JP2514527B2 - Roll seizure prevention method for pipe end taper rolling of mandrel mill - 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 preventing roll seizure during pipe end taper rolling of a mandrel mill.

[0002]

2. Description of the Related Art Conventionally, in order to improve the product yield by shortening the cut-off length of the pipe end crop of a stretch reducer material, the thickness of the pipe end portion to be thickened with a stretch reducer is pre-processed in advance. The mandrel mill is used to perform thin taper rolling, and some techniques have been disclosed (Japanese Patent Publication No. 51-43825, etc.).

[0003]

By taper rolling at the pipe end of the hollow shell, the wall thickness of the pipe end becomes thinner than the wall thickness of the hollow shell other than the pipe end. The outer diameter becomes larger than the outer diameters of other parts and swells, so that seizure of roll easily occurs. As a result, there is a problem that the rolled hollow shell, which should be able to improve the yield in terms of wall thickness by the polygonal taper rolling, cannot be a product due to the deterioration of the surface quality due to the seizure by roll. Further, the roll seizure remains as a surface flaw of the roll, which causes a flaw to be imprinted on the surface of the hollow shell to be subsequently rolled, which means that the rolling cannot be continued unless the roll is replaced,
There is a problem that the smoothness of work is significantly impaired.

In view of the above-mentioned problems, the present invention has no seizure of the pipe end portion in the taper rolling of the mandrel mill,
An object of the present invention is to provide a method for preventing roll seizure during pipe end taper rolling of a mandrel mill, which has a good product yield and enables stable rolling work.

[0005]

In order to achieve the above-mentioned object, the present invention installs a rolling oil application device in the vicinity of the roll entrance side of a target stand for pipe end taper rolling of a mandrel mill. A rolling oil application device applies rolling oil to the tapered portion of the pipe tip at the same time that the tip of the pipe is bitten, interrupts the application of rolling oil at the end of taper rolling, and taps the tapered portion of the pipe rear end. The rolling oil is applied at the same time as the start of rolling, and the rolling oil is applied when the trailing end of the pipe is slipped off. According to the present invention, in the rolling of a mandrel mill which has not been normally coated with rolling oil, rolling oil is applied to the pipe front end and the pipe rear end for the taper rolling of the hollow shell. When the next hollow shell is continuously rolled while the same mandrel bar is attached to the retainer, the applicability of the lubricant to the mandrel bar itself is not deteriorated, so that the sticking of rolling oil to the mandrel bar is avoided as much as possible. For this reason, it is preferable that the application of the rolling oil to the tapered portion at the rear end of the pipe is completed immediately before the trailing edge of the rear end of the pipe is removed.

[0006]

According to the method of preventing roll seizure during pipe end taper rolling of the mandrel mill of the present invention, a rolling oil application device is installed near the roll entrance side of the target stand for pipe end taper rolling of the mandrel mill. With the rolling oil application device, the rolling oil is applied to the pipe tip taper part at the same time as the pipe tip is bitten, and the application of the rolling oil is interrupted at the end of the taper rolling.
Rolling oil is applied to the taper portion at the pipe rear end at the same time as the start of taper rolling, and the application of rolling oil is completed when the tail end of the pipe is slipped off. Roll lubrication can be performed to prevent roll seizure.

[0007]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a mandrel mill consisting of four stands (the fourth stand, which is a round-up mill, is not shown),
The second stand and the third stand are target stands for taper rolling in which a taper portion is provided at the pipe front end and the pipe rear end. FIG. 1 shows that the hollow shell 2 having the mandrel bar 1 inserted therein is loaded into a mandrel mill, and the rolls 3a, 3b, 4a of the front three stands out of the four stands.
4b (not shown), 5a, 5b allow the hollow shell 2
Shows the state in which is rolled. In the present embodiment, since the target stands for the taper rolling of the pipe end are the second stand and the third stand, the rolling oil application device is placed close to the rolls 4a and 4b of the second stand and the rolls 5a and 5b of the third stand. Set up 6 and 7.

In FIG. 2, the roll 3 of the first stand 3
a, 3b are equipped with reduction cylinders 8a, 8b,
Rolls 4a, 4b of the stand, roll 5 of the third stand
Similarly, reduction cylinders 9a, 9b,
It is equipped with 10a and 10b. Among these reduction cylinders, the reduction cylinder 9 involved in the taper rolling of the pipe end
a, 9b, 10a, and 10b. The roll 4a is operated by the operation of the reduction cylinders 9b, 9a, 10a, 10b during rolling.
.About.4b and between the rolls 5a to 5b are varied for taper rolling of the pipe end. Each rolling cylinder has a load cell 11a, 11b, 12a, 12b, 1
3a and 13b are attached, the rolling load is measured, and the time when the tip of the pipe is caught and the time when the rear end of the pipe is slipped off is detected. The rolling oil application devices 6 and 7 are provided with rolling oil application nozzles 14 and 15 so that rolling oil can be applied to the entire circumference of the hollow shell 2, and the opening and closing of the rolling oil application nozzles 14 and 15 are performed by solenoid valves 16 and 17. In this embodiment, a mixture of grease, graphite and a friction modifier is used as rolling oil.

FIG. 3 shows the shapes of the pipe ends on the outgoing side of the first stand, the second stand, and the third slind when the pipe end taper rolling is performed. The lengths of the pipe tip taper portion and the pipe tip taper portion on the outlet side of the third stand are l (l <L
, L: stand spacing (Fig. 1)). Rolling oil is applied by the rolling oil application nozzle 14 before the second stand and the rolling oil application nozzle 15 before the third stand for the length of each hollow shell in the portion corresponding to the above l. Control for applying rolling oil to the lengths of the pipe front end and the pipe rear end will be described with reference to the control block diagram of FIG.

In FIG. 4, reference numeral 18 denotes a taper rolling control controller, which is a central portion for performing taper rolling. The taper rolling control controller 18 reduces the taper by the set values such as the taper shape, the pipe size, the drawing ratio, the roll diameter, and the roll rotation number, which are originally necessary conditions for the taper rolling control input to the taper rolling setting device 19. Cylinder 8
a, 8b to 10a, 10b, the speed of reduction, the amount,
Calculate timing. The application of the rolling oil for taper rolling will be described. Regarding the pipe tip, the roll reaction force when it is caught in the rolls 4a and 4b of the second stand and the rolls 5a and 5b of the third stand (Fig. 5 (a)) is described. Load cells 12a, 12b, 13 equipped on each stand
a, 13b, and when receiving the ON signal, the reduction cylinders 9a, 9b, 10a, 1 at the reduction timing and speed calculated in advance from the taper rolling control controller 18.
0b moves and imparts a predetermined taper, and at the same time, ON / OFF signals of the rolling oil solenoid valves 16 and 17 are output to apply the rolling oil to the taper rolling portion. Regarding the rear end of the pipe, the roll reaction force when the rolling rolls 3a and 3b of the first stand and the rolling rolls 4a and 4b of the second stand are slipped out (Fig. 5 (b)) is provided in each stand. Detected by the load cells 11a, 11b, 12a, 12b, the OFF signal is received, and the reduction cylinders 9a, 9b, 10a, 10b are moved at a predetermined reduction timing and speed calculated from the taper rolling control controller 18 in advance to obtain a predetermined taper. Solenoid valve for rolling oil 1
The ON / OFF signals of 6 and 17 are output to apply the rolling oil to the taper rolling portion. In order to finish the application of the rolling oil immediately before the trailing edge, the rolling oil application device 6 is determined from the trailing edge point at the first stand and the rolling speed of the hollow shell.
Regarding the rolling oil application device 7, the first stand or the second
The timing for finishing the coating is determined based on the time when the tail passes through the stand and the rolling speed of the hollow shell. Reference numeral 20 denotes a rolling oil application setting device, which sets the timing, amount, etc. of the rolling oil application, and inputs them to the taper rolling control controller 18.

When the taper rolling shown in Table 2 was performed for the objects having the dimensions shown in Table 1 below, a mixture of grease, graphite and a friction modifier was applied as rolling oil to the pipe front end and the pipe rear end. As a result, roll seizure did not occur and smooth rolling work could be performed.

[0012]

[Table 1]

[0013]

[Table 2] (Note) t ₁ , t ₂ , l ₁ parallel portion, and l ₂ inclined portion indicate the dimensions of the tapered portion at the pipe front end and the pipe rear end shown in FIG. 6.

[0014]

The present invention is configured as described above.
Product yield does not decrease due to deterioration of surface properties due to roll seizure, and roll replacement is prevented from occurring due to roll surface scratches due to roll seizure to ensure smooth work and improve work efficiency. Can be made.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention with a mandrel mill including four stands.

FIG. 2 is a diagram showing an example of a device used in an embodiment of the present invention.

FIG. 3 is a diagram illustrating the shapes of a pipe front end and a pipe rear end in taper rolling.

FIG. 4 is a diagram showing a control block diagram of taper rolling.

FIG. 5 is a diagram showing a state in which the front end of the hollow shell is bitten (a) and the rear end is slipped out (b).

FIG. 6 is a diagram showing a geometrical dimension of a pipe end of taper rolling.

[Explanation of symbols]

 1 Mandrel bar 2 Hollow shell 3a, 3b Roll 4a, 4b Roll 5a, 5b Roll 6 Rolling oil coating device 7 Rolling oil coating device 8a, 8b Rolling cylinder 9a, 9b Rolling cylinder 10a, 10b Rolling cylinder 11a, 11b Load cell 12a, 12b Load cell 13a, 13b Load cell 14 Rolling oil application nozzle 15 Rolling oil application nozzle 16 Solenoid valve 17 Solenoid valve 18 Taper rolling control controller 19 Taper rolling setting device 20 Rolling oil applying setting device

Claims (1)

(57) [Claims] 1. A rolling oil applicator is installed in the vicinity of the roll entry side of a target stand for pipe end taper rolling of a mandrel mill. Rolling oil is applied at the same time as biting, and the application of rolling oil is stopped at the end of taper rolling. A method for preventing roll seizure during pipe end taper rolling of a mandrel mill, which is characterized by terminating the application of rolling oil.