JPS59156966A - Alumina and alumina chromium castable refractories - 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 The present invention relates to the formulation of alumina and alumina-chromium castable refractories using a sodium phosphate binder, particularly for parts that come into contact with highly basic converter slag, such as molten steel ladle and tundish. The present invention also relates to gear stable refractories used in parts that come into contact with low basicity slag, such as hot metal sluices and hot metal pots.

Most alumina and alumina/chromium castable refractories are generally made using alumina cement as a binder, but in recent years, dense castable refractories that utilize the effects of dispersion and agglomeration using ultrafine powder and a small amount of alumina cement have become widespread. It is used.

However, dense castables using alumina or alumina/chromium aggregates have shown good results when used in kilns with small temperature fluctuations, but If a receiver is used in a container that undergoes repeated heating and cooling and undergoes rapid temperature changes, it will not have sufficient durability because peeling will occur due to thermal spalling and structural spalling.

Therefore, the inventors focused on a sodium phosphate-based binder that has been applied to maguro-based unfired bricks and has achieved high hot strength, and investigated in detail everything from the reaction characteristics of this binder to the characteristics of castable compounds. As a result, by adding alumina cement to the formulation and adjusting the amounts of condensed sodium phosphate and sodium carbonate, we were able to increase deformability at high temperatures and improve spall resistance while maintaining high hot strength. This product has developed high-quality alumina and alumina-chromium castable refractories.

The following has been clarified in the past regarding the application of a sodium phosphate binder to the above-mentioned maguro unfired bricks. That is, (1) Concerning sodium phosphate as a binder, condensed sodium phosphate with a degree of polymerization of about 21 is excellent in order to obtain high hot strength.

■ The presence of CaO is necessary for the formation of the binder phase, and Nato・2C, a compound of sodium phosphate and CaO, is required for the formation of the binder phase.
aO@P2O5 (sodium-reenanite, hereinafter rl
(abbreviated as tc2PJ) is the binder phase.

(5) If aggregate with a high 8i02 value is used, the strength will decrease in the high temperature range. The cause is the binder phase (NC2P)
reacts with 5io2 to form 7Ca0 at 1250°C or above.
aP205*2Si02 (Nagelschmittite, hereinafter abbreviated as "c7Pszz") is generated and free Na
It is presumed that this is because 2C1 enters the silicate liquid phase and destroys the shibinder phase, which is a low-melting glass.

The above findings are for unfired bricks using strong basic aggregates, but when applied to castable refractories with neutral to weak basic aggregates such as alumina and alumina-chromium. In particular, it is thought that the curing reaction at room temperature is different, and the bonding mechanism at high temperature is also different; on the other hand, the binder phase is similarly destroyed due to 5i07, an impurity component in the raw material for convenience, and the heat at high temperature It is thought that the interstitial strength will be significantly reduced.

This invention provides alumina and alumina-chromium materials that prevent the binder phase from breaking down at high temperatures even when using a sodium phosphate binder, have high hot strength, and have excellent spalling resistance and slag resistance. The purpose is to provide castable refractories.

First, let's talk about the CaO source necessary to generate the binder phase in the formulation. Commonly used CaO sources include quicklime, calcined dolomite, Ca(OH)2, and CaC03, but in castable refractories, water is added. When kneading and kneading, quicklime and calcined dolomite cannot be used because they cause a rapid exothermic reaction. Also, Ca(OH
) z and Ca C03, the following comparative experiment was conducted.

That is, condensed sodium phosphate (with a polymerization degree of about 21) is added to the alumina raw material aggregate as a sodium phosphate binder.
5% of glass H) manufactured by FMC, USA was added, and Ca (O
H) 5% of either 2 or Ca C03, 9% of water
As a result of adding and kneading, ・:C:a(OH)z
In the case of addition, a phenomenon of condensation along with an intense exothermic reaction was observed during kneading, and even if mixed wires were continued, no fluidity was obtained, making it difficult to cast into a castable product. This is CII
Since L(OH)2 is strongly basic and Glass H is weakly acidic (pH 6.3 in a 1% solution), it is thought that a rapid reaction between the two occurred.

- In the case of CaCO5 addition, although some heat generation was observed during crosstalk and there was viscosity characteristic of sodium phosphate, fluidity was good and normal casting was possible.

The above study revealed that CaCO3 is suitable as a CaO source necessary for generating the shibinder phase.

Next, in order to examine the reaction characteristics of the binder phase and 5in2 reacting and destroying the binder phase, we
NC2P') and various 8 i 0. The conditions for producing 907PS2 were confirmed as described above by causing the □ reaction, and will be described below.

Regarding the S i 02 source contained in the raw material aggregate, alumina raw materials such as mullite, clay shale, sintered alumina, and fused alumina contain S i O, and as minerals, ■free S i 02 and ■ Mullite (3At, O, ・2
SiOz-) can be considered. In addition, gangue in chromium ore, which is a chromium raw material, contains serpentinite, chlorite, and talc as Si02-containing minerals, but all of them decompose during heating to form forsterite (2Mgo-8i02) and free Generate S i 02 .

Therefore, typical sio sources are amorphous silica (reagent) and silica sand (mainly α-quartz) corresponding to (■) above, synthetic mullite (corresponding to ■), synthetic forsterite and synthetic dicalcium silicate (corresponding to ■). Five types were selected and the reactivity between condensed sodium phosphate (Grass H) and binder phase NC2P synthesized from CaCO3 was investigated.

If any sio source reacts with the binder phase,
Assuming that PS2 is generated and the binder phase is destroyed, the reaction equation is estimated to be as follows.

Na2O@2CaO-Pg06 +5CaCOs +
2SiO+→7CaO・PgOs−2sio2+ Na
2O+ 5CO2--・'・(1) Na20*2CaO
・PaOs + 5CaCOs + 3ALzO3”2
SiOz→7CaO・PaOs”2SiOz+ Na2
O+ 3A/40B+5CO1・・・・・・・・・(2
) NazO@2Cao @ p, o, + 5CaCOs
+ 2 (2Mg0 IIS i Os ) → 7Ca
O轡P2O6・2Si02+ Na2 Kano 4Mg0+ 5
co,・(3)NazO”2CaO@P20B+ Ca
CO3+ 2 (2CaOeSiO2) → 7CaO・Pg
Os・2Si02+Na2O+CO2−・・・・・・(
4) However, even when the compositions of formulas (1) to (4) above were heated at 1400° C. for 5 hours, no formation of C or PS2 was observed. Therefore, the 8102 source is C7PS2
1200°C, 1300°C, 1400°C.
℃ for 5 hours, and the results of an experiment to determine the production status of C7PS2 are shown in FIGS. 1 to 5.

In each figure, the * mark indicates a condition in which C7PSt was generated, and the ◯ mark indicates a condition in which C7PSt was not generated.

As can be seen from FIG. 5, it was found that 2CaO*5iOz did not decompose the binder phase N C* P, that is, the reaction of formula (4) did not proceed and multiplied. Figures 1 to 4, 5i
02 source is C? PS, caps from 1400°C in the case of amorphous silica and from 1600°C in the case of silica sand, mullite and forsterite in the composition range of more than twice the chemical equivalent.
It was found that the reaction of equations (1), (2), and (3) proceeds by producing 2 and decomposing the binder phase, NC2P. That is, the destruction of the binder phase by the 5i02 source proceeds under the above conditions.

Next, we investigated inhibitors of such reactions, that is, inhibitors of binder phase destruction, and found that the addition of alumina cement was effective, and in particular, the addition of high alumina cement with a low 5iOz content was very effective. I understand.

To give an example of an experiment, in the experiments shown in Figures 2, 6, and 4, JIS alumina cement No. When (S i 024.5%) is added and heated at 1400℃ for 5 hours, some C7PS
2, but similarly high alumina cement (S i
When 0.3% Os) was added, no C7PS2 was generated at all even after heating at 1400°C for 5 hours. In other words, it has been found that alumina cement has the effect of suppressing the reaction of formula (1) (21 (3)).

The above-mentioned reaction suppression effect was obtained by synthesizing CaO*A/403, which is the main mineral phase in alumina cement, using a reagent and conducting an addition experiment in the same manner as with the above alumina cement.
It has been found that the cause is that At203 reacts with 5io2 sources such as silica sand, mullite, and forsterite and is fixed as 2CaO-8i02 and Gehlenite (2CaOsA4203++5iOz), which eliminates the decomposition action of NC,P.

The appropriate formulation of alumina and alumina-chromium castable based on the above new knowledge will now be explained.

(1) Condensed phosphoric acid) Concerning the amount of IJum added.

Basic composition: High purity sintered alumina with particle size adjustment 87 weight ratio industrial C
aCo38〃 High alumina cement 5N Note: Sintered alumina is AL20g 99.66%r S
tOz 'J-04%The particle size adjustment is mesh Weight ratio coefficient 6-48 4-8 16 8-14 16 14-28 8 28-48 7 48-100 8 100-200 6 200 or less 21 Total 87 Industrial Ca The particle size of C03 is 200 mesh or less, and the electrified high alumina 72.5% is A120m.

S i 02 CJ, 5% Add 200 mesh or less of pulverized product of condensed sodium phosphate (trade name: Glass H) with a degree of polymerization of about 21 to the above basic composition 1
10 was added to the entire formulation in a range of 1 to 10 weight percent.
8.5 to 95% of water is added to the mixture and kneaded,
After vibration molding into a 25x25x150mI+ mold and curing and drying, the hot bending strength at 1400°C was measured.
This is the passage shown in FIG. Figure 6, the intensity of υ hot bending is 5.
The range where 0 town c or more can be obtained is when the amount of glass H added is 2 to 8 parts,
The preferred range is 3 to 7% by weight, which yields a weight of 90 kg or more.

Addition of glass H is 2%! It is thought that when D is small, the strength decreases rapidly due to less binder phase formation, and when it exceeds 8 inches, it is considered to be out of the range where NC2P, which is the binder phase, is formed.

(2) Concerning the degree of polymerization of condensed sodium phosphate, there are many types of condensed sodium phosphate with different degrees of polymerization, but if the degree of polymerization is less than 6, the alkalinity will be strong when it is made into an aqueous solution, so it should be kept at room temperature. The reaction characteristics are different and the strength is lower. Furthermore, when the degree of polymerization is greater than 40, the solubility in water is low and dispersion becomes poor, resulting in a decrease in strength.

Therefore, the range in which high hot strength can be obtained as a castable refractory is condensed sodium phosphate having a degree of polymerization of 6 to 40.

(3) Regarding the amount of calcium carbonate added The conditions for obtaining high hot strength with the amount of calcium carbonate added vary depending on the amount of condensed sodium phosphate and alumina cement added in the mix, the content of silica source in the aggregate, etc. It turned out that. So, add 2 condensed sodium phosphate (glass H)
Weight%, 2 levels of 8 weight cake, electrified alumina cement 1
Sixty-four types of formulations were prepared, with two levels of weight percent and 8 weight percent, the balance being high-purity alumina with the particle size adjusted as described above, and 1 to 16 weight percent of industrial CaCO3 crushed to 200 mesh or less added. As a result of kneading the outer layer A5~IO and SS, vibration molding into a 25 x 25 x 150 m mold, curing and drying, and measuring the hot bending strength at 1400 ° C., 1
It has been found that the amount of CaC0a added to obtain a hot bending strength of 50 to 6 or more at 400° C. is in the range of 2 to 15 weight percent.

If the amount of C, CO, added is less than 2%, the amount of binder phase generated decreases and the strength is low, and if it exceeds 15%, it is out of the region where the binder phase (NCgP) is generated, and 4CaO・p2Q
5. Since CaO and the like are generated, the strength decreases.

(4) Regarding the amount of alumina cement added, as mentioned above, adding alumina cement, especially non-alumina cement with a low SiOx content, is effective in suppressing the destructive reaction of the binder phase, but the appropriate amount As a result of the study, it was found that 1 to 8% by weight, preferably 2 to 8% by weight in the formulation.
It has been found that adding 7% by weight is most effective.

Note: Sintered alumina is A12oz 99.66
%5ift 0.04% machine rock chromite is cr
2o, °66.2% 5in24.20% electrified high alumina cement AAzOs 72.5% 8i0z
[j, 3%, i.e. electrified alumina cement for the basic composition as shown in Table 1, 0.5 to 0.5% for all compositions.
To 10 types of formulations added in a range of 90% by weight, 8 to 10% of water was added and kneaded, and 25x25x1
The hot bending strength at 1400° C. was measured after molding to a size of 50° C. and drying, and the results are shown in FIG.

As is clear from the figure, the range in which a hot bending strength of 50KM or more can be obtained is when the amount of alumina cement added is 1 to 8% by weight, and the preferable range in which a hot bending strength of 80 or more is obtained is 2 to 7%.
Weight%.

If the amount of alumina cement added is less than 1%, 5in2
This is thought to be due to the fact that the hot strength decreases because the destructive action of the binder phase (NCzP) cannot be suppressed, and when the content exceeds 8% gold, the amount of liquid phase generated increases due to the low-melting components in the alumina cement. .

The aggregate in Table 1 is alumina/chromium, and the
The i02 value is as high as 1.7, but instead of this aggregate, Si
As a result of conducting the same experiment as above using only sintered alumina with an Os value of 0.8% as aggregate, the hot bending strength level was 1.
0 to 15 (- increased, but the results were similar to those in FIG. 7).

In addition, JISi alumina cement (AkOs56.7chi, 5iOz4.5%) can be used to replace electrified high alumina cement.
] As a result of conducting a similar experiment using the following, the hot bending strength at 1400°C was reduced to about 2/6 of the level shown in Fig. 7.

Therefore, as a result of studying the 8102 content in alumina cement, we found that within the optimal addition amount range of alumina cement mentioned above, the hot bending strength at 1400°C was 80'f/,
It was found that the conditions obtained above were such that the content of SiO2 was 1% by weight or less.

In addition, in the various experimental processes described above, the castable refractories of the present invention were found to undergo deformation of about 5 m from the time a load was applied to the sample to the time it broke during hot bending strength measurement at 1400°C. -Blade Conventional alumina castable, which uses high-purity sintered alumina as the aggregate and ultrafine alumina powder and alumina cement as the binder, breaks at 2 inches and 8 degrees. That is, the castable refractory of the present invention has a large deformability at high temperatures.

It has been demonstrated that it has excellent spalling resistance.

Next, to explain the results of using an example of this invention in an actual furnace, Table 2 shows the alumina castable refractory of this invention (Example 1), the alumina-chromium castable refractory (Example 2), and the conventional A high alumina caster fill (conventional example) using ultrafine alumina powder and alumina cement as a binder was constructed by pouring its formulation, composition, characteristics, and these into the slag line of a 250T molten steel ladle 17 times at a thickness of 130 m. 6 ladle
After using 5 charges, I will tell you the situation of the big fish.

Table 2 Examples and Usage Results As is clear from Table 2, the Examples exhibited less peeling and damage than conventional products, and were therefore able to significantly extend the service life. This is because the product of this invention has high hot strength and large deformability at high temperatures, so it has excellent heat resistance and structural spalling properties.

As explained above, this invention produces a binder phase by the reaction of condensed sodium phosphate and calcium carbonate, and alumina and alumina cementola are added to prevent the binder phase from breaking.
It is a chromium castable refractory that has high hot strength, excellent slag resistance, and excellent spalling resistance, so it can be used as a lining material for various molten metal containers including slag lines. Since it has a service life approximately twice that of refractories, its industrial effects are significant.

[Brief explanation of drawings]

Figures 1 to 5 are graphs of experimental results showing the state in which the shibinder phase is destroyed at a specific temperature by the 5iO1 source in alumina and chromium raw materials, and Figures 6 and 7 are graphs of condensed phosphorus, respectively. 2 is a graph of experimental results showing that the amounts of sodium acid and alumina cement added do not affect the hot strength of refractories. Agent Patent Attorney San Kimura Snoring 1 piece 1200 +300 1400 1500 L(o
C) Fig. 3 Temperature ('C) Fig. 2 Temperature/L (0C) No. 4191 5≧ 5 ridges (0c)

Claims (1)

[Scope of Claims] 1. Alumina cement is added to a mixture of alumina or alumina-chromium refractory material as aggregate and condensed sodium phosphate with a degree of polymerization of 6 to 40 and calcium carbonate as the main binder phase. Alumina and alumina-chromium castable refractories made by adding 8% by weight. 2. In the entire formulation, the alumina voice alumina function according to claim 1, wherein the content of condensed sodium phosphate with a degree of polymerization of 6 to 40 is 2 to 8% by weight, and the content of calcium carbonate is 2 to 15% by weight. Rom type castable refractory. 6. - Claim 1, wherein the alumina cement is a high alumina cement with an S i 02 content of 1% by weight or less
Alumina and alumina-chromium castable refractories as described in Section 1 or Section 2.