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5 types of sealing surface hardening technology for hard seal butterfly valve

Author: Butterfly Valve manufacturers Source: Posted on: 2019-12-30 10:38:35

Do you know how hard seal butterfly valve manufacturers generally harden the sealing surface? 密封面硬化技术。 This article Xujing valve will explain five kinds of hard seal butterfly valve sealing surface hardening technology for everyone.

First, the surface of the hard seal butterfly valve is made of Stellite hardfacing

After treatment, the hardness is ≥30HRC, the surface of the sphere is hardfacing, and the advantages are low cost. Disadvantages: low production efficiency and easy to cause large area deformation of the valve seat.

Second, the hard seal butterfly valve surface hard chromium plating process

The hardness is ≥55HRC, and the plating thickness of the sphere surface reaches 0.06 to 0.10mm. After chrome plating, the sphere has high hardness, wear resistance, corrosion resistance, and can maintain surface finish for a long time. The process is relatively simple and the cost is low. Disadvantages: The hardness of the hard chrome coating will decrease rapidly due to the release of its internal stress when the temperature increases, and its working temperature cannot be higher than 427 ° C. In addition, the chrome plating layer has a low bonding force, and the plating layer is liable to fall off.


Third, the plasma nitriding process

The surface hardness can reach 50 ~ 55HRC, and the thickness of the nitrided layer is 0.20 ~ 0.40mm. Due to the poor corrosion resistance of the plasma nitridation and hardening process, it cannot be used in areas such as strong chemical corrosion.

Four, supersonic spraying process on the surface of hard-sealed butterfly valve

The highest hardness is 60 ~ 70HRC, the aggregate strength is high, and the thickness is 0.3 ~ 0.4mm. The supersonic spraying is the main process method for the surface hardening of the sphere. This hardening process is mostly used in high-viscosity fluids in thermal power plants, petrochemical systems, and coal chemical industries; mixed fluids with dust and solid particles, and highly corrosive fluid media. The supersonic spraying process is a process method in which high-speed air flow generated by the combustion of oxyfuel accelerates the powder particles to hit the surface of the workpiece to form a dense surface coating. During the impact process, due to the fast particle speed (500-750m / s) and the low particle temperature (-3000 ° C), after impacting the surface of the workpiece, high bonding strength, low porosity, and low oxide content can be obtained. coating.

The characteristic of HVOF is that the speed of alloy powder particles exceeds the speed of sound, even 2 to 3 times the speed of sound, and the speed of airflow is 4 times the speed of sound. HVOF is a new processing technology. The spray thickness is 0.3 ~ 0.4mm. The coating is mechanically bonded to the workpiece. The bonding strength is high (77MPa) and the coating porosity is low (<1%). The process has a low heating temperature (<93 ° C) for the workpiece, the workpiece does not deform, and can be cold sprayed. When spraying, the powder particles have high speed (1370m / s), no heat affected zone, no change in composition and structure of the workpiece, high coating hardness, and can be machined.

V. Spray welding is a thermal spraying process on the surface of metal materials

It uses a heat source to heat powder (metal powder, alloy powder, ceramic powder) to a molten or highly plastic state, and then sprays it on the surface of a pre-processed workpiece by airflow to form a layer on the surface of the workpiece. (Substrate) Bonds a strong coating (soldering) layer. In the spray welding and overlay welding hardening processes, both the cemented carbide and the substrate have a melting process. There is a hot melt zone at the collection of the cemented carbide and the substrate. The area is a metal contact surface, and the thickness of the hard alloy for spray welding or surfacing needs to be more than 3 mm.

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