Gas nitrocarburizing and vapor composite treatment technique

Abstract

The invention relates to a gas nitrocarburizing and vapor composite treatment technique which comprises the following steps: (1) putting a workpiece into a nitriding furnace, starting introducing nitrogen, heating to 590-610 DEG C, and keeping the temperature for 1 hour; (2) starting introducing carbon dioxide and ammonia gas, heating to 640-660 DEG C, keeping the temperature for 3 hours, stopping introducing the carbon dioxide, continuing keeping the temperature for 1 hour, and stopping introducing the ammonia gas; (3) cooling to 70-90 DEG C, and keeping the temperature for 40 minutes; (4) putting the workpiece treated by the step (3) into an oxidizing furnace, starting introducing nitrogen, heating to 290-310 DEG C, and keeping the temperature for 10 minutes; (5) starting introducing vapor, regulating the introduction quantity of the nitrogen, heating to 530-550 DEG C, and keeping the temperature for 100 minutes; and (6) regulating the introduction quantity of the nitrogen, cooling to 490-510 DEG C, keeping the temperature for 10 minutes, and discharging. The technique implements no loosening on the surface layer, and enhances the surface hardness, wear resistance, seizure resistance, contact fatigue strength and the like of the product.

Description

technical field [0001] The invention relates to a gas nitrocarburizing and steam composite treatment process. Background technique [0002] The metallographic structure of gas nitrocarburizing and water vapor composite treatment is: the surface is a bright white layer, a nitride layer, and the original structure of the core. The surface white layer can be divided into: the most surface layer is non-dense, porous layer and non-porous dense layer. The surface loose layer is an important defect of the white layer, which will seriously affect the nitrided surface hardness, wear resistance, Seizure resistance and contact fatigue strength, etc. [0003] The existing control method for the surface loose layer is to reasonably control the ammonia decomposition rate to achieve a certain proportion of second-stage porosity under the condition of constant temperature during gas nitrocarburizing. For example, the US standard ASTMA108 grade is 1215 free-cutting steel material. At prese...

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Problems solved by technology

For example, the US standard ASTMA108 grade is 1215 free-cutting steel material. At present, when the thickness of the total white layer is controlled to about 15 μm, the loose layer accounts for 25%-35% of the total white layer, but the large amount of gas used increases the cost of the enterprise. Production costs, and when the sulfur content in 1215 free-cutting steel material changes, the content of the loose layer will increase. At this time, the ratio of the loose layer to the total white layer will be greater than 40%, the risk index is high, and it cannot satisfy customers. Requirements for surface hardness, wear resistance, seizure resistance and contact fatigue strength of products

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