JPH0677012B2 - Protective tube for molten metal immersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is used for measuring temperature, oxygen concentration, carbon concentration, sampling, etc. by immersing a measuring device in a molten metal in a furnace in a steel mill or the like. The present invention relates to a protective tube used to protect a measuring device and lead wires connected to the measuring device from high heat.

[Prior art]

Generally, the temperature of molten metal is measured by immersing the measuring device in molten metal having a temperature of about 1500 to 1700 ° C. for 5 to 10 seconds.
Conventionally, a lance for measurement in which a measuring device is housed in a kraft paper tube has been used for this temperature measurement, but the kraft paper tube scatters molten metal due to rapid vaporization of contained water and organic components at high temperatures. The so-called splash is likely to cause the worker to be at risk, and since it burns out in a short time, the measuring device is not sufficiently protected,
We couldn't make reliable measurements.

Therefore, it has been considered to suppress the occurrence of splash by winding and stacking asbestos paper or a ceramic fiber sheet on the outside of the kraft paper tube to provide a layer having heat resistance and heat insulation. However, since asbestos releases water of crystallization at high temperatures, it is not possible to sufficiently prevent the generation of splashes, and asbestos dust and fibers are harmful to the human body, which is a problem in handling. On the other hand, since the molten metal easily penetrates the ceramic fiber sheet as it is, an inorganic adhesive layer such as silica sol or alumina sol is provided between the ceramic fiber sheet layers or on the surface of the protective tube, but these inorganic adhesive layers are fragile. Above all, it has not yet been put to practical use because it easily shrinks at high temperature, and in particular, if the inorganic adhesive layer is thick enough to prevent the permeation of the molten metal, it will be easily damaged.

[Problems to be solved by the invention]

The present invention has been made to solve the above-mentioned drawbacks of the prior art. When immersed in molten metal, the molten metal is prevented from permeating, and the internal measuring device and the lead wire are kept for a sufficient time required for measurement. The purpose is to provide a protective tube that can be protected from high heat.

[Means for solving problems]

The present invention relates to a protective tube for dipping a molten metal in which an inorganic fiber sheet is wound and laminated on a paper tube, and contains heat-resistant inorganic powder, a clay mineral having a film-forming ability, and an inorganic adhesive between layers of the inorganic fiber sheet. A protective tube for dipping molten metal, characterized in that a heat-resistant shielding layer is formed.

The inorganic fiber sheet used in the present invention is suitable to have an apparent density of 0.1 to 0.5 g / cm ^{3 in} order to have a heat insulating property, and, for example, a felt or an inorganic fiber of an inorganic fiber is an inorganic or organic type. A sheet or the like bonded with an adhesive is used, but a sheet in which inorganic fibers are bonded with a clay mineral capable of forming a film is particularly preferable because it can simultaneously satisfy strength, flexibility, and non-splash property.

Inorganic fibers include silica-based fibers, alumina-based fibers, silica-
Fibers such as alumina fibers, silicon carbide fibers, rock wool, and glass fibers having excellent heat resistance and an official moisture regain of almost 0% are used alone or in combination.

Further, the clay mineral having a film-forming ability is a clay mineral having a double-chain structure such as sepiolite containing hydrous magnesium silicate as a main component or attapulgite containing hydrous magnesium aluminum silicate as a main component. Formite-based minerals, montmorillonite-based minerals such as sodium montmorillonite and hectorite, and swelling fluoromica are used. These clay minerals can enhance the dispersibility of powders and fibers in water, and have the property of being solidified by drying, and therefore, they work as an effective binder when forming a sheet. Also, these clay minerals do not burn out like organic adhesives or cause splash, and they do not become brittle after drying like inorganic adhesives such as silica sol and alumina sol. It is suitable as a binder for fiber sheets. When using a clay mineral having a film-forming ability, it is preferable that at least 5% by weight of the clay mineral is contained in order to obtain the strength required for the inorganic fiber sheet, but if the clay mineral is too much, the sheet becomes Since it becomes too dense and the function as a heat insulating layer decreases, it is better not to exceed 30% by weight.

The inorganic fiber sheet may contain a heat resistant inorganic powder in order to improve heat resistance.

The above-mentioned inorganic fiber sheet is wound and laminated on a paper tube made of kraft paper or the like, and a heat-resistant shield layer containing heat-resistant inorganic powder, a clay mineral having film-forming ability, and an inorganic adhesive is formed between the layers. To be done.

The heat-resistant inorganic powder used for the heat-resistant shield layer is alumina, silica, mullite, cordierite, magnesia, titania, zirconia, zircon, chromium oxide, silicon carbide, silicon nitride, boron nitride, aluminum phosphate, dolomite. Powders such as clinker are suitable, but in order to enhance the shielding property, it is desirable that at least 50% of the powders used have a particle size of 10 μm or less.

Clay minerals with film-forming ability are formite-based minerals that are double-chain-structured clay minerals such as sepiolite containing hydrous magnesium silicate as a main component and attapulgite containing hydrous magnesium aluminum silicate as a main component. , Montmorillonite minerals such as sodium montmorillonite and hectorite, and swelling fluoromica are used. Among them, sepiolite has extremely fine fibrous shape, high powder retention and excellent binding strength. It is preferably used.

On the other hand, silica sol, alumina sol, silicate, phosphate, etc. are used for the inorganic adhesive. Especially when silica-based or alumina-based fiber is used for the inorganic fiber sheet, it is eroded by acid or alkali at high temperature. Therefore, it is preferable to use silica sol or alumina sol which is as neutral as possible for the inorganic adhesive.

The heat-resistant shielding layer is composed of heat-resistant inorganic powder, a clay mineral having film-forming ability, and an inorganic adhesive because the heat-resistant inorganic powder is added to the inorganic adhesive used for bonding between the inorganic fiber sheets. This is because by adding a clay mineral having a property of preventing the penetration of molten metal and having a film-forming ability, the holding power of the powder is increased and the strength of the heat-resistant shielding layer is improved.

Therefore, in order to obtain sufficient heat resistance and shielding properties, the heat-resistant shielding layer should contain at least 50% by weight of the heat-resistant inorganic powder, and the strength of the heat-resistant shielding layer should be improved so that the heat-resistant shielding layer can be exposed to high temperatures. At least 2% clay mineral with film-forming ability to prevent cracking and damage when exposed
As described above, preferably 5 to 20% is contained, and further, in order to sufficiently bond the inorganic fiber sheets, the inorganic adhesive is contained at least 2% or more, preferably 5 to 40%. It's better.

The protective tube for molten metal immersion of the present invention is coated on one surface of an inorganic fiber sheet with a solution in which a heat-resistant inorganic powder, a clay mineral having a film-forming ability and an inorganic adhesive are dispersed in water, and wound around a paper tube. It is obtained by forming a laminated tube of 3 to 8 layers and then drying. At this time, the clay mineral having a film-forming ability has an effect of uniformly dispersing the heat-resistant inorganic powder, an effect of increasing the viscosity of the solution to an appropriate viscosity for applying to the inorganic fiber sheet, and an adhesive property of the solution. It acts to increase. For this reason, it is a clay mineral having film-forming ability to uniformly disperse the powder in an inorganic adhesive, which has been difficult in the past, and to increase the viscosity without using an organic thickener that causes splash. Since it can be easily formed, the surface coating can be easily performed, the workability is improved, and the binding force of the substance in the layer is also increased, so that a thick and uniform heat-resistant shield layer can be formed.

Incidentally, the heat-resistant shield layer is preferably inserted into the inorganic fiber sheet in order to improve the bonding force between the inorganic fiber sheets, and 1/10 or more of the thickness of the heat-resistant shield layer is impregnated in the inorganic fiber sheet. Is desirable.

Further, in order to obtain sufficient molten metal shielding effect, the total weight of the heat-resistant shielding layer is preferably larger than the weight of the inorganic fiber sheet, and at least 200 g / m ² is better, but it is too heavy for handling. It is better not to exceed 600g / m ² because it does not exist.

〔Example〕

90 parts of silica / alumina fibers having a fiber diameter of 2 to 3 μm, 10 parts of sepiolite and 2 parts of an acrylic adhesive are stirred in water to form a dispersion liquid, which is made into paper, and then 2 parts of an acrylic adhesive is added. After drying, an inorganic fiber sheet having a basis weight of 150 g / m ² and a thickness of 0.6 mm was formed. Next, in order to form a heat-resistant shielding layer on this inorganic fiber sheet, the following aqueous dispersions of
0g / m ² (amount of solid content) coated, rolled flatly on a paper tube 5 times with this side facing inward, molded into a tube,
Finally, for hard finishing, it was immersed in a liquid of silica sol and dried to obtain a protective tube.

However, the protective tubes using the aqueous dispersions of the formulations 1 to 3 are referred to as Examples 1 to 3, and the protective tube using the aqueous dispersions of Examples 1 to 3 is referred to as Comparative Example 1.

A temperature measuring cartridge having a quartz glass tube is attached to the tip of the protective tube, and then the lead wire passing through the protective tube is connected to the lead wire connecting portion of the temperature measuring cartridge to create a consumable lance thermocouple. The time from the immersion of the thermocouple in molten steel at 1650 ° C until the occurrence of splash (hereinafter referred to as "immersable time") was measured. Regarding the measured value of the dipable time, 5 protective tubes were prepared for each, and the measurement was performed 5 times, and the average value was shown.

The protective tubes of Examples 1 to 3 were well prevented from permeating the molten metal, and the dipable time exceeded the 5 to 10 seconds required for normal measurement, so there was no problem with the occurrence of splash during use. . On the other hand, in the protective tube of Comparative Example 1, cracks were likely to occur in the heat-resistant shielding layer, and the dipping time was as short as about 10 seconds, so there was a risk of splashing during use.

〔The invention's effect〕

The protection tube for molten metal immersion of the present invention is composed of a material having excellent heat resistance, and has a structure in which a heat insulating layer and a heat resistant shielding layer made of an inorganic fiber sheet are alternately laminated, so that the penetration of molten metal is prevented. At the same time, it has the function of preventing high heat from being transmitted to the paper tube and internal measuring devices. In particular, in the protective tube of the present invention, the heat-resistant shielding layer contains a heat-resistant inorganic powder, a clay mineral having film-forming ability, and an inorganic adhesive, so that a thick and strong layer can be formed, so that the shielding effect of the molten metal is improved. Even if the internal pressure of the protective tube is high due to the high temperature and the generation of gas due to the high temperature, it is not easily damaged.

Therefore, even if the protective tube of the present invention is immersed in the molten metal, splash does not occur within the measuring time, the worker can safely work, and the measuring device stored in the protective tube and Accurate measurement is possible because the lead wires are also completely protected from high heat.

Moreover, since the protective tube of the present invention uses the clay mineral having the film-forming ability for the heat-resistant shield layer, the coating layer in which the heat-resistant inorganic powder is uniformly dispersed can be easily formed.

As described above, the protection tube of the present invention can be easily produced with good quality, and when used for measuring the temperature of molten metal, carbon concentration, oxygen concentration, sampling, etc., it is a safe and easy operation, and highly accurate measurement is possible. It can be extremely useful.

Claims (1)

[Claims] 1. A protective tube for dipping molten metal in which an inorganic fiber sheet is wound and laminated on a paper tube, and a heat-resistant inorganic powder, a clay mineral having a film forming ability, and an inorganic adhesive are provided between layers of the inorganic fiber sheet. A protective tube for dipping molten metal, characterized in that a heat-resistant shielding layer containing is formed.