JPS59174578A - Basic 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 This invention relates to the formulation of a basic castable material used as a lining material for various molten metal containers, melting furnaces, metal processing furnaces, etc. The object of the present invention is to obtain a castable refractory that suppresses peeling due to spalling and destruction due to mechanical stress by imparting hot strength.

In recent years, excellent refractory aggregates such as various synthetic products, baked crystals, and fused products have become commercially available, but the development of binders has been relatively slow, and for example, basic castable refractories is typically made by mixing basic refractory aggregate with alumina cement as a binder and curing at room temperature.
In this case, the strength decreases due to the dehydration of alumina cement in the intermediate temperature range of around 700°C during use, and in the case of basic refractories, magnesia is the main component.

Mg0kt in the matrix containing alumina cement
203 CaO-based low-melting substances are formed and the hot strength is significantly reduced. Therefore, basic gear staples # It has the disadvantage that it is prone to peeling due to polling and destruction due to mechanical stress, and has a short service life.

In order to improve this, the following techniques have become known in recent years.

(1) By using ultrafine powder and a de-By agent, the amount of alumina cement used is reduced, and castable casting is performed with low moisture to strengthen the structure.

(2) Using a phosphate binder such as monobasic aluminum phosphate and condensed sodium phosphate together with alumina cement,
Improves strength in intermediate temperature range.

(3) Condensed sodium phosphate with a degree of polymerization of 21 and a CaO source are added to the unfired bricks of the maguro thread, and the CaO source of the blend is added.
By optimizing O/P205 +S i 02, 100 Kp/r:r! The above hot bending strength can be obtained.

(4) Binder phase d that provides the above-mentioned high strength: Sodium lenanite (NaiO・2CaO・P2O5) produced by the reaction of sodium phosphate and CaO source during heating
It is.

(5) Recently, magnesia-based spraying has been done by adding the above-mentioned condensed sodium phosphate and CaO source to the refractory, and in this case as well, the binder phase that forms at high temperatures is sodium lenanite. being considered.

As mentioned above, many examples of improved binders have been reported, but each has the following problems.

The use of the ultrafine powder-peptizer in (1) above can make the structure denser, but since alumina cement and magnesia produce low-melting substances, the hot strength at 1400°C, for example, in the high temperature range is 9/10. − becomes very small.

In addition, in the case of (2) phosphate binding, large amounts of phosphate are used in castable refractories, and since this phosphate acts as an MI agent for alumina cement, even if a flocculant is added. It is trapped by phosphates and cannot be cured, making it impossible to achieve low moisture content and densification of the structure using ultrafine powder, deflocculant, and flocculant.

Regarding (3), (41, and (5)), condensed sodium phosphate and CaO source are added separately, so ■ condensed sodium phosphate has a high solubility in water of about 60%. is easily dissolved in water regardless of the particle size added, and the binder phase formed in the connective tissue of the refractory tends to become smaller.
Therefore, there are many parts that do not participate in bonding, so if the amount of binder added is small, the strength will decrease rapidly. ■For the same reason, only condensed sodium phosphate moves to the heated surface side before use or during heating and drying during the manufacturing process of refractories, resulting in a different concentration distribution in the construction object or product, resulting in uneven bonding. . ■Condensed sodium phosphate reacts violently with basic aggregate when mixed water is added, so it must be neutralized with ammonia etc. to suppress this reaction, and ammonia has a strong irritating odor. There are many problems both in terms of management and the work environment.

In addition, sodium lenanite (Na202CaO=P206), which is the binder phase mentioned above, is an impurity component in the aggregate used in the formulation. If 02 is high.

Both react and the binder phase is destroyed at 1250°C or higher, forming Nagelschmidtite (7CaO=P2O5・2S).
When 102) is produced, Na2O is liberated and enters the silicate liquid phase to produce a low-melting glass.
It is known that hot strength decreases at temperatures above 600°C.

This invention is a basic castable refractory made to solve the problems in the prior art as described above, and uses a basic refractory material as the main raw material and other weakly basic or neutral refractory materials as auxiliary raw materials. It is characterized in that sodium lenanite and alumina cement, which are pre-synthesized binder phases, are blended with aggregate whose particle size has been adjusted with or without addition.

In general, it has not been seen in the past that a binder phase that is produced at high temperatures is synthesized in advance and added, and it is believed that the synthesized binder phase does not provide sufficient strength. However, the inventors found that even if the synthesized binder phase was added to the blend,
Various experiments have shown that sufficient hot strength can be obtained by the synthesis method and usage method, and that the destructive action of the binder phase caused by the S l 02 component in the aggregate can be suppressed by adding alumina cement. Result sure 75
) It is a derivative of Mekokotomei.

First, the binder phase, sodium linapite, is synthesized by mixing condensed sodium phosphate and a CaO source in chemical equivalents and heating it to 750°C or higher, or by heating it to a temperature of 750°C or higher, or
Although various compounds containing Cart P20'5 can also be obtained by caloric heating, they were specifically synthesized as follows.

Synthesis Example 1: One unit of bound sodium phosphate with a degree of polymerization of around 21 and CaCO3 were mixed in chemical equivalents and heated at 1100°C for 6 hours.

Synthesis Example 2 Sodium dihydrogen diphosphate (N a H,!
P04) and CaCO3 are mixed in chemical equivalents, and 100
Heated at 0°C for 6 hours.

Synthesis Example 6: Sodium carbonate (NacO:+), phosphorus pentoxide (P2α) and CaCO3 are blended in chemical equivalents, and 1
The mixture was heated at 000°C for 1 hour.

As a result of X-ray diffraction, the mineral phase of each of the above synthetic products is β
-Most of the phase was composed of sodium lenanite and a trace amount of α-sodium lenanite was detected. The results of observing each composite product using a scanning electron microscope are shown in photos 1 and 2.6 of the attached reference material. Reference photo 1 (synthesis example 1 above), reference photo 2 (synthesis example 2 in A1r), and reference photo 5 (synthesis example 6 above) are all 200x magnification.
N) The size of the crystal grains of IJ umrenanite is 5 to 10 μm in Synthesis Example 1, and 5 to 10 μm in Synthesis Example 2.
20 to 50 μm 2 Synthesis Example 6 has a thickness of 40 to 200 μm. It was also found that the size of crystal grains can be controlled by changing the heating temperature and heating time according to necessity.

The following characteristics were found by crushing the sodium lenanite crystals synthesized as described above and blending them into a refractory aggregate.

1) Since it is not blended as sodium phosphate, it is possible to densify the structure of large, castable materials that can be reduced in water content by using ultrafine powder, deflocculating agent, and flocculant, thereby improving strength.

2) Since synthetic products have very low solubility in water, the blended particles act as a binder phase, making it possible to control the size of the binder phase. Specifically, by crushing and sieving, particles of 100 mesh (147 μm) or less, 200 mesh (74 μm) or less, 625 mesh (
46μm) J''W, lower, 20μm or less, 10μηI or less, etc., can be prepared as needed, and castable refractories can be created by increasing the number of fine particles of several μm, which are particularly effective for bonding. gives high hot strength.

6) For the same reason, the binder phase does not move during heating and drying of the refractory, so a uniform structure is created from the heated surface to the inside.

4) The synthesized sodium lenanite has little reaction with basic aggregates such as madanesia and dolomite when added to kneading water, and is easy to handle.

Next, add fire-resistant aggregate ((blended) IJ umrenanite in an amount of 1 to 15 oz per 1 oz of aggregate).
% by weight is preferred. The amount of binder phase added is 1
If the number is less than that of the holder, the refractory will not have sufficient hot strength,
On the other hand, it has been found that when the weight resistance exceeds 15%, the bond between the binder phases increases, but the bond is weak, and the eating properties are reduced.

Next, alumina cement is added for the purpose of suppressing the destructive action of the binder phase caused by the 8102 source as described above. The conditions under which schmisotite (7CaO-P20s .2Si02) is produced were investigated in a laboratory.

That is, as silica sources, amorphous silica, silica sand, synthetic mullite (3Atz 03.2SiOz), synthetic forsterite (2Mgo-81o2) and synthesized 2CaO-
8102 was selected and sodium lenanite (Na2o・
As a result of reacting with 2CaO-P255) in a wide range, 2C
Squid that does not react with aO・S i 02, 5iOz
75Z 1400 in the case of amorphous silica in the composition region more than twice the chemical equivalent of 7CaO・P2O5・2SiOz
℃, or from 1600℃ for silica sand, mullite, and forsterite 7CaO・P20S・2S i'o2
It was found that a reaction progresses that generates and decomposes the binder phase.

Next, as a result of various studies on substances that inhibit this reaction, it was found that adding SO to alumina cement is effective, and adding CaO and At, which is the main phase of alumina cement, was found to be effective.
203 reacts with the S i 02 source to form 2CaO・5iOz
and Gehlenite (2CaO-A720s ・S i
It was found that the effect of decomposing sodium l and renanite was eliminated by fixing it as o+).

As the alumina cement added in this invention, J
ISI Alumina Cement, Denka High Alumina Cement, Denka Alumina Cement Super, Alcoa CA
-25, Sekar 250, etc. can be used, but those with a low SiO2 content are more effective.

It is desirable that the amount of alumina cement blended is 1 to 8% based on the total amount of the refractory aggregate and sodium lenanite. If the weight is 10% less, the room temperature strength will be low and the hot strength will decrease because the reaction between 5iOz and sodium lenanite at high temperatures (destructive action of the binder phase) cannot be suppressed. On the other hand, if the temperature exceeds 8, the amount of liquid phase formed increases due to the low-melting components in the alumina cement being trapped, resulting in a decrease in corrosion resistance.

The refractory aggregate to which sodium lenanite and alumina cement are added is magnesia clinker.
, chromite, dolomite clinker - Particle size adjusted using one or more basic materials as main raw materials,
Alternatively, one or more of spinel, chromium oxide, alumina, graphite, and calcium carbonate may be added as an auxiliary raw material to adjust the particle size to a predetermined value.

The purpose of adding the auxiliary raw materials in the above aggregate is mainly as follows.

Spinel: It has a smaller thermal expansion coefficient than magnesia, so it is especially added to fine powder parts to improve heating characteristics.

Chromium oxide: Prevents slag infiltration.

Alumina: To obtain a cisvinyl bond through reaction with magnesia, and to create a densified structure as an ultra-fine powder.

Graphite: has the property of not being easily wetted by molten metal or molten slag, so it prevents infiltration of molten material.

Calcium carbonate: Enriches the matrix with CaO components, reacts with the slag when it enters the slag, and raises the melting point of the slag.

In addition to the aggregate, binder phase, and alumina cement described above, the castable refractory of this invention also contains sodium phosphate, polyphosphate, oxycarboxylate, Naphthalene sulfonate, and carboxylic acid, carboxylate, citric acid, borax, boric acid, as a hardening modifier for alumina cement.
It is effective to add a small amount of Ca(OH)zL r COs and metal aluminum or the like as a drying accelerator, appropriately selected, to improve workability.

Table 1 shows the formulation contents and test results of Examples of the present invention and conventional products (Comparative Examples).

As is clear from Table 1, alumina cement or 1d
The high-temperature hot strength of the conventional products of Comparative Examples 1 to 6 using Ca (OR)2 and sodium phosphate as the binder agent is all 10 K9/cA or less, whereas the example of the present invention has a hot strength of 62 K9/cA or less. It showed an extremely high hot strength of ~110 Ky/crl.

As explained above, this invention improves high-temperature hot strength compared to conventional products by adding a pre-synthesized binder phase to basic aggregate and alumina cement to suppress the phenomenon that the binder phase is destroyed at high temperatures. Compared to glaze melting metal containers and industrial furnaces, it is possible to obtain a significantly superior TTK of 10 times, and a more average structure.
It can achieve a long life as a large-sized product.

Daikonjin Bento 3-ψ± Kimura Sanro

Claims (1)

[Claims] 1. A refractory aggregate prepared by adjusting the particle size of one or more of magnesia clinker, chromite, and dolomite clinker, or spinel, chromium oxide, alumina, graphite and A basic castable refractory characterized by adding synthesized sodium lenanite and alumina cementola to a refractory aggregate whose particle size has been adjusted by adding one or more types of calcium carbonate. 2. The basic castable refractory according to claim 1, wherein the amount of sodium lenanite added is 1 to 15% by weight of the content with the refractory aggregate. 6. The basic castable refractory according to claim 1 or 2, wherein the amount of alumina cement added is 1 to 8 wt% based on the total frK of the refractory aggregate and sodium lenanite.