Questions regarding the material of valve internals
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I would like to ask the experts here: when specifying the material of the internal components of pneumatic control valves or shut-off valves, should we use names like 304, 316, etc., or can we also use CF8, CF8M? In other words, are there any cast components inside the valve?
The body can be cast, but the internal components are not easy to cast, right? The inner components are often denoted by 304 and 326; I’ve never seen them referred to as CF8
Control valves are generally made by processing round steel
I’ve also seen it written as CF8; it seems to be used on stainless steel pipelines
This post was last edited by zergvs on 2020-8-14 08:07. Writing 304 or 316 is a general term for the material of the internal components; in other words, as long as it is made of 304 or 316 material, it’s fine, and no requirements are placed on the way in which these internal components are shaped. CF8 and CF8M are the casting grades corresponding to 304 and 316, while the forging grades are F304 and F316. Depending on the type of valve, the materials used for its internal components can include forged parts, cast parts, rods, tubes, sheets, and other forms of manufactured materials. .
Whether to use castings or forgings depends mainly on the operating conditions. If high pressures are involved, forgings are required due to their higher strength; whereas in cases of lower pressures, castings can be used. The wall thickness also needs to be taken into consideration, as there are standards for this. For internal components, materials such as 304, 316, and 20Cr13 are commonly used.
CF8, CF8M, CF3, and CF3M are stainless steel castings specified in the American standard ASTM A351. CF8 is equivalent to 304, CF3 is equivalent to 304L, CF8M is equivalent to 316, and CF3M is equivalent to 316L
The material of the valve internals is not indicated with codes such as CF3M; instead, the materials are specified as 304, 316, etc. BALL VALVE, Class150, RF, FB, F316F/PTFE+316L+316L, FIRE SAFE ANTISTATIC DESIGN, API Std 608; CF8, CF8M, CF3, CF3M are stainless steel castings per the American standard ASTM A351
This is not just a matter of representation, right? The compositions of 304 and CF-8 are different, aren’t they?