Can 4140 Hot rolled material be welded to SA 350 material? 1

[TCBQCM]

I have a project that requires me to have SA 350 flanges that are 2 1/2" thick welded to 4140 Hot rolled mechanical tubing that is 1 3/8" thick. What would be the pre-heat temp? What would be the max interpass temp? Also should we PWHT this? If so at what temp and for how long? Thank you for any help that could be provided.

 

[metengr]

Before any welding specifics are provided, I have several questions;

1. Did you know the SA 350 specification contains various grades of steel, and that the steel grades referenced in this specification are used for low temperature service? What grade of steel are you intending to use?

2. Why on earth would someone join a 4140 steel, which is not really used for low temperature service because of less than desirable impact values, to a forging that is used for low temperature service?

3.What is the application for joining these two materials?

 

[TCBQCM]

metengr,

This is an eng. fitting. It is a spacer spool with branch assembly. Materials have been supplied I have regusted a review of all MTRs. I will have the grade shortly. W/P of this peice is 3000psi and the temp range is -20C to +100C. This was designed and eng. in a machine shop the 4140 is for the purpose of machining. I have been asked to weld and 4140 is not a material I have welded befor. This is way I am here. I will have more information shortly. Thank you metengr for your time and knowledge. Do you have any sugestions as to how I should move forward?

 

[metengr]

TCBM;
For this temperature range, I recommend using an SA 106 Grade B pipe material instead of a hot rolled 4140 structural tube. Why? The 4140 carbon content is above 0.35 mass percent, which requires more caution for welding and further, makes me question why this material was selected in the first place.

Regarding welding for the 4140 steel you are going to have to use an elevated preheat of 350 deg F. The interpass temperature will be 650 deg F, not to exceed.

For a 1-3/8" thick 4140 full penetration groove weld to the SA 350 flange you will need to PWHT the weld region. I can't see any way around this because of the base material thickness, and carbon content.

This is why, I would reject the 4140 steel and use a SA 106 material that is more desirable from a welding standpoint, and is well suited for your stated service temperature range.

 

[TCBQCM]

Thank you for your information metengr.
I have a couple more questions:

1. We must have a side entry on this spool that is machined then welded on at a 26 deg from side wall of the main body. the main body if we go with SA 106 B material. What material would you machine the side entry with. The machinest who designed this would like to use C1020 or C1045. What is you recomendation?

2. If we are able to weld C1020 or C1045 to SA 106 B. Would you know of a WPS for that? Pre-heat? Interpass temp? PWHT? Weld electrod? ETC?

Thank you again!!

 

[metengr]

TCBQCM;
What do you mean a side entry? Is this some type of nozzle that will be stubbed into the main spool? Can you provide a sketch showing this?

 

[TCBQCM]

Please see attachment. It has been uploaded to ENGINEERING.com. Please see link.
Thanks again for your help!!

 

[metengr]

Ok, I reviewed the drawing. I would manufacture the side entry tube out of SA 106, as well. The machinability of SA 106 is comparable to your original material selection of 4140, and 1020. Now, you have SA material for this application and only two grades of steel - SA 106 GRB and SA 350 Grade xxx for the flanges.

The WPS for this is P-No 1 to 1, and I would use E70xx or ER70 for the filler metal, depending on the welding process. I would also perform nondestructive testing (wet fluorescent MT) of all fabrication welds for 3,000 psi W/P.

 

[metengr]

TCBQCM;
I would suggest that if you go with the suggested material change for the pipe spool verify the wall thickness/pipe schedule with a Piping Code, like ASME B31.1 or B31.3 to ensure you have the correct wall thickness for the intended pressure and service temperatures. Also, your inspection, welding and documentation requirements will be outlined as well.

 

[TCBQCM]

Side entry: We are unable to find SA106B material with wall thicknes we need with the proper bore this part (I believe) needs to be machined from a solid shaft. I don't believe we can get SA106B solid shaft.

Do you have any other machinable solid shaft in mind that would be weldable.

We are looking at C1020 would consider C1045.

Do you know of a WPS for C1020 to P1 group material (SA106B)? PWHT procedure? Interpass temp max? pre-heat?

Thanks again!!!!

 

[metengr]

Use SA 105, this is a material specification for forged shapes, which can be turned into this custom side entry opening. Again, this is P-No 1 material and has stress lines for pipe design.