Weld compatibility between steels

[EngDM]

Is there a technical document that can be referenced to see what steels can be welded together and which cannot? I assume it goes much deeper than just matching the yield strength to the electrode. I have a supplier wanting to substitute some materials and the yields are the same, but I'm not sure if they are able to be welded together. RISA Connection throws out some errors when I try chosing different materials for a fillet weld (even if Fy and Fu for both materials are the same), but doesn't give a reference to why they cannot be used together even though the yields match. I'm thinking it might be due to chemical composition but I haven't really looked much into this before.

This post is strictly for subbing materials; I know different standards have different requirements for tolerance on shapes (I.E. ASTM A500 vs CSA G40.20) and have taken that into consideration.

 

[SWComposites]

Its very complicated and yes it is related to alloy composition. Suggest you post in the Welding forum with the specific materials in question.

 

[Enable]

Agreed with SW. Depends on what steels you're talking about. No document provides the list you're searching for, at least as far as I am aware. However, you can sometimes weld dissimilar materials, with a common one being certain types of stainless to mild steel (see AWS publication below). If you can try to find an AWS publication covering your situation that's at least one way to go.



You also may find this publication useful.

 

[milkshakelake]

AWS D1.1 (Structural welding code) 2020 Table 5.3 classifies a bunch of prequalified steel materials that can be welded to each other. There's like 100 different steels listed there, even some API spec metals, though most are ASTM. They are classified into 4 groups. Although you can weld any group to another group, the filler material (i.e. electrode or wire, like E70XX or something) changes. The Fu and Fy being the same has no bearing on this. It is possible that one of the materials in your case are not in Table 5.3, meaning they're not prequalified to be welded to one another. Prequalified means, more or less, that you can do it without the effort of going to the moon.

If two metals are not prequalified, I believe they may still be able to be qualified using custom testing procedures, which are complicated. I've never done that and don't know much about it.

I'm not going to post the whole thing for copyright reasons, but it looks kinda like this:

 

[EngDM]

AWS D1.1 (Structural welding code) 2020 Table 5.3 classifies a bunch of prequalified steel materials that can be welded to each other. There's like 100 different steels listed there, even some API spec metals, though most are ASTM. They are classified into 4 groups. Although you can weld any group to another group, the filler material (i.e. electrode or wire, like E70XX or something) changes. The Fu and Fy being the same has no bearing on this. It is possible that one of the materials in your case are not in Table 5.3, meaning they're not prequalified to be welded to one another. Prequalified means, more or less, that you can do it without the effort of going to the moon.

If two metals are not prequalified, I believe they may still be able to be qualified using custom testing procedures, which are complicated. I've never done that and don't know much about it.

I'm not going to post the whole thing for copyright reasons, but it looks kinda like this:

View attachment 2276

I'm looking at that table, and one of my materials is in groupe 1 but the other is in group 2.

If I scroll down to table 5.8, I can see that one material is listed in both Category A and B, and the other is just Category B. To weld the two together, does this mean I need to specify the catergory B welding process? I.e, is that how you would go about mixing the groups from table 5.3?

for reference, my steels are A500 Grade C, and A1018 HSLAS.

 

[milkshakelake]

Table 5.8 has nothing to do with this. It's about preheating, which has to do with the thickness of the materials. I think it will confuse you, and you should ignore it for the purposes of your question.

Per Table 5.3, A500 Grade C is Group I. A1018 HSLAS is Group II. Knowing the group affects the filler material (i.e. electrode). Are you concerned about what electrode to use? I can assist a bit further, though briefly, clause 5.6.1 will answer that (it's a confusing clause though). But to answer your initial question, these two can be welded together because they are both on the table.

There are some additional provisions you need to follow, like the preheat temperature you mentioned and the welding process (use SMAW, SAW, FCAW, or GMAW, I think). It's going to take a while to go through all that and figure it out. But it's all there in the tables and clauses in that chapter.

Edit: If you are engineer of record for this project, I think you only need to specify the welding symbol (fillet weld? flare groove weld? etc) and the electrode. I wouldn't get into any of the granular stuff like welding process or preheat temperature. That's for the fabricator to figure out.

 

[EngDM]

Table 5.8 has nothing to do with this. It's about preheating, which has to do with the thickness of the materials. I think it will confuse you, and you should ignore it for the purposes of your question.

Per Table 5.3, A500 Grade C is Group I. A1018 HSLAS is Group II. Knowing the group affects the filler material (i.e. electrode). Are you concerned about what electrode to use? I can assist a bit further, though briefly, clause 5.6.1 will answer that (it's a confusing clause though). But to answer your initial question, these two can be welded together because they are both on the table.

There are some additional provisions you need to follow, like the preheat temperature you mentioned and the welding process (use SMAW, SAW, FCAW, or GMAW, I think). It's going to take a while to go through all that and figure it out. But it's all there in the tables and clauses in that chapter.

Edit: If you are engineer of record for this project, I think you only need to specify the welding symbol and the electrode. I wouldn't get into any of the granular stuff like welding process or preheat temperature. That's for the fabricator to figure out.

I'm not really confused on what electrode to use, since I'd imagine that is all covered by the steel supplier/fabricator as you've mentioned. I'm just trying to approve a material substitution. As the EOR, as long as the yield/ultimate strengths and section properties are adequate to what I have designed for, I'm not sure if there is more to consider from my standpoint.

 

[milkshakelake]

As the EOR, as long as the yield/ultimate strengths and section properties are adequate to what I have designed for, I'm not sure if there is more to consider from my standpoint.

Agreed. You should be okay per welding code.

If you're designing the weld, keep in mind that you might need to use the lower electrode for the weld design strength. But I don't think it's any different from welding A992 to A36, which is the typical case in buildings, and it's also a Group I welded to Group II thing.

I hope I'm not missing anything. The welding code checks out. Hopefully someone else would know if there's other special code provisions for welding different steels, besides standard design checks. I can't think of anything else. It's certainly not something I've considered in the past besides making sure the materials are weldable, and I've been okay.