[MW:18274] Re: Cooling rate for 310S material after PWHT

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 

On Wednesday, July 24, 2013 8:39:52 PM UTC+5:30, Marc Vleminckx wrote:

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.

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