JPS61144218A - Manufacture of triple-ply seamless clad steel-pipe - Google Patents

Abstract

PURPOSE:To manufacture easily and inexpensively an intermediate corrosion- resistant and triple-ply clad steel pipe, by wrapping a stainless steel of specific components or a nickel-base alloy around a easy-to-work carbon steel by casting, and further wrapping the easy-to-work carbon steel around its outer circumference by casting, to bore and roll it. CONSTITUTION:A cast piece 12A of easy-to-work carbon steel is wrapped around with a stainless steel containing >=12wt% Cr or an Ni-base alloy 13A by casting, to obtain a double-ply cast piece 17. Further, the piece 17 is wrapped around with the easy-to-work carbon steel by casting, to obtain a triple-ply clad cast- piece 15. The piece 15 is pierced by a Mannesmann mill, etc. and is rolled by a plug mill, etc. into a seamless steel pipe. This intermediate, corrosion- resistant and triple-ply clad steel-pipe reduces the need for an expensive corrosion-resistant material to save expense, and the work is made easy by the easy-to-work carbon steel materials used for the outer and inner layers.

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a method for manufacturing clad steel pipes used in applications requiring excellent corrosion resistance, such as steel pipes used in line pipes for transporting oil and natural gas. , especially difficult-to-work materials with high corrosion resistance but poor hot workability, such as C"12
This is a method for manufacturing a three-layer seamless clad II4 pipe using stainless steel, Ni1 alloy, etc. containing 1% or more of carbon dioxide.

Conventional technology In recent years, line pipes for transporting oil and natural gas have been required to use steel pipes with even higher corrosion resistance than before. Stainless steel containing 12% by weight or more of Cr, Ni-based alloys, and the like are increasingly used as materials for steel pipes.

However, although these stainless steels and N1-based alloys containing 12% by weight or more of Cr have much better corrosion resistance than ordinary carbon steels and low-alloy steels, their hot deformability is significantly inferior, and therefore these materials cannot be used. When manufacturing seamless pipes by an inclined rolling method such as Mannesmann's perforation method, not only does the perforation-rolling cause defects on the inner and outer surfaces, causing problems in product quality, but also makes the perforation-rolling process itself difficult. There are many. Furthermore, since stainless steel and N1-based alloys as mentioned above contain extremely large amounts of expensive Cr and Ni, there is a problem in that they would be extremely expensive if manufactured using these materials alone.

However, such steel pipes are not necessarily required to have excellent corrosion resistance on both the inside and outside; for example, in a line pipe where corrosive oil flows inside the pipe, very high corrosion resistance is not required on the outside. Therefore, there is no need to use highly corrosion-resistant but expensive materials such as stainless steel or N1-based alloys as mentioned above for the entire wall thickness of the tube, and only for the inner surface or the portion near the inner surface. Even if a material with high corrosion resistance is used, it is considered to be sufficient for line pipes, etc. Therefore, for steel pipes such as line pipes, it has traditionally been considered to use clad steel pipes that combine the aforementioned highly corrosion-resistant, difficult-to-work, and expensive materials with inexpensive materials such as carbon steel. .

As a conventional method for manufacturing such a clad steel pipe, a method for manufacturing a three-layer clad UOε steel pipe has already been proposed as shown in Japanese Patent Laid-Open No. 54-45613. This proposed method involves placing a steel slab 2 containing 2.0 to 20.0% Cr in a steel ingot mold 1, as shown in FIG. Molten carbon steel 13 is poured on both sides to obtain a three-layer composite steel ingot 4 having alloy steel 2A in the core and carbon steel 3A on both sides, as shown in Fig. 5<8). After blooming and hot rolling this to form a three-layer clad steel plate 5 as shown in Fig. 5(C), it is made into a pipe by the UOEIi pipe method, and the butt part is made as shown in Fig. 5(D). 6 is welded to form 111UOE pipe 7.

On the other hand, as mentioned above, there is already a method disclosed in JP-A-58-13404 as a method of manufacturing seamless clad steel pipes by the Mannesmann pipe manufacturing method using stainless steel, which has excellent corrosion resistance but is a difficult-to-process material. is proposed. This proposed method involves creating a composite billet 10 with a hard-to-process material 8 with excellent corrosion resistance on the outside and an easy-to-process material 9 such as carbon steel on the inside, as shown in FIG. 6(A). A two-layer clad seamless steel pipe 11 as shown in FIG. 6(B) is produced from the composite billet 10 by the Mannesmann piercing rolling method or the like.

Problems to be Solved by the Invention The four three-layer clad steel pipes 7 obtained by the conventional method (Japanese Unexamined Patent Publication No. 54-45613) shown in FIGS. As is clear from (D), the butt weld 6 is made of Cr used as the intermediate layer.
It is formed only of carbon steel 3A, which has significantly lower corrosion resistance than alloy 1!2A containing 0 to 20.0%.

Even if there is a welded part made only of carbon steel, in the case of line pipes used for transporting iron ore, coal, etc., the welded part is placed at the top to prevent corrosion. However, when used as a line pipe for highly corrosive oil transportation (especially for gathering), where the amount of snow has been increasing in recent years, corrosion progresses from the welded parts made only of carbon steel. However, from the viewpoint of corrosion resistance, it was unsuitable for this type of use.

On the other hand, the method shown in FIGS.
13404) t', since the core of the billet 1o is made of easy-to-process material 9, there is little risk of internal defects occurring during piercing and rolling by the Mannesmann piercing-rolling method, etc., but the outer layer is made of difficult-to-process material 8. Because of this, shoe flaws may occur on the outer surface during piercing and rolling, which may pose a problem in terms of product quality. Furthermore, as already mentioned, line pipes for transporting petroleum, etc., do not require very high corrosion resistance on the outside surface, but the seamless clad steel pipe obtained by this proposed method is made of expensive stainless steel even on the outside surface. Since it is made of steel or the like, there is also the problem that it is disadvantageous in terms of cost compared to a three-layer clad steel pipe as shown in FIG. 5(D).

This invention was made against the background of the above-mentioned circumstances, and it is possible to use Rad steel pipes that have sufficient corrosion resistance and are inexpensive to use as line pipes for transporting oil, etc., without causing internal and external flaws. The purpose of this invention is to provide a method that can be manufactured without any problems.

Means for Solving the Problems The method of the present invention has a core made of carbon steel that is easy to work, and a medium 1 made of a difficult-to-work material with excellent corrosion resistance on the outer periphery of the core.
A composite steel ingot in which WIll is arranged and easy-to-work carbon steel is arranged on the outer periphery of the intermediate layer is created by the casting method, and after the composite steel ingot is bloomed and rolled, it is perforated and rolled by the inclined rolling method. The present invention is characterized by obtaining a seamless pipe having a three-layer clad structure in which the high corrosion-resistant and difficult-to-process material is used as an intermediate layer, and the inner and outer layers are made of carbon steel.

Detailed explanation for carrying out the invention In carrying out the method of this invention, first the method shown in FIG.
As shown in A) and (B), an easily workable carbon steel 12 is used as a core, and on the outer periphery of the core carbon steel 12, a difficult-to-work material 13 with excellent corrosion resistance contains, for example, 12% or more of Qr. A substantially cylindrical material, in which stainless steel or N: based alloy, etc., is arranged as an intermediate layer, and carbon steel 14, which is easy to work and is the same as or similar to the core, is arranged on the outer periphery of the intermediate layer 13, which is a difficult-to-work material. A three-layer composite steel ingot 15 is produced by a casting method.

Specifically, as shown in FIG. 2(A), for example, a round bar-shaped steel piece 12A made of carbon steel such as 5TPT38 is placed in the center of a bottom pouring mold 16 for casting a steel ingot, suspended from the top. , 5US329J1 or 5US316 by under pouring
Casting 1113A of high corrosion resistance machining material such as TP, the second
As shown in Figure (B), a steel ingot intermediate product 17 is obtained in which a difficult-to-process material 13 is arranged on the outer periphery of a carbon steel core 12. After cutting the top and bottom parts of this steel ingot intermediate product 17 as shown by Ml in FIG. 2(B), the steel ingot intermediate product 17 is cut as shown in FIG. 2(C).
As shown in FIG. 2, it is suspended in the center of the bottom pouring mold 18, and a molten metal 14A of the same carbon steel as the core carbon steel 12 or a similar carbon steel is poured by the bottom pouring method. In this way, three l! ? 11 and a composite steel ingot 15 are obtained.

Next, the three-layer composite steel ingot 15 as described above is subjected to blooming rolling to form a three-layer composite billet 19 having a required diameter as shown in FIG.

Thereafter, holes are formed by an inclined rolling method such as the Mannesmann piercing rolling method, and a seamless steel pipe is finished by plug mill rolling or the like. Specifically, for example, after heating to the required temperature,
After drilling with a piercer (Mannesmann drilling machine) and then rolling with an elongator, plug mill, reeler, or sizer, or after drilling with a piercer in the same manner as above, a mandrel mill or hot stretch reducer.
A method such as rolling by rolling can be applied.

As shown in FIGS. 4(A) and 4(B), these steps result in a three-layer clad seamless structure in which the hard-to-process material 13 with excellent corrosion resistance is used as the intermediate layer, and the easily processable carbon 11112.14 is used as the inner and outer layers. A steel pipe 20 can be obtained.

In the above process, the billet 19 to be perforated by the inclined rolling method can be easily perforated because the core is made of easily workable carbon steel 12, and there is no risk of flaws occurring on the inner surface of the pipe. The outermost layer of billet 9 is also easily processable carbon! 1114, there is extremely little risk of shoe flaws occurring on the outer surface during piercing and rolling. In general, the finally obtained three-layer clad seamless steel pipe 20 is a difficult-to-process material 1 with excellent corrosion resistance in all parts of its circumferential direction.
Since No. 3 is present as an intermediate layer, the steel pipe has excellent corrosion resistance over the entire circumference. In addition, since ordinary inexpensive carbon steel is used on both the inside and outside, the already mentioned JP-A-58-13
It is also cheaper in terms of cost than the two-layer clad steel pipe obtained by the method of No. 404.

EXAMPLE A three-layer composite steel ingot 15 as shown in FIG. 1 was produced by the casting method according to the method shown in FIGS. 2(A) to 2(C) already described. Here, carbon steel 1 of the core and outer layer of the raw material
5TPT38 was used as 2.14, and 5uS329J and 5tJS31 were used as the intermediate layer difficult-to-process material 13.
6TP was used.

The dimensions of the three-layer composite steel ingot 15 are 6001 m in diameter and 1 m in height.
500mm! =1. ．． , Mater E part 17) Diameter C 20 C
ogs, the thickness of the middle layer is 10011, the thickness of the outer layer is l0
C) ++*.

Next, this three-layer composite ingot 15 is subjected to blooming rolling to form a billet 19 with a diameter of 300111 m as shown in FIG.
Figure 4 (
A three-layer clad seamless pipe with an outer diameter of 298.4 ml and a wall thickness of 19.1 u+ was prepared as shown in A) and (B). The thickness of each layer of this three-layer clad seamless pipe is within
2.2mm, middle @ 6,6111, outer diameter 10.31m
It is 1.

When the corrosion resistance of the thus obtained three-layer clad seamless pipe was examined, it was confirmed that it had sufficient corrosion resistance as a line pipe for oil transportation, which is highly corrosive.

It was also confirmed that there were almost no scratches on the inner surface or the outer surface.

Effects of the Invention As is clear from the above explanation, the method of this invention has the following effects:
A rad seamless W4 tube with excellent corrosion resistance and low cost can be manufactured without producing inner paper or outer surface flaws.

[Brief explanation of the drawing]

Fig. 1 (A>, (B) shows a three-layer clad steel ingot which is an intermediate product in the method of this invention, (A> is a longitudinal cross-sectional view, and (B) is a cross-sectional view. Figures (A) to (C)
These are schematic vertical cross-sectional views showing step by step the process of manufacturing the above-mentioned three-layer composite steel ingot by the casting method. FIG. 3 is a longitudinal cross-sectional view showing a composite billet obtained by blooming the three-layer composite steel ingot, and FIGS. 4 (A) and (B) show a three-layer clad seamless steel pipe as a final product produced by the method of the present invention. (A) is a longitudinal cross-sectional view, and (B) is a cross-sectional view taken along line X--X of (A). FIGS. 5(A) to 5(C) are schematic diagrams showing step-by-step an example of a conventional method for manufacturing clad steel pipes, and FIG.
A) and (B) are perspective views showing step-by-step another example of the conventional method for manufacturing a clad steel pipe. 12.14... Carbon steel, 13... Difficult to process material, 1
5... Three-layer composite steel ingot, 19... Three-layer composite billet, 20... Three-layer clad seamless steel pipe. Figure 6 (A) (B) Procedural amendment writing method) % formula % 2. Name of the invention Method for manufacturing three-layer seamless clad steel pipe 3. Relationship with the person making the amendment Patent applicant address Hyogo Prefecture 1-1-28 Kitahonmachi-dori, Chuo-ku, Kobe City
Name (125) Kawasaki Steel Co., Ltd. 4, Agent address: 3-4-18-5, Mita, Minato-ku, Tokyo, "Figure 5 (A) ~" on page 12, line 11 of the statement of amendment order date (C)”
is corrected to "Fig. 5 (A) to (D)".

Claims (2)

[Claims] (1) A core made of easy-to-work carbon steel, an intermediate layer made of a highly corrosion-resistant and difficult-to-work material placed on the outer periphery of the core, and easy-to-work carbon steel placed on the outer periphery of the intermediate layer. A composite steel ingot is prepared by the casting method, and after blooming and rolling, the composite steel ingot is punch-rolled by the inclined rolling method, and the high corrosion-resistant and difficult-to-work material is used as the intermediate layer, and the inner and outer layers are made of carbon steel. A method for producing a three-layer clad steel pipe, characterized by obtaining a seamless pipe with a three-layer clad structure. (2) 12% by weight of Cr as the highly corrosion-resistant and difficult-to-process material
The method for manufacturing a three-layer seamless steel pipe according to claim 1, using the stainless steel or Ni-based alloy containing the above.