JPH10328704A - Lubricant for rolling of hot-rolled steel and rolling method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the galling between a roll and a steel material by using lubricant composed of water, iron oxide powder and/or iron hydroxide powder, water dispersive resin and dispersant and containing specific ratios of the iron oxide powder and/or the iron hydroxide and specific ratio of the water dispersive resin. SOLUTION: This lubricant is composed of 5-30 wt.% iron oxide powder and/or iron hydroxide powder and 3-20 wt.% water dispersive resin. The lubricant is coated on the outer peripheral surfaces of the rolling rolls 2 from nozzles 3 for spraying the lubricant and dried by the time of the beginning of the biting of a rolling material 1 to execute the rolling of the rolling material 1 after forming the dried lubricant film 6. A position for coating the lubricant is in the interval between the position of a nozzle 4 for spraying the roll cooling water and the position where biting the rolling material 1 begins. The dried lubricant film 6 has large strength and excellent stickiness to the roll, and therefore, the iron oxide powder and/or the iron hydroxide powder are held between the rolling material 1 and the rolling roll 2 and the galling are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricant for rolling a hot-rolled steel sheet and a method for rolling the same, and more particularly, it is effective for hot rolling a ferritic stainless steel sheet.

[0002]

2. Description of the Related Art In order to manufacture a so-called hot-rolled steel sheet by hot rolling (hereinafter referred to as hot rolling) a steel material to be rolled, a lubricant is usually supplied to a roll to be used, and the steel material is baked on the roll surface. Is preventing that. The lubricant is disclosed in
Liquid hot rolling oils such as those disclosed in US Pat. The hot rolling oil is, for example, a synthetic ester base oil to which a solid lubricant has been added. Examples of the solid lubricant include mica, graphite (graphite), potassium titanate, and potassium phosphate. is there. As a method for supplying this kind of oil-based lubricant to the hot-rolling roll, a material to be rolled (hereinafter simply referred to as a material) is directly in contact with the roll surface via a nozzle immediately before the roll bites into the roll. The method of spraying and applying is common.

At the time of hot rolling, a solid lubricant, that is, a wax-based solid lubricant is sometimes used. For example,
As disclosed in Japanese Patent Application Laid-Open No. 62-156199, there is generally proposed a grease or wax-based product to which a solid lubricant such as graphite is added. In order to actually supply the wax-based solid lubricant to the roll, for example, a screw-type extruder as disclosed in Japanese Patent Publication No. 60-55559 is used to apply the solid lubricant to the roll surface. A method has been proposed in which the material is directly pressed and applied.

Further, as disclosed in Japanese Patent Publication No. 1-167396, a method has been proposed in which a lubricant in which graphite (graphite) powder is dispersed in a viscous aqueous solution is spray-coated on the roll surface. In this case, since the graphite powder is supplied between the roll surface and the material in a state of being dispersed in the viscous liquid, it is essential to use an aqueous solution having a somewhat high viscosity in order to secure adhesion to the roll surface. . In addition, some lubricants using a viscous aqueous solution use iron oxide or iron hydroxide. A method for supplying the lubricant to a roll is disclosed in, for example, JP-A-8-300606. A method has been proposed in which an iron oxide powder or an iron hydroxide powder is dispersed in a viscous aqueous solution and spray-coated on a roll surface.

[0005]

As described above, in order to manufacture a steel sheet by hot rolling, it is necessary to provide an oil-based lubricant, a wax-based solid lubricant, or a graphite powder in a viscous aqueous solution between a roll and a material. And a dispersion of solid lubricant powder such as iron oxide powder. By the way, recently, there has been an increasing demand for inexpensively producing steel materials having higher deformation resistance than before, without modifying equipment. Then, the inventor tried hot rolling of ferritic stainless steel using the above-mentioned lubricant, and observed the state of seizure between the used roll and the material. As a result, a slight seizure reduction effect was observed as compared with non-lubricated rolling,
This is a level generally reported conventionally, and complete prevention of image sticking was not possible.

In view of such circumstances, the present invention provides a lubricant for rolling a hot-rolled steel sheet, which can reduce the seizure of the roll and the steel material even when used for rolling a ferritic stainless steel, and a use thereof. The purpose is to provide a rolling method.

[0007]

Means for Solving the Problems The inventor has conducted various studies to achieve the above object, and has concluded that it is effective to form a strong film on the roll surface. The present inventors have made great efforts to realize this idea and completed the present invention. That is, the present invention is a lubricant used for rolling of a hot-rolled steel sheet, comprising water, iron oxide powder and / or iron hydroxide powder, a water-dispersible resin, and a dispersant. It is a lubricant for rolling hot-rolled steel sheets.

Further, the present invention is characterized in that the iron oxide powder and / or iron hydroxide powder is 5 to 30% by weight and the water-dispersible resin is 3 to 20% by weight, A rolling lubricant for a hot-rolled steel sheet, wherein the steel sheet is a ferritic stainless steel sheet. Further, the present invention, when hot rolling the steel material to be rolled using a lubricant with a work roll of a finishing mill,
The lubricant is applied to the outer peripheral surface of the rotating work roll, and the lubricant is dried before the start of biting of the material to be rolled to form a resin film containing iron oxide powder and / or iron hydroxide powder. A method of rolling a hot-rolled steel sheet, characterized by rolling a material to be rolled, or a position where a lubricant is applied to the outer peripheral surface of the work roll, a position where cooling water is applied to the work roll, and A method for rolling a hot-rolled steel sheet, which is performed between a position and a position where a material to be rolled is engaged.

In addition, the present invention is also a method for rolling a hot-rolled steel sheet, wherein the hot-rolled steel sheet is a ferritic stainless steel sheet. According to the present invention, a lubricant consisting of water and iron oxide powder or iron hydroxide powder and a dispersant and a water-acidic resin is applied to the roll surface, and then dried and rolled at a portion where a strong film is formed. Therefore, the iron oxide powder or the iron hydroxide powder is more firmly held at the interface between the roll and the material than before, and can effectively contribute to lubrication. As a result, it has become possible to completely prevent seizure of a hot-rolled steel sheet, particularly a ferritic stainless steel sheet, which occurs during hot rolling of rolls, which cannot be eradicated by the prior art.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with a background to the invention. In hot finish rolling of a steel strip, it is usually extremely difficult to measure the roll surface temperature during rolling. Therefore, in general, a heat conduction simulation model relating to the roll surface temperature during rolling is created, and the roll surface temperature is estimated by calculation. According to this, when the temperature of the steel material to be rolled is, for example, 1000 ° C., the temperature of the outermost layer portion of the roll instantaneously rises to about 450 ° C. at the contact portion with the steel material. In addition, the roll is cooled by applying water to its surface during one rotation from the rolling-out side and reaching the entrance side (biting position) again.
It is estimated to be below 0 ° C. Accordingly, the surface temperature of the roll during this period is from 450 ° C. to 100 ° C. Of course, if the amount of the cooling water is reduced, the roll surface temperature rises in accordance with the amount of water reduction.

The inventor has made the present invention as described below, focusing on the change in the roll surface temperature. That is, as shown in FIG.
A lubricant consisting of water, solid powder, a water-dispersible resin, and a dispersant is rotated at a position sufficiently away from the position where the material is engaged again, for example, at a position at a rotation angle of 150 ° from the engaged position. Was applied by spraying to form a uniform coating film continuously. At this time, if the roll surface temperature is about 140 ° C., the moisture contained in the lubricant during the rotation of the roll evaporates in a very short time, for example, in 0.1 second, and the polymerization of the resin contained in the lubricant is performed. Since the reaction is accelerated, it has been found that the lubricant solidifies rapidly and forms a strong dry film. Then, the research was continued, and it was confirmed that when the solid powder was iron oxide or iron hydroxide, drying was performed smoothly, and the film became strong. As the water-dispersible resin used at that time, a vinyl acetate emulsion resin or an acrylic resin used as a raw material for an adhesive or a water-soluble paint was suitable. The dried film once formed with such a lubricant did not fall off by washing with water, and even if it was scraped off with a scraper or the like, it was extremely difficult to remove the thin film remaining fixed on the surface of the rolled iron. In the present invention, any resin other than those described above can be used as long as it forms a strong film after drying. The role of the resin is to form a strong dry film in a short time and to hold the iron oxide powder or the iron hydroxide powder firmly on the roll surface.

Preferred examples of the water-dispersible resin are shown below. Vinyl acetate copolymer resin, vinyl acetate acrylic copolymer resin, vinyl acetate vinyl oxide copolymer resin, vinyl acetate malate copolymer resin, vinyl acetate ethylene copolymer resin, vinyl acetate ethylene vinyl chloride copolymer resin, acrylic copolymer resin, styrene copolymer resin Acrylic / styrene copolymer resin, ethylene / acrylic copolymer resin, ethylene / acrylic ester-based multiple copolymer, polyvinyl alcohol resin, methacrylic acid resin, methacrylic acid styrene copolymer resin. In the present invention, the central angle of the roll is 10 to 170 ° from the position where the material is engaged.
It is preferred that it is located far away. If it is less than 10 °, it is too close to the biting position, and water evaporation is insufficient when viewed from the normal rotation speed of the roll. If it exceeds 170 °, the sprayed liquid lubricant is scattered and loss increases. . Further, in the present invention, the spraying position of the lubricant is determined by paying attention to the drying temperature of the lubricant, and the roll surface temperature is set to 100 to 1
The temperature may be set to 50 ° C. If the surface temperature of the roll 2 exceeds 150 ° C., moisture will rapidly evaporate and a strong film will not be formed, and if it is less than 100 ° C., water will not be sufficiently evaporated. Further, in the present invention, the iron oxide powder and / or the iron hydroxide powder contained in the lubricant is 5 to 30%.
% And the water-dispersible resin is preferably 3 to 20% by weight. The reason for this is that if the iron oxide powder and / or iron hydroxide powder exceeds 30% by weight, the strength of the formed film becomes too low and the adhesion strength of the powder is reduced. This is because a good image sticking prevention effect cannot be obtained. On the other hand, when the water-dispersible resin is 20
If the amount is more than 3% by weight, the film strength is saturated and no further effect can be expected. If the amount is less than 3% by weight, the film strength becomes insufficient.

Next, the effect of the method of rolling a hot-rolled steel sheet using this lubricant will be described. First, a conventional general method of supplying a lubricant to a roll is shown in FIG. 2. Rolling oil as a lubricant is spray-coated on the roll surface immediately before the material is bitten at the entry side of the rolling mill. I have.
The same applies to the case where a lubricant using a viscous aqueous solution is supplied instead of the rolling oil in that the lubricant is supplied in a liquid state between the roll and the material. The strength of these liquid lubricants adhering to the roll surface is extremely low, and can be taken off with a piece of cloth. Conventionally, when a solid lubricant is applied, a method of applying grease or wax to a roll surface on the side (entrance side) where the material bites is applied. However, the adhesive strength of grease and wax was also low enough to be wiped off with a piece of cloth, and the adhesive strength was weak.

On the other hand, in the present invention, after the lubricant is dried to form a film, the material is bitten and rolled. This coating has a high strength after drying, as well as a general paint or an adhesive, and has an extremely strong adhesive strength with the base iron. Therefore, the adhesive force to the roll is not only much better than the conventional liquid lubricant, but also superior to the adhesive force of the conventional solid lubricant. Iron oxide powder and / or iron hydroxide powder can be firmly held between the rolls, and the effect of preventing seizure as a lubricant can be maximized.

[0015]

EXAMPLES The following experimental rolling was carried out in order to confirm the effects of a lubricant and a rolling method for a hot-rolled steel sheet according to the present invention. (Conditions) Experimental rolling mill (four-high rolling mill, work roll diameter: 70 mm, work roll body length: 40 mm, backup roll diameter: 140 mm, backup roll body length:
40mm) and heated to 1000 ° C using a ferritic stainless steel sheet (sheet thickness 2mm x sheet width 20mm x length 3)
00m) at a rolling reduction of 50% to a thickness of 1 mm and a rolling speed of 1 mm.
Rolled at 00 mpm. The cooling water of the roll was sprayed onto the surface of the work roll on the exit side of the rolling mill. The used lubricant is installed on the entry side of the rolling mill, immediately after the wiper device for wiping water droplets remaining on the work roll surface,
The lubrication conditions are as follows:

(1) Non-lubricated, (2) A high viscosity esterified product obtained by adding 30% by weight of a graphite powder and a trace amount of a dispersant is spray-coated on the roll surface on the inlet side.
(3) Mineral oil to which 30% by weight of graphite powder and a trace amount of a dispersant are added is spray-coated on the roll surface on the entry side, (4) A wax containing 30% by weight of graphite powder is pressed and coated on the roll surface, (5) Water is added with 20% by weight of iron hydroxide powder, a cross-linkable acrylic acid polymer as a thickening agent is added with a trace amount of a dispersing agent, and the thickened one is spray-coated on the surface of the inlet roll. (6) Water 20% by weight of an iron oxide powder having an average particle size of 1 μm, 10% by weight of a vinyl acetate emulsion resin for forming a film after drying, and a small amount of a dispersant are spray-coated on a roll surface at about 130 ° C. And dried to form a strong dry film. In this case, the amount of roll cooling water is reduced in order to form a dry film in a short time. (Implementation results) Table 1 shows the implementation results collectively. The evaluation of the anti-seizure performance was carried out in the following manner.
m was pickled and the degree of seizure flaws was visually determined.
When the degree of burn-in flaws is large, it is represented by x, when it is medium, it is represented by Δ, when it is small, it is represented by Δ, and when it is not present at all, it is represented by ◎. That is, (1) of the comparative example is ×, (2), (3), (4) is Δ, (5) is Δ, and (6) of the rolling method according to the present invention.
, The result was ◎, and the seizure prevention was remarkably excellent.

[0017]

[Table 1]

[0018]

As described above, according to the present invention, a lubricant consisting of water, iron oxide powder or iron hydroxide powder, a dispersant, and a water-acidic resin is applied to the surface of a rotating roll. Since the lubricant is dried before the biting position to form a strong dry film and then rolled, the iron oxide powder or iron hydroxide powder is more firmly held at the boundary surface of the roll material than before. , Effectively contributing to lubrication. As a result, seizure flaws between the ferritic stainless steel sheet and the roll, which could not be eradicated by the prior art, could be completely prevented. In addition, the method of rolling a hot-rolled steel sheet using this lubricant was effective not only in the finish rolling mill but also in the rough rolling mill, with a significant effect of preventing seizure.

[Brief description of the drawings]

FIG. 1 is a diagram showing a situation in which a lubricant according to the present invention is supplied to a roll.

FIG. 2 is a diagram showing a situation in which a conventional general lubricant is supplied to a roll.

[Description of Signs] 1 Rolled material (material) 2 Roll roll 3 Lubricant spray nozzle 4 Roll cooling water spray nozzle 5 Liquid lubricant film immediately after application 6 Dry lubricant film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10M 143: 00) C10N 40:24 (72) Inventor Haruhiko Seki 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Pref. In the laboratory (72) Inventor Koji Kondo 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Pref.

Claims (6)

[Claims] 1. A lubricant used for rolling a hot-rolled steel sheet, comprising: water, iron oxide powder and / or iron hydroxide powder, a water-dispersible resin, and a dispersant. Lubricants for rolling hot-rolled steel sheets. 2. The iron oxide powder and / or iron hydroxide powder is 5 to 30% by weight, and the water-dispersible resin is 3 to 2%.
The lubricant for rolling a hot-rolled steel sheet according to claim 1, wherein the lubricant is 0% by weight. 3. The lubricant for rolling a hot-rolled steel sheet according to claim 1, wherein the hot-rolled steel sheet is a ferritic stainless steel sheet. 4. The lubricant according to claim 1, wherein, when hot rolling the steel material to be rolled on a work roll of a finishing mill using a lubricant, the lubricant according to any one of claims 1 to 3 is applied to the outer peripheral surface of the rotating work roll. Is applied, the lubricant is dried before the start of biting of the material to be rolled, a resin film containing iron oxide powder and / or iron hydroxide powder is formed, and then the material to be rolled is rolled. Hot rolled steel sheet rolling method. 5. The method according to claim 1, wherein the lubricant is applied to the outer peripheral surface of the work roll between a position where cooling water is applied to the work roll and a position where the rolled material bites. Item 6. The method for rolling a hot-rolled steel sheet according to Item 4. 6. The method of rolling a hot-rolled steel sheet according to claim 4, wherein the hot-rolled steel sheet is a ferritic stainless steel sheet.