Note: Descriptions are shown in the official language in which they were submitted.
All percentages referred to herein are percentages
by weight and are based on the total weight of the composition.
The present invention relates to the repairing of
ferrous metal bodies.
In U. K. Patent No. 1,479,146 of Goricon Metallur~ical
Services Ltd., published ~uly 6, 1977, inventor Glanville John
Richards, there are described a composition for, and method of,
filling a hole in a ferrous metal body by reacting exothermic-
ally therein a composition which produces a molten metal and a
molten slag in the presence of a particulate refractory mat-
erial. When the reaction products have cooled the hole is
filled at least partially by solidified material having an
upper non-metallic zone of solid slag and bound refractory
material and a lower zone of solidified metal. The slag-
bound refractory material provides a surface having erosion-
resistant properties which are attractive in the principal
application of the composition and method, i.e., in the repair
of the cast iron bases of ingot moulds used in the steel in-
dustry.
According to the said Specification, the particle
size of the refractory material is not critical and it is
indicated that good results have been obtained using, as the
refractory material, firebrick sieved to less than one-eighth
inch and improved results using firebrick granules which pass
a half-inch sieve but are retained on an eighth-inch sieve.
In accordance with the present invention there is
provided a composition for use in the filling of a hole in a
ferrous metal body which comprises (1) a mixture reactable
on ignition to yield a molten slag containing a first metal
in an oxidi~ed state and a second metal in the fused metallic
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~23196
state by reaction of the first metal provided in particulate
metallic form with the second metal provided in the form of
a compound reactable exothermically with the first metal and
(2) a modifier for modifying the slag when the slag has solidi-
fied by cooling, said modifier being a non-metallic refractory
material in particulate form which is present at least in part
in the form of particles of size less than one-eighth inch
whilst being substantially free from particles of size less
then 400 microns.
There is further provided a method of filling a hole
in a body of ferrous metal which comprises introduc,ing into
the hole a composition as provided by the present invention,
exo,hermically reacting the said compound with the first metal
- to form molten slag and the second metal in the fused metallic
state and allowing the second metal and the slag to set to
the solid state with the slag binding the particles of refrac-
tory material together, so that the hole is filled at least
partially by solidified material having an upper zone of solid
slag and bound refractory material and a lower zone of solidi-
fied second metal.
Having at least a significant proportion of a re-
fractory material present in the form of particles of smaller
size than in previous practice gives the slag-bound refractory
a desirably improved finish. Its appearance is more acceptable
to those concerned. Additionally, by having the refractory,
or a major part (e.g. more than 30%, desirably more than 80%
or even more than 95-98%) thereof, present in the form of
much finer particles than ha~e been employed heretofore, the'
inclusion of refractory in the adjacently formed part of the
ingot is minimized so reducing wear of the repair as well as
reducing difficulties in the use of the ingot,
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~æ~ 6
~urther the ignition of the composition is facilitated
and its rate of burning is increased. ~he proportion of
aluminium powder (aluminuum is the preferred first metal)
may be reduced correspondingly with consequent economy.
Previous attempts to include finely powdered refractory
material have produced difficulties with the progress of the
combustion. With the present composition the foll~wing further
advantages may be obtained in the combustion.
(a) When the composltion is ignited at the top, the rate
at which the combustion spreads downwards to the
bottom is improved. (Previously the presence of
refractory fines has inhibited the flow of liquid
products to tne lower parts of the fill and there !'
has been a marked tendency to burn from the top
downwards). ~he early combustion of lower materials
allows the filtering of fume by the unburnt materials
above. ~here is, therefore, a significant reduction
in fume level,
~b) Sometimes, in the method as previously practised, 3`:
-20 some unbound refractory particles are lef~ forming a -
part periphery around the completed repairO
~c) Problems caused by the segregation of fine refractory `
particles (poor ignition, incomplete burn, too slow
burning ~nd thus a poor repair) are significantl~ ;
reduced~
Increasing the lower limit of the size of the refractory
particles above the 400 micron level gives further enhanced
performance. A useful improvement is obtai~ed by increasing r
the limit to 600 microns which is our preferred level. ~urther
improvement is obtainable by increasing the limit beyond
600 microns but increasing beyond 1000 microns (eg to 1500
microns) has little further effect and may be avoided.
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. . . ~ .
~23~
Increasing the lower limit can cause segregation problems
in manufacture~ transport and useO
- The same proportion of refractory matérial may be
employed as previously ie. 15 to 30~ by weight based on the
total waight of the composition.
To illustrate the efficacy of the present invention, the ?:
following details, are given of a~ comparative test in which a ~;,
Mix A in accord~nce with the invention is compared with a ~,
Mix B. Mix B. contained particles of crushed firebrick or
other refractory having a range of particle sises extending
downwardly from 600 microns and containing a substantial
proportion of particles of sizes below 400 microns. 1!;
Mix ~ Mix B ~,
- 18~0 Al ~ 18~0 ~r
62.0 MilI Scale % 62.0 ~,
20.0 Refractory Particles ~ 20.0 ~;
Refractory ~izeRefractory Size
15O7 ~ ~-2?360 microns14.8
40.8 ~ 1180 to 2360 "28.6
39.3 % 710 to 1180 "37.2
4.2 % 600 to 710 " 4.0
Nil %' ~ess than 600 microns 5.4
Two bottom plates of the same type with erosion cavities
of similar area and depth were used for the test. The ~l
aluminium powder, mill scale and refractory particles of ',
A and B were the same in all respects excep,t that all
refractory fines of less than 600 microns were removed
from the refraotory used for mix A. 40Q Kg. of A wa~s ,'
, ignitéd in the erosion hold of one plate and 40 kg. of B
was ignited in the other plate. ~he same starting device
was used for A and B. ~he following was noted:-
-- 5 --
.
. .
~9L2~
Mix A Mix B
~ime taken before ignition 3 secs. 5 secs.
Time for complete combustion 55 secs. 75 secs~
Unreacted material None ~mall amount
Amount of fums Slight Heavy
~ife of repair 7 heats 5 heats
General observations were that Mix A ignited at the top ',
but the ignited material and liquid products of thè reaction
flowed to the bottom. ~here was very little fume. Mix B 5/
ignited at the ~op and the liquid products of reaction
flowed over the top of the mix thus igniting the top layer
of the powder. ~hus there was considerable fume. Mix A.
gave an important improvement in repair life compared to B.
In another test, results comparable with those given
by Mix A were ootained using crushed firebrick of the
following screen analysis: ~-
0.6 to 0.7 mm 5%
? to 1~2 mm 37
1,2 to 2~36 mm 39
72.36 mm to 3~1Z inch 20
~ he particle sizes referred to herein are sieve sizesO
~or irregular particles they are concerned with the maximum
linear dimension taXen across the minimum projected cross
section.
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