JP2976858B2 - Modification method of plug for manufacturing seamless steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention is piercer Mannesmann method relates to seamless steel Kai manufacturing plug-cutting method used by the inclined rolling mill, such as elongator.

[0002]

2. Description of the Related Art A piercing plug used in an inclined roll rolling mill such as a piercer or an elongator of the Mannesmann system is:
It is composed of a work part, a reeling part and a rear end part. The work part is further divided into a front end part and a rolling part. The tip of the work part is usually in an arc shape, but is easily melted during drilling due to its relatively small heat capacity compared to other parts, and the rolled part of the work part is subjected to strong pressure. Egure,
Wrinkles are likely to occur, and damage to these two locations is the main cause of plug disposal. The basic idea is to make the reeling part for finishing the wall thickness parallel to the roll surface. The material of the perforated plug is generally Cr-Ni cast steel, and a material added with Mo, Co, W, or the like is used to increase the high-temperature strength.

[0003] The perforated plug has a relatively small heat capacity at the distal end compared to other portions, and thus is easily damaged during perforation.
In addition, the rolling portion of the work portion is subject to strong pressure, so that it is easily scoured and wrinkled. For this reason, damaged drilled plugs are conventionally refurbished and reused.
As shown by hatching in FIG. 5, the entire diameter of the perforated plug 54 including the work part 51, the reeling part 52, and the rear end part 53 is changed from the front end to the rear end. It was impossible to use it for the target materials. For this reason, when the material to be used after plug modification is small, the modified plug remains in stock, making it difficult to improve the reuse rate.

One of the main measures for improving the life of the perforated plug is to improve the material of the plug.
It has been proposed to join a Mo-based alloy (Japanese Patent Application Laid-Open No. 63-203205). However, there is a limit to the life of a perforated plug that can be improved only by changing the material. As another method for improving the life, when the plug diameter Dp is a specific material and the plug effective length Lp is 1.5Dp ≦ Lp-50, the plug tip radius R is 10 mm or more and 30 mm or less. 4-147706).

[0005]

The perforated plug disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 4-147706 can improve the life in use per chance. However, in the plug shape, a parallel portion is provided in the reeling portion. Is not indispensable, and furthermore, there is no description regarding remodeling and re-use in order to cope with re-use when it cannot be used.

An object of this invention, provides the eliminating the drawbacks of the prior art, the modified cutting process breaks cutting reuse factors can be improved seamless steel pipe manufacturing plug perforation plug used in inclined rolling mill Is to do.

[0007]

Means for Solving the Problems The present inventors have intensively studied and studied to achieve the above object. As a result, the maximum diameter of the pierced plug is reduced at the time of remodeling by providing a parallel portion with a minimum length of 10 mm or more having the same diameter as the largest diameter portion at the rear end of the reeling portion which is the largest diameter portion of the pierced plug. Without cutting, the maximum diameter part at the rear end of the reeling part can be moved to the parallel part and re-cut, and it can be used again with the same diameter target material,
The inventors of the present invention have sought to improve the remodeling and reuse ratio, and have reached the present invention.

Namely this gun onset bright, toward the rear end from the plug maximum diameter, minimum same outer diameter as the plug maximum diameter portion length 10
A method for refining a plug for manufacturing a seamless steel pipe, wherein, when refining a plug provided with a parallel portion having a diameter of at least mm, the maximum diameter portion is moved to the parallel portion and refurbished.

[0009]

In DETAILED DESCRIPTION OF THE INVENTION This invention, toward the rear end from the plug maximum diameter portion, when cutting Kai plug having a minimum length of 10mm or more parallel portion L ₃ of the same outer diameter as the plug maximum diameter portion,
By moving to break cutting with FIG 1 (b) indicated by broken lines the parallel portion L ₃ of the maximum diameter portion as the, without reducing the plug maximum diameter Dmax, it is possible to implement the break-cutting.

In the present invention, the minimum length of the parallel portion having the same outer diameter as the maximum diameter portion of the plug is set to 10 mm or more because when the plug is re-cut and reused, the oxide scale adheres under appropriate conditions after the re-cut. Although heat treatment is generally performed, the diameter of the parallel portion is reduced due to the scale loss due to the heat treatment for attaching the oxide scale, thereby limiting the number of times of reusing and reusing the same plug diameter. Fig. 2 shows the amount of reduction in outer diameter of the 125 mm outer diameter plug by the number of times of heat treatment for attaching oxide scale. The lower limit of the reusable outer diameter range for the same plug diameter is generally -1 mm. 2 times of renovation and re-use
The times are the limit.

Further, as shown in FIG. 3, when the used plug is refurbished and reused, when the amount of rework L ₃ a is 5 mm, flaws remain in 100% of the reworked plug, and Unusable. Although when Aratamekezu amount L ₃ a is 10mm remaining scratches to 90% ,, modified cutting plug allowed the 10% break-cutting reuse. As you longer breaks cutting amount L ₃ a, Aratamekezu amount L ₃ a is at 50 mm, becomes reusable cutting 90% break. Therefore, the minimum length of the parallel part is
10 mm or more is required.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 The details of the present invention will be described below with reference to FIG. FIG. 1 (a) is a longitudinal sectional view showing a plug shape of the present invention, and FIG. 1 (b) is a longitudinal sectional view showing a state of remodeling of the present invention. In FIG. 1 (a) (b), 1 is a perforated plug, the work portion 2 of the length L _1, the length L ₂ of the reeling unit 3, after a length L parallel portion of ₃ 4 and a length L ₄ The end consists of 5 parts. Work part
2 is further divided into a tip portion 2a and a rolling portion 2b. 6 is an inclined roll, and 7 is a material. Tip 2a of work part 2
Has a curved surface with a predetermined radius of curvature R on the longitudinal side surface,
The material 7 is pressed against the center of the material 7 that is rotated and moved in the axial direction by the inclined rolling rolls 6, and pierces and rolls the material 7 together with the rolling section 2b. Further, reeling unit 3 of the length L ₂ is disposed in parallel to a predetermined angle of the tapered surface like the inclined rolling rolls 7 at a longitudinal side, with finishing the wall thickness of the mother tube 8 drilled and rolled by the work unit 2 , Smoothing the inner surface. The rear end of this reeling part 3 is the maximum diameter part Dma
x.

[0013] parallel part 4 of the length L ₃ is formed into a maximum diameter Dmax and a cylindrical same diameter. The rear end 5 of the length L ₄ has a curved surface with a predetermined radius of curvature or a tapered surface with a predetermined angle on the longitudinal side surface, and prevents stripping defects and inner surface hooking flaws caused by the inner surface of the tube 7 at the time of burst ripping. ing. Of perforated plug 1, piercing, rolling, to contribute to the smoothing is only reeling unit 3 of the tip portion 2a and the workpiece portion of the rolling unit consists of 2b length L ₁ 2 and length L _2, parallel Part 4
And the rear end part 5 does not participate in drilling, rolling and smoothing at all.

If the work part 2 and the reeling part 3 of the perforated plug 1 are damaged, as shown by a chain line in FIG. carrying out work, but the maximum diameter Dmax of the reeling unit 3 rear by the break cutting is moved from the position before Aratamekezu to L ₃ a by the parallel section 4, correspondingly parallel portion 4 is shortened. When the above-mentioned remodeling is completed, the oxide scale is subjected to a heat treatment for adhering to an oxide scale, and is then reused with the same diameter. Perforated plug of the present invention
1 is, by making the minimum length of the parallel part 4 10 mm or more,
As described above, since one of the modified cutting parallel part length L ₃ a required is minimal 10 mm, can be modified cutting reused one or more times with the same plug diameter.

Example 2 A perforated plug of the present invention having an outer diameter of 125 mm and a parallel portion length of 100 mm,
For each of the conventional perforated plugs having an outer diameter of 125 mm and no parallel parts, the remodeling and reuse rates were investigated. The results are shown in Table 1. The remodeling re-use rate was calculated by the following equation. Reuse rate of remodeling (%) = (number of usable parts after remodeling) / (number of plugs used) × 100 (%)
In this case, the plug inventory of the perforated plug of the present invention was investigated. The result is shown in FIG.

[0016]

[Table 1]

As shown in Table 1, the drilling plug of the present invention is re-used with the same plug diameter, so that the re-use rate of the first re-machining is 90% as compared with 45% of the conventional type. Is improving. In addition, the remodeling reuse rate for the second remodeling was 0 for the conventional model.
%, Compared to 81%. As a result, as shown in FIG. 4, the plug stock was reduced by 15 points as compared with the conventional plug.

[0018]

As described above, according to the present invention,
It is possible to greatly improve the rate of reusing and reusing drilled plugs for inclined roll rolling and reduce the stock of plugs. Also,
With the perforated plug of the present invention, the same effect can be obtained not only in a barrel-type rolling mill but also in a cone-type rolling mill.

[Brief description of the drawings]

FIG. 1 shows the shape of a plug according to the present invention and the state of refurbishment. FIG. 1 (a) is a longitudinal sectional view showing the shape of a plug according to the present invention, and FIG.
The figure is a longitudinal sectional view showing the state of remodeling of the present invention.

FIG. 2 is a graph showing the relationship between the number of times of heat treatment for depositing oxide scale and the amount of decrease in plug outer diameter.

FIG. 3 is a graph showing the relationship between the amount of rework L3a and the rate of occurrence of flaw residual plugs after rework.

FIG. 4 is a graph showing a comparison of plug stocks in the case of using the conventional type and the perforated plug of the present invention in Example 2;

FIG. 5 is an explanatory view showing a state of remodeling of a conventional perforated plug.

[Explanation of symbols]

1, 54 Drilling plug 2, 51 Work part 3, 52 Reeling part 4 Parallel part 5, 53 Rear end part 6 Inclined rolling roll 7 Material 8 Raw tube L _{1 to} L ₄ Length Dmax Maximum diameter part

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-54405 (JP, A) Iron and Steel Handbook (III) (2) Common facilities for strip steel, steel pipe, and rolling (Showa 55-11) -20) Maruzen p. 935 (58) Field surveyed (Int. Cl. ⁶ , DB name) B21B 25/00 B21B 19/04

Claims (1)

(57) [Claims] When a plug is provided with a parallel portion having a minimum length of 10 mm or more and having the same outer diameter as the plug maximum diameter portion from the plug maximum diameter portion to the rear end portion, the maximum diameter portion is moved to the parallel portion. A method of reworking a plug for manufacturing a seamless steel pipe, characterized in that the plug is reworked.