JPS63190155A - Highly siliceous material for thermal spraying - Google Patents

Abstract

PURPOSE:To obtain a highly siliceous material for thermal spraying forming a thermally sprayed repaired body which can withstand use over a long period by mixing SiO2 with Al2O3, CaO, Fe2O3 and Na2O in a specified ratio. CONSTITUTION:This highly siliceous material for thermal spraying consists of, by weight, 93.9-99.6% SiO2, <=1.5% Al2O3, <=2.0% CaO, <=1.0% Fe2O3 and 0.4-2% Na2O. The material is a powdery material suitable for the repairing of a kiln, especially a coke oven by flame spraying. The material forms a thermally sprayed body having >=about 60% degree of crystallinity immediately after thermal spraying and the volume is hardly shrunk by transition from the glass phase to the crystal phase, so cracking followed by stripping is not caused. The material gives a thermally sprayed repaired body having a coefft. of thermal expansion nearly equal to that of silica brick, independent of repeated changes of heat and capable of withstanding use for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a powder material for large flame thermal spraying used for repairing furnaces, particularly coke ovens.

[Conventional technology]

Currently, thermal spraying materials commonly used for repairing coke ovens include 5i02-based refractory materials such as AI! to
s, Fezes, Cab, MgO, Name,
Some contain K2O etc. After thermal spraying, this thermal spray material becomes glassy, which follows the expansion and contraction of the silica bricks that form the walls of the coke oven due to thermal changes when taking coke in and out, preventing cracks from forming. It has the characteristics of

[Problem that the invention seeks to solve]

However, when such a glassy thermal sprayed body is used for a long period of time, glass crystallization progresses and the volume changes, so especially when the thermal sprayed body is formed over a wide area,
Cracks occur and it becomes easy to peel off from the adhesive surface with the brick.
There is a problem that satisfactory durability cannot be obtained.

The problem to be solved by the present invention is to eliminate the disadvantage of short life due to crystallization when the high-silica sprayed material forming the above-mentioned glassy sprayed body is used for repairing a kiln.

[Means for solving problems]

The present invention was completed based on the basic idea that defects caused by glass crystallization can be eliminated by controlling the progress of crystallization.

That is, as a result of investigating the relationship between the elapsed time immediately after spraying and the crystallization rate of the sprayed body obtained by spraying the sprayed body onto a silica brick wall maintained at 1000°C using a flame spraying device, it was found that This is based on the knowledge that in the case of a thermally sprayed body having a crystallization rate of 60% or more, the repaired body will not be adversely affected by the subsequent progress of crystallization.

Specifically, the thermal spray material of the present invention has 5iO293,9~
99.6% by weight, ^1zoa 1.5% by weight or less, (:a
02.0% by weight or less, Pe20s 1.0% by weight or less, and Na200.4 to 2% by weight, and has the property of crystallizing immediately after thermal spraying.

In the present invention, SiO
In order to obtain a crystallization rate of 60% or more, 93.9% by weight
is necessary. However, if it exceeds 99.6% by weight, only a crystallization ratio of 60% or less can be obtained. Therefore, the blending amount of 5i 02 is 93.9% by weight or more and 9
It needs to be 9.6% by weight or less.

^RzOx and CaO are necessary in order to make the repaired body to be formed similar in composition to silica brick used as the lining of a kiln.

However, in the case of ^1xos, 1.5% by weight of the total formulation,
In addition, in the case of CaO, if it exceeds 2.0% by weight, it tends to vitrify, resulting in the drawback that only a crystallization ratio of 60% or less can be obtained immediately after thermal spraying.

In addition, Fe2O3 needs to be 1.0% by weight or less in order to increase the crystallization rate of the sprayed body to 60% or more.

Furthermore, Na and O are essential for making the construction material glassy, but if it exceeds 2% by weight, the fire resistance of the sprayed material will be low and it will become too soft, causing problems during construction.
If the content of a2O is less than 0.4% by weight, the flame-sprayed material will have too high a fire resistance and be difficult to work with, so it should be in the range of 0.4 to 2% by weight based on the total composition.

The thermal spray material of the present invention is obtained by mixing the above-mentioned components and having an overall particle size of 0. ．． The particle size may be adjusted and used so that it is 21u or less. In addition, starting materials such as fused silica, silica sand, silicate ore, alumina, sodium silicate, and silica brick scraps may be prepared in any combination, and the chemical composition may be heat-treated to uniformly mix these raw material powders. Preferable for adjusting within the range.

The above-mentioned heat treatment temperature is required to be 500° C. or higher in order to evaporate the crystallization water of the raw material powders and bond the raw material powders together and sinter them. However, the temperature needs to be below 1000°C to prevent too much evaporation of Na=0.

For the above reasons, the heat treatment temperature should be within the range of 500°C or more and less than 1000°C.

The present invention will be explained below with reference to Examples.

〔Example〕

A silica brick medium type (115
x 230 x 5 Qmm) and each silica stone
Thermal spray materials having the chemical compositions listed in Table 1 were sprayed onto the moths.

The spraying conditions were LPG: 15N rn'/Hr,
02: 7ON m'/)Ir.

Thermal spray powder amount: 50 kg/) Ir, burner movement speed: 4 m/min.

The distance between the burner and the brick wall surface (115 x 230 + mm surface) = 300 mm, the spraying time was about 20 seconds, and the thickness of the sprayed layer per silica brick drum shape was about 20 mm near the center.
It was about 1111T1.

One type of thermal spraying material is sprayed onto 6 drum-shaped silica bricks to form the above sprayed layer, then the first one is sprayed 1 minute after spraying, and the second one is sprayed 5 minutes after spraying. After the elapse of time, the third sheet was taken out from the furnace 10 minutes after the thermal spraying and rapidly cooled, and the crystallization rate of the thermally sprayed body was measured.

The remaining three drum molds were transferred to a furnace at a higher temperature of 1,300°C within one hour after spraying, and the changes in the sprayed body after one, two, and three months were examined to determine whether there were any cracks between the sprayed body and the bricks. The presence or absence of peeling was examined.

The crystallization rate is measured from the area intensity ratio of X-rays and is expressed as the content of cristobalite and tridymite.

Based on the test results in Table 1, an actual furnace test was conducted in an actual coke oven. The thermal spraying materials used are shown in Table 1)
Nα8. As a result of using Nα91Jα10, a peeling phenomenon occurred in Nα8 in the first year and in Nα9 in the 6th month, and Nα10
remained in good condition even after one and a half years.

(Hereinafter, the margin of this page) [Effects of the Invention] The thermal spray material of the present invention forms a thermal spray material with a crystallization rate of 60% or more immediately after thermal spraying, so even if thermal spraying is performed over a wide area, the glass phase does not change. There is little volumetric shrinkage during the transition to the crystalline phase, and no cracks that may lead to peeling occur. In addition, since it is high in silica and highly crystalline, it exhibits almost the same thermal expansion as silica bricks used in coke ovens, etc., so it is resistant to repeated changes in heat due to the loading and unloading of coke, and does not cause adverse effects due to aging. Therefore, it is possible to obtain a thermal sprayed repair body that can withstand long-term use.

Claims (1)

[Claims] 1. SiO_293.9-99.6% by weight, Al_2O
_31.5% by weight or less, CaO_2, 0% by weight or less, F
e_2O_31.0% by weight or less and Na_2O0.4
High siliceous thermal spray material consisting of ~2% by weight.