JPS6160917A - Manufacture of leg member of jack-up type rigger - Google Patents

Abstract

PURPOSE:To increase strength through reduction of a welded part, by a method wherein, after a steel lump is heated, it is formed into a rough-shaped material having a rack part, a mandrel bar is pressed in, an intermediate product, formed with a cord part and a rack part, is produced, and rack tooth profile is formed. CONSTITUTION:A steel lump is heated to a given temperature, and is hot-casted into a rough-shaped material having a solid cord part 20 and an integrally formed rack part 21. A mandrel bar 25 is pressed in by a press machine, a hole is bored in the solid cord part 20, and a steel lump is pressed in a ring die 26 by means of the press machine and the mandrel bar 25. A leg member is hardened and tempered, and a rack profile is formed in a rack part 21 integrally protruded from the cord part 20. This enables easy production of even a leg member having a large cross section, enables the thickness of the rack part and the cord part to be varied, where necessary, and permits easy increase of thickness.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a leg member of a jack-up type rig for drilling offshore oil fields, and particularly to a jack-up type rig in which a cord part and a rack part constituting the leg member are integrally molded. The present invention relates to a method of manufacturing a leg member of a type rig.

(Conventional technology) The development of offshore oil fields has become active in recent years, and the
Many improvements are being made to oppression devices.

Such drilling equipment (hereinafter referred to as "rig") can be broadly classified into submersible type, semi-submersible type, fixed type, jack-up type, etc. In particular, jack-up type is a mobile type and is mainly used at depths of 100 water due to its economical advantages. It is used in sea areas up to 1000m wide.

As shown in Figs.
It is equipped with As shown in FIG. 2, which is a cross-sectional view taken along the line ■-■ in FIG. During towing, the pedestal 5 is raised from the seabed using a rack and pinion system, and during excavation, the pedestal 5 is placed on the seabed, while the hull 2 is raised above the sea surface, allowing stable work even in harsh environments. It is designed to.

That is, the footnote 5 supporting the rig 1 can be raised and lowered with respect to the hull 2, and when towing, by raising the pedestal 5, that is, lowering the hull 2, the pedestal 5 is raised from the seabed and the hull 2 is raised to the sea level 9. On the other hand, during excavation, the footnote 5 is lowered and its lower end lands on the seabed as shown in Figure 1, and the hull 2 is raised above the sea level 9 to support it. It is. The pedestal 5 is formed from welded assemblies 8, typically three to four, in the illustrated case three, tubular leg members 8.
and an auxiliary material (place) that connects them to each other 10
A multi-truss structure is formed from the above.

In order to move the hull 2 and the pedestal 5 relative to each other, that is, to raise and lower the pedestal 5, a rack part is provided on the side of the leg member constituting the pedestal 5, a pinion part is provided on the hull 1, and this and the pinion・The rack mechanism causes the vertical motion of footnote 5 with respect to the hull 2 to be performed.

Leg members used in such applications have complex shapes and have conventionally been manufactured as welded structures. As shown in the cross section, a structure in which a cord part 7 is welded to a rack part 6 is adopted. In the illustrated example, the blacked out parts are along the longitudinal direction from the front to the back of the drawing. As can be seen from the diagram showing the welded parts, the production of the above-mentioned welded structure involves many steps such as press forming, many welded parts, and the length thereof is unavoidably long.

In particular, in the case of FIG. 3(A), such a tendency is remarkable because the reinforcing plate S is welded between both rack parts.

By the way, the conventional jack-amp type rig is suitable for medium water depth (1
The mainstay designs were those that could be used in seas up to 000 meters ago, but recently there has been a demand for products that can be used in even more severe ocean and weather conditions. Along with this, leg members are also required to be made of a material with higher strength.

That is, recently, the members of the rack part and the cord part are H.
Since it is designed using T80kg class high tensile strength steel, advanced welding techniques are required to weld it, and furthermore, a considerable length of the part must be welded.
It is becoming increasingly difficult to fundamentally eliminate problems such as weld cracks, deterioration of weld quality, and weld defects that occur during welding.

Therefore, many attempts have been proposed to reduce the number of welding locations as much as possible.

For example, JP-A-51-135135 discloses a leg member in which a rack portion is welded to a steel pipe manufactured by a centrifugal casting method instead of the above-mentioned welded steel pipe-rack welding method. Attempts to ensure strength by integrally molding the tube body using centrifugal casting have attracted attention, but this is not necessarily sufficient as welding of the rack section is essential.

In addition, in Special Publication No. 51-90101, including the rack part,
It is disclosed that it is manufactured by a centrifugal casting method. but,
With this method, it is difficult to ensure a sufficient rack width, and it is also difficult to obtain satisfactory quality in terms of strength and the like.

(Problems to be Solved by the Invention) One of the objects of the present invention is to reduce the number of welded parts as much as possible, and to make it possible to manufacture the product using, for example, high-strength steel of 80 to 90 kg HT class. The aim is to provide a method to

On the other hand, the characteristics required of the leg parts of jack-amp type rigs today are contradictory characteristics such as high strength and light weight.To achieve this, for example, it is possible to increase the thickness of the rack part and the cord part thickness. On the other hand, in general, the external force acting on the leg members of a jack-up rig with a truss structure is dominated by axial force (especially compressive force), and buckling performance becomes an issue. It is desirable to increase the strength and reduce the weight by increasing the cross-sectional rigidity and buckling strength by increasing the hole diameter and decreasing the wall thickness of the cord portion.

Furthermore, as a secondary role, the hole in the center can greatly contribute to the heat treatment effect (uniform hardening performance value of the inner and outer surfaces).

Thus, another object of the present invention is to integrally mold the cord part and the rack part, to increase the thickness of the rack part, and to increase the hole diameter in the cord part, and to increase the outer diameter accordingly. The purpose of the present invention is to provide a method that can ensure strength and reduce weight by reducing the wall thickness.

(Means to Solve the Problems) As a result of various studies to achieve the above-mentioned object, the inventors of the present invention have found that, as a means of integrally forming the welded parts, the number of welded parts is as small as possible. After repeated research focusing on the combination of each process of squeezing and stretching, it was found that by using such a combination process, it is easy to increase the thickness of the rack part, increase the hole diameter of the cord part, and make it thinner. Knowing this, he completed the present invention.

That is, as mentioned above, attempts to reduce the number of welded parts as much as possible are already known, but the present invention further develops and improves this, and employs forging and drawing processes to achieve this objective. This is what I am trying to do.

Here, the gist of the present invention is to provide a method for manufacturing a leg member of a jack-up type rig, which comprises a hollow columnar cord portion and a rack portion integrally protruding from the cord portion and extending in the longitudinal direction, the leg member being made of steel. After heating the ingot to a predetermined temperature, the steel ingot is forged into a rough material having a solid cord portion and a rack portion integrally protruding from the cord portion and extending in the longitudinal direction, and a mandrel bar is formed. A hole is formed in the solid cord part by press-fitting, and then the hollow columnar cord part and the cough cord part are integrally molded and protrude by being squeezed at least once with a ring die having an appropriate hole shape. The method for manufacturing a leg member of a jack-up type rig is characterized in that, after obtaining an intermediate product consisting of a rack portion extending in the longitudinal direction, a rack tooth profile is formed on the rack portion.

That is, according to the present invention, a rough material having a rack portion and a solid cord portion is formed by hot forging, and then after drilling,
This is shaped into a finished shape by drawing or sinking, and finally gears are cut by an appropriate means.Prior to gear cutting, a heat treatment consisting of quenching and tempering is usually performed.

(Operation) FIG. 4 is a process chart consisting of steps (1) to (5) of the manufacturing method according to the present invention. Figure 5 (al to 5
Figure (dl) is an explanatory diagram schematically showing a forging process, a drilling process, and a drawing process according to the present invention.

Step (1): After heating the steel ingot to a predetermined temperature, for example, after forging and stretching, the top and bottom parts of the steel ingot are cut to form the solid cord part 20 and the This is a step in which hot forging is performed from the cord part to a rough material having the rack part 21 integrally molded, for example, by rough forming using a vertical or horizontal press machine. Figure 5 (bl is 1 in Figure 5 fat)
It is a sectional view cut along the -fbl line.

Step (2): A receiver having a steel fixing jig 22 corresponding to the shape roughly formed in step (1) fixes the rough shaped material 24 to the container 23,
After the installation, a mandrel bar 25 having an appropriate diameter, that is, a punching mandrel, is press-fitted into the solid cord portion 20 using a press machine. FIG. 5 (tel) shows an example of the arrangement at this time in a schematic cross section.

Step (3): The above-mentioned receiver takes out the rough-shaped material 24 from the container 23, and presses the steel ingot into the ring die 26 having an appropriate hole shape with the above-mentioned mandrel 25 inserted using a press machine and a mandrel bar, and stretches it. It is. In this case, expansion is performed by drawing or sinking. The ring die 26 is passed at least once, usually 5 to 6 times, to achieve the final shape.

FIG. 5 (dl is a schematic explanatory diagram showing the situation at this time; in the illustrated example, it is so-called drawing, and the diameter of the rough material does not change substantially; however, in the case of so-called sinking) In other words, the diameter of the rough material is reduced, so to speak.

Step (4): This is a step in which the leg member obtained in this way is subjected to normal heat treatment consisting of quenching and tempering after the mandrel is taken out.

Step (5): This is a step of forming a rack tooth profile on the rack portion that integrally projects from the cord portion, for example, by fusing.

FIG. 6 shows a perspective view of the leg member 8 obtained by the method according to the present invention. As is clear from the example shown in FIG. It is composed of a relatively thick rack portion 6 that protrudes and extends in the longitudinal direction, and as described above, these are integrally formed by forging and drawing. A rack tooth profile 12 is formed on the rack portion 6.

In the illustrated example, the rack portion 12 is provided protruding from both opposing sides, but as a modification, it may be formed arbitrarily such that it protrudes from only one side or is eccentric. can. Further, the cross section of the cord portion 7 itself is not circular as in the illustrated example, but can be made into an arbitrary cross-sectional shape such as a hexagonal shape.

(Effects) (1) According to the present invention, since the hollow body is formed by forging, there is no restriction on roll equipment as in the case of rolling, and it is easy to manufacture a large cross-section. Further, the thickness of the rack portion and the cord portion can be changed as necessary, and it is easy to increase the thickness.

(2) Even when the cord portion is relatively thin and the leg member has a large hole diameter, it can be manufactured advantageously.

(3) According to the manufacturing method according to the present invention, a drilling process using a boring machine or the like is not necessary, improving work efficiency and increasing yield.

Such a leg member is formed to have a unit length, and in actual use, a backing metal whose tip can be inserted into the center hole is attached to one end with a length of 1/g! If? , and weld the ends to the specified length.

[Brief explanation of the drawing]

Figure 1 is a simplified BA diagram of a jack-up type rig;
The figure is a cutaway view taken along the line ■-■ in Figure 1; Figure 3 is a schematic cross-sectional view of the leg member of a conventional jack-up type rig, explaining the method of manufacturing the leg member; A process chart of such a method; FIGS. 5(8) to 5fdl are explanatory diagrams schematically showing a part of the processing steps in the present invention shown in FIG. 4;
FIG. 6 is a schematic perspective view of a leg member of a jack-up rig manufactured by the method according to the invention. l: Rig 2: Hull 3: l Suppressing structure 4: Lifting mechanism 5: Pillar 6: Rack part 7: Cord part 8: Leg member applicant Sumitomo Metal Industries Co., Ltd. agent Patent attorney Hirose Do - (and 1 others) name) L/Kouhata 2 illustration, 3121 f, 4 + + B)
(Cl'4, 4 concave $5 concave (Dosu, N2 II, 5 ji TJ (b Figure 5 (C) 2'') Hole 5 concave (d) Chikuro V

Claims (3)

[Claims] (1) A method for manufacturing a leg member of a jack-up rig consisting of a hollow columnar cord portion and a rack portion integrally protruding from the cord portion and extending in the longitudinal direction, the method comprising heating a steel ingot to a predetermined temperature. The steel ingot is forged into a rough material having a solid cord portion and a rack portion integrally protruding from the cord portion and extending in the longitudinal direction, and a mandrel bar is press-fitted to form the solid cord. A hollow columnar cord portion and a rack portion that protrudes and extends in the longitudinal direction are integrally formed from the cord portion by punching a hole in the portion and then squeezing at least once with a ring die having an appropriate hole shape. A method for manufacturing a leg member of a jack-up rig, the method comprising: forming a rack tooth profile on the rack portion after obtaining an intermediate product consisting of the above. (2) The method according to claim (1), wherein the squeezing is drawing. (3) The method according to claim (1), wherein the squeezing and stretching is sinking.