JP2533558B2 - Sheet material for hearth rolls - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a sheet material constituting a flaw-proof hearth roll for a heat-treated material used in a roller hearth-type continuous heating furnace.

[Prior Art] In a continuous heat treatment furnace for metals such as silicon steel plate, stainless steel plate, galvanized steel plate, and plate glass, rolls made of various materials are used as a hearth roll for carrying strips. Various types of heat-resistant alloy rolls, rolls obtained by inserting a ceramic sleeve into an iron core, and rolls obtained by laminating and assembling asbestos plates are used according to the type of heat-treated material and processing conditions.

For example, in this type of hearth roll used in continuous heating furnaces for stainless steel plates and sheet glass, defects on the material to be heated are extremely disliked, so asbestos plates are generally punched on donal-shaped discs and laminated. Asbestos rolls are often used with a core of iron inserted and compressed.

Asbestos rolls utilize the excellent heat resistance, durability, and resilience of asbestos fibers, and have appropriate cushioning and wear resistance for heat-treated materials, such as a stainless steel plate at 1000 ° C. It is often used as a hearth roll even at high temperatures reaching the above levels.

However, in the case of an asbestos roll, since the heat resistance of the asbestos fiber itself is low, when used at a temperature of 1000 ° C. or higher, it has a drawback that cracks on the roll surface, abnormalities such as adhesion of scale are likely to occur, and 1200 It cannot withstand use in high temperature parts reaching temperatures above ℃.

At the same time, due to the problem of asbestos pollution in recent years, it has become necessary to pay sufficient attention to the production and use of asbestos rolls that use asbestos fiber as the main raw material. Is the situation that is desired.

On the other hand, a ceramic roll (Japanese Patent Laid-Open No. 58-48619)
No. JP-A-58-71326), rolls made of mica particles, vermiculite and the like and a binder (Japanese Patent Publication No. 59-59).
No. 28771, Japanese Patent Publication No. 58-58307) and rolls using a sheet material composed of silica-alumina fiber and an inorganic binder (Japanese Patent Laid-Open No. 61-133310) have been proposed.

[Problems to be Solved by the Invention] The various rolls proposed so far as described above have many drawbacks.

For example, ceramic rolls have extremely little wear on the roll surface, so when used for heat treatment of stainless steel plates, etc., the steel plates may be flawed, or the ceramic part may crack due to the difference in coefficient of thermal expansion from the internal iron core. Yes, it is not practical.

On the other hand, rolls using a sheet composed of mica, vermiculite or alumina / silica fibers and a binder have a large amount of wear on the roll surface, and at 1200 ° C or higher, the roll surface melts or softens and It had a defect that the life of the roll was significantly inferior to that of the asbestos roll.

An object of the present invention is to use a non-asbestos furnace roll having a suitable cushioning property and a high heat resistance without giving a flaw to the heated material, which has solved the above-mentioned abrasion defect of the asbestos substitute roll. To get the sheet material.

[Means for Solving the Problems] The sheet material for hearth rolls of the present invention is characterized by containing sepiolite and mica as main components, and if necessary, inorganic or organic fibers and heat-resistant aggregates are added. is there. That is, the present inventors have found that the above-mentioned problems can be solved by producing a hearth roll using a sheet material containing sepiolite and mica as main components.

That is, the present invention is to provide a sheet material for a roller hearth type heating furnace hearth roll containing sepiolite and mica as main components.

[Operation] Sepiolite used in the present invention is one of clay minerals known as valigorskite and has a structural formula of Si ₁₆ Mg ₈ O ₃₀ (O
H) _{4 (OH 2)} with hydrated magnesium silicate mineral represented by 4 _· 8H ₂ O), is a fibrous natural mineral, also known as another famous mountains transdermal or sepiolite. Sepiolite has a fiber diameter of 0.1 to 0.3 μm, and the fiber length varies depending on the place of origin, but it is usually powder of 1 to 30 μm to long fibers of several cm.

Sepiolite is mineralogy completely different from asbestos fiber, but heat resistance similar to asbestos fiber, a fibrous mineral showing durability, heat resistance of the furnace roll of the present invention, wear resistance, It contributes to the improvement of cushioning property.

Mica, which is another essential raw material, is widely used for industrial purposes either alone or in combination with other raw materials due to its excellent electric insulation and heat resistance.

At present, there are two types of mica that are generally used, a muscovite type and a progopite type, both of which can be used in the present invention, but in order to make the mica dispersion in the sheet material of the present invention uniform. Is preferably ground to a particle size of 40 mesh or less.

In addition to heat resistance, these mica are excellent in elasticity, toughness and lubricity, and by adding them, the wear resistance of the hearth roll can be remarkably improved. Furthermore,
Although mica starts to sinter at about 1200 ° C., it also has an effect of significantly reducing thermal contraction at a temperature lower than this temperature, probably due to the expansion effect when water of crystallization is released.

The hearth roll sheet material of the present invention has excellent properties obtained by combining the above sepiolite and mica, and one of them cannot obtain sufficient performance.

That is, sepiolite is one of the main components of the hearth roll sheet material of the present invention, is extremely important as a heat-resistant inorganic fiber material, and has strength and flexibility comparable to asbestos fiber and is required for hearth roll performance. In order to obtain high density, which is indispensable for wear resistance, when the disc obtained from the sheet material is fastened to the iron core at high pressure, the fibers are not damaged, the strength required for the hearth roll is sufficiently satisfied, and the flexibility is extremely good. Can be maintained.

From the above viewpoint, the amount of sepiolite added is 40 to 95% by weight.
When the amount of sepiolite added is less than 40% by weight, a sheet material having the above-mentioned performance cannot be obtained. On the other hand, if it exceeds 95% by weight, the amount of added mica is reduced, which is not preferable.

On the other hand, mica significantly improves wear resistance due to its high toughness and lubricity, and reduces heat shrinkage due to expansion effect during heating, and is therefore extremely effective in crack prevention.
However, since mica melts or softens at a temperature of 1200 ° C or higher, if a hearth roll made of a sheet material for hearth rolls containing a large amount of mica is used at a temperature of 1200 ° C or higher, the inside of the roll will be protected to protect the iron core. Although it is water-cooled, it cannot be used as a hearth roll at all, because at least the surface layer portion undergoes melting and softening of mica and significant shrinkage accompanying it.

Therefore, the amount of mica added should be as small as possible within the range where the effect can be sufficiently exerted, and the range is 5
~ 20%. If the amount of mica added is within this range,
Even if it is used at a temperature of 1200 ° C. or higher, there is no influence of sintering of mica, and it is possible to obtain a sheet material for hearth rolls having excellent wear resistance and no cracks.

By the way, the hearth roll sheet material of the present invention has a temperature of 1100 ° C. or less, as is clear from the examples described below.
Extremely small heat shrinkage, but quite large at 1200 ° C or higher, nevertheless, as a reason why cracks do not occur even when the hearth roll using the hearth roll sheet material of the present invention is used at a temperature of 1200 ° C or higher, the following: It is possible that

That is, the hearth roll is used by inserting the sheet material of the present invention punched into a donut-shaped disc into an iron core, laminating and pressing under high pressure. At this time, as described above, The hearth roll is water-cooled to prevent softening and deformation. Therefore, even when used at a high temperature of 1200 ° C or higher, due to the cooling effect, it is only a small part of the surface layer of the hearth roll that actually reaches 1200 ° C or higher, and most of the others are 1100 ° C.
It is thought to be as follows.

Therefore, the hearth roll made from a sheet material having extremely small heat shrinkage at 1100 ° C. or lower obtained by using sepiolite and mica as in the present invention, even when used at 1200 ° C. or higher, most of the shrinkage is extremely high. Small and also 12
It is considered that, when the temperature is 00 ° C. or higher, even in the surface layer portion, cracking does not occur because the ratio of mica is small, so that it does not sinter or melt and the flexibility characteristic of sepiolite remains sufficiently.

Therefore, the hearth roll sheet material of the present invention is composed of 40 to 95% by weight of sepiolite, 5 to 20% by weight of mica, and no heat resistant filler.
-20% by weight and 0-20% by weight of reinforcing fibers.

Quartz sand, alumina, or the like can be used as the heat-resistant filler. Further, as the reinforcing fiber, glass fiber, carbon fiber, ceramic fiber or the like can be used. These components can be appropriately blended depending on the use of the sheet material and the like, but it is necessary to add them within the above range so as not to cancel the excellent performance of sepiolite and mica.

Below, an example of the manufacturing method of the sheet material for hearth rolls of this invention is described.

First, sepiolite, mica, an appropriate heat-resistant filler and reinforcing fibers are dispersed and mixed in water to form a slurry, and then dehydrated by an arbitrary method to form a sheet material having a thickness of 3 to 30 mm. As a molding method, an ordinary papermaking method, press dehydration method,
It is preferable to use a vacuum suction method or the like.

Here, when the papermaking method is used for forming the sheet material, a conventional papermaking auxiliary agent such as pulp, positive starch, synthetic rubber latex, silica sol, alumina sol, polyacrylamide type coagulant, etc. can be appropriately used. These components are added to facilitate the papermaking of the sheet material of the present invention, and disappear when the sheet material of the present invention is used as a hearth roll at high temperature.

Production of a hearth roll or furnace roll from the hearth roll sheet material of the present invention can be carried out by a conventional method, for example, after drying a dehydrated molded sheet material,
Punching into a doughnut-shaped disc, inserting a prescribed number into an iron core, compressing it axially with a pressure of 100 to 300 kg / cm ² , fixing it with a flange and nuts, and then polishing the surface smoothly. It can be a furnace roll.

The use of mica as a sheet material similar to the hearth roll sheet material of the present invention thus obtained is disclosed in Japanese Examined Patent Publication No. 59-28771 as described above, which is mainly composed of mica. It is used as a constituent material, and is different from the sheet material of the present invention mainly containing sepiolite and mica. Although the sheet material mainly composed of mica has excellent wear resistance and heat resistance at 1100 ° C or lower, it is melted or softened at 1200 ° C or higher as described above due to the addition of a large amount of mica. However, it cannot be used.

[Examples] Examples Using a slurry having a composition shown in Table 1 below, a dehydration molding was performed to a uniform sheet material having a thickness of 5 mm by using a round net papermaking machine. The operation will be described in detail below.

First, when adding sepiolite, mica, pulp, and reinforcing fiber and heat-resistant filler, they are dispersed and mixed in water to form a slurry, and then aluminum sulfate is added while adding and stirring the positive starch aqueous solution prepared by boiling. After the aqueous solution was added to fix the starch, dehydration molding was performed on a sheet material having a thickness of 5 mm using a round net papermaking machine. The properties of the obtained sheet material are also shown in Table 1.

After drying the sheet materials obtained in Examples 1 to 11, the outer diameter is 115 m.
A doughnut-shaped disc having an inner diameter of 49 mm and an inner diameter of 49 mm was punched, and 130 pieces of the obtained disc were inserted into an iron core and compressed at a pressure of 150 kg / cm ² to prepare a furnace roll having a length of about 400 mm.

The obtained furnace roll was heated in an electric furnace at 1150 to 1250 ° C. for 8 hours. The heating test was performed while flowing water of 5 minutes per minute on the iron core, and after rotating an iron load roll of 8 kg / cm ² on the test roll at 40 rpm, cracks and wear on the roll surface were observed. The results obtained are listed in Table 2. The cracks are visually observed, and the wear amount is based on the diameter reduction amount of the load roll portion.

Comparative Example A slurry having a composition shown in Table 3 below was used, and a thickness of 5 m was obtained by using a round-net papermaking machine as in the above-described example.
Dehydration molding was performed into a uniform sheet material of m. The properties of the obtained sheet material are also shown in Table 3.

Furnace rolls were manufactured using the sheet materials obtained in Comparative Examples 1 to 9 in the same manner as in Examples, and the cracks and wear on the roll surface were observed by the same test method as in Examples.
The results obtained are shown in Table 4.

[Effects of the Invention] Hearth rolls produced using the hearth roll sheet material of the present invention containing sepiolite and mica as main components are 12
It has good wear resistance even when used at high temperatures of 00 ° C or higher, does not cause cracks, does not scratch the material to be heated, and is suitable as a transfer hearth roll for various continuous heat treatment furnaces. It can be used for. Further, the hearth roll sheet material of the present invention does not use asbestos, and therefore there is no problem such as asbestos pollution.

Claims (1)

(57) [Claims] 1. A sheet material for a roller hearth-type heating furnace hearth roll, which contains sepiolite and mica as main components.