JP3082414B2 - Tube rolling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling method using an inclined rolling mill using a drilling machine (piercer) widely used in a Mannesmann pipe manufacturing method which is a typical method for manufacturing a seamless metal pipe.

[0002]

2. Description of the Related Art In general, a seamless metal pipe manufactured by the Mannesmann pipe method first obtains a hollow shell by first passing a round steel piece, which is a material to be rolled, through a piercer, pressing a plug into the center thereof to penetrate it, and drilling. If necessary or directly, if necessary, the hollow shell is passed through an elongator to expand and elongate and then rolled, for example, further elongated and rolled with a plug mill, and then refined, shaped and sized with a reeler and sizer. Manufactured through a regular process. By the way, in the above-mentioned piercer and elongator, a so-called inclined rolling mill in which a round bar, a barrel-shaped rolling roll (hereinafter referred to as an inclined roll) having a center line inclined with respect to a path center of a hollow shell and a plug are used. Can be

[0003] The piercer used for carrying out the above-mentioned Mannesmann pipe-making method includes a pair of inclined rolls which are respectively installed opposite to each other with a predetermined path center interposed therebetween, and a plug which is an inner surface regulating tool disposed on the path center. A configuration using a guide shoe or a disc roll as a pipe material guide member is generally used.

FIG. 5 is a schematic transverse sectional view of a piercer, and FIG. 6 is a longitudinal sectional view taken along line VI-VI of FIG. In the drawings, reference numerals 1 and 1 denote inclined rolls, 2 denotes a plug as an inner surface restricting tool, and 6, 6 denote disc rolls as guide members.

Each of the inclined rolls 1 and 1 has a gorge portion 11 having a maximum diameter at an intermediate portion in the axial length direction, and has a conical inlet surface on each side of the gorge portion 11 whose diameter is gradually reduced toward a terminal. 12, a barrel-type roll having an exit surface 13, and is disposed on the left, right or above or below the pass center XX of the material 3 to be rolled.

The plug 2 has a warhead shape as a whole, and its base end is supported by the front end of the mandrel bar M, and is positioned and held on the path center XX between the inclined rolls 1 and 1. . The base end of the mandrel bar M is connected to a thrust block in a forward / reverse device (not shown).

In FIG. 6, disc rolls 6 and 6 are discs having a concave outer peripheral surface facing the plug 2.
Upper, lower or left and right are paired, each driven by a drive motor (not shown), and alternately with the inclined rolls 1, 1 around the pass center XX of the round steel piece 3b and the hollow shell 3h of the material 3 to be rolled. Are located in

In such a piercer, the round piece 3b of the material 3 to be rolled is conveyed in the axial direction as shown by the white arrow, and the entrance surfaces 12, 2 of the inclined rolls 1, 1 are moved. 12, the screw rolls in accordance with the rotation of the inclined rolls 1, while being pressed down on the outer periphery thereof, and is perforated by the plug 2 penetrating into the axial position with this movement. At the same time, the roll is rolled between the plug 2 and the inclined rolls 1 and 1,
6 is slidably in contact with the outer periphery of the material 3 to be rolled during rolling, and piercing-rolling is performed while suppressing that this swells outward in the radial direction.

In such a piercer, when producing a thick-walled tube having a small piercing ratio (length of hollow shell after piercing / length of material to be rolled before piercing), the material to be rolled 3 When the material rolls through, the end (rear end) of the rolled material 3 does not separate from the inclined rolls 1 and remains between the inclined rolls 1 and 1, which is a so-called loose defect. Further, even when the end portion of the material 3 to be rolled is separated from the inclined rolls 1 and 1, the plug 2 remains in the hollow shell portion 3h, so-called plug clogging occurs. Together, it is referred to as stuffing.)

[0010]

As a method for preventing the clogging of the tail, the roll opening (inclined roll interval), the guide opening (guide shoe interval), and the plug advanced amount which is the moving amount of the plug in the path center direction are described. There has been proposed a method of judging the presence or absence of clogging before rolling by using a specific expression based on the method (JP-A-59-44927). However, since the piercing and rolling conditions are limited according to the specific formula as described above, the thickness of the pierced tube to be manufactured is limited. Further, the piercing and rolling conditions set before the rolling by the specific formula may be changed during the rolling. In this case, the conditions are set again by the specific formula, but there is a problem that a great deal of time and labor are required.

The present invention has been made in view of such circumstances, and is performed without substantially changing the draft ratio at the tip of a plug. An object of the present invention is to provide a tube rolling method capable of preventing the occurrence of inner surface flaws of a material to be rolled due to the effect, thereby improving the rolling efficiency and realizing high quality rolling.

[0012]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for rolling a pipe, comprising: a rolling material spirally moved along the path center by rotation of a pair of inclined rolls disposed opposite to each other across the path center; A pressure is applied between the plug and the inclined roll that have penetrated into the center position, and the swelling of the material to be rolled due to this is suppressed by a pair of pipe material guide members opposed to each other between the inclined rolls. In the method of rolling a pipe to be pierced, in rolling a predetermined length range from the end of the material to be rolled, without substantially changing the tip draft rate of the plug, reducing the opening degree of the inclined roll, It is characterized in that the amount of advanced plugs is increased.

[0013]

In the method of rolling a pipe according to the present invention, the end of the material to be rolled during rolling is detected using an appropriate detecting means ahead of the installation position of the inclined roll, and the time when this detection is performed is taken as a reference. In other words, the opening degree of the inclined roll is reduced, and the advance amount of the plug is increased. For this reason, the workability of the thickness of the end portion of the material to be rolled is increased, and the thickness of the end portion can be set to a thickness that does not cause clogging of the buttocks. In addition, the decrease in the opening degree of the inclined roll and the increase in the advanced amount of the plug are performed without substantially changing the tip draft rate of the plug. Therefore, the slip of the material to be rolled due to the decrease in the tip draft rate is increased. The occurrence of the clogging phenomenon due to the above is prevented. Furthermore, when the tip draft ratio increases, a crack occurs at the tip of the plug of the round steel piece due to the rotary forging effect, causing internal flaws. However, since the tip draft rate of the plug is not changed, the internal flaw of the material to be rolled is not changed. Is prevented from occurring.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a schematic block diagram showing a configuration of a piercer used for carrying out the method of the present invention, and FIG. 2 is a longitudinal sectional view showing a positional relationship between each roll and a material to be rolled in the piercing mill.

In FIG. 1, reference numerals 1 and 1 denote axes of the path center X-.
The inclined rolls are cone-shaped inclined rolls which are inclined at different crossing angles γ with respect to X at the same time and inclined at an inclination angle (not shown) necessary for screwing the material 3 to be rolled. The inclined rolls 1, 1 is an inlet surface forming a Pasusenta X-X and the angle theta ₁ of round steel piece 3b of the material to be rolled 3 on both sides of the gorge portion 11, the gorge portion 11 in the central portion of its axial length 12 and an exit surface 13 forming an angle θ ₂ with the path center XX.
The roll opening Rg, which is the roll interval between the inclined rolls 1 and 1, is:
The adjustment can be made by automatic roll positioning devices 52,52.

A mandrel bar M having a warp-shaped plug 2 is disposed between the inclined rolls 1 and 1 along the path center XX. At the rear end of the mandrel bar M, a thrust block 4 for moving the plug 2 is provided. The thrust block 4 is an automatic plug determining device.
The plug advance amount Lg, which is the protruding length of the plug 2 from the gorge portions 11, 11 at the tip of the plug 2 in the direction of the inlet surface 12, is appropriately adjusted. Disc roll 6,
Reference numeral 6 denotes a circular plate having a concave outer peripheral surface facing the plug 2 and a pair of upper, lower or left and right disks, each driven by a drive motor (not shown), and a round steel piece 3b of the material 3 to be rolled. And the inclined rolls 1 and 1 are arranged alternately around the path center XX of the hollow shell 3h.

An end sensor 54 for detecting the end (rear end) of the material 3 to be rolled is provided on the entry side of the inclined rolls 1 and 1, and the output of the end sensor 54 is given to the arithmetic and control unit 51. Can be In addition to the output of the termination sensor 54,
The output of the tip draft rate setting unit 55 for setting the tip draft rate of the end portion of the material 3 to be rolled, and the hollow shell portion 3h of the material 3 to be rolled so as not to cause clogging of the end portion of the material 3 to be rolled.
Thickness change amount setting device 56 for setting the thickness change amount set value Δt of
And the output of a roll condition setting unit 57 for setting various conditions of the inclined rolls 1 and 1 relating to rolling.

The output of the arithmetic and control unit 51 is supplied to automatic roll positioning devices 52 and 52 and an automatic plug positioning device 53. The output of the roll condition setting device 57 is also supplied to the leading edge draft rate setting device 55.

Next, a method of performing piercing and rolling by the apparatus configured as described above will be described. First, before the material to be rolled 3 is bitten into the inclined rolls 1, 1, the tip draft rate setting device is set based on the conditions set in the roll condition setting device 57.
55 obtains the initial value of the leading edge draft rate, and sets this initial value as the set value of the leading edge draft rate. The arithmetic and control unit 51 reads data set by the tip draft rate setting unit 55, the thickness change amount setting unit 56, and the roll condition setting unit 57, respectively, and according to the data, the plug advanced amount Ld and the roll opening Rg.
Control.

Next, a method of controlling the plug advanced amount Ld and the roll opening Rg will be described. In FIG. 1, the radius of the material 3 to be rolled is represented by r.
₀ , when the shortest distance from the path center XX at the tip of the plug 2 to the inclined roll 1 is r ₁ , the tip draft rate D
_f is represented by the following equation (1). However, the tip draft ratio D _f in this case is to be expressed as the ratio.

D _f = (r ₀ −r ₁ ) / r ₀ (1)

The change amount of the plug advanced amount Ld is ΔLd, the change amount of the roll opening degree Rg is ΔRg, the wall thickness change amount changed by the plug advanced change amount ΔLd is Δt ₁ , and the roll opening change amount ΔRg.
Assuming that the amount of change in wall thickness that changes with the change is Δt ₂ , the wall thickness change amounts Δt ₁ and Δt ₂ and the wall thickness change set value Δt are geometrically expressed by the following equations (2), (3) and (4). It is shown as follows. However, the polarity of the plug advanced change amount ΔLd is the inlet surface 1 of the inclined rolls 1, 1.
The direction toward the 2,12 side is positive, and the roll opening change ΔRg
Is positive in the direction in which the distance between the inclined rolls 1 and 1 increases.

Δt ₁ = −ΔLd tan θ ₂ (2)

Δt ₂ = ΔRg / 2 (3)

Δt = Δt ₁ + Δt ₂ (4)

Here, θ ₂ in the above equation (2) is an angle formed between the pass center XX and the roll exit surface 13. Further, since the above (2) and (3) are not strict equations, if correction is necessary, a correction term may be added to each equation.

Then, when the above equations (2), (3) and (4) are summarized,
The thickness change amount setting value Δt is expressed by the following equation (5).

Δt = −ΔLd tanθ ₂ + ΔRg / 2 (5)

In the present invention, in order to prevent clogging at the bottom, the thickness change amount setting value Δt is set to a negative value (a value at which the thickness decreases). In addition, the thickness change amount setting value Δt may be a value that takes into account each of the thickness change amount due to the mill spring of the rolling mill and the thickness change amount due to the thermal expansion of the tool.

The variation Δr ₁ of r ₁ with respect to the plug advanced variation ΔLd and the roll opening variation ΔRg is geometrically represented by the following equation (6).

Δr ₁ = ΔLd tanθ ₁ + ΔRg / 2 (6)

Here, θ ₁ in the above equation (6) is an angle formed between the pass center XX and the roll entrance surface 12.

[0033] As previously described, the change of the thickness change amount setting value Delta] t, may be changed plug advanced amount Ld and roll angle Rg, in the present invention, caused by the change of the tip draft ratio D _f, the material to be rolled In order to prevent the occurrence of internal flaws due to the rotary forging effect generated at the terminal end of No. 3 and the occurrence of clogging when the material to be rolled comes off, the plug advanced change amount ΔLd and the roll opening change amount ΔRg are determined by the tip draft. The rate D _f is constant (ie, Δr ₁
= 0). In order to realize this, the relationship between the plug advanced change amount ΔLd and the roll opening change amount ΔRg is as follows when Δr ₁ = 0 in the equation (6).
Equation (7) may be used.

-ΔLd tanθ ₁ = ΔRg / 2 (7)

[0035] Then, the plug advanced variation ΔLd when changing the wall thickness change amount set value Δt while the tip draft ratio D _f is constant, the (5), (7) than those obtained following equation (8) Is required.

ΔLd = −Δt / (tan θ ₁ + tan θ ₂ ) (8)

Further, the roll opening change amount ΔRg when changing the wall thickness change amount set value Δt while the tip draft ratio D _f is constant, the (7), (8) below obtained from equation (9) It is obtained by the formula.

ΔRg = 2 · Δt · tan θ ₁ / (tan θ ₁ + tan θ ₂ ) (9)

In the arithmetic and control unit 51, the above (8) and (9)
The plug advanced change amount ΔLd and the roll opening degree change amount ΔRg are calculated based on the equation, a setting change signal of the plug advanced amount Ld based on the calculated plug advanced change amount ΔLd is given to the plug automatic positioning device 53, and the calculated roll opening amount is calculated. A setting change signal of the roll opening ΔRg based on the degree change ΔRg is given to the automatic roll positioning devices 52, 52, whereby the plug advanced amount Ld and the roll opening Rg are respectively changed.

The output of the setting change signal of the plug advanced amount Ld and the roll opening Rg by the arithmetic and control unit 51 is performed at the time when the end sensor 54 detects the end of the material 3 to be rolled, or at the time of the detection. After that, the process is performed after a lapse of a preset time.

In this embodiment, the rolls of the inclined rolls 1 and 1 of the inclined punch used may be any of a barrel type and a cone type.

Next, the results of actual execution of piercing and rolling using the method of the present invention will be described. FIG. 3 is a diagram showing a first table summarizing the rolling conditions, and FIG. 4 is a diagram showing a second table summarizing the results of the piercing rolling.

The control according to the present invention was performed under the conditions shown in Table 1 of FIG. 3 using the piercer having the above-described configuration. In addition, the conventional example in which no control regarding the processing of the end portion of the material to be rolled at the time of trailing-out is performed, the plug advanced amount Ld and the roll opening degree
The piercing-rolling was performed with respect to the comparative example in which either one of the Rg controls was performed.

When piercing and rolling are performed under the above-described conditions, the roll opening change ΔRg, plug advanced change ΔLd, and wall thickness change Δ in the method of the present invention, the conventional example, and the comparative example.
t, the perforation ratio, the presence of clogging of the bottom, and the occurrence of internal flaws are shown in Table 2 in FIG. However, in Table 2, a mark “x” indicates a state of “present”, a mark “○” indicates a state of “absent”, and a mark “−” indicates that determination is impossible.

As is clear from Table 2, in the case of the conventional example, when the piercing ratio was 1.35 or less, clogging of the tail occurred and rolling became impossible. When only the roll opening Rg of the comparative example was reduced at the end rolling, the clogging of the buttocks could be prevented, but the draft rate at the tip became large, and cracks occurred due to the rotary forging effect, resulting in frequent occurrence of internal flaws. In addition, when only the advanced plug amount of the comparative example was increased at the time of rolling at the end portion, the thickness reduction of the end portion was increased and clogging was not generated. And rolling became impossible. According to the method of the present invention, even when the piercing ratio is 1.3 or less, it is possible to perform stable piercing and rolling in which a high-quality finish can be obtained without clogging of the buttocks and inner surface flaws. The feasible range was expanded. According to the method of the present invention, the thickness of the end portion of the hollow shell is smaller than that of the intermediate portion, but there is no problem because the thickening step is omitted in the subsequent process.

The present invention can be applied to all kinds of piercing and rolling mills provided with a disc roll or a fixing shoe as a guide member, and it goes without saying that the same effect can be obtained.

[0047]

As described in detail above, in the method of the present invention, the degree of opening of the inclined roll is reduced and the amount of advance of the plug is increased in a predetermined length range from the end of the material to be rolled. Since the tip draft rate of the plug is not substantially changed, the occurrence of buttocks clogging due to an increase in slip of the material to be rolled and the occurrence of internal flaws in the material to be rolled due to the effect of rotary forging can be prevented beforehand. The present invention has excellent effects such as improvement in rolling efficiency and high quality of rolling.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a configuration of a piercing mill used for carrying out a pipe rolling method according to the present invention.

FIG. 2 is a longitudinal sectional view showing a positional relationship between each roll and a material to be rolled in a piercing mill.

FIG. 3 is a table showing a summary of rolling conditions when piercing rolling is actually performed using the method of the present invention.

FIG. 4 is a diagram showing Table 2 summarizing rolling results when piercing rolling is actually performed using the method of the present invention.

FIG. 5 is a schematic cross-sectional view of a piercer for explaining a conventional technique.

FIG. 6 is a longitudinal sectional view taken along line VI-VI of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inclined roll 2 Plug 3 Material to be rolled 3b Round steel piece 3h Hollow tube part 51 Operation control device 52 Automatic roll positioning device 53 Automatic plug positioning device 54 Termination sensor 55 Tip draft rate setting device 56 Thickness change setting device 57 Roll condition setting device

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-143004 (JP, A) JP-A-3-13222 (JP, A) JP-B-59-44927 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) B21B 19/04-19/06 B21B 37/78

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein a pair of inclined rolls disposed opposite to each other with the path center interposed therebetween is rotated by a rotation of the pair of inclined rolls. In the rolling method of the pipe to pierce and roll by suppressing the swelling of the material to be rolled due to this, by a pair of pipe material guide members opposed to each other between the two inclined rolls, In rolling a predetermined length range from the end, the opening degree of the inclined roll is reduced and the advanced amount of the plug is increased without substantially changing the tip draft rate of the plug. Tube rolling method.