JP2898524B2 - Hot lubrication rolling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubrication method for hot rolling steel materials (such as ordinary steel, ultra-low carbon steel, and stainless steel) such as thin plates, thick plates, and bar steels. TECHNICAL FIELD The present invention relates to a hot lubricating rolling method for supplying and rolling a lubricant containing, as a main component, a liquid obtained by mixing mica having water with water.

[0002]

2. Description of the Related Art The purpose of using a lubricant during hot rolling is mainly to prevent seizure occurring on a friction surface between a working tool and a hot-worked steel material, and to cause wear and roughening of the working tool. It is to reduce surface damage. Conventionally, as a hot rolling lubricant used for such a purpose, a liquid lubricant obtained by mixing one or more of mineral oil, a synthetic ester, an extreme pressure additive, and the like, a grease, and the like are known ( Supervised by Toshio Sakurai, "Physical Chemistry of Lubrication", JP 6
No. 3-309590). However, in the hot rolling process, the mineral oil,
In the case of a synthetic ester or the like, it is difficult to exhibit a sufficient lubricating effect over the entire friction interface because it disappears or deteriorates in the friction surface.

[0003] As lubricants for hot rolling that can withstand such harsh environments, liquid lubricants such as the above-mentioned mineral oils and synthetic esters, greases and the like, include graphite, silicates, BN, iron oxide, A mixture of a powdery solid lubricant such as molybdenum sulfide has been used (JP-A-63-230796, JP-A-63-230796).
-254195). In addition to liquid lubricants and greases, hot lubricants obtained by mixing a solid lubricant such as graphite with a molten inorganic compound such as a silicate (Japanese Patent Publication No. 55-161897) are also known.

When such a liquid lubricant is directly sprayed onto a friction surface or a working tool, the friction coefficient is reduced, and troubles such as biting slip and rolling slip occur.
Because stable production is not possible, use the water injection method of supply, dilute in water and use
The goal is to minimize the decrease in the coefficient of friction and to prevent wear and seizure of the working tool. Since grease cannot be diluted with water, it is used by mixing a solid lubricant that increases the friction coefficient in the hot rolling temperature range to be used so as not to lower the friction coefficient. Since a lubricant obtained by mixing a solid lubricant in silicate is almost in a state of fluid lubrication, the friction coefficient is increased by increasing the viscous resistance of the glass. As a water-based lubricant, a liquid (hereinafter referred to as a swelled mica aqueous solution) obtained by mixing swellable mica powder (hereinafter referred to as a swelled mica powder) with water is known (Japanese Patent Application Laid-Open No. 54-1979). 116566, JP-A-55-71795).

[0005] On the other hand, such a method for supplying a lubricant includes a method called water injection, in which oil is mixed with water, and a method called steam atomization, in which oil is mixed with steam and supplied. A method used when supplying a highly viscous lubricant (such as grease) called an air atomizing method has been put to practical use. In these systems, all lubricants are supplied to a work roll and a backup roll.

[0006]

However, a lubricant containing a swelled mica aqueous solution as a main component is inferior in adhesion to a roll material as compared with a conventional oil or grease-based lubricant. Therefore, in the conventional method of supplying a lubricant (a method of spraying a roll onto a rolling roll), a sufficient amount of swelled mica powder is supplied to a friction interface to fully exhibit the performance of a lubricant containing a swelled mica aqueous solution as a main component. Is difficult to do. In addition, even in the supply method in which the material is directly sprayed on the friction interface between the roll and the material, since the viscosity of water and the adhesive force with the material are smaller than that of oil,
It is difficult to supply the fluid to the friction interface due to the fluid drawing effect, and the fluid stays at the entrance of the friction interface or flows down from the end of the plate, and a sufficient lubrication effect cannot be obtained.

An object of the present invention is to provide a hot lubricating rolling method capable of reliably supplying a lubricant mainly composed of a liquid obtained by mixing such swellable mica with water to a friction interface. It is the purpose.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a hot rolling process for steel material, which has an average grain size of 20 μm.
A lubricant mainly composed of a liquid in which mica having the following swelling property is mixed with water at a concentration of 1% by weight or more and less than 10% by weight or a lubricant obtained by further mixing a solid lubricant with the lubricant is used for a rolling roll. It is characterized in that it is supplied to the material surface and rolled before biting.

The swelled mica powder of the present invention is uniformly dispersed when mixed with water to form an aqueous solution. Using this swelled mica aqueous solution as a lubricant, we investigated the anti-wear effect and friction coefficient of the roll material, and despite the fact that the friction coefficient was almost the same as that of water lubrication, the anti-wear effect was also high. It has been found that it has a performance equivalent to that of the conventional mineral lubricating oil.

However, when the average particle size of the swelling mica powder exceeds 20 μm, the swelling mica powder precipitates without being uniformly dispersed in water. When a swollen mica powder having an average particle size of 20 μm or less is mixed with water, a uniform swollen mica aqueous solution is formed. Therefore, uniform supply to the material surface becomes possible. When a solid lubricant with excellent abrasion resistance and seizure resistance is mixed into this uniformly dispersed aqueous swelling mica solution, the dispersed mica powder will cause the buoyancy and gravity (settling force) of the solid lubricant to be dispersed.
To prevent sedimentation, aggregation and floating of the solid lubricant.
However, this effect depends on the concentration of the aqueous swelling mica solution, and when the amount of the swelling mica powder added is 1% by weight or less with respect to water when preparing the aqueous swelling mica solution, the buoyancy and settling of the solid lubricant added to the mica solution are reduced. I cannot support my power. On the other hand, when the amount of the swelled mica powder added to the aqueous swelled mica solution exceeds 10% by weight relative to water, the swelled mica powder exhibits thixotropy and becomes poor in fluidity, making it difficult to use it as a lubricant. Further, even with the above-mentioned lubricant in which a solid lubricant having a small friction coefficient is mixed with the swelled mica aqueous solution, the friction coefficient is almost equal to that of water lubrication, and the effect of preventing the roll material from being worn is further improved.

Now, since a lubricant containing a swelled mica aqueous solution as a main component has a high friction coefficient, unlike a conventional mineral oil-based lubricating oil, it can be directly supplied as a lubricant without being diluted with water. However, since the viscosity of the lubricant mainly composed of the swollen mica aqueous solution is small, it is impossible to expect the effect of introducing the lubricant to the friction interface by the hydrodynamic pull-in effect as in the conventional lubricating oil. In addition, since the adhesive force to the roll is small, it easily flows out from the roll surface or the vicinity of the friction interface together with the roll cooling water. For this reason, it has been difficult to efficiently supply the necessary amount of the aqueous swelling mica to the friction interface in order to sufficiently exhibit the excellent lubricating performance. Therefore, as a result of examining a method of efficiently supplying the swelled mica powder, the lubricant of the present invention is supplied to the surface of the material before the rolling roll bites, so that the swelled mica powder and the solid lubricant that is mixed are efficiently supplied. Can be introduced into the friction interface.

Since the swelled mica powder is an inorganic compound, it has better heat resistance than conventional mineral oil-based or ester-based lubricating oils, and depends stably without decomposition even at a high temperature of 1200 ° C. or higher. Therefore, even if the lubricant of the present invention is supplied, the material surface before hot working does not burn out or decompose before rolling, and the swelled mica powder can be stably present. . In addition, since this lubricant has a high coefficient of friction, even if water contained in the lubricant evaporates and its concentration becomes high, a rolling accident such as slip does not occur. In addition, the surface of the material has a greater surface roughness than the surface of the roll material, and the lubricant described in the claims is easily trapped in subtle depressions on the surface, so that even if the adhesive force is small, it is introduced into the friction interface. The amount of the lubricant is much larger than when the lubricant is supplied to the roll material surface, and the effect of the lubricant can be sufficiently obtained.

Since the lubricant has no effect of adhering to the material due to a chemical reaction, the location of the lubricant containing the aqueous swelling mica solution as a main component, the amount of the lubricant supplied, and the amount of time between the supply and the rolling. There is no need to limit the time required. If at least the material is supplied to the surface of the material before the rolling roll bites, the object effect of the present invention can be obtained. However, there is a preferable supply place depending on the process to which the present invention is applied. Then, since the lubricant supplied by the descaling is deleted together with the scale, it is better to supply the lubricant before the roll biting in the rough rolling mill. In the reversible rolling mill,
It is preferable to supply the lubricant during the main pass rolling after the completion of the pre-pass rolling. Therefore, even if the lubricant is supplied at the outlet side of the pre-pass rolling, the effect of the present invention can be obtained.

The solid lubricant to be mixed with the lubricant mainly composed of the swelled mica aqueous solution has excellent wear resistance and excellent seizure resistance according to the purpose of supplying lubrication. What is necessary is just to select suitably. Commonly used solid lubricants for hot rolling lubrication include graphite, molybdenum disulfide, tungsten disulfide, boron oxide, magnetite, potassium phosphate, non-swellable mica, calcium carbonate, sodium carbonate, etc. Inorganic compounds, polyethylene, polypropylene, polysretin, polyester,
Polyacetal, polycarbonate, polyamide, polyphenylene oxide, polysulfone, polyallerate,
Polyphenylene sulfide, ABS resin, ethylene-4
Fluorinated ethylene copolymer, diallyl phthalate resin,
Organic compounds such as phenolic resins, chitosan, and polyethylene glycol are known. Even if one or more of these solid lubricants are used in combination, the effect of the present invention is not lost.

The total amount of the solid lubricant is preferably not more than 30% by weight based on the total amount of the lubricant.
If more than 30% by weight of a solid lubricant is added, the fluidity of the lubricant is lost, making it difficult to supply the lubricant smoothly. Preferably, the total amount of the solid lubricant is 3 wt% to 15 wt%. Further, the solid lubricant to be added is one having a cleavage property such as graphite and one having a melting property such as KPO ₃ or a polymer. It is preferable to mix and add the types.

[0016]

【Example】

(Example 1) Using a two-cylinder hot rolling sliding friction tester (FIG. 1) that simulates frictional wear between a rolling roll and a material, a test piece (a roll test piece and a roll test piece) made of a rolled rolled mica aqueous solution. The wear amount and the coefficient of friction of the roll test piece were investigated for the case where it was supplied to the surface of a roll test piece and the case where it was supplied to the surface of a counterpart piece (referred to as a material counterpart piece) made of a rolled material.

The size of the roll test piece is an outer diameter of φ80 and a thickness of 10 mm. The material counterpart has an outer diameter of 165 mm and a thickness of 15 mm. A high chromium cast iron roll material was used for the roll test piece, and S45C was used for the material counterpart. Then, the material mating piece was heated to 850 ° C., and the roll test piece was heated to 300 ° C. immediately before the friction surface entry side, and the speed of the roll test piece was increased to 50 ° C.
0 rpm (125.6 m / min), the speed difference between the material counterpart and the roll test piece was set to 10% of the speed of the roll test piece, and the load was 70 kgf when rolling sliding friction was applied.
The torque and the amount of wear of the roll test piece were measured.

As the lubricant, a swelled mica aqueous solution (lubricant A) obtained by mixing swelled mica powder having an average particle diameter of 8 μm with water at a concentration of 7 wt%, and graphite powder having an average particle diameter of 5 μm as a solid lubricant in the lubricant A (Lubricant B) mixed with 10% by weight of the lubricant A, and water. When the lubricant is supplied to the roll test piece, the lubrication nozzle A shown in FIG.
Therefore, when supplying the lubricant to the material counterpart, these lubricants were supplied from the lubrication nozzle B shown in FIG. The supply of the lubricant was started 5 seconds before the start of the friction.

As a result, the coefficient of friction has almost no difference between the case where the lubricant is supplied to the surface of the roll test piece and the case where the lubricant is supplied to the surface of the counterpart material. Met. However,
The amount of abrasion is considerably smaller for the lubricant A and the lubricant B than for the water lubrication level, and is smaller when supplied to the surface of the material mating piece than when supplied to the surface of the roll test piece. The abrasion loss of the roll test piece was reduced to about 1/2. In the case of water lubrication, there was almost no difference in the amount of abrasion when supplied to either the surface of the roll test piece or the surface of the material mating piece. Further, when a solid lubricant is mixed with an aqueous solution containing swelling mica (lubricant A) (lubricant B), compared with a case where no solid lubricant is added (lubricant A), 20% or more.
The effect of reducing the amount of wear by about 30% was obtained (FIG. 2).

(Example 2) Using a 2Hi hot rolling mill, when the lubricant of the present invention was supplied to a material and when it was supplied to a roll, roughening and seizure of the roll surface after rolling occurred. The situation was compared. The roll used is a high chrome cast iron roll material having a roll diameter of 270 mm and a body length of 200 mm.
The rolled material is SUS430, width 100mm, thickness 10
It is a cutting board of 400 mm in length and 400 mm in length. Before rolling, the material was held in a heating furnace in a nitrogen atmosphere at 1200 ° C. for 30 minutes, and then taken out. After the material temperature was cooled to 1000 ° C. regardless of whether a lubricant was supplied to the material, rolling was performed.
The rolling conditions were a rolling reduction of 30% and a roll speed of 20 m / min. Then, after rolling, it was observed whether or not seizure or rough surface occurred on the surface of the roll. Example 1 was used for the lubricant.
The lubricant A, the lubricant B and the water described in the above were used. 3 seconds before lubricating the material into the rolls of the rolling mill,
Before 1 second, 30 seconds, 1 minute, 5 minutes, 10 minutes, and 30 minutes, 1 cc / cm ² · sec per unit area and unit time was supplied to the surface of the material or roll by spraying.

As a result, the advance rate measured by the roll mark method is almost the same when the lubricant is supplied to the roll surface or when the lubricant is supplied to the material surface, and is almost the same as in the case of water lubrication. Was. However, the condition of wear and seizure damage on the roll surface is minimal when lubricants A and B are supplied to the material surface, whereas when lubricants A and B are supplied to the roll, water lubrication is performed. The same degree of seizure and generation of fine cracks were observed. In addition, it was found that when the lubricant B was supplied to the surface of the material, the amount of seizure was slightly smaller than when the lubricant A was supplied, and the seizure resistance was improved by adding the solid lubricant. The same characteristics as described above were obtained when the lubricant was supplied at any time before the rolling roll biting.

[0022]

According to the present invention, it is possible to more effectively bring out the excellent lubricating properties of a lubricant containing a swelling mica aqueous solution as a main component, and to reduce troubles in various hot rolling processes. Lubrication rolling can be performed without causing a certain slip accident. In addition, it is possible to supply a large amount of a solid lubricant excellent in wear resistance and seizure resistance mixed with a lubricant containing a swelling mica aqueous solution as a main component to a friction interface more than before, so that abrasion and rolling of a rolling roll are reduced. It is possible to greatly reduce the seizure of the steel material and the flaws of the product generated thereby. Thereby, the roll change cycle can be greatly extended, and the productivity is greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a hot rolling wear tester that simulates frictional wear between a rolling roll and a material.

FIG. 2 shows a swelled mica aqueous solution (lubricant A), a lubricant (lubricant B) obtained by mixing a swelled mica aqueous solution with graphite powder, and water (water lubrication) supplied to a roll material and to a material piece. FIG. 6 is a diagram comparing the amounts of wear of roll materials at the time.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10N 20:06 40:24 (72) Inventor Kiyoshi Nishida 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Japan Nippon Steel Corporation Advanced Technology Research (56) References JP-A-6-234989 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B21B 27/10 B21B 45/02 C10M 173/02 C10M 103: 06 C10N 20:06 C10N 40:24

Claims (2)

(57) [Claims] In a hot rolling process for a steel material,
1% by weight of swelling mica having an average particle size of 20 μm or less
A hot lubricating rolling method characterized in that a lubricant mainly composed of a liquid mixed with water at a concentration of less than 10% by weight is supplied to the material surface and rolled before the rolling roll bites. 2. The hot lubricating rolling method according to claim 1, wherein a solid lubricant is mixed with a lubricant containing a liquid as a main component.