JPS62148018A - Production of clad pipe - Google Patents

Abstract

PURPOSE:To manufacture the seamless clad pipe of good quality simply and with good productivity by fitting a round billet into the pipe body of outer layer pipe, by performing the idle rolling the obtd. laminating billet with an inclination rolling mill after heating it, further by performing a piercing, elongation, rolling. CONSTITUTION:The round billet 2 composed of the metal which forms the inner layer is fitted into the pipe body of the outer layer pipe 1 composed of the metal which forms the outer layer. After fitting the pipe body which is composed of the metal forming the intermediate layer if necessary into the pipe body of said outer layer pipe 1, said round billet 2 is fitted into the pipe body thereof. After heating the laminating billet 4 in fitting state thus obtd. to the prescribed temp., rolling is performed by a inclination rolling mill 3 and the inner layer and outer layer are closely fitted. A clad original pipe 6 is obtd. by performing the piercing elongation rolling of the obtd. laminating billet 5 which is after rolling with light rolling reduction by the inclination rolling mill 3 and a piercer plug 7, and a seamless clad pipe is obtd. with its elongation work further.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method of manufacturing seamless clad pipes by a rolling method.

"Prior Art" Conventionally, various methods have been proposed for manufacturing clad pipes, such as an explosive crimping method, a casting method, and a rolling method. In the case of the explosive crimping method, there is a limit to the size that can be explosively bonded, and it becomes difficult to manufacture clad pipes especially when the length of the pipe becomes long.

In addition, in the case of the casting method, the bonding strength of the cladding is weak,
Since the structure is naturally a cast structure, workability is poor,
In addition, there are cases where there are cavities, and sometimes there are holes that go through.
This results in insufficient strength. On the other hand, in the rolling method, treatment is performed before heating, that is, Ni plating of approximately 5 to 10 microns is applied to one or both of the interfaces between the base material and the cladding material, and both ends of the base material and the cladding material are fitted together. Weld the entire circumference of the part. After heating it to an appropriate temperature, it is hot-rolled using various rolling mills, resulting in a clad pipe in which the base material and the cladding material are metallurgically joined at the interface, making it very useful and suitable for a variety of applications. method has been proposed. For example, JP-A-58-13
No. 404 discloses a method of directly perforating a rolled material billet, which is made of a difficult-to-process material on the outside and a steel material with good workability in the center, using an inclined perforator.

JP-A No. 55-141311 discloses a method in which an outer layer tube and an inner layer tube are fitted together, then cold drawn to form a solid mN billet, which is heated and then pierced and rolled.

JP-A-53-14155 and JP-A-53-19958 disclose a method in which a tubular body serving as a base material and a tubular body serving as a cladding material are fitted together, heated, and then crimped and stretched by hot rolling. It is shown.

JP-A-55-141314 discloses a method in which after fitting an outer layer tube and an inner layer tube, the metals of each layer are metallurgically joined by blooming rolling.

``Problems to be solved by the invention'' However, the above-mentioned means have the following difficulties.

That is, in JP-A No. 58-13404, since the two metals are not metallurgically joined at the interface in advance,
The movement of the inner steel material in the rolling direction during rolling is obstructed by the plug, and sufficient perforations cannot be made. In fact, most of the central steel material was pushed toward the rear end,
It is nearly impossible to manufacture a good rad tube.

In JP-A-55-141311, cold drawing alone does not metallurgically bond the metal between the inner and outer layers, and as in the case described above, it is impossible to produce a good rad tube.

In JP-A-53-14155 and JP-A-53-19958, it is difficult to manufacture long clad pipes because the laminated billet is already hollow before rolling and there are restrictions on the length of the heating furnace, conveyance table, etc. Problems such as difficulty remain.

In JP-A-55-141314, a blooming process that is different from the normal seamless pipe manufacturing process is involved, which not only makes the process more complicated, but also makes the billet diameter different in the blooming process. Since it is necessary to change the roll hole shape each time, it is difficult to say that this is the optimal manufacturing method.

As described above, the hot rolling methods described above have problems with the adhesion between the outer layer tube and the inner layer tube, productivity, etc. when producing a clad tube.

The gist of this is that by performing light reduction rolling in an inclined rolling mill without using plugs, it is possible to prevent defects called grain cracks from occurring on the inner surface and to maintain appropriate adhesion between the outer and inner layers. Based on the knowledge that it is possible1
．． When manufacturing a clad pipe made of two or more types of metals, a billet made of the metal to form the inner layer or a pipe made of the metal to form the intermediate layer is fitted into a tube made of the metal to form the outer layer. After heating the laminated billet in this fitted state to a predetermined temperature, it is subjected to slip rolling in an inclined rolling mill to form a laminated billet, and then the laminated billet is perforated and stretched, and before perforation, inclined rolling is performed. Since the outer layer and the inner layer are brought into close contact with each other in advance by applying light pressure in a machine, and then perforated and stretched, a good rad tube can be manufactured with high productivity.

That is, in the billet assembly of the present invention, as shown in FIG. 2, the billet 2 on which the inner layer is to be formed is inserted into the tube body 1 on which the outer layer is to be formed. However, if the inner layer material and outer layer material are metallurgically joined to either or both of the inner surface of the tube body 1 and the outer surface of the billet 2, the purpose is to prevent the diffusion of carbon from the base material to the composite material. , Ni plating is applied to a thickness of about 10 microns. The gap between the tubular body 1 and the billet 2 is continuously welded over the curve as shown in FIG. 3, which shows the state of the billet end face before heating at both ends. Note that a gas vent hole 9 is provided in the welded portion 8 . After heating the laminated billet 4 prepared by the above method to a predetermined temperature, as shown in FIG. 4 showing light reduction rolling, the laminated billet 4 is subjected to mass rolling without using a plug in an inclined rolling mill 3. Outer diameter reduction rate at this time [1 - (billet diameter after rolling)
/ (billet diameter before rolling)] must be set so as to be below the critical draft ratio of the inner billet, that is, the critical outer diameter reduction ratio at which Mannesmann cracking due to cross-rolling does not occur in the center of the billet. It won't happen. The gorge (roll interval) is determined in consideration of the above points.

The shoe spacing and roll inclination angle are determined as follows.

Generally, when slip rolling is performed, the outer diameter of the rolled material tends to increase. When the laminated billet 4 is rolled by the method of the present invention, if the outer layer tube 1 expands, the metallurgical bond between the outer layer and the inner layer will be inhibited, which will cause problems in the next drilling step.

Therefore, it is desirable that the shoe spacing be equal to or close to the outer diameter of the billet 4 before rolling. Also, the roll inclination angle is il! 1 Regular piercing or
By setting the value equal to or slightly smaller than the value during elongator rolling, it is expected that the metallurgical bond between the outer layer and the inner layer will be enhanced. However, making the roll inclination angle smaller than necessary is not only disadvantageous for the above-mentioned Mannesmann crack at the center of the billet, but also undesirable from the viewpoint of productivity. Note that the heating temperature of the laminated billet is a normal temperature for mass rolling.

As described above, by setting the optimal gorge, shoe spacing, and roll inclination angle, a laminated billet 5 in which the inner layer and the outer layer are metallurgically bonded can be obtained. By piercing this with a piercer plug 7, as shown in FIG. 5, which shows the piercing of the laminated billet, a predetermined master tube 6 of a cladding tube is obtained. FIG. 1 collectively shows all the steps of the invention described above. The rolling and perforation can be performed by the same inclined rolling mill 3, or can be separated by using a conventional elongator as the perforating mill. In addition, if difficult-to-process materials are used as laminate materials and the effect of a drop in material temperature on the deformability of the material is a problem, it is also effective to reheat the laminated billet 5 after rolling. It is.

The obtained cladding original tube 6 is subjected to the subsequent drawing and rolling process.

After going through a standard process, a clad pipe is created in which the outer and inner layers are completely metallurgically bonded.

In addition, in this explanation, the case of a two-layer clad pipe is shown, but even when there are three or more layers, or when a laminated billet is made into a laminated hollow, the ramming rolling using the inclined rolling mill according to the present invention will not affect the outer layer. It is effective for metallurgical bonding of the inner layer and is effective for manufacturing good quality rad tubes.

"Example" Examples of the present invention are shown below.

The outer layer is made of carbon steel (C: 0.25wtχ) as a base material.
For the inner layer, austenitic stainless steel 1lls [15316L] whose outer surface was plated with 20 microns of Ni was used as a mating material. Manufactured by Mannesmann-Pragmill method. Heating is at a temperature of 1200℃
The test was carried out for 9 hours and 2 hours.

In this case, the gorge is 203mm, and the shoe spacing is 206m.
.

The roll inclination angle was 6 degrees.

Below, the billet and tube dimensions on the exit side of each mill are shown in the diagram of FIG. 6.

The clad pipe after sizer rolling was subjected to an ultrasonic flaw detection test over its entire length and circumference. As a result, Kancho 8
It was revealed that the base material of the outer layer and the laminate material of the inner layer were completely metallurgically bonded except for 200 m at each of the front and rear ends.

The defective parts at the leading and trailing ends mentioned above are due to internal oxidation during heating and non-crimping caused by the difference in metal flow at the unsteady part of the leading and trailing ends during rolling between the inner layer material and the outer layer material. The effect was essentially different from that of the invention.

"Effects of the Invention" As explained above, the method of the present invention can be said to be a very effective means for effectively manufacturing seamless clad pipes. Its main characteristics are as follows.

(1) Since the laminated billets or laminated hollows in the fitted state are pre-rolled with a light reduction by hot rolling, it is possible to manufacture long tubes of excellent quality.

(2) As a means of light reduction rolling, a sloping rolling method using an inclined rolling mill is adopted, which not only simplifies the manufacturing process of the clad pipe, but also provides extremely high production efficiency.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the entire cladding pipe manufacturing method according to the present invention, FIG. 2 is a diagram showing the billet being assembled, FIG. 3 is a diagram showing the state of the end face of the billet before heating, and FIG. The figure shows a laminated billet being lightly rolled by an inclined rolling mill, Figure 5 is a diagram of perforating the laminated billet after being lightly rolled, and Figure 6 is the mill exit side in an example. 2 is a chart showing the billet and tube dimensions of Engineering・-Outer layer pipe, 2-・Inner layer billet, 3
- Incline rolling mill, 4- Laminated billet after fitting. 5-- Laminated billet after light reduction rolling, 6- Clad original tube, 7- Piercer plug, 8-...
End weld, 9- gas vent hole. Zu color 1 Zu ^ pretend

Claims (1)

[Claims] When manufacturing a clad pipe made of two or more types of metals, a round billet made of the metal forming the inner layer or a pipe body made of the metal forming the intermediate layer is fitted into a pipe made of the metal forming the outer layer. A round billet, which is the metal forming the inner layer, is fitted into this tubular body, and the fitted laminated billet is heated to a predetermined temperature, and then subjected to rolling with an inclined rolling mill to form a laminated billet. A method for manufacturing a clad pipe, which comprises then punching and stretching the laminated billet.