JPH03204111A - Manufacturing method and device for steel pipe with thick wall and small diameter - Google Patents

Abstract

PURPOSE:To execute a work of comparatively largely reducing diameter and increasing thickness, to make the surface skin fine and to improve the efficiency by executing the specific diameter reduction to a normalized or a hot finished pipe with the squeezing roll and then pressing the pipe into the drawing dies in cold state. CONSTITUTION:The blank pipe 1 of the normalized or hot finished steel pipe is subjected to the >=5% drawing work of outer diameter in cold state with the rotating squeezing roll 5, and then it is pressed into the dies 3 with the pressing device 4, so the outer diameter is reduced and the thickness is simultaneously increased, then the small diameter pipe 2 with thick wall is obtained. The squeezing roll 5 is a general squeezing roll which is provided with about 3 - 4 rolls in one section area over 1 stand. By this outer diameter drawing work, the blank pipe 1 is increased in its thickness and also is hardened due to working. Therefore, because the buckling can be prevented in the case of pressing the blank pipe into the dies 2 arranged for next process, the increasing ratio of thickness per one time can be enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a processing technique for increasing the wall thickness of a normalized or hot finished steel pipe.

[Prior Art] An example of a processing technique for increasing wall thickness by conventional hot pressing is JP-A-01-0442], which describes a thickness increasing processing method as shown in FIG. Are listed. According to this, the raw tube 1 is induction heated by the heating coil 8 while being pushed into the die through the moving end 4. Since the die 7 has an outer diameter constriction part 9, the induction heated part is easily thickened by being compressed in the axial direction, and the small diameter thick walled pipe 2
get.

At this time, the raw tube 1 tends to expand outward, but since the outer periphery of the raw tube 1 is covered with a ceramic die 7, it can be processed without buckling.

Further, as a simple method, a method is known in which the thickness is increased by pushing the material into a drawing die in a cold state as shown in FIG. 4.

Furthermore, a large number of squeezing rolls as shown in Fig. 5 are lined up,
A method of reducing the diameter and increasing the thickness by passing it through hot or cold is also known.

[Problems to be Solved by the Invention] The example of JP-A-01-044211 requires a heating device, resulting in high equipment costs. In addition, in the conventional method of cold pressing into a drawing die, the pushing force increases due to work hardening of the steel pipe, which tends to cause buckling or uneven thickness in the pipe axis direction.
It is not possible to obtain a large machining rate at the same time. Usually, steel pipes for mechanical structures are often hot-worked or normalized steel pipes. Such steel pipes have a low yield point and are particularly susceptible to buckling. Therefore, in order to obtain a predetermined thick-walled tube, it is necessary to press the tube several times, which increases the processing cost. Furthermore, the method of reducing the diameter and increasing the thickness by passing a large number of squeeze rolls through a number of strained rolls increases the equipment cost.

The present invention aims to solve the above-mentioned problems, reduce equipment costs, and provide an economical method and apparatus for producing small-diameter, thick-walled steel pipes.

[Means for Solving the Problems] The gist of the present invention is to reduce the diameter of a normalized or hot-finished steel pipe by 5% or more using a drawing roll, and then coldly push it into a drawing die. A method for manufacturing a thick-walled pipe characterized by increasing the wall thickness, and a pushing device for pushing a normalized or hot-finished steel pipe,
This is a thick-walled tube manufacturing device consisting of a driven squeezing roll and a squeezing die.

The present invention will be explained in detail below with reference to FIG.

A raw pipe 1, which is a normalized or hot-finished steel pipe, is cold-reduced to an outer diameter of 5% or more by a drawing roll 5 rotated by a drive device (not shown), and then pushed into a rice 3. The small diameter thick-walled tube 2 is obtained by pressing with the device 4 to decrease the outer diameter and increase the wall thickness at the same time. The squeezing roll 5 is a general squeezing roll in which 3 to 40 rolls are arranged in one cross section of one or more stands, and it is possible to reduce the outer diameter by several percent per stand. This outer diameter drawing process increases the thickness of the raw pipe 1 and work-hardens it. Therefore, the next placed dice 3
Since buckling can be prevented when the material is pushed into the material, the rate of increase in thickness per processing can be increased. Note that the kit roll 6 guides the raw pipe 1 and prevents buckling.

FIG. 2 shows experimental values showing the relationship between the outer diameter reduction rate of the roll and the maximum thickness increase rate. By applying a processing rate of 5% or more using the squeeze roll 5, the rate of increase in thickness per time is almost doubled. However, if the number of squeeze rolls 5 is increased too much, the effect on the maximum thickness increase rate will be small, so the processing rate of the squeeze rolls should be determined in consideration of equipment costs. Next, examples will be shown.

[Example] Metal tube 1: Material JIS standard STKM12A dimensions Outer diameter φ34.0 to 114.3 mm Wall thickness 4.0 to 10.0
m[I+ Squeezing roll: 30-ru type, 2-stand outer diameter drawing ratio 5-15% Die: Material Carbide shape Die half-width 20° with pushing device Maximum load 100Ton Maximum speed 3
0m 7 minutes Lubricating oil 2 Apply commercially available cold drawing oil at the inlet of die 3. Small diameter thick walled pipe: Dimensions Outer diameter φ25. O~J39.1mm
Wall thickness 5.0~13. [1 mm] The principle of the present invention is that when increasing the thickness of a raw tube 1 whose yield point has become smaller due to normalizing or hot finishing, the thickness is increased by 5% or more in advance to prevent buckling when pushing the die. The diameter reduction process is carried out using a drawing roll, which is easy to process. Therefore, although it is more efficient to perform the method of the present invention on the same line, it is more effective even on separate lines than the conventional method.

[Effects of the Invention] According to the present invention described above, a relatively large diameter reduction process can be achieved in a cold manner without requiring a special heating device or a large number of squeezing rolls, so equipment costs are low. It has advantages such as a clean surface and good efficiency. Furthermore, since the steel pipe is finally passed through a highly accurate die 7, a steel pipe with a highly accurate outer diameter can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is an experimental value showing the effect of the roll outside diameter reduction ratio of the present invention on the maximum thickness increase rate, and FIGS. 3, 4, and 5 is a sectional view showing an example of a conventional processing method. ! ...Main pipe, 2...Small diameter thick wall pipe, 3...Dice,
4... Pushing device, 5... Squeezing roll, 6...
Guide roll, 7...Dice, 8...Heating coil,
9... Squeezing section, 10 11... Squeezing roll

Claims (1)

[Claims] 1. A normalized or hot finished steel pipe is reduced in diameter by 5% or more using a drawing roll, and then coldly pushed into a drawing die to increase its thickness. A method for manufacturing thick-walled pipes. 2. A thick-walled tube manufacturing device consisting of a pushing device for pushing a normalized or hot-finished steel tube, a driven drawing roll, and a drawing die.