PURPOSE: To obtain a low strength mild steel wire having coarse grains of ≤2 in the crystal grain size number for a mild steel wire by subjecting the steel wire rod contg. C, Si, Mn and Al respectively at prescribed rates and contg. Al/N at a regulated ratio to drawing at a prescribed reduction of area or above then heating the wire rod up to a specific temp. region thereby annealing the wire rod.
CONSTITUTION: A steel wire rod contg., by weight %, ≤0.04% C, ≤0.1% Si, 0.1W0.6% Mn and 0.005W0.030% Al and having the relation 2.5≤Al(%)/N(%) ≤7.5 is manufactured. The steel wire rod is then subjected to drawing at ≥60% reduction of area to accelerate formation of coarse grains and is thereafter subjected to annealing in which the wire rod is heated to a temp. region of 750W 900°C and is held at said temp. for ≥10min. As a result a larger amt. of ≤0.1μm AlN than in the conventional steel wire is deposited in the wire rod by which coarse grains of ≤2 in the grain size number of ferrite crystal is stably formed in the stage of annealing and the mild steel wire having the lower strength than the conventional steel wire is obtd.
HIDA YOUJI
OOBA HIROSHI
