Abstract: Steel for forming a gear by carburizing and quenching consisting essentially of: 0.1 to 0.35 wt. % C, 0.5 to 2.5 wt. % Si, 0.2 to 2.5 wt. % Mn, 0.01 to 2.5 wt. % Cr, 0.01 to 0.7 wt. % Mo, and the balance being Fe and inevitable impurities. The steel has an Ac.sub.3 point parameter (Ac.sub.3) and an ideal critical diameter (D.sub.I), the Ac.sub.3 point parameter being in a range of 850.degree. to 960 .degree. C., the ideal critical diameter (D.sub.I) being in a range of 30 to 250 mm, and the Ac.sub.3 point parameter (Ac.sub.3) and the ideal critical diameter (D.sub.I) being defined by the following equations.Ac.sub.3 =920-203.sqroot.C+44.7 Si+31.5.times.Mo-30.times.Mn-11.times.CrD.sub.I =7.95.sqroot.C(1+0.70.times.Si) (1+3.3.times.Mn)(1+2.16.times.Cr) (1+3.0.times.Mo)The steel has a non-carburized portion after carburizing and quenching, an internal structure of the non-carburized portion comprising a dual phase of martensite and ferrite, said ferrite having an area percentage of 10 to 70% in the dual phase.

Abstract: A method for the rapid, direct cooling of a hot-rolled wire rod comprising the steps: transporting a hot-rolled and coiled wire rod on a conveyor, the wire rod being in a form of continuous series of loops; and blasting an air-water mist to the wire rod and simultaneously blasting air to the back side of the wire rod from below to cool the wire rod at a rate of 10.degree. to 100.degree. C./sec, while transporting the wire rod on the conveyor, the air-water mist providing 0.5 to 10 m.sup.3 /minute water and having an air to water ratio of 200 Nm.sup.3 /m.sup.3 or less.

Abstract: A method for direct patenting of a hot-rolled wire rod comprises the steps of: transporting a hot-rolled wire rod on a conveyer in a state that said wire rod is in a form of continuous series of loops; blasting mist to the surface of said wire rod at least from above and blasting air to the back side of the wire rod from below to cool the wire rod at a rate of 12.degree. C. to 50.degree. C./sec. down to 550.degree. C. to 400.degree. C. during the transportation, the mist provides 200 to 2400 l/min. water and has an air to water ratio of 200 Nm.sup.3 /m.sup.3 or less; and reheating the cooled wire rod at a rate of 3.degree. C./sec. or less, or cooling the cooled wire rod slowly at a rate of 2.degree. C./sec. or less during the transportation.

Abstract: A method for transporting a hot-rolled wire rod comprises changing directions of movements of the wire rod to the left and to the right relative to the center line of a conveyer at an interval of d/3 to 2d of a diameter of a ring of the wire rod and shifting the center of the ring of the wire rod from the center line of the conveyer by a length of 2d/100 to 30d/100 at its maximum.An apparatus for transporting hot-rolled wire rod comprises a conveyer for transporting a hot-rolled wire rod and guide means alternately arranged in an upper portion of the side of the conveyer to change the directions of movements of the wire rod to the left and to the right relative to the center line of the conveyer.

Abstract: A method for direct patenting of a hot-rolled wire rod comprises the steps of: transporting a hot-rolled wire rod on a conveyor in a state that said wire rod is in a form of continuous series of loops: blasting mist to the surface of said wire rod at least from above and blasting air to the back side of the wire rod from below to cool the wire rod at a rate of 12.degree. C. to 50.degree. C./sec. down to 550.degree. C. to 400.degree. C. during the transportation, the mist provides 200 to 2400 l/min. water and has an air to water ratio of 200 Nm.sup.3 /m.sup.3 or less; and reheating the cooled wire rod at a rate of 3.degree. C./sec. or less, or cooling the cooled wire rod slowly at a rate of 2.degree. C./sec. or less during the transportation.