oxyacetylene help on welds

[Discoman]

hello, i guess a little background first would be best.
my Ag class (i'm in high school) just started welding and i'm starting with gas as it is a better skill builder than starting with arc.
anyways, for the last couple weeks we have been doing rodless welds on really thin metal.
now the problem is half the metal is rusted, the other half is covered in damp grit(this metal is the better of the two) as it comes from the plasma cams water tray below the machine.
there isn't exactly much available to clean the metal, i have been using a scrap of denim material to get it cleaner.
i know the how to, i am having trouble laying a good consistent bead on this metal.
the beads are either really high on the metal or when i go slow enough, the grit or rust burns off and the metal burns through right after.
it isn't quality metal.

is there a good trick i should know that will help me?

[PaulChristenson]

Cleanliness of the material to be welded is a condition for successful Oxyacetylene-welding. All contaminating materials like rust, scale, dirt, oil, grease, paint or slag must be thoroughly removed from the area.

Do you have a wire bush?

What is the actual thickness of the metal involved?
What tip number are you using?
Are you using backhand on your really thin metal to reduce preheating?

[Roger]

4.5" right angle grinder with cup wire brush or flap sander disk will quickly clean your metal. Cheap from $20 - $30 at harbour freight to $150 + depending on quality and were you buy. The shop should have bench grinder with wire wheel. Use vice grips to hold small metal coupons or clamp metal in vice when using these tools. Protect your eyes.

[hankj]

Have you addressed this problem with the instructor?

One of the first learned priciples in oxy-fuel welding is cleanliness of the work pieces. If this is not being taught, the qualifications of your instructor are suspect.

No welding class can succeed without the basic tools needed for the job, and that definitely includes grinders or wire bruhes.

Hank

[usmcpop]

Take in a piece of concrete block or brick and a handful of sand. Sprinkle sand and rub with block. When questioned by your instructor, tell him it's "ghetto sandpaper" or "that's how we sharpen shivs in prison".

[Broccoli1]

Your class has a Plasmacam but no tools to clean the metal:confused:

[Discoman]

we were taught that clean metal is important for a good weld.
if there is a grinder somewhere, i sure can't find it (i think there is one for the arc/ag mech team people somewhere)
but it's pretty thin metal
3 or 4 mm is my guess

[Nitesky]

Can't you find that one?

[Discoman]

i'll continue looking is the best i can do
exactly how big of an improvement should perfectly clean metal provide?

[hankj]

i'll continue looking is the best i can do
exactly how big of an improvement should perfectly clean metal provide?

100%.

You can't gas weld dirty, painted, rusty, or otherwise contaminated steel. The one exception seems to be mill scale. I've been able to weld .125" plate without removing the mill scale.

Hank

[PaulChristenson]

we were taught that clean metal is important for a good weld.
if there is a grinder somewhere, i sure can't find it (i think there is one for the arc/ag mech team people somewhere)
but it's pretty thin metal
3 or 4 mm is my guess

With really thin metal...try laying your bead backhand...so you are NOT preheating the metal...;)

[metallurgy]

It's extremely difficult to make a good o/a weld without clean metal. I don't think you could learn to gas weld on dirty steel. It doesn't flow, it doesn't follow the heat, it doesn't hold the heat...

Also make sure the filler rod is clean. *edit: WHEN you use it :P

Mill scale is a major pain in the bee-hind, I can barely get it off with a wire brush on a grinder, it's better than nothing but to really make it clean you have to grind/sand it off.

Good luck!

[Discoman]

Can't you find that one?

sorry about the long wait, i finally got the welds to work in class:)
just scraping the metal on the firebrick worked to scrape some stuff off, then i just used the O2 to blow the dust off

and sadly, there is no grinder-i finally finished the required gas welds, and have moved on to arc.

and going into that, we were shown in our book that an arc butt weld should be beveled, we have nothing to create a bevel
so it's plate against plate no bevel weld, which isn't liking to work out too well.
i can't grind this on the stone, our arc plate (the thin stuff) is 1/4"

[whateg0]

Man! As has been said, what kind of ag instructor tries to teach welding without the tools? In the real world, you sometimes have to make due, but in a class you should be learning the right way.

What school do you go to? Maybe somebody needs to write to the school? Then again, they'd probably drop ag class for lack of funding then. I dunno.

Dave

[Roger]

When your first learning to arc weld don't need to spend time beveling so you can weld in grooves. Need to spend max time welding and watching others weld. Figure out what you and others your observing are doing wrong so your welds get better. 1/4 inch plate butt weld get better penetration with slight gap between plates. Don't need bevel.

[Discoman]

okay, i havent yet started on the butt weld, i'm still working on the sencond assignment (an arc pad)
but to comment on lack of funding, i might as well be grateful that there ast still is shop at my school-and a good shop too (the ag mech team does win events occasionally)

my only question is:
11 stick welders to use-all miller thunderbolts (rather new condition as well)
1 MIG unit in the main shop- Lincoln 350MP (brand new)
1 TIG in shop-Lincoln idealarc TIG with brand new torch

last i checked, a grinder was cheaper than any of those
around $100 for a cheap one?
even a bench grinder can be had for less than $50

[Discoman]

well, just finished the last of the arc welds, no grinder to be seen still:eek:
butt worked perfectly with a little gap:cool:
:D

[dearhuntn]

Hello
I used to weld car exhausts for a living and I know I have welded exhaust pipe that was almost all rust . I would hit the welding tourch to it and all the rust would flake off/burn off and I would weld all the holes left over up trying to save people money. There was not much I couldn't weld. Luckly my dad was an vo-ag teacher and the guy that was in the shop when I was hire showed me once how to blend the rod into the exhaust pipe. You can usually burn off the rust to get down to the metal.

[hankj]

. You can usually burn off the rust to get down to the metal.

Wow.

I'm really glad that you didn't do my last exhaust system!

The notion that one can "burn off the rust" to find good steel is pretty fancifull, IMHO.

I've seen muffler shop guys do what appears to be magic with small bore O/A tips, and I respect the ability to weld with mirrors and bent rods, etc., BUT there ain't no way to weld rusty steel, and considering the wall thickness of exhaust pipes, I would think that by the time you "burn off the rust to get to the metal" that you ain't got nothing left!

I may be wrong here, but for me, rust and weld are not compatible terms.

Hank

[Roger]

I have welded exhaust pipe that seem to be more rust than not in weld area. Not a real repair just a band aid that will hold until parts are bought or car is sold. It is amazing where you can weld when hardly able to see what your doing and make a good weld. Truth be told some of the weird side views are better than looking down at weld beginners use.