Lining materials

Materials suitable for lining vessels designed to hold molten iron or steel are provided herein. These materials are made of burned dolomite, containing 1-6% of a natural glyceride oil or a mixture of such oils and 2-6% by weight of a dry inorganic particulate bonding agent, such as potassium silicate or phosphate.

The invention relates to lining materials based on burned granular dolomite 
and containing organic and inorganic additives for lining vessels designed 
to hold molten iron or steel. 
Many materials are already known for lining vessels designed to hold molten 
iron or steel, particularly ladles, which can be applied to the vessel 
walls by projecting them horizontally from a centrifugal ramming machine 
without the use of a form or vertically behind a form by means of a 
so-called slinger. Such materials may be either basic or acidic, for 
instance as disclosed in the published specifications of German patent 
applications Nos. 2404026 and 1229438. These two publications describe the 
incorporation in such materials of organic additives in the form of 
mineral oils or mineral oils plus fatty acids, for the purpose of 
improving the properties of the materials. 
DESCRIPTION OF THE PRIOR ART 
The material described in the specification of German patent application 
No. 1229438 may consist of dolomite with an addition of 0.1 to 0.2% by 
weight of a neutral mineral oil to allay the evolution of dust. Materials 
based on burned dolomite have the disadvantage of a short storage life 
because burned dolomite has a very strong tendency to hydrate. In this 
connection the published specification of German patent application No. 
1471192, in column 2, at lines 10 to 32, states that hydration, i.e. due 
to the natural humidity of atmospheric air, cannot be effectively 
prevented by the introduction of hydrophobic agents, such as hydrocarbon 
oils. Materials based on burned dolomite containing the presently known 
organic additives cannot therefore be kept in store for any length of 
time. 
Apart from the possible lengthening of their storage life by the 
introduction of mineral oils and fatty acids, basic materials based on 
dolomite, like those based on magnesia, are provided in all the above 
named publications with additions of pitch or tar. These are a nuisance 
because of the fumes and odour which evolve on burning when such materials 
are employed. No additions of inorganic binders are proposed. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide materials based on 
burned dolomite which can be stored for extended periods of say 3 and more 
months without hydration, in other words which will tend not to change 
their properties by taking up moisture from the atmospheric air. 
It has been found that such materials based on burned dolomite of a grain 
size appropriate for their intended use and containing organic and 
inorganic additives can be obtained by introducing a natural triglyceride 
oil or a mixture of such triglyceride oils as an organic additive and a 
dry inorganic binder as an inorganic additive into the mixture. 
The materials proposed by the invention may be characterised by a content 
of 1 to 6% by weight of a natural triglyceride oil or of a mixture of 
triglyceride oils and by a content of 2 to 6% by weight of a dry ground 
inorganic binder.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Thus according to the present invention, a material suitable for use as a 
lining for vessels designed to hold molten iron or steel comprises burned 
granular dolomite, 1 to 6% by weight of a natural triglyceride oil or of a 
mixture of triglyceride oils and 2 to 6% by weight of dry inorganic 
particulate, e.g. ground, binding agents, e.g. a sodium or potassium 
silicate or a sodium or potassium phosphate or mixtures thereof, and 
optionally paper flour or finely shredded paper or carbon-containing 
substances or a mixture thereof. 
In a preferred embodiment the content of triglyceride oil may be between 2 
and 4% by weight. With advantage the triglyceride oil may be of vegetable 
origin, particularly soy-bean oil. 
It has further been found that an addition of 0.5 to 3% by weight of a 
dried paper flour (finely shredded paper ) further improves the 
suitability of the proposed material for application by a slinger machine 
because it promotes rapid drying after application. Preferably the 
addition of paper flour will be between 1 and 2% by weight. Other 
additions of carbon-containing substances, e.g. in the amounts of 1% to 3% 
by weight; for example carbon black, graphite, or ground coke are also 
possible. It should be mentioned that the above quantities in percent by 
weight relate to the total dry mass. 
The proposed materials may be applied in the conventional manner. For 
instance when lining ladles for molten iron or steel the finished mass is 
projected with great force and at high speed from above by the impeller 
head of a slinger machine into the space between the ladle wall and a 
special form that is introduced for the purpose. 
When the lining is complete the form is removed. The inner cohesion of the 
mass is so great that it not only retains its shape, but its green 
strength is high enough to withstand further handling, such as 
transportation of the ladle to the firing oven without the lining being 
damaged. The values measured with the conventional Fischer instrument for 
measuring indentation depth are over 90. The lining is then heated and 
sintered or fired by the first heat of molten iron or steel filled into 
the ladle. 
The burned dolomite used for the proposed materials may be obtained from 
any natural dolomite source, submitted to conventional firing followed by 
crushing and/or grinding and possibly screening for the removal and 
recombination of specified grain size fractions or the removal of 
specified grain size fractions. The term dolomite is understood to include 
not only substances having the chemical formula CaCO.sub.3. MgCO.sub.3, 
but also materials in which the proportions of CaCO.sub.3 and MgCO.sub.3 
are subject to major fluctuations, as well as materials in which some of 
the magnesium in the dolomite is replaced by iron or manganese. For 
instance, dolomites containing 54.5% CaCO.sub.3 and 42.8% MgCO.sub.3 as 
well as dolomites containing 3.9% CaCO.sub.3 and 89.22% MgCO.sub.3 are 
known naturally occuring minerals. 
The grain size analysis of the burned dolomite which is used for the 
preparation of the proposed materials preferably comprises at least 35% 
under 0.09 mm, i.e. having the consistency of flour, whereas the remaining 
65% should have a grain size distribution ranging from 0.09 mm to 4 mm or 
6 mm. The upper limit of the grain size distribution may, if desired, be 2 
or 3 mm. Preferably the proportion having a grain size under 0.09 mm may 
be as high as 50%. 
The binders used for the proposed materials may be dry ground sodium or 
potassium silicate, a sodium or potassium metaphosphate or a mixture 
thereof. Preferably a quantity of binder between 2 and 6% by weight may be 
added. Primarily the binder should be an inorganic water-soluble 
substance. The proposed material may be prepared by any method 
conventionally used for mixing dry components. For instance, the burned 
dolomite and the dry ground binder may be mixed first and the appropriate 
quantity of natural triglyceride oil introduced afterwards. On the other 
hand, it would also be possible first to mix the burned dolomite with the 
triglyceride oil and then to mix this mixture with the dry ground binder 
to ensure that the triglyceride oil will preferentially coat the particles 
of burned dolomite and thus reduce the tendency of the burned dolomite to 
hydrate. 
However, according to the invention it is preferred to introduce the 
triglyceride oil and to mix it before any possible addition of paper flour 
is made, to prevent the triglyceride oil from being preferentially 
absorbed by the highly porous paper flour. 
The triglyceride oil is conveniently introduced by first heating the 
triglyceride oil, e.g. to a temperature of 60.degree. C., to reduce its 
viscosity and by then spraying it through a nozzle on the solids particles 
whilst these are being agitated in a mixer, thereby ensuring as uniform a 
distribution as possible without excessively long mixing times. 
The paper flour or finely shredded paper which may be added to the proposed 
composition is a disintegrated paper reduced to a maximum fibre length of 
1 to 3 mm and dried. 
It transpires that the addition of paper flour to the proposed materials 
reduces the time needed for heating after application of the mass to the 
walls of the vessel for instance by a slinger machine. 
The addition of carbon black, graphite or ground coke imparts improved 
properties to the mass in resisting chemical attack by the melt. 
The proposed materials are of crumbly consistency for use and suitable for 
application by a slinger machine. 
The natural triglyceride oils used for the preparation of the proposed 
materials are so-called "fatty oils", i.e. liquid fats which consist 
principally of mixed glycerol esters of higher fatty acids having an even 
number of carbon atoms, and so-called "drying oils", i.e. liquid "fats" 
which contain a relatively high proportion of fatty acids having several 
unsaturated bonds. 
Examples of such natural triglyceride oils are the following vegetable 
oils:- Soybean oil, blown soybean oil, steam treated soybean oil, linseed 
oil, corn germ oil, poppy seed oil, rapeseed oil, safflower oil, olive 
oil, cotton seed oil, peanut oil, and wood oil. Examples of animal 
triglyceride oils are the different fish oils, such as herring oil, (cod) 
liver oil, sardine oil, whale oil and sperm oil. These natural 
triglyceride oils may possibly be subjected to a preliminary treatment, 
such as "blowing with steam" as practised in the case of "blown soybean 
oil". The triglyceride oil may also undergo a conventional treatment, such 
as a treatment with fuller's earth or a deodorising treatment. 
In the above examples linseed oil, soybean oil and safflower oil are 
counted among the "drying oils". 
Soybean oil and particularly deacidified and bleached soybean oil has 
proved to be particularly useful for incorporation in materials according 
to the invention. It also creates no environmental nuisance, such as 
evolution of odours and fumes. The soybean oil has a flow point of minus 
10-16.degree. C. (method Ubbelohde) and a flash point of 282.degree. C. 
(Din 7732, page 1). 
Naturally, instead of only one triglyceride oil, a mixture of triglyceride 
oils may be added. The triglyceride oils should be liquid at a temperature 
of 10.degree. C. 
The invention will now be illustrated by the following examples: 
EXAMPLE 1 
1000 kg of a mixture of burned dolomite having a grain size analysis of 35% 
by weight under 0.09 mm and 65% by weight of 0.09 to 3 mm was filled into 
a heated mixer at 180.degree. C. 4% by weight, related to the finished 
mass, of a commercial soybean oil was sprayed on the moving mixture with a 
nozzle. The mixing was continued until a crumbly mass was obtained. 2.0% 
by weight of a finely ground sodium phosphate together with 0.5% by weight 
of a finely ground sodium silicate (grain size under 0.09 mm) were then 
added as inorganic binding agents, mixing being continued for another 4 
minutes. The overall mixing time amounted to 12 minutes. This mass was 
applied by a slinger to the inside wall of a raw steel ladle to provide it 
with a wear resistant lining. Mixing could also have been accomplished in 
a cold mixer at room temperature. 
A second batch of the proposed ready mixed mass was stored under seal for 
three months. At the end of this period of storage the mass proved to be 
just as satisfactory in use as a freshly prepared mass. 
EXAMPLE 2 
The method of preparation described in Example 1 was repeated excepting 
that the normal soybean oil was replaced by a bleached deacidified oil.