Electron Beam Welding Standards? 4

[salmon2]

Hi Experts,

We are planning to EB weld the following combinations:

1) 4140 and 718
2) K500 and 718
3) K500 and MP35N

The first material is a cylinder piston and 2nd material is a pin to be welded into a tight fit hole in the piston. Hole is perpendicular to piston axis. Penetration depth is fine since we have talked to couple welders. But just wondering if any industry standards relevent we can use to establish welding procedure and also NDT and mechanical testing since this is a subsea application and we have to meet NACE0175, API 6A, etc.

Background: These parts are going to see differential pressure - tend to break weld and pop out the pin and axial force to piston axis on the pin - bending the pin. Prior welding, these materials are in the condition close to the hardness limits set by NACE.

Ideally we don't want to do any PWHT since they are dissimilar material and we figure it is pretty hard to do so. Any comments or ideas are highly welcome and appreciated.

 

[metengr]

salmon2;
For starters, I would use ASME B&PV Code, Section IX for guidance regarding development of a Weld Procedure Specification and qualification of the procedure using coupons for tensile, bend and hardness traverses.

Regarding nondestructive testing requirements and acceptance criteria, I would use ultrasonic testing, as a volumetric examination method for the EB weld along with Liquid penetrant testing. Perhaps look at NORSOK standards for NDT acceptance.

 

[salmon2]

metengr,

Does ASME Sec. IX cover EB welding and these materials specifically? In your experience, can we possibly get away with PWHT? Thanks a lot for your replay.

 

[stanweld]

Do you mean make the weld without PWHT? Often times effective heat treatment can be achieved by using a defocused beam after making the strength weld.

 

[metengr]

salmon2;
To answer your first question, no not all of your materials are listed in Section II. But this does not matter because Section IX is a service code book meaning it can be used for development of welding and brazing procedures and qualification of welders/brazers.

Agree with stanweld regarding a defocused beam and generous preheat. This is why microhardness testing as part of WPS qualification will be necessary.

 

[salmon2]

stanweld, yes. Really? That is something we are really interested. I remember somebody probably you mentioned this before - I did my homework before I asked this question. Anywhere I can read more about refocused beam method? I assume this is a local PWHT. Really the weld isn't on critical load path which is the 2nd load condition in my original post.

 

[stanweld]

We used a defocused beam to preheat and heat treat hardenable ferritic alloys and to heat treat high temperature alloys of Molybdenum and Niobium in rocket engine applications. The degree of defocussing and time at temperature produced by the defocused beam were pretty much originally done by trial and error, subsequently by experience. It is assumed that you have a welding engineer fully versed in the operational capabilities of your EBW unit.

 

[salmon2]

metengr, I agree ASME Sec. IX is probably the one we will use eventually but that is a project from scratch. I was hopping if there is any standards have been proven successful and we can save some time and cost. I assume we have to do tensile, CVN, bend tests for each of those combinations even if everything goes as expected. That is a lot of material just for testing specimen, a lot of $s. Microhardness test is fine because it can be done non-destructively. What is the as-welded structures of K500, 718 and MP35N.

 

[salmon2]

stanweld, we will use other shops and we don't have EBW in house. So you are saying it is done in the vacuum chamfer as EBW or it is a built-in function of EBW? Anyone doing this commercially?

 

[metengr]

salmon2;
If what you are asking are there actual WPS qualified for you to review and use? No. You need to customize this setup and optimize the welding essential variables yourself. Section IX provides an excellent guide for what variables to select. Yes, it will take time and cost but this is what is needed to ensure a quality product. There are no shortcuts.

Regarding welded structures, you will have to generate weld coupons and evaluate the resultant mechanical and possible corrosion properties (if applicable) since these are autogenous welds. Good Luck.

 

[salmon2]

metengr, thank you for your valuable comments and I highly appreciate them. One more question if I may what are the as welded structures of K500, 718 and MP35N? I want to see what their as-welded properties are.

 

[metengr]

salmon2;
I would search the web sites below for general welding information related to 718 and K500.

http://www.specialmetals.com/products/index.php

For MP35N

http://www.cartech.com/techarticles.aspx?id=1450

 

[TVP]

salmon2,

In addition to the ASME B&PV Code, there are some ISO standards that are applicable to electron beam welding:

ISO/TR 17671-7 Welding — Recommendations for welding of metallic materials — Part 7: Electron beam welding

ISO 13919-1 Welding — Electron and laser-beam welded joints — Guidance on quality levels for imperfections — Part 1: Steel

ISO 15614-11 Specification and qualification of welding procedures for metallic materials — Welding procedure test — Part 11: Electron and laser beam welding

ISO 15609-3 Specification and qualification of welding procedures for metallic materials — Welding procedure specification — Part 3: Electron beam welding

 

[salmon2]

Thank you, TVP. I found some iso standards covering EBW but yours are addition to them.

Thank you, metengr. I will check them out.

 

[ptrebw]

Also, you can go to a reputable EB weld shop and have them do the weld development for you. Based off there experience they will typically know best which standards your application should be following and can recommend the appropriate testing as well- eliminating some of the guess work.

It's a shameless plug none the less, but we do provide this service if you are interested:

http://www.ptreb.com/EB_Welding_EBW_Job_Shop_Welding_Services/

BUT there are others out there as well.. EBW can be complicated process and not all shops are created equal- but if you go with someone that has been around awhile you should be able to find the expertise you are looking for to ensure a quality, repeatable weld.

 

[salmon2]

ptrebw,

Thanks a lot for your info and that is one of things I asked for originally. A star for your post. We have another engineer leading this right now and he has in talk with couple shops. I will for sure contact you if those don't go well. I like the information on your webpage.