DE2011828B2 - Aqueous, liquid, refractory coatings for block molds - Google Patents

Description

2 Oil 828

There are also various aqueous sizes known containing magnesium oxide and alkali silicite. However, these sizes also include those above and, as tests have shown, do not lead to proper protection especially the bases and bottom panels of block molds.

The object of the invention is to create an aqueous, liquid, refractory sizing that does not Has disadvantages of the known coatings and a perfect protection of floor slabs or the like. guaranteed.

The aqueous, liquid, refractory sizing for block molds according to the invention with a content particulate refractory material consisting of or comprising magnesium oxide and on Alkalisih'cat, in particular sodium metasificat as a binder, and optionally other additives characterized in that the magnesium oxide has a residual hydration capacity of less than 4 percent by weight.

The residual hydration capacity of the magnesium oxide can be determined as follows: The magnesium oxide is immersed in water for 2 days and then dried at 110 ° C. for 4 hours. One weighed sample of magnesium oxide is then heated to 600 C for 2 hours and there is weight loss certainly. The percent weight loss is the percent remaining hydration capacity.

The importance of residual hydration ability of less than 4 percent by weight, in particular less than 3 percent by weight, is from the drawing seen in the graph of% hydration of magnesia versus viscosity of magnesium oxide in water (6 hours, 2: 1 by weight) is given. Each of the points poses a magnesium oxide of various hydration properties.

Optionally, the size may be a particulate suspending agent, e.g. B. bentonite included. the The amount of magnesium oxide present in the sizes according to the invention is preferably sufficient to combine with all of the alkali silicate present.

The particulate refractory material may e.g. Include alumina, titania or zirconium. The weight ratio of such other particulate refractory to magnesia is within preferably in the range from 4: 1 to 1: 100, in particular between about 1: 1 and 1: 4. That is, that Magnesium oxide should preferably be at least 20 percent by weight of the total refractory present Represent material. The particulate refractory material is preferably a fine quality, e.g. B. a Material with a particle size of less than 0.075 mm.

The particular magnesium oxide provided according to the invention should preferably have a very low calcium oxide content (to prevent the formation of less refractory materials to a minimum). Preferred magnesium oxides are Soldered magnesite obtained by heating magnesite to a temperature of at least 1500 C have been received. The magnesium oxide used preferably has residual hydration ability less than 3 percent by weight.

It has been found that refractory coatings according to the invention provide greatly improved floor slab protection in comparison with e.g. B. with known zirconium flour-silicate or chromite flour-silicon dioxide sol layers or in comparison to the above-mentioned magnesium oxide-sodium metasilicate size.
When sodium silicate is used, the magnesium oxide and sodium silicate react in use to form the high refractory silicate forsterite. which (in the free state) has a melting point of about 1890 ⁰ C (about 200 ° C above the highest steel casting

ίο temperatures). An analogous reaction probably occurs with other alkali silicates.

The floor slab coatings according to the invention can contain ferrous metals with a high iron oxide content with no adverse results or on floor slabs with

a coating of iron oxide. The reason for this is presumably the very high melting points of solid MgO / FeO solutions that can be formed. Even with a content of 50 percent by weight FeO, the melting point is such

solid solution only around 1950 ⁰ C (see A. Muan &

E. F. Osborne "Phase equilibrium among oxides in

steelmaking ”, published by Addison & Wesley 1965, p. 79).

The alkali silicate used preferably consists of sodium silicate, in particular sodium metasilicate. The silicate can either be in the form of an aqueous solution or a dry powder Application. The floor tarpaulin according to the invention can either be liquid

Form or be produced as a powder, which gives the required coating mass with the mere addition of the desired amount of water to the powder. The amount of water present in the liquid size according to the invention must be sufficient to cause hydration of the alkali silicate to at least 10 H ₂ O.

Because of the ease of application, the coatings are sprayable compositions preferred. The lower the viscosity, the more

however, the refractory material of the coating is prone to settling, creating a dense cake at the bottom of the container which can be very difficult to redisperse. It is difficult to find suspending agents which work satisfactorily in sizes according to the invention, since the liquid sizing compositions according to the invention have a pH as high as 12 can. It has been found, however, that suspending agents of particular value are Xanthomonas collous

5u ide are.

According to a particular embodiment of the invention, it is therefore an aqueous liquid size provided that a particulate refractory material that includes magnesium oxide and used as a binding

agent comprises alkali silicate and which contains a xanthomonas colloid as a suspending agent which is capable. eic stable suspension under highly alkaline conditions to deliver. The amount of xanthomonas colloid suspension included in the size

medium is preferably 0.01 to 1.9 percent by weight. The preferred alkali silicate is sodium silicate.

In some cases, a small amount of a metal ion sequestrant is included in the size

Complexing agents. z. B. ethylenediaminetetraacetic acid (EDTA): usually an amount less than 2 "" of one Sufficient funds.

5 6

It has been found that, when finishing, 2 kg of steel are cast per second. After 90 seconds of the invention the magnesium oxide, preferably some casting time, the steel did not have the coating by percent iron oxide as an impurity, e.g. B. 1 to 6%, penetrated.
of which may contain.

The invention ensures good protection 5 Example 3

of an object against attacks at temperature,. .... ·· ,,

of molten ferrous metal when looking at the ^Es _P 7 ^rd ^ ™ "" ^ coating composition

Subject matter a coating made of a refractory from the following

Size applies, as indicated above, dead-burned magnesite

became. The protected item usually consists of io (100% <0.075 mm)

made of metal, e.g. B. a block shape or base plate, _with a remaining hydration capacity

or handling and handling devices of 2.00 weight percent 45

of molten metal, but sodium metasilicate · 5H ₂ O

refractory non-metallic articles such as refractory (35 weight percent aqueous solution). 22.75

insulated block mold bottom plates, in this way 15 suspension medium 0.15

to be protected. Water 32.1

The invention is illustrated below with reference to FIG

Examples explained in more detail. This size was sprayed onto a heated cast iron plate and allowed to dry. The over Example 1 ²⁰ tensile thickness was 2 mm. After that, the cast iron plate was coated with the side up and in one

A size was obtained with the following composition plane at an angle of 45 ° to the horizontal

made arranged. A stream of molten steel with

dead-burned magnesium oxide at ^a temperature of 1620 ° C was then added to the

(containing 4% iron oxide) * 5 plate from a height of 45 cm in an amount of

Cast with a residual hydration ^{capacity of 2 k} S steel per second. After 90 seconds

At 0.08 weight percent 55 ^{, the plate was} cooled and the exposed one became

Suspending agent 0.15 surface of the coating polished and under a

Ethylenediaminetetraacetic acid 0.7 microscope brought. It became the crystal structure

liquid sodium silicate (SiO ₂ : Na ₂ O- 3o analyzed in terms of area to determine the relative proportions of

Ratio 3.3: 1, 37.9% solids; spec. various existing refractory components

Gew 1 39) ^{to determine 15.0 m of} the special observation plane.

Wasser'auf ICK) '^ s the following results were then obtained.

The results were

This size had an easily sprayable 35 ₍ ° / _{area of} the photomicrograph)

Consistency and showed no tendency to rapid periclase (MgO) ... 35

Sediment formation or gel formation. The Forsterit 50

Size was sprayed onto hot cast iron plates (300 ⁰ C; spinels, glasses and other silicates ". '.'. '. 15 150 x 150-36 mm) to a thickness of 1 mm, and 200 kg of completely calmed 40 An X-ray diffraction analysis an amount of steel having a temperature of 162O ⁰ C to the over- coating of the powdered residue showed a total coated side of the plate during a period of forstentgehalt based poured 100 seconds on the Gesannüberzugsdichte. of 6 to 8%.

After cooling and testing it was found that

the coating was contiguous and that the 45 Example 4

Plates were not eroded. ^,. _. ,. ,

It was a dry powder mixture as follows:

Composition prepared Example 2

_J. ... - _f - _T1 _ Magnesite (100% <0.075 mm) A liquid coating composition _{50 having a residual} hydration _{ability of 130} weight percent 77.5 was prepared from the following

dead burned magnesite sodium metasilicate 5 H ₂ O (powder) 19

(100% <O, O75mm) suspension medium (powdery ben-

with a residual hydration tonite tone) 3.5

speed of 0.16 percent by weight 33.75 55

Alumina (all <0.15 mm) 11.25 ^To establish a base plate size, di

Sodium silicate (as in Example 1) 12.00 ^for use in the usual manner, e.g. B. durc

Suspending agent 0.15 spray, is suitable, it is necessary to comply with the above

Water 42.85 named composition for any purpose

60 gen ratio between 60:40 and 40:60 (related to ai

This size was applied to a heated cast iron to dilute the weight).

plate sprayed and left to dry. The coating - a special finish that is mixed with water in the Vei

thickness was 2 mm. After that the cast iron plate ratio of 50:50 had been made, wi

with the coated side up and in one described in Example 2, tested. After a Giel

The steel did not deform the plane at an angle of 45 ° to the horizontal for 90 seconds

arranged. A stream of molten coating was then permeated.

zenem steel with a temperature of 1620 ° C. For comparison purposes, two were refractory

the plate made from a height of 45 cm in an amount of finishing as follows

2 Oil 828

Comparative example 1
A dry powder mix was made

Magnesium oxide (calcined at 100 C)
with a remaining hydration capacity

speed> 15 percent by weight

Sodium Metasilicate · 9H ₂ O

g of the powdery mixture were applied to a hot test plate (300 ° C), after which the Water of crystallization was driven off and a hard, 2 mm thick, solid coating was left on the plate.

Comparative example 2

A liquid size was produced with the following composition

Olivine sand (91% forsterite) 50

liquid sodium silicate (38% solids;

SiO,: Na ₂ O ratio 3.3: 1) 13.5

Suspending agent 0.15

Water 36.35

The size was sprayed onto the hot test panels, with a dry coating in one Thickness of 2 mm.

These finishes were made according to the methods such as

they were used in Examples 2 to 4 were tested. The coatings failed, i.e. that is, erosion of the test cast iron plates began at 16 seconds (comparative example 1) and at 14 seconds (comparative example 2).

Comparative example 3

A liquid size was produced with the following composition

Magnesium oxide with residual hydration ability of 5.7 weight percent 45.00

Suspending agent 0.15

liquid sodium silicate

(3.9% solids; SiOo: Na "0 ratio

3.3: 1) '....'. 15.00

Water 39.85

After a few hours, the size had solidified as a result of a chemical reaction between sodium silicate and magnesium oxide. The solidified size was applied to a hot cast iron plate (300 ^c C) with a trowel in a thickness of 2 mm. The coating produced was powdery and lacking strength. Killed steel of 1620 ° C was poured onto the coated part of the plate. The steel penetrated the coating in 25 seconds and eroded the cast iron plate.

1 sheet of drawings

Claims (10)

2 Oil 828 block molds have come into extensive use prior to pouring molten metal. These coatings serve to protect the lower part or the base plate and the walls against erosion by the 1. Aqueous, liquid, refractory sizing for 5 molten metal to protect and block molds with a content of particles to prevent splashes from the molten metal shaped, refractory material, which adhere to the walls of the mold made of magnet. Furthermore, this is intended to silicon oxide, and adherence of the cast ingot in the mold Alkali silicate, especially sodium metasilicate, are reduced to a minimum. Floor slab human binding agent, and optionally further additives, io ten generally have the form of a suspension of a characterized in that the particulate refractory material is in a liquid magnesium oxide a remaining hydration-capable medium. The plain is painted on, honesty of less than 4 percent by weight. sprayed or in some other way onto the lower part of the mold 2. Refractory sizing according to claim 1, characterized and applied to the walls and usually under the characterized in that the water in the size 15 influence the residual heat in the form to a thin Dried sufficient to allow hydration of the alkali silicate coherent coating. to cause at least IO H _{2 O.} Floor finishes are very in use 3. Refractory size according to claim 1 or 2, subjected to strict conditions: The size must characterized in that it is a suspension of the highly erosive power of molten medium, preferably XaiUhomonas colloid, in such a way as to resist steel from a height of several Amount from 0.01 to 1.9 percent by weight of the meter and at a temperature of 1600 C or Contains sizing. more applies, the size must be satisfactory 4. Refractory sizing according to one of the and on the base plate during the whole work process Claims 1 to 3, characterized in that they adhere, and the size should also preferably up to 2 percent by weight of a metal ion can be applied quickly and easily. So far there are many Contains sequestering agent. Attempts have been made to finish floor slabs 5. Refractory sizing according to claim 3, to produce the desired performance. Avoid that characterized in that the suspension of these sizes consists of aqueous medium consists of bentonite. Coating compositions comprising a particulate refractory 6. Refractory size according to one of the claims 30 include material and a binder. Claims 1 to 5, characterized in that there are cheap sizes, the silicon dioxide. Magnesium oxide has a residual hydration capacity- contain sodium silical and graphite; their effect is less than 3 percent by weight. however, it is not very satisfactory. 7. Refractory sizing according to one of the following. Furthermore, comparatively expensive sizing are known, Claims 1 to 6, characterized in that the fused silica in amorphous particulate form Refractory material all have a stand and contain colloidal silica. At an particle size less than 0.075 mm. However, turns of this type of finishing occur 8. Refractory sizing according to one of the particular problems. Colloidal silica is Proverbs 1 to 7, characterized in that frost-sensitive and is already comparatively at least 20 percent by weight of the particulate 40 low degree of cold destroyed. That kind of trickery Refractory material made of magnesium oxide must also only be asked for shortly before use stand. two separate containers holding amorphous powder 9. Refractory sizing according to one of the following on the one hand and liquid with colloidal silica Claims 1 to 8, characterized in that the other hand are present, are prepared. the refractory material aluminum oxide, titanium dioxide 45 prepared aqueous size hardens very quickly in the or contains zircon. Lance, and when colloidal silica on hot 10. If refractory coating is sprayed according to one of the floor panels, dangerous and dangerous Proverbs 1 to 9, characterized in that the irritating mist. Amount of magnesium oxide present from- It is a mass for the protection of floor slabs is sufficient to unite with the whole of the foregoing, which essentially consist of a powder mixture which alkali silicate to unite. of sodium metasilicate · 9H ₂ O and a refractory Filler, such as silicon dioxide, siliceous graphite, kaolin, carborundum, zirconium, chromite or mixtures thereof. Calcined at 100 ⁰ C 55 Magnesia is also said to be suitable. That Powder is applied immediately to the hot bottom plate and the sodium metasilicate dissolves then in its own water of crystallization, and the water then evaporates and gives> .: in a dry place The invention relates to an aqueous, liquid, coating consisting of filler particles, which Refractory coatings for block molds, specifically solid sodium silicate with a low melting point on finishing for block mold bases and point connected. It can be seen that a Floor tiles. Although the sizes outside of this such dried coating are very considerable Area can apply, may have variations in the setting of the structure, so that In the following, they will be referred to in particular as "soil areas with a very high content of solid sodium plate finishes" designated. silicate and areas with very low content or In recent years, refractory sizes for even no sodium silicate content have been found the application to the base and the walls of are.