Understanding of overall heat treatment
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A few days ago, I encountered a problem: the facility has a large tower over 50 meters in length, made of 09MnNiDR material, and the drawings require overall heat treatment. Since it is not possible to heat treat the entire piece in the furnace, it must be divided into several sections for heat treatment; after welding these sections together, local heat treatment is applied to the welded ring seams. A few colleagues started arguing; some believed that this did not constitute a full-scale heat treatment, as such treatment could not completely eliminate welding stresses. Moreover, since welding was carried out again after the heat treatment (ring seam welding), and the heat treatment reports consisted of several reports on segmented heat treatments and several reports on local heat treatments, these could not replace a report on full-scale heat treatment. Some also believe that, according to GB150, when overall heat treatment is not possible, segmented heat treatment can be used (with an overlap of no less than 1500); in the case of local heat treatment, as long as the heating width meets the corresponding requirements, it can be considered as overall heat treatment. What are people’s views on such issues, and how do they understand them?
Formulating reasonable process measures should be possible!
The original poster is right; I agree with what you said.
It is not considered overall heat treatment. If it is not possible to carry out overall heat treatment inside the furnace, the equipment can be heated in a tower using multiple nozzle flames; this is indeed what we do in practice. During the heat treatment process, it is necessary to control the temperature rise properly and manage each heated surface to ensure even heating of the container.
“\"Segmented heat treatment\" can refer to either performing heat treatment in segments first and then welding, or welding first and then carrying out segmented heat treatment. Personally, I think it’s the latter.
The owner’s equipment is too long to allow for overall heat treatment inside the furnace; instead, segmented heat treatment inside the furnace can be carried out, with the length of each heating cycle being determined accordingly. It is necessary to insulate the parts outside the furnace in order to avoid excessive temperature gradients. If the standards and procedures are followed strictly, such heat treatment can be considered equivalent to overall heat treatment.
“When overall heat treatment is not possible, segmented heat treatment can be used (with an overlap of no less than 1500). In my understanding, this means that heat treatment is carried out after the equipment has been fully assembled； And at least 1500 in length requires two heat treatments.
Overall heat treatment means that the entire part has been heat-treated. The specific methods of operation are as follows: 1. The operations described above ； 2. Overall heat treatment in the furnace – it is necessary to confirm the manufacturer’s capabilities in advance.