characteristics of CO2 laser welds in advanced high strength steel

Cited by 23 publications

References 12 publications

Tensile–Shear Fracture Behavior Prediction of High-Strength Steel Laser Overlap Welds

Tensile–Shear Fracture Behavior Prediction of High-Strength Steel Laser Overlap Welds

Retraction: Microstructure and Properties of Fiber Laser Welded Joints of Ultrahigh-strength Steel 22MnB5 and its Dissimilar Combination with Q235 Steel

Effects of Phase Evolution on Mechanical Properties of Laser-Welded Ferritic Fe-Al-Mn-C Steel

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