Abstract: This invention relates to a partially carbonitriding heat treated stainless steel ferrule, having a first region with a first hardness and a second region with a second hardness, wherein the first region includes a nitrogen layer having a nitrogen concentration higher than a carbon concentration, and a carbon layer formed under the nitrogen layer and having a carbon concentration higher than a nitrogen concentration, so that the first hardness is greater than the second hardness. Thereby, partial heat treatment is effective at preventing rotational torque of the region, except for the portion to be heat treated, from increasing due to the total hardening.

Abstract: This invention relates to a partially carbonitriding heat treated stainless steel ferrule, having a first region with a first hardness and a second region with a second hardness, wherein the first region includes a nitrogen layer having a nitrogen concentration higher than a carbon concentration, and a carbon layer formed under the nitrogen layer and having a carbon concentration higher than a nitrogen concentration, so that the first hardness is greater than the second hardness. Thereby, partial heat treatment is effective at preventing rotational torque of the region, except for the portion to be heat treated, from increasing due to the total hardening.

Abstract: This invention relates to a surface heat treatment method in a salt bath at low temperature, suitable for partially hardening the surface of a workpiece through heat treatment, including plating the surface of a workpiece with a first metal layer; partially peeling the first metal layer; heat treating the workpiece at a temperature of 400 to 500° C. for a predetermined period of time; and totally peeling the first metal layer. Thereby, low-temperature heat treatment is effective at heat treating the workpiece while minimizing deterioration of corrosion resistance.

Abstract: This invention relates to a surface heat treatment method in a salt bath at low temperature, suitable for partially hardening the surface of a workpiece through heat treatment, including plating the surface of a workpiece with a first metal layer; partially peeling the first metal layer; heat treating the workpiece at a temperature of 400 to 500° C. for a predetermined period of time; and totally peeling the first metal layer. Thereby, low-temperature heat treatment is effective at heat treating the workpiece while minimizing deterioration of corrosion resistance.

Abstract: This invention relates to a partially carbonitriding heat treated stainless steel ferrule, having a first region with a first hardness and a second region with a second hardness, wherein the first region includes a nitrogen layer having a nitrogen concentration higher than a carbon concentration, and a carbon layer formed under the nitrogen layer and having a carbon concentration higher than a nitrogen concentration, so that the first hardness is greater than the second hardness. Thereby, partial heat treatment is effective at preventing rotational torque of the region, except for the portion to be heat treated, from increasing due to the total hardening.

Abstract: This invention relates to a partially carbonitriding heat treated stainless steel ferrule, having a first region with a first hardness and a second region with a second hardness, wherein the first region includes a nitrogen layer having a nitrogen concentration higher than a carbon concentration, and a carbon layer formed under the nitrogen layer and having a carbon concentration higher than a nitrogen concentration, so that the first hardness is greater than the second hardness. Thereby, partial heat treatment is effective at preventing rotational torque of the region, except for the portion to be heat treated, from increasing due to the total hardening.

Abstract: Disclosed herein is a partial heat treatment method using a double metal layer, in which a surface of a workpiece is hardened by heat treatment, including the steps of: primarily plating the surface of the workpiece with a first metal layer; secondarily plating the surface of the first metal layer with a second metal layer; partially stripping the first metal layer and the second metal layer to expose a part of the surface of the workpiece; heat-treating the workpiece to harden the exposed surface of the workpiece; and removing the first metal layer and the second metal layer remaining on the surface of the workpiece.