A processing method for ion nitriding of steel gas valve

Abstract

The invention discloses an ionic nitriding machining method for a steel air valve. The method comprises the following steps that (1) sputtering is conducted; (2) first-section ionic nitriding is conducted; (3) second-section ionic nitriding is conducted; and (4) a furnace is cooled till the temperature is lower than or equal to 150 DEG C, the steel air valve is discharged, and air cooling is conducted. According to the method, the three technical problems of X33CrNiMnN23-8 steel air valve nitriding are successfully solved, the nitriding speed is obviously increased, nitriding time is shortened by almost half, the polishing procedure before nitriding is omitted, and the production cost is reduced. In addition, the nitriding quality is stable and is remarkably improved, the depth and hardness of a nitrided layer are much more uniform than those of air valves manufactured through traditional techniques, brittleness is obviously improved, and a nitrided face is free of swelling and peeling. Through practical application, no unaccepted X33CrNiMnN23-8 air valve nitrided through the new technique exists; and by being verified through installation and application by users, the abrasion resistance and the fatigue strength of the air valve are remarkably improved, and the service life of the air valve is remarkably prolonged compared with the past.

Description

technical field [0001] The invention relates to a processing method for ion nitriding of a steel valve. Background technique [0002] The X33CrNiMnN23-8 steel valve is one of the key moving parts of the heart of the diesel engine, and it is also its basic part and consumable part. [0003] As a heart moving part, it is a key moving part that determines the performance and reliability of a diesel engine. [0004] As a basic part, it plays a very important role in the diesel engine. [0005] Failure of the air valve during use will directly lead to serious consequences such as deformation or damage of cylinders, pistons, superchargers and other components. [0006] As the air valve is a consumable, it is located in the heart, and the diesel engine needs to be disassembled when replacing it, which is labor-consuming and time-consuming. If a failure occurs during use, it will definitely cause a parking accident, especially for marine diesel engines. The economic loss caused by...

AI Technical Summary

Problems solved by technology

In the actual production process, due to the limitation of conditions, even if the passivation film has been completely removed by the above method, but then due to the length of time in contact with the air, the product will generate new oxides of different degrees.

That is: during nitriding, there are more or less dense oxides that are invisible to the naked eye that seriously hinder nitriding on the surface of the workpiece, making the depth and hardness of the nitrided layer of the material very uneven

[0009] The second technical problem of X33CrNiMnN23-8 gas valve nitriding is: when the nitrided layer depth reaches the technical requirement ≥ 0.10mm, the nitriding hardness often exceeds the technical requirement of 750-950HV1, sometimes even as high as 1100HV1, and the brittleness is often Grade 1-3 (process requirements brittleness ≤ grade 2)

[0010] The third technical problem is: because the nitrogen potential in the furnace is difficult to control during nitriding, the tissue stress in the nitrided layer is large, and hydrogen atoms infiltrate. After the hydrogen atoms combine into hydrogen molecules, they work together with the tissue stress. Sometimes there will be bulges in the deep part of the nitrided layer of X33CrNiMnN23-8. In severe cases, the nitrided layer will peel off, which will cause scrapping

[0011] The above three common problems have always been a technical problem for every company that produces X33CrNiMnN23-8 valves, because it often leads to rework of the nitriding process, or even scrapping

[0015] Relatively speaking, ion nitriding is more suitable for this product, but the traditional ion nitriding process (cleaning after polishing, loading the furnace, starting and heating up, gradually increasing the ammonia supply to 0.9-1.0L / min, and raising the temperature to 620 -630°C, furnace pressure 340-400Pa, voltage 580-650V, heat preservation for 35 hours, furnace cooling to ≤150°C and air cooling) slow speed and poor effect on sputtering oxides