Yet another rollcage question. Pulse welding.

[Suvi]

Greetings from Estonia.

I have little problem. I've read that in some cases when welding rollcage, the only right way to go is to pulse weld it. But problem is that i havent found anywhere any parameters. How many Hz's and what upper and lover amperage. Material is 4130. 40x2mm

Without pulse i would go around 60-80A.

My welder is Cea Matrix 250AC/DC

Any suggestions?

(sorry if there are some grammar mistakes)

[ASKANDY]

Suvi,
Pulse welding is NOT required to weld this material. It's nice, but not required.
The pulse will reduce the total heat going into the 4130 (which is good) and it gives you a more uniform, consisitant looking weld bead. Depending on how high you set your pulse rate, the bead ripple will be tighter. If you set it real high, 250 and higher, the high pulse rate aggitates the puddle and give you a better grain structure of the weld bead with the filler and parent material.

Id say start slow.
1 PPS (pulse per second)
Dab filler on high side of the pulse and move torch on low side. This also build rythm.
55-60% on PEAK %
25 - 30% on BKGD%

You may have to set your main amps a little higher to compensate for the overall lower heat with the pulser on.
If you normally welded at 60-80A you may have to go up to 100A

Good luck!
Andy

[crawdaddy]

Why increase overall amps to compensate,Why not just bump up the peak % to 90 and leave BKGD at 20-30%? I am asking this because I find the pulser function puzzling at times. On another note If you increase the PPS and leave the % the same do you get more overall heat due to the fact the pulses are occuring more frequently? Thanks Mike

[crawdaddy]

Greetings from Estonia.

I have little problem. I've read that in some cases when welding rollcage, the only right way to go is to pulse weld it. But problem is that i havent found anywhere any parameters. How many Hz's and what upper and lover amperage. Material is 4130. 40x2mm

Without pulse i would go around 60-80A.

My welder is Cea Matrix 250AC/DC

Any suggestions?

(sorry if there are some grammar mistakes)

If you are welding steel you shouldnt be concerned with HZ/Freq which is a function of A.C welding.If you are tigging steel it it should be D.C.Mike

[PipeLayer]

If you are welding steel you shouldnt be concerned with HZ/Freq which is a function of A.C welding.If you are tigging steel it it should be D.C.Mike

I believe he was thinking the pulse was measured in Hz instead of PPS. But you can DC pulse.

[ASKANDY]

Mike,
You can increase the peak time to gain overall heat but then you reduce the cooling period of the bkgd pulse and are really taking the advantage of pulse away. Also if using the pulse for rythm control, that 90% peak on time is too much time on the adding of filler cycle to the time you have to move the torch on the low side of the pulse.
Adding more PPS does not increase the heat either. It's still and average of peak amps & peak time vs background %. The number of PPS does not change this ratio. In otherwords, if you have 1 PPS at 50% on time at 100amps. you can increase the PPS to 100 and you still only have 50% on time at 100amps.

Andy

[Aerometalworker]

Andy,
Have any test data on your comment of changing the grain structure by using pulsing? How was it changed? Was it the grain structure of the reinforcement or the base material?
Thanks!

[dseman]

I've read articles from the AWS journal indicating the weld nugget has a finer grain structure when high speed pulsing is applied. Not sure about the HAZ, and it wouldn't include the base metal beyond the HAZ. If you go to the AWS site you can search the journals for yourself. If I have time and can find the article, I'll post it.
--dseman

[crawdaddy]

Mike,
You can increase the peak time to gain overall heat but then you reduce the cooling period of the bkgd pulse and are really taking the advantage of pulse away. Also if using the pulse for rythm control, that 90% peak on time is too much time on the adding of filler cycle to the time you have to move the torch on the low side of the pulse.
Adding more PPS does not increase the heat either. It's still and average of peak amps & peak time vs background %. The number of PPS does not change this ratio. In otherwords, if you have 1 PPS at 50% on time at 100amps. you can increase the PPS to 100 and you still only have 50% on time at 100amps.

Andy

Thank You.Mike

[Aerometalworker]

I've read articles from the AWS journal indicating the weld nugget has a finer grain structure when high speed pulsing is applied. Not sure about the HAZ, and it wouldn't include the base metal beyond the HAZ. If you go to the AWS site you can search the journals for yourself. If I have time and can find the article, I'll post it.
--dseman

'
I have seen reference due to the rapid "freeze-thaw" that pulsing does provide for a smaller grain size (basics of casting physics there), but I was thinking more of the grain structure with reguards to the specific alloy mentioned by the OP. I suppose this is more of a topic to discuss between engineers but the information could be very helpful to the at-home user.