JPH06218512A - Manufacture of composite metallic tube - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of a composite metallic tube where excellent adhesivity can be obtained even in the vicinity of the end on the molten metal tip side of the molten metal of the inner layer material when the centrifugal casting of the inner layer is executed on the inner circumferential surface of the outer layer. CONSTITUTION:After the centrifugal casting of the outer layer is executed on the inner circumferential surface of a mold 1 for centrifugal casting through a coating 2, the molten metal of the inner layer is poured from one end A of the mold 1, and the centrifugal casting of the inner layer is executed on the inner surface of the outer layer. In this operation, the coating thickness on the molten metal tip side of the molten metal of the inner layer material is formed thinner than that on the pouring side. The thickness of the mold on the molten metal tip side of the molten metal of the inner layer material is formed thicker than that on the pouring side. The preheat temperature of the mold on the molten metal tip side of the molten metal of the inner layer material is set higher than that on the pouring side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the improvement of the adhesion between the outer layer and the inner layer of a composite metal tube in which the inner layer of the different material is welded to the inner surface of the outer layer.

[0002]

2. Description of the Related Art Some piping materials are required to have not only strength but also peculiar properties such as corrosion resistance and wear resistance depending on the object to be transported. As such a pipe material, a composite metal pipe in which an inner layer or an outer layer is formed of a required metal material and both layers are welded and integrated is used. For example, in transport pipes for high pressure / corrosive fluids such as sour oil well piping materials, high strength carbon steel such as carbon steel for machine structure and low alloy steel for machine structure is used for the outer layer.
A highly corrosion resistant alloy such as SUS316L, IN825, IN625 is used for the inner layer. Such a composite pipe is usually cast by a centrifugal force casting method because the outer layer and the inner layer are easily welded to each other. That is, the molten outer layer material is cast into a centrifugal casting mold, after the outer layer is centrifugally cast, the mold is subsequently rotated, and the molten inner layer material having the desired characteristics is cast on the inner surface thereof. The inner layer is integrally formed by welding on the inner surface of the outer layer.

[0003]

When performing two-layer casting by the centrifugal casting method, after the molten metal for the outer layer material is cast, the inner surface temperature of the outer layer is usually measured on the casting side to determine a predetermined temperature from the solidification temperature of the outer layer material. When the temperature ΔT drops, the inner layer material molten metal is cast from one end of the mold. However, when the pipe length is long or the viscosity of the inner layer molten metal is high, it takes a considerable time for the cast inner layer molten metal to flow from the casting end of the mold to the other end (tip end). In some cases, when the molten metal of the inner layer reaches the end on the tip side, the temperature of the inner surface of the outer layer near the end on the tip side is ΔT.
It may be considerably lower. When such a state occurs, the welding of the inner layer becomes insufficient on the side of the molten metal and the adhesion between the outer layer and the inner layer deteriorates.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing a composite metal tube which can obtain good adhesion even in the vicinity of the end of the molten metal for the inner layer material.

[0005]

The method for producing a composite metal pipe of the present invention is a method of centrifugally casting an outer layer on an inner peripheral surface of a die for centrifugal force casting through a coating die, and then applying the force from one end of the die. In a method of manufacturing a composite metal pipe in which a molten inner layer material is cast and an inner layer is centrifugally cast on the inner surface of the outer layer, a coating thickness of the molten metal of the inner layer material is formed thicker than that on the casting side. Further, the die thickness of the molten metal of the inner layer material is formed thinner than that of the casting side. Further, the die preheating temperature on the tip side of the inner layer material molten metal is set higher than that on the casting side.

[0006]

The cooling speed of the outer layer material on the tip side can be made slower by forming the coating thickness of the molten metal of the inner layer material on the tip side to be thicker than on the casting side. Therefore, it is possible to suppress the temperature drop of the outer layer material in the vicinity of the tip side end, which occurs while the molten metal for the inner layer material flows from the casting side end to the tip side end, and it is possible to suppress the temperature of the outer layer / inner layer near the tip side end. It is possible to prevent defective welding.

In addition to the method of changing the thickness distribution of the coating type,
By forming the die thickness of the molten metal of the inner layer material thinner than that of the casting side, and by setting the die preheating temperature of the molten metal of the inner layer material higher than that of the casting side, It is possible to reduce the cooling rate of the outer layer material on the side and improve the welding failure on the tip side.

[0008]

FIG. 1 shows a centrifugal casting mold 1 according to a first embodiment of the present invention. A mold 2 is applied to the inner peripheral surface of the mold 1, the thickness of which is the inner layer. The molten metal is gradually thickened from the casting end (A end) to the tip end (B end). At this time, it is preferable that the difference between the minimum thickness and the maximum thickness of the coating mold 2 be within the allowable value of the outer diameter of the pipe. The mold 1 is rotatably supported on a roller 3, and end plates 4 for stopping the melt are attached to the openings at both ends thereof.

The coating mold 2 is an outer layer material and a metal material having a melting point of 1000 ° C. or more as the inner layer material, for example, when various alloy steels are used, high melting point aggregates such as Al ₂ O ₃ , SiO ₂ and ZrO _2. It is preferable to use those containing as a main component (for example, mullite flour, composition: 71 wt% Al ₂ O ₃ , 27 wt% SiO ₂ ). The mold is usually formed by spray coating an inner peripheral surface of the mold with a mold prepared by mixing an aggregate, an appropriate binder such as bentonite or montmorillonite, and water. At this time, in the present invention, the mold coating material is sprayed so as to thicken the tip side of the inner layer material melt.

In order to carry out the present invention, the mold 1 is rotated and the molten metal for the outer layer material is usually cast from the B end side. That is, the outer layer material is cast from the side opposite to the mold with respect to the inner layer material. Casting from the opposite side in this way facilitates the placement of the casting device, and since the temperature of the molten outer layer material after casting is low on the A end side and high on the B end side, This is because it is advantageous in terms of preventing melting damage by the inner layer material molten metal and weldability at the B end side.

After the molten outer layer material is cast, the inner surface temperature of the outer layer is measured, and when the temperature reaches a predetermined temperature, the molten inner layer material is cast from the end A. The inner layer material melt cast from the A end is B
Although it flows to the end side, since the outer layer on the B end side is less likely to have a temperature drop due to the coating mold formed thicker than the casting side, even if it takes time for the inner layer material molten metal to reach the B end, The outer and inner layers are welded well in the vicinity.

FIG. 2 shows a centrifugal casting mold 1A according to a second embodiment of the present invention. In this embodiment, the centrifugal casting mold 1A has a thickness gradually increasing from the A end to the B end. It is thinly formed. For this reason, the cooling rate of the outer layer is reduced on the tip side of the inner layer material melt, and the welding failure on the B end side is improved.
In this embodiment, the coating mold 2A may have a uniform thickness (about 1.5 mm) as in the conventional case.

According to the present invention, there is no need to use a mold having a thickness distribution as described above or a mold for centrifugal force casting having a wall thickness distribution, which is a normal mold having a constant thickness. It can also be carried out by using a centrifugal casting mold having a constant wall thickness. That is, for example, when centrifugally casting a double-layer cast steel pipe made of steel material, a mold having a wall thickness of about 130 mm is conventionally used, and the mold is uniformly preheated to about 200 ° C. over almost the entire mold. However, when preheating the mold, from the A end side to B
The present invention can also be implemented by preheating with a gas burner or the like so that the mold temperature is increased to about 50 ° C. toward the end side.

[0014]

As described above, according to the method for manufacturing a composite metal pipe of the present invention, when the inner layer is centrifugally cast on the inner surface of the outer layer, the coating thickness of the inner layer material molten metal on the tip side is cast. Since it is formed thicker, or the mold thickness on the tip side of the inner layer material melt is formed thinner than that on the casting side, or the mold preheating temperature on the tip side of the inner layer material melt is set higher than that on the casting side, It is possible to suppress the temperature drop of the outer layer material near the end of the pouring side, which occurs while the molten metal of the inner layer material flows from the end on the casting side to the end on the pouring side, and to prevent welding defects of the outer layer and the inner layer near the end on the pouring side. Can be prevented.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a centrifugal force casting mold that is used in an example and is provided with a coating mold having a thickness distribution.

FIG. 2 is a cross-sectional explanatory view of a centrifugal force casting mold having a wall thickness distribution, which is used in another embodiment.

[Explanation of symbols]

 1 Mold for centrifugal casting 1A Mold for centrifugal casting 2 Coating type 2A Coating type 3 Roller 4 End plate A End of molten metal for inner layer material B Edge of molten metal for inner layer material

Claims (3)

[Claims] 1. An outer layer is centrifugally cast on an inner peripheral surface of a centrifugal force casting die through a coating die, and then a molten metal for an inner layer material is cast from one end of the die to centrifugally force the inner layer on an inner surface of the outer layer. A method for producing a composite metal tube for casting, characterized in that the coating thickness of the molten metal for the inner layer material is formed to be thicker than the casting side. 2. An outer layer is centrifugally cast on the inner peripheral surface of a centrifugal force casting die through a coating die, and then a molten metal for the inner layer material is cast from one end of the die to centrifugally force the inner layer on the inner surface of the outer layer. A method for manufacturing a composite metal tube for casting, characterized in that the die thickness of the molten metal of the inner layer material is formed thinner than that of the casting side. 3. An outer layer is centrifugally cast on the inner peripheral surface of a centrifugal casting mold through a coating die, and then a molten metal for an inner layer is cast from one end of the mold, and the inner layer is centrifugally applied to the inner surface of the outer layer. A method for producing a composite metal tube for casting, comprising setting a mold preheating temperature on the tip side of the molten inner layer material to be higher than that on the casting side.