JPH0598408A - Method for calculating heat gain in alloying furnace of galvannealed steel strip - Google Patents

Abstract

(57) [Summary] [Purpose] When calculating the required heat input for the heating zone of the alloying furnace, it is necessary to always obtain the correct heat input, even in actual operation where the steel grade, strip running speed, coating weight, etc. vary greatly. Calculate the amount of heat. [Structure] A two or more-dimensional space that defines a calculation formula is divided into a plurality of regions, and an independent calculation formula is assigned to each divided region. At the boundary between regions, a membership function is used to Calculate the contribution rate of each position to each area,
The heat input is calculated by calculating the weighted average using the calculation formulas of multiple regions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to calculation of heat input for controlling an alloying furnace in a manufacturing process of hot-dip galvanized steel strip.

[0002]

2. Description of the Related Art In the process of manufacturing hot-dip galvanized steel strip, the steel strip is generally passed through a hot-dip galvanizing bath to deposit a galvanized layer on the surface of the strip, and then a gas is blown onto the surface of the strip. The coating amount is adjusted by attachment, the steel strip is then passed through an alloying treatment furnace, and the plated layer is made of an alloy of iron and zinc by diffusion by heat treatment in the alloying treatment furnace.

It is important in terms of quality that the hot-dip galvanized steel strip produced in this manner has excellent flaking resistance and powdering resistance. In order to obtain a hot-dip galvanized steel strip having a preferable quality, the temperature of the alloying furnace and the strip-passing speed in the manufacturing process are controlled, and the degree of alloying (for example, the content of iron in the plating layer is represented. ) Should be controlled to a predetermined state to prevent insufficient alloying or excessive alloying.

For example, in the manufacturing method disclosed in Japanese Patent Application Laid-Open No. 1-279738, it is shown that the flaking resistance can be improved by specifying the initial heat treatment conditions in the alloying treatment.

[0005]

According to the investigation by the present inventors, the flaking resistance and the like are improved in the alloying control of the hot-dip galvanized zinc plating containing 6 to 13% of iron in the plated alloy. In order to suppress the formation of η phase, etc. on the surface of the plating layer, and for alloying through the heat-retaining zone after the heating zone for uniform alloying control, the steel type, strip speed, coating amount, etc. in the heating zone It has been clarified that it is effective to calculate and control the amount of heat input based on the specifications.

However, the alloying process is very complex and non-linear. Therefore, in an actual operation in which specifications such as steel type, strip running speed, and amount of deposited coating change greatly, it is not possible to always obtain an appropriate heat input amount with a single calculation formula. Also, it is possible to selectively use multiple calculation formulas according to the contents of specifications, but it is very difficult to judge which calculation formula should be selected in which range to calculate the proper heat input, Especially in the vicinity of the boundary of the range where the calculation formula is changed, it is often the case that an appropriate heat input amount cannot be obtained by using any of the calculation formulas.

Therefore, an object of the present invention is to always obtain an appropriate heat input amount even in an actual operation in which specifications such as steel type, strip running speed, and amount of deposited coating change greatly.

[0008]

In order to solve the above problems, in the first invention of the present application, a steel strip to which molten zinc is adhered is passed through an alloying furnace, and the steel is heated by heating in the alloying furnace. When calculating the heat input of the alloying furnace in the step of forming the alloyed layer of iron and zinc in the zone, at least the space for defining the calculation formula for calculating the heat input, the axis of the steel type constant and the plating adhesion amount A two-dimensional or more space represented by the axis and the space is divided into three or more independent regions and boundary regions existing between the plurality of independent regions, and an independent calculation formula is obtained for each independent region. At the same time, two or more membership functions are prepared for each axis that determine the contribution rate to each of the divided independent areas inside the boundary area. From the input steel type constant and its membership function, Steel grade constants for each independent area The rate of contribution is calculated, and the contribution rate of the plating coverage to each independent area is calculated from the input plating coverage and its membership function, and the formula assigned to each independent area and the calculated contribution rate Calculate the heat input by performing the calculation based on

Further, in the second invention of the present application, the space for defining the calculation formula for calculating the heat input is a three-dimensional space represented by the axis of the steel type constant, the axis of the coating deposition amount, and the axis of the strip running speed. And the space is divided into three or more independent regions and a boundary region existing between the plurality of independent regions, and an independent calculation formula is prepared for each divided independent region,
Two or more membership functions that determine the contribution rate to each of the divided independent regions inside the boundary region are prepared for each axis, and the steel type constant and the steel type constant are input from the input steel type constant and its membership function. The contribution rate to the independent area is calculated, and the contribution rate of the plating adhesion amount to each independent area is calculated from the input plating adhesion amount and its membership function, and the input strip speed and its membership function are calculated. Then, the contribution rate of the strip running speed to each independent area is calculated, and the heat input amount is obtained by carrying out the calculation based on the calculation formula assigned to each independent area and each obtained contribution rate.

[0010]

In the present invention, the space for defining the calculation formula for calculating the heat input is at least a two-dimensional space represented by the steel type constant and the plating adhesion amount, and this space is divided into a plurality of spaces. Since a calculation formula suitable for each space is prepared, the heat input amount can be calculated using a calculation formula suitable for each divided space (independent region). Moreover, in the space between the independent areas adjacent to each other, the contribution rate to each independent area at that position is obtained by a predetermined membership function, and a calculation formula assigned to each independent area is obtained. Since the heat input is calculated by calculating a plurality of calculation formulas based on the calculated respective contribution rates, even if the boundary between regions is unclear, the member-
By using an appropriate ship function, the calculation result can be matched with the actually required heat input amount even in the boundary region. In other words, by adjusting the range of each divided region and each membership function that determines the contribution ratio at the boundary between the regions, it is possible to obtain a precisely consistent calculation result even for a very complicated alloying process. You can

[0011]

EXAMPLE FIG. 1 shows the structure of the main part of the manufacturing process of hot-dip galvanized steel strip. This will be described with reference to FIG. The steel strip 2 is conveyed in the direction of the arrow in the figure, and after the molten zinc is adhered to its surface through the molten zinc bath 1, the amount of molten zinc adhered is adjusted by blowing gas when passing through the nozzle 3. Then, the alloying furnace 4 is entered. The interior of the alloying treatment furnace 4 is divided into a heating zone 4a, a heat retaining zone 4b, and a cooling zone 4c. The steel strip 2 that has entered the alloying treatment furnace 4 is first heated rapidly in the heating zone 4a at 470 ° C or higher. It is heated to the plate temperature, then kept at a constant temperature in the heat retaining zone 4b for alloying treatment, and then cooled in the cooling zone 4c so that the iron content is 6 to 1
A zinc-iron alloy plating layer of about 3% is formed near the surface. The steel strip 2 exiting the alloying treatment furnace 4 is conveyed to the next step through the roll 20.

In this embodiment, heat is supplied to the heating zone 4a of the alloying furnace by gas combustion, and the heating zone 4a is controlled by controlling the flow rate of the supplied fuel gas.
The heat input amount of a is controlled. This control is performed by the calorie controller 1
1 is performed by adjusting the opening degree of a flow rate control valve (not shown). A heat quantity set value (target value: heat quantity) output from the heat quantity calculator 13 is applied to the heat quantity controller 11. The thermometer 10 measures the furnace temperature of the heating zone 4a and inputs the measured value to the heat input calculator 13. The flow rate of the gas discharged from the nozzle 3 is controlled by the plating amount controller 12. The coating amount controller 12 controls the flow rate of the gas supplied to the nozzle 3 in accordance with the input coating amount (set value). Process computer (Pro computer) 14
Manages the entire manufacturing process of the hot-dip galvanized steel strip, outputs the set value of the coating weight to the coating weight controller 12, and outputs the set value of the coating weight to the heat input calculator 13.
Outputs information on coating weight, steel grade, strip speed, strip width and strip thickness. The heat input amount calculator 13 calculates the heat input amount, that is, the heat amount set value, based on the input furnace temperature and the information of the amount of deposited coating, the steel type, the plate passing speed, the plate width, and the plate thickness, and the result is the heat amount. Apply to regulator 11.

The process by which the heat input calculator 13 calculates the heat input will be described below. The alloying process is very complicated and non-linear, and in actual operation, it changes according to the operating conditions such as steel type constant, coating deposition amount, strip running speed, etc. Therefore, in this embodiment, the calculation of the heat input amount is performed. For this purpose, a two-dimensional space represented by an axis (x) corresponding to the steel type constant and an axis (y) corresponding to the plating adhesion amount is defined, and this two-dimensional space is defined as a region 1, a region 2, as shown in FIG. It is divided into six areas, area 3, area 5, and area 6. However, since the boundaries between the parts adjacent to each other in these regions are not clear, the boundary part, that is, the part shown by hatching in FIG. 2, has five membership functions X1, X2, and
Using Y1, Y2, and Y3, the contribution rate of that portion to each area is obtained.

Specifically, the contribution rate c1 to the area 1 at a given position (x, y) in this two-dimensional space, the contribution rate c2 to the area 2, the contribution rate c3 to the area 3, and the contribution rate c4 to the area 4. , The contribution rate c5 to the area 5 and the contribution rate c6 to the area 6 are respectively expressed by the following equations.

[0015]

## EQU00001 ## c1 = Min [X1 (x), Y1 (y)] ... (1) c2 = Min [X1 (x), Y2 (y)] ... (2) c3 = Min [X1 ( x), Y3 (y)] (3) c4 = Min [X2 (x), Y1 (y)] (4) c5 = Min [X2 (x), Y2 (y)]・ (5) c6 = Min [X2 (x), Y3 (y)] (6) However, select the minimum value in Min []: [] X1 (), X2 (): Member of steel type constant -Ship function Y1 () to Y3 (): Member of plating adhesion amount-Ship function x: Value of steel grade constant y: Value of plating adhesion amount For example, at the position indicated by point P1 in FIG. Since (x) is 1, X2 (x) is 0, Y1 (y) is 0, Y2 (y) is 1, and Y3 (y) is 0, it is 0 except for the contribution ratio c2 to the region 2, which is obvious. The point P1 belongs to the area 2 only. However, at the position indicated by the point P2, the membership functions X1 (x), X2 (x), Y1 (y),
And Y2 (y) each take a value between 0 and 1, and therefore have a certain contribution rate to each of the four regions 1, region 2, region 4, and region 5, and the region to which P1 belongs Is ambiguous.

In this embodiment, the heat input amount Q1 regarding the region 1, the heat input amount Q2 regarding the region 2, the heat input amount Q3 regarding the region 3, the heat input amount Q4 regarding the region 4, the heat input amount Q5 regarding the region 5, and the heat input amount Q6 regarding the region 6. Are respectively calculated by the following equations.

[0017]

[Equation 2] Q1 = a01 + a11 × furnace temperature + a21 × heat input correction value + a31 × steel grade constant (7) Q2 = a02 + a12 × furnace temperature + a22 × heat input correction value + a32 × steel grade constant (8) Q3 = a03 + a13 x furnace temperature + a23 x heat input correction value + a33 x steel grade constant (9) Q4 = a04 + a14 x furnace temperature + a24 x heat input correction value + a34 x steel grade constant (10) Q5 = a05 + a15 x furnace temperature + a25 x Heat input correction value + a35 x steel type constant ... (11) Q6 = a06 + a16 x furnace temperature + a26 x heat input correction value + a36 x steel type constant ... (12) Heat input correction value = coating adhesion amount x strip running speed x [ 1 + k1 (plate width-plate width standard value) + k2 (plate thickness-plate thickness standard value)] (13) However, a01 to a36, k1, k2: constants The final heat input Q is in six areas. Calculation result in Q
It is calculated by obtaining the weighted average by the following equation (14) based on 1 to Q6 and the contribution rates c1 to c6 to each area.

[0018]

[Equation 3] Q = (c1 × Q1 + c2 × Q2 + c3 × Q3 + c4 × Q4 + c5 × Q5 + c6 × Q6) / (c1 + c2 + c3 + c4 + c5 + c6) (14) Number of space divisions shown in FIG. 2, division position, each member-of the ship function Estimated expression of contents and heat input (Equation (7) to (1)
The contents of formula 3) are changed as necessary. The position to be divided is determined at that point by referring to past operation performance data and finding a point at which the heat input estimation formula changes. As the estimation formula of the heat input amount, for example, the following formula may be used.

[0019]

[Equation 4] Qi = a0i + a1i × (plating adhesion amount × passing speed) + a2i × steel grade constant ・ ・ (15) Qi = a0i + a1i × plating amount + a2i × passing speed + a3i × steel grade constant ・ ・ (16) Qi = a0i + a1i × Furnace temperature + a2i × Plating adhesion amount + a3i × Plate passing speed + a4i × Plate width + a5i × Plate thickness + a6i × Steel type constant ... (17) i: 1 to number of area divisions In the embodiment, five membership functions X1,
The space is divided into six regions by using X2, Y1, Y2 and Y3. For example, the membership function is divided into two axes, and the space is divided into three as shown in FIG. It is also possible to divide the space into four as shown.

In the embodiment shown in FIG. 5, the space is a three-dimensional space consisting of an x-axis showing a steel type constant, ay-axis showing the amount of plating deposit, and a z-axis showing the strip running speed, and two memberships are provided for each axis. The functions X1, X2, Y1, Y2, Z1 and Z2 are assigned to divide the space into eight regions (region 1 to region 8). In FIG. 5, hatched portions are boundary portions between regions. The heat input amount can be obtained in the same manner as in the above-mentioned embodiment except that the number of heat input amount estimation formulas changes according to the difference in the number of divided regions and the content of the formula for obtaining the weighted average changes.

In the above-mentioned embodiment, the absolute value of the heat input amount is obtained. However, since the heat input amount is repeatedly calculated in a constant cycle, the deviation of the heat input amount is repeatedly calculated. The control content may be changed so that the deviation amount of the obtained heat input amount is added to the heat input amount up to that point.
In that case, the heat input deviation may be calculated using the following calculation formula. Note that here, the change of the variable during one calculation cycle (Δt) is indicated by Δ.

[0022]

[Equation 5] ΔQi = a0i + a1i × Δ furnace temperature + a2i × Δheat input correction value + a3i × Δ steel grade constant i: 1 to number of zone divisions ...
(18) Δ Heat input correction value = Δ [Amount of plating adhered x plate passing speed x {1 + k1 (plate width-plate width standard value) + k2 (plate thickness-plate thickness standard value)}] (1
9) ΔQ = (c1 × ΔQ1 + c2 × ΔQ2 + c3 × ΔQ3 + c4 × ΔQ4 + c5 × ΔQ5 + c6 × ΔQ6) / (c1 + c2 + c3 + c4 + c5 + c6) (20) (when the number of area divisions is 6) Formula (15), (16) The equation and the equation (17) are respectively changed to the following equations.

ΔQi = a0i + a1i × Δ (amount of plating adhered × passing speed) + a2i × Δ steel grade constant ... (22) ΔQi = a0i + a1i × Δ furnace temperature + a2i × Δ plating deposit amount + a3i × Δ strip speed + a4i × Δ strip width + a5i × Δ strip thickness + a6i × Δ steel grade constant (23)

[0024]

As described above, according to the present invention, the space for defining the calculation formula for calculating the heat input is at least a two-dimensional space represented by the steel type constant and the plating deposition amount, and the space is made plural. Since the calculation formula suitable for each space is prepared for each space, the heat input amount can be calculated using the calculation formula suitable for each space (independent region). Moreover, in the space between the independent areas adjacent to each other, the contribution rate to each independent area at that position is obtained by a predetermined membership function, and a calculation formula assigned to each independent area is obtained. Since the heat input is calculated by calculating multiple formulas based on the calculated contribution ratios, use an appropriate membership function even if the boundaries between regions are unclear. Therefore, the calculation result can be matched with the actually required heat input amount even in the boundary region. In other words, by adjusting the range of each divided region and each membership function that determines the contribution ratio at the boundary between regions, an appropriate calculation result suitable for a very complicated alloying process can be obtained. be able to.

As a result, the flaking resistance and powdering resistance of the steel strip can be improved even when the heat input amount is completely automated, and the iron amount in the plating layer can be accurately adjusted to the target value. Since it can be controlled, the quality of the hot-dip galvanized steel strip can be significantly improved, and at the same time
The burden on the computer is also significantly reduced. Needless to say, this leads to a reduction in manufacturing cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a manufacturing process of a hot-dip galvanized steel strip.

FIG. 2 is a map showing a division of a space defining a calculation formula and a membership function.

FIG. 3 is a map showing a modified example of FIG.

FIG. 4 is a map showing a modified example of FIG.

FIG. 5 is a map showing an embodiment in which a space defining a calculation formula is changed to a three-dimensional space.

[Explanation of symbols]

1: Molten zinc bath 2: Steel strip 3:
Nozzle 4: Alloying treatment furnace 4a: Heating zone 4
b: tropical zone 4c: cooling zone 10: radiation thermometer 1
1: Heat quantity controller 12: Plating adhesion amount controller 1
3: Heat input calculator 14: Process control

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichi Sashihara 5-3 Tokai-cho, Tokai City Nippon Steel Corporation Nagoya Steel Works

Claims (2)

[Claims] 1. A heat input amount of the alloying furnace in the step of passing a steel strip to which molten zinc is adhered through an alloying furnace and forming an alloyed layer of iron and zinc on the steel strip by heating in the alloying furnace. In calculating the heat input, the space that defines the calculation formula for calculating the heat input is at least a two-dimensional space represented by the axis of the steel type constant and the axis of the coating deposition amount, and the space is defined as three or more independent regions and An independent calculation formula is prepared for each independent region divided into boundary regions existing between the plurality of independent regions, and the contribution rate to each divided independent region inside the boundary region. Two or more membership functions that determine the above are prepared for each axis, and the input steel grade constant and the contribution rate of the steel grade constant to each independent region are calculated from the membership function, and the input plating adhesion amount and its From the membership function A hot-dip galvanized steel strip that calculates the heat input by calculating the contribution rate of the amount of adhesion to each independent area and performing the calculation based on the calculation formula assigned to each independent area and each calculated contribution rate. Calculation method of heat input to alloying furnace. 2. A space for defining a calculation formula for calculating the heat input is a three-dimensional space represented by an axis of steel type constant, an axis of coating adhesion amount, and an axis of plate passing speed, and the space is 3 or more. Independent regions and boundary regions existing between the plurality of independent regions, and an independent calculation formula is prepared for each divided independent region, and each of the partitioned independent regions inside the boundary region is prepared. Prepare two or more membership functions for each axis that determine the contribution rate to each axis, calculate the contribution rate of the steel grade constant and the steel grade constant to each independent region from the entered steel grade constant, and input the plating Calculate the contribution rate of the plating adhesion amount to each independent area from the adhesion amount and its membership function, and calculate the contribution rate of the plating speed to each independent area from the input strip speed and its membership function. Assigned to each independent area The heat input amount is calculated by carrying out a calculation based on the calculated calculation formula and each calculated contribution ratio.
A method for calculating heat input to an alloying furnace of a hot-dip galvanized steel strip as described.