The effect of trace element such as V. Mo, Nb and W on the hadfield steel has been studied. Work hardening by high Cr-ball in the ball mill has been simulated by the hammering installation. Results obtained from this experiment are as follows ; 1) The as-cast hardness of hadfield steel as well as alloy steels shows almost the same in case of adding alloying elements less than 0.1w/o, while over 0.1w/o alloy steels are slightly higher than hadfield steel. 2) The hardness of as-cast hadfield steel was reduced by half by water-toughening. But the hardness of alloy steels adding a very small amount of alloying elements increased a little, while over 0.1w/o much improved. 3) The change of hardness owing to work hardening was not shown till 10²impact cycles. But over than 10³cycles remarkable work hardening appeared. The effect of addition elements on work hardening was gradually increased in the order of Mo, V, Nb and W. 4) The transformation of austenite to martensite began from over than 10⁴impact cycles. 5) The effect of trace elements remaining on the hearth of melting furnace on the characteristics of hadfield steel doesn`t make any difference below 0.1w/o of alloying elements.