純鉄の衝撃引張試験

Abstract

The behavior of pure iron under impact tensile loading was studied with two kinds of pure irons and a commercial low carbon steel. One half of specimens were annealed in vacuum at 600, 700, 800, 850, 920 and 1000°C for 1 hour and the others were quenched in oil after keeping them at these temperatures for 1 hour in vacuum.At the impact tensile test, in which the specimen was loaded by the hammex, falling by gravity and weighing 25kg, the load acting on the specimen was measured by the use of piezoelectricity of quartz crystals and the cathode ray oscillograph. X-direciion of the oscillograph was fed by piezoelectricity, Y-axis corresponded to time axis There was no electronic circuit between quartz and a deflection plate of the oscillograph and the load-time curve was directly recorded on the film inside the oscillograph. The strain rates at the impact tests were approximately 20-1201/secThe results obtained in this investigation were as follows.(1) The peak appeared in the load-time curve under impact test seemed to be upper yield point.(2) Yield stress and tensile strength were larger and total elongation was smaller than those under static test.(3) Increasing the strain rate, both yield stress and tensile strength increased and total elongation decreased slightly. The rate of increase of yield stress was greater than that of teasile streagth.(4) The test specimens annealed at comparatively lower temperatures sucb as 600°C-700°C fractured in brittle manner even after the completion of recrystallization but this phenomenon was not observed under the statical test. It was supposed that thin phenomenon was due to the manner of distribution af cementite. Quenched specimens shawed mare ductile fracture.