JPH0230311A - Skew rolling method for seamless steel tube and seizure preventing agent - Google Patents

Abstract

PURPOSE:To prevent the seizure between a guide shoe and a rolled stock irrespective of a material of the rolled stock by supplying an seizure preventing agent containing a water soluble borate compound and a film forming agent to the surface of the guide shoe for abutting on the rolled stock and rolling its stock, while forming a film. CONSTITUTION:By a skew rolling mill provided with a disk roller type guide shoe 11, piercing of a seamless steel pipe, thickness reduction, drawing and rolling are executed. In this case, to the surface of the guide shoe 11 for abutting on a rolled stock 10, a seizure preventing agent whoce main components are a water soluble borate compound and a film forming agent is supplied from an injection nozzle 5. While forming a film on the surface of the guide shoe by said seizure preventing agent, the stock is rolled. In such a way, the seamless steel tube having a good quality can be produced with high efficiency.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for inclined rolling of seamless steel pipes and an anti-seizure agent, particularly when performing perforation and thinning stretching of seamless steel pipes in an inclined rolling mill. In addition, the present invention aims to effectively prevent scratches (hereinafter referred to as shoe mark defects) on the outer circumferential surface of the tube, which are feared to occur due to seizure of the guide shoe surface.

(Prior Art) In general, the piercing and thinning drawing rolling of seamless steel pipes involves rolling a rolled material 10 with a pair of rolling rolls 7 and plugs 9 that face each other at an angle, as shown in FIG. However, the pair of plate-type guide shoes 8 restricts the outer diameter of the rolled material 10 from expanding due to thinning rolling.

In addition, a large amount of cooling water is supplied from nozzle 6 in order to suppress the rise in temperature of the rolling rolls and reduce wear.

By the way, when rolling such a seamless steel pipe, the rolling material 10 and the guide shoe 8 are rolled in a state of sliding friction on the entire surface, so seizure occurs on the surface of the shoe, which causes the rolling material 1
Shoe mark flaws occur on the outer surface of 0. Therefore, such rolling causes deterioration of the quality of the pipe material (and also causes inconveniences in actual operation, such as increased downtime of the rolling mill required for shoe maintenance and shoe replacement, which reduces productivity). is remarkable.

For this reason, in recent years, disc roll type guide shoes, which are superior in wear and rolling efficiency to the plate type guide shoes described above, have been adopted.

FIG. 3 shows a rolling procedure using an inclined rolling mill equipped with a disc-roll type guide shoe.

It is the same as in Fig. 2 except that a disc roll type guide shoe 11 is installed in place of the plate type guide shoe, and a large amount of cooling water is used to suppress the temperature rise of the shoe and reduce wear. It is.

However, even in rolling using such a disc-roll type guide shoe, the circumferential rotation of the rolled material is still completely in a sliding state, so the occurrence of shoe mark defects cannot be completely prevented.

Further, since rolling is performed while pressing the bulge of the rolled material onto the guide shoe with the guide shoe roll, the contact surface pressure between the guide shoe roll and the rolled material becomes large, and the surface of the guide shoe roll still remains baked.

In particular, when the rolled material is high Cr alloy steel, the occurrence of this seizure phenomenon is remarkable due to the small amount of oxides on the surface of the material and the high deformation resistance.

In order to solve the above problem, attempts have been made to cool the guide shoe or to improve the material of the guide shoe as disclosed in Japanese Patent Application Laid-Open No. 61-253105, but these efforts have not been effective enough. It has not yet reached that point.

In addition, JP-A-60-56406 proposes a method in which a lubricant containing fine graphite particles and fine solid asphalt particles is applied between the guide shoe and the rolled material while piercing and rolling is carried out. In this method, the lubricant is transferred to the main roll, and the forward speed of the rolled material is significantly reduced. As a result, the slip becomes thick (and the perforation efficiency is reduced), which is a serious drawback, and it cannot be put to practical use.

Furthermore, Japanese Patent Publication No. 58-3444 proposes a method of piercing and rolling while supplying non-combustible, non-fusible and hard sand-like powder between the plate-type guide shoe and the rolled material. However, under conditions where a large amount of cooling water is applied, it is not always possible for sandy particles to enter between the shoe and the rolled material, so it is extremely difficult to apply it effectively, and it can seriously damage the surrounding environment. It had the disadvantage of being damaged.

(Problems to be Solved by the Invention) This invention was developed to eliminate the drawbacks of the above-mentioned prior art, and it prevents seizure between the guide shoe and the rolled material regardless of the material of the rolled material, Furthermore, we would like to propose a method for inclined rolling of seamless steel pipes that can effectively prevent slip between the two and obtain high-quality seamless steel pipes with high efficiency, together with a suitable anti-seizure agent. purpose.

(Means for Solving the Problem) The inventors have proposed a method for preventing seizure between a guide shoe and a rolled material when perforating and thinning a seamless steel pipe using an inclined rolling mill, and for both We have conducted intensive research to develop an anti-seize agent that minimizes the slippage between guides and does not cause guide shoe marks even on high-alloy steel with low oxides on the material surface and high resistance to hot deformation.

As a result, when an anti-seizure agent containing a water-soluble borate compound and a film-forming agent is used, a film with excellent water resistance and firm adhesion is formed on the shoe surface, completely preventing slippage and seizing. We obtained knowledge that it can be suppressed.

This invention is based on the above knowledge.

That is, the present invention provides a method for applying a water-soluble borate compound to the surface of the guide shoe that comes into contact with the material to be rolled when perforating and thinning a seamless steel pipe in an inclined rolling mill equipped with a disc-roll type guide shoe. This is a method for inclined rolling of seamless steel pipes, which comprises supplying an anti-seizure agent mainly consisting of a film-forming agent and a film-forming agent, and rolling the pipe while forming a film.

This invention also provides a water-soluble borate compound with a word of 0.5 to 3
This is an anti-seize agent containing 0-t% (hereinafter simply expressed as %) and a film forming agent of 5-40%.

The experimental results that led to this invention will be explained below.

The inventors first tried to find a method that could reliably prevent shoe seizure without causing slip between the main roll and the material. (The inventors conducted experiments using a model machine in the following manner. In other words, the anti-seizure agent shown in Table 1 was applied to the shoe surface under the coating conditions shown in Table 2, and the shoe surface was rolled under the drilling conditions shown in Table 3. A comparative study was conducted.

The experimental results are summarized in Table 4.

Table 1 As is clear from the table, No. 4 without an anti-seize agent and No. 1-1 using a water-soluble borate compound in an undried state caused seizing on the shoe surface and plugged the rear end of the tube. There was a situation where I couldn't completely get rid of it. On the other hand, when a water-soluble borate compound, water-dispersed boron nitride, and water-dispersed graphite are applied to the shoe surface and then forcedly dried and rolled with a film interposed therein, NO, 1-2
, No. 2, and No. 3, metal adhesion did not occur on the shoe surface, and as a result, it was found that the occurrence of shoe mark defects could be reliably prevented.

However, it was also found that when water-dispersed graphite was used, the drilling efficiency was significantly reduced, making it practically unusable.

From the above results, in order to reliably prevent shoe seizure without causing slip between the main roll and the material, it is necessary to add a water-soluble borate compound or water-dispersed boron nitride to the shoe surface. It was discovered that it is sufficient to roll the material while interposing it as a film.

Therefore, the inventors next investigated various problems when introducing the above knowledge into an actual machine.

When selecting an anti-seize agent, we proceeded with development keeping the following points in mind.

(1) It is inexpensive and easy to handle.

(2) Good adhesion even under conditions where the surface temperature of the shoe is low.

(3) It should not be washed away by the cooling water of the main roll, and should have excellent water resistance.

(4) There should be no problem with drainage.

From this viewpoint, the above two types of anti-seize agents were comprehensively evaluated. The results are shown in Table 5.

As is clear from the table, the cost of water-dispersed boron nitride as an anti-seize agent is 1.5 to 2 times higher than that of water-soluble borate compounds.

Therefore, the inventors proceeded with the development of an anti-seize agent based on a water-soluble borate compound that has improved adhesion and water resistance at low temperatures, and also developed a new anti-seize agent that can reliably prevent seizure even under actual operation. In order to develop the method, we conducted extensive research.

In actual machines, the anti-seize agent flows out due to the large amount of cooling water supplied, making it impossible to fully demonstrate its performance.

Also, if a problem occurs during rolling, the mill will stop,
The surface temperature of the guide shoe decreases significantly. Therefore, in order to select an anti-seize agent that can appropriately deal with such problems,
The following experiment was conducted.

That is, after spraying anti-seize agents having various compositions shown in Table 6 onto test pieces heated to a predetermined temperature under the conditions shown in Table 7, water was immediately sprayed to check the adhesion of the anti-seize agents at this time. We investigated the amount.

The survey results obtained are shown in Figure 4.

As is clear from the figure, anti-seize agent A, which does not contain a film-forming agent, almost flowed out regardless of the temperature of the test piece, whereas anti-seize agent B and anti-seize agent C, which contain a film-forming agent, flowed out regardless of the temperature of the test piece. The heating temperature of the test piece is 80″, respectively.
At temperatures above 140°C, it remained as a film on the surface. In particular, anti-seize agent C containing a water-soluble solvent had excellent adhesion at low temperatures.

Next, using anti-seize agents B and C shown in Table 6, a model experiment was conducted assuming the rolling environment of an actual machine, and the seizure on the shoe surface, shoe mark defects on the outer surface of the tube, and perforation efficiency were investigated. . Table 8 shows the experimental conditions, and Table 9 shows the survey results.

Table 8 As is clear from the same table, there were some differences in the anti-seizure effect depending on the shoe surface temperature, but anti-seize agent B had a shoe surface temperature of 100°C, and anti-seize agent C Seizure was reliably prevented even at a lower temperature of 60°C, and as a result, no shoe marks were generated. Furthermore, it was found that the drilling efficiency was the same as in the case of water cooling, and the slip prevention effect was also good.

In addition, when the surface temperature of the shoe drops at the start of operation or during rolling due to trouble, it is more advantageous to use an anti-seize agent that contains a water-soluble solvent that has excellent low-temperature adhesion. Therefore, it is desirable to use them appropriately depending on the operating situation.

The reason why the anti-seizure agent according to the present invention, which contains a film-forming agent in a water-soluble borate compound, has superior anti-seizure properties compared to other agents is considered to be as follows. In other words, when the anti-seize agent according to the present invention is sprayed onto the shoe surface, it instantly adheres to the surface as a strong film due to the heat content of the shoe, and when it comes into contact with the high-temperature material, it becomes an amorphous glass, and the shoe and the rolled material are bonded together. To effectively prevent seizure by reliably preventing metal-to-metal contact between the metal and metal parts.

As mentioned above, it has been found that a water-soluble borate compound containing a film-forming agent is particularly excellent in anti-seizure properties, so the appropriate content thereof was next investigated.

First, we investigated the appropriate content of water-soluble borate compounds. That is, after applying anti-seize agents having various compositions as shown in Table 10 to the shoe surface, rolling was performed under the perforation conditions shown in Table 11, and the seizure state on the shoe surface and perforation efficiency were compared.

The survey results are shown in Table 12.

Table 10 (χ) Table *Stability evaluation of liquid 〇2 No separation after 30 days left at room temperature X: Left at room temperature 3
As is clear from the table, at least 0.5% of a water-soluble borate compound is required to reliably prevent seizure, but if it exceeds 30%, the treatment solution The content is preferably about 0.5 to 30%, since the stability of the compound deteriorates.

Next, we investigated the appropriate content of the synthetic resin emulsion as a film-forming agent.

The experiment was conducted using an anti-seize agent having the composition shown in Table 13.As is clear from the table, at least 5% or more of the synthetic resin emulsion is required to maintain good water resistance.
If it exceeds 40χ, it will not only not be easily dispersed but also separated.
Since the drilling efficiency also decreases, the content is preferably about 5 to 40%.

(Function) The water-soluble borate compounds that are the main components of the anti-seize agent used in this invention include alkali salts of boric acid (sodium borate, potassium borate), ammonium salts of boric acid, and boric acid. Examples include alkanolamine salts and salts of halonic acid and water-soluble amines, such as tetraethylenepentamine, cyclohexylamine, diethylenetriamine, alkylamine, and the like. Furthermore, it goes without saying that boric acid dispersed in water or dissolved in water also exhibits similar effects and is effective.

In addition, the film forming agent must be dissolved or dispersed in water and water-soluble solvents, and must have good adhesion to metals and water resistance, and synthetic resin emulsions are preferred. In addition to styrene-acrylic emulsions, emulsions include vinyl acetate emulsions, styrene-butadiene emulsions, acrylic emulsions, vinyl acetate methacrylic emulsions, and epoxy resin emulsions.However, basically, once a film is formed, Any resin that can be cured by heat can be used.

Further, as the water-soluble solvent, water-soluble alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, secondary butyl alcohol, tertiary butyl alcohol, and mixtures thereof can be used.

Acetone and carpitol water-soluble solvents can also be used alone or as a mixture. It is advantageous to use such a water-soluble solvent in an amount of 20% or more mainly as a drying accelerator under conditions where the surface temperature of the shoe is low.

Further, as a water-soluble viscosity improver for improving spreadability, for example, methyl cellulose, polyvinyl alcohol, carboxymethyl cellulose, polyethylene oxide, etc. can be used in a range of about 0.1 to 1%.

Next, an example of a method for supplying an anti-seize agent will be explained based on FIG. 1. A water-soluble anti-seize agent is stored in tank 1.

Air is used as a medium for injecting this anti-seize agent onto the shoe surface, and the pressure is increased to a predetermined pressure by a pump 2. Then, a predetermined amount of anti-seize agent is pumped in by a pump 3, mixed with a bold gun 4, and then the anti-seize agent is sprayed in a mist form from an injection nozzle 5 onto the upper and lower shoe surfaces.

Since the sprayed anti-seize agent instantly adheres to the shoe surface as a film due to the heat content of the shoe, there is no fear that the film will peel off due to the roll cooling water 6.

In order to prevent seizure, it is sufficient to form a film on the contact area between the rolled material and the shoe, and the feeding method is not particularly limited, and the feeding method may be either continuous or intermittent. It's okay.

As mentioned above, when an anti-seize agent containing a water-soluble borate compound, a film-forming agent, and a small amount of a spreading agent is supplied to the guide shoe and rolling is performed while forming a film, seizure has conventionally occurred. Even with rolled materials, seizure does not occur at all, and the friction coefficient of the anti-seize agent is as high as 0.2 to 0.3, so it can be used without causing deterioration of biting properties or occurrence of slips. Rolling is possible.

Although the explanation has been mainly given to the case of piercing rolling by piercer rolling, it goes without saying that similar effects can be obtained in a thinning/stretching mill, that is, an elongator mill, which rolls a hollow shell in the same type.

The anti-seize agent according to the present invention can also be used as an anti-seize agent in fields other than the manufacture of seamless steel pipes, such as hot or cold plastic working. Hot plastic working here refers to forging, plate rolling, bar steel, extrusion, etc., while cold plastic working refers to roll forming, press forming, plate rolling, etc.

As an anti-seize agent using a boron compound, Japanese Patent Publication No. 57-57118 discloses a lubricant made of an organic boron compound, but such a lubricant is not applicable to the present invention for the following reasons. It cannot be used for hot rolling of such seamless steel pipes.

1) Since a large amount of cooling water is applied, hydrolysis easily occurs and the lubricant is not formed as a film on the surface of the rolled material.

2) Since the lubricant is easily removed by water, it cannot be applied to hot rolling that requires a large amount of coolant.

On the other hand, since the anti-seize agent according to the present invention is a liquid dissolved in water, it not only has excellent liquid stability, but also forms a strong film by utilizing the heat content of the shoe. In addition, the lubrication system is simple and maintenance-free, and stable and continuous supply is possible at all times.

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

Example 1 The anti-seize agent used here was water-dispersed graphite having compositions B and C shown in Table 6 above and a comparative material.

A piercer mill equipped with a disc-roll-type guide shoe, which is the first bath of the Mannesmann mandrel mill process, is used to produce 1% C with an outer diameter of 110 mm and a length of 3000 mm.
r+5%Cr, 13%Cr, 22%Cr steel, 5
US304 steel, 5US316 steel, 5US321 steel,
5US347 steel, 100 pieces each, outer diameter 115mm,
When rolling into a hollow tube with a wall thickness of 12.5 mm, apply the above anti-seize agent on the surface of the upper and lower guide shoes at 0.8 f/min.
Rolling was performed after injection at a ratio of . At this time, the surface temperature of the shoe was set to two types, 60°C and 100°C, and was maintained at a predetermined temperature while actually being measured online using a thermometer. This temperature control was performed by adjusting the cooling water for the main roll and the shoe. Furthermore, to examine the effect on water resistance, testing was conducted under two conditions: with and without cooling water.

The results obtained are shown in Tables 15-17.

As is clear from the same table, under the conventional conditions without anti-seize agent, the material side of the shoe surface decreases in rolled materials with relatively poor oxidation resistance, such as 1% Cr, 5% Cr, and 13% Cr steel. Although no metal transfer or seizure was observed,
・Scale was attached to the surface of the shoe, and slight shoe mark flaws and indentation flaws due to scale had occurred on the outer surface of the rolled material.

Also, 22% Cr, 5US304.5US316.5
When the tlS321.5US347 steel was used without an anti-seize agent, seizure was observed on the shoe surface, and shoe mark flaws occurred over the entire length of the outer surface.

On the other hand, when conventional water-dispersed graphite was used, although seizure was improved and shoe marks did not occur, the problem occurred that the drilling efficiency was significantly reduced.

On the other hand, when the anti-seize agent according to the present invention is supplied and rolled, there is no decrease in perforation efficiency, no scale adhesion or seizure occurs on the shoe surface regardless of the material, and no shoe mark defects occur. There was no occurrence of any problems, and there were no problems with the pipeability of the material. Furthermore, since metal contact was prevented, abnormal wear of the rolls was reduced and the lifespan of the rolls was increased by about 30%, and roll consumption and changeover time were significantly shortened.

In the above embodiments, only steels with 1% Cr or more were mainly described, but it goes without saying that similar effects can be obtained by applying the present invention to general carbon steels such as low carbon steels and medium carbon steels.

(Effects of the Invention) Thus, according to the present invention, shoe marks that occur due to seizure between the rolled material and the guide shoe that is in contact with the rolling material during rolling of a seamless steel pipe by an inclined rolling mill having a disc-roll type guide shoe. Scratches can be effectively prevented, and therefore the downtime of the rolling mill due to guide shoe maintenance can be drastically reduced, and the need for repeated maintenance materials can be advantageously achieved.Moreover, even with high Cr alloy steel, high efficiency and high quality can be achieved. It can be made into a good seamless steel pipe, and its industrial significance is extremely large.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the anti-seizure agent supply procedure, Figure 2 is a schematic diagram of an inclined rolling mill equipped with a plate type guide shoe, and Figure 3 is a schematic diagram of an inclined rolling mill equipped with a disc roll type guide shoe. , FIG. 4 is a graph showing the relationship between test piece heating temperature and film deposition amount. Figure 3

Claims (1)

[Claims] 1. When perforating and thinning a seamless steel pipe using an inclined rolling mill equipped with a disc-roll guide shoe,
A seamless steel pipe characterized in that an anti-seizure agent mainly composed of a water-soluble borate compound and a film forming agent is supplied to the surface of the guide shoe that contacts the material to be rolled, and rolling is performed while forming a film. Incline rolling method. 2. An anti-seize agent characterized by containing 0.5 to 30 wt% of a water-soluble borate compound and 5 to 40 wt% of a film forming agent.