JP3409199B2 - Manufacturing method of continuous hot-dip aluminized steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust system for an automobile.
Excellent heat and corrosion resistance, which is useful as a material for home appliances and heat appliances for home appliances.
On the production method of
Of Fe-Al-Si alloy layer inevitably formed in plating layer
The thickness of the layer can be controlled accurately. [0002] 2. Description of the Related Art Molten aluminum by a continuous hot-dip plating line
Of aluminum-plated steel sheets (hereafter, “galvanized steel sheets”)
In the manufacturing, as shown in FIG.
Al-Si plating adjusted to a constant bath composition and bath temperature
Alloy bath (1) is introduced and is passed through sink roll (2)
Gas wiping device on the bath after being led out on the bath (3)
Thereby, the plating layer thickness is adjusted. In addition, plated steel sheet
Before reaching the upper top roll (5), the plating layer
Cooling device placed at the top of the bath so that solidification of the
(4) forced cooling (such as spraying air jets)
Will be applied. Hot-dip aluminized steel sheet manufactured in this way
Indicates the interface reaction between the base steel sheet and the plating layer (from the base steel sheet
Fe-Al-Si based alloy layer)
Inevitably generate. The alloy layer is a hard and brittle layer,
Material that promotes peeling of the plating layer during press working of plated steel
Cause. Therefore, it is necessary to suppress the thickness of the generated layer.
It is important, especially for applications where strong processing such as drawing and ironing is performed
Then, it is necessary to suppress the alloy layer thickness to about 5 μm or less.
(Japanese Patent Publication No. 51-46739, etc.). [0003] The formation of the above-mentioned Fe-Al-Si alloy layer is suppressed.
Cooling system (4)
Liquid or gas-liquid mixed flow
Use body to enhance forced cooling action (Japanese Patent Laid-Open No. 52-60239)
No.), a coating layer of a low melting point metal is formed on the surface of the base steel sheet in advance.
And keep the steel sheet temperature until plating is completed.
Maintain a constant temperature (500 ° C or lower) (Japanese Patent Laid-Open No. 1-104752)
Report), Al-Si plating bath with a certain composition (Si content 3 ~ 13
%) And the base metal steel sheet when entering the bath is constant
Adjust to the temperature range (plating bath alloy melting point-melting point + 40 ° C)
(Japanese Unexamined Patent Publication No. 4-176854), a sheet when a steel sheet enters a plating bath.
Control the temperature within a temperature range of 50-100 ° C lower than the plating bath temperature
(Japanese Patent Application Laid-Open No. 5-287488).
You. Further, WO 96/26301 discloses a steel plate.
After entering the bath, it passes through the plating bath and
After being derived, until the solidification of the plating layer is completed (FIG. 15).
Medium, the process from the A position to the C position) and the alloy
Based on a certain correlation with the layer formation thickness,
It is disclosed to control the alloy layer thickness of product plated steel sheet
ing. [0004] SUMMARY OF THE INVENTION The composition and bath temperature of the plating bath
Adjustment, sheet temperature control when steel sheet enters plating bath, or
Various factors in plating operation such as enhancement of forced cooling action of the coating layer
In the conventional operation method of individually picking up and controlling
-It is difficult to obtain a sufficient effect of suppressing the thickness of the Al-Si alloy layer. Steel plate surface
Pre-coated with a specific metal film increases man-hours
Disadvantages such as increased costs. In addition,
These methods also have a quantitative relationship between the rate of alloy layer formation and operating conditions
Is unknown, and it is difficult to control the thickness of the generated layer accurately.
It is. On the other hand, from the point when the base steel sheet enters the plating bath,
Elapsed time to complete solidification of the plating layer derived to
Based on the correlation between the
The method of adjusting the gap precisely controls the thickness of the generated alloy layer
(The above-mentioned international publication). The present invention
Is the molten aluminum that controls the alloy layer thickness based on the above correlation
Regarding the continuous plating operation of nickel-plated steel sheets,
Of alloy layer formation reaction kinetics from liquid phase to solid phase
Analyze the effects of various operating factors and refine the thickness of the formed alloy layer.
Forecasts, and changes between the estimated layer thickness and the target layer thickness.
By adjusting operating conditions according to the
To accurately control the product
It can be manufactured efficiently. [0005] DISCLOSURE OF THE INVENTION Continuous molten aluminum of the present invention
The method for producing a nickel-plated steel sheet is as follows.
% Of the Al-Si bath composition, and the bath temperature is from melting point to melting point + 70.
Base metal sheet in a hot-dip aluminum plating bath maintained at
To form a plating layer, and the cooling device
Molten aluminum that forcibly cools the plating layer
In the method for producing a galvanized steel sheet, the base steel sheet and the plating layer
The thickness of the Fe-Al-Si alloy layer formed at the interface with
[A₁] Or [A_Two], And the calculated prediction
Layer thickness (τ_C) And the target layer thickness
The power ratio of the cooling device on the bath, the transfer speed of the steel plate,
By adjusting the bath temperature, the thickness of the formed alloy layer can be reduced.
It is characterized in that the target layer thickness is controlled. [0006] (Equation 2) (1) T_P× V_L> C₂in the case of τ_C(Μm)   = 0.833√ [{3.564 × exp (-1647 / 1.987 / T_M) /0.833}² × 60 × L_AB/ V_L+ (C₁−K × R_C) × (T_P× V_L-C₂)]… [A₁] (2) T_P× V_L≤C₂in the case of τ_C(Μm)   = 0.833√ [{3.564 × exp (-1647 / 1.987 / T_M) /0.833}²     × 60 × L_AB/ V_L] ... [A₂] [Where, T_M： Plating bath temperature (absolute temperature, K) L_AB： From the entrance of the plating bath to the cooling device entrance
Steel sheet transfer distance (m) T_P: Thickness of base steel sheet (mm) V_L： Transfer speed of steel sheet in line (m / min) C₁： Product of base steel sheet thickness and transfer speed, cooling of cooling device
Set based on capacity and forced cooling time of plating layer
Constant (sec · min / mm / m) K: Product of base material steel sheet thickness and transfer speed, cooling capacity of cooling device
Set based on force and forced cooling time of plating layer
Coefficient (sec · min / mm / m) C₂： Product of base steel sheet thickness and transfer speed, and steel plate
Based on the atmosphere between the bath and the cooling device
Constant (mm ・ m / min) R_C: Output ratio of cooling device (ratio to maximum output,%)
                 ] [0007] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a formula for estimating the thickness of a formed alloy layer will be described.
[A₁] And [A_Two] Will be described. Steel plate surface
The plating layer is as shown in the Al-Si based equilibrium diagram of FIG.
Then, from the liquid phase (region I) to the solid-liquid coexisting phase (region II),
It becomes a solid phase (region III). Starting point of steel sheet plating bath intrusion
15 to the inlet of the cooling device (transfer between AB in FIG. 15)
(Solid phase) is a liquid phase and passes through a cooling device to complete solidification.
In the process (transfer process between B and C in FIG. 15)
Becomes a solid-liquid coexisting phase, and thereafter becomes a solid phase single phase. FIG.
And FIG. 3 show the liquid phase, the solid-liquid coexisting phase, and the solid phase of the plating layer.
Formation of Fe-Al-Si based alloy layer in phase state (regions I-III)
Relationship between layer thickness τ and square root of elapsed time (reaction time) t
Is shown with the plating layer temperature as a parameter.
Composition: Al-8 to 10% Si, thickness: 1.0 mm, plating layer thickness: 25 to
35 μm / one side]. As shown, generation of alloy layer in each region
The layer thickness τ (μm) is the square root of the elapsed time (reaction time) (√se
proportional to c). [0008] From FIGS. 2 and 3, the rate of formation of the alloy layer is
V_R(= Τ / √t) and its common logarithm (logV_R) Vertically
On the axis, the reciprocal of the plating layer temperature (absolute temperature) (1 / T_M)
On the horizontal axis, as shown in FIG.
Is obtained. It is of the same type as the Arrhenius equation,
Is the generation speed V_R(Μm / √sec) is represented by the following formula [1]
Which can be rewritten as [2]. (Equation 3) V_R= Aexp (-Q / R / T_M…… [1] LogV_R= LogA-Q / 2.303 / Rx1 / T_M        … [2] [Where A: frequency factor (here, μm / √sec) Q: Activation energy (cal / mol) R: gas constant (= 1.987cal / mol · K)] Therefore, first, in region I (liquid phase, about 640 ° C. or lower)
Regarding the above-mentioned alloy layer formation reaction, the region I shown in FIG.
Calculating equation [2] based on the straight line, logA = 0.552
A = 10^0.552= 3.564, and Q / (2.303 ×
R) = 360, Q = 360 × 2.303 × 1.987 = 1647 (cal / mol)
Is required. Substituting this into equation [1], the alloy in region I
Layer formation rate V_R1(Μm / √sec) to obtain equation [3]
You. Thus, the alloy layer thickness τ in the region I_C1(Μm)
Equation [4] is obtained. (Equation 4)   V_R1= 3.564 x exp (-1647 / R / T_M1…… [3]   τ_C1= V_R1× √t₁= 3.564 × Δt₁× exp (-1647 / R / T_M1…… [4] [Where, t₁: Elapsed time in area I (sec) T_M1： Plating layer temperature of region I (absolute temperature, K)] In region II (solid-liquid coexisting phase, about 580-640 ° C)
Alloy layer formation speed V_R2(Μm / √sec) and generated layer thickness τ_C2
(Μm), and region III (solid state, about 580 ° C or less)
Alloy layer formation speed V_R3(Μm / √sec) and generated layer thickness τ
_C3(Μm) is obtained by the same procedure as above.
Equations [5] to [8] are obtained. (Equation 5)   V_R2= 16.90 x exp (-5281 / R / T_M2…… [5]   τ_C2＝ 16.90 × Δt₂× exp (-5281 / R / T_M2… [6]   V_R3= 2.716 × 10²³× exp (-93036 / R / T_M3…… [7]   τ_C3= 2.716 × 10²³× √t₃× exp (-93036 / R × T_M3…… [8] [Where, t₂, t₃: Elapsed time in area II and area III respectively (sec) T_M2, T_M3： Plating layer temperature of area II and area III respectively
(Absolute temperature, K)] Of the regions I to III, the region III (solid phase)
The activation energies are in Region I (liquid phase) and Region II (solid-liquid coexistence).
Phase) is much larger than that of_R3Is author
Small. Therefore, as in continuous hot-dip plating line operation,
In addition, under operating conditions with short reaction times,
Thickness τ_C3Can be ignored. Below, product plated steel sheet
The alloy layer thickness is determined by the alloy layer formation reaction in regions I and II.
Will be described as being dependent on. The reaction process for forming the alloy phase in region I (liquid phase) (FIG. 1)
5) Transfer distance between A and B)_ABThen, in the meantime
Elapsed time t₁(Sec) is t₁= 60 × L_AB/ V_LIn
Substituting this into equation [4] yields equation [9].
You. In addition, the reaction process of alloy layer formation in region II (solid-liquid coexisting phase)
The transfer distance of [stroke between B and C in FIG. 15] is L_BCAnd that sutra
Overtime t₂(Sec) = 60 × L_BC/ V_LInto the above equation [6]
Upon entering, equation [10] is obtained. (Equation 6)   τ_C1(Μm) = 3.564 × √ (60 × L_AB/ V_L) × exp (-1674 / R / T_M1)                                                             … [9]   τ_C2(Μm) = 16.90 x √ (60 x L_BC/ V_L) × exp (-5281 / R / T_M2)                                                             …[Ten] [0013] The alloy layer thickness of the product plated steel sheet is in the region I (liquid
Phase) and Region II (solid-liquid coexisting phase)
However, the thickness of the alloy layer of the product plated steel sheet is
Obtain as a simple addition value of expressions [9] and [10]
Can not. The formation reaction of both regions is a parabola as shown in Fig. 5.
Because it proceeds according to the rules, each of the areas I and II
It is necessary to summarize the elapsed time (reaction time) of
It is important. The present invention relates to the following method.
Is converted to the elapsed time of area II, and both are 1 term (within square root)
To determine the alloy layer thickness of the product plated steel sheet.
I am trying to do it. That is, in the liquid phase region I (A-B stroke)
Plating layer temperature is approximately constant (substantially equal to plating bath temperature)
However, the plating layer in region II (B-C process) of the solid-liquid coexisting phase
The liquidus temperature (approximately 640
° C) to the solidus temperature (about 580 ° C). So
Here, the elapsed time in the liquid phase region I (A-B stroke) (at the time of reaction)
Time) in the solid-liquid coexistence region II (B-C process)
Response time)
The plating layer temperature in region II to the middle temperature in that region.
At 610 ° C (= 883 K), the above formulas [9] and [10]
, The following equation [11] is obtained as a conversion coefficient (κ).
Can be This conversion factor is the reaction time in the liquid phase (A-B process)
Is multiplied by the reaction time in solid-liquid coexisting phase (B-C process) (t
_sl,sec), which is represented by the following equation [12]. Obedience
Thus, from the liquid phase region I (A-B process) to the solid-liquid coexistence region II (B-
Alloy layer thickness caused by alloy reaction over the C process)
(Τ_C) (= Τ₁+ Τ_Two) Applies the above conversion factor
Thus, it can be expressed as the following equation [13]. [0015] (Equation 7)   κ (t_SL/ t_L) = {3.564 × exp (-1647 / R / T)_M1) /0.833}²    … [11]   t_SL= {3.564 × exp (-1647 / R / T_M1) /0.833}²× 60 × L_AB/ V_L                                                                 … [12]   τ_C(Μm)       ＝ 0.833√ [｛3.564 × exp (-1647 / 1.987 / T_M1) /0.833｝²         × 60 × L_AB/ V_L+ (B-C elapsed time)] ... [13] [B-C elapsed time] included in the above equation [13]
Is that the plating layer solidifies from the liquid phase due to the forced cooling action of the cooling device
This is the elapsed time to complete
_P) X transfer speed (L_V), And the cooling output ratio of the cooling device
(%). This BC elapsed time and T_P
× V_L(Mm x m / min), and the cooling device output ratio (%)
6 to 9 (FIG. 6: cooling output).
(10%, Fig. 7: 25%, Fig. 8: 55%, Fig. 9: 65%). You
That is, for each output ratio of the cooling device, "B-C elapsed time (se
c) "and" T_P× V_L(Mm × m / min) ”
To establish. Figure 10 shows the slope of these lines and the cooling at that time.
4 is a graph showing a relationship with an output ratio of the device. This is it
Equation [14] is obtained as a general expression representing the BC elapsed time.
By substituting this into equation [13], the above equation [A
₁] Is obtained. (Equation 8)   B-C elapsed time (sec) = (C₁−K × R_C) × (T_P× V_L-C₂) …[14] The graphs in FIGS. 6 to 9 and FIG.
When the specific examples of the above constants and coefficients are calculated from FIG.
9 is expressed by equation [15] (α in the equation is the gradient of the straight line).
Since the straight line in FIG. 10 is represented by equation [16],
From these equations, C₁= 0.549961, C₂= 50, K = 0.006225
Can be B−C elapsed time = α × (T_P× V_L−50)… [15] α = T_P× V_L/ B-C elapsed time = -0.006225 × R_C+0.549961… [16] The constant C in the above equation_TwoDerived from plating bath
When the cooled steel sheet enters the cooling device (4),
Is a constant that represents the boundary of whether
As described above, the value is the product of the thickness of the steel sheet and the transfer speed._,You
From the derivation of the plating bath for steel and steel plate to the entrance of the cooling device
Determined by the type and temperature of the atmosphere. Atmosphere is generally room temperature
Of the atmosphere and the above constant C_Two= 50 is also a room temperature atmosphere
In this case, other atmosphere compositions such as liquid (mis
If a gas-liquid mixed atmosphere containing g) is applied,
Since the heat transfer from the steel sheet surface is different from that of
The values are different even at the ambient temperature. This constant C₂[T] in equation [14] containing_P× V
_L-C₂Is zero or a negative value (T_P× V_L≤C₂)
When the steel plate reaches the entrance of the cooling device
At that point, the solidification of the plating layer has already been completed.
is there. This is due to the thickness (T_P) Is thin,
Feeding speed (line speed) (V_L) Is likely to occur when
No. As the thickness of the sheet is smaller, the heat capacity of the steel sheet is smaller, so the cooling rate
The higher the temperature and the lower the steel sheet transfer speed, the longer the cooling time
Because it is given. The atmosphere before reaching the cooling device on the bath
The constant C depends on the composition and temperature of the gas.₂Is relatively large
If set, "T_P×
V_L-C₂The value of the term "" becomes smaller. "T_P× V_L-C
₂If the value of “” is zero or negative, the B-C process is plating
Increased formation of alloy layer because the layer is already in the solid state
Is negligibly small and this term is calculated as a negative value.
The alloy layer thickness decreases with time
Produce reasonable results. Therefore, T_P× V_L≤C₂Place
If the formula [A₁] Instead of "(C₁−K × R_C) × (T_P
× V_L-C₂)) Has no term [A₂] Has been applied
You. The hot-dip aluminum plating bath used in the present invention
As an Al-Si-based composition having a Si content of 3 to 13% by weight.
The reason is to obtain the effect of suppressing the alloy layer by adding Si
Which requires a content of at least 3% by weight.
(At 6% by weight or more, corrosion and erosion of members immersed in the bath
Is also obtained). On the other hand, if it exceeds 13% by weight,
Since the corrosion resistance and workability of the plated metal layer decrease,
The upper limit is set. Adjustment of this bath composition is based on the conventional continuous melting
It is not particularly different from that in the aluminum plating operation. What
Note that Al-Si alloy baths are usually used as inevitable impurities.
It is accompanied by an Fe content of about 5% by weight or less.
The presence does not impair the spirit of the invention. Plating
Needless to say that the bath temperature is kept above the melting point (mp)
No melting point +2 for stabilization of plating surface quality
The temperature is preferably set to 0 ° C. or higher. Adjust the upper limit of plating bath temperature.
The point specified at + 70 ° C is that a high-temperature bath exceeding
Not only the disadvantage of cost efficiency but also the formation of an alloy layer
It difficult to obtain effective control effect of alloy layer of aluminum?
It is. Next, the continuous molten aluminum plating of the present invention is described.
The manufacturing process of the steel sheet will be described with reference to FIG.
You. The alloy layer thickness control means (10) controls the cooling output of the cooling device.
Ratio detecting means (11), steel sheet transfer speed in line (line
Speed) detecting means (12), plating bath temperature detecting means (1)
3), setting means (14), control means (20), cooling output
Ratio control means (31), line speed control means (32),
And a bath temperature control means (33). cold
The cooling device (4) uses, for example, air as a refrigerant and a large number of slips.
So that the air flow injected from the
It is an air jet cooler configured. Gas-liquid mixed flow
What uses a body etc. as a refrigerant | coolant etc. is applied suitably. Cooling system
The cooling output ratio is, for example, a refrigerant blowing amount ratio (to the maximum blowing amount).
Ratio detected by the cooling output ratio detecting means (11).
Is done. Since the fan speed is approximately proportional to the air flow,
The ratio of the rotation speed to the maximum rotation speed of the fan
You may make it detect. Line speed (Steel sheet transfer speed
Degree) is the drive mode provided on the bridle roll (6).
(6). Line speed detection means (1
1) is a pulse generator, for example, within a certain time.
The transfer speed of the steel sheet is detected from the number of pulses counted in the above.
The plating bath (1) is connected to a heating device (8) such as a resistance heating system.
The temperature is adjusted by heating, and the bath temperature detecting means (13)
Such as a thermocouple. FIG. 12 shows the electric power of the alloy layer thickness control device (10).
2 shows an embodiment of a gas configuration. Cooling output ratio detection means
(11) detects the output of the cooling device (4) and outputs the detected value.
It is sent to the predicted layer thickness calculator (22) and the comparator (23).
Line speed detecting means (12) and plating bath temperature detecting means
(13) calculates the detected values by the calculation means (15) and
And to the comparator (23). The setting device (14)
Thickness (T_P), Steel plate transfer distance between A and B (L_AB),prediction
Constant C in equation [A1] [A2]_1,C_2,The coefficient K, etc., is calculated by an arithmetic
5) and the maximum output (R_MAX),
Upper limit of line speed (V_{L UL}), Lower limit of plating bath temperature (T
_{M LL}), Target alloy layer thickness (τ_S) Etc. are set in the comparator (23).
I do. The computing unit (15) is provided with each of the detection means (11) to
The detected value of (13) is sent to the control means (20). The control means (20) includes a memory (21)
Layer thickness calculator (22), comparator (23), and correction
It has a calculator (24) to process each received signal
Outputs a control command signal. The memory (21) has an alloy layer
Predicted layer thickness calculation formula [A₁] [A₂] Is stored. Forecast
The layer thickness calculator (22) is a cooling output ratio detecting means (11).
And a memory based on a signal from the arithmetic means (15).
The predicted layer thickness calculation formula [A stored in (21)₁]Also
Is [A₂] And select T_P× V_L> C₂Is the expression
[A₁], T_P× V_L≤C₂Is the formula [A₂]
C₁, C₂, K, R_CSubstitute the estimated thickness of the alloy layer
(Τ_C) Is calculated. The comparator (23) calculates a predicted layer thickness.
Layer thickness (τ) calculated by the vessel (22)_C) And settings
The target layer thickness (τ) set by the means (14)_S) And compare
And the predicted layer thickness (τ_C) Is the target layer thickness (τ_SSatisfies
If not, target layer thickness (τ_S) To meet that strange
Order (τ_S−τ_C), Depending on the output ratio of the cooling device
(R_C), Line speed (V_L) Or plating bath temperature (T
_M) Is output. The correction operation unit (24) is provided by the comparator (23).
In response to the output, the modified cooling output ratio, modified line speed, or
Or the corrected plating bath temperature is calculated and the cooling output ratio control means (3
1), line speed control means (32), or plating bath temperature
A command signal is output to the control means (33). This process is
Layer thickness (τ_C) Is the target value (τ_S)
Repeated. The cooling output ratio control means (31)
Blast of the cooling device (4) in response to the output of the control means (20)
Adjust fan speed of machine (9) and set cooling output ratio to command value
Control to match. Line speed control means (3
2) Adjust the drive motor (7) to command the line speed
The plating bath temperature control means (3
3) Adjust the plating bath heating device (8) to adjust the plating bath temperature.
Is controlled to match the command value. Next, the operation of the control device will be described with reference to the flowchart of FIG.
Explanation is given according to the chart. In step S1,
Target layer thickness of gold layer (τ_s), Between A and B
Transfer distance (L_AB), Maximum output value of cooling device
(R_MAX), Etc., and as the set value, the thickness of the steel plate
(T_P), Line speed upper limit (V_{L UL}) 、 Plating bath temperature
Lower limit (T_{M UL}) Etc. are set. Also, the predicted value
[A₁] [A₂] Constants and coefficients (C₁, C₂, K) is set
In addition, the cooling power ratio (R_C), Line speed (V_L) 、 Me
Bath temperature (T_MFixDoCorrection amount (ΔR_C, ΔV
_L, ΔT_M) Is set based on past operation results
You. The amount of this correction is the unit for performing gradual correction
The amount of correction, the predicted layer thickness (τ_C) To reduce
Used as an amount correction. In step S2, the output ratio (R_C)
_,Line speed (V_L), Plating bath temperature (T_M) Etc.
Is detected. In step S3, the equation (A1) or
Is the predicted layer thickness (τ) from [A2]_C) Is calculated. Step
In step S4, the predicted generation layer of the alloy layer calculated in step S3
Thickness (τ_C) Is the target layer thickness (τ_S)
Refused. The judgment is positive (τ_C≤τ_S)
The hot-dip plating operation is continued as it is, and the process proceeds to step S13.
If the determination in step S4 is negative (τ_C> Τ_S)
If not, the process proceeds to step S5. In step S5,
The output ratio of the cooling device (R_C) Is the maximum output
Value (R_MX) It is determined whether or not the following is true, and the determination is affirmative
(R_C<R_max), Increase the output ratio of the cooling device.
It is possible to further reduce the thickness of the alloy layer
Then, the process proceeds to Step S6 for controlling the cooling output ratio. Steps
In S6, the cooling output ratio correction amount set in step S1 and the
From the cooling output ratio detected in step S2,
Corrected cooling output ratio R in (4)_C'(= R_C+ ΔR_C) Is calculated
Is done. Modified cooling output ratio R_C', Calculate step S11
Proceed to. On the other hand, if the determination in step S5 is negative (R_C
= R_MAX), Adjust the cooling device (4)
It is determined that the alloy layer thickness cannot be controlled, and the process proceeds to step S7.
No. In step S7, the line speed (V_L) Is the upper limit
(V_{L UL}) It is determined whether it is lower. The judgment is positive
(V_L<V_{L UL}), Increase the line speed to increase the alloy layer
Proceed to step S8 to reduce the thickness. In step S8
Is the corrected line speed V_L'(= V_L+ ΔV_L) Is calculated
Then, the process proceeds to step S11. The judgment in step S7
No (V_L= V_{L UL}), The line speed cannot be increased
Therefore, the process proceeds to step S9. In step S9, the plating bath
Temperature is lower limit (T_{M LL}) It is determined whether it is higher. So
Is positive (T_{M LL}<T_M)
Since the alloy layer thickness can be reduced by the temperature, step S1
Proceed to 0 and correct plating bath temperature T_M'(= T_M+ ΔT_M)
After the calculation, the process proceeds to step S11. In step S11, the cooling output ratio (R_C), Rai
Speed (V_L) Or plating bath temperature (T_M) Control
It is. That is, the determination in step S5 is affirmative (R_C
<R _max), The cooling output ratio (R_C) Fixes
And the determination in step S5 is negative (R _C= R_MAX)
If the determination in step S7 is affirmative, the line speed
(V_L) Is modified. If the determination in step S7 is no (V
_L= V_{L UL}), And the judgment in step S9 is affirmative (T
_{M LL}<T_M), The plating bath temperature (T_M) Fixes
It is. After completing the correction operation in step S12,
Proceed to step S13. On the other hand, step S5, step S7, step
If each judgment in S9 is negative, the cooling output ratio (R_C), Rai
Speed (V_L), And plating bath temperature (T_M)
Cannot make the necessary modifications to reduce the alloy layer.
In this case, go to step S12
(Visual display with blinking indicator light, sound display with buzzer
Etc.) are issued. In this case, the alloy layer of the product plated steel sheet
Because the thickness may be out of the target value,
A quality inspection is performed and actions are determined. After the warning is issued,
Proceed to step S13. In step S13, control of the alloy layer thickness
It is determined whether to end the control operation. This judgment is
All of the specified steel sheet throughput has passed through the cooling device (4)
Or not, and the judgment is affirmative (complete processing of all amounts)
If so, end the plating operation;
Continue the operation. [0030] [Example] In the continuous hot-dip galvanizing line, the pre-
Layer thickness (τ_C) And target layer thickness (τ_S) And the displacement
And the cooling output ratio R of the cooling device (4)_COperation to adjust
To manufacture a hot-dip aluminum-plated steel sheet. Eye
Standard plating layer thickness (τ_S) Indicates the prescribed
(About 3 to 6 μm). [1] Plating bath (a) Composition: Al-8 to 10% Si (Fe ≦ 5%) (b) Bath temperature (T_M): 650 ℃ (= 923K) [2] Base material steel plate (a) Grade: Ultra-low carbon titanium added steel sheet (C ≤ 0.005, Si ≤ 0.10, Mn
0.10-0.20, P ≤0.020, S ≤0.010, Al 0.04-0.06, Ti
0.05-0.07, N ≦ 0.005) Low carbon aluminum killed steel sheet (C ≤ 0.08, Si ≤ 0.10, Mn 0.1
0-0.40, P ≤ 0.020, S ≤ 0.030, Al 0.02-0.06, N ≤ 0.005
 ) Medium carbon aluminum killed steel sheet (C 0.12-0.15, Si ≤0.10, Mn
 0.50-1.00, P ≤0.030, S ≤0.030, Al 0.02-0.06, N≤
0.005) (b) Thickness (T_P): 0.4 to 3.2 mm [3] Transfer distance between A and B (L_AB): 5.9m [4] Line speed (V_L): 30-140m/ min [5] Cooling device (air jet cooler) (a) Refrigerant: air (b) Injection pressure: 80 ~ 430mmAq (c) Injection amount: 400-2400m³/ min (d) Cooling zone length: 8.6m (e) Output ratio (R_C): 0-80% [6] Constants and coefficients C1: 0.54996 (sec ・ min / mm / m) C2: 50 (mm / m / min) K: 0.006225 (sec · min / mm / m) FIG. 14 shows the results obtained by the continuous plating operation.
WasProductAlloy layer thickness (measured value) and predicted layer thickness of galvanized steel sheet
(Τ_C) Is illustrated. Prediction of alloy layer
Layer thickness (τ_C) Indicates alloy layer thickness of product plated steel sheet (actual measurement)
(N = 376, correlation coefficient γ = 0.81)
6). [0033] EFFECT OF THE INVENTION Molten aluminum produced by the present invention
Plated steel sheets reduce the thickness of the Fe-Al-Si alloy layer in the coating layer.
As a control effect, it has good peeling resistance,
Plating layer hardly peels off, ensuring good plating quality
It is. According to the present invention, complicated measures as in the conventional method are used.
For example, adjusting the sheet temperature when the steel sheet enters the plating bath,
No measures such as forming a certain metal film on the
Implemented based on the amount of displacement between the alloy thickness and the target layer thickness
By controlling the cooling output ratio of the cooling device, line speed, etc.
Economically advantageous and accurate alloy layer thickness of product plated steel sheet
Can be well controlled. The present invention relates to an exhaust system for an automobile.
Aluminum alloy for use in components, thermal equipment, etc.
To meet the demands of improving the quality of
It has great industrial value. What
In addition to the hot-dip aluminum plating, the present invention
Plating, zinc-aluminum alloy plating, pure aluminum plating, etc.
In continuous hot-dip coating operations,
This is effective as a means for controlling the thickness of the gold layer.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing an equilibrium diagram of an Al—Si binary alloy. FIG. 2 is a graph showing the relationship between the thickness of a formed alloy layer and the square root of elapsed time. FIG. 3 is a graph showing the relationship between the thickness of a formed layer of an alloy layer and the square root of elapsed time. FIG. 4 is a graph showing a relationship (log V−1 / T) between a formation speed V of an alloy layer and a plating layer temperature (T). FIG. 5 is a graph schematically showing a change in an alloy layer formation rate from a liquid phase region to a solid-liquid coexistence. [6] (time spent in the solid-liquid coexisting phase) BC elapsed time and the relationship between the plate thickness × line speed (T _P xV _L) (cooling power ratio:
10%). [7] the relationship between the BC elapsed time and the thickness × line speed (time spent in the solid-liquid coexisting phase) (T _P xV _L)) (cooling power ratio: is a graph showing 25%). [8] the relationship between the BC elapsed time and the thickness × line speed (time spent in the solid-liquid coexisting phase) (T _P xV _L)) (cooling power ratio: is a graph showing 55%). [9] the relationship between the BC elapsed time and the thickness × line speed (time spent in the solid-liquid coexisting phase) (T _P xV _L)) (cooling power ratio: is a graph showing 65%). 10 is a graph showing the relationship between the cooling power ratio R _C of BC elapsed time / (T _P xV _L) and the cooling device. FIG. 11 is a system diagram schematically illustrating a configuration example of an alloy layer control device for continuous hot-dip plating. FIG. 12 is a block diagram illustrating an example of an electrical configuration of the alloy layer control device. FIG. 13 is a flowchart illustrating the operation of the alloy layer control device. FIG. 14 is a graph showing a correlation between an estimated layer thickness of an alloy layer and an alloy layer thickness of a product plated steel sheet according to the present invention. FIG. 15 is a schematic diagram showing the configuration of a continuous hot-dip aluminum plating facility. [Explanation of Signs] 1: Hot-dip plating bath 2: Sink roll 3: Gas wiping device 4: Cooling device 5: Top roll 6: Bridle roll 8: Plating bath heating device 9: Blower A: Steel plate plating bath entry start position B : Cooling system inlet C: Plating layer solidification completed position

Continuation of the front page (56) References JP-A-4-176854 (JP, A) JP-A-52-60239 (JP, A) JP-A-5-156419 (JP, A) WO 96/026301 (WO, A1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 2/00-2/40

Claims (1)

(57) [Claim 1] Al-Si having a Si content of 3 to 13% by weight
A base material steel plate is introduced into a hot-dip aluminum plating bath having a bath composition and a bath temperature maintained at a melting point of + 70 ° C. to form a plating layer, and the plating layer is formed by a cooling device disposed on the bath. In the method for producing a continuous hot-dip aluminum-plated steel sheet forcibly cooling, the thickness of the Fe-Al-Si-based alloy layer generated at the interface between the base steel sheet and the plating layer is calculated by a prediction formula [A ₁ ] or [A ₂ ]. Calculated by
By adjusting the output ratio of the cooling device on the plating bath, the transfer speed of the steel sheet, or the plating bath temperature, based on the calculated amount of displacement between the predicted layer thickness (τ _C ) and the target layer thickness, A method for controlling the alloy layer thickness of a continuous hot-dip aluminum-plated steel sheet, comprising controlling the thickness of a layer formed of steel to a target layer thickness. [Number 1] _{(1) T P × V L} > For _{C 2 τ C (μm) =} 0.833√ [{3.564 × exp (-1647 / 1.987 / T M) /0.833} 2 × 60 × L _AB / V _L + (C ₁ −K × _RC ) × ( _TP × V _L −C ₂ )]... [A ₁ ] (2) When _TP × V _L ≦ C ₂ τ _C (μm) = 0.833√ [{3.564 × exp (-1647 / 1.987 / T M) /0.833} 2 × 60 × L AB / V L] ... [A 2] [ wherein, _{T M:} a plating bath temperature (absolute Temperature, K) L _AB : Transfer distance of steel sheet from ingress of plating bath of steel sheet to entrance of cooling device (m) _TP : Thickness of base steel sheet (mm) _VL : Transfer speed of steel sheet in line (m) / min) C ₁ : Constant (sec · min / mm / m) set based on the product of the thickness of the base steel sheet and the transfer speed, the cooling capacity of the cooling device, and the forced cooling time of the plating layer. Coefficient (sec · min / mm / m) set based on the product of the thickness of the steel sheet and the transfer speed, the cooling capacity of the cooling device, and the forced cooling time of the plating layer. C ₂ : The thickness of the base steel sheet and the transfer speed From the product and the plating bath Constant is set based on atmosphere while leading to (mm · m / min) R C: power ratio of the cooling device (the ratio of the maximum output,%)
]