JPS59110713A - Vessel for dephosphorization treatment of hot metal - Google Patents

Abstract

PURPOSE:To extend the life of vessel by improving the corrosion resistance to sodium carbonate family slag, by lining the vessel for dephosphorization treatment of hot metal with refractory containing a fixed ratio of carbon and silicon nitride making main body of alumina aggregate. CONSTITUTION:At least the slag line part of the vessel for dephosphorization treatment of hot metal is internally lined using the alumina.carbon.silicone nitride refractory or alumina.carbon.SIALON refractory containing 5-20% carbon and silicon nitride or SIALON. Thus, the corrosion resistance to the sodium carbonate family desulphurizing dephosphorizing reagent is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hot metal processing vessel using a soda carbonate flux, and a refractory lining thereof.

Conventionally, desulfurization agents mainly composed of CaC2 or CaCO3 have been used in the desulfurization treatment in a mixed pig iron car or hot metal ladle in the preliminary treatment of molten iron, but recently a soda-based flux has been used to remove S and P in the hot metal. Simultaneous desulfurization and dephosphorization methods that simultaneously remove

Naz co is generally used as a carbon-based soda flux.
3, Na2304, iron ore, manganese ore, etc. are used, and this has excellent properties as a desulfurization and dephosphorization agent for hot metal. However, on the other hand, it has a low melting point and low viscosity, and has a large corrosive effect on the refractory lining of the processing container. Conventionally, the lining refractories for the above-mentioned processing vessels have mainly been Aj20z-Si 02 series chamotte refractories, high alumina refractories, or Aj20z-Si 02 series refractories.
hOl, SiC, and carbon refractories are used.
Other materials used include magnesia refractories and magnesia-chromium refractories.

A h O3・5i02 series chamotte refractories are N
The reaction between U2CO3 and SiO□ produces a low melting point substance of the Na20.5i02 series with a eutectic point at 800°C, which easily dissolves during use.

In high alumina refractories, Heslag easily penetrates into the matrix, and β-A1203 (Na20 ・11 AL2
03) or Na20-A! Compounds such as 203 are generated, and cracks occur due to volumetric expansion, causing peeling.

In addition, in the case of A h O3, SiC, and carbonaceous refractories, although they have excellent corrosion resistance against slag, they have poor oxidation prevention effects that prevent oxidation of carbon in the matrix, and a decarburized layer is formed during preheating, which affects durability. .

In the case of magnesia refractories, MgO grains have relatively good corrosion resistance, but slag easily penetrates into the brick structure.
Cracks are likely to occur.

Although magnesia/chromium has relatively good corrosion resistance,
Since hexavalent chromium is eluted into the slab, it poses a pollution problem.

As described above, all of the refractories listed above have many problems in terms of durability against soda carbonate-based fluxes.

The present invention solves the above-mentioned problems and desulfurizes hot metal.
It was developed with the aim of improving the corrosion resistance of the refractory lining of the dephosphorization processing container against soda carbonate-based desulfurization and dephosphorization agents and extending the life of the processing container. Carbon and silicon nitride (hereinafter referred to as S,3N4) or sialon (S,3N4 and A!20) are used in the matrix of the refractory.
We have discovered a technology that prevents permeation of soda carbonate-based slag and oxidation of carbon by disposing a solid solution of *), thereby creating a refractory with excellent durability.

In other words, alumina, which has excellent corrosion resistance against soda carbonate slag, is used as an aggregate, carbon prevents the soda carbonate slag from entering through the pores in the refractory, and carbon oxidation is prevented by S, 3N. 4 or Sialon, the durability of the refractory against soda carbonate slag can be improved. The present invention is a hot metal pretreatment vessel in which the slag line is lined with such a refractory. □ The present invention will be explained in detail below.

Dense alumina aggregate does not easily generate low-melting substances when reacting with soda carbonate slag, and has high corrosion resistance. Carbon only generates gas according to the following formula by reacting with Na20 of soda carbonate slag, and this gas pressure and carbon's inherent property of not getting wet with the slab prevents slag from penetrating. .

Na2O + C- + 2Na + CO (1) If an alumina refractory with carbon as part of its matrix is used in a non-oxidizing atmosphere, slag penetration will be prevented and structural spalling will be prevented. , the durability of refractories is improved. However, in hot metal processing vessels and the like, there are many opportunities for exposure to the atmosphere, such as during exhausting, and oxidation of carbon in the matrix occurs. Oxidation of carbon loosens the tissue and increases pores, making it easier for slag to penetrate and increase damage.

To prevent this carbon from oxidizing, it is desirable to have a material that forms an oxidation-preventing protective film during use. The present inventors selected 5t3N4 or Sialon as being expected to have an antioxidant effect, and examined the antioxidant effect and reactivity with Na2CO3. A study was conducted using SiC as a comparative material, and the results are shown in Tables 1 and 2.

Table 1 shows the formation of a decarburized layer when a sample material with dimensions of 40 x 40 x 40 mm was treated in the atmosphere at 1400°C for 1 hour.As is clear from Table 1, S t3 N 4 or Sialon both have a large oxidation prevention effect when used as a refractory.

Table 2 shows the gas generated acid (in argon) when 4 S L3 N grains, Sialon grains, and SiC grains were each dropped into a 1200°C Na2CO3 bath, and 5j3
N4 or Sialon has low reactivity with N a2 CO3.

Table 1 Formation of decarburized layer at 1400°C Table 2 N
Amount of gas generated when dropped into a2CO3 bath (1200℃) Also, S j3 N 4 or Sialon powder and Na
When mixed with 2CO3 and heat treated at +200'0 in the atmosphere, the reaction proceeds according to the following formula, and Na
20*5i02 series or Na2Oa Al2O3*S
It was found that i02-based compounds were formed.

S 43 N4 +N a2 C03 -h 3Na2 0@2Si 020
N2 + CO.

Sialon (3Si3N4-4A1203) + Na2
C.O.

Shun N a20 e AL203 ・2 S i 02
+ N2+ CO2 From the above, the following conclusion can be drawn. Carbon and St5 in a refractory matrix mainly made of alumina
When N4 or Sialon is used, carbon in the matrix exposed on the refractory surface at the beginning of use,
Si3N4. A reaction occurs between Sialon and soda carbonate slag, but after the initial reaction, the effect of carbon on preventing slag penetration, the gas pressure caused by the reaction between carbon and slag, and the reaction between S43N4 or Sialon and slag occur. Na20-3i02 series or Na2O・Al2
Slag penetration is prevented by forming an O2* Si 02-based film. Further, the formation of the above-mentioned film has the effect of preventing oxidation in the matrix when the refractory is exposed to the atmosphere after exhausting the pig iron, and the durability of the refractory is improved.

The amount of carbon added is 5 to 25%. If it is less than 5%, the penetration prevention effect will be small, and if it exceeds 25%, the matrix will be easily eroded by reaction with slag.

The amount of SJN4 or Sialon added is 5 to 20
%. This is because if the amount is less than 5%, the antioxidant effect of carbon is small, and if it is more than 20%, the reaction products are likely to be liquefied.

As described above, the present invention provides a hot metal pretreatment vessel in which at least the slag line is lined with a refractory matrix consisting of alumina aggregate and carbon and 5L3N+t or sialon, which is a soda-carbonate based refractory. It has excellent durability against slag, making it possible to significantly extend the life of the processing container.

Examples of the refractory used in the container of the present invention will be described below.

Examples Examples of alumina/carbon used in containers of the present invention
For a total of four types, two types of silicon nitride refractories and alumina/carbon/sialon refractories, and two types of high alumina refractories and alumina fist carbon/silicon carbide refractories as comparative examples, the composition was NazCO ; Near 5%, SiO
, : 15% and P2O5: 10%. An erosion test was conducted using soda carbonate based slag.

A rotational erosion test is adopted, and each specimen is approximately 50 mm
Two 40 mm x 120 mm +73 test pieces were cut out, a regular octagonal cylindrical horizontal furnace with a 50 mm x 120 mm surface facing inside was formed, heated with an oxygen/propane burner, and hot slag was poured into the furnace. After rotating for a predetermined time, the slag was discharged and forcedly cooled with 2 Kg/am'' compressed air.The test was repeated three times at 1400°C for 1 hour, and the cross section after the test was examined to determine the thickness of erosion, The thickness of the altered layer,
The presence or absence of cracks was also examined.

Table 3 shows the characteristics of the test materials and the results of the twice-repeated experiment, including the average value of corrosion resistance and the occurrence of cracks. As is clear from the table, among the comparative examples, the high alumina refractories containing no carbon, silicon nitride, or sialon had a large amount of erosion and a large amount of altered layer, and cracking was also observed. In Table 3, the erosion ratio is an index with high alumina as 100. Large-sized materials made of alumina, carbon, and silicon carbide do not cause cracks or deteriorated layers, but have the disadvantage of a rather large amount of erosion. In comparison, in the alumina-carbon-silicon nitride material and alumina-carbon-sialon material of the examples of the present invention, no altered layer or cracks were observed, and the amount of erosion was significantly improved. .

In addition, the relationship between the distance from the eroded surface and the amount of Na permeation for the sample after the test was determined and shown in FIG. It is clear from the figure that the refractory according to the present invention has significantly improved permeability to soda carbonate slag compared to the comparative example.

In the processing container of the present invention, it is of course possible to use the refractory of the above embodiment not only for the slag line but also for the entire lining.

1 2

[Brief explanation of the drawing]

FIG. 1 is a graph showing changes in the amount of Na permeated into various refractories with respect to the distance from the sample surface after the erosion test.
・ r□ Patent applicant Kawasaki Steel Corporation Kawasaki Rozai Co., Ltd. Showa Denko Co., Ltd. Agent Patent attorney Yoshio Kosugi,'

Claims (1)

[Claims] ■ 5-20% carbon and silicon nitride or Sialon 5
~20% alumina/carbon/silicon nitride refractories or alumina/carbon iron-based refractories,
A hot metal dephosphorization treatment vessel using a soda carbonate flux, characterized in that at least a slag line portion is lined with slag.