JP3518316B2 - Control method of pickling plant and its pickling plant - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pickling plant for removing oxide scale formed on the surface of a novel hot-rolled steel strip, a control method therefor, a continuous continuous descaling rolling method for ordinary steel strip, and a descaling process. Regarding continuous integrated manufacturing equipment.

[0002]

2. Description of the Related Art Generally, ordinary steel plate (carbon steel) is 800-
Since it is rolled at 900 ° C., a black oxide scale mainly composed of Fe ₃ O ₄ is formed on the surface. This scale is
Scale removal is essential because it causes damage due to scale entrainment during subsequent cold rolling. As a method for removing the scale of ordinary steel strip, a catenary-type pickling method in which a steel sheet is immersed in a bath of hydrochloric acid solution to continuously pass through it and the scale is removed by a chemical reaction is the mainstream. The hydrochloric acid solution is injected from the downstream side and taken out from the upstream side. At this time, the acid concentration of the hydrochloric acid washing solution decreased to about 3-5%, and conversely FeCl
_{2 The} concentration rises to around 10%. This solution is AR
It is regenerated as a hydrochloric acid solution of about 18% through P (acid recovery system) and supplied again to the downstream side of the pickling tank. Normally, the capacity of ARP is set so that the Fe ion concentration in the pickling solution recovered from the upstream side is 120 g / l. This one
The value of 20 g / l corresponds to the Fe ion concentration contained in the pickling solution when the scale is completely dissolved and the descaling is completed at the end of the pickling tank.

Considering the case of deviation from normal operation, for example, when the line speed must be reduced,
If the temperature of the pickling solution is left as it is, the staying time of the steel sheet in the pickling tank will be longer, so descaling will be completed at a stage before the end of the pickling tank, and the uncleaned surface The ejected steel plate is immersed in an acid solution (per pickling). In this case,
Not only does the base become rough and product quality deteriorates,
The pickling solution is consumed and deteriorates. Also, if steel materials with different scale thicknesses come in, if the operating conditions are the same, for example, in the case of steel materials with a thick oxide film, there is a possibility that the steel materials will come out of the pickling tank before descaling is completed, In the case of a thin oxide film, it will be in a state of overpickling as in the case where the line speed becomes slow.

At present, no fixed method has been established for each case. For example, when the line speed decreases, it is better to lower the temperature. It has not been clarified whether or not it should be lowered, and the optimum value was determined by looking at the surface condition of the steel material that appears.

Japanese Unexamined Patent Publication (Kokai) No. 59-209415 discloses a descaling method in which the pickling rate is controlled based on the temperature at the time of winding a hot-rolled steel strip. A descaling method for controlling the jet speed of acid in the pickling tank based on the temperature of the steel strip before entering the molten salt when passing the rolled steel strip through the molten salt and then pickling, JP-A-1-254313 Is a descaling method for controlling the discharge amount from the pickling nozzle based on the plate thickness, material and hot pressing conditions when pickling a hot rolled steel strip. JP-A-6-212462 discloses a steel plate surface. There is disclosed a method of pickling while changing the acid concentration and the temperature based on the state of the oxide film formed in the above.

[0006]

When using the empirical method, it is difficult to find the optimum value to lower the temperature when the line speed decreases. Prior to that, there has been no theoretical examination as to whether or not the method of lowering the temperature is the optimum method. As mentioned earlier, the optimum value was determined by looking at the surface condition of the steel material that emerged, and how much the parameter should be changed. There is no material to judge.

None of the above known examples shows the acid concentration distribution, the Fe concentration distribution and the descaling efficiency in the pickling tank.

An object of the present invention is to provide an algorithm in an optimal control method of a pickling plant for obtaining a plain steel having excellent smoothness after descaling, a pickling plant with the same and a plain steel strip using the same. It is to provide a continuous descaling rolling continuous manufacturing method and its equipment.

[0009]

[Means for Solving the Problems] In order to change the control based on the empirical one into the control by the calculation algorithm, the relation between the operating condition of the plant and the state quantity of the steel sheet and the descaling efficiency is made into a mathematical expression and accumulated. The operating conditions of the plant may be determined so that the descaling efficiency is 100% near the outlet of the pickling tank.

The optimum operating conditions during normal operation are
The value may be controlled by using this algorithm. Also, when the operating conditions change, for example, when the line speed, plate thickness, plate width, scale amount, etc. change, the liquid temperature, which is the operating condition of the plant, is calculated using this algorithm.
The plant can be operated under optimum operating conditions by calculating how much the hydrochloric acid concentration from the ARP and the hydrochloric acid injection amount should be changed.

According to the present invention, the thickness of the steel sheet, the width of the steel sheet, the state quantity of the steel sheet represented by the scale amount, the concentration of the acid supplied to the pickling tank, the supply amount of the acid, the temperature of the acid, the line speed and the acid. The operating state quantity relating to the strip temperature immediately before entering the washing bath, preferably the line length and the scale breaker spread rate is monitored, and the value of the state quantity is used to descaling the efficiency of any part of the pickling bath. Preferably, the acid pickling plant control method is characterized in that the concentration distribution of acid and the concentration distribution of iron are further obtained, and the operating state quantity of the plant is determined based on the values.

According to the present invention, the concentration of acid in the pickling tank, the concentration of iron,
A method for controlling a pickling plant, which is characterized in that the temperature of acid and the amount of descaling are monitored for arbitrary plural parts.

The amount of acid consumed is a function of temperature and acid concentration by previously descaling in various temperature and acid concentration solutions.

Descaling efficiency near the exit is 100
The operating state quantity of the plant is determined so as to be%.

According to the present invention, the thickness of the steel sheet, the width of the steel sheet, the state quantity of the steel sheet represented by the scale amount, the concentration of the acid supplied to the pickling tank, the supply amount of the acid, the temperature of the acid, the line speed and the acid. The operating state quantity relating to the strip temperature immediately before entering the washing tank, preferably the line length and the scale breaker spread rate is monitored, and the value of the state quantity is used to flow in at any part of the pickling tank. The mass balance of the acid, the outflowing acid, and the acid consumed in the part is calculated, and the descaled amount in the part is calculated using the calculated value, and by repeating this step in succession, the multiple values in the pickling tank can be obtained. Descaling efficiency of a part, preferably further obtaining an acid concentration distribution and an iron concentration distribution, determining the operating state quantity of the plant based on the values, and operating the plant based on the values. The control method of.

The present invention provides a sensor for monitoring the state quantity of a steel sheet represented by the thickness, width, and scale of the steel sheet, the concentration of acid supplied to a plurality of pickling tanks, the supply amount of acid, and the acid. Temperature, line speed and strip temperature immediately before entering the pickling tank, preferably a sensor for monitoring the operating state quantity of the plant with respect to the line length and scale breaker spread rate, and the pickling rate using the value of the state quantity. The acid concentration of the part is calculated from the mass balance of the acid flowing into and out of the arbitrary parts of the tank, the acid flowing out, and the acid consumed at that part, and the descaled amount at that part is calculated using the value.
By sequentially repeating the above, the descaling rate of a plurality of parts in the pickling tank, preferably the arithmetic processing means for further obtaining the acid concentration distribution and the iron concentration distribution, and the operating state quantity of the plant based on the calculated values The pickling plant is characterized by having control means for controlling the above.

The present invention is represented by the concentration of the acid to be injected into the pickling tank, the supply amount of the acid, the temperature of the acid, and the operating state amount represented by the line speed, the plate thickness of the steel plate, the plate width, and the scale amount. In the method for controlling a pickling plant in which the quantity of state of the steel sheet is changed during plant operation, the amount of acid consumed in that portion is newly obtained from the relationship between the acid flowing into any portion and the acid flowing out. It is preferable to determine the operating state quantity.

In the present invention, the concentration of the acid to be injected into the pickling tank, the supply amount of the acid, the temperature of the acid, and the operating state amount represented by the line speed, the plate thickness of the steel plate, the plate width, and the scale amount are represented. In a method for controlling a pickling plant, in which the state quantity of a steel sheet to be changed during plant operation, at least one operating state of at least the concentration and supply amount of acid injected into the pickling tank, the temperature of the acid, and the line speed. It is preferable to change the amount. That is, the present invention relates to the thickness of a steel sheet, the width of the steel sheet, the state quantity of the steel sheet represented by the amount of scale, the concentration of the acid supplied to the pickling tank, the supply amount, the liquid temperature of the acid, the line speed, the pickling tank. At least one of the operating state quantities of the plant, which is represented by the strip temperature immediately before entering, is monitored, and by using the values, the acid flowing into any part, the acid flowing out, and the acid substance consumed in that part Determining the acid concentration of that part from the balance, using that value to determine the descaling amount in that part, and by repeating it sequentially, the descaling rate of multiple parts in the pickling tank, preferably further acid concentration distribution The iron concentration distribution is obtained, the optimum operating state quantity of the plant is determined based on the value, and the plant is operated based on the value.

The present invention is a mechanical scale breaker for mechanically removing scale on the surface of a hot-rolled ordinary steel strip,
A washing plant comprising a plurality of pickling tanks containing dilute hydrochloric acid solution, means for moving the dilute hydrochloric acid solution from the downstream side to the upstream side of the plate, and means for moving the ordinary steel strip from the upstream side to the downstream side of the tank. In the continuous descaling cold rolling continuous manufacturing facility having the above, the pickling plant is configured as described above. Further, it is possible to have a cold rolling mill for cold rolling the pickled ordinary steel strip.

A continuous casting machine for producing ordinary steel sheet castings,
A hot rolling mill for hot rolling the thin sheet casting, a mechanical scale breaker for mechanically removing the scale of the rolled ordinary steel strip surface, a plurality of tanks for storing the dilute hydrochloric acid solution and the descaled An acid provided with means for passing the ordinary steel strip while immersing it in the acid solution in the plurality of tanks, heating means for heating the acid solution, and means for moving the acid solution from the downstream side to the upstream side of the strip. In the descaling continuous integrated production facility comprising a washing plant, a means for washing the ordinary steel strip discharged from the pickling plant, and a means for drying the washed ordinary steel strip, the pickling plant is as described above. Composed. Further, it is possible to have a cold rolling mill for cold rolling the dried ordinary steel strip.

In the present invention, ordinary steel is rolled by a hot rolling mill,
In the method for controlling a pickling plant, which comprises contacting the rolled ordinary steel strip with an acid solution to remove the scale formed on the surface of the ordinary steel strip by pickling, the pickling is performed by the above-mentioned pickling. .

In the present invention, ordinary steel is rolled by a hot rolling mill,
In the method of controlling a pickling plant, wherein the rolled ordinary steel strip is brought into contact with an acid solution to remove the scale formed on the surface of the ordinary steel strip by pickling, the scale of the ordinary steel strip surface discharged from the rolling mill is The present invention is a continuous continuous descaling rolling continuous steel strip manufacturing method, characterized in that the steel strip is mechanically removed and then subjected to the above-mentioned pickling, and the pickled ordinary steel strip is cold-rolled.

The present invention provides a means for supplying ordinary steel strip rolled by a hot rolling mill, a means for cutting the ordinary steel strip to an arbitrary length, and a mechanical stress applied to the scale produced on the ordinary steel strip. Means for providing, a plurality of tanks for storing an acid solution in contact with the ordinary steel strip, a pickling plant for removing the scale by passing the ordinary steel strip through the acid solution in the plurality of tanks while stripping In the descaling equipment for hot-rolled ordinary steel strip, which comprises means for washing the treated ordinary steel strip discharged from the pickling plant and means for drying the washed ordinary steel strip, the pickling plant is as described above. It is composed.

For control by the calculation algorithm,
It is necessary to formulate the relationship between the plant operating conditions and the quantity of state of the steel sheet and the descaling efficiency. Therefore, by dividing the pickling tank into a plurality of parts, considering the material balance of the acid in that part, and solving the equation, the hydrochloric acid concentration, descaling amount, Fe amount, etc. at that part can be obtained.
The contents of the algorithm mentioned here are as follows.

Here, the pickling tank is divided into n pieces.

From the entrance of the pickling tank,
₁ , l ₂ ... l _n [m] , and the acid concentration is C ₁ , C ₂ ... C _n [g /
l] , the average temperature of the steel sheet is t ₁ , t ₂ ... t _n [° C] , the strip residence time is τ ₁ , τ ₂ ... τ _n [min] , the initial strip
Temperature θ ₀ [° C] , liquid temperature θ _f [° C] , scale amount X ₀ [kg /
m ² ] , line speed V [m / min] , heat transfer coefficient α [kc
al / (m ² · h · ° C)] , strip specific heat Cv [kca
l / (kg · ° C.)] , concentration of injected acid from ARP C _{n + 1} [g
/ L] , HCl injection amount Q [kg / min] , plate width h [m] ,
The plate thickness is d [m] . The average residence time of the strip in each _{site, τ 1 = l 1 / V} ... (1) τ n = l n / V ... (2) temperature of the steel material is determined by the following equation.

The inlet temperature of the first part is T ₀ , the outlet temperature is T ₁ , the inlet temperature of the second part is T ₁ , the outlet temperature is T ₂ ,
In the n-th part, the inlet temperature is T _n−1 and the outlet temperature is T _n−1 .
_{Let n} be T ₀ = θ ₀ (3) T ₁ = θ _f − (θ _f −θ ₀ ) × exp (−2 × α × l ₁ / (C _v × d × V × 60 × 7850)) (4) T ₂ = θ _f − (θ _f −θ ₀ ) × exp (−2 × α × (l ₁ + l ₂ ) / (C _v × d × V × 60 × 7850)) (5) T _n-1 = θ _f − (θ _f −θ ₀ ) × exp (−2 × α × (l ₁ + l ₂ + l ₃ … + ln ₁ ) / (C _v × d × V × 60 × 7850)) (6) T _n-1 = θ _f − (θ _f −θ ₀ ) × exp (−2 × α × (l ₁ + l ₂ + l ₃ ... + ln _{) -1 + l n) / (C} v × average strip temperature in the d × V × 60 × 7850) ) ... (7) each _{site, t 1 = (T 0 +} T 1) / 2 ... (8) t 2 = (T ₁ + T ₂ ) / 2 (9) t _n-1 = (T _n-2 + T _n-1 ) / 2 (10) t _n = (T _n-1 + T _n ) / 2 (11) In the steady state, the balance of the acid balance is Q × C _{n + 1} = Q × C _n + γ _{n in} the n-th part (12) Q × C _n = Q × C _n-1 + γ _{n in} the n-1 part _{-1 ... (13) Q × C} 3 part 2 = Q × C ₂ + γ _{2 (14) Q × C 2 =} Q × C 1 + γ 1 ... (15) where gamma _n represents an acid consumption rates in Part 1, it can be converted to the descaling speed X _n. For example, when the reaction formula is FeO + 2HCl = FeCl ₂ + H ₂ O (16), γ _n = X _n (17) However, the unit here is (Kg / min) Q and C _n in the nth part. _{It is a +1} setting value and can be arbitrarily determined. X _n in order as a function of t _n and C _n, if previously determined the function equation, equation (12) can be determined easily C _n becomes linear equations related to C _n. If C _n can be determined, X _n can be determined from the functional expressions of t _n and C _n with respect to X _n .

In the n-1st part, it can be set arbitrarily.
Q and C obtained in n part_n And X_n-1Against
t_n-1And C_n-1 Substituting the functional expression of
C as in the case of n part_n-1Becomes a linear function of_n-1
Can be determined. Similarly C_n-1 X can be determined_n-1Against
To t_n-1And C_n-1From the functional expression of X_n-1To decide
You can By repeating this in order,
Acid concentration distribution C_n, C_n-1… C₁ andDescaling speed X
_n  , X_n-1... X₁Can be asked. X_nSeeds for
T determined under various temperature and acid concentration conditions_n And C_n Seki
The formula is, for example, when the acid is hydrochloric acid and the steel is ordinary steel.
Then, the following formula is given.

[0029] ^{_{X n = 1.3328 × 10 7 ×}} exp (-7168 / (273+ t n)) × l n × h × C n × 2 ... (18) other acids, for example acid used is sulfuric acid there For example, the descaling rate at various temperatures and concentrations in sulfuric acid may be similarly obtained in advance. The cumulative descaling rate Z can be obtained by the following method. That is, the amount of descaling per unit area at each site is obtained and accumulated. Descaling amount Y per unit area at each site, the n-th unit in the _{Y n = X n × τ n} / (l n × h × 2) ... (19) Y n-1 in the (n-1) part = X _n-1 × τ _n-1 / (l _n-1 × h × 2) (20) In the second part, Y ₂ = X ₂ × τ ₂ / (l ₂ × h × 2) (21) In one part Y ₁ = X ₁ × τ ₁ / (l ₁ × h × 2) (22) Cumulative descaling rate Z up to each part is up to the first part outlet Z ₁ = Y ₁ / X ₀ (23) ) To the outlet of the second part Z ₂ = (Y ₁ + Y ₂ ) / X ₀ (24) To the outlet of the _n -th part Z _n = (Y ₁ + Y ₂ + ... + Y _n ) / X ₀ (25) Therefore, the above The cumulative descaling rate in the pickling tank is obtained by using the equation shown in (4), and the parameters can be arbitrarily controlled so that it is around 100% near the outlet, that is, t _n , C _{n + 1} , Q, V. By giving feedback to It can be controlled to.

In addition, operating conditions of the plant, for example, line speed V, liquid temperature θ _f , ARP capacity C _{n + 1} , Q
Also, even when the state of the steel material, for example, the plate width h, the scale amount X _0, etc., changes, the cumulative descaling rate is obtained using the above algorithm, and is fed back to a controllable parameter at that stage, which is 100 at the exit. Each value can be set so that it becomes%.

The determination of which parameter should be changed is made based on the time required to reach a steady state after moving the parameter and the uniformity of descaling. For example, when V changes, C _{n + 1} , Q and θ _f which can be changed at this time.

[0032] The time to reach up to a steady _{state, V · dC n = Q ·} C n + 1 · dt-Q · C n · dt-γ n · dt ... (26) V · dC n-1 = Q · C _n・ dt-Q ・ C _n-1・ dt-γ _n-1・ dt (27) ………………………………………… V ・ dC ₁ = Q ・ C ₂・ dt It is possible to find out by solving the simultaneous differential equation of −Q · C ₁ · dt−γ ₁ · dt (28).

The uniformity of descaling can be judged by the distribution of the cumulative descaling rate in the pickling tank. That is, when the cumulative descaling of the steel sheet gradually progresses as it goes through the pickling tank, it means that the steel sheet is uniformly descaled and the surface roughness is small. On the other hand, when the cumulative descaling rate sharply increases in a certain section, the descaling rapidly progresses in that section, and in that case, the surface roughness becomes large.

From such operations, it is necessary to determine what optimum control parameter should be set, and which parameter should be changed and how much when the operating state of the plant and the state of the treated steel sheet are changed. You can

[0035]

DETAILED DESCRIPTION OF THE INVENTION

(Example 1) FIG. 1 shows a pickling apparatus equipped with the present algorithm. In the monitoring unit, plate thickness, plate width, initial strip temperature, acid liquid temperature, scale amount, line speed, concentration of hydrochloric acid injected from ARP (acid recovery system), A
Information on the injection amount of hydrochloric acid from the RP is input to the monitoring unit 7 through the sensors 9 and 10. The input data is calculated in the arithmetic system 8 from these data using the algorithm of the present invention to calculate the optimum operating conditions, and the information is fed back to adjust the liquid temperature, set the line speed, and inject. Each operation such as setting the hydrochloric acid concentration and adjusting the injected hydrochloric acid concentration is performed. The content of the algorithm is as shown in the section of action. The sensor 9 is a sensor for detecting the concentration and flow rate of the acid, and 10 is a sensor for detecting the line speed and the film thickness meter.

FIG. 1 shows a catenary type pickling tank. The pickling tank consists of three or four tanks, and the steel plate is supported by rolls installed at both ends of each tank. The flow direction of the solution and the traveling direction of the steel sheet are opposite to each other, so that the relative speed is increased. Therefore, at the entrance of the steel sheet, the steel sheet comes into contact with the acid solution having a low concentration and the steel sheet is not sufficiently heated, so that the steel sheet temperature is low. As the steel sheet progresses, the concentration of acid that comes into contact increases, and since the steel sheet is sufficiently heated, the temperature of the steel sheet becomes almost the same as the solution temperature. The acid solution flows from the upstream side to the upstream side in the traveling direction of the steel sheet so as to overflow from the upper part of the pickling tank. Further, the pickling tank is provided with a heater for heating the acid solution in the tank.

The sensor 9 measures the injection hydrochloric acid concentration and the injection amount of hydrochloric acid. Sensor 10 measures strip thickness, strip width, initial strip temperature, scale amount, and line speed. The sensor 11 detects the liquid temperature.

The solid line in FIG. 1 shows the flow of liquid and the dotted line shows the flow of information. Therefore, the dotted line from the sensor 10 to the monitoring unit transfers the measurement results of plate thickness, plate width, initial strip temperature, scale amount, and line speed.
Similarly, from the sensor 9, the measurement result of measuring the injection hydrochloric acid concentration and the injection amount of hydrochloric acid is transferred.

The dotted line from each tank transfers the measurement result of the solution temperature. The optimum parameter values calculated by the arithmetic processing system through the monitoring unit are sent to the acid solution concentration / flow rate control system 13 through the monitoring unit, and new optimum values are set therein. . The strip passing speed is set to an optimum value by the strip passing speed control system 12 in a similar manner.

FIG. 2 shows a flow chart of the operation at the time of starting operation according to the present invention. Each parameter shown in the flow chart is initially input, and then the desquaning rate at the exit is calculated by using the above equations (1) to (25). If the value is in the range of 100-105%,
Start operation under that condition. If it is not within the range, re-enter the initial hydrochloric acid concentration (injected hydrochloric acid concentration) and the solution temperature hydrochloric acid flow rate, which are changeable operating parameters.
When the production amount can be changed, the strip passing speed is also a change parameter. Recalculate the cumulative descaling rate.

FIG. 3 shows a flow chart of the operation when the scale amount, which is a steel grade parameter, according to the present invention changes during operation. Cumulative descaling rate is 100-
Although it was operating under the condition of 105%, if the annealing condition changes and the scale amount changes and the operation condition (1) of FIG. 4 is reached, the cumulative descaling rate is recalculated. If the value is in the range of 100-105%, the operation is continued with the operating condition parameters as they are. If it does not fall within that range, it becomes necessary to reset the operating condition parameters again. The parameter that can be most easily changed among the operating parameters is the strip running speed.

FIG. 5 shows the relationship between the strip running speed obtained by calculation and the descaling rate (the same as the cumulative descaling rate). Based on this relationship, the appropriate passing speed is 225-252 m.
Since this is / min, re-enter this value to continue operation. When the productivity cannot be changed (when the strip running speed cannot be changed), other operating parameters such as initial hydrochloric acid concentration,
The solution temperature and the flow rate of hydrochloric acid will be changed. FIG. 6 shows the change in the descaling rate when each value is changed, which is calculated. As shown in FIG. 6, it is possible to determine the optimum set value for each operation. Further, by performing the operation, the transient response time to reach the next stable state can be obtained by using the equations (26)-(28). Regarding the optimum control method, it is preferable that the transient response time is short. However, as shown in FIG. 6B, when the hydrochloric acid temperature exceeds 100 ° C., the operation cannot be performed due to the performance of the apparatus, and the operation is excluded. In FIG. 6, (a) shows the case where the hydrochloric acid flow rate is changed, (b) shows the case where the hydrochloric acid temperature is changed, and (c) shows the case where the hydrochloric acid concentration is changed.

Example 2 FIGS. 7 and 8 show the initial strip temperature θ ₀ 10 ° C., the liquid temperature θ _f 85 ° C., and the scale amount X ₀ 0.07 kg / m ² , under the operating conditions of the current plant in the steady state. Line speed V25
0 m / min, heat transfer rate α 20,000 kcal / m ² h ℃, strip specific heat Cv 0.11 kcal / kg ℃, length l _n of each pickling tank
1 tank 20.7m 2 tanks 21.75m 3 tanks 21.75m
4 tanks 26m, HCl concentration injected from ARP C _{n + 1} 180
The graph shows the HCl concentration, Fe ion concentration, and temperature distribution in the pickling tank obtained by substituting g / l, HCl injection amount Q80 kg / min, plate width h1 m, and plate thickness d 0.0035 m into the algorithm of the present invention. The diagonal line in the graph showing the concentration distribution shows the distribution of the HCl concentration during the operation of the actual machine. The HCl concentration distribution obtained by the algorithm of the present invention is in good agreement with the concentration distribution in the actual machine, confirming that the present algorithm is operating correctly. The cumulative descaling rate at each place in the pickling tank obtained using this algorithm is shown in FIG. According to this, the cumulative descaling rate at the point of leaving the pickling tank is 110%, which exceeds 100% at the end of descaling. Considering that 100% indicates the end point of descaling, it can be seen that under this operating condition, a slight overpickling is performed.
In the case of overpickling, in order to elute the base material remarkably and roughen the surface to reduce the product value, it is necessary to bring the cumulative descaling rate to 100% as close to the pickling tank outlet as possible. Therefore, using the present algorithm, when the temperature is lowered, for example, the cumulative descaling rate becomes as shown in FIG. 10 and becomes 100% at the outlet, and the per-pickling can be reduced. By using the algorithm of the present invention to instantaneously find the optimum control method and its value and feeding them back to the operating conditions, it is possible to operate under the optimal conditions and obtain a steel sheet of good quality with less skin roughness.

(Acid Concentration Distribution) In Part n, C _n = Q × C _{n + 1} / (Q + 7996800
00 × 2 × 1 _n × h × exp (−7168 / (273 + t _n ))) In the n-1th part, C _n-1 = Q × C _n / (Q + 7996800)
00x2x1 _n-1 xhxexp (-7168 / (273 + t
_n-1 ))) In Part 2 C ₂ = Q × C ₃ / (Q + 799688000
0 × 2 × 1 ₂ × h × exp (−7168 / (273 + t ₂ ))) In the nth part, C ₁ = Q × C ₂ / (Q + 79968000)
0 × 2 × 1 ₁ × h × exp (−7168 / (273 + t ₁ ))) (Iron concentration distribution) In the nth part, D _n = (C _{n + 1} −C _n ) × 56/72 the n-1 part D _n-1 = (C _{n + 1} −C _n-1 ) × 56/72 in the second part D ₂ = (C _{n + 1} −C ₂ ) × 56/72 in the nth part D ₁ = (C _{n + 1} −C ₁ ) × 56/72 (Example 3) When the line speed was reduced to 50 m / min during operation of the pickling apparatus under the conditions shown in FIGS. 7 and 8, the operation was continued under the same operating conditions. When it is continued, calculation using the algorithm of the present invention, as shown in FIG. 11, the cumulative descaling rate has already exceeded 100% around the second half of the second pickling tank, and at the exit. Is 58
It can be seen that the amount becomes 0% and the super-pickling is remarkable. Possible actions to be taken in this case are (1) changing the concentration of hydrochloric acid from ARP, (2) changing the liquid temperature, and (3) changing the injection amount of hydrochloric acid from ARP. A value that must be set so that the cumulative descaling ratio near the exit is near 100% by each operation is calculated by using the algorithm of the present invention.
From 80 g / l to 32 g / l (2) From 85 to 45 ° C (3) From 80 kg / min to 12 kg
/ Min, and an arbitrary value can be obtained without experience. FIG. 11 shows the cumulative descaling rate at each location of the pickling tank when the operations (1) to (3) were performed.
In the operations of (1) and (2), descaling is performed at a constant rate in the pickling tank, but in the operation of (3), almost no descaling is performed in the initial stage, and in the latter half of the pickling tank. It can be seen that the cumulative descaling rate rises sharply and that descaling occurs in a very short interval. In such a case, the surface becomes rough, which is not appropriate, and in this case, it can be determined that the plant should not be controlled by the operation of (3). When the operations of (1) and (2) are compared, the time until the steady state is reached after the operation is performed by using this algorithm, the operation of (1) is 15 minutes, and the operation of (2) is It turned out to be 80 minutes. Comprehensive determination of these results shows that the operation of (1) is the most optimal. By using the algorithm of the present invention to instantaneously find the optimum control method and its value and feeding them back to the operating conditions, it is possible to operate under the optimal conditions and obtain a steel sheet of good quality with less skin roughness.

(Example 4) When the plate width was changed from 1 m to 1.5 m during the operation of the pickling apparatus under the conditions shown in FIGS. 7 and 8, when the operation was continued under the same operating conditions, When calculated using the algorithm of the invention, as shown in FIG. 13, the cumulative descaling rate becomes 81.6% at the exit of the pickling tank, which shows that descaling is not completed. The measures taken in this case are (1)
Change hydrochloric acid concentration from ARP (2) Change liquid temperature
(3) Change the injection amount of hydrochloric acid from ARP. (4) Change the line speed. Similar to the third embodiment, the cumulative descaling rate near the exit must be set to approach 100% by each operation, but if the value is calculated using the algorithm of the present invention, the operation of (1) is performed. Then, from 180 to 225 g / l, in the operation of (2) the cumulative descaling rate was 90.3% even if it was increased from 85 to 100 ° C, and in the operation of (3) it increased from 80 to 108 kg / min. And (4) the speed drops from 250 to 205 m / min. Considering factors such as the cumulative descaling rate and the time to reach a stable state as in the case of Example 2, it can be seen that in the operation of (1), the descaling does not end even if the temperature is raised to 100 ° C. However, the operations (2) and (3) place a heavy load on the ARP. Increasing the density also increases the damage of the line. From these judgments, it is understood that the optimum control is the operation (4). By using the algorithm of the present invention to instantaneously find the optimum control method and its value and feeding them back to the operating conditions, it is possible to operate under the optimal conditions and obtain a steel sheet of good quality with less skin roughness.

(Embodiment 5) FIGS. 14 to 17 are block diagrams of an integrated manufacturing apparatus for pickling a hot-rolled ordinary steel strip and then cold-rolling it.

In FIG. 14, the steel strip wound around the entry side coil car is continuously fed out while being joined by a welder, and then a bridle roller is used to form cracks in the scale formed on the steel strip. Next, after passing through a mechanical scale breaker that separates the scale from the steel strip through a roll having a small radius of curvature, the scale adhering to the surface is scraped off with a mechanical brush, and then sent to the pickling device in FIG.

The pickling apparatus shown in FIG. 15 comprises the apparatus described in the first embodiment. As described above, the pickling speed in this example is as high as 500 m / min or more, and descaling can be performed at a high speed. Therefore, the cold rolling shown in FIG. 16 can be directly performed.

In FIG. 16, a thin plate is manufactured by an HC mill in which pickled steel strips are arranged in four stands in tandem through a centering device. In the HC mill, an intermediate roll is arranged between a backup roll and a work roll, and a plate having a uniform thickness can be obtained by moving the intermediate roll in the axially opposite directions. Other UC mills, CVC mills, cross mills, etc. are used for the cold rolling mill used in this embodiment, and these can be used in combination. As an example, there are combinations in which the HC mill is a front stand and the UC mill is a rear row stand, the CVC mill is a front stand and the HC mill is a rear row stand, and the cross mill is a front stand and the HC mill is a rear row stand.

By using the composite rolls as the work rolls, the intermediate rolls and the backup rolls in this embodiment, it is possible to perform rolling at a higher speed. The composite roll is formed by forming a high alloy steel having higher wear resistance than the shaft material on the surface of the shaft material by electroslag overlay welding to form an outer layer material containing fine carbide. The shaft material is C0.2-1.5 by weight.
%, Si 3% or less, Mn 2% or less, Cr 5% or less, or alloy steel containing Ni 0.5% or less, Mo 1% or less is used. Outer layer material is C0.5-1.5%, Si3% by weight
Below, Mn 2% or less, Cr 2 to 10%, Mo 1 to 10
%, W 20% or less, V1 to 5%, Co 13% or less of a high alloy steel, which was quenched and tempered by forcibly quenching after low frequency surface heating and quenching so as to have an HS hardness of 80 or more. It is a thing.

A material having an HS of 80 or more is used as a work roll, the intermediate roll has a smaller hardness than that, and the backup roll has an alloying element amount adjusted to have a hardness smaller than that of the intermediate roll. All have an HS hardness of 5 to 1
It is better to reduce it to 0 Both mills consist of 4 or 6 rolls. The work roll and the intermediate roll have the same diameter, but the backup roll having a larger diameter is used.

FIG. 17 is a view showing the construction in which a cold-rolled steel strip is wound by an exit coil car. The steel strip is appropriately cut by a rotary scratch chopper, passed through an oiler, and wound by a carousel tension reel.

Also in this embodiment, as in the case of the embodiment, the scale can be completely removed and the skin can be obtained.

(Embodiment 6) FIG. 18 shows the results of continuous casting,
It is a block diagram which shows the integrated manufacturing apparatus which hot-rolls. Since a thin plate having a thickness of 20 to 40 mm is continuously manufactured by alternately using two continuous casting devices, the thin plate is directly hot-rolled without cooling. The continuously cast sheets are alternately sent to the rolling mill through a transfer device. The fed thin plate is passed through an edger, then heated by an edge heater, appropriately cut by a shear, and hot-rolled by an HC mill. The hot-rolled product is cooled through a cold device and is sent to the pickling device shown in FIG. 1 through a bridle roller, a mechanical scale breaker and a mechanical brush shown in FIG.
When the speed in the continuous casting apparatus does not reach the pickling speed, the steel sheet is wound by a carousel tension reel through a cooling device after hot rolling, and then, in Examples 1 to 4.
It is pickled in the step shown in.

Also in this embodiment, as in the case of the first embodiment, it is possible to obtain the one in which the scale is completely removed and the skin is not roughened.

The continuous casting machine in this embodiment has a method of pouring a molten metal into a mold in which side end molds are provided between cooled steel plate belts, and side end molds are provided between wide molds and vibrated in the casting direction. A method of casting a thin plate at high speed is used.
Further, as the rolling roll, the composite roll shown in Example 5 can be used.

In the present embodiment, after hot rolling, descaling is carried out by pickling and winding is carried out, but continuous casting is carried out without winding, as shown in FIG. 16 and FIG. -Continuous continuous manufacturing equipment of hot rolling-mechanical descaling-pickling-cold rolling-winding becomes possible. This allows efficient manufacturing.

[0058]

EFFECTS OF THE INVENTION According to the present invention, not only is it possible to operate under optimum operating conditions for removing oxide scale of hot-rolled ordinary steel sheet, but as a result, a ordinary ordinary steel sheet having a beautiful and extremely good surface condition is obtained. It is effective.

[Brief description of drawings]

FIG. 1 is an apparatus diagram of a descaling process according to an embodiment of the present invention.

FIG. 2 is a flowchart of an operation at the start of operation according to the present invention.

FIG. 3 is a flowchart of an operation during driving according to the present invention.

FIG. 4 is a parameter showing operating conditions of the present invention.

FIG. 5 is a diagram showing a relationship between a strip running speed and a descaling rate.

FIG. 6 is a diagram showing a method of setting optimum operating conditions in each operation.

FIG. 7: Temperature of pickling tank, H according to the algorithm of the present invention
The figure which shows the distribution calculation result of Cl and Fe concentration.

FIG. 8: Temperature of pickling tank, H according to algorithm of the present invention
The figure which shows the distribution calculation result of Cl and Fe concentration.

FIG. 9 is a diagram showing a calculation result of a cumulative descaling rate in the pickling tank according to the algorithm of the present invention.

FIG. 10 is a diagram showing a calculation result of a cumulative descaling rate in the pickling tank according to the algorithm of the present invention.

FIG. 11 is a diagram showing a calculation result of a cumulative descaling rate in the pickling tank according to the algorithm of the present invention.

FIG. 12 is a diagram showing a calculation result of a cumulative descaling rate in the pickling tank according to the algorithm of the present invention.

FIG. 13 is a diagram showing the calculation result of the cumulative descaling rate in the pickling tank according to the algorithm of the present invention.

FIG. 14 is a block diagram of a descaling-cold rolling integrated manufacturing apparatus showing an embodiment of the present invention.

FIG. 15 is a configuration diagram of an integrated descaling-cold rolling manufacturing apparatus showing an embodiment of the present invention.

FIG. 16 is a configuration diagram of an integrated descaling-cold rolling manufacturing apparatus showing an embodiment of the present invention.

FIG. 17 is a block diagram of an integrated descaling-cold rolling manufacturing apparatus showing an embodiment of the present invention.

FIG. 18 is a configuration diagram of a continuous casting-hot rolling integrated manufacturing apparatus showing an embodiment of the present invention.

FIG. 19 is a configuration diagram of mechanical descaling equipment showing an embodiment of the present invention.

[Explanation of symbols]

1 ... Pickling tank, 2 ... Steel strip, 3 ... ARP (acid recovery system), 4 ... Acid reserve tank, 5 ... Acid tank, 6 ... Water tank, 7 ... Monitoring unit, 8 ... Arithmetic system, 9, 1
0, 11 ... Sensor, 12 ... Strip speed control system, 1
3 ... Acid solution concentration and flow rate control system.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuneo Nakamura 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (72) Shinichi Yokosuka 3-1-1, Saiwaicho, Hitachi, Ibaraki No. 1 Hitachi, Ltd., within the Hitachi factory (56) Reference JP-A-57-26178 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C23G 3/02 B21B 45/06 C23G 1/08

Claims (10)

(57) [Claims] 1. A state quantity of a steel sheet relating to the thickness, width and scale of the steel sheet, the concentration of acid supplied to the pickling tank, the supply amount of acid, the temperature of the acid, the line speed and the pickling tank. The operating state quantity related to the immediately preceding strip temperature is monitored, and the descaling rate of any plurality of parts in the pickling tank is obtained using the values of the state quantity and the operating state quantity of the steel sheet, and the obtained value is obtained. A method for controlling a pickling plant, wherein the operation state quantity of the plant is determined based on the above. 2. A state quantity of a steel sheet with respect to a thickness, a width and a scale amount of the steel sheet, a concentration of an acid supplied to the pickling tank, a supply amount of the acid, a temperature of the acid, a line speed and a pickling tank. The operating state quantity related to the immediately preceding strip temperature is monitored, and the inflowing acid, the outflowing acid, and the flowing out acid in any part of the pickling tank are monitored by using the values of the state quantity and the operating state quantity of the steel sheet. While determining the mass balance of the acid to be consumed, the descaling efficiency of a plurality of parts in the pickling tank is determined using the determined value, and the operating state quantity of the plant is determined based on the determined value. , A method of controlling a pickling plant, which is characterized by operating. 3. A sensor for monitoring the state quantity of the steel sheet concerning the thickness, width and scale amount of the steel sheet, and a sensor for supplying the pickling layer.
Acid concentration, acid supply, acid temperature, line speed and
Plant for strip temperature just before entering the pickling layer
A sensor for monitoring the operating state quantity, and using the value of the state quantity, the acid flowing into any of a plurality of parts in the pickling tank, the acid flowing out and the acid balance of the acid consumed at that part An arithmetic processing unit that obtains the concentration and obtains the descaling rate of a plurality of parts in the pickling tank using the obtained value, and controls the operating state quantity of the plant based on the arithmetically processed value. A pickling plant having a control means. 4. A control of a pickling plant in which ordinary steel is rolled by a hot rolling mill, and the rolled ordinary steel strip is contacted with an acid solution to remove scales formed on the surface of the ordinary steel strip by pickling. A method for controlling a pickling plant, wherein the pickling is performed by the pickling according to any one of claims 1, 2 and 4. 5. Control of a pickling plant for rolling ordinary steel with a hot rolling mill and contacting the rolled ordinary steel strip with an acid solution to remove scales formed on the surface of the ordinary steel strip by pickling. 5. A method according to claim 1, 2 and 4 after mechanically removing the scale on the surface of the ordinary steel strip leaving said rolling mill.
The method for continuous continuous descaling of ordinary steel strip, which is characterized in that it is carried out by pickling. 6. Control of a pickling plant in which ordinary steel is rolled by a hot rolling mill, and the rolled ordinary steel strip is contacted with an acid solution to remove scales formed on the surface of the ordinary steel strip by pickling. 5. A method according to claim 1, 2 and 4 after mechanically removing the scale on the surface of the ordinary steel strip leaving said rolling mill.
The method for continuous continuous descaling of ordinary steel strip, which is characterized in that the ordinary steel strip subjected to pickling is cold-rolled. 7. A means for cutting an ordinary steel strip rolled by a hot rolling mill into an arbitrary length, a means for applying a mechanical stress to a scale formed on the ordinary steel strip, and an acid which comes into contact with the ordinary steel strip. A plurality of pickling tanks for storing a solution, a pickling plant for removing the scale by passing the ordinary steel strip while dipping the ordinary steel strip in the pickling solution of the pickling tanks, and leaving the pickling plant 4. A descaling equipment for hot-rolled ordinary steel strip, comprising means for washing the treated ordinary steel strip with water and means for drying the washed ordinary steel strip, wherein the pickling plant comprises the descaling equipment according to claim 3. 8. A mechanical scale breaker for mechanically removing scale on the surface of a hot-rolled ordinary steel strip, a plurality of pickling tanks containing dilute hydrochloric acid solution, and moving the dilute hydrochloric acid solution from the downstream side to the upstream side of the plate. A pickling plant having means for moving the ordinary steel strip from the upstream side to the downstream side of the pickling tank, and a cold rolling mill for cold rolling the pickled ordinary steel strip. In the continuous integrated descaling cold rolling continuous manufacturing equipment, the pickling plant is the continuous continuous descaling cold rolling continuous manufacturing equipment for a plain steel strip according to claim 3. 9. A continuous casting machine for producing ordinary steel sheet castings,
A hot rolling mill for hot rolling the thin sheet casting, a mechanical scale breaker for mechanically removing the scale of the rolled ordinary steel strip surface, a plurality of pickling tanks for storing a dilute hydrochloric acid solution, and after the descaling A means for passing the ordinary steel strip while dipping it in the plurality of pickling tanks, a heating means for heating the dilute hydrochloric acid solution, and a means for moving the dilute hydrochloric acid solution from the downstream side to the upstream side of the plate. A pickling plant, a means for washing the ordinary steel strip discharged from the pickling plant with water, and a means for drying the washed ordinary steel strip. Is a continuous descaling continuous production facility for ordinary steel strip according to claim 3. 10. The continuous descaling continuous production facility for ordinary steel strip according to claim 9, comprising a cold rolling mill for cold rolling the dried ordinary steel strip.