JPH01257171A - Refractory material for thermal spraying and production thereof - Google Patents

Abstract

PURPOSE:To form a corrosion resistant refractory lining having satisfactory adhesive property, a high bonding rate and a uniform structure on an industrial furnace by bonding primary particles of a refractory material with an inorg. binder, removing volatile matter by heating, and using the resulting secondary particles. CONSTITUTION:The refractory material such as alumina, magnesia or chromite ore is pulverized to obtain primary particles of <=40mum particle size. The inorg. binder such as sodium silicate is added to the primary particles, a proper amt. of water is further added as required and they are well mixed and granulated by rolling granulation or other method to obtain secondary particles. These particles are heated at 400-1,000 deg.C to remove matter evaporating at <=1,000 deg.C and the resulting secondary particles of 30-300mum particle size are used as a refractory material for thermal spraying.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal spray refractory material used for forming and repairing refractory linings of industrial furnaces, and a method for producing the same.

[Conventional technology]

For example, as described in Japanese Patent Application Laid-Open No. 57-126964, in recent years flame spraying has been used to form and repair refractory linings for industrial kilns, in which refractory powder is flown through a high-temperature, high-velocity flame, melted, and sprayed. started to be used.

For thermal spraying in ordinary industrial furnaces, methods using LPG-oxygen, kerosene-oxygen, coke powder-oxygen flame, plasma, etc. are adopted.

This method of spraying refractory materials by thermal spraying is a relatively new technology and there are many unresolved problems.

One of them is the problem of particle morphology of thermal spray materials. In other words, if the thermal spray material is made into fine powder to make it more easily melted by the flame, its fluidity will be impaired, the ejection from the nozzle will become pulsating, the degree of melting of the material will be uneven, the structure of the thermal spray layer will become brittle, and Conversely, if the particle size of the material is increased,
The problem is that the parts are welded without being completely melted.

Therefore, as a refractory material that satisfies the requirements of both prevention of pulsation in the nozzle and ease of melting, a thermal spray material consisting of a structure in which large particles are bound together with a structural binder to form secondary particles has been developed. It is disclosed in Japanese Patent No. 10418. Since this thermal spray material is composed of secondary particles having a large particle size, which are made up of a large number of primary particles bonded together, there is no pulsating jetting caused by the small particle size.

In addition, the missing particles are fine particles, and the flame is quickly transmitted through the sprayed material due to the voids between the primary particles formed when the organic binder is burned away by the flame heat after being ejected from the nozzle, so it easily melts. There is an effect.

[Problem to be solved by the invention]

However, when the primary particles are bound using such an organic binder, the water or the binder decomposes when passing through a flame, making it easy for the missing particles to scatter. For this reason, particles of the refractory material fly through the flame separately, which tends to make the structure of the refractory lining uneven, and the number of scattered particles increases, resulting in the generation of dust. As shown in Comparative Example 3 of Publication No. 10418, secondary particles are simply composed of fine primary particles, and even when sodium phosphate is used as a binder, the binder is not burned out and -
Since the porosity between secondary particles is low, it has drawbacks such as difficulty in melting and poor thermal sprayability.

An object of the present invention is to eliminate the drawbacks of thermal spray powders made of secondary particles using an organic binder or secondary particles only bound with an inorganic binder, and which has good adhesiveness and adhesion rate, and The object of the present invention is to obtain a refractory material for thermal spraying that can provide a refractory lining for an industrial kiln that has a uniform structure and is corrosion resistant.

[Means to solve the problem]

The refractory material for thermal spraying of the present invention has secondary particles formed by bonding missing particles with an inorganic binder.
It is manufactured by removing substances that evaporate at temperatures below 1000°C by heat treatment at a temperature of 0°C to 1000°C.

As a result, it is possible for the missing particles to pass through the thermal spraying flame while remaining in the state of secondary particles, which reduces scattering of the sprayed particles and improves meltability, resulting in a refractory lining structure that is It will be kept uniform.

Fireproof materials to which the present invention can be applied include alumina, magnetic screw zirconia, zircon, and silica.

Any material such as mullite, chromite, spinel, etc. can be used.

The refractory material for thermal spraying of the present invention is prepared by pulverizing the refractory material into ultrafine particles of 40 g or less to obtain primary particles, adding an inorganic binder to this, adding an appropriate amount of water as necessary, and thoroughly mixing. , well-known spray drying granulation, fluidized bed granulation, transfer granulation,
Secondary particles are obtained by a granulation method such as compression granulation or crush granulation.

The inorganic binder to be added is sodium silicate.

40 such as aluminum phosphate, alumina sol, silica sol, etc.
Any material having the property of exhibiting bonding strength at a temperature of 0° C. or higher can be used. The amount of inorganic binder used in granulation is determined so as not to reduce the fire resistance of the sprayed layer, but it is usually preferable to add it in an amount of 2 to 20% by weight based on the fire resistant material. If the inorganic binder content is less than 2% by weight, secondary particles are likely to decompose while passing through the thermal spray flame, and if it exceeds 20% by weight, the fire resistance will decrease and the physical properties against slag will deteriorate.

Furthermore, as the granulation method, spray drying granulation, fluidized bed granulation, transfer granulation, etc., which are easy to obtain relatively spherical secondary particles, are preferable because the fluidity of the thermal spray material is further improved.

The granulated secondary particles are heat-treated at 400°C or higher and 1000°C or lower to remove substances that evaporate at 1000°C or lower. Even if the temperature is lower than 400° C., water will evaporate, but this is not preferable because crystal water and the like in the thermal spraying material will remain, and the thermal spray powder will evaporate while passing through the thermal spraying frame and decompose the secondary particles. Further, if heat treatment is performed at a temperature exceeding 1000° C., the fine powder of the missing particles is sintered and bonded, which lowers the heat absorption ability of the secondary particles and lowers the melting ability, which is not preferable. Depending on the type of material, the problem of secondary particle sintering can be solved by using fine powder that is difficult to sinter even at temperatures exceeding 1000°C, but in order to remove evaporated matter in the binder,
A temperature below 00°C is sufficient.

In the present invention, the particle diameter of each particle is 4 on average for the primary particle.
0- or less, the secondary particle size is 30 to 300 m, and is appropriately determined according to the nozzle hole diameter of the thermal spraying equipment, flame heat capacity, etc. -The particle size of the second particle is 40u! If it exceeds n, it becomes difficult to melt, and if the secondary particle diameter of the secondary particles deviates from the range of 30 to 300 μm, the thermal spray material will pulsate out from the nozzle during thermal spraying, resulting in uneven melting, resulting in a good thermal spray layer. I can't.

〔Example〕

Regarding chromite ore and calcined alumina powder consisting of primary particles with a particle size of 0.5 to 40 mm, chromite ore 6
0 parts by weight, 40 parts by weight of calcined alumina powder, 3 to 6 parts of sodium silicate or alumina sol, and 15 parts of water for a total of 100 parts by weight of chromite ore and calcined alumina powder.
~30 parts were added and granulated using a transfer granulator, and the granulated secondary particles were heat-treated at 600°C for 10 hours.

After the heat treatment, it was passed through a 300 μm sieve.

The above secondary particles are L P G1ONm'/hrS0245
Nm'/hr, powder supply rate 20 kg/hr, spraying distance 400 mm, burner parallel movement speed 4 m/lTl1n, preheating was performed using an LPG O2 flame spray gun for 10 min.
Thermal spraying was carried out on a sprayed surface of 0.25 m'' at 00°C.

For comparison, we used materials that did not use a binder, materials that used PVA (polyvinyl alcohol) as an organic binder, and inorganic materials. 4 (20 even if a binder is used)
(heat treated at 0°C and 1400°C) was thermally sprayed under the same conditions as in the previous example. The results are shown in Table 1.

As is clear from the table, among the comparative products thermally sprayed as primary particles, Comparative Example 1, which had small particles, had poor fluidity and was not uniformly ejected from the nozzle. Furthermore, in Comparative Example 2 using large particles, the sprayed layer formed was non-uniform because it was difficult to melt. In addition, even if secondary particles were used, Comparative Example 3 using PVA as a binder
．． Comparative Example 4 and Comparative Example 5, in which the heat treatment temperature was low even though sodium silicate was used as the binder, had poor thermal spraying characteristics because the binder decomposed in the thermal spraying flame.

In addition, even if sodium silicate is used as a binder, in Comparative Example 6 where the heat treatment temperature is high, the meltability of the thermal spray material decreases.
Adhesion rate is low.

On the other hand, in the thermal spraying refractory material according to the present invention, the primary particles having a particle size of 40p or less are treated with an inorganic binder, sodium silicate, to a secondary particle size of 30 to 300s+.
By granulating it into secondary particles and heat-treating it at 600°C, it satisfies the fluidity and meltability of the powder, and reduces scattering (
A dense and good sprayed layer could be formed.

(Hereinafter, the margins of this page) [Effects of the Invention] The fireproof material for thermal spraying of the present invention has good powder fluidity and meltability, and the binder does not decompose even when passing through a thermal spraying flame, so it is possible to suppress the generation of dust. In addition, the adhesion rate during thermal spraying is good, the structure of the applied body is dense and uniform, and it is possible to produce a corrosion-resistant refractory lining for industrial furnaces.

Claims (2)

[Claims] 1. Primary particles made of refractory material with a particle size of 40 μm or less are bound together with an inorganic binder, and
A refractory material for thermal spraying consisting of secondary particles of 30 to 300 μm that are heat-treated at temperatures below ℃. 2. A large number of primary particles made of a refractory material with a particle size of 40 μm or less are bonded, and secondary particles with a secondary particle size of 30 to 300 μm are bonded by an inorganic binder. A method for producing a refractory material for thermal spraying, characterized by heat treatment.