Problems with the heat treatment test plates for the head base material
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This post was last edited by zjq1962 on 2017-12-28 at 10:52. For steel end caps that are supplied and used in a normalized state, if the finishing temperature for their heat shaping is not lower than the minimum normalization temperature of the material, then no further normalization is required after heat treatment shaping. In such cases, is it necessary to use a test plate that has undergone the same heat treatment process as the end cap, or in other words, a test plate made from the same material?
There’s no problem in principle; take a look at HG/T 20584 and GB/T 25198 – they both convey the same meaning. Of course, as a container manufacturing company, it is necessary to conduct an analysis based on the importance of the container and the requirements regarding the normalizing of the material. For important equipment, it is advisable for the head manufacturer to perform normalizing again, and heat treatment test plates of the base material should also be prepared.
There’s no problem in principle; take a look at HG/T 20584 and GB/T 25198 – they both convey the same meaning. Of course, as a container manufacturing company, it is necessary to conduct an analysis based on the importance of the container and the requirements regarding the normalizing of the material. For important equipment, it is advisable for the head manufacturer to perform normalizing again, and heat treatment test plates of the base material should also be prepared.
It is difficult to ensure that the termination temperature for heat forming is not lower than the minimum normalizing temperature of the material; in our factory, normalizing is carried out again, with the base metal test pieces remaining in the furnace.
One is whether the temperature can be controlled during thermoforming. Secondly, the properties of the material after normalizing are not only related to the holding temperature/time during normalizing, but are more closely associated with the cooling rate of the base material after that holding period. It’s ultimately up to you to decide whether to make a base metal test plate or not.
One is whether the temperature can be controlled during thermoforming. Secondly, the properties of the material after normalizing are not only related to the holding temperature/time during normalizing, but are more closely associated with the cooling rate of the base material after that holding period. It’s ultimately up to you to decide whether to make a base metal test plate or not.
Since normalizing is no longer required after hot forming, it is then possible to omit the test plate with the base material undergoing heat treatment; however, there must be written evidence stating that \"the termination temperature of hot forming is not lower than the minimum normalizing temperature of the material.\" If such evidence cannot be provided, re-quenching should be carried out, and a base metal heat treatment test plate should be prepared. Test plates that have not been re-tempered cannot demonstrate the cooling process during head pressing, and are therefore not representative.
During the thermoforming process, the test plate and the product are different. Although the standards specify that the termination temperature for hot forming of normalized sheets should not be lower than the minimum normalization temperature, thereby allowing exemption from normalization, this rule is actually the root cause of chaos in the industry. It results in large variations in the quotes provided by different companies. Those that truly prioritize quality by following the rules inevitably incur higher costs. As a result, companies tend to opt for the approach outlined in the standards – avoiding normalization – to keep prices low and still meet the standards; however, the quality of the products cannot be guaranteed, and no one takes responsibility if problems arise. The manufacturers may comply with the standards, but no one is held accountable for them. One of the criteria should be that, if it is possible to ensure that the sample taken from the core is of satisfactory quality, then the method of ensuring the final pressure temperature can be used; if normalizing is not feasible and it is not possible to obtain a sample from the core to verify its quality, then normalizing must be performed again.
Test plates with the same heating process as the head. It seems to be the minimum requirement – it’s essential to bring it.
But according to the standards and certain articles, this method of shaping does not constitute a restoration of performance nor an improvement in it; it merely maintains the original performance. There is no need for test specimens, so neither are there costs associated with normalizing or conducting physical and chemical tests. Considering costs, many people naturally tend to overlook quality, and standards also play a key role in this regard. This standard can no longer meet current needs.