A quench oils composition containing a sulfur compound capable of improving the brightness of a metal material after a heat treatment, such as quenching, while preventing the sulfur content from being excessively increased. This is achieved by a quench oils composition containing one or more base oil selected from a mineral oil, a synthetic oil, and a vegetable oil, and one or more sulfur-containing aromatic compound selected from a particular sulfide compound and a particular sulfone compound.

A quench oils composition containing a sulfur compound capable of improving the brightness of a metal material after a heat treatment, such as quenching, while preventing the sulfur content from being excessively increased. This is achieved by a quench oils composition containing one or more base oil selected from a mineral oil, a synthetic oil, and a vegetable oil, and one or more sulfur-containing aromatic compound selected from a particular sulfide compound and a particular sulfone compound.

A rolling-contact shaft member, which is made of high-carbon steel and whose outer peripheral surface serves as a rolling-contact surface that rolling-contacts a mating material, includes: a carbonitrided layer having a carbon concentration of 1.1 to 1.6 wt % and a nitrogen concentration of 0.05 to 0.6 wt % in the range from the surface to the depth of 10 μm. The rolling-contact shaft member has a Vickers hardness of 700 to 840 HV at the outer peripheral surface and has a Vickers hardness of 600 HV or less in its central portion. A maximum value of an absolute value of a gradient of a change in the Vickers hardness from the outer peripheral surface to the central portion is 100 to 340 HV/mm.

A rolling-contact shaft member, which is made of high-carbon steel and whose outer peripheral surface serves as a rolling-contact surface that rolling-contacts a mating material, includes: a carbonitrided layer having a carbon concentration of 1.1 to 1.6 wt % and a nitrogen concentration of 0.05 to 0.6 wt % in the range from the surface to the depth of 10 μm. The rolling-contact shaft member has a Vickers hardness of 700 to 840 HV at the outer peripheral surface and has a Vickers hardness of 600 HV or less in its central portion. A maximum value of an absolute value of a gradient of a change in the Vickers hardness from the outer peripheral surface to the central portion is 100 to 340 HV/mm.

Disclosed herein is a method of using a water-based coolant for quenching or cutting a metal material. The water-based coolant is formed of: water; at least one inorganic acid salt selected from the group consisting of a carbonate, a hydrogen carbonate, a sesquicarbonate, a phosphate, a borate, a molybdate and a tungstate; a metal corrosion inhibitor; and optionally at least one of a bactericide, a water-soluble rust inhibitor, an antioxidant and a detergent dispersant.

Disclosed herein is a method of using a water-based coolant for quenching or cutting a metal material. The water-based coolant is formed of: water; at least one inorganic acid salt selected from the group consisting of a carbonate, a hydrogen carbonate, a sesquicarbonate, a phosphate, a borate, a molybdate and a tungstate; a metal corrosion inhibitor; and optionally at least one of a bactericide, a water-soluble rust inhibitor, an antioxidant and a detergent dispersant.

High productivity plant for the continuous quenching of steel bars which comprises a loading station suitable to dispose a plurality of bars separated and distanced from each other. Such plant also comprises a first treatment line, a quenching machine, a transfer station disposed downstream of the quenching machine, and a second treatment line.

High productivity plant for the continuous quenching of steel bars which comprises a loading station suitable to dispose a plurality of bars separated and distanced from each other. Such plant also comprises a first treatment line, a quenching machine, a transfer station disposed downstream of the quenching machine, and a second treatment line.

A method of manufacturing a sliding camshaft for an internal combustion engine includes providing the sliding camshaft from a steel alloy having a carbon content between 0.25% and 0.60%. The sliding camshaft is then processed with a carbon infusing heat treatment process, such as carburization or carbonitriding. After the sliding camshaft has been processed with the carbon infusing heat treatment process, the sliding camshaft is then processed with a quenching heat treatment process, such as a mar-quenching heat treatment process.

A method of manufacturing a sliding camshaft for an internal combustion engine includes providing the sliding camshaft from a steel alloy having a carbon content between 0.25% and 0.60%. The sliding camshaft is then processed with a carbon infusing heat treatment process, such as carburization or carbonitriding. After the sliding camshaft has been processed with the carbon infusing heat treatment process, the sliding camshaft is then processed with a quenching heat treatment process, such as a mar-quenching heat treatment process.