JP2003112250A - Cooling pipe cast-in cast iron product and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To prevent the propagation of cracks to a cooling pipe and to provide an excellent cooling effect even if a crack or the like occurs in a cast iron product body due to a thermal shock or an external stress or the like. The present invention provides a cooling pipe cast-in cast iron product and a method for producing the same. SOLUTION: A metal pipe having an aluminum alloy layer and a metal aluminum coating formed on an outer surface is cast in a non-fused and closely adhered state. Here, the non-fusion means that the metal pipe and the casting body are not fused. Also,
The state of close contact means that there is no air gap between the metal pipe and the casting body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast iron product such as a cooling stave for a metallurgical furnace such as a blast furnace, in which a cooling pipe is cast, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A cast iron product such as a cooling stave used in a metallurgical furnace such as a blast furnace, in which a cooling pipe is buried by a cast packet, and a method for manufacturing the same are proposed, for example, as follows. ing.

(1) Japanese Patent Laid-Open No. 60-3960: A metal pipe having good heat conductivity such as a copper alloy filled with a sand for casting and hardened is used, and the metal pipe is heated by the heat of the molten metal during pouring. A method of melting the surface of the molten metal and integrating the molten metal and the pipe (hereinafter referred to as prior art 1).

(2) Jikkei 6-38592: A method in which a heat and corrosion resistant pipe (made of stainless steel) is fixed in a mold, and a pressurized cooling gas is flowed in the pipe to pour and cast. , Referred to as Prior Art 2).

(3) Japanese Patent Publication No. 58-49607: A cooling stave equipped with a non-fusion type double cooling pipe, and 0.08 to 0.25 m outside the drawn double steel pipe.
A method of forming an alumina coating having a thickness of m and then casting it with spheroidal graphite cast iron (hereinafter referred to as prior art 3).

(4) Japanese Patent Application Laid-Open No. 9-71875: A method for coating a refractory material on the pipe surface by immersing a casting pipe cooling pipe in a slurry of refractory material such as heated alumina, pulling it up and drying it. Hereinafter, referred to as Prior Art 4).

(5) Japanese Unexamined Patent Publication No. 2000-141021: A cooling stave provided with a non-fusing type cooling tube. An aluminum diffusion coating layer and an alumina layer are formed on the outer surface of the cooling tube by a calorizing treatment. After that, it was casted with spheroidal graphite cast iron (hereinafter referred to as prior art 5).

(6) Japanese Patent No. 2528397 relates to a furnace mouth metal of a converter, in which a metal powder is sprayed on the surface of an outer pipe in a brick holding portion of the furnace mouth metal, and cooling water flows in the inner pipe. In which a cooling conduit consisting of a double pipe through which the water flows is buried (hereinafter referred to as prior art 6).

[0009]

Each of the above prior arts has the following problems. Prior art 1 requires the removal of the foundry sand filled in the metal pipe,
The pipe shape is restricted. In addition, since the copper alloy of the pipe material is easily melted, if cracks or melt damage occur in the casting body, cooling water may flow out from the molten portion of the pipe and a steam explosion may occur.

In the prior art 2, since the outer peripheral surface of the pipe to be cast is completely encapsulated in the cast body, if the cast body is cracked or melted, it immediately propagates to the pipe. Similar to the technique 1, the cooling water may flow out and a steam explosion may occur.

In the prior art 3, since the cooling pipe has a double pipe structure consisting of an inner pipe and an outer pipe and an alumina coating is formed on the outer side of the outer pipe, even if a crack occurs, its propagation is prevented. be able to. However, since an air gap is generated between the inner pipe and the outer pipe and between the outer pipe and the casting insert, there is a problem that the cooling effect is lowered by the air gap.

In the prior art 4, the coating film layer of the refractory material on the surface of the cooling pipe is thick, and the refractory film layer and the air gap are formed between the cooling pipe and the base material after the cast-in, so that the cooling effect is significantly lowered. is there.

In the prior art 5, an aluminum diffusion coating layer is formed on the outer surface of the cooling pipe and an alumina coating is formed on the outer surface of the cooling tube by a calorizing treatment, and even if a crack occurs in the casting body, its propagation is prevented. However, since a thin air gap is generated between the pipe and the base material after casting, the cooling effect is still reduced.

In the prior art 6, since the cooling pipe has a double pipe structure consisting of an inner pipe and an outer pipe, and the outer surface of the outer pipe is subjected to thermal spraying treatment of metal powder (aluminum powder), cracks occur. However, the propagation can be prevented, but there is a problem that an air gap exists between the inner pipe and the outer pipe, and the cooling effect is lowered as in the case of the prior arts 3 to 5.

In summary, the problems of the prior art are summarized as follows: In the prior arts 1 and 2, since the cooling pipe and the casting body are fused, there is no problem of deterioration of the cooling effect, but cracks in the casting body, There is a problem that the melting loss immediately propagates to the cooling pipe. On the other hand, in the prior arts 3 to 6, since the coating layer is provided on the outer surface of the cooling pipe so that the coating layer and the casting body are not in close contact with each other, even if the casting body has cracks or melt damage, it does not affect the cooling pipe. Although there is no (small) problem of propagation, there is a problem that an air gap is created in this part because the coating layer and the casting body are not in close contact, and the cooling effect is reduced.

The present invention has been made to solve the above problems, and even if cracks or the like occur in the cast iron product body due to thermal shock, external stress, or the like, cracks in the cooling pipe will occur. An object of the present invention is to provide a cooling pipe cast-in cast iron product which is prevented from propagating and has an excellent cooling effect, and a manufacturing method thereof.

[0017]

(1) A cooling pipe cast-in cast iron product according to the present invention casts a metal pipe having an aluminum alloy layer and a metal aluminum coating formed on the outer surface in a non-fused and intimate contact state. It is a package. Here, non-fusing means that the metal tube and the casting body are not fused.
Moreover, the state of close contact means that there is no air gap between the metal tube and the casting body. Such a non-fused and intimate contact state can be achieved by controlling the temperature when casting a metal tube having an aluminum alloy layer and a metal aluminum coating formed on the outer surface. Specifically, the surface temperature of the metal tube is controlled to be lower than the melting point of the aluminum alloy layer and higher than the melting point of the metal aluminum coating.

(2) The aluminum alloy layer and the metallic aluminum coating are formed by hot dip aluminum plating.

(3) The aluminum alloy layer has a thickness of 0.02 mm to 0.3 mm.

(4) Further, in the method for producing a cast-in cast iron product for cooling pipes according to the present invention, a metal tube is subjected to a molten aluminum plating treatment to form an aluminum alloy layer and a metal aluminum coating film on the outer surface of the metal tube. And a step of setting the metal tube on which the aluminum alloy layer and the metal aluminum coating are formed in a mold having a predetermined shape, and casting a molten cast iron to cast and wrap the metal tube. is there.

(5) Further, the present invention is characterized in that the cast iron molten metal is cast into a metal tube set in a mold having a predetermined shape while flowing an inert gas.

(6) Further, it is characterized in that the hot dip aluminum plating treatment temperature is 660 ° C. to 740 ° C. and the treatment time is 10 minutes to 50 minutes.

[0023]

FIG. 1 is an explanatory view of an embodiment of the present invention, and is a schematic plan view of a cooling stave 1 of a blast furnace. 2 is a sectional view taken along the line AA in FIG. The cooling stave 1 of the present embodiment is shown in FIGS.
As shown in, the cooling pipe 5 made of a metal pipe (steel pipe) is cast in the main body 3 made of cast metal. Cooling pipe 5
Is connected to a water supply pipe (not shown), and the other end of the cooling pipe 5 is connected to a drain pipe (not shown).

As shown in FIG. 2, the cross section of the cooling pipe 5 of the cooling stave 1 has an aluminum alloy layer 9 formed on the outer surface of the metal pipe 7, and the outside of the aluminum alloy layer 9 is covered by the casting body 3. It is a structure. As can be seen from FIG. 2, the aluminum alloy layer 9 is interposed between the metal tube 7 and the casting body 3, and the metal tube 7 and the casting body 3 are in a non-fused state. Therefore, when there is a crack or melting loss in the casting body 3 caused by the fusion of the metal tube 7 and the casting body 3, the prior art 1, which propagates to the cooling tube 5,
Problem 2 does not occur.

The aluminum alloy layer 9 on the outer surface of the metal tube 7 is formed on the outer surface of the metal tube by, for example, hot dip aluminum plating, and the metal tube 7 and the aluminum alloy layer 9 are in close contact with each other. The heat transfer property is kept good. Further, the aluminum alloy layer 9 and the casting body 3 are also in close contact with each other and there is no air gap, and the heat transfer property between them is also kept good. Details of the close contact state between the aluminum alloy layer 9 and the casting body 3 will be described later in the description of the manufacturing process.

Next, a method of manufacturing the cooling pipe cast-in cast iron product of the present invention will be described. (1) Hot-dip aluminum plating process The hot-dip aluminum plating process is performed on the metal pipe 7 that becomes the cooling pipe 5. By this plating process, as shown in FIG. 3, the aluminum alloy layer 9 and the metal aluminum coating 11 are formed on the outer surface of the metal tube.

When performing the molten aluminum plating treatment,
Hot-dip aluminum plating temperature range is 660 ℃ ~ 74
Set to 0 ° C. This is because if the treatment temperature is lower than 660 ° C, molten aluminum is solidified and treatment is impossible, while if it exceeds 740 ° C, surface oxidation or the like may occur. A desirable processing temperature is 680 ° C to 720 ° C.

The aluminum alloy layer 9 formed by the hot dip aluminum plating has a thickness of 0.02 mm to 0.
3 mm. The thickness of the aluminum alloy layer 9 is 0.02
If it is less than mm, after casting, the aluminum alloy layer 9 may partially or entirely melt, and the metal tube 7 and the base material (cast body 3) may be fused, while if it exceeds 0.3 mm, the aluminum alloy This is because the layer 9 is likely to be peeled off and the metal tube 7 may be fused. The preferable thickness of the aluminum alloy layer 9 is 0.08 mm to 0.16 mm.

In order to keep the thickness of the aluminum alloy layer 9 within the above range, it is necessary to define the time for the hot dip aluminum plating treatment. Therefore, the inventor tested the relationship between the processing time and the thickness of the aluminum alloy layer 9 when the processing temperature was 700 ° C. The results are shown in Table 1.

[0030]

[Table 1]

As shown in Table 1, when the processing temperature is 700 ° C., the thickness of the aluminum alloy layer 9 is 0.02 mm to
In order to achieve 0.3 mm, it is necessary to set the processing time to 10 minutes to 50 minutes. In addition, as shown in Table 1, the preferable thickness of the aluminum alloy layer 9 is 0.08 mm to 0.16 mm.
Since the processing time corresponding to this is 20 minutes to 30 minutes, the preferable processing time is 20 minutes to 30 minutes.

The metal aluminum coating 11 is to be attached to the outer periphery of the aluminum alloy layer 9 at the stage of hot dip aluminum plating, and the thickness thereof is at least 0.00.
5 mm is required. The preferred thickness is 0.01
~ 0.05 mm.

(2) Cast-in process When the aluminum alloy layer 9 and the metal aluminum coating 11 are formed on the outer surface of the metal tube 7 by the above-mentioned hot dip aluminum plating process, they are then placed in a mold having a predetermined shape. The metal pipe 7 is set and wrapped by casting the molten cast iron.

At this time, the most important thing is to prevent the aluminum alloy layer 9 from being melted to prevent the metal tube 7 and the casting body 3 from being fused together, and the metal aluminum coating 11 to be melted so that the base material (casting body 3) is melted. And the aluminum alloy layer 9 are adhered to each other with good wettability. Therefore, temperature control is performed during casting. That is, an inert gas for cooling is made to flow inside the metal pipe 7, the flow rate is adjusted, and the pouring temperature is controlled. Specifically:

The melting point of the aluminum alloy layer 9 is 1160 ° C.
˜1170 ° C., and the melting point of the metallic aluminum coating 11 is 660 ° C. Therefore, the surface temperature of the metal tube 7 is set to be lower than the melting point of the aluminum alloy and higher than the melting point of the metal aluminum coating 11 by controlling the pouring temperature and adjusting the flow rate of the inert gas (normal temperature) flowing on the inner surface of the metal tube. Control.

By performing such temperature control, the aluminum alloy layer 9 remains without being melted, and the metal aluminum coating 11 is melted so that the aluminum alloy layer 9 and the cast iron base material can have good wettability. .

The flow rate of the inert gas for cooling is determined by the wall thickness of the cast iron product and the diameter and length of the metal tube to be cast and wrapped. As an example, in the case of a cast iron product having a wall thickness of 400 mm and a steel pipe having a diameter of 50 A and a length of 2000 mm,
It is set to ⁵ Nm ³ / H to 600 Nm ³ / H. Also, caliber 50
A, 5Nm ³ / H in case of 1000mm long steel pipe
˜200 Nm ³ / H. If it is less than 5 Nm ³ / H, replacement with air is insufficient and there is a possibility that it will be oxidized on the inner surface of the pipe after casting, while the upper limit value (in the above cast iron products, 600 Nm ³ / H, length 1000
If the thickness exceeds 200 Nm ³ / H), the cooling effect on the metal tube is too large, and the metal aluminum coating 11 is not sufficiently melted, and the aluminum alloy layer 9
This is because an air gap may occur between the base material and the base material.

FIG. 4 shows an enlarged photograph of a cross section obtained by cutting a part of the cast iron product manufactured as described above. FIG. 4 shows the state of the interfacial structure between the metal tube and the base material (material is FCD). The aluminum alloy layer 9 remains soundly on the surface of the cast-in metal tube, and the aluminum alloy layer 9 and the base material It was confirmed that there was no air gap between the materials.

Next, the performance of the cooling pipe cast-in cast iron product manufactured as described above will be described. (1) Cooling performance The cooling effect evaluation test method shown in FIG. 5 shows the cooling effect of the cooling pipe cast-in cast iron product according to the method of the present invention and the cast-in method of the prior arts 3 to 5 described in the section of the conventional technique. Compared by. The test method was as follows: the furnace atmosphere temperature was kept constant at 650 ° C., and the flow rate of cooling water in the cast-in test piece was 30 to 160 l /.
The temperature is changed within the range of min, and the body temperature of 10 mm is measured from the inner surface of the furnace.

An example of the results is shown in FIG. It can be seen that the cast-in product of the present invention has a much lower surface temperature of the test piece than the prior art cast-in casting method, has excellent heat transfer properties, and significantly improves the cooling effect.

(2) Propagation of cracks Assuming that cracks have occurred in the product body, a notch is provided in advance on the base metal (cast iron) side, and a bending test is performed. Experiments were carried out to see if it could be propagated to. As a result, it was confirmed that the base material was cracked from the notch due to the bending, but at this time, peeling occurred between the aluminum alloy layer 9 and the base material, so that the crack did not propagate to the metal tube 7.

That is, the metal aluminum coating 11 is melted at the time of casting to give the aluminum alloy layer 9 and the cast iron base material good wettability. However, between the aluminum alloy layer 9 and the cast iron base material, this metal aluminum is provided. It is in close contact with the film 11 due to melting, and is fragile in strength. Therefore, when an external force acts, peeling occurs at this portion, the metal pipe 7 and the casting body 3 are separated, and a crack on the casting body side is prevented from proceeding to the metal pipe side 7. That is, when the metal aluminum coating 11 is melted during casting, the aluminum alloy layer 9 and the cast iron base material are closely adhered to each other without forming a gap to maintain good heat transferability, but the contact portion is weak in strength. Since the peeling occurs due to the action of the external force, it is possible to prevent the crack from propagating to the metal pipe 7.

As described above, in the blast furnace cooling stave 1 shown in this embodiment, the cooling stave 1 is cooled by the cooling water flowing in the metal tube because of its excellent heat transfer property.
The cooling effect is improved and its life can be extended. Further, even if a crack or the like occurs in the casting body 3 due to a thermal shock, an external stress, or the like, the crack can be prevented from propagating to the cooling pipe 5, and the cooling water flows out or a steam explosion due to this occurs. Can be prevented.

Further, in the above embodiment, since the method of controlling the molten metal pouring temperature and adjusting the flow rate of the inert gas was used as the method of controlling the temperature during casting, extremely thick cast iron with slow solidification was used. Even products can be temperature controlled,
A sound cast-in can be realized without causing fusion on the surface of the metal tube.

It should be noted that in the above-described embodiment, the processing of the outer surface of the pipe has been mainly described in the step of performing the molten aluminum plating treatment on the metal pipe 7. However, the hot dip aluminum plating treatment may be performed on the inner surface of the tube. As a result, an anticorrosive effect on the inner surface of the pipe is obtained.

Further, the cast-in-die cast iron product of the metal tube according to the present invention is not limited to the cooling staves for the blast furnace described above, and for example, cooling water such as a converter furnace mouthpiece, an injection molding machine die is circulated. It can also be applied to various cast iron products in which a cooling pipe is cast and wrapped.

[0047]

Embodiments of the present invention will be described below. Example 1 The following cooling staves for a blast furnace were manufactured by the method of the present invention. (1) Product name: Blast furnace cooling stave Material: Alloy FCD Dimensions: Length 1900mm, width 1000mm, casting wall thickness 4
00mm (2) Cast metal tube material: STB340 (Aluminum alloy and metallic aluminum coating are formed on the outer surface by molten aluminum plating) Diameter: 50A Length: 1800mm (3) Temperature and time of molten aluminum plating: Treatment The temperature is 700 ° C., and the treatment time is 30 minutes. (4) The metal tube having the aluminum alloy layer of 0.16 mm formed on the outer surface is set in the mold having a predetermined shape, and the nitrogen gas is supplied at a flow rate of 100 Nm ³ / H. Then, the molten cast iron was cast at a temperature of 1300 ° C. while being blown. (5) Thus, the pipe and the base material are non-fused and in close contact with each other, which is excellent in achieving heat transfer, and even if a crack or the like occurs in the cooling stave due to a thermal shock or external stress, the pipe is not cracked. It was possible to manufacture a product that does not propagate.

Example 2 The following converter core metal for a converter was manufactured by the method of the present invention. (1) Product: Furnace mouthpiece Properties: FC200 As-cast dimensions: length 2400 mm, width 1350 mm, wall thickness 2
00mm (2) Metal tube to be cast and wrapped Material: STB410 (Aluminum alloy layer and metallic aluminum coating are formed on the outer surface by hot dip aluminum plating) Diameter: 50A Length: 2000mm (3) Hot dip aluminum plating temperature and time: Treatment The temperature is 700 ° C. and the treatment time is 25 minutes. (4) A metal tube having an aluminum alloy layer of 0.12 mm formed on the outer surface is set in a mold having a predetermined shape, and nitrogen gas is supplied at a flow rate of 50 Nm ³ / H. Then, the molten cast iron was cast at a temperature of 1290 ° C. while being blown. (5) Thus, the pipe and the base material are non-fused and in close contact with each other, excellent heat transfer is achieved, and even if a crack or the like occurs in the furnace mouth metal due to thermal shock or external stress, the pipe will crack. It was possible to produce a product that does not propagate.

[0049]

As described above, according to the present invention, the metal pipe having the aluminum alloy layer and the metal aluminum coating formed on the outer surface is cast in a non-fused and non-fused state. Excellent in cooling, high cooling effect, and
Even if a crack or the like occurs in the cast iron body, the crack is prevented from propagating into the cooling pipe.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, and is a schematic plan view of a cooling stave of a blast furnace.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is an explanatory diagram of an embodiment of the present invention, showing a state in which a metal tube is subjected to a molten aluminum plating treatment.

FIG. 4 is an enlarged photograph of a metal interface structure between a cast-in pipe and a cast body according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of a cooling effect evaluation test method according to an embodiment of the present invention.

FIG. 6 is a graph showing a comparison of heat transfer between the product of the present invention and the prior art.

[Explanation of symbols]

1 cooling stave 3 body 5 cooling tubes 7 Metal tube 9 Aluminum alloy layer 11 Metal aluminum coating

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsuneo Araki             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Shigeshi Matsuyama             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Takashi Watanabe             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Liu Zhimin             2-1, Shiraishi-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa             Inside Hon Foundry Co., Ltd. (72) Inventor Tatsuhiko Kobayashi             2-1, Shiraishi-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa             Inside Hon Foundry Co., Ltd. (72) Inventor Mitsuhiko Anaga             2-1, Shiraishi-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa             Inside Hon Foundry Co., Ltd. F-term (reference) 4K015 CA05

Claims (6)

[Claims] 1. A cooling pipe cast-in cast iron product, which is obtained by casting a metal pipe having an aluminum alloy layer and a metal aluminum coating film formed on the outer surface thereof in a non-fused and intimate contact state. 2. The cooling pipe cast-in cast iron product according to claim 1, wherein the aluminum alloy layer and the metal aluminum coating film are formed by hot dip aluminum plating. 3. The aluminum alloy layer has a thickness of 0.02 m.
It is m-0.3 mm, The claim 1 or 2 characterized by the above-mentioned.
Cooling pipe cast-in cast iron product described in. 4. A step of forming a aluminum alloy layer and a metal aluminum coating on the outer surface of the metal tube by subjecting the metal tube to a molten aluminum plating treatment, and a metal tube on which the aluminum alloy layer and the metal aluminum coating are formed. Is set in a mold having a predetermined shape, and the cast metal melt is cast into the metal pipe to cast and encase the metal pipe. 5. The method for producing a cast iron product for cast-in cooling pipe according to claim 4, wherein the molten cast iron is cast into a metal pipe set in a mold having a predetermined shape while flowing an inert gas. 6. The molten aluminum plating treatment temperature is 66.
The cooling pipe cast-in cast iron product manufacturing method according to claim 4 or 5, wherein the treatment time is 0 ° C to 740 ° C and the treatment time is 10 minutes to 50 minutes.