JPH0263668A - Manufacture of seamless pipe - Google Patents

Abstract

PURPOSE:To manufacture a seamless steel pipe without necessitating a piercing process by injecting a molten metal between a mold and a common steel pipe inserted into its inside and forming a hollow cast piece, bringing this case piece to swaging and bringing it to pickling. CONSTITUTION:A common steel pipe 2 is inserted into a mold 3. By injecting a molten metal 6 for a seamless pipe between both of them 3, 2 and bringing the steel pipe 2 to cast-in, a hollow cast piece is formed. This hollow cast piece is brought to swaging, and generated scale oxide is brought to pickling. Also, it is desirable that the hollow cast piece is brought to hot working after a soaking heat treatment. In such a manner, since a piercing process of a stock is not required, when inclined rolling as hot swaging is executed, it is released from the constraint of an object material and a size, and when hot extrusion is executed, the drop of the yield which follows up piercing does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing seamless pipes made of stainless steel, high alloy steel, Ni-based alloy, etc.

[Prior Art] Methods for producing seamless pipes include inclined rolling methods such as the Mannesmann Plaque Mill method and Mannesmann Mandrel Mill method, and pressing methods such as the Ushin-Sejournet method (hot extrusion method) and the Bushbench method. In the inclined rolling method, a solid material is perforated using a hot roll perforator, and then rolled and elongated using a Plaque mill, a mandrel mill, an Aracell mill, a Deirasha mill, a Pilger mill, or the like. In the hot extrusion method, a solid material is cold drilled, then heated and extruded through the gap between the die and the mandrel.In the Bushbench method, a mandrel is hot pressed into the solid material. It is a hollow material with an eave shaped like a tip (Erhard Press), and is produced by hot punching using a die and mandrel. As the material, cast material, forged material, rolled material, etc. are used.

[Problems to be Solved by the Invention] In the conventional seamless pipe manufacturing method, there are many problems in the process of drilling a solid material.

In other words, hot roll perforation in the inclined rolling method is a harsh process in which the grab is pushed into the material while rolling with inclined rolls, and materials with high hot strength and materials with poor hot workability cannot be perforated. Or they were produced in a very narrow range of materials and sizes. In addition, in the hot extrusion method, the holes are made by cold machining, so
Yield loss of materials is significant and costs are high.

The present invention aims to produce seamless pipes without the need for a drilling process.

[Means for Solving the Problems] The present invention involves first inserting an ordinary steel pipe into a mold, injecting molten metal for a seamless pipe between the mold and the ordinary steel pipe, and casting the ordinary steel pipe with the molten metal. to make a hollow slab. For example, as shown in FIG. 1, a tummy bar 1 is inserted into a mold 3, an ordinary steel pipe 2 is fixed in the center of the dummy bar 1, and a tummy bar 1 is inserted into the mold 3 and the ordinary steel pipe 2 are passed from a tundish 4 through a nozzle 5.
Inject molten metal 6 for seamless pipe between
is drawn downward and the ordinary steel pipe 2 is cast continuously to obtain a hollow slab. Further, as shown in Fig. 2, the ordinary steel pipe 2 is inserted into the center of the mold 3 and made to stand up, and the molten metal for seamless pipe is poured from the ladle 7 between the mold 3 and the ordinary mold 2, and the ordinary steel pipe 2 is inserted into the mold 3. After being solidified in a cast casing, it can be extracted from the mold 3 to obtain a hollow slab.

Seamless pipes include stainless steel, high alloy steel, Ni
It may be made of various metals such as base alloys or alloys, and preferably has a melting point lower than that of ordinary steel.

In claim 1 of the present invention, the hollow slab thus obtained is hot stretched and pickled. In the second aspect of the present invention, the hollow cast piece is subjected to a soaking heat treatment, followed by hot stretching and pickling.

As the hot stretching process, a rolling method using a plug mill, a mandrel mill, an Arasel mill, a Deirasha mill, a pilger mill, etc., and a hot extrusion method, which are performed after perforation in the above-mentioned inclined rolling method, can be performed.

After hot stretching and pickling, processing such as cold drawing or cold rolling is performed depending on the material or size requirements.
Heat treatment or rough pickling can be performed as necessary.

[Function] The hollow slab obtained by casting according to the method of the present invention has a hollow inner surface made of ordinary steel.

In the first aspect of the present invention, such a hollow cast piece is heated and hot-stretched, and the generated oxide scale is removed by pickling. In this process, the ordinary steel that existed on the inner surface of the hollow slab becomes partially or completely oxidized scale during heating, during hot drawing, or in the hot state after drawing. By pickling, scale is removed and the remaining ordinary steel is dissolved and removed.

In claim 2, since the ordinary steel on the inner surface of the hollow slab is subjected to soaking heat treatment before the hot drawing process, the ordinary steel on the inner surface of the hollow slab is likely to become oxidized scale by this treatment. At this time, if air or oxygen is introduced into the inner surface of the hollow slab, oxidation of the ordinary steel is promoted.

Soaking heat treatment is usually carried out depending on the material requirements such as stainless steel, high alloy steel, N1 base alloy, etc., but it may also be carried out for the purpose of removing the ordinary steel on the inner surface when there is no necessity in terms of the material properties.

After soaking and heat treating a hollow slab, it is desirable to remove the oxidized scale on the inner surface by brushing, etc., and then perform hot drawing, but the scale removal at this time may be incomplete. .

In claims 1 and 2, when cold working is performed after hot drawing and pickling, even if ordinary steel remains on the inner surface before cold working, the This can be removed by heat treatment and pickling.

[Example Example 1] A common steel pipe with an outer diameter of 42.7 mm and a wall thickness of 4.9 mm was inserted into the center of a mold with a diameter of 156 mm, and molten steel of 5US304 stainless steel was injected between the common steel pipe and the mold. Hollow slabs were continuously cast using ordinary steel pipes. The outer surface of the obtained hollow slab was shaved to an outer diameter of 150 mm,
It was cut to a length of 50 mm, processed, and hot extruded using a glass lubricant to obtain a seamless tube with an outer diameter of 38.1 mm and a wall thickness of 5.0 mm. The seamless tube has oxide scale and glass adhered to it, and the inner surface has about 200μ
Plain steel was present at a thickness of m. This was immersed in a mixed acid of hydrochloric acid and hydrofluoric acid for 2 hours, and then soaked in a mixed acid of nitric acid and hydrofluoric acid for 1 hour.
By dipping, the oxide scale and glass were removed, and the ordinary steel on the inner surface was also melted and removed.

Example 2 Outside diameter 42.7m in the center of a mold with a diameter of 156n++++
While inserting an ordinary steel pipe with a wall thickness of 4.9 mm, molten steel of 5IJS3]6 stainless steel was injected between the ordinary steel pipe and the mold to cast the ordinary steel pipe, and a hollow slab was continuously cast. When this was heated to 1260° C.] and subjected to soaking heat treatment, all of the ordinary steel on the inner surface became oxidized scale, and oxidized scale with a thickness of about 0.2 mm was present on the inner surface. The outer surface was shaved to an outer diameter of 150 mm, cut to a length of 50 mm, and the inner surface was brushed to remove scale, thereby removing the ordinary steel on the inner surface. This was heated and hot-extruded in the same manner as in Example 1 to form a seamless tube with an outer diameter of 38.1 mm and a wall thickness of 5.0 mm, which was then pickled under the same conditions as in Example 1 to oxidize the inner and outer surfaces. Removed scale and glass.

Example 3 A common steel pipe with an outer diameter of 76.3 mm and a wall thickness of 9.5 mm was inserted into the center of a mold with a diameter of 210 mm, and molten steel of 5115310 stainless steel was injected between the common steel pipe and the mold to cast the common steel pipe. Continuous casting of hollow slabs was carried out. This is 1
When soaking heat treatment was performed at 260°C for 3 hours, ordinary steel and its oxide scale were found to be about 7.5 mm on the inner surface.
There was a thickness of 3 mm. The outer surface was shaved to an outer diameter of 200 mm, cut into lengths of 50 mm, the inner surface was brushed to remove scale, and heated to obtain Example 1.
It was hot extruded in the same way as , with an outer diameter of 82.9 mm and a wall thickness of 5.
It was made into a 5 mm seamless tube. Approximately 450μm on the inner surface
Plain steel was present in the thickness. When this was pickled under the same conditions as in Example 1, the oxide scale and glass on the inner and outer surfaces were removed, but ordinary steel was present on the inner surface to a thickness of about 150 μm. Then, it was cold drawn to an outer diameter of 60.5 mm.
When the wall thickness was set to 4, 0++ on, and heat treated at 50°C for 3 minutes, the thickness of the ordinary steel on the inner surface was approximately 208 Jm. By pickling this with a mixed acid of nitric acid and hydrofluoric acid for 1 hour, the oxidation scale of the stainless steel was removed. At the same time, ordinary steel was also completely removed.

Example 4 A common steel pipe with an outer diameter of 60.0 mm and a wall thickness of 5.5 mm was placed upright in the center of a mold with a diameter of 176 mm and a height of 800 mm, and molten steel of Ni-based alloy Incoloy 625 was injected between the common steel pipe and the mold. A hollow slab was continuously cast using an ordinary steel pipe. When this was subjected to soak heat treatment by heating at 1200° C.], ordinary steel and its oxidized scale existed on the inner surface to a thickness of approximately 8n++n.

The outer surface is shaved to have an outer diameter of 170 mm and a length of 5 mm.
After cutting to 0 mm, brushing the inner surface to remove scale, heating and hot extrusion processing in the same manner as in Example 1,
It was made into a seamless tube with an outer diameter of 86.0 mm and a wall thickness of 17.5 mm. Plain steel was present on the inner surface to a thickness of about 250 μm. When the stiffness was pickled under the same conditions as in Example 1, the oxide scale and glass on the inner and outer surfaces were removed, but ordinary steel was present on the inner surface to a thickness of about 3 f)+um. Then, it was cold drawn to an outer diameter of 76 mm and a wall thickness of 15 mm.
When heat treated at 1150℃ for 3m1n, all the ordinary steel on the inner surface became scale, and by pickling it with a mixed acid of nitric acid and hydrofluoric acid for 1 hour, the oxidation scale of the N1-based alloy was removed and the oxidation scale of the ordinary steel was removed. removed.

[Effects of the Invention] Since the seamless pipe manufacturing method of the present invention does not require the step of perforating the material, when performing inclined rolling as a hot drawing process, it is freed from restrictions on the target material and size associated with the perforation work, When hot extrusion is performed, there is no decrease in yield due to perforation.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are diagrams showing an example of a means for manufacturing a hollow cast piece according to the present invention. DESCRIPTION OF SYMBOLS 1...Dummy bar, 2...Ordinary steel pipe, 3...Mold, 4...Tandish, 5...Immersion nozzle, 6...
... Molten metal, 7... Ladle.

Claims (1)

[Claims] 1. Inserting an ordinary steel pipe into a mold, injecting molten metal for seamless pipes between the mold and the ordinary steel pipe, and casting the ordinary steel pipe with the molten metal to form a hollow slab; A method for manufacturing a seamless pipe, which comprises hot stretching the hollow cast piece and pickling it. 2. Insert an ordinary steel pipe into the mold, inject molten metal for seamless pipes between the mold and the ordinary steel pipe, cast the ordinary steel pipe with the molten metal to form a hollow slab, and soak the hollow slab. A method for producing a seamless pipe, which includes heat treatment, hot stretching, and pickling.