JPH07148507A - Method for piercing seamless tube - Google Patents

Abstract

PURPOSE:To improve the service life of a plug to be used in the piercing process when the seamless alloy steel tube is manufactured, and to improve the basic unit of the tool, the productivity and the quality of the inner surface. CONSTITUTION:In the seamless tube piercing method, the service life is improved by reducing the load due to the lubrication effect and supplementing the surface scale of a plug 3 through the piercing after the lubricant containing the graphite crystallized cast iron powder is preliminarily coated on the surface of the plug 3 to be used in the process where a square billet 1 is drilled by the press roll piercing method (advance-piercing).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press roll punching method in a seamless pipe rolling manufacturing process for metals, alloys and the like.

[0002]

2. Description of the Related Art Press roll piercing / rolling in a seamless pipe manufacturing process is widely known in Japanese Patent Publication Nos. 54-23675 and 59-37127. The plug used in the drilling process of the billet is generally 3% C
r-1% Ni-based or 1% Cr-3% Ni-based low alloy steel material is used, and in order to secure heat insulation and wear resistance, oxides such as Fe ₃ O ₄ and FeO are applied to the surface layer by heat treatment. A so-called black skin treatment is performed to form it. Such a plug comes into contact with a work piece having a high temperature of 1200 to 1300 ° C.,
In addition, since it is used under high surface pressure, the black skin is consumed by continuous use, the heat insulation effect disappears, and the plug is worn due to direct contact with the work material, which has a serious adverse effect on the inner surface properties of the product that has been drilled. give.

When the work piece steel is ordinary steel, the work piece itself produces scale and the scale moves to the plug side to some extent during drilling, so the life until plug replacement, that is, the plug life is 500 or more. There is no problem with. However, when the work material is alloy steel, the scale generation is small, there is almost no migration to the plug, and the deformation resistance of the alloy steel is high and the surface pressure of the plug increases and the coefficient of friction is high, so the surface scale of the plug is Consumes early. Actually, 13Cr steel has a few plug lifespan, which causes serious problems such as cost increase due to frequent tool changes, productivity drop, and product quality drop.

In order to improve the quality of the inner surface, it may be considered to lubricate the inner surface. However, it is difficult to supply the lubricant because the hole is formed by piercing and rolling a solid material. Only the method of applying a lubricant is considered possible. In order to investigate the metal flow in Mannesmann drilling, which is one of the seamless steel pipe manufacturing methods, a high-sulfur-embedded steel wire 2 was embedded in a round steel slab (piercing material) 1 and drilled with a plug 3 in an experiment, as shown in FIG. As shown in Fig. 3, the metal flow is subjected to shear deformation and extends in the circumferential direction, so the shape of the inner surface is non-uniform, and since the metal flow is torn in the longitudinal direction and drilling progresses, the lubricant is consumed early and a sufficient lubrication effect is expected. Can not.

On the other hand, in an experiment similar to the above with press roll perforation according to the present invention, as shown in FIG. 1 (b), a dead metal is not formed during perforation and a uniform layer is formed in the longitudinal direction without being split. It is thinly extended and perforation proceeds.
For this reason, the lubricant previously applied to the plug lasts longer than the former.

The present inventors have already disclosed in Japanese Examined Patent Publication No. Sho 58-4932.
It has been shown that the load can be further reduced by plug lubrication as presented in Japanese Patent Publication No.

[0007]

DISCLOSURE OF THE INVENTION The present invention aims to further improve the product quality and yield of seamless pipes.
Improving the life of the plug and improving the quality of the inner surface of the pipe when manufacturing a seamless pipe by perforating a steel slab of metal, alloy, etc. In particular, in alloy steel, positively utilizing plug lubrication Therefore, it is an object of the present invention to provide a drilling method capable of improving the plug life and quality.

[0008]

In order to solve such a problem, the present invention is to preliminarily supply graphite crystallized cast iron powder to the surface of a plug for perforation. That is, the present invention, in the step of perforating a seamless pipe in which a square steel piece is perforated by a press roll perforation method (indentation perforation) using a plug, a lubricant containing graphite crystallized cast iron powder is applied to the surface of the plug in advance. After that, the hole is punched.

[0009]

The operation of the punching method according to the present invention will be described in detail below. The inventors have clarified a method of applying a grease to a plug to reduce the load on the plug in order to improve the inner surface quality in punching a press roll as described in the prior art. According to this method, the load can be certainly reduced and various alloy steels can be drilled, but the life of the plug is not yet sufficient.

In order to further improve the life of the plugs, the present inventors have focused their attention on the load reducing effect utilizing the lubricating performance of graphite as a lubricant and the effect of forming a plug surface scale by supplementing iron. Layered. as a result,
It has been found that the use of graphite crystallized cast iron powder can replenish the surface layer of the plug during drilling with scale to prevent premature wear. In addition, the graphite contained in the graphite crystallized cast iron powder exhibits a lubricating effect, and the cast iron itself has a drilling temperature of about 12
It was found that since it melts at 50 ° C, it exhibits a fluid lubrication action in addition to the solid lubrication action of graphite, and can significantly reduce the load.

It is sufficient that the graphite area ratio in the cast iron structure before crushing the graphite crystallized cast iron powder to be used is 3 to 30%. If it is less than 3%, the amount of graphite crystallized is insufficient and the lubricating action of graphite is not sufficient. If it exceeds 30%, it is difficult to crystallize graphite in the casting method.

The general composition of cast iron has a C content of 2.5-3.
5% by weight, 0.8 to 2.5% by weight of Si, Mn, P,
It may be composed of a trace element such as S, but a composition having a carbon equivalent (C + 1 / 3Si) of 3% or more is preferable because it melts at the piercing temperature. The particle size of the cast iron powder is preferably fine from the viewpoint of ease of melting during perforation and ease of application, but if the cost for grinding is taken into consideration, it is 30-100.
About μm is sufficient.

In order to apply the graphite crystallized cast iron powder to the plug, the powder may be added to grease or dispersed in a resin binder and then applied. As the resin binder, acrylic resin, styrene resin, vinyl acetate, or a mixture thereof may be used.
In this case, the content of the graphite crystallized cast iron powder may be 10 to 30% by weight. If it exceeds 30%, the coating property becomes poor. As a coating amount, a thickness of 50 to 300 μm is sufficiently effective. In addition, as a coating method,
It may be performed by a known means such as brush or spray.

[0014]

EXAMPLES As examples, the results of evaluation with a press roll punching machine of a 1/3 model of an actual machine will be described below. The perforation conditions and lubrication conditions are as follows. -Punching condition- (1) Pass schedule Steel billet size: 80 mm x 80 mm x 500 mm length (steel type S
US304) Size after perforation: 93mmφ × 23.25mm thickness × about 63
0mm length (2) Roll caliber diameter: 92mmφ (3) Plug diameter: 46.5mmφ (4) Roll speed / Pusher speed = 120mm / S / 15
0mm / S (5) Lubricant application procedure: 20% of graphite crystallized cast iron powder (particle size about 40 μm) in Table 1 in resin binder (acrylic resin)
Add about 50% by weight and spray the plug with a lubricant for about 150
It was applied to a thickness of μm. The conventional method was compared with the case where grease was applied and the case where grease was not applied. The evaluation results are shown in Table 1. The force applied to the bar holding the plug at the time of drilling (4 in FIG. 1 (b)) and the life of the plug are shown by the ratio based on the case where no lubrication is performed.

[0015]

[Table 1]

From Table 1, by using the graphite crystallized cast iron powder as a lubricant, the load is reduced by about 30% and the plug life is improved 2.5 to 3 times as compared with the case where it is not applied.
In addition, the load is improved by about 15% and the plug life is improved by about twice as compared with the case of grease lubrication.

[0017]

Industrial Applicability According to the method of the present invention, the load at the time of punching alloy steel is reduced, it becomes possible to punch higher alloy steel, and it is expected that the number of steel types to be manufactured can be expanded and the life of the plug is improved. , The prevention of productivity deterioration due to plug replacement, the improvement of inner surface quality, etc. are extremely effective in industry.

[Brief description of drawings]

FIG. 1 is a typical seamless pipe perforation method, a Mannesmann perforation method (a) and a press roll perforation method (b).
The figure which shows the metal flow in.

[Explanation of symbols]

 1 ... Perforated material 2 ... Embedded steel wire 3 ... Plug 4 ... Plug holding bar

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fuyasu Yamamoto 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd.

Claims (1)

[Claims] 1. In the step of piercing a seamless pipe in which a square steel piece is pierced by a press roll piercing method using a plug, the surface of the plug is preliminarily coated with a lubricant containing graphite crystallized cast iron powder and then pierced. A method for drilling a seamless pipe, which is characterized in that