| 摘要 |
<p>PURPOSE: Plastic mold steel is provided to obtain uniform hardness by reducing the segregation of carbon intensified when the large plastic mold steel is coagulated as an ingot. CONSTITUTION: A method for manufacturing plastic mold steel with uniform hardness and excellent workability is as follows: a step of preparing molten metal containing 0.25-0.35 wt.% of C, 0.02-0.08 wt.% of Si, 0.65-0.84 wt.% of Mn, 0.020 wt.% or less of P, 0.020 wt.% or less of S, 0.30 wt.% or less of Cu, 0.20-0.50 wt.% of Ni, 1.00-1.50 wt.% of Cr, 0.20-0.45 wt.% of Mo, 0.03-0.12 wt.% of V, 0.020-0.050 wt.% of Al, 0.0008-0.0050 wt.% of B, 0.0050-0.0500 wt.% of Zr, and the rest of Fe and inevitable impurities with a vacuum carbon deoxidation process; a step of casting the molten metal to form an ingot; a step of primarily upsetting the ingot by heating the ingot at 1200-1250 degrees Celsius; and a step of secondarily upsetting and free-forging the ingot after the ingot is reheated at 1200-1250 degrees Celcius. [Reference numerals] (AA) Invented steel: 34 spots; (BB) Existing steel: 66 spots</p> |
