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.

Heat supply network compensator bellows does not need heat treatment to meet the needs
The results of repeated corrosion cycle experiments imitating the heating cut-off conditions indicate that the normal working medium of the heat supply network has little impact on the corrosion resistance of the shrink joint bellows. The following is a case of a company in Northeast China to compare the service life of the shrink joint of the heat supply network with that of the two shrink joints. The customer said that the shrink joint of the DN600 heat supply pipeline of a city's primary network has 316L bellows data, The bellows did not stop the solution treatment after forming, and it was still safe after 20 years of operation. At the same time, another manufacturer's contraction joints were purchased, and the solution treatment was stopped after the bellows was formed. After five years of use, batch calibration occurred. The examples in other regions also proved that the corrugated tubes of the heat supply network contraction joints do not need to stop the heat treatment, and can fully meet the requirements of the heat supply network's excellent management cycle