JP6051944B2 - Manufacturing apparatus and manufacturing method of differential steel plate - Google Patents

Description

  The present invention relates to a manufacturing apparatus for manufacturing a differential steel sheet having a thickness difference in the longitudinal direction using a rolling mill having a work roll, and a manufacturing method thereof.

  In recent years, weight reduction has been promoted in order to improve the fuel efficiency of automobiles. One way to reduce the weight is to improve the metal material constituting the body of the automobile. Specifically, in addition to the method of changing the steel material of the automobile body component to a thin and high strength steel material, or the method of changing the material of the component member to an aluminum alloy or magnesium alloy having a lighter specific gravity than steel, For example, there may be mentioned a method of imparting a thickness distribution to the constituent members so as to reduce the thickness of the constituent members to the limit that can ensure the performance.

  Among these, regarding the method of attaching the plate thickness distribution to the constituent members, the steel plate provided with the plate thickness distribution is generally called a differential thickness steel plate. There are various types of differential thickness steel plates depending on the application. For example, a material having a length of about 2000 mm and a width of about 500 mm, a plate thickness of 2 mm from both ends in the longitudinal direction to 300 mm, and a central portion having a plate thickness of 1.6 mm (plate thickness 2 level symmetrical type), or conversely in the longitudinal direction From the both ends to 300 mm, a plate type with a plate thickness of 1.8 mm and a central portion with a plate thickness of 2.0 mm (plate thickness 2 level symmetrical type) can be mentioned. Other examples include those in which the plate thickness is changed in a taper shape in the longitudinal direction, and those having a multi-level thickness or a symmetric or asymmetric type.

  As a method for producing such a differential thickness steel sheet, for example, a method of operating a rolling position (roll gap) of a work roll during rolling using a rolling mill is conceivable (for example, Patent Document 1). In particular, in the rolling method described in Patent Document 1, a load cell for detecting a rolling load is provided, and the rolling load detected by the load cell is reduced so as to be a required load calculated based on a required plate thickness. The device is controlled. In addition, as a manufacturing method of the differential thickness steel plate, in addition to a method using a rolling mill, a method by a press, etc. can be considered, so in this specification, in particular, a method of manufacturing the differential thickness steel plate using a rolling mill, This is referred to as a method of manufacturing a differential thickness steel plate by a rolling method.

  By the way, as a manufacturing method of the differential thickness steel plate by the rolling method, the plate thickness detecting device provided on the rolling mill delivery side detects the thickness of the material to be rolled on the rolling mill delivery side, and the reduction position based on the detected value. It is conceivable to control. However, in the differential thickness steel plate, the length in the rolling direction of the portion where the plate thickness is constant is generally short. For this reason, since there is a certain distance from the roll bite outlet to the plate thickness detection device, a dead time occurs, and this method cannot perform appropriate plate thickness control.

  In addition, another method for producing a differential thickness steel sheet by rolling is to detect the thickness and speed of the material to be rolled on the entry side of the rolling mill and the speed of the material to be rolled on the exit side of the rolling mill, and use a constant mass flow rule. It is also conceivable to estimate the thickness of the material to be rolled on the exit side of the rolling mill and to control the reduction position based on the estimated value. However, even in the method using the constant mass flow rule, it is difficult to install a device for detecting the speed of the material to be rolled on the exit side of the rolling mill in the immediate vicinity of the roll bite outlet, resulting in wasted time, Since an estimation error occurs in the thickness of the material to be rolled due to the widening of the width, appropriate thickness control cannot be performed even by this method. In addition, this method requires a plurality of speed detection devices and plate thickness detection devices, which increases the equipment cost.

  In consideration of such a situation, a preset rolling method and an absolute value rolling method have been proposed as methods for producing a differential thickness steel plate by a rolling method. In the preset rolling method, the relationship between the rolling position of the rolling mill and the thickness of the material to be rolled that has been rolled by the rolling mill is obtained in advance by experiments or numerical calculations. During rolling, the rolling length, which is the length in the rolling direction of the part already rolled by the rolling mill, of the material being rolled by the rolling mill is calculated based on the rotation speed of the work roll, and in advance Based on the relationship between the obtained reduction position and the thickness after rolling, and the calculated rolling length, the reduction position is controlled so that the thickness distribution of the material to be rolled becomes a target thickness pattern.

  In the absolute value rolling method, the relationship between the rolling load and the deformation of the rolling mill (deformation characteristics of the rolling mill) is obtained in advance by experiments, numerical calculations, and the like. During rolling, the rolling length is calculated based on the rotation speed of the work roll, the rolling load is detected, and the roll bite exit is determined based on the previously determined deformation characteristics of the rolling mill and the detected rolling load. The thickness of the material to be rolled at is estimated. Then, based on the calculated rolling length, the reduction position is controlled so that the thickness estimated in this way becomes the target thickness.

JP-A-3-281010

  By the way, as described above, in the manufacturing method of the differential thickness steel plate by the rolling method, the plate thickness of the material to be rolled is basically changed by changing the rolling position of the rolling mill. When such a method is used, it is necessary to increase the control speed of the reduction position in order to increase the production speed (productivity) of the differential thickness steel sheet. In general, since the hydraulic pressure reduction device has high responsiveness, it is essential to install the hydraulic pressure reduction device in order to increase the control speed of the reduction position. However, since the hydraulic reduction device is expensive, the equipment cost increases, and as a result, the manufacturing cost of the differential thickness steel sheet increases.

  On the other hand, as the reduction device, there is an electric reduction device in addition to the hydraulic reduction device. Since the electric reduction device is less expensive than the hydraulic reduction device, the use of the electric reduction device as the reduction device can reduce the equipment cost. However, since the responsiveness related to the reduction position of the electric reduction device is low, when using the electric reduction device, the rolling speed (speed at which the material to be rolled is fed from the rolling mill) must be slowed down. Production speed will be slow.

  Then, in view of the said subject, the objective of this invention is providing the manufacturing apparatus and manufacturing method of a differential thickness steel plate which can raise a manufacturing speed, restraining equipment cost low.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research and heated the material to be rolled on the rolling mill entrance side without almost operating the reduction position, and thus the temperature distribution in the longitudinal direction of the material to be rolled. It is used at this time because it is possible to produce a differential thickness steel sheet at a relatively high production speed by rolling with a rolling mill in the state in which it is generated, and in this case it is almost unnecessary to operate the reduction position. It has been found that the reduction device that does not need to be a highly responsive hydraulic reduction device.

This invention was made | formed based on the said knowledge, and the summary is as follows.
(1) A rolling mill having a reduction device, a heating device that is provided on the entry side of the rolling mill and heats a material to be rolled that enters the rolling mill, and a heating amount control device that controls the heating amount in the heating device A rolling length estimation device that detects or calculates a rolling length that is a length in a rolling direction of a portion that has already been rolled by the rolling mill among the material being rolled by the rolling mill, and sends out from the rolling mill A rolling material cooling device for cooling the rolled material that has been rolled ,
The heating amount control device uses the rolling length estimation device according to a target thickness pattern that is a thickness distribution in the rolling direction of the differential thickness steel plate to be manufactured by the manufacturing device during rolling of the material to be rolled. The heating amount of the heating device is changed based on the detected or calculated rolling length, and the rolling material cooling device cools strongly as the thickness of the material to be rolled cooled by the rolling material cooling device decreases. Differential thickness steel plate manufacturing equipment.
(2) The heating amount control device increases the heating amount when the thickness of the portion of the material to be rolled from now on by the rolling mill is made thinner than the thickness of the portion of the material to be rolled immediately before rolling. The difference according to (1) above, wherein when the thickness of the portion of the material to be rolled from now on by the rolling mill is made thicker than the thickness of the portion of the material to be rolled immediately before, the heating amount is reduced. Thick steel plate manufacturing equipment.
(3) The apparatus for producing a differential thickness steel sheet according to (1) or (2), wherein the reduction position in the rolling mill is maintained constant over the entire rolling period of one rolled material.
(4) The heating amount control device holds a relationship between a steel sheet temperature and a rolling reduction ratio of the material to be rolled entering the rolling mill as a map or a calculation formula, and the material to be rolled is the target by the rolling mill. The heating amount is determined using the rolling length detected or calculated by the rolling length estimation device based on the relationship between the inlet side steel plate temperature and the reduction rate held in the heating amount control device so as to form a thickness pattern. The apparatus for manufacturing a differential thickness steel sheet according to any one of (1) to (3), wherein the apparatus is changed.
(5) The apparatus for manufacturing a differential thickness steel sheet according to any one of (1) to (4), further including a pattern input device for inputting the target thickness pattern.
( 6 ) The rolling mill comprises a pair of work rolls for rolling the material to be rolled,
The manufacturing apparatus of the differential thickness steel plate further includes a work roll cooling device that cools the pair of work rolls, and the work roll cooling device changes a cooling condition with the rotation of the work roll. The apparatus for producing a differential thickness steel sheet according to any one of 1) to ( 5 ).
( 7 ) The difference according to any one of (1) to ( 6 ), wherein the rolling mill includes a pair of work rolls for rolling the material to be rolled, and the work rolls have a sintered layer on the surface thereof. Thick steel plate manufacturing equipment.
( 8 ) A rolling mill having a reduction device, a heating device that is provided on the entry side of the rolling mill and that heats the material to be rolled and enters the rolling mill, and a heating amount control device that controls the heating amount in the heating device A rolling length estimation device that detects or calculates a rolling length that is a length in a rolling direction of a portion that has already been rolled by the rolling mill among the material being rolled by the rolling mill, and sends out from the rolling mill In the manufacturing method of the differential thickness steel sheet by the manufacturing apparatus of the differential thickness steel sheet provided with the rolling material cooling device that cools the rolled material that has been made,
According to the target thickness pattern which is the thickness distribution in the rolling direction of the differential thickness steel sheet to be manufactured by the manufacturing method, the heating amount for heating the material to be rolled by the heating device is changed during the rolling of the material to be rolled. The rolled material cooling device is a method for manufacturing a differential thickness steel plate , wherein the rolled material cooling device performs cooling more strongly as the thickness of the material to be rolled cooled by the rolled material cooling device becomes thinner .
( 9 ) When the amount of heating of the material to be rolled by the heating device is set to be smaller than the thickness of the portion of the material to be rolled that has been rolled immediately before the portion of the material to be rolled to be rolled by the rolling mill. are greatly, is reduced when thicker than the plate thickness of the portion of the rolled material which has been rolled immediately before the plate thickness of the portion of the material to be rolled which is now rolled by the rolling mill, according to the above (8) The manufacturing method of the difference thickness steel plate.
( 10 ) The method for producing a differential thickness steel sheet according to ( 8 ) or ( 9 ), wherein the reduction position in the rolling mill is maintained constant over the entire rolling period of one rolled material.
( 11 ) Heating by which the relationship between the inlet side steel plate temperature, the inlet side plate thickness, and the outlet side plate thickness of the material to be rolled entering the rolling mill is determined in advance as the relationship between the temperature and the reduction ratio, and the material to be rolled is heated by the heating device. The amount is changed according to any one of the above ( 8 ) to ( 10 ), which is changed based on the relationship between the temperature and the rolling reduction ratio so that the material to be rolled becomes the target thickness pattern by the rolling mill. The manufacturing method of the difference thickness steel plate.

  According to the manufacturing apparatus and the manufacturing method of the differential thickness steel sheet of the present invention, the manufacturing speed can be increased while keeping the equipment cost low.

FIG. 1 is a diagram schematically showing an apparatus for producing a differential thickness steel sheet according to the present invention. FIG. 2 is a diagram showing the relationship between the inlet side plate temperature, the rolling reduction, and the rolling load in a 60-kilometer with a thickness of 3.06 mm and a width of 400 mm. FIG. 3 is a diagram showing the relationship between the target thickness with respect to the rolling length and the heating amount. FIG. 4 is a cross-sectional view showing dimensions of the differential thickness steel plate manufactured in this example. FIG. 5 is a diagram showing a heating device used in the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

  FIG. 1 is a diagram schematically showing a production apparatus 1 for a differential thickness steel plate according to a first embodiment of the present invention. As shown in FIG. 1, the manufacturing apparatus 1 includes a payoff reel 11 on which a metal strip S as a material to be rolled is unwound and a metal strip S wound on the payoff reel 11 on the entry side of the rolling mill 10. A pinch roll 12 to be unwound, an entrance deflector roll 13 for changing the traveling direction of the metal strip S (the direction indicated by the arrow in FIG. 1), a heating device 14 for heating the metal strip S entering the rolling mill 10, and A temperature sensor 15 is provided between the heating device 14 and the rolling mill 10 to detect the temperature of the metal strip S delivered from the heating device 14.

  In addition, the manufacturing apparatus 1 includes a rolling material cooling device 21 that cools the metal strip S rolled by the rolling mill 10 on the exit side of the rolling mill 10, and a downstream side of the rolling material cooling device 21 in the traveling direction of the metal strip S. A temperature sensor 22 for detecting the temperature of the metal strip S delivered from the rolling material cooling device 21, an outlet deflector roll 23 for changing the traveling direction of the metal strip S, and a tension for winding the metal strip S And a reel 24.

  In the manufacturing apparatus 1 configured as described above, the metal strip S that is a material to be rolled is set in the manufacturing apparatus 1 in a state of being wound around the payoff reel 11. A pinch roll 12 is provided on the downstream side of the payoff reel 11 in the traveling direction of the metal strip S. The pinch roll 12 is driven by a driving device (not shown) such as a motor, and unwinds the metal strip S wound around the payoff reel 11. An entrance deflector roll 13 is provided on the downstream side of the pinch roll 12 in the traveling direction of the metal strip S. The entrance side deflector roll 13 is a rotatable roll that is not driven by a driving device or the like.

  In this embodiment, the rotational speed of the pinch roll 12 is controlled so that a predetermined slack is formed in the metal strip S between the pinch roll 12 and the entrance deflector roll 13 as shown in FIG. . By forming a predetermined slack in the metal strip S in this way, a tension applied to the metal strip S on the inlet side of the rolling mill 10 by the dead weight of the metal strip S (hereinafter referred to as “roller inlet side tension”) is a predetermined tension. Can be kept in. As a method for keeping the rolling mill entry side tension constant, it is generally necessary to separately provide an expensive facility for controlling the tension. In this embodiment, however, the pinch roll 12 and the entry side deflector roll 13 are not provided. The tension on the entry side of the rolling mill is controlled only by controlling the slack of the metal strip S. For this reason, according to this embodiment, the rolling mill entry-side tension can be controlled with inexpensive equipment.

  As shown in FIG. 1, a heating device 14 is provided on the downstream side of the entrance deflector roll 13 in the traveling direction of the metal strip S and immediately upstream of the rolling mill 10. In the present embodiment, the heating device 14 is an induction heating device that includes induction heating coils disposed above and below the metal strip S, and that induction-heats the metal strip S by causing a current to flow through these induction heating coils. . The heating device 14 does not necessarily have to use an induction heating coil, and any heating device may be used as long as the metal strip S can be locally heated. Therefore, for example, various methods such as an energizing heating apparatus that heats the metal strip S by contacting the metal strip S with the upper and lower sides of the metal strip S and passing an electric current between the energizing heating rolls and an apparatus using infrared heating. A heating device using can be used.

  A temperature sensor 15 that detects the temperature of the metal strip S is disposed immediately downstream of the heating device 14 in the traveling direction of the metal strip S. Both the heating device 14 and the temperature sensor 15 are connected to the control device 16. The heating device 14 is feedback-controlled based on the temperature detected by the temperature sensor 15 so that the temperature of the metal strip S entering the rolling mill 10 becomes the target temperature. Note that the heating device 14 does not necessarily need to be feedback-controlled based on the temperature detected by the temperature sensor 15, and can be controlled by various methods such as feed-forward control based on the target temperature.

  In the present embodiment, the rolling mill 10 is a four-high rolling mill and includes a pair of work rolls 17 and a pair of backup rolls 18. Each work roll 17 is formed to have a sintered layer on its surface. On the upper portion of the upper chock (not shown) of the upper backup roll 18, an electric reduction device 19 that controls the reduction position of the work roll 17 (that is, the roll gap between the work rolls 17) is provided. Further, a load cell (not shown) for detecting a rolling load is provided on the upper portion of the upper backup roll 18. The electric reduction device 19 and the load cell are connected to the control device 16. Therefore, the rolling load detected by the load cell is input to the control device 16 and the electric reduction device 19 is controlled by the control device 16.

  In the present embodiment, the work roll 17 is provided with a speed detection device (not shown) for detecting the rotation speed of the work roll 17. The speed detection device is connected to the control device 16, and the control device 16 uses the rolling mill 10 out of the metal strip S rolled by the rolling mill 10 based on the rotation speed of the work roll 17 detected by the speed detection device. The length in the rolling direction of the portion that has already been rolled (hereinafter referred to as “rolling length”) is calculated. The detection or calculation (estimation) of the rolling length may be performed by other methods. For example, the estimation of the rolling length may be performed based on the output of a device that detects the speed of the metal strip S sent from the rolling mill 10.

  In addition, a work roll cooling device 25 that cools the work roll 17 is provided in the vicinity of the work roll 17. In the example shown in FIG. 1, the work roll cooling device 25 is arranged only in the vicinity of the upper work roll 17 to cool the upper work roll 17, but in the vicinity of the lower work roll 17. The lower work roll 17 may be arranged and cooled, or may be arranged near the upper and lower work rolls 17 to cool the upper and lower work rolls.

  In the present embodiment, the rolling material cooling device 21 performs cooling by spraying a cooling medium (for example, emulsion lubricant) to the work roll 17 at room temperature. For this reason, the part of the work roll 17 sprayed with the cooling medium is strongly cooled as the amount of the cooling medium sprayed onto the work roll 17 increases. As the work roll cooling device 25 for cooling the work roll 17, any cooling device may be used as long as the work roll 17 can be locally cooled.

  A rolling material cooling device 21 is provided immediately downstream of the rolling mill 10 in the traveling direction of the metal strip S. In the present embodiment, the rolling material cooling device 21 performs cooling by spraying a cooling medium at normal temperature onto the metal strip S. For this reason, as the amount of the cooling medium sprayed on the metal strip S increases, the portion of the metal strip S on which the cooling medium is sprayed is strongly cooled. As the rolling material cooling device 21 for cooling the metal strip S sent from the rolling mill 10, any cooling device may be used as long as the metal strip S can be locally cooled.

  A temperature sensor 22 that detects the temperature of the metal strip S is disposed immediately downstream of the rolling material cooling device 21 in the traveling direction of the metal strip S. Both the rolling material cooling device 21 and the temperature sensor 22 are connected to the control device 16. The rolled material cooling device 21 is subjected to Ford back control based on the temperature detected by the temperature sensor 22 so that the temperature of the metal strip S cooled by the rolled material cooling device 21 becomes the target temperature. The rolled material cooling device 21 does not necessarily need to be feedback-controlled based on the temperature detected by the temperature sensor 22, and is controlled based on the thickness of the metal strip S sent from the rolling mill 10 as will be described later. May be.

  An outgoing deflector roll 23 is provided downstream of the temperature sensor 22 in the traveling direction of the metal strip S. The exit deflector roll 23 is a rotatable roll that is not driven by a driving device or the like. A tension reel 24 is provided on the downstream side of the outlet deflector roll 23, and the metal strip S is taken up by the tension reel 24.

  In the present embodiment, a plurality of roller guides (not shown) are provided on the upstream side of the rolling mill 10 in the traveling direction of the metal strip S in order to fix a horizontal position perpendicular to the traveling direction of the metal strip S. Is provided. In the present embodiment, a lubricating oil supply device (not shown) for supplying rolling lubricating oil (for example, emulsion lubricating oil) for rolling lubrication to the roll bite inlet of the rolling mill 10 is provided. In particular, the lubricating oil used in the lubricating oil supply device and the cooling medium used in the work roll cooling device 25 are the same lubricating oil. For this reason, the lubricating oil is supplied to the lubricating oil supply device and the work roll cooling device 25 from a common lubricating oil tank, and via a lubricating oil recovery tank (not shown) provided in the lower part of the rolling mill 10. Collected in the lubricating oil tank. The control device 16 has an input device (not shown) for inputting a thickness distribution in the rolling direction of the differential thickness steel sheet to be produced by the production device 1 (hereinafter referred to as “target thickness pattern”). May be.

  Moreover, in the said embodiment, the rolling of a difference thickness steel plate is continuously performed using the continuous metal strip S. FIG. However, for example, a metal strip S having a predetermined length may be supplied to the rolling mill 10. In this case, instead of the payoff reel 11 and the tension reel 24, a storage device or the like that stores a predetermined length of the metal strip S in a stacked manner is used.

  By the way, the inventor of the present application changes the temperature of the metal strip S entering the rolling mill 10 (hereinafter referred to as “entrance side plate temperature”) using the apparatus as shown in FIG. And the relationship between rolling load was investigated. Specific experimental conditions are as follows.

  First, as the metal strip S, a material having a tensile strength of 600 MPa called 60 kg high tensile strength was used. The metal strip S was a hot-rolled slit material having a plate thickness of 3.06 mm and a plate width of 400 mm (coil having an oxide scale on the surface called a black skin material). The work roll 17 of the rolling mill 10 has a diameter of 300 mm and a trunk length of 500 mm, and the backup roll 18 has a diameter of 1200 mm and a trunk length of 500 mm.

  As a result of experiment using such a metal strip S and the rolling mill 10, the result as shown in FIG. 2 was obtained. From FIG. 2, it can be seen that the rolling load decreases as the entry side plate temperature increases, and the rolling load increases as the rolling reduction increases. In FIG. 2, for example, when the rolling load at the time of rolling is 1 MN, the entry material temperature is about 2% reduction at room temperature, about 8% reduction at 500 ° C., about 18% reduction at 700 ° C., 900 ° C. Then, rolling is performed at a rolling reduction of 40%. In other words, it is understood that when the rolling load is rolled at 1 MN, the outlet side plate thickness can be changed by adjusting the inlet side plate temperature without operating the reduction position.

  Therefore, in the present invention, the entry side plate temperature is changed during rolling according to the thickness distribution (target thickness pattern) in the rolling direction of the differential thickness steel plate to be produced by the production apparatus 1. In addition, since the entry side plate temperature changes depending on the heating amount of the heating device 14, it can be said that the heating amount of the metal strip S by the heating device 14 is changed during rolling according to the target thickness pattern in the present invention. .

  More specifically, when the thickness of the portion of the metal strip S to be rolled by the rolling mill 10 is made thinner than the thickness of the portion of the metal strip S rolled immediately before, the heating amount is increased. Therefore, when the plate thickness of the portion of the metal strip S to be rolled is made thicker than the plate thickness of the portion of the metal strip S rolled immediately before, the heating amount is reduced.

  Moreover, in this embodiment, rolling is performed in the state maintained constant, without changing the reduction position or rolling load in a rolling mill over the whole rolling period of one metal strip S.

  FIG. 3 shows the relationship between the target thickness with respect to the rolling length and the heating amount when, for example, a differential thickness steel plate as shown in FIG. 4 is manufactured. As can be seen from the figure, the target thickness is changed so as to be thinner at the portion where the rolling length is the length ab, and is further reduced at the portion where the rolling length is the length c-d. To change. The target thickness is changed so as to be thicker at the place where the rolling length is the length ef, and is changed so as to be thicker further at the place where the rolling length is gh. The extension returns to the same target thickness as the target thickness from 0 to a.

  With respect to such a target thickness pattern, the heating amount in the heating device 14 gradually increases when the rolling length becomes the lengths a to b, and is accordingly rolled by the rolling mill 10. The thickness of the metal strip S gradually decreases. Thereafter, a constant heating amount is maintained until the rolling length reaches the length c, and during that time, the thickness of the metal strip S rolled by the rolling mill 10 is also maintained constant. Thereafter, when the rolling length becomes the length c to d, the heating amount in the heating device 14 increases again, and accordingly, the thickness of the metal strip S rolled by the rolling mill 10 is gradually reduced. Become. After that, when the rolling length becomes the lengths ef and gh, the heating amount in the heating device 14 decreases, and accordingly, the metal strip S rolled by the rolling mill 10 is reduced. The plate thickness gradually increases.

Further, the specific heating amount is calculated based on the following formula (1).
r = (aT ² + bT + c) P + d (1)
In equation (1), r is the rolling reduction, P is the rolling load, and T is the temperature. The coefficients a, b, c, and d are values calculated based on the experimental results as shown in FIG. 2, for example. In addition, although the quadratic approximation is performed in the expression (1), other approximate expressions such as a cubic approximation may be used.

  By using the above equation (1), the target entry side plate temperature can be calculated based on the target reduction rate calculated from the target thickness pattern and the set value of the rolling load. Based on this, the heating amount by the heating device 14 is calculated. Therefore, in the present embodiment, the above-described equation (1) or a similar map is held in the control device 16, and when the rolling is actually performed, the metal strip S and the target thickness pattern are rolled by the rolling mill 10. As described above, the heating amount by the heating device 14 is changed using the rolling length calculated in the control device 16 based on the reduction ratio held in the control device 16 and the relationship between the rolling load and the entry side steel plate temperature. .

  According to the present invention, by changing the entry side plate temperature in this manner, the differential thickness steel sheet can be rolled and manufactured without changing the rolling position of the rolling mill 10 at all or almost. For this reason, even if it uses the electric reduction device with a low response speed regarding the change of the reduction position, the differential thickness steel plate can be manufactured at a relatively high manufacturing speed.

  By the way, generally, when the rolling reduction and temperature at the time of rolling differ, a difference occurs in the quality (for example, strength) of the differential thickness steel sheet after rolling. The differential thickness steel sheet is pressed or hot press-molded after rolling to produce a final structural material. If the quality of the differential thickness steel sheet after rolling varies, variations such as springback are caused. For this reason, generally, a difference thickness steel plate is often heat-treated after rolling.

  Here, as described above, a sample of the differential thickness steel plate was produced by rolling by changing the inlet side plate temperature (the conditions of the material, the rolling mill, and the like are the same as the conditions used in the experiment). This sample was obtained by rolling at a temperature of 20 ° C. and 900 ° C. with a rolling load of 1MN, and is a differential thickness steel plate having a portion with a plate thickness of 3 mm and a portion with a plate thickness of 1.87 mm. is there. During the production of the differential thickness steel plate sample, cooling was performed under the same conditions in all regions of the differential thickness steel plate.

  As a result, in the case of no cooling, in the sample of the differential thickness steel plate, the yield strength in the portion with the plate thickness of 3 mm was 400 MPa, and the yield strength in the portion with the plate thickness of 1.87 mm was 350 MPa. When a V-bending test of R10 mm was performed on this material, a difference of 3 degrees in the bending angle was caused by the difference in springback between the portion having a plate thickness of 3 mm and the portion having a plate thickness of 1.87 mm.

  Therefore, in the present embodiment, the rolled material cooling device 21 is configured to change the cooling condition according to the plate thickness of the metal strip S cooled by the rolled material cooling device 21. In particular, in the present embodiment, the cooling is performed more strongly as the plate thickness of the metal strip S cooled by the rolled material cooling device 21 becomes thinner. As described above, in the present embodiment, the cooling is performed by spraying the cooling medium, so that the amount of the cooling medium sprayed onto the metal strip S increases as the thickness of the metal strip S decreases.

  Here, the plate thickness of the metal strip S changes according to the inlet side plate temperature and the rolling reduction in the rolling mill 10. The higher the entry side plate temperature, the higher the rolling reduction in the rolling mill 10, and as a result, the thickness of the metal strip S becomes thinner and the yield strength of the thinner plate thickness portion becomes larger. Therefore, in this embodiment, the metal strip S is cooled more strongly as the entrance side plate temperature becomes higher and the reduction ratio becomes higher.

  Thereby, the proof stress of the metal strip S can be set to the same value in regions having different plate thicknesses. As a result, it is possible to manufacture a differential thickness steel plate with almost no material variation, and thus, the differential thickness steel plate is conventionally heat-treated after rolling, but this step can be omitted, and thus the manufacturing cost can be reduced. .

The specific supply amount of the cooling medium is calculated based on the following formula (2).
σ _y = eQ ² h + fQh + g (2)
In Equation (2), σ _y is the proof stress, Q is the supply flow rate of the cooling medium, and h is the thickness of the rolled metal strip S (that is, the metal strip S entering the rolled material cooling device 21). The coefficients e, f, and g are values that are calculated in advance through experiments and numerical calculations. In addition, although the quadratic approximation is performed in Expression (2), other approximate expressions such as a cubic approximation may be used.

By using the above equation (2), the thickness h of the metal strip S entering the rolling material cooling device 21 and the target yield strength (for example, constant over the entire rolling period of one metal strip S) σ _y Based on this, the flow rate Q of the cooling medium, which is the cooling condition, can be calculated.

  Using this knowledge, as a result of changing the cooling conditions at the time of sample production of the above-mentioned differential thickness steel plate according to the plate thickness, the proof stress in the portion where the plate thickness is 3 mm is 400 MPa, the proof strength in the portion where the plate thickness is 1.87 mm. The pressure could be 405 MPa. When this material was subjected to an R 10 mm V-bending test, a bending angle of only 0.1 degree was generated between a portion having a plate thickness of 3 mm and a portion having a plate thickness of 1.87 mm.

  By the way, the work roll 17 contacts the metal strip S whose temperature changes during rolling. For this reason, a temperature distribution is formed in the circumferential direction of the work roll 17 in contact with the metal strip S. Thus, when the circumferential temperature distribution occurs in the work roll 17, the degree of thermal expansion changes in the circumferential direction of the work roll 17, and as a result, the thickness of the metal strip S rolled by the rolling mill 10 is reduced. There is a possibility of reducing the thickness and reducing the flatness of the surface.

  Therefore, in the present embodiment, when the work roll 17 is cooled by the work roll cooling device 25, the portion of the work roll 17 that is in contact with the high-temperature metal strip S is strongly increased by increasing the spray amount of the cooling medium. The part of the work roll 17 that is cooled and comes into contact with the low-temperature metal strip S is cooled weakly by reducing the spray amount of the cooling medium. Thereby, the surface temperature of the work roll 17 can be maintained substantially constant over the circumferential direction, and as a result, the work roll 17 is suppressed from being deformed in the circumferential direction due to thermal expansion.

  In the present embodiment, a sintered layer is provided on the surface of the work roll 17. Since the sintered layer thus provided is difficult to thermally expand, when the sintered layer is provided on the surface of the work roll 17 as described above, the work roll 17 is suppressed from being deformed in the circumferential direction due to the thermal expansion. .

  Next, with reference to FIG. 5, the manufacturing apparatus of the differential thickness steel plate which concerns on 2nd embodiment of this invention is demonstrated. The configuration of the differential thickness steel plate of the second embodiment is basically the same as that of the differential thickness steel plate of the first embodiment. However, in the second embodiment, a heating device different from that in the first embodiment is used.

  FIG. 5 is a diagram schematically showing the heating device 14 ′ in the present embodiment, and the arrows in the figure indicate the traveling direction of the metal strip S. As shown in FIG. 5, the heating device 14 ′ includes a heating control device 31, a heating transformer 32, an energizing roll 33, a turndown roll 34, a sink roll 35, a pot 37 in which a molten metal bath 36 is stored, and a conductive wire. 38.

  The heating control device 31 supplies AC power to the heating transformer 32 (primary winding) based on the target temperature of the metal strip S. When the target temperature of the metal strip S is high, that is, when the required heating amount of the metal strip S is large, the AC power supplied to the heating transformer 32 is increased, and when the target temperature of the metal strip S is low, that is, the necessity of the metal strip S When the amount of heating is small, the AC power supplied to the heating transformer 32 is reduced.

  The heating transformer 32 is a so-called ring transformer, and includes an iron core and a primary winding wound around the iron core. In the present embodiment, the primary winding is provided with a plurality of taps, and the output destination of the AC power supplied from the heating control device 31 is switched between the plurality of taps to change the primary winding of the heating transformer 32. The number can be changed.

  The energizing roll 33 is a roll for energizing the metal strip S conveyed from the upstream side in the traveling direction of the metal strip S, and at least the surface thereof is formed of a conductive material. The energizing roll 33 becomes one of the electrodes on the secondary side of the heating transformer 32. The metal strip S that has passed through the energizing roll 33 passes through the heating transformer 32, more specifically, through the hollow portion of the iron core of the heating transformer 32.

  The turn-down roll 34 is a roll that changes the traveling direction of the metal strip S conveyed in the horizontal direction from the energizing roll 33 to a direction (diagonally downward) toward the sink roll 35 in the pot 37. The metal strip S that has passed through the turn-down roll 34 enters the molten metal bath 36 in the pot 37, and the surface thereof is plated. The molten metal bath 36 is, for example, a molten zinc bath or a molten zinc-based alloy bath, and becomes one of the electrodes on the secondary side of the heating transformer 32. One end of the conductive wire 38 is connected to the energizing roll 33, and the other end is immersed in the molten metal bath 36.

  As shown in FIG. 5, in the present embodiment, the heating transformer 32 includes the energizing roll 33, the metal strip S between the energizing roll 33 and the molten metal bath 36, the molten metal bath 36, and the conductive wires 38. Secondary circuit (secondary winding) is formed. The secondary winding of the heating transformer 32 is one turn, whereas the number of turns of the primary winding included in the heating transformer 32 is, for example, 50 to 100 turns (changeable by switching taps). In this way, by making the number of turns of the primary winding much larger than the number of turns of the secondary winding, even if the AC power supplied to the primary winding of the heating transformer 32 is small, the secondary winding is large. Current can flow.

  Using the apparatus shown in FIG. 1, a differential steel plate having a thickness difference in the longitudinal direction was produced. The material and the like are the same as the above-described sample of the differential thickness steel plate. FIG. 4 shows the dimensions of the differential thickness steel plate manufactured in this example. FIG. 4 is a cross-sectional view of the manufactured differential thickness steel sheet cut in the longitudinal direction. Moreover, the length of the taper part (inclination part between the parts from which plate | board thickness differs) was 10-40 mm.

  In this example, an electric reduction rolling mill was used, and the reduction position during normal temperature rolling was set so that the rolling load was 1 MN. During rolling, the rolling length is estimated from the rotation speed of the work roll, the target value for the thickness of the differential thickness steel plate is given based on the estimated value, and the target value for the inlet side plate temperature is calculated so as to be the target value for the thickness. Then, the heating amount of the heating device was controlled so as to reach the target value of the plate temperature. Moreover, the cooling conditions (flow rate) in the rolling material cooling device were controlled based on the thickness after rolling so that there was no material variation. Specifically, the rolling load was changed to about 1 KN, and the inlet side plate temperature was changed in three stages of room temperature, about 708 ° C., and about 911 ° C. The target values for the cooling conditions were 4000 cc / min in the region where the inlet side plate temperature was room temperature (the region where the plate thickness was the thickest), 6680 cc / min in the region of about 708 ° C., and 8150 cc / min in the region of about 911 ° C. This value was calculated using the same formula as formula (2) above.

  As a comparative example, an electric rolling mill was used to control the rolling position of the rolling mill using the relationship between the rolling position (rolling load) and the plate thickness obtained in advance by experiments. During rolling, the rolling length is estimated from the rotation speed of the work roll, the target thickness value of the differential thickness steel sheet is calculated based on the estimated value, and the reduction position of the rolling mill is set so that the target thickness value is obtained. Controlled. At this time, heating of the metal strip by the heating device and cooling by the rolling material cooling device were not performed.

  In this example, the differential thickness steel plate shown in FIG. 4 could be manufactured at a rolling speed of 50 m / min within a plate thickness accuracy of ± 10%. Also in the comparative example, the differential thickness steel plate shown in FIG. 4 could be manufactured with a plate thickness accuracy of ± 10%. However, since the reduction speed under electric reduction is 300 μm / sec, the rolling speed is limited to about 0.3 to 1.5 m / min in order to keep the length of the tapered portion between 10 and 40 mm. It was done. In this comparative example, the rolling speed was 1 m / min.

  Further, the material variation (proof strength) in the longitudinal direction after rolling was within 5% (maximum sheet thickness standard) in the present example, but within + 40% (maximum sheet thickness standard) in the comparative example. Note that the variation in the comparative example was improved to almost the same extent as in the present example by heat treatment in a separate process.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 10 Rolling machine 11 Payoff reel 12 Pinch roll 13 Deflector roll 14 Heating apparatus 15 Temperature sensor 16 Control apparatus 17 Work roll 18 Backup roll 19 Electric reduction apparatus 21 Rolling material cooling apparatus 22 Temperature sensor 23 Deflector roll 24 Tension reel 25 Workpiece Roll cooling device S Metal strip

Claims (11)

A rolling mill having a reduction device, a heating device that is provided on the entry side of the rolling mill and heats the material to be rolled and enters the rolling mill, a heating amount control device that controls a heating amount in the heating device, and A rolling length estimation device that detects or calculates a rolling length that is a length in a rolling direction of a portion that has already been rolled by the rolling mill among the rolled material that has been rolled by the rolling mill, and a workpiece that is sent from the rolling mill. A rolling material cooling device for cooling the rolled material ;
The heating amount control device uses the rolling length estimation device according to a target thickness pattern that is a thickness distribution in the rolling direction of the differential thickness steel plate to be manufactured by the manufacturing device during rolling of the material to be rolled. The heating amount of the heating device is changed based on the detected or calculated rolling length, and the rolling material cooling device cools strongly as the thickness of the material to be rolled cooled by the rolling material cooling device decreases. Differential thickness steel plate manufacturing equipment.   The heating amount control device increases the heating amount when the plate thickness of the portion of the material to be rolled from now on by the rolling mill is made thinner than the plate thickness of the portion of the material to be rolled immediately before, and the rolling The production of the differential thickness steel sheet according to claim 1, wherein the heating amount is reduced when the thickness of the portion of the material to be rolled from now on is made larger than the thickness of the portion of the material to be rolled immediately before rolling by the machine. apparatus.   The apparatus for producing a differential thickness steel sheet according to claim 1 or 2, wherein the rolling position in the rolling mill is maintained constant over the entire rolling period of one material to be rolled.   The heating amount control device holds the relationship between the entry side steel plate temperature and the rolling reduction ratio of the material to be rolled entering the rolling mill as a map or a calculation formula, and the material to be rolled is the target thickness pattern by the rolling mill. So as to change the heating amount using the rolling length detected or calculated by the rolling length estimation device based on the relationship between the entry side steel plate temperature and the reduction rate held in the heating amount control device, The apparatus for producing a differential thickness steel sheet according to any one of claims 1 to 3.   The apparatus for manufacturing a differential steel sheet according to any one of claims 1 to 4, further comprising a pattern input device for inputting the target thickness pattern. The rolling mill includes a pair of work rolls for rolling the material to be rolled,
The apparatus for producing the differential thickness steel sheet further includes a work roll cooling device that cools the pair of work rolls, and the work roll cooling device changes a cooling condition as the work roll rotates. The apparatus for manufacturing a differential thickness steel sheet according to any one of 1 to 5 . The rolling mill comprises a pair of work rolls performing the rolling of the rolled material, they work rolls have a sintered layer on the surface, the production of tailor welded blank according to any one of claims 1 to 6 apparatus. A rolling mill having a reduction device, a heating device that is provided on the entry side of the rolling mill and heats a material to be rolled that enters the rolling mill, a heating amount control device that controls a heating amount in the heating device, and A rolling length estimation device that detects or calculates a rolling length that is a length in a rolling direction of a portion that has already been rolled by the rolling mill among the rolled material that has been rolled by the rolling mill, and a workpiece that is sent from the rolling mill. In the manufacturing method of the differential thickness steel plate by the manufacturing apparatus of the differential thickness steel plate provided with the rolling material cooling device for cooling the rolled material ,
According to the target thickness pattern which is the thickness distribution in the rolling direction of the differential thickness steel sheet to be manufactured by the manufacturing method, the heating amount for heating the material to be rolled by the heating device is changed during the rolling of the material to be rolled. The rolled material cooling device is a method for manufacturing a differential thickness steel plate , wherein the rolled material cooling device performs cooling more strongly as the thickness of the material to be rolled cooled by the rolled material cooling device becomes thinner . The amount of heating of the material to be rolled by the heating device is increased when the thickness of the portion of the material to be rolled from now on by the rolling mill is made thinner than the thickness of the portion of the material to be rolled that has been rolled immediately before. The difference-thickness steel plate according to claim 8 , which is made smaller when the thickness of the portion of the material to be rolled from now on by the rolling mill is made larger than the thickness of the portion of the material to be rolled immediately before rolling. Manufacturing method. The method for producing a differential thickness steel sheet according to claim 8 or 9 , wherein the rolling position in the rolling mill is maintained constant over the entire rolling period of one material to be rolled. Obtaining in advance the relationship between the inlet side steel plate temperature and the inlet side plate thickness and the outlet side plate thickness of the material to be rolled entering the rolling mill as the relationship between temperature and rolling reduction,
The heating amount for heating the material to be rolled by the heating device, the through rolling mill as the material to be rolled becomes the target thickness pattern, is caused to change based on the relationship of the temperature and reduction ratio, according to claim 8 to 10. The method for producing a differential thickness steel sheet according to any one of 10 above.

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