Localized Heat Treatment for 17-4 2

[jparaiso]

I have some cast 17-4 pipe (5/8"OD 3/8" ID) that has been heat treated to H925. I would like to make a section of this tube more ductile so I can bend it slightly. I have access to an induction coil. Is there a localized heat treatment that I could perform that would make the material easier to bend?

 

[jwhit]

Before you do anything else, determine whether or not you can give up the strength you will lose by heating it to a point where it is ductile enough to bend readily. Is it something you can put into a furnace at the solution treating temperature, pull out, then bend hot? After bending, allow it to cool to below 90F, then re-age at 925f to restore strength. Also, I seem to recall that filling tube and pipe with sand to reduce crimping of the inside of the bend was a practice used in race car shops.
I would be concerned about doing it locally using an induction coil because of a possible Heat Affected Zone adjacent to ends of the coil. I will admit that my experience with induction coils is nil, so take my thoughts under consideration but do more research.

 

[metengr]

Not without giving up original strength properties. If you need the have the minimum strength of H925, you should probably re-heat treat the 17-4 back to the H925 condition. The only other option is to overage for forming and live with the slightly lower properties.

You should review the information from AK Steel on 17-4 material;

http://www.aksteel.com/pdf/markets_...tation/17-4_PH_Stainless_Steel_PDB_201404.pdf

 

[EdStainless]

As Metengr said, if you don't need the full strength then you could age a section to 1025F (or whatever was suitable) and bend it. Check your actual properties also. It may be that 925 was selected because someone needed >160ksi UTS, and in reality your parts may be 195ksi. You could raise the aging temp to 1025F, still meet your required strength, and pick up some ductility.
In the H925 you need a minimum elongation of 10%, if the actual value isn't at least 14% I would be concerned about the material.
If you heat the whole piece to 900F, and then hot bend you will not need to do any re-heat treatment.
If you need a very accurate bend hot bending is probably not your answer though.
We used to do this for very general bends, we filled sections with Olivine sand (MgO, not SiO2) to support them when bending since you can't use ID tooling hot. We made OD form out of Oak and charred them, they held up very well.

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Plymouth Tube

 

[jparaiso]

Strength in this bend section is not really an issue. In order to get the properties of an H1025 age at the bend area, would my localized heat treat need a resolution or could I just heat to 1025F? Also how long would you suggest I heat the section for at 1025F?

 

[EdStainless]

The std HT is 4 hours.
If you could use a multi-zoned furnace and heat the entire part to 900-925F, and the bend section to 1000-1025F.
If you can't then just insulate the entire part that is not being heated.
You want to minimize temperature gradients or you could get a lot of distortion.

There are companies that do field HT work by wrapping insulted elements directly onto the parts. That would work for this.

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Plymouth Tube

 

[MagBen]

why not over-aged to 1150H, if the strenght is not an issue? 1025H and 925H have a comparable YS and elognation.
if slightly bending, you probably no need to re-age for a residual stress relief. For a heavy deform, you do need to re-age to restore tooughness.