Mig Welding Questions

[gaza01]

Hi
Recently started welding. Bought all the kit and got stuck straight in, made a complete mess of my first weld (to be expected) but then after some advice on here got a feel for things - slightly. I now want to understand some theories / principles of welding. (Practical followed by theoretical is how I learn best).

It's difficult watching videos on line and reading comments because I don't think there is 1 post online where there isn't conflicting views on what is right vs what isn't. Welding videos just seem to be a magnet for arguments in the comments so it's difficult to gauge at times.

Anyway my current questions are:

Weaving vs not weaving.
Seems like weaving isn't necessarily required? Is this purely for aesthetics?

Root passes
Appreciate some root passes have quite a big void to fill but on smaller ones why not just slow the pass down and fill in one go? I'm not alluding to this being right just trying to understand the principle for multiple passes
What I've seen online is the first root pass done with no weaving. Apparently straight passes are stronger then weaved passes...is that right? The subsequent welds are then weaved. Again is this just aesthetics? If I wanted to focus on strength would I make all the passes straight?

Welding vertically
What exactly makes this different and thus requiring different settings to welding horizontally?

Pre-heating
When does this start to provide a benefit? Is it based upon the thickness of material being welded?

 

[chrismac]

To help answer some of your question with my views.....

weaving, is dependant on weld requirements, ie if its a 6mm fillet required your not going to be weaving, weaving lets you wash the molten metal in a big V prep of example to try to eliminate lack of fusion. (also answering another question you have, why not just fill out the weld in one pass.) and gives you a slightly wider weld allowing more build up of weld metal.

root pass. what are you meaning here open butts in plate? or just the first run on a fillet, the reason there is no or little weaving on a fillet will be to get weld penetration into the parent metal, open butt in plate (not used so often) weaving would probably be a thing so you wont burn the V prep edges away.

welding vertically, gravity will take charge and if you dont have the correct setting and speed your weld will be either down your neck or on the floor.

Pre heating, very cold or heavy material, it will help.

now for the arguments

Good luck

 

[Erie Fred]

What kind & size of welder ?'
What material and thickness's ?

 

[gaza01]

What kind & size of welder ?'
What material and thickness's ?

rtech 180
mild steel 5mm and below for now.
The questions are more to start getting a good general understanding of mig welding

 

[Erie Fred]

rtech 180
mild steel 5mm and below for now.
The questions are more to start getting a good general understanding of mig welding

Weaving, root pass and the like are more for thick materials in general.

 

[gaza01]

Weaving, root pass and the like are more for thick materials in general.

Yep I gathered that but my questions aren't in relation to what I'm currently working with.

 

[mike 109444]

Not sure this doc will help but it is very informative for a machine operator manual!

 

[Erie Fred]

Yep I gathered that but my questions aren't in relation to what I'm currently working with.

and just how was I to determine that from what you typed ?
Contrary to popular belief, we ain't mind readers...just yet.

 

[gaza01]

and just how was I to determine that from what you typed ?
Contrary to popular belief, we ain't mind readers...just yet.

Wasn't expecting any mind reading skills...just very basic reading and comprehension.

 

[addjunkie]

Not sure this doc will help but it is very informative for a machine operator manual!

One of the better ones Ive seen.

 

[diggadyl]

I weave my butt weld filler runs but that’s mainly it. You want to be careful weaving fillets as that’s a sure way of getting undercut if the settings are on the hotter side.

With root passes, I’m assuming you’re talking about butt welds. You can’t really dictate what’s needed to fill it up. For example if you have a >10mm butt it you can’t make the settings cool enough to fill it all in one pass as you run the risk of a whole host of welding defects when it comes to UT. If your material is only 5mm I’d say it’s safer to do a quick root pass to join them together, clean it out with I grinder then lay a nice straight run over the top.

Pre-heating is only required if the material is really cold, really wet or really thick. Maybe a combined thickness of 75mm hope this helped

 

[Erie Fred]

Wasn't expecting any mind reading skills...just very basic reading and comprehension.

G.I.G.O.

 

[gaza01]

I weave my butt weld filler runs but that’s mainly it. You want to be careful weaving fillets as that’s a sure way of getting undercut if the settings are on the hotter side.

With root passes, I’m assuming you’re talking about butt welds. You can’t really dictate what’s needed to fill it up. For example if you have a >10mm butt it you can’t make the settings cool enough to fill it all in one pass as you run the risk of a whole host of welding defects when it comes to UT. If your material is only 5mm I’d say it’s safer to do a quick root pass to join them together, clean it out with I grinder then lay a nice straight run over the top.

Pre-heating is only required if the material is really cold, really wet or really thick. Maybe a combined thickness of 75mm hope this helped

Thank you. Every little helps

 

[CastolinEutectic]

Hi
Recently started welding. Bought all the kit and got stuck straight in, made a complete mess of my first weld (to be expected) but then after some advice on here got a feel for things - slightly. I now want to understand some theories / principles of welding. (Practical followed by theoretical is how I learn best).

It's difficult watching videos on line and reading comments because I don't think there is 1 post online where there isn't conflicting views on what is right vs what isn't. Welding videos just seem to be a magnet for arguments in the comments so it's difficult to gauge at times.

Anyway my current questions are:

Weaving vs not weaving.
Seems like weaving isn't necessarily required? Is this purely for aesthetics?

Root passes
Appreciate some root passes have quite a big void to fill but on smaller ones why not just slow the pass down and fill in one go? I'm not alluding to this being right just trying to understand the principle for multiple passes
What I've seen online is the first root pass done with no weaving. Apparently straight passes are stronger then weaved passes...is that right? The subsequent welds are then weaved. Again is this just aesthetics? If I wanted to focus on strength would I make all the passes straight?

Welding vertically
What exactly makes this different and thus requiring different settings to welding horizontally?

Pre-heating
When does this start to provide a benefit? Is it based upon the thickness of material being welded?

Hi, we asked our technical colleagues about your questions, they responded the following, hope this helps:

Weaving:
Purpose: Weaving is often used to cover a wider area and to ensure better fusion at the edges of the weld. It can also help in controlling the heat input and managing the weld pool.
Aesthetics: While weaving can improve the appearance of the weld, it is not purely for aesthetics. It can also help in achieving better penetration and fusion, especially in thicker materials.

Not Weaving:
Purpose: Straight passes (stringer beads) are typically used for root passes and in situations where deep penetration is required. They are generally faster and can be stronger because they focus the heat and filler material in a narrow area.
Strength: Straight passes can indeed be stronger because they concentrate the heat and filler material, leading to deeper penetration and a more uniform weld.

Root Passes
Single Pass vs Multiple Passes: For smaller root gaps, a single slow pass might be sufficient. However, for larger gaps, multiple passes are often necessary to ensure complete penetration and to fill the void properly.
Strength: The first root pass is usually done with a straight pass to ensure deep penetration and a strong foundation. Subsequent passes can be weaved to cover a wider area and to ensure good fusion with the base material and previous weld layers.
Aesthetics vs Strength: While weaving can improve the appearance, it also helps in achieving better fusion and coverage. If focusing purely on strength, straight passes are generally preferred for the root pass, but weaving can be used for subsequent passes to ensure good fusion and coverage.

Welding Vertically
Differences: Welding vertically (vertical up or vertical down) requires different techniques and settings compared to horizontal welding.
Vertical Up: Requires lower heat input and slower travel speed to prevent the weld pool from sagging. It provides better penetration and is often used for thicker materials.
Vertical Down: Faster travel speed and higher heat input. It is generally used for thinner materials and provides less penetration.
Settings: Adjustments in voltage, wire speed, and travel speed are necessary to control the weld pool and prevent defects like sagging or undercutting.

Pre-heating
Benefits: Pre-heating helps in reducing the risk of cracking, especially in thicker materials or materials with high carbon content. It also helps in achieving better penetration and fusion.
When to Use:
Pre-heating is generally recommended for:
Thicker Materials: Typically, materials thicker than 1/2 inch (12.7 mm) benefit from pre-heating.
High Carbon or Alloy Steels: These materials are more prone to cracking and benefit from pre-heating.
Cold Environments: Pre-heating can help in preventing thermal shock and reducing the risk of cracking.

If you have any other questions, we'll do our best to respond.

 

[gaza01]

Hi, we asked our technical colleagues about your questions, they responded the following, hope this helps:

Weaving:
Purpose: Weaving is often used to cover a wider area and to ensure better fusion at the edges of the weld. It can also help in controlling the heat input and managing the weld pool.
Aesthetics: While weaving can improve the appearance of the weld, it is not purely for aesthetics. It can also help in achieving better penetration and fusion, especially in thicker materials.

Not Weaving:
Purpose: Straight passes (stringer beads) are typically used for root passes and in situations where deep penetration is required. They are generally faster and can be stronger because they focus the heat and filler material in a narrow area.
Strength: Straight passes can indeed be stronger because they concentrate the heat and filler material, leading to deeper penetration and a more uniform weld.

Root Passes
Single Pass vs Multiple Passes: For smaller root gaps, a single slow pass might be sufficient. However, for larger gaps, multiple passes are often necessary to ensure complete penetration and to fill the void properly.
Strength: The first root pass is usually done with a straight pass to ensure deep penetration and a strong foundation. Subsequent passes can be weaved to cover a wider area and to ensure good fusion with the base material and previous weld layers.
Aesthetics vs Strength: While weaving can improve the appearance, it also helps in achieving better fusion and coverage. If focusing purely on strength, straight passes are generally preferred for the root pass, but weaving can be used for subsequent passes to ensure good fusion and coverage.

Welding Vertically
Differences: Welding vertically (vertical up or vertical down) requires different techniques and settings compared to horizontal welding.
Vertical Up: Requires lower heat input and slower travel speed to prevent the weld pool from sagging. It provides better penetration and is often used for thicker materials.
Vertical Down: Faster travel speed and higher heat input. It is generally used for thinner materials and provides less penetration.
Settings: Adjustments in voltage, wire speed, and travel speed are necessary to control the weld pool and prevent defects like sagging or undercutting.

Pre-heating
Benefits: Pre-heating helps in reducing the risk of cracking, especially in thicker materials or materials with high carbon content. It also helps in achieving better penetration and fusion.
When to Use:
Pre-heating is generally recommended for:
Thicker Materials: Typically, materials thicker than 1/2 inch (12.7 mm) benefit from pre-heating.
High Carbon or Alloy Steels: These materials are more prone to cracking and benefit from pre-heating.
Cold Environments: Pre-heating can help in preventing thermal shock and reducing the risk of cracking.

If you have any other questions, we'll do our best to respond.

Haven't been on for a while. Thanks for the reply!