JPH06305545A - Ceramic tip for belt conveyer cleaner - Google Patents

Abstract

PURPOSE:To reduce the number of replacement times and cost of equipment by remarkably improving durability as compared with a conventional sintered hard alloy-made tip and other ceramics tip, in a ceramic-made cleaner tip used in a belt conveyer for carrying a material containing an iron component of iron ore, sintered ore, etc. CONSTITUTION:By compounding 10 to 90wt.% preferably 10 to 50wt.% boron carbide in alumina, a sintered material having small reactivity with iron and high hardness is prepared, to form a ceramic tip for a belt conveyer cleaner remarkably excellent in wearing resistance. Thus by compounding the alumina and the boron carbide, the ceramic tip excellent in strength and toughness can be provided at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt conveyor for carrying a raw material containing an iron component such as iron ore, sinter or the like, for removing and scraping off the residue adhering to the belt surface. For ceramic chips for automobiles.

[0002]

2. Description of the Related Art Conventionally, in a belt conveyor or the like, a tool steel, a high speed steel or a WC-having a high hardness and an excellent wear resistance is used for the purpose of removing a residue adhered on the belt during use.
Co-based cemented carbide has been used as a cleaner tip. The wear resistance or life of these metal or cermet cleaner tips containing the metal binder phase is not always sufficient, and therefore it is necessary to replace them frequently, and the belt conveyor is stopped during that time, which reduces work efficiency. At the same time, there is a problem in that replacement requires labor and cost. Therefore, application development of cleaner tips using a ceramic material having higher hardness and excellent wear resistance has been conventionally performed.

In Japanese Patent Laid-Open No. 63-185858, Z
Although application of rO ₂ -3 mol% Y ₂ O ₃ material to belt conveyor cleaner chips is described, partially stabilized ZrO ₂ ceramics have characteristics of high strength and high toughness, When exposed to temperature for a long time, the tetragonal system undergoes a phase transformation to a monoclinic system, and volume contraction at that time causes cracks in the sintered body, resulting in poor wear resistance.

In practice, when partially stabilized ZrO ₂ is applied to a belt conveyor cleaner chip for sinter transfer,
Its durability is about 1/2 of that of the conventional WC-15% Co cemented carbide, and it has been revealed that ZrO ₂ was actually phase-transformed from tetragonal to monoclinic. This is a cleaner chip that is used at room temperature on an actual belt conveyor, but since its scraping surface is in constant contact with the belt conveyor, frictional heat is generated, and due to the low thermal conductivity of ZrO ₂ and other characteristics. It can be seen that a phase transformation occurred because the temperature rose to 200-300 ° C.

Further, Si-based non-oxide ceramics such as SiC and Si ₃ N ₄ (including sialon ceramics) have excellent heat resistance and high hardness, and therefore generally have extremely excellent wear resistance. Show. However, even in the case of these Si-based non-oxide ceramics, when sliding with iron or iron oxide, the surface is oxidized to form SiO ₂ , which reacts with the iron component to become 2FeO · SiO ₂ . It is known to wear hard. In fact, SiC, Si ₃ N ₄ or Sialon ceramic cleaner chips, which have excellent durability in belt conveyors for iron-free products such as limestone, are also applied to belt conveyors for sinter transfer. In this case, the durability is about 1/4 to 1/5 that of WC-15% Co cemented carbide.

In Japanese Patent Laid-Open No. 2-192453, Al
_A belt cleaner chip made of a sintered body containing one or more of ₂ O ₃ , Al ₂ O ₃ —Cr ₂ O ₃ solid solution, and Cr ₂ O ₃ is disclosed. Al ₂ O ₃ is a ceramic having high hardness, no phase transformation at low temperature, and extremely low reactivity with iron or iron oxide. In addition, by adding Cr ₂ O ₃ having a hardness higher than that of Al ₂ O ₃ , wear resistance is improved, and when it is used for belt or cleaner chips for conveying sinter, it becomes WC-15% Co alloy. It is described that the durability is 2-3 times that of the conventional one. However, when the inventors of the present invention previously applied the same material to a belt conveyor cleaner chip for sinter ore application and made additional tests, the durability was about the same as that of the Wc-Co cemented carbide material.

Generally, a ceramic material does not have a metal phase unlike a cermet material, and therefore has extremely high hardness and excellent wear resistance. However, simply applying ceramics to the cleaner tip does not improve wear resistance. That is, as a chemical property, it is difficult to react with iron or iron oxide, and in terms of crystallinity, transformation does not occur in the middle to low temperature range of about room temperature to 300 ° C., and as a physical property, Vickers hardness is It needs to be expensive. Especially as Vickers hardness, at least the conventional material WC-
It is desired to be 1500 kgf / mm ² or more of Co-based cemented carbide.

Al ₂ O ₃ ceramics, especially high density Al
₂ O ₃ is crystallographically stable up to high temperatures, has low reactivity with iron or iron oxides, and has a Vickers hardness of 1800.
It is as high as −2000 kgf / mm ^2, which is a preferable material for cleaner tips for belt conveyors. However, as described above, Al ₂ O ₃ ceramics or Cr ₂ O ₃ was added to strengthen the Al ₂ O ₃ —Cr ₂ O ₃
Ceramics were not necessarily superior to WC-Co based cemented carbides in terms of their durability as cleaner chips. That is, in order to impart wear resistance higher than that of the WC-Co based cemented carbide, it is necessary to further strengthen and increase the hardness.

On the other hand, B ₄ C ceramics has a Vickers hardness of 3000-4000 kgf / mm ² ,
Among ceramics, diamond and cubic BN (c-
The hardness is second only to BN). B ₄ C is also crystallographically stable up to a high temperature and has low reactivity with iron or iron oxide. Therefore, a high-density sintered body of B ₄ C alone is useful as a cleaner chip, but on the other hand, B ₄ C is an expensive raw material, and is difficult to sinter and has low toughness, so chipping easily occurs. It also has the drawback of being difficult to process.

As described above, a ceramic material, which is generally considered to have a higher hardness than WC-Co type cemented carbide, and thus is superior in wear resistance, is actually used as a belt conveyor cleaner chip for iron or iron oxide transport. It was not always easy to apply. On the other hand, the present inventors
No. 243559, the above Al ₂ O ₃ and B ₄
In order to overcome the weakness of C simple substance ceramics, an Al ₂ O ₃ -B ₄ C-based high-density sintered body in which both are compounded and a manufacturing method are disclosed. That is, by providing a high-density and high-strength Al ₂ O ₃ -B ₄ C-based sintered body having a relative density of 90% or more composed of 10 to 50% by weight of B ₄ C and the balance of Al ₂ O ₃ , The characteristics of ₂ O ₃ and B ₄ C, especially toughness, are improved. And the present inventors have found that Al ₂ O ₃ -B
We have earnestly studied to apply the ₄ C sintered body to belt conveyors and cleaner chips.

[0011]

SUMMARY OF THE INVENTION The present invention is a belt conveyor cleaner chip made of current tool steel, high speed steel or cermet, especially a belt cleaner chip having wear resistance higher than that of WC-Co cemented carbide. To provide the material.

[0012]

DISCLOSURE OF THE INVENTION The present invention is characterized by being superior in wear resistance to WC--Co type cemented carbide, and
Ceramic chips for belt conveyor cleaners made of ₂ O ₃ -B ₄ C based sintered bodies.

[0013]

The present inventors have made the following conclusions as a result of extensive studies on applying various ceramics sintered bodies to belt conveyor / cleaner chips. That is, even if ceramics are simply applied to cleaner chips, the wear resistance is not improved, and as a chemical property, it is difficult to react with iron or iron oxides, and in terms of crystallinity, it is from room temperature to about 300 ° C. It is necessary that transformation does not occur in the middle and low temperature range and that the physical properties are high Vickers hardness. Especially, the Vickers hardness is 2100 kgf / mm, which is at least higher than the hardness of conventional Al ₂ O _3.
It is desirably ² or more, and B ₄ C present was enhanced by the addition of Al ₂ O ₃ -B ₄ C-based sintered body is newly to exhibit excellent wear resistance as a belt conveyor cleaner chips It has been discovered.

The present invention will be described in detail below. In the present invention, Al ₂ O ₃ which is relatively inexpensive and has good sinterability, and Al
By compounding B ₄ C having a hardness higher than that of ₂ O ₃ , a material for a belt conveyor / cleaner chip having excellent wear resistance is provided. With this combination, B
The problems of high cost and low sinterability of ₄ C are solved.
Further, Al ₂ O ₃ and B ₄ Al ₂ O ₃ -B ₄ that C was complexed
The C-based high-density sintered body has a structure in which high-hardness B ₄ C grains are dispersed in Al ₂ O ₃ , so that the hardness is significantly improved.

Further, since B ₄ C has a higher thermal conductivity than Al ₂ O ₃ , the thermal conductivity of the Al ₂ O ₃ -B ₄ C sintered body of the present invention is also improved and it is used as a cleaner chip. In this case, in order to efficiently dissipate the friction heat generated at the tip of the tip,
It is desirable. Furthermore, by adding B ₄ C grains,
The so-called particle dispersion effect improves the fracture toughness value, and along with the improvement in the toughness, the fracture strength also improves, and the problem of difficult workability also improves.

In the present invention, the Vickers hardness is 2100 kg, which exceeds the hardness of conventional Al ₂ O ₃ ceramics.
It is preferably f / mm ² or more. This is normal Al ₂ O ₃ ceramics (Vickers hardness 1800-2
000 kgf / mm ² ), when actually used as a belt conveyor cleaner chip, WC-C
This is that there was no significant difference from the o-based cemented carbide. That is, these problems can be solved for the first time by using a ceramic in which Al ₂ O ₃ having high hardness and B ₄ C having extremely high hardness are compounded as in the present invention.

The composite amount of B ₄ C with respect to Al ₂ O ₃ is 10 to 90% by weight, preferably 10 to 50% by weight. When the amount of B ₄ C is less than 10%, the hardness of Al ₂ O ₃ ceramics is not improved so much, and when it exceeds 90%, the hardness is improved, but at the same time as the disadvantage that a large amount of expensive B ₄ C is required, The toughness of the sintered body deteriorates, causing a problem of difficult workability.

In the production of the ceramic chip for a belt conveyor cleaner of the present invention, a usual ceramic molding / sintering method may be applied. For example, a predetermined amount of Al ₂ O ₃ and B ₄ C raw material powder having an average particle diameter of 1 μm or less is weighed, then sufficiently mixed using a ball mill or the like, and molded into a predetermined shape by uniaxial pressing, rubber pressing, slip casting, etc., It suffices to obtain ceramics by firing.

As a firing method, a pressure sintering method such as a hot press sintering method (HP method) or a hot isostatic pressing sintering method (HIP method) is used to obtain a high density and high hardness sintered body. Is preferred. Also, Al ₂ O ₃ and B during firing
_The pressure sintering method is desirable also from the viewpoint of preventing the reaction with ₄ C.

The ceramic thus obtained is processed and polished to a predetermined size to obtain the belt conveyor cleaner chip of the present invention. Cleaner tip,
In particular, it is not necessary to be formed of a ceramics integrated body, and the ceramics may be attached only to the scraped portion by bonding or the like. Hereinafter, a more specific description will be given with reference to examples.

[0021]

EXAMPLE An α-type Al ₂ O ₃ powder (average particle size: 0.2 μm, purity: 99.99% or higher) was added to a B ₄ C powder (average particle size: 1 with an average particle size of 1 to ₄ shown in Table 1). 0.0 μm, purity 98% or more) was added. After thoroughly mixing the powders using a ball mill, 4 hours in argon gas at a temperature of 1750 ° C.
Hot press sintering was performed at a pressure of 00 kgf / cm ² .

The obtained sintered body was processed into a test piece of 3 mm × 4 mm × 38 mm in accordance with JIS-R1601, the density was measured by the Archimedes method, and then a three-point bending test was performed at room temperature. Pre-crack introduction method (SEPB method: JIS-R)
1607) to measure fracture toughness value of sintered body; K _IC ,
As a hardness evaluation, a Vickers hardness of 1 kg is applied.
f, the retention time was 30 seconds. Furthermore, the thermal conductivity was also measured using the laser flash method.

In Table 1, Examples 1 to 4 summarize the relative density, bending strength, fracture toughness value, thermal conductivity and hardness of each sintered body. Further, in Table 1, Comparative Examples 1 and 2 are sintered bodies obtained by hot pressing Al ₂ O ₃ simple substance at respective temperatures of 1350 and 1500 ° C., and Comparative Example 3 are made of B ₄ C simple substance.
The characteristics are similarly shown for a sintered body that is hot-press fired at a temperature of 50 ° C.

[0024]

[Table 1]

By adding B ₄ C as compared with Al ₂ O ₃ alone, the properties such as bending strength are remarkably improved, and it is clear that a sintered body having a Vickers hardness of 2100 kgf / cm ² or more can be obtained. Is. Further, it can be seen that B ₄ C alone has high hardness but extremely low toughness, and the fracture toughness value is remarkably improved by the addition of Al ₂ O ₃ .

Next, 60% of the sintered body used in Examples 1 to 4 was used.
It was processed into a cleaner chip shape of mm × 20 mm × 2.5 mm and applied to a belt conveyer that conveys sinter ore and compounded raw materials, and an abrasion amount evaluation test was performed.

In Table 1, Examples 1 to 4 summarize the wear indexes during transportation of the sinter and the blended raw materials. In Table 1, the characteristics (hardness) and wear test were performed on Comparative Example 1 for Al ₂ O ₃ alone, and on Comparative Examples 4 to 7 for various commercially available ceramics and WC-Co based cemented carbides. The results are shown.

Vickers hardness is 2100 kgf / cm
^The amount of wear of the sintered body of less than ² is W, which is the conventional material.
While not superior to C-Co based cemented carbide (Comparative Example 4), the Al ₂ O ₃ -B ₄ C based sintered body of the present invention has a wear index of 1/2 to 1/4, That is, it is apparent that the life is 2 to 4 times longer. Also, Vickers hardness is 21
Even if it is more than 00kgf / cm ² , S like SiC
It can be seen that the i-based non-oxide ceramics are not suitable for cleaner chips for belt conveyors that carry raw materials containing iron components.

[0029]

The Al ₂ O ₃ -B ₄ C based ceramics belt conveyor cleaner chip according to the present invention has significantly higher durability than conventional WC-Co based cermet chips and other ceramics chips. There are remarkable effects such as improvement, reduction in the number of exchanges, and reduction in equipment cost.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroshi Kubo 1618 Ida, Nakahara-ku, Kawasaki City, Kanagawa Pref., Advanced Technology Research Laboratories, Nippon Steel Corporation

Claims (1)

[Claims] 1. A ceramic chip for a belt conveyor cleaner, comprising an Al ₂ O ₃ -B ₄ C based sintered body, which is used in a belt conveyor for carrying a raw material containing an iron component.