JP3082678B2 - Manufacturing method of small diameter seamless metal pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a seamless metal pipe using an inclined roll type piercing mill.
The present invention relates to a manufacturing method suitable for obtaining a cold-finished small-diameter seamless metal pipe having an outer diameter of, for example, 80 mm or less.

[0002]

2. Description of the Related Art A small diameter seamless metal pipe having an outer diameter of, for example, 80 mm or less is obtained by a method of manufacturing a seamless metal pipe using an inclined roll type piercing mill, a so-called Mannesmann pipe manufacturing method. In this case, usually, a method in which a Mannesmann-mandrel mill method and cold working are combined is used.

That is, the outer diameter is, for example, 140 to 160 m.
m, and a solid round billet heated to a predetermined temperature is passed through an inclined roll type piercing mill called a piercer to form a hollow shell having an outer diameter of 150 to 170 mm. The raw tube is passed directly or directly through a stretching rolling mill called a mandrel mill to have an outer diameter of 110 to 130.
mm, and then passed through a reheating furnace to reheat it to a predetermined temperature, and then passed through a drawing mill called a stretch reducer to be hot-finished into a product pipe having an outer diameter of 25 to 110 mm. You.

Further, when it is necessary to reduce the diameter of the product,
In order to improve the inner and outer surface quality and the dimensional accuracy, the product pipe which has been hot finished by the above-mentioned Mannesmann-mandrel mill method is used as a raw pipe, and this raw pipe is subjected to cold drawing or cold rolling. The outer diameter is reduced and cold finished into a small diameter seamless metal pipe with a predetermined outer diameter.

Here, a pair of main rolls (barrel type or cone type) disposed opposite to each other around a path center and a pair of material guides are provided in the inclined roll type piercing mill (hereinafter simply referred to as piercer). A combination of a member (a guide shoe or a disc roll) and a plug, which is an inner surface regulating tool disposed on a path center, is used.

FIG. 4 is a schematic plan view showing an example of the piercer, FIG. 5 is a side view thereof, and FIG. 6 is a vertical sectional view taken along the line II-II in FIG. Denotes a main roll, 2 denotes a plug which is an inner surface regulating tool, and 3 and 3 denote disk rolls which are material guide members.

The main rolls 10, 10 are of a barrel type,
A gorge portion 11 having a maximum diameter is provided at an intermediate portion in the axial direction, and the diameter of the gorge portion 11 is gradually reduced toward both ends on both sides of the gorge portion 11 so that the entrance surface 12 and the exit surface 1 have a conical shape.
3 is provided. The solid round billet B, which is the material to be rolled, is disposed to face left and right (or up and down) of the pass center XX, and is set at a predetermined roll opening degree Rg.

The plug 2 is formed in a warhead shape as a whole, and its base end is supported by the tip of the mandrel bar M. The plug 2 is positioned and held with a predetermined lead Ld (distance from the gorge portion 11 to the tip of the plug) while aligning its axis on the path set center XX between the main rolls 10 and 10. It is rotatable around -X as a rotation axis. Note that the base end of the mandrel bar M is connected to a thrust block (not shown) that can move forward and backward.

The disk rolls 3, 3 are discs having a concave outer peripheral surface facing the plug 2, and are disposed above and below (or left and right) the path center XX, and are rotated by a drive motor (not shown). It is designed to be driven.

In the piercer constructed as described above, the solid round billet B is transported in the axial direction as shown by the white arrow, and the entrance surfaces 12, 1
After biting between the two, the main rolls 10, 10 are screwed forward, a hole is made in the axial center portion by the plug 2, and the hollow shell H is pulled out to the right in the figure by the main rolls 10, 10. The hollow shell H is obtained by piercing and rolling while suppressing the hollow shell from bulging outward in the radial direction by the disc rolls 3 and 3.

The hollow shell H after piercing and rolling obtained as described above is reduced in thickness by a mandrel mill which is a drawing and rolling mill having 6 to 10 hole-shaped roll stands and a mandrel bar. After being reheated to a predetermined temperature in a reheating furnace, the diameter of the tube is reduced by a stretch reducer, which is a reduction rolling machine having 20 to 26 hole-shaped roll stands, and the tube is hot-pressed into a tube having a predetermined outer diameter. Finished to be finished product tube or raw tube for cold working.

However, the above-mentioned method for producing a small-diameter seamless metal pipe by the Mannesmann-mandrel mill method involves a number of hot rolling steps and rolls for producing a small-diameter pipe from a large-diameter solid round billet. Need
In addition, there is a problem that a large building area in which a stretching rolling mill and a reducing rolling mill can be installed is required. In particular, equipment cost is too high to manufacture a small number of product pipes, and the manufacturing cost is high.

Further, in addition to the problem that the setup change of each rolling mill is complicated, for example, when a stainless steel having high deformation resistance is rolled by an elongating rolling mill, the rolling load of the rolling mill due to the temperature drop of the hollow shell is reduced. In addition, there is a problem in that misroll and deterioration of inner and outer surface quality are caused due to the increase of the diameter, thereby lowering the productivity and the product yield, and increasing the production cost of the product tube.

[0014] For this reason, there has been a demand for the development of a method of manufacturing a cold-finished small-diameter seamless metal pipe capable of reducing the manufacturing cost of a product pipe as much as possible.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the problem is that the outer diameter is, for example, 8 mm.
It is an object of the present invention to provide a method of manufacturing a seamless metal pipe which requires only one hot rolling step to obtain a cold-finished small-diameter seamless metal pipe having a diameter of 0 mm or less.

[0016]

The gist of the present invention resides in the following method for manufacturing a seamless metal pipe.

A solid round billet having an outer diameter of 100 mm or less is pierced and rolled by a piercing and rolling machine of an inclined roll type provided with a pair of main rolls and a pair of material guides arranged opposite to each other around a path center. A method for producing a small-diameter seamless metal pipe, characterized in that the obtained hollow shell is subjected to a cold-diameter drawing process in a cold state.

In the above method of the present invention, it is desirable to remove the scales of the inner and outer surfaces of the hollow shell before the cold-diameter drawing. Further, a solid round billet of a steel or an alloy containing Ni and / or Cr is heated to 1100 ° C.
Heat to a temperature of less than 0 ° C. and make the billet surface temperature 100
It is desirable to supply the material to the inclined rolling mill while the temperature is at least 0 ° C. and perform piercing and rolling at a piercing ratio of less than 3.

The present inventors have found the following as a result of various experiments, and have accomplished the present invention.

That is, conventionally, a raw pipe which has been pierced and rolled by an inclined roll type piercing mill has poor dimensional accuracy and surface properties, and has a desired dimensional accuracy and surface properties even when subjected to cold working. It was thought that product tubes would not be available.

However, in order to reduce the production cost of the product, it is necessary to omit the elongation rolling step and the drawing rolling step which are the biggest causes of the increase in production cost. Therefore, when a raw tube is manufactured only by the piercing and rolling process, and when the raw tube is subjected to drawing by a cold drawing machine or cold rolling by a cold pilger mill, a product tube having desired dimensional accuracy and surface properties is obtained. An experiment was carried out to determine whether or not was obtained.

As a result, it was surprisingly found that a product tube having desired dimensional accuracy and surface properties can be obtained even with a raw tube manufactured only by the piercing and rolling step. Also, at this time, as the solid round billet to be provided to the inclined roll type piercing mill, an outer diameter of 100 mm or less may be used, whereby the piercing mill can be reduced in size and further reduction in manufacturing cost can be achieved. It was found that it can be achieved.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, a hollow shell is conventionally obtained by piercing and rolling a large diameter solid round billet having an outer diameter of 140 to 160 mm, and thereafter a drawing rolling mill and a drawing rolling. A raw tube for cold working having substantially the same outer diameter (40 to 100 mm) as that manufactured through the machine is manufactured only by piercing and rolling using a piercer.

For this reason, it is not necessary to use a large-diameter solid round bitlet as in the prior art, and a small-diameter solid round bitlet is used. However, its outer diameter is 100m
If it exceeds m, the rolling load at the time of piercing and rolling is large, and it is practically difficult to reduce the size of the piercer, and the effect of reducing the equipment cost and reducing the production cost of the product becomes insufficient. Therefore,
In the present invention, the outer diameter of the solid round billet used is 100 mm.
It was as follows.

The solid round billet may be made of any material. However, when the material is Ni-based alloy containing Ni or / and Cr or stainless steel such as austenitic stainless steel, ferritic stainless steel, and duplex stainless steel, the solid round billet is heated to 1100 ° C. or more. The material is heated to a temperature of less than 1300 ° C. and supplied to a piercer while its surface temperature is 1000 ° C. or more, and piercing-rolling is performed with a piercing ratio EL (material length after piercing / billet length) of 3 or less. Is preferred.

This is because the heating temperature of the billet is 1100 ° C.
If it is less than 1, the deformation resistance of the material is too large, not only misroll and outer surface flaws are generated at the time of piercing and rolling, but also the uneven wall thickness of the obtained raw tube becomes large, and conversely, the heating temperature of the billet If the temperature is 1300 ° C. or higher, not only does the deformability of the material decrease, but also a large amount of oxide scale is generated on the surface, and external flaws caused by the oxide scale are generated.

If the piercing ratio EL exceeds 3, the swelling of the material in the direction of the material guide member becomes too large, so that the frictional force between the material and the material guide member becomes large, and external flaws are liable to occur. In addition, the frictional force between the plug and the material is increased, so that the inner surface flaw caused by the plug is liable to occur, and the uneven wall thickness is increased.

The raw pipe pierced and rolled as described above may be subjected to cold working as it is. However, in order to obtain a product tube with better surface properties, the oxide scale on the inner and outer surfaces is descaled using pickling, shot blasting, sandpaper or a grindstone, and then cold worked. Is preferred. Also, if the bending of the raw tube is large, the cold working becomes a cause of uneven thickness in the case of drawing using a die or a die and a plug,
For example, it is preferable to use a bending straightener such as a rotary stretcher to make the state as straight as possible before subjecting to cold working.

Further, as the piercer to be used, a barrel-type main roll shown in FIGS. 4 to 6 may be used. However, in order to obtain a raw tube having more excellent surface properties, it is preferable to use a cone-shaped piercer for the main roll, and to minimize the occurrence of external flaws in the piercer, it is necessary to use a material guide. It is preferable to use a piercer in which the guide member is a disk roll.

1 to 3 are schematic views showing an example of a piercer having a cone-shaped main roll suitable for producing a raw tube in the present invention. FIG. 1 is a plan view and FIG. 2 is a side view. FIGS. 3 and 3 are cross-sectional views taken along the line II of FIG. 1. In the drawing, reference numeral 1 denotes a main roll, 2 denotes a plug, and 3 denotes a disc roll.

The main rolls 1 and 1 are cone-shaped and have a gorge portion 11 in the form of a short cylinder at the center in the axial direction, and a truncated cone on both sides of the gorge portion 11 whose diameter is reduced toward the end. An inlet portion 12 is formed in a shape, and an outlet portion 13 is formed in a substantially frustoconical shape whose diameter is increased toward an end. And
The main rolls 1 and 1 are arranged around the path center XX at a predetermined intersection angle γ (see FIG. 1) and an inclination angle β (see FIG. 2) so that they can be rotated in the same direction by a driving device (not shown). It has become.

The plug 2 has a shell shape as a whole, and its base end is supported by the front end of a mandrel bar M, and the base end of the mandrel bar M is connected to a thrust block of a reversing device, not shown, in front. .

The disk rolls 3, 3 are provided at the path center X-
A sliding surface 3d having an R-shape (concave shape) is provided opposite to the moving area of the material to be rolled, with X therebetween.

In such a piercer, a solid round billet B heated to a predetermined temperature in a heating furnace is supplied to the inlets 12 of the main rolls 1 and 1 as shown by white arrows in FIG. Is transported from the side to the path center XX with its axis aligned, and the leading end thereof is positioned at the entrances 12, 12 of the inclined rolls 1, 1.
The plug 2 which is inserted between the disc rolls 3 and 3 is then moved along the path center XX by the disc rolls 3 and 3, which is screwed by the rotation of the two main rolls 1 and 1 and penetrates into its axial center position. And the main rolls 1 and 1 are subjected to piercing and rolling once intermittently per half turn. When not subjected to this reduction, as shown in FIG. 3, the material to be rolled swells radially outward due to its rotation, but the rolls 3 and 3 slidably contact the outer circumference of the swollen portion. Also suppresses outward bulging. As a result, it is rolled while exhibiting an elliptical shape, and as it moves downstream in the moving direction,
The hollow shell H is gradually formed into a circular shape.

Although the above description is for the case where the main roll is a cone type piercer, the main roll shown in FIGS. 5 to 7 may be a barrel type piercer. However, in order to obtain a hollow shell having better quality, it is preferable to use a piercer whose main roll is a cone type.

[0036]

【Example】

(Example 1) An outer diameter of 60 to 72 m under the conditions shown in Table 1.
m, a raw tube having a wall thickness of 4 to 13 mm was manufactured, and after removing the oxide scale on the inner and outer surfaces thereof, the outer diameter was reduced to 30 by a cold drawing method.
The product was cold-worked into a product pipe having a thickness of 、 50 mm and a thickness of 2.5 to 5 mm. Then, the influence of the heating temperature of the billet and the perforation ratio EL on the quality of the product pipe after cold working was examined.

The evaluation was made based on the case where the inner and outer surface flaws caused by the raw tube were generated and the thickness deviation of the product tube after cold working was deteriorated, and the case where one of these was generated, ”, And the case where neither occurred was evaluated as“ ○ ”.
The result is shown in FIG.

[0038]

[Table 1]

As can be seen from the results shown in FIG. 7, the product pipe obtained by cold drawing the raw pipe obtained by piercing and rolling under the conditions preferred in the present invention has the desired dimensional accuracy and surface properties. Was.

(Example 2) A tube having an outer diameter of 60 to 66 mm and a wall thickness of 4 to 13 mm was manufactured under the conditions shown in Table 2, and the oxide scale on the inner and outer surfaces thereof was removed. And cold-rolled into a product pipe having an outer diameter of 30 to 50 mm and a wall thickness of 2.5 to 5 mm. Then, the influence of the heating temperature of the billet and the perforation ratio EL on the quality of the product pipe after the cold working was examined.

The evaluation was the same as in Example 1. The results are shown in FIG.

[0042]

[Table 2]

As can be seen from the results shown in FIG. 8, the product tube obtained by cold drawing the raw tube obtained by piercing and rolling under the preferable conditions in the present invention has the desired dimensional accuracy and surface texture. Was.

Example 3 A tube having an outer diameter of 60 to 66 mm and a wall thickness of 4 to 13 mm was manufactured under the conditions shown in Table 3, and the oxide scale on the inner and outer surfaces thereof was removed. And cold-rolled into a product pipe having an outer diameter of 30 to 50 mm and a wall thickness of 2.5 to 5 mm. Then, the influence of the heating temperature of the billet and the perforation ratio EL on the quality of the product pipe after cold working was examined.

The evaluation was the same as in Example 1. The result is shown in FIG.

[0046]

[Table 3]

As can be seen from the results shown in FIG. 9, the product pipe obtained by cold drawing the raw pipe obtained by piercing and rolling under the preferable conditions in the present invention has the desired dimensional accuracy and surface properties. Was.

Example 4 Under the conditions shown in Table 4, a raw tube having an outer diameter of 60 to 66 mm and a wall thickness of 4 to 13 mm was manufactured, and after removing the oxide scale on the inner and outer surfaces, a cold pilger mill was prepared. And cold-rolled into a product pipe having an outer diameter of 30 to 50 mm and a wall thickness of 2.5 to 5 mm. Then, the effect of the piercing ratio EL on the quality of the product pipe after cold working was examined.

The evaluation was performed on the presence or absence of inner and outer surface flaws caused by the raw tube and the occurrence of uneven wall thickness of the product tube due to the uneven thickness of the raw tube. ,
A case where no occurrence occurred was marked as “○”. Table 5 shows the results.
It was shown to.

[0050]

[Table 4]

[0051]

[Table 5]

As can be seen from the results shown in Table 5, the product pipe obtained by cold drawing the raw pipe obtained by piercing and rolling under the preferable conditions in the present invention has the desired dimensional accuracy and surface properties. Was.

The pipe of this embodiment was baked by cooling after releasing the pierce, and the surface layer became hard. Therefore, the pipe was subjected to softening heat treatment, descaling was performed, and then, the bend was corrected and then cooled. It was subjected to cold working.

[0054]

According to the method of the present invention, a raw pipe is manufactured with only one small and inexpensive piercer, and this is processed into a cold pipe to manufacture a small-diameter seamless metal pipe. It can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an example of a cone-shaped piercer having a main roll.

FIG. 2 is a schematic side view of the piercer.

FIG. 3 is a vertical sectional view taken along line II of FIG. 1;

FIG. 4 is a schematic plan view showing an example of a piercer having a main roll of a barrel type.

FIG. 5 is a schematic side view of the piercer.

6 is a vertical sectional view taken along line II-II of FIG.

FIG. 7 is a diagram showing the results of Example 1.

FIG. 8 is a diagram showing the results of Example 2.

FIG. 9 is a diagram showing the results of Example 3.

[Explanation of symbols]

 1: Main roll, 11: Gorge part, 12: Inlet face (or inlet part), 13: Outlet face (or outlet part), 2: Plug, 3: Disc roll, B: Solid round billet, M: Mandrel bar H: hollow shell.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B21B 17/00-21/06

Claims (3)

(57) [Claims] 1. A solid round billet having an outer diameter of 100 mm or less is pierced and rolled by a slant roll type piercing and rolling mill having a pair of main rolls and a pair of material guides disposed opposite to each other around a path center. A method for producing a small-diameter seamless metal pipe, comprising forming a raw pipe, and subjecting the obtained hollow raw pipe to cold-diameter drawing. 2. The method according to claim 1, wherein the inner and outer surface scales of the hollow shell are removed before the diameter-reducing stretching in the cold.
2. The method for producing a small-diameter seamless metal pipe according to item 1. 3. A steel or alloy solid round billet containing Ni and / or Cr is heated to a temperature of not less than 1100 ° C. and less than 1300 ° C., and the inclined roll type is heated while the billet surface temperature is not less than 1000 ° C. The method for producing a small-diameter seamless metal pipe according to claim 1, wherein the pipe is supplied to a piercing mill and pierced and rolled at a piercing ratio of less than 3. 4.