Nitriding process for maraging steel

A maraging steel, nitriding treatment technology, applied in the direction of heat treatment furnace, heat treatment equipment, coating, etc., can solve the problems of limited compression residual stress increase, insufficient reduction treatment, etc., achieve high compression residual stress, promote nitrogen The effect of increasing the concentration of the surface

CN102666907AInactive Publication Date: 2012-09-12HONDA MOTOR CO LTD
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2012-09-12
Estimated Expiration
Not applicable · inactive patent

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Abstract

Provided is a nitriding process for maraging steel, by which the compressive residual stress of maraging steel can be enhanced. On the surface of a work of maraging steel, part of the titanium solid-soluted in the work is oxidized with oxygen to form titanium oxide (TiO2) on the surface of the work positively, whereby the concentration of titanium oxide on the surface is enhanced (solution treatment step); since titanium present in the form of an oxide does not react with nitrogen in a nitriding step, the resulting work is subjected to sufficient reduction pretreatment prior to a nitriding step to conduct the removal of oxygen; thus, the surface concentration of titanium present in an active state is enhanced; and then the work thus pretreated is subjected to nitriding, whereby the reduced titanium and the solid-soluted titanium are bonded to nitrogen to form titanium nitride (TiN). In this nitriding step, the titanium present in the work is in an active state and therefore can be easily nitrided. Further, the surface concentration of titanium present in an active state is high, so that much nitrogen can penetrate into the work.
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Description

technical field

[0001] The present invention relates to a method for nitriding treatment of maraging steel containing titanium, and in particular to an improvement in the control technology of compressive residual stress. Background technique

[0002] In steel, compressive residual stress is imparted to the surface by nitriding for the purpose of increasing the strength. At this time, when an excessive compressive residual stress is applied, the notch susceptibility becomes sensitive and the toughness is lost. Therefore, it is necessary to apply an appropriate residual stress.

[0003] When nitriding treatment is applied to hard-to-nitride steel, the oxide film existing on the steel surface hinders nitriding. For example, in maraging steel, when the surface concentration of atoms such as titanium, which are easily bonded to oxygen, is high in the solution step, an oxide film of the atoms is formed. For this reason, since nitriding is inhibited in the nitriding step, suffic...

Examples

Embodiment Construction

[0023] Hereinafter, the present invention will be described in detail with reference to specific examples. In the examples, the method of nitriding treatment of maraging steel according to the present invention was applied to the method of manufacturing an endless metal belt.

[0024] In the manufacture of endless metal belts, such as figure 2 As shown, first, a thin plate 1 made of maraging steel is formed into a cylindrical shape by welding both ends of the thin plate 1 to form a drum 2 (welding process). At this time, due to the heat of welding, a part 2a of the drum 2 is hardened. Therefore, by performing the first solid solution treatment on the drum 2 in the heating furnace 3, the hardness of the drum 2 is homogenized (first solution treatment). process). Next, the drum 2 is cut to a predetermined width to form a plurality of endless belt-shaped rings 4 (drum cutting step). Next, the ring 4 is rolled to a predetermined thickness (ring rolling process). At this time,...