JPH02295603A - Method for preventing seizure of guide shoe in rolling of seamless steel pipe - Google Patents

Abstract

PURPOSE:To effectively prevent the formation of the shoe mark flaws generated by seizure by rolling a material to be rolled while supplying a seizure preventive agent on the outside surface of the material to be rolled over the entire contact length region of guide shoes and the material to te rolled. CONSTITUTION:The seizure preventive agent is continuously supplied over the total contact length region of the guide shoes 4, 4' and the material 0 to be rolled in the axial direction of a seamless steel pipe 1 at the time of rolling of the above-mentioned pipe. The seizure preventive agent is, therefore, spread between the fresh surface incessantly generated on the surface of the material 0 by the rolling thereof and the guide shoes 4, 4 ', by which the seizure is exactly prevented. As a result, the formation of the shoe mark flaws arising from the seizure is effectively prevented.

Description

Detailed Description of the Invention (Field of Industrial Application) This invention collectively refers to the processing steps such as perforation, thinning drawing, and polishing in the manufacturing process of seamless steel pipes, simply referred to as "rolling J". When carrying out such rolling processes, the guide shoes used to control the vibration of the material during rolling and the expansion of the outside diameter are likely to seize, resulting in scratches on the outer surface of the pipe. The present invention relates to a guide shoe seizing prevention method aimed at avoiding the occurrence of shoe mark defects (hereinafter referred to as shoe mark defects).

(Prior Art) A mill that performs rolling processing such as perforation, thinning drawing, or polishing, which is generally used in the manufacturing process of seamless steel pipes, has a second mill, for example.
Monolithic casting with the external shape as shown in the figure (composition example (w)
t%); C/1.1, Si/0.5, Mn/0
．． 3, Ni/30, Cr/30, Mo/0.9.
Ti/0.5. W/0.8, Zr/0.3, Cu
It is equipped with a guide shoe 4.4' which is made of steel.

As an example of a rolling mode by an inclined rolling mill equipped with this guide shoe, the case where a billet O is punch-rolled into a hollow shell 1 will be described as follows, with reference to FIG.

The billet 0 is perforated by the rolling rolls 2, 2' and the plug 3 arranged vertically opposite each other. At this time, a guide shoe is used to prevent the vibration of the hollow tube l and to prevent the outer diameter from expanding more than necessary. 4.4' is arranged (see cross section AA in FIG. 3(b)).

By the way, in this type of rolling, rolling is performed in a state where there is sliding friction on the entire surface between the material to be rolled and the guide shoe.
When rolling alloy steel containing elements such as Cr, Ni, and No as the material to be rolled, seizure is likely to occur on the surface of the guide shoe, which causes shew mark defects to occur on the outer surface of the material to be rolled. do. Therefore, in this type of rolling, not only does the quality of the pipe material deteriorate, but also the downtime of the rolling mill required for maintenance and replacement of guide shoes increases, resulting in a decrease in productivity, which is a significant inconvenience in actual operation. .

Regarding this problem, Japanese Patent Laid-Open No. 58-68409 proposes supplying grease between the guide shoe and the rolled material from the direction of rotation of the material downstream of the roll gorge.

Furthermore, JP-A No. 62-220204 discloses a guide shoe lubrication method in which a lubricant made of graphite dispersed in mineral oil is continuously injected from the guide shoe entry side using a nozzle 6 as shown in FIG. Proposed.

However, in all lubrication methods, the following major problems remain.

First, since the lubricant is transferred to the rolling rolls, no forward thrust is applied to the rolled material, resulting in a significant drop in perforation efficiency, which is unfavorable in terms of rolling workability and quality.

Second, since the lubricant is supplied only from the entrance side of the guide shoe, the lubricant is not sufficiently supplied to the new surface created by the plastic deformation of the material during rolling, and the gap between the guide shoe and the material is The drawback is that it is difficult to reliably prevent seizure.

(Problem to be Solved by the Invention) The inventor has previously developed a method for preventing seizing without reducing perforation efficiency even during rolling, which is an aqueous solution containing a water-soluble borate compound as a main component. A hot rolling method using an inhibitor was proposed. In this case, the anti-seize agent was supplied only to the entry side of the guide shoe surface, so even if a considerable anti-seizure effect was observed when the shoe surface temperature was high, it could be used to prevent problems such as rolling problems. There was a drawback that seizure could not be reliably prevented when the surface temperature of the guide shoe was low, such as when the mill was temporarily stopped for a while or during the initial stage of rolling, such as when starting up operations. This invention was further developed to eliminate the above-mentioned drawbacks, and it reliably prevents seizure between the guide shoe and the rolled material and produces high-quality seamless steel pipes that do not generate shoe marks. The purpose of the present invention is to provide a method for preventing seizure of guide shoes in seamless steel pipe rolling that can be manufactured with high efficiency.

(Means for Solving the Problems) When the present invention prevents seizure of a guide shoe using an anti-seizure agent in rolling a seamless steel pipe, the total contact length between the guide shoe and the rolled material in the tube axis direction is This is a method for preventing seizure of guide sheets in seamless steel pipe rolling, which is characterized in that rolling is carried out while supplying an anti-seize agent to the outer surface of a material to be rolled over a region.

The inventor of the present invention has discovered that when rolling with an inclined rolling mill, in addition to reliably preventing seizure between the guide shew and the material to be rolled, slipping between the two can be effectively suppressed, and in particular, Ni. Cr
We conducted extensive research to develop a method that can prevent guide screens from seizing even when rolling steel pipes containing alloy components that are likely to cause seizing, such as Mo and Mo.

As a result, the nozzle 5 for supplying the anti-seize agent is installed as shown in FIG. Since it can be supplied to the outer surface of the rolled material, by rolling it while it is being supplied, the third component to prevent seizure is interposed on the outer surface of the rolled material, blocking metal contact with the guide shoe and preventing slippage. We obtained the knowledge that seizure can be reliably suppressed from the early stage of rolling.

Below, the experimental results that led to this invention will be explained.

In the experiment, graphite (20% content), ^IltO'x (1
0% content), PezO = (10% content). Sing
(containing 10%) and BN (containing 4%) in water and containing methylcellulose to improve spreadability at high temperatures, and boric acid as a water-soluble borate compound related to the above-mentioned prior development. Both 1. Of/mi
An injection amount of n was used, and the method of injection supply at the contact portion between the guide shoe and the material to be rolled was varied at the following three levels.

■ When only the half of the guide shoe 4 is on the rolling entry side that extends almost to the center in the longitudinal direction (type (A)), ■ When it is only the half of the rolling exit side from the longitudinal center of the guide shoe 4 ( (B) type), ■ When the material is supplied to the entire outer surface of the rolled material l over the entire contact length area between the guide shoe 4 and the rolled material l ((C) type), the rolling conditions are 207 mmφ x 20001 MlN. 22%
A billet of Cr steel was heated to 1250°C and rolled into a hollow hollow measuring 225 mm in diameter and 20.5 mm in diameter.

Items to be investigated include the state of seizure on the shoe surface, the occurrence of shoe mark defects in the longitudinal direction of the pipe, and the drilling efficiency.

The experimental results are shown in Table 1.

As is clear from the same table, in type (C), when multiplied by the total length of contact between the guide shoe and the material, the seizure and shoe mark depth, which are problems in actual operation, are slight.

On the other hand, shoe seizure was observed in both type (A) when applied from the inlet side and type (B) when applied from the center to the outlet side, and 0.2
Occurrence of shoe mark flaws of 5 to 0.35 m+ was observed.

By the way, let's look at the influence of the anti-seize agent used in the supply type (C). A 1 203+ Sin2,
Fe203 and BN have only slight seizure and shoe mark depth, which are problems in actual operation, but water-soluble borate compounds are even better, with no metal adhesion or shoe mark depth. Met. The reason why this method of supplying the anti-seize agent over the entire length that contacts the guide shoe is superior to other supply methods is that the anti-seize agent is continuously applied to the new surface created by plastic deformation during rolling. It is thought that this prevents metal contact between the material to be rolled and the surface of the guide shoe, thereby eliminating the occurrence of seizure.

Furthermore, regarding the drilling efficiency, it was found that water-dispersed graphite had a low coefficient of friction in any type of injection method, resulting in a significant drop, making it unusable.

On the contrary, A l 203, FegOit S! 0!
, BNI and water-soluble borate compounds performed well without any decrease in drilling efficiency.

From the above experimental results, it was found that the water-soluble borate compound described above is particularly suitable as an anti-seize agent between the guide shoe 4 and the rolled material 1 in the present invention. However, A 1 gOff+' Fez(1++ SiOz,
It goes without saying that an anti-seize agent such as ON can also be used because the seize and shoe mark depth that are problems in actual operation are slight.

(Function) In this invention, when rolling a seamless steel pipe, by continuously supplying an anti-seize agent over the entire contact length region between the guide shoe and the material to be rolled in the tube axis direction, the surface of the material to be rolled can be rolled. The anti-seize agent spreads between the newly created surface and the guide shoe, which is constantly created by this process, and seize can be accurately prevented.

As the anti-seize agent, it has been found from the results of the above experiments that a water-soluble borate compound such as a water-soluble borate compound can be used with water as a dispersion medium or solvent together with a necessary spreading agent such as methyl cellulose, and the preferred concentration is 1% to 35%. % and the supply amount is 0.3 to 2. Compatible with O R/mill.

(Example) Examples of the present invention will be described below.

The composition of the anti-seize agent used here was a water-soluble borate compound consisting of 15% boric acid alkanolamine salt and the remainder water. A via thermill equipped with a fixed guide shoe (composition of components is similar to that in the prior art), which is the first pass of the Mannesmann plug mill process, was used to produce a diameter of 207 mm. length 20
00mm 1% Cr steel, 5% Cr steel, 22% Cr steel,
300 pieces each of SUS304 steel and SUS321 steel, each with an outer diameter of 225 m. When rolling a hollow tube with a wall thickness of 20.5++n, a type (C
) was compared with a type (A) in which fuel is injected only from the inlet side of the guide shoe according to the conventional method, and a type (B) in which fuel is injected from the longitudinal center of the guide shoe toward the exit side. Here, the injection amount of anti-seize agent is l ffi/
I went with win. At this time, a drain wiper was attached to the roll side to prevent the cooling water from the roll from getting around to the guide shoe side.

The results were as shown in Table 2.

As is clear from Table 2, when the anti-seize agent is injected only from the entrance side of the guide shoe according to the conventional method (A) and when it is injected from the longitudinal center of the guide shoe toward the exit side (B)
), for rolled materials with relatively low oxidation resistance, such as 1%Cr and 5%Cr steels, no transfer of the material to the guide shoe surface, that is, seizure, is observed, but scale is attached to the guide shoe surface. As a result, shoe mark flaws of about 0.2 mm and indentation flaws due to scale are generated on the outer surface of the tube.

In addition, when using conventional injection methods for 22% Cr, SUS304, and SUS321 steels, metal from the material side adheres to the shoe surface and seizes, resulting in 0.5 to 0.7 cracks on the outer surface of the tube almost the entire length. It occurred over the period.

On the other hand, in the feeding method according to the present invention, no scale adhesion or burning occurred on the surface of the shoe, and no shoe marks were generated at all, regardless of the material.

In this example, piercing rolling was exemplified, but it has been found that similar effects can be obtained by applying the method to the elongator and reeler rolling in the thinning drawing step of the next step, as well as in the reeler rolling of polished tube beads.

Moreover, although the description has mainly been made of I%Cr steel or higher as the material to be rolled, it goes without saying that similar effects can be obtained by applying the present invention to general carbon steels such as low carbon steel and medium carbon steel.

(Effects of the Invention) According to the present invention, shoe mark defects that occur due to seizure between the rolled material and the guide shoe in contact with the rolling material can be effectively reduced in rolling seamless steel pipes using an inclined rolling mill having a guide shoe. Therefore, it is possible to dramatically reduce downtime of the rolling mill due to guide shoe maintenance and reduce the need for repeated maintenance materials in the process, making it possible to manufacture high-quality seamless steel pipes with high efficiency even with high Cr alloy steel. The industrial significance of this is extremely large.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the present invention, Fig. 2 is a perspective view showing a conventional guide shoe used in an inclined rolling mill, and Fig. 3 is a schematic diagram and cross section of an inclined rolling mill equipped with a fixed guide shoe. It is a diagram. 0... Billet 1... Hollow tube 2, 2'
... Roll roll 3 ... Plug 4.4' ... Guide shoe 5 ... Anti-seizure agent supply nozzle Patent applicant Kawasaki Steel Corporation

Claims (1)

[Claims] 1. When using an anti-seize agent to prevent seizure of the guide shoe during rolling of seamless steel pipes, on the outer surface of the rolled material over the entire contact length area between the guide shoe and the rolled material in the tube axis direction, A method for preventing guide shoes from seizing in seamless steel pipe rolling, which comprises rolling while supplying an anti-seizure agent.