JPH06234989A - Lubricant for hot rolling and method of supplying the lubricant - Google Patents

Abstract

(57) [Abstract] [Purpose] A solid lubricant with excellent wear resistance and seizure resistance is evenly dispersed in water that does not reduce the coefficient of friction, resulting in stable biting and running stability. While reducing the wear and seizure of rolling rolls and tools. A lubricant for hot rolling in which a powdered solid lubricant is mixed in a liquid prepared by mixing swelling mica having an average particle size of 20 μm or less with water at a concentration of 1% by weight or more and less than 10% by weight. . Adhesion efficiency can also be improved by mixing a resin therein at a concentration of 1% by weight or more and 10% by weight or less. Then, by starting the supply of the material before it is bitten into the rolling mill and ending the supply of the lubricant after the material is completely removed from the rolling mill, seizure flaws can be prevented over the entire length of the coil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to plastic working such as hot rolling and piercing of steel materials such as thin plate, thick plate, bar steel and steel pipe (normal steel, ultra low carbon steel, stainless steel, etc.). Related to the lubricant used when
In particular, the present invention relates to a lubricant for hot plastic working in which a powdery solid lubricant is mixed and a method for supplying the same.

[0002]

2. Description of the Related Art The purpose of using a lubricant when performing hot plastic working is mainly to prevent seizure that occurs on the friction surface between the working tool and the hot working steel material and to reduce wear of the working tool. That is. Abrasion is microscopic fracture of surface due to shearing force of friction interface (ablation, plowing, etc.)
Wear is reduced by forming a lubricating film even at the frictional interface even partially. Therefore, the hot plastic working lubricant is required to have a function of reducing the frictional shearing force acting on the surface of the material to be rubbed. Further, seizure has a great influence on the surface quality of the steel material, and therefore it is desired to be completely prevented. It is generally said that this seizure occurs when a hot working steel material is plastically worked and a new surface generated due to an increase in surface area contacts a working tool to cause metal adhesion. Also, in the case of metals that are difficult to oxidize, such as stainless steel, the scale layer on the surface is thin, so the scale layer is removed even with light load machining where a new surface does not occur, and the base metal and processing tool cause metal adhesion and seizure. Leading to. Therefore, a lubricant for hot plastic working is also required to have a function of preventing contact between the newly formed surface or the base material and the working tool.

Conventionally, as a lubricant for hot plastic working used for such purposes, a liquid lubricant prepared by mixing one or more kinds of mineral oil, synthetic ester, extreme pressure additive, and the like, and
Grease and the like are known (Toshio Sakurai, "Physical Chemistry of Lubrication", JP-A-63-309590, etc.). However, since the hot plastic working process is exposed to a high temperature for a long time, it is difficult to exhibit a sufficient lubricating effect over the entire friction interface with the mineral oil, synthetic ester, etc., which is burnt or deteriorated in the friction surface. is there. As a lubricant for hot plastic working that can withstand such harsh environments,
Liquid lubricants and greases such as mineral oils and synthetic esters mixed with powdered solid lubricants such as graphite, silicate, BN, iron oxide and molybdenum disulfide may be used. It has become (Japanese Patent Laid-Open No. 63-23
0796, JP-A-63-254195).
In addition to liquid lubricants and greases, hot lubricants in which a solid inorganic lubricant such as graphite is mixed with a molten inorganic compound such as silicate are also known (JP-A-55-161897).

On the other hand, since the hot plastic working process is often not continuous, it is necessary to maintain a stable biting property between the working tool and the worked steel material for stable production. Further, when rolling a shaped steel or the like, if the coefficient of friction is not maintained to some extent, there may be a large variation in product dimensions. Therefore, it is preferable to perform processing while maintaining the friction coefficient at the time of biting and the friction coefficient at the friction interface as high as possible. That is, the lubricant used for hot plastic working must have a high coefficient of friction to some extent. If the above-mentioned liquid lubricant is directly sprayed on the friction surface or the processing tool, the friction coefficient will decrease and stable production will not be possible.Therefore, use the water injection method of supply and dilute it with water to reduce the friction coefficient. It is trying to exert the function of minimizing wear and seizure of machining tools. Since grease cannot be diluted with water, a solid lubricant having a high friction coefficient in the hot plastic working temperature range used is mixed to prevent the friction coefficient from decreasing. Since a lubricant obtained by mixing a solid lubricant into silicate is almost in a fluid lubrication state, the friction coefficient is increased by increasing the viscous resistance of glass.

Further, as a slip suppressing method from the viewpoint of a method of supplying a lubricant for hot rolling, by starting the supply of the lubricant after the material has been bitten, the friction coefficient at the time of biting can be reduced. Non-lubrication of the roll surface by making the friction coefficient of lubrication state to prevent slipping, stopping the supply of lubricant before the material comes out of the rolling mill, and burning the lubricant adhering to the roll surface with the heat of the material After rolling, the material is rolled so that slip does not occur when the next material is bitten.

[0006]

However, in the above-mentioned conventional liquid lubricants of mineral oil and synthetic ester or liquid lubricants in which solid powder is mixed with them, in order to prevent the reduction of the friction coefficient, a low concentration is used. Since it is diluted to be supplied to the friction surface, sufficient wear resistance and seizure resistance cannot be obtained. Further, if the concentration is increased in order to obtain a sufficient wear resistance effect and seizure resistance effect, the friction coefficient decreases and it cannot be used.

On the other hand, in order to suppress the reduction of the friction coefficient, water is used instead of mineral oil or synthetic ester, and a powdery solid lubricant having excellent wear resistance and seizure resistance is added to the lubricant. However, since the powdered solid lubricant is not uniformly dispersed in water, it cannot be used in a stable production process. In addition, if a surfactant such as a resin is added to enhance the dispersibility of such powder,
The surfactant acts to reduce the coefficient of friction, eliminating the advantage of using water. A lubricant obtained by mixing a silicate with a solid lubricant exerts a sufficient lubricating effect, but the lubricant adheres to the product and remarkably deteriorates the surface quality of the product.

On the other hand, when a lubricant such as mineral oil, ester or grease which has been conventionally used is used, in order to prevent bite slip, the supply of the lubricant is started after the bite and the material is removed from the rolling mill. The supply of the lubricant was stopped before the lubricant on the roll surface was burned out. Therefore, the rolling is performed in a non-lubricated state immediately after biting, and seizure easily occurs at this time. When seizure occurs at the coil top, the material rolled after that also has many defects due to seizure (roll surface roughness), and the surface quality becomes extremely poor.

In order to eliminate the above-mentioned drawbacks, the present invention uses water in place of the mineral oil or synthetic ester conventionally used as a dispersion medium in order to suppress the decrease in the friction coefficient, and the interface between resins and the like. The present invention provides a lubricant that can uniformly mix and disperse solid powder (solid lubricant) having excellent wear resistance and seizure resistance without using an activator. It is also intended to provide a method of supplying a lubricant, which completely prevents seizure flaws that occur when the rolling material is bitten and slips out, which was difficult by the method.

[0010]

MEANS FOR SOLVING THE PROBLEMS AND ACTION THEREOF The present invention relates to a powdery form in a liquid obtained by mixing swelling mica having an average particle size of 20 μm or less with water at a concentration of 1% by weight or more and 10% by weight or less. It is a hot rolling lubricant in which the solid lubricant of Further, when the lubricant of the present invention is sprayed onto the working tool and supplied to the friction surface, a hot rolling lubricant to which an adhesive resin is added can be used, if necessary. Further, when the lubricant for hot rolling of the present invention is supplied during rolling, it is supplied to the roll or the friction interface before the biting of the rolled material and the supply of the lubricant is stopped after the material is removed.

When organic lubricants such as mineral oil, synthetic ester and grease which have been conventionally used are used, the friction coefficient is inevitably lower than that in the case of no lubrication or water lubrication.
The present inventors considered using water, which does not cause a reduction in the friction coefficient, instead of the conventionally used mineral oil, synthetic ester, and grease. Naturally, it is clear that water is much less lubricative than mineral oils, synthetic esters, greases and the like. Therefore, focusing on powdered solid lubricants that have been used in recent years as a mixture with mineral oils, synthetic esters, greases, etc., secure and maintain the friction coefficient necessary for stable processing with water. However, it was considered that the solid lubricant exerts lubricating performance (antiwear effect, anti-seizure effect, etc.). However, aside from grease having high viscosity and excellent dispersibility of solid lubricant, if powdered solid lubricant is mixed in water having a larger surface tension than mineral oil or synthetic ester, the solid lubricant has a specific gravity. In most cases, most of them float or settle in water and cannot be uniformly dispersed in water. Also, in order to disperse the powdered solid lubricant in mineral oil or synthetic ester, it is possible to add a kind of surfactant to improve the compatibility with mineral oil or synthetic ester, In order to disperse the solid lubricant, it is difficult to freely disperse many solid lubricants having excellent lubricating performance in the world with conventional resin-based surfactants. Therefore, the present inventors have dispersed other fine particles in water in order to uniformly disperse and hold the solid lubricant in water, and use these fine particles to cause the buoyancy and sedimentation force of the solid lubricant. As a result of searching for one that is uniformly dispersed as fine particles in water, it was found that a swelling mica powder is suitable.

Conventionally, mica is well known as one of the lubricating substances (Japanese Patent Publication No. 54-116566 and Japanese Patent Publication No. 55-71795). However, the present invention does not use mica as a lubricant as conventionally known, but uses fine particles of mica as a surfactant to provide excellent wear resistance or seizure resistance. It is characterized in that it is used to uniformly disperse a solid lubricant having a. Therefore, the present invention is completely different in concept from the conventionally known mica-based lubricant. At the same time, by using water that does not reduce the friction coefficient, it is a lubricant that exhibits an anti-wear effect and an anti-seizure effect while securing the interfacial friction force (friction coefficient) necessary for stable processing. Since the hot rolling lubricant of the present invention does not use the resin-based surfactant that has been used in the conventional water-based lubricant, it does not cause a reduction in the friction coefficient.

This effect is exhibited by mixing swelling mica with water in a certain ratio. When swelling mica is mixed with water, it becomes fine particles and is uniformly dispersed in water. However, this characteristic greatly differs depending on the particle size of the mica powder, and when the average particle size exceeds 20 μm, the mica when added to water does not progress into fine particles and the mica powder precipitates without being uniformly dispersed in water. When mica powder having an average particle size of 20 μm or less is dispersed in water, the mica powder is made into fine particles,
Disperse evenly in water to form a mica solution. When a solid lubricant with excellent wear resistance and seizure resistance is mixed into this uniformly dispersed mica solution, the mica powder dispersed in the form of fine particles will increase the buoyancy and gravity (settling force) of the solid lubricant. Supports and prevents sedimentation, aggregation, and floating of solid lubricants. However, this effect depends on the concentration of the mica solution, and if the amount of mica added when making the mica solution is less than 1 wt% with respect to water, it will support the buoyancy and sedimentation force of the solid lubricant added to the mica solution. I can't. Further, when the amount of mica added when making a mica solution exceeds 10 wt% in terms of weight% with respect to water, thixotropic properties are exhibited, making it difficult to use as a lubricant.

On the other hand, in many cases, the method of using the lubricant used in the hot working is roughly classified into two methods, that is, supplying to the friction interface and supplying to the working tool. this house,
When supplying the lubricant to the working tool, the adhesion between the working tool and the lubricant becomes a problem. If the adhesion between the processing tool and the lubricant is poor, it is difficult to smoothly supply the lubricant to the frictional interface by the processing tool. Therefore, the lubricant (in the present invention, the lubricant was mixed with the mica water dispersion liquid) was used. Solid lubricant) It is difficult to fully exhibit the original performance (wear resistance and seizure resistance). However, an adhesive resin can be added to the hot rolling lubricant prepared by mixing the mica water dispersion of the present invention with a solid lubricant to enhance the adhesiveness. Adhesive resins used at this time include styrene / ethylene / butadiene block copolymers, polyethylene / polymethylmethacrylate block copolymers, maleic anhydride grafted polypropylene, styrene / maleic anhydride copolymers, ethylene /
It is selected from glycidyl methacrylate copolymer, methyl cellulose, cellulose, starch, thermosetting resin and the like, and among them, those having water solubility are preferable. The addition of the adhesive resin should not impair the excellent lubricating properties of the solid lubricant already mixed. The above-mentioned resin ensures the adhesiveness with the working tool without impairing the performance of the solid lubricant. Moreover, since the swelling mica is dispersed, the adhesiveness can be secured without lowering the friction coefficient unlike the conventional resin-based surfactant mixed with the water-based lubricant. .

However, the amount of the adhesive resin added is 10
If it exceeds wt%, the fluidity of the lubricant deteriorates due to the adhesive resin, making it difficult to use in engineering. If the amount of the adhesive resin added is less than 1 wt%,
Adhesion to the processing tool is insufficient.

The solid powder (solid lubricant) mixed with the lubricant for hot rolling of the present invention is a conventionally known graphite, molybdenum disulfide, tungsten disulfide, boron oxide, magnetite, potassium phosphate, swelling property. Inorganic compounds such as mica, calcium carbonate, sodium carbonate and the like, polyethylene, polypropylene, polystyrene, polyester, polyacetal, polycarbonate, polyamide, polyphenylene oxide, polysulfone, polyarylate, polyphenylene sulfide, ABS resin, ethylene-4fluoride Examples thereof include ethylene copolymers, diallyl phthalate resins, phenolic resins, organic compounds such as chitosan and polyethylene glycol.

The present invention does not cause a reduction in the coefficient of friction,
The present invention provides a lubricant capable of stably supplying a solid lubricant having excellent wear resistance and seizure resistance. Therefore, if the purpose of using the lubricant is to reduce the wear of machining tools,
When using a solid lubricant with excellent wear resistance (for example, graphite or molybdenum disulfide) to prevent seizure of the material and tool, a solid lubricant with excellent seizure resistance (for example, Graphite or boron oxide) may be mixed.
That is, the solid lubricant to be mixed may be appropriately selected according to the purpose.

Furthermore, since the lubricant for hot rolling of the present invention has a high friction coefficient as described above, it does not cause bite slip even if it is supplied before biting. The timing of starting the supply of the lubricant of the present invention may be such that there is a time margin for the roll to make one rotation before the material is bitten, and in consideration of the rotation speed of the roll in the hot rolling process of the steel material. The feed should be started almost immediately before the material is bitten. The supply of the lubricant may be stopped at any time after the material is removed.

[0019]

【Example】

(Example 1) The effect of the particle size and addition amount of mica powder on the uniform dispersibility of mica powder and the dispersibility of a solid lubricant was investigated. As the mica powder, one having swelling property is used,
Graphite was used as the solid lubricant to investigate the dispersibility. Then, the uniform dispersibility of the mica and the dispersion retention of the solid lubricant at the particle size and the addition amount shown in Table 1 were investigated. The results at that time are also shown in Table 1.

[0020]

[Table 1]

In Table 1, the added amount of mica powder (wt%)
Is based on the total amount of water and mica powder, and the solid lubricant is
5 wt% based on the total amount of water, mica powder and solid lubricant
% Added. Further, in Table 1, in each item of uniform dispersibility in water and dispersion retention of the solid lubricant, ○, △,
Regarding x, when the mica powder or the mica powder and the solid lubricant are mixed in water and sufficiently stirred, and the solution is allowed to stand as it is, ○ means that separation or precipitation does not occur even if left standing for 24 hours, and On the other hand, mica powder, etc. shows a uniform mixed state, △ shows a nearly uniform mixed state although there are some shades in the liquid after standing for 24 hours, × indicates before 24 hours It means that completely precipitates.

Example 2 The effect of the addition of resin on the adhesion to a processing tool was investigated. The swelling mica used had an average particle size of 6 μm and was added to water so that the concentration was 8 wt% (water + mica 2100) based on the total amount of water and mica. Graphite as a solid lubricant was added thereto in an amount of 4 wt% based on the total amount of water, mica and graphite. Adhesive resin (epoxy acrylate) was added to the lubricant prepared in this way in an amount of 3 wt% based on the total amount of water, mica, graphite and adhesive resin. I investigated if there was a difference. As a method of examining the adhesion, the above-mentioned lubricant is sprayed on the vertical surface of SKD61 in parallel with the ground using the same spray for 10 seconds, and it is sufficiently dried by a dryer, and then SK
The adhesiveness was evaluated by measuring the weight of the lubricant remaining in D61. As a result, it was found that the amount of the adhesive agent resin added was 4.2 times as much as the amount of the remaining lubricant agent, and the adhesiveness was excellent, as compared with the case where the resin was not added. Also, when the amount of the adhesive resin added is changed to 0.4 wt%, 4 wt%, and 10 wt%, only when the amount is 0.4 wt%,
There was almost no difference in the amount of adhesion with that without resin.

(Example 3) The friction coefficient and the wear amount of the lubricant of the present invention were investigated using a two-cylinder type hot rolling sliding friction tester. The test piece has an outer diameter of 80 mm and a thickness of 1
It was 0 mm. The mating piece has an outer diameter of 165 mm and a thickness of 15
It was mm. SKD61 was used for the test piece, and S45C was used for the mating piece. Then, the mating piece was heated to 850 ° C. and the test piece was heated to 500 ° C., the test piece speed was 500 rpm, and the speed difference between the mating piece and the test piece was 10% of the speed of the test piece.
While spraying the lubricant, a load of 70 kgf was applied to cause friction, and the torque and wear amount of the test piece were measured. For lubricant,
A mica solution was prepared by mixing mica having an average particle size of 8 μm with water at a concentration of 7 wt%, and graphite (a typical solid lubricant) and aluminum oxide (generally solid lubricant (Those not considered) and three types without solid lubricant were used. As a result, the coefficient of friction is
Almost no change was found in any lubricant, which was about 10% lower than that in the case of water lubrication. For the amount of wear, see Fig. 1.
As shown in, the lubricant of the present invention has a small amount of wear and can exhibit the performance of a solid lubricant.

(Example 4) Using a 2Hi laboratory rolling mill, a conventional mineral oil type lubricating oil (0.5% emulsion) was used.
And (lubricant A), the graphite and KPO ₃ grease, graphite and KPO ₃ of the total amount grease lubricant were mixed in 10 wt% based on the (B), and the swelling mica powder having an average particle size of 10μm in water, water And a lubricant (C) in which 5 wt% of graphite powder is mixed in water, 5 wt% of the total amount of mica and graphite in an aqueous solution mixed with 5 wt% of the total amount of mica, and four lubrication conditions of water lubrication. The critical rolling reduction was measured. The material used is 10 mm thick, 150 mm wide, 250 mm long plain steel,
After heating and holding at 1000 ° C. for 15 minutes in a heating furnace, it was bitten into a rolling mill. The roll diameter, roll material, roll rotation speed, and roll roughness were all constant.
As a result, under the water lubrication condition, the rolling reduction was possible up to about 50%. When the rolling reduction was higher than this, rolling could not be performed because the load capacity of the rolling mill was insufficient. On the other hand,
The lubricant A did not bite at a rolling reduction of about 20%, and the lubricant B did not bite at a rolling reduction of about 15%. However, the lubricant C could bite to about 50% and perform normal rolling.

(Example 5) Rough rolling machine (roll diameter: 780 mm, cylinder length 1700 mm) in the hot rolling process for thin plates
Viscosity of 130 cS from the entrance side of 4Hi rolling mill
t of the lubricating oil containing a mineral oil-based ester additive was supplied as a 0.5% emulsion (lubricant D), the case of supplying the lubricant C used in Example 4, and the case of water lubrication, The biting condition of the material was investigated. The supply of lubricant is
Two types of feeding methods were performed, one before feeding and the other immediately after biting. As a result, when an attempt was made to roll at a rolling reduction of 30% set in the normal pass schedule, bite slip did not occur with any lubricant when it was supplied immediately after bite, but it was supplied before biting. When the start was started, the lubricant D caused a bite slip and rolling could not be performed, but the lubricant C did not cause a bite slip and normal rolling could be performed.

[0026]

EFFECTS OF THE INVENTION By using the lubricant of the present invention, it is possible to reduce wear and seizure between a working tool and a hot-worked steel material, and to reduce product defects caused thereby, as compared with a conventional lubricant. . Since this lubricant has a low viscosity, it can be supplied by a water injection type lubrication supply device that is widely used in hot working processes at present, so the equipment must be modified when using the lubricant. The effect of the present invention can be easily obtained at low cost without the need.

[Brief description of drawings]

FIG. 1 is a graph showing the results of comparison of wear resistance (wear amount) of lubricants in a two-cylinder hot rolling sliding friction tester according to Example 3.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C10M 103: 02 Z 9159-4H 103: 06 F 9159-4H 107: 32 103: 06) D 9159- 4H C10N 20:06 Z 8217-4H 30:04 8217-4H 30:06 30:08 40:24 Z 8217-4H (72) Inventor Kiyoshi Nishida 20-1 Shintomi, Futtsu, Chiba Shin Nippon Steel Co., Ltd. (72) Inventor Tsutomu Sugiura 20-1 Shintomi, Futtsu City, Chiba Nippon Steel Co., Ltd. Technology Development Headquarters

Claims (3)

[Claims] 1. A lubricant used in a hot plastic working process of a steel material, wherein swelling mica having an average particle size of 20 μm or less is used in an amount of 1% by weight or more and less than 10% by weight based on the total amount of the mica and water. Lubricant for hot rolling, which is obtained by mixing powdery solid lubricant into liquid mixed with water at the concentration of. 2. The hot rolling lubricant according to claim 1, wherein the adhesive resin is 1 based on the total amount of the water, mica and the adhesive resin.
A lubricant for hot rolling, which is mixed in a concentration of not less than 10% by weight and not more than 10% by weight. 3. The lubricant for hot rolling according to claim 1 or 2 is supplied to a roll or a friction interface before biting of a rolled material, and the supply of the lubricant is stopped after the material comes off. And a method for supplying a lubricant for hot rolling.