Investigation of the ductile fracture properties of type 304 stainless steel plate, welds, and 4-inch pipe

Abstract

J-integral fracture toughness tests were performed on welded 304 stainless steel 2-inch plate and 4-inch diameter pipe. The 2-inch plate was welded using a hot-wire automatic gas tungsten arc process. This weldment was machined into 1T and 2T compact specimens for single specimen unloading compliance J-integral tests. The specimens were cut to measure the fracure toughness of the base metal, weld metal and the heat affected zone (HAZ). The tests were performed at 550°F, 300°F and room temperature. The results of the J-integral tests indicate that the J Ic of the base plate ranged from 4400 to 6100 in lbs/in 2 at 550°F. The J Ic values for the tests performed at 300°F and room temperature were beyond the measurement capacity of the specimens and appear to indicate that J Ic was greater than 8000 in lb/in 2. The J-integral tests performed on the weld metal specimens indicate that the J Ic values ranged from 930 to 2150 in lbs/in 2 at 550°F. The J Ic values of the weld metal specimens tested at 300°F and room temperature were 2300 and 3000 in lbs/in 2 respectively. One HAZ specimen was tested at 550°F and found to have a J Ic value of 2980 in lbs/in 2 which indicates that the HAZ is an average of the base metal and weld metal thoughness. These test results indicate that there is a significant reduction in the initiation fracture toughness as a result of welding. The second phase of this task dealt with the fracture toughness testing of 4-inch diameter 304 stainless steel pipes containing a gas tungsten arc weld. The pipes were tested at 550°F in four point bending. Three tests were performed, two with a through wall flaw growing circumferentially and the third pipe had a part through radial flaw in combination with the circumferential flaw. These tests were performed using unloading compliance and d.c. potential drop crack length estimate methods. The results of these test indicate that the presence of a complex crack (radial and circumferential) reduces in the initiation toughness and the tearing modulus of the pipe material compared to a pipe with only a circumferentially growing crack.