DE1271425B - Method and device for determining the compressive stress and expansion of molding sands and other refractory building materials at high temperatures - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

GOIn

German class: 42 k -49/02

Number:
File number:
Registration date:
Display day:

P 12 71 425.9-52
October 2, 1961
June 27, 1968

The invention relates to a method and a device for determining the compressive stress and expansion of molding sands and other refractory building materials at high temperatures which the expansion of a compressed and heated test specimen is measured.

It is already known to use a cylindrical test specimen made of sand to determine the tensile strength to be heated on one side. The one-sided heating of the sample has the purpose that a moist, hot condensation layer is formed in it, in which then the material tears.

It has also already been proposed to use a cylindrical one again to determine the extent Test specimens at test temperatures of approx. 1000 ° C for a duration of approx. 3 minutes on all sides and to be heated evenly within the specimen. A used compact or hollow one cylindrical test specimen was always dried before exposure to the aforementioned test temperature. The different test methods provided different statements, so that generally valid Correlations between the properties found and the tendency to error are not given could.

The invention is based on the object of a method and a device for measuring the Compressive stress and at the same time expansion of molding sands and other refractory building materials at high levels Create temperatures. It is used to determine the properties that influence the behavior of the molding sand or a refractory lining when heated in practical use. The heating and evaluation of moist samples should also be carried out within a few seconds be.

According to the invention, this object is achieved by the fact that a disc with a concave surface compacted test specimen fully or partially clamped or held at its outer edge is then heated the disc on its concave side and the resulting additional The curvature of the test specimen is measured.

The disk can have different base areas, including being rectangular.

In addition to the usual water content, the test specimen can also contain customary or intended additives exhibit. The thickness of the disk is as small as possible, preferably 2 to 5 mm, in order to be as short as possible Time to complete heating and thus to obtain a constant measured value.

Since thin slices of molding sand are difficult to determine the method and device
the compressive stress and expansion
of molding sands and other refractory materials

Building materials at high temperatures
5

Applicant:

Dr.-Ing. Wilhelm Patterson,
ίο 5100 Aachen, Intzestr. 5;

Dr.-Ing. Dietmar Boenisch, 5100 Aachen

Named as inventor:
Dr.-Ing. Wilhelm Patterson,

Dr.-Ing. Dietmar Boenisch, 5100 Aachen

are to be compacted evenly and in many cases also a mechanical one that is insufficient for testing Have strength, the test specimen is preferably made of two layers, with that of the heating source trimmed layer of about 2 mm from the test sand and the turned-away surface a substance with little or no thermal expansion, in particular zircon sand. These substances are preferably compacted into a disk at the same time as the test sand. For the fabrics low thermal expansion, binders that have a low wet strength should also preferably be selected result so that the expansion of the test sand layers is hindered as little as possible. There Measurable compressive stresses of interest arise only in the test sand layer and this test sand layer only needs to be about 2 mm thick, the desired measured value can be achieved in a very short time, for example 20 seconds can be achieved.

The method according to the invention and the design of the test specimen as a thin disk are excellently suited to the effects of sizing, blackening and similar coatings to measure the compressive stress and expansion of molding sands. These coatings are used to do this applied to the surface of the test specimen to be heated. Similar to finishing in connection with the molding sand can also be constructed from different layers of sand, with the Compressive stress and expansion of the multi-layer test specimen Statements about the expansion restriction or expansion promotion of the individual molding sand

809 567/251

3 4

layers among each other. The pressure direction can also be arranged in such a way that the concave side tension and expansion other than with cloning of the test body is heated. After another bonded sands, such as carbonic acid feature according to the invention, the retaining ring rests on Solidification sand, cement sand, synthetic resin-bonded vertically aligned quartz tubes, and that as quartz sands and cores are measured, as well as furnace tube-shaped transmission elements for measuring device chucks and wall linings made of rammed earth and processing and possibly for the application of an additional refractory bricks, the durability of which is largely centered by loading in the bottom of the flask, the compressive stress and the hot deformation de- The unilateral heating of the disc with concave

like this substance is determined. Furthermore the surface can be done in different ways. she However, the method according to the invention by means of a suitable design should, if possible, cover the entire test body surface The heating chamber is suitable for heating the pressure evenly. The heating is possible through stresses and thermal expansions of the test substances, an electrical radiation source, for example in especially those with the combustible or gasifiable form of arc electrodes in the vicinity Have additives, surfaces to be heated in different atmospheres. The heating can also Sphere, in particular oxidizing or reducing- 15 made by electrical resistance wires. May to investigate. borrowed is the additional use of radiation

In that one is used to measure the pressure span in order to make the surface to be heated evenly expansion and expansion of a thin slice and heat up quickly. Particularly useful and goes out and heats it on one side in a very short time, it is easy to use a gas burner with it is achieved that in the test specimen from green 20 an oxygen-luminous gas flame, the ZuSand volatile, flammable or composition contained in it, read on dial gauges and with gas-liquid ends Molding sand additives can be calibrated and regulated with their influence on taps, The compressive stress and expansion are also measured. The measurement of compressive stress and strain

must be taken into account. Furthermore, through a thin, can also be done in various ways. So Sample heated very quickly and on one side a very 25 can be the amount of curvature of the bowl feeder Temperature gradient reached, for example, the moderate disc when heated and thawed out Agreement with the conditions in the tending reduction in the radius of curvature op-form, be measured especially in the presence of the strong table. The expansive becomes very simple Quartz sand, a strong expansion of the test specimen over a quartz glass tube gradient results, whereby between the one 30 transferred up to a tactile clock, individual sand grain layers considerable tension The measuring device is advantageous from the heating

occur and the compressive stress and expansion source through a protective wall or a can be influenced very considerably overall. Shielded for protective housing made of asbestos, the testing of molding sands with normal water. An increasing load on the sample takes place over

content is still as a result of the changing 35 the resting on the convex side of the sample Temperature gradients create a condensation zone flasks by placing weights or continuously, being due to the overtaking of the nuierlich by a z. B. from cylinder and piston Sand in the condensation zone the bond strength existing additional equipment, which with increasing and with it the later hot deformability hydraulic or pneumatic pressure one more Sand is affected. Furthermore, the increasing load on the piston causes the wet strength of the invention a specific MASS device transfers the condensation zone. Elongation hindrance from dry to damp By testing several different

Surface layers on top of sand zones. performance or through continuous load application.

The test specimens can be used in the usual compression of the test, that load can be produced experimentally and found in the following 45 or graphically extrapolated, which prevents a heating and testing device for determining the expansion of the test specimen. Be inserted from compressive stress and expansion. Because of this load, the diameter and the curvature, the compressive stress can be quantified in order to obtain precise measurement results of the compressive stress in kg / cm ² , and to obtain expansion and expansion, because this very small manufacturing tolerance radius of the sample Compressive stress can, however, also be taken from a nomogram after a determination that the parts surrounding the test specimen single measurement in the case of incomplete expansion in the subsequent determination of the compressive stress impediment, expansion and expansion can be used. As a result, if the values of the expansion of the relevant, it is possible to make the disc relatively thin, test load and the diameter of the test surface on the piston of the device according to the invention because it rests on parts of the compression device and 55 and, according to the later test device, is continuously pressing on this test surface in this is surrounded and held in this. can be used.

A device for carrying out the described- In addition to expansion measurements of the unloaded

benen process with a heating device and or evenly loaded or differently strong an organ resting on the test body for the over-stressed sample and the quantitative determination carry its expansion to a measuring device is he the compressive stress can with the invention according to the invention characterized by a piston MAESSEN device still other sizes such. B. with a concave head surface and a piston with the hot deformation, measured and using a concave The stress-deformation surface surrounding the head surface protrudes beyond the head-suitable writing device and can be recorded as a guide for the piston 65 diagrams. For this, the Serving retaining ring, which can be entden with an all-round test according to the respective requirements Abutment is provided with inclined contact surfaces for the speaking incomplete to complete test body, and that the heating expansion is loaded until it breaks and from the grain

pressibility determines the hot deformability.

The value of the compressive stress in kg / cm ² obtained with the method according to the invention, taking into account the wet strength, is a clear measure of the stability of the mold cavity walls in the casting heat. With increasing compressive stress, the tendency to form expansion defects such as scabs, grooves, rat tails, fillets, veins, veins and the like increases with the same wet strength.

The strength of the fault tendency of a molding sand can be according to the rule of thumb

_ ... Compressive stress

Tendency to error =

Wet strength

to be determined.

The invention is explained in more detail in the drawings using an exemplary embodiment. It shows

F i g. 1 parts of the pile-driving device for manufacturing the test specimen,

F i g. 2 parts used in the pile-driving device when testing the high-temperature properties of the Test body,

F i g. 3 the unloaded sample,

4 shows the load on the sample, which causes the expansion partially prevented

F i g. 5 a sample loaded to such an extent that it is completely prevented from expanding,

F i g. 6 a test specimen made of two layers,

F i g. 7 shows an exemplary representation of an entire test device for measuring the compressive stress and expansion.

According to FIG. 1 is in a compression device with the ram 10 and the punch of the Piling device 11, the guide ring 12, the retaining ring 13, the piston of the test head 14 and the Ramming base 15 compacts the test sand 16 into a thin disc. According to the concave design of the head surface of the piston of the test body 14 and the convex design of the Ram 11 has the shape of a spherical shell, the edge of the spherical shell running all around on the inclined surface 17 of the retaining ring of the test head 13 is supported. The test body has a diameter of 50 mm and a thickness of 3 mm.

The retaining ring 13 and the piston 14 of the ramming device are embedded together with the Test body 16 is also used to test the compressive stress, as shown in Figure 2. Fig.2 shows Furthermore, the storage of the retaining ring 13 on quartz glass tubes 18 and the transfer of the to the sample 16 exerted load via a quartz glass tube 19 and the transfer of the expansion of the test specimen 16 to a measuring device to be described later in detail through the same quartz glass tube 19, which is guided centrally within the piston 14 and is therefore centered in the bottom of the piston. At 20 in FIG. 2 schematically shows the heating device for one-sided heating of the test body 16 shown in the form of a gas burner. The heating time is about 30 to 40 seconds.

F i g. 3 shows an unloaded test specimen that can expand freely. The point of contact between the test body and the piston is punctiform. The free expansion h does not occur during the measurement, since the test piston itself already represents a load.

According to Figure 4, the test body is loaded with a load P which partially prevents the expansion h. The point of contact between the test piston and the test body is a circular area with the diameter d.

In the illustration according to FIG. 5, the load exerted on the test body is so great that this is completely prevented from expanding. The compressive stresses are quantitative through rearrangement of the individual quartz bodies degraded. The entire surface of the sample lies against the test piston at.

F i g. 6 shows a test sand consisting of two layers, the surface of the test body facing the heating source 20 consisting of the test sand 16 and the surface facing away from zircon sand 21. 14 with the piston of the test head is in turn designated it and 13 with the retaining ring. The dotted line shows the condensation zone with 22, with S the thickness of the dried-out sand layers, with F _n the area of action of the wet strength and with jF the area of action of the compressive stress. The mold surface is heated in the direction of the arrows 23.

F i g. 7 shows the overall structure of an apparatus for measuring compressive stress. About the representation in Fig. 2 in addition, the dial gauge is shown at 24 and a plate with the weight 26 at 25. 27 designated Gas taps to regulate the combustion gas and the oxygen for the gas burner. With 20 and 28 measuring devices are designated to read the composition of the combustion gas and to be able to adjust.

Claims (12)

Patent claims: 1. Procedure for determining the compressive stress and expansion of molding sands and of other refractory materials at high temperatures, at which the expansion of a compacted and heated test body is measured, characterized in that the compacted to a disc with a concave surface Test specimen fully or partially clamped or held at its outer edge is then heated the disc on its concave side and the resulting additional The curvature of the test specimen is measured. 2. The method according to claim 1, characterized in that when heating one green molding sand is assumed. 3. The method according to claims 1 and 2, characterized in that the test body on the surface to be heated is provided with a molding coating. 4. The method according to claims 1 to 3, characterized in that the test body in a oxidizing or reducing atmosphere is heated. 5. The method according to one or more of claims 1 to 4, characterized in that the test body is designed in the shape of a spherical shell. 6. The method according to claims 1 to 5, characterized in that the test body from _ two layers is produced, the layer facing the heating source of about 2 mm from the test sand and the area facing away from a substance with little or no material Thermal expansion, in particular zircon sand, is produced. 7. The method according to claims 1 to 6, characterized in that the test body surrounding parts (13, 14) of the compression device in the subsequent determination of the Compressive stress and expansion are used. 8. Apparatus for performing the method according to claim 1 with a heating device and an organ resting on the test body for transmitting its expansion to a measuring device, characterized by a piston (14) with a concave head surface and one surrounding the piston (14) in the area of the head surface retaining ring (13) protruding beyond the top surface and serving as a guide for the piston, the one with a circumferential abutment (17) with inclined contact surfaces for the test body (16) is provided, and that the heating device is arranged such that the concave side of the test body is heated. 9. Apparatus according to claim 8, characterized in that the retaining ring (13) on vertical directed quartz tubes (18) rests and the transmission element designed as a quartz tube (19) to the measuring device and possibly to apply an additional load in the bottom of the Piston (14) is centered. 10. Device according to claims 8 to 9, characterized in that the heating device consists of a gas burner (20). 11. Device according to claims 8 to 10, characterized in that as a measuring device for ίο expansion of the specimen a dial gauge (24) serves. 12. Device according to claims 8 to 11, characterized in that the measuring device shielded from the heat source by a protective wall or protective housing made of asbestos is. Considered publications:
German Patent No. 557 757;
French Patent No. 1,236,250;
U.S. Patent No. 2,448,964;
Chemisches Zentralblatt, 1951, p. 2518 (WH Moore). 1 sheet of drawings 809 567/251 6.68 © Bundesdruckerei Berlin