Iron and Steel on Mars

JoshNH4H · 2012-03-16 23:36:03

On Earth, Iron and Steel are vital parts of an industrial economy, and on Mars I would expect things to be no different. To give a bit of context, steel consumption in the United States is about 400 kg/(person-year) (Source- okay, that's from 1990, but other sources are in agreement that today it's around 400. More generally, there is a lot of fascinating information about materials use in an industrial economy here, both from the USGS). On Mars, I would think that we could expect levels at least as much as in the America of today if not more. In any case, Iron and steel will be absolutely vital.

GW Johnson gave a superb summary of the process of steelmaking on Earth in another thread:

GW Johnson wrote:

Well, steelmaking is a little more complicated than just a hot fire. Although that is exactly how one makes small wrought iron nodules: in a campfire with decent ore and a positive air blast.
Once made, these nuggets can be forged together into a useful-sized ingot, for fashioning various items, but it's still wrought iron. Very high in both carbon content (like cast iron) and slag inclusions (which make it easily formable, hence the name "wrought").
To make real steel, you have to remelt a big pot of this stuff (about 3000 F, 1650 C), then blow oxygen through the puddle, to burn out the carbon to just the right trace amount for steel. The slag floats to the top as a thick layer, rather like the scum floating on overheated hot chocolate. Then, you decant the steel through the bottom, out from under the slag layer, and cast it into ingots (usually about half the size of a diesel submarine battery cell).
Cast steel still has lousy properties, variable all through the ingot. You have to reheat it to just below melting (about 2800 F, 1540 C), and forge it, usually with repeated hammer blows and roller-forming operations, both measured in multiple tons for a typical ingot. This operation produces the typical shapes coming from the steel mill as product, and these shapes have the structural properties we are used to (for mild steel around 36 ksi yield, 80-100 ksi ultimate, in tensile, with a Young's modulus near 30,000 ksi, and a Poisson's ratio near 0.3).
The alloy steels are made similarly, they just add things like nickel and vanadium in the initial melt after carbon burnout. Some of these are heat-treatable after manufacture to very high strengths, others (like 300-series stainless) are not.
To make these materials in industrial quantities requires a pretty big plant. It did in a relative sense, even 300 years ago, when railroads were first attempted here on Earth. Cast irons and wrought irons were usually just not suitable for rails and boilers. It took real steel, just like that used in sword- and gun-making, only just a whopping lot of it. Ship-building did a lot better by the beginning of the 20th century, once steel became available in 10,000 ton+ quantities.
How one would do all this on Mars, I dunno. Certainly not in some analog to a campfire, or even in an analog to a 17th century puddling furnace. But it certainly needs to be done, especially once we start planting bases.
GW

Now, I would suggest that the primary reason why Carbon is used in smelting on Earth is because it is "free energy" so to speak, in that all you have to do is dig it up from the ground. Doing the reaction with hydrogen with hydrogen will simplify things significantly, as I will argue later, but the lure of this (mostly) free energy makes it more than worth it.

On Mars, Carbon will be produced from Hydrogen. Therefore, it makes more sense to simply use Hydrogen as an energy storage mechanism unless there is a good reason to do otherwise, which I don't think there is. Delta-G calculations show that the reaction of Fe2O3 and Hydrogen to form water and Iron becomes thermodynamically favorable above 910 C. However. I know that with Carbon the reaction actually proceeds in several steps, all of which happen inside the reaction vessel, and this lowers the temperature significantly from its theoretical maximum. I would presume the temperature inside the smelter would not be significantly different.

This will produce little carbon-free Iron particles in the mixture. I would suggest that the best way to separate this would be the mond process: Iron in a Carbon Monoxide atmosphere under pressure and mildly elevated temperatures forms Iron Pentacarbonyl. This is a volatile compound (bp 103 C) which can be decomposed at a slightly elevated temperature, leading to near pure Iron. This could be melted and mixed with alloying agents to produce the desired alloys.

The energy input is 6 g of Hydrogen per 112 g of Fe. Assuming that your electrolysis machine is 75% efficient, that is an energy input of 8.5 MJ (electric) per kilo of Iron.

Last edited by JoshNH4H (2012-03-18 10:12:24)

Void · 2012-03-17 10:42:57

I like it.

GW Johnson · 2012-03-17 11:18:42

Steel-Making

I’m an old man, and memory fades, so I went and looked up iron and steel-making in my old college manufacturing processes textbook (yep, I still have it). It’s basically two stages: you have to make pig iron, then you refine the pig iron into the product you want.

Pig Iron: variable composition, many “pollutants” in it, but it is mostly iron

There are two processes that create the pig iron. They are the blast furnace and the direct-reduction process. The direct reduction process actually creates “sponge iron”, but you can refine it the same way as pig iron.

Blast Furnace (98% of production)

The one used here on Earth commercially today is the blast furnace. It is a vertical tubular structure packed with layers of iron ore, limestone, and coke (a hot pure carbon derived from charcoal or coal). This structure is already burning, because of the coke. You blast air under pressure into the bottom to intensify the combustion and raise the temperatures near the injection point above the meltpoint for iron (and the slag).

The iron and the slag both liquefy and percolate down through the bed to puddle at the bottom (so gravity is very important!!). The slag floats on top of the heavier iron. You periodically decant both separately. Most modern mills transport the molten pig iron directly to the refiner, but you can cast pig iron ingots, if you wish (you will have to re-melt them later, though).

The charge ratios for the blast furnace are for every ton of pig iron produced, you need 2 tons of ore, 0.8 tons coke, 0.5 tons limestone, and 4 tons of hot air. (Yep, that’s tons mass of heated air at Earthly pressures, and is that ever an incredible volume!) The usual production lot size ca. 1960 was 1000 tons of pig iron from a furnace around 25 feet in diameter and around 200 feet tall.

Direct Reduction (under 2% of production)

The direct reduction process is an extension of the old campfire process. You crush the ore and react it at elevated temperature with a reducing agent. There is (at least, was, ca. 1960) a plant in Mexico that made pig iron this way in 500 ton batches. That plant used a mixture of carbon monoxide and hydrogen derived from natural gas and water as the reducing agent. There were two reactors in operation: the reducing-gas former, and the iron reactor. The gas feed to the iron reactor was hot, and the ore well-crushed. The product was something called sponge iron, a spongy, granular, clinker-like material. This is rather similar to the product from the old campfire process of 3+ millennia ago. (That process required a lot of manual stirring to agglomerate the iron into little balls that could be recovered after the fire was out.)

This direct reduction process is probably the basis of any process we would use on Mars. Carbon monoxide can be derived from the local atmosphere, although compression from 6-7 mbar to 1000’s of mbar will be difficult and expensive. Perhaps direct mining of dry ice from the polar caps would be better, since closed vessel vaporization automatically compresses the gas to usable pressures. The hydrogen can be derived from ice deposits by mining.

It sure would be nice if we knew where some iron ores were on Mars, no? That’s what exploration (manned or unmanned) is all about: “what all is there?”, and “where exactly is it?” My old book says they liked to use hematite at 70% iron, magnetite at 72% iron, siderite at 48% iron, limonite at 60+% iron. These are all high-quality ores.

Products (wrought iron, steel, cast irons)

What you do with the pig (or sponge) iron depends upon the product you wish to make. Wrought iron is under 0.1% carbon, but has 1-3% finely divided slag particles dispersed within it. It is very resistant to corrosion, easily welded, and able to take a variety of finish coats. It’s very ductile at 30-35%, and tests at 35-47 ksi tensile, with Brinnell hardness 90-110. Here on Earth, it is produced by the puddling process, or by a sequence of the Bessemer process and the Ashton process. These are all air-fired combustion processes. Something new would have to be developed for Mars

Steel is a crystalline alloy of iron and carbon, and perhaps other alloying additives. It contains no slag at all. Carbon content ranges from 0.1% to at most about 1.4%. Low carbon plain steel ranges from 0.1% to 0.3% carbon. A medium carbon plain steel ranges from 0.3% to 0.7% carbon. A high-carbon plain steel ranges from 0.7% to 1.4% carbon. Alloy steels classify by the type and quantity of the principal alloying additive. Low-alloy steels are up to 8% alloy additive total. High-alloy steels exceed 8% alloy additive total. Alloying elements include manganese, nickel, molybdenum, and chromium. Steels can be made by the Bessemer process, the open-hearth process or the electric process. Bessemer and open-hearth processes are air-fired and air/oxygen injected. The electric process holds potential for Mars, as it requires either vacuum or an inert atmosphere.

Cast iron is a general term for iron-carbon-silicon alloys exceeding 2% carbon. These are not malleable, unless converted by appropriate processes involving heat to a different internal structure involving carbon or carbide nodules. Gray cast iron is around 3-3.5% carbon, and 1-2.75% silicon. White cast iron is around 1.75-2.3% carbon, and 0.85-1.2% silicon. The malleable and nodular iron materials are made from white cast iron. Only these last have any ductility. Gray iron is manufactured by the cupola process, and malleable irons by the air furnace process. Both of these are air-fired combustion processes. Something new would have to be developed for Mars. Tensile strengths range from 16 ksi to around 40 ksi. Ductility is 0-2% except for malleable iron, which can run as high as 20%. Brinnell hardnesses range from 100 to 150.

Electric Furnace Processes

This is a big closed room lined with refractory materials, into which gigantic carbon electrodes are extended. There are acid and basic linings. Composition control of the phosphorus and sulfur is far easier with the basic lining, so that’s what is most commonly used. This is a magnesite lining on structure and walls of magnesite and alumina brick. They usually use alumina brick for the roof of a basic-lined furnace. The electrodes are nearly a meter-diameter graphite, and over 25 meters long, and are consumed slowly in the process. The best way seems to be immersion in the melt puddle, which implies charging with molten pig iron (or re-melted sponge iron). You can add recycled scrap to the melt puddle, quite easily. Just watch your composition.

Voltage potential is only around 40 volts, but currents are in the 12,000 amps range, or more. This is for heats ranging from ½ to 20 tons of product. It’s a batch process. On Mars, this will require a substantial nuclear power plant, well over 500 KW. I doubt you can easily generate electricity like that from photovoltaics or even concentrated solar power. (Tons here was really the American 2000 lb ton, but the metric ton is quite comparable at 2205 lb.)

The big advantage on Mars is a furnace atmosphere of vacuum or inert gas. 6-7 mbar CO2 is essentially a vacuum, as far as this process is concerned. The fact that it’s CO2 should not really matter.

Converting Raw Steel to Final Product

You can cast the steel directly to shape, but the properties are not so great, so most steel is cast into ingots (from a few hundred pounds up to 25 tons in size), and sent to a steel mill, where it is re-heated and forged, pressed, and/or rolled to final shape. This would be plate, bar stock, pipe, beams, etc. You’ve all seen movie or video footage of this. The ingot is reheated to forming temperature (yellow-orange heat, almost but not quite welding temperature), and hammered or pressed or rolled into a thinner, more elongated shape. There’s a whole sequence of forming operations for each shape and each ingot size. Rolls are the most common forming equipment for making plate, bar stock, structural shapes, even pipe. Reheat is required between forming operations.

Plain and non-stainless alloy steels emerge from this process more-or-less annealed. Further heat treat / quench operations will harden the steel to high tensile strength, at the expense of ductility. Stainless does not heat-treat (nor is it magnetic, too much nickel). The final stages of forming the structural shape with stainless need to be cold-working, if a hard, high-strength product is desired. Otherwise the material is weak but ductile.

Finished commercial steels can range anywhere from 40 to 300 ksi tensile strength, at 15-22% ductility (I’ve seen stronger at less ductility in military-grade alloy materials). Brinnell hardness can be anywhere from about 110 to 500. All this is specific alloy-dependent.

Okay, that’s the broad highlights of steelmaking. There’s a lot (and I do mean a lot!!) more detail to it, of course. The book included nonferrous materials, too. It was 754 pages. I used it about 44 years ago in a freshman introduction to engineering class. I kept it, because it had so much “good stuff” in it.

Looks like my only failure of memory was the carbon content in wrought iron. I misremembered it as high, like cast iron, when it actually is very low.

GW

John Creighton · 2012-03-18 00:17:45

I'm going to guess that on mars at first we would use either the direct reduction process or the electric furnace. I presume that blast furnaces would be too large. You mention lower gravity, this would mean that for any type of gravity separation you would probably need a taller fractionate. For these two steel process any suggestions on how small they could be made and still give reasonable ores.

If we don't have good ores I presume more energy intensive process would be needed.

GW Johnson · 2012-03-18 09:44:54

The main consequence of low-grade ore is that you have to process much higher volumes of material for more effort and energy expended, and you use a lot more resources to do it. I suspect the first steel plant on Mars will have to be located near the South polar cap, where both ice and dry ice can be mined easily to support the direct reduction process. It'll need a big nuclear power plant. That makes it a major base to be established.

It would be nice if there were usable iron ore deposits nearby, too, but I doubt we can count on that. Being the smallest volume component of the process, it would be the ore we would have to ship to the otherwise-sited plant. That makes the entire problem a chicken-and-egg problem, seeing as how we need the steel to build the surface transportation necessary to make the steel.

This stuff is too heavy to transport by flying/rocket ballistics in any practical sense, even at 0.38 gee. At 6-7 mbar pressure, the "air" is too thin for practical winged flight, with such heavy loads. So, it's surface transportation that makes the most sense.

That situation makes it a gilt-edged priority to look for a suitable place on Mars to build a steel plant with the next generation of exploration probes, be they manned or unmanned. Ice seems fairly ubiquitous, dry ice not so very much. Iron ore? Who yet really knows? We need some prospectors on the ground all over the planet, be they robot or human. It would be nice to find all 3 within a few miles of each other.

As for the effects of lower gravity on direct-reduction reactors or electric furnaces, that's not so very much of a problem. Fortunately. You just need enough to hold the puddles in place in the furnace, and 0.38 gee is plenty. The hot gas reactor is all gas with no separations. It would likely work even in zero gee.

It's the other combustion-driven processes, like the blast furnace, that require something closer to 1 gee to hold processing times to something reasonable, due to the inherent "drag" affecting separations in the column. Since these require enormous masses of oxygen, not widely available on Mars directly, I doubt those processes would be preferred anyway.

Building from scratch the infrastructure for an industrial civilization is hell. It took many centuries to do it here at home, and it was still hell in an environment benficial to our form of life. Mars is lethal to us.

This kind of thing is not something you do with a half a dozen "flag-and-footprints" landings on Mars. And you can't just count on the transplanted locals to invent it all out of nothing for themselves, because it's not the environment we evolved to live in. Done that way, we'd never survive the Martian "stone age", much less progress beyond it.

GW

John Creighton · 2012-03-18 10:43:22

That answers a little bit about steel. I guess how expensive it is to make will in part depend on the quality of the ores and how close they are to the base. Iron is a pretty common element which makes steel production likely.Steel is great for structures and for tools. However, for wires typically on earth we use copper or aluminum. Perhaps steel word work fine for low powered conductors but might not work so well at higher power applications. Perhaps steel wave guides would work better for higher power applications than steel conductors.

Given that steel might be scarce and expensive early on, Martians could look for alternatives for some tools. For instance perhaps once could make a hammer head from a piece of stone. Early civilizations made blades out of stone but I am not sure such blades would be of much use in a modern society. I say steel is good for tools but I don't even ask what tools the early martians will need and how else they might be made.

JoshNH4H · 2012-03-18 14:39:58

There's a lot of good conversation in this thread.

Firstly: What does everyone think of replacing the Carbon/Carbon Monoxide with Hydrogen, as well as the use of the Mond process to separate out the produced Iron? I put my thoughts on both of these in the first post in this thread, and I think they're very viable options for the production of Iron on Mars. Different circumstances and resources mean that different technical solutions will probably be optimal. Specifically, using Hydrogen will eliminate a step or two in the production of Carbon, and the Mond process makes it possible to use ore of an arbitrarily low grade without too much loss of product. Because of the energy required to heat the material, a higher grade ore will still be desirable. I would think that Hydrogen would have to use direct reduction, or a variation thereof.

Secondly: I think it's time air compression gets its own thread. This is a technology that is absolutely vital to colonization, and there are going to be cases where it is absolutely impractical to use dry ice to pressurize things. Given that the south polar region is not as germane to colonization as the equatorial regions (higher radiation and lower temperatures, as well as the need for up to ten thousand kilometers of additional rail lines to connect the different outposts) it would be very beneficial if we had an idea of what kind of energy and material inputs would be required to pressurize gases without the vaporization of dry ice (which, by the way, the heat of sublimation of CO2 is 26.2 kJ/mol CO2 (600 kJ/kg CO2). That energy is on the whole going to have to be input from your power source. I'll make a thread (of if the topic catches your interest and anyone else would like to frame the discussion they can feel free to) on the topic when I have time.

Generally speaking I would think that the formation of alloys will be similar on Mars to on Earth. Just one question, though: Why is the Iron melted twice? Wouldn't it make more sense to melt the iron once, form the alloy, and then stir at the same time?

Especially given the lower gravity, in a lot of applications the Martians won't be looking for the highest strength steel, necessarily. I would also point out that some alloying elements which are common on Earth may be difficult to obtain on Mars due to low production rates and general scarcity. I might also suggest that if higher tensile strength is desired, it might make sense to alloy with Basalt Fiber.

GW Johnson · 2012-03-18 15:42:16

You need not "melt the iron twice" if your reduction reaction produced molten pig/sponge iron instead of solid. I am not familiar with the Mond process, but the net effect should be similar to that old plant in Mexico, I suspect in solid form. Once you get this stuff, you have to convert its composition to that of steel, and that is a melt process, no way around it. That's what the electric furnace would do, at essentially local ambient conditions as a substitute for vacuum on Mars. You may need to blow or bubble oxygen through the puddle.

Once you have molten steel, you cast the ingots, but you need not let them cool all the way. Temperature distributions will be necessarily very, very nonuniform during cooling, but once solidified, you bring the ingot to a uniform forming temperature. Then you can forge, roll, and hammer to your heart's content. It is hard to describe just how useful, plate, flat, bar stock, pipe, angle, tubing, and I-beams are.

GW

JoshNH4H · 2012-03-18 20:53:54

I guess I misread. Looking at your posts a little closer, I was talking about the two heating steps required to form ingots and parts, but in actuality you were very clear that doing things in that manner greatly improves strength of the product steel. My mistake entirely.

My concern with the Mond process is reducing the operating temperature of the heating arrangement to the lowest value possible, because this saves energy and makes it easier to deal with.

I also like the idea (originally Zubrin's, unless he got it from somewhere else) that the production of Iron depletes the stock material of Iron and thus potentially makes it suitable as a feedstock for Glass. At present I am under the impression that we don't know of any concentrated silica reserves. That's not to say necessarily that they're not there, of course, this is the whole prospecting issue that you (with good reason) talk about. Iron content makes glass opaque, and if you're going to use opaque glass you might as well make it cast basalt. So by adding the highest available purity silica reserves to your Iron smelter you can get material of acceptable quality for glassmaking, for a relatively small marginal energy input (e.g., the energy required to heat up the additional material) you can relatively easily get materials out of which to make Glass.

I have no doubt how useful the basic pieces that can be made of steel can be- I need only look around me. The University is building something I can see from my window, and at this point it looks like it's made of I-beams and concrete. Though it will be avoided in favor of Basalt Fiber and Icecrete where possible, Steel will be absolutely vital for many, many things.

Void · 2012-03-21 20:03:17

This is a segway, but Iron Pentacarbonyl;

A fluid it seems, a fuel perhaps. (Toxic)

http://en.wikipedia.org/wiki/Iron_pentacarbonyl

But if a fuel, then can you manufacture it from Phobos and Demos? If so, I would presume that you could also get Oxygen from those two moons. I am thinking that
some of the materials of those moons contain Carbon, and there must be some magnetic Iron.

So, could you power a return to Earth Rocket with a Oxygen/Iron Pentacarbonyl engine? I bet it might be prone to clogging.

However with Mars having a CO2 atomosphere, and Mars, and I presume Phobos and Demos having Iron, and our Moon having Iron and CO, if this could work it would be much better than trying to get Methane off of the surface of Mars for a return trip. Also, such a propulsion system would useful in the asteroid belt.

Still, you are the experts would it be better than getting Methane and Oxygen off of Mars itself?

RobS · 2012-03-26 12:38:35

Regarding the issue of an iron supply, there should be plenty of meteoritic nickel-iron available. Hundreds of tonnes was harvested from Barringer crater in northern Arizona. Spirit and Opportunity have both seen nickel-iron fragments; they're scattered all over the surface. I suspect the regolith is several percent nickel-iron, and it should be separable magnetically, right? A robotic vehicle could probably harvest it for you.

I have also heard that the nickel-iron recovered from Sudbury, Ontario, made some very good, tough, and stainless building steel. I read once of a bridge that doesn't rust because of the nickel content of the steel.

So I wonder whether that's the way to go; start with nickel-iron, then either melt it or convert it to carbonyl using hot carbon monoxide gas. For construction purposes it wouldn't have to be high quality initially, either.

RobertDyck · 2012-04-16 01:46:28

Great stuff. I would like to recommend hematite concretions as the primary iron ore. It's high grade iron oxide. The concretions are spheres about the size of blueberries, and very hard. Their embedded in soft sedementary rock, primarilly jarosite. So crushing and tumbling can separate the hematite from matrix rock. Once you have pure hematite, use a stronger crusher to crush the hematite to fines.

A few years ago, and probably still, there's a smelter in South Africa using the direct iron method, also known as direct reduction. It requires highly pure iron oxide and it must be crushed to fines, but it works at +900°C. That's low enough temperature to produce with a nuclear reactor. So you can produce this heat directly with a reactor, and not melt the reactor. Tempertures hot enough to melt steel would melt the steel parts of the reactor. GW Johnson said his book lists hematite as the prefered ore. There's plenty of hematite at Meridiani Planum.

Robert Zubrin wrote a paper on concentrating CO2 from the atmosphere of Mars. Temperature at night is almost cold enough to freeze CO2 as dry ice, so he used this. His "Mars Atmosphere Carbon DiOxide Freezer" (MACDOF) freezes atmosphere to accumulate dry ice. Do it in a canister with fans blowing atmosphere in and out. At dawn just when the temperature starts to rise, close the intake and outlet vents, and warm the canister. Sublimating the dry ice will produce pure CO2 gas at high temperature. This process is energy efficient because night temperatures are so close to dry ice freezing. Mars Pathfinder measured -77°C at 5:30am. CO2 freezes at -79°C at 1 atmosphere pressure, I have the formula for different pressures somewhere but it isn't handy right now. It isn't much lower at Mars pressure. You could easily achieve 10 bar (10,000 mbar) pressure just by sublimating accumulated dry ice.

John Creighton · 2012-04-16 12:14:14

Some magma flows are high in Iron
http://en.wikipedia.org/wiki/Tholeiitic_magma_series

Someone mentioned Basalt on mars:
http://en.wikipedia.org/wiki/Basalt

which is magma which cools quickly, perhaps bellow this their is magma which cools slower letting Iron participate out. Would Basalt high in Iron suggest Iron ores near by?

GW Johnson · 2012-04-16 13:15:24

Once you have the frozen CO2 from your freezer, just be sure there's very little free volume in your canister. The sublimating dry ice will pressurize the canister quite nicely, to perhaps multiple atm.

GW

Mark Friedenbach · 2012-04-16 16:31:17

JoshNH4H wrote:

Firstly: What does everyone think of replacing the Carbon/Carbon Monoxide with Hydrogen, as well as the use of the Mond process to separate out the produced Iron? I put my thoughts on both of these in the first post in this thread, and I think they're very viable options for the production of Iron on Mars. Different circumstances and resources mean that different technical solutions will probably be optimal. Specifically, using Hydrogen will eliminate a step or two in the production of Carbon, and the Mond process makes it possible to use ore of an arbitrarily low grade without too much loss of product. Because of the energy required to heat the material, a higher grade ore will still be desirable. I would think that Hydrogen would have to use direct reduction, or a variation thereof.

I'm not sure I understand the question. Carbon is a necessary part of steel. Carbon impurities are what reduce brittleness and give it its strength. Am I misunderstanding what you are trying to do?

RobertDyck · 2012-04-16 17:53:33

First, the Mond process only works with metal. It doesn't work with iron oxide. I can be used on a metal asteroid, but not on Mars. We have to smelt on Mars.

As Mark said, carbon is a necessary part of steel. In fact steel is iron/carbon alloy. But a blast furnace uses nothing but carbon monoxide to reduce iron ore, resulting in too much carbon in the steel. You can use the direct reduction method with only carbon monoxide, but again you end up with too much carbon. More carbon makes steel hard, too much carbon makes it brittle. A Bessemer converter blows oxygen into molten steel to burn off some of the carbon. But the direct reduction method that GW Johnson describes uses a balance of carbon monoxide and hydrogen. Hydrogen doesn't work as well at reducing iron, that means removing oxygen from it, but it doesn't get dissolved in steel. Furthermore hydrogen is more expensive here on Earth. The right balance will control how much carbon gets into your steel. This eliminates the need for a Bessemer converter.

As I said, the direct reduction method has the additional advantage that it works at a temperature that a nuclear reactor can produce directly. That makes a very efficient process. But GW Johnson said the result is sponge. Oops. How do we make that into solid steel? I guess we have to melt it. That will require electricity from the reactor to heat the steel further, costing a lot of energy. Well, it's still more efficient than a Bessemer converter: use electricity to convert water into hydrogen and oxygen, use that hydrogen to reduce CO2 into carbon monoxide, use that CO to smelt steel, then a Bessemer would use some of the oxygen to convert some of the carbon in steel back into CO2. Not efficient. It's more efficient to start with the right balance of CO and H2, create steel with the right carbon content, then just melt it to solidify the sponge.

GW Johnson · 2012-04-19 09:54:27

It would be very hard to build a Bessemer converter that worked in a near-vacuum CO2 atmosphere. Direct reduction would be much better. Easier to do, because it's all closed reactor vessels that don't care what's outside.

You'll have to melt the sponge iron in an electric furnace, adding just the right amount of carbon and alloying elements. The electrical demand to power that is enormous.

We do it all the time here with our electric grid, but on Mars with no grid at all, that's going to take dedicated atomic power of large capacity. I would suggest a big water electrolysis plant powered by a big reactor. The electrolysis goes offline in favor of the furnace when making steel. That way the reactor itself runs a constant power.

GW

RobS · 2012-04-19 17:24:23

Robert, in The Case for Mars, Zubrin talks about the reduction of pure iron (I suppose meteoritic nickel-iron) with hot carbon monoxide gas into iron carbonyl, which is a gas at 400 C but at 200 C or so it becomes a liquid. I don't recall the details, other than this. What do you know about this process? Nickel-iron should be readily available on Mars; a robotic digging/raking machine with a magnet could collect it. This strikes me as the easiest way to make iron items; pour the iron carbonyl into molds, heat up to drive off the CO, and you have iron parts. Granted, they may be one third as strong as rolled steel, but that would be plenty for making furniture, air locks, and other items that don't have to be flown or driven (I doubt it'd be a practical material for space vehicles or rovers). It may also be possible to mix metal carbonyls to make alloys, or electrically heat and roll the cast parts. What do you think? We don't do this on Earth, but we don't have abundant nickel-iron.

Void · 2012-04-19 19:09:55

With respect truely,

Could there be anyway to mineaturize the process to the head of a 3D printer? That is refine steel as you print? I don't care which process. It would then not require huge draws from the power source, but only power at the time of printing, a tiny hot spot, where the needed chemicals would be injected, and perhaps with an action to remove slag?

louis · 2012-04-19 20:10:28

GW Johnson wrote:

It would be very hard to build a Bessemer converter that worked in a near-vacuum CO2 atmosphere. Direct reduction would be much better. Easier to do, because it's all closed reactor vessels that don't care what's outside.
You'll have to melt the sponge iron in an electric furnace, adding just the right amount of carbon and alloying elements. The electrical demand to power that is enormous.
We do it all the time here with our electric grid, but on Mars with no grid at all, that's going to take dedicated atomic power of large capacity. I would suggest a big water electrolysis plant powered by a big reactor. The electrolysis goes offline in favor of the furnace when making steel. That way the reactor itself runs a constant power.
GW

I suspect, since we won't need huge quantities of iron and steel to begin with, that we will simply be working indoors in a pressurised environment. I think we might require a mix of solar reflectors and PV panel current to get the required temperatures. We would probably need a system of outdoor reflectors and then a mirror/light pipe system to bring down a concentrated beam on to a furnace which would also be heated by cable.

Another possible approach is to burn carbon with oxygen, having first extracted the carbon from the atmosphere and the oxygen from water. So it would be like a charcoal furnace, which I think can produce the required temps if I recall correctly.

RobertDyck · 2012-04-19 22:00:39

RobS,

The Mond process is regularly used by the nickel industry here on Earth. Iron is often found in nickel deposits, so smelting nickel from oxide ore produces iron/nickel mixtures. This following website describes the process: nickel combines with CO at 50°C at 1 atmosphere pressure to form metal carbonyl, then at 230°C decomposes to pure nickel metal and CO gas.

http://wwwchem.uwimona.edu.jm/courses/nickel.html

This also works with iron, at different temperatures and substantially higher pressure. At 5-30 MPa (49.3 to 296 atmospheres) and 150-200°C it will form iron pentacarbonyl. It decomposes at 200°C. But you have to be careful to not expose it to oxygen; if any oxygen is present it'll form iron oxide.
http://www.freepatentsonline.com/4056386.html

Iron pentacarbonyl can also be chemically decomposed to carbonyl iron, a powder used as the magnetic coating for recording media, and various other applications.
http://en.wikipedia.org/wiki/Carbonyl_iron
And how it's made, in a BASF glossy brochure:
http://www.inorganics.basf.com/ca/inter … l_PO_e.pdf

Ps: The Canadian mine in Sudbury is one of the largest nickel deposits on Earth. It's a giant iron-nickel asteroid that hit Earth about 2 billion years ago. They're mining the asteroid pieces from the surrounding rock.

Last edited by RobertDyck (2012-04-19 22:03:54)

RobertDyck · 2012-04-19 22:15:15

Void,

Interesting... Iron pentacarbonyl is liquid at 1 atmosphere pressure between -20°C and +103°C. You could feed that liquid to a print head. It would have to heat the liquid and squirt it the way an ink jet printer works. The liquid would have to be "set" by a laser in the print head further heating the work piece above +200°C. An electric arc may work to "set", but a laser would be more precise. The liquid has to be heated as close to decomposition temperature as practical, but must remain liquid. It would be nice to heat it to +190°C, but it boils at +103°C, so pre-heat it to +102°C. Iron pentacarbonyl is toxic, and the work has to be done in an atmosphere devoid of oxygen, and it'll produce copious quantities of carbon monoxide as it decomposes, so this would definitely have to be sealed. And I don't know what the carbon content would be. But you could build such a 3D printer.

Last edited by RobertDyck (2012-04-20 06:49:18)

RobS · 2012-04-20 08:52:39

The other thing we don't know about iron pentacarbonyl "printing" is what the strength of the resulting iron part would be.

Thanks, Robert, for this explanation of the use of carbonyls. Considering the lack of limestone on Mars and the availablity of carbon monoxide, it seems to me the standard metal processing techniques used there will be different than on Earth, and carbonyls may be the way to go.

Void · 2012-04-20 14:41:13

I have this information to add:

http://en.wikipedia.org/wiki/Carbonyl_metallurgy

http://www.space-mining.com/IRONRECOVERY.htm

http://en.wikipedia.org/wiki/Alloy
Quote from the above:

History
A meteorite is shown below a hatchet that was forged from meteoric iron.
Bronze axe 1100 BCThe use of alloys by humans started with the use of meteoric iron, a naturally occurring alloy of nickel and iron. As no metallurgic processes were used to separate iron from nickel, the alloy was used as it was.[7] Meteoric iron could be forged from a red heat to make objects such as tools, weapons, and nails. In many cultures it was shaped by cold hammering into knives and arrowheads. They were often used as anvils. Meteoric iron was very rare and valuable, and difficult for ancient people to work.[8]

More History: (Pattern Welding)

The first known smelting of iron began in Anatolia, around 1800 BC. Called the bloomery process, it produced very soft but ductile wrought iron and, by 800 BC, the technology had spread to Europe. Pig iron, a very hard but brittle alloy of iron and carbon, was being produced in China as early as 1200 BC, but did not arrive in Europe until the Middle Ages. These metals found little practical use until the introduction of crucible steel around 300 BC. These steels were of poor quality, and the introduction of pattern welding, around the 1st century AD, sought to balance the extreme properties of the alloys by laminating them, to create a tougher metal.[11]

Nickle has toxic problems as well I believe. However I did encounter the information that Nickle and Iron are best separated with magnets, which I presume means grinding the Meteor metal very fine, I would think there are limits to the amount of purity easliy achived.

So, I am convinced that you are on the right track for the 3D printer.

I found some more very intersting information concerning Plastics from C02, and a spray on glass with UV protective properties, so I am going to try to find an old thread about greenhouses and wake it up and talk about metals, plastics, and glass spray to make greenhouses and such, which in the end would after all be very valuable, and it appears they could be printed. I am glad I encountered you guys.

Oh an afterthought, maybe a flame with just a bit more oxygen than fuel, could be periodically be put to the surface of the object being printed, to remove a bit of excess carbon. I understand that CO is explosive, but if the Oxygen and pressure levels were kept low, and the CO removed from the area of manufacture reasonably well, perhaps each layer could have a different amount of Carbon and other additives, making a laminated structure, and not causing a explosion or fire. (See Pattern Welding Above).

Last edited by Void (2012-04-20 14:59:53)

knightdepaix · 2014-07-09 02:15:33

Adding more to carbonyl metallurgy, iron, nickel or transition metal carbonyls are useful because they change phase under relatively mild but high temperature, which is useful for molding. To extract metal from ore, hydrochloric acid (or sulfuric acid for that matter but sulfate can be reduced to sulfide, wasting carbon or carbon monoxide designated for metallurgical use) can be used to leach the metals as metal chlorides, leaving silicon and titanium oxides. The metal chlorides solution are converted to oxides, metal by metal and regenerating HCl acid. Each metal oxides is then reduced with hugely excess carbon monoxide, not carbon; this late process generates carbon dioxide which can be splitting into carbon monoxide for recycling use or released to atmosphere. The amount of CO not used for reducing iron oxides react to form iron pentacarbonyl which is drained away from reaction vessels. Any residues of iron (or transition metals for that matter) or CO can be oxidized by native perchlorate into metal chloride and CO2 which are both treated as mentioned.

For native source of HCl acid, also look into perchlorate.

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