JPH07185607A - Rolling equipment train for seamless pipe - Google Patents

Abstract

PURPOSE:To produce product pipes of a wide range of outside diameters from a continuously cast hollow pipe stock at low cost. CONSTITUTION:This rolling equipment train for seamless pipes is provided with an expansion rolling line for finishing continuously cast hollow pipe stock 2 to the final outside diameter larger than the outside diameter of the continuously cast hollow pipe stock 2 by expanding with an expansion rolling mill 4 and a reduction rolling line for finishing the continuously cast hollow pipe stock 2 to the final outside diameter smaller than the outside diameter of the continuously cast hollow pipe stock 2 by reduction with a reducing machine 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a row of rolling equipment for seamless pipes such as seamless steel pipes.

[0002]

2. Description of the Related Art The Mannesmann method is the mainstream manufacturing process for seamless pipes, and it is roughly classified into a plug mill method and a mandrel mill method depending on the rolling method. Basically, a round billet is punched. It consists of a piercing step, a drawing and rolling step of thinning and drawing the pierced hollow shell, and a finish rolling step of squeezing the drawn and rolled hollow shell to a predetermined outer diameter or a constant diameter.

The mandrel mill system generally has a small diameter (outer diameter 1
This method is said to be suitable for manufacturing seamless pipes of about 1 inch to 7 inches. In the mandrel mill system, for example, as shown in FIG. 9, a material billet 22 is placed in a rotary hearth type heating furnace 21 at a predetermined temperature (generally 1100 ° C. to 1300 ° C.).
C.) and then pierced and rolled by the Mannesmann piercer 23 to slightly expand the outer diameter and to form the hollow shell 24.
a. Since the hollow shell 24a is thick and short,
The mandrel mill 26, which is a stretching and rolling machine, performs thinning and stretching. The mandrel mill 26 is a rolling machine that stretches and rolls the hollow shell 24a with the mandrel bar 25 having a surface coated with a lubricant for hot rolling inserted into the hollow shell 24a, and usually has 6 to 8 units. Each roll stand is equipped with a pair of hole-type rolls, and the rotation axis of the hole-type rolls is mutually shifted by 90 degrees in a plane perpendicular to the rolling axis between adjacent roll stands. It is arranged. The temperature of the raw pipe in the mandrel mill 26 is generally 1050 ° C to 1200 ° C on the rolling mill inlet side and 800 ° C to 1000 ° C on the rolling mill outlet side. The mandrel mill 26 reduces the outer diameter of the hollow shell 24a,
Is stretched to a length of 4 times to form the raw material tube 24b for the finishing rolling mill. The finish rolling mill tube 24b is heated to a predetermined temperature (generally 850 ° C. to 10 ° C.) by the reheating furnace 27, if necessary.
After being reheated to 00 ° C., it is finish-rolled by a finish rolling machine, for example, a stretch reducer 31. Stretch reducer 31 maximizes the outer diameter of the raw pipe.
It is relatively excellent because it is squeezed by 75% and stretched to 40 times or more of the length of the material billet, and the outer surface of the stretch reducer 31 has a constant diameter on the final side of several round holes. A finished pipe 30 having an accurate outer dimension can be obtained.

[0004]

[Problems to be Solved by the Invention]
In order to reduce the number of processes, a hollow continuous casting method has been developed in which a hollow shell is directly cast from molten steel.
As disclosed in Japanese Patent Application Laid-Open No. 4-111907,
A method has been proposed in which a continuously cast hollow shell is used instead of the round billet of the mandrel mill rolling method described above, and the piercing and rolling step in a piercer mill is omitted.

However, in the mandrel mill system, only a product having an outer diameter smaller than the outer diameter of the hollow shell at the mandrel mill entrance side can be obtained. Therefore, in order to obtain a product having a large outer diameter, it is necessary to increase the outer diameter of the hollow shell on the mandrel mill entrance side, that is, the outer diameter of the continuously cast hollow shell. Also,
There is also an upper limit on the rate of contraction in a contracted diameter constant diameter machine such as a stretch reducer, and when manufacturing products with greatly different outer diameters, it is also necessary to prepare continuously cast hollow shells of various kinds of outer diameters.

However, when an attempt is made to obtain a continuously cast hollow shell having a large outer diameter, the diameter of the break ring and the core used in the continuous casting machine becomes large, and cracks and cracks easily occur due to thermal strain or the like. There is a problem that the life of the break ring and the core is shortened and the manufacturing cost is significantly increased.

Further, preparing a large number of continuously cast hollow shells having a large number of outer diameters requires a large number of continuously casting molds, break rings, and cores, resulting in significantly high equipment costs and size changes. However, there is also a problem that the manufacturing cost becomes extremely high.

An object of the present invention is to make it possible to manufacture a product pipe having a wide range of outer diameters from a continuously cast hollow shell at low cost.

[0009]

SUMMARY OF THE INVENTION The present invention according to claim 1 is a continuous casting hollow shell in a seamless rolling mill line for producing a seamless tube having a wide range of outer diameters from the continuous casting hollow shell. And a pipe expanding and rolling line for expanding the continuous casting hollow shell to a final outer diameter larger than that of the continuous casting hollow shell and a continuous casting hollow shell by a shrinking machine And a contracted rolling line for finishing to a final outer diameter having a small diameter.

According to a second aspect of the present invention, in addition to the first aspect of the present invention, the pipe expanding machine arranges a pair of cone type rolling rolls at an inclination angle β with respect to the pass line. Together with the entrance line angle α _{1 with} respect to the pass line
And a projecting side angle α ₂ and an inclined rolling mill crossed with the pass line at an intersecting angle γ, and a plug inserted into the hollow shell between the pair of cone type rolling rolls. It is designed to be an inclined pipe rolling mill.

According to a third aspect of the present invention, in the present invention according to the first or second aspect, the pipe expanding and rolling line is expanded on the outlet side of the pipe expanding machine by the pipe expanding machine. It is configured such that a constant diameter machine that determines the outer diameter of the is installed.

The present invention according to claim 4 is based on claims 1 to 3.
In any one of the present inventions, further, a descaling device for descaling the inner surface of the continuously cast hollow shell to be expanded is installed on the inlet side of the expander.

The present invention according to claim 5 provides the invention according to any one of claims 1 to 4.
In any one of the present invention according to any one of, further, on the inlet side of the tube expansion and rolling line and the tube contracting line, a mandrel mill is installed, and after continuously thinning the continuously cast hollow shell by the mandrel mill, the tube expansion or It was made to contract.

[0014]

The present invention will be described below in detail with reference to the drawings. In FIG. 1, reference numeral 1 denotes a hollow shell casting apparatus, in which the material hollow shell 2 is continuously cast. When the material hollow hollow tube 2 is subsequently finished to have a final outer diameter larger than that of the hollow hollow tube 2, the blank hollow tube 2 is sent to the tube rolling mill 4 of the tube rolling line 101 to be expanded and rolled into a product 5. . On the other hand, in the case of finishing to a final outer diameter having an outer diameter smaller than that of the hollow shell 2, it is sent to the reduced-tube constant diameter machine 3 of the reduced-pressure tube rolling line 102, and the reduced tube is reduced in diameter to obtain the product 5.

The expanded tube mill 4, as shown in detail in FIGS. 5 to 7, with sloping arrangement a pair of cone rolls 41 and 42 at a constant advance angle beta, a side exit and entrance face angle alpha ₁ An inclined rolling mill having a crossing angle γ with respect to the pass line so as to have an angle α ₂ , a plug 43 inserted into the hollow shell 2 between the rolling rolls 41, 42, and a rolling roll 4
It is preferable to use an inclined pipe rolling mill including a guide shoe 44 that guides the outer surface of the hollow shell 2 between the first and second portions.
The guide shoe 44 may be a fixed type, a disc type, a roller type, or a drive roller type.

Further, as shown in FIG. 2, after the pipe is expanded by the inclined type pipe expanding and rolling machine 4, the outer diameter is fixed by the constant diameter machine 6 such as a sizer mill to suppress the fluctuation of the outer diameter in the longitudinal direction, It is possible to obtain the finished pipe 7 having excellent dimensional accuracy.

Immediately before pipe rolling by the inclined pipe rolling mill 4, a descaler 12 as shown in FIG. 4 is used, and high-pressure water is jetted onto the inner surface of the hollow shell 2 by its nozzle 12a to descale the inner surface. By doing so, it is possible to effectively prevent the scale indentation flaw that may occur at the contact surface between the hollow shell 2 and the plug 43 inserted in the inner surface of the tube rolling mill 4.

Further, as shown in FIG. 3, by reducing the thickness of the hollow shell 2 produced by the hollow shell casting apparatus 1 by a mandrel mill 8 before the step of expanding or contracting the hollow shell 2, A thin finished pipe can be obtained, and various types of thick products can be obtained without changing the size of the core used in the hollow shell casting device 1. The mandrel mill 8 may be a two-roll system, a three-roll system, a four-roll system, or a combination thereof, a retained system that performs bar speed control, a full float system that does not perform bar speed control, or a combination thereof. A semi-float system that controls the speed of a partial bar in the middle may be used.

Now, the pipe rolling mill 4 will be described in detail. In the tube expansion rolling mill 4, the cone type rolls are inclinedly arranged at a constant advancing angle β and are also arranged at a crossing angle γ with respect to the pass line, so that the roll diameter is temporarily increased toward the rolling-out side and the peripheral speed is increased. As a result, the roll exerts no brake on the rolled material. For this reason,
In the inclined rolling by the pipe rolling mill 4, there is no twist of the material to be rolled due to the brake exerted on the material to be rolled by the roll, and additional shear strain in the cross section does not occur. The hollow shell can be highly expanded without causing hollow breakage due to flaring.

However, the inventors of the present invention have found that when the hollow shell is expanded and rolled by the cone-shaped rolls that are arranged in a crossed manner, the rolled material is not caught properly, the tail is not slipped out, and the hollow is broken due to flaring. As a result of a detailed study, a pair of cone type rolling rolls have a constant lead angle β with respect to the pass line.
In addition to sloping at a crossing angle of γ with respect to the pass line so as to have an entrance side angle α ₁ and an exit side angle α ₂ with respect to the pass line, in order to expand the hollow shell highly, , Γ, β + γ are set within the following range, and 5 ° ≦ β ≦ 2
5 °, 10 ° ≦ γ ≦ 40 °, 20 ° ≦ β + γ ≦ 50 ° and α ₁ ,
Set α ₂ in the range below and set 0.5 ° ≤ α ₁ ≤
5 °, 3 ° ≤ α ₂ ≤ 10 °, α ₁ ≤ α ₂ , and the metal loss rate R
_{Between t} and expansion ratio E _r , 1 ≤ E _r / R _t ≤ 3, but R
_t = (t _i -t _o ) / t _i , E _r = (D _o -D _i ) / D _i ,
t _i : wall thickness of inlet hollow shell, D _i : outer diameter of inlet hollow shell, t
By satisfying the relations of _o : outlet pipe wall thickness, D _o : outlet pipe outer diameter, it is possible to remarkably prevent the occurrence of bite failure, defective tail slippage, and hollow breakage due to flaring, yield, and productivity. It was found that high pipe rolling can be performed without hindering the above.

[0021] That is, FIGS. 5 to 7 are shown such cone type rolls Gore - di section diameter D _R is 700 mm, the roll barrel length L
_R is 600 mm, roll length L ₁ from the entrance end to the gorge part
Is 250 mm, the entrance side angle α ₁ is 3 °, the exit side angle α ₂ is 5 °,
It is an inclined rolling mill with a crossing angle γ of 20 ° and a lead angle β of 15 °. It uses a hollow shell with a diameter _DH of 80 to 120 mm and a wall thickness t _H of 15 to 40 mm as the material to be rolled, and the roll gap E and the plug are advanced. The amount L was variously changed and the wall-thickness reduction ratio R _t and the pipe expansion ratio E _r were changed for pipe expansion rolling, and the occurrence of hollow biting due to defective biting and flaring was investigated. FIG. 8 shows the results organized by taking R _{t on} the horizontal axis and E _r on the vertical axis.

As is clear from the figure, a pair of cone type rolling rolls are arranged at an inclination with a constant advance angle β, and γ
In the slant rolling method of the pipes which are crossed with each other, the thinning rate R _t
And tube expansion ratio E _r in the range of 1 ≤ E _r / R _t ≤ 3, it is possible to avoid defective biting, defective slippage, and hollow breakage due to flaring, and the degree of freedom in rolling setting is improved. It is possible to raise it.

In the present invention, 5 ° ≦ β ≦ 25 °, 10 ° ≦
The reason for setting γ ≦ 40 ° and 20 ° ≦ β + γ ≦ 50 ° is as follows. Within a certain range, the larger the advancing angle β, the crossing angle γ, and the sum β + γ, the more the twist of the material to be rolled and the additional shear strain in the cross section can be reduced, which prevents the hollow tear due to flaring. Effective against
However, β <5 °, or γ <10 °, or β + γ <20
If the angle is °, the effect is not sufficient and hollow breakage due to flaring tends to occur. Therefore, the lower limit of β is 5 °, γ
The lower limit of is 10 °, and the lower limit of β + γ is 20 °. On the other hand, β>
At 25 °, or γ> 40 ° or β + γ> 50 °, the twist of the material to be rolled increases in the opposite direction, and additional shear strain in the cross-section also occurs in the opposite direction, rather causing hollow tearing due to flaring. It tends to occur. Therefore, β is 25 ° and γ is
40 ° and β + γ shall not exceed 50 °.

The reason why 0.5 ° ≦ α ₁ ≦ 5 ° is set is as follows. The entrance side angle α ₁ has an important influence on the biting property of the material to be rolled. If α ₁ exceeds 5 °, the material to be rolled is rapidly reduced during biting, and the drag force from the rolling roll required for deformation exceeds the thrust in the forward direction transmitted from the rolling roll. . Therefore, α ₁ is 5 °
Shall not be exceeded. On the other hand, if α ₁ becomes too small, it is necessary to considerably lengthen the roll barrel on the inlet side in order to obtain the outer diameter reduction of the material to be rolled necessary for the thrust in the forward direction. Becomes higher and not practical. Therefore, the lower limit of α ₁ is 0.5 °.

The reason why 3 ° ≦ α ₂ ≦ 10 ° is set is as follows. The larger the flank angle α ₂ is, the shorter the roll barrel on the exit side, which is necessary for the amount of pipe expansion, and the equipment can be downsized, but if it is too large, hollow breakage due to flaring will occur. Is likely to occur.
Therefore, α ₂ shall not exceed 10 °. On the other hand, α ₂
If is too small, it is necessary to lengthen the roll barrel on the outlet side considerably in order to obtain a predetermined amount of pipe expansion, resulting in high facility construction cost and impracticality. Therefore, the lower limit of α ₂ is 3 °.

The reason for setting α ₁ ≦ α ₂ is as follows.
When the exit side angle α ₂ becomes smaller than the entrance side angle α ₁ , in order to obtain a predetermined pipe expansion amount, the roll barrel length is longer than that when the exit side angle α ₂ is larger than the entrance side angle α _1. Becomes relatively long. Therefore, α ₁ does not exceed α ₂ .

[0027]

EXAMPLE A concrete example of the distribution of the working amount of the seamless steel pipe manufacturing method of the present invention by the above line arrangement is shown in Table 1 together with that of the conventional method.

In Table 1, the conventional example is rolled in the rolling equipment row of FIG. 9, and the invention A is rolled in the rolling equipment row of FIG. 1 in each of the pipe rolling line 101 and the pipe rolling line 102. Invention C is also rolled in each of the tube rolling line 101 and the tube rolling line 102 in the rolling equipment row of FIG. 2, and Invention D is in each of the tube rolling line 101 and the tube rolling line 102 in the rolling equipment row of FIG. It was rolled in.

As is apparent from Table 1, when the material hollow shell continuously cast by the conventional hollow shell casting apparatus is supplied to the manufacturing line of the mandrel mill system, the hollow shell is less than the outer diameter of the hollow shell. According to the present invention, it is possible to easily manufacture a product having a wide range of outer diameters without changing the outer diameter of the material hollow shell, whereas only a product can be manufactured.

[0030]

[Table 1]

[0031]

As described above, according to the present invention, a product having a wide range of outer diameter can be manufactured at low cost without changing the outer diameter of the material hollow shell.

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of a rolling equipment train according to the present invention.

FIG. 2 is a schematic view showing a second embodiment of the rolling equipment train according to the present invention.

FIG. 3 is a schematic view showing a third embodiment of the rolling equipment train according to the present invention.

FIG. 4 is a schematic diagram showing a descaler.

FIG. 5 is a plan view showing a pipe rolling mill according to the present invention.

FIG. 6 is a side view of FIG.

FIG. 7 is a front view seen from the rolling direction in FIG.

[Fig. 8] Fig. 8 is a diagram showing a situation of occurrence of defective biting, defective slip-out, and hollow tear due to flaring when pipe rolling is performed while changing the wall thickness reduction rate and the tube expansion rate.

FIG. 9 is a schematic diagram showing a conventional mandrel mill type rolling equipment row.

[Explanation of symbols]

 1 Hollow Element Pipe Manufacturing Equipment 2 Hollow Element Tube 3 Compacting Machine 4 Inclination Type Expanding Rolling Machine 5 Product 6 Constant Diameter Machine 7 Finished Tube 8 Mandrel Mill 12 Descaler 21 Rotating Hearth Heating Furnace 22 Material Billet 23 Mannes Man Piercer 24a, 24b , 24c, 24d Hollow shell pipe 25 Mandrel bar 26 Mandrel mill 27 Reheating furnace 30 Product 31 Stretch reducer 41, 42 Cone type rolling roll 43 Plug 44 Guide shoe 81 Mandrel bar 101 Expanding rolling line 102 Reduction pipe rolling line

Claims (5)

[Claims] Claim: What is claimed is: 1. In a seamless pipe rolling equipment line for producing a seamless pipe having a wide range of outer diameters from a continuous cast hollow shell, the continuous cast hollow shell is expanded by a pipe expander, A pipe rolling line that finishes to a final outer diameter with a large outer diameter, and a pipe rolling line that contracts a continuous casting hollow shell by a shrinking machine to finish to a final outer diameter that is smaller than the continuous casting hollow shell. A row of seamless pipe rolling equipment, which is characterized by being provided. 2. The tube expander arranges a pair of cone-type rolling rolls at an inclination angle of a constant advance angle β with respect to a pass line, and an entrance side angle α ₁ and an exit side angle α ₂ with respect to the pass line. And a plug which is inserted into the hollow shell between the pair of cone-shaped rolling rolls, and a tilt rolling mill having a cross angle of γ with respect to the pass line. The seamless rolling mill train according to claim 1. 3. The pipe expanding and rolling line is provided with a constant diameter machine for adjusting the outer diameter of the pipe expanding raw pipe expanded by the pipe expanding machine on the outlet side of the pipe expanding machine. A row of seamless pipe rolling equipment. 4. The seamless pipe according to claim 1, wherein a descaling device for descaling the inner surface of the continuously cast hollow shell to be expanded is installed on the inlet side of the expander. Rolling equipment row. 5. A mandrel mill is installed on the inlet side of the expanding and rolling line and the contracting and rolling line, and the continuously cast hollow shell is thinned and rolled by the mandrel mill, and then expanded or contracted. The seamless pipe rolling equipment row according to any one of to 4.