| Blister Steel 2 Dave Dietzler 2008 |
| Lunar Steel, Not So Simple The blister steel, also called crucible steel, process is a realistic alternative to carbon monoxide reduction furnaces for producing steel on the Moon. But let’s not be naïve. First, we need a mining tractor that can magnetically separate meteoric iron fines from regolith without yanking out the less magnetic minerals like Fe2SiO4 or Fe2Si2O6. There’s a billion dollars. Chicken feed. Then we need machines that grind and magnetically separate the iron fines that will be fused with some other mineral grains to get a pure feed of iron-nickel fines. Yeah, more money. Then we melt the iron fines and pour them in shallow sand slab molds to get iron sheets. We also need carbon, so we need a mining tractor that roasts volatiles like H2, N2, CO, CO2, CH4, He4, He3 and Ar out of the regolith and we need machines to separate these gases, cool them and liquefy them for storage like some compressors and radiators and tanks. More money. Then we need to take the CO, CO2 and CH4 that form from the heating of carbon atoms with oxygen and hydrogen in the moon dust and break them down so we have pure carbon. This can be done in a system (another gizmo !) that reacts CO and CO2 with H2 to make CH4 that is then decomposed at 900 C. to get carbon and recover H2 for reuse . So then we take our iron plates or sheets and lay them in the furnace with carbon dust in the right amount between the plates and roast it all at 1000 C. for several days until the carbon dissolves into the cherry red iron plates and steel forms. My furnaces are naïve. The first ones I drew were of cast basalt with graphite resistors to heat the whole stone box and heat the iron and carbon by conduction. Well, cast basalt can handle 1000 C. I hope but to get the steel out we can’t melt it at 1500 C because it will melt the furnace, so we lift it out with a robot crane and electromagnet after it cools down of course. Then I drew furnaces of cast basalt using induction heating. That would be better than conduction ‘cause it will mostly heat the iron and not the whole stone box. Better yet, I suspect that microwaves will do a better job of heating the iron ‘till it is cherry red. But then comes the steel cleaning furnace. We want to purify sulfur out of the steel. That furnace has to stand up to molten steel. We will use a flux of CaAlO4, calcium aluminate, obtained by roasting anorthite, CaAlSi2O8 from highland regolith, in a solar furnace in the vacuum. This ( roasting anorthite to CaAlO4) has been done experimentally (1). What can stand up to molten steel? Fused silica? How do we get that? Sulfuric acid leaching of highland regolith for various materials (see: Basic Chemistry for Moon Miners) and roasting highland regolith at over 1500 C. to boil off FeO, MgO and SiO2 (silica) would be the methods to use. Perhaps we will need cooling for the steel cleaning furnace. These furnaces-the carburizing furance and the steel cleaning furnace must consist of a massive stack of welded cast basalt blocks to give them some thermal inertia because they will absorb heatl albeit slowly because cast basalt's thermal conductivity is only 0.8 w/mK compared to 401 w/mK for copper!. Both will probably need a cooling system of drilled passages that an inert gas circulates thru and goes to a space radiator. The pipes and radiator itself must be made of metal with good thermal conductivity. Then we get this good steel and have to make something with it. We could do sand casting and machining. What do we make? How do we make it? What manufacturing devices do we need? More billions of dollars. And lots more brainstorming, planning, designing, prototyping, etc. Once we are making steel machines on the Moon we can stop importing machines and make all the machines we need on the Moon….but we might need a little titanium, some special metals like copper and zinc that are lacking on the Moon, some magnesium made on the Moon, aluminum for wiring, glass; some imported plastics, silicones and computer chips. At least those last three items don’t weigh much. We will also have to heat treat the steel and that will mean furnaces using microwaves or salt baths, but some kind of microwave furnace would be preferable because there is some sodium and magnesium but very little chlorine on the Moon. Then we need water to plunge the steel into to harden it. Forget about using oil. But there seems to be water and we will also get H2 from volatile mining and oxygen by some process, perhaps magma electrolysis, that can be combined to make water. So we need fuels cells to make water from H2 and O2. As for annealing the steel I think it would cool slowly in the vacuum. Also, you can anneal steel by heating it and putting it in vermiculite and vermiculite can be made by flushing steam thru raw regolith. We will have to reckon with cracking of the iron carburizing and molten steel cleaning furnaces. This will take lots of thermal analysis before we just go and slap some cast basalt blocks together and see what happens. So let’s not be naïve. This is all going to take a lot of doing. We need: 1) Cast basalt lego block making and welding systems including a backhoe to dig up maria regolith and dig sand molds as well as molds, grinders, jigs, fixtures and sand blasters see: Moon Bricks 2) Electric power hammers and chisels, motorized rotating wire brushes 3) Oxygen production, magma electrolysis or some other process deemed workable 4) Iron fine mining tractors 5) Iron fine grinders and magnetic separators 6) A rolling mill to flatten crude iron slabs into thinner plates or sheets 7) Volatile mining tractors 8) Cryonic or membrane gas separators 9) Gas compression, liquefaction and storage systems 10) Sabatier reactors to convert CO and CO2 to CH4 and thermal decomposition systems to get pure carbon 11) A crane with an electromagnet 12) Cables, wiring, Amplitrons (microwave generators), switches 13) Power sources like solar panels or small nuclear reactors and fuel cells (for H2O as well as power storage) 14) Solar reflectors for solar furnaces We need to build on the Moon from cast basalt lego blocks three kinds of furnaces – an iron carburizing furnace, a steel cleaning furnace and a solar anorthite roasting furnace to get flux for the steel cleaning furnace. Oops! Actually, we will need four furnaces instead of three. We will need a furnace, probably a solar or microwave furnace, to melt down the purified iron fines. Molten iron will be poured into shallow wide molds in the moondust surface dug with a robotic backhoe to make iron slabs that then will rolled into iron plates or sheets. We will use the crane and electromagnet to lift the solidified and rolled iron plates and place them in the carburizing furnace. Could we make the steel cleaning furnace do double duty? That is use it to melt down the iron fines as well as clean molten steel in a CaAlO4 flux???? heat treating systems….at least those won’t have to get as hot as the carburizing furnace or other furnaces water for rapid cooling of steel and pressurized work chambers with dehumidifiers in them to recover the steam/water….might be inflatable habitats upported to the Moon or we will weld up plain iron chambers from iron plates. As for working with steel we may need pressurized work chambers with concrete floors in case any liquid metal spills and starts eating thru the thin metal or kevlar shell. See: Casting Chambers Manufacturing gizmos of all sorts Finally, a reason to do all this work on the Moon. If we can’t turn a profit on something then nobody is going to invest and NASA would probably just operate a scientific research station on the Moon similar to stations in Antarctica that nobody is making profits off of, although we have learned much about the Earth in Antarctica. |
| Problem: Evaporation of Molten metals in the vacuum Evaporation of molten iron in the vacuum may be a problem. Would a Kevlar-Nomex insulating blanket do the trick of preventing evaporation of molten iron??? Or do we make slabs of basalt to cover the shallow iron slab sand molds??? A colleague of mine, Rufus Anderson, has suggested an electrostatic screen to capture iron vapors. As for the steel from the steel cleaning furnace, it will be covered with floating slag that prevents evaporation of the metal. When it all hardens we would use big electric power hammers to chisel off all the slag. And run some electric drill powered wire brushes over it to remove that last bits of slag clinging to the steel ingots. And I wonder if we could use fine particles sieved from regolith and high pressure gaseous oxygen to sand blast things. Perhaps we could smooth out cast basalt blocks with sand blasting. Perhaps we could sand blast the last bit of slag off the steel too. We can produce plenty of oxygen on the Moon, and I don’t think it will rust the steel when sand blasting. So steel evaporation won't occur because of a protective layer of floating slag but we will still have more work to do. Fused Silica Most likely, we will use H2SO4 leaching and roasting of highland regolith to obtain silica. Also, if we can mine some volcanic glass deposits, melt the glass and pour it in molds to make cylinders, sand blast off any clinging regolith, then zone refine the glass cylinders to get pure silica, melt it down and cast blocks in metallic molds, grind, sand blast/polish the blocks, then stack them inside the hollows of the big basalt cubes or pyramids that will be furnaces, weld them together, then we would have a furnace with a lining that could withstand molten steel especially if we added some kind of cooling system. See: Molds and Mold Materials and Silicon Production for image of zone refining. This will be a major job all by itself. Details, details....nothing is easy. Perhaps we could use small pure silica bricks welded together to make molds for casting basalt, but do we have to break the molds to get the solid basalt out?? We’d be making one hell of a lot of fused silica brick molds. Details, details …. So blister steel and male/female interlocking cast basalt "lego blocks" are simple products but there is nothing simple about producing them. |
| Sulfur Contamination Sulfur is an undesirable contaminant in steel, although very tiny trace won't hurt. Phosphorus contaminants really hurt steel, but I don't see much P getting in the steel if we avoid KREEP laden regolith. The carbon should be rather pure. Kulcinski recommends keeping the volatilie roaasting temp down to about 700 C if I am correct, because at higher temps sulfur will boil out and react with H2 and O2 to form sulfuric acid that will be hard on the equipment. So we shouldn't get sulfur in the carbon. The iron on the other hand might not be so pure. About 1% of moondust is troilite, FeS, of meteoric origin. FeS does not have a very high magnetic susceptibility so it might not be yanked out of the moondust in the magnetic separators as will the iron-nickel fines. If we can prevent getting FeS mixed in with the iron fines we wouldn't need a steel cleaning furnace or a CaAlO4 flux making furnace. That would greatly simplify things. We would not need a steel cleaning furnace and we would not need a flux making furnace. We'd be down to two furnaces and if we can carburize the iron to steel in the iron melting furnace we'd be down to one furnace ! Melt the iron fines at 1200 to 1500 C and pour them out into slabs and roll them thin then put them back in the furnace with carbon sandwhiched between the iron plates and just run the furnace up to 1000 C. for a few days. Now that would make industry more viable on the Moon ! |
| A Riddle A riddle: So how do you melt regolith to make cast basalt when you don’t have any cast basalt to make blocks and a furnace??? And you don’t have any fused silica either because you don’t have any kind of furnace. And we will not ship up a 100 or 200 ton stone furnace to the Moon !!! The answer is magma electrolysis. Use the ceramic blocks from magma electrolysis to make the first furnaces on the Moon. We will have to learn all about those ceramic blocks and how to grind, cut and shape them into interlocking blocks. An 80 ton magma electro. unit is said to require 3.5 Mwe and will produce 1000 tons of O2 a year and a couple of thousand tons of ceramic and ferrosilicon. Thru put will be 5000 tons of raw unbenificiated moondust per year. So we need a digging machine like a bobcat sized backhoe. Haskin said it might be possible to control the voltage and draw out iron, then silicon, then FeSi alloy as well as ceramics sequentially. If we could do that we wouldn’t have to glean for iron fines unless we wanted them because of their nickel and cobalt content. Do we really need an 80 ton magma electro unit??? We could probably do okay with a lighter smaller one. And then build bigger units on the Moon out of lunar produced materials. We will probably have to upport the Amplitrons for the iron melting and steel making furnaces from Earth, but those won’t be to heavy will they??? |
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| 1) Rudolf Keller and David B. Stofesky of EMEC Consultants " Selective Evaporation of Lunar Oxide Components" reported in SPACE MANUFACTURING 10 PATHWAYS TO THE HIGH FRONTIER Proceedings of the Twelfth SSI-Princeton Conference May 4-7, 1995; pg. 130. |
| NOTE: Where metal pipes to and from the radiator contact the fused silica crucible there must be high temp. gas tight asbestos or silicone seals. The metal must have the same thermal coeff. of expansion as the silica. Let's consider light bulbs. The contact wires that feed the filament were once made of pricy platinum because of it's similar thermal coeff. expansion. A cheaper alloy of 54% iron and 46% nickel replaced Pt and is in std. use. A similar alloy will be needed for the flanges, bolts and pipes contacting the fused silica crucible., NIckel extraction from iron fines on the Moon is possible. See: Nickel and Cobalt |
| What to Make with Steel I have asked repeatedly, "What will we make out of steel?" Suggestions: Vehicle frames (see: Lunar Model T); plates, webs, beams and bulkheads for cubical or rectangular habitat modules (see: Modular Iron Moon Bases), shielded space radiators, pots and pans, cutlery; pocket knives, butcher knifes; farm implements like shears, rakes, shovels, hoes, pitchforks, scythes or sickels, trowels and bamboo machetes, sundry items like scissors and razor blades; medical items like scalpels, hypo needles, operating tables, large machine tools like lathes, grinders, drill presses and hand tools like hand drills, screw drivers, hammers, saws, ratchet wrenches and impact wrenches, electric motor casings and armatures, nuts and bolts using our best steels, furniture parts, bed springs, leaf springs for vehicle suspensions, pressure tanks for various gases, rock chipping tools, gears and cams for machines, sheet metal, fan blades, bolt cutters, ball bearings, roller bearings, bearing races, sledge hammers, steel file drawers, safes and vaults, door hinges, doors, airtight hatches, axel rods for vehicles. monorail rails (ATVs and monorail cars will have aluminum pressurized cabins like hi altitude aircraft), bull dozer blades, mining tractor buckets that can withstand hitting a rock, high pressure lines, corrgurated flexible pipes, threaded fittings of all sorts, suitcases, needles and sewing machines, table legs, compressor casings and rotors, pumps, brackets, shelves, drive chains, stoves, ovens, steel cables, pulleys, hooks, small wheels for carts and the carts themselves, small crush proof boxes of various sizes, trash cans, trash dumpsters, waste baskets, chicken coops, cages for other livestock, prison bars for the brigg, robot arms, cranes, jaw crushers, rod mills, cement mixers, railway levitation magnets, etc. Water pipes, toilets, sinks, sewage pipes, electrical conduits, hand basins, bath tubs, spigots and many other items will be made of cast basalt but we will need steel for the faucets and valves. We will just thread the basalt pipes, coat the threads with some upported sealer and screw on the steel faucets and valves. Algae pools and fish ponds will be made of cemented sintered basalt blocks too. |
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