JP4010663B2 - Thin-walled steel pipe rolling thread processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for thread rolling a thin steel pipe. More specifically, the present invention relates to a thin-walled steel tube rolling threading method capable of preventing the thin-walled steel tube to be processed from being reduced in diameter and insufficiently threaded when the thin-walled steel tube is thread-rolled.
[0002]
[Prior art]
In order to plastically process a taper screw on a conventional thin steel pipe for gas piping, it is possible to perform thread rolling using a thread rolling head as shown in FIG.
[0003]
As shown in FIG. 3, this thread rolling head has a taper peripheral surface portion equal to a desired taper gradient and forms a desired thread, and the above-mentioned roll forming screw portion. A plurality of rolling rollers 5 each having a tapered peripheral surface portion (for example, 8 °) having a taper circumferential surface portion (for example, 8 °) larger than the taper gradient adjacent to 5 a are formed on the circumferential surface of the housing 6. They are disposed at an angle (for example, 1 ° 47 ') that is substantially equal to the effective diameter lead angle of the desired screw thread with respect to the peripheral bus.
[0004]
Then, the head 4 is fixed, and the work tube 7 is pushed in between the screw rolling rollers 5 while rotating, so that the work tube 7 is moved in the direction of the arrow A by the lead angle of the screw rolling rollers 5. The taper screw is rolled and formed on the outer periphery thereof. Note that rolling is possible even if the head 4 is rotated without rotating the tube 7 to be processed.
[0005]
[Problems to be solved by the invention]
When thread rolling a thin steel pipe with such a thread rolling head, it is possible to form a complete screw even if the thickness is reduced by about 15% from the standard wall thickness of the JIS standard steel pipe. Is pressed by the thread rolling roller from the outer periphery during the thread rolling, and the diameter is reduced. For this reason, there is a problem that the thread does not swell normally and the surface of the thread is stripped and the appearance is poor.
[0006]
In view of the above-described conventional problems, the present invention has a thin-walled steel pipe that can be machined to a smooth surface with little diameter reduction and no thread surface even when thread rolling is performed on the thin-walled steel pipe. It aims at realizing the rolling thread processing method.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a thread rolling method for forming a screw by pressing a rolling roller against a rotating thin steel pipe to be processed and plastically deforming the thin steel pipe to be processed. In the method, at the end of the thin-walled steel pipe 13 to be processed, a flange 11 having an outer diameter that is at least equal to or less than the root diameter of the screw to be formed is formed at one end at the end of the cylindrical thread having a length equivalent to at least the complete thread processing length. The cored bar 10 is inserted, and the screw 15 is rolled by the thread rolling roller 14 in that state.
[0008]
By adopting this configuration, the cored bar supports the thin-walled steel pipe to be processed from the inside, and the diameter reduction during thread rolling can be suppressed, so that the thread rises well and the thread surface is peeled off. And can be processed into a smooth surface.
[0009]
The invention of claim 2 is a screw rolling method in which a thread is pressed by pressing a rolling roller against a rotating thin steel pipe rotating to form a screw by plastic deformation of the thin steel pipe to be processed. A cylindrical shape having a length equivalent to at least the full threading length at the end and an outer diameter flange 11 equal to or smaller than the root diameter of the screw to be formed are provided at one end. The cored bar 10 formed with is inserted, and the screw 15 is rolled by the thread rolling roller 14 in this state.
[0010]
By adopting this configuration, the cored bar supports the thin steel pipe to be processed from the inside, and the diameter reduction at the time of thread rolling can be suppressed. Furthermore, by having a slit, it becomes easy to pull out the cored bar after thread rolling.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram for explaining a thin-walled steel pipe rolling screw machining method according to a first embodiment of the present invention. In the processing method of the present embodiment, first, a metal core 10 as shown in FIG. The metal core 10 is formed in a cylindrical shape having a flange 11 at one end using a steel material. The outer diameter of the cylindrical portion 12 is equal to the inner diameter of the thin-walled steel pipe to be processed, the length is at least the length of a complete screw formed on the thin-walled steel pipe to be processed, and the outer diameter of the flange 11 is to the thin-walled steel pipe to be processed. It is set below the root diameter of the screw to be formed.
[0012]
Next, the cored bar 10 formed as described above is inserted into the end of the thin-walled steel pipe 13 to be threaded as shown in FIG. Next, as shown in FIG. 5C, the screw rolling process is performed by the screw rolling roller 14 to form the screw 15.
[0013]
In this way, the thin-walled steel pipe 13 to which the thread is rolled is increased in thickness by the core bar 10, and the diameter reduction at the time of thread rolling is smaller than that when the core bar is not used. Therefore, the bulge of the thread is good, and the thread surface is not peeled off and can be processed into a smooth surface. The flange 11 of the core metal 10 increases the rigidity of the end of the core metal, prevents reverse taper during thread rolling, and enables the core metal to be pulled out after threading.
[0014]
Further, after the thread rolling, the cored bar 10 may be extracted from the thin-walled steel pipe 13 to be processed, or may be left as it is in the thin-walled steel pipe 13 to be processed without being extracted. When leaving the cored bar 10 in the thin-walled steel pipe 13 to be processed, the flange 11 may not be provided. Even when the cored bar 10 is left in the thin-walled steel pipe 13 to be processed, there is no problem in connection with the joint. In addition, according to this method, it was possible to further reduce the wall thickness compared to the conventional JIS standard steel pipe. For example, the conventional method, which was about 15%, can be reduced by about 30% according to this method.
[0015]
2A and 2B are diagrams showing a cored bar used in the thin-walled steel pipe rolling screw machining method according to the second embodiment of the present invention. FIG. 2A is a front view, and FIG. 2B is a line bb in FIG. It is sectional drawing. The cored bar 10 'of this embodiment is substantially the same as the cored bar 10 of the previous embodiment as shown in the figure, and the difference is that a slit 16 is formed in the axial direction.
[0016]
The cored bar 10 'of the present embodiment formed in this way is used for thread rolling of a thin steel pipe in the same manner as in the first embodiment. Therefore, it has the same operation and effect as the first embodiment, and the slit 16 provided in the core metal can facilitate the extraction of the core metal after the thread rolling process. Further, by providing the core bar with a hole 17 for hooking the extraction tool as shown in FIG. 2C, the extraction can be further facilitated.
[0017]
【The invention's effect】
According to the thin-walled steel pipe rolling thread processing method of the present invention, when the thin-walled steel pipe is thread-rolled, the diameter can be reduced by the pressure applied by the rolling roller. As a result, the bulge of the screw thread becomes good and the thread surface is not peeled off and can be processed into a smooth surface. As a result, it is possible to prevent leakage of the connecting portion with the joint, and it is possible to reduce the thickness compared to the conventional case, thereby contributing to the cost reduction of the piping work.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a thin-walled steel pipe rolling screw machining method according to a first embodiment of the present invention. FIG. 1 (a) shows a core bar used in the thin-walled steel pipe rolling screw machining method of the present embodiment. Sectional view,
(B) is sectional drawing which shows the state which inserted the metal core in the edge part of a thin-walled steel pipe to be processed, (c) is a figure which shows the state which performs a thread rolling process with a thread rolling roller in the state of (b) figure. is there.
FIG. 2 is a view showing a core bar used in a thin-walled steel pipe rolling screw machining method according to a second embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a conventional taper thread rolling head.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Core metal 11 ... Flange 12 ... Cylindrical part 13 ... Thin-walled steel pipe 14 to be processed ... Rolling roller 15 ... Screw 16 ... Slit 17 ... Hole

Claims (2)

In a screw rolling method in which a rolling roller is pressed against a rotating thin-walled steel pipe to form a screw by plastically deforming the thin-walled steel pipe to be processed,
The end portion of the processed thin steel pipe (13), at least fully threaded length equivalent to a cylindrical shape having a length, and core metal of the root diameter equal to or smaller outer diameter than that of the screw to form a (10) The cored bar (10) has a flange (11) at one end and at least one hole (17) on the inner peripheral surface in the vicinity of the flange (11). The thread (15) is rolled by the thread rolling roller (14) in a state in which is inserted , the extraction tool is hooked into the hole (17), and the metal core (10) is removed from the thin-walled steel pipe (13) to be processed. A thin-walled steel pipe rolling screw machining method characterized by extracting . In a screw rolling method in which a rolling roller is pressed against a rotating thin-walled steel pipe to form a screw by plastically deforming the thin-walled steel pipe to be processed,
The end portion of the processed thin steel pipe (13), at least fully threaded length equivalent to a cylindrical shape having a length, and core metal of the root diameter equal to or smaller outer diameter than that of the screw to form a (10) The cored bar (10) has a flange (11) at one end and at least one hole (17) on the inner peripheral surface in the vicinity of the flange (11), and is axially slit (16). In the state in which the core bar (10) is inserted, the screw (15) is rolled by the thread rolling roller (14) , and the extraction tool is hooked into the hole (17) and the core bar ( 10) A thin-walled steel pipe rolling screw machining method , wherein the thin-walled steel pipe (13) is extracted .

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