JP3125712B2 - Method and apparatus for manufacturing seamless metal pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a seamless metal pipe, and more particularly to a seam using a hot constant diameter rolling mill capable of finishing the outer diameters with different diameters using the same caliber roll. The present invention relates to a method for manufacturing a metal-free tube.

[0002]

2. Description of the Related Art A general process for manufacturing a seamless metal pipe is to reduce the thickness of a hollow shell pierced by a piercer using a stretching rolling machine such as a mandrel mill, and then to reduce the diameter of the hollow pipe to a sizer such as a sizer or a stretch reducer. After the outer diameter of the pipe is rolled to a predetermined size, the pipe is cooled to room temperature by a cooling bed and straightened by a straightening mill such as a rotary straightener to bend and round the pipe. To correct.

[0003] The sizer, which is the above-mentioned constant diameter rolling mill, has a plurality of roll stands (typically, 5 caliber rolls) in which three caliber rolls are radially incorporated around a pass center O at an interval of 120 ° in the same plane. 1 to 28 units), as shown in FIG. At this time,
Adjacent roll tands are successively provided with a phase difference of 60 ° around the path center O so that the arrangement of the three caliber rolls is in the relationship shown in FIGS. 2A and 2B. Then, at the time of constant diameter rolling, the number of roll stands to be used is determined according to the outer diameter of the pipe to be finished.

On the other hand, the above-described rotary straightener, which is a straightening mill, comprises a pair of drum-shaped rolls or a plurality of rolls each including a single drum-shaped roll, which are disposed opposite to each other with respect to the pass center. For example, as shown in FIG. 3, the stands are continuously arranged as “2-2-2-1”. At the time of straightening rolling, the height of the pass center of the adjacent roll stand (offset amount), the amount of reduction (crush amount) by the pair of drum-shaped rolls of each roll stand, and the By setting the inclination angle with respect to the path center to an appropriate value, the bending and roundness of the pipe are corrected (for example, Japanese Patent Application Laid-Open No. Sho 62-17301).
No. 5).

[0005] In the above-mentioned constant diameter rolling by the sizer, as described above, the number of roll stands to be used is determined according to the outer diameter or thickness to be finished. When finishing to an outside diameter or wall thickness that cannot be performed, it is necessary to replace the caliber rolls of each roll stand with caliber rolls having different dimensions.

[0006] For this reason, when manufacturing small products having greatly different outer diameters or wall thicknesses, frequent replacement of caliber rolls is required, and a great deal of time and labor must be spent for this. As a result, production efficiency is reduced. In addition, there is a problem that a large number of caliber rolls having different dimensions according to the outer diameter or wall thickness to be finished are required, or the caliber dimensions must be frequently reworked to cope with the problem.

As a method for solving the above problem, there is, for example, a method disclosed in JP-A-7-16616. That is, the method is to open and close the roll gap of the caliber roll of the upstream plurality of roll stands excluding the downstream plurality (usually 2 to 3) finishing roll stands used for rounding. In this method, the ellipticity of the caliber is changed, and the same caliber roll is used to finish tubes having different wall thicknesses and the same outer diameter. For this reason, the roundness defined by the following equation of the tube after rolling did not cause any problem.

Roundness (%) = ｛(maximum outer diameter−minimum outer diameter)
/ Average outer diameter｝ × 100 (%) However, when finishing pipes with different outer diameters using the same caliber roll, it is necessary to open and close the roll gap of the caliber roll of the finishing roll stand used for rounding. However, if the opening / closing amount is not appropriate, the roundness of the tube after sizing is inferior, and even if the tube cooled to room temperature by the cooling floor is subjected to straightening rolling, the roundness is ± 1%. There was a problem that did not become within.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a plurality of roll stands in which three or four caliber rolls are incorporated in the same plane so that the gap can be adjusted. A seamless metal pipe having a step of performing constant diameter rolling to pipes having various outer diameters by adjusting a gap of a caliber roll of the constant diameter rolling machine, comprising a hot constant diameter rolling mill having a plurality of bases arranged in series. In the manufacturing method, a method for manufacturing a seamless metal pipe capable of keeping the roundness of a pipe after straightening by a rotary straightener within ± 1%, and a manufacturing apparatus for a seamless metal pipe used for performing the method are described. To provide.

[0010]

Means for Solving the Problems The inventor of the present invention has conducted a number of experiments in order to achieve the above object, and has found the following.

The first finding is that the average outer diameter to be finished by adjusting the gap of the same caliber roll at the time of rolling by the sizer, which is a constant diameter rolling mill configured as described above, is determined by the gap of the caliber roll. ± 2 of the outer diameter of a perfect circular pipe obtained when constant diameter rolling is performed with
It must be finished to an average outer diameter in the range of%.

The second finding is that, instead of feeding a tube finished to an average outer diameter within the above range to a cooling bed and cooling it to room temperature, and then straightening it by a rotary straightener, the temperature of the tube becomes 500 After performing the straightening while the temperature is 〜650 ° C., the tube may be fed to a cooling floor and cooled to room temperature.

[0013] A third finding is that, in order to perform the above treatment, a layout in which a sizer and a rotary straightener are connected and arranged as a manufacturing apparatus, and a cooling floor is arranged downstream of the rotary straightener. What you need to do.

Further, the fourth finding is that the pipe temperature is 500 to
Since it is necessary to perform straightening rolling using a rotary straightener while the temperature is 650 ° C., when a heat treatment furnace is interposed between the sizer and the rotary straightener, in addition to enabling online heat treatment, energy saving is possible. Is to be achieved.

The gist of the present invention based on the above findings is the following method (1) and (2) for producing a seamless metal pipe and the following (3) and (4) for producing a seamless metal pipe. .

(1) A constant-diameter rolling mill using a hot constant-diameter rolling mill in which a plurality of roll stands in which three or four caliber rolls are incorporated in the same plane so that a gap can be freely adjusted is continuously arranged. A method for producing a seamless metal pipe having a step of performing constant diameter finish rolling to pipes of various outer diameters by adjusting the same caliber roll gap, wherein the average outer diameter of the pipe finished by the hot constant diameter rolling mill After the finish rolling of the caliber roll within the range of ± 2% of the outer diameter of the round pipe obtained by rolling while setting the gap of the caliber roll to the reference gap, while the temperature of the pipe is 500 to 650 ° C. A method for producing a seamless metal pipe, wherein the pipe is straightened by a rotary straightener.

(2) A fixed diameter rolling mill using a hot fixed diameter rolling mill in which a plurality of roll stands in which three or four caliber rolls are incorporated in the same plane so that a gap can be freely adjusted is continuously arranged. A method for producing a seamless metal pipe having a step of performing constant diameter finish rolling to pipes of various outer diameters by adjusting the same caliber roll gap, wherein the average outer diameter of the pipe finished by the hot constant diameter rolling mill Is finished rolled within the range of ± 2% of the outer diameter of the round pipe obtained when the caliber roll gap is set to the reference gap and then subjected to a predetermined heat treatment on the pipe after the constant diameter rolling. And then straightening and rolling by a rotary straightener while the temperature of the tube is 500 to 650 ° C.

(3) A manufacturing apparatus used in the method for manufacturing a seamless metal pipe according to the above (1), wherein a plurality of roll stands in which three or four caliber rolls are incorporated in the same plane so that a gap can be adjusted. An apparatus for producing a seamless metal pipe, wherein a hot constant-diameter rolling mill in which a plurality of bases are continuously arranged and a rotary straightener are continuously arranged.

(4) A manufacturing apparatus used in the method for manufacturing a seamless metal pipe according to the above (2), wherein a plurality of roll stands in which three or four caliber rolls are incorporated in the same plane so that a gap can be freely adjusted. An apparatus for producing a seamless metal pipe, characterized in that a hot constant diameter rolling mill having a plurality of bases and a rotary straightener are continuously arranged via a heat treatment furnace.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

<< Manufacturing Method >> In the manufacturing method according to the present invention, as described above, the same outer diameter of the pipe to be finished by adjusting the gap of the caliber roll is set to the constant diameter by setting the gap of the caliber roll to the reference gap. It is necessary to finish within the range of ± 2% of the outer diameter of the round pipe obtained by rolling. This is because if the average finish outer diameter exceeds ± 2% of the outer diameter of the perfect circular pipe, the roundness of the pipe after the constant diameter rolling becomes too poor, and it is also desired by straightening rolling by a rotary straightener applied thereafter. This is because the roundness cannot be ensured.

Here, the gap adjustment of the caliber rolls of each roll stand constituting the sizer is performed by using a finishing roll stand (usually 2 to 3) used for rounding.
It is sufficient to perform only the caliber rolls of (base), but it may be performed on the caliber rolls of all roll stands.

The finishing roll stand used for rounding is sequentially transferred to the upstream roll stand as the outer diameter of the pipe to be finished increases. Then, the caliber roll of at least the most downstream roll stand among the roll stands is replaced with a caliber roll of a perfect circular caliber at the time of the reference gap,
For example, a transport roller or the like is incorporated in the roll stand located downstream of the roll stand.

On the other hand, the temperature of the pipe after the fixed diameter rolling by the sizer or the pipe which has been subjected to a predetermined on-line heat treatment by a heat treatment furnace disposed between the sizer and the rotary straightener is 500 to 650 ° C. , It is necessary to end the straightening rolling. This is because even if straightening rolling is performed after the temperature of the tube is lower than 500 ° C., the straightening effect is small and desired roundness cannot be obtained.
Conversely, when the straightening is finished in a temperature range where the temperature of the tube exceeds 650 ° C., the tube is deformed into an ellipse on the cooling floor sent after the straightening and the desired roundness cannot be secured.

Here, the conditions of the straightening and rolling by the rotary straightener other than the temperature of the tube are not particularly limited, and it is sufficient to carry out under normal conditions, for example, the following conditions.

Offset amount: 1 to 15 mm, Crash amount: 0 to 10 mm, Tilt angle of drum roll: 25 to 35 °.

The sizer which is a constant diameter rolling mill in the present invention may be a stretch reducer or an extractor sizer. Further, the number of caliber rolls is not limited to three, but may be four.

<< Production Apparatus >> As shown in FIG. 4, there are two types of production apparatus according to the present invention. One of them is
As shown in FIG. 4 (a), an apparatus having a layout in which the above-mentioned sizer and rotary straightener are directly connected and arranged, and as shown in FIG. 4 (b), the above-mentioned sizer and rotary straightener This is a layout device that is continuously arranged via a heat treatment furnace.

When the layout is arranged as described above, the rotary straightener is provided with a sizer in the case of FIG. 4 (a), and a space between the rotary straightener and the heat treatment furnace in the case of FIG. If it is too long, it is difficult to perform straightening rolling in the above-mentioned temperature range. Therefore, it is most preferable that the installation position is provided at a distance from which the above-mentioned tube temperature can be obtained or with a cooling floor interposed. However, in the actual factory design, it is not possible to secure the required separation distance or intervene the cooling floor due to the site shape and other circumstances, and the spacing may be shorter or longer than necessary. In this case, a thermometer and a suitable heating device or cooling device are arranged on the outlet side of the sizer or heat treatment furnace, and the heating device or cooling device is operated based on the temperature measurement result of the tube by the thermometer to the rotary straightener. It goes without saying that the temperature of the pipe to be fed may be adjusted to be within the above-mentioned temperature range.

[0029]

EXAMPLE In order to prove the effect of the present invention, fifteen roll stands incorporating three caliber rolls are arranged in a row, and as shown in FIG. A sizer in which caliber rolls having the dimensions shown in Table 1 were incorporated in each roll stand and a 2-2-2-2-1 type rotary straightener were prepared, and the following experiment was performed.

[0030]

[Table 1]

The experiment was conducted using the above sizer with an outer diameter of 160 m.
m, a 7 mm-thick carbon steel tube with an outer diameter of 80 mm and a thickness of 8
In the case of constant diameter rolling to a diameter of mm, the gap of the caliber roll of stand No. 15 is variously changed, and the average outer diameter of the tube after the constant diameter rolling is -2.5 to + of the true circle outer diameter at the reference gap.
It was rolled to eight types within a range of 2.5%.

In order to prevent the load applied to the caliber roll of No. 15 during the rolling from becoming extremely large as compared with the reference gap, the stand No. 14 is used.
Gap of No. 15 and No. 13 gap
No. 15 was adjusted at the same time in an amount of 1/4.

Next, for the obtained eight kinds of pipes, the pipe temperature was variously changed between 450 to 700 ° C., and the above-mentioned rotary straightener was subjected to straightening rolling under the following conditions, and then the pipe was formed. Was fed to a cooling bed and allowed to cool to room temperature while rotating at 0.1 rpm.

The amount of offset: 5 mm, the amount of crush: 2 mm, the inclination angle of the drum roll: 30 °.

The roundness defined by the above equation was examined for the cooled pipe. The results are shown in Table 2 together with the average finish outer diameter by a sizer, the roundness at that time, and the tube temperature during straightening rolling.

[0036]

[Table 2]

As is evident from the results shown in Table 2, the roundness of the tube manufactured according to the method of the present invention is less than 1%,
A product tube having the desired roundness has been obtained.

On the other hand, when the pipe temperature at the time of straightening by the rotary straightener is 700 ° C., the pipe is deformed on the cooling floor due to the high pipe temperature, and the product pipe having a roundness of 1% or less cannot be obtained. Could not be obtained. In addition, the pipe temperature at the time of straightening is 5
At 450 ° C. below 00 ° C., when the average finish outer diameter by the sizer was ± 2.5% of the outer diameter of the round pipe, a product pipe having a roundness of 1% or less could not be obtained.

[0039]

According to the present invention, a product pipe having a roundness of 1% or less can be reliably obtained even when pipes having different outer diameters are rolled with a single type of roll of a sizer.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing the entire configuration of a three-roll sizer.

FIG. 2 is a schematic front view showing the arrangement of caliber rolls of a three-roll sizer.

FIG. 3 is a schematic side view showing the entire configuration of a 2-2-2-1-1 type rotary straightener.

FIG. 4 is a view showing an apparatus for manufacturing a seamless metal pipe according to the present invention.

FIG. 5 is a schematic diagram showing a caliber shape and dimensions of a caliber roll used in an experiment.

[Explanation of symbols]

 1: Roll stand, 2: Caliber roll, 3: Metal tube, 4: Hour roll, O: Pass center.

Claims (4)

(57) [Claims] 1. A hot constant-diameter rolling mill comprising a plurality of roll stands in which three or four caliber rolls are incorporated in the same plane so that a gap can be freely adjusted. A method for producing a seamless metal pipe having a step of performing constant-diameter finish rolling to pipes of various outer diameters by adjusting the gap of the same caliber roll, wherein the average outer diameter of the pipe finished by the hot constant-diameter rolling mill is After the calender roll is set to the reference gap and rolled in a range of ± 2% of the outer diameter of the round pipe obtained when rolling is performed, the rotary is performed while the temperature of the pipe is 500 to 650 ° C. A method for producing a seamless metal pipe, comprising straightening and rolling with a straightener. 2. A hot constant-diameter rolling mill comprising a plurality of roll stands in which three or four caliber rolls are incorporated in the same plane so that a gap can be freely adjusted. A method for producing a seamless metal pipe having a step of performing constant-diameter finish rolling to pipes of various outer diameters by adjusting the gap of the same caliber roll, wherein the average outer diameter of the pipe finished by the hot constant-diameter rolling mill is The caliber roll gap was set to a reference gap, the finish rolled to a range of ± 2% of the outer diameter of the round pipe obtained when rolling was performed, and then the pipe after the fixed diameter rolling was subjected to a predetermined heat treatment. rear,
A method for producing a seamless metal pipe, wherein the pipe is straightened by a rotary straightener while the temperature of the pipe is 500 to 650 ° C. 3. A manufacturing apparatus for use in the method for manufacturing a seamless metal pipe according to claim 1, comprising a plurality of roll stands in which three or four caliber rolls are incorporated in the same plane so that a gap can be adjusted. An apparatus for manufacturing a seamless metal pipe, wherein a hot constant diameter rolling mill and a rotary straightener, which are continuously arranged, are continuously arranged. 4. A manufacturing apparatus for use in a method for manufacturing a seamless metal pipe according to claim 2, comprising a plurality of roll stands in which three or four caliber rolls are incorporated in the same plane so that a gap can be adjusted. An apparatus for manufacturing a seamless metal pipe, wherein a hot constant diameter rolling mill and a rotary straightener, which are continuously arranged, are continuously arranged via a heat treatment furnace.