Forge scale

I cannot answer that directly as I get my blanks heat treated in bulk in vacuum ovens. But I was speaking to a pal today who supplied my last batch and they were heat treated in a salt bath and came out covered in scale and some rust marks.

Normally I struggle with a belt to remove the scale but I was told to using wet sand blasting which is your cheap garden jet washer and a cheap sand blasting attachment from Ebay and some cheap dry sand for the media to go with the water.

It was superb, the thickest, hardest and toughest scale washed away before my eyes.....easy! The result was clean metal.

Oh and no wear on your belts...

Might be an idea?
 
Forging too hot?
Oxygen/fuel mix not right?
Someone better equipped to answer will be along soon.
 
Make sure that you have plenty of "dragon's breath" coming out of the forge. That's unburned propane which indicates that the fire inside the forge is on the lean side or low in oxygen. As Dan said, forging too hot will cause scale to form as the super hot steel contacts the air. A hard thing to avoid if you are doing forge welding.

A way to get the scale off your blades without chewing up your grinding belts is to pickle (soak) the blade overnight in white vinegar and then brushing it off under running water with a brass or steel brush
 
Yeah, I'd mostly just reiterate what the others have said. If you're using a gas forge, you want to make sure you have a neutral or reducing atmosphere. Take a look at the flames coming out of the forge. You want the flame tips to have somewhat feathered ends.

Another random thought... if you're using a gas forge where the burners are pointed directly at the forge floor and you're placing your knife directly under the burner, you might want to try moving it slightly over to the side as sometimes the air coming in from the flame can cause some excess oxidation.
 
Good deal. Another option which I use for scale removal is sodium bisulfate. It's a bit more aggressive than vinegar so won't take as long, and I believe it is what is used in industry. I find it convenient because it can be purchased in a powder form and you just mix up some with water.

You can find it in a pool supply store marketed as a product called "PH Minus" intended to lower the ph in pools, etc.
 
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