Author Topic: Oil fired crucible furnace  (Read 67873 times)

Offline AdeV

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Re: Oil fired crucible furnace
« Reply #200 on: November 04, 2013, 08:25:23 PM »
Are there any nice'n'simple plans for a high-output oil burner out there anywhere? I see lots of these things on Youtube & the like, but rarely a set of plans or easy to follow instructions...

I've acquired a barrel full of old motor engine oil, I was planning to centrifuge it and use it as fuel for the old Lister CS engine, but with winter approaching & not having started on the centrifuge yet, I wondered if I couldn't make an oil-burning stove to help keep me warm while I slave over a cold Jag engine...

Fortunately, my dockside location means I'm not in a smoke-free zone, and I could (in theory at least) put the burner unit outside & use a heat-exchanger to extract the heat without having to vent the fumes.

(PS: Sorry for the thread hijack, just seemed that anyone who was interested in oil burners are probably tagging along here.... pls feel free to reply via PM rather than pollute this thread - ESPECIALLY if you are warning me about fumes, the legality of burning old motor oil, etc.)
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Or: Zhengzhou, China. An even longer way from anywhere...
Skype: adev73

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #201 on: November 04, 2013, 10:40:55 PM »
Vtsteam,
Have you seen this burner?
Comments.

Hi unc1esteve,

1.) I believe what he melted was pot metal, which you can do over even a wood fire -- considerably lower melting point than even aluminum. The door handles he melted were, I believe brass plated over the pot metal. They are cheap and widely available.

2.) oil is overkill for that purpose -- though it can be done. But charcoal briquets would have worked as well and been less dangerous than his particular setup.

3.) The oil delivery pipe was huge, and plastic, and the gate valve oversized and difficult to control. 1/4" copper pipe with a needle valve would have been more appropriate.

4.) No shutoff valve at the oil reservoir. His control valve is his shutoff valve. A fire in this area would prevent interrupting the flow, which is gravity feed instead of siphon.

5.) Oil reservoir located too close to burner.

6.) Furnace looks to be cement -- inadequate for brass melting temps. Okay maybe for pot metal.

7.) water and waste motor oil have very different viscosity, so something that atomizes water may not do well with that kind of oil -- also dependent on temperature. Diesel fuel is more like water in viscosity, if a burner does not work well for waste oil.

The style of burner is standard blown oil pipe. Ironman was one of the earliest users I'm aware of to develop this for small furnaces like ours. Lionel of backyard metalcasting /alloyavenue was a much later popularizer. WC Amen in his book shows earlier incarnations. Steve Chastain gives good engineering info on flares for oil burning, etc, but I think Ironman's is by far the simplest and best developed of these. His pressurizes the oil line, I believe.

The type of burner I use (Kwiky) is also requires a source of pressure, not just a blower. The difference is that the oil is atomized by a air jet -- like a spray gun -- before being mixed with the blower air. I have never tried any other burner so I can't fairly compare mine with any other. It does work, though, and melts iron.

I would like to see the above list of problems corrected by anyone contemplating an oil burner. I don't think it is hard to accomplish a safer system than the one shown, at minimal expense. The most expensive part for doing brass work will probably be the furnace itself, not the burner. Inexpensive hi temp refractories are a challenge to find nowadays.  I happened to have firebrick on hand, but also needed fireclay, and good refractory sand. A lot of our local sand has shale and other sedimentary rock in it so isn't very refractory.


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Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #202 on: November 04, 2013, 10:59:57 PM »
Are there any nice'n'simple plans for a high-output oil burner out there anywhere? I see lots of these things on Youtube & the like, but rarely a set of plans or easy to follow instructions...

Adev, here's an oldie that I've always like the looks of:

http://www.motherearthnews.com/renewable-energy/free-heat-zmaz70sozgoe.aspx
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #203 on: November 04, 2013, 11:19:26 PM »
unc1steve -- a few more thoughts about that video:

He wasn't prepared with an ingot mold to pour the remainder of his metal into after the mold pour.

His crucible was very tall for its diameter, and so therefore difficult to pour from.

He was pouring what looked like a lost foam pattern in loose sand, not a conventional removable pattern (like your wooden plaque) in a greensand filled flask. That's quite a different process.

He seemed like a person who had not done any reading outside of some internet or youtube dabbling. I strongly suggest that anyone contemplating casting read David Gingery's furnace book(s) and or Terry Aspin's books. Reading both will give a good background in all aspects of molding and casting in an easy to read format. They are all inexpensive paperbacks.
I love it when a Plan B comes together!
Steve
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Offline unc1esteve

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Re: Oil fired crucible furnace
« Reply #204 on: November 05, 2013, 11:40:19 AM »

When I first saw the video I thought it
was a joke.  This guy could have easily
set himself on fire when the 'furnace'
flamed over.  His clothing looked like
the flammable synthetic type.
What I am interested in is the simplicity
of the burner.  Will continue on today.
Need to set up outside.

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #205 on: November 19, 2020, 04:29:33 PM »
I'm going to be firing this baby up for the first time in 7 years tomorrow.  :zap:
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Steve
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Offline tom osselton

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Re: Oil fired crucible furnace
« Reply #206 on: November 19, 2020, 07:17:01 PM »
Should be fun our season is over I’m afraid.

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #207 on: December 12, 2020, 10:47:57 PM »
Both my furnaces could use re-lining after living unused for a couple years outdoors. I did fire the plaster-lined propane furnace and did a few brass and zinc castings with it last month (mentioned in my lathe thread) But brass is too difficult to cast now in December -- last two tries were cold shorts. Cause was mainly low outdoor temperatures leading to low furnace temperature (also due to a somewhat deteriorated lining) and low greensand temperatures. Well, that plus a poured part with thin sections. Zinc and aluminum are still fine to melt in it though.

I didn't get around to firing the oil fired iron furnace after all,  and ended up moving the foundries around and organizing my lean-to casting space. If I'm to cast brass in winter I'll need to do it in the oil furnace with it's much higher output burner, and thicker insulation. But also I want to cast iron again. So it also needs re-lining.

 This time I've decided to bite the bullet and re-line with ceramic insulating blanket and reflective coating ala Ironman. The spare money is available, and I am finally able to buy the esoteric hard coating (which was unavailable before -- at least to non-commercial buyers like me). This should (I hope) heat up faster, and be better insulation against the winter cold. We'll see. The blanket insulation arrived today, but the coating is delayed -- supposedly arriving later in the week.

The iron will be for castings for an engine I want to build. Really looking forward to seeing how this new lining works out! :dremel:
I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #208 on: December 13, 2020, 05:21:02 PM »
It was fairly warm out today for this time of year, so I made a start on the new lining for the oil fired iron furnace.  After scraping away the cap, of sand and fire clay mix, The top layer of fire bricks were revealed. They looked in very good condition.

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Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #209 on: December 13, 2020, 05:26:36 PM »
Removing the firebricks. The sand and clay mix was quite crumbly. The fire bricks were somewhat weakened by the iron melts, and had hairline cracks, but were all substantially intact, and would have probably lasted for many more years, from the looks of it. There was no surface degradation or disintegration at all.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #210 on: December 13, 2020, 05:28:43 PM »
The firebricks actually had a vitrified surface buildup, rather than erosion. The white flecked area is the additional material, and the outer black shiny area is a glaze.

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Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #211 on: December 13, 2020, 05:32:21 PM »
I saved both the firebricks and the sand clay material to serve as a backing to the new mineral wool furnace insulation I will be adding. Here used firebricks have been used to build up the bottom of the furnace.

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Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #212 on: December 13, 2020, 05:34:07 PM »
Then some of the sifted crumbly sand and clay mortar has been used as infill.

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Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #213 on: December 13, 2020, 05:44:54 PM »
I sifted the rest of the old mortar and added a bucket of sand, and a bucket of fireclay. Mixed it up in a wheelbarrow with a hoe, gradually adding water until it was a nice stiff rammable mix.

Next, I took a quart of the mix and added more water to make a mud. This was smeared lightly all over the inside of the furnace shell to wet it and make the stiffer mortar stick better to the metal.

Then I pressed handfulls of the stiffer mortar/refractory into the furnace by hand, then pounding it into place with a piece of brick to get it to pack in place really well. I had just enough to apply an inch thick coating throughout the furnace shell by evening. I covered it over to finish tomorrow. Next will be molding into the bottom an Ironman style plinth, and then firing the shell to dry it out and prepare it for adding the mineral blanket insulation.

Here's what it looked like at the end of the day:

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #214 on: December 14, 2020, 01:33:27 PM »
Plinth added:

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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #215 on: December 14, 2020, 01:40:18 PM »
And then I loaded the furnace up with split kindling to dry out and initial fire the refractory. It started to snow, though the temperature was just above freezing. Just a light snow. As I recall when it, the same thing happened when I went to fire the lining the first time I built this furnace -- as a cupola.  :loco:

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Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #216 on: December 14, 2020, 01:43:43 PM »
Baking under way. The kindling has burnt down into a 6" layer of hot embers, and I'm adding larger split wood to build that up higher:

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Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #217 on: December 14, 2020, 02:28:25 PM »
An hour later, I have about a 10" bed of glowing embers so far:



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Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #218 on: December 14, 2020, 02:33:18 PM »
I decided this was enough baking for today and put a disk of 1/8" steel on top as a cover.

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Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #219 on: December 14, 2020, 02:38:24 PM »
Then blocked the tuyere opening, and sprinkled sand around the edge of the cover to seal it. This will convert all of the remaining brands in the furnace to charcoal, which I will have a use for when I start melting iron. The furnace should continue to bake for some time after.

Kind of curious experiment to see if powdered charcoal can substitute for plumbago in mold facings, and also whether (per Ironman video with plumbago and coke) it will convert steel to cast iron in a crucible.

I love it when a Plan B comes together!
Steve
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Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #220 on: December 14, 2020, 11:19:48 PM »
hmmmm, just recalled that powdered charcoal probably won't work as a gas producing facing the way plumbago does, because it actually needs the impurities of coal to produce the momentary gassing that gives it the characteristic smooth finish. Charcoal is too pure carbon. I think I recall that from some conversation here -- somewhere -- maybe with ironman.....

But charcoal still might work in a steel conversion to cast iron experiment where pure carbon is wanted. And for plumbago substitution, I wonder if store bought charcoal briquets, powdered are impure enough to make the gas layer. Well, the only way to find out is to experiment!  :zap: :zap: :zap:


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Steve
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Offline awemawson

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Re: Oil fired crucible furnace
« Reply #221 on: December 15, 2020, 02:30:44 AM »
I understand that finely powdered bituminous coal was added to the greensand in iron foundries to create this gas boundary layer to achieve a smooth casting.
Andrew Mawson
East Sussex

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #222 on: December 15, 2020, 09:19:01 AM »
Yes, Andrew, "seacoal".

I actually have some coal that I could powder, but it's anthracite, the common coal here. I don't think it will do the same thing as bituminous coal. It will not work in a cupola either, Or I should say, it has been used historically only when it was discovered that it absolutely required a heated blast to work, unlike coke. At one time I wanted to experiment to see if a hot blast would work with anthracite on my "sawed off" cupola (now the re-configured oil furnace) but never did. Charcoal was tried, but found to be not energy dense enough on the very small scale of my short and narrow cupola.
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Offline awemawson

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Re: Oil fired crucible furnace
« Reply #223 on: December 15, 2020, 10:21:57 AM »
I thought that 'Seacoal' was just washed up coal found on the beach originating where eroding cliffs have an exposed coal  seam. So in North East England it is found in significant quantities and used to be 'gleaned' to fuel cottage hearths.

So presumably if this is the case 'seacoal' can be any sort of coal, bituminous or not  :scratch:

(Another source of seacoal was from the myriad of colliers that plied up and down the East coast of England for centuries with coal from the Newcastle coal fields to London - any that went overboad due to accident or sinking could be washed up on the beach.)

 (Hence the expression 'taking coals to Newcastle' ie a pointless action)


 

Andrew Mawson
East Sussex

Offline vtsteam

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Re: Oil fired crucible furnace
« Reply #224 on: December 15, 2020, 11:36:20 AM »
Well, Andrew here's a lengthy reference from from American Foundryman, (January- February 1951), which we can take with a grain of seacoal, as usual re. foundry opinions and beliefs. Personally I wouldn't be surprised if seacoal got it's name from the floaties you mention, being an obvious relationship. Unless of course we really do have good old  "Dud" Dudley to thank for invention of the name :)
Quote
SEACOAL
History
The use of "coal dust" in molding sand originated in England. It was later introduced to the North American foundrymen as "sea­coal." One particular English or Welsh coal seam appeared to be the most satisfactory for foundry purposes and became the standard with which other coals were compared. Some authors believe that since the coal seam was near the Welsh coast and the mines were deep under the ground, extending under the sea, the term "seacoal" emphasized both its origin and its sea transportation to the U.S.A. However, the author has pursued the term "seacoal" for many years and believes that it originated from Lord Dudley's nomenclature in his patent applications in 1620. Lord Dudley applied for a patent in behalf of his son, "Dud" Dudley, for "melting oron ewre (ore) and of making the same into caste workes or barrs with "SEA-COLES" or "pit-coles" in furnaces with bellowes. " These "sea-coles" were described as being low in ash, sulphur and impurities for making the metal. The foundryman thought the same coal should be used in making sand molds. After a long and tiring search by the author, an old English file produced this answer after many years of investigation.

Characteristics
Seacoal (coal dust) is a highly volatile bituminous coal, ground to various degrees of fineness by pulverizing mills which is then graded by screening or by air classification methods. It is mixed and mulled with molding sand in various proportions. When it, or the products of its destructive distillation come into direct contact with molten iron, seacoal seems to improve the casting finish. Where molds are cast which contain seacoal, the sand peels more freely from the castings and the cleaning of the castings are more easily accomplished. Seacoal is one of the least expensive materials used in molding sand to give these results. Seacoal has been termed a "facing" in the foundry as a result of this property.

Effect
The effect of seacoal is so well known that it is accepted as a requirement in the pr3oduction of gray iron, ductile (nodular or S.G.) iron and malleable castings. The many advantages it offers have perpetuated its foundry use.

Factors
Several principal factors must be considered in the selection of seacoal (coal dust). The Volatile Combustible Matter, Fixed Carbon, Ash Content, Sulphur, and Moisture Content of the coal source measures its quality. Cost and reliability of the producer are the most important factors when purchasing the coal. Other factors to be considered in the selection of a specific grade of seacoal are: 1) The grain fineness of the base sand, coupled with its sand grain distribution. 2) Type and amount of bonding material used. 3) Permeability of the molding sand desired. 4) Weight of the casting to be produced. 5) Desired surface finish of the casting. 6) System of gating the pattern. 7) Metal pouring temperature and length of pouring time. 8) Density of the rammed sand mass around the casting. 9) Length of time the molds stand after pouring. 10) Type and temperature of the metal poured.

There are many additional variables to be considered, as seacoal affects most of the properties of the molding sand. Investigators claim that seacoal principally acts as a reducing agent, thus it prevents sand from adhering, or burning-on to the casting. Others dispute this claim.

Functions of Seacoal as a Sand Additive
Coal and coke in the molding sand burn, thus consuming the oxygen in the mold cavity to provide a reducing atmosphere as the mold is initially poured. Heat is absorbed by the mold from the molten metal. The temperature is increased to the "coking" temperature range of the seacoal present. During "coking," uncondensable reducing gases are produced, such as, hydrogen, methane, ethane, tars, light oils, and others which are distilled-off. The tar fraction plus the light oils burn and then contribute a carbon film or "sooting" action on the mold as a "bonus" factor, acting as an inhibiting agent. The volatile matter in seacoal consumes some of the oxygen immediately in the mold cavity as the metal ignites the seacoal upon entering the mold. This sooting prevents cutting action of the flowing metal against the molding sand and inhibits fusion of the silica sand grains. The gas content from the seacoal tends to form a cushion at the surface of the mold-metal interface, and the metal lies more evenly and quietly. Metal penetration is re­duced by the formation of the gas cushion which is aided by the coal's coking action. The gas pressure fills all the mold's voids between the sand grains giving the desired smooth casting surface but still permitting the venting of noxious gases. A certain amount of mold gas pressure is desired to help prevent metal penetration.

Sizing of The Seacoal
It is believed that seacoal should approximate the same size as the base sand grain in order to not alter the permeability of the mold­ing sand, but this is only an opinion. Seacoal on losing its volatile matter becomes coke, a fixed carbon. Some coals on coking swell to nearly three times their original volume, which may be detrimental to the surface of the castings. The coking theory has not been fully defined or proven, but the author believes it is a functioning part of the seacoal in helping to overcome apparent metal shrinkage. Some foundrymen claim that fines (those less than the U.S. No. 200 Standard Sieve) should be removed from commercial seacoal. It is the author's opinion that to narrow the range of particle sizes might exhibit a lag in the formation of the seacoal's gas cushion which it generates on heating. The reducing atmosphere which seacoal de­velops should form instantaneously, and removal of the fines may act as a disadvantage in certain cases. To cite an example, one cubic foot of coal in the solid state burns rather slowly when thrown into a flame; whereas, if it is ground to fine particle sizes, the coal would instantan­eously ignite, if subjected to the flame combustion. Time is a factor to be considered. Foundries find it detrimental to remove too many fines from foundry sands, as metal penetration and rough casting sur­faces can result. Since sand surfaces in the drag side of the casting is subjected to metal weight, the metal tends to force easier into the interstices of the sand grains, as the sand voids increase in size. Wash­ing and cutting of the metal may also result around the gates from too-open sands as they are more brittle. Open sands are also difficult to patch, or work. A carbon film is highly desirable in most cases to improve the finish of the castings.

Amounts Added
Too much seacoal increases the temper water demand due to increased surface area of the mixture. This causes rougher castings. Excess seacoal creates an evolution of gas which may cause blows, or porosity in the castings. Molding sand which is too rich in seacoal may promote defects called, "Map of Ireland," "Fins" or "Veining." Seacoal in moderate amounts is very beneficial, but as with the case of any other raw material used in the foundry, too much is detrimental. Seacoal depreciates hot compression strength at 1250°F. and 2000°F. (1010° C. and 1093° C.) rather effectively.

Grades
Seacoal is sold by grade designations namely: A, B, C, D, D-½. A and B grades are coarser and are used for molding heavier castings, C to D-½ grades are recommended for lighter to medium castings and for giving more detailed surface finish. Foundry facing suppliers have attempted to standardize on the best three commercial grades, namely: B, C, or D grades. "Dustless" seacoal (treated) and standard non-treated grades are available through most foundry supply houses. "Dustless" seacoal is a ground coal which has received a secondary treatment of oil or waxes to minimize dust when it is handled in the foundry.

Analyses and Screen Tests of Seacoal

Seacoal Analysis

The analyses and screen tests (Table No. 25) are approximate. They may vary at least 5% on each sieve depending upon the sup­pliers choice of sieves, and arrangement of sieving with the customer.

The Properties of Seacoal

 Properties of Seacoal

Summarizing
SEACOAL AFFECTS THE FOLLOWING PROPERTIES:
Green Compression Strength-Increases (generally, as long as the temper water doesn't increase).
Dry Compression Strength-Increases, as temper water increases. (6% by weight of seacoal increases dry compression strength approximately 35%, as temper water is also increased to give workability-moldability.)
Hot Compression Strength-Decreases, as seacoal furnishes a reducing mold cavity atmosphere.
Permeability-Generally decreases, due to the high "fines" content of the commercial grades of seacoal.
Flowability-Decreases, as the water demand increases in the molding mixture.
Temper Water Required-Increases by 10% of the weight of seacoal contained in the mixture. (Most of this water is held on the seacoal's surface, instead of being absorbed as in bonding agents. However, seacoal which is coked or formed into an ash sometimes acts as a sponge and absorbs an excessive amount of temper water. This build-up must be avoided by new clean sand additions, otherwise the molding sand becomes ashy and brittle.)
Mold Hardness-Increases, if the same effort or work force is applied. (Even though the mold hardness increases, the metal tends to lie more quietly in the mold when seacoal is present, than when it is not. Avoid high mold hardness on thin section castings which freeze rapidly.)
Deformation-Increases up to 6.5% by weight seacoal. The increase is dependent upon the seacoal's grain size. Temper water is gen­erally increased. If the water does not increase slightly, the mold­ing sands become brittle and break easily. Both wood flour and seacoal (coal dust) tend to make a smoother, softer and more moldable molding sand when used in regular amounts up to 4% to 5% seacoal, or 1% wood flour additions. Excessive amounts of seacoal and wood flour result in molding sands becoming low in resilience, they become brittle, they are difficult to handle and are poor in general practice.
Refractoriness and Sintering-Increases, which is possibly due to the carbon or carbon film developed during pouring of the metal.
Volume Changes in Molding Sand-Less expansion and contraction characteristics of the mold is beneficiated by the use of seacoal. Many of the common defects which are directly associated to the expansion and contraction of sand mixtures seem to disappear when seacoal is present. Seacoal is related to the clay content, moisture content, sand grain distribution and particle grain size. The beneficial limits of seacoal when added to the molding sand tend to vary under different working conditions.
Mold-Wall Movement-Effect of: ( 1) It is found that variations in mold materials influence metal solidification. Seacoal minimizes mold-wall movement. (2) As carbonaceous materials such as seacoal and wood flour are gradually increased in a molding mixture, within a definite limit, the piping of an iron riser of the casting decreases. (3) In comparison to western bentonite or fire clay, southern bentonite appears to lessen mold wall movement, but seacoal addi­tions improve all three bond mixtures. (4) In experiments, wood flour decreases the piping tendency of the metal, which is further aided by seacoal additions. (5) As the temper water of the molding sand mixtures increases, the piping tendency of the metal increases, but seacoal additions help to overcome excessive additions of temper water. (6) It appears that a dense, hard rammed mold results in less movement of the mold-metal interface and less seacoal is required. (7) Oil bonded core sands produce sound castings, but so does seacoal when added to green sand mixtures. Metal exudes slightly from the riser instead of piping when there is a lack of mold-wall movement. Sufficiently rammed molds in green sand act similarly. (8) Mixtures of molding sands and bonding agents are very complex. It is illogical to make definite comparisons between different mixtures. Each base mixture should be considered on an individual basis, but 5% by weight of seacoal in gray iron, ductile (nodular or S. G.) iron and/ or malleable iron castings helps to hold castings closer to pattern size and to have lesser mold-wall movement."

I love it when a Plan B comes together!
Steve
www.sredmond.com