Best heat treatment of C1018 steel for lowest permeability?

[catcheral]

I am trying to find the best temperature (C) and time (minutes) at temperature for annealing C1018 steel to obtain the lowest permeability. Please suggest the amount of time per cross-sectional thickness. What permeability should I expect to get?

Thank you.

 

[MagMike]

You want to lower the permeability? Annealing is not they way to achieve that.

 

[dgallup]

Assuming you want increased permeability and decreased remanence, the following should work well:

Vacuum anneal at 1 micron or less mercury at 740 C for 4 hours. Cool to 535 C at a rate not exceeding 110 C per hour. Nitrogen with a dew point of -50 C can be used to assist cooling. Below 180 C air cooling is permissible.

We use this for small parts (~ 50 mm long, less than 4 mm thick), you will have to increase times for massive parts.

 

[EdStainless]

for max perm I would suggest 950-1000 C.
For max Br then 800c should give good results.

If you really want to go for maximizing everything then you should look at annealing in dry hydrogen for longer times. You can actually remove impurities from the alloy if you anneal hot enough and long enough. For our pole pieces in test equipment we used to use 20 hours at 1375C. The highest temp that I have ever seen used for this is 1480C.

Regardless of the temperature that you use the slow cooling down to near 500C is important. We used to use 5C/min. Slower in vacuum is fine, don't go slower in hydrogen.

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Plymouth Tube

 

[catcheral]

MagMike, sorry for the confusion. I meant "maximum".

 

[dgallup]

I guess it depends on whether you want a few optimum parts or millions of good enough parts. My recipe is for millions of production parts category. In my experience, the difference is performance is usually negligible and the difference in cost is large. If the OP has a really critical application I suspect he would have already known the answer.