JPS6092006A - Production of seamless pipe - Google Patents

Abstract

PURPOSE:To produce efficiently a long-sized seamless pipe having no thickness deviation by forming a blank material having a round sectional shape into a hollow blank pipe by a three-roll type inclined piercing method, forming a pseudo-bottom to one end thereof, inserting a mandrel into the pipe and rolling the pipe by a push-bench rolling method. CONSTITUTION:A blank material 1 having a circular section is heated in a heating furnace 7 to the temp. at which said material can be pierced and thereafter the blank material is pierced to a relatively thick walled hollow blank material by an inclined rolling method 8 having three rolls each having a drum-shape and a piercing plug. Such blank pipe is diametrally reduced by an outside sinking rolling method 9 according to need and thereafter one end thereof is drawn to a tubular body provided with a pseudo-bottom by a pipe end swaging method 10. A mandrel 6 is then inserted into the pipe from the open side at the other end by a driving rack and the pipe is rolled by a push-bench rolling method 5. The blank pipe is thereafter finished of the pipe surface by reeler rolling 11 and is cut to a standard size by a saw 12. The cut pipe is finished to a specifed diameter and round shape by a sizing method or is reduced to a desired pipe diameter by a drawing method 15 after heating, by which the product of the seamless pipe is obtd.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing seamless pipes.

(Prior Art) FIG. 1 shows a known bush bench rolling method for producing seamless pipes.

The material 1 is a cast or rolled material with a rectangular or polygonal cross section, and after being heated to a temperature that allows plastic working, it is punched into a thick-walled hollow body 3 with a bottom using a press drilling method 2, followed by a known method. It is stretched using the Arasel tilt rolling method 4, which consists of three stepped rolls, and after adjusting the uneven wall thickness, outer diameter, and wall thickness of the perforated material, it is stretched into the required seamless pipe using the Bush bench rolling method 5.

Among the many seamless pipe manufacturing methods, the rolling process is particularly easy, the equipment cost is low, and the product quality is excellent, whereas other seamless pipe manufacturing methods have difficulty in rolling. Although this method has various advantages such as easy production of thin-walled pipes and a wide range of steel types that can be made into pipes, it has some drawbacks.

The first problem is that the press perforation method becomes a bottleneck and it is not possible to obtain a rolling extension having a sufficient length after bush bench rolling.

In the press drilling method, the uneven thickness of the drilling material is caused by the eccentricity of the press mandrel 6, etc., but it tends to increase significantly as the drilling ratio (drilling length/boring inner diameter) increases.

The reason why the Arasel inclined rolling method is placed after the press perforation method is to effectively correct the uneven thickness of the perforation through the action of its stepped (hump) rolls, and to send the longer perforation material to the subsequent process. However, the practical maximum limit of the perforation ratio of the perforation press obtained in this way is up to 7.5.

It is conceivable to increase the I\amp height of the roll in an attempt to achieve a greater thickness correction effect and stretching effect with the Arasel mill, but in terms of quality, there is an optimum value due to efficiency constraints, and the stretching ratio can be kept below 1.7 at most.

There is almost no change in the length of the material before and after perforation, and the maximum stretch ratio in the Arasel inclined rolling method is 1.7 or less, so the total stretch ratio in combination with the rerolling method is still at most 1.7 or less. This means that it is often impossible to obtain a sufficient length of compression at the outlet of the bushing bench, except for some thin-walled pipes. As the required wall thickness of rolled material increases and the pipe weight per unit length increases, the rolling length becomes shorter, resulting in the disadvantage that the standard product length (L5m) cannot be achieved for important products such as oil country tubular goods and line pipes. I will carry it.

The second drawback of the conventional Butsch bench rolling method is related to the insufficient total stretching ratio of the press perforation method and the Ancel tilt stretching method mentioned above, and the processing burden ratio in the Butsch bench rolling method is insufficient. This is about relatively large disadvantages.

The wall thickness of the raw pipe in which the press perforation material is rolled by the Arasel inclined roll rolling method is excessively thick.In particular, when rolling a thin-walled pipe on a Bushu bench, the required drawing specific force on the Bushu bench must be less than 17. It is no longer rare for the rolls to be crossed, and for this reason, a large number of forming roll stands, up to 17 or more, must be arranged with each skewer mold.

Requiring a large number of bush bench stands to roll one product size increases tool costs as the number of stand stands increases, increases the length of the 7-frame support stand and the rack for driving the mandrel rod, Due to this, there will be an inherent loss in equipment costs due to the lengthening of the factory building, etc.
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(Objective of the Invention) The present invention preserves the above-listed advantages of the conventional method by 4±100%, and the above-mentioned 1. The second purpose is to completely eliminate the disadvantages of the two conventional methods and to obtain a more perfect method for manufacturing seamless pipes.

(Structure of the Invention φ Effect) In the method for manufacturing a seamless pipe according to the present invention, a material having a round cross section is heated to a temperature at which it can be perforated, and then a relatively thick After drilling a hole in the hollow raw tube, one end of the raw tube is drawn into a pseudo-bottomed tubular body using the swage method, and a mandrel rod is inserted from the open tube side at the other end to form the raw tube. It is rolled together with the pipe using the Butsch bench rolling method.

Another seamless pipe manufacturing method according to the present invention involves heating a material with a round cross-section to a temperature that allows drilling, and then using an inclined drilling method using three wooden rolls to form a relatively thick hollow pipe. After drilling, the outer diameter is reduced by a sinking rolling method, one end of the raw pipe is drawn into a pseudo-bottomed tubular body by a swage method, and the open tubular body side force on the other end side is reduced. ), a mandrel rod is inserted into the pipe, and the pipe is rolled with the bush bench rolling method.

(Example) The present invention will be explained in detail with reference to FIG. 2 showing an example of the present invention.

After a material 1 with a circular cross section is heated to a temperature at which it can be perforated in a heating furnace 7, it is first rolled using three wooden barrel-shaped rolls, and an inclined roll rolling method 8 having an inner surface TJL and a perforation plug is performed. Drill holes into relatively thick raw pipes.

The raw tube rolled by the 30-mill inclined rolling method is reduced in outer diameter to a small diameter by a sinking rolling method 9, and then one end of the tube is swaged by a mandrel 6 in a bush bench rolling 5 by a swaging method 10. Form into a punchable pseudo-bottomed tube. Mandrel 6 from the open side of the other end of the raw pipe
Bush bench rolling 5 can be completed by inserting the bushing and moving it forward with the drive rack.

In the above pipe manufacturing method, placing the sinking rolling method for outer diameter reduction after the 30-hole inclined rolling method is effective in consolidating the types of perforated material dimensions, but such a necessity If there is no such rolling method, this rolling method can be omitted. The post-process of the Bushbench rolling method is configured in exactly the same manner as in the conventional Bushbench rolling method.

That is, a slight wall thickness reduction is applied to the pipe that has been bench-rolled by rolling 11, and the pipe surface is finished smooth.
Cut into required dimensions using a saw 12.

Subsequently, the tube is finished into a constant diameter and a right circle using a sun plug 13. If the outer diameter of the cut tube is to be considerably reduced, the tube is reheated 14 and then reduced to a desired diameter by rolling 15.

(Effect of the invention) The advantages of the present invention compared to conventional methods are as follows.

1) Since the 30-hole inclined drilling method uses the principle of rotary rolling and has little thickness deviation, the maximum length of the hole is not limited by the thickness deviation as in the case of press drilling.

The maximum length of the 30-hole oblique drilling method is determined by the durability of the inner tool plug 2 against mechanical and thermal loads, but it is not possible to obtain a much longer and more profitable drilling material than with the press drilling method. , is publicly known.

Tables 1 and 2 are examples comparing the neck-to-ring schedules of the conventional method and the embodiment according to the present invention in the standard bush bench pipe manufacturing method with a maximum rolling outer diameter of 5".

Table 1 is for the conventional method, but where the bush bench outlet pressure length is marked *, it points out that it is regulated by the north limit of drilling of the press drilling method, 7.5.

When the maximum length of bush bench rolling is limited to 18 mm, it is clear that most of the dimensions, except for some thin-walled pipes, become a perforation press neck and cannot reach that value.

Table 2 is for examples according to the invention.

It is clear that even if the Bush Bench outlet pressure extension is increased to 25 degrees, pipes of all sizes will not become unsuitable for drilling, and there is still room to increase the extension even further if necessary.

If the maximum possible drilling length in the 30-hole inclined drilling method is 8 cm, it is clear that there is sufficient drilling length and sufficient drilling capacity for the bush bench drilling method.

2) The second advantage of the present invention is that by using 30 mm, the total stretching ratio between the press perforation method in the conventional method and the Arasel inclined rolling method is limited to about 1.7 at most. The reason for this is as mentioned above, and I also pointed out the disadvantage that the wall thickness of the hollow tube that arrives at the bush bench is still excessively thick. On the other hand, the 30-angle oblique drilling method according to the present invention allows for a large stretching ratio, up to 2.3
It is well known that it is easy to take values up to .

As a result, in the present invention, as long as the mandrel punching does not cause an accident, the dimensions of the raw tube in the bush bench rolling method can be brought as close to the dimensions after rolling as possible.

In other words, by relatively increasing the processing load in the 30-roll inclined roll JE rolling method, which has excellent processing efficiency, and greatly reducing the processing load on the Bush bench, even when rolling thin-walled tubes, the processing load can be reduced to about 13 or less at most. The number of roll stands will be reduced accordingly.

It has already been explained above that many advantages can be obtained in connection with the reduction in the number of roll stands, and the explanation thereof can be omitted.

3) The third advantage of the present invention is that among the inclined roll drilling methods, in the case of the 30-roll inclined drilling method of the present invention, the hole internal quality of the continuously cast material is sound, and the steel grade limit that can be drilled is It should have good perforation characteristics in accordance with the law.

It is a well-known fact that in the case of the 30-roll slanted drilling method, the drilling section is performed under compressive stress, just as in press drilling, and this makes the advantages of the slanted roll drilling method and the press drilling method different from each other. This is a feature of the drilling method of the present invention.

It may be possible to replace the 30-hole inclined drilling method of the present invention with the well-known 20-hole inclined drilling method (Mannesmann method), but in this case, the third advantage of the present invention is as follows: It must be taken into account that this results in an unsatisfactory bush bench rolling process.

This is because in the Mannesmann drilling method, the center of the material to be drilled is under tensile load and shearing load, making the drilling conditions more severe for the material, making it difficult to drill into materials with inferior inner surfaces. In addition, drilling in high alloy steel, which has poor workability, tends to be accompanied by technical difficulties.

In the 30-ru oblique drilling method, there is no guide in the forming zone, which fundamentally eliminates the occurrence of scratches caused by the guide shoe during drilling and the stopping of the rolling mill for replacement due to wear, as in the case of the Mannesmann drilling method. From this point of view, it is clear that the 30-hole perforation method is more compatible with the perforation method of the bush bench rolling process.

[Brief explanation of drawings]

Fig. 1 is a process schematic diagram showing the conventional bush bench rolling method for producing seamless pipes, and Fig. 2 is an implementation of the present invention@-
FIG. l...Material, 2...Erhardt press perforation method, 3.
...Thick-walled hollow body, 4...30-Luatssel stretching method, 5
... Butsch bench rolling method, 6... Mandrel, 7
... Heating furnace, 8 ... Inclined roll perforation method, 9 ... Outer diameter sinking rolling method, 10 ... Tube end swaging method, 11
...Reeler rolling, 12...Saw, 13...Sizing method, 14...Reheating furnace, I5...Reducing rolling method. Patent applicant Representative patent attorney Tomoyuki Yafuki (and 1 other person) Figure 1 °45

Claims (2)

[Claims] (1) After heating a material with a round cross section to a temperature that allows drilling, a relatively thick hollow blank tube is drilled using the MM drilling method using three rolls, and then the blank tube is drilled. A seamless pipe characterized in that one end is drawn into a pseudo-bottomed tubular body by a swage method, a mandrel rod is inserted from the open tubular body side on the other end side, and the raw pipe is rolled together with the raw pipe by a Bush bench rolling method. Production method. (2) After heating a material with a round cross-section to a temperature that allows drilling, a relatively thick hollow blank tube is perforated by an inclined perforation method using three rolls, and subsequently by a sinking rolling method. Then, one end of the raw tube is drawn into a pseudo-bottomed tubular body using the swage method, and then a mandrel rod is inserted from the other end of the open tube body, and the raw tube and the raw tube are pushed together. A method for manufacturing a seamless pipe, characterized by rolling it using a bench rolling method.