Position welding of 960 MPa ultra-high-strength steel

Kah

Mvola

et al. 2019

Metals

The effect of heat input on the microstructure and mechanical properties of dissimilar S700MC/S960QC high-strength steels (HSS) using undermatched filler material was evaluated. Experiments were performed using the gas metal arc welding process to weld three samples, which had three different heat input values (i.e., 15 kJ/cm, 7 kJ/cm, and 10 kJ/cm). The cooling continuous temperature (CCT) diagrams, macro-hardness values, microstructure formations, alloy element compositions, and tensile test analyses were performed with the aim of providing valuable information for improving the strength of the heat-affected zone (HAZ) of both materials. Micro-hardness measurement was conducted using the Vickers hardness test and microstructural evaluation by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The mechanical properties were characterized by tensile testing. Dissimilar welded samples (S700MC/S960QC) with a cooling rate of 10 • C/s (15 kJ/cm) showed a lower than average hardness (210 HV5) in the HAZ of S700MC than S960QC. This hardness was 18% lower compared to the value of the base material (BM). The best microstructure formation was obtained using a heat input of 10 kJ/cm, which led to the formation of bainite (B, 60% volume fraction), ferrite (F, 25% volume fraction), and retained austenite (RA, 10%) in the final microstructure of S700MC, and B (55%), martensite (M, 45%), and RA (10%), which developed at the end of the transformation of S960QC. The results showed the presence of 1.3 Ni, 0.4 Mo, and 1.6 Mn in the fine-grain heat-affected zone of S700MC. The formation of a higher carbide content at a lower cooling rate reduced both the hardness and strength.

Section: Introductionmentioning

confidence: 99%

Effect of Heat Input and Undermatched Filler Wire on the Microstructure and Mechanical Properties of Dissimilar S700MC/S960QC High-Strength Steels

Kah

Mvola

et al. 2019

Metals

“…By increasing softening the heat-affected zone (HAZ) of dissimilar welded joints of high-strength and ultra-high-strength steel when using overmatched filler wire can lead to the beneficial outcomes of lighter weight and increase of strength in the HAZ [5], [7], [8]. The gas metal arc welding process (GMAW) is an arc welding process that is suitable for welding high and ultra-high-strength steels [9][10][11][12][13]. Welding of dissimilar high-strength and ultra-high-strength steel is a difficult task that depends mainly on the heat source parameter for it to improve mechanical properties in the HAZ [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…It is the temperature range of the suppressed recrystallization. On the 960QC side, this steel has a higher strength of more than 900 MPa and above [4], [11], [23]. The production process is obtained by carefully defined chemical composition and manufacturing methods used [24,25].…”

Section: Introductionmentioning

confidence: 99%

Thermo mechanical and microstructural constituents of dissimilar S700MC-S960QC high-strength steel welded joints using overmatched filler wire

Kibong

Timba

et al. 2022

IJET

In this study, a mechanical and microstructural constituent of welded joints of dissimilar high-strength and ultra-high-strength steels (S700MC/S960QC) using overmatched filler wire was evaluated. Three different heat inputs (18 kJ/cm, 8 kJ/cm, and 10 kJ/cm) and overmatched filler wire were applied using the GMAW process. Micro-hardness measurement was conducted using Vickers hardness test, tensile test, and microstructural constituents by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were performed in this analysis. A dissimilar welded sample with a cooling time of 51s (18 kJ/cm) showed a substantial hardness reduction in the fine grain heat-affected zone (HAZ) of the S700MC steel side, which was between 220-240 HV5. The cause could be the increase of heat input but also the use of overmatched filler wire, which can be the result of an increase of ferrite to austenite formation in the HAZ. SEM/EDS results confirmed the increase of carbide clusters, and tempered Martensite in the CGHAZ of the S960QC side, and ferrite-bainite on the S700MC side. An increase in the presence of high carbide content and the formation of Ni, Mo, and Mn were observed on the S960QC side. The increase of carbide formation in the CGHAZ of both sides reduced the hardness and strength of the welded joints. The tensile test confirms the softening observed in the FGHAZ of the S700MC side, which caused the joint fracture on this side during the test.

“…Other research concentrates on increasing processing methods for alreadydeveloped UHSS/AHSS materials. Many researchers see occasions for emerging new approaches to generate and form these brand-new steels, such as introduction heating procedures and advanced cooling techniques [6,[11][12][13]. In the research, some results were carried out in the prevention of carbide precipitation by investigated the optimal quenching temperature in the exceptional steel products such as sheet steel [14,15].…”

Section: Introductionmentioning

confidence: 99%

Feasibility study of welding dissimilar Advanced and Ultra High Strength Steels

Reviews on Advanced Materials Science

Kah

Salminen

et al. 2020

This study concerns the weldability of dissimilar Ultra high-strength steel (UHSS) and advanced high-strength steel (AHSS), which is used in the modern machine industry. The materials offered superior strength as well as relatively low weight, which reduces microstructure contamination during a live cycle. The choice of the welding process base of the base material (BM) and welding parameters is essential to improve the weld joint quality. S700MC/S960QC was welded using a gas metal arc welding (GMAW) process and overmatched filler wire, which was performed using three heat input (7, 10, and 15 kJ/cm). The weld samples were characterized by a Vickers-hardness test, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The test reveals a decrease of softening areas in the HAZ and the formation of the stable formation of Bainite-Ferrite for S700MC and Bainite-martensite for S960QC when the heat input of 10 kJ/cm is used. It is recommended to use the GMAW process and Laser welding (Laser beam-MIG), with an optimal welding parameter, which will be achieved a high quality of manufacturing products.