Investigation of the microstructure and tensile properties of dual-phase steels of different strength levels joined by resistance spot welding

Abstract

In this study, DP600/DP1000 and DP600/DP1200 resistance spot welding processes were performed. Welding applications were carried out at 7 kA constant welding current and 5 different electrode pressures (2, 3, 4, 5 and 6 Bar). The study focused on microstructural analysis, microhardness and tensile-shear testing. It was found that the welds consisted of 3 distinct regions. The microstructure differed between the regions. The volume fraction of martensite increased in the weld metal. As the electrode pressure decreased, the tensile-shear force increased for both joint types. The failures occurred on the DP600 side. The pull-out type failure occurred in all joints. Hardness values increased from base metal to weld metal in all parameters.

Keywords

• Resistance spot welding
• Microstructure
• Tensile-Shear force
• Pull-out type failure
• Microhardness

Nokta direnç kaynağı ile birleştirilen farklı dayanım seviyelerine sahip çift fazlı çeliklerin mikroyapı ve çekme özelliklerinin incelenmesi

Öz

Bu çalışmada, DP600/DP1000 ve DP600/DP1200 nokta direnç kaynak işlemleri gerçekleştirilmiştir. Kaynak uygulamaları 7 kA sabit kaynak akımı ve 5 farklı elektrot basıncında (2, 3, 4, 5 ve 6 Bar) gerçekleştirilmiştir. Çalışma mikroyapısal analiz, mikrosertlik ve çekme-makaslama testlerine odaklanmıştır. Kaynakların 3 farklı bölgeden oluştuğu tespit edilmiştir. Mikroyapı, bölgeler arasında farklılık göstermiştir. Kaynak metalinde martenzit hacim oranı artmıştır. Elektrot basıncı azaldıkça çekme-makaslama kuvveti her iki bağlantı tipi için de artmıştır. Kırılmalar, DP600 tarafında meydana gelmiştir. Düğme tipi kırılma tüm bağlantılarda meydana gelmiştir. Sertlik değerleri tüm parametrelerde esas metalden kaynak metaline doğru artmıştır.

Anahtar Kelimeler

• Nokta direnç kaynağı
• Mikroyapı
• Çekme-Makaslama kuvveti
• Düğme tipi kırılma
• Mikrosertlik

Kaynakça

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