JPH03264175A - Production of clad pipe - Google Patents

Abstract

PURPOSE:To decrease the fluctuation in a cladding ratio in a longitudinal direction and to improve a yield by securely fixing and closing an outside pipe and an inside pipe, covering the inter-pipe spacing on the rolling end side of a double-layered pipe with a covering material and heating the double-layered pipe, then inserting a plug into the pipe and rolling the pipe with cross helical rolls. CONSTITUTION:Ti inter-pipe spacing part 3 on the rolling start end side of the double layered pipe formed by inserting the inside pipe 2 into the outside pipe 1 to form double layers is welded, brazed or screwed to securely fix the outside pipe 1 and the inside pipe 2, by which the spacing part is closed. The inter-pipe spacing part 4 on the rolling end side of the clading pipe is coated with the covering material 5 and is closed by the structure to allow the sliding of the outside pipe 1 and the inside pipe 2. After this double layered pipe is heated, the plug or mandrel 6 is inserted into the double layered pipe and the pipes are rolled between plural pieces of the cross helical rolls 7, by which the pipes are joined to each other. The fluctuation in the cladding ratio in the longitudinal direction is small and the clad pipe having the good yield is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a clad pipe in which circular pipes are made into multiple layers and joined together.

[Conventional technology] Conventionally, when joining circular pipes in multiple layers, they were extruded by hot extrusion, but with this method, the cladding ratio changes greatly in the length direction, making it difficult to guarantee the cladding thickness. There wasn't. When an attempt was made to manufacture this by rolling without closing the gaps between the tubes at both ends, the surfaces to be joined were oxidized during heating, resulting in incomplete joining. Furthermore, when the gap between the tubes at both ends is closed by welding, the tubes in one layer during rolling will elongate differently due to the difference in deformation resistance between the materials that make up the multilayer. baggy,
Alternatively, the welding at the rear end was damaged and remained as a flaw, and the end portion beyond this welded portion could not be manufactured into a product.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for manufacturing a clad pipe with small fluctuations in cladding ratio in the length direction and a high yield.

[Means for Solving the Problems] In order to achieve the above object, the method for manufacturing a clad pipe of the present invention is configured as follows. In other words, in Figures 1 to 5, l. The inter-pipe gap 3 on the rolling start end side of the multilayer pipe made by inserting the inner pipe 2 into the outer pipe 1 is welded, brazed, or screwed. The outer tube 1 and the inner tube 2 are firmly fixed and closed, and the inter-pipe gap 4 on the rolling end side of the multilayer tube is covered with a covering material 5, so that the outer tube 1 and the inner tube 2 are slid together. The method is characterized in that after the multi-layer pipe is closed with a movable structure and heated, a plug or mandrel 6 is inserted into the multi-layer pipe and rolled between a plurality of inclined rolls 7 to join the pipes together. This is a method for manufacturing crat pipes.

The interpipe gap 3 on the rolling start end side of this multilayer pipe is firmly fixed and closed by welding, brazing, or screwing to prevent each layer from shifting significantly from the front end at the start of rolling. Construct it so that the front end will not be damaged due to damage. The inter-pipe gap 4 at the end of rolling of the multi-layer pipe is not fixed so as to absorb the difference in elongation of each layer during rolling, and is not fixed to prevent oxidation contamination of the surface to be joined during and before heating starts. A thin plate is wrapped around and tied with wire 10 to cover and close this gap. The tubes are then rolled between preferably three or more, most preferably four, inclined rolls 7 to reduce the outer diameter and wall thickness of the multi-layered tubes and join the tubes together.

2. In the present invention, preferably either the outermost layer tube 1 or the innermost layer tube 2 is made of titanium or a titanium alloy, and either the innermost layer tube 2 or the outermost layer tube 1 is made of steel or a high alloy. Item 1 above, characterized in that the covering material 5 covering the side interpipe gap 3.4 is made of titanium, the heating temperature is 700°C to 900°C, and the wall thickness reduction rate is 10% to 25%. This is a method for manufacturing the described clad pipe.

However, the wall thickness reduction ratio R is defined by the following formula, where t is the total wall thickness at the entrance side of the rolling mill, and t2 is the total wall thickness at the exit side of the rolling mill.

Direct welding of titanium or titanium alloy and steel or high alloy will easily damage the weld, so as shown in Figure 1, the same materials should be welded together, and titanium and copper should be welded together using threaded joints or brazed joints. It is best to use it as a side dish. In this case, this covering material 5 is equivalent to the metal to be joined so that the covering material 5 covering the interpipe gap 3.4 on the rolling end side consumes oxygen and prevents oxygen from entering into the joining surface. The metal is more active than titanium, which is more easily oxidized. The heating temperature was set at 700°C to ensure sufficient interdiffusion of iron and titanium at the joint, and at 90°C to prevent oxidative deterioration and growth of intermetallic compounds at the joint.
The temperature should be below 0℃. The thickness reduction ratio is preferably 10% or more to achieve sufficient bonding, and 25% or less to prevent large fluctuations in the cladding ratio.

Fig. 1 shows an intermediate material 8, and the function of this intermediate material is not particularly limited. Materials with good or bad thermal conductivity, materials with good or bad electrical conductivity, materials to reduce manufacturing costs, etc. can be interposed. has already been deformed to such an extent that it cannot fully exert its covering function, or at the end of rolling, when rolling starts, gases mainly composed of hydrogen and carbon monoxide are blown out due to the heat generated during rolling, so oxygen is no longer intruding. Rather than worrying about this, it is better to have a structure in which the covering material is easy to tear, come off, or deform so that these gases can be easily blown out.

[Example] In Fig. 1, the outer tube 1, the coupling 9, and the gap covering material 5 are made of pure titanium, the inner tube 2 is made of steel, and the outer tube 1 and the coupling 9 on the rolling start end side are welded, The coupler 9 and the inner tube 2 are fixed with springs, and the inter-tube gap 3.4 at the end of rolling is covered with a thin plate of covering material 5 wrapped around and tied with wire. After heating to 750°C, Rolling was carried out using four inclined rolls 7 shown in FIGS. 2 to 5. At this time, the cross section of the outer tube 1 before rolling has an outer diameter of 88 mm, an inner diameter of 80 mm, and an inner tube 2.
The cross section of the pipe is outer diameter 79 mm, inner diameter 44 mm, mandrel 6 diameter is 42 mm, finished clad pipe has outer diameter 68 mm, total thickness 1
2IIIIIIl, the bonding condition was good, and the cladding ratio was within the range of 21% to 26% over the entire length, which was good.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a method for manufacturing a clad pipe with small fluctuations in the cladding ratio in the length direction and a high yield.

[Brief explanation of drawings]

1 to 5 are explanatory diagrams of the method of the present invention, and the first
Figure 2 shows the assembled state of the layered pipe; Figure 2 shows the state in which the multilayer pipe is rolled with an inclined roll rolling mill; Figures 3, 4 and 5 show the A-A and B- of Figure 2 respectively B, CC sectional view. 1... Outer tube, outermost layer tube, 2... Inner tube, innermost layer tube, 3
．． 4... Inter-pipe gap, 5... Covering material, 6... Plug or madrel, 7... Inclined roll, 8... Intermediate material, 9... Coupling, I O-... Tighten the covering material by the material, 1], -... welded part, 12 -... seam part.

Claims (1)

[Scope of Claims] 1. In a multi-layered pipe formed by inserting an inner pipe into an outer pipe, the gap between the pipes on the rolling start end side is connected to the outer pipe and the inner pipe by welding, brazing or screwing. is firmly fixed and closed, and the gap between the tubes on the rolling end side of the multilayer tube is covered with a covering material and closed with a structure that allows the outer tube and the inner tube to slide, and the multilayer tube is closed. A method for manufacturing a clad pipe, which comprises heating, inserting a plug or a mandrel into the multilayer pipe, and rolling the pipes between a plurality of inclined rolls to join the pipes together. 2. Either the outermost layer tube or the innermost layer tube is made of titanium or a titanium alloy, and either the innermost layer tube or the outermost layer tube is made of steel or a high alloy, and a cover that covers the gap between the tubes on the rolling end side. The material is titanium and the heating temperature is 700℃ to 90℃.
2. The method for manufacturing a clad pipe according to claim 1, wherein the temperature is 0° C. and the wall thickness reduction rate is 10% to 25%. However, the wall thickness reduction rate R is defined by the following formula, where t_1 is the total wall thickness on the inlet side of the rolling mill, and t_2 is the total wall thickness on the outlet side of the rolling mill. R=[(t_1-t_2)/t_1]×100