JPS6092007A - Rolling method for seamless pipe - Google Patents

Abstract

PURPOSE:To manufacture efficiently a seamless pipe having substantial length without thickness deviation by piercing a square columnar blank material to a thick walled hollow blank pipe then drawing the pipe to form a pseudo bottom at one end, inserting a mandrel into the pipe and rolling the pipe by a push bench rolling method. CONSTITUTION:A blank pipe 1 having a square or polygonal shape section is heated to the plastically workable temp. in a heating furnace 7 and is pierced to a thick walled hollow pipe by a press roll piercing method 8 and thereafter the pipe is drawn to a thin walled blank pipe and is corrected in thickness deviation by an inclined roll rolling method 9. Such blank pipe is reduced by an outside diametral sinking method 9 according to need and thereafter one pipe end is formed to a pipe shape with a pseudo bottom by a swaging method 11. A mandrel 6 is inserted into the pipe from the open side at the other end and the blank pipe is rolled by a push bench method in which the pipe is advanced by a driving rack. The rolled pipe is further finished to have the smooth surface by reeler rolling 12 and is cut to a standard size by a saw 12 and thereafter the pipe is finished to a fixed diameter and circular shape by a sizing method or is reheated in a furnace 15 and is reduced to a desired diameter by a reducing method 16, 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. The perforated material is stretched by the Arasel tilt rolling method 4 using three stepped rolls to adjust the uneven wall thickness, outer diameter, and wall thickness of the perforated material, and then stretched into the required seamless pipe by the Bush bench rolling method 5.

Among the many seamless pipe manufacturing methods, the rolling method is particularly popular because it has simple rolling operations, low equipment costs (low cost, excellent product quality, and a wide range of steel types that can be manufactured). Although this manufacturing method has advantages such as ease of manufacturing thin-walled tubes that are difficult to manufacture, it also has the disadvantages of other methods.

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 arranged after the press perforation method is that the uneven thickness of the perforation can be effectively corrected by the action of its stepped rolls, and the longer perforation material can be used in the subsequent process. However, the maximum practical limit of the perforation ratio of the perforation press obtained in this way is up to 7.5.

It is conceivable to increase the hump height of the roll in an attempt to achieve a greater thickness correction effect and stretching effect with the Arasel mill, but due to quality and efficiency constraints, there is an optimal value, and the stretching ratio is at most 1. It can be kept below .7.

In the press roll perforation method, the characteristic is that 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.
The total stretching ratio in combination with the re-rolling method is at most 1.
7' or less, which means that it is often impossible to obtain a sufficient length of rolled extension 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, rolling extensions exceeding 10+s cannot be obtained, and the standard product length of oil country tubular goods and line pipes, which are currently growing in the market, has become increasingly difficult to achieve. It becomes difficult to respond to the situation.

The second drawback of the conventional Butushu bench rolling method is related to the insufficient total stretching ratio of the press perforation method and the Arasel inclined stretching method mentioned above, and the processing load ratio of the Butushu bench rolling method is relatively low. This is about the disadvantage that becomes extremely large.

As a result, especially when rolling thin-walled pipes, the required drawing ratio on the bush bench becomes a high value of nearly 20. It is not uncommon for a large number of forming roll stands, 15 or more, to be arranged in a medium size.

The high drawing ratio required by the Bush bench rolling method and the need for a large number of forming stands means that the increased number of stands in stock means the tool costs, stand support frames and mandrel drive rack devices, and the associated factory costs. This means that there will be an inherent increase in equipment costs due to longer buildings, etc.

(Objective of the Invention) The present invention preserves the advantages of the conventional method listed above by 100 times, while preserving the advantages of the above-mentioned 1%1. The second objective is to completely eliminate the disadvantages of the two conventional methods and to obtain a more perfect seamless pipe manufacturing method.

(Structure and operation of the invention) In the seamless pipe rolling method of the present invention, a material with a rectangular or polygonal cross section is heated to a temperature that allows plastic processing, and then a thick-walled hollow tube is perforated by a press roll perforation method. 2. After correcting the uneven thickness of the hollow perforated material and obtaining the required wall thickness, one end of the hollow tube is subsequently formed into a pseudo-tubular body by swaging. After that, a mandrel is inserted from the other open tube end side, and the hollow tube is rolled by a bush bench rolling method.

In another seamless tube rolling method of the present invention, a material with a square or polygonal cross section is heated to a temperature that allows plastic processing, and then a thick-walled hollow tube is perforated by a press roll perforation method, followed by inclined roll rolling. After correcting the uneven thickness of the hollow perforated material and obtaining the required wall thickness,
Subsequently, one end of the hollow shell obtained by reducing the outer diameter by the sinking rolling method is formed into a pseudo-bottomed tubular body by swage processing, and then a mandrel is inserted from the other open pipe end to form the hollow shell. The tube is rolled using the push-beft rolling method.

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

Material l with a square or polygonal cross section heated in the heating furnace 7
First, a thick-walled hollow tube is perforated using a press roll perforation method 8, and then a thinner-walled tube is formed using an inclined roll rolling method 9, and uneven thickness at the time of perforation is corrected.

In this case, it is more appropriate for the inclined roll rolling method to have two or three barrel-shaped rolls and use a plug as an internal tool.

After the outer diameter of the raw pipe rolled by inclined rolls is reduced to a small diameter by the sinking rolling method NO, one end of the pipe is swaged by the swage processing method 11 to form a pseudo-pipe that can be punched out with a mandrel 6 in the bush bench rolling 5. Form into a tube with a bottom. The bush bench rolling 5 can be completed by inserting the mandrel 6 from the open side of the other end of the blank pipe and moving it forward with a drive rack.

In the above pipe manufacturing method, the sinking rolling method 10 for reducing the outer diameter, which is placed behind the inclined roll rolling method 9, is aimed at reducing the size of the perforated material and increasing the unit weight of the perforated material. Yes, it can be omitted if it is not necessary.

The subsequent steps of the bush bench rolling method 5 may be completely the same as those of the conventional bush bench rolling method.

That is, a slight wall thickness reduction is applied to the tube beam-roller rolled 12 that has been bench-rolled, and the tube surface is finished smooth.
Cut into required dimensions using a saw 13.

Next, the pipe is sized to have a constant diameter and a right circle by sizing 14.
Bearded. In addition, when the outer diameter of the cut tube is to be considerably reduced, the tube is reheated +5L and reduced by 16 steps to finish the tube to the required diameter.

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

1) In the case of the present invention, the push bench outlet pressure extension is sufficient for the length of commercially available products, and the standard length of long oil country pipes and line pipes is insufficient due to the lack of pressure extension as in the past. Disadvantages such as not being able to collect them are eliminated. In other words, in the conventional method, the maximum length limit for the press drilling method is 7.5mm at the drilling ratio, even though it is supported by the uneven thickness correction effect of the Arasel rolling method.
Although it was limited to 5th place, the press roll perforation method in the new method can easily roll a perforated hollow body with a perforation ratio of 40, with the aid of the effective effect of eliminating uneven thickness with the inclined roll.

This means that, under conditions of the same material cross-sectional dimensions, the present invention can use a perforated material that is five times or more heavier than the conventional method. As a result, in the present invention, it is possible to solve the problem that the drilling weight becomes a bottleneck regarding the rolling length, and the length of the rolling length is determined by setting the length of the bush bench equipment to the most economical value while considering the required rolling length. It is only necessary to consider it from this point of view.

Tables 1 and 2 are examples comparing the rolling schedules of the present invention and the conventional method in the standard bush bench pipe manufacturing method with a maximum rolling outer diameter of 5y2''.

Table 1 is for the conventional method, but where the Bush bench outlet pressure t-i is marked with an * (blue, it points out that it is regulated by the perforation limit of 7.5 for the press perforation method) The maximum length of bush bench rolling is 16tm.
If it is limited to 1, it is clear that most of the dimensions, except for some thin-walled pipes, will become a drilling press neck and the value of 1 cannot be achieved.

Table 2 shows the case of the embodiment according to the present invention, but even if the bush bench outlet pressure extension is increased to 25 m, it will not become unsuitable for drilling for pipes of all sizes, and if necessary, further It is clear that there is room to increase the rolling length.

As described above, since the present invention can ensure a long rolling length, it can be said to be a more advantageous rolling method than the conventional method in terms of rolling efficiency, 9 yield, etc.

2) The second advantage of the present invention is that the drawing ratio in the bush bench rolling method can be set lower than in the conventional method, and the burden of equipment costs, tools, etc. can be reduced. In the conventional method, the total stretching ratio between press perforation and Aracel inclined rolling method (Arasel exit pipe length/material length before press perforation) is limited to about 1.7 at most, as mentioned above, but this The wall thickness of the hollow member when it reaches the bush bench is still extremely thick. This means that the processing load in the next process, the Bushu bench rolling method, increases relatively, and when rolling a thin-walled pipe immediately, the hair stretch ratio on the Bushu bench rarely exceeds 17. Instead, a large number of roll stands (17 or more) must be lined up on the punch bench frame. In other words, in the conventional method, the number of roll stands required increases, and equipment costs are lost due to increases in the length of the push-punch frame, the length of the mandrel drive rack, and the size of the factory building.

'A. The inclined roll rolling method using comb-shaped rolls and plugs used in the invention has the characteristic of achieving a large drawing ratio, and it is well known that a maximum drawing ratio of about 2.5 can be easily achieved, and According to the law, punching with a mandrel can be used to punch thin-walled raw pipes in front of bush bench rolling equipment, as long as it does not cause an accident.

Due to the second feature of processing distribution of the present invention, the amount of processing in the Bush bench rolling method can be significantly reduced compared to the conventional method, and even when rolling thin-walled pipes, it is sufficient to stretch the tube by at most about 13 or less, and the roll roll The number of stands has decreased,
Related to this is the construction of a bush bench [I length can be greatly shortened.

3) The third advantage of the present invention is that economical materials such as steel ingots and continuously cast materials can be used, and a wide range of steel types can be drilled.

When comparing the press roll perforation method used in the present invention with the Mannesmann inclined perforation method, which has traditionally been most commonly used as a perforation method, it is found that perforation in the press roll perforation method is performed under a compressive load. In the Mannesmann drilling method, drilling is performed under tensile or shear loads. Further, the strain rate in the press roll perforation method is on the order of 1/10 to 1150 in the case of the Mannesmann perforation method. These are the technical reasons why the press roll perforation method is able to produce sound perforations even when using materials inferior in quality to those of the Mannesmann perforation method, and the steel grade limit is wider.

Once a sound perforated material is obtained, it is easy to further stretch it in the blowdown process while maintaining quality by using the inclined roll rolling method.

By combining the press roll perforation method and the inclined roll rolling method, the new method is characterized by being able to use economical materials and widening the range of steel types that can be rolled, which was a special advantage of the conventional Butsch bench method. This can be preserved without sacrificing the

It is conceivable that the combination of the press roll perforation method and the subsequent inclined roll rolling method could be replaced by a single Mannesmann perforation machine; The possibility of rolling, etc., would have to be sacrificed to a large extent.

The new bush bench rolling method described above eliminates the technical limitations of the conventional bush bench, and the bush bench rolling method becomes a powerful seamless pipe manufacturing method.

[Brief explanation of drawings]

FIG. 1 is a process schematic diagram showing a conventional bush bench rolling method for producing seamless pipes, and FIG. 2 is a process schematic diagram showing an embodiment of the present invention. l...Material, 2...Press perforation method, 3...Thick-walled hollow body, 4...30-luatsu cell #f oblique rolling machine, 5...
・Butsch bench rolling method, 6... mandrel, 7...
- Heating furnace, 8... Inclined roll perforation method, 9... Inclined roll stretching method, lO... Outer diameter sinking method, 11...
Tube end swage method, 12... Reeler rolling, 13...
saw, 14... sizing method, 15... reheating furnace, 18
...Squeeze rolling method. Patent applicant Representative patent attorney Tomoyuki Yabuki (and 1 other person)

Claims (2)

[Claims] (1) A material with a rectangular or polygonal cross section is heated to a temperature that allows plastic processing, and then a thick-walled hollow tube is perforated using a press roll perforation method, and then stretched using an inclined roll rolling method to form a hollow perforated material. After straightening the wall and obtaining the required wall thickness, one end of the hollow tube is formed into a pseudo-bottomed tubular body by swaging, and a mandrel is inserted from the other open tube end. Pull the hollow tube.
Seamless pipe rolling method characterized by rolling using bench rolling method. (2) After heating a material with a rectangular or polygonal cross section to a temperature that allows plastic processing, it is perforated into a thick hollow tube using a press roll perforation method, and then stretched using an inclined roll rolling method to form a hollow perforated material. After straightening the wall and obtaining the required wall thickness, one end of the hollow tube obtained by reducing the outer diameter by sinking rolling was formed into a pseudo-bottomed tubular body by swage processing. A seamless tube rolling method characterized in that a mandrel is then inserted from the other open tube end side and the hollow shell is rolled by a bush bench rolling method.