What is the purpose of hardening the surface of the ball valve’s core?
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This post was last edited by flute6 on 2010-3-23 at 12:39. I’m new to valves and work with ball valves. Know more about the relative work. Is it necessary to harden the surface of the ball in a hard-sealed ball valve? Is hardening done only to improve wear resistance? (With the valve seat) What is the relationship between the hardening of the valve seat and that of the valve ball? Hardness charts for various hardening treatments. What operating conditions require hardness? Thank you! ! !
Surface hardening is required for transporting solid materials or materials containing particles, as well as in conditions prone to erosion
It enhances the wear resistance of the sealing surface, preventing erosion when the valve passes through dusty fluids and thus protecting its sealing performance
Theoretically, hardening is necessary, as ordinary stainless steels such as 316SS have a relatively soft surface; the friction that occurs during opening and closing against the metal valve seat quickly damages the valve ball and the valve seat. It’s just that under different operating conditions, the materials and processes used for hardening vary. Common forms of hardening involve surface electrochemical or physicochemical treatments, as well as carburizing and nitriding. For more advanced applications, surface welding of Stellite alloys is used, among other methods. In situations requiring extremely high wear resistance, plasma spraying of cemented carbides followed by heat treatment, or spraying of tungsten carbide followed by heat treatment, is employed. Hardening treatment not only improves wear resistance (by spraying Cr-based alloy hardening materials), but also enhances resistance to high temperatures, corrosion (such as by spraying Ni-based alloy hardening materials), as well as erosion in various operating conditions. When hardening, the principle to follow is that the hardness of the valve ball should be slightly higher than that of the valve seat; generally, a difference of 5 Rockwell units is sufficient. The purpose of this is to ensure that when the two components are used together for sealing, it prevents sticking due to prolonged contact between materials of the same kind ； Secondly, from the perspective of damage, it is also necessary to protect the valve ball and sacrifice the valve seat, as the cost of replacing the valve seat is lower.
4# Lixuming5888: What are the specifications regarding the thickness of the hardened layer? If the ball and the valve seat are subjected to the same hardening treatment, can they have different hardness levels?
Thank you; this problem has been bothering me for a long time. I finally understand it now, and with consistent practice I’ll become more familiar with it.
Generally, it’s sufficient to harden the ball