Hans Richter

I’m ready for serious casting?

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After buying 2 real crucibles (graphite, size A4), assembling two strong ingot moulds and melting several badges of pure bronze (then copper) badges. All to get the feeling for base material behaviour and consistence (no pyrometer). Also build 4 pure chamotte clay cast moulds with the negatives (wood models) of historical founding’s (axe, arrow point, dagger etc.) reusable instead of petrobond (at least I hope ;-) )

Carrie out my first cast this evening and keep you informed about the results.

Cheers, Hans

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Hi Hans did you pour through the side/ parting of the mould?  Some high volume moulds are poured on their side but typically moulds are poured through the cope into a well in the drag.  The metal then flows through a runner bar parallel to the casting and finally enters casting cavity through ingates.  Pouring directly into the casting cavity you often end up with sand erosion where the metal hits the cavity.  Pouring through the gating system helps slow the metal down preventing erosion.   Pouring perpendicular  to your mould will also help prevent burning your flasks.  I assume you left them in place while pouring?

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Hans: Do you know how much bronze or copper shrinks as it cools? The spru and riser supply metal under pressure as the casting cools. You've made the molds without a reservoir and with the multiple thin sections I see problems.

Just being able to melt the metal and owning the tools doesn't mean a class wouldn't make success more likely.

Frosty The Lucky.

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Hi gents,

the question in the topic wasn’t  only a rhetorical yell ;), thanks for feedback and tips, and of course the honest answers.

Thomas –placed de moulds in an extra shell because they didn’t close well after kiln the clay so there are a lot of ‘organic’ vents all filled with bronze after pouring

JN –used the setup of an historical mould shown at a local museum, when I step over (and I do) to lost sand I will use the method you describe

Frosty –an honest answer and remark ;-) with one small addition from my side I’m not only ‘own’ the tools but made them by myself with exception of the PPE’s and crucibles. After all ‘the way is the goal’ isn’t it?

Please see the results below –still a long way to a good cast and I will practice further, follow some classes and read your threats and tips on IFI. Keep the blank of the pugio as an reminder on my first cast.

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Yep, I have cast the first first ax and several bronze spear points without inclusions and errors, unfortunately the stone molds can not be used again. In the long run, it will then be able to make steel samples for continuous casting during the workshops. Does not matter, a next step in the right direction. For me it is important to have a good result without having to sharpen and auction for hours.

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Copper has an affinity for oxygen which can cause a lot of porosity in the piece. We used lithium at the foundry as a degasser just before pouring.

Looks like fun!

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Are you set on using stone molds? I'd be making gang patterns and casting in green sand. Maybe oil bonded sand. Student's were invented for mulling sand you know. ;) 

Frosty The Lucky.

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I have grand myself a new pyrometer, going up to 2450 ° F. Have reached a temperature of 2050 ° F in the small gas forge within 15 minutes. Also use it for better control of the melting temperatures in the melting furnace.
The pyrometer with sensor has cost me just 90 dollars. I had to drive more than 200 miles to the nearest art supplies store and on that occasion I also bought 12 refractory soft bricks, a whole roll of superwool, 55lbs of casting sand, ridgidizer and AlSi mortar. All together for $ 370. Just make several casting flasks of wood and metal in the shop and follow Frosty's advice to play at first in the sandbox;) 

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Now if you get yourself a PID controller and a solenoid gas valve, connect those in with your thermocouple, you could set different temps for your foundry or forge.

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Thanks for the tip John in Oly, WA,

however, pimped the venturi burner with a compressed air injection. To maintain the temperatures in the forge and melting furnace, the burners operate by the venturi pricipe with a nozzle nbr.65 at a gas pressure of 14psi and fully opened valves (cylinder + torch) and natural respiration. To apply welding and melting temperatures I use a gas pressure of 28psi and compressed air injection controled by a needle valve.

 Do not be the best electrician but think that I then need two solenoid valves and a control unit to control both parameters. Think the power of a gas forge and oven lies on a uniform setup. Once the good parameters are found, constant temperatures are reached that can easily be maintained.

Perhaps not the most fuel-efficient method but I get in both cases a full rich flame cone, the good temperature, no/less dragon breath and the CO meter / alarm showes non or very low ppm's CO

Cheers, Hans 

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Hans, Love that set up.  Don't think I will be getting a foundry any time soon, but it is very interesting.  

Regarding your pyrometer.  is the thermocouple the type that has the junction where the two dissimilar metals are at the end and a twist of two of the wire then going into ceramic beads to separate the wires?  is the thermocouple in the forge atmosphere?  is it left there or only used to take periodic measurments?  could the end of the thermocouple just enter the forge and have a coating of refractory such as satinite over the tip to protect it from atmosphere?  or would this alter the readings?

 

 

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Hi MM, I bought the pyrometer at the nearby art supplies shop, it is normally used to monitor the temperature in a Raku furnaces (nice ceramic stuff). I think the meter itself is a common multimeter, which translates the obtained resistance values into temperature. Think that the most expensive part of the meter is actually the sensor (sensor type F) made of tungsten or something like that and at a certain temperature gives a certain resistance that the device measures and translates in to celsius. I placed the sensor in the outlet of the forge / foundry furnace and did not expose it to the torch itself. If you are interested, look at the link below. Like always at your service. Kind regards, Hans

https://www.gebruikershandleiding.com/Voltcraft-VC150/preview-handleiding-493149.html

 

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Hans, thank you for your response. do I understand that the tip of the thermocouple is in the forge atmosphere near the exit but not directly in the flame impinging area?  And does the tip stay there or do you only insert it for a reading?  I tried your link but got lost.  

 

 

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Ah, maybe my comment doesn't apply to your set up. I was just thinking of easy adjustment for different melting temps of different metals. But if you're controlling air and gas separately, it sounds like it might be a complicated addition to end up with "easy" adjustment.

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Hi Mike, figured out that de sensor is indeed a thermocouple “ Type K (chromel–alumel) is the most common general-purpose thermocouple with a sensitivity of approximately 41 µV/°C.[10] It is inexpensive, and a wide variety of probes are available in its −200 °C to +1350 °C (−330 °F to +2460 °F) range. Type K was specified at a time when metallurgy was less advanced than it is today” mention Wikipedia

And if you Google “Voltcraft VC 150-1” you will find the multi-meter to, I guess.

Use the device till know only to take periodic measurements and ‘squeeze’ it between the lids of forges an furnaces also afraid to hurt the ceramic body. In the future I will drill holes in the recipients to insert the sensor and measure (maybe permanent) the temperature of the heat containment but not the expose it to the flame itself.

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Do not have so much bronze anymore and have now called on my brass reserves. Have used the brass to make a brass anvil of 4lbs and a heel ax of the wooden pattern. At the heel ax you will find back even the grain of the pine example. A nice improvement if you compare the result with the first casting attempt that you will find earlier in this thread. Now looking for the right tree branches to make a suitable handle for the axes. Have a look at the finished roman spear point to;) 

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Finally put the big lady on a cast soot coloured concrete block attached to a rough forged bar and fixed with poured tin. Looking forward to the first pieces of sandstone to carve my own pedestals. Till now damaged chisels and hands/fingers after the first attempts with granite and Greystone.

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Sold one of the 16lbs melting furnaces on CL and started to build a bigger furnace ‘New style 3.0’ -hope to use them with 2 burners and a A12 or A16 crucible in it. Will build them from thin hard stone refractory tails as direct flame face on the bottom and soft bricks higher up. The backup and insolation will be a 1in Superwool layer.

Cheers, Hans

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Only one inch? I'd think insulation would be more important but I'm not a caster. What I THINK is often wrong, I'm used to it. 

Frosty The Lucky.

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OK Frosty, will doubble it, it will also made a closer connection between the tail sections around the burners. However I THINK you are being wrong, -to think to being wrong :P Always better to listen to an expert and obey his (indirect) advice.

Kind salutions, Hans

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Oh man you make me nervous when you say things like "obey" . . .anything I suggest or ask. I know it's a translation software thing. Truth is you're the expert where casting furnaces are concerned I haven't done any casting since high school, say 1970. I held the helper end of the ladle thing on a bronze pour in 2013 I THINK. 

I'm wrong a LOT I just try to learn from the mistakes and the good folk here are quick to correct me. It's another thing I love about Iforge. I get to learn from other people's mistakes, saves me time and money. ;)

Frosty The Lucky.

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