On the High Speed Impact Tensile Test of Tough Steel-IN Steel

Abstract

This paper describes the tensile impact properties of IN Steel which have been lately developed by the Ishikawajima-Harima Heavy Industries Co., Ltd., By using a high speed impact tensile testing machine with a large rotary disk installed at Tokyo Institute of Technology, the authors have obtained some results from the experiment.The impact velocity was varied from static region to 80m/s, and the test was performed at room temperature.The results obtained are summarized as follows:[1] Test results of the plain test pieces;(1) The impact tensile strength of IN Steel increased up to the impact velocity of 5m's and thereafter it was almost constant regardless of the impact velocity.(2) The maximum value of impact energy per unit volume of plain test pieces (d=8mm, l/d=5) was about 40kg·m/cm3 at the impact velocity of 40m/s.(3) The observed critical impact velocity was about 50m/s regardless of the gauge length of test pieces.(4) The contraction percentage of area decreased a little at the impact velocity of 5m/s, and thereafter it was not affected much by the value of impact velocity. It was about 80 percent.[2] Test results of the notched test pieces;(1) The impact tensile strength of notched test pieces was 60% larger than that of the plain test pieces and it was kept unchanged in the test until 20m/s of the impact velocity, but increased remarkably from that velocity up to 80m/s.(2) As the radii of curvature at the root of the notch is smaller, the impact tensile strength somewhat increased, but the value of impact energy per unit area was kept unchanged.(3) If the diameter of notched test pieces and radii of curvature were constant, the impact tensile strength and the value of impact energy per unit area were kept unchanged, even if the outer diameter varied D/d=1.75, 1.875 and 2.125.(4) On the effect of the size of notched test pieces, having similar shapes, the smaller ones in size had larger impact tensile strength, but the value of impact energy per unit area showed a reversal tendency.Generally speaking, it may be concluded that IN Steel provides excellent mechanical properties against high speed impact loading.