COOPERATIVE PROGRAM OF FRACTURE TESTING OF AISI 4340 STEEL PLATE: CHARPY IMPACT RESULTS.

Tests were conducted, by utilization of Charpy impact tests, relative to the ductile-to-brittle transition temperature of 4340 steel. Both longitudinal and transverse specimens were supplied half of each group were tempered at 475 degrees F and half at 550 degrees. For both the tempering treatments examined, there was small energy change with testing temperature. The longitudinal specimens changed about 8 ft-lb and the transverse only 2 12 ft-lb, while the fracture appearance changed from 100 to 20 fibrous over a testing range of 200 to 22 degrees C. Comparison was made with a heat of AISI 4340 58-in. square bar stock heated at 1650 degrees F to normalize, 1550 F oil quenched, and tempered one hour. The transition temperatures 100 degrees F fibrous fracture were in fairly good agreement with the earlier results. This work was part of a cooperative program by the Fracture Committee of the American Society for Testing Materials.