Questions about valve trim selection at high temperatures?
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Material selection for butterfly valves in coke oven gas flues: The temperature of coke oven gas is around 300–350°C, with a maximum of 350°C, and the pressure is negative. According to available information, at 350°C, the required stress for Q345 is greater than that for 15CrMo. There are the following questions: 1. Simply from the perspective of strength requirements, it seems appropriate to choose Q345 material for valve internals – is that correct? 2. Since the internal components of the valve are designed to be thin and lightweight (for example, the pipe diameter is large but the valve disc used is relatively thin), if the only consideration is preventing deformation, would 15CrMo be a better choice than Q345 for preventing deformation? 3. For 15CrMo and Q345 of the same specifications, such as a diameter of 3000 and a thickness of 12 mm, which steel plate is more likely to deform over time at 350°C?
15CrMo is a heat-resistant steel with a pearlitic microstructure; it exhibits high thermal strength at high temperatures (δb≥440MPa) and oxidation resistance, as well as certain resistance to hydrogen corrosion. Due to the high contents of Cr, C, and other alloying elements in steel, it has a pronounced tendency to harden, resulting in poor weldability. For comparison, the performance parameters are as follows: Grade: 15CrMo; Tensile strength in MPa: 440–640; Yield strength in MPa: 235; Elongation (%): 21. Q345 is a type of steel material. It is a low-alloy steel that is widely used in bridges, vehicles, ships, construction, pressure vessels, special equipment, and more. "Q stands for yield strength; Q345 indicates that the yield strength of this steel is 345 MPa. Mechanical properties of Q345A: Tensile strength: 490–675; Yield strength: ≥345; Elongation: ≥21. Personally, I think that in high-temperature applications, we should give priority to 15CrMo, as this steel has better heat resistance.