Advice on Welding Parameters for 10mm Thick Low Carbon Steel

[Aidan O'Brien]

hello, I might sound like an absolute tool asking this question but I really need some advice on an assignment I am currently struggling on.
I am doing an engineering technicians course at college to become a CAD technician.
One of my subjects being "Welding Technology" as i started off on a welding course.
The assignment explains that 10mm thick low carbon steel is to be welded in both butt and fillet joints.
it then asks me to descirbe a suitable welding process for this task.
Personally i would say MIG would be the best process to use for this. but it then goes on to ask what parameters would be used for the joining process. As I work in a Drawing Office i do not have a lot of experience welding or interpriting parameters for specific welding procedures. as well as this it asks for consumables required for the process. as well as a comprehensive work plan of all tools and equipment required. i was wondering if anyone would be able to shine a little light on the subject for me?
i dont want to seem like im asking for answers for college work as i actually do want to learn something from this as i do have a general interest in engineering.
if anyone can give even the slightest bit of advice on this subject i would be truly grateful.
Thank you in advance people ).

 

[Richard.]

There is no answer for this based on the very limited info provided.
The conditions will vary on the position of the plate . Flat, v up, over head.
There will also need to be a prep for the butt joint as to which a root is needed (different conditions again ) then hot/filling passes which will be worked in accordance of interpass temp to ensure heat input is low and mechanicals are optimum. This can also be done with solid wire, rutile flux core, metal cored wire.
There are so many variables .

 

[Richard.]

I did a trial last week on solid wire roots rutile flux core filling and cap . Best results I got was
PF position(v up) 60 degree inclusive prep angle. This was 15mm thick.
Open root 2mm gap 1mm face no backing was allowed.
Solid wire root (1mm)full pen was 17volts 130-150 amps 4.0-4.5 m/min
Flux core 1.2mm filling 24volts 180amps 7-8 m/min.

 

[Aidan O'Brien]

This is all really helpful information mate thank you. It says all positions like. So do you think if I mention that the butt joints require preperation, for 10mm thick would you recomend single v, double v or just a bevel? And im sorry im am amatuer but could you explain what a hot/filling pass is? And would you reccomend more than 1 run or would that depend on the settings and wire used as this would affect the root fusion and the side wall fusion?

 

[Richard.]

A butt weld on a pipe would almost certainly be done single V as a double v would require access from both sides. On 10 mm with a mig it would take a number of passes to fill it. The first would be the root and the idea would be to gain full penetration from the front side so that it can be seen nicely from the back if you can still see the root side walls then it's lack of root penetration. The next run is the hot pass this is the run that punches right into the root and Side walls giving good penetration into the root bead but not going right through the first bead (root) should still be seen from the back.
Then you fill it up , quite often this is done with the same conditions as the hot pass but with a bit more speed as penetration is no longer a big deal now as it's all about side wall and inter run fusion. The reason a joint like this is not filled in one big fat run is heat input. This is the biggest limitation as far as welding is concerned , how much heat can the parent material take before it loses it's mechanical properties.
Too much heat makes for large grain structure in the joint which the effect is low toughness.
More runs at higher speeds finer grains high strength in the joint.

 

[CRB]

I come from plastics so my input may seen distant but the same applies. The unfortunate viewpoint is that those who are in the drawing office NEED to know what is required on the shopfloor but are not TAUGHT it in the first place.

No reflection on you at all Aiden, but there does seem to be an amount of disassociation when leapfrogging.

A great many of the members will have come from fabricating and therefore will know how to do root, hot pass etc, and it pains me that you need to ask on a forum to expand your knowledge in this way.

Not that you are a Makkem or anything like that

 

[Aidan O'Brien]

Thats excellent mate you have been a huge help, this might be asking a bit much but would you mind if I send you a quick rough draft of what I have written down to see if it makes sense to an experienced welder?
And CRB you are totally right in what you say, a bit experience on the tools can never go a miss when working in the technical side of engineering. And hahaha mackem and proud mate good to see a fellow northener on here, it truly is a small world