Apparatus for testing and taking samples from liquid metal

Equipment for testing or test sampling liquid metal by introducing a protection sleeve (3; 3'; 3") together with a testing or sampling means (2; 11) provided inside the protection sleeve. The protection sleeve comprises a thermoinsulating tube (3; 3'; 3") made of synthetic amorphous mineral fibers, preferably fibres of diabase type and having a sagging point of 1,000.degree.-1,200.degree. C. according to the standards of the Swedish Institute for Materials Testing, and bound with an evenly distributed binder comprising or including among other things a binder component of organic type, for instance a thermosetting resin like phenol resin, carbamide resin or melamine resin and/or substances incorporated in the fiber material, for instance crystal water containing salts or carbonates which at the temperature of the liquid metal spontaneously and successively emit gases. The mineral fibre tube (3; 3'; 3") can be manufactured from mineral fibres having an original weight per unit of volume of 20-70 kg/m3, which have been compressed to a weight per unit of volume of 200-800 or preferably 500-700 kg/m3. Preferably the binder is added in an amount of 2-8 % by weight. The intensity of the turbulent flow in the molten metal is controlled by varying the amount of binder in the thermoinsulating mineral fibre tube and/or by varying the hardness of the mineral fibre tube.

The present invention generally relates to a method and an apparatus for 
testing and taking test samples from or making measurements in liquid 
iron, steel or any other metal or metal alloy, and the invention is more 
particularily concerned with an apparatus for protecting the testing and 
sampling equipment against the heat from the molten metal. 
For determinating certain parameters of a liquid metal, for instance the 
temperature of the molten metal, the content of oxygen, carbon or 
different alloy materials, a test is made or a test sample is taken in 
that a lancet having a testing or sampling equipment at the end thereof is 
introduced into the liquid metal. By modern methods the test can be made 
or the sample can be taken within the course of about 6-8 seconds, but the 
liquid metal generally has a substantially higher temperature than the 
lancet and some testing or sampling equipment can stand even for the said 
relatively short period of time such parts have to be protected against 
the heat of the molten metal. 
For protecting the lancet and the sampling equipment it is known to make 
use of a sleeve of compressed cardboard which is mounted round the portion 
of the lancet with the sampling equipment which is to be introduced, into 
the molten metal. 
When introducing the lancet with the cardboard sleeve in the liquid metal 
moisture is separated from the cardboard sleeve in the form of water 
steam. At the same time the cardboard sleeve is burnt and becomes charred 
whereby in addition thereto gases are developed. The said gases cause a 
heavy turbulent flow or cooking around the cardboard sleeve. Such heavy 
cooking makes the molten metal splash and sputter which creates a serious 
risk of accident for the operator of the testing or sampling equipment. 
Since cardboard is relatively heavily hydroscopic the cardboard sleeve 
normally contains some amount of water. 
In order to avoid the disadvantages involved in a protection sleeve of 
cardboard it has been suggested to form the protection sleeve of a fire 
proof material for instance a fire proof fibrous wool material. Since 
molten steel often has a temperature of 1600.degree.-1800.degree. C. the 
fire proof fibrous wool must be of a type which is able to stand such 
temperature for at least 6-8 seconds which are needed for taking the test 
or sample. The said fibrous wool material is expensive and it may often be 
difficult to design or mount the fibrous wool, so as to provide a solid 
protection sleeve which thermally protects the lancet and the testing or 
sampling equipment and at the same time allows a movement of the liquid 
metal around the testing or sampling equipment. 
A protection sleeve of refractory or fire proof material gives no or 
practically no turbulent flow or cooking around the protection sleeve and 
the disadvantage of heavy cooking and splashing as when using the 
cardboard sleeve is thereby eliminated. Also the fire proof fibrous wool 
does not add carbon or any other substances to the liquid metal which may 
adversely effect the result of the analysis of the sample which has been 
taken. 
It has, however, been shown that in some cases a large scattering of the 
test values and sometimes obvious false values are obtained. It is 
supposed that the reason therefor is that the molten metal around the 
protection sleeve moves in a laminar flow passing along the surfaces of 
the protection sleeve, the lancet and the sampling equipment, whereby the 
molten metal is cooled and possibly subjected to structural changes before 
reaching the sampling equipment. It has especially been shown that the 
scattering of the results when measuring the temperature of a liquid metal 
by means of a protection sleeve of refractory or fire proof material is 
very large. While normally an accuracy of measurement for the temperature 
of about .+-.1.degree. C. is supposed to be obtained when measuring liquid 
metal at about 1550.degree. C., it has been shown that a scattering of the 
measured temperature of about 10.degree.-20.degree. C. results when using 
a protection sleeve of refractory or fire proof material. Consequently a 
false value of the temperature is obtained which can be of great 
importance for guiding the quality of the liquid metal. 
It has consequently been shown that some turbulent movement or cooking 
around the protection sleeve during the sampling is advantageous or even 
necessary for giving a good and safe result. Such cooking, however, must 
take place under controlled conditions and no substantial amount of carbon 
or any other substances which may adversely effect the test results are 
allowed to be introduced into the liquid metal. 
According to the invention the protection sleeve is made of a material 
which does not burn in the same way as a cardboard sleeve and which is 
also not directly fire proof like a sleeve made of fire proof fibrous 
wool. The movement or cooking of the molten metal also should be 
relatively constant during the entire period of testing or sampling 
irrespective of the fact that the protection sleeve successively melts or 
is consumed in any other way. 
According to the invention it is therefore suggested that the protection 
sleeve be made of a material which does not burn but melts at reasonable 
speed in the liquid metal and which during the melting successively 
develops gases providing a predetermined bubbling or cooking and thereby a 
turbulent flow round the protection sleeve in the molten metal. A 
particularly suitable material for this purpose has proved to be a 
compressed material of synthetic amorphous mineral fibres having a sagging 
point of less than about 1200.degree. C. as measured according to the 
method stipulated by the National Swedish Institute for Materials Testing, 
and which comprises a binder which is evenly distributed in the material 
and which is decomposed at the temperature of the liquid metal while 
developing gas bubbles. The mineral fibres may be bound by different tpes 
of binders, but preferably at least some portion of the binder should be 
of the organic type, preferably a thermosetting resin such as phenol 
resin, carbamide resin or melamine resin. At the manufacture of said 
mineral fibres, they normally obtain a weight by unit of volume of about 
20-70 kg/m3, and for providing a stable protection sleeve having a 
suitable consumption in the liquid metal the mineral fibre preferably 
should be compressed to a weight by unit of volume of about 200-800 or 
preferably 500-700 kg/m3. 
Since the mineral fibres only successively melt in the liquid metal the 
fibrous material can be considered substantially inert and what provides 
the intended bubbling or cooking is a binder. By an intimate mixing of 
mineral fibres with a suitable amount of binder it is thereby possible to 
foresee a cooking which is controlled and can be predetermined and which 
is substantially constant independently of the consumption of the 
protection sleeve during the course of sampling. Consequently the gas 
developing binder determines the amount of bubbling or cooking. A suitable 
addition of the organic binder is 2-8% by weight as calculated on the 
weight of the ready protection sleeve. 
The wall thickness and the hardness of the mineral fibre sleeve is 
calculated so that the protection sleeve does not melt completely and so 
that it maintains some intended stability during the course of the testing 
or sampling. Depending on which metal is to be tested and most importantly 
the temperature of the actual metal, the amount of organic binder, the 
weight by volume of the sleeve material and the wall thickness of the 
sleeve is varied. 
According to a preferred further development of the invention the 
protection sleeve of mineral wool is formed with an inner relatively thin 
cardboard sleeve which provides an additional bar as a protection for the 
lancet for instance if the mineral fibre sleeve should be defective or has 
uneven wallthicknesses which cannot be discovered by the eye. Also the 
cardboard sleeve can be used to provide a signal that the mineral fibre 
sleeve has melted down in that a heavy cooking appears as soon as the 
molten metel penetrates into the cardboard sleeve when the testing or 
sampling period is exceeded.

The apparatus shown in FIG. 1 for taking analysis samples from a liquid 
metal bath 1 generally comprises a sampling tip 2 which by means of a 
protection sleeve 3 is mounted on a lancet 4. In the illustrated case the 
sampling tip is formed with a shot mould 5 which is moulded in a sampling 
tip body 6 of sand and into which a refractory tube extends, for instance 
a tube 7 of quartz glass. The sampling or test equipment, however, can be 
of any other type, since the type of sampling or testing equipment is out 
of the area of interest of the invention. 
The sampling tip 2 is mounted at the end of the protection sleeve 3, for 
instance by means of glue, and the protection sleeve 3 in turn is mounted 
round a lancet 4 by means of which the sampling equipment together with 
the protection sleeve can be handled during the course of the sampling or 
testing. The object of the protection sleeve 3 is both to protect the 
lancet and any other parts of the equipment against damage depending of 
the high temperature of the liquid metal, and also to provide a turbulent 
flow in the liquid metal round the protection sleeve and at or adjacent 
the sampling or testing means which can be a sampling tip as shown in FIG. 
1 or a thermo testing element as shown in FIG. 2, an oxygen probe, a 
pyrometer or similar means. 
According to the invention the thermoinsulating sleeve 3 is made of a 
material which is not fireproof and can be burnt but has a sagging point 
which is lower than the temperature of the molten metal. By sagging point 
is meant the temperature as defined by the National Swedish Institute for 
Materials Testing, at which the material gets a special sagging or 
softening structure. A material suited for most generally appearing liquid 
metals is mineral fibres having a sagging temperature of 
1000.degree.-1200.degree. C. Preferably synthetic amorphous mineral fibres 
are used, preferably mineral fibres of diabase type which have a melting 
temperature of about 1400.degree. C. and which for short periods of time 
can be subjected to the above mentioned high temperatures without any risk 
that the material melts too quickly. Mineral fibres of diabase type have a 
sagging point according to the stipulations of the National Swedish 
Institute for Materials Testing of between about 1000.degree. and 
1200.degree. C. 
A normal sampling or testing by the use of modern equipment or a manual 
sampling or testing takes a time of 6-8 seconds, and the protection sleeve 
3 therefore must be able to stand the high temperature of the molten metal 
for at least such period of time. For obtaining a protection sleeve which 
is consumed in a suitable time the thermoinsulating sleeve 3 must have a 
predetermined hardness and a predetermined thickness. When manufactured, 
mineral fibres normally have a weight per unit of volume of about 20-70 
kg/m3, but in order to obtain a suitable hardness for the practice of this 
invention, the mineral fibres are compressed to a weight per unit of 
volume of about 200.degree.-800.degree. or 500.degree.-700.degree. C. For 
keeping the mineral fibres together a binder of a type known per se is 
used. 
In order to obtain the above mentioned turbulent movement of the liquid 
metal round the protection sleeve 3, the binder, or at least some portion 
of the binder, is preferably an organic binder which at contact with the 
molten metal develops gases which give the molten metal a movement in the 
upward direction which can be controlled and predetermined, in that the 
binder at least partly is of organic nature. Alternatively, or in 
addition, the binder may comprise one or more substances incorporated in 
the fibrous material, for instance crystal water containing salts or 
carbonates, which at the temperature of the molten metal spontaneously and 
successively produce gases. As examples of suitable binders can be 
mentioned thermosetting resins like phenol resin, carbamide resin or 
melamine resin. The binder should be evenly distributed in the mineral 
fibre sleeve 3. The sleeve can be manufactured as a solid tube or in the 
form of two tube halves which are interconnected, and preferably 
manufacture is such that the mineral fibres are sprinkled with the organic 
binder during manufacture of the mineral fibre, whereupon the binder is 
brought to set at the same time as the mineral fibre tube is compressed to 
the intended weight by volume. By adding larger or smaller amounts of 
binder it is possible to determine the extent of bubbling or cooking which 
is intended to appear. A large amount of binder gives a more heavy cooking 
and a small amount of binder gives a gentle cooking. A suitable addition 
of the organic binder is 2-8% by weight as calculated on the mineral fibre 
tube. 
The same effect achieved by adding the organic binder to the mineral fibre 
can alternatively be obtained by adding salts to the mineral fibre, which 
sales, when contacted by the hot molten metal, emit H.sub.2 O or CO.sub.2. 
There are, however, certain difficulties in obtaining a controlled and 
predeterminable turbulent movement in the molten metal round the 
protection sleeve, and it is preferred that the mineral fibre material 
contains an organic binder. 
Preferably the sleeves are manufactured with a predetermined minimum amount 
of binder, and the sleeves are additionally impregnated with further 
binder or possibly solutions of salt and other substances which emit gases 
when heated so that the correct gas emittance property is obtained for 
each specific application. 
The desired bubbling or cooking in the liquid metal should be at a limit, 
where on the one hand there is no longer a laminar flow of the liquid 
metal round the protection sleeve and on the other hand where there is 
splashing. As mentioned above the extent of cooking is controlled with 
reference to the temperature and the type of molten metal by controlling 
the amount and the type of gas emitting substance in the thermoinsulating 
sleeve and by controlling the hardness and thereby the consumption 
capacity of the liquid metal on the protection sleeve. It should be 
observed that gas emission in most cases is endothermic, and this may be 
utilized for instance by providing a heavier impregnation of the inner 
layers of the sleeve than the outer layer or layers. 
When using the apparatus shown in FIG. 1, the protection sleeve with the 
sand mold sampling tip 2 is mounted on the lancet, whereupon the sampling 
equipment with the tip is introduced in the molten metal 1 through a layer 
8 of slag or other impurities. Thereby molten metal flows through the 
quartz glass tube 7 as shown by arrow 9 and the metal fills the cavity 10 
of the mold 5. The hot molten metal, which comes into contact with the 
outer surface of the protection sleeve 3 successively melts the outermost 
layers of the thermoinsulating sleeve 3, and at the same time the organic 
binder of the mineral fibre sleeve is decomposed so that gas bubbles are 
developed which provide a rising turbulent movement in the molten metal. 
By the inevitable cooling of the molten metal when the molten metal 
contacts the protection sleeve there is a tendency for a thin layer of 
molten metal to flow downwards along the protection sleeve. Depending on 
the turbulent movement provided by the action of the rising bubbles such 
movement downwards of the molten metal, however, is prevented and the 
tubulent movement thereby eliminates the action of the slight cooling of 
the metal layer just adjacent to the surface of the protection sleeve. 
Also no particles or substances are capable of flowing down towards the 
quartz glass tube 7 and the sample taken from the molten metal really 
becomes representative of the average composition of the molten metal. 
Since the organic binder is intimately and evenly distributed in the 
mineral fibres, a unitary gas formation and cooking is obtained during the 
course of the sampling or testing following the melting of the mineral 
fibre tube. 
In FIG. 2 there is shown an apparatus for measuring the temperature of the 
liquid metal. The apparatus comprises a temperature measuring probe 11 
which is mounted at the end of a protection sleeve 3' which in turn is 
mounted on a lancet 4'. At the end of the lancet 4' there are means 12 for 
connection of the temperature probe 11. From the connection means 12 
conduits 13 extend to some suitable instrument for reading the temperature 
observed by the temperature probe 11. 
For getting a correct temperature statement it is of great importance that 
the layer of molten metal which is cooled by the contact with the 
protection sleeve 3' is not allowed to flow downwards towards the 
temperature probe 11, and this is eliminated in that the protection sleeve 
according to the invention is continuously and to a controlled degree 
emitting gas bubbles providing a rising turbulent flow of the metal layer 
closest to the protection sleeve. The cooled metal layer thereby is 
prevented from flowing down towards the temperature probe. 
For certain applications it may be wanted to provide a further improved 
thermal protection for the lancet or the sampling or test means provided 
inside the protection sleeve, and for this purpose the protection sleeve 
3' as shown in FIG. 3 may be formed as a mineral fibre tube 14 which at 
the inside thereof carries a thin sleeve 15 of cardboard. Such a cardboard 
sleeve 15 provides an improved thermal insulation, and the cardboard 
sleeve further can be used as a last signal of warning that the mineral 
fibre tube 14 is consumed. Such signal of warning is obtained in that the 
cooking is accelerated when the molten metal from the outside of the 
protection sleeve reaches the cardboard sleeve 15. In order not to damage 
the test means the test equipment is quickly retracted from the molten 
metal. 
It is to be understood that the above specification and the embodiments of 
the invention shown in the drawings are only illustrating examples and 
that many different modifications may be presented within the scope of the 
appended claims.