Sign in to follow this  
chris freeman

Refractory cracking problems

Recommended Posts

This is not the first time i have applied refractory cement to my forge. In fact I've done it several times. I've been having a hard time getting my forge up to welding temp and staying there long enough to weld at a efficient rate. I doubled up the kaowool hoping that reducing the space would help. I only have one burner in my propane bottle forge. I applied a coat of refractory then filled in the cracks that weren't actually too bad. When That cured the cracks were much worse. I let it cure for 48 hours both times. I want to fire it but don't want any cracks as the goal is to not let any heat escape to behind the refractory lining. I was wondering if anyone else has had this problem and how they took care of it. I could fill in the cracks again but it seems that they would just come back through. I also was wondering if I should fill in the cracks then fire it on low heat. then obviously increase to complete the firing process.

Thanks, Chris

20181123_125308.jpg

20181123_125316.jpg

20181123_125324.jpg

20181123_125330.jpg

Share this post


Link to post
Share on other sites

By the way, the doors have 1.5" of kaowool lining as well.  The space as of right now is about 10" deep  X 6" high. I don't know how to get the cubic inches but that's the space I'm heating. I guess the other question I have is, is that too much area for one burner with forced air. I live in Colorado so I can't do atmospheric. Please and thank you again for any help.

Chris

Share this post


Link to post
Share on other sites

The heat problem isn't related to the crack problem.

The crack problem is from using refractory cement instead of a proper castable refractory. We advice people not to use the cement over and over; but the do...and then they have problems.

Your lack of heat could be related to what you are using for forge doors; then the answer would involve baffle walls.

Your heat problem could be related to what you are using for a burner; if it doesn't develop a hot enough flame, your forge design will not overcome the lack. How about providing a flame photo?

 

Share this post


Link to post
Share on other sites

Thanks Mikey, I actually bought the plans for the forge and burner 10 years ago and i know it's a good design as a lot of smiths have used it and still do. I just don't know if the mods that I've done have made it not do as well. I'm not familiar with baffled walls, although the flame is kinda hard to see,  I do know what it's supposed to look like and it is a good crisp blue flame.

 

20181123_152342.jpg

20181123_152350.jpg

20181123_152407.jpg

20181123_152416.jpg

20181123_152454.jpg

20181123_152502.jpg

20181123_152510.jpg

20181123_152722.jpg

I thought i was using the proper castable refractory. It fires real well and does withstand the heat very well. It does not burn, melt or deform at all. I've used stuff that didn't withstand that kind of heat but this stuff that I ordered does and it hardens very well. I just don't like the cracking.  If you have a suggestions on something better then please, I'm all ears.

Share this post


Link to post
Share on other sites

Is the floor of your forge insulated? As in is there ceramic wool under it, or is it just refractory or fire brick?

Its difficult to tell from the pics, but it appears that it’s not?

Share this post


Link to post
Share on other sites

A good example of a baffle wall would be some bricks piled upon each other in front of a forge opening, a part of an inch away from the opening, with the middle row of bricks containing a gap just large enough to admit stock through. From there the concept can be used in as elaborate a manner as you wish.

Share this post


Link to post
Share on other sites
7 hours ago, stevomiller said:

Is the floor of your forge insulated? As in is there ceramic wool under it, or is it just refractory or fire brick?

Its difficult to tell from the pics, but it appears that it’s not?

No it's just a 1" brick, I thought about that and am going to insulate it. 

Edited by chris freeman
I miss understood the profile part when I signed up to this forum and I thought what I posted was rude and didn't mean to come on like that.

Share this post


Link to post
Share on other sites

Welcome aboard Chris, glad to have you. Putting your general location in the "Header" rather than just the profile puts it under your AVATAR on every post so we don't have to go looking. We are NOT going to remember where you are after opening another post.

Did I misunderstand or did you really buy plans for that? It's a mess of a design.

Try swapping your blower and gas jet, turbulence is good for mixing propane and air but that arrangement is likely to inhibit propane flow through back pressure from the blower.

You can run a Naturally Aspirated NA burner in Colorado sea level to more than 7,000' is just a matter of tuning it. Easy Peasy.

Ditto Mike, castable refractory NOT refractory cement, they are two entirely different things. This liner has lasted because you aren't getting it HOT. 

Stick with us, we'll get it working for you.

Frosty The Lucky.

Share this post


Link to post
Share on other sites
19 minutes ago, Frosty said:

Welcome aboard Chris, glad to have you. Putting your general location in the "Header" rather than just the profile puts it under your AVATAR on every post so we don't have to go looking. We are NOT going to remember where you are after opening another post.

Did I misunderstand or did you really buy plans for that? It's a mess of a design.

Try swapping your blower and gas jet, turbulence is good for mixing propane and air but that arrangement is likely to inhibit propane flow through back pressure from the blower.

You can run a Naturally Aspirated NA burner in Colorado sea level to more than 7,000' is just a matter of tuning it. Easy Peasy.

Ditto Mike, castable refractory NOT refractory cement, they are two entirely different things. This liner has lasted because you aren't getting it HOT. 

Stick with us, we'll get it working for you.

Frosty The Lucky.

I don't have any idea of what I would swap my blower and gas jet with. I'm a single dad of 3 teenage boys so I do everything on a budget as I always have. If I can build it I will. I buy materials as needed though. I did but the plans for that forge 10 years ago. Is there a post with a tutorial to show me how to build a better forge? I'm all for it. Actually I'd like to get the one I have working well instead of rebuilding a whole new one. I've always been that way. I will also redo my profile so it's done right.

Thanks for the help Frosty

9 minutes ago, chris freeman said:

I don't have any idea of what I would swap my blower and gas jet with. I'm a single dad of 3 teenage boys so I do everything on a budget as I always have. If I can build it I will. I buy materials as needed though. I did but the plans for that forge 10 years ago. Is there a post with a tutorial to show me how to build a better forge? I'm all for it. Actually I'd like to get the one I have working well instead of rebuilding a whole new one. I've always been that way. I will also redo my profile so it's done right.

Thanks for the help Frosty

I guess I meant a tutorial for a  different burner.

Share this post


Link to post
Share on other sites

Chris,not having insulation on the bottom of your forge is causing a lot of heat to be lost, a 1” hard brick is a heat sink and pulling a lot of your heat to outside the forge. If it’s insulated underneath, yes you will still have to heat that brick but the heat will stay in the forge working as thermal mass to even temps out inside. Think of this, you wouldn’t lay down on cold concrete and just put a blanket on top of you, you would still be very cold. Put a mattress and blankets under you and you conserve your heat and now you are warm. 

The others will explain the baffles. I’d get that in order then take a look at your burne and work to tune it up before trying any different burner.

Share this post


Link to post
Share on other sites

I think making changes step by step as needed, without being in a big hurry to spend money, is good. Changing the floor can be a small investment. two K26 insulating bricks from eBay is a  cheap change.

Building a "T" burner is a small investment. It can be used as part of a ribbon burner later on for small money too.

Take changes one at a time as needed, but remember that once you start using that forge, how efficient it is well have a lot more to do with money than it does right now.

Share this post


Link to post
Share on other sites

Chris: By change around I mean swap the two on your burner, put the blower where the gas jet is and the gas jet where the blower is. It might not make a big difference but without as much back pressure against the gas flow it can deliver more fuel. More fuel and air per second burning in the forge means more heat. Provided it isn't flowing so fast it's blowing right through the forge and burning on the outside.

Frosty The Lucky.

Share this post


Link to post
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.

Guest
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.

Sign in to follow this