JPS6036323B2 - Drilling method for metal blooms - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of drilling a metal bloom having a polygonal cross section into a circular pipe.

One of the methods for perforating a metal bloom having a polygonal cross section into a circular pipe is the press roll perforation method, and the present invention relates to an improvement thereof.

What is the press roll perforation method?
664,52-24977,52-11156,52-
11157, 52-24970, a caliber is composed of two or more rolling rolls, and two of the rolling rolls are
This general term refers to a method in which a plug is driven into a polygonal cross-section bloom by applying pressure in the axial direction, and the plug is inserted into the bloom to form a hole. In the conventional perforation method using rolls, there is a problem with uneven thickness due to poor biting, and although the press roll perforation method has already reached a level equal to or higher than the inclined roll perforation method, rolling efficiency still remains. This is the most important factor governing the dimensional accuracy of finished products, and improvement is desired.

The purpose of the present invention is to provide a method for manufacturing a tube with excellent dimensional accuracy without the problem of poor biting and a small thickness deviation in a press roll perforation method, and a method that also enables pipe expansion at the same time as perforation. do.

The present invention achieves the above object in the press roll drilling method by reciprocating the plug back and forth during drilling, and further ensures the effect by jetting lubricant from the front end of the plug. .

To explain the present invention in detail, FIG. 1 is an explanatory diagram of the perforation method of the present invention, in which a substantially circular caliber 2 is constructed by Rolloux, and a polygonal cross-section bloom 3 is directed toward the caliber in the direction of the axis 4. The plug 6 is inserted into the bloom 3 by applying pressure by the pushing device 5, and drilling is started.

At this time, the plug 6 is reciprocated back and forth in the same direction as the marking line 4 to facilitate biting. To explain the effect of reciprocating the plug of the present invention in comparison with the conventional method, the problems caused by the conventional method are: (1) when the pushing force is too weak, (2) when the pushing speed is too slow relative to the roll speed, ■ If the front end of the plug protrudes too far to the entry side, ■ If the cross-sectional area of the polygonal cross-section bloom is small compared to the caliber dimensions, ■ If the roll diameter is small, ■ If the friction coefficient of the roll is small, etc. As a result of the experiment, I found out. In case of ■, pushing device 5
If a reaction occurs, this can be solved by giving the ability to increase the pushing force to a level higher than the yield stress of the material to be rolled, but this may lead to the possibility of crushing the material to be rolled. In the case of ■, the pushing force and the retracting force of the rolls are out of timing and do not work together, and the forward force generated at the moment the front end of the polygonal cross-section flume is deformed by the rolls is the plug. This is the case when the pushing force is transmitted after this has disappeared. The forward force by the rolls reaches a sufficiently high value only by the high rolling pressure in the process of deforming the material, and this and the pushing force work together to ensure smooth biting. In order to expect the forward force of rolling to occur once again in a material that has completed its deformation,
The only option left is to create a new transformation. The present invention intends to utilize the rolling forward force caused by this increased deformation, as will be described later. ■, ■, ■, ■ are all problems related to the retraction force of the roll, and can be improved by setting and tool shape, but if the conditions of ■■ are not favorable, the above-mentioned tendency will occur. The plug reciprocating motion of the present invention utilizes these findings, and during the plug retraction (movement to the exit side), the material to be rolled is drawn in to facilitate its advance, thereby increasing the pulling force of the material to be rolled. let

While the plug advances (moves to the entry side), the pushing device pushes the material to be rolled, and at the same time the plug bulges out the material from inside to generate a pulling force by the rolls, so biting is carried out smoothly. Ru. Therefore, the above ■
Even when the conditions of ~(2) are incomplete, it becomes possible to apply the forward force necessary for dovetailing to the material to be rolled. To explain the present invention in more detail, the reciprocating movement of the plug is generated by rotating the eccentric cam 7, for example.

In this case, the appropriate amplitude of the reciprocating motion is 1 to 30 m, preferably 10 to 20 m, with the lower limit being the point at which the biting improvement effect is clear, and the upper limit being the point at which wall thickness fluctuations can be tolerated. .
The boundary point P between the conical part and the cylindrical part of the plug is on the roll axis plane B-
By reciprocating across B, fluctuations in the wall thickness of the tube due to the reciprocating movement of the plug can be reduced. Note that if the purpose is only to improve biting, the plug may be reciprocated only during biting, and if the purpose is only to improve uneven thickness, the amplitude may be as small as, for example, about 1 French.

An example of such an amplitude is ultrasonic vibration. In this case, the plug vibration speed 2 m (a) must be greater than the bloom pushing speed v. For example, the frequency limit is 30KHz, and the flume pushing speed v is 40KHZ.
If Aihan/S, then the amplitude a of the plug can be found using the following formula. a>v/2　〆=400/2　X30xlpi=2
．． In other words, the amplitude a of the plug should be 2.1 degrees or more. If you keep reciprocating the plug back and forth while drilling,
Uneven thickness is improved.

This thickness unevenness improvement effect is within a range that can be used industrially even when the amplitude is less than 10 ribs. The effect of correcting uneven thickness by reciprocating the plug can be explained as follows. In other words, if the tip of the plug, which has once started to become eccentric due to some reason, remains fixed in the direction of movement of the material to be rolled as in the conventional method, the eccentricity will gradually increase, and the uneven wall thickness of the circular pipe will gradually increase. However, when the plug is reciprocated as in the present invention, the eccentricity of the plug is temporarily alleviated when the plug retreats, and when it moves forward, the plug strongly hits the thick side of the material to be rolled, preferentially targeting this part. to improve uneven thickness.
In order to make the most of this effect, the retraction speed of the plug is instantaneously greater than the forward speed of the material to be rolled, creating a gap 8 at the tip of the plug as shown in Figure 2. is desirable. In the case of using the eccentric cam, such conditions can be obtained approximately by nr>v/2, where r is the eccentricity of the cam and n is the number of revolutions, and v is the flume pushing speed. In this case, by spouting lubricant from inside the plug 6 through the lubricant spout 6', the plug enters the bloom smoothly, and the mandrel thrust force is reduced.
The deflection of the mandrel 9 is reduced, and uneven thickness is improved. In the conventional method, an extremely high pressure of approximately 10k9/might is generated at the tip of the plug over its entire circumference in the case of steel, making it impossible to squirt lubricant. The lubricant used in the present invention is not particularly limited, and any lubricant that is generally used as a lubricant for hot rolling may be used, for example, a mixture of heavy oil and graphite powder may be used. Such lubricant can be jetted out from the lubricant 6' at the tip of the plug through the inner hole 9 of the mandrel 9. Figures 3, 4, and 5 show the case of pipe expansion in the present invention, in which the boundary P between the plug conical part and the cylindrical part performs reciprocating motion on the exit side from the roll axis plane B-B. It is desirable that the roll caliber be configured to form a substantially perfect circle at the center of the reciprocating motion.

With this configuration, it becomes possible to expand the tube following the drilling. In this case, the inner surface of the drilled material is expanded by a plug whose cross-sectional area increases toward the exit side,
This bulges out to enable rolling on the outlet side from the roll axis plane B-B. In the case of large pipe expansion, it is preferable that the boundary P between the plug cone and the cylinder not move back and forth beyond the roll axis plane B-B to the entry side. In such a case, it is also possible to make the plug diameter C2 larger than the caliber minimum diameter b2. In this way, when expanding a pipe by punching a hole, the shape of the caliber is configured to be circular in the C-C cross section closer to the exit side than the roll axis plane B-B, and the point on the plug is It is best to reciprocate P across the C-C cross section in order to obtain a tube with small roundness and wall thickness variation. In addition, in order to reduce uneven thickness, it is desirable that the front end 6'' of the plug be kept on the exit side from the point where the caliber and bloom corner first come into contact and on the entry side from the B-B cross section during drilling. The gunwale ratio E according to the method was kept within the range of the following formula to avoid both poor engagement and increased uneven thickness by using the numbers as shown in Figure 4.
'11a,. For simplicity, b is expressed as the side length of a square cross section, but in the case of a bloom with a polygonal cross section, a, 0 can be replaced by its cross-sectional area.

Once the cross-sectional dimensions of the plume are determined in this way, the upper limit of the geometric mean value of the pipe diameter, a3b3, is determined, and the outer diameter of the pipe that can be drilled from a certain bloom cross-section is severely restricted. The example shown in Fig. 4 described above is a case where there are two rolling rolls, but the fifth roll
The same applies to the case where there are four rolling rolls as shown in the figure.
In this case, two or more opposing rolls are driven. Examples of the invention are shown in Table 1.

Table 1 Method 1 of the present invention compares the effect of reciprocating plug motion with the conventional method, and the method of the present invention has a defective biting rate of 6% compared to the conventional method.
From 0% to 0%, center thickness deviation rate (= (maximum wall thickness - minimum wall thickness)
/average wall thickness xlooo%) was improved from 27% to 13%.

In the method 2 of the present invention, when the tube expansion ratio is roughly increased, even if the tube expansion ratio is 1.30, the biting failure rate is 0%, and the center thickness unevenness rate is 1.
5%, which is superior to the conventional method. Such a large pipe expansion ratio is a value that would not allow the conventional method to completely penetrate and drill holes. By configuring and implementing the present invention as described above, in the press roll perforation method, it is possible to produce a pipe with excellent dimensional accuracy without the trouble of poor biting and with small thickness deviation, and to simultaneously perform the perforation of the gunwale. This greatly contributes to improving quality and productivity by making it possible to

[Brief explanation of the drawing]

Fig. 1 is an overall explanatory diagram of the present invention, Fig. 2 is an explanatory diagram of plug lubrication of the present invention, Fig. 3 is an explanatory diagram of the case of pipe expansion according to the present invention, and Fig. 4 is a cross section of Fig. 3. In the figure, Figure 4 A is the third
The diagrams are AA, FIG. 4B is BB, FIG. 4C is CC, and FIG. 4D is DD. Fig. 5 is a cross-sectional view when there are four rolls in the method of the present invention, Fig. 5A is AA in Fig. 3, and Fig. 5B is B-
B, FIG. 5C is a sectional view taken along CC, and FIG. 5D is a sectional view taken along DD. 1... Rolling o-ru, 2... Caliber
, 3... flume, 5... pushing device,
6...Plug, 6'...Lubricant spout, 7...Eccentric cam, 8...Gap, 9...Mandrel. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A substantially circular caliber is formed by two or more rotationally driven rolling rolls, and a metal bloom having a polygonal cross section is pushed into the caliber by applying a pressing force in the axial direction of the metal bloom, and the rolling roll is 1. A method of perforating a metal bloom, the method comprising perforating a metal bloom using a plug placed between rolls, characterized in that perforation is performed while reciprocating the plug back and forth. 2. A generally circular caliber is constituted by two or more rotatably driven rolling rolls, a metal bloom with a polygonal cross section is pushed into the caliber by applying a pushing force in the axial direction of the bloom, and a plug is placed between the rolling rolls. A method for drilling a metal bloom, characterized in that drilling is performed by reciprocating the plug back and forth and jetting lubricant from the front end of the plug.