JP2006272358A - Method for supplying lubricant in hot rolling - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for supplying a lubricant in hot rolling, which method uses the gas-atomization supply method which does not cause fire accidents due to the ignition or taking-fire of the lubricant caused by the temperature rise of the environment at the portion supplied with the lubricant due to the heat radiated from the material to be rolled, when a hot rolling process is carried out while supplying the lubricant. <P>SOLUTION: In the method for supplying the lubricant in the hot rolling process (the gas-atomization supply method), the lubricant having a viscosity of 8 cm<SP>2</SP>/s at 40°C is supplied to a roll by being jetted as particles having a mean diameter of 5 mm or less together with a noncombustible gas. In this case, the lubricant is supplied while forming a water film having a mean thickness of 10 μm on the surface of the roll or from above the formed water film. By this method, the water film formed on the surface of the roll suppresses the temperature rise of the lubricant supplied by being jetted, and as a result, excellent lubrication effects can be achieved while preventing the occurrence of fire accidents. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for supplying a lubricant in a hot rolling process in a steel manufacturing process.

  The purpose of lubrication hot rolling is various, such as reducing the wear of the roll by reducing the friction force during rolling, obtaining energy saving effect, and improving the surface quality of the product. As a lubricating oil supply method in hot rolling, for example, as described in Non-Patent Document 1, in addition to a method of mixing lubricating oil with water and injecting and supplying it in the form of an emulsion, lubricating oil and steam There is known a method (steam atomization system) for mixing and supplying the mixture.

Further, as a method for producing a hot-rolled steel sheet for deep drawing having excellent thickness uniformity, Patent Document 1 and Patent which are based on supplying a lubricant supply amount of 0.2 to 10 cm ³ per 1 m ² of roll surface area. Document 2 and Patent Document 3 are known. These known methods are emulsion lubrication methods in which water and lubricating oil are mixed by water injection.

  When the emulsion lubrication method is used, a drain wiper is provided between the roll cooling water supply unit and the lubrication supply unit so that the roll cooling water is not applied to the lubrication supply unit. However, when the roll rotates and the wiper wears and there is a gap, if the roll cooling water leaks into the lubrication supply section, the lubricating oil supplied by emulsion lubrication becomes difficult to adhere to the roll. This is because the leaked roll cooling water forms a water film on the roll surface, and when mixed with this cooling water, the emulsion concentration (the amount of lubricating oil with respect to water) decreases, making it difficult to obtain a lubricating effect. Because. It is known that the same problem occurs in the steam atomization method.

  In emulsion lubrication, the emulsion concentration always changes due to subtle differences in the viscosity of the lubricating oil due to changes in temperature and humidity. As a result, dirt in the lubrication piping system and clogging of the nozzles are caused, and a problem that the lubrication effect varies due to these external factors is also recognized.

On the other hand, for example, in Patent Document 4, a lubricating oil having a viscosity at 40 ° C. of 8 cm ² / s or less is granulated with an average particle diameter of 5 mm or less, and is not mixed with water per lubricating nozzle. A lubricant supply method for injecting and supplying to a roll together with a non-combustible gas having a flow rate of 1000 cm ³ or more per minute is disclosed (hereinafter referred to as a gas atomization supply method). In this lubricant supply method, even if some water film remains on the roll, the supplied gas blows off the water film on the roll surface, so that the lubricant reliably reaches the roll surface and adheres to it. Various effects can be efficiently derived.

JP 11-279656 A JP-A-11-279657 Japanese Patent Application No. 11-293345 JP 2003-94104 A Japan Iron and Steel Institute “Theory and Practice of Sheet Rolling” p218

  However, when a highly flammable lubricant is used as the lubricant, there is a problem that the injected lubricant may be ignited by radiant heat from the steel material, or the lubricant accumulated around the rolling equipment may be ignited. there were.

  Therefore, the present invention has been made in view of such problems, and the object thereof is excellent in the gas atomization supply method while preventing ignition of the lubricating oil, which has not been a problem in the conventional emulsion lubricant supply method. The present invention provides a new and improved lubricating oil supply method capable of obtaining a lubricating effect.

  In order to solve the above problems, the present inventor has conducted extensive research on a lubrication method and a lubricant ignition prevention method in hot rolling. As a result, a water film having a predetermined thickness is formed on the surface of a roll for supplying the lubricant. It has been found that, even if a highly flammable lubricating oil is injected and supplied by the gas atomization supply method, the lubricating effect, that is, the friction coefficient reducing effect can be maintained, and the ignition phenomenon of the injected lubricating oil can be prevented. The present invention has been completed based on the findings.

That is, the gist of the present invention is as follows.
(1) Lubricating oil in a hot rolling method in which a lubricating oil having a viscosity at 40 ° C. of 8 cm ² / s or less is granulated with an average particle diameter of 5 mm or less and injected into a roll together with a nonflammable gas. A method of supplying a lubricant in hot rolling, wherein a water film having an average thickness of 10 μm or more is formed on the surface of an entrance roll to which the agent is injected, and the lubricant is injected and supplied from above the water film.
(2) The method for supplying lubricant in hot rolling according to (1), wherein the thickness of the water film formed on the surface of the entry side roll is 20 μm to 3000 μm.
(3) Lubricating oil in a hot rolling method in which a lubricating oil having a viscosity at 40 ° C. of 8 cm ² / s or less is granulated with an average particle size of 5 mm or less and injected into a roll together with a non-combustible gas. While supplying an amount of water corresponding to an amount capable of forming a water film having an average thickness of 10 μm or more when the lubricant is not sprayed on the entry side roll surface where the agent is sprayed, the lubricant is supplied to the supply location. A method for supplying a lubricant in hot rolling, characterized by being supplied by injection.
(4) The supply amount of the lubricant to be injected and / or the flow rate of the incombustible gas is controlled according to the thickness of the water film formed on the surface of the entry side roll or the amount of water supplied to the surface of the entry side roll. The lubricant supply method according to any one of (1) to (3).

The control in the above (4) is performed, for example, as described in (1) and (2) when a water film having an average thickness of 10 μm or more is formed on the inlet roll surface or when a considerable amount of water enters. When supplied to the surface of the side roll, if the flow rate of the nonflammable gas is 1000 cm ³ per minute per lubricating nozzle, the lubricant does not ignite and efficient lubrication rolling is possible. .

  According to the present invention, in the gas atomization supply method, even in a high temperature environment, the lubricant can be ignited and an efficient lubrication rolling can be performed without causing a fire accident. In addition, the stabilization of lubricated rolling can be expected to contribute to the reduction of power source units and the resulting reduction of carbon dioxide emissions, and to suppress rough rolls and wear.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

  Based on FIG. 1, a method for supplying lubricating oil according to the present embodiment will be described. In addition, FIG. 1 is explanatory drawing which showed schematic structure of the quadruple rolling mill used for the lubricant supply method which concerns on one Embodiment of this invention.

  As shown in FIG. 1, the lubricating oil is usually supplied at the entrance of the rolling mill. A cooling water header 6 for cooling the roll is installed on the entrance side of the rolling mill. The upper roll (upper work roll 3) is below the cooling water header 6 so that the cooling water does not reach the material 5 to be rolled. In the lower roll (lower work roll 4), a draining wiper 7 is attached on the cooling water header 6 to expel the water on the roll surface. In the lower roll, since the supplied roll cooling water is taken upward by the rotation of the roll, the arrangement is as shown in FIG. The cooling water header 6 is provided with nozzles arranged at predetermined intervals in the axial direction of the roll, so that cooling water and lubricating oil can be simultaneously injected and supplied to the entire roll. The draining wiper 7 prevents the roll cooling water from being applied to the material 5 to be rolled, so that the material 5 to be rolled is cooled and cannot be formed into desired material characteristics, or the deformation resistance is increased and the rolling load is increased. Is provided to do.

  The lubricant header 8 for injecting the lubricating oil is usually installed below the draining wiper 7 for the upper roll and above the draining wiper 7 for the lower roll. By arranging in this way, a conventional lubricant (emulsion lubricant) can be supplied in the state where there is no water film on the roll surface, and a certain level of lubricating oil adhesion effect can be obtained even in an emulsion. Thus, it is possible to obtain a lubricating effect such as reduction of rolling load and reduction of roll wear. Emulsion lubricants are those in which flammable lubricant is forcibly stirred and mixed with water, so water prevents temperature rise of the lubricant and does not cause fire trouble. In this embodiment, it is known that an excellent lubrication effect can be obtained because the lubricating oil is directly supplied to the work rolls 3 and 4 by using the gas atomizing supply method, but the flammability is close to the hot steel material. There is a concern about fire troubles because the lubricant itself is supplied by injection.

  The present inventor has found a method of supplying lubricating oil from above the water film by a gas atomizing supply method in a state where the water film is formed on the roll surface. Specifically, when the water film is formed on the surfaces of the work rolls 3 and 4, the position of the drainage wiper 7 is set so that a slight gap is formed between the draining wiper 7 and the surface of the work rolls 3 and 4. It adjusted and formed so that a part of roll cooling water from the cooling water header 6 might remain on the surface of the work rolls 3 and 4. When lubricating oil is supplied by the gas atomizing supply method in such a state, the lubricating oil is transported to the surface of the work rolls 3 and 4 by the gas flow injected from the lubricant header 8, and at the same time, the water film on the surface of the work rolls 3 and 4 There is an effect to blow away. Further, the blown water creates a heat shielding effect between the lubricating oil supply part on the surface of the work rolls 3 and 4 (the part where the lubricating oil is supplied on the roll surface) and the hot steel material, and the temperature of the lubricating oil Suppresses the rise. Further, the blown water adheres onto the lubricating oil film adhering to the surfaces of the work rolls 3 and 4, and the temperature rise of the lubricating oil film on the surfaces of the work rolls 3 and 4 can be suppressed.

  Such an effect cannot be obtained unless the average thickness of the water film formed on the surfaces of the work rolls 3 and 4 is 10 μm or more. If the thickness is 20 μm or more, the above-described blocking effect can be obtained sufficiently. If the thickness of the water film is thinner than 10 μm on average, a sufficient shielding effect for preventing the ignition of the lubricating oil due to the radiant heat from the hot steel material cannot be obtained. When the thickness of the water film increases, the effect of shielding the radiant heat from the hot steel material can be obtained without increasing the lubrication effect by increasing the supply amount of the lubricating oil and gas in the gas atomization supply method. Can do.

  On the other hand, if the thickness of the water film exceeds 3000 μm, the lubricating oil may be diluted by the blown water film. Further, since it is necessary to supply useless lubricating oil in terms of cost, it is not preferable to exceed 3000 μm. Therefore, the thickness of the water film formed on the surfaces of the work rolls 3 and 4 is preferably 20 μm or more and 3000 μm or less on average, and more preferably 20 μm or more and 1000 μm or less. Even if there is a part where no water film exists locally on the roll surface, if a water film of 10 μm or more is formed on the surface of the work rolls 3 and 4 on average, a water film exists due to the gas flow by the gas atomization supply method Water is also supplied to the non-applied portion, and the same effect is obtained as when a water film having a uniform thickness is formed on the entire surface of the work rolls 3 and 4 before the lubricating oil is supplied.

  The water film is not only formed by providing a gap between the draining wiper 7 and the surfaces of the work rolls 3 and 4 as described above, but a water film forming header used for forming the water film is separately installed. And it can also form by spraying water on the work rolls 3 and 4 surface from this water film formation header. Thus, what is the means for forming the water film as long as the water film thickness can be realized so as to obtain a heat shielding effect between the lubricating oil supply section on the work roll surface and the hot steel material? May be.

  Furthermore, the site | part which forms a water film on the work rolls 3 and 4 surface, and the site | part which supplies lubricating oil with a gas atomization supply method may overlap. Even if the water is supplied in an overlapping manner, if the amount of water that can form a water film having an average thickness of 10 μm or more is supplied, the above-described fire trouble prevention effect can be achieved even if the water film has a thickness of less than 10 μm. can get. That is, as long as a sufficient amount of water is supplied to the inlet side to block the radiant heat from the hot steel material, the film thickness at the time of supplying the lubricant does not necessarily have to be 10 μm or more.

Example 1
A lubrication rolling experiment was conducted by installing a gas atomized lubrication supply device in the 2HI coil rolling experiment device. By changing the thickness of the roll water film, the friction coefficient at the time of lubrication ON / OFF and the occurrence of ignition phenomenon at the time of lubrication supply were investigated. The roll used was a SKD51 material having a diameter of 400 mm and a body length of 100 mm, and the material to be rolled was a coil of SPCC material having a thickness of 1 mm, a width of 50 mm, and a length of 10 ⁶ mm. The inlet coiler is a heating furnace, and the rolling experiment was conducted after heating to 1000 ° C. in a nitrogen atmosphere. The rolling speed was set to 100 mm, and lubrication was not supplied during acceleration and deceleration, and experiments were performed under various conditions after reaching a steady speed. The plate tension on the entry / exit side was about 1 to 4 kgf / mm ² . The roll gap was set so that the reduction ratio was about 25%. In normal hot rolling experiments, roll cooling water is only applied from the exit side of the rolling mill, but in this experiment, injection / Separately, a roll water film forming nozzle was provided above and below the portion (lubricant supply portion) where the supplied lubricant hits the work roll. Since it is a 2HI rolling mill, a part of the roll cooling water applied on the exit side goes around to the entry side by the rotation of the roll. In order to prevent this water from wrapping around, a draining wiper was attached between the roll cooling water supply section on the outlet side and a portion where water was supplied by a water film forming nozzle provided separately. As a result, it was possible to carry out an experiment reproducing the same situation as the positional relationship of the cooling water header, draining wiper and lubricant header of the actual machine shown in FIG. The thickness of the water film formed on the surface of the work roll was set by adjusting the flow rate of water from a separate nozzle dedicated to water film formation. The relationship of the following formula (1) is established between the thickness of the water film when all of the supplied water adheres to the roll surface and the amount of water supplied from the nozzle. However, the following formula (1) is established when the roll body length is longer than the spread width of the spray cone.

Using the above formula (1), the amount of water that can form a roll water film having a desired thickness is ejected from the water film forming nozzle to form a water film on the roll surface, and the lubricating oil is applied under various conditions (gas Supply amount, lubricating oil supply amount). The nozzle used in this experiment was the same as the roll barrel length in which the spray cone spreads on the roll surface. The coefficient of friction was used as an index for judging the presence or absence of the lubricating effect. The coefficient of friction is determined by using the rolling load, rolling speed, sheet tension on the entry / exit side, advanced rate obtained from the exit plate speed and rolling speed (roll speed), and rolling reduction data measured during the rolling experiment. Obtained using Orowan's rolling theory. In addition, the presence or absence of a lubricant igniting phenomenon during lubrication supply was evaluated as the presence of a igniting phenomenon when a flame was generated inside or outside the plate path or around the rolling mill and continued to burn for more than one second. On the other hand, if the flame disappeared within 1 second, it was determined that there was no lubricating oil ignition phenomenon. The lubricating oil used in the experiment was a commercially available lubricating oil based on a mineral oil having a viscosity of 1.2 cm ² / s at 40 ° C., which is used in an actual hot rolling mill. This lubricating oil is a commercially available lubricating oil based on mineral oil and / or ester, to which various oil agents, extreme pressure additives, lubricants and the like are added.

  The experimental results are shown in Table 1 below together with the experimental conditions. Condition No. 1 shows the coefficient of friction when rolling without using lubrication. A smaller value than this friction coefficient means that the lubricating effect is excellent. Conditions Nos. 2 and 3 are given as examples when the thickness of the water film on the roll surface is small, that is, as comparative examples of the present invention. In this case, although the lubrication effect was obtained, the ignition of the lubricating oil occurred. Conditions No. 4 to 9 are examples of the present invention, and when the water film thickness on the roll surface averaged 10 μm or more, the ignition phenomenon of the lubricating oil did not occur. Even if the water film thickness on the roll surface is increased, an excellent lubrication effect can be obtained by increasing the supply amount of the lubricating oil or the gas supply amount when supplying the gas atomization.

  Also, for conditions 2 to 9 in Table 1, the direction of the water film forming water supply nozzle was changed, the water supply location for forming the water film was the same as the lubrication supply location, and the experiment was performed under the same conditions as above. As a result, as shown in Table 2, almost the same result as described in Table 1 was obtained. Therefore, regardless of where the water film is formed on the roll surface, if lubricating oil is supplied by the gas atomization method while supplying water with an average thickness of 10 μm or more to the roll surface in terms of water film thickness, ignition and ignition of the lubricating oil will occur. It was found that an excellent lubrication effect can be obtained without causing fire troubles.

(Example 2)
A gas atomized lubrication supply device was installed by modifying the existing lubrication supply device on the entrance side of the fifth stand of the finishing mill at the hot rolling mill (4HI rolling mill installed in the fifth of all seven tandem rolling mills). Then, lubrication rolling was performed. A water supply header for forming a water film for forming a water film on the roll surface is separately provided between the drainer wiper and the lubricant header, and the water supply amount of the water supply header for forming the water film is changed. Using 1), a water film having a predetermined thickness was formed on the roll surface. When the nozzle used was used, the spread width of the spray cone on the roll surface was about 300 mm. In addition, the water supply header for forming a water film can adjust the supply direction so that a water film is formed on the roll surface in advance and the lubricating oil is supplied from above by a gas atomized lubrication supply method. Experiments were conducted in both cases where the water supply location for forming a water film and the lubrication supply location were the same. Also, in order to verify the practicality of the present invention, the presence or absence of a lubrication effect is judged by the value of the friction coefficient when rolling is performed using lubrication and when rolling is performed without using lubrication, and the supplied lubricating oil is ignited. The existence of fire troubles was investigated by observing the presence or absence. The coefficient of friction was obtained by the same calculation as in Example 1. Whether or not the lubricating oil was ignited was also determined based on the same criteria as in Example 1. As the lubricating oil, a commercially available lubricating oil based on a mineral oil having a viscosity at 40 ° C. of 1.42 cm ² / s was used. The work roll was a high-speed roll material having a diameter of 683 mm and a trunk length of 1820 mm. The rolled material was 0.3% low carbon steel, the entry side plate thickness was about 7.5 mm, and the plate width was about 1180 mm. The temperature of the rolled material on the entry side of the first stand of the finishing mill was about 990 ° C. The rolling speed was about 560 mm at the time of steady rolling, and rolling was performed at a reduction rate of about 35%. The plate tension on the entry / exit side was set to about 0.5 to 1.0 kgf / mm ² .

  The experimental results are shown in Table 3 together with the experimental conditions. Condition No. 1 indicates the coefficient of friction when rolling without using lubrication. A smaller value than this friction coefficient means that the lubricating effect is excellent. Condition No. 2 is an example in which the thickness of the water film on the roll surface is thin, that is, a comparative example of the present invention. In this case, although the lubrication effect was obtained, the ignition of the lubricating oil occurred. Conditions No. 3 to 5 are examples of the present invention. When the water film thickness on the roll surface averaged 10 μm or more, the ignition phenomenon of the lubricating oil did not occur. It was also found that even if the water film thickness on the roll surface is increased, an excellent lubrication effect can be obtained by increasing the amount of lubricating oil supplied and the amount of gas supplied when gas atomizing is supplied.

  In addition, for conditions 2 to 5 in Table 3, the direction of the water film forming water supply nozzle was changed, and the water supply place for forming the water film and the lubrication supply place were overlapped, and the experiment was performed under the same conditions. As shown in Table 4, the results are almost the same as those shown in Table 3. Therefore, regardless of where the water film is formed on the roll surface, if lubricating oil is supplied by the gas atomizing supply method while supplying water with an average thickness of 10 μm or more to the roll surface in terms of water film thickness, ignition of the lubricating oil will occur. It was found that an excellent lubrication effect can be obtained without causing a fire trouble due to or ignition.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are of course within the technical scope of the present invention. Understood.

  The present invention can be widely applied in hot rolling of steel materials, not only hot rolling of flat products such as thin plates and thick plates, but also hot rolling of H-shaped steel for building materials and hot rolling of pipes. It can be applied as an efficient means of the lubrication supply method used in hot rolling of steel products.

It is explanatory drawing which showed schematic structure of the quadruple rolling mill used for the lubricant supply method which concerns on one Embodiment of this invention.

Explanation of symbols

1 Upper backup roll 2 Lower backup roll 3 Upper work roll 4 Lower work roll 5 Rolled material 6 Cooling water header 7 Drain wiper 8 Lubricant header

Claims (3)

In a lubricant supply method in hot rolling, a lubricant having a viscosity at 40 ° C. of 8 cm ² / s or less, having an average particle size of 5 mm or less, and sprayed to a roll together with a nonflammable gas,
A lubricant in hot rolling, characterized in that a water film having an average thickness of 10 μm or more is formed on the surface of the entrance roll to which the lubricant is sprayed, and the lubricant is sprayed and supplied from above the water film. Supply method. In a lubricant supply method in hot rolling, a lubricant having a viscosity at 40 ° C. of 8 cm ² / s or less, having an average particle size of 5 mm or less, and sprayed to a roll together with a nonflammable gas,
While supplying water at a supply amount corresponding to an amount capable of forming a water film having an average thickness of 10 μm or more when the lubricant is not sprayed on the surface of the entrance roll to which the lubricant is sprayed, A method of supplying a lubricant in hot rolling, characterized by injecting and supplying a lubricant to a supply location. The supply amount of lubricant to be injected and / or the flow rate of nonflammable gas is controlled in accordance with the thickness of the water film formed on the surface of the entry side roll or the amount of water supplied to the surface of the entry side roll. The method of supplying a lubricant according to claim 1 or 2.

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