this post was submitted on 27 Jul 2023
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Welding

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What should I know before welding flux core for automotive work? (self.welding)
submitted 11 months ago by DominicHillsun to c/welding
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Been doing stick welding for a bit, but when it comes to thin steel such as on cars, sticks blow right through. I was thinking about getting a flux core machine to do some exhaust work on my car because I don't want to mess with gas.

What should I know about flux core? What are the biggest cons about it?

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[–] Three_word_reply 2 points 11 months ago (1 children)

Unfortunately, many of the problems you had with stick will follow you with flux core. Flux core as a process was intended to be more productive version of stick welding. It requires more heat than gas shielded mig to burn the flux to generate the shielding gases.

If you can swing the extra cost for a solid wire mig welder and shielding gas, you will have a much easier time with any automotive welding. You might be able to struggle through an exhaust will flux core, but it's going to be a struggle for sure.

[–] DominicHillsun 1 points 11 months ago (1 children)

Okay, yesterday I tried out MIG and here are the comparisons with stick welding:

  1. Mig doesn't leave much of slag at all, the residue you get is more in a "dust" form which is much easier to brush off compared to the slag stick welding leaves
  2. Much harder to get impurities into the weld itself
  3. Harder to follow the weld line compared to stick welding using pencil holding technique
  4. Have to play with the settings quite a bit before you get consistent line
  5. Much better for spot welding because you can position your hand and electrode, and press the trigger when you are ready, avoiding additional hand movement.
  6. Surprisingly the spatter is more aggressive and gets stuck to surface more than my electrodes. Could be due to the wire I am using

These are my notes so far.

[–] Three_word_reply 2 points 11 months ago* (last edited 11 months ago) (1 children)

Regarding your points:

  1. this just requires practice.

  2. the settings require more adjustment for sure. The voltage is set based on the wire diameter and metal temperature. Wire feed speed is set based on metal thickness. There are charts you can look up that give you good starting points for dialing the machine in.

  3. mig should have virtually zero spatter, and what is there should just brush off. If you're getting a lot of spatter there are three likely issues: a) voltage is set too high b) contact tip to work piece is too far c) the material is dirty, such as rust or paint, heavy mill scale, or a coating like zinc or galvanizing like on aluminized exhaust tubing

You'll find that the more you use mig, the more you will prefer it. It's an all around better process for home hobbiests and light fabrication.

[–] DominicHillsun 1 points 11 months ago (1 children)

Ah sorry, I guess it's called FCAW and not MIG. I am not using any gas to protect the weld. From what I've seen on the internet it will spatter no matter what, but I will check the polarity of the cables

[–] Three_word_reply 1 points 11 months ago

Yeah that's something you'll just have to deal with. It's better if you have a dc welder and not a super cheap ac machine