JP2009242726A - Lubricant for cold rolling and cold rolling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain improvement of a consumption unit compared with that of emulsion rolling oil when a solution type lubricant is circularly used as a coolant in a cold rolling process, by securing its lubricity equal to or above that of the emulsion rolling oil, even in the case of the solution type lubricant. <P>SOLUTION: Solid grains with the average grain size of 0.01 to 0.5 μm are contained in water-soluble polyalkylene glycol. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solution type cold rolling lubricant having a lubricity equivalent to or higher than that of a conventional emulsion type lubricant in cold rolling, and a cold rolling method using the same.

  In cold rolling of a metal plate such as a steel plate, an emulsion rolling oil that can be diluted with water by adding a surfactant to mineral oil, natural fat, synthetic ester, etc., which is a base oil of a water-insoluble oil agent. It is used as a lubricant. This emulsion rolling oil is an oil-in-water type (O / W type) in which a water-insoluble oil agent is contained at a concentration of about 1 to 5%, and has both lubricating performance and cooling performance.

This emulsion rolling oil is mixed with water in advance and stirred to form an emulsion having an average particle size of about 5 to 15 μm, and is supplied from a rolling oil tank to a steel plate or a roll bite. At this time, in order to reduce the amount of rolling oil used and the amount of waste liquid treated, emulsion rolling oil is usually used in a circulating manner, which is called a circulating oil supply system.
When emulsion rolling oil is spray-supplied to a steel plate or a roll bite, an oil film is formed while water is removed on the steel plate or at the roll bite inlet, and the oil film thus formed improves the lubricity in the roll bite. . That is, the thicker the oil film introduced into the roll bite, the better the lubricity, and even a hard metal plate can be rolled under high pressure.

  On the other hand, in terms of operation, it is important not only to have good lubricity but also to reduce the amount of rolling oil used (unit consumption) in order to reduce costs. When emulsion rolling oil is used, the main factors that deteriorate the basic unit of rolling oil include filter loss, scum out, fume loss, and carry-out by steel plate.

  First, regarding filter loss, wear powder generated by cold rolling is taken into the emulsion, and when the wear powder is separated by a filter provided in the oil supply circulation path, oil droplets in the emulsion are also captured by the filter. It is because it ends up.

The scum-out is a loss of oil caused by the occurrence of scum, which is a mixture with deteriorated rolling oil, because wear powder and the like are embraced in the emulsion oil during the cold rolling operation.
Fume loss means that when using natural fats and oils with a high pour point, the temperature of the entire coolant is heated to around 50-60 ° C and circulated, and the resulting fumes contain oil. This is a loss that occurs.
Moreover, since the steel plate after rolling is wound up as a coil with the oil component attached, the steel plate after rolling is due to the oil component taken out from the circulation system by the steel plate.

  Therefore, in order to improve the basic unit of emulsion rolling oil, it is necessary to eliminate these causes, and measures such as selection of base oil type and viscosity, optimization of surfactant type and addition amount, etc. It has been.

Further, the coil after the cold rolling is usually subjected to a cleaning step prior to annealing as the next step. In this cleaning process, alkaline electrolytic degreasing is often used, and the more oil that adheres to the steel sheet, the lower the cleaning performance. Therefore, the basic unit of the alkaline liquid and the cost for maintaining the temperature are low. It is also a cause of raising costs.
As described above, emulsion rolling oil is required to reduce costs including the basic unit of rolling oil while maintaining good lubricity and cooling performance.

  On the other hand, the rolling lubricant used when rolling a softened metal sheet under light pressure, such as temper rolling, does not require excellent lubricity. Conversely, in order to obtain a stable elongation, a friction coefficient Is required to be expensive. The lubricant used for wet temper rolling is a solution type that is made of a water-soluble material, does not form micelles in water, and is in a dissolved state.

  Solution-type lubricants do not form large oil droplets like emulsions because the lubricating components themselves are soluble in water. Therefore, it is very easy to separate the wear powder generated in the cold rolling and the wear powder from the lubricant, and the filter equipment can be simplified. Moreover, since wear powder is not embraced in the oil, the loss due to scum generation is extremely reduced. In addition, solution type lubricants can be used at room temperature, have low fume loss, excellent cleanability, very little lubricating components remain on the steel sheet after temper rolling, and carry-out loss due to the steel sheet Can be reduced.

  However, in cold rolling using a tandem rolling mill, reverse rolling mill, or the like, which uses a large rolling reduction, emulsion rolling oil that is still excellent in lubricity is still used. In the reduction zone, solution type lubricants with a high friction coefficient are used, and both are clearly used according to rolling conditions.

In addition, a solution type lubricant for performing high pressure with a reduction ratio of about 20% in temper rolling is disclosed in Patent Document 1. However, although this lubricant can be applied to 1-pass rolling of a softened steel sheet after annealing, it is suitable for severe rolling conditions that cause work hardening in multi-pass rolling such as tandem rolling and reverse rolling. Cannot obtain sufficient lubricity.
Thus, it is considered difficult to use solution type lubricants for cold rolling such as ordinary tandem rolling, and water-based lubricants in ordinary cold rolling are limited to emulsion rolling oils. This is the current situation.
JP 61-7395 A

  As described above, since the solution type lubricant exhibits solubility in water at room temperature, it does not cause wear powder to be embraced like emulsion rolling oil, and it does not cause deterioration of the rolling oil. No scum, which is a mixture, is generated. Further, even when a fine mesh filter is used, the filter loss can be reduced because separation from the wear powder is easy and the lubricating component is hardly trapped in the filter. In addition, if the coolant temperature can be lowered, fume loss can be reduced, and the amount of lubricant taken out by the steel sheet can be reduced due to excellent cleanability. There is an advantage of not having.

  On the other hand, solution type lubricants have poor lubricity in cold rolling, and are not applicable to cold rolling conditions that increase the total rolling reduction by multi-pass rolling. Was a problem.

  The present invention enables emulsion rolling when a solution type lubricant is circulated and used as a coolant in the cold rolling process by ensuring lubricity equivalent to or better than that of emulsion rolling oil even if it is a solution type lubricant. The objective is to achieve an increase in unit consumption compared to oil.

Now, in order to achieve the above object, the inventors have conducted intensive research on means for improving the lubricity of a solution type lubricant, and as a result, found that the addition of fine solid particles is effective, The present invention has been completed.
That is, the gist of the present invention is as follows.
(1) A cold rolling lubricant comprising a water-soluble polyalkylene glycol and solid particles having an average particle size of 0.01 to 0.5 μm.

(2) The cold rolling lubricant according to (1), wherein the solid particle content is 1 to 25% by mass.

(3) The cold rolling lubricant according to (1) or (2), wherein the water-soluble polyalkylene glycol has a molecular weight of 500 to 10,000.

(4) The cold rolling lubricant according to any one of (1) to (3), wherein a cloud point of a 1% by mass aqueous solution of the polyalkylene glycol is 30 to 80 ° C.

(5) The solid particles are one or more selected from graphite, molybdenum disulfide, silicon dioxide, titanium dioxide, silicon carbide, boron nitride, tungsten disulfide, nickel oxide, copper oxide and zirconium dioxide. The cold rolling lubricant according to any one of (1) to (4).

(6) Cold using a coolant obtained by mixing the cold rolling lubricant according to any one of (1) to (5) above in an amount of 0.5 to 20% by volume with respect to water. Rolling method.

  According to the present invention, the lubricating component can be made to contain fine solid particles, and the lubricity can be improved to the same level or more as that of the conventional emulsion rolling oil. In addition, since the solid particles that contribute to the improvement of lubricity are fine, they are not trapped by a filter or the like in the lubricant circulation system, and the lubricant component dissolves in water. Can be maintained.

Hereinafter, the lubricant of the present invention will be described in detail.
The lubricant of the present invention is applied to cold rolling of a metal strip. As the cold rolling mill, ordinary cold rolling mills including a tandem rolling mill and a reverse rolling mill are targeted. The material to be rolled is not particularly limited, but is mainly effective as a lubricant for cold rolling of thin steel plates. Of course, in addition to ferrous materials such as ordinary steel, high carbon steel and stainless steel, aluminum and copper You may apply to cold rolling of nonferrous metals, such as.

The lubricant of the present invention contains solid particles having an average particle size of 0.01 to 0.5 μm in water-soluble polyalkylene glycol. First, water-soluble polyalkylene glycol is used as the main component of the rolling lubricant. Preferably, polyalkylene glycol having a molecular weight of 500 to 10,000 is used.
Polyalkylene glycol is also called polyglycol, polyether, polyalkylene oxide, and is obtained by ring-opening polymerization of alkylene oxide (AO) such as ethylene oxide (EO) or propylene oxide (PO) to a substance having active hydrogen. It is a polymer. This is a synthetic lubricant, and by changing the polymerization degree, alkyl group, etc., it is possible to obtain a polymer having a wide range of characteristics from water-soluble ones having various viscosity grades to water-insoluble ones. It is a substance.

  In general, the polyalkylene glycol tends to increase in viscosity and increase in viscosity index as the molecular weight increases. In the present invention, it is preferable to use polyalkylene glycol having an average molecular weight of 500 to 10,000 when used for cold rolling. This is because the larger the molecular weight, the higher the viscosity and the better the adhesion to the metal band, so the average molecular weight is preferably 500 or more. On the other hand, if the molecular weight is too large, the pour point becomes high and the washing in the subsequent process may be hindered. Therefore, the average molecular weight is preferably 10,000 or less.

  Polyalkylene glycols include monool type, diol type, and triol type. By changing the degree of polymerization, alkyl group, etc., it is possible to design a molecule having characteristics according to the purpose. In general, PO homopolymers are water-insoluble and EO homopolymers are water-soluble. In EO / PO random copolymers, the higher the EO ratio, the higher the water solubility, and the solubility in water depends on the molecular design. Although adjustment is possible, water-soluble polyalkylene glycol is used in the present invention.

The polyalkylene glycol, which is the main component of the lubricant, dissolves in water, so that the lubricant is immediately separated from the wear powder during circulation of the coolant mixed with water, and the wear powder is removed from the coolant. It becomes extremely easy to remove, and the filter loss can be reduced.
Further, unlike emulsion rolling oil, the wear powder is not embraced in the oil, so that the loss due to scum generation is extremely small. Accordingly, it is not necessary to raise the temperature to cause the scum to flow, so that it can be used at room temperature, and fume loss can be reduced.

  Furthermore, since it is excellent in cleaning properties, there are very few lubricating components remaining on the metal band, and take-out loss due to the metal band can be reduced. Even when sprayed onto a rolling roll for cooling, it is excellent in cleanability, so that even if a lubricating component adheres to the roll surface, cooling can be performed while washing it off. Therefore, it is advantageous in that the cooling performance can be improved as compared with the emulsion rolling oil, and the metal foreign matter adhering to the rolling roll can be easily washed off from the surface by the excellent cleaning property, and the surface on the surface of the roll. It is hard to generate wrinkles.

  Furthermore, there is an advantage that the management of the lubricant is simplified in that it does not require the management of the emulsion stability as in the case of the emulsion rolling oil.

Next, it is important that the lubricant contains solid particles having an average particle size of 0.01 to 0.5 μm.
Now, although the aqueous solution of polyalkylene glycol itself is drawn into the roll bite during cold rolling and exhibits a fluid lubrication action, it is inferior to the lubrication action at the boundary contact portion between the work roll and the material to be rolled. The lubrication performance is poor. When solid particles with an average particle diameter of 0.01 to 0.5 μm are interposed here, the solid particles are drawn into the roll bite together with the polyalkylene glycol, thereby reducing the friction coefficient in the boundary contact region as a solid lubricant, and wear. And play a role in preventing surface damage.

  However, it is important to use those solid particles having an average particle size of 0.01 to 0.5 μm. More desirably, a film having a thickness of 0.01 to 0.1 μm is used. That is, since the film thickness of the lubricant in the roll bite in the cold rolling is in the range of 0.05 to 0.5 μm, if the average particle size of the solid particles exceeds 0.5 μm, the soft and easily deformable solid particles are excluded. This is because abrasive wear may occur in the roll bite, which may promote wear of the work roll. On the other hand, if the average particle size of the solid particles is less than 0.01 μm, the solid particles supplied to the roll bite as a lubricant are not easily drawn into the roll bite, and the effect as a solid lubricant component is diminished.

  Here, conventionally, the solid lubricant used in the rolling oil in hot rolling acts as a spacer that prevents direct contact between the work roll and the material to be rolled in the roll bite, thereby preventing seizure. The main effect is to prevent the occurrence, and thus relatively large solid particles are used. On the other hand, in the present invention, since the solid fine particles having the above average particle diameter are used, the flow of the oil film in the mixed lubrication state in the roll bite, that is, the fluid lubrication performance is not hindered. It can act directly on the contact portion to exert an effect as an extreme pressure agent, or can be adsorbed on the friction surface with high activity to prevent seizure or the like.

  The solid particles used in the present invention can be produced by a so-called nanoparticle production method. Typical methods for producing nanoparticles are a liquid phase method and a gas phase method. The liquid phase method includes a solution method such as a liquid phase reduction method, reverse micelle method, or a molten metal, in which a precipitant or water is added to a solution to cause a chemical reaction, and fine particles are generated by nucleation and growth of the generated substance. A spray pyrolysis method in which fine particles are produced by spraying and a melt method such as a plasma jet method can be applied. Further, a vapor phase method such as a CVD method or a PVD method using laser or plasma can be used. Furthermore, it has become possible to produce submicron to nano-sized ultrafine particles by a wet bead mill, which has been conventionally considered unsuitable for the production of ultrafine particles.

  The solid particles are preferably prepared as a cold rolling lubricant by mixing with a cold rolling lubricant content in the range of 1 to 25% by mass. That is, if the solid particle content is less than 1% by mass, sufficient boundary lubrication performance cannot be obtained. On the other hand, if the content exceeds 25% by mass, the viscosity of the entire lubricant increases, and in the lubricant. This is because the particles may not be sufficiently dispersed and agglomerates may be formed and deposited in the lubricant piping.

  Furthermore, if the content of polyalkylene glycol is less than 10% by mass, the fluid lubrication performance in cold rolling decreases, while if it exceeds 60% by mass, the consumption of lubricant increases and becomes uneconomical. A range of 60% by mass is preferred. Further, if necessary, the following various additives may be contained under an upper limit of 15% by mass.

  In addition to these components, a carboxylic acid or a salt thereof for improving lubricity may be appropriately added to the lubricant. Antioxidants, extreme pressure additives, rust inhibitors, and the like can also be added. As antioxidant, a phenolic antioxidant, an amine antioxidant, etc. can be used. As extreme pressure additives, chlorinated compounds such as chlorinated oils and fats, chlorinated fatty acid esters, synthetic sulfur compounds such as sulfurized oils and fats, alkyl polysulfides, phosphorus compounds, organometallic salt compounds, and the like can be used. As a water-soluble rust preventive, what added alkanolamine etc. as a basic substance to fatty acids, such as aliphatic monocarboxylic acid, can be used. Furthermore, you may use what added antiseptic | preservative and surfactant as needed.

  Moreover, as for the said polyalkylene glycol, it is desirable that the cloud point of the 1 mass% aqueous solution is 30-80 degreeC. The cloud point refers to the property that when the temperature of the solution is increased, the solubility rapidly decreases at a certain temperature and becomes white turbid. Here, when the temperature of the aqueous solution is changed, the cloud point is represented by the temperature at which white turbidity is visually confirmed. For example, FIG. 1 illustrates the difference between the appearance of an aqueous solution at a temperature lower than the cloud point and the appearance at a temperature higher than the cloud point for an aqueous solution having a cloud point of 40 ° C.

  The use of an aqueous solution of polyalkylene glycol having a cloud point as a cold rolling lubricant has the property that the characteristics as a coolant change between a temperature range below the cloud point and a temperature range above the cloud point. It is for use. Because, in the temperature range above the cloud point, the polyalkylene glycol has a cloudy appearance due to a decrease in the solubility of water in the water. This is because it is easy to separate and the adhesion to the surface of the metal strip is improved, and the fluid lubrication characteristics of the roll bite can be improved.

  That is, the cloud point of the aqueous solution of polyalkylene glycol was set to 30 to 80 ° C. When the cloud point is less than 30 ° C., the temperature at which the polyalkylene glycol dissolves in water is lowered, so that the entire coolant in the circulation system This is because the equipment cost of the heat exchanger for that purpose must be maintained at a lower temperature. On the other hand, when the cloud point exceeds 80 ° C., higher fluid lubrication performance cannot be exhibited unless the coolant itself is heated.

  Here, as the solid particles used, inorganic layered structure compounds such as molybdenum disulfide, tungsten disulfide, graphite and their intercalation compounds, graphite fluoride, natural mica, synthetic mica, and the like can be used. . In addition to silicon dioxide, titanium dioxide, silicon carbide, silicon nitride, etc. as ceramic particles, soft solid metals such as gold, silver, tin, copper, and metal oxides such as nickel oxide and copper oxide are used as metal solid particles. Zirconium dioxide may be used. As the organic material, polymer materials such as PTFE and polyimide, metal soap such as wax or lithium stearate, and the like can be used as solid particles. Furthermore, what is marketed as ultrafine particles, such as fullerene, a carbon nanotube, and a cluster diamond, may be used.

  The solid particles include, in particular, one or more selected from the group consisting of graphite, molybdenum disulfide, silicon dioxide, titanium dioxide, silicon carbide, boron nitride, tungsten disulfide, nickel oxide, copper oxide, and zirconium dioxide. It is desirable to use it. This is because it is conventionally considered that there is little adverse effect on the quality of the material to be rolled. Moreover, because graphite and molybdenum disulfide have a layered structure, the effect of reducing the friction coefficient can be obtained even at the boundary contact portion in the roll bite. On the other hand, silicon dioxide, titanium dioxide, silicon carbide, boron nitride, and tungsten disulfide are difficult to change even when used as ceramic particles as a cold rolling lubricant. Moreover, it is a hard particle | grain and has the characteristic which is hard to deteriorate. Furthermore, nickel oxide, copper oxide, and zirconium dioxide can be expected to have properties as extreme pressure agents under high surface pressure conditions.

  Note that graphite can be refined by applying an arc discharge method or a laser evaporation method to a particle having a particle size conventionally used. Molybdenum disulfide can be pulverized by using fine beads in a wet medium stirring mill. Titanium dioxide is commercially available as photocatalyst particles, and silicon dioxide is also commercially available as a fluorescent labeling reagent material. Further, these oxide ceramics can obtain fine particles of submicron or less by a pulverization method relatively easily like other ceramics such as silicon carbide, boron nitride and tungsten disulfide.

  It is preferable to circulate and use the cold rolling lubricant described above as a coolant by mixing 0.5 to 20% by volume with respect to water. This is because, as the cold rolling lubricant, the required lubricating performance differs depending on the type of rolling mill and the type of material to be rolled, and therefore it is desirable to use it at a concentration corresponding to it. In addition, when the concentration is less than 0.5% by volume, the lubrication performance necessary for cold rolling of the metal strip cannot be obtained, and when the concentration is 20% by volume or more, excessive lubrication occurs, and solid particles are sufficiently contained in the coolant. This is because they do not disperse and may agglomerate during recycling.

  When such a coolant is circulated, the polyalkylene glycol dissolves in water, and the solid particles are smaller than wear powder or other foreign matters generated during rolling, so that they are not captured by filters. . Therefore, filter loss such as emulsion rolling oil hardly occurs, and the occurrence of scum can be suppressed. In addition, as a filtering means at the time of circulation use, a filtering method of a commonly used format such as a Hoffman filter or an electromagnetic filter may be used.

Hereinafter, based on an Example, this invention is demonstrated more concretely.
In producing the lubricant according to the present invention, the polyalkylene glycol includes trade names “Adeka Pluronic L31” (hereinafter referred to as “polyalkylene glycol A”) and “Adeka Pluronic L72” (hereinafter referred to as “Adeka Pluronic L72”) manufactured by Asahi Denka Co., Ltd. , Referred to as “polyalkylene glycol B”). Polyalkylene glycol A has an average molecular weight of 1100, a cloud point of 40 ° C. at a concentration of 1% by mass, and a kinematic viscosity at 25 ° C. of 196 mm ² / s. Polyalkylene glycol B has an average molecular weight of 2850, a cloud point of 22 ° C. at a concentration of 1% by mass, and a kinematic viscosity at 25 ° C. of 461 mm ² / s.

Next, as the solid particles, those having an average particle diameter adjusted by a wet pulverization method using silicon dioxide and titanium dioxide were used.
Moreover, what contained caprylic acid which is a C8 linear fatty acid and triethanolamine as additives as a carboxylic acid and was diluted with water was prepared as a cold rolling lubricant.
The composition of the cold rolling lubricant is as shown in Table 1.
This cold rolling lubricant was diluted with water to a concentration of 3% by volume and used as a coolant.

  On the other hand, as Comparative Example 1, an emulsion rolling oil used for ordinary cold rolling was used. This is a cold rolling oil whose base oil is composed of 60% by mass of synthetic ester, 30% by mass of natural fats and oils, 5% by mass of higher fatty acids and 2% by mass of nonionic surfactants and 3% by mass of extreme pressure additives. It is. In Comparative Example 1, cold rolled oil was diluted with water to a concentration of 3% by volume and used as a coolant.

  Further, as another comparative example, as shown in Table 1, the solid particle size was changed from the above-described invention example, and was diluted in water to a concentration of 3% by volume as described above. Used as coolant.

Cold rolling was carried out under the conditions of a work roll diameter of 500 mmφ and a rolling speed of 1200 m / min using plain steel with a thickness of 1 mm as the material to be rolled, and the lubricating performance of the coolant with each lubricant was investigated.
FIG. 2 shows the rolling load during cold rolling. FIG. 2 shows that the rolling load according to the invention example is almost equal to or lower than that of Comparative Example 1 using the conventional emulsion rolling oil, and even if it is a solution type lubricant, the conventional emulsion It can be seen that the lubricating properties are equal to or higher than that of rolling oil. On the other hand, in Comparative Example 2, the size of the contained solid particles is too small and does not act effectively on the boundary contact portion in the roll bite. Furthermore, in Comparative Examples 3 and 4, since the size of the solid particles was too larger than the fluid film thickness in the roll bite, it is considered that the friction coefficient increased and the effect of reducing the load could not be obtained.

  Further, as a result of carrying out cold rolling while circulating and using the coolant for the inventive example and the comparative example 1, in the case of the comparative example 1, the wear powder is mixed in the circulating coolant, and the appearance of the coolant has been darkened. On the other hand, in the invention example, the abrasion powder was removed by the filter, but the solid particles were not captured by the filter, and the transparent appearance was maintained during circulation. Further, the amount of the lubricant component brought out by the filter was also greatly reduced, and the overall consumption of the lubricant was significantly reduced to about 1/3 or less in any of the inventive examples as compared with Comparative Example 1.

It is the photograph which illustrated the external appearance of the aqueous solution in the temperature lower than a cloud point, and the external appearance of the aqueous solution in the temperature higher than a cloud point. It is a graph which shows the rolling load at the time of using the coolant by each lubricant.

Claims (6)

  A cold rolling lubricant comprising a water-soluble polyalkylene glycol and solid particles having an average particle size of 0.01 to 0.5 µm.   The lubricant for cold rolling according to claim 1, wherein the solid particle content is 1 to 25 mass%.   The lubricant for cold rolling according to claim 1 or 2, wherein the water-soluble polyalkylene glycol has a molecular weight of 500 to 10,000.   The cold rolling lubricant according to any one of claims 1 to 3, wherein a cloud point of a 1 mass% aqueous solution of the polyalkylene glycol is 30 to 80 ° C.   2. The solid particles are one or more selected from graphite, molybdenum disulfide, silicon dioxide, titanium dioxide, silicon carbide, boron nitride, tungsten disulfide, nickel oxide, copper oxide and zirconium dioxide. 5. The cold rolling lubricant according to any one of 4 to 4.   A cold rolling method, wherein a coolant obtained by mixing the cold rolling lubricant according to any one of claims 1 to 5 in an amount of 0.5 to 20 vol% with respect to water is circulated.