Post-carburization surface strengthening method for low-carbon steel part

Abstract

The invention discloses a post-carburization surface strengthening method for a low-carbon steel part; the method strengthens the surface of the low-carbon steel part that is carburized by means of existing ultrahigh-pressure digital control water jet, i.e. mixed abrasive is charged into a mixing pipe through self-gravity and negative pressure that is produced by a high-speed water flow to mix with water, and the mixed abrasive accelerated by the water flow, in conjunction with the water flow, is sprayed from a nozzle to the surface of the part at a high speed; during spraying, steel pellets of high hardness provide high impact on the surface of a workpiece, whereas glass pellets of low hardness will partly break during spraying and mix with the water flow to produce liquid grinding action on the surface of the workpiece; therefore, after being strengthened by mixed abrasive jet blasting, the workpiece surface has higher residual pressure stress than that from traditional blasting and also has small surface roughness.

Description

technical field [0001] The invention relates to a method for strengthening the surface of a low-carbon steel part after carburizing, and belongs to the technical field of metal surface modification. Background technique [0002] Limited by current equipment and processes, after carburizing and quenching steel, a 20-200 μm decarburization layer is usually formed on the surface, and decarburization reduces the surface hardness and compressive stress of the material, and even tensile stress appears on the surface, thereby greatly reducing the metal workpiece. The use of vacuum carburizing technology cannot completely avoid the problem of surface decarburization. On the other hand, due to the limited space and high cost of vacuum carburizing equipment, it is difficult to use vacuum carburizing methods for long and large workpieces. After carbon quenching, the workpiece is subjected to shot peening, which can remove part of the decarburized layer and oxide layer on the surface, a...

AI Technical Summary

Problems solved by technology

[0002] Limited by current equipment and processes, after carburizing and quenching steel, a 20-200 μm decarburization layer is usually formed on the surface, and decarburization reduces the surface hardness and compressive stress of the material, and even tensile stress appears on the surface, thereby greatly reducing the metal workpiece. The use of vacuum carburizing technology cannot completely avoid the problem of surface decarburization. On the other hand, due to the limited space and high cost of vacuum carburizing equipment, it is difficult to use vacuum carburizing methods for long and large workpieces. After carbon quenching, the workpiece is subjected to shot peening, which can remove part of the decarburized layer and oxide layer on the surface, and produce significant work hardening, and obtain a certain depth of compressive stress layer, thereby improving the fatigue resistance of the metal workpiece

However, after the workpiece undergoes the existing shot peening technology, the surface roughness will increase sharply, and the maximum residual compressive stress is difficult to reach above -1000MPa. In addition, overspray is very easy to occur, resulting in a large number of microscopic defects, which hinders the process to a certain extent. The improvement of the fatigue life of the workpiece, so the influence of residual stress and roughness must be considered when considering the surface strengthening process

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