JPH0516924B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for inclined rolling of seamless steel pipes, and in particular, when performing perforation and thinning drawing rolling of seamless steel pipes using an inclined rolling mill, the present invention relates to a method for inclined rolling of seamless steel pipes. This is intended to effectively prevent scratches (hereinafter referred to as scratch marks) on the outer circumferential surface of the pipe, which are likely to occur. (Prior Art) In general, in the piercing and thinning drawing rolling of seamless steel pipes, a rolled material 10 is rolled by a pair of rolling rolls 7 and plugs 9 that face each other at an angle, as shown in FIG. 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, in order to suppress the temperature rise of the rolling rolls and reduce wear,
A large amount of cooling water is supplied from nozzle No.6. 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.
Due to this, dust marks occur on the outer surface of the rolled material 10. Therefore, such rolling not only causes deterioration of the quality of the pipe materials, but also causes inconveniences in actual operation, such as increased downtime of the rolling mill required for maintenance and replacement of the shaft, reducing productivity. is remarkable. For this reason, in recent years, day scroll type guide shoes, which are superior in wear and rolling efficiency to the plate type guide shoes described above, have come into use. FIG. 3 shows the rolling procedure using an inclined rolling mill equipped with a day scroll type guide shaft. It is the same as in Fig. 2 except that a day scroll 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 guide shoe and reduce wear. It is. However, even in rolling using such a day-scroll type guide shoe, the circumferential rotation of the rolled material is still entirely in a sliding state, so it has not been possible to completely prevent the occurrence of shoe marks. In addition, since rolling is carried out while pressing the bulge of the rolled material onto the guide shaft with the guide shaft roll, the contact surface pressure between the guide shaft roll and the rolled material becomes large.
Seizing on the surface of the guide roll still remains. In particular, when the rolled material is high Cr alloy steel, the occurrence of this seizure phenomenon is significant due to the small amount of oxides on the material surface and high deformation resistance. In order to solve the above problems, 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. I haven't gotten to the point yet. In addition, JP-A-60-56406 proposes a method of piercing and rolling while applying a lubricant containing fine graphite particles and fine solid asphalt particles dispersed between the guide shaft and the rolled material. However, this method has serious disadvantages in that the lubricant is transferred to the main roll, the forward speed of the rolled material is significantly reduced, and as a result, the slip becomes large and the perforation efficiency is reduced, so that 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 a plate-type guide shaft and the rolled material. However, under conditions where a large amount of cooling water is applied, it is not always possible for sand-like particles to enter between the steel sheet and the rolled material, making it extremely difficult to apply this method effectively. 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, Moreover, it is an object of the present invention to propose a method for inclined rolling of seamless steel pipes, which can effectively prevent slips between the two and obtain high-quality seamless steel pipes with high efficiency. (Means for Solving the Problems) The inventors have proposed a method to prevent seizure between a guide shaft and a rolled material when perforating and thinning a seamless steel pipe using an inclined rolling mill, and to We conducted intensive research to develop an anti-seize agent that minimizes slip between the parts and does not cause guide 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-seize agent containing a water-soluble borate compound and a film-forming agent is used, a film with excellent water resistance and strong adhesion is formed on the surface of the shoe, completely suppressing the occurrence of slips and seizures. I gained knowledge of what I can do. This invention is based on the above knowledge. That is, in this invention, when perforating and thinning a seamless steel pipe in an inclined rolling mill equipped with a day-scroll type guide shoe, a water-soluble borate compound: 0.5 ~30wt% (hereinafter simply expressed as %),
A method for inclined rolling of seamless steel pipes, which comprises supplying an anti-seize agent containing 5 to 40% of a film forming agent, with the remainder consisting essentially of water and/or a water-soluble solvent, and rolling while forming a film. It is. The experimental results that led to this invention will be explained below. The inventors first conducted experiments using a model machine in the following manner in order to find a method that could reliably prevent the build-up of paint without causing slips between the main roll and the material. In other words, the anti-seizure agent shown in Table 1 was applied to the shoe surface under the application conditions shown in Table 2, and when rolling was performed under the drilling conditions shown in Table 3, the seizure status of the shoe surface, the drilling efficiency, and the pipeability of the material. A comparative study was conducted. The experimental results are summarized in Table 4.

【table】

【table】

【table】

[Table] As is clear from the table, No. without anti-seize agent.
In No. 4 and No. 1-1, in which a water-soluble borate compound was used in an undried state, seizure occurred on the surface of the tube and the rear end of the tube could not be completely removed from the plug. On the other hand, when a water-soluble borate compound, water-dispersed boron nitride, and water-dispersed graphite were applied to the surface of the shoe, they were forcibly dried and rolled as a film, No. 1-2; It was found that in both No. 2 and No. 3, metal adhesion did not occur on the shoe surface, and as a result, the occurrence of shoe marks could be reliably prevented. However, when using water-dispersed graphite,
It was also found that the drilling efficiency was significantly reduced, making it unusable in practice. From the above results, in order to reliably prevent the film from seizing without causing slips between the main roll and the material, it is necessary to apply a water-soluble borate compound or water-dispersed boron nitride to the surface of the film. It was discovered that it is sufficient to roll the film while it is interposed 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) Cheap and easily available. (2) Good adhesion even under conditions of low surface temperature. (3) Must not be washed away by main roll cooling water, etc., and have excellent water resistance. (4) There are no problems with drainage. From this point of view, the above two types of anti-seize agents were comprehensively evaluated. Table 5 shows the results.
Shown below.

[Table] 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. Furthermore, if trouble occurs during rolling, the mill will stop, and the surface temperature of the guide shaft will drop significantly. Therefore, in order to select an anti-seize agent that can appropriately deal with such problems, we conducted the following experiments. In other words, Table 6 was applied to the test piece heated to a predetermined temperature.
After spraying the anti-seize agents having various compositions shown in Table 7 under the conditions shown in Table 7, water was immediately sprayed, and the amount of the anti-seize agent adhered at this time was investigated.

【table】

【table】

[Table] Figure 4 shows the survey results obtained. 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, which contains a film-forming agent, and anti-seize agent C reliably remained as a film on the surface when the heating temperature of the test piece was 80° C. and 40° C. or higher, respectively. 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 simulating the rolling environment of an actual machine, and the seizure on the sew surface, sew mark flaws 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】

【table】

[Table] As is clear from the table, although some differences were observed in the anti-seizure effect depending on the surface temperature of the film, anti-seize agent B had a surface temperature of 100
℃, and anti-seize agent C reliably prevented seizure even at a lower temperature of 60 degrees Celsius, and as a result, no smoke 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, if the surface temperature of the steel drops due to troubles occurring at the start of operation or during rolling,
As the anti-seizing agent, it is more advantageous to use one containing a water-soluble solvent which has excellent low-temperature adhesion properties, and therefore it is desirable to use it appropriately depending on the operating conditions. 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 surface of a film, it instantly adheres to the surface as a strong film due to the heat content of the film, and when this comes into contact with a high-temperature material, it becomes an amorphous glass, and the film becomes amorphous. To effectively prevent seizure by reliably preventing metal-to-metal contact between rolled materials. 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 attaching anti-seize agents having various compositions as shown in Table 10 to the shoe surface, rolling was performed under the drilling conditions shown in Table 11, and the seizure state on the shoe surface and drilling efficiency were compared. The survey results are shown in Table 12.

【table】

【table】

【table】

[Table] 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 stability of the processing solution deteriorates. Therefore, the content is preferably about 0.5 to 30%. Next, we investigated the appropriate content of the synthetic resin emulsion as a film-forming agent. In the experiment, an anti-seizure agent having the composition shown in Table 13 was attached to the shoe surface, and then rolling was performed under the drilling conditions shown in Table 11 above, and the seizure status of the shoe surface, drilling efficiency, and water resistance were compared. . The survey results are shown in Table 14.

[Table] As is clear from the table, in order to maintain good water resistance, a synthetic resin emulsion of at least 5% is required, but if it exceeds 40%, it not only does not easily disperse but also separates. Since the drilling efficiency also decreases, the content is preferably about 5 to 40%. (Function) 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 borate salts, alkanolamine borate salts, and boric acid and water-soluble borate compounds. salts of amines such as tetraethylenepentamine, cyclohexylamine,
There are salts of diethylenetriamine, alkylamine, etc. 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 a particularly suitable one is a synthetic resin emulsion. Examples of such synthetic resin emulsion include styrene-acrylic emulsion, vinyl acetate emulsion,
Examples include styrene-butadiene emulsion, acrylic emulsion, vinyl acetate methacrylic emulsion, and epoxy resin emulsion. However, basically it is sufficient that a film is formed;
Any resin that hardens with 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, sec-butyl alcohol, tertiary-butyl alcohol, and mixtures thereof can be used. Acetone and carbitol-based water-soluble solvents can also be used alone or as a mixture.
It is advantageous to use such a water-soluble solvent as a drying accelerator mainly in a range of 20% or more under conditions where the surface temperature of the film is low. Furthermore, as a water-soluble viscosity improver for improving spreadability, for example, methyl cellulose, polyvinyl alcohol, carboxymethyl cellulose, and polyethylene oxide can be added in an amount of 0.1 to 1%.
It can also be used within a range of degrees. Next, an example of a method for supplying an anti-seize agent will be explained based on FIG. 1. Tank 1 for water-soluble anti-seize agent
can be stored in Air is used as a medium for spraying this anti-seize agent onto the surface of the screen, and the pressure is increased to a predetermined pressure by a pump 2. Then, a predetermined amount of anti-seize agent is fed by a pump 3, mixed with a bolt gun 4, and then the anti-seize agent is sprayed in the form of a mist onto the upper and lower shoe surfaces from an injection nozzle 5.
Since the sprayed anti-seize agent instantly adheres to the surface of the film as a film due to the heat content of the film, 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 shu, 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 shaft 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-seizure agent is as high as 0.2 to 0.3, so good rolling is possible without deterioration of biting properties or occurrence of slips. be. Although the explanation has mainly been 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 rolling, 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. It cannot be used for hot rolling of seamless steel pipes. (1) Because a large amount of cooling water is applied, hydrolysis easily occurs and the lubricant does not form 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 where a large amount of coolant is used. 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 film. Furthermore, 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 the compositions B and C shown in Table 6 above and a comparative material. A piercer mill equipped with a day-scroll type guide shaft, which is the first pass of the Mannesmann mandrel mill method, has an outer diameter of 110 mm and a length of 3000 mm.
1% Cr, 5% Cr, 13% Cr, 22% Cr steel,
SUS304 steel, SUS316 steel, SUS321 steel, SUS347 steel,
When rolling 100 of each tube into a hollow tube with an outer diameter of 115 mm and a wall thickness of 12.5 mm, the above anti-seize agent was injected onto the surface of the upper and lower guide shoes at a rate of 0.8/min before rolling. . At this time, the surface temperature of the shell is 60℃
and 100°C, and the temperature was maintained at a predetermined temperature while being measured online using a thermometer. This temperature control was performed by adjusting the main roll cooling water and the shower cooling water. 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.

[Table] * ◎: Very beautiful ○: Surface scale adhered ×: Seizure occurred

[Table] * ◎: Very beautiful ○: Surface scale adhered ×: Seizure occurred

[Table] * ◎: Very beautiful ○: Surface scale attached ×: Seizure occurrence As is clear from the table, under the conventional conditions without anti-seize agent, 1% Cr, 5% Cr, and 13% Cr steel In rolled materials with relatively poor oxidation resistance, such as, no transfer of metal from the material side to the surface of the shoe, that is, no seizure was observed, but there was scale adhering to the surface of the shoe, and there was a slight amount of scale on the outer surface of the rolled material. There were large scale scratches and indentation scratches caused by scale.
In addition, 22% Cr, SUS304, SUS316, SUS321,
In the case of SUS347 steel without anti-seize agent, seizure was observed on the shoe surface, and a shoe mark flaw occurred over the entire length of the outer surface. On the other hand, when conventional water-dispersed graphite was used, although the seizure was improved and there was no occurrence of shoe marks, there was a problem in 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 drilling efficiency, no scale adhesion or seizure occurs on the surface of the shoe, and no shoe mark defects occur in any material. 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 1% Cr steel or more was mainly explained, but 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) Thus, according to the present invention, during rolling of a seamless steel pipe by an inclined rolling mill having a day-scroll type guide shoe, snow marks that occur due to seizure between the rolled material and the guide shoe in contact with the rolled material can be reduced. 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 reduced.
Moreover, even if high Cr alloy steel is used, it is possible to make seamless steel pipes with high efficiency and good quality, which has extremely great industrial significance.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the supply procedure for anti-seize agent, Figure 2
The figure is a schematic diagram of an inclined rolling mill equipped with a plate type guide shoe, Figure 3 is a schematic diagram of an inclined rolling mill equipped with a day scroll type guide shoe, and Figure 4 is a diagram showing the relationship between test piece heating temperature and coating amount. It is a graph showing a relationship.

Claims (1)

[Claims] 1. When perforating and thinning a seamless steel pipe in an inclined rolling mill equipped with a day-scroll type guide shoe, a water-soluble borate compound: 0.5~
30 wt%, a film forming agent: 5 to 40 wt%, and the rest is supplied with an anti-seize agent consisting essentially of water and/or a water-soluble solvent, and is rolled while forming a film. Incline rolling method for steel pipes.