JPS60200948A - Composite materials for supporting members of heating furnaces - Google Patents

Abstract

PURPOSE:To provide a titled composite material having improved resistance to oxidation, compression, thermal impact, etc. by dispersing uniformly a prescribed ceramic particles having a specific grain size into a matrix consisting of a heat resistant metal. CONSTITUTION:50-90vol% >=1 kinds of ceramics having <=5mm. average grain size are uniformly dispersed and incorporated into the matrix consisting composed of an alloy consisting essentially of Co or Ni or heat-resistant metal or alloy consisting of a stainless steel, etc. The ceramics are selected from Al2O3, 3Al2O3, 2SiO2, ZrO2, SiC2, Si3N4, AlN, TiN, sialon, etc. The composite material having excellent resistance to compressive creep at a high temp., mechanical impact, thermal impact, oxidation, wear, etc. excellent weldability is formed by such compsn. The material is applied for a supporting member of a heating furnace such as skid rail, skid button, etc.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a composite material for a support member of a heating furnace.

More specifically, the present invention relates to a composite material in which a heat-resistant metal is used as a matrix and ceramic particles are dispersed therein.

Prior Art In general, rail materials for heating furnace hearths such as slabs, such as skid rails, and supporting members such as skid buttons, have various properties such as oxidation resistance, compression resistance, thermal shock resistance, weldability, and high temperature. Long-term stability, mechanical shock resistance, etc. are required.

Therefore, in the past, rail 4 was used in the hearth of such a heating furnace.
Refractories are used when there is no risk of large mechanical shocks being applied during the movement of the heated object, while heat-reducing metals cooled with air or water are used when there is a risk of large mechanical shocks being applied. It was used. For example, as shown in FIG. 1, a conventional hearth has a structure in which a hearth rail 1 is placed on a water-cooled pipe 2 via a heat insulator 3, and a rail support 4 is insulated from the water-cooled pipe 2. The object to be heated 5 is placed between the hearth rail 1'' and the hearth rail 1''.

Furthermore, the well-known push type furnace (pusher type continuous furnace)
It is most frequently used in rolling mills because it can be applied to a wide range of types and sizes of workpieces, from small steel ingots to slabs and billets. In this pusher type heating furnace as well, a cooled heat-resistant metal is used because the refractory will crack if a mechanical impact force is applied to the rail when the object to be heated moves.

However, in this case, the portion of the object to be heated that is in contact with the heat-resistant metal may not be sufficiently heated, resulting in the formation of low-temperature spots called skid marks.

Therefore, it is of great significance in this field to develop a new material for producing a support member for a heating furnace hearth that solves this problem.

OBJECTS OF THE INVENTION An object of the present invention is to provide a novel composite material for manufacturing a heating furnace support member, which overcomes the drawbacks of the above-mentioned conventional methods. A support member for a heating furnace hearth made of the composite material is also an object.

Structure of the Invention In view of the current state of the conventional methods, the present inventor has conducted various studies and researches to develop materials for manufacturing support members used in heating furnace hearths. It has been found that uniformly dispersing a predetermined amount of ceramic particles is extremely effective in achieving the above object. The present invention is based on this new finding.

That is, the composite material used for the support part of a heating furnace of the present invention comprises a matrix of heat-resistant metals or alloys, and at least one type of ceramic having an average particle size of 5+11Tl+ or less uniformly dispersed in the matrix. ~90% by volume.

According to the present invention, it has been found that by making the material for a support member of a heating furnace into the above-described configuration, the problems of conventional skidmer 9 formation can be effectively avoided in the support member obtained from the material.

The heat-resistant metal used in the composite material of the present invention is not particularly limited as long as it has excellent heat resistance and oxidation resistance, but alloys mainly composed of Co, alloys mainly composed of N1, stainless steel, etc. are preferable. , Furthermore, those containing these as main components and containing appropriate amounts of C, A1, Sl, Mo, etc. can also be advantageously used.

In addition, the ceramics used in the present invention include
For example, A9.20s, 3AS! 20+ -23i02
, oxide ceramics such as ZrO2, SiC, Ti
Carbide ceramics such as C or 813N7, A
Examples include nitride ceramics such as 9N and TiN, and Xialon. These can be used alone or in combination of two or more.

All of the ceramics added to the heat-resistant metal have higher hardness than ordinary metal materials, but in order to impart the performance aimed at by the present invention to the composite material and the supporting member for a heating furnace, the particle size and The addition rate is an extremely important factor. That is, according to the creep deformation and impact strength test results, the average particle size of the ceramic dispersed particles was 5 m.
m or less, and the addition rate is 50 to b
I know that it is necessary.

When using ceramic dispersed particles whose average particle diameter exceeds the upper limit of 5 mm, when the ceramic and the heat-resistant metal are mixed in the furnace and heated in a high-frequency furnace,
Stresses based on the difference in coefficient of thermal expansion between the two occur, which tends to cause local damage to the ceramic, cause cracks to occur in the steel, and deteriorate toughness. Therefore, it is essential to use ceramics with an average grain size of 5 mm or less in order to achieve the object of the present invention.

In addition,) ■ In order to improve the properties, it is preferable to make the ceramic powder as fine as possible, but when using the casting method (large pieces cannot be obtained with the compression molding method), it is necessary to Pressure is required, and the equipment must be enlarged. Therefore, considering these economical advantages, it is preferable to set the lower limit to about 0.01 mm.

As mentioned above, in the present invention, the amount of ceramics added is also critical, and if the amount of ceramics added exceeds the upper limit of 90% by volume, the impact strength decreases significantly; If used in too small an amount, the creep deformation resistance will deteriorate. I can't do anything.

The composite material of the present invention can be manufactured using, for example, a high frequency furnace. A manufacturing method using this high frequency furnace will be briefly described below.

First, as schematically shown in FIG. 2, the high-frequency furnace used in the present invention consists of an outer wall 10, a hollow high-frequency coil 11 embedded therein and wound spirally, and a cylindrical refractory crucible inside the outer wall 10. Contains 12. These are further housed in a furnace frame (not shown) made of non-magnetic steel. The hollow coil is designed to cool and protect the coil itself and the crucible 12 by passing cooling water thereinto, and also to allow a high frequency current to flow therein.

In the present invention, the crucible 12 further includes a crucible 13 (A
s! 203), graphite ring 14 and crucible 15 (A
s! 203) are arranged and used in this order. The object to be processed is put into the crucible 15 . Also, A9! has an outer diameter slightly smaller than the inner diameter of the crucible 15! . A holding refractory 17 is provided above the high frequency furnace through a crucible 16 made of 03, so that the object to be processed can be pressurized ff1).

Using a high frequency furnace such as the one described in Section 2, a mixture of heat-resistant metal powder and ceramic particles of a predetermined particle size is charged into a crucible 15 and heated. When the heat-resistant metal is melted, pressure is applied from above by pressure means 1G and 17 so that the molten metal evenly fills the gaps between the ceramic particles.

According to the method for forming a composite material of the present invention, the ceramic particles and the heat-resistant metal powder are heated together in a mixed state, so the ceramic particles are not heated rapidly.
Therefore, there is no risk of spalling occurring.

Further, by molding the thus obtained composite material according to a conventional method, a support member for a heating furnace, such as a skid rail or a skid button, can be obtained.

Effects of the Invention Thus, according to the composite material for a support member of a heating furnace of the present invention, its composition includes a matrix of a heat-resistant metal such as an alloy containing Co as a main component, an alloy containing N1 as a main component, stainless steel, etc. By combining 50 to 90% by volume of ceramic particles with an average particle size of 5 mm or less uniformly dispersed in the matrix, the desired compression creep resistance, mechanical impact resistance, and thermal shock resistance at high temperatures can be achieved. A product with excellent properties such as oxidation resistance, weldability, and abrasion resistance was obtained, and by using this product, it is possible to meet the above-mentioned required properties of rail materials for heating furnace hearths such as slabs. Become. That is, by forming the support member from such a composite material, it is possible to improve the heat resistance of the support member that comes into contact with the object to be heated, and to reduce the formation of skid marks on the object to be heated. .

Furthermore, by using a support member for a heating furnace hearth having such a configuration and characteristics, it is possible to suppress variations in the thickness of the slab during hot rolling to within 0.81%, and as a result, the rolling yield can be greatly increased. It becomes possible to improve the width. Furthermore, the skid rail and skid button of the present invention can reduce the amount of heat transferred to the lower part (water-cooled skid pipe), resulting in significant energy savings.

This is based on the fact that the heat resistance of the support member (hearth rail) has been improved as described above, making it possible to reduce the amount of heat extracted by the water-cooled pipe.

EXAMPLES Hereinafter, the present invention will be explained in more detail according to examples, but these examples are merely illustrative of the present invention, and
This does not limit the scope of the invention in any way.

As heat-resistant metals, we use various alloys with the compositions shown in Table 1, to which CoXNi, Cr, Fe, etc. are added.
Also, as ceramics, A father 203.3A9.203
- 2SiO2, SiC and A9N were used. The average particle diameters and amounts added of these ceramics are shown in Table 2.

These heat-resistant metal powders and ceramic particles were mixed at the compounding ratio shown in Table 2, and the resulting mixture was charged into a high frequency furnace as shown in FIG.

A current is passed through a high-frequency heating coil to raise the temperature of the mixture to 14
The temperature was gradually increased to 50 t- to melt the refractory metal in the mixture, and then each composite material was cast under a molding pressure of 2 kgf/cm2.

Such operations were sequentially performed on the 14 types of samples shown in Table 2 to obtain corresponding cast composite materials.

The amount of creep deformation, impact strength, and occurrence of skid marks were investigated for the 14 types of composite materials thus obtained. Each test was conducted as follows.

l) Creep deformation amount This is effective for evaluating the compressive deformability of the rail due to slab load, for example, and it is
βmm) was heated to 1200℃, a load (-axis pressure) of 2kgf/mm2 was applied for 1 hour, and the deformation rate (
mm/h).

11) Impact strength This is because, for example, in a pusher-equipped heating furnace, when the slab moves, it rises and falls, and when it falls, it gives an impact to the skid rail that supports it.
It is effective to evaluate the strength of the rail against such impact, and a test piece (50φX3 (if! mm)
Heat it to 1200℃ and add a weight with a wedge (5k) to it.
It is obtained as the impact energy (kgf-m) required to cause a crack to occur in the test piece by dropping the test piece.

111) Occurrence of skid marks Due to the occurrence of skid marks, variations in plate thickness occur during rolling. The plate thickness after treatment was measured for a slab with a plate thickness of 25 mm, and the thickness was expressed as a relative variation (%) in plate thickness.

Table 4: Composition of heat-resistant metal components Table 2 As is clear from the test results shown in Table 2, the support member for a heating furnace made of a composite material according to the present invention is superior in various physical properties compared to conventional ones. ing.

Generally, a material suitable for this type of use needs to have a creep deformation of 0.05 or less, and a tk impact strength of 50 Jf-m or more.

Looking at the test results for creep deformation and impact strength, the composite materials of the present invention (Experiments 1 to 9) all meet the above requirements, that is, a creep deformation of at most 0.03 and an impact strength of at least 86 kg/m. It can be seen that because of its strength, it is extremely useful for use as a support member for a heating furnace.

On the other hand, comparative examples (Experiments 10 to 12) and conventional method (Experiment 1
In 3.14), one of the above two requirements is satisfied, but the other is unsatisfied, and as a result, the generation of skid mater is more significant than that of the present invention, and it cannot be used as a material for a support member for a heating furnace. It turns out that this is insufficient.

[Brief explanation of drawings]

FIG. 1 is a sectional view for explaining the configuration of a conventional hearth rail, and FIG. 2 is a sectional view for explaining a high frequency furnace used for manufacturing the composite material of the present invention. (Main reference numbers) 1... Hearth rail, 2... Water cooling pipe, 3... Insulating material, 4... Rail support stand, 5... Heated object, 10
...Outer wall,',1...High frequency coil, 12.13
．． 15.16... Crucible, 14... Graphite ring, 1
7... Refractory for presser foot, Patent applicant: Sumitomo Metal Industries Co., Ltd. Agent: Masahiko Arai, patent attorney

Claims (5)

[Claims] (1) A heat-resistant metal or alloy matrix) IJ sock, a heating furnace characterized by containing 50 to 90 volume % of at least one type of ceramic having an average particle size of 5 mm or less uniformly dispersed in the matrix. Composite materials for support members. (2) The composite material according to claim 1, wherein the heat-resistant metal or alloy is selected from the group consisting of Co-based alloy, Ni-based alloy, and stainless steel. . (3) The heat-resistant metal or alloy further includes Cr5All,'
The composite material according to claim 2, characterized in that it also contains Si and Mo. (4) The ceramic is Al1203.3A9203
・2S+ 02, ZrO2, 5IC2, 513
4. The composite material according to claim 1, wherein the composite material is selected from the group consisting of N, TiN, SiAlON. (5) The composite material according to any one of claims 1 to 4, wherein the support member is a skid rail or a skid button.