stress relieving carbon steel 2

[Jamesliska]

I have a component made from Carbon steel, it is assembled from a cold formed cone welded onto 2 backing flanges with webs welded between both flanges, we would like to stress relieve this component prior to machining to prevent distortion, can anyone suggest what temperature this should be performed at and for how long, the maximum material thickness is 35 mm.

Thanks in advance
James

 

[arunmrao]

What grade of carbon steel,atleast a low carbon or medium carbon please?

 

[Jamesliska]

The grade is S355 J2

 

[Jamesliska]

Further to last comment, this could be regarded as a low carbon steel.

James

 

[metengr]

Use 595 deg C to 620 deg C for PWHT and hold for 1 hour per 25 mm.

 

[Tmoose]

Is there really only one of these?
If you are in production, and If your finish machining is simple (just machining the flanges flat with bolt patterns, etc) you may not need stress relief. Have you made any parts yet to see what happens?

 

[Jamesliska]

We are welding the webs onto the cold formed cone, this cone is then to be worked on the inside face to produce an accurate shape.

 

[Jamesliska]

Thanks Metenger, do you know of a procedure for stress relieveing a weld on site where access is difficult, would it be possible to heat a component using oxy/propane and allow the component to cool naturally?

 

[arunmrao]

You can use wrap around induction heaters for on site jobs. These are available on rental basis.

 

[metengr]

Can you use portable electric resistance contact heaters? Torch PWHT can be done but it is tricky because you want uniform heating and being able to hold the heat at a specific temperature.

If you absolutely need to use gas torches, I would build a small enclosure to house the torches to keep heat it (similar to a small furnace) and keep the flame off of the component.

Air cooling is fine.

 

[Jamesliska]

Thanks for the good advice guys.

 

[TomEun]

First of all, the need of stress relieving are based on the industrial codes, service, and end-user’s requirement. What are the applicable code and service? Is the stress relieving really required?

If it is a part of pressure vessel, I believe the need of stress relieving of the cone section which was cold formed per the fiber elongation may be more concerned than that of the weld joint. If the heat treatment is required and the components are exposed to corrosion cracking environments, the higher heat treatment temperature (i.e., 620-675C) is recommended.

The heat treatment by torch is not recommended because it can produce the second problems, such as 2nd residual stress or grain growth by overheating locally.


Thomas Eun