Deep level ion nitriding process for engine cylinder bushes

Abstract

The invention discloses a deep level nitriding process for engine cylinder bushes, comprising the procedures of cleaning, charging, ion nitriding and tapping, wherein in the charging procedure, a bottom supporting disk is supported on a cathode disc by using a conductor column, cylinder bushes are uniformly arranged on the bottom supporting disk, a top plate is arranged on the cylinder bushes, and through holes are arranged on the top plate and the bottom supporting disk corresponding to the positions of the cylinder bushes; and in the ion nitriding procedure, arc light starts when the vacuum degree in a furnace reaches 50Pa below and the voltage is set at 650V, then the voltage and the duty cycle are sequentially increased, ammonia gas is fed into the furnace after the voltage is adjusted to 700V and the arc light frequency is reduced, the voltage in the furnace is adjusted to 750V when the arc light basically disappears, the glow is stable and the flow of the ammonia gas is not increased, heat preservation is carried out at 520 DEG C for 15h and 540 DEG C for 25h, the flow of the ammonia gas is 0.5-0.8L / min and the vacuum degree is 500-800Pa, and the temperature of the cylinder bushes are gradually reduced under the glow state, and furnace shutdown, gas cutoff and cooling are carried out after the temperature is reduced to 300 DEG C below. Based on the ion nitriding process disclosed by the invention, the nitriding speed is high, the diffusion layer is deep, and the technical requirements of engine cylinder bushes are met.

Description

technical field [0001] The invention relates to a method for surface heat treatment of iron and steel parts, in particular to an ion nitriding process. Background technique [0002] The cylinder liner is one of the important parts of the engine. The cylinder liner of the engine is the guide surface for the reciprocating movement of the piston group. The sealing pressure of the piston ring and the side thrust of the piston directly act on the inner wall of the cylinder liner, causing the cylinder liner and piston ring to be strongly rubbed. This friction is often in a semi-dry friction state. Especially in the case of poor lubrication, dirty intake air, improper cooling and abnormal combustion, it will cause strong wear on the cylinder liner and piston ring. Therefore, the inner surface of the cylinder liner is required to have high hardness, wear resistance, corrosion resistance and high thermal fatigue resistance. To meet the requirements of use, the inner wall of the cyl...

AI Technical Summary

Problems solved by technology

Compared with gas nitriding, ion nitriding has the advantages of fast nitriding speed, control of the structure of the permeated layer, small deformation of parts, energy saving and environmental protection. However, the depth of the nitriding layer of ion nitriding is generally shallow. For parts with harsh environments, too shallow seepage layers often cannot withstand the test of huge pressure and friction

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