Heat Treatment / Stress Relieving in Carbon Steel

300 degrees C~ = 572 degrees F.

thats right smack in the Blue Brittleness range my friend.

what is an inch per hour? Heating rate should be deg F/hr, no?

Our practice commercially is charge steel into furnace that is already at temperature (on roller hearth multi zone furnaces, into first zone the speed from zone to zone usually respects that figure,depending on delta T per zone.). We do not cycle furnace up and down in temperature. Too hard on refractories and energy cost.

So I am saying that it will take an hour per inch of section uniformly up to temperature. That is based on my experience and commercial technology here in North America.

On parts in baskets, the maximum distance from center of mass of parts in basket to edge of basket is the "inch" measure you want to use.

Your mileage may vary, But I am giving you what has worked for me.

30+ years and no lawsuits!

milo

Dear Sir,

When we are going for induction coil heating then what will be the rate of heating.

It is going to heat up almost instantaneously.

And beyond the temperature range requested... And we have no knowledge of mass, symmetry what the purpose of the treatment is, to name but a few.

At this point, until further details are provided, it is best to not further encourage this. Do we really want to become the engineers of record?

milo

For post weld heat treating, I believe that the rate should be 100F/hr per inch of material thickness to 1150F. Hold at 1150F 1hr per inch of material thickness ( Hold at 1150F for at least 1hr if the material is leas than 1 inch) then cool at the same rate.

The following example is actually proceeded for Pressure Vessel fabricated from killed carbon steel material as per ASME SA-516 Grade 70, thickness 41 mm, and the PWHT is calculated based on the rules of ASME code, Section VIII, Division 1, Para. UCS-56 and Table UCS-56.

Note. 593 ^oC can be assumed to be 620 ^oC ± 25 ^oC.

(A PDF file is here: PWHT-Example)

SWEET! Nicely done!

However, original poster is now talking about Induction heating.

Also, original poster specified stress relieving, not post weld heat treatment.

And up to 300 C max...

If original poster's application is Postweld Heat Treatment, you have SERVED HIM WELL!

Always a pleasure, Abdel Halim Galala.

Always a pleasure.

milo

Oh, yes

Thank you Milo.

Dear Mr. Abdel Halim Galala,

In your response you have mentioned A PDF FILE PWHT-Example.

I down-loaded but it is not opening, may be due to some deficiency in the soft-ware in my system. Please suggest me in which soft-ware this file will open.

I request you to mail a copy og the PWHT so that I can study the same.

THANKS,

DHAYANANDHAN.S,

CR4 MEMBER.

Dear Mr. dhayanandhan,

The file is just one page in PDF format and can be opened by any software like "Adobe Acrobat 8 Professional" which can be free downloaded from internet.

we anneal 7/8 bar that we bend into lifting devices to be set in concrete . in a batch oven .....heat to 1200 deg. Fahrenheit and hold it for one hour at that temp. then remove and let cool at ambient temp... the bar gets to be a very dull burnt Orange

Hi,

control of heating and cooling rate is necessary if distortion is a problem.

Any industrial heating and cooling is so fast that the thermal expansion differences between inside and outside and between left and right side will cause plastic yield.

Inside to outside because the temperature will take some time to get in or out. Left to right side (also for and aft and top and bottom) because heating/cooling is not symmetric.

So if you look to precision equipment: post the size, the length to diameter ratio, the material, how it is suspended and centered inside the induction coil, how is the cooling done and we can go a step further into precision parts.

Measurement devices, optical instruments, inertial technology, ball-bearings and fluid/gas-bearings need these extra precautions to get a nearly undistorted part with nearly zero built-in residual stress. (Have a look to my website.)

RHABE

Our standard is typically 50degC up, 50deg down with a total time of 36hrs. The ramp rate can be doubled for small bore piping.