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(Resistance) spot welding HR MS?

JasonPAtkins

Hot Rolled
Joined
Sep 30, 2010
Location
Guinea-Bissau, West Africa
Hi folks,
I have a lot of welding experience but haven't used my spot welder all that much. I have a project where (to limit distortion) I want to spot weld a 16ga (1.5mm) piece of hot rolled (can't get cold here) mild steel onto a rectangle made of rolled 1/8" (3mm) thick angle iron.

I'm using a Miller 2.5kva spot welder.

I have read that HR is hard to spot weld because of the mill scale, but we ground that off of both sides of both prices with a flap wheel, and I'm still getting no penetration on the weld, it gets orange but them pulls apart easily by hand.

Anything I can do, or just switch to mig?
 

DDoug

Diamond
Joined
Oct 18, 2005
Location
NW Pa
Can you drill/punch a hole in the 16ga where you want the weld, and then plug weld with the MIG ?

How much MIG power doo you have avail ?
I recall reading in one of the Lincoln awards books, where John Deere developed settings to use a MIG welder as a spot welder, no hole required.
 

Pathogen

Hot Rolled
Joined
Oct 18, 2016
For spot welding the parameters you have to pay attention to
electrode material
electrode shape
current amplitude
current duration
pinch pressure
pinch pressure release
material being welded
any one of these parameters will interact with the other

cut some material up to practice with, keep your welding electrodes clean and properly shaped
adjust what you can to learn what works

take notes as you go
 

rogertoolmaker

Cast Iron
Joined
Jan 3, 2016
Hi folks,
I have a lot of welding experience but haven't used my spot welder all that much. I have a project where (to limit distortion) I want to spot weld a 16ga (1.5mm) piece of hot rolled (can't get cold here) mild steel onto a rectangle made of rolled 1/8" (3mm) thick angle iron.

I'm using a Miller 2.5kva spot welder.

I have read that HR is hard to spot weld because of the mill scale, but we ground that off of both sides of both prices with a flap wheel, and I'm still getting no penetration on the weld, it gets orange but them pulls apart easily by hand.

Anything I can do, or just switch to mig?
I am not familiar with a miller spot welder; however, I have done a lot of industrial spot welding over the years.
16ga steel spot diameter is Mallory 3 flat electrode at the tip, .250 diameter top and bottom electrodes. Maintain the spot diameter. Allowing the spot to go from .250 to .312 requires double the current to obtain the same weld quality. The parts should be clean, free of scale in the weld area.
 

metalmagpie

Titanium
Joined
May 22, 2006
Location
Seattle
I think of Miller spot welders as coming in 3 tiers: their little 125VAC one, their 250VAC one, and their bigger ones. IIRC the 125 volt one can weld to a total thickness of 1/16", the 250 volt one can weld to a total of 1/8", and for thicker you need one of their bigger spot welders. I am guessing your welder simply isn't rated for 3/16" of total thickness.

Miller manuals are all online, suggest you look up your welder's specs.
 

Scruffy887

Titanium
Joined
Dec 17, 2012
Location
Se Ma USA
I have a 115 volt Miller and have no problem with 2 pieces of 16 gauge using the shorter tongs. The 220 volt ones I have easily do 3/16 max.
 

Strostkovy

Stainless
Joined
Oct 29, 2017
I would think that you are probably dishing the metal a bit when you grind it, meaning you aren't get enough contact pressure where you actually need it.
 

DDoug

Diamond
Joined
Oct 18, 2005
Location
NW Pa
MIG is probably a good idea and most popular among welders. I've been using the Weldmax 395 (like this one here) for many years and can personally vouch for it. A versatile welder with suitability for many metal types.
What "Metal types" would that include ?
 








 
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