Must the inner cylinder of multi-layer wrapped containers be supplied in the normalized state using Q345R steel plates?
Thread Content
I would like to ask my colleagues: Must the inner cylinder of multi-layer wrapped containers be supplied in the normalized state using Q345R steel plates? GB150.2-2011 4.1.4 stipulates that the following carbon steel and low-alloy steel plates shall be used in the normalized state a. Q245R and Q345R for inner cylinders of multi-layer containers ； However, section 4.1.3 stipulates that for carbon steel and low-alloy steel sheets that require normalizing, normalizing followed by tempering, or quenching and tempering heat treatment during the container manufacturing process, the condition in which the sheets are delivered by the manufacturer may differ from the condition specified in Table 2. Can this provision be interpreted as meaning that the material is not in a normalized state at the time of delivery, and that the manufacturer can carry out normalizing treatment afterwards? Please discuss this.
It can be used in the normalized state; it’s not necessarily normalized at the time of manufacture, and normalization can be carried out later
I have looked into other similar issues to see if any insights can be gained: 17. A certain equipment design requires the use of normalized plates; once the equipment was manufactured, the manufacturer discovered that normalized plates had not been used, so they carried out overall normalizing heat treatment on the already manufactured pressure vessel as a remedy. Question: Is this method feasible? Why? Answer: It’s not feasible. The reasons are as follows: 1) Normalizing: The workpiece is heated to 30–50°C above Ac3, held at that temperature for a certain period of time, and then cooled in air. (If the requirements for normalized plates are ignored in the design, it is a technical error.) 2) Full annealing: The workpiece is heated to 30–50°C above Ac3; after holding at that temperature, it is cooled in the furnace until its temperature drops below 500°C, followed by cooling in air, in order to obtain a microstructure in equilibrium. 3) The biggest difference between normalizing and full annealing is that normalizing has a faster cooling rate. The consequence of performing overall normalizing treatment on the equipment is that, for the material, it is not normalizing but rather complete annealing ； For the device, it is easy to cause the device to burn and deform. 4) The differences between normalized and hot-rolled steel plates are multifaceted; it is difficult to compare and evaluate them using single mechanical properties or welding performance indicators at room temperature, as there are differences in grain size, banded structure, networked carbides, and so on.
I have looked into other similar issues to see if any insights can be gained: 17. A certain equipment design requires the use of normalized plates; once the equipment was manufactured, the manufacturer discovered that normalized plates had not been used, so they carried out overall normalizing heat treatment on the already completed pressure vessel products as a remedy. Question: Is this method feasible? Why? Answer: It’s not feasible. The reasons are as follows: 1) Normalizing: The workpiece is heated to 30–50°C above Ac3, held at that temperature for a certain period of time, and then cooled in air. (If the requirements for normalized plates are ignored in the design, it is a technical error.) 2) Full annealing: The workpiece is heated to 30–50°C above Ac3; after holding at that temperature, it is cooled in the furnace until its temperature drops below 500°C, followed by cooling in air, in order to obtain a microstructure in equilibrium. 3) The biggest difference between normalizing and full annealing is that normalizing has a faster cooling rate. The consequence of performing overall normalizing treatment on the equipment is that, for the material, it is not normalizing but rather complete annealing ； For the device, it is easy to cause the device to burn and deform. 4) The differences between normalized and hot-rolled steel plates are multifaceted; it is difficult to compare and evaluate them using single mechanical properties or welding performance indicators at room temperature, as there are differences in grain size, banded structure, networked carbides, and so on.
Steel plate manufacturers can carry out normalizing treatment as a remedy.
The Q&A in the attached illustration is exactly the answer to the original poster’s question
The normalizing heat treatment carried out by the container manufacturer during the manufacturing process cannot replace the condition of the steel plate at the time of delivery, but normalizing heat treatment performed by the material manufacturer can.
Using normalized steel plates, the plate manufacturer can carry out supplementary processing
Supply is not guaranteed, but the plates must be in the normalized state when used; equipment heat treatment cannot replace the normalized state of the steel plates