DE2624299C3 - Use of a hydraulically setting, high-alumina, refractory refractory concrete for wear parts of sliding locks - Google Patents

Description

The invention relates to the use of a hydraulically setting refractory refractories with high alumina content for with metallic melt in Wearing parts that come into contact, such as sleeves and, in particular, locking plates for sliding locks on containers containing molten metal.

Wear parts are generally parts that are renewed or replaced after a wear limit has been reached must be in order not / u to endanger the safety of the units operated with them. they are mostly exposed to high thermal, chemical and possibly erosive attacks and must be in in some cases can also withstand considerable strength loads. This is the case, for example, with locking plates for sliding locks on containers containing molten metal, it is necessary that the sliding panels, in spite of deficiencies in the to which the refractory sheet material is exposed due to unavoidable temperature differences, with reliable sealing remains perfectly movable and the pair of plates with regard to the thermal, chemical and erosive attacks on the flowing melt with a controllable pouring stream cross-section withstands at least one emptying of the container

For such and similar loads

ίο previously wearing parts made from high-quality dry, semi-dry and plastic refractory material compositions in relatively complex ramming, shaking and pressing processes with more or less expensive post-treatment produced wear parts with

i => require right training after expiry of regarding Temperature and duration of the heat treatment process to be adhered to precisely, in addition to a careful one machining deformation. For example, on panels of sliding locks, the areas marked with other surfaces should work together to form a seal with ease of adjustment, to grind evenly. but also holes, grooves or the like. Are often provided by machining deformation, so that primarily Correctly fitting, mechanical processing requiring wear parts, considerable production costs cause.

From Neue Hütte 1965. Issue 5, pages 275 to 279, the use of hydraulically setting refractory refractory concretes with fillers such as corundum up to temperatures of 1700 ¹⁵ C in industrial furnace construction and in spouts for pig iron pans is known to be relatively less corrosive and erosive. After Spree hsaal. 107. | g "pp. 904 to 913 the use of chemically setting refractories

J5 refractory concrete for pouring stones for ladle slide closures proposed, but it is precisely the low wear resistance of the refractory concrete that is used for this purpose is to subject the flow opening of the Auägussstein to a gradual widening during casting.

■ to throw so that the casting speed remains largely constant despite the decreasing ferrostatic pressure. Made of cement-lime-plaster. No. 10. 1973. pp. 457 to 463 the use of hydraulically setting refractory refractory concretes in the cement industry, that is to say also for low loads in a cement kiln, is known. From Lehmann. H., Series of stones and earths. Vol. 3. Refractory concrete made of alumina fused cement. 1959. Hermann Hübner Verlag Goslar, pp 52-53, it is known per se, such that little wear-resistant concrete can aben a volume stability of about 0.2% at a temperature not mentioned ^L and the cold compression strength of cement amount Zuschlagsa ··· and grain structure. In the Koppers leaflets. Issued April 1971. is »one of hydraulic

«Setting, refractory refractory concrete existing tamped mass is known per se, which at an AhOj content of 95% has a firing shrinkage of -0.95 at 1800" C., a thermal expansion of 1.60 at 1800 ° C and a cold compressive strength on the unfired product of 400kp / cm ^J and after fire at 1800 "C of 720 kp / cm> DE-OS 20 48 488 proposes refractory mixtures with hydraulic setting for the production of refractory concretes which, at a content of 92% _{Al 2} Oj, have a cold compressive strength of 400 bar on the dried Röherzeügms and after a fire at 1600 ° C of 1200 baf, the change in dimension after a fire at 1600 ° C is -0.52. From The Refractory journal, SeptyOkt, 1975, S-10 to 19 it is known per se that

Ceramic refractory material for wear parts of snap closures can have a cold compressive strength between 175 and 245 kg / cm ² and a dimensional stability after fire at 1650 ⁰ C of ± 0.2%. The ceramic refractory materials known from Transactions and Journal of the British Ceramic Society, Vol. 74, 1975, pp. 41 to 47 have, for example, a cold compressive strength at an unspecified temperature between 56.80 and 118.88 MN / m ² and a dimensional stability Fire at 1650 ⁰ C from -1.259 to + 0.453.

The object of the present invention is to simplify the manufacture of refractory wear parts.

This object is achieved according to the invention by the use of a hydraulically setting, high-alumina refractory concrete with a cold compressive strength of the dried raw product of at least about 4 10 ⁷ Pa, with a cold compressive strength after a fire at about 1673 ° K of at least about 7 χ 10 ⁷ Pa and with a dimensional stability after a fire at around 1673 ° K of at least ± 0.2% for wear parts on slide closures that come into contact with molten metal. By using refractory concrete according to the invention that fulfills certain requirements, not only is the aforementioned object achieved in a surprisingly simple manner, but at the same time? Refractory concretes also made accessible to new areas of application avoided by experts because of incalculable risks. UsguB of a container used for pouring steel, especially with regard to the extraordinary stresses caused by the outflowing melt, consisting of sudden temperature shocks and strong erosive washing-off effects of the pouring jet up to 120 mm thick, until now hopeless.

The use according to the invention allows the production of pairs of plates in particular for Sliding locks simplify significantly, since concrete poured into a mold exactly matches the mold surfaces adapts and smooth, clean surfaces of the mold also provide smooth, clean counter surfaces on the molded body. As a result, it is possible to measure the sliding surfaces of slide plates with great accuracy during the To achieve shaping of the plates, so that tedious mechanical reworking is unnecessary. Likewise can the flow openings or special parts molded directly and so the plates in the finished state Form can be taken.

The high-alumina concretes with the physical properties prescribed according to the invention guarantee the operational safety of the wear bodies made from them, even with respect to high ones Stresses due to thermal stress as well as chemical and erosive attacks.

It is of great advantage if the refractory made of corundum and active alumina as aggregates. Less than 22% calcium aluminate cement containing lime, preferably less than 15%, and optionally refractory concrete consisting of a liquefying agent, an analysis of at least 96% Al ₂ O ₃ , less than 3% CaO and less than 0.5% SiO ₂ . The high proportion of Al ₂ O ₃ has an advantageous effect on the thermal shock resistance of the concrete molding. There is also one for them

10

15th

20th

25th

30th

35

40 Resistance to temperature changes, favorable total porosity between 23 and 27% by volume of open pores that are ideally suited, for example, for tar soaking. In the case of the additives corundum and active alumina, the proportion of alumina is expediently between 5 and 15%.

According to a further feature of the invention, it can be particularly expedient for certain application purposes to replace up to 5%, preferably 1 to 5%, of the aggregates with a spinel-forming compound, preferably a compound that provides MgO or MgO. The magnesia contained in the concrete reacts at around 1273 ° K with the decomposition products formed after the dehydration of the binding agent to form spinel, MgO · Al ₂ O ₃ . The structure of the concrete becomes stronger: and denser and consequently also more resistant to infiltration by molten steel and to attack by slag, the occurrence of which in the steel bath has already resulted in spinel formation. Instead of MgO, NiO, CoO and ZnO as well as compounds that form these oxides can also be used.

If a further increase in the slag resistance of the i-shaped body is desired, this can be useful by adding up to 5% carbon black, pitch or graphite.

In some cases it is recommended to replace up to 7% of the aggregates with chromium oxide in order to reduce the Counteract wetting of the shaped body by liquid melt and slag.

In addition, the aggregates below 03 mm are expediently in the form of round grains, which for the The strength of the molded body also has a positive effect.

The wearing parts produced using the refractory refractory concrete according to the invention are suitable Particularly suitable for sliding closures on containers containing molten steel.

The resistance of the wearing parts can be significantly improved by following them the molds are soaked in tar.

The manufacture of a refractory wear part is below on the basis of a mixture, grain size and property values of five within the scope of the invention table containing refractory concrete.

Concrete according to items 1 to 5 was poured into a mold corresponding to the shape of a slide plate and vibrated. The subsequent setting and hardening took 12 hours. After molding, the plate remained at room temperature for 41 hours in order to then be subjected to drying at about 383 ° K, which concludes the manufacturing process.

To test the strength values at higher temperatures, the plate was first ^{heat-treated at about 873 r} K and, after cooling, the cold compressive strength was measured. The process was repeated at about 1673 'K.

The burn rate given in the table after the fire at around 1673 ° K in% is identical to the dimensional stability of the refractory concrete required according to the invention.

Notes on the usability of refractory concrete for wear parts, in particular for the pair of panels from The peeling test also gives slide closures. This is executed under the following conditions:

A plate piece 100 χ 100 mm with a smooth (ground) surface is on a zone of approx. 30 mm

Diameter heated by means of an autogenous welding torch suitable for burning through 20 to 30 mm thick sheet metal. The oxygen pressure is about 3.5 IQ ⁵ Pa, the pressure of the acetylene gas is about 0.5 10 ⁵ Pa. The distance between the nozzle of the burner held by a stand and the plate is 50 mm and the test time is 15 s

If it splinters, the material is very suitable for making pairs of plates for shoe soles. The material can be used if, however, particles become detached when the test specimen is subsequently scratched unusable as soon as chips occur during the test.

example 1

Sintered corundum with 99% Al ₂ O ₃

3.15-6 mm

1-3.15 ram

0.5-1 mm

0.09-0.5 mm
<0.09 mm

Chromium oxide, <0.09 mm
Active clay, <0.09 mm
Alumina cement with 80% Al ₂ O ₃ and 19% CaO

Liquefier for calcium aluminate cement
(Polyelectrolyte)

MgO, <0.09 mm
Graphite powder, <0.09 mm

17.50 22.50 7.50 12.50 21.00

Water addition (1/100 kg dry matter)

Cold pressure resistance (~ x 10 ⁵ Pa)
after drying at about 383 ° K
after heat treatment at about 873 ° K
after burning at around 1673 ^° K

Total porosity after heat treatment

about 873 ⁰ K, (vol .-%)

Firing shrinkage after the fire

about 1673 ⁰ K, (%)

% 100.00 5.5

logo
1000
1100
24

+ 0.1

17.50 17.50 17.50 17.50 22.50 22.50 22.50 22.50 7.50 7.50 7.50 7.50 12.50 12.50 12.50 12.50 16.00 21.00 15.00 16.00 5.00 - - - 9.00 5.00 11.0 9.00 9.95 9.95 13.95 9.95 0.05 0.05 0.05 0.05

4.00

-0.1

+ 0.1

5.00

100.00 100.00 100.00 100.00 6.0 6.0 5.0 6.0 720 550 1200 630 720 550 1200 560 *) 810 1200 1300 1060 *) 22nd 23 23 27 *)

*) Reduced fire.

Claims (8)

Patent claims: 1. Use of a hydraulically setting, high-alumina refractory concrete with a cold compressive strength of the dried raw product of at least about 4 10 'Pa, with a cold compressive strength after a fire at about 1673 ° K of at least about 7 χ 10 ⁷ Pa and with a dimensional stability after a fire at around 1673 ° K of at least + 0.2% for wear parts of slide closures that come into contact with molten metal. 2. Use of a refractory refractory concrete according to claim 1, characterized in that the refractory concrete consisting of corundum and active alumina as aggregates, less than 22% calcium aluminate cement and optionally a liquefying agent, an analysis of at least 96% Al ₂ O ₃ , less than 3 % CaO and less than 0.5% SiO ₂ . 3. Use of a refractory refractory concrete according to claim 2, characterized in that in the refractory concrete up to 5% of the aggregates by a spinel-forming substance, preferably MgO or MgO-supplying compounds are replaced. 4. Use of a refractory refractory concrete according to claim 2, characterized in that in Up to 5% of the aggregates in the refractory concrete have been replaced by soot, pitch or graphite. s use of a refractory refractory concrete according to claim 2, characterized in that in In refractory concrete, up to 7% of the aggregates have been replaced by chromium oxide. 6. Use of a refractory refractory concrete according to any one of claims 1 to 5 thereby characterized in that the aggregates in the refractory concrete are below 0.5 mm in the form of round grains are present. 7. Use of a refractory refractory concrete according to one of claims 1 to 6 for wear parts of slide closures on containers containing molten steel. 8. Use of a refractory refractory concrete according to one of claims 1 to 7, characterized characterized in that the molded wear parts are impregnated with tar.