| Title of Invention | "HOT-ROLLING OIL FOR ROLLING STEEL MATERIALS" |
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| Abstract | The present invention provides a hot-rolling oil for rolling a steel material, which can efficiently reduce the rolling load when rolling a steel material, while heating the material at a temperature ranging from 200 to 1200°C and which can reduce the rolling cost as well as a method for hot-rolling a steel material, which makes use of the foregoing hot-rolling oil. The hot-rolling oil for rolling a steel material comprises a base oil, and at least one polymer selected from the group consisting of isobutylene homopolymers and isobutylene copolymers, each having a number average molecular weight ranging from 8,000 to 100,000," and the method for hot-rolling a steel material is characterized in that the foregoing hot-rolling oil for rolling a steel material is supplied to a rolling machine according to the water-injection system. |
| Full Text | Hot-Rolling Oil for Rolling Steel Materials and Hot-Rolling Method of Steel Materials Technical Field [0001] The present invention relates to a hot-rolling oil for a steel material and a method for hot-rolling a steel material. More particularly, the present invention relates to a hot-rolling oil for a steel material, which can adjust the frictional coefficient between a roll and a steel material to be rolled to a level identical to or higher than that observed under oil-free condition to thus permit the reduction of rolling load, during the hot-rolling process of a steel material carried out while heating the steel material to a temperature ranging from 200 to 1200°C and a method for hot-rolling a steel material using the rolling oil. Background Art [0002] Recently, when a steel material such as a carbon steel, a stainless steel, a tool steel or a silicon steel is warm-rolled or hot-rolled, there has been used a lubricant for high temperature in order to prevent the occurrence of any roughening of the roll surface and a desired effect has thus been accomplished. As such lubricants, there have currently been used, for instance, solid lubricants, which can show their lubricating effect at a high temperature, such as graphite, glass, boron nitride, mica, molybdenum disulfide, iron oxide, fluorinated graphite and calcium carbonate,' extreme-pressure lubricants such as sulfurized fats and oils, sulfurized olefins, zinc dialkyl dithio-phosphate, and phosphoric acid esters! oihness-imp roving agents such as mineral oils, fats and oils, polymers of fats and oils, and synthetic esters! lubricants simultaneously serving as adhesion-improving agents and pour point-depressants such as methacrylate copolymers and butylene-butadiene copolymers, which may be used alone or in any combination of at least two of them and which may optionally be combined with an antioxidant such as di'tert-butyl cresol or a naphthy lamine. [0003] Such a lubricant for high temperature applications shows an effect of reducing the coefficient of friction between a rolling roll and a material to be rolled in the hot-rolling process of a steel material. The reduction of the friction coefficient between rolling rolls and a material to be rolled would permit the reduction of the rolling load and the reduction of the contact pressure between the rolls and the material, encountered when producing materials each having the same finished thickness in a rolling machine. This in turn results in the control of the increase in the surface-roughness of the material to be rolled and the rolls and the prevention of the occurrence of any partial roughening thereof to thus maintain the roll surface in its good conditions and accordingly, the resulting rolled steel material may have good surface quality. However, it would be quite difficult to effectively make the hot-rolling oil adhere onto the roll surface since the oil may be washed away therefrom by the action of cooling water intensively sprayed on the working rolls. [0004] To eliminate the influence of this cooling water, each of the working rolls is provided with a water-draining plate or a water-deflector. The water-deflector is brought into contact with the working roll along the longitudinal length of the roll body without leaving any space between them and it accordingly prevents any flowing of the roll-cooling water onto the surface of the roll which is sprayed with an emulsion of a rolling oil. More specifically, in the working roll-oil supply technique as a commonly used oil-supply method, the water film of cooling water formed on the roll surface must be removed by the action of a water-deflector in order to effectively adhere, to the roll surface, an emulsion of a rolling oil which is injected onto the working roll. However, it is quite difficult to make the water-deflector follow-up the working roll which is rotating at a high speed and this in turn leads to the formation of a space between the water-deflector and the working roll and the flow of the roll-cooling water on the working roll surface in the form of a water film. This accordingly results in the reduction of the amount of the rolling oil adhered to the roll surface and in its turn, any sufficient effect of reducing the rolling load cannot be accomplished. As an alternative method of injecting a hot-rolling oil, there has been known a method in which a hot-rolling oil is sprayed onto the surface of a backup roll, but this method is inferior to the method in which the oil is supplied onto the working roll in that the amount of the oil adhered to the roll surface is lower than that achieved by the working roll-oil supply method and that the effect of reducing the rolling load observed for this method is likewise lower than that observed for the latter method since the rolling oil adhered to the roll surface passes through the working roll surface and arrives at the interface between the roll and a material to be rolled. [0005] To solve this problem, there has been proposed a device for draining water from the rolls of a rolling machine (Patent Document 1 specified below), but the follow-up properties thereof with the roll rotating at a high speed is not clearly defined therein and the water-draining mechanism thereof is quite complicated. Therefore, this device is not practical. There have been known a method for hot-rolling a thick plate which is characterized by supplying a lubricant mainly comprising a highly basic metal sulfonate onto the surface of rolls (see Patent Document 2 specified below); a lubricant composition for use in roll-processing, which comprises a highly basic metal sulfonate, graphite, calcium carbonate and a sulfonic acid ester (see Patent Document 3 specified below); and a hot-rolling oil mainly comprising palm-olein oil and a hot-rolling method (see Patent Document 4 specified below), but all of these lubricants are still insufficient in the anti-seizing properties and the lubricating properties and, for this reason, they have not yet been able to accomplish any intended effect. On the other hand, to carry out an endless rolling process, there have likewise been proposed a hot-rolling method in which a lubricant is supplied onto each of the both working rolls and backup rolls (see Patent Document 5 specified below) and a method for injecting a rolling oil onto the surface of upper and lower working rolls and the surface of upper and lower backup rolls (see Patent Document 6 specified below), but both of these methods are unclear in respect of the influence of roll-cooling water on the roll-processing. [0006] Under such circumstances, there have been proposed, for instance, a water-dispersible cold-rolling oil composition for processing aluminum materials, which makes use of 80 to 95% of a base oil consisting essentially of at least one of polypropylene, polyisobutylene and polybutene, each having a molecular weight ranging from 200 to 330, (see Patent Document 7 specified below); a lubricant composition for use in the hot roll-processing, which comprises a liquid component and a combination of a synthetic ester oil and polyacrylate as an additive oil of a high molecular weight compound incorporated therein (see Patent Document 8 specified below); and a lubricant for use in the high temperature plastic working, which comprises, in combination, a base oil and polyisobutylene branched fatty acid (see Patent Document 9 specified below). [0007] Patent Document l: JP-A-H-08-215718; Patent Document 2: JP-A-H-07-062375; Patent Document 3: JP-A-H-09-040998; Patent Document 4- JP-A-H-11-080764; Patent Document 5: JP-A-H-11-290903; Patent Document 6: JP-A-2006-110555; Patent Document 1- JP-A-H-05-98284; Patent Document 8: JP-A-H-07-70576; Patent Document 9: JP-A-H-10-259391. Disclosure of the Invention Problems That the Invention is to Solve [0008] It is an object of the present invention to provide a hot-rolling oil for rolling a steel material, which can efficiently reduce the rolling load when roll-processing a plate-like material, a tube-like material, a rod-like material, a wire rod and a shape steel made of a material such as a carbon steel, a stainless steel, a tool steel or a silicon steel, while heating the material at a temperature ranging from 200 to 1200°C and which can reduce the rolling cost as well as a method for hot-rolling a steel material, which makes use of the foregoing hot-rolling oil. Means for the Solution of the Problems [0009] The inventors of this invention have conducted various studies to solve the foregoing problems and have thus succeeded in the development of a rolling oil which can show an effect superior to that achieved by the working roll oil-supply technique at the same supplied amount of oil when applying the same not only in the working roll oil-supply technique, but also in the backup roll oil-supply technique. The backup roll oil-supply technique has such characteristic properties that the maintenance of the rolling machine is easy and that the backup roll oil-supply technique is superior to the working roll oil-supply technique, since the working roll is not necessarily equipped with any fine water-draining device in the former and accordingly, the injection device is not influenced, at all, by a rolled steel material having a high temperature. [0010] Accordingly, the present invention herein provides a hot-rolling oil for rolling a steel material and a hot-rolling method as will be detailed below: 1. A hot-rolling oil for rolling a steel material comprising a base oil, and at least one polymer selected from the group consisting of isobutylene homopolymers and isobutylene copolymers, each having a number average molecular weight ranging from 8,000 to 100,000. 2. The hot-rolling oil for rolling a steel material as set forth in the foregoing item 1, wherein the isobutylene copolymer is a copolymer of isobutylene and butylene. 3. The hot-rolling oil for rolling a steel material as set forth in the foregoing item 1 or 2, wherein the hot-rolling oil comprises 0.05 to 15.0 parts by mass of the polymer per 100 parts by mass of the base oil. 4. A method for hot-rolling a steel material characterized in that a hot-rolling oil for rolling a steel material as set forth in any one of the foregoing items 1 to 3 is supplied to the backup rolls of a 4-stage rolling machine for rolling steel materials according to the water-injection system. 5. The method for hot-rolling a steel material as set forth in the foregoing item 4, wherein the hot-rolling oil for rolling a steel material as set forth in any one of the foregoing items 1 to 3 is further supplied to the working rolls of the rolling machine. Effect of the Invention [0011] The hot-rolling oil for rolling a steel material according to the present invention can be supplied to the backup rolls of a 4-stage rolling machine for rolling steel materials according to the water-injection method to thus permit the considerable reduction of the rolling load and to thereby permit the significant reduction of the rolling cost. Best Mode for Carrying Out the Invention [0012] The present invention will hereunder be described in more detail. Examples of the base oils used in the hot-rolling oil for rolling a steel material according to the present invention include one or at least two members selected from the group consisting of mineral oils (such as spindle oil, machine oil, and cylinder oil); synthetic esters (such as octyl esters of fatty acids, trimethylol-propane fatty acid esters, and pentaerythritol fatty acid esters); fats and oils (such as rapeseed oil, tallow oil, lard oil, and pamrolein oil); polymerized fats and oils (such as polymerized soybean oil, polymerized rapeseed oil, and polymerized castor oil); sulfurized fats and oils (such as sulfurized rapeseed oil, and sulfurized lard oil); and silicone oils. Among them, particularly preferably used herein are refined mineral oils, rapeseed oil, tallow oil, lard oil, palnrolein oil, pentaerythritol tri-fatty acid esters, trimethylol-propane iso-fatty acid esters, sulfurized rapeseed oil, and sulfurized lard oil. [0013] The polymer used in the hot-rolling oil for rolling a steel material according to the present invention may be at least one member selected from the group consisting of isobutylene homopolymers and isobutylene copolymers each having a number average molecular weight ranging from 8,000 to 100,000. The inventors of this invention have already taken notice of the effectiveness of polyisobutylene as a rolling oil component and have made the most use of the same as a component system for the hot-rolling oil (Patent Document 9), but this is quite limited in its application such that it is simply added to a base oil and a branched fatty acid and the efficiency thereof is likewise unsatisfied. The present invention is characterized by the use of polymers whose molecular weight falls within a desired or predetermined range and these polymers whose molecular weight falls within a predetermined range permits the significant increase in the residual amount thereof on the rolling rolls even if cooling water is injected onto the same as compared with that observed for polymethacrylate as a polymer compound disclosed in Patent Document 8 and it effectively serves to reduce the rolling load. More specifically, the amount of the rolling oil adhered to the roll surface observed for the working roll oil-supply technique is usually high as compared with that observed for the backup roll oil-supply technique and the reduction in the amount of rolling load observed for the former oil-supply technique is likewise higher than that observed for the latter technique. However, the use of at least one polymer selected from the group consisting of isobutylene homopolymers and isobutylene copolymers each having a molecular weight falling within the aforementioned desired range would permit the dramatic improvement of the water resistance of the rolling oil which has been adhered to the roll surface in the form of an oil film with respect to the roll-cooling water when comparing it with that accomplished by the use of the conventional rolling oil and accordingly, the rolling load-reduction effect achieved by the backup roll oil-supply technique is greatly superior to that achieved by the working roll oil-supply technique. On the other hand, in case of the working roll oil-supply technique, the water-deflector would not efficiently show its effect and the cooling water may pass through the gap between the water-deflector and the rolling roll to thus form a water film on the roll surface and accordingly, an emulsion injected through a nozzle cannot reach the roll surface and accordingly, the rolling oil is not adhered to the roll surface in a sufficient amount. [0014] The number average molecular weight of the polymer used in the present invention falls within an extremely limited range on the order of 8,000 to 100,000 and more preferably 30,000 to 60,000. In this respect, if the number average molecular weight thereof is less than 8,000, there is observed such a tendency that it does not sufficiently show its desired effect, while if the number average molecular weight thereof exceeds 100,000, the solubility of the polymer is liable to be insufficient. In this connection, the number average molecular weight herein used means one determined according to the gel permeation chromatography technique while using polystyrene as a reference material. Such polymers particularly preferably used herein include, for instance, poly(isobutylenes) and copolymers of isobutylene and butylene. The butylene may be 1-butylene or 2-butylene and the content of the isobutylene units present in the copolymer of isobutylene and butylene preferably ranges from 5 to 99% by mass and more preferably 20 to 90% by mass. [0015] In the isobutylene copolymer used in the hot-rolling oil for use in rolling a steel material according to the present invention, monomers other than butylene may likewise be used as comonomer components. Examples of such monomers include olefins such as ethylene, propylene, butadiene, isoprene and diolefinsJ acrylonitrile, acrylic acid, acrylic acid esters, methacrylic acid and methacrylic acid esters (such as methyl methacrylate). The hot-rolling oil used for rolling a steel material according to the present invention comprises the isobutylene homopolymer and/or isobutylene copolymer preferably in an amount ranging from 0.05 to 15.0 parts by mass and more preferably 0.50 to 5.00 parts by mass per 100 parts by mass of the base oil. This is because, if the content thereof is less than 0.05 parts by mass, the resulting hot-rolling oil is liable to insufficiently show its desired effect, while if it exceeds 15.0 parts by mass, the solubility thereof becomes insufficient and the polymer is accordingly apt not to be able to show its expected quality. [0016] The hot-rolling oil used for rolling a steel material according to the present invention may further comprise additives such as an extreme-pressure agent and a solid lubricant. Specific examples of such extreme-pressure agents include oil-soluble organometallic compounds containing, for instance, zinc, molybdenum and/or cobalt such as zinc dialkyldithiophosphate, molybdenum carbamate and cobalt salt of octylic acid,' sulfur atom-containing compounds such as sulfurized fats and oils, and didodecyl polysulfide; phosphorus atom-containing compounds such as phosphoric acid esters, phosphorous acid esters and acidic phosphoric acid esters,' and highly basic organic acid salt compounds such as highly basic calcium sulfonate and highly basic calcium salicylate. In addition, specific examples of the foregoing solid lubricants are graphite, glass, boron nitride, mica, molybdenum disulfide, iron oxide, fluorinated graphite, calcium carbonate, silicic acid salts, potassium phosphate, polyphenylene sulfide, talc, sericite, and carbohydrates. When using such additives, one or at least two thereof are added to and dispersed in the hot-rolling oil. The amount of these additives is not restricted to any specific one, but they are in general incorporated into the hot-rolling oil used for rolling a steel material in an amount ranging from 1 to 30% by mass on the basis of the mass of the hot-rolling oil. [0017] An antioxidant may additionally be incorporated into the hot-rolling oil used for rolling a steel material according to the present invention to prevent the occurrence of any deterioration, through oxidation, of the hot-rolling oil used for rolling a steel material according to the present invention. Specific examples of such antioxidants are a -naphthylamine and di-tert-butyl phenol. It is also possible to further incorporate, into the hot-rolling oil of the present invention, a pour point depressant and/or an adhesion-improving agent such as a methacrylate copolymer and a polyolefin. [0018] The hot-rolling oil used for rolling a steel material according to the present invention is preferably diluted with water to a concentration on the order of 0.1 to 5.0% by mass and then supplied onto one and preferably both of the upper and lower backup rolls of a 4-stage rolling machine for rolling a steel material. In addition to the foregoing, the hot-rolling oil of the present invention for rolling a steel material may be supplied onto at least one of the upper and lower working rolls of the rolling machine. The amount of the hot-rolling oil to be supplied onto the backup rolls may vary depending on the rolling conditions, but it is preferably not less than 0.5 g/m2, and more preferably it falls within the range of from 1.0 to 5.0 g/m2 as expressed in terms of the amount of the hot-rolling oil (stock solution). This is because, if the amount thereof is less than 0.5 g/m2, the intended effect is insufficiently accomplished in some cases, while if it exceeds 10.0 g/m2, the amount of the rolling oil adhered to the roll surface is considerably increased and the rolling load is excessively reduced. For this reason, slip occurs between rolls and a material to be rolled and accordingly, this sometimes makes the normal rolling of the material impossible. The amount of the hot-rolling oil to be supplied to the working roll may likewise vary depending on the rolling conditions, but it is preferably not less than 0.3 g/m2, and more preferably it falls within the range of from 0.5 to 3.0 g/m2. This is because, if the amount thereof is less than 0.3 g/m2, the intended effect is insufficient in some cases, while if it exceeds 5.0 g/m2, slip occurs between rolls and a material to be rolled and accordingly, this sometimes makes the normal rolling of the material impossible as in the case in which the hot-rolling oil is supplied to the backup rolls. [0019] The hot-rolling oil used for rolling a steel material according to the present invention can be supplied onto a rolling machine or the rolls thereof according to the water-injection oil-supply system, in which water is used as the injection medium; the air-spray oil-supply system in which air and a rolling oil are blended together and then sprayed onto the rolls; the airless-spray oil-supply system in which a rolling oil is subjected to an airless spray process using a high pressure plunger pump; or the premix oil-supply system. Most preferably used herein as the oil-supply system is the water-injection oil-supply system among others. [0020] The hot-rolling oil used for rolling a steel material according to the present invention is herein evaluated using high-speed steel rolls, whose utilization factor in the working rolls of a rolling machine has recently been increased gradually, but the same effect can be obtained even when using rolls made of high chromium-containing cast iron, adamite cast iron, or Ni* grain. Examples [0021] The present invention will hereunder be described in more specifically with reference to the following Examples. Examples Using a 4-stage hot-rolling machine provided with upper and lower backup rolls and upper and lower working rolls, each of the rolling oil samples as shown in the following Tables 2 to 7 was supplied onto the upper and lower backup rolls and/or the upper and lower working rolls under the conditions specified in the following Table 1, according to the water-injection oil-supply system. During the rolling operation, the rolling load was determined using a rolling load-determining meter attached to the rolling machine. In this respect, the rolling load-reduction rate (%) was calculated using the following relation^ Rolling Load-Reduction Rate (%) = 100 X (X - Y)/X In the foregoing relation, X represents the rolling load observed when any rolling oil is not supplied to the rolling machine,' and Y represents the rolling load observed when each rolling oil sample is supplied to the machine. [0022] Table 1 [0023] Table 2 [0024] Table 3 [0025] Table 4 [0026] Table 5 [0027] Table 6 [0028] table 7 [0029] Polymer A: Isobutylene/butylene copolymer (Content of isobutylene units: 60% by mass); Polymer B: Isobutylene homopolymerJ Polymer C- Methaerylate homopolymer* TMPTO: Trimethylol-propane tri-oleate,' TMPIO: Trimethylol-propane iso-stearate/iso-oleate. [0030] As has been shown in the foregoing Examples 1 to 45, when supplying the hot-rolling oils for rolling a steel material comprising an isobutylene homopolymer or an isobutylene copolymer onto the backup rolls, the rolling load is significantly reduced. Contrary to this, as has been shown in Comparative Examples 1 to 8, there is observed almost no reduction in the rolling load even when supplying the hot-rolling oils for rolling a steel material not comprising isobutylene homopolymer or isobutylene copolymer onto the backup rolls. What is claimed is: 1. A hot-rolling oil for rolling a steel material comprising base oil, and at least one polymer selected from the group consisting of isobutylene homopolymers and isobutylene copolymers, each having a number average molecular weight ranging from 8,000 to 100,000. 2. The hot-rolling oil for rolling a steel material as set forth in claim 1, wherein the isobutylene copolymer is a copolymer of isobutylene and butylene. 3. The hot-rolling oil for rolling a steel material as set forth in claim 1 or 2, wherein the hot-rolling oil comprises 0.05 to 15.0 parts by mass of the polymer per 100 parts by mass of the base oil. 4. A method for hot-rolling a steel material characterized in that a hot-rolling oil for rolling a steel material as set forth in any one of the claims 1 to 3 is supplied to the backup rolls of a 4-stage rolling machine for rolling steel materials according to the water-injection system. 5. The method for hot-rolling a steel material as set forth in claim 4, wherein the hot-rolling oil for rolling a steel material as set forth in any one of claims 1 to 3 is further supplied to the working rolls of the rolling machine. |
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| Patent Number | 268429 | |||||||||
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| Indian Patent Application Number | 5127/DELNP/2009 | |||||||||
| PG Journal Number | 36/2015 | |||||||||
| Publication Date | 04-Sep-2015 | |||||||||
| Grant Date | 30-Aug-2015 | |||||||||
| Date of Filing | 07-Aug-2009 | |||||||||
| Name of Patentee | KYODO YUSHI CO., LTD. | |||||||||
| Applicant Address | 2-30 TSUJIDO KANDAI 2-CHOME, FUJISAWA-SHI, KANAGAWA 2518588, JAPAN. | |||||||||
Inventors:
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| PCT International Classification Number | C10M 143/06 | |||||||||
| PCT International Application Number | PCT/JP2008/051942 | |||||||||
| PCT International Filing date | 2008-02-06 | |||||||||
PCT Conventions:
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