JP2993125B2 - Hot rolling method for steel and roll for hot rolling steel - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for hot-rolling steel and a roll for hot-rolling steel, and more particularly to a steel bar, a section steel, a steel plate, a steel strip,
Prevents seizure between rolls and rolled steel, which occurs when hot rolling steel, such as steel pipes, flat steel, and wire rods, especially stainless steel, wear of rolls, and roughening of rolls and rolled steel. The present invention relates to a method for hot rolling a steel material and a roll for hot rolling a steel material.

BACKGROUND ART In recent years, since various kinds of steel products have been required, hot rolling of steel materials is often performed under severe conditions. In the case of rolling under such severe conditions, a roll for hot rolling (a roll for hot rolling composed of an iron-based material, hereinafter, also simply referred to as a "roll")
Seizure occurs between the steel and the rolled steel material. Further, as the roll wears, the roll becomes rough, and the rough surface of the roll is transferred to the surface of the rolled steel material. For example, when hot rolling an H-section steel by a universal rolling mill, particularly in a portion where the sliding speed with the rolled steel material is large or a portion where the surface pressure is locally high,
Seizure occurs between the roll and the rolled steel material, causing trouble. This necessitates frequent maintenance of rolls and rolled products.
The time and cost of this care is immense.

In particular, when rolling a stainless steel H-section steel, the above-mentioned seizure is extremely likely to occur, and various measures for preventing the seizure have been studied from several viewpoints. For example, high chromium cast iron and high-speed steel have been developed from the viewpoint of roll material. However, even if these materials are used as a roll material, seizure cannot always be completely prevented. Therefore, at present, a lubricant such as graphite must be used to prevent seizure.

Means for applying a surface treatment to the roll surface to prevent seizure has been attempted. For example, the surface of a roll is coated with Cr, TiN, and TiC by chrome plating, CVD (chemical vapor deposition), and PVD (physical vapor deposition), respectively.

However, the time and cost required for these processes are enormous. Further, even if a roll having been subjected to the above surface coating treatment is used, the coating of the roll is easily peeled off under severe use conditions such as hot rolling. Therefore, it has not yet been able to stably exhibit seizure resistance and wear resistance.

Various studies have also been made on lubricants for hot rolling rolls. Of these lubricants, organic lubricating oils often cause oil film breakage and combustion, so that a sufficient lubricating effect cannot be expected. For this reason, Japanese Patent Application Laid-Open No. 5-212419 discloses a technique in which graphite is adhered to the roll surface by a combustion burner using hydrocarbon as a fuel to produce a lubricant. The method proposed in this publication is certainly effective in preventing image sticking. However, because of the use of graphite, "carburized" occurs in the steel to be rolled during hot (high temperature)
Easy to slip when the rolled steel material bites into the roll,
There was a problem. Furthermore, there is also a problem that graphite particles are scattered to deteriorate the working environment.

In Japanese Patent Publication No. 3-25241, piercing-rolling is performed while continuously supplying and applying a mixed liquid paint of an anti-seizure agent composed of metal oxide powder and a binder to the peripheral surface of a disk-roll type guide shoe. Techniques are disclosed. The method proposed in this publication is also effective in preventing image sticking. However, it is necessary to use water glass as a binder in order to firmly attach the anti-seizure agent to the roll surface. For this reason, when the state of application of the mixed liquid paint on the roll surface is not uniform, indentation flaws are generated on the surface of the rolled steel material, which causes deterioration of the surface properties. Furthermore, since the metal oxide powder as an anti-seizure agent does not dissolve in water glass as a binder, it will precipitate if left as it is mixed with water glass, which may cause clogging of the coating nozzle. In some cases it occurred.

As for the lubricant, inorganic solid lubricants such as molybdenum disulfide and glass have been studied. Some of these lubricants exhibit lubricity at high temperatures. However, similarly to graphite, its application conditions and removal of the remaining lubricant are difficult, and there is a concern that it may adversely affect product performance and work environment.
Also, since the above-mentioned lubricant has an effect of lowering the friction coefficient,
There is also a problem that slip occurs during hot rolling.

On the other hand, it is known that calcium carbonate also has an effect as a solid lubricant. However, this calcium carbonate is also difficult to apply, and if it is applied as it is as a solid powder, dust is generated and the working environment is deteriorated. Furthermore, calcium carbonate is difficult to dissolve in water, an organic solvent, oil, or the like, as in the case of the inorganic solid lubricant such as molybdenum disulfide or glass, and is left as it is mixed with water, an organic solvent, or oil. There is a property that will precipitate. Therefore, there is a problem that the stirring of the liquid must be constantly repeated in order to maintain the best condition at the time of coating.

When steel is cold-worked by various methods, a chemical conversion coating such as phosphate or oxalate is used to increase the adhesion and retention of lubricant and prevent contact with tools. Have been. Above all, under severe conditions that cannot be covered by oil lubrication, a chemical conversion coating as a base treatment and a soap lubricating coating as a lubricant reduce the frictional force between the tool and the workpiece to prevent wear and seizure doing.

For example, in Japanese Patent Publication No. 4-4045, a solution of phosphate or oxalate is supplied to the surface of a metal strip immediately before rolling,
A technique for forming a phosphate film or an oxalate film on the surface of a metal strip during cold rolling is disclosed. The method proposed in this publication surely has an anti-seizure effect when cold rolling steel. However, when steel is hot rolled, the effect of preventing seizure cannot be obtained.
This is because the phosphate film and the oxalate film are 400 to 5
If it is exposed to a high temperature of 00 ° C or more, it will be thermally decomposed,
This is because a phosphate film or an oxalate film cannot be stably supplied to the surface of the steel material to be rolled at a high temperature of about 800 ° C. or higher. Alternatively, since a heated scale is generated on the surface of the rolled steel material heated for hot rolling, even if a phosphate film or an oxalate film can be supplied to the surface of the rolled steel material, The effect of preventing seizure cannot be obtained.
Furthermore, in the technique described in the above publication, a phosphate or oxalate solution must be directly supplied to the surface of the rolled steel material. However, if the least expensive water is used as a solvent and a salt that is hardly soluble in water (for example, a calcium salt of oxalic acid) is used, a poorly soluble salt in water is clogged in a pipe or a nozzle. In some cases, it is not possible to supply the steel to the surface of the rolled steel material. As described above, the technique disclosed in Japanese Patent Publication No. 4-4045 can be applied to cold working of steel, but cannot be applied to hot working.

DISCLOSURE OF THE INVENTION The object of the present invention is to reduce the seizure between a roll and a rolled steel material, which occurs when hot rolling a steel material, especially a stainless steel material, abrasion of the roll, and roughening of the roll and the rolled steel material. An object of the present invention is to provide a hot rolling method for a steel material and a roll for hot rolling a steel material, which are effective in preventing such a problem.

The gist of the present invention is that (I) the roll is immersed in an oxalic acid aqueous solution before hot rolling, or an oxalic acid aqueous solution is applied to or sprayed on the roll, or at least the cooling water of the roll during hot rolling. In part, by using an aqueous solution containing oxalic acid or an oxalate soluble in water, and an aqueous solution containing a compound of an alkaline earth metal such as a calcium compound soluble in water, at least on the roll surface A method of hot rolling the steel by forming an oxalate film in the contact area with the rolled steel to prevent seizure occurring during hot rolling; (II) at least a contact area of the roll surface with the rolled steel And a roll for hot rolling a steel material having the oxalate film formed thereon.

According to the present invention, as will be described in detail later, by preventing seizure between a roll and a rolled steel material generated during hot rolling, so-called "ordinary steel" including carbon steel and low alloy steel is used. In addition to the prevention of operation troubles when rolling steel, the operation troubles due to the above-mentioned seizure that frequently occur when rolling stainless steel, especially stainless steel H-section steel, are eliminated,
Work for maintenance of rolls and products can be reduced.
Further, it is possible to improve the working efficiency by reducing the frequency of the roll change and to greatly extend the life of the large roll.

The present inventors have proposed the above-described prevention of seizure and the use of a steel material to be rolled when a steel material is hot-rolled with a hot-rolling roll made of an iron-based material using various aqueous solutions as a lubricant. Investigation was conducted in detail on the improvement of the surface properties of the product). As a result, the following important findings were obtained.

The oxalate film formed on the roll surface prevents the seizure and significantly improves the surface properties of the product.

When the oxalic acid solution constituting the coating is the following (a) to (c),
The above effects are observed.

(A) Iron oxalate.

(B) Oxalates of alkaline earth metals (such as calcium oxalate and barium oxalate).

(C) A salt in which iron oxalate and an alkaline earth metal oxalate are mixed.

In the case of using the above oxalate coating, there is no problem that the coefficient of friction becomes too low to cause slip,
Moreover, the seizure prevention effect is extremely large.

Under an appropriate condition, a hot-rolling roll is rolled under an appropriate condition, with an aqueous solution containing oxalic acid or a water-soluble oxalate (for example, an alkali metal oxalate or ammonium oxalate) and a water-soluble alkaline earth metal compound ( For example, if the treatment is performed using an aqueous solution containing a calcium compound, a barium compound, or the like), the films (a) to (c) can be formed on the roll surface.

The term "aqueous solution containing a water-soluble alkaline earth metal compound" as used herein means "at least 20 ppm
Aqueous solution containing the above alkaline earth metal ions ".

In the case of "alkaline earth metal", the same action and effect can be obtained in any case such as "calcium" and "barium". For the sake of simplicity, "alkaline earth metal" will be represented by "calcium" hereinafter. Will be explained.

Calcium oxalate in the oxalate film is thermally decomposed to calcium carbonate when it comes into contact with a high-temperature rolled steel material.

As described above, calcium carbonate has an effect as a solid lubricant, and the removal of calcium carbonate is easier than other inorganic solid lubricants such as molybdenum disulfide and glass. However, if calcium carbonate is applied as it is as a solid powder, dust is generated and the working environment is deteriorated. Moreover, calcium carbonate hardly dissolves in water, organic solvents, oils, etc., and precipitates if left as it is mixed with water, organic solvents, oils, etc.
This may cause clogging of piping and nozzles.

However, when the calcium carbonate is generated by the thermal decomposition of calcium oxalate in contact with the steel material to be rolled at a high temperature, there is no problem that the working environment is deteriorated and the calcium carbonate is clogged in the pipes and nozzles.

Of the oxalate coatings, calcium oxalate has relatively weak adhesion to the roll, but the adhesion of the calcium oxalate coating alone has a large seizure prevention effect. This is because calcium oxalate composed of particles having a diameter of 0.3 to 20 μm penetrates into the concave portions of the roll surface and adheres to the surface to form a film, thereby preventing metal contact between the hot rolled steel material and the roll. Because.

When a film in which iron oxalate and calcium oxalate are mixed is formed on the roll surface, as shown schematically in FIG.
And the effect of preventing seizure is even greater.

Of the oxalate coatings, iron oxalate, in particular, can be repaired very easily even if it is peeled off during hot rolling, for example, by spraying or applying an aqueous oxalic acid solution to a roll.

When a film in which iron oxalate and calcium oxalate are mixed is formed on the roll surface, the repair of iron oxalate is extremely easy, and the repair of calcium oxalate protected by this is also easy.

The formation of an oxalate film on the roll surface can be performed at extremely low cost as compared with the surface coating treatment by plating, CVD, PVD, or the like.

According to the method or roll of the present invention, for example, at least one of an oxalate film (iron oxalate film and calcium oxalate film) is formed on the roll surface by performing the following processes (d) to (f).
By forming (seed), seizure between the roll and the rolled steel material can be prevented, so that the roll life (time until roll change) is greatly improved and the surface properties of the product are also improved.

(D) Before the roll is subjected to hot rolling, at least the contact area of the roll surface with the rolled steel material is appropriately treated with an aqueous oxalic acid solution.

(E) An aqueous oxalic acid solution is used for part or all of the cooling water of the roll during hot rolling.

(F) Cooling of the roll during hot rolling is performed by two systems of cooling water, and oxalic acid or a water-soluble oxalate (for example, alkali metal oxalate or oxalate) An aqueous solution containing a calcium compound soluble in water is used in a part or whole of roll cooling water of another system.

If the oxalate film is formed by the method described in (f) above, the so-called "poorly soluble in water" calcium oxalate is generated on the roll surface, so that the cooling water injection nozzle is not clogged. Further, calcium oxalate does not precipitate in the cooling water.

By treating the roll with an aqueous oxalic acid solution, the behavior of film formation on the roll surface is based on the reaction of the following formula (A).

Fe + C ₂ H ₂ O ₄ → FeC ₂ O ₄ + H ₂ (A) More specifically, when a roll is immersed in an oxalic acid aqueous solution, or when an oxalic acid aqueous solution is applied or sprayed on the roll and oxalic acid adheres, On the surface of the roll, iron is dissolved to generate hydrogen as shown in the following formulas (B) to (E),
Iron ions react with oxalate ions to produce FeC ₂ O ₄ . The thus produced FeC ₂ O ₄ forms a film and covers the roll surface.

^{Fe → Fe 2+ 2e - ··· (} B) C 2 H 2 O 4 → 2H + C 2 O 4 2- ··· (C) 2H + + 2e - → H 2 ··· (D) Fe 2+ + C ₂ O ₄ ^2- → FeC ₂ O ₄ (E) This iron oxalate film is thermally decomposed into iron oxide as shown in formula (F) upon contact with a high-temperature rolled steel material. Iron oxide prevents metal contact between the rolled steel material and the roll.

FeC ₂ O ₄ → FeO + CO ₂ + CO (F) Next, the formation of the calcium oxalate film is based on the reaction of the following equation (G).

C ₂ O ₄ ²⁻ + Ca ²⁺ → CaC ₂ O ₄ (G) During hot rolling of steel, the above calcium oxalate is almost
As described above, calcium carbonate is formed by contact with a steel material to be rolled at a high temperature of 800 ° C. or more and effectively acts as a solid lubricant.

CaC ₂ O ₄ → CaCO ₃ + CO (H) The CO generated as described above is rapidly changed to CO ₂ as shown in the formula (I) by being exposed to the high-temperature steel material to be rolled.

_{2CO → C + CO 2 ··· (} I) It should be noted, for example, in the cooling water of the roll, Na ⁺ introduced from oxalates and calcium ^{compounds, K +, Mg 2-, Cl} - ions, such as may be contained, The formation of the desired oxalate coating is not compromised.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing formation of an oxalate film on a roll surface.

FIG. 2 shows the “ring-disk system” used in the first embodiment.
FIG. 3 is a diagram showing friction test conditions according to the present invention.

FIG. 3 shows the “ring-disk system” used in the first embodiment.
FIG. 6 is a diagram showing a friction characteristic evaluation method according to the first embodiment.

FIG. 4A is a view showing a result of a friction test in Example 1 in which a test piece corresponding to a roll was not subjected to a coating treatment, and a friction characteristic evaluation result was obtained. FIG. 4 (b) is a view showing the frictional property evaluation results in the present invention in which a test piece corresponding to a roll was formed with an iron oxalate film as an oxalate film in the friction test of Example 1.

FIG. 5 is a diagram illustrating a friction characteristic evaluation method using the “disk-disk method” used in the second embodiment.

FIG. 6 shows the “disk-disk method” used in the second embodiment.
FIG. 3 is a diagram showing friction test conditions according to the present invention.

FIG. 7 shows the third, fourth, fifth and sixth embodiments.
It is a figure which shows the friction test conditions by the "cylinder-block system" used in FIG.

FIG. 8 is a view showing the “cylinder −” used in Examples 3 and 6.
It is a figure which shows the friction characteristic evaluation method by "block method."

FIG. 9A is a diagram showing a frictional property evaluation result in the case where a coating treatment was not applied to a test piece corresponding to a roll in the friction test of Example 3. FIG. 9 (b) is a view showing the frictional property evaluation results in the present invention in which a calcium oxalate film was formed as a oxalate film on a test piece corresponding to a roll in the friction test of Example 3.

FIG. 10 is a diagram showing a friction characteristic evaluation method by the “cylinder-block method” used in Example 4.

FIG. 11 (a) is a view showing a result of a friction test in Example 4 in which a test piece corresponding to a roll was not subjected to coating treatment. FIG. 11 (b) is a diagram showing a friction test result of the present invention in which a test piece corresponding to a roll was formed with a film in which iron oxalate and calcium oxalate were mixed as an oxalate film in a friction test of Example 4. It is.

FIG. 12 is a view showing a friction characteristic evaluation method by the “cylinder-block method” used in Example 5.

FIG. 13 (a) is a view showing a result of a friction test in Example 5 in which a test piece corresponding to a roll was not subjected to coating treatment, FIG. 13 (b) is a view showing the results of the friction test of the present invention in which, in the friction test of Example 5, a test piece corresponding to a roll was formed with an iron oxalate coating as an oxalate coating.

FIG. 14 (a) is a view showing a friction test result of the friction test of Example 6 in the case where a test piece corresponding to a roll was not subjected to coating treatment. FIG. 14 (b) is a view showing the results of friction characteristics evaluation in the present invention in which a calcium oxalate film was formed as a oxalate film on a test piece corresponding to a roll in the friction test of Example 6.

FIG. 15 is a diagram showing a supply state of cooling water to a roll portion forming a flange during a line test using an actual machine.

FIG. 16 is a diagram showing conditions of a line test using an actual device.

FIG. 17 is a diagram showing a product shape rolled in an actual machine test.

FIG. 18 is another diagram showing the state of supply of cooling water to the roll portion forming the flange during the line test using the actual machine.

FIG. 19 is a diagram showing another condition of the line test using the actual machine.

BEST MODE FOR CARRYING OUT THE INVENTION In order to form an oxalate film in a short time at least on a contact surface of a roll surface with a rolled steel material, the concentration of an aqueous oxalic acid solution, the concentration of an aqueous solution containing an oxalate soluble in water, The concentration of the aqueous solution containing the calcium compound soluble in water, the processing temperature of each of the above solutions, the amount of the solution, and the material of the roll for hot rolling may be defined as follows.

(1) Concentration of oxalic acid aqueous solution The concentration of the oxalic acid aqueous solution need not be particularly limited. However, in order to form the desired coating in a short time, it is preferable that the concentration containing oxalic acid (C ₂ H ₂ O ₄₎ in 1 liter of water per 10 to 100 g.

(2) Treatment temperature of the aqueous oxalic acid solution on the roll surface The temperature of the treatment (for example, spraying) of the aqueous oxalic acid solution on the roll surface for forming an oxalate film is not particularly limited. However, in order to form a film in a short time, the above-mentioned processing temperature is preferably set to 20 to 90 ° C.

(3) Amount of oxalic acid aqueous solution In order to form a desired oxalate film in a short time, it is preferable to treat the roll with the following amount of oxalic acid aqueous solution.

For the process of coating or spraying an aqueous oxalic acid solution on the roll surface, the roll surface area 1 m ² per above (1)
Oxalic acid aqueous solution at a rate of 1 liter or more per minute at the processing temperature of (2) above,
Apply.

When immersing the roll in oxalic acid aqueous solution, the roll surface area is 1m
² per 1 liter or more of the concentration of (1) above
Immerse in an aqueous solution of oxalic acid at 0-90 ° C.

(4) Aqueous solution containing oxalate soluble in water The oxalate soluble in water is not particularly limited. For example,
Alkali metal oxalate or ammonium oxalate may be used.
Further, the concentration of the aqueous solution containing oxalate soluble in water is not particularly limited. However, in order to form a desired film in a short time, the concentration of the aqueous solution is preferably a concentration containing 10 to 100 g of oxalate soluble in water per liter of water as described above.

(5) Treatment temperature of aqueous solution containing oxalate soluble in water on roll surface An aqueous solution containing oxalate soluble in water and an aqueous solution containing a calcium compound soluble in water are reacted on the roll surface. A film of calcium oxalate is formed. The temperature of the treatment (for example, spraying) of an aqueous solution containing a water-soluble oxalate on the roll surface for forming the above-mentioned film is not particularly limited. However, in order to form a desired film in a short time, the above-mentioned processing temperature is preferably set to 20 to 90 ° C.

(6) Amount of aqueous solution containing oxalate soluble in water In order to form a desired oxalate film in a short time, an aqueous solution having the above-mentioned concentration (4) is used per 1 m ² of the roll surface area, It is preferable to treat the roll surface at a rate of 1 liter or more per minute under the treatment temperature of 5).

(7) Aqueous solution containing calcium compound soluble in water The calcium compound soluble in water is not particularly limited.
For example, chlorides and nitrates may be used. In addition, the aqueous solution containing a calcium compound soluble in water is "at least 20%".
An aqueous solution containing calcium ions of not less than ppm may be used, and the concentration is not particularly limited. But,
In order to form a desired film in a short time, the concentration of the aqueous solution is 10 to 100 g per 1 liter of water.
Preferred concentrations are included.

(8) a treatment temperature of a roll surface of an aqueous solution containing a calcium compound soluble in water; an aqueous solution containing a calcium compound soluble in water;
Oxalic acid or an aqueous solution containing oxalate soluble in water is reacted on the roll surface to form a calcium oxalate coating. The temperature of the treatment (for example, spraying) of the aqueous solution containing the water-soluble calcium compound on the roll surface for forming the above-mentioned coating film is not particularly limited. However, in order to form a desired film in a short time, the above-mentioned processing temperature is preferably set to 20 to 90 ° C.

(9) Amount of aqueous solution containing calcium compound soluble in water In order to form a desired oxalate film in a short time, an aqueous solution having the above-mentioned (7) concentration per 1 m ² of the roll surface area is used. It is preferable to treat the roll surface at a rate of 1 liter or more per minute under the treatment temperature of 8).

By setting the conditions (1) to (9) above, the iron oxalate film of the oxalate film and the calcium oxalate film of the calcium oxalate having a particle size of about 0.3 to 20 μm can be formed in a short time. The thickness can be 80 to 100 μm with the grains. The more preferable thickness of the iron oxalate coating is 15 to 20 μm.
It is. The more preferred particle size of the calcium oxalate particles is 0.
3 to 5 μm.

(10) Roll material The material of the roll is not particularly limited as long as it is an iron-based material.
However, in order to form a desired film in a short time, it is preferable that the material of the roll contains 70% or more by weight of Fe. For example, an adamite cast steel, a ductile cast iron, a high-alloy grain cast iron, a high chromium cast iron, a high-speed steel, or the like may be used as a roll material.

If the above conditions (1) to (10) are satisfied, of the desired oxalate film, the iron oxalate film requires a processing time of 1 second to 60 minutes, and the calcium oxalate film has an extremely short processing time of 1 second or less. Is formed.

It is more desirable to add sodium thiosulfate or the like as a reaction accelerator to the aqueous oxalic acid solution in order to further shorten the formation time and increase the film thickness of the oxalate film, especially the iron oxalate film.

The method for hot rolling steel according to the present invention is as described in the above (1) to (1).
(3) and (10) can be appropriately defined, and can be carried out by hot rolling a steel material using a roll immersed in an oxalic acid aqueous solution or a roll sprayed or coated with an oxalic acid aqueous solution. Further, the method for hot rolling steel according to the present invention provides the above-mentioned (1) to (10) appropriately, wherein an aqueous solution containing oxalic acid or water-soluble oxalate in at least a part of the roll cooling water, It can also be carried out by hot rolling a steel material while using an aqueous solution containing a soluble calcium compound and spraying the aqueous solution onto the roll surface during hot rolling from a nozzle of another system. According to this hot rolling method, seizure between the roll and the rolled steel material, abrasion of the roll, and roughening of the roll and the rolled steel material can be prevented.

The roll for hot rolling a steel material according to the present invention is as described in (1) above.
(3) and (10) can be easily obtained by appropriately defining and immersing the roll in an aqueous oxalic acid solution, or spraying or applying an aqueous oxalic acid solution to the roll. Further, the roll for hot rolling of a steel material according to the present invention defines the above (1) to (10) as appropriate, and includes an aqueous solution containing oxalic acid or water-soluble oxalate as a roll cooling water, and a water-soluble oxalate. An aqueous solution containing a calcium compound can also be easily obtained by injecting these aqueous solutions from a different type of nozzle onto the roll surface.

(Examples) Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

(Example 1) Various roll materials for hot rolling composed of an iron base were treated with an aqueous oxalic acid solution to investigate the state of formation of an iron oxalate coating. That is, the surface of a test piece cut out of adamite cast steel, ductile cast iron, and high-alloy grain cast iron is polished with a de-greased state after finish machining or with an # 80 to # 180 emery paper after finish machining. And then degreased, add oxalic acid (C ₂ H ₂ O ₄ ) at a rate of 30
The substrate was immersed in an aqueous solution of oxalic acid heated to 80 ° C. containing g for 10 minutes. In this case, the surface area of the test piece 1 m ²
The solution volume per unit was 10 liters.

Thereafter, the iron oxalate film formed on the surface of each test piece was observed with a scanning electron microscope and an optical microscope, and the thickness of the iron oxalate film was measured with an electromagnetic film thickness meter.

As a result, the surface portion of each test piece excluding the carbide was covered with dense crystals of iron oxalate (FeC ₂ O ₄ ) having a length of about 5 to 10 μm. The thickness of the iron oxalate coating formed on the surface of the test piece was 15 to 20 μm.

Next, the friction characteristics of the iron oxalate coating were evaluated by the method shown in FIG. 3 under the conditions shown in FIG. Here, FIG. 3 shows a test piece 1 corresponding to a roll (a material made of adamite cast steel) as a ring, and a test piece 2 corresponding to a rolled steel material (a material SU).
While rotating the disc of S304), the test temperature (800
C.), and presses the ring of the test piece 1 against the disk of the test piece 2 with a load P (980 N). This test makes it possible to evaluate the seizure resistance of the coating.

In order to ensure the accuracy of the evaluation results of the friction characteristics of the film formed on the roll surface, in a test corresponding to the method of the present invention, the friction surface (surface) of the test piece 1 was polished with # 180 emery paper. Then, a degreasing treatment was performed, and then an iron oxalate film was formed on the surface by the treatment described above, and a test was performed. Further, in the test of the comparative method corresponding to the conventional rolling method, the friction surface (surface) of the test piece 1 was adjusted only by degreasing after polishing with # 180 emery paper, and the iron oxalate film was formed. Used something not.

Here, the “slip ratio” under the test conditions in FIG.
When v ₁ and v ₂ are the peripheral velocities of the test pieces 1 and ₂ , respectively, the slip ratio (%) is defined as 100 (v ₂ −v ₁ ) / v ₂ .

FIGS. 4A and 4B show the results of a friction test performed under the above conditions. FIG. 4A shows the test results of the comparative method when the coating treatment was not applied to the test piece 1 corresponding to the roll. On the other hand, FIG. 4 (b) shows the evaluation results of the friction characteristics in the test of the method of the present invention in which a film of iron oxalate was formed as the oxalate film on the test piece 1.

In the case of the comparative method (FIG. 4 (a)), severe seizure occurs immediately after the start of friction, whereas in the case of the method of the present invention in which a film of iron oxalate is formed on the surface of the test piece (FIG. 4 (b)). Thus, it is clear that the occurrence of seizure is suppressed.

(Example 2) In order to evaluate the friction characteristics of the coating film in a state close to actual rolling, a test piece 2 corresponding to a steel material to be rolled was used in the method shown in FIG.
After rotating to the test temperature (800 ° C) with a high frequency induction heating device (only the heating coil 3 is shown) while rotating (disk shape, material is SUS304), the test piece 1 corresponding to a roll
A friction test was performed by a “disk-disk method” of pressing a disk (high-speed steel material). Also in this test, the test piece 1 was polished on its surface with # 180 emery paper and then degreased in order to approach the rolling conditions in an actual machine, and then subjected to the test.

In the test corresponding to the method of the present invention, an oxalic acid aqueous solution having a oxalic acid (C ₂ H ₂ O ₄ ) concentration of 50 g per liter of water was used as the cooling water (roll cooling water) 4 of the test piece 1 corresponding to a roll. . On the other hand, tap water was used as the cooling water 4 in the test of the comparative method corresponding to the conventional rolling method. In each case, just before the test piece 1 and the test piece 2 rubbed, the cooling water 4 was supplied at a rate of 0.1 liter per minute.

FIG. 6 shows the conditions of the above friction test. The “slip ratio” under the test conditions in FIG. 6 is also the same as the test condition in FIG. 2, where v ₁ and v ₂ are the peripheral speeds of the test pieces 1 and ₂ , respectively, and the slip ratio (%) = 100 ( v ₂ −v ₁ ) / v ₂ .

As a result of the friction test performed under the above conditions, as in the case of Example 1, in the case of the test of the comparative method, streaks that appear to be seizing immediately after the start of friction frequently appear on the friction surface, and as the friction time elapses, The situation got worse.

On the other hand, when the aqueous oxalic acid solution corresponding to the method of the present invention was used for the cooling water, the occurrence of streak flaws observed in the test of the comparative method was not observed. In this case, the thickness of the oxalate (iron oxalate) film formed on the surface is considered to be very thin, but no seizure is observed on the friction surface. Therefore, it is considered that a film of iron oxalate was formed between the test pieces 1 and 2, and the presence of this film prevented seizure.

(Example 3) In the same manner as in Example 2 described above, in order to evaluate the frictional characteristics of the coating film in a state close to actual rolling, an investigation was carried out under the conditions of FIG. That is, a test piece 2 (block-shaped, material is SUS304) corresponding to the steel material to be rolled is heated to a test temperature (800 ° C.) by a high-frequency induction heating device (only the heating coil 3 is shown) and then rolled with a load P (980 N). So-called "cylinder-", which is pressed against a test piece 1 (cylindrical, made of adamite cast steel, and rotating at 10 rpm)
A friction test was performed using the "block method".

Incidentally, "slip ratio" in the test conditions of FIG. 7, v _1,
v ₂ When were respectively the peripheral speed of the test pieces 1 and 2, the slip rate _{(%) = 100 (v 1} -v 2) are as defined and / v _1.

By the way, the shape of the test piece 1 in the third embodiment is called “cylindrical”, and the test pieces 2 in the above-described first embodiment and the test pieces 1 and 2 in the second embodiment having the same shape.
Is referred to as "disc-shaped" only according to a common name of a friction test method.

In this test, the surface of the test piece 1 corresponding to the roll made of adamite cast steel was polished with # 180 emery paper after finish machining, then degreased, and then subjected to the test.

In the test corresponding to the method of the present invention, 50 g of oxalic acid (C ₂ H
An oxalic acid aqueous solution having a concentration of ₂ O ₄ ) and an aqueous solution containing 50 g of calcium chloride per liter of water are supplied from nozzles 5a and 5b of different systems, respectively, and simultaneously before the test piece 1 and the test piece 2 rub. The same portion (position) was sprayed at a rate of 0.05 liter / min.

On the other hand, tap water was used as the cooling water 4 in the test of the comparative method corresponding to the conventional rolling method.
Immediately before friction, 0.1 liter per minute was injected from the nozzle 5a.

FIGS. 9A and 9B show the results of a friction test performed under the above conditions. FIG. 9A shows the test result of the comparative method when the coating was not applied to the test piece 1 corresponding to the roll. On the other hand, FIG. 9B shows the evaluation results of the friction characteristics in the test of the method of the present invention in which a calcium oxalate film was formed as the oxalate film on the test piece 1.

In the case of the comparative method (FIG. 9A), severe seizure occurred immediately after the start of friction, whereas in the case of the method of the present invention in which a calcium oxalate film was formed on the surface of the test piece (FIG. 9A).
In (b)), it is clear that the occurrence of image sticking can be prevented.

(Example 4) Under the conditions shown in Fig. 7, a friction test was performed by the "cylinder-block method" shown in Fig. 10. The test method and conditions were the same as in Example 3 except that the cooling water 4 was supplied to the test piece 1 corresponding to the following roll.

In a test corresponding to the method of the present invention, 50 g of oxalic acid (C ₂ H ₂ O ₄ ) aqueous solution of oxalic acid (C ₂ H ₂ O ₄ ) per liter of water was sprayed from the nozzle 5 a at a rate of 0.05 liter per minute as cooling water 4 of the test piece 1. Then, an aqueous solution containing 50 g of calcium chloride per liter of water was sprayed at a rate of 0.05 liter per minute from a nozzle 5b of a different system from the nozzle 5a. According to this cooling method, it is possible to first form an iron oxalate coating on the surface of the test piece 1 and then form a calcium oxalate coating.

On the other hand, tap water was used as the cooling water 4 in the case of the test of the comparative method corresponding to the conventional rolling method, and an amount of 0.1 liter per minute was injected from the nozzle 5b.

FIGS. 11A and 11B show the results of a friction test performed under the above conditions. FIG. 11 (a) shows the test results of the comparative method when the coating treatment was not applied to the test piece 1 corresponding to the roll. On the other hand, FIG. 11 (b) shows the evaluation results of the friction characteristics in the test of the method of the present invention in which the iron oxalate coating was formed on the surface of the test piece 1 and the calcium oxalate coating was also formed.

In the case of the comparative method (FIG. 11 (a)), severe seizure occurs immediately after the start of friction, whereas in the case of the method of the present invention in which a film in which iron oxalate and calcium oxalate are mixed is formed on the test piece surface ( In FIG. 11B, it is clear that the occurrence of image sticking can be prevented.

(Example 5) Under the conditions shown in Fig. 7, a friction test was performed by the "cylinder-block method" shown in Fig. 12. The test method and conditions were the same as those in Examples 3 and 4 except that the cooling water 4 was supplied to the test piece 1 corresponding to the following roll.

In a test corresponding to the method of the present invention, 50 g of oxalic acid (C ₂ H ₂ O ₄ ) aqueous solution of oxalic acid (C ₂ H ₂ O ₄ ) per liter of water was sprayed from the nozzle 5 a at a rate of 0.1 liter per minute as cooling water 4 of the test piece 1. . On the other hand, tap water was used as the cooling water 4 in the case of the test of the comparative method corresponding to the conventional rolling method, and an amount of 0.1 liter / min was injected from the nozzle 5a.

FIGS. 13A and 13B show the results of a friction test performed under the above conditions. FIG. 13 (a) shows the test results of the comparative method when the coating treatment was not applied to the test piece 1 corresponding to the roll. On the other hand, FIG. 13 (b) shows the evaluation results of the friction characteristics in the test of the method of the present invention in which an iron oxalate coating was formed on the surface of the test piece 1.

In the case of the comparative method (FIG. 13 (a)), severe seizure occurred immediately after the start of friction, whereas in the case of the method of the present invention in which an iron oxalate film was formed on the surface of the test piece (FIG. 13 (b)). ,
It is clear that the time to seizure can be greatly extended.

(Example 6) Under the conditions shown in Fig. 7, a friction test was performed by the "cylinder-block method" shown in Fig. 8. The test method and conditions were the same as those in Examples 3 to 5 except that the cooling water 4 was supplied to the test piece 1 corresponding to the following roll.

In a test corresponding to the method of the present invention, an aqueous solution containing 50 g of potassium oxalate per liter of water and an aqueous solution containing 50 g of calcium chloride per liter of water were used as cooling water 4 for test piece 1 in separate systems. Nozzle 5a,
5b, and sprayed at the same rate (0.05 liter / minute) to the same site (position) immediately before the test piece 1 and the test piece 2 rub.

On the other hand, tap water was used as the cooling water 4 in the test of the comparative method corresponding to the conventional rolling method.
Immediately before friction, 0.1 liter per minute was injected from the nozzle 5a.

FIGS. 14A and 14B show the results of a friction test performed under the above conditions. FIG. 14 (a) shows the test results of the comparative method when the coating treatment was not applied to the test piece 1 corresponding to the roll. On the other hand, FIG. 14B shows the evaluation results of the friction characteristics in the test of the method of the present invention in which a calcium oxalate coating was formed on the surface of the test piece 1.

In the case of the comparative method (FIG. 14 (a)), severe seizure occurred immediately after the start of friction, whereas in the case of the method of the present invention in which a calcium oxalate film was formed on the surface of the test piece (FIG. 14).
In (b)), it is clear that seizure can be prevented.

The above is an example in which the seizure resistance when an oxalate film was formed on the surface of a test piece equivalent to a roll for hot rolling was evaluated on a laboratory scale. Next, an embodiment tested on a real machine line will be described.

(Example 7) In order to clarify the effect of the present invention, an iron oxalate film was formed on the surface of a hot rolling roll, and an actual machine test was performed by the rolling method of the present invention. Here, a finish rolling roll of a universal rolling mill used for manufacturing a section steel was selected as the target equipment. A pair of upper and lower horizontal rolls 6 and one left and right
The rolled steel material 8 is rolled by the pair of hard rolls 7. Rolls 6 and 7 made of a high-alloy glen cast iron which had been subjected to grind polishing after finishing the surface by lathing were used as test rolls. SUS304 was used as the steel material 8 to be rolled.

As shown in FIG. 15, the supply of the aqueous oxalic acid solution to the surfaces of the rolls 6 and 7 in the rolling method of the present invention is performed, as shown in FIG. An aqueous solution of oxalic acid having a concentration of oxalic acid (C ₂ H ₂ O ₄ ) was sprayed at a rate of 1 liter per minute using a nozzle. For comparison, a conventional method of rolling by spraying normal industrial water at a rate of 10 liters per minute to the above parts a to d was also performed. FIG. 16 shows the conditions of a line test using an actual machine. FIG. 17 shows the product shape.

As a result of the actual machine line test performed under the above conditions, in the case of the conventional rolling method, crescent-shaped scratches (seizure) occurred on the flange portion of the product from the first rolling start.
In addition, abrasion of the roll and roughening of the roll and the product were also observed. In contrast, in the rolling method of the present invention, the rate of occurrence of scratches was 10% or less.

Further, an actual machine line test was performed using carbon steel or low alloy steel as the rolled steel material 8 under the same conditions. as a result,
In the rolling method of the present invention, generation of scratches was not recognized for a total rolling amount of 100 tons.

(Example 8) On a surface of a hot rolling roll, a film in which iron oxalate and calcium oxalate were mixed was formed as an oxalate film, and an actual machine test by the rolling method of the present invention was performed. Also in the case of this actual machine test, a finish rolling roll of a universal rolling mill used for manufacturing a section steel was selected as a target facility.

The test roll and the steel to be rolled are the same as in the case of the seventh embodiment. That is, rolls 6 and 7 made of a high-alloy glen cast iron which had been subjected to grind polishing after finishing the surface by lathing, and a rolled steel material 8 of SUS304 were used.

The supply of the roll cooling water to the surfaces of the rolls 6 and 7 in the rolling method of the present invention was performed by the method shown in FIG. That is, 50 g of oxalic acid aqueous solution (C ₂ H ₂ O ₄ ) concentration per liter of water and an aqueous solution containing 50 g of calcium chloride per liter of water are applied to the roll portions a to d forming the flange. Were sprayed at a rate of 1 liter / minute using a nozzle of a different system immediately before rolling. Similarly, only the oxalic acid aqueous solution having the above concentration was sprayed at a rate of 1 liter per minute immediately before rolling to the roll portions e to h forming the flange.

According to this roll cooling method, a film in which iron oxalate and calcium oxalate are mixed can be formed as an oxalate film on the roll surface.

For comparison, a conventional rolling method in which ordinary industrial water is jetted at a rate of 10 liters per minute to the roll portions a to d forming a flange was also performed. FIG. 19 shows the conditions of a line test using an actual machine. The product shape is shown in Fig. 17.
This is shown in FIG.

As a result of the actual machine line test performed under the above conditions, in the case of the conventional rolling method, crescent-shaped scratches (seizure) occurred on the flange portion of the product from the first rolling start.
In addition, abrasion of the roll and roughening of the roll and the product were also observed.

On the other hand, in the rolling by the method of the present invention, generation of scratches was not recognized. Further, with respect to the total rolling amount of 100 tons, almost no abrasion of the roll was observed, and no roughening of the roll and the product was observed.

Furthermore, the same actual machine line test was performed using carbon steel or low alloy steel as the rolled steel material 8. As a result, in the rolling method of the present invention as well, scratches were not observed for a total rolling amount of 100 tons.

As shown in the above embodiment, according to the hot rolling method of the present invention, it is possible to prevent roll seizure during rolling of a section steel. Further, the wear of the roll can be suppressed, and the roughening of the roll and the rolled steel material can be prevented. In addition, it was confirmed that the above-described effect by the formation of the oxalate coating film was exhibited not only in the rolling of the H-section steel but also in the rolling of other sections. Further, the same effect was obtained in the case of hot rolling of steel bars, steel plates, steel strips, steel pipes, flat bars and wires.

In addition, it was confirmed that the same effect as in the case of “calcium” described above was obtained when “alkali earth metal” was another element such as “barium” or “strontium”.

INDUSTRIAL APPLICABILITY The use of the hot-rolling roll of the present invention can prevent seizure, abrasion, and rough skin that occur when hot-rolling a steel material. This roll can be obtained by an inexpensive and simple method.

Furthermore, for example, the roll is immersed in an aqueous oxalic acid solution before rolling, or the oxalic acid aqueous solution or water-soluble oxalate (for example, oxalate of an alkali metal or ammonium oxalate) is applied to the roll surface during rolling. An aqueous solution containing a calcium compound soluble in water and an aqueous solution containing a calcium compound soluble in water are subjected to hot rolling according to the present invention, such as rolling by online spraying under appropriate conditions. Seizures that occur during rolling of various types of steel materials can be prevented. For this reason, the surface properties of the rolled product are greatly improved.

Further, if hot rolling is performed by the method of the present invention, it is possible to greatly extend the roll life (time until roll change). For this reason, the economic effect of extending the roll life is very large. Further, since the frequency of the roll care is reduced, the work efficiency is improved. In addition, when lubricating oil is used, wastewater treatment equipment is required and a large investment is required. However, according to the present invention, there is a seizure prevention effect equal to or higher than that of oil, and there is a great merit that no wastewater treatment equipment is required. . Thus, the industrial effect of the present invention is remarkably large.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-165115 (JP, A) JP-A-58-202905 (JP, A) JP-B 63-41646 (JP, B2) JP-B 4- 4045 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) B21B 27/10 B21B 45/02 310

Claims (13)

(57) [Claims] A hot roll of steel material is immersed in an aqueous solution of oxalic acid, or an aqueous solution of oxalic acid is applied to or sprayed on a hot roll of steel material, so that at least the surface is in contact with the rolled steel material. Form a film of iron oxalate,
A hot rolling method for a steel material, wherein the steel material on which the iron oxalate film is formed is rolled using a hot rolling roll. 2. An oxalic acid aqueous solution is used for at least a part of cooling water of a hot rolling roll for steel material, and at least an area of contact of the surface of the hot rolling roll with the rolled steel material is coated with iron oxalate. Hot rolling method for rolling steel while forming. 3. An aqueous solution containing oxalic acid or a water-soluble oxalate, and an aqueous solution containing a water-soluble alkaline earth metal compound in at least a part of the cooling water of a hot rolling roll for steel material. A hot rolling method for a steel material, wherein the steel material is rolled while forming an oxalate film on at least the contact area of the surface of the roll for hot rolling of the steel material with the steel material to be rolled. 4. The hot rolling method for a steel material according to claim 3, wherein the oxalate constituting the coating is an oxalate of an alkaline earth metal. 5. The method for hot rolling steel according to claim 3, wherein the oxalate constituting the coating is a salt in which iron oxalate and oxalate of an alkaline earth metal are mixed. 6. The method for hot rolling steel according to claim 3, wherein the oxalate constituting the coating is calcium oxalate. 7. The method for hot rolling steel according to claim 3, wherein the oxalate constituting the coating is a salt in which iron oxalate and calcium oxalate are mixed. 8. A hot-rolling roll for a steel material having an oxalate film at least in a contact area of the surface with the steel material to be rolled. 9. The roll for hot rolling steel according to claim 8, wherein the oxalate constituting the coating is iron oxalate. 10. The roll for hot rolling steel according to claim 8, wherein the oxalate constituting the coating is an oxalate of an alkaline earth metal. 11. The roll for hot rolling steel according to claim 8, wherein the oxalate constituting the coating is a salt in which iron oxalate and oxalate of an alkaline earth metal are mixed. 12. The roll for hot rolling steel according to claim 8, wherein the oxalate constituting the coating is calcium oxalate. 13. The roll for hot rolling steel according to claim 8, wherein the oxalate constituting the coating is a salt in which iron oxalate and calcium oxalate are mixed.