JP7215010B2 - Blast furnace tuyere and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tuyere for a blast furnace and a manufacturing method thereof.

Blast furnace tuyeres (hereinafter also simply referred to as "tuyeres") protrude into the furnace of the blast furnace, and the protruding tip is exposed to a high-temperature atmosphere, so excellent heat resistance is required. In addition, since ore and coke in the furnace may collide with the tip of the tuyere, excellent wear resistance is also required.

A water channel is provided inside the tuyere main body, and the temperature near the tip protruding into the blast furnace is reduced by flowing cooling water through the water channel. The material of the tuyere main body is usually copper or a copper alloy with excellent thermal conductivity. However, water-cooling the inside of the tuyere alone cannot sufficiently reduce the temperature at the tip, and copper has low hardness and is inferior in terms of wear resistance. A protective layer is provided to enhance durability. Although the provision of a protective layer increases the life of the tuyeres, long-term use nevertheless leads to tip damage and the need to replace the tuyeres. Since the blast furnace must be shut down to replace the tuyeres, if the tuyeres are damaged, not only the replacement cost but also the production of hot metal will decrease.

A nickel-based material is often used for the protective layer of the tuyere. The reason for this is that nickel alloys are excellent in strength and corrosion resistance at high temperatures, and the hardness can be increased by precipitating hard intermetallic compounds in the matrix or by mixing carbides, nitrides, etc. When a nickel alloy with high hardness is applied to the protective layer, for example, as described in Patent Documents 1 to 3, by providing a protective layer of a metal that has a high bondability with copper, which is the main body of the tuyere, Adhesion of the high-hardness protective layer can be enhanced.

JP-A-59-15374 JP-A-4-246113 JP-A-11-217610

In Patent Document 1, a nickel or nickel alloy or stainless steel thin plate material is diffusion-bonded to a copper tuyere body by hot isostatic pressing, and a heat-resistant and wear-resistant material is applied on the thin plate material. It is described that a protective layer is provided by fill welding.

Patent Document 2 describes a protective layer in which a build-up layer of Ni--Mo alloy is provided on a build-up layer of Ni--Cr alloy. Further, Patent Document 3 describes a protective layer in which a hard facing material containing ceramic particles dispersed in a metal matrix such as nickel is welded to the surface of the tuyere base material (or further on the intermediate layer). . As in the inventions of these documents, the heat resistance and wear resistance of the tuyeres can be improved by stacking the weld surfacing layers. However, it is necessary to pay attention to fatigue characteristics because the outermost layer is subjected to repeated stress due to temperature fluctuations in the furnace and thermal shock from the melt. Cracks caused by fatigue occur and propagate, and if ore or coke in the furnace collides with these crack initiation sites, the cracks propagate more easily. I have no choice but to change my mouth.

The present invention has been made to solve the problems of the prior art, and provides a blast furnace tuyere having excellent heat resistance, wear resistance, and fatigue resistance against thermal fluctuations in the furnace, and its manufacture. The purpose is to provide a method.

The protective layer provided on the outer surface of the tuyere main body is a hard protective layer at room temperature, but when the temperature rises during operation of the blast furnace, the hardness decreases and wear resistance deteriorates. As described above, the tuyere main body has cooling water flowing through the water channel provided inside to reduce the temperature near the tip protruding into the blast furnace, which can also reduce the temperature of the protective layer.

Therefore, first, in order to avoid the temperature rise of the protective layer during operation of the blast furnace, the protective layer should have a multi-layer structure, and the inner layer should be made of a material that has excellent adhesion to the tuyere body and high thermal conductivity. It is effective to provide a protective layer composed of and as the outer layer, a protective layer composed of a material having excellent wear resistance that can withstand collisions with ore and coke in the furnace. Conventionally, various studies have been made on such materials, and certain effects have been confirmed.

Here, even if a protective layer having high thermal conductivity and excellent wear resistance is formed, it is subject to fatigue damage due to repeated thermal fluctuations during blast furnace operation. When such fatigue damage occurs, cracks due to fatigue occur and propagate, and if a wide area of the protective layer tends to fall off from the tuyere main body, the life of the tuyere for blast furnaces will be shortened. , the frequency of repair and replacement work increases, resulting in a decrease in the operating efficiency of the blast furnace.

Therefore, the present inventors investigated the form of damage that leads to the extensive drop-off of the protective layer when the protective layer is provided at the tip of the blast furnace tuyere by overlay welding. In one form of damage, a crack that occurs on the surface of the protective layer due to fatigue, etc., propagates in the direction perpendicular to the surface (thickness direction of the protective layer) and reaches the interface between the first protective layer and the second protective layer. After that, it was observed to propagate along the interface, leading to extensive delamination. With respect to this form of damage, the present inventors have proposed a first protective layer made of a material with excellent adhesion to the tuyere main body and a structure that can withstand collisions with ore and coke in the furnace during operation of the blast furnace. In the two-layered protective layer with the second protective layer, which has excellent abrasion resistance, even if cracks occur due to fatigue, we investigated how to suppress the propagation of cracks as much as possible and prevent extensive delamination. By making the second protective layer a layer in which two or more types of build-up welds are mixed, even if a crack occurs in the protective layer during operation of the blast furnace, the crack propagation will occur at the build-up weld. It stops at the interface and can reduce the fall-off range of the protective layer. As a result, the life of the protective layer as a whole was improved, and the life of the tuyeres for blast furnaces was extended.

The gist of the present invention is as follows.
[A] A method for manufacturing a tuyere for a blast furnace, comprising the following steps (1) and (2).
(1) providing a first protective layer on the outer surface of the tuyere body including at least the tip by diffusion bonding or overlay welding;
(2) A step of providing a second protective layer in which two or more types of build-up welds are mixed by sequentially changing the type of welding material on at least a portion of the surface of the first protective layer.

[B] In the step (1),
wherein the first protective layer is made of Ni or a Ni—Cr alloy;
The method for manufacturing a tuyere for a blast furnace according to the above [A].

[C] In the step (2),
The welding material comprises a Ni or Ni alloy dispersed with one or more hard particles selected from carbides, nitrides, oxides and borides.
The method for manufacturing a tuyere for a blast furnace according to the above [A] or [B].

[D] In the step (2) above,
The welding material includes two or more materials with different contents of the hard particles,
The method for manufacturing a tuyere for a blast furnace according to the above [C].

[E] In the step (2) above,
The welding material includes a material made of a Ni-Cr alloy,
A method for manufacturing a tuyere for a blast furnace according to any one of [A] to [D] above.

[F] a tuyere body portion made of copper or a copper alloy, the tip of which protrudes into the blast furnace;
a first protective layer made of diffusion bonding or overlay welding covering the outer surface of the tuyere main body including at least the tip;
a second protective layer consisting of a build-up welding layer that covers at least part of the surface of the first protective layer,
The second protective layer is a build-up weld layer in which two or more types of build-up welds are mixed,
Blast furnace tuyeres.

[G] the first protective layer is made of Ni or a Ni—Cr alloy;
The above [F] tuyere for blast furnace.

[H] The second protective layer includes an overlay weld in which hard particles of one or more selected from carbides, nitrides, oxides and borides are dispersed in Ni or Ni alloys.
The above [F] or [G] tuyere for blast furnace.

[I] the second protective layer includes two or more types of build-up welds with different contents of the hard particles;
The above [H] tuyere for blast furnace.

[J] the second protective layer includes a build-up weld made of a Ni—Cr alloy;
A tuyere for a blast furnace according to any one of [F] to [I] above.

According to the present invention, it is possible to obtain a tuyere for a blast furnace that is excellent in heat resistance, wear resistance, and fatigue resistance against thermal fluctuations in the furnace.

It is a schematic diagram explaining the manufacturing method of the tuyere for blast furnaces which concerns on this invention. It is a schematic diagram which shows the cross-sectional shape of the flattened first protective layer. It is a schematic diagram which shows the cross-sectional shape of the tuyere for blast furnaces which concerns on this embodiment. FIG. 4 is a schematic diagram showing a cross-sectional shape of a second protective layer according to the present invention (an example in which build-up layers of different types are arranged in parallel). FIG. 4 is a schematic diagram showing a cross-sectional shape of a second protective layer according to the present invention (an example in which build-up layers of different types are arranged on the same line). FIG. 4 is a schematic diagram showing a cross-sectional shape of a second protective layer according to the present invention (another example in which build-up layers of different types are arranged on the same line). Cross-sectional shape of the second protective layer according to the present invention (an example of stacking two layers in which different types of overlay layers are arranged on the same line: an example in which the welding direction of the first layer and the welding direction of the second layer are parallel) It is a schematic diagram showing. Cross-sectional shape of the second protective layer according to the present invention (an example of stacking two layers in which different types of overlay layers are arranged on the same line: an example in which the welding direction of the first layer and the welding direction of the second layer are perpendicular) It is a schematic diagram showing. FIG. 4 is a schematic diagram showing a cross-sectional shape of a second protective layer according to the present invention (an example in which three layers in which different types of overlay layers are arranged on the same line are stacked: an example in which the welding directions of all three layers are parallel). . Second protective layer according to the present invention (an example of three layers in which different types of overlay layers are arranged on the same line: the welding direction of the first layer and the welding direction of the third layer are parallel, and the welding direction of the first layer Fig. 3 is a schematic diagram showing a cross-sectional shape of an example in which the direction and the welding direction of the second layer are perpendicular to each other. FIG. 4 is a schematic diagram showing a cross-sectional shape of a second protective layer according to the present invention (an example in which three build-up layers of different types are stacked).

1. Method for Manufacturing Tuyeres for Blast Furnace The method for manufacturing tuyeres for blast furnace according to the present invention comprises a step of providing a first protective layer and a step of providing a second protective layer. Each step will be described below taking as an example the case where the first protective layer is provided by build-up welding.

(1) Formation of First Protective Layer Referring to FIG. 1(a), in this step, a first protective layer 3a is formed on the outer surface of the tuyere body 1 including at least the tip (not shown) by overlay welding. It is a step of providing. As the material of the first protective layer 3a, a material having excellent adhesion to the tuyere main body 1 and high thermal conductivity can be selected. As the material of the first protective layer 3a, for example, Ni or a Ni--Cr alloy can be selected. Specific materials will be described later.

As the overlay welding method, a known method can be adopted, and examples thereof include shielded arc welding, MAG welding, carbon dioxide gas arc welding, MIG welding, TIG welding, and submerged arc welding. Among them, it is preferable to adopt the TIG welding method in order to improve the workability of welding Ni or Ni—Cr alloy to the tip of the tuyere, which has a three-dimensional curved shape.

A step of flattening the surface of the first protective layer 3a may be provided before providing the second protective layer 3b. Referring to FIG. 1(b), this step is a step of grinding or polishing the surface of the first protective layer 3a to planarize it. In the figure, the dashed line is a schematic diagram before flattening, and the solid line is a schematic diagram after flattening. Flattening can use, for example, lathes, milling machines, machining centers, and the like. Moreover, you may planarize by grinding with a grinder.

The planarized surface of the first protective layer 3a preferably has a maximum height (maximum valley depth) of 0.20 mm or less between a valley bottom and a peak adjacent to the valley bottom. Here, referring to FIG. 2, the heights of the valley bottom and the peaks adjacent to the valley bottom are, for example, symbols h ₁ , h ₂ and h ₃ in FIG. The maximum valley depth is _h2 . If this maximum valley depth is too large, voids (unwelded portions) will increase at the interface when the second protective layer 3b is formed later, increasing the interfacial thermal resistance. The maximum valley depth is preferably 0.15 mm or less, more preferably 0.10 mm or less.

The maximum valley depth can be measured by observing a cross section including the thickness direction of the first protective layer 3a. , a three-dimensional shape measuring instrument, or the like can be used to measure the surface shape.

Although the case where the first protective layer 3a is provided by build-up welding has been described above, the first protective layer 3a may be provided by diffusion bonding. When the first protective layer 3a is provided by diffusion bonding, a plate material processed into a shape along the shape of the tuyere main body 1 is attached to the tuyere main body 1, heated in that state, and the interface is diffusion-bonded. It's good.

(2) Formation of Second Protective Layer Referring to FIG. 1(c), this step is a step of providing a second protective layer 3b by build-up welding on at least part of the surface of the first protective layer 3a. When providing the second protective layer 3b by build-up welding on at least a part of the surface of the first protective layer 3a, the type of welding material is sequentially changed so that two or more types of build-up welds 30 and 31 are mixed. It is important to provide the second protective layer 3b. Moreover, it is also possible to first open a gap and overlay-weld one welding material, and then overlay-weld the gap with a different type of welding material. The material of the second protective layer 3b is located in the outer layer of the protective layer 3, and has wear resistance (specifically, Vickers hardness of 180 Hv or more) that can withstand collisions with ore and coke in the furnace during operation of the blast furnace. ) and high thermal conductivity (specifically, 10 W/mK or more) can be selected. For example, a material in which hard carbides such as TiC are dispersed in Ni can be used. Specific materials will be described later.

The second protective layer 3b may be provided on at least part of the surface of the first protective layer 3a. For example, since the lower part of the tuyere is a place where ore and coke in the furnace are unlikely to collide during operation of the blast furnace, it is not necessary to provide the second protective layer 3b on this part. Therefore, at least a portion of the surface of the first protective layer 3a specifically means the surface of a portion including at least the uppermost portion of the tuyeres installed in the blast furnace. In particular, it is preferable that the second protective layer 3b is provided on the surface of the portion constituting the upper half of the tuyere installed in the blast furnace. At this time, the thickness of the first protective layer 3a in the portion where the second protective layer 3b is not provided, the total thickness of the first protective layer 3a and the second protective layer 3b in the portion where the second protective layer 3b is provided are substantially the same.

As the overlay welding method, a known method can be adopted, and examples thereof include shielded arc welding, MAG welding, carbon dioxide gas arc welding, MIG welding, TIG welding, and submerged arc welding. Among them, it is preferable to adopt the TIG welding method in order to improve the workability of welding Ni or Ni alloy to the tip of the tuyere, which has a three-dimensional curved surface shape.

2. Blast Furnace Tuyere Referring to FIGS. and a second protective layer 3b consisting of a layer. Although there is no particular restriction on the welding direction of the overlay welding layer 3b, it is preferable that the welding direction coincides with the circumferential direction of the cylinder constituting the tuyere main body 1. As shown in FIG. Description will be made on the assumption that the horizontal direction in (a) of each of FIGS.

(1) Tuyere Main Body The tuyere main body 1 is arranged in the blast furnace such that the tip 1b protrudes from the inner wall of the blast furnace, and the tip 1b is exposed to high temperatures during operation of the blast furnace. A water channel 2 is provided inside the tuyere body 1, and cooling water is caused to flow through the water channel 2 to reduce the temperature near the tip 1b. The tuyere main body 1 has a cylindrical shape, and hot air having a high temperature (for example, about 1200° C.) is blown into the cylinder during operation of the blast furnace. The material of the tuyere main body is usually copper or a copper alloy with excellent thermal conductivity.

(2) First Protective Layer The first protective layer 3a is a build-up weld layer that covers the outer surface 1a of the tuyere main body 1 including at least the tip 1b. As the material of the first protective layer 3a, a material having excellent adhesion to the tuyere main body 1 and high thermal conductivity can be selected. From the viewpoint of adhesion with the tuyere main body 1, a material having a coefficient of thermal expansion close to that of copper or a copper alloy used for the tuyere main body 1, specifically, a coefficient of thermal expansion (linear expansion coefficient) of 13 to Materials can be selected that are in the range of 16×10 ⁻⁶ /°C. A material with high thermal conductivity is, for example, a material with thermal conductivity in the range of 10 W/(m·K) or more. As the material of the first protective layer 3a, for example, Ni or a Ni--Cr alloy can be selected.

More specifically, in mass %, Cr: 0 to 40.0%, Mn: 0 to 4.0%, Ti: 0 to 3.0%, Al: 0 to 3.0%, Nb: 0 to 3.0%, Fe: 0 to 9.0%, the balance being Ni and impurities. The term "impurity" means a component that is allowed to enter into Ni or a Ni alloy from raw materials such as ores, scraps, and other factors in the industrial production of Ni or Ni alloys as long as it does not impair the effects of the present invention.

Since Cr improves corrosion resistance, it may be contained in the material of the first protective layer 3a. If the content is excessive, cracks will occur during welding, so the upper limit is made 40.0%. In order to exhibit the above effect, the content is preferably 5.0% or more, more preferably 10.0% or more. More preferably, it is 14.0% or more. Moreover, the upper limit is preferably 35.0%, more preferably 30.0%, and even more preferably 25.0%.

Mn enhances fluidity during welding and suppresses the occurrence of weld defects, so it may be contained in the material of the first protective layer 3a. If the content is excessive, the ductility and toughness are lowered and cracks are likely to occur, so the upper limit is made 4.0%. In order to exhibit the above effect, the content is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more. Also, the upper limit is preferably 3.5%, more preferably 3.0%, and even more preferably 2.5%.

Ti forms an intermetallic compound with Ni to increase the hardness of the protective layer and improve wear resistance, so it may be contained in the material of the first protective layer 3a. If the content is excessive, the ductility and toughness are lowered and cracks are likely to occur, so the upper limit is made 3.0%. In order to exhibit the above effect, the content is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more. Also, the upper limit is preferably 2.5%, more preferably 2.0%, and even more preferably 1.5%.

Al forms an intermetallic compound with Ni to increase the hardness of the protective layer and improve wear resistance, so it may be contained in the material of the first protective layer 3a. If the content is excessive, the ductility and toughness are lowered and cracks are likely to occur, so the upper limit is made 3.0%. In order to exhibit the above effect, the content is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more. Also, the upper limit is preferably 2.5%, more preferably 2.0%, and even more preferably 1.5%.

Nb forms an intermetallic compound with Ni to increase the hardness of the protective layer and improve wear resistance, so it may be contained in the material of the first protective layer 3a. If the content is excessive, the ductility and toughness are lowered and cracks are likely to occur, so the upper limit is made 3.0%. In order to exhibit the above effect, the content is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more. Also, the upper limit is preferably 2.5%, more preferably 2.0%, and even more preferably 1.5%.

Fe may be contained in the material of the first protective layer 3a because Fe improves the strength of the protective layer and improves the wear resistance by forming a solid solution in the Ni alloy. Further, when Ni is added in combination with Nb, it forms an intermetallic compound with Nb to increase the hardness of the protective layer and improve wear resistance. If the content is excessive, there is a problem that ductility and toughness are lowered and cracks are likely to occur, so the upper limit is made 9.0%. In order to exhibit the above effect, the content is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more. Also, the upper limit is preferably 8.5%, more preferably 8.0%, and even more preferably 7.5%.

The thickness (average thickness) of the first protective layer 3a is preferably 2.0 to 6.0 mm. If it is less than 2.0 mm, it may be difficult to maintain sufficient wear resistance, and if it exceeds 6.0 mm, it may be difficult to sufficiently cool the tip of the tuyere.

(3) Second Protective Layer The second protective layer 3b is a layer made of a build-up weld layer that covers the surface of the first protective layer 3a. The material of the second protective layer 3b is located in the outer layer of the protective layer 3, and has wear resistance (specifically, Vickers hardness of 180 Hv or more) that can withstand collisions with ore and coke in the furnace during operation of the blast furnace. ) and high thermal conductivity (specifically, 10 W/mK or more) can be selected. For example, a material in which hard particles of one or more kinds selected from carbides, nitrides, oxides and borides are dispersed in Ni or Ni alloys can be used. Examples of carbide include TiC, WC, NbC, and VC, among which TiC is preferred. This is because TiC has a high hardness and is a material that is extremely effective in improving wear resistance. The welding materials of different types include, in addition to the case where the chemical composition of Ni or Ni alloy constituting the matrix is different, the case where the hard particles are different in kind, the hard particle content is different, and the like.

Referring to FIG. 4, when the second protective layer 3b is provided by build-up welding on at least a part of the surface of the first protective layer 3a, the build-up welding is performed using an arbitrary welding material to form a linear build-up. After the build-up weld 30 is provided, build-up welding is performed using a different kind of welding material, and another type of build-up weld 31 is build-up welded along the build-up weld 30 . By repeating this operation, the second protective layer (overlay welding layer) 3b in which the linear build-up welds 30 and the linear build-up welds 31 are mixed is obtained. As a result, even if a crack occurs and propagates in one of the build-up welds 30 and 31 while ensuring wear resistance, it can be limited to a narrow range, so that the protective layer falls off over a wide range. can be prevented.

5 and 6, when the second protective layer 3b is provided by build-up welding on at least a part of the surface of the first protective layer 3a, an arbitrary build-up weld layer 30 is build-up welded, Another type of build-up weld 31 is build-up welded on the same line as the build-up weld 30 . Along the obtained overlay welds 30 and 31, a overlay weld 31 using another welding material is formed on the same line as the overlay weld 30 using an arbitrary welding material by the same method as described above. is overlay welded. By repeating this operation, a second protective layer (overlay welding layer) 3b in which the overlay welding part 30 and the overlay welding part 31 are mixed on the same line is obtained. The overlay weld layers shown in FIGS. 5 and 6 can make each overlay weld 30, 31 smaller than the overlay weld layer shown in FIG. can do.

7 and 8, when providing the second protective layer 3b by build-up welding on at least part of the surface of the first protective layer 3a, any build-up weld layer 30 is built-up welded, Another type of build-up weld 31 is build-up welded on the same line as the build-up weld 30 . This operation is repeated to obtain a build-up weld layer (first build-up weld layer) in which the build-up welds 30 and the build-up welds 31 are mixed on the same line. After that, the same operation is repeated on the first build-up weld layer to form a second build-up weld layer, thereby obtaining a second protective layer (build-up weld layer) 3b having a two-layer structure. At this time, the welding direction of the first overlay welding layer and the welding direction of the second overlay welding layer may be the same (FIG. 7) or different (FIG. 8). In addition, the total thickness of the two overlay welding layers can be made thinner than the thickness of a single overlay welding layer. 7 and 8, the weld overlays 30 and 31 are made smaller than the overlay weld layers with the single layer structure shown in FIGS. 5 and 6. Therefore, crack propagation can be suppressed to a smaller extent.

9 and 10, when the second protective layer 3b is provided by build-up welding on at least part of the surface of the first protective layer 3a, an arbitrary build-up weld layer 30 is built-up welded, Another type of build-up weld 31 is build-up welded on the same line as the build-up weld 30 . By repeating this work, a build-up weld layer (first build-up weld layer) in which the build-up weld 30 and the build-up weld 31 are mixed on the same line is obtained. By repeating the same operation on the layers, second and third build-up weld layers are formed to obtain a build-up weld layer with a three-layer structure. At this time, the welding directions of all overlay welding layers may be the same or different. The example shown in FIG. 9 is an example in which the welding directions of all the first to third overlay welding layers are the same, and the example shown in FIG. The welding direction of the second build-up weld layer is different, and the welding direction of the first build-up weld layer is the same as the welding direction of the third build-up weld layer. In addition, the total thickness of the three overlay welding layers can be made relatively thinner than the thickness of the two overlay welding layers. The overlay weld layers shown in FIGS. 9 and 10 can further reduce the size of the weld overlays 30 and 31 compared to the overlay weld layers shown in FIGS. can be suppressed to a smaller range.

Referring to FIG. 11, when the second protective layer 3b is provided by build-up welding on at least a part of the surface of the first protective layer 3a, an arbitrary build-up weld layer 33 is built-up welded, and the first layer A built-up weld layer 33 is obtained. Next, on the overlay welding layer 33 of the first layer, another welding material is used for overlay welding to obtain the overlay welding layer 34 of the second layer, and further on the overlay welding layer 34 of the second layer Then, another welding material is used for build-up welding to obtain a third built-up weld layer 35 . At this time, when using a material in which hard particles of one or more kinds selected from carbides, nitrides, oxides and borides are dispersed in Ni or Ni alloy, for example, as the overlay welding layers 33, 34, and 35 For this purpose, it is preferable that the content of hard particles on the outer layer side is higher than that on the inner layer side. In the example shown in FIG. 11, the second layer is larger than the first layer, and the third layer is larger than the second layer. The content of hard particles in the layer 34<the content of hard particles in the third build-up weld layer 35 is preferable. As a result, the overlay weld layer becomes harder as it approaches the outer layer, improving wear resistance, and even if a crack propagates in the second protective layer, it can be restricted within a narrow range, so it can be protected in a wide range. It is possible to prevent layers from coming off.

As the overlay welding layer of the second protective layer 3b, a overlay welding layer obtained by welding a material in which hard particles of one or more kinds selected from carbides, nitrides, oxides and borides are dispersed in Ni or Ni alloy. , When using a material including a build-up weld layer in which a material made of Ni-Cr alloy is welded, wear resistance can be maintained with hard particles, and ductility can be maintained with the Ni-Cr alloy, so the protective layer is difficult to fall off. can be configured.

It is preferable that the carbides in the material of the second protective layer 3b are uniformly dispersed. If the particle size of the carbide is too large, it becomes difficult to uniformly disperse the particles. Therefore, the maximum particle size of the carbide is preferably 200 μm or less. Also, the average particle size of the carbide is preferably in the range of 40 to 100 μm. In addition, even if the volume ratio of carbides is too high, it becomes difficult to disperse them uniformly. 25% is more preferable.

The thickness of the second protective layer 3b is preferably 3.0 to 6.0 mm. If the thickness is less than 3.0 mm, it may be difficult to maintain sufficient wear resistance, and if it exceeds 6.0 mm, it may be difficult to sufficiently cool the tip of the tuyere.

The sum (T _a +T _{b )} of the thickness T a of the first protective layer 3a and the thickness T _b of the second protective layer 3b is preferably 6.0 to 9.0 mm. This is because if it is less than 6.0 mm, there is a risk that sufficient wear resistance cannot be ensured, and if it exceeds 9.0 mm, there is a risk that the tuyere tip cannot be sufficiently cooled.

10 Tuyere for blast furnace 1 Tuyere main body 1a Outer surface 1b Tip 2 Channel 3 Protective layer 3a First protective layer 3b Second protective layer 5 Unwelded portion 30 Overlay weld layer 31 Overlay weld layer 33 Overlay weld layer ( first layer)
34 overlay welding layer (second layer)
35 Overlay welding layer (third layer)

Claims (10)

A method for manufacturing a tuyere for a blast furnace, comprising the following steps (1) and (2).
(1) providing a first protective layer on the outer surface of the tuyere body including at least the tip by diffusion bonding or overlay welding;
(2) A step of providing a second protective layer in which two or more types of build-up welds are mixed by sequentially changing the type of welding material on at least a part of the surface of the first protective layer, The second protective layer is provided on the surface of one protective layer and on the upper half including the top of the tuyere main body, and the second protective layer is not provided on the lower half of the outer surface of the tuyere main body. . In the step (1) above,
wherein the first protective layer is made of Ni or a Ni—Cr alloy;
The method for manufacturing a tuyere for a blast furnace according to claim 1. In the step (2) above,
The welding material comprises a Ni or Ni alloy dispersed with one or more hard particles selected from carbides, nitrides, oxides and borides.
The method for manufacturing a tuyere for a blast furnace according to claim 1 or 2. In the step (2) above,
The welding material includes two or more materials with different contents of the hard particles,
The method for manufacturing a tuyere for a blast furnace according to claim 3. In the step (2) above,
The welding material includes a material made of a Ni-Cr alloy,
A method for manufacturing a tuyere for a blast furnace according to any one of claims 1 to 4. a tuyere main body made of copper or a copper alloy, the tip of which protrudes into the blast furnace;
a first protective layer made of diffusion bonding or overlay welding covering the outer surface of the tuyere main body including at least the tip;
a second protective layer consisting of a build-up welding layer that covers at least part of the surface of the first protective layer,
The second protective layer is a build-up weld layer in which two or more types of build-up welds are mixed , and is provided on the surface of the first protective layer and in the upper half including the top of the tuyere main body. and not provided on the lower half of the outer surface of the tuyere body ;
Blast furnace tuyeres. wherein the first protective layer is made of Ni or a Ni—Cr alloy;
A tuyere for a blast furnace according to claim 6. wherein the second protective layer comprises an overlay weld in which hard particles of one or more selected from carbides, nitrides, oxides and borides are dispersed in Ni or Ni alloys;
A tuyere for a blast furnace according to claim 6 or 7. The second protective layer includes two or more types of build-up welds with different contents of the hard particles,
The tuyere for blast furnace according to claim 8. The second protective layer includes a build-up weld made of a Ni—Cr alloy,
A tuyere for a blast furnace according to any one of claims 6 to 9.

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