Welding Tips and Tricks

A friend is building a three wheel electric car. He found some spindles and control arms from a 4WD ATV and had me turn axles to press into the spindles. The chip coming off the spindles when I was boring them out to accept the axles looked more like cast iron than steel, almost like black sand. I'd intended to tack them with ER70S6 wire in my MIG but worried that it might generate cracks in the casting so now I'm considering TiG brazing. The tacks would be only about 1/2" long on opposite sides. Would this be a good fit for material?

Thanks,
Rick

I think you're on the right track...

I would lean toward a soldering/brazing process.

I am NOT a fan of TIG brazing. The penetration/heat soak is far too shallow. In your case I'd have to suggest a true (full heat-soak)brazing, whether with silver or bronze.

I broke a "TIG braze" joint three days ago with a 36" pipe wrench and about 60 seconds of serious heat. There was no penetration, just a surface bond.

Steve S

Probably cast steel
As Otto says full heat brazing/silver solder

It looks more like cast steel than cast iron to me. Cast iron will chip. It's unlikely that you would get swarf seen in the image from iron.
Moreover, the design of the piece obviously requires some strength. Cast iron would be less likely to be up to the task.
I agree about the heat soak brazing method too.

It looks like you have a pretty reasonable insertion length with the axles into the housing, and this will provide a good deal of support.

What material are the axles produced from?

Should be ductile iron. Ok to weld.

I would have machined an interference fit then heated the housing until it pressed together.

FYI other posters, if your TIG brazing has insufficient pen, you were not hot enough.

Note that TIG brazing is a misnomer, it is actually TIG bronze welding. The bronze will not flow through a joint as in furnace brazing, therefore sufficient veeing and melting of the based metal is required and the finished product is therefore a fusion weld. At 50K tensile, the strength of the bronze is not the weak link in a TIG bronze fusion weld.

Trackranger, The axles are low carbon steel.

Rick

lsamech104 wrote:Trackranger, The axles are low carbon steel.

Rick

LCS would be fine to bronze. I was just wondering if it was free-cutting, 1040 etc.

I note salmonella's comment about interference fit. That's great but won't allow the bronze to wick will.

It seems you've already machined the correct clearance fit anyway.

Plenty of gentle preheat on the casting, and let it return to room temperature slowly.