JPH05228512A - Manufacture of long size tube - Google Patents

Abstract

PURPOSE:To form a long size small diameter tube by using thermal energy effectively. CONSTITUTION:A heat resisting tube body 1 is cast by cetrifugal casting, the mold is removed directly after it is cast, the tube body is passed between rolling rolls to draw its outer diameter to a desired diameter and to manufacture the long size small diameter tube. Since the tube body at a high temperature state directly after it is cast is reduced by rolling rolls 2 in diameter, the diameter can be reduced about 30-40% even when it is a heat resisting steel tube low in workability and the tube can be elongated in proportion to the reduction of the diameter. Since high temperature energy in time of casting is used, the long size small diameter tube can be manufactured at low cost. Since the tube is elongated, a weld joint part can be reduced remarkably and the cost can be decreased. Further, the life of the tube can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a long tube by using centrifugal casting and drawing with a rolling roll.

[0002]

2. Description of the Related Art The formation of a tubular body by centrifugal casting is a heat-resistant steel that has no seams in the tubular body, can easily form a two-layer pipe having different inner and outer layer characteristics, and has poor workability. However, there is an advantage that the tubular body can be easily formed.

However, it has been extremely difficult to cast a long tube having a small diameter by centrifugal casting. The reason for this is that when the molten metal is poured from the end of the high-speed rotary mold, its pouring port becomes small, and it is technically difficult to pour it. Also, while pouring the molten metal from such a small pouring port, the mold There is a problem in safety when rotating at high speed. Furthermore, since the solidification is completed before the molten metal is evenly spread on the inner surface of the long mold, it is not possible to obtain a sound product having a uniform thickness.

For example, in the case of an ethylene cracking tube having an outer diameter of 50 mm and an inner diameter of 38 mm, the required length of one tube is 10 to 12 m, but such a small diameter long tube cannot be manufactured by centrifugal casting. , Centrifugal casting 2.5
It is necessary to weld and join 4 to 5 tubes of about 3 m to form one tube. Since there are many welding points, various problems caused by welding are feared, and under severe operating conditions such as a cracking tube, the life of the tube is shortened and the manufacturing cost is increased, which is not preferable. Although a long tube having a small diameter can be formed by drawing or extruding, the workability of heat-resistant steel becomes a problem.
That is, the heat-resistant steel needs to have a C content of about 0.4% in order to secure the creep strength, but the content of C that can be drawn or extruded is up to about 0.2%, and the content of C or more is higher. When the amount is large, the workability is significantly reduced.

The present invention clarifies a method capable of easily forming a long tube having a small diameter by effectively utilizing thermal energy during centrifugal casting.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a tubular body by centrifugal casting.
(1) is cast, and after casting, it is immediately demolded, and while the tube is in a high temperature state, the tube is passed through a rolling roll (2) to reduce its diameter to produce a long tube.

[0007]

[Operation and effect] In the centrifugal casting, a tubular body (1) having a diameter and a length that is not difficult for the centrifugal casting is formed, and the tubular body is reduced in diameter to a desired diameter by the drawing process in the next step to be long. Therefore, the advantages of centrifugal casting are not impaired.

Rolling rolls are used to roll a tube in a high temperature state immediately after casting
Since the diameter is reduced by reducing it by (2), it is possible to reduce the diameter by 30-40%, and even heat-resistant steel with poor workability is 900
In the high temperature condition of ° C, it is possible to reduce the diameter.
Since the temperature of the pipe immediately after casting is 1000 ° C or higher, reheating is not necessary.

Since the tubular body is simply passed through the rolling roll (2), the unevenness of the outer surface casting surface caused by centrifugal casting does not pose a problem, unlike the case where the tubular body is pulled out by a die.

High-temperature energy immediately after centrifugal casting is effectively used, energy efficiency is improved, and manufacturing can be performed at low cost.

By lengthening the pipe, the number of welded portions can be reduced even when welding and joining to a required length, and the life of the pipe can be improved even under severe operating conditions such as cracking tubes.

[0012]

EXAMPLES Centrifugal casting pipe body (1) is a heat-resistant steel pipe, and contains (wt%) C 0.41, Si 1.48, Mn 0.95, Cr 25.2, Ni 35.
3, Mo 1.2 outer diameter 72 mm, inner diameter 51 mm, total length 3.5 m.

Immediately after centrifugal casting, the above pipe was demolded to 100
While keeping the temperature at 0 ° C or higher, it is passed through a single-stage or several-stage rolling roll (2), the outer surface of the pipe is pressed toward the axial center, and the pipe diameter is reduced. If the outer diameter is reduced to about 50 mm (reduction of about 30%), the length will be about 4.6 m.

Further, in the case of processing to a small diameter, the tube is reheated to 1200 ° C., passed through the rolling roll (2) again, and the outer diameter is reduced to about 35 mm, the length becomes about 6 m.

As described above, centrifugal casting is performed on a tubular body having a diameter suitable for centrifugal casting, and the tubular body is reduced in diameter to a desired diameter by a drawing process in the next step to increase the length. Will not damage.

Rolling rolls of hot pipe immediately after casting
Since the diameter is narrowed down by (2), it is possible to reduce the diameter by about 30 to 40%. 900 even for heat-resistant steel with poor workability
If it is in a high temperature state of ° C or higher, it is possible to perform the diameter reduction work to that extent, and since the temperature of the tubular body immediately after casting is 1000 ° C or higher, there is no problem in the diameter reduction work.

Since the tubular body is simply passed through the rolling roll (2), the unevenness of the outer surface casting surface by centrifugal casting does not pose a problem, unlike the case where the tubular body is pulled out by a die.

The high temperature energy immediately after centrifugal casting can be effectively used to enhance energy efficiency, and manufacturing can be performed at low cost.

It is possible to manufacture a long pipe having a small diameter exceeding the limit of centrifugal casting, and by lengthening the pipe, it is possible to reduce the number of welded portions even when welding and joining to a required length, and it is possible to reduce cracking of the cracking tube. The life of the pipe can be improved even under such severe use conditions.

In carrying out the present invention, the rolling rolls (2) (2)
As a matter of course, the rolls (2) and (2) may be arranged in multiple stages so that the circular space between them is gradually narrowed, and the pipe diameter can be gradually reduced to produce a small-diameter pipe. However, the present invention is not limited to the configuration described above, and various modifications can be made within the scope of the claims.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a diaphragm state.

[Explanation of symbols]

 (1) Tubular body (2) Rolling roll

Claims (2)

[Claims] 1. A long body is obtained by casting a tubular body (1) by centrifugal casting, immediately after casting, demolding and passing the rolling body (2) through a rolling roll (2) to reduce the diameter while it is in a high temperature state. A method of manufacturing a tube. 2. A tubular body (1) is cast by centrifugal casting, and immediately after casting, the die is demolded, and the tubular body is passed through a rolling roll (2) while the temperature is high to reduce the diameter. A method for producing a long tube by heating the body (1) and passing the heated tube again through a rolling roll (2) to reduce the diameter.