JPS607565B2 - Tube rolling method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of rolling a tube.

Seamless metal pipes (for example, seamless steel pipes) are perforated by an appropriate method, then a mandrel is inserted into the pipe and continuously rolled by a caliber row made up of a set of rolls. Continuous rolling of pipes can be roughly divided into full floating mandrel milling and semi-floating mandrel milling, depending on the state of restraint of the mandrel during rolling. During rolling, the rear end is supported and restrained to a desired speed. In the conventional method of separating the tube and mandrel, in the full-floating mandrel mill method, the mandrel and tube advance together to the exit side of the rolling mill, the tube end is supported by a stopper, and in some cases, the tube body is held by a clamping device. Grip the rear end of the mandrel with a stripper block and pull out the mandrel in the opposite direction to the rolling direction (this method will be described below as A).
law). In the semi-floating mandrel mill method, the same A method as the floating mandrel mill method is used, or an extractor is installed next to the continuous rolling mill to slightly reduce the outer diameter of the tube, and the rear end of the mandrel is connected to the continuous rolling mill. The mandrel and the tube are separated by gripping with a thrust block on the entry side and advancing only the tube with an extractor (this method is hereinafter referred to as method B). After this, the mandrel is either retreated to the rolling start position while being held by the thrust block (called the BI method), or is released from the thrust block, passes through the extractor, and is transferred to the exit device (called the B2 husband). ). These conventional methods each have the following problems. In method A, the rear end of the tube supported by the stopper gets wedged between the mandrel and the wall of the stopper hole passing through the mandrel, making it difficult to remove the mandrel. The length of the tube is shortened and the tube becomes bellows-like, and the mandrel is tightened by the tube, making it difficult to remove it.
■Since the stripper cannot be placed on the rolling line and is separated from the continuous rolling mill, it takes time to start removing the mandrel after rolling is completed, and the tube is cooled by the mandrel and shrinks, making it difficult to remove the mandrel. In the BI method, (1) the thrust block is placed in the forward position until the tube is removed from the mandrel even after the continuous rolling of the tube is completed; therefore, the time required for the thrust block to retreat to the rolling standby position becomes longer, reducing rolling efficiency. In the case of B2, the mandrel passes through the extractor, so the extractor's caliber size must be larger than the mandrel diameter, and if the extractor cannot generate enough force to extract the pipe. Not only that, but the rolling efficiency is also unavoidably lowered in the same manner as in the BI method. The present invention overcomes the problems of the conventional methods described above, and provides a pipe rolling method that allows efficient and error-free removal of mandrels in the full floating mandrel mill method and the semi-floating mandrel mill method. It is something.

Embodiments of the present invention will be described below.

FIG. 1 shows an example of equipment arrangement for carrying out the present invention, in which a continuous rolling mill 1 and a sizing mill 2 extend linearly on the exit side thereof, and a mandrel gripping device 3 is disposed between the two. Here, the sizing mill 2 includes a tube rolling mill such as a reducer and a stretch reducer similar to the sizing mill. The pipe is placed on the entrance table 4 or 5 of the continuous rolling mill 1.
A mandrel is charged at the step, and continuous rolling is performed by a continuous rolling mill 1. The rolling method at this time may be either a full floating mandrel method or a semi-floating mandrel mill method. In the full floating mandrel mill method, the movement of the mandrel is not restrained by external force during rolling, so it moves integrally with the tube to the exit side of the continuous rolling mill 1, and in the semi-floating mandrel mill method, its movement is controlled by the mandrel moving device 6. After rolling is completed or during rolling, it is released and moves to the exit side of the continuous rolling mill 1 together with the tube. In such a rolling method, the front end of the mandrel is retracted from the front end of the tube by, for example, 2 hours or more, and the rear end is exposed from the tube. In the method of the present invention, after the front end of the pipe where no mandrel is present is started to be reduced by a sizing mill, the rear end of the mandrel is gripped by a mandrel gripping device to restrain the forward movement of the mandrel.
The rolling force of the sizing mill continues to advance the tube and separate it from the mandrel. After that, the pipe is connected to the outlet table 7.
The mandrel passes through the mandrel transfer tables 8 and 9 and moves to the entrance side of the continuous rolling mill 1. The above method can overcome the drawbacks of the conventional method. The disadvantages of the conventional method (■~■) can be solved by using a sizing mill without using a stripper, and the disadvantage (■) can be solved by sending the tube and mandrel together to the exit side of the continuous rolling mill 1. Problem (2) was solved by removing the mandrel in front of the sizing mill 2 and making the caliber diameter of the sizing mill smaller than the mandrel diameter to increase the forward force of the tube by the sizing mill. The second feature of the present invention is that during rolling in the sizing mill 2, the mandrel M
The purpose is to advance the tube at a speed lower than the entrance side advancement speed of the tube, that is, the initial roll circumferential speed of the sizing mill.

This prevents slippage between the roll and the tube, which tends to occur when the frictional force between the tube and the mandrel increases rapidly. In other words, when the movement of the mandrel is stopped, once a roll slip occurs, the forward movement of the tube stops and the deformation of the tube stops, so the forward force due to rolling is no longer applied to the tube, and the tube The chance to move forward again is lost. If the mandrel is moving forward, even if roll slip occurs, the tube can move forward at a speed higher than the mandrel speed, and the forward force acting on the tube will only slightly decrease, and the tube will move forward again at a steady speed. can do. Such a mandrel gripping device includes a gripping device 3' that grips the small diameter portion MI near the rear end of the mandrel by an appropriate mechanism, and a hydraulic cylinder 1 that moves this in the rolling direction.
1. In the method of the present invention, the mandrel M is transported horizontally between the continuous rolling mill 1 and the sizing mill 2 and extracted from the rolling line, so the length m of the mandrel is made shorter than the interval n between the two rolling mills.

When rolling with a sizing mill while moving the mandrel forward, it is important that there is a margin of length k remaining between the tip of the mandrel at the forward limit of the mandrel and the sizing mill 2 to allow the mandrel to be loaded as it is for efficient extraction of the mandrel. desirable for. It is also possible to enter the mill to the extent that the tip of the mandrel does not interfere with the sizing mill rolling, and after the rolling is completed, the mandrel is moved back by the hydraulic cylinder 11 and then transported laterally to extract the material. Not good. FIG. 2a shows the positional relationship between the mandrel and the sizing mill and the direction of movement thereof during sizing mill rolling according to the present invention.

That is, the pipe P is being rolled by the sizing mill 2 and is moving forward in the direction of the arrow 12. The mandrel is held by the mandrel gripping device 3 and moves forward in the direction of the arrow 13, and the broken line portion M' indicates the forward limit of the mandrel, leaving a margin k between it and the sizing mill 2. Figure 2b shows that the front end P' of the pipe P is at the center of the first roll axis 2 of the sizing mill.
1, the tube and mandrel advance at the same speed, at least up to this point.

Thereafter, the mandrel M is gripped by a mandrel gripping device. Figure 2c shows that the mandrel is gripped, and Figure 2d shows that the sizing mill has completed rolling, the mandrel is at its forward limit, and there remains a margin k that can be extracted in the rolling line by crossfeeding. It shows. As explained above in detail, in the present invention, the tube is rolled forward by the sizing mill while the rear end of the mandrel is held between the continuous rolling mill and the sizing mill, so that the mandrel can be easily removed from the tube. It can be carried out easily and reliably following continuous rolling, and the tube can be rolled with high working efficiency.

[Brief explanation of drawings]

Fig. 1 shows an example of equipment arrangement according to an embodiment of the present invention, and Fig. 2 shows the positional relationship between the mandrel and sizing mill of the present invention, where a shows a case in which the mandrel is held and moved forward while rolling a pipe in the sizing mill, and b When the pipe is to start rolling, c
is the same case as a, but shows another example of the front end position of the tube, and d shows the state after completion of sizing mill rolling. 1... Pipe continuous rolling mill, 2... Sizing mill, 3...
... Mandrel gripping device, 4, 5... Entry side table,
6... Mandrel moving device, 7... Exit table table,
8, 9... Mandrel delivery table, 11... Hydraulic cylinder, M... Mandrel, P... Pipe. Figure 1 Figure 2

Claims (1)

[Claims] 1. After inserting a mandrel into a pipe and rolling the pipe by a continuous rolling mill, the pipe and mandrel are sent together to the exit side of the continuous rolling mill, and the continuous rolling mill and the continuous rolling mill are The mandrel gripping device disposed between the sizing mill extending to the exit side grips the rear end of the mandrel, and the sizing is performed while the mandrel gripping device is advanced at a speed slower than the initial roll circumferential speed of the sizing mill. A method for rolling a tube, characterized in that the tube and the mandrel are separated by rolling with a mill. 2. The method according to claim 1, characterized in that the caliber diameter of the sizing mill is smaller than the diameter of the mandrel.