What is the Recovery Time in heat treatment?

One result that we need to pay attention to during the Temperature Uniformity Survey (TUS) is the time differences in which the sensors placed in the furnace enter the lower limit of tolerance.

The difference between the fastest green sensor and the slowest white sensor entering the lower tolerance is the recovery time. This time is 44 minutes in the chart above.

While some TUS software can automatically calculate this parameter, which we can call recovery time, if your software does not have this feature, you must calculate it yourself. Essentially, it is the time between the sensor reaching the TUS lower temperature the fastest and the slowest.

Why is recovery time important?

This period is stated in the following article of AMS 2750G as follows:

3.5.14.1.3 The time required to achieve TUS sensor temperature recovery, stabilization or a recurrent temperature pattern
shall not have exceeded the time limit specified in the applicable material or process specification.

It is also important that the oven achieves the desired homogeneity and that the recovery time is compatible with the time required for the process performed in that oven.

For example, if there is a recovery time of 25 minutes in a furnace where you austenitize for 45 minutes, it can be said that this furnace cannot show the desired performance. Recovery for this austenitizing period should not exceed 10 minutes.

When evaluating a TUS made according to either CQI-9 or AMS 2750G, a good pyrometry inspector should always take into account the production details made in the relevant furnace and decide on the success of the TUS in line with this information.

The way to obtain good heat treatment results is through properly calibrated furnace management. As BDI Metal , we are happy to offer this service to you.