④ Surface A is matched with other parts to improve the smoothness and ensure the sealing performance. 17-4PH steel has a high hardness after aging treatment, so it can be reduced when used as friction parts such as valve seat and disc.; Locked death; Occurrence of phenomenon. After heat treatment, 17-4PH steel has achieved martensite+copper rich phase strengthening, reaching the mechanical properties of the valve seat. Its hardness reaches 329HB or below, meeting the requirement of friction pair hardness difference of more than 50HB.

Common performance of non-metallic compensators and three characteristics of non-metallic contraction joints
As a flexible element, non-metallic corrugated contraction joint has common performance. It is widely used in fluid escort pipelines and equipment in mining, metallurgy, power, cement, nuclear energy, petrochemical and other industries.
Ordinary non-metallic corrugated contraction joints can compensate axial, transverse and angular directions, so according to these functions, non-metallic contraction joints can be divided into straight cylinder type, compound type, angular type and square type. Like rubber damping block and V-shaped seal ring, it has the characteristics of high temperature resistance, corrosion resistance, noise elimination and shock absorption. Because it has the function of no thrust and simplifying the design of support, it is generally applicable to hot air pipeline and smoke and dust pipeline.
The improvement of maintenance equipment requires the compensation of non-metallic corrugated contraction joints. The main reason is that this kind of compensator is easy to install and has strong applicability. Its application time is longer than that of ordinary contraction joints. In terms of basic structure, it can be divided into skin, stainless steel wire mesh, insulation cotton, insulation filler layer, frame and baffle.
The non-metallic compensator is also called non-metallic corrugated contraction joint. Its expansion function is particularly good, so that it can maintain the safe operation of the pipeline. Because this type of contraction joint uses the advantages of compensation to absorb the axial, transverse and angular thermal deformation of the pipeline. The main component of non-metallic corrugated contraction joint is elastic stainless steel bellows, which can expand and bend freely to compensate for errors. Rubber damping blocks and V-shaped sealing rings can reduce vibration