Cooling rate for 310S material after PWHT

[Marc Vleminckx]

We are building a 310S vessel, 22mm thick, that needs solution annealing. Within our organisation there are some questions about the cooling rate this vessel needs.

ASME II SA-480 only say's the material needs to be quenched in water or rapidly cooled by other means. 

Somebody mentioned the temperature should drop from 1040°C to 427°C within 15 minutes to guarantee material requirements. Because of the design of the vessel and possible difficulty to maintain an equal cooling rate along the surface the choice was made to cool with forced air. To some of us a 600°C temp. drop with forced air in 15min is nearly impossible with forced air. So the main questions are "What is the definition of rapidly?", "Are there other means to reach this cooling rate?" and "Is there somebody who can provide this service within Holland or maybe Germany?". Heating rate is between 150 and 200°C/h starting from 482°C, and holding time 1h at 1040°C.

[Ramin Kondori]

Reputable heat treatment companies will give you the best solution.

But Just if you failed to find a reliable reference, try Simulation heat treatment with different cooling rates on two or three coupons of your 310 material.

Then test them (mechanical tests or metallographic evaluation or whatever test is required for your PQR).

Record the results and put them on a curve.
Vertical axis for the results and horizontal axis for cooling rates.
By interpolation (or extrapolation) you can draw a curve which relates cooling rate to results of each type of test.

Let's say you have done an impact test.
Draw the curve by interpolation or extrapolation
Min acceptable result is 27 J

Draw a horizontal line passing from 27 on vertical axis

wherever the horizontal line meets the curve, draw a vertical line and you will find the minimum cooling rate.

apply a safety factor on it and you will have your minimum cooling rate.

for example if it was 100C/min you should go for minimum 110C/min

Of course this is costly and time consuming but gives you a solid base for your decision and if things went wrong, you can defend your decision. Before you do this, officially discuss this with your client and agree on the method.

Regards

Ramin Kondori

Sr. QA/QC Engineer

SINOPEC

r.ko...@petroyada.com
+98-2123592322
+98-9132150320

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[kannayeram gnanapandithan]

Cooling rate in 9 to 5 temp for austenetic is very critical

[SV Swamy]

310S is a highly stabilized grade with Chromium and Nickel content of about 22% and carbon content of about 0.1% (I am writing now from memory). Even if the chromium carbide precipitation takes place because of slow cooling rate, there would still be adequate chromium to ensure that the steel remains stainless (>14%). So, the cooling rate is not critical. However water cooling is not advisable because it can introduce distortion and residual stresses. We have in fact used 310S vessels in the service temperature range of 500 - 900 C very successfully for many years. 

I would suggest that you use chilled air or chilled argon (if the extra expense is not an issue) to minimize the distortion and also provide a fast cooling rate. 

If you need any more clarifications, pl. feel to write. 

Regards

Swamy

Retired QA/QA Manager (Metallurgist)

Nuclear Fuel Complex, Dept. of Atomic Energy

Hyderabad, India 

[Pierre Benzoni]

I'm reading what both groups are saying and the quick solution should with all High Chromium and Nickel would be to cool with at a quick rate. If not the chrome and nickel burn. My first move while metal is hot would be to hand brush with a SS Hand brush. Once brushed and any burned nickle is removed, use a spray bottle with demineralized water and mist the welds to as a aid in cooling process. Just saved you from running a PQR.

 Signed very experanced 

Union pipefitter welder 

of 32 years of Local 9

Sent from my iPhone

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[kannayeram gnanapandithan]

SS310S is not a stabilized steel, in ASS only 321,347 &348 , some time 316Ti

Pandithan

Welding Consultant

[SV Swamy]

It is not a stablilized steel but is suited for service in the sensitization temperature range because of its high chromium content. With the allowed chemistry, 310S would have enough chromium to prevent rusting even if all the carbon gets precipitated as chromium carbide (the main cause of sensitization). 

As mentioned, we have used SS 310S extensively for chemical reactors which work in the temperature range of 500 - 900 C. No PWHT was ever needed or used. 

Swamy

[kannayeram gnanapandithan]

SS310S is best suited for high temp service due to its high oxidation temp (above 900 deg celsius) not suitable for high corrosive service. SS 310S generally will not  get hardened if cold worked.

Pandithan

[Ramin Kondori]

Dear Marc:

You may refer to plate MTC and extract the parameters for solution
annealing heat treatment from there. For any PWHT, the material
certificate could be a very reliable reference.

If you do not have that info, you have to tell us more about the material,
which type of SS310 are you using...?
Is it a Nb-stabilized...?
What about Nitrogen...?

Regards
Ramin

On 7/30/13, kannayeram gnanapandithan <kgpan...@gmail.com> wrote:
> SS310S is best suited for high temp service due to its high oxidation temp
> (above 900 deg celsius) not suitable for high corrosive service. SS 310S
> generally will not get hardened if cold worked.
> Pandithan
>
>
> On Tue, Jul 30, 2013 at 11:28 AM, SV Swamy <svs...@gmail.com> wrote:
>
>> It is not a stablilized steel but is suited for service in the
>> sensitization temperature range because of its high chromium content.
>> With
>> the allowed chemistry, 310S would have enough chromium to prevent rusting
>> even if all the carbon gets precipitated as chromium carbide (the main
>> cause of sensitization).
>>
>> As mentioned, we have used SS 310S extensively for chemical reactors
>> which
>> work in the temperature range of 500 - 900 C. No PWHT was ever needed or
>> used.
>>
>> Swamy
>>
>>
>> On Monday, July 29, 2013 4:54:28 PM UTC+5:30, kannayeram gnanapandithan
>> wrote:
>>>

>>> *SS310S is not a stabilized steel, in ASS only 321,347 &348 , some time
>>> 316Ti*

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*Ramin Kondori*
*Sr. QA/QC Engineer
*
*SINOPEC*

r.ko...@petroyada.com
+98-2123592322
+98-9132150320