GB2030920A - Producing coated spheroidal particles - Google Patents
Producing coated spheroidal particles Download PDFInfo
- Publication number
- GB2030920A GB2030920A GB7928566A GB7928566A GB2030920A GB 2030920 A GB2030920 A GB 2030920A GB 7928566 A GB7928566 A GB 7928566A GB 7928566 A GB7928566 A GB 7928566A GB 2030920 A GB2030920 A GB 2030920A
- Authority
- GB
- United Kingdom
- Prior art keywords
- spheroidal particles
- binder
- particles
- container
- coated
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000002245 particle Substances 0.000 title claims abstract description 40
- 239000000463 material Substances 0.000 claims abstract description 41
- 239000011230 binding agent Substances 0.000 claims abstract description 21
- 238000000576 coating method Methods 0.000 claims abstract description 13
- 239000011248 coating agent Substances 0.000 claims abstract description 12
- 239000000843 powder Substances 0.000 claims abstract description 11
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052593 corundum Inorganic materials 0.000 claims abstract description 5
- 229910001845 yogo sapphire Inorganic materials 0.000 claims abstract description 5
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 4
- 229910052751 metal Inorganic materials 0.000 claims abstract description 3
- 239000002184 metal Substances 0.000 claims abstract description 3
- 229910052845 zircon Inorganic materials 0.000 claims abstract description 3
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 24
- 239000000203 mixture Substances 0.000 claims description 18
- MWKFXSUHUHTGQN-UHFFFAOYSA-N decan-1-ol Chemical group CCCCCCCCCCO MWKFXSUHUHTGQN-UHFFFAOYSA-N 0.000 claims description 10
- QDOXWKRWXJOMAK-UHFFFAOYSA-N chromium(III) oxide Inorganic materials O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 claims description 3
- 238000010304 firing Methods 0.000 claims description 2
- 239000007788 liquid Substances 0.000 claims description 2
- 239000002054 inoculum Substances 0.000 abstract description 6
- 239000000155 melt Substances 0.000 abstract description 4
- 229910052718 tin Inorganic materials 0.000 abstract description 3
- 238000005245 sintering Methods 0.000 abstract 1
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 4
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 239000008187 granular material Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000012798 spherical particle Substances 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- XSTXAVWGXDQKEL-UHFFFAOYSA-N Trichloroethylene Chemical group ClC=C(Cl)Cl XSTXAVWGXDQKEL-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000011863 silicon-based powder Substances 0.000 description 1
- UBOXGVDOUJQMTN-UHFFFAOYSA-N trichloroethylene Natural products ClCC(Cl)Cl UBOXGVDOUJQMTN-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
- B01J2/28—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic using special binding agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
- B01J2/12—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic in rotating drums
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/10—Making spheroidal graphite cast-iron
- C21C1/105—Nodularising additive agents
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Glanulating (AREA)
- Powder Metallurgy (AREA)
Abstract
Spheroidal particles of a first material, especially a metal, are made by applying a gyratory motion to a container carrying a powder of the material and a binder. The particles are then coated with a second material, such as Al2O3, TiN or zircon, by adding a powder of the second material with a binder and continuing the gyratory motion. Finally, the coated particles are sintered. The structure of the coated particles is able to accommodate shrinkage during sintering without deleteriously affecting the integrity and adhesion of the coating. Also, a wide range of combinations of first and second materials may be used. A particular application of the coated particles is as inoculants to be added to a melt.
Description
SPECIFICATION Improvements in or relating to coating
This invention relates to a method of preparing coated spheroidal particles.
Claim 1 of our U.K. Patent Specification No.
1 033 1 43 reads:
"A method of producing spheroids of fissile or fertile materials or a mixture thereof, comprising the steps of placing granules of the material in a container, applying a gyratory vibration to the container so as to cause the granules to be moved over the internal surface of the container and thereby form spheroids of the material, and after formation of spheroids, causing enlargment of spheroids to a desired size by addition of further quantities of said material."
Reference is also made, in this respect, to "Fabrication of Spheres of Controlled Size from
Powdery Materials by a Planetary Rolling
Technique" by G. H. Williams published in Proc.
Brit. Ceram. Soc No. 12 pp 1 79-192, March 1969 and also to U.K. Patent Specifications Nos.
938,671 and 992,237.
We have now devised a method of preparing
coated spheroidal particles which is related to the methods described in the aforementioned
references.
The present invention provides a method of preparing coated spheroidal particles wherein,
in each particle, a core of a first material
in the form of a spheroidal particle carries a
coating of a second material, which method comprises
(i) applying a gyratory motion to a container
carrying a mixture comprising a powder of the first
material and a binder thereof so as to cause the
mixture to be moved over the internal surface of the container to produce spheroidal particles of the first material;
(ii) applying a gyratory motion to a container carrying a mixture comprising spheroidal particles
produced as in step (i), powder of the second
material and a binder therefor so as to cause the
mixture to be moved over the internal surface of the container to produce spheroidal particles coated with the second material; and
(iii) firing to sinner the coated spheroidal particles.
By "spheroidal particles" is meant agglomerated powder of roughly spherical shape.
Thus, the spheroidal particles are not necessarily of a perfectly spherical shape.
The structure of the product of step (ii) in the method of our invention is well able to accommodate the shrinkage which takes place in step (iii) without deleteriously effecting the integrity and adhesion of the coating. The method is also very versatile in that a wide range of combinations of first and second materials may be used, depending on the intended use of the coated spheroidal particles. We prefer that each of the first and second materials is refractory. Examples of first materials are metals such as chromium, cobalt and molybdenum and ferro silicon and examples of second materials are AI2O3, Al203/FeO mixtures, zircon, TiN, Al203/Cu mixtures,
Al203/CuO mixtures, Al2OCo mixtures and Cr2O3.
From the above examples, it will be noted that each of the first and second materials is not necessarily a single element or compound but may be a mixture comprising two or more such elements and/or compounds.
Step (i) may comprise a single stage in which small (e.g. 1 50 tzm size) spheroidal particles are obtained directly and which may then be used in step (ii). However, when larger (e.g. 600 m) spheroidal particles are required, it may be necessary to carry out step (i) in two or more stages e.g., by firstly forming small spheroidal particles as 'seed' particles as above, secondly adding further powder of the first material and binder to the container and applying a gyratory motion thereto to produce a coating of the first material on the 'seed' particles and thirdly, if necessary, producing still further coatings of the first material by the same procedure.
In step (i) the binder is used to assist formation of spheroidal particles, and in step (ii) it is used to assist formation of the coating. Such a binder is most suitably a liquid binder, such as n-decanol.
The mixtures used in step (i) and in step (ii) should, for best results, each be intimate and if their preparation requires use of a dispersing agent for the binder, such as trichloroethylene, then the dispersing agent must be removed before carrying out steps (i) and/or (ii). The binder has to be removed at some stage and this may take place automatically during step (iii) if sufficient care is taken during this step. If desired, however, the binder may be removed by carrying out a
separate debonding step before carrying out step (iii).
The coated spheroidal particles of our invention
may, for example, be produced in sizes in the range from 1 50 um to 600,us. They have a number of potential applications, principally in the metallurgical field. For example, they may be used as inoculants which are added to a melt. The coating protects the first material, constituting the inoculant, from a too rapid dissolution into the melt. Inoculants may be used to promote grain nucleation and hence to reduce grain size which is advantageous in a number of applications such as production of tougher welds. Inoculants may also be used to provide other beneficial structural modifications to solidified melts.
It may, for some inoculant applications, be desirable to introduce flaws into the coating to increase the rate of disintegration of the coating.
This may readily be done in our method by incorporating a suitable flaw-generating material in combination with the second material in step (ii) above.
The invention will now be particularly described, by way of example only, as follows.
EXAMPLE 1
Milled ferro silicon constituting the first material was throughly mixed with n-decanol binder (14 ml per 100 g of ferro silicon) using a mortar and pestle and sieved through a 22 mesh sieve. 50 g of the resulting mixture were placed in a closed cylindrical pot such as described in the aforementioned Proc. Brit Ceram. Soc. paper. The pot was then subjected to an eccentric gyratory motion for 5 to 10 minutes which caused the powder to densify and form small spheres of about 1 50 ym diameter. The size of the spheres was increased by adding to the pot 5 g portions of ferro silicon powder mixed with n-decanol (concentration: 11 ml of binder per 100 ml offerro silicon) and subjecting the contents to 45 seconds of eccentric gyratory motion.This gave rise to stepwise build-up of the particles and was cbntinued until the product consisted of spheroidal particles of 350,us to 500ym diameter.
The spherical particles were removed, the pot was cleaned out and 60 g of the spherical particles returned to the pot. 20 g of a mixture of titanium nitride powder and n-decanol binder (concentration: 8 ml of binder per 100 g TiN) was added to the pot in 5 g portions which was again subjected to an eccentric gyratory motion after each 5 g addition. This gave rise to titanium nitride coated spheroidal particles which were removed from the pot, debonded by heating to 4000C in a stream of carbon dioxide and sintered at 11 000C in argon. The resulting product consisted of coated spheroidal particles having an integral, welladhered coating of titanium nitride.
Claims (12)
1. A method of preparing coated spheroidal particles wherein, in each particle, a core of a first material in the form of,a spheroidalparticle carries a coating of a second material which method comprises the steps of
(i) applying a gyratory motion to a container carrying a mixture comprising a powder of the first material and a binder therefor so as to cause the mixture to be moved over the internal surface of the container to produce spheroidal particles of the first material;
(ii) applying a gyratory motion to a container carrying a mixture comprising spheroidal particles produced as in step (i), powder of the second material and a binder therefor as so as to cause the mixture to be moved over the internal surface of the container to produce spheroidal particles coated with the second material; and
(iii) firing to sinter the coated spheroidal particles.
2. A method according to claim 1 wherein each of the first and second materials is refractory.
3. A method according to claim 2 wherein the first material is a metal.
4. A method according to claim 2 or to claim 3 wherein the second material is Al203,Cr203, zircon, TiN our a mixture of Awl203 with FeO, Cu, CuO or Co.
5. A method according to any of the preceding claims wherein step (i) comprises a single stage in which spheroidal particles are obtained directly for use in step (ii).
6. A method according to any of claims 1 to 4 wherein step (i) is carried out in at least two stages by, in a first stage, forming spheroidal seed particles in the container and, in a second stage, adding further powder of the first material and binder to the container and applying a gyratory motion thereto to produce a coating of the first material on the seed particles.
7. A method according to any of the preceding claims wherein the binder is a liquid binder.
8. A method according to claim 7 wherein the binder is n-decanol.
9. A method according to any of the preceding claims wherein a separate debonding step is carried out after step (ii) and before step (iii).
10. A method according to any of the preceding claims wherein a flaw-generating material is incorporated in combination with the second material in step (ii).
11. A method of preparing coated spheroidal particles substantially as described herein with reference to the example.
12. Coated spheroidal particles made buy a method according to any of the preceding claims.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7833727 | 1978-08-17 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2030920A true GB2030920A (en) | 1980-04-16 |
| GB2030920B GB2030920B (en) | 1982-07-28 |
Family
ID=10499120
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7928566A Expired GB2030920B (en) | 1978-08-17 | 1979-08-16 | Producing coated spheroidal particles |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2030920B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0292205A1 (en) * | 1987-05-22 | 1988-11-23 | Foseco International Limited | Metallurgical treatment agents |
| WO2002100548A3 (en) * | 2001-06-13 | 2003-10-30 | Inhale Therapeutic Syst | Centrifuged rotating drum for treating cohesive powders |
-
1979
- 1979-08-16 GB GB7928566A patent/GB2030920B/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0292205A1 (en) * | 1987-05-22 | 1988-11-23 | Foseco International Limited | Metallurgical treatment agents |
| US4849165A (en) * | 1987-05-22 | 1989-07-18 | Foseco International Limited | Metal treatment agents |
| WO2002100548A3 (en) * | 2001-06-13 | 2003-10-30 | Inhale Therapeutic Syst | Centrifuged rotating drum for treating cohesive powders |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2030920B (en) | 1982-07-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |