Ultra-low temperature nitridation method for engine cylinder liner of large-scale watercraft

Abstract

The invention discloses an ultra low temperature nitridizing method for a large ship engine cylinder sleeve, comprising the steps as follows: (1) towel is used to clean up the oil stain on a work piece; (2) the work piece is put into a clamping apparatus; (3) the work piece is put into a decontamination agent tank to carry out oil coating at the temperature of 75-95 DEG C for 5-8min; (4) the coated work piece is washed by running water; (5) the work piece is preheated at the temperature of 200-250 DEG C for 50-60min; (6) Na2SO4 with the weight of 8% is added into the nitridizing agent in the nitridizing furnace; the nitridizing temperature is 350 plus/minus 5 DEG C and the period is 2.5-3h; (7) the nitridized work piece is cooled in the air to below 150 DEG C; (8) the work piece is washed by running water; (9) the nitridized cylinder sleeve is checked; (10) the qualified cylinder sleeve is soaked into rust preventative oil; (11) the soaked cylinder sleeve is packaged and stored for transportation. The invention adopts low temperature nitrogen treatment, so that the nitridizing period is shortened, the production cost is lowered, and the product quality is improved, thus being suitable for industrialized mass production.

Description

technical field [0001] The invention relates to a processing method for an engine cylinder liner, in particular to an ultra-low temperature nitriding method for a large ship engine cylinder liner. Background technique [0002] The cylinder liner is an important core component of the engine, which directly affects the function and service life of the engine. However, the phenomenon of cavitation and early wear and tear of the engine cylinder liner is common, ranging from pockmarks and honeycombs on the outer surface of the cylinder liner to forming holes, seriously affecting the service life of the engine, and even causing damage to the engine. This phenomenon is more prominent in ship engine cylinder liners. [0003] In response to this situation, many engine cylinder liner manufacturers at home and abroad have studied various methods and measures to prevent cavitation and improve wear resistance: first, to improve the overall performance of materials, adding many high-allo...

AI Technical Summary

Problems solved by technology

However, the phenomenon of cavitation and early wear and tear of the engine cylinder liner is common, ranging from pockmarks and honeycombs on the outer surface of the cylinder liner to forming holes, seriously affecting the service life of the engine, and even causing damage to the engine. The damage leads to the occurrence of major accidents, endangering human life and the loss of national property. This phenomenon is more prominent in the ship engine cylinder liner

[0003] In response to this situation, many engine cylinder liner manufacturers at home and abroad have studied various methods and measures to prevent cavitation and improve wear resistance: first, to improve the overall performance of materials, adding many high-alloy elements Cr, Mo, Cu, W, Re, etc. are used to enhance wear resistance and improve cavitation resistance. This method can be used to improve, but the manufacturing cost is quite expensive, and some alloy elements in our country are very rare, so we need to rely on imports; , use surface heat treatment process to improve cavitation resistance and wear resistance, such as surface quenching, surface oxidation, surface phosphating, isothermal bainite, high temperature nitriding, etc., but the effect is not very ideal; among them, high temperature nitriding exists more Many defects: First, the high temperature is 650°C±5°C, and the nitriding cycle is more than 30 hours. The high cost is not suitable for mass production; the second is that the deformation of the high-temperature nitriding workpiece is large, which affects the manufacturing accuracy and installation accuracy of the workpiece. The third is that the high-temperature nitrided layer is brittle and easy to peel off, and the peeled medium forms a high abrasive agent, which accelerates the wear of the cylinder liner; the fourth is that after the nitrided layer peels off, countless holes are formed, which doubles the oil consumption increase, not only the cost of use has risen sharply, but also the pollution of the environment is very serious