JPH0514149U - Skid button for heating furnace - Google Patents

Abstract

(57) [Abstract] [Purpose] By increasing the high temperature strength and oxidation resistance of the skid button and relaxing the forced cooling of the button top,
We aim to reduce uneven heating (skid marks) of the steel to be heated and to improve the thermal economy of the furnace. [Structure] Skid button, upper layer 11, middle layer 1
2 and a three-layer laminate of lower layers, and the upper layer 11 is C
r-Fe alloy (Cr: 60 to 95%, melting point: 1600 ° C
As described above, a composite having a mixed phase structure in which ceramics are mixed as a dispersed phase in a matrix having an average crystal grain size of 50 μm or more, a ceramic sintered body as an intermediate layer, and a heat-resistant alloy as a lower layer.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to improvement of a skid button which is a member for supporting heated steel material in a heating furnace.

[0002]

[Prior Art]

 The skid beam, which is a means for transferring heated steel in the heating furnace, has a structure in which skid buttons are attached to the top of the peripheral surface of a skid pipe (carbon steel pipe, etc.) at regular intervals in the pipe axial direction. .. In FIG. 4, P is a skid pipe, and 10 is a skid button attached to the pipe P by welding W1. The skid button 10 is a block made of a heat-resistant alloy steel typified by nickel-chromium alloy steel (SCH 12, etc.) and having a columnar / conical trapezoidal shape or a prismatic / pyramidal trapezoidal shape. Contact is placed. Cooling water is sent into the skid pipe P, and its cooling action alleviates the thermal effect of the high-temperature oxidizing atmosphere in the furnace on the skid button 10, maintains the strength to withstand the load of the steel to be heated, and its surface. It is designed to prevent oxidative damage. The side surface of the skid button 10 is usually coated with an amorphous refractory layer R for blocking contact with the high temperature oxidizing atmosphere in the furnace.

[0003]

[Problems to be solved by the device]

 Recently, high-temperature operation at 1300 ° C or higher has been generalized for the purpose of improving the operating efficiency of heating furnaces. Along with this, the skid button is accelerating the compressive deformation due to the load of the steel material to be heated and the oxidative damage on the surface, which shortens the service life and increases the maintenance load. This reduction in strength and oxidative damage of the skid button under high temperature operation can be suppressed and mitigated to some extent by strengthening the forced cooling effect of the cooling water in the skid pipe. This is because the cooling water is forced to increase the loss of the amount of heat inside the furnace that is taken out of the furnace, and the uneven heating of the steel to be heated (the so-called skid mark, which is the local low temperature part that occurs on the contact surface with the skid button). ) Is promoted, which inevitably results in the subsequent deterioration of the rolling quality of steel products.

As a countermeasure, it has been attempted to use a ceramic sintered block as a skid button. However, since ceramic is a brittle material, cracks and fractures are likely to occur due to repeated impacts in the process of transporting the steel to be heated, making stable use difficult. The present invention provides an improved skid button that solves the above problems.

[0005]

[Means and Actions for Solving the Problems]

 The present invention relates to a skid button which is mounted on a skid pipe with the top surface serving as a support surface for heated steel. The skid button includes an upper layer on the top surface, a lower layer on the skid pipe side, and an intermediate layer between these layers. Has a Cr content of 60 to 95%, a mixture of C of 0.8% or less and Si of 5% or less is allowed, and the balance is substantially Fe, and has a melting point of 1600 ° C. or more. , A composite composed of a matrix of Cr-Fe alloy having an average crystal grain size of 50 μm or more and 40% by volume or less of a ceramic dispersed phase, an intermediate layer of a ceramic sintered body, and a lower layer of a heat-resistant alloy steel. It is characterized by being a layer stack.

Hereinafter, the present invention will be described in detail. Unless otherwise specified, “%” in the description means% by weight. The skid button of the present invention is a three-layer laminate including an upper layer, an intermediate layer, and a lower layer. In FIG. 1, 11 is an upper layer, 12 is an intermediate layer, and 13 is a lower layer.

The upper layer is 11, the Cr content is 60 to 95%, the melting point is 1600 ° C. or more, and the crystal grain size (average) is 50 μm or more is used as a matrix, and a ceramic is used as a dispersed phase in the matrix. It is formed of a composite having a multiphase structure in which are uniformly mixed (hereinafter, “composite alloy”). The matrix Cr-Fe alloy allows C, Si, etc. to be mixed within the range where a melting point of 1600 ° C. or higher is ensured, and C may be mixed in about 0.5% or less and Si in about 5% or less. ..

The matrix of the composite alloy forming the upper layer 11 is the Cr—Fe alloy having the above-mentioned chemical composition and crystal structure because it is heated in an oxidizing atmosphere at a high temperature exceeding 1300 ° C. This is because it has a high compressive deformation strength that causes almost no deformation even when a high load of steel is repeatedly applied, and oxidation resistance that hardly suffers oxidative damage over a long period of time. Its oxidation resistance is due to its high Cr content (60% or higher) and high melting point (1600 ° C or higher), and its compressive deformation strength is high Cr content and high melting point, with an average particle size of 50 μm or more. It is given as an effect of having a coarse grain crystal structure of. The upper limit of the Cr content is 95% in order to secure the toughness of the matrix.

Ceramics mixed as a dispersed phase in the Cr-Fe alloy matrix are oxide-based (Cr ₂ O ₃ , ZrO, Al ₂ O ₃ , SiO ₂ , Y ₂ O ₃ etc.), nitride-based (Si ₃ N ₄ , TiN, BN, AlN, etc.), carbides (Cr ₃ C ₂ , WC, SiC, B ₄ C, etc.), silicides (Mo ₂ Si, Cr ₂ Si, etc.), or borides (CrB). ₂ , TiB ₂ etc.), and the high temperature strength of the upper layer 11 is enhanced by the dispersion strengthening effect of the mixture of one or more ceramics (particle size is 0.1 to 5 μm, for example). The proportion of the dispersed phase in the mixed phase structure is about 40% by volume.

The composite alloy that is the upper layer 11 is a cast body block obtained by mixing a ceramic powder that is a dispersed phase into a molten Cr—Fe alloy having a predetermined composition by high-frequency melting or the like, injecting the mixture into a mold, and solidifying the mixture. Alternatively, it is a sintered block produced by a hot isostatic pressing method using a mixture of Cr—Fe alloy powder having a predetermined composition and ceramic powder as a sintering raw material. The coarse-grained crystal structure (average grain size: 50 μm or more) of the matrix metal in the composite alloy block is formed in the cast block by solidifying at a relatively slow cooling rate using a sand mold for casting, for example. In the case of a sintered body block, use coarse particles (average particle size: about 200 μm or more) as Cr-Fe alloy powder in the sintering raw material, or after sintering, By heat-treating at an appropriate temperature (for example, 1300 to 1600 ° C) higher than the processing temperature (about 1000 to 1500 ° C) for an appropriate time (for example, 10 to 20hr), the crystal structure of the crystal grain is coarse particles with an average grain size of 50µm or more. It can be an organization.

Since the composite alloy forming the upper layer 11 has strength and oxidation resistance to withstand a high temperature of 1300 ° C. or higher, strong forced cooling as in the case of a conventional heat-resistant alloy skid button is required. Not. The ceramic sintered body interposed as an intermediate layer on the lower surface side of the composite alloy layer suppresses forced cooling from the skid pipe to the composite alloy layer in order to avoid excessive cooling and cooling of the composite alloy layer. It also serves as a heat insulating layer.

That is, in the composite alloy forming the upper layer 11, the thermal conductivity κ of the Cr—Fe alloy matrix is about 30 to 40 kcal / m · hr · ° C., which is a high thermal conductivity (this is compared with the conventional skid). Since the heat conductivity of the heat-resistant alloy such as SCH12, which is the button material, is higher than about 20 to 30 kcal / m · hr · ° C), the effect of forced cooling from the skid pipe is large and it is difficult to keep it at high temperature. is there. On the other hand, that of ceramic has low thermal conductivity of about 2 to 8 kcal / m · hr · ° C, depending on the material type. When the upper layer is a composite alloy in which ceramics are mixed, the thermal conductivity is lower than that of the Cr-Fe alloy single phase and it is advantageous for holding at a high temperature, but that is not enough. Therefore, in the present invention, a ceramic sintered body is interposed as an intermediate layer on the lower surface side of the upper layer 11. Due to the adiabatic effect of this ceramic as the intermediate layer, the cooling action from the skid pipe to the Cr-Fe alloy layer of the upper layer is effectively mitigated, and the upper layer can be maintained at a high temperature of 1300 ° C or higher. Becomes

The ceramic forming the intermediate layer 12 is an oxide type, a nitride type, a carbide type, or the like, and the kind of material is arbitrary, but the sintered body is a hot isostatically isostatic-fired. A highly dense material produced under the uniform action of a high pressure (for example, 1000 to 2000 kgf / cm ² ) such as a binding method is preferably used from the viewpoint of mechanical strength and the like.

A heat-resistant alloy layer is provided as the lower layer 13 on the lower surface side of the intermediate layer 12 made of ceramic. This makes it possible to apply welding to the attachment of the skid button to the skid pipe, which is strong and stable. This is because it is easy to secure the fixed state. Since the lower layer 13 is sufficiently forcibly cooled by the skid pipe, there is no difficulty in selecting the material of the heat-resistant alloy, and nickel-chromium heat-resistant cast steel or the like used as a conventional skid button material is sufficient. Is.

The joining of the composite alloy block which is the upper layer 11 and the ceramic sintered body block which is the intermediate layer 12, and the joining of the ceramic sintered body block and the heat resistant alloy block of the lower layer 13 are performed, for example, It can be sufficiently achieved by applying a hot isostatic pressing method and applying treatment under pressure / heating (for example, 1200 to 1300 ° C. × 1000 to 1200 kgf / cm ² × ^{2 to} 8 hr).

Alternatively, a powder of a transition metal or an alloy thereof (Cr, Fe, Ni, Cr-Fe, Cr-Ni, Fe-Ni, Cr-Ni-Fe, etc.) is used as an adhesive, and the overlapping surfaces of the blocks are used. After coating and superimposing it on the substrate, it is heated in an oxidizing atmosphere (atmosphere) furnace at a temperature lower than the melting point of the bonding agent metal (for example, melting point -30 to 400 ° C.) and maintained for a suitable time (for example, 1 to 3 Hr). It can also be applied. Specific examples of the bonding agent metal include 15 to 25% Cr-15 to 25% Fe-Ni alloy.

Regarding the shape of the overlapping surface between the blocks of the upper layer 11, the intermediate layer 12, and the lower layer 13, FIG. 1 shows an example in which the overlapping surface is a flat horizontal surface. Without being limited, for example, by using an upwardly or downwardly convex overlapping surface having a conical slope, the resistance against damage and peeling of the contact surface when a horizontal external force is applied during actual use is enhanced. You can also do it.

The skid button of the present invention has the same external appearance as that of a normal skid button except that it has a three-layer laminated structure, and is a columnar body having a height of about 100 to 200 mm. Although the layer thickness of each layer is not particularly limited, for example, the upper layer 11 of the Cr—Fe alloy is 40 to 60 mm, the intermediate layer 12 of the ceramic sintered body is 20 to 60 mm, and the lower layer 13 of the heat-resistant alloy is 60 to 150 mm. ..

[0019]

[Action]

 The upper layer 11 made of the composite alloy of the skid button of the present invention can withstand use at a high temperature around 1300 ° C. If the temperature at the time of use is about 1300 to 1350 ° C, the addition of forced cooling is not substantially required. By maintaining this high temperature, the skid marks on the steel to be heated are alleviated and the heat loss due to cooling water is reduced. The intermediate layer 12 made of a ceramic sintered body suppresses the action of forced cooling of the skid pipe on the upper layer 11 due to its heat insulating effect, and makes it possible to keep the upper layer 11 in a high temperature state. The lower layer 13 made of a heat-resistant alloy enables welding to be used for attaching the skid button 10 to the skid pipe P, and can easily secure a strong attachment state required as a heated steel support surface member. ..

[0020]

【Example】

(1) Cast member block (by sand mold casting) of a solid-liquid mixture in which ceramic powder is added to a melt of Cr—Fe alloy, which is an upper layer of constituent members of a skid button. Matrix (Cr-Fe alloy): Cr 84.5%, C 0.02%, Si 2.5%, Bal Fe. Melting point 1680 [deg.] C. Average crystal grain size 200 μm. Dispersed phase (ceramic): Alumina. Average particle size 1 μ. Volume ratio 5%. Intermediate layer The following a and b types of ceramic sintered body blocks (hot isostatic isotropic pressure sintered products) a: Zirconia (sintering treatment: 1500 ° C x 1100 kgf / cm ² x 2Hr) b: alumina (sintering treatment 1600 ° C. × 1100 kgf / cm ² × ² Hr) Lower layer 27% Cr-20% Ni-40% Co-Fe heat-resistant cast steel cast block

(2) Material Properties of Upper Layer (Composite Alloy Block) High Temperature Compressive Deformation Strength: High temperature compressive deformation test in which a load of 0.5 kgf / mm ² is repeatedly applied (loading 4 seconds-no-loading 4 seconds repetition / test) Comparing the compression deformation amount after 10 ⁴ repetitions at a temperature of 1350 ° C.) with the conventional skid button material heat resistant cast steel SCH12, the deformation amount of SCH12 is about 4.5%. About 1.5% (or less), about 1/3 or less.

Oxidation resistance: Oxidation weight loss when kept in an air atmosphere at 1350 ° C. for 100 hours is about 4 g / m ² · Hr or less, which is 1/10 or less, compared to about 70 g / m ² · Hr of SCH1 2. It is as follows.

(3) Assembly of skid button Test skid button A in which each block is joined between the overlapping surfaces by hot isostatic pressing (1300 ° C. × 1100 kgf / cm ² × ² Hr) , B were produced. Skid button A : Sintered zirconia block is used for the intermediate layer Skid button B : Alumina sintered block is used for the intermediate layer Height H: 160 mm, upper layer thickness h ₁ : 40 mm, intermediate layer thickness h ₂ : The thickness is 40 mm, the lower layer thickness h _{3 is} 80 mm, and the top surface diameter d is 90 mm (FIG. 2).

Further, the following two skid buttons C and D were prepared as comparative examples. The composite alloy in the upper layer and the heat-resistant alloy in the lower layer have the same composition as above. Test skid button C : A two-layer laminated body consisting of the upper layer of the composite alloy block and the lower layer of the heat-resistant alloy. Test skid button D : A single-layer body that is entirely a composite alloy block from the top to the bottom.

(4) Heating Test Each test skid button is attached by welding onto the skid pipe P by welding as shown in FIG. 2, the refractory coating layer R is applied, and the surface in an atmosphere of 1350 ° C. Measure the temperature distribution of. Reference symbols a to n in the figure indicate temperature measurement positions. A to F are positions in the radial direction from the center of the top surface, and T to N are positions in the vertical direction along the side surface from the top ridge to the boundary with the intermediate layer.

The results of the above heating test are shown in FIG. The symbols of the graphs in each figure are the symbols of the skid button under test. As shown in the figure, in the skid button C (a two-layer laminate of a composite alloy block and a heat-resistant alloy block) and the skid button D (a single layer of the composite alloy block), the temperature near the central portion of the top surface was 1250 ° C. or less, In contrast to the temperature difference of 100 ° C or more with respect to the atmosphere in the furnace, the skid button A (intermediate layer: zirconia ceramic) and the skid button B (intermediate layer: alumina ceramic) having the three-layer structure of the devised example are Due to the adiabatic effect of the intermediate layer, the top surface temperature is about 1330 ° C or higher.

[0027]

[Effect of the device]

 The skid button of the present invention can be used more stably than a conventional skid button in a high temperature oxidizing atmosphere furnace at 1300 ° C or higher, and reduces the skid marks on the steel to be heated to achieve more uniform heating. can do. In addition, the effect of suppressing forced cooling of the skid button is to reduce the amount of heat loss carried out of the reactor by the cooling water. Therefore, it is possible to obtain the effects of improving the quality of the heated steel material and improving the thermal economy.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a skid button of the present invention.

FIG. 2 is an explanatory view of the shape and temperature measurement position of a skid button related to an embodiment.

FIG. 3 is a graph showing the temperature distribution on the surface of the skid button.

FIG. 4 is a vertical sectional view showing a conventional skid button.

[Explanation of symbols]

10 skid buttons, 11: upper layer, 12: middle layer,
13: lower layer, P: skid pipe, R: refractory coating layer, S: heated steel material.

Claims (1)

[Scope of utility model registration request] 1. A skid button mounted on a skid pipe with the top surface serving as a support surface for steel to be heated, comprising an upper layer on the top surface, a lower layer on the skid pipe side, and an intermediate layer between these layers. The layer has a Cr content of 60 to 95%, a mixture of C of 0.8% or less and Si of 5% or less is allowed, and the balance has a chemical composition of substantially Fe, and a melting point of 1600 ° C. or more. The composite intermediate layer consisting of a matrix of Cr—Fe alloy having an average crystal grain size of 50 μm or more and a ceramic dispersed phase accounting for 40% by volume or less is a ceramic sintered body, and the lower layer is a heat-resistant alloy steel. A skid button for a heating furnace, which is a laminated body.