JPS6395168A - Spray material for repairing industrial furnace - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a spray material used for repairing worn parts of industrial kilns.

(Prior art) RH-DH vacuum degassing furnace used in the steel industry, hot metal
In industrial furnaces such as molten steel ladles, electric furnaces, and converters, the refractory linings or coatings are damaged by contact with molten iron and slag, but the progress of this damage is uneven. Therefore, it is common practice to spray repair mainly on the parts that are severely worn out in order to extend the life of the furnace.

Here, the spraying materials used in conventional spraying repairs will be explained as follows.

(a) As taught in Japanese Patent Publication No. 55-6598, a spraying material based on a basic material such as magnesia or maguro.

佽) JP-A-49-108113 and JP-A-50-4
As taught in Japanese Patent No. 9311, a spray material to which phosphates, silicates or calcium salts of alkali metals or alkaline earth metals are added as binder auxiliaries.

(C1 JP-A-56-104781 and JP-A-50-1989)
As taught in No. 101409, a spray material in which the structure of the binder is mainly studied, such as using a potassium phosphate salt, a sodium phosphate salt, or a silicate as a binder.

Problems to be Solved by the Invention) However, the sprayed materials according to the above-mentioned conventional techniques (a) to (C) all suffer from chemical wear and tear due to slag, abrasion due to molten iron and slag, or peeling over time from the adhesion interface after adhesion. Therefore, it could not be said that the durability was sufficient.

The present invention has been made to solve the above-mentioned drawbacks of conventional sprayed materials, and by blending zircon sand, zircon flour, or a mixture thereof in a predetermined ratio to magnesia refractory raw materials, the present invention can be made into sprayed materials. It is intended to provide residual expansion properties and to take advantage of the properties of basic spray materials while preventing their drawback, ie, peeling.

(Means for solving problems) The configuration of the present invention will be explained below.

That is, the gist of the present invention is that the refractory raw material mixture contains 5 to 50-t% of zircon sand, zircon flour, or a mixture thereof, and the remainder is a magnesia refractory raw material, and an appropriate amount of a binder. A spraying material for repairing industrial kilns, characterized by the following.

As is well known, zircon sand is a refractory raw material mined in Australia, America, India, etc., and has a particle size of mainly 50 to 300 μm. On the other hand, zircon flour is made by crushing zircon sand into fine particles, and the particle size cannot be specified because it is adjusted appropriately depending on the purpose of use, but it is generally less than 200 mesh, or less than 325 mesh. It is true. and,
The blending ratio of this zircon sand, zircon flour, or a mixture thereof is 5% to the magnesia refractory raw material.
~50wt%, and the reason for this limitation is 5w
If it is less than t%, the peeling prevention effect will be poor, and if it exceeds 50wt%, the erosion resistance will decrease. Particularly preferably 8 to 35-t
%.

On the other hand, as the magnesia-based refractory raw material, synthetic or natural magnesia clinker or brick waste containing these magnesia clinkers as a main component can be used.

In some cases, it is also possible to replace a part of the magnesia refractory raw material with dolomite clinker, spinel clinker-1 limestone, or other refractory raw materials.
It is desirable to reduce the proportion as much as possible so as not to impair the effect of magnesia clinker. The particle size of the magnesia refractory raw material is the same as that of conventional spray materials, for example, 7 cranes or less, preferably 5 cranes or less. Furthermore, as a binder, any commonly used binder may be used; examples thereof include alkali metal, alkaline earth metal phosphates, silicates, borates, aluminum phosphates, etc. Or two or more types can be used. The addition ratio of these binders is preferably about 2 to 104% in percentage based on the refractory raw material mixture.

In addition, one or more types selected from bentonite, clay, dextrin, CMC, etc. may be added as a plasticizer to the spraying material of the present invention, and slaked lime, silica, etc. may be added as a hardening accelerator for the binder. One or more selected from sodium chloride, aluminum chloride, calcium chloride, magnesium sulfate, calcium silicate, chromium slag, etc. may be added, and the addition ratio should be adjusted as described above so as not to impair the effects of the present invention. The outer layer is preferably 10-t% or less based on the refractory raw material blend.

By the way, the zircon sand or zircon flour used in the present invention has a specific gravity of about 4.5 to 4.7, which is particularly large among refractory raw materials. However, by adding fibers in advance at the raw material blending stage, specific gravity separation can be prevented, and the effect of the present invention is even more remarkable due to the homogenization of the structure. Become something. By the way, fibers that can be added include glass fiber, asbestos, magnesia fiber, silica fiber, alumina fiber, and silica fiber.
There are inorganic fibers such as alumina fibers, metallic fibers such as stainless steel fibers, iron fibers, and aluminum fibers, and organic materials such as vinylon fibers, polynisdel fibers, cotton, wool, thread waste, and beaten waste paper.

All of these have the effect of preventing specific gravity separation, but organic substances that are burnt out and decomposed when heated during use and do not remain as impurities are particularly preferred. The proportion of these fibers added differs depending on the specific gravity of the material used, so it is not particularly limited, but if we take organic material as an example, it is 3wt%.
Below, it is preferably 0.01"1 wt%. Also, the dimensions are, for example, a length of 50 days or less and a diameter of 1 inch or less.

Further, in the case of inorganic fibers, the addition ratio is 5 wt% or less, preferably 0.1 to 2 wt%.

The method for spraying the spraying material of the present invention configured as described above uses a dry or wet gun to spray the material onto the surface to be repaired, as in the conventional method.

(Function) After the spraying material of the present invention adheres to the surface to be repaired,
When heated by contact with molten iron, zircon (ZrO□
・SiO□) becomes monoclinic ZnO□ and amorphous S at high temperature.
in, and the resulting zirconia (Z
rO2) No. 1, the expansion associated with the monoclinic C-square transition at around 1,000°C imparts residual expandability to the sprayed material, preventing volumetric shrinkage due to sintering and allowing the sprayed material to peel off from the surface to be repaired. prevent.

Furthermore, since MgO, which is a component of the magnesia refractory raw material, has the property of easily bonding with SiO□ among the zircon components Zr0z and Sin, in the present invention, the combination with the magnesia refractory raw material further reduces the dissociation of zircon. It will promote this.

(Example) Next, examples of the present invention will be described together with comparative examples.

Using the main raw materials listed in Table 1, the spraying material has the composition shown in Table 2 (Examples of the present invention!lhl~13, Comparative Example 1)
~Adhesion ■Hot strength (hot bending strength) by adjusting ~4)
The following test items were investigated: ■ Volume stability (linear change rate) ■ Corrosion resistance (erosion dimensions) ■ Peeling resistance (number of times until peeling) ■ Durability (number of times it can be used). Of these, Comparative Example 1 and Comparative Example 2 have a ratio of zircon refractory aggregate that is outside the range of the present invention, and Comparative Example 3 is a conventional type basic sprayed material that does not contain zircon refractory material. Comparative example 4
indicates a non-basic material mainly composed of zircon and silica. Among the blended raw materials used in the present invention, the chemical analysis values of the main raw materials are as shown in Table 1 (the unit is -t%).
, Table of Test Methods, *l) Adhesion: Sprayed onto magnesia chromium bricks heated to 1,000°C using a dry gun, and expressed as adhesion rate wt%.

*2) Hot bending strength: It was cast into the shape of a 40x40x160m grave, and the bending strength at 1.400°C was measured.

*3) Linear change rate: Cast into a 40x40x160 dragon shape, heat at 400℃ for 3 hours, and pass JISR26.
The linear change rate was calculated according to 54.

*4) Corrosion resistance: A test piece was cast and subjected to a rotary erosion test using a weight ratio of converter slag:steel slab = 4:l as the corrosive agent. The smaller the erosion dimension, the better the corrosion resistance.

*5) Peeling resistance: Spraying is performed using a dry gun on magnesia chromium bricks heated to 1,000°C, placed in an electric furnace, and heated and cooled repeatedly until peeling is observed. Checked the number of repetitions. The conditions for heating and cooling are 1.
, after heating at 500°C for 30 minutes, cooling to 800°C, and repeating this process.

*6) Actual furnace test: R consisting of alumina castable refractories on the inner and outer peripheries and magnesia chromium bricks on the inner periphery.
The immersion pipe of the H vacuum degassing furnace was repaired by spraying using a dry spray gun, and the service life of the sprayed material was investigated. Note that the temperature of the outer surface of the immersion tube at the start of spray repair is approximately 1,000°C. In addition, the durability of the sprayed material is evaluated by visual observation.

As described above, considering the results of the experimental examples and comparative examples according to the present invention, the conventional basic spraying material (Comparative Example 3) is inferior in peeling resistance, and the zircon-silica spraying repair material (comparative example 3) is inferior in peeling resistance. Example 4) has poor corrosion resistance. On the other hand,
According to the sprayed material of the embodiment of the present invention, it is possible to eliminate the peeling caused by sintering shrinkage, which is a drawback of the basic sprayed material, without reducing the corrosion resistance of the basic sprayed material. As a result, in actual furnace tests, durability was approximately 1.5 to 3 times that of conventional products. Also,
Regarding the corrosion resistance test, according to the rotary erosion test, the slag penetration depth of the product of the present invention was significantly shallower than that of conventional magnesia-based sprayed materials, and this is thought to be one of the reasons for the improvement in corrosion resistance. This is thought to be because SiO2 generated by dissociation of zircon becomes vitrified and prevents slag penetration. It is generally known that zircon refractory raw materials are inferior in corrosion resistance to basic slag, but in the present invention, by combining them with magnesia refractory raw materials and by limiting the amount added to a specific range, the corrosion resistance can be reduced. do not have.

(Effects of the Invention) When the spray material of the present invention configured as described above is applied to the repair of damaged parts of industrial kilns, it has good adhesion, extremely excellent durability after adhesion, and is easy to peel off. Since there is no occurrence of any damage, effects such as stabilization of furnace operation, reduction in repair costs due to reduction in spray material consumption and repair man-hours, and improvement in furnace operating efficiency due to reduction in the number of repairs can be achieved. −

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the blended amount of zircon sand and the linear change rate after firing at a temperature of 1,400°C for 3 hours in magnesia-zircon sprayed material, and Figure 2 is a graph showing the relationship between magnesia-zircon sprayed material 2 is a graph showing the relationship between the amount of zircon sand and corrosion resistance.・,'A-4・ :,;-IR・-2 ・--ノ'

Claims (1)

[Claims] A spraying material for repairing an industrial kiln, comprising a refractory raw material composition consisting of 5 to 50 wt% of zircon sand, zircon flour, or a mixture thereof, and the remainder being a magnesia refractory raw material, and an appropriate amount of a binder.