Welding robot by Joel Sullivan - video

[Frank S]

> perhaps localized induction heating cooled with a spray of liquid nitrogen could do the trick

Wouldn't that cause waves in the sheet? (I ask in ignorance.)

I was referring to the possibility of the need to re surface harden the repairs on a press die
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I have used heat and cold to flatten thin sheet metal such as hail dents in the roofs of cars.sometimes in reverse by super cooling a very small depression then warming the area around it will do the trick other times vacuum and vibrations in the ultrasonic range will pull a small dent from an auto body other times when ever possible to work from behind the dents can be massaged out.
But as I was saying in the case of a press die a weld repair will leave the area softer than the rest of the die that was why my suggestion of heat and rapid cooling.

[nova_robotics]

As Paul Harvy used to say and now the rest of the story.
Thank's Joel. Your comment about repairing dents or divots in the press die reminds me of some sheet steel we bought one time that was made entirely from recycled automobiles the problem was when this is done some of the metals are quite hard like bearings for instance once the cars are run through a shredder there is hardly anyway to insure no bearings are in the mix. Forming shearing machining or even just drilling these sheets were a challenge. I can see these as causing problems in press dies
Do you have a way to re harden the surface area of the repairs? perhaps localized induction heating cooled with a spray of liquid nitrogen could do the trick

I never really thought about hardening the surface. It would be difficult to do anything thermally. These presses are HUGE and they're filled with thermal oil for heating. Maybe some sort of hard coating? Maybe change up my mig wire for something designed for hard coating? It's certainly something to think about. Thanks!

[Frank S]

Do you know what RC the surface was supposed to be originally?
There are many grades of hard surface wires. Study products is a famous brand, however as you may already know when making a repair on a flat surface it is often difficult to blend the repair into the rest of the surface. If in a short arc mode the weld has very little penetration due to the low voltage and amperage. Globular transfer is the most popular method of welding for joining structural members together and is also the method by which 90% of all welding is performed. due to the balance in voltage and amperage this yields a nice fluid puddle altering the type of gas used IE straight CO2 versus 75/25 Argon mix greatly changes the penetration puddle freezing and material deposit flow. Mig wires are formulated differently as well some work better on straight CO2 than a mix gas.
If at all possible to actually get into a spray arc mode then the deposit will have much lower splatter deeper penetration and a flatter weld deposit But spray arc will require using an even more exotic gas like 98/2 or a tri mix of gas 98/2 is 98% Argon and 2% oxygen Tri mix gas might contain many different mixtures which is most often a custom mixture right at the welding facility this may include Argon nitrogen Helium or even in some cases a percentage of oxygen as well.
any and all of these a fore mentioned processes can alter the surface hardness of the weld deposit as well as tensile strength wear properties and penetration.
Since most of my builds and repairs require the best possible strength I mostly use a duel shielded flux cored mig wire with CO2 as my filler material and gas. for real thin metal I use ER70 S6 copper coated bare wire with 75/25 gas. But I have had to go with a non coated solid wire with 98/2 gas back when I was welding up derricks for foundation drilling rigs. the Spray arc mode was to make the welds appear to look like joint and welds on the tubing were molded in and to spread the heat effected zone further into the core of the structure like fluc core gas shielded wire does but without the clean up.
My suggestion would be if your local welding supply company has a welding analysis engineer on staff would be to ask them for their recommendations and procedure It never hurts to seek the advice of a 3rd party if they have familiarity with the situation you are encountering.
I see that you have done testing on scrap samples already and this is probably the single most important way of learning which process works best for you.

[nova_robotics]

Wow. Okay. That's a lot of information. I'm obviously far too ignorant when it comes to welding processes. I'll have to do some reading. If I do some experimentation and get it dialed in maybe it could be a value adder for the client. Thanks!