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

摘要

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℃ 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{sup 1/2}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 t100 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.