JPS60112595A - Leg member of jack-up-rig and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention is applicable to a jack used in offshore oil drilling, etc.
This invention relates to the leg system of an up rig and its manufacturing method.

(Prior Art) As shown in FIGS. 1 and 2, the jack-up rig has legs made up of a plurality of leg members consisting of a rack 1 and a cord 2 assembled into a truss structure. The system allows the legs to be raised when towing, and when excavated, the legs touch the seabed and the deck is raised above the sea surface, allowing stable work even in harsh environments.

Such leg parts have the shape of glazes, and conventionally, the rack 1 and cord 2 are assembled by welding, as shown in FIGS. 3(A), (B), and (C). There is.

However, in the case of such a welded structure, the rack and cord are designed mainly from HT80-90 class high-tensile steel, so advanced welding techniques are required;
Equivalent welding is required, and various problems caused by welding (
(weld cracks, unbalanced weld quality, weld defects, etc.)
It is difficult to fundamentally eliminate it.

In addition, conventional jack-up rigs use the gray water method (3
Although most of the designs are designed to be applied to sea areas up to 0.000 ft (approximately 0.000 ft), there is a need for products that can be applied to even more severe sea conditions. As a result, stronger members are required, and it seems that conventional types have reached their production limits.

Further, as a method of manufacturing such a leg member, FIG.
As shown in Figure 5, there is a problem in that there is a lot of manual labor and the construction period is long.

(Purpose of the invention) This invention was proposed in view of the above circumstances, and its purpose is to eliminate welding and obtain products of stable quality, while also allowing free cross-sectional shapes to match the strength. An object of the present invention is to provide a leg member that can be obtained and a method for manufacturing the same.

(Structure of the Invention) The leg member according to the present invention is formed by integrally forming a tubular cord and a rack protruding from the cord by rolling or forging.

A method for manufacturing a leg member according to the present invention involves heating a steel ingot to a predetermined temperature and then rolling the steel ingot using a blooming mill to form a solid columnar cord portion and a rack portion integrally protruding from the cord portion. After an intermediate product is obtained and a through hole is bored in the center of the cord part, a rack tooth profile is formed in the rack part.

(Embodiment) The present invention will be described below based on an illustrative embodiment. As shown in FIGS. 6 to 8, in the leg member according to the present invention, a relatively thick tubular cord 11 having a center hole 1o and a rack 12 protruding from the cord 11 are formed by rolling or forging. It is integrally molded.

As shown in Fig. 6, the rack 12 may be protruding from both sides, as shown in Fig. 7, it may be protruding from one side, or as shown in Fig. 8, it may be eccentric. However, it can be shaped arbitrarily. Furthermore, the cross section of the cord 11 can also be made into an arbitrary cross-sectional shape such as a hexagonal shape. In this case, the directly cut place groove can be welded perpendicularly to the surface, which can reduce the number of man-hours.

As shown in FIG. 9, such a leg part is formed with a unit length, and as shown in FIGS. The gold 13 is attached by welding, the ends are joined together, and the connection is made by bath welding. The joining shown in FIG. 10 is normally used, and is mainly used for connecting short pieces. In some places, the joints shown in Figure 8811 are used to absorb errors during large-scale assembly.

Next, an example of a rolling method for manufacturing such a leg member will be described. Although rolling is performed using a blooming mill, in normal slot rolling, the material is twisted during biting, the material collapses during etching, and the cast structure remains due to underfilling of the cord and insufficient rolling ratio, resulting in quenching and tempering. 7, particularly deterioration of the Charpy value, a rolling method as shown in FIG. 12 is performed.

First, the steel ingot 15 is heated to a predetermined temperature of 1200° C. or higher, and the upper and lower end portions in the width direction are chamfered 16 by groove rolling (see FIG. 12(B)).

Next, after reheating the powder 16',
It is rotated 0 and rolled down by -1 in the hole shape with the width direction facing up and down (see FIGS. 12(C) and (D)).

Here, the central portion bulges left and right to form a rack portion R and a cord portion C.

Next, turn the rack part R by 900 turns and apply -2 to the hole shape.
The length of the rack part is made constant by etching the ends (see Fig. 12 (E)).
7 (see FIG. 12(F)).

With such a rolling method, since the cord portion R is directly rolled down, complete filling is possible, there is less twisting and collapse of the material, and the number of passes is also reduced.

Furthermore, the rolling ratio of the steel ingot can be increased, and a product with uniformity and high toughness can be obtained.

After the profile rolling as described above is performed, the material is sent to the following steps in order.

Q) After reheating if necessary, perform bending.

(♀) After both end surfaces of the rack portion R are made flat by machining, a center hole 10 is bored in the center of the cord portion C.

(3) After heating at about 900°C for 2 to 3 hours, water quenching is performed, and then tempering at about 600°C to 630°C.

(4) If necessary, remove the bend by hot or cold pressing.

■ If hot straightening is performed, additional annealing is necessary.

■ Perform short blast.

■ Gas cut the rack tooth profile using NC. In the case of both teeth, both teeth are machined at the same time to improve accuracy.

■ Perform bevel processing.

■ Inspect mechanical properties, tooth hardness, and accuracy.

Although the method for obtaining an intermediate product by rolling has been described above, it goes without saying that it can also be easily obtained by forging instead of rolling.

(Effects of the Invention) As described above, the present invention provides the following effects.

■ Since it is integrally molded, there is no vertical welding that takes up a large amount of welding, and problems caused by welding can be avoided.

■ Products of uniform quality can be obtained regardless of welding skills.

■ Free cross-sectional shapes can be obtained. For example, rack thickness,
It is possible to increase the thickness of the cord, and it can be used in a wide range of applications, from conventionally required strength to high strength.

■ Can be made lighter. In general, the legs of a truss-structured jack-up fist rig are dominated by axial force (compressive force in %), and buckling performance becomes a problem, but if the legs are the same shape as the conventional type, Since the cross section of the member is on the outside (buckling strength is large), it is possible to reduce the weight if the material has the same strength.

(!1()ltt2, punching shear (pushing shear)
It has a high yield strength and requires special reinforcement on the inside of the cord.

In addition, a place (branch pipe) is welded to the cord (column), and external forces that push or pull the cord wall are applied, so
If a large stress is generated locally or the cross-sectional rigidity is insufficient, shear failure will occur.

To prevent this, stiffeners are generally attached to the inner surface of the cord.

(There is no deterioration in toughness due to bending. The legs of jack-up rigs receive direct wave loads, so it is better to have a small pressure-receiving area, and legs that are light for towing are required. Therefore, high tension It is made of steel (HT80) and has a compact cross section.For this reason, in the past, bending of the cord material (generally cold working) caused deterioration in the toughness of the base material and the specifications could not be met. There are many.

■ Less inspection man-hours.

Since there is no welding involved in processing the parts, there is no inspection of welded parts. (Material inspection and dimensional inspection only) ■ Short construction period. The process is simple, and by utilizing the power of the machine, there is less manual labor, the quality is stable, and the construction period is shorter than before.

■ Block construction is easy.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing a jack up rig;
The figures are a sectional view taken along the line 11-1 in Figure 1, Figures 3 (A) and (B).
), (C) are cross-sectional views showing conventional leg separation, and Fig. 4 (
A) or) L), FIG. 5 is a process diagram and a flowchart sequentially showing a conventional method of assembling a leg member, FIG. 6 is a cross-sectional view showing a leg member according to the present invention, FIGS. Figure 8 is
9 is a side view of FIG. 6, FIGS. 10 and 11 are partially enlarged sectional views showing the joint portion of the leg member, and FIGS. 12(A) to F ) is a process diagram showing an example of the manufacturing method according to the present invention. 1... Rack, 2... Cord, IO... Center hole, 11... Cord, 12... Rack, 13... Backing metal, 14... Gap material, 15... Steel ingot, 16... Chamfer, 16'...Material, 17...Intermediate product. Figure 1 □ - Leh □□ Nimah - 32 (A) (B) Figure 2 (C/) Figure 4 (A) (B) (C) 10 (G) (H) Figure 5 Figure 6 Figure 7 Figure 8

Claims (3)

[Claims] (1) A leg member of a jack-up rig that consists of a rack and a cord and has the function of supporting the hull and raising and lowering the hull, and the tubular cord and the rack that protrudes from the cord are rolled or The leg parts of the Jatsuki Up Rig are characterized by being integrally formed by forging. (2) After heating the steel ingot to a predetermined temperature, profile rolling is performed using a blooming mill to obtain an intermediate product consisting of a solid columnar cord portion and a rack portion integrally protruding from the cord portion;
A method of manufacturing a leg part A/l of a jack-up rig, characterized in that a through hole is then bored in the center of the cord part, and then a rack tooth profile is formed in the rack part. (3) Profile rolling involves shaping a steel ingot into a shape with both ends chamfered, then rolling it down in the width direction to bulge out the center, and then sequentially forming the cord part and rack part using a hole die. The second claim characterized in that
A method for manufacturing a leg member of a jack-up rig as described in .