JPH0585252B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a rolling method using an elongator in the Mannesmann pipe manufacturing method, which is a typical manufacturing method for seamless metal pipes. [Prior Art] Generally, in the Mannesmann pipe manufacturing method, a heated round piece of steel is first passed through a piercer, and a hollow shell is obtained by piercing the center of the piece. Then, this is passed through an elongator and elongated and rolled, and then further elongated and rolled in, for example, a plug mill, polished, shaped, and sized using a reeler and a sizer, and a seamless pipe is manufactured through a refining process. By the way, as the elongator, an inclined elongation rolling mill is used in which a rolling mill equipped with two inclined rolls and two guide shoes (or disc guide rolls) carries out rolling through a tube to be rolled in which a plug or a mandrel bar is inserted. It is being FIG. 3 is a schematic plan view of the main parts of an elongator using a mandrel bar as an inner tool, and FIG.
FIG. 2a is a radial cross-sectional view of the tube A to be rolled during rolling. The cross-sectional shape of the tube during rolling in the reeling portions 11a and 12a becomes a rectangular shape as shown in FIG. This square shape is corrected at the exit side portions 11b and 12b of the inclined rolls, and becomes a circular cross-sectional shape. FIG. 7 is a graph showing the relationship between the elapsed time of rolling and the rolling load of the inclined rolls, with the elapsed time of rolling taken on the horizontal axis and the rolling load of the inclined rolls taken on the vertical axis. Regarding the correspondence between the time axis and the rolling state in the figure, a is the biting point (rolling start point), b is the steady rolling start point, c is the steady rolling period, d is the steady rolling end point, and e is the end point ( rolling end point). By the way, when rolling a thin-walled tube using such an elongator, the degree of squareness at the reeling part is large, and especially at the rear end of the tube to be rolled, the degree of squareness is even greater due to an increase in the outer circumference length, causing the tube to become square. It becomes difficult to pass the inclined roll, resulting in poor bottom removal and bottom clogging. It is known from experience that this phenomenon begins to appear from the steady rolling end point d shown in FIG. Fig. 8 is a graph showing the relationship between the distance from the entrance side of the reeling part of the tube that has caused tail clogging and the outer circumference of the pipe to be rolled, and the horizontal axis shows the distance from the entrance side of the reeling part. In addition, the vertical axis is the outer circumference of the tube to be rolled, and the relationship between the two is expressed as the outer circumference in the rolling direction during rolling at the center of the tube (black circle) and at the rear end of the tube (black triangle). are shown. As shown in the figure, the outer circumferential length at the reeling portion is significantly larger at the rear end of the tube than at the center. This shows that as the outer circumferential length increases, the degree of squareness increases significantly, leading to poor trailing and jamming at the trailing edge. Therefore, in order to suppress the occurrence of such tailing failures and tailing clogging, a method has been proposed for determining rolling conditions such as plug diameter, roll spacing, plug advance amount, guide shoe interval, etc. that satisfy the conditions for less occurrence of tailing failures. (Special Publication No. 59-44928, JP-A No. 55-106612
issue). [Problems to be Solved by the Invention] However, the above method is aimed at an elongator that uses a plug as an inner tool, and cannot be applied to an elongator that uses a mandrel bar that is moved during rolling, unlike a fixed plug. was the reality. The present invention has been made in view of the above circumstances, and provides a tube that can be rolled stably even with thin walls by alleviating the squareness caused by the increase in the outer circumferential length, eliminating poor bottom pull-out and bottom clogging. An object of the present invention is to provide an inclined stretch rolling method. [Means for Solving the Problems] A first inclined stretch rolling method according to the present invention involves passing a tube to be rolled through a mandrel bar inserted into a rolling mill equipped with an inclined roll and a plate guide shoe or a disc guide roll. In the method of elongating and rolling the pipe, the rolling load on the inclined rolls is measured, and the plate guide shoe or disc guide roll is used to make the outer diameter of the rear end of the pipe the same as the outer diameter of the other part. Adjust the spacing of
The method is characterized in that the measurement is carried out from the starting point of the reduction of the rolling load measurement value at the rear end of the pipe to the rear end of the pipe. Further, a second inclined stretch rolling method according to the present invention is a method in which a pipe to be rolled is passed through a rolling mill equipped with an inclined roll and a plate guide shoe or a disc guide roll with a mandrel bar inserted therein. In order to make the outer diameter of the rear end of the tube the same as the outer diameter of other parts, the interval between the plate guide shoe or the disc guide roll is adjusted at least from the rear end of the tube after rolling to the rear end. The rolling process is characterized by starting at a distance twice the outside diameter after rolling of the parts other than the rolling part, and continuing to the rear end of the pipe. [Effect] At the rear end of the tube to be rolled, due to the compressive force received from the inclined rolls, the tube overhangs in the direction in which the guide shoe or disc guide roll is arranged, increasing the outer circumference and changing the shape from a circular shape to a square shape. In response to transitional phenomena, reducing the distance between the guide shoes or disc guide rolls provides a force to suppress the overhang of the pipe in the direction of the guide shoes or disc guide rolls,
This prevents the outer circumferential length from increasing. In this case, by measuring the rolling load of the inclined rolls, it is possible to know from the measured value the rolling state where the outer circumferential length begins to increase, and the interval between the guide shoes or disc guide rolls can be adjusted in accordance with the rolling state. Furthermore, it is possible to prevent an increase in the outer circumference length even when the guide shoe or disk guide roll is reduced at least in an area that is twice the outer diameter after rolling of the portion other than the rear end of the pipe. . [Example] The present invention will be described below based on drawings showing examples thereof. FIG. 1 is a schematic side view of the main parts of an elongator (plate guide shoe type) used for carrying out the first method of the present invention, and the inclined rolls are omitted. Moreover, FIG. 3 is a schematic plan view of an elongator using a mandle lever as an internal tool. The pipe A to be rolled, which has been passed through the piercer and whose center has been pierced, is passed through the mandle lever 20 and sent to the elongator, where it is rolled in the axial direction around the axial center line X by the inclined rolls 11 and 12 that transfer to the outer peripheral surface. While being spirally moved (in the direction of the white arrow), it is stretched and rolled by force from the inner and outer peripheries. Guide shoe setting adjustment devices 41 and 42 are attached to the guide shoes 31 and 32, respectively. The guide show setting adjustment device 41 (or 42) receives control pressure oil supplied from the hydraulic pump 70 via the supply oil pressure adjustment device 41b (or 42b).
A pair of cylinders 41a, 41 with rod tips attached to the front and rear of the guide shoe 31 (or 32)
a (or 42a, 42a) to adjust the oil pressure of the cylinders 41a, 41a (or 42a, 42a). Supply hydraulic pressure adjustment device 41b (or 42b)
By increasing the oil pressure in the cylinders 41a, 41a (or 42a, 42a) according to the control signal output by the arithmetic control unit 50, the rod is moved up and down and the interval between the guide shoes 31 (or 32) (hereinafter referred to as guide interval η) ). Arithmetic control unit 5 that controls adjustment of the guide interval η
0 is determined in advance for each rolling condition, with the starting point at which the inclined roll rolling load signal measured by the inclined roll rolling load measuring device 60 provided in the inclined roll bearing (not shown) starts to decrease at the rear end of the pipe. A control signal for decreasing the guide interval η is output to 41b and 42b. Furthermore, the guide show setting adjustment devices 41 and 42
The positions of the guide shoes 31 and 32 are adjusted so that the guide interval η corresponds to the signal. Then, such a procedure is repeated, and the guide interval η is controlled so as to suppress an increase in the outer circumferential length at the rear end portion of the pipe A to be rolled. The amount of adjustment of the guide interval η described above is determined by the relationship between the outer circumferential length and the guide interval. FIG. 4 is a graph showing the relationship between the guide interval and the outer circumferential length of the tube to be rolled after rolling, with the horizontal axis indicating the guide interval and the vertical axis indicating the outer circumferential length of the tube after rolling. This shows that there is a proportional relationship between the guide interval and the outer circumference length of the tube to be rolled after rolling. From the relationship between the outer circumferential length and the guide interval, the required amount of adjustment of the guide interval η is determined in advance for each specification of the tube to be rolled, and is provided to the calculation control section 50.
When the specifications of the pipe are input to the calculation control unit 50 prior to rolling, the calculation control unit 50 reads the value of the guide interval η corresponding to the outer circumference length from its memory, and sends the necessary guide interval adjustment signal to that value. It is output to the guide shoe adjustment devices 41 and 42. Next, a specific implementation result will be described in which control was performed to suppress an increase in the outer circumference length in order to alleviate the squareness phenomenon of the tube to be rolled. Control according to the present invention was carried out under the conditions shown in Table 1 using a two-roll inclined stretching mill configured as described above.

〔effect〕

As described in detail above, according to the method of the present invention, the square-stretching phenomenon at the rear end of the tube to be rolled after rolling is improved, and as a result, the problem of shedding at the rear end of the tube to be rolled during thin-walled tube rolling is improved. , bottom clogging is eliminated and stable rolling is achieved.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic side views of the main parts of the device used to implement the method of the present invention, Figure 3 is a schematic plan view of the main parts of an elongator using a mandrel bar as an inner tool, and Figure 4 is a guide. A graph showing the relationship between the interval and the outer circumference length of the tube to be rolled after rolling. Fig. 5 is a graph showing the results of control using the device used to carry out the method of the present invention. Fig. 6 is a graph showing the relationship between the interval and the outer circumference length of the tube to be rolled. A radial cross-sectional view of the pipe to be rolled during rolling in the reeling section, Fig. 7 is a graph showing the relationship between the elapsed rolling time and the rolling load of inclined rolls, and Fig. 8 shows the distance from the reeling part and the subject to be rolled. This is a graph showing the relationship between the diameter and the outer circumference of the tube. 11, 12... Inclined roll, 20... Mandrel bar, 31, 32... Guide shoe, 41, 4
2... Guide shoe setting adjustment device, 50... Arithmetic control unit, 60... Inclined roll rolling load measuring device,
80... Rolling length measuring device.

Claims (1)

[Claims] 1. In a method of elongating and rolling a tube through a tube to be rolled through a mandrel bar inserted in a rolling mill equipped with inclined rolls and plate guide shoes or disc guide rolls, the rolling load on the inclined rolls is reduced. To make the outside diameter of the rear end of the pipe the same as the outside diameter of the other parts, the interval between the plate guide shoes or disc guide rolls is adjusted by measuring the rolling load at the rear end of the pipe. A method for inclined elongation of a pipe, characterized in that the process is carried out from the starting point of value reduction to the end of the pipe. 2. In a method of elongation rolling a tube through a tube to be rolled through a mandrel bar inserted in a rolling mill equipped with inclined rolls and plate guide shoes or disc guide rolls, the outer diameter of the rear end of the tube is In order to make the outer diameter of the part other than the rear end the same as the outer diameter of the part other than the rear end, adjust the interval between the plate guide shoes or disc guide rolls so that the distance from the rear end of the pipe after rolling is at least twice the outer diameter of the part other than the rear end after rolling. A method for inclined elongation of a pipe, characterized in that the process is performed from a starting point at a distance of 100 m to the rear end of the pipe.