THE NI-CR-MO LOW ALLOY STEEL IMPROVED RESISTANCE OF TEMPER EMBRITTLENESS AND THE MANUFACTURING METHOD THEREOF

摘要

The purpose of the present invention is to provide Ni-Cr-Mo low alloy steel with improved temper embrittlement resistance and a manufacturing method thereof. The Ni-Cr-Mo low alloy steel comprises 0.19-0.22 wt% of C, 0.10-0.35 wt% of Mn, 2.00-3.60 wt% of Ni, 1.00-1.80 wt% of Cr, 0.40-0.60 wt% of Mo, 0.15-0.40 wt% of Si, 0.001-0.03 wt% of V, and the rest of Fe and inevitable impurities. Furthermore, the present invention provides the manufacturing method of the Ni-Cr-Mo low alloy steel including a step (step 1) of mixing, melting, and forging raw materials of the low alloy steel; a step (step 2) of homogenizing the raw materials forged in the step 1; a step (step 3) of austenizing the raw materials homogenized in the step 2; and a step (step 4) of tempering the raw materials austenized in the step 3. The Ni-Cr-Mo low alloy steel according to the present invention has rigidity and toughness which are not remarkably lower than those of existing ASTM SA508 Grade 4N low alloy steel; and obtains excellent resistance against brittleness. [Reference numerals] (AA) Comparative example 5(H-Mn); (BB) Comparative example 1; (CC) Example 3(L-Mn); (DD) Comparative example (VL-Mn); (EE) Comparative example (H-Cr); (FF) Comparative example 1; (GG) Example 2(L-Cr); (HH) Comparative example 2(H-Ni); (II) Comparative example 1; (JJ) Example 1 (L-Ni); (KK) Content ratio of each element per each component