JPH0241363B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Description of the Technical Field The present invention is directed to a multi-stand pipe mill.
MPM, in particular, relates to tube end control methods for continuous steel tube rolling mills.

(b) Description of the prior art The conventional technology has a plurality of stands equipped with a pair of grooved rolls and the roll positions of the odd and even stands are shifted by 90 degrees, and a mandrel bar is inserted into the raw pipe that is the material to be rolled. A continuous steel pipe rolling mill that reduces the wall thickness of the raw pipe between the rolls is called a full floating mandrel mill FFM. In this type of product, a mandrel bar is inserted into the raw tube to be rolled on the input side of the mandrel mill, and the mandrel bar and the raw tube are inserted into the mill and rolled. That is, in such a mill, a restraining device for holding the mandrel bar in a predetermined position is not provided, so that the mandrel bar is held by friction with the raw pipe and can freely move in the axial direction.

In this full-floating mandrel mill, the mandrel bar inserted into the tube to be rolled is rolled without restraint, so the speed of the rolling stand is controlled to control the thickness increase at the leading and trailing ends. During rolling, a method is used in which an excessive tension is applied between a plurality of stands compared to the rolling state in the central portion. In response to this, recently, semi-floating mandrel mills SFM and restrained and retracted mandrel mills, which have mandrel bar insertion machines equipped with mandrel bar restraining mechanisms, have been developed, and multi-stand pipe mills MPM.
It is often used as.

(c) Purpose of the Invention The present invention was made in view of the above circumstances, and utilizes the phenomenon in which the wall thickness of the tube decreases by increasing the relative speed between the tube to be rolled and the mandrel bar in these new mills. The purpose of the present invention is to provide a tube end control method for a continuous steel tube rolling mill.

(d) Structure and operation of the invention A detailed explanation will be given below with reference to the drawings shown in FIGS. 1 and 2. FIG. 1 is a schematic configuration diagram showing the relationship between a mandrel mill and a mandrel bar insertion machine. In the figure, 1 is a group of stands of the mandrel mill, for example, eight sets of stands are provided, but in this example, there are four sets of stands. It shows. 2a, 2
b, 2c, and 2d are load detectors provided on each stand. 3 is a material to be rolled, and a mandrel bar 4 restrained by a bar restraint mechanism 5 attached to an insertion machine 6 is inserted into the hollow part of the material. This restraint mechanism 5 can be opened and closed by, for example, a solenoid valve, and the mandrel bar 4 can be opened by a control signal to the solenoid valve. The insertion machine 6 is driven by a DC motor 8 via a reduction gear 7, and is detected by a rotation speed detector 9.

FIG. 2 is a block diagram showing the configuration of the present invention.
is operated by the thyristor Leonard device 11 with . Reference numeral 12 denotes a main control device which processes the speed set values set by the speed setters 13 and 14 according to the signals from each stand load detector 2a to 2d and the set value of the timer setter 15, and sends the processed speed values to the thyristor Leonard device 11. A speed reference signal 13a is provided. That is, the main control device 12 first controls the tip of the material to be rolled 3 from the first stand to the third stand,
Until biting is completed, a signal corresponding to the setting value of the speed setter 13 is set as the speed reference 1 by the selection signal 12a.
3a to the thyristor Leonard device 11. Then, the thyristor Leonard device 11 compares the signal 13a with the speed feedback signal 11a detected by the speed detector 9, and performs speed control so that the set speed is achieved. Further, the fact that the rolled material 3 is caught in the three stands can be obtained from the logical product of the detection signals from the load detectors 2a to 2c. Therefore, when it is detected from the logical product value of these detection signals that the material to be rolled 3 is to be rolled in stands 1 to 3, the selection signal 12a of the mandrel bar insertion machine switches the speed setting device 14 to set the speed. A signal corresponding to the setting value of the timer setting device 14 is outputted to the thyristor Leonard device 11 as the speed reference 14a, and at the same time, counting of the timer value 15a set by the timer setting device 15 is started. The thyristor Leonard device 11 compares the signal 14a with the speed feedback signal and performs speed control to achieve the set speed. Then, as the rolling of the material 3 to be rolled progresses and the timer value 15a set by the setter 15 finishes counting, the selection signal 12a is again set as the speed reference 13a,
It is assumed that the tip has passed through the third stand, and control for the tip ends.

When the control of the tip end of the tube to be rolled 3 is completed, the mandrel bar insertion machine operates the mandrel bar restraint machine 5 to release the restraint of the mandrel bar 4. The unrestricted mandrel bar 4 is moved downstream by the rolls of the rolling mill at the same speed as the rolled tube 3 (relative speed zero).

Next, the timing of the end of the rolled steel pipe 3 is detected by the aforementioned load detectors 2a to 2d, and at the timing when the rolled steel pipe 3 passes through a predetermined stand, for example, two stands, the same control as that for the tip end is performed. However, in order to end the control of the rear end when the final stand ends, in this case, timer setting device 1
The setting value of 5 is no longer necessary. Although the above embodiment is explained using four sets of stands, for example, in the case of eight sets of stands, the eight stands are usually installed to adjust the diameter of the steel pipe to be rolled without performing rolling. The control start signal for the leading end is obtained from the 6-stand engagement signal, and the control start signal for the rear end is obtained from the 5-stand tail-off signal.

The above embodiments show the case of a restrained and retracted mandrel mill RRM, and in the case of a semi-retrained floating mandrel mill SFM, only the tip portion is controlled. This is because semi-restrain floating mandrel mill SFM shortens the rolling pitch for the purpose of increasing production, so the steel pipe to be rolled releases the bar restraint mechanism 5 from the intermediate stand, for example, by the 2-stand exit signal 2b. , the mandrel bar 4 is released. This is because the rolling method cannot achieve the control of this method.

Also, depending on the type of mill, the speed reference signal 13a may be in the same direction or in the opposite direction to the advancing direction of the rolled material 3. Therefore, the mandrel bar can be differentiated by positive and negative polarity signals depending on the direction. Control is also possible by moving 4 forward or backward.

(e) Effects of the Invention As detailed above, in the present invention, the moving speed of the mandrel bar is adjusted so that the tip and rear ends of the steel pipe to be rolled pass through a predetermined stand, for example, two sets of final rolling stands. By controlling the relative speed between the steel pipe and the mandrel bar to be increased compared to when rolling the central part, the shortcoming of continuous steel pipe rolling mills, such as thickening at the leading and trailing ends, can be solved. , it is possible to provide a pipe end control method for a continuous steel pipe rolling mill that can obtain high-quality products by taking advantage of the characteristics of the new mill.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of a continuous steel pipe rolling mill, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1... Mandrel mill stand group, 2a to 2d...
Load detector, 3... Rolled material, 4... Mandrel bar, 5... Bar restraint mechanism, 6... Bar insertion machine, 7... Speed reducer, 8... DC motor, 9... Speed detector, 10...
AC power supply, 11... Thyristor Leonard device, 1
2... Master control device, 13, 14... Speed setting device, 1
5...Timer setting device.

Claims (1)

[Claims] 1. A stand having a pair of grooved rolls is sequentially
Continuous steel pipe rolling comprising a rolling mill in which the roll positions are alternately changed by 90 degrees, and a mandrel bar insertion machine that inserts a mandrel bar into the tube to be rolled and moves the mandrel bar during rolling of the tube to be rolled. In the machine, each of the plurality of stands is provided with a load detector for detecting rolling load,
When a predetermined load detector detects the tip of the tube to be rolled, the mandrel bar insertion machine restrains the mandrel bar that was moving together with the tube to be rolled, and increases the relative speed between the mandrel bar and the tube to be rolled. A pipe end control method for a continuous steel pipe rolling mill, characterized in that the pipe end is controlled as follows. 2. Sequentially install stands with a pair of grooved rolls.
Continuous steel pipe rolling comprising a rolling mill in which the roll positions are alternately changed by 90 degrees, and a mandrel bar insertion machine that inserts a mandrel bar into the tube to be rolled and moves the mandrel bar during rolling of the tube to be rolled. In the machine, each of the plurality of stands is provided with a load detector for detecting rolling load,
When a predetermined load detector detects the rear end of the tube to be rolled, the mandrel bar insertion machine restrains the mandrel bar that was moving together with the tube to be rolled, increasing the relative speed between the mandrel bar and the tube to be rolled. A pipe end control method for a continuous steel pipe rolling mill, characterized in that the pipe end is controlled so as to 3. Sequentially install stands with a pair of grooved rolls.
Continuous steel pipe rolling comprising a rolling mill in which the roll positions are alternately changed by 90 degrees, and a mandrel bar insertion machine that inserts a mandrel bar into the tube to be rolled and moves the mandrel bar during rolling of the tube to be rolled. In the machine, each of the plurality of stands is provided with a load detector for detecting rolling load,
When a predetermined load detector detects the tip of the tube to be rolled, the mandrel bar insertion machine restrains the mandrel bar that was moving together with the tube to be rolled, and increases the relative speed between the mandrel bar and the tube to be rolled. When the tip of the tube to be rolled passes through a predetermined rolling mill, the mandrel bar insertion machine releases the restraint of the mandrel bar, the mandrel bar moves together with the tube to be rolled, and the rear end of the tube to be rolled passes through the rolling machine. When a predetermined load detector detects this, the mandrel bar insertion machine controls the mandrel bar that was moving together with the tube to be rolled again to increase the relative speed between the mandrel bar and the tube to be rolled. Features: Pipe end control method for continuous steel pipe rolling mill.