JPS6081058A - Magnesia baked 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 a refractory G characterized by spinel dispersed periclase aggregate grains and having excellent erosion resistance, thermal shock resistance and structural spalling resistance.

Originally, magnesia is very advantageous as a refractory material for steelmaking due to its high melting point and high chemical stability, but in order to overcome its relatively large coefficient of thermal expansion, it is The problem is that it has poor resistance to thermal shock. In order to improve this drawback, there are mags and black bricks manufactured by adding chromite to magnesia, mags made by combining two magnesia grains with graphite, and carbon bricks. However, with the advancement of steelmaking technology, the conditions for these furnace materials are becoming increasingly severe, and furthermore, restrictions are beginning to appear on the components contained in furnace materials for special steel refining (particularly for the purpose of clean steel). Under the processing conditions of low chromium, extremely low sulfur, extremely low carbon steel, etc., the material itself becomes a problem.

As a material that meets the above points, red sea bream/sheer spinel type material can be considered. However, although attempts have been made to develop magnesia-spinel refractory bricks, which are theoretically expected to be superior, there have been no examples of successful practical use. The main reason for this is thought to be that the form of existence of spinel was not suitable for improving its properties. That is, if spinel is simply uniformly dispersed in M2O, structural spalling due to slag infiltration cannot be completely suppressed, and sufficient hot strength is also difficult to obtain. Therefore, the effective existence form of spinel is its existence as a uniform layer with a thickness of /μ to 10 μ at the periclase grain boundaries, which contributes to improving hot strength and protecting periclase, and O51 in the periclase crystal grains suppresses excessive growth and disperses and absorbs internal stress caused by expansion and contraction of periclase.
It must be present as microcrystalline grains of less than 1 to 3 microns.

If spinel does not characteristically exist at the periclase grain boundaries with a thickness of 0.5 μm to 10 μm, the hot strength is poor and structural spalling is likely to occur. If there are no microcrystals of ~3μ, the thermal shock resistance is poor.

This invention was invented as a result of various researches based on the above-mentioned findings, and the gist is that M.
qOJ'! ~93%, Al2O3/S ~5%, O
tl O/, 0 to 2.0%, and other components of 2% or less.

As a microstructure, spinel fills the periclase grain boundaries with a thickness of /μ to 10μ, and spinel grains are deposited within the periclase grains with a size of O5-3μ. Spinel-dispersed periclase aggregate grains obtained by rapid cooling treatment after hot melting so as to be dispersed, as a dispersion device in the refractory, containing go% or more in the coarse and medium grain parts and 50% or more in the fine grain part, The rest is M O and 0% or more + A'203
This is a magnesia-based fired refractory characterized by having excellent erosion resistance, thermal shock resistance, and structural spalling resistance by comprising fine particles in a proportion of 20% or less.

This invention will be explained in detail below.

The microstructure of the spinel-dispersed periclase aggregate grains, which is a feature of the magnesia-based fired refractory in this invention, is Al
It is thought that this is made up of the amount of 2O3 and CaO contained as a trace component, and the appropriate quenching treatment after hot melting. That is, MfOf5~95%, “203/!;
-3%, a a o /, 0 to 2.0%, and other blends adjusted to 2% or less are heated at 2000°C ~ /70
By rapidly cooling to around 000, spinel uniformly fills the periclase grain boundaries with a thickness of /μ to /011, and spinel microcrystal grains with a size of 05 to 3μ are deposited within the periclase grains. Dispersed spinel-dispersed periclase aggregate grains are obtained. A12o3/j-5%, OaO/, Q below this heat melting and rapid cooling treatment
The range of ~2.0% is the result of several experiments conducted by the inventor and others.

173,000 to 1g3 while having the above prescribed ingredients
The Talinker obtained by firing 00c does not have the desired microstructure, but has a structure in which periclase and spinel are simply mixed uniformly. In this organization (
Since most of the bonds between crystals are periclase-periclase bonds, resulting in a structure similar to that of magnesia bricks, it is considered to be inferior in heat S shock resistance and structural spalling resistance. In addition, the structure formed under firing temperatures of about 750°C to 500°C is likely to undergo structural changes when bricks are exposed to high temperatures for a long time, causing structural spalling. Tissue stability by highly wet and heated vagina is required.

On the other hand, when a given compound is thermally melted and then slowly cooled, there are few dispersed layers of spinel microcrystals within the periclase crystals, and the thermal shock resistance is poor.
Appropriate rapid cooling and processing to about 700°C is required.

For CaO shields, if 20% or more, 2 digits 15 M f O-000-AI, 03 at the periclase grain boundaries
Excessive production of low-melting substances causes a decrease in hot strength and the size of spinel microcrystals grows to 3μ or more.

Furthermore, if O(l O/, Q% or less), the filling of spinel at the periclase grain boundaries becomes non-uniform.

Next, regarding the amount of Al2O3, if it is less than 5%, the amount of spinel filling in the periclase grain boundaries is insufficient, and the amount of spinel microcrystal grains dispersed within the periclase grains is also small, so the thermal shock resistance and structural spalling resistance are reduced. sexuality is impaired. Also, if the amount of Al2O3 exceeds 73%, the erosion resistance decreases. cause.

The content of the spinel-dispersed periclase aggregate grains in the large-sized material is set to 02 or more in the aggregate part and 50% or more in the bonded parts because of the excellent heat resistance of the spinel-dispersed periclase aggregate grains and the rigid structure of the substrate. This is to make the refractory sufficiently exhibit IJing properties, and the reason why the remainder is set to be MqOgO% or more and A12o3 to be 20% or less is because 0% M2O is added to the M2O.
This is because if the Al203 content is less than 20% or more than 20%, the erosion resistance will decrease.

EXAMPLES Examples of the red sea bream and sea bream fired refractories according to the present invention will be described below together with comparative examples, and the present invention will be explained in detail.

Table 1 shows the existence form of spinel in Talincar produced under the conditions of Yuzu. In the clinkers of A and above that are outside the scope of the present invention, spinel does not have a predetermined existing form.

Table 1 shows spinel m grains within α-kehericlese grains.

β indicates a spinel layer at the periclase grain boundary.

2) Test method: tioxao×n in a high frequency induction furnace.

Steel (SSM/) and slag were melted in a container lined with a mm-shaped sample, and the melting loss rate of the slag line portion was measured.

Basicity of slag: 2.0 (M & O = 3%) Thermal conditions: /Otsu 50°C ~ /7gO°c x 4 hours 3) Test method: The slag placed in the Kurofune crucible was melted in a high frequency induction furnace,
20X 20X/302 preheated above the crucible
A 71 m-shaped sample is immersed in the slag and rotated. After the sample was lifted out of the slag and cooled, the erosion rate of the slag immersion area was measured.

Basicity of slag, Otsu 0 (A1203=30%) Thermal conditions: /6za0~/730°C x 20 minutes Sample rotation speed: /Qr, ir, m.

Hiroshi) Test method: In an electric furnace heated to 7100°C, 5
After inserting half of a 11 mm sample into the sample and heating it for 1S minutes, it is immediately poured into water and cooled.

Table 2 shows the state of cracks that occurred in the sample by visual observation. The number of Jg was displayed.

/0. Few cracks, ///, 2 cracks or less, ///5
．． Articles 3 to 5, ////, Article S and above'' 2. Seating.

Collapse, 5) Test method; JO x 60 x //1 in a cylindrical drum
A sample of 11n7n shape was lined and heated in a propane-oxygen flame/700'C trench while rotating the drum, and then slag (0/s = , 2.0) was introduced.

After further raising the temperature to 7750°C, heating is stopped, and air is blown onto the sample surface to rapidly cool it to around 500°C. After repeating this heating and cooling three times, the sample was cut and the degree of cracking was determined by visual inspection.

This is a brick made by mixing Example AI+ A2+ A3+ A4 in Table 2 with 9 anchors of the glue A in Table 1 within a predetermined range, and has higher durability when compared with the group of bricks outside the invention shown as comparative examples. Bath + ta properties and thermal shock resistance.

Excellent structural spalling resistance. When compared with Zaraani Maguku Semi-bond and Maguku V' direct bond bricks, the difference is clear, and the bricks of the present invention are far superior. In general, Madai N'a bricks have high melting resistance due to their high moltenium oxide content, but they are significantly inferior in thermal shock resistance and structural spalling resistance.

When a brick of the same quality as Example A1 of the present invention was used for (1) slag line, it became possible to extend the service life by approximately 1/1 of the service life of conventional magcro direct bond bricks.

[Brief explanation of drawings]

The drawing shows an electron micrograph of a brick structure according to the present invention. The magnification is 7,000 times Procedural Amendment IIl□ (i: ujza July 17, 1977, Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office) Display of the case Showa 5g I1 Special Patent Application No. 111 No. 191116
No. 7 No. 2, Relationship with the title of invention case Special feature 1v “Applicant 4/Agent 〒, 2㎡Address: Riyu Yta-ku, Meizuya City j <j--]' 1]/
Raku / 0-Share 8 Contents of the correction 411 Contents of the sleeve stop of the paper /, Akira f, lll, 'shi! Let's define the range σ terms as follows: 1 chemical component A) IψzQ33~9j% + A
'20+17S~S%l O/J O/, 0-;2.0
%, what is the component ratio of 32% or more? t&4
As a periclese crystal f1/, the periclase crystal has a thickness of /μ ~ 10/μ and characteristically emits light of 1.
! Spinel dispersed periclase aggregation obtained by quenching and burying 7 norms after hot melting so that it is deposited and dispersed with a size of p ~ 3//. % or more Q・2 fine grains N cloth contains SO% or more, the remainder is 1φqOl; 0% or more, A /, α fine grains 20
By performing IM formation at ν)1 of % or more, fQ
Leta bath resistance 41. l 11, l radiant heat? Jts management and he; 1llJ'::'f a sporlingj raw] makushisia-yaki+j'y,
, face 1 671 course 01 . 2. 1! If details, 4 (page 3, line 3, 1 special 1/I
: and -1 notes and precepts 1-characteristics'' on the sleeve. 3. The third one is (1st S row L1's 1st Hl,), 1st
-1 is amended to read ``1. t Same page S page 1 Otsu? TI', J's 1st invention and Σ(Next experimental result?) 1-shot・IJ] I17 Corrected 11th century as ``The result of several experiments in 17'', S same number. 70 ji L No. 2. "Next 2 people": Unisode 115 tsuru. Procedural amendment dated March 3, 1982 Kazuo Wakasugi, Commissioner of the Patent Office ・ 1 Indication 11 of Naka A 11 (3 Japanese 5 g < 1 Patent Station I No. 17/137
Relationship with Case No. 211 Patent Applicant 4 Agent Address Name 1 J Kaiichi Netsuhi” Ward 4 (Upper-Cho 1” / J10 No. 6 Number of Inventions Increased by Amendment 7 Subject of Amendment 8. Contents of the amendments Oki IA1 (no's) Contents of the amendments The brief explanation of the drawings section has been added to the section below. ', shows an IL microscopy image. Magnification: 1000x.

Claims (1)

[Claims] Based on chemical analysis, the weight percentage is MqO 5~S%, A7j, ・
/、! ; ~! %, aao/, Q ~ 20%, and other component ratios of 2% or less, the microstructure is that spinel fills the periclase grain boundaries with a thickness of ~ 10μ, and the periclase Spinel-dispersed periclase aggregate grains obtained by rapid cooling treatment after hot melting so that spinel crystal grains with a size of 05 μm to 3 μm are precipitated and dispersed in the crystal grains are mixed in coarse and medium amounts in the resistor. It contains 0% or more in the grain group, and sO% or more in the fine grain part, and the remainder is 0 Mq o 8
A magnesia-based fired refractory characterized by having excellent erosion resistance, thermal shock resistance, and structural spalling resistance by comprising A'203 fine particles in a proportion of 0% or more and 20% or less.