Patent ID: 11905571
Assignee: POSCO CO., LTD
Field: Materials, metallurgy (Chemistry)
Classification: CPC C  B | IPC B  C

Claim 4:
5. A manufacturing method of a CHQ wire rod according to claim 2, the method comprising:
heating a billet comprising, in percent (%) by weight of the entire composition, C: 0.3 to 0.5%, Si: 0.1 to 0.3%, Mn: 0.5 to 1.0%, Cr: 0.5 to 1.5%, Mo: 0.5 to 1.5%, V: 0.01 to 0.2%, the remainder of iron (Fe) and other inevitable impurities, and having a value of 3.56 or more in the following formula (1), at 900 to 1200° C.;
finishing rolling the heated billet at 850 to 1150° C.;
controlling the average austenite grain size to be 30 μm or less by cooling the rolled billet at rate of 0.2 to 0.5° C./s;

[Cr]+2.7*[Mo]+6*[V]  (1), (Here, [Cr], [Mo], and [V] mean the weight % of Cr, Mo, and V, respectively)
thereby producing the CHQ wire rod of claim 2.