Fatigue performance of Q420C steel fillet-welded joints at low temperatures

This paper focuses on the fatigue performance of Q420C steel fillet-welded joints at low temperatures. The tensile tests and Charpy V-notch tests were first performed to evaluate the mechanical properties of Q420C steel filletwelded joints under room and low temperatures. It reveals that the yield and ultimate strengths increased with reducing temperature from 20 degrees C to -50 degrees C. The Charpy impact energy transition temperature (ETT50) was -33.67 degrees C. Subsequently, the fatigue test was conducted on the fillet-welded cruciform joint specimens of Q420C steel at 20 degrees C, 0 degrees C, -15 degrees C, -30 degrees C, 40 degrees C and -50 degrees C considering three stress ranges (i.e., 0.0-0.5 ftw, 0.0-0.7 ftw and 0.0-0.9 ftw), where ftw was the design strength of fillet weld. The micro-morphologies of fatigue fracture surfaces were observed by scanning electron microscope (SEM), and the river patterns indicating brittle fracture occurred at -50 degrees C. The S-N curves and P-S-N curves with a survival probability of 95% were fitted from experimental fatigue life. With decreasing temperature from room temperature (20 degrees C) to -40 degrees C, the fatigue life increased at low-stress range (0.0-0.5 ftw), while shrank at high-stress range (0.0-0.9 ftw). Then, the fatigue life presented a declination trend at -50 degrees C for these three stress ranges, compared with that at -40 degrees C.

Automated summary

This paper investigates the fatigue performance of Q420C steel fillet-welded joints at low temperatures. Tensile tests and Charpy V-notch tests were conducted to assess the mechanical properties of the joints under room and low temperatures. It was found that the yield and ultimate strengths increased as the temperature decreased from 20 degrees C to -50 degrees C. The fatigue test revealed that the fatigue life increased at low-stress range but decreased at high-stress range as the temperature decreased from room temperature to -40 degrees C. At -50 degrees C, the fatigue life showed a declining trend for all stress ranges compared to that at -40 degrees C.