Effects of Cover Sheets on the Nugget Growth and Fracture Behavior of Resistance Spot Welded Q&amp;P980 Steel Joints

Ling, Zhang; Chen, Ting; Kong, Liang; Wang, Min

doi:10.1186/s10033-022-00717-0

Cited by 4 publications

(1 citation statement)

References 23 publications

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“…It is also believed that this contributed to the formation of coarse grains in the welded joint due to the delayed cooling of the joint caused by the RPH process. The region where the highest temperature is reached in coarse-grained HAZ is above the Ac 3 value and is the area where there is enough time for the growth of austenite grains [34,35].…”

Section: Microstructure Investigationsmentioning

confidence: 99%

Regional Pre-Heat Treatment System Development and Applications for HAZ in RSW Joining of High-Strength Steels

Aydın

HIDIROĞLU²,

Kahraman³

2023

Preprint

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STRENX and DP steels are advanced high-strength dual-phase steel types used in the automotive industry for producing lightweight vehicles that have low cost, high fuel efficiency, and can carry more load volume. In this study, STRENX 700 CR and DP 800 steels were joined by resistance spot welding (RSW) using medium frequency direct current (MFDC). Some parts were joined under atmospheric conditions, while others were joined by applying regional pre-heating (RPH) to their heat-affected zones (HAZ) before welding. The design, manufacturing, and adaptation of the RPH system to the RSW machine were carried out as part of this study, considering it as a new system. After the joining process, non-destructive (visual inspection, magnetic particle) and destructive (microhardness, tensile-shear, cross-tension, fatigue) tests were performed on RSW connections between STRENX 700 CR and DP 800 steels. Hardness tests revealed that the RPH applied to the HAZ before welding reduced the hardness of the weld metal by approximately 8%, while the microstructure analysis showed that the RPH increased both the weld metal and the HAZ width. The tensile-shear strength increased by about 7%, and the cross-tension test strength increased by about 5% with the RPH applied to the HAZ before welding. In both the tensile-shear and cross-tension tests, all failures occurred in the form of button shearing from the HAZ. The RPH treated specimens showed the highest fatigue life, with an average of 947,632 cycles.

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Section: Microstructure Investigationsmentioning

confidence: 99%

Regional Pre-Heat Treatment System Development and Applications for HAZ in RSW Joining of High-Strength Steels

Aydın

HIDIROĞLU²,

Kahraman³

2023

Preprint

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Lap-Shear Performance of Weld-Bonded Mg Alloy and Austenitic Stainless Steel in Three-Sheet Stack-Up

Manladan,

Hamza,

Ramesh

et al. 2024

Chin. J. Mech. Eng.

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With the growing interest in utilizing Mg and austenitic stainless steel (ASS) in the automotive sector, joining them together in three-sheet configuration is inevitable. However, achieving this task presents considerable challenges due to the large differences in their physical, metallurgical and mechanical properties. To overcome these challenges, the feasibility of using weld-bonding to join Mg alloy/ASS/ASS was investigated. The nugget formation, interface characteristics, microstructure and mechanical properties of the joints were investigated. The results show that the connection between the Mg alloy and upper ASS was achieved through the combined effect of the cured adhesive and weld-brazing in the weld zone. On the other hand, a metallurgical bond was formed at the ASS/ASS interface. The Mg nugget microstructure exhibited fine columar grains composed predominantly of primary α-Mg grains along with a eutectic mixture of α-Mg and β-Mg17Al12. The nugget formed at the ASS/ASS interface consisted largely of columnar grains of austenite, with some equiaxed dendritic grains formed at the centerline of the joint. The weld-bonded joints exhibited an average peak load and energy absorption of about 8.5 kN and 17 J, respectively (the conventional RSW joints failed with minimal or no load application). The failure mode of the joints changed with increasing welding current from interfacial failure via the Mg nugget/upper ASS interface to partial interfacial failure (part of the Mg nugget was pulled out of the Mg sheet). Both failure modes were accompanied by cohesive failure in the adhesive zone.

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Enhancing weld strength in high-strength steels: the role of regional preheating in RSW

Aydin,

Hıdıroğlu,

Kahraman

2024

Materials Testing

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In this study, automotive in sector use STRENX 700 CR and DP 800 steels were joined by resistance spot welding using medium frequency direct current. Some parts were joined under atmospheric conditions, while others were joined by applying regional preheating to their heat-affected zones before welding. The design, manufacturing, and adaptation of the preheating system to the welding machine were carried out as part of this study, considering it as a new system. After the joining process, nondestructive and destructive tests were performed on resistance spot welding connections between STRENX 700 CR and DP 800 steels. Hardness tests revealed that the preheating applied to the heat-affected zones before welding reduced the hardness of the weld metal by approximately 8 %, while the microstructure analysis showed that the regional preheating increased both the weld metal and the heat-affected zones width. The tensile-shear strength increased by about 7 %, and the cross-tension test strength increased by about 5 % with the preheating applied to the heat-affected zones before welding. In both the tensile-shear and cross-tension tests, all failures occurred in the form of button shearing from the heat-affected zones. The regional preheating treated specimens showed the highest fatigue life, with an average of 947,632 cycles.

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Effects of Cover Sheets on the Nugget Growth and Fracture Behavior of Resistance Spot Welded Q&P980 Steel Joints

Cited by 4 publications

References 23 publications

Regional Pre-Heat Treatment System Development and Applications for HAZ in RSW Joining of High-Strength Steels

Regional Pre-Heat Treatment System Development and Applications for HAZ in RSW Joining of High-Strength Steels

Lap-Shear Performance of Weld-Bonded Mg Alloy and Austenitic Stainless Steel in Three-Sheet Stack-Up

Enhancing weld strength in high-strength steels: the role of regional preheating in RSW

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