JPH0832942B2 - Composite sintered alloy, heat resistant member and steel support member in heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a composite sintered alloy having a rare earth oxide particle and a Fe-Cr alloy and having a uniform mixed structure, and a block of the composite sintered alloy as a main member. And a steel support member in a heating furnace.

[Conventional technology]

As shown in FIG. 3, a member for supporting heated steel materials (slabs, billets, etc.) in the steel material heating furnace, such as a walking beam conveyor type heating furnace, is formed on the skid pipe (20) that is a moving beam and a fixed beam. As a skid button (10) to be used (steel material is carried on the top surface), high alloy steel (10Ni-20Cr-Fe series steel) or high Co alloy steel (50Co-20Ni-Fe series steel) etc. Heat resistant alloys have been used.

In recent years, the heating furnace operation has become higher in temperature, and high temperature operation exceeding 1300 ° C is becoming common. In such a high temperature operation, it is difficult to guarantee sufficient strength with the conventional heat resistant alloy, and there is a problem that compressive deformation and the like due to repeated loading of steel material easily occur. To improve the skid button material, ceramic sintered materials such as chromium carbide, silicon nitride, and alumina, or fine particles of these ceramics, and refractory metals such as metallic cobalt and Co alloy (UMCo50
Etc.) or high alloy steel (0.1C-27Cr-17Ni-40Co-Fe)
Practical application of a sintered material (composite sintered alloy) having a mixed structure obtained by compositing with a (system) is attempted.

[Problems to be Solved by the Invention]

Ceramic sintered materials have hard and high wear resistance and high-temperature strength that cannot be obtained with conventional heat-resistant alloys, but due to their poor toughness, mechanical impact due to heavy steel materials such as skid buttons is repeated. In addition, there is a drawback that chips and cracks are likely to occur.

On the other hand, the composite sintered alloy is intended to alleviate the brittleness of the ceramic single-phase sintered material by the effect of combining the ceramic particles and the metal and to secure the high temperature characteristics superior to the heat-resistant metal single-phase material. However, due to the combined ceramic particles and metal materials, in a high temperature use environment exceeding 1300 ° C., mutual reaction occurs between the two, resulting in deterioration of the ceramic particles (for example, deterioration of oxidation resistance due to double carbide formation of chromium carbide particles), Alternatively, there is a drawback that deterioration of the material due to a change in the composition of the metal component (for example, deterioration of resistance to high-temperature compression deformation due to melting point decrease) occurs.

The present invention has been made in view of the above, high temperature strength useful as a skid button for high temperature furnaces over 1300 ° C, a composite sintered alloy excellent in oxidation resistance and the like, and a main component of the composite sintered alloy. To provide a heat resistant member and a steel material supporting member.

[Means and Actions for Solving the Problems]

The composite sintered alloy of the present invention is F containing 5 to 50% by weight of Fe.
It is characterized in that it is a sintered body having a mixed structure in which 5 to 80% by weight of rare earth oxide particles are uniformly dispersed in a base metal made of an e-Cr alloy.

 Hereinafter, the present invention will be described in detail.

The Fe-Cr alloy, which forms the base metal of the composite sintered alloy of the present invention, is a solid solution type alloy (at 80% by weight of Fe, the liquid phase line forms a local minimum portion in contact with the solid phase line, and its temperature is about 1510 ° C).
The Fe content in the Fe-Cr alloy is set to 5 to 50% by weight in order to secure good sinterability and to have sufficient compression deformation resistance and oxidation resistance in a high-temperature use environment exceeding 1300 ° C. This is because

That is, from the viewpoint of the high temperature oxidation resistance and the compressive strength of the composite sintered alloy, it is more advantageous to use a chromium simple metal (melting point: about 1830 ° C) as the base metal than the Fe-Cr alloy, but the metallic chromium is It is difficult to sinter, and even if it is sintered under a high pressure like hot isostatic pressing, sintering defects such as pinholes and cracks are likely to occur. For that reason, the sintered alloy has a high melting point but a low resistance to compressive deformation. Therefore, the present invention uses an Fe-Cr alloy containing a certain amount of Fe. The lower limit of the Fe content in the Fe-Cr alloy is set to 5% by weight (liquidus temperature: about 1810 ° C, solid solution temperature: about 1775 ° C) in order to ensure compactness without sintering defects such as pinholes. It is a thing. More preferably, it is 10% by weight or more. Although the sinterability is improved as the amount of Fe is increased, the oxidation resistance is decreased. For this reason, in the present invention, the upper limit is 50% by weight, and thereby, the oxidation resistance that can withstand use in a high-temperature atmospheric furnace exceeding 1300 ° C. is ensured. Further, by limiting the Fe content within this range, the compression deformation resistance that can be used as a skid button or the like in the above-mentioned high temperature environment is also ensured.

The rare earth oxide particles complexed with the Fe-Cr alloy as the base metal are, for example, oxides of yttrium, lanthanum, cerium, neodymium, etc., or complex oxides thereof. The particle size may be about 1-10 μm.

The ratio of rare earth oxide particles in the composite sintered alloy can be adjusted arbitrarily, but the present invention is a working environment in which a high compressive load repeatedly acts under the influence of high temperature heat such as a skid button in a steel heating furnace. In order to obtain improved compressive strength to withstand, the content of rare earth oxide particles is 5% by weight.
That is all. More preferably, it is 10% by weight or more. However, if the ratio is made too high, the toughness tends to decrease with the decrease in the relative ratio of the matrix metal, so in the case of skid buttons, the impact resistance required to prevent cracks and cracks due to the impact of the steel material. To ensure
The proportion of rare earth oxide particles is preferably up to 80% by weight, more preferably up to 70% by weight.

The composite sintered alloy of the present invention comprises a rare earth oxide powder, Fe-
It is produced by using a uniform mixed powder with a Cr alloy powder as a starting material and applying various known sintering methods, preferably hot isostatic pressing.

In the preparation of the sintering raw material powder mixture, it is preferable to carry out the mixing and pulverization by a high energy ball mill such as an attritor from the viewpoint of the uniformity of the mixing and pulverization and the MA (mechanical alloying) effect. When mixing and pulverizing with a high-energy ball mill, replace Fe-Cr alloy powder with Fe powder.
A mixture of Cr powders can be used.

In hot isostatic pressing, the raw material powder mixture is filled in an appropriate metal capsule (for example, mild steel, carbon steel, stainless steel), degassed and hermetically sealed, and the temperature is about 1000 to 1300 ° C, and the pressure is about 1000. It can be achieved by holding at ˜2000 kgf / cm ² for a suitable time (for example, 2 to 4 hours). During the sintering process, the rare earth oxide particles and the Fe-Cr alloy do not cause a reaction that causes a change in the material. Cooling after the completion of sintering may be carried out by lowering the temperature to room temperature, for example, taking 24 hours.

As another process of the sintering process, the raw material powder mixture was filled in rubber and cold isostatic pressing was applied to form a powder compact, which was subjected to rough machining and then sealed in a capsule. Hot isostatic pressing method, or a method of sintering a powder compact with a rough mechanical machine under normal pressure in an inert atmosphere or hydrogen gas atmosphere, or under vacuum. Thus, a method of further hot isostatic pressing and sintering of the sintered body, a method of subjecting the raw material powder mixture to hot pressing and sintering, or the like can be used.

FIG. 1 shows a block made of the composite sintered alloy of the present invention. When the composite sintered alloy block (1) is used as, for example, a skid button which is a steel material supporting member in a heating furnace, the member does not necessarily have to be the composite sintered alloy of the present invention in its entirety, and the skid pipe (20 ), The lower half (12) of the side that abuts against), namely the skid pipe (20)
The part that is sufficiently cooled by conduction heat transfer from the conventional heat-resistant alloy (for example, high Cr high Ni alloy steel), the upper half (11) of which is formed by the composite sintered alloy of the present invention May be The skid button has an upper half (11)
Welding the block of the composite sintered alloy of the present invention, which is to be described below, and the block of the heat-resistant alloy to be the separately prepared lower half part (12),
Alternatively, it can be manufactured by a method of binding by solid welding or the like, or the raw material powder of the composite sintered alloy or its powder compact is sealed in a capsule together with the heat resistant alloy block and hot isostatic pressing is performed. It can also be manufactured by a method of binding.

The composite sintered alloy of the present invention, if desired, is covered with a heat-resistant steel casing to form a heat-resistant member having a combined integral relationship with the heat-resistant steel casing. FIG. 2 shows an example thereof.
(2) is a heat-resistant steel casing, and the composite sintered alloy block (1) is a heat-resistant steel casing (2) except for its top surface.
And the contact interface is solid-phase bonded.

The heat-resistant steel casing (2) encapsulating the composite sintered alloy block (1) functions as a protective member for preventing chipping or cracking due to impact on the composite sintered alloy block (1). The heat-resistant steel that is the material of the casing means a steel material that can withstand the high-temperature oxidizing environment of the heat-resistant member of the present invention, for example, SUS310, 310S, 304, HK, HP, UMCo50, and other known alloys. It may be appropriately selected from steel.

The heat resistant member is a mixture of sintering raw material powders made of rare earth oxide powder and Fe—Cr alloy powder for forming the composite sintered alloy block (1), and a heat resistant steel capsule made of a casing (2). It can be manufactured by a hot isostatic pressing method. Regarding the sintering process in that case as well, in addition to the step of filling the sintering raw material powder mixture in the capsule as described above, degassing and sealing and subjecting to hot isostatic pressing, cold isostatic pressing A step of forming a powder compact by molding or the like, sealing it in a heat-resistant steel capsule, and subjecting it to hot isostatic pressing can be performed. After performing hot isostatic pressing and then subjecting the sintered body to machining and removing the encapsulant on the top surface side, as shown in FIG. 2, a composite sintered alloy block ( A heat-resistant member having 1) and a heat-resistant steel casing (2) enclosing the periphery and bottom of the body is obtained. When the heat resistant member is used as a skid button, it can be easily attached to the skid pipe by welding through the heat resistant steel casing (2).

〔Example〕

Ceramic powder and base metal powder are mixed and pulverized with a high energy ball mill, and the powder mixture (ceramic particle average particle size: 2 μm, metal powder average particle size: 10 μm) is filled in a mild steel capsule, degassed and sealed, and then heated. Sintered hydrostatic pressure sintering, temperature of 1250 ℃, pressure of 1200kgf / cm ² for 2 hours, and then 24 hours, and the temperature is lowered to room temperature. Block (Φ100 × 150, mm) was obtained.

Table 1 shows the component composition of each test sintered alloy. N in the table
Inventive Examples Nos. 101 to 103, o.1 to 6 are composite sintered alloys composed of rare earth oxide particles and an Fe-Cr alloy containing an appropriate amount of Fe.
Is a comparative example, No. 101 is a sintered alloy in which rare earth oxide particles are compounded with metallic chromium, No. 102 is rare earth oxide particles, a sintered alloy in which Fe-rich Fe-Cr alloy is compounded, No. 103
Is one of the most typical conventional skid button materials, including chromium carbide particles and high Co alloy steel (0.1C-27Ni-17Cr-40Co-
Fe) and is an example of a composite sintered alloy.

Sintering defects (pinholes, etc.) for each test sintered alloy
And the melting point, high temperature compression strength (at 1350 ° C. measurement, and oxidation resistance test) were carried out to obtain the results shown in the right column of Table 1.
In addition, in the table, "sintering defect" indicates a result obtained by cutting and dividing the composite sintered alloy block in the radial direction and the axial direction and observing the cut surface under a microscope. The “oxidation resistance” was determined by observing the condition of surface deterioration due to oxidation after the oxidation test in which each of the test sintered alloy blocks was held in an air atmosphere furnace set at 1350 ° C. for 48 hours. A circle mark in the same column means “no oxidation” and a cross mark means “oxidation”.

As shown in Table 1, composite sintered alloy (No. 101) consisting of metallic chromium and rare earth oxide particles has a high melting point, but it is difficult to sinter, so pinholes and cracks And the like, and the high temperature compressive strength remains at a low level.

In addition, a sintered alloy (N containing 70% by weight of Fe-Cr alloy)
o.102) has soundness without pinholes, etc.
Significant deterioration due to oxidation occurs in the temperature range over 300 ° C. Furthermore, the composite sintered alloy block (No. 103) consisting of high Co alloy steel and chromium carbide ceramic particles, which is one of the conventional typical skid button materials, has a high melting point (high Co alloy steel). : Approx. 1380 ℃, Cr ₃ C ₂ particles: 1950 ℃)
However, the melting point of the composite sintered alloy is as low as 1290 ° C, and therefore the compressive strength in the temperature range exceeding 1300 ° C is low.

In contrast, invention examples Nos. 1 to 6 in which Fe-Cr alloy containing 5 to 50% by weight of Fe was used as a base metal and compounded with rare earth oxide particles.
Has good soundness such as pinholes and cracks due to its good sinterability, has a high melting point of approximately 1500 ° C or higher, and exhibits high compressive strength in the high temperature range of over 1300 ° C. Further, it has stable oxidation resistance without quality deterioration in the high temperature oxidizing atmosphere. In addition,
Although there is no difference in melting point between Comparative Example No. 102 (composite sintered alloy of Fe-70% Fe-Cr alloy and rare earth oxide particles) and No. 5 of Inventive Example, high temperature compression in Inventive Example The high level of strength is due to the formation of iron in the sintered alloy structure.
It is considered that the dispersion strengthening action of the chromium compound (FeCr) phase contributes. Further, the melting point of Comparative Example No. 103 (composite sintered alloy of high Co alloy steel and chromium carbide particles) is significantly lower than the melting point of the sintering raw material because the sintering of the composite sintered alloy During the process, the carbon concentration of the base metal increased due to the diffusion of carbon from the chromium carbide particles into the high Co alloy steel base.

[Effects of the Invention] The composite sintered alloy according to the present invention has high density and soundness without pinholes, cracks, etc., and has a high melting point and does not lose high strength in a high temperature range, and also has a high temperature. Since it has oxidation resistance, it is useful as a member that requires these various characteristics, especially as a steel material supporting member such as skid buttons in a heating furnace. Its durability is improved, maintenance is reduced, and furnace operation efficiency is improved. To bring about various effects.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a composite sintered alloy block, and FIG.
FIG. 3 is a cross-sectional view showing an example of a heat-resistant member composed of a composite sintered alloy block and a heat-resistant steel casing, and FIG. 3 is a cross-sectional view showing an example of a steel material supporting member in a heating furnace. 1: Composite sintered alloy block, 2: Heat resistant steel casing, 10: Skid button, 20: Beam (skid pipe)

Front page continuation (72) Inventor Akira Shinozaki 1-1-1, Nakamiya Oike, Hirakata-shi, Osaka Prefecture Kubota Iron Works Co., Ltd. Hirakata Works (72) Inventor Hiroyuki Ran 1-1-1, Nakamiya Oike, Hirakata-shi, Osaka Prefecture Kubota Iron Works Co., Ltd. Hirakata Factory (56) References JP-A-61-261416 (JP, A) JP-A-61-221303 (JP, A) JP-B-49-40761 (JP, B1)

Claims (4)

[Claims] 1. A sintered body having a mixed structure in which 5 to 80% by weight of rare earth oxide particles are uniformly dispersed in a base metal composed of an Fe-Cr alloy containing 5 to 50% by weight of Fe. Characteristic composite sintered alloy. 2. A steel material supporting member for supporting a steel material to be heated in a heating furnace, wherein at least a top side in contact with the steel material to be heated is made of the composite sintered alloy according to claim 1. Steel support member. 3. A composite calcination which is a sintered body having a mixed structure in which 5 to 80% by weight of rare earth oxide particles are uniformly dispersed in a base metal made of an Fe-Cr alloy containing 5 to 50% by weight of Fe. It has a bonded gold block and a heat-resistant steel casing that covers at least the periphery of the body except the top surface of the composite sintered alloy block, and the contact interface between the composite sintered alloy block and the heat-resistant steel casing is solid. A heat-resistant member, which is a hot isostatic pressing sintered body that is phase-bonded. 4. A heated steel support member for a heating furnace, comprising the heat resistant member according to claim 3 and having a top surface of the composite sintered alloy block as a heated steel support surface.