JPS5844906A - Endless rolling method for stretch reducer - Google Patents

Abstract

PURPOSE:To prevent the thickening phenomena at the preceding and succeeding ends of pipes by coupling preceding and succeeding base pipes while running both pipes in the axial direction thereof between a reheating furnace and a stretch reducer. CONSTITUTION:In the stage of reducing the metallic base materials heated in a reheating furnace with a stretch reducer, first a cylinder 33 which is threaded on inside and outside surfaces is put on the preceding end of a successing SR base pipe 1'. The part thereof is compressed by a compressing machine to the diameter smaller than the inside diameter of a preceding base pipe 1''. The preceding end part of the pipe 1' compressed by the cylinder 33 put thereon is inserted into the succeeding end part of the pipe 1'', whereby a coupled part is formed. The coupled part is compressed with a compressing machine to the diameter smaller than the outside diameter of the SR product. It is effective to cool the coupled part forcibly by water cooling or the like. Thus the tension during rolling is maintained always in the state in which the pipes are rolled in all stands and the thickening phenomena are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing thickening of the tube tip and rear end of the product when manufacturing small diameter circular tubes by the drawing and rolling method. The present invention will be described in detail below based on a stretch reducer rolling mill.

For example, when rolling a seamless steel pipe, a stretch reducer is installed as the final step after a plug mill, mandrel mill, or semi-floating mandrel mill, and then through a reheating furnace. The rolling equipment has a structure in which several to several 20 rolls of highly rigid rolling stands each consisting of 2 to 4 rolls are continuously arranged in series. The product is rolled to a predetermined size using the tension between the stands. Figure 1 shows the principle of the stretch reducer.

That is, 2 to 4 whose rotational axes make an angle of 180°, 1200°, or 90° in a plane perpendicular to the rolling direction.
This is a rolling method in which the outer diameter of the tube 1 is reduced by the rolls 2 and 2', and the wall thickness is reduced by applying tension T to the tube between rolling mills.

When rolling a tube using such a stretch reducer, there are the following problems. This is a phenomenon in which the wall thickness near the ends of a finished product becomes thicker than in the center.

The reason why such a phenomenon occurs can be explained as follows. This is due to the fact that in a stretch reducer, the wall thickness is adjusted by the tension between the stands, but in actual rolling, no tension is generated unless the front and rear ends of the double pipe are placed on the next stand. This is because this tension differs between the state in which the tube is rolled by all the stands and the state in which the end of the tube passes through the stands, and the phenomenon of thickening occurs as a result of the difference in the shape of the tube.

This increased thickness near the end of the pipe does not meet the dimensional specifications and is therefore cut off, which poses a major problem in terms of product yield.

It has become. The present invention solves the problem of thickening the pipe end,
This was done to improve yield. That is, an object of the present invention is to carry out endless rolling to bring the tension during rolling to a state where the tube is always being rolled at all stands, thereby preventing the phenomenon of thickening. The gist of the present invention is that in a pipe rolling method, when a metal tube is drawn and rolled in a tube drawing rolling mill row in which a plurality of rolling stands are arranged in series, the metal tube is rolled to a length in the preceding stage of the rolling mill row. It is to connect in the horizontal direction.

The present invention will be explained in detail below.

When performing drawing and flat rolling with tension applied to the tube, fluctuations in the tension value applied to the tube, i.e., the tip and rear ends of the tube are not bitten by the rolling rolls of two or more rolling mills at the same time. In order to prevent the tube from becoming unsuitable (too thick) due to being rolled under no tension due to this, when supplying the rolled tube to the stretch reducer, It is necessary to connect them sequentially in the length direction to eliminate unsteady parts related to tension application.

Welding, pressure welding, forge welding, wire explosion welding, and other methods can be considered as methods for joining pipes to continuously roll them, but stretch reducers (hereinafter referred to as SR) do not apply deformation resistance to the pipes. The strength of the joint must be strong enough to withstand the tension applied during the rolling process.

Furthermore, in order to carry out continuous rolling, it is necessary to prevent the joining time of the tubes from becoming a factor that causes variations in the rolling speed. Endless rolling is a very effective method for achieving yield improvement, and has been tried in various types of rolling. However, SR rolling is accompanied by difficulties in achieving endless rolling that are not found in other rolling methods. There is. As mentioned above, this means that the tension between the stands is close to the deformation resistance, and because of this, it is possible to greatly reduce the wall thickness in SR. The magnitude of this inter-stand tension is also clear in one example shown below.

In other words, even if two SR main pipes are cold welded and charged into a reheating furnace for SR rolling, the welded part a may break during rolling due to incomplete welding due to variations in welding conditions. 0 is sometimes seen.

Creating a joint that can withstand such tension requires either hot or cold welding with virtually no defects, or a mechanical bond of sufficient strength.

The present invention relates to the latter mechanical bonding method. A screw connection is a well-known means of achieving a mechanically sufficient connection. However, it is obvious that cutting threads in the SR main pipe and then threading the SR main pipes together on-line before positive rolling would impair productivity and would be practically impossible.

One means for solving such problems is shown in FIG.

SR main pipe 11. , lI, solid or hollow screws 3, . 31 and 32 are inserted, and this part is subjected to centripetal compression using a press and swaging machine, etc., so that the inner surfaces of the main tubes 1' and 1# and the surfaces of the screws 3, 31, and 32 are brought into close contact. This creates the same condition as a screw connection. However, in this case, since the temperature of this joint is lower than that of other parts of the main tube, it is desirable to shrink the tube to an outside diameter that will not be rolled. FIG. 2C shows an example in which the joint member 32 is tapered to increase the joint strength.

Furthermore, other bonding methods are shown in FIGS. 3-5.

Figure 3 shows a cylinder 33 with threads cut on both the inner and outer surfaces.
This is a method of inserting it between the l# ends, and the processing procedure is shown below.

The procedure will be explained below.

(a) Cover the tip of the trailing SR main tube 1/ with the cylinder 33 with internal and external threads.

(b) This part is compressed using a compression machine. Make the inner diameter smaller than that of the preceding SR main pipe l'/.

(c) Insert the tip of the trailing bus tube, which has been compressed by pressing the cylinder 33, into the rear end of the leading bus tube to form a joint. - (d) Place this joint in a compression processing machine. r cylinder, outer diameter ft
Make it smaller than the outer diameter of the 5R product.

FIG. 4 shows a processing procedure for a method of threaded connection without using a joint member. This procedure will be explained below.

(a), (b) The tip of the trailing SR main pipe l/ is compressed using a compression machine. At this time, by forming thread-like irregularities on the surface of the tool 4, thread-like irregularities are formed on the surface of the main tube l'. By pouring water onto this surface, the temperature of the main pipe 1/ is lowered to near room temperature, and it can be regarded as a joint member having thread-like irregularities at room temperature.

(c) Insert the main pipe l' into the tail end of the preceding main pipe 1g to form a joint part.

(d) This joint is compressed using a compression machine to make the outer diameter smaller than the outer diameter of the finished product.

Figure 5 shows a connection [
This figure shows an example of a joint member that is thought to have f. Rod-shaped body 34 with anchor-shaped protrusions at both ends, SR main pipe 1
This is done by inserting it into both ends of the 1#, and shrinking this part to make the outer diameter smaller than the finished product's outer diameter. In addition, before processing or reheating, holes may be drilled in the main tube in advance so that the protrusions of each rod-shaped body can easily penetrate therethrough.

Above, we have explained the mechanical bonding method that can obtain strong bonding strength using examples shown in Figs. Forced cooling is effective.

A more detailed explanation will be given below based on preferred embodiments.

FIG. 6 shows one of the apparatuses for carrying out the invention.

In FIG. 6, 6 is a tube being rolled by a stretch reducer, and 7 is a blank tube to be rolled next.

8 is a coupling device. The coupling device 8 is movable in synchronization with the axial movement speed of the tubes 6 and 7, and has a supply means and a nozzle for injecting water, gas, etc. to the coupling portion. are doing. 9 is a stretch reducer, for example, the angle between its rotation axes in a plane perpendicular to the rolling direction is 1
It consists of 24 rolling mills with 3 rolls of 200 rolls.

10 is a reheating furnace, which reheats the tube whose temperature has dropped during the rolling process up to that point.

To explain the operation of the device configured as described above, 1.
The tube reheated in the reheating furnace 10 is supplied to the stretch reducer 9, where tension is applied between rolling mills to reduce the wall thickness and outer diameter.

The rear end of the leading tube 6 and the tip of the trailing tube are axially connected in a connecting device 8, and then the connecting part is water-filled.

Gas is injected into it and it is cooled down to a sufficiently low temperature.

This cooling provides tensile strength that can withstand the tension between the stands during rolling of the bonded area.

The joining and cooling of the tubes is performed while the joining device 8 moves in synchronization with the moving speed of the tubes.

In this way, the bonded portion that has been given sufficient strength is fed into the stretch reducer 9.

In this embodiment, after the tubes are joined, the outer diameter of that part is smaller than the hole diameter of the final stand. In addition, the outer diameter of the joint part may be such a size that even if the joint part comes into contact with the hole, it is not substantially rolled, so that it can be lightly rolled.

Figure 7 shows 1. This is an example of the operation of a compression processing machine for coupling.

The press 12 is configured to move forward and backward in the radial direction of the main pipe 11, and when displaced in the compression direction shown in FIG. 7, the outer diameter of that portion of the rτ main pipe 11 is reduced. This device also has the effect of cooling the main pipe by coming into contact with it.

Next, the present invention will be explained in detail.

The embodiment shown in FIG. 4 relates to the case where steel pipes are longitudinally joined by the above-mentioned joining means.

□ Table 1 shows the initial cost of steel pipes at that time.

The steel pipes were heated to 950C in a reheating furnace and bonded using the press shown in FIG. 7 in the manner shown in FIG. 4. The outer diameter of the joint was 98% of the outer diameter of the finished product. The first and second compression processes shown in FIG. 4 were performed using the same press shown in FIG. 7.

The steel pipes were thus successively joined and endlessly rolled.

FIG. 8 and FIG. 9 show the wall thickness of the tube end on the tube size standard side for the case of the prior art and the results of the above-mentioned embodiment in which the present invention was implemented.

As is clear from FIGS. 8 and 9, when comparing the amount of cut-off when the allowable range of wall thickness increase at the pipe end is set to 12.5%, it is found that according to the present invention, the amount of cut-off is significantly greater than that in the prior art. is decreasing.

Comparison of Example 1 and Example 2 and Example 3 and 1 Example 4
As can be seen from the comparison, the tube end wall thickness changes depending on the temperature of the joint, so by setting this temperature to an appropriate value, it is possible to achieve extremely small yield loss. be.

The yield loss was reduced by half in both tube sizes of 25A and 40A.

Since the present invention is constructed and operated as described above, it is possible to significantly reduce the yield loss caused by the wall thickness of the tube.

The method described above enables endless rolling and significantly improves the tube end yield, but in order to accomplish this, SR
Cutting at the exit must be done effectively.

In order to cut the pipe end online at the SR outlet, it is important to accurately detect the position of the pipe end and to cut it accurately at the same time.

The following three methods are suitable for detecting this tube end position.

(a) Measure the temperature at the tube end at the SR outlet.

Measure the outer diameter of the tube end at the tsR outlet.

(C) Detecting the joint position by tracking changes in rolling loads such as roll load, roll torque, and current at the final stand or at multiple stands including the final stand.

As the cutting means, a well-known flying shear or the like may be used.

At this time, better results can be obtained by synchronizing the advancing speed of the flying shear in the rolling direction with the exit speed of the product (ft8R).

The method described above completes the joining of the main tubes and the cutting of the ends of the finished tube, making endless rolling possible, but if the SR main tube is thick, it is effective to add the following measures. . In other words, when connecting the main pipes between the reheating furnace outlet and the SR inlet, the end of the main pipe in the reheating furnace is extracted from the reheating furnace in order to increase the temperature drop at the end of the pipe. Let it cool down before using. The following three methods are suitable for this cooling method.

(a) When using the induction heating method, no current is passed through the coil at both ends.

(b) A method in which both ends of the main tube protrude from the reheating furnace.

(e) A method in which rod-shaped cold blocks are inserted into both ends of the main pipe before extraction in a reheating furnace and are removed before compression processing.

A sufficient improvement in yield can be achieved just by carrying out the above-mentioned sprouting process, but there is the following method that can further improve this.

When the temperature of the joint is lowered in order to improve the strength of the joint, the temperature of the peripheral portion also decreases, and the wall thickness after rolling becomes slightly thicker than that of the central portion.

In order to prevent this, the temperature around the joint must be raised to the same temperature as the center, that is, to a temperature suitable for rolling. This can be done by heating by induction heating or the like during compression processing, forced cooling of the joint, or immediately before SR rolling.

If there is not enough space and time between the reheating furnace and the SR rolling mill row to fully connect the above-mentioned main tubes, the main tubes should be It is effective to process the end portions in advance into a shape suitable for compression processing to form the joint.

For example, in the case of Fig. '2, both ends of the SR main pipe are shrunk using a compressor, swaging machine, tilt rolling mill, etc. to make the inner diameter just large enough to accommodate the joint members 3, 31, and 32. put.

In the cases of FIGS. 3, 4, and 5, the same effect can be obtained by previously shrinking the tube ends. Finally, the reheating furnace to SR section, the compression processing machine and compression processing method before the reheating furnace will be explained in detail.

First, the following apparatus and method are suitable for pipe shrinking between the reheating furnace and the SR.

FIG. 10 is an example of compression processing using a press machine. 10th
Figures (a), et al., and (c) show compression tools 41 and 4, respectively.
This shows cases where 2.43 is 2, 3, and 4.

The first step and the second step may each be the same press machine, or may be two press machines.

Moreover, the purpose of tube contraction can be achieved with only the first step. It is also possible to shrink the tube using the swaging machine shown in FIG.

In FIG. 11, the die 15 is supported by a hammer 16 and rotated by a rotating main shaft 17.

The rotating main shaft 17 rotates in a cage 19 having rollers 18t. When the hammer 16 comes to the position of the roller 18 while rotating together with the rotating main shaft 17, the die 15 is compressed. Furthermore, when the hammer 16 comes between the rollers 18, the die 15 opens due to centrifugal force. If the rotation speed is fully increased, compression processing using the die 15 can be repeated many times. Note that by changing the shape of the die 15, various cross-sectional shapes can be provided. Further, in this embodiment, the number of dice 15 is two, but the number of dice 15 may be four.

Next, the equipment and method for pre-processing before the reheating furnace will be described. Of course, FIG. 10 mentioned above.

Although the method shown in FIG. 11 can be used, the apparatus shown in FIG. 12 is also effective here. This work procedure will be explained below.

(a) Insert the tapered mandrel 13 into the end of the S R main pipe 1'.

(b) Perform the first compression process using the compression tool 44.

(c) Pull the mandrel 13 to the right and perform the second compressive force U process.

(Pull the mandrel 13 to the right to perform the third compression process.

As the compression tool 44, a tool similar to that shown in FIG. 10 may be used. Also, the number of steps is arbitrary.b Different compression □
A 2t2-rule inclined rolling mill, a 30-rule inclined rolling mill, a 30-rule planetary inclined rolling mill, etc. are also effective.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view for explaining the principle of the stretch reducer, Fig. 2 is a cross-sectional view showing an example in which the SR main tube is connected to the straw material of the joint, Figs. 3, 4, and 5. The figure is SR
6 is an arrangement diagram of a reheating furnace, a coupling device, and an SR rolling mill row implemented according to the present invention, and FIG. 7 is an illustration of a coupling device using a press machine. An explanatory diagram of an example of the operation status of the tool, and FIGS. 8P and 9 are graphs showing a comparison of the variation of the inner door between the present invention and the conventional method, respectively.
Fig. 1θ is an explanatory diagram showing an example of compression processing, Fig. 11 is a front view showing an example of a swaging machine, and Fig. 121 is an explanatory diagram showing an example of compression processing.
g is a diagram illustrating an example of pre-processing before a reheating furnace. D... SR main pipe 1/... Trailing SR main pipe 1j.
...Advanced SR main pipe 2, 2'...Roll 3, 31
．． 32.33.34...Joint member 4, 41.42
．． 43.44... Compression tool 6... SR during rolling
Main pipe (leading main pipe) 7...SR main pipe (trailing main pipe) 8
... Compression machine with cooling device 9 ... SR rolling mill row 10 ... Reheating furnace 11 ... SR main tube joint
12... Compression tool for press machine 13... Mandrel 15... Die 16... Hammer 17.
...Rotating spindle 18...T roller 19...Cage patent applicant Representative patent attorney Tomoyuki Yafuki (and one other person) 1st r'! ri・,′++rη ri)−N−1

N-I Figure 5 Figure 6 Figure 7 Figure 78 Figure 9g3 (b) Top
Shift 1 set 1 (x),
K) 4 101st District Orste 0. a ? 2 steps: Knob 1st step 11. A 2nd stage, Puo' stage 11.
B 2nd stator
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Claims (1)

[Scope of Claims] 1. Endless rolling performed by joining the rear end of the leading bus and the tip of the trailing bus when a metal bus heated in a reheating furnace is subjected to drawing rolling with a stretch reducer. During rolling, while the leading and trailing bus tubes are running in the tube axis direction between the reheating furnace and the stretch reducer, the ends of both bus tubes are fitted together or adjacent to each other, and the tube shrinking process is performed. 1. An endless rolling method for a stretch reducer, characterized in that a connecting portion of both φ tubes is formed, and both main tubes are connected by a concavo-convex portion or a bonding material formed at the tube end. 2. When a metal bus heated in a reheating furnace is subjected to drawing rolling with a stretch reducer, in the endless rolling performed by joining the rear end of the leading bus and the tip I of the trailing bus, the reheating While the leading and trailing header tubes run in the tube axis direction between the furnace and the stretch reducer, the ends of both header tubes are fitted together or adjacent to each other, and the two header tubes are joined by tube shrinking processing. At the same time, the two main pipes are joined by a concavo-convex part or a binding material formed at the end of the pipe, so as to obtain a tensile strength that will not break due to the tension between the stands during rolling of the joint part tX. An endless rolling method for a stretch reducer, characterized in that the joint portion is cooled.