JPH04744B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a heat-insulating composite pipe having a three-layer structure consisting of outer and inner metal layers and a ceramic heat-insulating layer as an intermediate layer. The heat-insulating composite tube manufactured according to the present invention is useful as, for example, a furnace roll, a conveyor roll, and the like.

Furnace rolls in heating furnaces and the like are powerfully cooled by an internal water-cooling structure to prevent softening and strength loss due to the high-temperature atmosphere inside the furnace.
Therefore, a large amount of heat inside the furnace is carried away by the cooling water to the outside of the furnace. In order to save the combustion energy of the furnace, it is desirable to reduce the amount of heat discharged outside the furnace through such rolls as much as possible.

Further, in the process of transporting a high-temperature slab or heated steel material by the transport rolls, the transport rolls lose heat from the transported object due to thermal conduction. If this transport roll is internally cooled to protect the transported object from the thermal effects, the amount of heat lost by the transported object increases. If heat loss during the conveyance process can be reduced and the conveyed object can be maintained at as high a temperature as possible before being sent to the next process, the energy consumption required for reheating in the next process can be reduced accordingly.

The present invention has been made in view of the above, and provides a method for manufacturing a heat-insulating composite pipe having a three-layer structure in which a ceramic heat-insulating layer is provided inside the wall thickness to reduce heat flow in the wall thickness direction.

The manufacturing method of the insulating composite pipe of the present invention is a two-layer pipe (raw pipe) in which the outer peripheral surface of a metal pipe is covered with a ceramic layer.
is concentrically fixed in a centrifugal casting mold, and molten metal is cast into the gap between the inner wall surface of the mold and the outer peripheral surface of the ceramic layer, and solidified under centrifugal pressure.

The method of the present invention will be explained with reference to the accompanying drawings.
0 is a centrifugal casting mold, and A is a two-layer pipe consisting of a metal pipe 1 and a ceramic layer 2 of uniform thickness covering the circumferential surface thereof.

The metal pipe 1 is, for example, a centrifugally cast pipe or a plastically worked pipe made of heat-resistant steel. The ceramic layer 2 is made by attaching a plurality of ring-shaped molded bodies 21, which are sintered products made of, for example, carbide-based, nitride-based, or oxide-based ceramics, to the outer circumferential surface of the metal pipe 1, so that each molded body is attached to the outer peripheral surface of the metal pipe 1. It can be formed by bringing the metal disks 4, 4 into close contact with each other and welding metal disks 4, 4 to both end surfaces.

Reference numeral 11 denotes a band (disc-shaped end plate) fitted to the open end of the mold for fixing the two-layer blank tube A, and each band has an annular projection 12 on the inner surface. The two-layer blank tube A is fitted into the annular projections 12, 12 of the tube band and fixed concentrically within the mold 10.

Reference numeral 13 denotes a gap defined between the inner wall surface of the mold 10 and the outer peripheral surface of the ceramic layer 2 of the two-layer blank tube. This gap is a part where a metal layer is formed around the two-layer blank tube using cast metal.

Further, in the two-layer blank pipe A, a suitable number of holes 5 are formed distributed in the circumferential direction for allowing the molten metal poured into the mold to flow into the above-mentioned pipe gap 13.

While rotating the above-mentioned mold around its axis according to the usual centrifugal casting method, the casting gutter 14 is inserted into the band 11.
A molten metal M such as heat-resistant cast steel is poured into the mold through the central hole 15 of the mold. The cast molten metal flows into the gap 13 on the outside through the molten metal inflow hole 5 of the two-layer blank tube A under the action of centrifugal force, filling the gap 13 over the entire circumference and length. If the mold continues to rotate as it is, the molten metal in the gap 13 will solidify under the pressure of the centrifugal force, forming a dense outer layer around the two-layer blank tube. After solidification is complete, take it out of the mold and the second
As shown in the figure, metal inner layer 1 provided as a blank tube
A composite tube having a three-layer structure is obtained, which has a ceramic layer 2 surrounding the ceramic layer 2, and an outer layer 3 made of cast metal covering the ceramic layer.

In addition, if the ceramic layer 2 in the two-layer pipe is not made into an integral hollow cylindrical molded body with the same length as the body length of the metal pipe 1, but made into a large number of ring-shaped divided bodies as described above, the molding In addition to being easy to manufacture the body and fixing the ring to a metal pipe, it is also advantageous in that the ceramic layer will not be damaged even if axial distortion occurs due to external loads during actual use as a roll etc. be.

Since the composite tube manufactured by the method of the present invention has the ceramic heat-insulating layer 2 as an intermediate layer between the inner layer 1 and the outer layer 3, which are metal layers, it has an excellent effect of suppressing heat flow in the thickness direction of the tube wall. If we focus only on the heat insulating effect, we can achieve our goal with a two-layer pipe consisting of a metal pipe 1 and a ceramic layer 2, but the ceramic layer itself is brittle and easily breaks when subjected to mechanical shock, so it is not practical. I can't stand it. According to the present invention, since the ceramic layer is coated and protected with the outer metal layer, it has both impact resistance and abrasion resistance, and is highly practical as rolls and the like.

As an embodiment of the present invention, a metal pipe 1 [HK heat-resistant cast steel centrifugally cast pipe] is used. Outer diameter 100mm x wall thickness 5mm x length
400mm] ring-shaped ceramic molded body [chromium carbide sintered product. Two-layer base tube A with ceramic layer 2 formed by fitting a large number of ceramic layers (outer diameter 120 mm x wall thickness 10 mm x width 10 mm)
As shown in Fig. 1, the centrifugal casting mold mold 10 [outer diameter
160mm x inner diameter 140mm x length 400mm] and fixed in a concentric ring. The gap 13 between the inner wall surface of the mold and the outer peripheral surface of the ceramic layer is 10 mm. Near one end (on the molten metal casting side) of the two-layer blank pipe A, six holes with a diameter of 30 mm are bored at approximately equal intervals in the circumferential direction as molten metal flow holes 5 to the gap 13. While rotating the above-mentioned mold around the axis so that the gravitational force multiplier on the inner wall surface of the mold is 50G,
Then, molten metal (HK heat-resistant cast steel) was poured into the casting trough 14 at a casting temperature of 1600°C, filled into the gap 13 through the hole 5 of the two-layer pipe, and solidified under centrifugal pressure. The amount of molten metal cast is sufficient to fill the gap 13 and close the hole 5. Through this casting, a robust three-layer composite tube with excellent strength and impact resistance was obtained. This is converted into a high temperature slab (temperature
The temperature gradient in the thickness direction is 10°C/mm when used as a transport roll (1100-1200°C).

As described above, according to the present invention, a composite pipe having a ceramic heat insulating layer as an intermediate layer can be manufactured relatively easily by centrifugal casting. The composite tube obtained by the present invention has a small heat flow in the wall thickness direction and has excellent robustness due to the three layers being firmly connected, so it is useful as a steel-related conveyance roll, a furnace roll, etc., and is useful in these applications. This is effective in reducing heat loss in the furnace and in the transported objects, thereby saving energy. Of course, it is useful as an energy saving measure not only for rolls but also for various equipment and equipment. Furthermore, the present invention is useful as a method for producing radiant tubes. If the obtained composite tube is used as a radiant tube, the intermediate layer (ceramic heat insulating layer) will alleviate uneven temperature distribution in the circumferential and axial directions on the tube surface, so heat will be uniform throughout the entire circumference and length. Radiation is possible.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a specific example of the casting procedure according to the present invention, FIG. 2 is an axial cross-sectional view showing an example of a composite pipe obtained by the present invention, and FIG. 3 is a Y-Y cross-sectional view. 1: Metal inner layer, 2: Ceramic layer, 3: Metal outer layer, 10: Centrifugal casting mold, 13: Gap, 14:
Casting gutter, A: 2-layer pipe, M: molten metal.

Claims (1)

[Claims] 1. A metal pipe whose outer circumferential surface is covered with a ceramic layer is encircled and fixed in a concentric circle in a centrifugal casting mold, and molten metal is cast into the gap between the inner wall surface of the mold and the outer circumferential surface of the ceramic layer, and is then placed under centrifugal pressure. A method for manufacturing an insulated composite pipe characterized by solidification.