Differences in the use of Q345R in the normalized state, hot-rolled form, and controlled rolling form
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If a product is designed, the design temperature is -19°C/50°C, and the design pressure is 1.77 MPa. During the production process, Q345R steel plates with a thickness of 46 mm are used for the flange covers. Neither the drawings nor GB150 require that these components be used in the normalized state; however, normalized steel plates are actually used for these flange covers in production. If the material data sheet for the flange covers indicates that they meet the requirements for impact resistance at 0°C, is it then necessary to retest their impact resistance at -20°C?
Standard requirement: Q345R shells with a thickness greater than 36 mm, and other compressed components such as flange covers with a thickness greater than 50 mm. Although your 46mm is within the standard range, it still sits on the edge of that range. It is recommended to use the normalized state. Steel plates in the normalized state can better ensure the mechanical properties of the material. The flange cover steel plate passes the 0°C impact test, but it can only be used at 0°C. According to your design parameters, this does not meet the safety requirements; therefore, the flange cover should be tested for impact at -19°C
My understanding is as follows: For this product, the thickness of the flange cover designed is 46 mm. According to Table 4 in GB/T150.2, there are two supply conditions for steel plates with a thickness of 46 mm – one is hot-rolled, controlled rolling, and normalized (with a minimum operating temperature of -10°C), and the other is normalized (with an operating temperature of -20°C). For this thickness, although the material data sheet specifies impact testing at 0°C, since the design temperature is -19°C, impact testing at -20°C should be carried out as well to determine whether the material meets the design requirements.
Personal understanding: 1. The main component of this device is definitely a normalized plate； 2. The flange cover must definitely be subjected to -20°C impact testing ； A plate this thick should normally be normalized, and it is also recommended to use normalization.
The flange cover steel plate passes the 0°C impact test, but it can only be used at 0°C. According to your design parameters, it does not meet the safety requirements; therefore, the flange cover should be required to withstand impacts at -20°C
The flange cover is made of 16Mn forgings, designed for impact at -20 degrees Celsius