JPS60130406A - Method and device for manufacturing seamless steel pipe - Google Patents

Abstract

PURPOSE:To manufacture a seamless steel pipe free from inner-surface flaws caused by the generation of scales by spraying simultaneously cooling water and a lubricant in the inside of a pipe stock, in rolling a pipe stock between rolls and a plug by plug mill rolling. CONSTITUTION:A plug 2 attached to a plug bar 1 is inserted in a pipe stock 3 to roll it between the plug 2 and rolls 4. At that time, a cooling-water supplying pipe 7 is connected to a cooling-water spraying port 5 provided to the front end of plug bar 1, and a lubricant supplying pipe 8 is connected to a lubricant spraying port 6 provided to the slightly rear side of port 5. The cooling water and lubricant are sprayed at the same time from the spraying ports 5, 6, to perform rolling while maintaining the inner surface temperature of pipe stock 3 at >=800-<=900 deg.C. In this way, a seamless steel pipe having excellent quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing seamless steel pipes by plug mill rolling and an apparatus used to carry out the method.

In manufacturing seamless steel pipes using the plug mill rolling method, a plug attached to a plug bar is inserted into a hollow shell tube obtained by heating and piercing rolling a raw steel billet, and the hollow shell tube is then rolled from both the inside and outside. A steel pipe whose dimensional accuracy such as wall thickness and length is adjusted is obtained by elongation rolling or reeler rolling. At this time, the new hollow inner surface of the steel billet formed by piercing and rolling the raw steel billet is oxidized and scale is generated when the inner surface comes into contact with air. When scale is generated on the inner surface of the raw tube that has been pierced and rolled, if a plug is inserted into the raw tube and then elongated or rolled as described above, the scale will be trapped inside the tube. Internal flaws, called internal flaws, occur in the resulting steel pipe. Particularly when thick materials are reel-rolled, the occurrence of such internal flaws is remarkable, and the flaws are so deep that they must be cleaned on the subsequent finishing line.

This is because thin-walled materials easily drop in temperature on the inner surface of the tube while being transported from the plug mill to the leak, causing the scale on the inner surface of the tube to become brittle and disintegrate into sand during reeler rolling. In the case of raw materials, the temperature on the inner surface of the raw tube does not drop easily during the time it takes to transport the raw tube from the plug mill to the reeler.
This is to maintain the strength to the extent that the scale will cause internal flaws.

On the other hand, various improvements have been made to solve these problems, but among them, the method of injecting lubricant and high-pressure water in the pre-rolling process, as shown in Japanese Patent Application Laid-Open No. 5-151ffi, reduces cycle time. Not only is the shell long and requires separate equipment, but the shell is cooled by high-pressure water, but when it is sent to the mill, the inner surface regenerates heat and has no cooling effect. Another disadvantage was that some of the lubricant oxidized.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a method for manufacturing a seamless steel pipe that is free from internal flaws caused by scale formation, and an apparatus for manufacturing a seamless steel pipe for carrying out the method. With the goal.

In other words, the method for manufacturing a seamless steel pipe of the present invention involves inserting a plug into the raw pipe and rolling the raw pipe between the rolls and the plug, and in which cooling water and a lubricant are added to the raw pipe. A seamless steel pipe manufacturing apparatus of the present invention is characterized in that the raw pipe is rolled while jetting at the same time. A cooling water injection port and a lubricant injection port are provided at the tip, and a cooling water supply pipe leading to the cooling water injection port and a lubricant supply pipe leading to the lubricant injection port are arranged through a plug bar. It is something to do.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the seamless steel pipe manufacturing apparatus of the present invention, which is used to carry out the seamless steel pipe manufacturing method of the present invention, will be described with reference to FIGS. 1 to 6.

FIG. 1 is a perspective view showing a state in which a wood pipe is reeled using a seamless steel pipe manufacturing apparatus according to an embodiment of the present invention.
A plug 2 attached to a plug bar l is inserted into the raw tube 3, and the raw tube 3 is rolled between rolls 4.

FIG. 2 shows an enlarged sectional view of the tip of the plugper 1. A cooling water injection port 5 is provided at the tip of the plug par 1, and a lubricant injection port 6 is provided slightly behind the cooling water injection port 5. A cooling water supply pipe 7 communicates with the cooling water injection port 5), and a lubricant supply pipe 8 communicates with the lubricant injection port 6.

3 and 4 are enlarged sectional views of portions shown as section A and section B in FIG. 1. As shown in the figure, the cooling water supply pipe 7 and the lubricant supply pipe 8 are arranged from the truck 9 through the plug bar 1, and the cooling water supply pipe 7 is connected to the truck 9 near the truck 9.
The lubricant supply pipe 8 has a double pipe structure, with the outer pipe being the outer pipe and the lubricant supply pipe 8 being the inner pipe.

Note that the trolley 9 and the plug bar are connected by a flange and can be replaced with bars of various outside diameters.

The cooling water is configured so that the cooling water for the bar and the cooling water for cooling the inner surface of the tube are supplied from the truck side through the same route, and the water branches off at point C near the tip of the bar as shown in Fig. 3. .

The metal fitting 11 is attached to the truck side by the holding metal fittings 12° (5) 13 so that it does not fly out, but since there is a gap of 2 to 3 m on the 0 side of the metal fitting 12, the spherical metal fitting 11 is attached to the spherical center 0. It is possible to swing the head in the center.

Therefore, the plug bar 1 has a bolt 14 attached to the spherical metal fitting 11.
Since the plug bar is fastened by , the plug bar is freely supported.

Because of this structure, the cooling water supply pipe 7', lubricant supply pipe 8', and in-bar cooling water drain pipe 15 in the rotating truck 9' are partially made of flexible materials such as rubber. Therefore, even if the bar bends, the supply pipes 7', 8' and the drain pipe 15 can follow the bend by f. 16.17 shows the branch pipes on the plug bar side and the truck side. Rubber seals 18, 19 are inserted into the sealing surfaces of both limb canals. Cooling water and lubricant are supplied from the rear end of the rotating main shaft 9' (not shown) and flow as indicated by the arrows. As for the cooling water, the bar cooling water and the tube inner surface cooling water are supplied through the same route, and only the bar cooling water is branched off at point C shown in Fig. 3, and after cooling the bar, it is supplied to the drain pipe 8'.
is discharged to the outside through the

(6) As described above, a major feature of the present invention is that the connecting portion between the thrust block and the plug bar has flexibility, which allows the plug bar to freely flex around the spherical seat. The stress on the plug bar neck is alleviated, and the overturning moment applied to the thrust block truck can be reduced.

FIG. 5 shows a cross-section taken along line 2--2 in FIG. 2, and shows the position in the circumferential direction of the cooling water injection port 50 provided at the tip of the plugper 1. As shown in the figure, three cooling water injection ports 5 are provided, and they are provided at equal intervals in the circumferential direction. Figure 6 is Figure 2■
-■ A cross section is shown, and the circumferential position of the lubricant injection hole 60 and the circumferential position of the cooling water supply pipe 7 in that part are shown.

As shown in the figure, three lubricant injection ports 6 are provided at equal intervals in the circumferential direction, and a lubricant supply pipe 8 communicates with each of the lubricant injection ports 5 . Three cooling water supply pipes 7 are arranged outside the lubricant supply pipe 8.

Next, a method for manufacturing a seamless steel pipe according to the present invention using the above-described seamless steel pipe manufacturing apparatus will be specifically explained.

First, the material is pierced and rolled by a piercer, then elongated and rolled by a plug mill, and then fed to a reel mill. Simultaneously with the start of rolling in the reel mill, injection of cooling water from the cooling water injection port 5 at the tip of the plug par 1 and injection of lubricant from the lubricant injection port 6 are started and continued until rolling is completed. During rolling, the inner surface of the tube 3 is cooled by a jet of cooling water, so the scale that had formed on the inner surface of the tube 3 is cooled, becomes brittle, collapses, and becomes sand-like. No digging into the inner surface of the tube 3 occurs, and there is no damage to the inner surface of the raw tube 3 due to scale during rolling. In particular, the cooling temperature of the inner surface of the raw pipe 3 by cooling water is 800°C when the target raw pipe 3 is a steel pipe.
It is desirable that the temperature be above 900°C or below. This is because if the temperature exceeds 900°C, the scale is not sufficiently embrittled, and the inside of the raw tube 3 may be damaged by the scale.

It should be noted that rolling can be carried out without particularly limiting the lower limit of the cooling temperature, but excessive cooling is rather wasteful as it increases the cost of cooling water, and according to the inventors' experiments,
The temperature is preferably about 800°C.

In addition, since the lubricant is also injected at the same time as the cooling water in the above process, even if some of the lubricant flows out of the tube due to the injection of cooling water, it will be replenished one after another, reducing rolling efficiency. Work is carried out without any interference.

Examples of the method for manufacturing a seamless steel pipe of the present invention will be described below.

The diameter of the exception is 3564 mm, the wall thickness is 23.83 mm, and the length is 113 mm.
051111111 A raw pipe made of 0.22 inch carbon steel was subjected to reel rolling by implementing the method of the present invention.

The amount of cooling water injected from the cooling water injection port 5 during rolling is 30
m'/h 1 The injection amount of lubricant graphite from the lubricant injection port 6 is set to 6 to lo Vs, and the rolling speed is 05rrV/
It was set as s. Also, the inner surface temperature of the raw tube during rolling is 850℃.
Met.

Comparative Example The other conditions were the same as in the above-mentioned Examples, except that reeler rolling was carried out without injecting cooling water into the tube (9) during rolling. The inner surface temperature of the raw tube during rolling was 974°C.

A test piece 15 having a length of 1 m as shown in FIG. 7 was taken from the steel pipe obtained as above, and the depth and number of flaws on the inner surface of the test piece 15 were examined. The results are shown in FIGS. 8 and 9. As shown in Fig. 8, there were fewer than 100 specimens obtained in the example with flaw depths of 0.1 to Q and 19w1, and there were no flaws with a depth of 0.5 m or more. As shown in FIG. 9, in the sample obtained in the comparative example, there were more than 800 flaws with depths of 0, 1 to Q, and 29+ m, and a considerable number of flaws with a depth of 0.8 m or more.

From the above, it can be seen that in the examples of the present invention, the occurrence of inner surface flaws during the manufacturing process of seamless steel pipes was significantly less than in the comparative examples, and the degree of the flaws was also small.

As described above, according to the present invention, by rolling the raw pipe while simultaneously injecting cooling water and lubricant into the raw pipe, inner surface defects caused by the presence of scale (10) on the inner surface of the raw pipe can be eliminated. can be prevented from occurring,
Good quality products can be obtained efficiently.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a state in which reeler rolling is performed using the seamless steel pipe manufacturing apparatus of the present invention, and FIG. 2 is a plug bar tip of the seamless steel pipe manufacturing apparatus shown in FIG. FIG. 3 is a longitudinal sectional view of the plug bar, and is a sectional view of part A shown in FIG. 1, FIG. 4 is a sectional view of part B in FIG. 1, and FIG. Figure 6 is a cross-sectional view taken along line ■-■ in Figure 2. Furthermore, FIG. 7 is a perspective view showing the shape of a test piece for investigating the occurrence of flaws in steel pipes obtained by an example of the present invention and a comparative example thereof, and FIG. Figure 7 shows the results of taking specimens from the steel pipes obtained and examining the depth and number of existing flaws. It is a figure which shows the result of taking the sample and investigating the depth of the existing flaw and its number. 1...Plug bar, 2...Plug, 3...Main pipe,
5... Cooling water injection port, 6... Lubricant injection port, 7...
- Cooling water supply pipe, 8... Lubricant supply pipe, 9... Cart. Applicant: Kawasaki Steel Co., Ltd. Agent: Taketo Toyota, patent attorney (and one other person)

Claims (3)

[Claims] (1) In a method for manufacturing a seamless steel pipe in which a plug is inserted into the raw pipe and the raw pipe is rolled between the rolls and the plug, the raw pipe is rolled while simultaneously injecting cooling water and lubricant into the raw pipe. A method for manufacturing a seamless steel pipe, characterized by performing the following steps. (2) In a seamless steel pipe manufacturing apparatus in which a plug is attached to the tip of a plug bar, a cooling water injection port and a lubricant injection port are provided at the tip of the plug bar, and cooling water is supplied to the cooling water injection port. A seamless steel pipe manufacturing device characterized in that a pipe and a lubricant supply pipe leading to a lubricant injection port are arranged through a plug bar. (3) A method for manufacturing a seamless steel pipe according to claim 1, characterized in that the inner surface temperature of the silicon pipe is set to 800°C or more and 900'C or less by injecting cooling water into the raw pipe. .