CA1063835A - Method and apparatus for continuous passivation of sponge iron material - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A method and apparatus for continuous passivation of hot sponge iron material, the method consisting of feeding hot sponge iron material to a compactor, compacting the material to a high density elongated strip-like mass, cutting the mass longitudinally into a plurality of strips while simultaneously compacting the freshly cut longitudinal edges, ????ing the strips transversely of their longitudinal dimensions while simultaneously compacting these freshly cut transverse edges. The apparatus consists of a feeder, a roll compactor for forming a high density continuous elongated mass and longitudinal and transverse shearing devices, along with the requisite control and transporting mechanisms.

Description

BACKGROUND OF lHE INVENTION

¦ Sponge iron, metalllzed pellets or reduced metal materials are produced by the dlrect reduction of ores. "Metall7zed" in this sense ¦ does not mean coated with metal, but means nearly completely reduced to l metal, I.e., always in excess of 75% metal, and normally in excess of 85%
¦ metal in the product. Thls metalllzed product is suitable for charging ¦ dlrectly to a metal ref1nlng furrlace as the feed material. In ferrous I metallurgy, the product referred to is metallized iron materia1, which is I ¦ charged dlrectly to a steelmaking furnace, such as an electrlc arc furnace.
I Steel plants w;lich utilize metallized iron as a feed material have no need I ¦ for metallurglcal coal or coke. Further, such plants are economica1 a~
¦ smal1 capacit;es and thus do nor require the high capital Investment of plants whlch employ blast furnace.

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One of the problems associated with the use of sponge iron as a raw material in steelmaking is its inherent tendency to reoxidize upon exposure to atmospheric conditions. Hot sponge iron is extremely reactive and oxidizes , spontaneously if contacted by oxygen in any form. Thus, sponge iron must be cooled in a reducing or neutral atmosphere. At room temperature, sponge iron is -. so reactive that it oxidizes even when stored in the open air. Contact with water, likewise, causes rapid oxidation, which is commonly termed rusting. Since the oxidation of sponge iron is an exothermic reaction, this oxidation can result in spontaneous heating and ignition of the sponge iron during storage or transport.
For this reason, metallized sponge iron has heen classified a hazardous material by the U.S. Coast Guard~ and its bulk shipment in the unstablized condition is prohibited. ' In some instances, reduced iron in such form as sponge iron or metallized iron pellets is produced in an integrated steel plant as a raw materia]
for the steelmaking furnaces. If it were possible to feed the hot reduced iron, at a temperature above 500C (about 930~F)~ directly into the steelmaking furnace, this would result in a more economical stee:Lmaking process, inasmuch as the energy requirements would be greatly reduced and h:Lgher productivity would be obtained.
It would be imperative that hot sponge iron material be transported and handled in a controlled atmosphere, as exposure to atmospheric air would result in an extremely hazardous situation. If the hot sponge iron could be passivated suffi-ciently that it could be transported by conventional equipment with a minimal heat loss, the steelmaking process for which it serves as a raw material could ~; realize the full benefit of its heat content with attendant savings in energy consumption.
Passivation of sponge iron is also desirable because o~idation of sponge iron, after having once been reduced, requires a second reduction with an attendant increase in energy consumption and cost.
Many attempts have been made in the past to overcome, or reduce, the reoxidation of metallized pellets and to passivate sponge iron. Illustrative jb/i~ - 2 -..
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''' ' ' , , ~ ,, examples include the proposal to cover a bulk shipment of sponge iron with a thin polyurethane foam coating or other type of plastic film to prevent oxygen or moisture from contacting the sponge iron. It has also been suggested to cover such a bulk shipment with a thin glass coating. U.S. Patent No. 3 125 437 teaches a process for passivating s~onge iron against oxidation in air by creating a thin protective skin on the sponge iron surface. Hot briquetting with roll type briquetting machinery are taught in U.S. Patents 3 116 ~96 and 3 174 846 to densify the sponge iron, thereky minimizing the surface area of the reduced iron ore exposed to the oxidizing elements. These illustrative, hut not exhaus-tive examples demonstrate the many attempts to solve the problem.
Coatings on sponge iron require the use of a foreign material which contaminates sponge iron without guaranteeing passivation. Such coatings are easily damaged, for instance, a mere shifting of the material in its container during transit may rupture the coating. Although a protective oxide skin is a proven inhibitor to oxidation in air, it is subject to rusting to hydrated ferric oxide. Thus, such skin does not prevent further oxidation by rusting.
H~retofore, the hot briquetting of sponge iron has been a very promising process for passivation inasmuch as it can be used to passivate bulk shipments to a high degree, as well as to passivate hot sponge iron with temp-eratures as high as 900C (about 1650 F), so that it can be transported on conventional hot conveyillg systems at high temperature without either a prohibitively high loss of metallization or spontaneous ignition. Densification of sponge iron, at least on its surface, is accomplished by hot briquetting.
The exterior of the briquet is compressed to a dense layer which is table or passivated. The interior of the briquet remains less dense, i.e., spongy, and thus is active and readily oxidized, but is protected by the more dense surface layer.

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Ho~ briquetting encounters certain mechanical problems.
Before the briquetting rolls start to wear, single briquets are easily produced. As soon as wear beings, briquets become connected to each other by webs, which requires that they be broken apart prior to shipment or handling. As roll wear increases, the problem of breaking the briquets apart becomes more and more difficult. In addition, the breaking procedure produces fines and exposes the ~-~` less densified interior of each briquet to oxidation, particularly if the breakage occurs through the briquet rather than through the web. With increasing web thickness due to increasing wear, this occurs more and more frequently, Thus, although the greater pro-portion of each briquet is passivated, there is still a sufficient ; proportion of the briquet which is less passivated and subject to reoxidation with a high loss of metallization.
For known strip breaking mechanisms, see German Patent 1,533,827.
OBJECTS OF THE INVENTION
It is an ob~ect of this invention to provide a simplified and efficient method and apparatus for the passivation of sponge ` 20 iron.
- BRI~F SUMMARY OF THE INVENTION
The aforesaid objects o~ this invention, and other objects which will become apparent as this description proceeds, are achieved by providing hot sponge iron compacting apparatus followed by a shearing apparatus. The hot compacting apparatus rolls the sponge iron into an elongated mass. The shearing apparatus cuts the mass - across its longitudinal dimension, compacting the newly exposed edges, and creating small "compacts" which are easily handled, transported, and used in subsequeut processes.

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Where the compacting apparatus produces a relatively wide strip, apparatus may be provided for slitti~g the elongated mass longitudinally to produce a plurality of elongated masses.
In one particular aspect the present invention provides a method for forming a plurality of small, passivated, compact products from hot reactlve particulate sponge iron comprising:
a) feeding said particulate sponge iron at a temperature of at least 600~C
to a compacting apparatus;
b) compacting said particulate sponge iron to form a continuous densified elongated metal strip;
c) longitudinally cutting said densified elongated strip into a multipli-city of longitudinal strips, and d) further dividing said multiplicity of longitudinal strips at regular intervals by shearing them transversely to their longitudinal dimension and simultaneously densifying the newly created surfaces normal to the longitudinal ~ , .
dimension, thus producing a plurality of small compacted sponge iron products, each having a dense skin on all faces, whereby the products a~e resistant to atmospheric oxidation and suitable for bulk handling, storing, and shipping without addltional passivating steps.
In another particular aspect the present invention provides a compacted passivated metallized iron product useful as a feed material for a steelmaking process, said product being in the shape of a generally rectangular parallelepiped and having dense, substantially pore-free faces with a densified surface layer on each face, a less dense center with an average density of at least 4.5 grams per cubic centimeter, and wherein from about 75% to about 96%
of the total iron present is in the metallic state.
;~ While this invention is described in terms of sponge iron, it will be readily understood by those skilled in the art that the jbl~ ` - 5 -, , ,,, , , , , , :

-~ invention is equally applicable to the compaction of metallized iron material in other forms such as pellets or fines, as well as other metals which have been directly reduced from their oxides, or ores and which metals react in the same manner as and have comparable properties to sponge iron under oxidizing conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
For better understanding of this invention, reference should be had to the accompanying drawings, wherein:
Figure 1 is an elevational view of the preferred embodiment - 10 of my invention with some parts removed.
Figure 2 is a plan view of a pair of slitter rolls showing their interfitting configuration.
Figure 3 is a plan view similar to Pigure 2 on a larger scale taken through the workpiece.
Figure 4 is a sectional view taken along the line IV-IV
of Figure 3.
Figure 5 is an end view of the compactor rolls and their associated parts.
Figure 6 is a sectional view taken along the line VI-VI
of Figure 5.
Figure 7 is a schematic cross-sectional view of a work-` piece about to be sheared longitudinally.
Figure 8 is a schematic view of a workpiece undergoinglongitudinal shearing and concomitant densification of its sheared edges.
Figure 9 is a schematic elevational view of a workpiece about to be sheared transversely.

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Figure 10 is a schematic elevational view of a workpiece undergoing transverse shearing and concomitant densification of its sheared edges.
DETAILED DESCRIPTION
With specific reference to the form of the inven-tion illustrated in the drawings and referring particularly in Figure 1, apparatus for continuously passivating hot re-active particulate metal material consists essentially of three basic parts, a material accumulator 10, a compactor 12 and a divider-densifier 14.
Accumulator 10 may take the form of a surge bin 15 having a slide valve 16 at the bottom thereof positioned above a feed hopper 18, which hopper is adapted both to contain hot feed material 20 and to control the rate of feed of the material to the compactor apparatus 12. The ` feed material 20 may be sponge iron, pellets or lump ore, or a combination thereof, which material has been reduced in an associated directed reduction furnace 8. Feed hopper 18 includes cheek plates 22, shown in Figure 7 and 8, which bear against the ends of the bodies of power driven, large diameter compactor rolls 24 and 26 to seal the interior of the hopper 18 against atmospheric air. As shown, roll 2~
is fixed in its chocks 28 whereas roll 26 is movably mounted in horizontally movable roll chocks 30, the movement of which is controlled by hydraulic cylinders 32. Rolls 24 and 26 may have a flat contour or may have a small collar at each end of the roll body. -~
The region from slide valve 16 to the nip of rolls . , : : .:

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24 and 26 is designated hereunder as the feeding and com-paction zone.
Scrapers 44a and 44h are pivotally mounted beneath the compacting rolls at pivot points 46a and 46b respectively, each of which is well below the center of gravity of its respective scraper. Thusj the upper edge of each scraper tends to maintain contact with its respective compacting roll.
A tension spring 48 biases each scraper against its com- ;
pacting roll to ensure sure contact.
Beneath the compactor rolls and aligned with the pass-line thereof are a pair of horizontally opposed shearing or slitting rolls 34 and 36 for longitudinal slitting of wide strip. Roll 34 is mounted in fixed chocks 38 while roll 36 is mounted in horizontally movable chocks 40 the motion of which is controlled by hydraulic cylinders 42. The shearing rolls advantageously have a configuration as shown in Figures 2 and 3.
A doctor device 50 which may also be known as a roll stripper or guide is located on the discharge side or bottom 20 of each roll 34 and 36. Such a guide may have the full contour of the roll, extending completely across the roll body. Alternatively, the device may consist of a number of guides each of which fits into a recess 34a or onto a collar ,:. .
34b (Fi~ure 3) of the roll, respectively.

Aligned with the pass-lines of the compactor rolls :, .
and the slitter rolls is anvil 54, which likewise may have , a horizontal contour matching that of roll 34. A rotating shear 56, containing a number of blade holders 58 with `
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their associated blades 59, is mounted beneath the anvil 54 in such manner that the shear blades transversely cut the workpieces b~ shearing them against the anvil. Blades 59 preferably have a flat shearing face 60. A feed chute 61 may be provided beneath the rotary shear to collect the metallized iron compacts 62 and direct them into a cooling tank 64 which is filled with water. An apron conveyor 66 removes the compacts from the cooling tan, transferring them to a belt conveyor 68 for transshipment to a stockpile 70. The small amount of fine material that may be produced by the shearing and abrasion of the compacts falls through the perforations in the apron conveyor and collects in a funnel 72 which has a lock valve 74 at its lower extremity. The funnel can be emptied into a trough car 76 periodically to remove the fines from the system.
'" In operation, hot sponge iron, pellets and/or lump material, including fines, is charged into surge bin 12.
Level control devices 80 (such as a C-E Invalco Nuclear Level ' Control manuPactured by C-E Invalco Di~ision of Comb'ustion ;l 20 Engineering; Inc., Tulsa, Oklahoma, U.S.A.) may be inter-locked with the speed control on the roll drives for roll9 24 and 26 to ensure suf~icient vo]ume of material to maintain ' a constant wldth of the elongated strips (Flgure 1).
The hot sponge iron has a temperature of at least 600 C preferably 700 to 800 C and an average metallization ` of at least about 75%, but normally at least 85%, and pre-ferably at least 90% metallized. The hot sponge iron passes from the surge bin 12 through the region of the slide valve 16 into feed hopper 18. The slide valve is in the open , ,: :
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position during operation of the apparatus, and is closed only when the machinery is shut down. The feed hopper, slide valve and surge bin must be gas tight to prevent ambient air from contacting the hot, extremely reactive material.
The flow rate of hot sponge iron to the nip of the two com-pacting rolls 24 and 26 may be controlled by a movable feed tongue mechanism 86. This controls the volume of sponge iron reaching the rolls, and thus the thickness and density of the strip produced by compaction. If too great a volume of ma-terial is fed into the rolls, they will open, producing a thicker strip having an unfavorable density distribution or gradient. The feed tongue 88 is pivotally attached to the feed hopper, and has an adjusting arm 90 which extends out-- side the hopper~ The tongue may extend the full width of the hopper, or a number of narrower tongues may be employed, Hot sponge iron is fed to the compacting rolls by gravity. An alternative feeder arrangement such as a screw feeder may be used which will exert a positive feed pressure on the material entering the roll nip. Thls will control both the rate and volume of flow of the feed material.
After entrainment of the hot sponge iron into the roll nip, the sponge iron is continuously densified by the counterrotating rolls 24 and 26 which exert large compressive forces on the sponge iron causing formation of an increasingly ~ compacted iron mass until it reaches the narrowest gap at -' the hori~ontal centerline of the rolls, During thïs densi-fication procedure, the individual pellets or lumps are de-formed and the spongy structure of the iron is destroyed by the pressure of compaction exerted by the compacting rolls, ``' ' . ' ~, 10 ph/~
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and the fines are assimilated into the densified mass. The gas which has been in the interstices between the hot pellets as well as in the pores of the pellets, is forceably expelled therefrom and escapes from the hopper 18 through gaps be-tween the ends of the compacting rolls and the cheek plates 22 as well as through gaps between the roll body and the base of feed hopper 18. This gas, which remained in and around the pellets on discharge from the direct reduction furnace 8 is reducing in character, and provides a steady stream of non-oxidizing gas to protect the feeding and com-paction zone against contact by the surrounding atmospheric air, Thus it is unnecessary to provide a sophisticated sealing system. At startup a nitrogen purge is used. ~itrogen or other non-oxidizing gas is introduced to the feed hopper through orifice 92 ~Figures 5 and 6) in the cheek plates 22 near the nip of the rolls. After a few feet of compacted strip has been formed, the nitrogen purge is stopped~ as the reducing gas forced out of the pores will displace the ni-trogen and maintain a reducing atmosphere.
Compaction of the hot sponge iron forms a continuous strip or sheet S (Figure 1) having such high density that the-formerly very high affinity of the iron for oxygen is so far reduced that it is no longer subject to catastrophic - reoxidation, In fact oxidation of the surface of this ex-. .::: ;, tremely denee material will now result in a very small loss of metallization.
The mean density of the strip depends on the thick-ness of the strip. A pronounced density gradient toward the less dense center of the strip reduces the mean density with ph/~;, increasing strip thickness. The mean density must be at least 4.5 grams per cubic centimeter, and preferably should be between 5 and 6 grams per cubic centimeter. Below a den-sity of 4.5 grams per cubic centimeter, passivation is in-; sufficient for long-term open bulk storage without signifi-cant loss of metallization. Note that while the mean density of a thick strip may be only 4.5, the surface contacted by -- the surrounding atmosphere has a very high density with an attendant high degree of passivation.
During compaction, the compacting rolls 24 and 26 be-come heated due to conduction of heat from the hot feed ma-terial 20, the temperature of which has been increased by the extremely great amount of energy input that has been transformed into heat and is absorbed by the feed material.
Exhaust fans 100 (Figures 5 and 6) may be employed to remove excess heat from the rolls. For the exhaust fans to work efficiently, the compacting rolls 24 and 26 should be sur-rounded by an enclosure 102 best shown in Figure 5. Enclosure 102 has at least one, but preferably a multiplicity of air intakes 104 along each side of its bottom face. The suction ; created by exhaust fans 100 will circulate ambient air through intakes 104 around compacting rolls 24 and 26 and out of enclosure 102 through the exhaust fans 100. These fans may be associated with a dust collector, bag house or precipitator to remove particulate material from the exhaust air.
Scrapers 44 act as roll guides for the compacting rolls 24 and 26 to prevent the elongated strip from wrapping :~ "
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around one of ~he rolls. In addition the scrapers assist in guiding the strip into the 51itting rolls 34 and 36. The scrapers 44 are biased against the compacting rolls by springs 48 and guide the strip into the pass-line of the slitting rolls.
Since the workpiece is a wide strip A upon exiting the densification rolls, it is cut into narrower S' strips (Figure 4) by the roll slitter 34~ 36 which forces the hot, highly malleable strip S into the alternating grooves in each roll. This process creates sufficient compressive for-ces on the edges of the newly slit strips S' to increase the density of the material on the strip edges sufficiently to accomplish the desired passivation along the longitudinal edges. Deformation of the workpieces by slitting is shown in Figures 7 and 8.
The strips S' produced in the slitting apparatus are 9ub~equently subdivided into small~ completely passivated pieces or compacts 62 which can be handled, stored and shipped ;~
in bulk without degradation, using only conventional equip-ment. The outer surface of each compact must be highly densified to achieve complete passivation. Since the center of the strip is less dense chan the strip surface, the divid-ing process must sufficiently densify the newly created transverse surfaces to obtain complete passivation. The temperature of the strip at this point in processing is suf-ficiently high to maintain the iron strip in a highly malleable condition, particular]y since the strip density is only about 70 to 80% of its theoretical density.
An alternative method of achieving simultaneous ph/~

division and densification of passivated pieces of material i5 high speed cutting in which so much energy is introduced locally that the resulting heat melts a thin layer of the metallic material. Solidification oE the material forms a dense protective skin on the new surfaces.
Simultaneous division and densification of the strip is accomplished by moving the strip past anvil 54 while driving blades 59 of rotary shear 56 against the strip This action and the deformation of the sheared faces of the resulting compacts are shown in Figures 9 and 10. The stresses from ~ i deformation actually cause densification of that portion of the material comprising the sheared faces. In fact, hot shearing compresses the material at each face, rendering the sheared dimension less than that of the normal workpiece thickness.
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i ~ If the compacts have been produced for shipment, they i~ must be cooled to ambient temperature. Since the compacts are completely passivated cooling can be accomplished by quenching in or by water, or by any other available means.
Suitable apparatu8 for water quenching has been illustrated in Figure 1 and described above.
Upon shearing, the compacted products remain hot. If ;~ these compacts are to be used in an adjacent steel producing -~
- mill, the inherent heat in the compacts may be utilized to reduce the energy input required in the melt shop and increase productivity. To accomplish this, the compacts are transferred without quenching or cooling to a heavy-duty steel apron con-veyor to be transported directly to a melting furnace. Since the compacts are in a passivated condition~ they can be trans-~: :

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ported with no special precautions in ambient air. It is desirable, however, to protect the compacts from cooling by wind, rain, snow, etc. Thus, the conveyor may be enclosed to protect it from cooling effects of the elements, and the conveyor may be insulated to prevent heat loss from the com-pacts, particularly by convection~ If waste gas is available ` having a temperature greater than 700 C from either the steel mill or from the direct reduction facility, this gas may be - introduced to the enclosure surrounding the apron conveyor to `
minimize heat loss of the compacts during transport. Suitable gases are blast furnace gas, waste gas or spent reducing gas from a direct reduction furnace, off gas from a metal refining furnace such as an electric furnace, and gaseous hydrocarbons.
It is preferable that the gas be non-oxidizing in character?
but this is not necessary due to the passivation of the com-pacts In its simplest form, my method for continuously passi-vating a ho~ reactive particulate metal comprehends feeding the partlculate metal 20 to a comp~cting apparatus such as compacting rolls 24 and 26, compacting the particulate metal material to form a dense elongated metal mass, followed by the simultaneous division of the elongated metal mass by cutting it across its longitudinal dimension by apparatus such as shear 56 and anvil 54, while simultaneously densifying the newly created surfaces caused by such cutting, ~hus producing a completely passivated product suitable for bulk handling, storing and shipping without additional passivating steps.
The iron compacts produced by this process have gen-erally rectangular faces which form a substantially rectan-gular parallelepiped.

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It is clear from the foregoing that I have overcome the difficulties of prior art practices and have invented a method and apparatus for passivating metallic materials which are highly reactive and readily subject to oxidation. I
have provided a simplified and efficient method and apparatus , for the passivation of sponge metal, the product of which has consistently high quality and which apparatus requires a i minimum of maintenance. My passivating system produces a hot product that can be directly transported to a metal re-fining facility at the high temperature at which it completed the passivation process whereby the inherent heat content of "~ the product will reduce the energy input required in the metal refining process and reduce the melting time. Alterna-tively the hot passivated product can be cooled for safe storage, handling and bulk shipment.
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Claims (20)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for forming a plurality of small, passivated, compact products from hot reactive particulate sponge iron compris-ing:

a) feeding said particulate sponge iron at a temperature of at least 600°C to a compacting apparatus;
b) compacting said particulate sponge iron to form a continuous densified elongated metal strip;
c) longitudinally cutting said densified elongated strip into a multiplicity of longitudinal strips; and d) further dividing said multiplicity of longitudinal strips at regular intervals by shearing them transversely to their longitudinal dimension and simultaneously densifying the newly created surfaces normal to the longitudinal dimension, thus pro-ducing a plurality of small compacted sponge iron products, each having a dense skin on all faces, whereby the products are resist-ant to atmosphereic oxidation and suitable for bulk handling, storing, and shipping without additional passivating steps.

2. A method according to Claim 1 wherein compacting is accomplished by compressing a sufficient amount of hot particulate metal between two rotating rolls and maintaining sufficient com-pressive force between said rolls to cause the particles of said metal to form a cohensive mass.

3. A method according to Claim 1 wherein said longitudinal cutting is accomplished by rotary shearing.

4. A method according to Claim 1 wherein said longitudinal cutting is accomplished by a pair of shearing rolls having alternate mating collars and recesses.

5. A method according to Claim 1 wherein transverse cutting or said elongated mass is accomplished by rotating at least one shear knife, mounted for angular movement, about a horizontal axis while maintaining longitudinal movement of said metal mass across the face of a shear knife anvil whereby said elongated metal mass is cut into a multiplicity of compact pieces.

6. A method according to Claim 1 wherein said metal is at least 75% reduced iron.

7. A method according to Claim 1 wherein said metal is at least 85% reduced iron.

8. A method according to Claim 1 wherein said sponge iron is in lump form.

9. A method according to Claim 1 wherein said sponge iron is in pellet form.

10. A method according to Claim 1 further comprising cooling said product to ambient temperature.

11. A method according to Claim 10 in which said product is cooled by water quenching.

12. A method according to Claim 1 wherein hot reducing gas is entrained in the interstices of said particulate metal, said method further comprising performing the compacting step in an enclosure whereby gases forceably expelled from said particulate metal during compaction protect the feeding and compaction zone against contact by the surrounding atmosphere.

13. A method according to Claim 12 further comprising introducing a non-oxidizing gas to the particulate material in the compaction zone during startup of the process.

14. A method according to Claim 2 further comprising controlling the rate of feed of said particulate metal to the com-pacting apparatus, relative to the speed of the rolls to maintain an elongated metal mass of optimum cross-sectional area.

15. A method according to Claim 2 further comprising cooling said rolls by passing a cooling gas over at least a portion of the surface of each roll not in contact with said particulate material or said elongated metal mass.

16. A method according to Claim 15 wherein said cooling gas is air.

17. A compacted passivated metallized iron pro-duct useful as a feed material for a steelmaking process, said product being in the shape of a generally rectangular parallelepiped and having dense, substantially pore-free faces with a densified surface layer on each face, a less dense center with an average density of at least 4.5 grams per cubic centimeter, and wherein from about 75% to about 96% of the total iron present is in the metallic state.

18. A product according to Claim 17 having an average density from about 5 to about 6 grams per cubic centi-meter.

19. A product according to Claim 17 wherein at least 85% of the total iron present is in the metallic state.

20. A product according to Claim 17 wherein from about 90 to about 96% of the total iron present is in the metallic state.