Hadfield 鋼에 Ni을 3.5% 添加하여 炭化物과 pearlitic constituents의 析出線圖와 析出物의 形態 및 硬度에 미치는 組織變化를 調査하였으며 아울러 Ni에 依한 析出의 影響도 比較 檢討하였다. 여기서 얻은 結果를 要約하면 다음과 같다. 1) Hadfield鋼에 Ni을 添加하면 炭化物析出 溫度區間은 좁아지며, pearlitic constituents의 析出溫度區間은 거의 變化하지 않는다. 2) 炭化物新出은 670∼700℃에서 가장 빠르며 pearlitic constituents의 析出은 600℃에서 가장 빨리 일어난다. 3) 炭化物析出은 低溫區域을 除外하고는 먼저 粒界에 film狀의 炭化物이 形成되며, 加熱時間이 길어지고 溫度가 上昇함에 따라 針狀炭化物, 粒狀炭化物, chain狀의 炭化物이 形成된다. 4) 針狀炭化物보다 pearlitic constituents가 硬度增加에 크게 寄與하는 것으로 推定된다. 5) 炭素量의 增加에 따라 pearlitic constituents의 析出開始時間이 빨라지며, 이 現象은 Ni添加에 依해 더욱 促進된다.

The effects of Ni addition on the precipitation of carbides and pearlitic constituents in Hadfield steel were investigated by means of microscopy and hardness measurements. From this experiment the following results were obtained. 1) By the addition of Ni, the temperature range of precipitation of carbides became narrow, but that of pearlitic constituents was nearly unchanged. 2) Carbides were precipitated preferentially in the range of 600-700℃ and pearlitic constituents at 600℃. 3) Except the lower temperature range, carbides were precipitated in the shape of film at the grain boundaries in the earlier heating stage, but with the increase in heating time and temperature, the shape of carbides was changed as follows; acicular, granular and chain-like carbides. 4) Increased hardness was mainly affected by pearlitic constituents precipitation rather than acicular carbides. 5) With the increase in carbon contents, the pearlitic constituents precipitation rate was accelerated remarkably by the addition of Ni in Hadfield steel.