D1.1 MIG Plate Test Question

Date 02-09-2010 13:25

I'm substituting this week as a teacher and gonna start a guy on his 3g in mig. He's using bare wire with 75/25 and an open root/carbon steel. I did this test awhile ago and was told the root opening was the same size as the wire? Is this correct? I tried it and ended up putting a 1/16th root opening or so on the plate, it just did not work out for me with that .035 root opening. Anyhow, I know that for mig they want you to use a 30 degree angle, 60 included but in the books we have at the school they all show using a backing plate with 1/8th gap. What does AWS say about an open root gap with mig? I don't want to give the guy shoddy info and would like to know exactly what AWS says for future reference. Any help would be appreciated and many thanks!

Shawn

By Lawrence (*****)

Date 02-09-2010 14:01 Edited 02-09-2010 14:17

Shawn.

There is a little wiggle room for personal preference.

For short circuit GMAW Vert-up I like a *tight* 3/32 root opening and a 1/16 inch land.

For .035 wire about 180-195 ipm... 17.5-19 volts. Inductance toward the high end for the root and toward the low end for the covers. I also like to increase WFS to about 200-205 ipm for the cover passes

Edit:

As far as what "AWS" Says about open roots and GMAW.. There are two important things of note.

1. Open roots welded from one side are not prequalified, so any welder performance qualification testing WPS's must be supported by PQR's in compliance with Section/Clause 4

2. Short circuit GMAW is not a prequalified process... So any procedures for production or welder performance qualification must be supported by PQR's in compliance with Clause/Section 4

By Cumminsguy71 (*****)

Date 02-09-2010 14:06

Hey thanks for the quick reply Lawrence!

By mightymoe (**)

Date 02-09-2010 23:11 Edited 02-10-2010 00:56

Hello Cummingsguy71,
Our school has the students run the open root/ no backing plate downhill. After the root all other passes are uphill. Root gap 3/32 to 5/32.

By Lawrence (*****)

Date 02-09-2010 23:51

We do both up and down (all passes) with short circuiting GMAW

I have them do V-up first because its harder :)

But just like open roots and SMAW... Depending on where you go.. You may be asked to do roots either way.

By Cumminsguy71 (*****)

Date 02-10-2010 02:16

I guess I forgot to mention that part, open root uphill is what they've been having the students do since I can remember. Although thinking about a downhill open root seems like it could offer some of it's own challenges.