Jump to content
I Forge Iron

scale, cracks and then some


Recommended Posts

Let me start by saying that I have learned more since joining this site than I had the rest of the time I have been at the forge. Thank you all!

Now for the problems.
I told a friend that I would do 40 tent stakes for him. (Oops)
In the process I was having trouble with the square stock cracking when I bent the hook. (3/8 hot rolled) I have had occasional cracking problems before but never a lot or regularly. A machinist where I work said it was too cold and I was bending it too fast. So I got it bright orange before bending and bent it very slowly, which did cure the problem. But I haven't normally had to be that careful. Was it more a temp or speed issue?

Also, I have a propane forge with a grill regulator and forced air. I produce a ton of scale that normally brushes off ok. Sometimes, however, I get spots that almost look like water drops on the steel even where I didn

Link to comment
Share on other sites

Mild steel will bend readily at red heat. Speed is not the issue, temperature is.
Generaly speaking a gas forge will not burn steel, but if it were able to reach welding temperature it would be close to burning. So much scale means too long in the forge. Too many irons in the fire?

Link to comment
Share on other sites

i was taught to work the metal at bright orange.....if you use the horn of your anvil, be sure to line the squareness of the way you bend ...cause the horn is tapered you wont get a nice even turn on the peice. ... you do get more scale in the gas forge...the changing of the color of the exhaust, and the water drop thing...where are you getting your metal?? the color sounds like your burning off some coating or maybe some old flux is lighting up.... i leave a scrap[ piece in my propane to set items on so it heats more evenly...that piece of metal goes thru lottsa of heatings and does form an inordinate amount of scale on it, i dont care cause its a sacraficial piece of scrap...when you chip the scale away the metal is ooce and shiny...it would be interesting to weigh a piece and reheat it many times to see how much mass you would loose.....i digress

Edited by fat pete
Link to comment
Share on other sites

You need to work it at a bright orange to yellow, depending on your shop lighting. It could also be the metal. I've had nothing but troubles putting leafs on hooks with one batch of round rod and no problems doing the same with other. Although the scale would say other wise, make sure the iron has heated long enough for the center to be hot too. Too much scale may also mean an oxidizing fire and there is too much oxygen.

When you burn the metal, there are usually sparks. Butter yellow is getting close to welding temperature. To prevent cracks, you may need to work close to that temperature with the steel batch you have.

Link to comment
Share on other sites

Too long in the forge might be part of the scale problem. I'm guessing multiple heats probably doesn't help either. ?

As far as bending at red that's what I thought too but this stock had some cracking at orange. I'm glad to hear that the batch of metal might be problematic. I've had a lot more trouble with what I've bought here lately than I used to and thought it had to be something I was doing.

Link to comment
Share on other sites

A36 is what most hot rolled is now unless you pay the premium for 1018 hot rolled mild. A36 has consistency issues sometimes being pretty high C and perhaps other metals in the alloy that can cause problems.

Of course a propane forge can burn the steel if you have too much air and it doesn't need to be at welding heat to do it. Excessive scaling in the forge is burning.

Combustion (burning) being the oxidation of a material though it is usually thought of as being exothermic it doesn't have to be. Iron is rusting outside, just not fast enough to give off significant quantities of heat though giant piles of rusting steel are often warmer than ambient.

Anyway, if it's scaling in the forge give it less air or more propane just be aware that the forge will be exhausting more CO the richer the fire.

If it's scaling outside the forge that's normal. It will oxidize at an accelerated rate in open air at heat. You can flux it to keep the air off but that makes a mess.

The alloy could be more susceptible to oxidization at heat which would just illustrate the mystery metal aspects of A36.


Edited by Frosty
Link to comment
Share on other sites

Just to menting my favorite trick on making lots of stakes: do them in 2 stake lengths and hotcut them apart at a sharp angle so that instead of forging out points all you have to do is to move the point left by the cut to the middle.

I wish you'd told me that before I had them all cut out!


I played with the gas air mixture and managed to get rid of about 75% of my scale problem. Thanks.

I think the cracking is an issue with the steel. I hope it doesn't break being used as stakes. Even at orange some pieces were still cracking.

I have done 50 of these stakes now. I think I got it down by the last 5 or 6.
Link to comment
Share on other sites

  • 2 weeks later...

The problem with the water like marks appearing could be that part of your refractory lining is melting due to too high a heat in your furnace. We have on occasion used lower temperature bricks for furnace roofs when we need to repair a furnace in a hurry, after a week or two we find the bricks start to melt and drop drips of glass like material onto our jobs as they are getting hot.
Just a thought

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...