DE3631645A1 - Process for measuring temperatures - Google Patents

Abstract

A test crucible (3) has a light guide (2) sealed into the crucible wall, which runs from the interior or the inner surface of the crucible wall to beyond the outer surface of the crucible wall for conducting the thermal radiation of the melt (4) to a pyrometer (5) that can be attached to it in a simple fashion. Such a test crucible (3) is particularly suitable for performing a procedure for measuring the temperature of metallurgical melts, in which the temperature in the interior of the melt (4) in the test crucible (3) is measured with an NiCrNi thermocouple (1), for example, and at the same time, the temperature at a surface area (4a) is measured. This makes it possible to draw conclusions as to the form of solidification of the melt, the occurrence of flaws, and other properties, such as thermal conductivity etc. <IMAGE>

Description

The invention relates to a test crucible for receiving and Temperature measurement of a metallurgical melt and Ver drive to its manufacture.

One uses for the assessment of metallurgical melts in addition to chemical analysis, above all temperature measurement against the solidifying one in a test crucible Melt. Is the temperature measurement in the thermal Center of a test crucible with a built-in thermo element, so you can use the cooling cure obtained with it ven, e.g. B. on the phase parts formed per unit of time and the rate of heat dissipation from the melt ze or the cast from it are closed. To make further statements about the solidification behavior and other essential properties of the melt, the resultant to hit the solidified workpiece and the molding material one during the solidification of the melt sample in the test crucible the temperature inside the melt and the temperature on a surface area of the melt.

The ratio of the inside of the melt and that at de The surface temperature measured gives an image of the Solidification form of the melt: With a shell-like Er the heat source moves away from the surface the melt (solidification from the outside in), the outside temperature drops more than inside measured temperature. With a slurry-like solidification sets the solidification in many places, including inside, a. The temperature measured on the surface remains almost the same as the temperature measured inside. Of course, mixed types also come from mushy and scha len-like solidification. They even occur in practice most often and are the normal course in the sphere molding.  

Porridge-like solidification occurs especially when the Melt is heavily inoculated. Error symptoms are common Open gaps and sucked-in areas. Schalenar solidification occurs when the magnesium content increases in the absence of vaccination, and by adding tellurium and Sulfur on. Gray cast iron also solidifies like a shell Lamellar graphite (GGL).

By such a measuring method in which the temperature measured inside and at the edge of the melt in the test crucible sen, the influence of the added vaccine quantity and type, as well as other substances such as magnesium etc., determine the melt quality. About him averaged form of solidification are statements about typical expected casting errors possible. It can also heat conductivity of the melt and the molding material on simp be determined way.

There is already a test pan for carrying out the be Written measurement method known in which a thermo ment arranged essentially in the middle of the melt and another thermocouple in the container wall is ordered. A disadvantage of the known test crucible is that the Ther used in the container wall the fast cooling process is not suitable ge on the enamel surface, so always the actual current surface temperature of the melt specify. The container wall temperature corresponds to the rapid cooling processes in a test pan not the actual temperature of the melt at the edge.

The object of the invention is an inexpensive pro betiegel, especially for performing the described Measuring method in which the temperature of the melt in the Pro besides the center of the melt, also seal on one measured surface area facing the crucible wall will create with which the current temperature of the Melt in the surface area even with rapid cooling  operations can be recorded easily and precisely.

This is achieved in that in that Crucible wall at least one of which absorbs the melt interior to over the outer surface of the crucible wall light guide for guiding the from the Melt outgoing temperature radiation used tightly is.

On a test crucible designed in this way, simple and quick a common optical pyrome Connect ter, for example plug it in. Optical pyro meters measure from the surface area concerned outgoing temperature radiation and react immediately a change in temperature of the test object by the temperature radiation associated with the change in temperature Change quickly grasp what is particularly on the surface the melt is important. Warming up or cooling down times of the Temperature measuring element, such as a thermocouple, or the whole container wall, fall away. The z. B. as glass rod-shaped light guide goes during the measurement lost, but the trial pan is still inexpensive manufacture and offers the possibility of an exact and rapid temperature measurement on the surface or inside a melt when the light guide goes into the melt is introduced. The advantage over measuring the Thermal radiation on the free surface of the melt is that there is slag and oxides on the surface and lateral interference does not affect the measurement result can flow and still a quick and inexpensive Temperature measurement is possible. The pyrometer is located heat protected outside of the crucible wall and is after the measurement is of course reusable. Are two accordingly arranged light guide provided or for example a thermocouple in the middle and a light conductor for surface temperature measurement, the Trial crucible in particular also an advantageous implementation  tion of the measurement method mentioned, in which the temperature the melt inside the melt and on a top area is measured. Under light guide means one is a facility for the transmission of electromagnetic radiation is suitable, in particular also for invisible radiation, such as infrared rays lungs. The wall of the crucible usually consists of Sei walls and a floor. But they are also different possible, for example hemispherical test crucibles.

For the measurement on the surface of the melt it is particularly favorable if the one facing the interior Entry surface of at least one light guide essentially lies in the inner surface of the crucible wall, in the light guide is inserted. The entrance area the light guide is above the inner surface of the The crucible wall is neither in front, nor is an indentation in the inner surface of the crucible wall. A problem loose surface temperature measurement is good Ensure contact of the entry surface with the melt.

The light guide can also be used to measure inside the Melt can be used if according to a preferred one Feature of the invention at least one light guide over the inner surface of the crucible wall extends into the interior and except for an entrance area with one Radiation-inhibiting envelope is surrounded. The there is, for example, a radiation barrier as made of insulating fibers and glued on causes sure only the temperature at the inside the entrance surface of the melt is measured.

For calibration of the connected to the light guide Pyrometers, but also for measuring the temperature of the Melt inside and outside (surface), is suitable Trial crucible with at least one through the crucible wall running light guide and at least one in Interior thermocouple is provided.  

You can use a commercially available test pan with fix Built thermocouple can be used in which the light head is used according to the invention.

Particularly simple and inexpensive light guides are refractory quartz rods that are similar because of their physical properties, such as the crucible wall, ins special with regard to thermal expansion, especially for installation in test jars made of synthetic resin-bonded quartz sand. These test pots are preferably used to in the sand to process cast melts because they come close to the sand casting conditions. For molds founders would be melting samples in test crucibles made of copper or mold material more meaningful. The delay free optical surface temperature measurement is with the high cooling speeds in metal molds from be special advantage.

In general, the exact surface temperature measurement should using light guides and pyrometers and of course also measuring the temperature inside the melt that Do not influence the setting of the sample or influence it as little as possible.

The measurement inside creates fewer problems. Around Eliminate interference caused by surface measurement, one forms the one with the surface of the melt in Contact standing light guide made of a material similar Thermal conductivity like that of the rest of the crucible wall, if possible. In addition, the Entry surface of the light guide in relation to the inside area of the wall should be as small as possible. This throws everyone However, the problem is that the measurement in a very small surface area may not decisive for the surface temperature is. The solution is there in a compromise, being preferred according to another  Feature of the invention is provided that in the interior entry surface of the crucible wall Light guides between 0.1% and 5% of the total of which Make up the melt-covered inner surface of the crucible wall.

To investigate special forms of solidification, it can nevertheless be advantageous, the solidification behavior of the To deliberately affect melt. This is given if provided that the sample pan at least one from the inner surface of the crucible wall through the crucibles wall leading to the outside component made of good thermal conductivity Material, preferably a metallic cooling nail, for Influencing the solidification form of the melt.

In the manufacture of the test crucible according to the invention there is the advantageous possibility that in the crucible wall a hardened sample crucible at least one opening is attached, in which one preferably with the light guide a hardened layer of alcohol suspended Graphite powder or a high-melting oxide glued tightly. If the aforementioned possibility, one or more cooling to use nails, should be given, are appropriate to provide further holes in the crucible wall.

Especially with the mechanical production of a large However, it can also be cheap with a larger amount of test jars if at least one light guide (possibly also cooling nails) in the formation of the crucible walls, for example se pressing or casting, molded into the crucible wall becomes.

The invention is based on execution examples through the figures of the drawings tert.  

There, Figs. 1, Fig. 2, Fig. 3 and Fig. 4 respectively crucible measurement in section an embodiment of the sample crucible according to the invention, Fig. 5 a schematically depicted example of a use of the sample according to the invention for performing a method for temperature, Fig . 6, Fig. 7 and Fig. 8 are highly diagrammatic cooling curves of temperature at the surface and in the center of the melt together with the ring zugehö schematic solidification forms schematically shown.

In Fig. 1 an existing resin-bonded quartz sand test crucible 3 is shown, in which a refractory glass rod 2 made of quartz glass by means of a layer 15 as a light conductor tightly in a side wall 3 a of the side walls 3 a and a bottom 3 b existing crucible wall tight is used. The with its entrance surface 2 a in the inner surface of the side wall 3 a lying glass rod 2 , serves for the rapid and exact surface temperature measurement of a melt, not shown, which can be filled into the crucible by guiding the thermal radiation through the crucible wall to the outside, where it then approximates can be evaluated with a two-color pyrometer, not shown. For the desired simultaneous measurement of the temperature inside the melt, for example, a NiCrNi thermocouple only needs to be hung in the test crucible 3 from above.

The sample crucible 3 shown in Fig. 1 made of synthetic resin bound quartz sand can be produced simply and inexpensively by drilling an opening in the crucible wall of an otherwise finished sample crucible and sealingly gluing a small glass rod 2 there, for example by means of size 15 . However, it is also possible to shape the light guide (glass rod) in the crucible wall when the crucible wall is formed. The test crucible 3 is advantageously suitable for the simple and quick connection of a conventional pyrometer, which is reusable after the measurement and, because of the guidance of the temperature radiation in the light guide, delivers exact measurement results.

A crucible made of quartz sand provides the best results, especially when examining melts that are to be cast using the sand casting process. It is favorable that the properties of the glass rod, in particular the coefficient of thermal expansion, are similar to those of the crucible material. In order on the one hand to be able to obtain measurement results relevant to the true surface temperature of the melt and on the other hand not to adversely affect the solidification behavior of the melt due to excessively large entry areas of the light guide, the entry area 2 a is between 0.1% and 5% inner area of the crucible wall 3 a , 3 b .

In the test crucible 3 according to FIG. 2, which is filled with melt 4 , a thermocouple 1 for temperature measurement is installed in the interior of the melt in addition to the glass rod 2 . Otherwise, the structure corresponds to the test crucible according to FIG. 1. The test crucible with an additional built-in thermocouple 1 is also inexpensive and simple to produce, it being possible to start with a test crucible with a thermocouple 1 already installed, in which the glass rod 2 is then inserted according to the invention in a sealed manner .

In a test crucible, as shown in FIG. 2, a cooling nail 16 ( FIG. 3) can be provided to examine certain forms of solidification of the melt 4 , which influences the solidification behavior of the melt 4 , the solidification on the cooling nail 16 starting from metal. It is of course also possible to attach the cooling nail 16 in the one of the tread 2 a opposite side wall 3 a or in the bottom 3 b of the sample crucible.

In addition to the measurement by thermocouples 1 inside the melt 4 , the measurement can also be carried out photoelectrically there, in particular for rapid cooling processes. For example, a test crucible 3 according to FIG. 4 is used, in which a glass rod 2 'is guided through the crucible wall into the center of the melt for measuring inside the melt 4 , the glass rod 2 ' except for the entrance surface 2 ' a with a by means of size 15 glued th, a radiation entry-inhibiting shell 17 is surrounded. If you bring a thermocouple, not shown, in the vicinity of the entry surface 2 ' a , this arrangement also permits calibration of a pyrometer connected to the glass rod 2 ' via this thermocouple.

The test crucibles shown in FIGS . 1 to 4 can advantageously be used to carry out a measuring method in which the temperature of the melt is measured in the interior of the melt in the test crucible and at the same time on a surface area.

With the measuring arrangement shown in FIG. 5, the temperature of the metallurgical melt 4 located in the sample crucible 3 according to the invention is moved according to the aforementioned Ver by the NiCrNi thermocouple 1 inside the melt 4 and at the same time on the surface area 4 a of the melt 4 facing the crucible wall measured pyrometrically. The pyrometric measurement essentially takes place by measuring the temperature radiation emanating from the surface region 4 a of the melt 4 by means of a pyro meter 5 , the glass rod 2 inserted into the crucible wall and a radiation transmission device 6 detachably attached to it, belonging to the pyrometer 5 , the radiation radiation temperature lead to pyrometer 5 .

The measurement signals supplied by the thermocouple 1 , which correspond to the internal temperature of the melt 4 , and the measurement signals emanating from the pyrometer 5 , which correspond to the surface temperature of the melt 4 , are each processed in evaluation circuits 7 and 8 , and the determined temperature values and courses via separate output units 9 and 10 (screen, printer, plotter etc.). In addition or instead of the separate output units 9 and 10 , the measuring arrangement can have a signal processing unit 11 , the output signals of the evaluation circuits 7 and 8 , which treat the internal temperature and the surface temperature of the melt 4 , and whose output unit 12 has, for example, both cooling curves (internal temperature, surface temperature), the Differential temperature curve or other determined data of the relevant melt 4 , such as solidification form, occurrence of residual melt (porosity), or its thermal conductivity.

If the temperatures inside and on at least one surface area 4 a of a solidifying melt 4 at least from the beginning of the solidification process, where the melt 4 is essentially in the liquid phase, until at least into the final phase of the solidification process, in which a large part of the melt 4 solidified, measured continuously, conclusions can be drawn about the solidification form from the plotted cooling curves. In Figs. 6 to 8, the solidification forms of GGG-iron and the influence on the temperature profile in the interior and on the surface of the melt 4 are shown highly schematically. The supercooling and the differences in the speed of the phase change are not taken into account in this scheme.

The cooling curve 13 each schematically shows the temperature curve inside the melt 4 measured by the thermocouple 1 , while the cooling curve 14 corresponds to the temperature curve on the surface of the melt 4 which is determined via the glass rod 2 and the pyrometer (not shown here ) . The shell-like congealing shape is shown schematically with zigzag lines and the mush-like congealing form with small circles.

The melt shown in Fig. 6, heavily inoculated solidifies after formation of a thin peripheral shell (range a) mushy (range b and c), wherein while the inner and outer From cooling curves 13,14 extend quite the same. In the case of such melts with little edge shell, the case occurs that at the edge a part of the pulp-like solidified structure is already solid, while there are still liquid components in the middle. Due to the increased distance between the heat source and the edge (surface), the temperature at the edge drops before it falls in the middle (area c) . Solidified melts of this type tend to appear incorrectly, such as open gate links and sucked-in points (areas b and c) .

The solidification of the melt shown in FIG. 8 by the strong addition of Mg solidifies almost like a shell after the formation of a thicker edge shell (region a) . With this solidification form of white solidifying melts, the liquid quantity in the middle decreases sharply towards the end of the solidification. This means that less heat reaches the edge (surface). The temperature drops before it drops in the middle. With such solidified melts, increased shrinkage occurs, among other things.

Curves as in Fig. 7 (mixed form) occur most frequently and are the normal course in spheroidal iron (GGG).

The evaluation of the real cooling curves determined inside and the surface of the melt allows not only the determination of the solidification form and the detection of residual melts (range c) but also other qualitative and quantitative statements about the melt, for example about its heat conductivity, and about the heat dissipation through the molding material (e.g. material of the crucible wall).

The invention is not based on the embodiment described examples limited. For example, depending on wanted melt and casting method also metallic or ceramic test crucibles can be used. Also differently built light guides than the refractory glass rods are conceivable and possible. Of course, the invention can In principle, trial crucibles also for purposes other than Implementation of the measurement method described, in which the Temperature of the melt inside and on a surface area is measured, can be used.

Claims (11)

1. test crucible for recording and measuring the temperature of a metallurgical melt, characterized in that in the crucible wall ( 3 a , 3 b) at least one of the melt receiving interior to the outer surface of the crucible wall ( 3 a , 3 b) light guide ( 2 , 2 ') for directing the temperature radiation emanating from the melt ( 4 ) is tightly inserted. 2. Sample crucible according to claim 1, characterized in that the surface facing the interior entrance face (2 a) at least one light guide (2) is (3 a, 3 b) is substantially in the inner surface of the crucible in which the light guide (2) used is. 3. Test crucible according to claim 1 or 2, characterized in that at least one light guide ( 2 ') extends over the inner surface of the crucible wall ( 3 a , 3 b) into the inner space and except for an entry surface ( 2 ' a) with a radiation-retardant envelope ( 17 ) is given. 4. Sample crucible according to one of claims 1 to 3, characterized in that at least one through the crucible wall (3 a, 3 b) extending light conductors (2, 2 ') and at least one is arranged in the interior of the thermocouple (1) is provided. 5. Test crucible according to one of claims 1 to 4, characterized in that in the inner surface of the crucible wall ( 3 a , 3 b) lying entry surfaces ( 2 a) of the light guide ( 2 ) between 0.1% and 5% of the total , from the melt ( 4 ) covered inner surface of the crucible wall ( 3 a , 3 b) . 6. Test crucible according to one of claims 1 to 5, characterized in that at least one light guide has at least one refractory glass rod ( 2 , 2 '), preferably made of quartz glass. 7. test crucible according to one of claims 1 to 6, characterized in that the test crucible ( 3 ) consists of resin-bonded quartz sand. 8. test crucible according to one of claims 1 to 7, characterized in that the test crucible ( 3 ) at least one of the inner surface of the crucible wall ( 3 a , 3 b) through the crucible wall ( 3 a , 3 b) outwardly leading component good heat-conducting material, preferably a metallic cooling nail ( 16 ), to influence the solidification form of the melt ( 4 ). 9. A method for producing a test crucible according to one of claims 1 to 8, characterized in that an opening is made in the crucible wall of a hardened test crucible ( 3 ), into which the light guide ( 2 , 2 ') is preferably provided with a hardening layer ( 15 ) from graphite powder suspended in alcohol or a high-melting oxide. 10. Method for producing a test crucible according to a of claims 1 to 8, characterized in that at least one light guide when forming the crucible walls, for example pressing or casting, into the Crucible wall is molded.   11. Use a test crucible to hold a me tallurgical melt, in which in the crucible wall at least one of the interior receiving the melt space to beyond the outer surface of the crucible wall running light guide to guide the from the Schmel outgoing temperature radiation is used tightly and is a temperature sensor in the interior has to carry out a measurement process at which the temperature inside the melt and the Temperature essentially at least one of the Surface area of the melt facing the vessel wall ze is measured, an op table pyrometer is connected.