Speed of traveling and penetration

[AMALGAM]

Hello you guys,
Someone told me that the faster I travel with a MIG gun the better penetration I get and the thiner the bead will be. Is that true at all?
Thank you
Alfredo

[Rocky D]

Originally posted by AMALGAM
Hello you guys,
Someone told me that the faster I travel with a MIG gun the better penetration I get and the thiner the bead will be. Is that true at all?
Thank you
Alfredo

If you are traveling too slow you will be piling metal on top of metal and not increasing your penetration...well, it would depend on the thickness...too fast will give you less penetration. (Which could be better depending on the joint). And you would with faster travel, get a thinner bead. All depends on what you're doing.

[HELLTACO]

In general da tiner da bead da less penetration. Go slower an' makes a wider bead fer more penetration.

[Scott V]

HA-HA Rocky,you probably thought I was your only one that gets under your skin!

[G Austin]

There is a point at which excessive travel speed is bad and also a point at which slow travel speed becomes bad. With the GMAW process it is very easy to slow down and fill a joint since there is no slag and the weld is easy to observe. One thing to remember during welding is that something has to be keeping a large puddle molten. That something is the energy released by the arc!

This problem is less liklely in vertical up welds since gravity usually keeps the molten metal below/behind the arc and allows the arc energy to melt the base metal.

AWS D1.1 restricts the maximum thickness of an individual weld pass to 3/16" for prequalified joints.

On thinner metal, slowing W A Y down may not have as much of a reduction on penetration since there is little energy needed to melt the base metal.

You could experiment yourself on some 1/4" or 3/8" flat fillet welds. MIG weld a single pass 1/4" weld and a single pass 3/8" fillet weld using the same heat settings and then either saw them in two and polish the cross section or break them after sawing them into pieces that could be broken with a small press or hammer.

[maddmatt]

if u go to fast you will have less penatration

[Seldom]

It’s an industry proven, documented fact that with mig-SC, in order to achieve optimum depth of fusion into the base metal or depth of penetration into the root of any joint the wire has to be maintained on the leading edge of the molten puddle! This is proven not to happen if you sit back on the puddle while trying to fill the joint with short-circuiting mode transfer. The speed of travel is in direct correlation to the amount of amps being used. More amps applied, more travel speed is required to keep the wire on the leading edge!

Sure you can go too fast. If you drag a bead as fast as you can across a plate or down a fillet root you’ll see the bead will be very narrow and humped in the center. With the drags on the plate, there will be little depth of fusion into surface because of the lack of heat input from an already inherently low heat input welding process. Concerning the root bead in the T-joint there’ll be full depth of penetration to the bottom of the joint but as with the plate, reliable depth of fusion!

Sure you can go too slowly. Using the same scenarios and going slow enough, characterized by sitting back from the leading edge of the puddle, a thicker pass can be made. With the plate you will have a very nice looking bead profile but with very little depth of fusion into the plate surface. With the T-joint root bead the weld metal usually will not make it to the bottom of the root (no penetration) and even if it does (about like caulking), there will be complete lack of fusion at the root. The only fusion that can be anticipated will occur out toward the surface of the weld where there was enough heat input to allow fusion to happen but certainly not at the bottom of the weld!

Mig-SC is an inherent low-heat input process! Many folks forget this fact and think that if they have a puddle, they’re getting fusion. Nothing could be further from the truth! Just because you can create a puddle has been historically proven not to necessarily facilitate fusion into the base material. Both the base material and puddle have to be sufficiently heated in order for fusion to occur and speed of travel in relation to amps has everything to do with it.

[Rocky D]

Seldom, that is just what I have been saying...only you used more words...I'll bet you can even type without having to look at the keys, too! Very well put!

[Seldom]

Hi ya Rocky!
Yup, it's exactly what you said but I thought some folks were maybe missing your point so I thought I'd step in with a little backup!

Type without looking? Ha, you gotta be kidding! LOL LOL I have to turn the lights on for crying out loud when I type but I do use fingers on both hands though! How many is relative! LOL

[HELLTACO]

Tree tings wat give good penetration wit MIG. Most important has ta be joint preparation (an' dat ain't wat kinda papers ya juse). Next ya gots method of transfer. Ya gots about 5 choices here. Chort circuit is fer thinner stuff an' is why so many peoples gets in trouble wit MIG on thicker stuff. Lotsa people thinks MIG is not a pre-qualified method in AWS D1.1, but it is, if ya juse da proper transfer method an' gas. The third way ta gets penetration is da way ya manipulate da puddle. Chu cud gets anyting ta penetrate if ya mess 'round enough. Put da wire to da leadin' edgeof da puddle ta dig in, dan linger at da back edge ta build up heat. Repeat slowl

[Franz]

Seldom, 1 finger on each hand is exactly what my stepson worked his way up to after 1 semester of typing class.
He got an A+ for the course. So much for the value of public education.
The typing teacher couldn't understand my concern.

[Seldom]

Hi Franz,
I hear what you’re saying about our public school educational system. I know a couple of instructors for the local ABC training facility here and they’ve all commented on the overall lack of reading, writing, and math skills of their students being at a sub-high school level compared to their own high school education in the early 60’s.

I took a typing class in the 11th grade and barely eked out a C if I remember correctly but I did meet my wife there!