scholarly journals Analysis of Fracture Modes of Resistance Spot Welded Hot-Stamped Boron Steel

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 764 ◽  
Author(s):  
Yixi Zhao ◽  
Yansong Zhang ◽  
Xinmin Lai
Keyword(s):  
Transition Zone ◽  
Base Material ◽  
High Strength ◽  
Boron Steel ◽  
Delta Ferrite ◽  
Fracture Modes ◽  
Resistance Spot ◽  
Pull Out ◽  
Lap Shear ◽  
Spot Welded

Fracture modes of resistance spot welded ultra-high strength hot-stamped boron steel via lap-shear test are different from that of the traditional advanced high strength steel due to the difference in geometrical size and material property of the spot welds. In this paper, lap-shear fracture modes of resistance spot welding joints were analyzed and joint characteristics that affecting the fracture behavior were discussed. Three fracture modes were found to change from interfacial fracture (IF) to pull-out fracture (PF) with the increase of nugget diameter. For PF I mode, the fracture initiated at the transition zone between the fusion zone and upper-critical heat affected zone (HAZ) and propagated along the thickness of the nugget. For PF II mode, during which the failure initiated at the sub-critical HAZ where the softest zone occurred, and it propagated to the base material. Obvious hardness decrease was observed in the transition zone with the formation of the delta ferrite at the fusion boundary due to the relatively high amount of alloying element in the hot-stamped boron steel, which could provide the reason for route of PF I extending along this zone. Fluctuation in the hardness in the transition zone led to the existence of both PF I and PF II at the same welding current.

scholarly journals Microstructure and Mechanical Performance of Resistance Spot Welded Martensitic Advanced High Strength Steel

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1021
Author(s):  
Yunzhao Li ◽  
Huaping Tang ◽  
Ruilin Lai
Keyword(s):  
Mechanical Properties ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Strong Dependence ◽  
High Strength ◽  
Weld Nugget ◽  
Resistance Spot ◽  
Pull Out ◽  
Cross Tension ◽  
Spot Welded

Resistance spot welded 1.2 mm (t)-thick 1400 MPa martensitic steel (MS1400) samples are fabricated and their microstructure, mechanical properties are investigated thoroughly. The mechanical performance and failure modes exhibit a strong dependence on weld-nugget size. The pull-out failure mode for MS1400 steel resistance spot welds does not follow the conventional weld-nugget size recommendation criteria of 4t0.5. Significant softening was observed due to dual phase microstructure of ferrite and martensite in the inter-critical heat affected zone (HAZ) and tempered martensite (TM) structure in sub-critical HAZ. However, the upper-critical HAZ exhibits obvious higher hardness than the nugget zone (NZ). In addition, the mechanical properties show that the cross-tension strength (CTS) is about one quarter of the tension-shear strength (TSS) of MS1400 weld joints, whilst the absorbed energy of cross-tension and tension-shear are almost identical.

Failure Performance Analysis of Resistance Spot Welded Advanced High Strength Steel Sheets

2015 ◽  
Vol 651-653 ◽  
pp. 895-900 ◽  
Author(s):  
Woo Ram Noh ◽  
Young Woo Koh ◽  
Jong Hwa Hong ◽  
Xin Yang ◽  
Kwan Soo Chung
Keyword(s):  
High Strength Steel ◽  
High Strength ◽  
Tension Test ◽  
Weld Nugget ◽  
Advanced High Strength Steel ◽  
Resistance Spot ◽  
Steel Sheets ◽  
Lap Shear ◽  
Simple Tension ◽  
Spot Welded

A numerical method to predict failure performance was developed for resistance spot welded AHSS (advanced high strength steel) sheets in this work and applied for a TRIP (transformation induced steel sheets) 980 sheet. For the numerical analysis, utilizing the numerical inverse calibration method, hardening data and fracture criteria were characterized for the base and the weld nugget based on the standard simple tension test and a newly designed miniature tension test, respectively. The characterized properties of the base and the weld nugget were then applied to analyze failure performance in the coupon tests of the lap-shear and U-shape tension tests carried out for welded sheets. The analysis was performed under the quasi-static condition in this early effort and showed reasonably good agreement with experiments both in failure modes and strength.

Evaluation of High Temperature Properties and Microstructural Characterization of Resistance Spot Welded Steel Lap Shear Joints

2016 ◽  
Vol 35 (2) ◽  
pp. 145-151
Author(s):  
R. K. Gupta ◽  
V. Anil Kumar ◽  
Paul G. Panicker
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Joint Strength ◽  
Microstructural Characterization ◽  
Parent Metal ◽  
Resistance Spot ◽  
Lap Shear ◽  
Stainless Steel 304 ◽  
Ss 304 ◽  
Spot Welded

AbstractJoining of thin sheets (0.5 mm) of stainless steel 304 and 17-4PH through resistance spot welding is highly challenging especially when joint is used for high temperature applications. Various combinations of stainless steel sheets of thickness 0.5 mm are spot welded and tested at room temperature as well as at high temperatures (800 K, 1,000 K, 1,200 K). Parent metal as well as spot welded joints are tested and characterized. It is observed that joint strength of 17-4PH steel is highest and then dissimilar steel joint of 17-4PH with SS-304 is moderate and of SS-304 is lowest at all the temperatures. Joint strength of 17-4PH steel is found to be >80% of parent metal properties up to 1,000 K then drastic reduction in strength is noted at 1,200 K. Gradual reduction in strength of SS-304 joint with increase in temperature from 800 to 1,200 K is noted. At 1,200 K, joint strength of all combinations of joints is found to be nearly same. Microstructural evaluation of weld nugget after testing at different temperatures shows presence of tempered martensite in 17-4PH containing welds and homogenized structure in stainless steel 304 weld.

scholarly journals Effect of Retained Austenite and Non-Metallic Inclusions on the Mechanical Properties of Resistance Spot Welding Nuggets of Low-Alloy TRIP Steels

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1064 ◽  
Author(s):  
Víctor H. Vargas Cortés ◽  
Gerardo Altamirano Guerrero ◽  
Ignacio Mejía Granados ◽  
Víctor H. Baltazar Hernández ◽  
Cuauhtémoc Maldonado Zepeda
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Retained Austenite ◽  
High Strength ◽  
Microstructural Characterization ◽  
Spot Welds ◽  
Trip Steels ◽  
Resistance Spot ◽  
Lap Shear ◽  
Metallic Inclusions

The combination of high strength and formability of transformation induced plasticity (TRIP) steels is interesting for the automotive industry. However, the poor weldability limits its industrial application. This paper shows the results of six low-alloy TRIP steels with different chemical composition which were studied in order to correlate retained austenite (RA) and non-metallic inclusions (NMI) with their resistance spot welded zones to their joints’ final mechanical properties. RA volume fractions were quantified by X-ray microdiffraction (µSXRD) while the magnetic saturation technique was used to quantify NMI contents. Microstructural characterization and NMI of the base metals and spot welds were assessed using scanning electron microscopy (SEM). Weld nuggets macrostructures were identified using optical microscopy (OM). The lap-shear tensile test was used to determine the final mechanical properties of the welded joints. It was found that NMI content in the fusion zone (FZ) was higher than those in the base metal and heat affected zone (HAZ). Whereas, traces of RA were found in the HAZ of highly alloyed TRIP steels. Lap-shear tensile test results showed that mechanical properties of spot welds were affected by NMI contents, but in a major way by the decomposition of RA in the FZ and HAZ.

Microstructures in a resistance spot welded high strength dual phase steel

2010 ◽  
Vol 61 (3) ◽  
pp. 341-346 ◽  
Author(s):  
Xinsheng Liao ◽  
Xiaodong Wang ◽  
Zhenghong Guo ◽  
Min Wang ◽  
Yixiong Wu ◽  
...  
Keyword(s):  
Dual Phase Steel ◽  
High Strength ◽  
Dual Phase ◽  
Resistance Spot ◽  
Spot Welded

Corrosion Characterization of Resistance Spot Welded Aluminum and Steel Couple

2019 ◽  
Author(s):  
Surender Maddela ◽  
Blair E. Carlson
Keyword(s):  
Corrosion Resistance ◽  
Shear Strength ◽  
Galvanic Corrosion ◽  
Corrosion Testing ◽  
Lap Shear Strength ◽  
Resistance Spot ◽  
Lap Shear ◽  
Cyclic Corrosion ◽  
Steel Substrates ◽  
Spot Welded

Abstract The corrosion resistance of resistance spot welded (RSW) Al-steel couples of varying combinations of 6016-T4 aluminum alloys and steel substrates, including with and without adhesive at the faying interface has been successfully evaluated, and compared to corresponding self-pierce riveted (SPR) couples. The corrosion resistance of resistance spot welded Al-steel couples has performed well in cyclic corrosion testing (GMW 17026) and the results are comparable to or better than that of self-pierce riveted couples. SPR couples are more susceptible to galvanic corrosion than resistance spot-welded couples based upon experimentally measured electrochemical potentials from actual joints. The presence of adhesive acts significantly to reduce galvanic corrosion between aluminum alloy and steel substrates, and moreover tensile lap-shear strength significantly increased with structural adhesive for both RSW and SPR joining systems. However, despite the presence of adhesive the lap-shear strength was reduced by more than 50% after cyclic corrosion testing to strength levels comparable to the lap-shear strength of couples having no adhesive and tested in ambient conditions.

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