JP2014168802A - Apparatus and method for producing differential thickness steel plate having tapered plate thickness difference in plate width direction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for producing a differential thickness steel plate, allowing for inexpensive production of a tapered differential thickness steel plate in a plate width direction having a large plate thickness difference in the plate width direction.SOLUTION: The apparatus for producing the differential thickness steel plate having the tapered plate thickness difference in the plate width direction includes a plate mill. The plate mill includes on the inlet side of a broadside mill: a device for measuring or inputting a width of a slab; a measuring instrument for measuring a rotational speed of a work roll of the broadside mill; a rolling length calculation device for calculating a rolling length using a measured value of the rotational speed of the work roll; a pattern input device for inputting a pattern of the rolling length and a plate thickness in advance; a device for controlling a roll gap based on a signal of the pattern input device and the rolling length measuring device; a position adjusting device for controlling a position of the turned sheet to an optional desired position with respect to a rolling line in accordance with a cross-sectional shape of the turned sheet; and a device for controlling the roll gap of a finishing mill in such a manner that the crown ratio of the cross-sectional shape of the sheet does not change.

Description

  The present invention relates to a rolling equipment and a rolling method capable of inexpensively and efficiently producing a differential thickness steel sheet having a taper thickness difference in the sheet width direction using a thick plate rolling mill.

  In recent years, weight reduction has been promoted in order to improve the fuel efficiency of automobiles. Specific methods for weight reduction include changing the steel grade of the member to a thinner and higher strength, changing to a lighter specific aluminum alloy or magnesium alloy, and the thickness distribution of the member. There is a method of giving to the limit where acceptable performance can be secured.

  Among the above-described methods, a steel plate provided with a member thickness distribution is generally called a differential thickness steel plate. The difference thickness steel plate is, for example, a material having a length of about 2000 mm and a width of about 500 mm, a concave type with a plate thickness of 2 mm from both ends to 300 mm in the longitudinal direction and a central portion of 1.6 mm (plate thickness difference 2 level) Symmetric type), conversely, the length is 1.8mm from both ends to 300mm in the longitudinal direction, and the central part is a convex type with 2.0mm thickness (plate thickness difference 2 level symmetrical type), or the thickness is tapered. Depending on the application, there are various types, such as those that have changed to symmetries and those that are symmetrical and asymmetrical with multi-level thickness differences.

Among such differential thickness steel plates, a differential thickness steel plate having a thickness difference in the longitudinal direction is manufactured by operating a roll gap (operating a reduction position) during rolling using a rolling mill (for example, Patent Documents). 1).
Moreover, as a manufacturing method of a differential thickness steel plate having a taper thickness difference in the plate width direction, a method of manufacturing with a hot tandem rolling mill is disclosed in, for example, Patent Document 2, but in this way the plate width When the distribution of the plate thickness difference in the direction is asymmetric, camber is generated, so batch rolling cannot roll from the coil tip, and the coil tip is wound on a take-up reel, and the front and back of the material to be rolled are wound. After being constrained by the return and winding mechanism, there is a restriction that the work roll must be manufactured by being tilted or manufactured by being continuously rolled and tilted from the coil joint. For example, when a taper-shaped differential thickness steel plate is used as a winding coil, the outer diameter is different in the plate width direction and becomes an isosceles trapezoidal shape. Therefore, when the coil is removed from the take-up reel and transported to the table without rotating in the vertical direction, the coil becomes unstable, and when transported by a crane, the coil cavity is inclined, so that the crane operability is improved. There is also a problem of significantly inhibiting the above.
In the former batch rolling, the yield drop is large because there is a distance of several tens of meters from the final stand to the take-up reel, and in the latter continuous rolling, an apparatus for joining the hot coil upstream and making it continuous is necessary. In addition, the equipment cost is increased, and the first coil has a large yield drop as in batch rolling.

JP-A-3-281010 JP-A-4-84607

  The present invention makes it possible to efficiently manufacture a difference thickness steel plate having a taper thickness difference in the plate width direction by preventing the above-described large yield drop and without employing expensive equipment. It is an object of the present invention to provide a production apparatus and a production method for a differential thickness steel sheet that can be manufactured at low cost with existing facilities and that facilitates handling of the differential thickness steel sheet produced on a line.

  In order to achieve the above object, the present inventors have conducted intensive research and can efficiently manufacture a differential thickness steel sheet having a desired taper thickness difference in the sheet width direction using an existing thick plate rolling mill. Have discovered a rolling device and a rolling method.

The present invention based on the above findings
(1) A tentering mill for producing a sheet having a desired width by subjecting the heated slab to tenter rolling, a turning device for turning the sheet, and a position adjusting device for centering the position of the turned sheet. An apparatus for measuring or inputting the width of the slab on the entry side of the tenter rolling mill in a thick plate rolling mill having a finish rolling mill for rolling the centered sheet to produce a sheet with a desired thickness Measuring device for measuring the rotation speed of the work roll of the tenter rolling mill, rolling length calculation device for calculating the rolling length from the measured value of the rotation speed of the work roll, and pattern input for previously inputting the pattern of the rolling length and the plate thickness An apparatus, a device for controlling a roll gap based on signals from the pattern input device and the rolling length measuring device, and a rolling line according to the cross-sectional shape of the sheet at the position of the rolled sheet. A taper shape in the sheet width direction, characterized in that a position adjusting device for controlling to a desired position and a device for controlling the roll gap of the finish rolling mill so that the wedge ratio of the cross-sectional shape of the sheet does not change are provided. The apparatus for producing a differential thickness steel plate having a difference in thickness.

  (2) When manufacturing the differential thickness steel sheet using the differential thickness steel sheet manufacturing apparatus having a taper thickness difference in the sheet width direction as described in (1) above, the rolling length calculation device and the pattern input device The roll gap of the tentering mill is controlled based on the signal of the sheet to manufacture the sheet, and the sheet is turned to an arbitrary desired position with respect to the rolling line according to the cross-sectional shape of the sheet. A method for producing a differential thickness steel sheet having a taper thickness difference in the sheet width direction, wherein the roll gap of a finish rolling mill is controlled so that the wedge ratio of the cross-sectional shape of the sheet does not change.

(3) In the method for producing a differential thickness steel sheet having a taper thickness difference in the sheet width direction as described in (2) above, the length in the rolling direction of the sheet after the tenter rolling (the width direction during tenter rolling) The length in the rolling direction of the sheet after the tentering rolling exceeds the preset length and the limit value for the off-centerless rolling of the thickness. The off-center amount is obtained from the relationship between the thickness and the off-center amount, the sheet is off-centered in finish rolling based on the off-center amount, and the sheet thickness ratio in the plate width direction of the sheet is kept constant. By controlling and rolling the roll gap inclination and roll gap in finish rolling, a method for producing a differential thickness steel sheet having a taper thickness difference in the sheet width direction,
It is.

  ADVANTAGE OF THE INVENTION According to this invention, the difference thickness steel plate which has a taper-shaped difference in plate | board width direction can be produced efficiently and at low cost, without a possibility of the occurrence of a camber or meandering.

It is a schematic diagram which shows the outline of a structure of the rolling equipment of a difference thickness steel plate. It is a figure which shows the sheet thickness distribution and rolling direction of tentering rolling and finish rolling. (A) shows the contact state of the work roll edge part by centering of a rolling material, (b) is a figure which shows the avoidance situation of the contact state of the work roll edge part by the off center of a rolling material. It is a figure which shows an example of the difference thickness steel plate manufactured by this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an outline of the configuration of a rolling equipment for differential thickness steel sheets according to the present embodiment, which is a thick plate manufacturing equipment started from, for example, Japanese Patent Application Laid-Open No. 2007-216278.

  In FIG. 1, a thick plate manufacturing facility includes a heating furnace 1, a scale removing device 2, a turning device 3, a turning table 4 as another turning device, a tentering rolling mill 51, a finishing rolling mill 52, and a straightening machine. 6 and the cooling device 7 are provided in this order. The heating furnace 1 is a walking beam type continuous heating furnace, for example, and can heat the cast slab S to a temperature necessary for rolling or a temperature for obtaining a desired material.

  The scale removing device 2 can remove oxide (scale) on the surface of the slab, for example, by jetting high pressure water onto the slab. The turning device 3 is, for example, a tong-type lifting and turning device, and can hold the side surface of the slab S and lift it to turn the slab S by 90 °.

  The turning device 3 is provided at a position away from the downstream rolling mill 51 by more than the maximum rolling length of the operation steel material. The turning table 4 is provided immediately before the tentering mill 51, for example, at a position within 20 m of the tentering mill 51. In the turntable 4, for example, a plurality of rolls having a large diameter portion and a small diameter portion on the same axis are juxtaposed along the roller conveyance table, and the plurality of rolls are arranged so that the positions of the large diameter portions are alternately staggered. The slabs S on the turning table 4 can be turned by the adjacent rolls rotating in opposite directions.

  As the tentering mill 51, for example, a reverse type is used, and reciprocating rolling can be performed by passing the slab S back and forth. The straightening machine 6 behind the finish rolling mill 52 can correct the shape of the rolled steel sheet with a roll, and the cooling device 7 can lower the temperature of the rolled steel sheet to a predetermined temperature.

A search experiment was conducted using the apparatus shown in FIG.
The slab S is a material having a tensile strength of 400 MPa, which is called 40 km high tensile, has a plate thickness of 280 mm, a plate width of 1300 mm, and a total length of 3000 mm. The work roll of the tentering mill 51 has a diameter of 900 mm and a barrel length of 5000 mm, the backup roll is a 4Hi rolling mill with a diameter of 1800 mm and a barrel length of 5000 mm, and the work roll of the finish rolling mill 52 has a diameter of 900 mm and a barrel length of 5000 mm. The backup roll is a 4Hi rolling mill having a diameter of 1800 mm and a body length of 5000 mm.

FIG. 2 is a diagram showing the thickness distribution and rolling direction of tentering and finishing rolling.
First, a slab S having a thickness H ₀ , a length L ₀ , and a width W ₀ is extracted from the heating furnace. The slab is rotated 90 degrees by a turning device, and after slabing, the slab is rolled out. In other words, in the rolling direction, the sheet has a width L ₀ and a length W ₁ , and is finished into a sheet having a thickness distribution in a taper shape from a thin plate thickness h ₁ to a thick plate thickness H _{1 in} the longitudinal direction.
This tenter rolling only changes the thickness in the rolling direction and rolls to a uniform thickness in the width direction (left-right direction) of the slab, so there is little risk of cambering or meandering.

Here, assuming that the thin plate thickness in the width direction of the differential thickness steel plate, which is the final product, is h ₂ and the thick plate thickness H ₂ , the following equations hold for h ₁ and H ₁ .
h ₁ = αh ₂
H ₁ = αH ₂
α is a constant volume constant condition L ₀ · W ₀ · H ₀ = L ₀ · W ₁ · (h ₁ + H ₁ ) / 2
= L ₂ · W ₁ · (h ₂ + H ₂ ) / 2
However, L ₂ = αL ₀
From this, if α is given, the rolling length W ₁ at the time of tentering rolling can be calculated.

An experiment was conducted in advance, and a roll gap g ₁ (roll at the end of the plate corresponding to the thin plate thickness h ₁₎ when rolling the width L ₀ material from a rectangle with a plate thickness H to a thin plate thickness h ₁ and a thick plate thickness H ₁ Gap) and G ₁ (roll gap at the end of the plate corresponding to the thick plate thickness H ₁ ) are determined and set to, for example, the roll gap g ₁ at the start of rolling, and the roll gap is set to g corresponding to the distance X from the start of rolling. _{By controlling to} 1+ [g ₁ + (G ₁ −g ₁ )) X / W ₁ ], a sheet having a thickness distribution in a taper shape from a thin plate thickness h ₁ to a thick plate thickness H _{1 in} the longitudinal direction is finished. It is done. Alternatively, the roll gap may be controlled so as to obtain a desired plate thickness by measuring the load during rolling and estimating the plate thickness at the roll bite outlet in real time using the mill stretch characteristic.

Α is determined by the capacity of the rolling mill and the material and dimensions of the sheet. For example, when finishing with three passes, the first two passes are rolled with a constant plate thickness in the normal longitudinal direction, and in the third pass of the final pass, the taper is formed from a thin plate thickness h ₁ to a thick plate thickness H ₁ in the longitudinal direction. Finish the sheet with thickness distribution.

Thereafter, the sheet is turned 90 degrees, centered, the roll gap is inclined so as not to change the wedge ratio (left and right plate thickness ratio), and the finish is finished to the target plate thickness using the finish rolling mill 52. By rolling, a product having a length L ₂ in which the thin plate thickness in the width direction is h ₂ and the thick plate thickness H ₂ can be manufactured.

  In finish rolling, there is a difference between the left and right reduction positions, and rolling with a difference in sheet thickness in the width direction of the rolled material is performed. Since the sheet thickness difference in the sheet width direction in the finish rolling process is caused by the 90-degree rotation, the difference thickness ratio in the sheet width direction before finish rolling (if the rolling reduction ratio on the left and right of the finish rolling mill is maintained at the same value ( (Wedge ratio) will be rolled while maintaining the ratio as it is, and it will theoretically not cause camber and meandering despite rolling with different thickness difference and absolute value of the reduction amount on the left and right. Rolling operation is possible, but in actuality, due to differences in deformation resistance due to differences in the cumulative amount of reduction until then in the width direction of the rolled material, differences in thermal history due to temperature differences or sheet thickness differences themselves, etc. , Some key It may cause members or meandering, but the absolute amount is small, the correction is easy.

  In the case of the plate rolling machine 5, the barrel length is generally long. Accordingly, when the plate width is narrow and the plate thickness difference is large, when rolling the material with the roll gap inclined as shown in FIG. 3 (a), one side of the work roll (FIG. 3 ( In the case of a), there are cases where the upper and lower work rolls contact at the left end of the work roll. In such a case, it may be difficult to control the inclination of the roll gap without changing the wedge ratio.

Basically, this determination can be easily inferred from the geometric relationship between the upper and lower work rolls. More strictly, the deflection of the roll may be calculated and obtained.
In the above case, as shown in FIG. 3B, by rolling the material off-center to the narrow roll gap, it is possible to prevent the upper and lower work rolls from coming into contact with one of the work rolls. To do this, simply estimate from the geometric relationship between the upper and lower work rolls, or strictly calculate the deflection of the roll and calculate the off-center amount, or calculate it in advance and hold it on the table. Thus, the off-center amount is determined, and off-center is performed so as to correspond to the off-center position.

(Example)
Using the apparatus shown in FIG. 1, a differential thickness steel sheet having a thickness difference in the sheet width direction was manufactured. FIG. 4 shows the dimensions of the differential thickness steel sheet having a thickness difference in the sheet width direction manufactured by the present invention.
The slab is a material having a tensile strength of 400 MPa called 40 kg high tensile, a plate thickness of 280 mm, a plate width of 1300 mm, and a length of 3000 mm. After this slab was heated, it was turned 90 degrees, and the first pass reduction rate 22% (rectangular), the second pass reduction rate 24% (rectangular), and the third pass reduction rate 22% (tapered) at the center in the longitudinal direction. To produce a sheet having a plate thickness (central plate thickness in the longitudinal direction) of 130 mm, a plate width of 3000 mm, and a length of 2800 mm. The plate thickness in the longitudinal direction at the end of the third pass was 104 mm at the thinner side and 156 mm at the thicker side.

  The sheet was turned 90 degrees again, centered, and rolled in 9 passes with an average rolling reduction of about 35% (the rolling reduction was higher in the initial pass) until the thickness in the center of the plate width became 3 mm. . At this time, the gap of the work roll was inclined so that the crown ratio (wedge ratio) of the material did not change.

As a result, as shown in FIG. 4 in the width direction, a differential thickness steel sheet having a tapered thickness distribution of 2.4 mm at the end on the thin side and 3.6 mm at the end on the thick side is manufactured with a length of about 130 m. And almost no camber occurred. However, since the velocities of about 1 m were generated at the tip and tail, respectively, the effective length of the rectangle was 128 m.
By shearing this material, about 1000 products having a width of 120 mm could be produced.
As a prior art, a rectangular sheet having a thickness of 4 mm is manufactured by the above-mentioned thick plate rolling machine, sheared to prepare a sample having a width of 120 mm and a length of 2800 mm, and this sample is used in a rolling direction with a small rolling mill. It was manufactured by a rolling method (for example, application of JP-A-3-281010) that changes the roll gap.

In either method, the desired difference thickness steel plate could be manufactured, but in the present invention, the product was almost completed in the process of the plate rolling mill, whereas the rolling operation in the longitudinal direction was operated by the conventional rolling mill. In the case of making, it is made on a separate line after making the material with a thick plate mill. In addition, it is clear that a large yield drop occurs in tandem in a conventional batch type hot rolling mill as described above.
For this reason, it is clear that the present invention has fewer steps, higher production efficiency, and lower production cost.

  According to the present invention, the rolling operation can be performed while keeping the rolling reduction constant in the width direction of the slab even in the tenter rolling and finish rolling, and the occurrence of camber and meandering is suppressed to the minimum in the sheet width direction. The so-called tapered steel plate having a difference in plate thickness can be efficiently produced without using an expensive hydraulic pressure reduction device, and thus the industrial utility value is great.

1 oven 2 descaling device 3 turn 4 turn table 5 plank rolling mill 51 tentering mill 52 finishing mill 6 straightener 7 cooling device S ₁ Slab (same as issued from the furnace direction)
S ₂ slab (turned 90 degrees from the direction from the heating furnace)

Claims (3)

  Centered with a tentering mill for producing a sheet of a desired width by tentering and rolling the heated slab, a turning device for turning the sheet, and a position adjusting device for centering the position of the turned sheet An apparatus for measuring or inputting the width of the slab on the entry side of the tentering mill, and a tentering machine, comprising a finishing mill that rolls the sheet to produce a sheet having a desired thickness. Measuring device for measuring the rotation speed of a work roll of a rolling mill, a rolling length calculation device for calculating a rolling length from a measured value of the rotation speed of the work roll, and a pattern input device for previously inputting a pattern of the rolling length and plate thickness And a device for controlling the roll gap based on the signals of the pattern input device and the rolling length measuring device, and the rolling line depending on the cross-sectional shape of the sheet at the position of the rolled sheet. And a position adjusting device for controlling the desired position of the sheet and a device for controlling the roll gap of the finish rolling mill so that the wedge ratio of the cross-sectional shape of the sheet does not change. An apparatus for producing a differential thickness steel plate having a thickness difference.   When the differential thickness steel sheet is manufactured by the differential thickness steel sheet manufacturing apparatus having a taper thickness difference in the sheet width direction according to claim 1, based on signals from the rolling length calculation device and the pattern input device. And controlling the roll gap of the tentering mill to produce a sheet, and controlling the rolled line to any desired position with respect to the rolling line according to the cross-sectional shape of the sheet, A method for producing a differential thickness steel sheet having a taper thickness difference in a sheet width direction, wherein a roll gap of a finishing mill is controlled so that a wedge ratio of a cross-sectional shape of a sheet does not change.   The length in the rolling direction of the sheet after tentering rolling (the length in the width direction during tentering rolling) in the method for producing a differential thickness steel plate having a taper thickness difference in the sheet width direction according to claim 2 Is measured or calculated, and when the length in the rolling direction of the sheet after the tenter rolling exceeds a preset length and thickness limit value for off-centerless rolling, a preset length, thickness, and off-center The off-center amount is obtained from the amount relationship, the sheet is off-centered in the finish rolling based on the off-center amount, and the roll in the finish rolling is maintained in a state where the sheet thickness ratio in the sheet width direction is kept constant. A method of manufacturing a differential thickness steel sheet having a taper thickness difference in the sheet width direction by controlling and rolling the gap inclination and the roll gap.

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