Mechanical and corrosion properties of spot‐welded high‐strength austenitic stainless steel EN 1.4318

Mechanical and corrosion properties of spot‐welded high‐strength austenitic stainless steels EN 1.4318 2H/C1150 and EN 1.4318 2H/C850 were studied. Microhardness measurements, lap shear and cross‐tension tests, corrosion fatigue tests and corrosion tests were carried out. The corrosion environment was 3.5% sodium chloride solution at +50 °C in the corrosion fatigue tests and 3.5% sodium chloride solution at ambient temperature in the electrochemical pitting corrosion tests. Stainless steel EN 1.4318 2H/C850, t  = 1.92 mm, exhibited better fatigue endurance than EN 1.4318 2H/C1150, t  = 1.2 mm, and EN 1.4318 2H/C850, t  = 1.0 mm, stainless steels did. There were no significant differences between the stainless steels of different strength levels (2H/C850 vs . 2H/C1150) in the line load range analysis of the fatigue data. High hardness gradient was found in the heat‐affected zone (HAZ) of EN 1.4318 2H/C1150 stainless steels. EN 1.4318 2H/C1150, t  = 1.2 mm, stainless steels seemed to have slightly higher lap shear strength with the same nugget diameter as EN 1.4318 2H/850, t  = 1.9 mm, stainless steel. In the case of EN 1.4318 2H/C1150 stainless steel increase in the nugget diameter bigger than required 5√ t did not increase the cross‐tension force significantly. The pitting corrosion susceptibility of the spot‐welded samples and the base materials of the steels EN 1.4318 2H/C850 and EN 1.4318 2H/C1150, t  = 1.2 mm, was investigated by measuring the corrosion current for 1 h at +100 mV versus saturated calomel electrode (SCE) in 3.5% sodium chloride solution at ambient temperature. Pitting corrosion occurred in all spot‐welded samples but not in the base materials. There was a difference between the investigated steels in the location of the pits. In stainless steels EN 1.4318 2H/C850 the pits appeared around the spot weld, but in the steel EN 1.4318 2H/C1150, t  = 1.2 mm, the pits are located mainly at the spot‐weld area.