JPS5842144B2 - graphite casting nozzle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a graphite casting nozzle, and its gist is to provide a casting nozzle made of graphite, alumina, fused silica, feldspar, and ferrosilicon.

Conventionally, in the continuous casting method, a long nozzle (air seal pipe) is used to connect the molten steel ladle to the dandy pipe to prevent oxidation of the molten steel during casting.

Further, as a nozzle connected from the dandy to the mold, a submerged nozzle is used to prevent oxidation of molten steel, control the flow of molten steel within the mold, and prevent splash and slag from being involved.

These long nozzles or submerged nozzles are required to have high stability in terms of spall resistance, corrosion resistance, and airtightness in order to obtain good quality slab properties and to operate continuous steel casting smoothly.

Therefore, many studies have been conducted on such casting nozzles, and currently, fused silica, graphite-based
Alumina-siliceous nozzles are commonly used.

However, all of these casting nozzles have advantages and disadvantages, and they are not completely satisfactory in terms of stability.
The current situation is that this is not the case.

For example, a fused silica nozzle has excellent spalling resistance, but has the disadvantage that it suffers from greater melting loss and is inferior in corrosion resistance compared to high manganese steel.

In addition, although graphite-alumina-silica nozzles have excellent corrosion resistance and spalling resistance, they have poor oxidation resistance, making them susceptible to oxidation wear during use.Also, they have high thermal conductivity and poor high-temperature softening properties, so they cannot be used easily. Blockages and nozzle blockages are likely to occur, and the fit with the stopper head may be irregular, resulting in poor stopping of hot water.

As a result of repeated research to solve the drawbacks of the above-mentioned graphite-alumina-silica casting nozzles, the present invention has developed a composition that combines graphite, alumina, silica, feldspar or chinastone, and ferrosilicon, which has excellent oxidation resistance and wear resistance. The result is a casting nozzle with excellent hot softening properties and good hot water retention.

To describe the present invention in more detail, natural or artificial graphite having a particle size of 0.5 or less is used in a weight ratio (hereinafter expressed as a weight ratio).

) with 3 to 55 rice cakes, A120365 rice cake or more containing 0,
5im or less alumina raw material 30-80%, SiO□9
Fused quartz raw material O to 5 with 0, 3 or less peaks containing 5φ or more
0%, 0,074 containing an alkali component of 2.5φ or more
Total of one or two types of feldspar or pottery stone less than mm 1.
0.07 containing 5-30% and silicon 50-90%
31n7IL~ is mixed by adding a normal organic binder (tar pitch, phenolic resin, etc.) to a compound containing 0.5~20% of ferrosilicon powder of 4 mm or less.
After granulating to 0.1 mm, rubber press molding to 10,000
This relates to a casting nozzle fired at a temperature of C to 1400C.

Here, graphite has poor spall resistance when it is less than 3 parts, and 55φ
The range of 3 to 55% is preferable because if it exceeds 30%, the corrosion resistance decreases, and for alumina raw materials, if it is less than 30%, the corrosion resistance is poor, and if it exceeds 80%, the spalling resistance is lacking, so the range is 30 to 80'%. is preferred.

Further, if the fused quartz raw material exceeds 50%, the corrosion resistance will be poor, so a ratio of 0 to 50 is preferable.

Feldspar or pottery stone contains 2.5% or more of alkali, and the content is preferably in the range of 1.5 to 30%.

If it is less than 1.5%, it is difficult to obtain sufficient softening properties in hot conditions, and the effects of preventing graphite from oxidation, improving hot water retention, and preventing nozzle clogging will not be sufficiently exhibited.

Moreover, if the diameter exceeds 30φ, the softening property becomes excessive, resulting in poor corrosion resistance.

Ferrosilicon Fe: 8~4.5φSi: 50~90%
is oxidized during use to form Fe2O3 and silica, which reacts with feldspar to produce a glass with higher viscosity, which is necessary to prevent graphite from oxidation, wear resistance, and improve hot properties. If it is less than 0.5%, there is almost no effect; if it exceeds 20%, the softening property becomes excessive, resulting in poor corrosion resistance, and the preferred range is from 0.5 to 20%.

The effects of the present invention are achieved by adding feldspar or chinastone powder and ferrosilicon to strengthen the bond between the particles of the three types of aggregates, graphite-alumina-silica, during firing and during use. Feldspar and ferrosilicon react at the temperature and atmosphere of , forming a low-melting, high-viscosity glass between the aggregates, which has oxidation resistance, abrasion resistance, and plasticity in hot conditions. This makes it possible to enhance the hot water stopping effect.

As an aggregate, in addition to graphite-alumina-silica, it is also possible to use a combination of silicon carbide, aluminum titanate, cordierite, boron carbide, borax, boric acid, etc. for the same effect.

The present invention will be explained in detail below based on examples.

Example The raw material mixture shown in Table 1 was mixed and kneaded using pitch as an organic binder, then granulated to a size of 2.0 to 0.3 degrees, dried, and then rubber press molded at a pressure of 1000 kg/crA. .

The molded body was baked at a temperature of 1350°C and the results are shown in Table 2.
A casting nozzle with the characteristics shown in was obtained.

When the firing temperature is 1350°C or less, the strength is even lower, but since the temperature during use is 1500 to 1600°C, it is possible to expect the same effect.

As a result of using each of these products of the present invention in a continuous casting nozzle, a service life of more than 5 hours was obtained, which confirmed the effectiveness of the present invention, whereas the conventional nozzle suffered oxidative wear and lasted for 3 hours. did.

Claims (1)

[Claims] 1. Weight ratio: 30-80% alumina, 3-55mm graphite,
Fused quartz O~50φ, alkaline component at least 2.5
A graphite casting nozzle comprising a total of 1.5 to 30 pieces of one or two types of feldspar or pottery stone containing 0.5 to 20 φ of ferrosilicon and an organic binder. 2. The graphite casting nozzle according to claim 1, wherein the blend is kneaded, granulated and dried between 3 mr/L and 0.1 mr/L, followed by rubber press molding and firing.