JPH08206710A - Skew rolling method of seamless tube - Google Patents

Abstract

PURPOSE: To more effectively prolong the life of a plug by optimizing the coating quantity of a lubricant on the surface of the plug in accordance with rolling conditions. CONSTITUTION: As for the coating quantity of the lubricant on the surface of the plug 12 in a skew rolling method of a seamless tube, a ratio X/DB which is the ratio of the traveling distance X of the billet from the point where the billet is brought into contact with a rolling roll 11 to the tip of the plug to the outside diameter DB of the billet or the range of the proper coating quantity by which the life of the plug is improved with respect to piercing efficiency is preliminarily determined, and the coating quantity of the lubricant on the surface of the plug at the time of actual rolling is controlled in the range of the proper coating quantity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inclined rolling of a seamless pipe such as a seamless steel pipe, and more particularly to a method for inclined rolling of a seamless pipe in which a lubricant is supplied to the surface of a plug for rolling.

[0002]

2. Description of the Related Art The Mannesmann tube making method has been widely practiced as a hot method for producing a seamless steel tube. In this method, a round steel piece heated to a predetermined temperature (hereinafter referred to as a billet) is first pierced and rolled by a piercing and rolling machine to manufacture a hollow shell (hereinafter referred to as a hollow), and the hollow is an elongator, A method of obtaining a seamless steel pipe of a predetermined size by reducing the wall thickness with a drawing mill such as a plug mill or mandrel mill, and then reheating it if necessary, and then mainly reducing the outer diameter with a drawing mill or constant diameter mill. Is.

There are various types of piercing and rolling mills. Two
A so-called Mannesmann piercer, which is a combination of two inclined rolls and a plug and two guide shoes, a so-called three-roll piercer, which is a combination of three inclined rolls and a plug, or a so-called, which is a combination of two hole-type rolls and a plug. Press roll piercers are common.

In the piercing and rolling process, the plug is constantly exposed to high temperature and high load due to constant contact with the heated billet and hollow.
Easy to wear and melt. Therefore, generally 900-10 for plugs
Scaling is performed at a high temperature of 00 ° C, and the surface of the plug is tens
A scale film of several 100 μm is formed to prevent damage. However, when such a plug is used for high alloy steel rolling, which has been particularly increased in demand in recent years, it can be used only several times.

As a method of extending the life of such a plug for piercing and rolling a seamless steel pipe, as disclosed in JP-A-51-133167, a hot lubricant is used between the plug and the hollow inner surface. A method has been proposed in which jetting is performed to effectively perform lubrication. Further, JP-A-62-207503 and JP-A-63-104.
As disclosed in Japanese Patent No. 707 and Japanese Patent Laid-Open No. 63-203205, there has been proposed a method of manufacturing the entire plug or the tip portion thereof with a molybdenum alloy or ceramic having excellent high temperature strength. Alternatively, as disclosed in Japanese Examined Patent Publication No. 6-243, there has been proposed a method in which a plug is used for high alloy steel rolling after being used for low alloy steel rolling a certain number of times.

[0006]

However, in the conventional method of ejecting the hot lubricant between the plug and the inner surface of the hollow, the structure of the plug bar and the plug is complicated, and maintenance such as clogging of the lubricant is difficult. Although the cost is high, there is a drawback that the lubricating effect is not remarkable.

In the conventional method in which only the tip of the plug is made of molybdenum alloy or ceramic and reinforced, the effect of preventing the wear of the tip is great, but the effect of preventing the wear of the body is weak, and the effect of extending the life of the plug is low. not enough. The conventional method in which the entire plug is made of molybdenum alloy has drawbacks such as extremely high plug cost and weakness against impact load and thermal fatigue.

Further, in the conventional method in which the plug is used for rolling the high alloy steel after being used for rolling the low alloy steel, the life of the plug cannot be expected to be extended so much when rolling the high alloy steel of 13% Cr steel or more, which is in high demand in recent years. At the same time, there was a drawback that the operation of the plug was complicated and labor was required.

An object of the present invention is to realize a more effective improvement in the life of the plug by optimizing the amount of lubricant applied to the surface of the plug according to the rolling conditions.

[0010]

DISCLOSURE OF THE INVENTION The present invention uses a slant rolling mill having a rolling roll inclined with respect to a pass line of a rolled material and a plug arranged on the pass line. Is a seamless pipe inclined rolling method that is repeatedly used for rolling the subsequent rolled material after being cooled after rolling the preceding rolled material, with respect to the amount of lubricant applied to the plug surface,
X / determined by the distance X from the contact of the billet to the rolling roll to the tip of the plug and the billet outer diameter DB
A suitable application amount range for improving the plug life with respect to DB or piercing efficiency is set in advance, and the lubricant application amount on the plug surface during actual rolling is controlled within the appropriate application amount range.

[0011]

[Function] Lubrication of the plug surface protects the scale coating on the plug surface during rolling and reduces its wear. As a result,
It is intended to prevent wear of the plug. However, according to the knowledge of the present inventor, it has been acknowledged that the plug life changes with a change in the piercer setting condition even if the length of the hollow chamber is about the same. Therefore, in the present invention, the amount of lubricant applied to the plug surface is optimally controlled according to the change in the piercer setting condition, and the plug life is more effectively improved.

(Relationship between X / DB and plug life) (FIG. 2) X is the distance from the contact of the billet to the rolling roll to the tip of the plug (the billet causes Mannesmann cracks during this time), and the billet outer diameter Is DB, X /
The relationship between DB and plug life is as shown in FIG. X
As / DB becomes larger, the plug starts to pierce the billet having a larger Mannesmann crack, so the load applied to the tip of the plug becomes smaller and the relationship shown in FIG.

However, if X / DB is too small (smaller than a), a billet biting failure occurs, and if X / DB is too large (larger than b), an inner surface flaw is generated in the hollow chamber, resulting in poor biting. In order to prevent the occurrence of internal defects and the occurrence of internal defects, a ≦ X / DB ≦ b is set as the limiting range.

In FIG. 2B, 1 is a billet,
2 is a hollow room, 10 is an inclined rolling mill, 11 is a rolling roll, 12 is a plug, and 13 is a plug bar.

(Relationship between perforation efficiency and plug life) (FIG. 3) The actual perforation time against the theoretical perforation time calculated from the roll inclination angle and the roll peripheral speed assuming no slip between the rolling roll and the rolled material. When the ratio of the drilling time is defined as the drilling efficiency η, there is the relationship of FIG. 3 between the drilling efficiency and the plug life.
As the drilling efficiency becomes higher, the actual drilling time becomes shorter, so that the load applied to the plug becomes smaller.
It becomes a relationship.

(Relationship between X / DB and perforation efficiency) (FIG. 4) Even when rolling a hollow room having the same outside diameter and length, if the roll history is different, the surface texture of the rolling roll changes, resulting in X Since / DB and the drilling efficiency change, even if the same amount of lubricant is applied to the plug surface, the plug life will be different. The relationship between X / DB and the drilling efficiency is as shown in FIG.

(Relationship between X / DB, drilling efficiency and lubricant application amount) (FIGS. 5 and 6) In the present invention, the lubricant application amount on the plug surface is X / D.
B, the effect of improving the life of the plug by applying the lubricant can be more stably ensured by changing the value according to the value of the drilling efficiency.

An appropriate range Q1 of X / DB and the lubricant application amount is shown in FIG. 5, and an appropriate range Q2 of the drilling efficiency and the lubricant application amount is shown in FIG.

Although X / DB and perforation efficiency have a relationship as shown in FIG. 4, basically, X / DB and perforation efficiency may be managed independently of each other.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 12 is a plug and 13 is a plug bar. The plug 12 is repeatedly used in the inclined rolling mill. That is, the plug 12 that has been used for rolling one rolled material is introduced into the cooling water tank 20 together with the plug bar 13 to be cooled, and then is transported by the plug bar transport roller and the plug bar transport table, and is again inclined rolling mill. Be delivered to. Then, the plug 12 carried into the inclined rolling mill is used for rolling the next rolled material.

However, the cooling water tank 20 is provided with the lifter device 21 in the middle of the moving path of the plug 12 and the plug bar 13 by the plug moving conveyor 27, and the plug bar 13 supported by the bar support 22 of the lifter device 21. Can be temporarily lifted out of the water tank 20 together with the plug 12 to interrupt the water cooling. A lubricant application header 23 is arranged on the front surface of the plug 12 lifted by the lifter device 21. Then, the lubricant in the lubricant tank 24 is pressure-fed through the pump 25 and the lubricant application amount adjusting valve 26, and is sprayed and applied from the lubricant application header 23 to the entire surface of the plug 12.

At this time, the lubricant application amount control device 28 controlled by the process computer 27 operates in the following (1) and (2).
Fulfill the function of. (1) Regarding the amount of lubricant applied to the plug surface, X / DB,
And / or proper application amount ranges Q1 and Q2 for improving the plug life with respect to the drilling efficiency are set in advance as shown in FIGS. 5 and 6, for example.

(2) By controlling the lubricant application amount adjusting valve 26 in accordance with the rolling condition (piercer setting condition) at the time of actual rolling, the amount of lubricant applied to the plug surface at the time of actual rolling is
Control within the proper coating amount range Q1 and Q2 of (1).

The concrete results of the present invention will be described below. (1) A 175 mm diameter 13% Cr steel billet heated to 1250 ° C. is pierced and rolled into a hollow with a diameter of 185 mm, a wall thickness of 18 mm and a length of 7.5 m.

(2) The plug has a diameter of 145 mm, 3% Cr-1%
It is made of Ni-based material for hot tools, and has a scale of several hundred μm generated on the surface by heat treatment for scale adhesion at 950 ° C for 4 hours.

(3) The lubricant is "water glass (SiO ₂ 70
%, Na ₂ O 30%) 40% + water ”.

(4) The amount of lubricant applied was as follows. The coating amount was constant. 6 cc / sec × 5 sec X / DB was taken into consideration and the coating amount was set in the proper range Q1.

[Equation 1]

The coating amount was set in the proper range Q2 in consideration of the punching efficiency η.

[Equation 2]

(5) Results (a) The relationship between X / DB and the plug life (when the drilling efficiency is 65%) when the lubricant coating amount is controlled is as shown in FIG.

(B) The relationship between the drilling efficiency and the plug life (when X / DB = 0.59) when the lubricant coating amount is controlled is shown in FIG.
It became like.

(C) FIG. 9 shows the average plug life of the conventional method with a fixed amount of lubricant applied and the average plug life of the method of the present invention in which the amount of lubricant applied was controlled according to X / DB and drilling efficiency. Show.

It is recognized that the method of the present invention can significantly improve the plug life.

[0033]

As described above, according to the present invention, the life of the plug can be more effectively improved by optimizing the amount of lubricant applied to the plug surface according to the rolling conditions.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the relationship between X / DB and plug life.

FIG. 3 is a schematic diagram showing the relationship between drilling efficiency and plug life.

FIG. 4 is a schematic diagram showing a relationship between X / DB and perforation efficiency.

FIG. 5 is a schematic diagram showing a relationship between X / DB and an appropriate range of lubricant application amount.

FIG. 6 is a schematic diagram showing the relationship between the drilling efficiency and the appropriate range of the lubricant application amount.

FIG. 7 is a graph of X / DB when the lubricant application amount is controlled.
It is a schematic diagram which shows the relationship between a plug life and.

FIG. 8 is a schematic diagram showing the relationship between the drilling efficiency and the plug life when the lubricant application amount is controlled.

FIG. 9 is a schematic diagram showing the effect of the method of the present invention in comparison with the conventional method.

[Explanation of symbols]

 10 Inclination Rolling Machine 11 Rolling Roll 12 Plug 13 Plug Bar 20 Cooling Water Tank 23 Lubricant Application Header 28 Lubricant Application Amount Control Device

Claims (1)

[Claims] 1. An inclined rolling mill comprising a rolling roll arranged obliquely with respect to a pass line of a rolled material and a plug arranged on the pass line, wherein the plug is cooled after rolling of the preceding rolled material. In the seamless pipe tilt rolling method, which is repeatedly used for rolling the subsequent rolled material, the amount of lubricant applied to the plug surface is the distance X from when the billet contacts the rolling roll to when it reaches the tip of the plug.
And the billet outer diameter DB, X / DB, or an appropriate application amount range that improves the plug life with respect to the piercing efficiency is set in advance, and the lubricant application amount on the plug surface during actual rolling is set to the above-mentioned appropriate application amount range. A seamless pipe tilt rolling method characterized by controlling.