Newbie Question - Steel practice drill

sru_tx · Fri Oct 23, 2015 10:28 pm

I'm a newbie teaching myself how to TIG weld. I'm using 3/32 2% Lanthanated electrode, 3/32" ER70-S2 filler, on 3/16" hot rolled steel and some 14 gauge hot-rolled steel as my practice coupons. I've ground off the mill scale using a grinding disc to bare metal (not just shined up mill scale with a flap wheel, been there done that).

I'm doing the steel welding drill that Jody discussed. Laying beads. Getting seat time. As suggested in the video, after a few beads, quench the piece in water. What I have found is that after a few quenches I can no longer get a decent bead. Nothing sticks. Looks awful. I wiped it down with acetone and still no change. Today, after having this problem show up again, I took the flap wheel to the remainder of the coupon and took off any discoloration. Back to shiny silver metal. Voila, good beads (relatively speaking).

So am I missing something? As I'm quickly learning, TIG needs clean surfaces but I didn't think I was going to have to re-grind the surface after quenching.

Am I missing something?

thanks,

newbie Steve
Houston, TX

Poland308 · Fri Oct 23, 2015 11:05 pm

It's possible that when you dunk the hot metal in the bucket that any oil on the unground portions is creating a film on the top of the water. When you pull the part out of the water it is redepositing oil on the whole part.

Poland308 · Fri Oct 23, 2015 11:06 pm

Or it could just be oxidation building up from the repeated dunks.

Braehill · Fri Oct 23, 2015 11:17 pm

Steve,
The water causes an oxidation layer on the surface and it changes the temper of the metal. It shouldn't take much to get it clean enough to weld again. A better suggestion might be to set up multiple coupons and rotate through them while the others are cooling.

Len

Mike · Sat Oct 24, 2015 7:58 am

Welcome to the forum Steve.

sru_tx · Sat Oct 24, 2015 8:08 am

thanks for the suggestions. I'll probably just rotate multiple coupons as I practice.

Louie1961 · Sun Oct 25, 2015 11:17 am

I found that the mill scale comes back after repeated heating and cooling and you need to re clean your coupon (sander, grinder, etc.). I also found that if you are doing this drill, you get farther if you use a larger/thicker piece of steel.