Home shop crack detection?

[Cord]

Have a piece of cast iron that was previously welded and the weld didn't hold. I'll be grinding it out and replacing the welds. I can see several cracks which are parallel to the original weld that will now need to be repaired as well. Once I start grinding out the welds I'll probably loose sight of these secondary cracks. I've heard of people mixing chalk with acetone, but I don't want to risk contaminating the weld. Is there something else that can be used in the home shop? Please don't say manga flux because that's prograde stuff that requires special equipment.

 

[tomplum]

Would naval jelly be an option to accentuate the crack?

 

[bcp]

One old way was gasoline. It evaporates quickly from the good surface, then seeps from the crack for a while.

Bruce

 

[tjkubota93]

Mark them with a file?

 

[rustyshakelford]

Drill the ends? Do you have any plumbers in the family?

Brett

 

[TCJatko]

How about dye penetrant? That should work; it should show any cracks. As for contamination, you're going to want to grind out any cracks for welding/brazing anyway. Be sure to stop drill ends of cracks if possible.

 

[Egon]

As suggested, Dye Penetrant in a spray bottle might be one way.

You may have to do more grinding than anticipated.

 

[Cord]

I did a little research last night and was able to find this stuff: Products | Detroit | Weld-Aid You need all three products and they're roughly $10 a can. I placed an order with Grainger and it'll be available on Tuesday. I'll report the results when available.

 

[CincyFlyer]

Have a piece of cast iron that was previously welded and the weld didn't hold. I'll be grinding it out and replacing the welds. I can see several cracks which are parallel to the original weld that will now need to be repaired as well. Once I start grinding out the welds I'll probably loose sight of these secondary cracks. I've heard of people mixing chalk with acetone, but I don't want to risk contaminating the weld. Is there something else that can be used in the home shop? Please don't say manga flux because that's prograde stuff that requires special equipment.

What is the part? If it's critical to safety, and it has parallel cracks, it should be professionally tested! I usually tig-braze cast iron, unless I can heat the whole piece, then I weld it with nickel. It's my least favorite material to weld (I'd rather weld titanium!)

 

[Cord]

Engine block

 

[Shield Arc]

Here is a good article on welding cast iron.
Guidelines for Welding Cast Iron

 

[tnjind]

I did a little research last night and was able to find this stuff: Products | Detroit | Weld-Aid You need all three products and they're roughly $10 a can. I placed an order with Grainger and it'll be available on Tuesday. I'll report the results when available.

I have used that product. Seems to work OK.

 

[Cord]

Excellent. Any problems with shelf life? The literature says only 2 years.

 

[dfkrug]

Please don't say manga flux because that's prograde stuff that requires special equipment.

Yeah, some engine shops have a U-shaped electromagnet that might even have the MagnaFlux brand on it.

But you may be able to detect cracks in ferrous metal with a strong permanent magnet, too. I like the Neodymium
magnets you can get free from hard drives, or cheap, from China. After you stick your magnet (in a baggie) on the
block in the test area, sprinkle it with sweepings from around your grinder. The lines of magnetic flux become
visible.

 

[tnjind]

Excellent. Any problems with shelf life? The literature says only 2 years.

I haven't had long. maybe 10 months.

 

[crazyal]

If doing penetrant testing make sure to follow the directions. You must allow time for the dye to seep into the cracks. Often people who don't know what they are doing don't wait long enough. Magnetic particle testing was "invented" by a machinist who was running a mill of some sort. He noticed that the millings would get attracted to any cracks or joints in the metal he was working on if the metal was magnetized.

 

[tjkubota93]

Yeah, some engine shops have a U-shaped electromagnet that might even have the MagnaFlux brand on it.

But you may be able to detect cracks in ferrous metal with a strong permanent magnet, too. I like the Neodymium
magnets you can get free from hard drives, or cheap, from China. After you stick your magnet (in a baggie) on the
block in the test area, sprinkle it with sweepings from around your grinder. The lines of magnetic flux become
visible.

Dude found a crack on my sbc I took for machine work with a part out of a junk microwave he had rigged up.

 

[yomax4]

You can also take the block to a shop and have them magna flux it. probably cost the same as buying the other product and they have done it many times. On the engine block it also matters where on the block you want to weld. If the cracks are next to a combustion area you will likely not get good results. If it's just outer water jacket or outer part of block no worries. I'd use spray powder on it. Hot spray process. I've done many. Never had a failure. Still depends on where exactly the cracks are and how bad. If it's a spider crack mess I feel for you.

 

[yomax4]

Some folks use pure anti freeze as a crack check. You just have to mark the cracks well and then spray the anti freeze out with carb cleaner. Takes a day to be sure.

 

[dfkrug]

You can also take the block to a shop and have them magna flux it.

Indeed. If you are going to an engine machine shop anyway for boring, or even hot-tank cleaning, you should
have them do it. They have the tool, and it takes a minute or 2. The charge is minimal in my experience,
since I am there to get other services done.

Using hi-frequency microwaves would be interesting.