Perform heat treatment again
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The composite plate column is made of 16MnR+00Cr19Ni10; its thickness is 54+3 and 72+3. The medium used is CH4+C2H4 along with potassium carbonate and boric acid (at the bottom of the column). The heat treatment process involves a heating rate of 50–200°C, a constant temperature of 620±20°C, and a holding time of 2.25 hours. Cooling is done by furnace cooling, with the temperature after exiting the furnace being ≤400°C. This heat treatment process follows the requirements specified in clause A8.4 of JB/T4709. The drawing specifies that HG20584-1998 Table 6-1 is recommended for use. The client requires that, in accordance with the standards specified in the drawings, the heat treatment temperature be 550°C. After checking the time-temperature-sensitization diagram for 304L, it was found that its sensitization temperature is below 650°C. Please help to resolve this issue.
:Lol, this problem is likely difficult to solve. To avoid the sensitization temperature, it may be necessary to lower the heat treatment temperature and increase the holding time, but it’s hard to determine the exact settings for temperature and time.
It is recommended to follow Table 6-1 of HG20584-1998 as indicated in the drawings; the tables in JB/T4709 are not applicable to composite panels. Personal opinion: For 16MnR+00Cr19Ni10 54+3, the heating rate is 80°C/h; the temperature is maintained at 550±20°C for 2.15 hours; cooling in the furnace occurs at a rate of 110°C/h, with the temperature upon exit of the furnace being ≤400°C. For 16MnR+00Cr19Ni10 72+3, the heating rate is 66°C/h; the temperature is maintained at 550±20°C for 2.25 hours; cooling in the furnace occurs at a rate of 85°C/h, again with the temperature upon exit of the furnace being ≤400°C. It should be noted that the holding time should not be too long.