Practical MIG Welding: Out of Position Welding

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Out of Position Welding

05.23

00:00	Ideally we'd always perform our welding with the workpiece laid flat on our workbench which allows gravity to help the weld pool settle.
00:07	Unfortunately this just isn't always practical or possible and particularly in automotive fabrication, we'll inevitably end up finding ourselves needing to weld in what we refer to as out of position.
00:18	This refers to any welding position that isn't flat but generally we can break this down into 3 types, horizontal, vertical and overhead.
00:26	There's a convention for referring to different weld orientations if you want to be super specific.
00:31	This is first broken down into the weld position where flat is 1, horizontal is 2, vertical is 3 and overhead is 4.
00:39	Next, we have a letter that refers to the type of weld, fillet or groove and designated by F or G respectively.
00:46	So, with this name and convention, 3F would refer to a vertical fillet weld while 2G would refer to a horizontal groove weld.
00:53	There are some additional designations for welding tube or pipe which are beyond the scope of this particular module.
00:59	While gravity is a benefit when we're welding flat, it makes things really tricky with out of position welding and this requires techniques that counteract gravity, maintain arc control and prevent defects like sagging, undercutting or lack of fusion.
01:12	Let's explain the problem by considering the trickiest out of position weld, the overhead weld.
01:17	When we strike an arc and form a molten weld pool, gravity is trying to make the weld pool fall from the workpiece, coincidentally, usually directly onto us, before the weld can cool and solidify.
01:27	The more heat we apply and the larger the weld pool becomes, the more risk there is of this happening.
01:32	Even if the weld pool doesn't fall off, it's very likely there'll be a visible sag in the finished weld that can affect both its appearance and strength.
01:40	The trick to out of position welding is to reduce the amount of heat that we're inputting into the workpiece to control the weld pool but of course this comes with its own set of challenges if we still want to achieve good penetration and fusion into the base metal.
01:54	Let's start by dealing with vertical welds which leave us with two options.
01:58	We can start at the bottom and weld up, referred to as vertical up, or the opposite which unsurprisingly is referred to as vertical down.
02:05	Vertical up is preferable on thicker material as it's easier to achieve good penetration and strength, while vertical down is better suited to thinner material as we can travel faster with the gun.
02:15	Regardless which method we choose, we'll generally need to make a slight reduction to both the voltage and wire speed.
02:22	Vertical welding will also benefit from a slightly reduced gun angle of around 10° in the angle of travel compared to welding flat.
02:29	The actual welding technique also benefits from a side to side weave or triangular movement pattern with a slight pause at each side to ensure proper tie in to the base metal, while moving more quickly across the centre of the weld.
02:41	For thinner materials, using a vertical down method, a straight run weld is generally preferable.
02:47	In this situation we'll want to focus on keeping the arc concentrated on the leading edge of the weld pool.
02:52	Next, we'll cover overhead welding which as previously mentioned can be quite challenging.
02:57	As with vertical welding, a slight reduction in wire speed and voltage can be beneficial, however this only needs to be minor, perhaps 10 -15% less than we'd be using for the same material when welding flat.
03:09	The reason for this is that we actually want to retain the power of the arc to help essentially drive the weld pool into the seam that we're welding.
03:16	This specific technique is going to depend on material thickness and similar to vertical welding, for thinner material a straight run weld is preferable, concentrating on keeping the arc at the front edge of the weld pool and travelling slightly faster than we would for a flat weld.
03:30	For thicker material, achieving good tie in to the base metal as well as good penetration can benefit from a side to side weave, pausing briefly at each side and again moving faster across the middle of the weld.
03:42	Regardless of the material thickness, we want to maintain a consistent stick out length and in the overhead position we can actually improve arc stability by reducing this slightly below our 10mm rule of thumb.
03:53	In addition we're best to use a reduced gun angle that should be in the range of perpendicular to the workpiece through to approximately 10° in the direction of travel.
04:01	Lastly let's deal with horizontal welding which includes elements of vertical and overhead welding.
04:07	In this position the challenge is preventing the weld pool from sagging under the force of gravity or rolling over the lower edge.
04:14	To help with this we're going to make sure that our gun is angled upwards towards the top part of our workpiece by 10-15°.
04:22	We'll also use a shallower gun angle of 10-15° in the direction of travel.
04:27	As usual a slight reduction in wire speed and voltage will be beneficial.
04:30	For thin material, a straight run weld will be best, concentrating on keeping the arc at the front edge of the weld pool while a weave or triangle movement pattern is preferred for thicker material.
04:40	In this instance, pausing slightly at the upper toe of the weld can help ensure good fusion to the base material.
04:46	Let's quickly recap the main points from this module.
04:50	While there are subtle differences between the three out of position welding techniques, all will benefit from a slight reduction in wire speed and voltage compared to what we'd use when welding flat.
04:59	Thinner material will benefit from a straight run weld while thicker material will benefit from a weave or triangular movement pattern, pausing briefly at each edge while travelling faster across the centre of the weld.
05:11	Maintaining a short stick out length and focusing the arc at the leading edge of the weld puddle is also important to prevent the weld pool from being affected by gravity.