JPS6312689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to a method for manufacturing laminated metal pipes such as seamless steel pipes.

A laminated metal pipe is a pipe with a laminated structure of two or more layers, with an inner layer, an outer layer, and an intermediate layer made of two or more types of metals. Generally, inexpensive base materials (usually
It is manufactured by combining a large number of layers).

For example, a metal pipe with a two-layer structure in which the base material is carbon steel and the composite material is stainless steel, and this composite material is the inner layer.
That is, the following method is known as the most widely used method for manufacturing clad steel pipes. That is, as shown in Fig. 6, the inner peripheral surface of a thick-walled tube 1' made of carbon steel is plated with nickel to a thickness of 30 to 50 μm as a medium to prevent carbon diffusion. A tube body 2' made of stainless steel is inserted inside tube body 1', and both ends of tube body 2' positioned inside tube body 1' are welded to the inner peripheral surface of tube body 1' over the entire circumference. Also, there are tubes 1' and 2' at the ends of tube 1'.
A gas vent hole 1a' communicating between the two is bored. Then, such an assembly is used as a raw material for pipe production, heated under predetermined conditions, and then passed through a rotary forge mill with the gas vent hole 1a' on the bottom side for pipe production.

However, in this method, the medium is used as the base material as described above to strengthen the metallurgical bond between the tubes 1' and 2' and to prevent carburization from the tubes 1' to 2'. Inner circumferential surface of tube 1' (or outer circumferential surface of tube 2' may be used)
Since it is formed by plating, the equipment cost for the plating equipment and its auxiliary equipment is high, and the handling for plating requires a lot of manpower, and moreover, the plating is done by electrolysis. The running cost is high, and since there is a limit to the size of the plating tank, there is a limit to the size of the pipe bodies 1' and 2' that are to be plated, and the pipe manufacturing cost per unit weight is high. There were drawbacks such as low yield.

The present invention has been made in view of the above circumstances, and its purpose is to use a belt-shaped metal foil as a medium to be interposed between the base material and the composite material, and to use the medium to be placed between the base material and the composite material, To provide a method for manufacturing a laminated metal tube, which can be wound spirally around a surface, thereby significantly reducing equipment costs and running costs, and improving work efficiency and yield.

The method for manufacturing a laminated metal tube according to the present invention includes an outer tube body made of a metal to form an inner layer, an inner tube body (or rod A foil made of a metal that easily diffuses into the tube and rod by cleaning the surrounding surfaces of the intermediate tube and inner tube (or rod) made of metal to form the intermediate layer and inner layer. After wrapping the medium around the outer circumferential surface of the inner tube (or rod) or intermediate tube and inner tube (or rod) without any gaps, insert the inner tube (or rod) or intermediate tube inside the outer tube. The body and inner tube (or rod) are fitted together, and the fitted tube and rod are simultaneously cold drawn to reduce their cross-sectional area (or hollow). After welding and closing the boundary line between the tubes (or between the tube and the rod) at the end face of the laminated billet, and heating this laminated billet to a predetermined temperature,
(For solid laminated billets, after drilling)
It is characterized in that the tube is made by stretching and rolling.

The present invention will be specifically explained below based on the drawings.
Figures 1A to 2D are explanatory diagrams showing the main parts of the process in the method for manufacturing a laminated metal tube according to the present invention (hereinafter referred to as the method of the present invention), and Figures 2A and 2B are explanatory diagrams showing the state of cold drawing. Figures 3A to 3D are explanatory diagrams showing the main parts of the process in other embodiments of the present invention, and Figures 4A and 4B are explanatory diagrams similarly showing the cold drawing state. In Figure 2, 1 is the base material tube body,
Reference numeral 2 denotes a rod which is a composite material, and 3 a metal foil which is a medium.The metal foil 3 is wound around the outer circumferential surface of the rod 2 in a spiral shape so that the ends thereof slightly overlap each other. It is inserted into the tube body 1.

In FIGS. 3 and 4, 31 is a large-diameter tube that is a base material, 32 is a rod that is also a composite material, and 33 is a metal foil that is a medium. The rod 32 is inserted in a spirally wound state as described above. For example, when manufacturing clad steel pipes, the base material is a seamless pipe made of carbon steel or low alloy steel, and the composite material is stainless steel, nickel, nickel alloy, chrome, chrome alloy, titanium, Titanium alloy, copper, copper alloy, etc. are selected, and as a medium, a metal foil that easily diffuses into both the base material and the composite material is used depending on the combination of the base material and composite material.

As mentioned above, it is common to have a structure in which the base material is the outer layer and the composite material is the inner layer, but there is also a reverse structure, and a three-layer structure in which the base material is the middle layer and the composite material is the inner and outer layers. Some are structural.

The inner circumferential surfaces of the selected tubes 1 and 31 and the outer circumferential surfaces of the tubes 2 and rods 32 are subjected to cleaning treatment. Although the cleaning means is not particularly limited, examples thereof include various polishing, shot blasting, and pickling treatments. After wrapping the metal foils 3 and 33 as media around the circumferential surfaces of the tube body 2 and the rod body 32 in a spiral shape so that the ends thereof overlap slightly so that the entire foil is covered, the tube body 2 is wrapped. Alternatively, the rod body 32 is inserted into the tube bodies 1 and 31, and the ends of the fitted tube bodies 1 and 2 or the tube body 31 and the rod body 32 are subjected to a drawing process, and then, for example, a hydraulic drawing machine, or Using a chain drawing machine or the like, cold drawing is performed as shown in FIGS. 2 and 4 to obtain hollow or solid laminated billets 4, 41 as shown in FIGS. 1 and 3 (b).

Figures 2 and 4 A and B schematically show the manufacturing status of the laminated billets 4 and 41, and on the left side of each figure are the tube bodies 1 and 2 (or the tube body 31 and the rod body 3) in the fitted state.
2), the center shows the longitudinal section of the material passing through the drawing machine, and the right side shows the cross section of the laminated billets 4, 41. Figures 2A and 2B show the production of a hollow laminated billet 4; the former shows the mandrel drawing using a plug P, and the latter shows empty drawing using only a die without a plug.

Figures 4A and 4B show the case of manufacturing a solid laminated billet 41. The former uses a small-diameter rod, and the laminated billet 41, which is suitable for manufacturing clad steel pipes whose inner layer is made of composite material, is also manufactured. The latter uses a thin-walled tube body 31 to obtain a laminated billet suitable for manufacturing a clad steel pipe whose outer layer is made of composite material.

In the case of core drawing, a mandrel may be used instead of the plug P, and the number of drawings is preferably one, but may be two or more. Furthermore, regarding the processing degree, the outer tube 1, 31 and the inner tube 2 or rod 3
This is done to such an extent that the cross-sectional areas of both tubes 1 and 31 are reduced, and the inner circumferential surfaces of the tubes 1 and 31 are brought into close contact with the outer circumferential surfaces of the tube 2 or the rod 32. The laminated billet 4 (or 41) manufactured in this way is in a state in which the tubes 1 and 2 (or the tubes 31 and the rod 32) are mechanically tightly adhered, and no air remains between them. It is becoming.

Next, the laminated billets 4, 41 are cut into regular lengths, placed in a heating furnace, and heated to a predetermined temperature. In the case of the method of the present invention, the laminated billets 4, 4
1 (or tube 31 and rod 3)
2), but there is a possibility that minute voids may occur between the inner and outer layers due to the difference in thermal expansion coefficient between the inner and outer metals. For this purpose, circumferential welding is performed on the end faces of the laminated billets 4, 41 along the boundary line between the inner and outer layers as shown in Figures 1 and 3 (c) to prevent air from entering even if minute voids occur. It is desirable to do so. However, the inner tube body 2 or rod body 32 is made of carbon steel,
When the outer tubes 1 and 31 are made of ferritic stainless steel, or when the former is austenitic stainless steel and the latter is carbon steel, the coefficient of thermal expansion of the inner metal is larger than that of the outer metal. In some cases, the above-mentioned welding may be omitted since there is no possibility that a gap will be formed between the laminated billets even when they are heated. In other cases, this welding is not particularly necessary unless the difference in thermal expansion coefficients between the inner and outer metals is extremely large and the length of the laminated billet is short to a certain extent.

The laminated billet heated to a predetermined temperature is transferred to the tube manufacturing process, and in the case of a hollow laminated billet, it is stretched and rolled using a so-called elongation mill, such as a rotary elongator, a plug mill, an Atsel mill, a mandrel mill, a pilger mill, or a reducer. In the case of a tubular or solid laminated billet, first perforation is performed using a piercing rolling mill, such as a rotary piercer or a press piercing mill, and then elongation is carried out using a stretching mill in the same manner as in the case of the hollow laminated billet. to make pipes. By this, the first
As shown in FIG. 3D, desired laminated metal tubes 5, 51 are obtained. Note that the laminated metal tubes 5, 51 obtained in this way
may be cold drawn again if necessary.

Next, examples of the present invention will be described using specific numerical values. The tube body 1, which is the base material constituting the outer layer, is made of killed steel with C: 0.18% and has an outer diameter of 214 mm.
The inner diameter is 151 mm, the wall thickness is 31.5 mm, and the pipe body 2, which is the composite material that makes up the inner layer, is C: 0.06%, Ni:
Made of austenitic stainless steel with 8.2% and Cr: 18.2%, outer diameter 148 mm, inner diameter 122 mm, wall thickness 13
mm was used. The inner surface of the tube 1 and the outer surface of the tube 2 are polished, and a nickel foil with a thickness of 50 μm is wrapped around the entire outer surface of the tube 2 in a spiral shape so that the ends overlap slightly with each other. After wrapping the tubes so as to cover them, the tubes 1 and 2 are fitted together, and the tubes are drawn and then cold drawn in a 200 ton hydraulic drawing machine, with an outer diameter of 205 mm, an inner diameter of 121 mm, and a wall thickness of 42 mm. (outer layer
A hollow billet 3 with a diameter of 30 mm and an inner layer of 12 mm was obtained. This laminated billet 4 is cut to a specified length, circumferentially welded at the boundary between the inner and outer layers on both end faces, heated at 1170°C for 100 minutes in a rotary hearth type heating furnace, and then this specified length billet is cut into a rotary shape. Stretched and rolled using an elongator to an outer diameter of 223 mm, an inner diameter of 198 mm, and a wall thickness of 12.5 mm.
Next, it was stretched and rolled in a plug mill to an outer diameter of 217 mm, an inner diameter of 196 mm, and a wall thickness of 10.5 mm, and then passed through a reeler to reduce the outer diameter.
230 mm, inner diameter 209.5 mm, and wall thickness 10.25 mm.Finally, it was drawn and rolled in a 6-stand sizing mill to form an outer diameter of 219 mm, inner diameter 198 mm, and wall thickness 10.5 mm (outer layer 8
A clad steel pipe with a diameter of 2.5 mm and an inner layer of 2.5 mm was obtained.

Figure 5 is a 100x metallurgical micrograph of a cross section near the end of the clad steel pipe obtained as described above, showing the base material carbon steel (upper part of the photo: pearlite structure) and the composite material stainless steel ( It is clear that the austenitic structure (lower side of the photo: austenite structure with less carbide) is completely metallurgically integrated and bonded with the interposition of the nickel layer (middle of the photo), which is the medium 3.

In the method of the present invention, (1) the outer surface of the tube or rod forming the inner layer and the inner peripheral surface of the tube forming the outer layer are cleaned, and the inner and outer surfaces of the tube or rod forming the inner layer are cleaned; Metal foil, which is a medium made of a metal that can easily diffuse into tubes and rods, is wound in a spiral shape, fitted to the tube that forms the outer layer, and then cold drawn, so it is not necessary to use the medium as before. Compared to the case where the adhesive is attached to the outer surface of the inner layer by plating, special equipment such as plating equipment is not required at all, and the initial cost is zero.

(2) Furthermore, by adopting the method of winding the medium, there are no restrictions on the length or size of tubes, rods, etc., and it is possible to manufacture long billets. In the plating method, the running cost per unit weight is extremely low compared to the case where the size and length of the tube and rod are limited by the size of the plating tank, and the pipe manufacturing yield is extremely high.

(3) The cost of the metal foil as a medium is extremely low compared to the cost of plating, and even considering the manpower required for wrapping, the cost can be reduced to approximately a few percent of the cost of plating. In addition, laminated billets formed by combining tubes or tubes and rods are stretched and rolled in the case of hollow ones, and perforated after heating in the case of solid ones, and then stretched and rolled. By rolling, the medium interposed between the tubes or between the tube and the rod firmly joins the tubes or the tube and the rod metallurgically through diffusion bonding. , no problems such as mutual peeling occur.

There are effects such as

Note that the above explanation has been made for the case of manufacturing a laminated metal tube with a two-layer structure, but in the case of three or more layers, the tube bodies 1 and 31 forming the outer layer, the tube body 2 and the rod body 32 forming the inner layer. In between, metal foil 3, 3 is placed on the circumferential surface.
3 is inserted and cold drawn in this state to produce a hollow or solid laminated billet with three or more layers, and thereafter the tube can be manufactured using the same steps as described above.

As described above, the method of the present invention can produce high-quality laminated metal tubes at a significantly lower cost than conventional methods, and the yield is also high, so the present invention has excellent effects. .

[Brief explanation of the drawing]

Figures 1A-D are explanatory diagrams showing the main parts of the process of the present invention, Figures 2A and 2B are explanatory diagrams showing the state of cold drawing, and Figure 3A-D are explanatory diagrams showing the main steps of the method of the present invention. An explanatory diagram showing the main parts of the process in the implementation state, Figures 4A and 4B are explanatory diagrams also showing the cold drawing state,
The figure is a metallurgical micrograph showing a joint in a cross section of a clad steel pipe obtained by the method of the present invention.
The figure is a longitudinal cross-sectional view of a tube-making material for explaining an example of a conventional method. 1, 2... Tube body, 3... Metal foil, 4... Laminated billet, 5... Laminated metal tube, 31... Tube body, 32
... Rod body, 33 ... Metal foil, 41 ... Laminated billet, 51 ... Laminated metal tube.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a laminated metal tube made of two or more metals, comprising: an outer tube made of a metal to form an outer layer, an inner tube or intermediate layer made of a metal to form an inner layer, and Clean the surrounding surfaces of the intermediate tube and the inner tube made of metal to form the inner layer, and apply a foil-like medium made of a metal that easily diffuses into each tube. After wrapping the inner tube around the outer circumferential surface of the inner tube without any gaps, the inner tube or the intermediate tube and the inner tube are fitted into the outer tube, and the cross-sectional area of both of the tubes in the fitted state is reduced. At the same time, cold drawing is performed to form a hollow laminated billet, the boundary line between the tubes at the end face of the laminated billet is closed by welding, and this laminated billet is heated to a predetermined temperature.
A method for manufacturing a laminated metal pipe, which comprises forming the pipe by elongation rolling. 2. In a method for manufacturing a laminated metal tube made of two or more metals, an outer tube body made of a metal to form an outer layer, a rod made of a metal to form an inner layer, or a metal to form an intermediate layer and an inner layer, respectively. Clean the circumferential surfaces of the intermediate tube and the rod, and apply a foil-like medium made of metal that easily diffuses into the tube and rod into gaps between the rod or the outer circumferential surfaces of the intermediate tube and the rod. After winding the rod, the rod or the intermediate tube and rod are fitted into the outer tube, and the fitted tube and rod are simultaneously cooled so that their cross-sectional areas are reduced. After drawing a solid laminated billet into a solid laminated billet, welding and closing the boundary line between the tube and the tube or rod at the end face of the laminated billet, and heating this laminated billet to a predetermined temperature,
1. A method for manufacturing a laminated metal pipe, which comprises performing perforation using a piercing rolling machine, and then elongating and rolling the pipe using an elongating rolling machine.