Large holding/heat treat furnace

Discussion in 'Furnaces and their construction' started by Red97, Feb 11, 2018.

  1. Red97

    Red97 Copper Banner Member

    Figured I would share the first furnace I've built.

    Need to scale it down a bit for melting/foundry work.


    Panels are 4x8(mostly) with 2" ceramic board insulation on the inside.


    Ran out of panels, used steel mesh and 2" kwool, wrapped in welding blanket.

    Man in the pic is 6ft tall for some scale.

    Used 16 NG burners to heat to 400* and maintain while welding.


    Made 4 of these to help get the temp up around 1100 for stress relieving.

    Tossed 3 skids worth of lump charcoal in to help maintain those temps.

    The frame is close to 400k lbs. The building it is in was just a giant portable hut. Temps dropped as low as 40* in the hut. Wad quite the challenge for sure. But it all worked out.

    Now I just have to figure out how to build a smaller version for actually melting metals.
  2. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Quite the undertaking but compared to moving or scrapping that beast, I'm certain repair in place was quite attractive. You must have a good track record with longevity of your repairs.

    Red97 likes this.
  3. Red97

    Red97 Copper Banner Member

    That one was at a dealers yard. Local to us, customer bought it and wanted it fixed/machined before shipping it.

    This was the 5th one the customer has had welded up. 1st one I worked on, 3 welders + myself. 2 guys in each shift. Just over 14k lbs of weld was put in. 55 days.

    Then we re machine every surface for a complete rebuild.

    Now I'm getting ready to start welding another. I've learned a lot about the processes involved.
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Next time you guys fire up your OA torch to preheat a weld, think of Red's preheating routine.....:cool:

    Red97 likes this.
  5. Jason

    Jason Silver Banner Member

    I'm going out on a limb here.... But that place doesn't have a whimpy 7" wc gas pressure going to it.
  6. Red97

    Red97 Copper Banner Member

    I don't remember the pressure, that was back in 2014. Do believe it was slightly more than residential.

    Had a 8-10" main line, place used to be a forge shop running many a blast furnace.
  7. PatJ

    PatJ Silver Banner Member

    That is quite a process.
  8. Red97

    Red97 Copper Banner Member

    The finished weld puddle. Had to trim some off in the front. We were filling the "wedge pocket" just on a taper, they wanted it brought up flat and get rid of the wedge setup. Trimmed the front off cause it was to high.

    Then whittle it back off . Fix the twist introduced in the casting etc. Pretty big/time consuming projects.
  9. PatJ

    PatJ Silver Banner Member

    My dad use to repair the cracked frames on planers that were used in the lumber industry, and he used a similar process on a very small scale compared to what you did.
    I remember he had a number of asbestos blankets that he used, and he preheated with a big oxy-acetylene torch.
    His filler rod was coated bronze.

    He was able to salvage a number of relatively expensive planers and other machines.
    I remember he said preheat was important, as well as a very slow cool-down.

    It begs the question though, how do you weld on/around something that is at 400 F without getting cooked?
    Red97 likes this.
  10. Red97

    Red97 Copper Banner Member

    These frames are cast steel, we use a .120" flux core wire that is really similar hardness to the base material.

    As for the heat, layers of clothes, layers of kaowool. Normally use a 3ft extension to stay back out of the heat a bit, fan at my back and a chiller hooked to my welding hood pumping in cool air.

    Also have 4ft extension, sometimes add another ft of split copper pipe to stiffen the liner to reach out 5-6ft. That gets pretty heavy though.
  11. PatJ

    PatJ Silver Banner Member

    It would seem that repairs of that type are sort of a niche market thing.
    I could be wrong, but I have not met a lot of folks who did repairs like that.
    And sort of an art too I guess if you are fixing casting twists.

    I prefer to work in niche markets that other's consider too hot/difficult/dangerous/risky etc. because there is little or no competition.

    My dad knew I guy whose specialty was to crawl up inside of large ship engines and repair crankshaft journals after they had spun a bearing.
    He said the guy would hand-file a flat across the top of the journal, then a parallel surface across the bottom, and kept repeating that process all the way around the journal until he got back to a series of smooth flat surfaces.
    Then he would attach an adjustable strap with a handle on it, and he would rotate the strap around the bearing, using various grits of grinding compound, and tightening the strap slowly, and get the journal repaired and back in tolerance.

    I saw another guy one time, and his job was to put on a full diver's suit and helmet, and go down to the bottom of watewater structures (in wastewater), and repair large gates and valves that had failed.
    Not sure I would want that job, but it probably paid rather well.

    At one time I was going to get a job as the guy who climbed 1,500 ft transmission towers to change light bulbs, but as I was looking at the adverts, there was an incident in the paper where five guys were in a bucket lift going up the side of a large tower, and the cable broke. I decided something down on the earth would perhaps give me a better chance at survival, even thought it may be a lot more boring.
    There is a fine line between not-boring and safe.

    Cool stuff you are doing.
  12. Red97

    Red97 Copper Banner Member

    Pretty well a niche market.

    I know of a few companies that do the same type of machine work most are larger/global even. Very few do these type of welding project's

    Just dad and I doing the machine work, and have a welder experienced in this type of work (20+ years) helping me on the one starting tuesday.
  13. Jason

    Jason Silver Banner Member

    Getting NG to throw a bad ass flame is a no brainer on an 8-10" supply! Try getting it to work on tiny whimpy household pressure. Totally different animal.
    Red97 likes this.
  14. Red97

    Red97 Copper Banner Member

    Don't think residential supply would work very well at all.

    The next one to be welded, has a very nice furnace. Made entirely out of the insulated panels. The shop only has a 2 in supply to that area. They have to bring in a 1000gallon propane tank and some 150# tanks to get/hold 1050*+ for stress relief.

    Last one was 10 day ramp up to temp, hold 1050*~ for 16 hr, took 8 days to get back down to 80* that casting is only in the 200k lbs range.

    Something to be said seeing a piece that size with glow about it.
  15. Red97

    Red97 Copper Banner Member

    I'll post a picture of the burners. Maybe someone can share a way to make them more efficient?

    Since this is a newer factory all induction furnace, gas supply is only used for building heat. (Northern Wisconsin) needs it this time of year.

    With the furnace running the building heaters can't keep up. -30 outside temps will bring the building temps to 35-40*. Hopefully they are running production, otherwise it gets pretty cold while welding. Lol

    The burners are a 3/4" pipe about 4' long. Cap on the end 1/8" nozzle, 2" washer welded on with a series of holes. Wi th a 2" x 6" long pipe welded to the washer.

    Can't help but wonder if adding some air would raise the efficiency. These just throw a long mostly orange flame.? 12-14 of them all the way around the base/tickest part of the press.
  16. Red97

    Red97 Copper Banner Member

    Customer did a very very nice job on the current furnace.

    They wanted to be in charge of the heating/cooling. And had enough manpower to build the furnace

    I will try an take a picture this weekend .

    Nice large platforms, and large exhaust hoods built on.
  17. Jason

    Jason Silver Banner Member

    That's some pretty wild stuff Red. You are kinda new around here and probably havent seen the burner on my NG forge I built. It's a ribbon burner and runs on whimpy 7" wc gas here at home. It is forced air with a microwave blower on it. Here is it running. It took me months to get it work on such low pressures. Now that I've figured it out, the thing really is bad ass. So much so, I'm considering my next furnace build will be centered around this design.
    The build is found here.

    Red97 likes this.
  18. Red97

    Red97 Copper Banner Member


    Little extra trimming before I can start welding.
  19. Red97

    Red97 Copper Banner Member


    The exhaust hoods can't quite keep up, but helps some
  20. Red97

    Red97 Copper Banner Member

    20180214_161618.jpg 20180214_161639.jpg

    Burners. Currently have 6 running off l.p. to maintain 500*

    Running a bit higher than normal because of the location of the damage

    Not enough natural gas to run the building heat and the furnace. So using 1000 gallon tank.

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