JPS6283355A - Powdery binder composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industry! (2) Process Separation The present invention relates to a powder binder composition (hereinafter referred to as "dry material") mainly used for monolithic refractories. The principles of the present invention can also be applied to building materials and other cured heat-resistant materials.

Conventional Summer Technique (Explanation of Dry Materials) Dry materials are often used as lining materials for electric induction heating type crucible furnaces that melt cast iron, cast steel, or non-ferrous metals (copper alloys, etc.). In this case, the lining thickness required between the furnace shell (for crucible furnaces, the lining thickness is
Set a gap (often 100 mW to 15 ON), set a metal frame inside the furnace, and shake the metal frame with a vibration motor while introducing dry material into the gap, or attach a vibrator to the input material. The molded material is compacted and filled with a taming rod, but in this state the molded material is not strong enough, so the metal frame is heated to strengthen the bonds contained in the dry material (formed material). The bond strength is obtained by melting the wood (in most cases boric acid is used) and the metal frame is removed. Alternatively, the dry material (molded body) is sintered by heating to a temperature at which the metal frame melts, and the metal frame is also processed.

As can be seen from this example, dry lumber is similar to other monolithic refractories in that it is composed of heat-resistant aggregate as the main component and a binder that binds them together. Unlike rammed refractories and plastic refractories, water or liquid binders are not used, but they are powder-based.For example, like castable refractories (fireproof concrete), refractory powder is A major feature of this method is that the powdered material can be directly fed into the furnace without adding water and kneading it with a mixer.

Furthermore, dry materials are similar in that they are constructed by setting up a metal frame and pouring refractory material into the gap, but unlike plastic refractories and ramming refractories, they are constructed after stamp construction, and castable refractories are constructed after stamping. Unlike other monolithic refractories, in which the strength of the molded body develops and the metal rod can be removed after construction, the strength is developed through heat treatment and the metal frame must be removed, which is a big difference from other monolithic refractories. There is. By the way, in order to remove the metal frame, the molded body must have a compressive strength of at least 1 to 2 kg/cat, and considering safety, 5 kg/cat is preferable.
This has been obtained as empirical knowledge.

(Characteristics of dry materials) Based on the experience of the crucibles mentioned above, dry materials, unlike other monolithic refractories, contain a large amount of moisture and components that decompose and evaporate, even if the binder contains a small amount of crystal water. Many benefits can be found because it is not included. First of all, since it does not contain moisture, it will not freeze during storage and lose its product value, and it will not undergo reactions inside the material at high temperatures and become hard, making it impossible to install. The key point is that it can significantly reduce construction time losses and economic losses due to deterioration due to temperature changes, which is a common complaint with other monolithic refractories. Secondly, since it does not contain moisture, there is no need for drying to remove moisture from the molded body, and for example, it can be heated at a rate more than 10 times faster than castable refractories and used for operation. This provides extremely large economic benefits in terms of energy savings and shortened construction times, allowing for quick start-up.

Furthermore, for example, in the case of castable refractories, when heating and raising the temperature for drying, the moisture remaining inside the molded product turns into water vapor, which destroys the molded product and generates fragments. Splashing, so-called steam explosions (explosion) often occur. This can lead to losses due to interruptions in operations, and most importantly, it often leads to personal accidents, making it a major safety management issue.

Dry materials have the great advantage of being a material that does not cause such problems, both in principle and as a result of experience.

(Binding material for dry materials) Dry materials are applied and molded into a metal frame in a state that does not contain moisture, and the strength is then developed by heating from the metal frame, so as a binding material for this purpose, ■Available as powder.

■Can be stored as powder.

■It is non-toxic and safe to handle.

■ Bond strength is developed at the lowest possible temperature.

Therefore, boric anhydride, boric acid, and borates have been mainly selected and used in the past. Dry materials using this type of binder have a lower melting point (boric anhydride; Approx. 450℃, Sodium silicate No. 2; Approx. 700
℃), the binder gradually begins to form a liquid phase.
It can be baked and hardened by heating at a low heating temperature of about 0° C., giving it the strength necessary to remove the metal frame. On the other hand, other inorganic powder binders can develop great strength when dissolved in water and reacted as a solution, but when used as a powder, at least the temperature at which a liquid phase begins to form is over 700°C. Strength cannot be obtained unless heated.

-a＜：Shiyotorukuchi As shown above, dry materials using borate powder binders, which are highly effective in terms of strength development at low temperatures, become corrosion resistant when they come into contact with a flow of molten metal or slag at high temperatures. Problems such as decreased performance may occur. This type of powder binder has a low melting point, so it is not only leached into the molten metal flow and leads to melting of the dry material, but also reacts with a part of the aggregate, causing glass engineering problems. It is thought that melting loss is accelerated by producing a low-melting component like borosilicate glass, which is well known in the art, but in any case, there is a major limitation in that corrosion resistance against molten metal flow cannot be improved.

Products using borate-based binders have excellent initial strength at low temperatures, but as vitrification progresses, their strength at hot temperatures decreases, and as a result, they are washed away by the flow of molten metal. Lead to results.

In addition, the formation of low-melting components or glass phases naturally promotes spalling failure of the dry material lining refractory due to the thermal history of heating and cooling of the furnace body during operation. This becomes a factor that hinders the improvement of the fire resistance of the lining material.

As mentioned above, there is a need for an alternative to borate binders, which limit the durability of dry materials due to their increased vitrification. Therefore, we focused on phosphoric acid bonds, which are used in plastic refractories and rammed refractories, because of their high corrosion resistance and high hot strength at high temperatures.

A common method for phosphoric acid bonding is to use phosphoric acid and activated alumina as binders to gradually generate aluminum phosphate, which is then polycondensed by heating to increase strength. Another method is to add aluminum phosphate as a binder to the aggregate from the beginning. Of course, the occurrence of spalling fracture due to the progress of vitrification can also be suppressed. However, although powdered aluminum phosphate can also obtain phosphoric acid, it cannot be used as a binder for dry materials because powdered aluminum phosphate cannot be used as a binder at low temperatures, as is the case with powdered silicate binders. This is because no strength is developed at all. This has a very high melting point (1700 for Ail!PO4)
(melting point above ℃).

As a result of studying the combination of various powder binders with aluminum phosphate, we found that adding and combining alkali metal salts of phosphoric acid and ammonium phosphate to aluminum dihydrogen tripolyphosphate revealed the strength of dry materials in the low temperature range. It was discovered that this combination could be used as a binder for dry materials.

In other words, the present inventors believe that the functions that a dry material should have are that the powder binder itself does not change and is stable at room temperature, at least 80°C or lower, and that it is stable when mixed with refractory powder particles. It also has stability and shelf life at the same temperature, and is usually in the low temperature range (e.g. 10
0 to 500℃), the reactant does not vitrify (become amorphous), and in addition, the reactant exhibits the property of being difficult to vitrify even in the high temperature range, and maintains spall resistance. Moreover, from the viewpoint of corrosion resistance, we considered that it is desirable to not have a vitrified structure and to easily generate phosphoric acid bonds.

As a result of examining various dry materials that can satisfy these requirements, the present inventors have developed an alkali metal salt or an ammonium salt (hereinafter referred to as a "phosphate") of orthophosphoric acid or condensed phosphoric acid.
It was discovered that a series of systems consisting of aluminum dihydrogen tripolyphosphate (1) and aluminum dihydrogen tripolyphosphate satisfies these conditions, and the present invention was achieved.

The present invention will be explained in more detail.

In other words, in the commonly used low temperature range,
A phosphate is used that causes phosphoric acid condensation. Although these phosphates have excellent ability to form phosphoric acid bonds, they also vitrify (become amorphous) and have major problems in corrosion resistance, spalling resistance, and the like.

On the other hand, aluminum dihydrogen tripolyphosphate is used as another component. Aluminum dihydrogen tripolyphosphate has the chemical formula H2Ae P3010.2H20, is extremely acidic, poorly soluble in water, and has a temperature of about 1200°C.
It has a melting point of , and the protons it possesses easily undergo ion exchange with cations such as alkali metal ions or ammonium ions.

For example, taking sodium phosphate as an example of the present invention, 2NaHzPO+ ・2H20+HzAeP30+o
・2H202)+3PO4+ NQzMP30Io+6
) tzO (11) The reaction proceeds and phosphoric acid is liberated.In other words, since the phosphate and aluminum dihydrogen tripolyphosphate are mixed dry, so-called ion exchange reactions do not occur at room temperature, so they remain stable as they are. exists in

However, when these are heated, the above reaction occurs due to temperature activation (in the so-called low temperature range related to refractory materials), and as a result, phosphoric acid is produced. The generated phosphoric acid naturally performs phosphoric acid bonding, but since it is a liquid, the mixture of these powders appears to be in a molten state. This melting temperature is much lower than the melting temperature of each composition alone. That is, it exhibits binding strength in a low temperature range. What should be noted here is that the sodium tripolyphosphate produced as a result of the reaction (generally aluminum tripolyphosphate alkali salt) retains crystallinity and is extremely difficult to vitrify (hard to amorphous). Therefore, it has the property of improving corrosion resistance and spalling resistance. Furthermore, it is well known that aluminum dihydrogen tripolyphosphate is used as a refractory binder in a high temperature range, and can exhibit properties as a binder in a high temperature range where vitrification is most likely to proceed.

As mentioned above, it has been found that by using a mixture of phosphate and aluminum dihydrogen tripolyphosphate, it is possible to make use of the characteristics of the single substances themselves while compensating for their shortcomings, thereby producing an extremely excellent dry material. Aluminum dihydrogen tripolyphosphate may be used in combination with monoaluminum phosphate as appropriate.

As shown in the examples below, as the phosphate, not only orthophosphate but also condensed phosphates such as birophosphate, tripolyphosphate, and hexametaphosphate can be used. Cation species include sodium,
Alkali metal ions such as potassium and ammonium ions can be used.

Moreover, these phosphates can be used alone, but several types of phosphates can also be used in combination.

The method for producing aluminum dihydrogen tripolyphosphate used in the present invention is known, for example, as shown in Japanese Patent Publication No. 55-50884. 3 or less raw materials with air 1
200 containing 0.5 kg or more of water per kg
It can be obtained by firing in a hot steam atmosphere at ~650°C.

In preparing the dry material of the present invention, the above-mentioned various phosphates and aluminum dihydrogen tripolyphosphate may be mixed in advance, or may be mixed immediately before use. However, care must be taken when mixing, as if the temperature rises too much due to frictional heat, for example, when the mixture is passed through a pulverizer, a portion of the mixture may soften and melt.

In order to use the dry material of the present invention for monolithic refractories, silicon carbide, alumina, magnesia, aluminum silicate,
Used with refractory aggregates such as chromite, silica, graphite, zirconia, and zircon. The mixing ratio of aggregate and dry material is
Since it varies significantly depending on the particle size, particle shape, particle distribution, etc. of the aggregate used, it is necessary to determine in advance the mixing ratio that will provide the highest strength through experiments.

Next, the monolithic refractory mixed with the dry material and aggregate of the present invention is placed in a mold of the desired shape, and densified by a suitable vibration method, press method, stamp method, or injection method using an injection machine. make a change. The densified refractory is heated and then fired to bond the aggregate. Any heating method may be used, but the simplest method is to heat the mold from outside with a gas burner.

After cooling, the mold is demolded to obtain the desired refractory molded body.

It has already been mentioned that aluminum dihydrogen tripolyphosphate extracts the sodium from sodium phosphate and isolates phosphoric acid as shown in reaction formula (1). A reaction formula similar to reaction formula (1) can be written for other phosphates. That is, N(2211PO4-12H2
0+HzAeP30+o -2HzO-◆)I3P04
+ Nd2AeP3Cho+14HzOf212N(L
3PO4-12H20+ 3H2AeP301o ・
2H202H3PO4+3N(lzMP3cho+30
H20(31N(1zHzPzOr+HzMP3Ct+
o-28zO-1 → 2H3PO4+ NdzMP3C
ho+HzO(4)N(1+PzOr+ 2N2MP
30m-2HzO-m-→2H3PO4+ 2N control MP
301O+3H2O(5)2N<15P3010+
5HzAeP30+o・2H20683PO4+5N(
1% M, P30+o+68zO(6)(NaPO
a) s + 3H2Ai! P30+o ・2H20
6H3PO4,0003N42Ai! Pa0Io(7)2NH
4H2PO4+ HzMP3(ho ・2H20-1 →
HaPOa + (NH4)2PiP30 bite +2
H20(81(NH4)2HPO4+HzMP3α0・
2H20−−→ H3PO4+ (NH4)2AeP
3cho +2H20(9)2(NH4)2PO4・
3t(zO+ 3N2M!P30+o・2H202
H3PO4+ 3(NH4)2AeP30Io+6H
2M1 of zOα (zPO4+HzM, P3Cho ・2
H20-1→2H3PO4+mu AI! , Pa import +2H2
0θυ Regarding the evaluation of the bonding strength when a mixture of these phosphates and aluminum dihydrogen tripolyphosphate is heated, from the viewpoint that a liquid phase is generated, sintered, and develops strength, In order to observe the formation status, tablets of dry material were made and placed in an electric furnace, and the apparent softening and melting status of the bond was examined. As a result, ■ Phosphates such as sodium dihydrogen phosphate dihydrate, tetrasodium birophosphate dihydrate, potassium dihydrogen phosphate, and ammonium hydrogen phosphate have a concentration of 30% compared to aluminum dihydrogen tripolyphosphate. % or more, the apparent melting point decreases.

- Alkali metal and ammonium salts of orthophosphoric acid and condensed phosphoric acid, when used in combination with aluminum dihydrogen tripolyphosphate, all soften and melt at the same temperature as the single substance or at a lower temperature.

(2) Specifically, in the case of sodium dihydrogen phosphate dihydrate, it softens and melts at an apparent temperature of 100°C.

■ From the above melting state, the combination for aluminum dihydrogen tripolyphosphate is potassium dihydrogen phosphate and ammonium hydrogen phosphate.

It is thought that in the order of sodium dihydrogen phosphate dihydrate, the melting point decreases and the effect of temperature development (bonding strength) increases.

On the other hand, when we analyze their melts by X-ray diffraction, we find that those with a mixed composition of aluminum dihydrogen tripolyphosphate are not completely vitrified, but depending on the content of aluminum dihydrogen tripolyphosphate, The diffraction line of the crystal showed a high peak at 20=11.2°, which revealed that it had a crystalline composition.

This apparent melting, in other words, the mechanism of strength development is considered to be due to (1) to (11).

That is, N (22P/! P30Io
On the other hand, the strength is developed by the phosphoric acid that precipitates.

Next, an example of a dry material using the binder of the present invention will be shown below, based on an aggregate for a handle material of a monolithic refractory used in a tap barrel of a blast furnace.

Table 1 shows the raw material composition of the dry materials tested.

Comparative Example 1 is a total binder (not containing a binder), and Comparative Examples 2 to 4 are a binder used in ordinary dry materials (the amount of binder added is within the normal usage range, a small amount and a large amount) Comparative Example 5 is a representative example of an inorganic binder used other than dry materials.

The main qualities of the raw materials used in the Examples and Comparative Examples are as follows.

Fused alumina: AezOa content is 99%, α-M,
Consists of zOa (corundum) crystals, 5 to 1 crane, 1
Commercially available products that have been ground to an accuracy of 0.3 m or less and 0.3 + im or less.

Calcined alumina: Ai! A commercial product of fine powder alumina having a 20s content of 99.8%, consisting of microcrystalline α-M203 crystals produced at a relatively low temperature range (approximately 1100°C), and exhibiting a particle morphology of 0.1 u or less.

Silicon carbide: SiC content is 85.6%, 0.1n
Commercial products crushed below.

Boric anhydride: Contains 96.5% as B2O3, 0.3
Commercial product for industrial use with accuracy of D or less.

Powdered sodium silicate: 5iOz/NazOs molar ratio is 2
．． 5, 5t (lz content 57%, Na2O 23
% and has a particle size distribution of 0.3■ or less.

Aluminum tripolyphosphate dihydrate: Trade name, Nipond #80 (Teikoku Kako Manufacturing) Sodium dihydrogen phosphate: Special grade reagent Potassium dihydrogen phosphate; Special grade reagent Aluminum dihydrate tripolyphosphate: Special grade reagent (below) Margin) Samples of Examples 1 to 8 and Comparative Examples 1 to 5 were prepared by mixing each of the formulations shown in Table 1 in a laboratory V-type mixer with a capacity of 20β, and each weighing about 15 kg.

(Curing Strength Test) Each of the formulations shown in Table 1 was placed in an iron frame placed on a vibrating table equipped with an electric pie break at the bottom. The metal frame has a diameter of 50 m and a height of about 50 cranes, and has a split structure that can be divided into three parts so that a cylindrical molded body can be obtained after the vibration is finished, and the film can be attached to the vibration table with bolts. I used something.

After putting the sample mixture into the metal frame, an iron disk with a diameter of about 48 cm and a thickness of 10 cm was set on top of the test piece as a drop lid to prevent scattering of the powder on the top of the vibrating body. Prevented. The molding conditions are
The strength of the vibration was set to the extent that an excitation force of 5 G, which is in the middle range, was applied, and the vibration table was vibrated for 20 minutes to shape the specimen in the metal frame.

After molding, each specimen was removed from the shaking table, placed together with the metal frame in a hot air circulation type electric drying oven, and heated at 100°C and 200°C.
The sample was heated at temperatures of 300°C and 300°C, and after 4 hours, it was taken out and cooled at room temperature. The strength of each sample heat-treated body excluding the metal frame was determined using an electric-shaft compression testing machine.

The measurement results are shown in Table 2.

(Left below) Sodium silicate is ineffective in its powder form below 300 t'. Boric anhydride achieves strength at 300°C, and the greater the amount added, the greater the effect. The samples of the present invention develop strength by heat treatment as low as 200°C. As in Example 1, aluminum dihydrogen tripolyphosphate alone has no effect;
Unless it is used in combination with an alkali phosphate salt and the former is not more than 70%, it will not be possible to obtain the strength to remove the frame.

(Spalling resistance) Comparative Examples 2 and 4 and Example 3 are thought to be able to develop enough strength to remove the frame at low temperatures from the test results of curing strength.
．． Each of the mixture samples Nos. 5 to 8 was placed in a cylindrical iron metal frame with an inner diameter of 100 cm, and was molded by applying vibrations. This is a larger version of the metal frame whose compressive strength was measured, and the structure is the same. Moreover, the molding conditions are also the same.

After heat treatment at 300"C, these molded bodies were unframed and inserted into a large electric furnace using a silicon carbide heating element.
Raise the temperature to 1400'C at a rapid rate of °C/min,
There, it was heated and held for 3 hours. After that, it was taken out of the furnace, put into water as it was, rapidly cooled, and left in water for 3 minutes, then taken out again, kept at 1350°C, immediately inserted into an electric furnace, heated rapidly, and heated there for 30 minutes. did.

It was taken out again and put into water for rapid cooling. A spalling test was conducted by repeating such rapid heating and cooling. The results are shown in Table 3.

(The following is a blank space) When observing the cross section of Comparative Examples 2 to 4, the more boric anhydride there is, the more foamed glass-like products are seen, and the color tone indicates that silicon carbide is oxidized and whitened. .

In the example, only slight hair cranks were generated, and the spall resistance was far superior to that in the comparative example.

(Hot bending strength) Comparative example 3 was added to Examples 3.5 to 8 to measure the hot bending strength, taking into consideration the development of sufficient strength to enable deframing at low temperatures and spalling resistance.

Take a portion from these mixture samples prepared earlier and
A molding frame for castable refractories that yields a 40x40x1601 prismatic molded product as specified in IS R2553 is used, and the molding is filled in a heaping amount into the metal frame, with an area that can cover the top surface of the metal frame and a thickness of 15 nm. An iron plate was placed on a vibrating table, and the metal frame was vibrated and molded.

However, the metal frame was not fixed to the vibration table, and the hand was placed on the iron plate cover to prevent movement due to the vibration of the metal rod. Note that the vibration conditions were the same as in the case of the hardening strength test.

After the vibration, unnecessary material was cut off using a mortar trowel so that the surface was flat on the top of the metal frame.

Next, the metal frame was heated to 300°C and inserted into an electric furnace, and after heat treatment for 2 hours, the frame was removed and the sample molded body was taken out. Each test molded body was inserted into a hot bending test furnace using a silicon carbide heating element and heated at a rapid rate of 10°C/win to 1450°C, the highest temperature obtainable in this type of furnace. After holding there for one hour, the strength was measured by placing it on a two-point support type bending strength measuring jig set in the furnace. Table 4 shows the results of this hot strength measurement at 1450°C.

(The following is a blank space) Comparative Examples 2 and 3 using boric anhydride have so small hot strength that they cannot be measured, but all of the Examples have the ability to maintain strength at high temperatures.

(Corrosion resistance test results) It has the strength to be removed from the frame at low temperatures, has excellent spalling resistance,
Example 3.5, which was found to have high hot bending strength
- 8 and conventional type Comparative Example 3 were subjected to a corrosion resistance test against hot metal and slag.

Take a part of each test mixture sample prepared previously, and make a trapezoid with a cross section of base x top x height of 53 x 36 x 20.
Each of them was filled into a metal rod having a split mold structure that yielded a molded body with a length of 120 nm.

As in the case of hot bending strength measurement, the metal rod was filled in heaps, the top surface was covered with an iron plate with a thickness of 15 fins, and the metal frame was placed on a vibration table and vibrated together with the metal frame. Since the metal frame was not fixed, the iron plate used for the cover was lightly held down by hand to prevent it from moving on the shaking table.

After the vibration, the material protruding from the top surface of the metal bar was cut off with a mortar trowel to give it a smooth finish. Next, as in the case of hot bending strength measurement, the metal frame was heat treated at 300° C. for 2 hours to harden the molded body, and the metal frame was removed.

These molded bodies were inserted into an electric furnace using a silicon carbide heating element, heated at a rapid rate of 10 °C/min to 1200 °C, held for 1 hour, then allowed to cool and taken out for comparison. A total of 8 pieces, 2 pieces of Example 3, 2 pieces of Example 3, and 1 piece of each of the others, were combined to make an octagonal cylinder and placed in a heating coil of a high frequency furnace. Inside the octagonal tube, pig iron F
A cylindrical erodible material made of C20 with a diameter of 80 mm and a height of 100 w1 was inserted, and blast furnace slag pulverized to 6 mm or less was added thereto in an amount equivalent to 10% by weight of Fe12. Then, the Fe12 and slag were melted by high frequency and held at 1600°C for 2 hours to erode the specimen.

The high frequency was then turned off, the melt was discharged, and the octagonal specimen was removed and eroded by the cast iron and slag. Corrosion resistance was investigated by measuring the thickness of the specimen. The results are shown in Table 5.

These results show that all of the examples based on the present invention have much better corrosion resistance than Comparative Example 3 of the conventional type.

The purpose of the present invention is to provide an effective means for increasing the corrosion resistance of conventional dry materials and improving their durability.
More importantly, corrosion resistance, spalling resistance, and high hot strength are required for blast furnace tap troughs and tundish furnaces used in the steel ingot making process, which were difficult to meet with conventional dry materials. This makes it possible to expand the range of uses.

Claims (2)

[Claims] (1) A powder binder composition comprising one or more compounds selected from alkali metal salts and ammonium salts of orthophosphoric acid and condensed phosphoric acid, and aluminum dihydrogen tripolyphosphate. (2) The powder binder composition according to claim 1, wherein the content of aluminum dihydrogen tripolyphosphate is 70% or less.