A 516 Gr 70 for 450°C

Question

A 516 Gr 70 for 450°C

rjain1848 (Materials)

(OP)

24 May 17 10:29

A 516 Gr 70 can be used for exhaust system having temperature 450°C at atmospheric pressure. How the note G10 from ASME BPVC
Sec-II D will affect if I select the above material.

metengr (Materials) · Answer 1 · 2017-05-24 12:01:55

This note means this material will degrade at this temperature, over time. The degradation could be either spheroidization or graphitization damage. However, since this is being used as an exhaust system and not under pressure, should degradation occur there most likely would be no serious consequences. It is your choice, if it were me I would use a 1.25% Cr-1/2% Mo material.

rjain1848 (Materials) · Answer 2 · 2017-05-25 10:29:01

Actually initially we also planned for Alloy material but the cost and the welding process is stringent as per construction point of view. So the topic of using CS is initiated. Is it possible to calculated degradation over the period of time or any kind of thumb rule consideration.

metengr (Materials) · Answer 3 · 2017-05-25 12:11:19

rjain1848;

Quote:
but the cost and the welding process is stringent as per construction point of view

Disagree. The cost of using SA 387 plate, Gr 2 or Gr 11 is not that much more than SA 516 Gr 70 plate, and the welding being stringent means you use preheat. I doubt the plate thickness will require PWHT for an exhaust system. Why bother to evaluate CS when you have a better option????

MJCronin (Mechanical) · Answer 4 · 2017-05-25 14:55:13

Automotive and diesel exhaust systems have been made from T409 and T321 stainless steels for decades.

They have shown a very long life and are the preferred materials for OEMS.

"Thumb rules" for the corrosion rate in this kind of service are a joke

Can your welding division work with these materials, or is carbon steel the only material that they are familiar with ?

MJCronin
Sr. Process Engineer

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A 516 Gr 70 for 450°C