Surface carburization and nitridation treatment method for steel workpiece

Abstract

The invention discloses a surface carburization and nitridation treatment method for a steel workpiece, which comprises the following steps: placing a steel workpiece into a heating chamber; vacuumizing, then introducing nitrogen gas to ensure that the steel workpiece is in a nitrogen gas atmosphere, and controlling the atmosphere pressure in the furnace to be 100 Torr or above; then heating to enable the steel workpiece to reach a carburization and nitridation temperature, keeping the aforementioned pressure in the furnace, and alternately introducing unsaturated hydrocarbon gas and ammonia gas to perform high-temperature carburization and nitridation; after the high-temperature carburization and nitridation is completed, cooling to a quenching temperature, and then performing quenching heat preservation and quenching cooling; and finally, completing the surface carburization and nitridation treatment of the steel workpiece. The method disclosed by the invention has the advantages of simple equipment, low investment, high heating efficiency and good product quality.

Description

technical field [0001] The invention relates to a surface hardening treatment method of mechanical parts, in particular to a surface carburizing and nitriding treatment method of mechanical parts. Background technique [0002] The vacuum carburizing method in the existing carburizing treatment method is to heat the processed steel workpiece in a vacuum furnace to a specified carburizing temperature and keep it uniformly heated, and then introduce it into the heating chamber as a carburizing gas. Gaseous saturated hydrocarbons (saturated hydrocarbons) such as methane, propane, butane, etc. are thermally decomposed, and the resulting activated carbon penetrates into the surface of the steel workpiece as the object to be processed. Compared with the existing gas carburizing technology, the vacuum carburizing method has the advantages of high temperature and short time treatment, no need for metamorphic furnace, simple gas environment management, basically no particle oxidation,...

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Problems solved by technology

However, since the chemical stability of chain unsaturated hydrocarbons such as acetylene and ethylene is not as good as that of saturated hydrocarbons, the thermal decomposition of unsaturated hydrocarbon gases will be more intense than the carburizing reaction, and impurities will also be produced. Therefore, The traditional idea is that unsaturated hydrocarbon gas is not suitable as a carburizing medium

However, the unsaturated hydrocarbon gas used as the carburizing medium and the ammonia gas supplied as the nitrogen source can realize carburizing and nitrogen infiltration on the surface of the workpiece at the same time, but due to the pressure in the furnace in the vacuum carburizing method Too low makes the supply of ammonia gas as a nitrogen source technically more difficult; moreover, under vacuum conditions, after carburizing and nitriding, the temperature is lowered to the quenching temperature and kept at the quenching temperature range, the infiltrated Nitrogen will escape, which makes simultaneous carburizing and nitriding more difficult for industrial applications

[0004] In addition, the vacuum carburizing and nitriding method is to set the heating chamber in a vacuum state below 1kPa for heating and carburizing, so the furnace body needs to have a high degree of sealing structure, which increases the cost of equipment at the same time, because the inside of the furnace Atmospheric gas does not convect. When the workpiece is loaded into the furnace at high density for processing, not only the heating rate is slow, but also the workpiece only absorbs heat through the heat radiation of the heating element, and the position of the workpiece varies greatly when the furnace is loaded. It is easy to cause temperature unevenness

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