Cylinder heat treatment
Thread Content
The pressure vessel cylinder is made from 16mm thick Q235B steel in the form of a DN900 cylinder; its thickness is then reduced to 12mm while the inner diameter remains unchanged. The design pressure is 0.88 MPa and the design temperature is 200°C. Is heat treatment necessary?
According to GB150.4, this should not be necessary. But when a cylinder body is to be machined on a lathe, it is usually the inner wall that is machined. In the case described, the \"inner diameter remains unchanged\", so the thickness is machined to 12 mm.
This level is also quite high; with such thin-walled tube sections, how well can the roundness be controlled after rolling? And how can it be ensured that the inner diameter and wall thickness remain accurate after external machining?
Is it troublesome to conduct re-inspection when using Q235B steel plates for pressure vessels?
No heat treatment is required, but can you guarantee that the inner tube will be perfectly circular? Once the turner adjusts the tool according to the inner diameter and starts machining, it’s likely that some areas will not have a thickness of 12, while other areas will still have a thickness greater than 12.
For Q235B used in pressure vessel shells, the thickness should not exceed 16 mm; according to standard requirements, heat treatment is not necessary. It is sufficient to ensure that the minimum thickness after machining meets the pressure requirements
Why is 16 millimeters to be turned down to 12 millimeters?
For papermaking rolls, it is necessary to ensure external roundness
If that’s the case, I think machining is necessary both on the inside and outside; otherwise, the wall thickness is likely to be uneven, as the errors caused by the rolling machine are definitely much greater than those resulting from machining with a lathe
The original poster should provide a more comprehensive description of the operating conditions or scenarios, so that everyone can understand better. The processing technology can be determined by process, technical, or welding engineers. For the key heat treatments of concern, check whether they meet the criteria for performance-restoring heat treatment or post-welding heat treatment; if so, carry out the treatment, otherwise do not. We have encountered this situation before as well; it involves a similar function, where it is necessary to control the ellipticity of the tubular sections after machining, followed by heat treatment. Its purpose is to relieve stress in the welded joint, reduce the hardness of the joint, and facilitate machining; it has nothing to do with the heat treatment required by standard specifications, but is considered solely from the perspective of the machining process!