I am having difficulty in assessing "T" joint 6061 fillet weld. Welding is per AWS 17.1. Sheet metal substrate is 0.080" and 0.035". Welders are so concerned with visual "blister" type indications on backside that they are not getting any fusion on side walls. There seems to be no in between, its either lack of fusion or heat showing up on back side of thin sheet. I can' t find any criteria for indications on backside only the desirable weld profile. Any suggestions?
Hello Tom, you may wish to include some more information on parameters, tungsten type and grind, machine type and features, filler metal sizes, etc. Are you using heat sinks/backing bars? The more information that you can provide, the better the responses that you will likely get. Best regards, Allan
Tungsten 100%, although the welder said he used 2% at times They grind tip to a point but it balls up as soon as they start Machine - Miller Synchrowave 250, Argon gas with a foot pedal Ran on A/C Setting 1/2 on balance filler wire is 1/16" 4043
Reducing fillet size and increasing travel speed are going to be the keys to getting the weld you want.
It appears you have thought about heat sinks from the look of your fixturing so I will leave that alone for now.
Note: D17.1 requires full PQR's for your WPS's and the type of electrode you use is an essential variable (5.4.2 {8})
Lanthanum 1.5 or Cerium electrodes provide the best current carrying capacity and are most likely to keep a pointed tip longer.
Pure tungsten electrodes should have been eliminated 20 years ago... Make them go away now and save frustration.
For the base metals you mention I would recommend: *1/16" dia. electrode sharpened to a 60 degree included angle, flatten the tip.
**Set balance control on your Synchrowave to 55-60% DCEN (meaning 7-8 on the dial) "Max Penetration" setting on a Synchrowave provides 68% EN dwell time and usually surface prep is not adequate to use this setting and get sufficient cleaning action.
***The arc length MUST be kept as short as possible without the electrode contacting the work. The operator should use about a 5-15 degree push angle. Any greater angle and the weld pool becomes oblong and hard to control.
****The operator can "slightly" favor the thicker member with the electrode placement in the joint. This will help reduce the blisters on the thin member.
At this point the operator needs to practice! I'm not going to discuss current/amperage because this will vary somewhat (within your WPS range). The operator needs to learn to move quickly across the joint in order to reduce heat building up and causing the melt-thru (blisters) you are experiencing. The foot pedal will go down far at the beginning and the operator will begin to raise it as the weld progress and the puddle begins to expand... Cool the puddle with dipping the filler and move as quickly as possible.
Making sure that there are minimal oxides on the weld zone is also key... Final surface prep should be right before striking the arc. Oxides build fairly quickly and excess arc energy and EP dwell time used to "clean" oxides will make it harder to make the small fillet with minimal overall heat input. There are a number of good posts on the forum here about surface prep for aluminum.. Just give a quick search.
An exercise that will help your welders gain confidence in keeping the arc length short is to weld pop cans together (believe it or not). Just rinse them out and poke a hole in one hemispherical end, butt them, make 4 tacks, and weld from tack to tack, rotating the can.
This is the type of weld that would benefit from an inverter style of welding power supply; one that has the ability to adjust frequency to 200 Hz. The increased AC frequency will make the arc more conical and help push the arc to the tip of the tungsten and keep it there.
Hello Tom, I was going to reply and then noticed that Lawrence gave a response. It doesn't get much better than that and I will second the "suggestion" for the newer technology that allows for expanded hertz control of the arc delivery. Good luck and best regards, Allan
No penetration into the root of the joint as indicated in the cross section of the joint which suggests incorrect work and travel angle, and the back side showing only the member with melt thru on it's edge... You're probably also finding that the edges of both members where they meet aren't exhibiting the wet fusing puddle that you would normally find in a root bead... this is a classic symptom of incorrect work and travel angles being used to weld...
Are you dipping filler metal into the middle of the weld pool, or are you feeding the filler into the leading edge of the weld pool or puddle? more importantly, are you establishing a puddle prior to feeding the filler metal? These questions are given on purpose to suggest that your technique probably needs adjustment also... Get an inverter like a Miller Dynasty and you'll be able to do sooo much more like what Lawrence has already suggested...
Too much "heat" isn't what's wrong with the joint... It is the work and travel angle that needs adjustment along with adapting the recommendations Lawrence has suggested that should make a very big difference and it will be evidenced when you compare the two macro's to each other and notice how much more penetration @ the root of the joint will be as well as the backside free from any melt thru... So tighten up your technique and make the recommended changes from Lawrence's suggestions and you'll notice substantial improvements in both penetration and melt thru.
"Weldcome" Tom to the AWS Welding Forum!
