Pickling method for strip steel plate and pickling unit

Abstract

The present invention provides a strip steel plate pickling method, after removing the iron oxide scale on the surface of the strip steel plate, according to the surface roughness of the strip steel plate at the inlet of the pickling tank, the parameters of each pickling tank are adjusted, and the greater the roughness value, the higher the free acid concentration in the pickling solution, and the higher the acid solution temperature; a strip steel plate pickling unit is also provided, including a plurality of groups of pickling tanks, a roughness detector is arranged at the inlet of the first group of pickling tanks, the roughness detector is used to detect the surface roughness of the strip steel plate entering the pickling tank, and the parameters of each pickling tank are adjusted according to the roughness. In the present invention, the parameters of the pickling tank are controlled by the surface roughness of the strip steel plate, so that the pickling effect and pickling time of the strip steel plate can be guaranteed to the greatest extent, and the acid consumption and energy consumption can be reduced.

Description

Technical Field

[0001] The invention relates to hot rolling, in particular to a strip steel plate pickling method and a pickling unit. Background Art

[0002] Silicon steel is one of the most commonly used soft magnetic materials, widely used in the manufacture of cores for motors, transformers, etc. When the silicon content is higher than 1.5%, after normalization of the hot-rolled strip, a shot blasting machine is usually used to remove most of the surface oxide scale, followed by pickling and rolling.

[0003] Shot blasting usually uses hard pellets with a diameter of 0.1-0.7mm, which are sprayed onto the surface of the strip at a speed of 40-100m / s, usually increasing the surface roughness of the strip to an average of 0.1-5μm. Different roughnesses make the surface pits difficult to be wetted by acid, and the pickling difficulty is also different. The acid concentration, temperature, pickling time, rinse water flow, squeeze roller pressure, etc. during pickling need to be adjusted according to the roughness, otherwise it is easy to cause high acid consumption and high energy medium consumption. However, the current pickling process does not take into account the surface roughness of the strip, which in turn affects the pickling effect of the strip. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a strip steel plate pickling method and a pickling unit to ensure the strip steel pickling effect.

[0005] The present invention is achieved in that:

[0006] An embodiment of the present invention provides a hot-rolled plate pickling method. After removing the iron oxide scale on the surface of the steel plate, the parameters of each pickling tank are adjusted according to the surface roughness of the steel plate at the entrance of the pickling tank. The larger the roughness value, the higher the free acid concentration in the pickling solution and the higher the acid solution temperature.

[0007] Further, the hydrochloric acid concentration of each pickling tank is:

[0008] C i =C i，min +[(RR min ) / (R max -R min )+(t max -t) / (t max -t min )]×(C i，max -C i,min ) / 2×k1

[0009] Where: i—the i-th pickling tank, i=1, 2, 3, ...; C i —free hydrochloric acid concentration in the i-th pickling tank, in g / L; C i，min—Minimum concentration of free hydrochloric acid in the i-th pickling tank, in g / L; C i，max —The maximum concentration of free hydrochloric acid in the i-th pickling tank, in g / L; R—Surface roughness of the strip at the inlet of the pickling tank, in μm; R min —Minimum roughness of the strip surface at the pickling tank entrance, in μm; R max —Minimum roughness of the strip surface at the pickling tank entrance, in μm; t—pickling time, in s; t min —Minimum pickling time, unit: s; t max —Maximum pickling time, unit: s; k1—coefficient.

[0010] Furthermore, the concentration of free hydrochloric acid ranges from 20 to 10 g / L, the temperature of the acid solution ranges from 35 to 60° C., and the pickling time ranges from 20 to 120 s.

[0011] Furthermore, a roughness detector is provided at the inlet side of the first pickling tank, and the surface roughness of the strip steel plate is detected by the roughness detector.

[0012] Furthermore, the roughness of the upper and lower surfaces of the strip steel plate is detected at the inlet side of the first pickling tank, and the higher value of the roughness is taken as the actual roughness of the strip steel plate.

[0013] Furthermore, there are three pickling tanks, each of which is arranged in sequence, and a squeezing roller is arranged at the entrance of each pickling tank.

[0014] Furthermore, after pickling, the strip steel plate enters into a plurality of rinsing tanks for sequential water washing, and a squeeze roller is arranged at the exit of each group of rinsing tanks.

[0015] Furthermore, the process parameters of the rinsing tank include rinsing water temperature and fresh water flow rate, and the rinsing water temperature range is 20-60°C, and the fresh water flow rate range is 0.5-5m 3 / h.

[0016] Furthermore, a dryer is provided at the outlet side of the last set of rinsing tanks.

[0017] An embodiment of the present invention also provides a strip steel plate pickling unit, comprising several groups of pickling tanks, wherein a roughness detector is provided at the entrance of the first group of pickling tanks, and the roughness detector is used to detect the surface roughness of the strip steel plate entering the pickling tank, and adjust the parameters of each pickling tank according to the roughness.

[0018] The present invention has the following beneficial effects:

[0019] In the present invention, the surface roughness of the steel strip is first detected before entering the pickling tank, and then the parameters of the pickling tank are adjusted according to the surface roughness of the steel strip. Specifically, the larger the roughness value, the higher the free acid concentration in the pickling solution, and the higher the acid solution temperature, which can maximize the pickling effect and pickling time of the steel strip and reduce acid consumption and energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of the process flow of a strip steel plate pickling unit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The embodiment of the present invention provides a method for pickling a steel strip 1, which is aimed at pickling a steel strip after hot rolling, especially a high silicon hot rolled steel strip. Specifically, after the iron oxide scale on the surface of the steel strip 1 is removed by shot blasting, the parameters of the pickling tank 2 are adjusted according to the roughness of the steel strip surface at the entrance of the pickling tank 2, and the greater the roughness value, the higher the free acid concentration in the pickling solution, and the higher the acid solution temperature.

[0024] Before the strip steel plate 1 enters the pickling process, it is necessary to use shot blasting to remove the iron oxide scale, which will affect the roughness of the surface of the strip steel plate 1 after the iron oxide scale is removed. When the roughness of the surface of the strip steel plate 1 changes, it will affect the pickling effect of the strip steel plate 1 in the pickling tank 2. When the corresponding pickling effect needs to be achieved, the acid parameters and the pickling time in the pickling tank 2 need to be adjusted. When the surface roughness of the strip steel plate 1 detected is large, it will increase the difficulty of pickling the strip steel plate 1. Therefore, the free acid concentration in the pickling solution can be adjusted to be large. Within a certain range, the greater the concentration of free acid in the pickling solution, the better the pickling effect; or when the concentration of free acid in the pickling solution is constant, the acid temperature can be increased, which can shorten the pickling time of the strip steel plate 1; or the free acid concentration and the acid temperature in the pickling solution can be increased at the same time to ensure the pickling effect and pickling time of the strip steel plate 1.

[0025] In a preferred embodiment, since the steel strip 1 needs to pass through multiple groups of pickling tanks 2 in sequence during pickling, the pickling solution in each pickling tank 2 is mainly hydrochloric acid, and the concentration of hydrochloric acid in each pickling tank 2 is not necessarily the same, it is adjusted according to the roughness of the steel strip 1, and the following adjustment method is specifically adopted:

[0026] C i =C i，min +[(RR min ) / (R max -R min )+(t max -t) / (t max -t min )]×(C i，max -C i,min ) / 2×k1

[0027] Where: i—the i-th pickling tank 2, i=1, 2, 3, ...; C i —free hydrochloric acid concentration in the i-th pickling tank 2, in g / L; C i，min —Minimum concentration of free hydrochloric acid in the i-th pickling tank 2, in g / L; C i，max —The maximum concentration of free hydrochloric acid in the i-th pickling tank 2, in g / L; R—The surface roughness of the strip at the entrance of the pickling tank 2, in μm; R min —Minimum roughness of strip steel surface at the entrance of pickling tank 2, in μm; R max —Minimum roughness of the strip surface at the entrance of pickling tank 2, in μm; t—pickling time, in s; t min —Minimum pickling time, unit: s; t max —Maximum pickling time, unit: s; k1—coefficient.

[0028] In the above calculation method, the surface roughness of the strip steel plate 1 has a certain range, that is, the surface roughness of the strip steel plate 1 is controlled within a certain range during shot blasting and dephosphorization, which is pre-set, so that the roughness of the strip steel plate 1 has R max —Minimum surface roughness of strip steel at the entrance of pickling tank 2 and R min —Minimum roughness of the strip steel surface at the entrance of the pickling tank 2. In addition, in the actual working process, the surface roughness of the strip steel plate 1 after shot blasting and dephosphorization is relatively stable, that is, the roughness value is basically the same over a period of time, so the acid parameters in each pickling tank 2 are not adjusted in real time.

[0029] The concentration of free hydrochloric acid in the pickling tank 2 also has a certain range. Although the greater the concentration of free hydrochloric acid within a certain range, the better the pickling effect, when the temperature is constant, the greater the concentration, the shorter the pickling time, but when it reaches a certain concentration, the pickling effect is not obvious, for example, when it is higher than 160g / L, on the one hand, the pickling effect is not significantly improved, and at the same time, the volatilization increases. In a preferred embodiment, the free acid concentration range in the pickling tank 2 is 40-150g / L. Similarly, the temperature of the acid solution in the pickling tank 2 is also controlled within a certain range, and the preferred embodiment is 55-85℃, and when the temperature is greater than 85℃, the pickling effect is not significantly improved, and at the same time, the volatilization increases significantly. The pickling time is controlled according to the overall unit. Usually, the pickling time range is pre-set, such as 20 to 120s, and then the hydrochloric acid concentration of the pickling tank 2 in the above calculation method is determined according to the actual pickling time.

[0030] For the parameters of pickling tank 2, the Fe content in the acid solution in pickling tank 2 is also considered. 2+ concentration, as Fe 2+ As the concentration increases, the pickling time increases, but when it is less than 50g / L, as Fe 2+ As the concentration increases, the pickling time increases slowly. After >50g / L, as the concentration increases, the pickling time increases rapidly. However, if the iron content is very low, new acid needs to be added frequently, which seriously increases the burden of acid regeneration, making the acid regeneration unit too large, the energy consumption is very high, and it is not economical. Therefore, Fe 2+ The preferred control range of concentration is 30-130 g / L.

[0031] Furthermore, a roughness detector 3 is used to detect the surface roughness of the strip steel plate 1. Specifically, a roughness detector 3 is provided at the entrance side of the first pickling tank 2. The roughness detector 3 can be provided in one group or two groups. When it is provided in one group, the roughness detector 3 can detect the roughness of the upper and lower surfaces of the strip steel plate 1 at the same time. When it is provided in two groups, the roughness detectors 3 are respectively provided on the upper and lower sides of the strip steel plate 1 to detect the roughness of the upper and lower surfaces of the strip steel plate 1. In actual calculation, the high value of the roughness is taken as the actual roughness of the strip steel plate 1, and it is brought into the above calculation formula.

[0032] In another embodiment, after pickling, the steel plate 1 enters multiple groups of rinsing tanks 4 for sequential water washing. For example, three groups of rinsing tanks 4 are provided, and the steel plate 1 sequentially passes through the three groups of rinsing tanks 4. The process parameters of each rinsing tank 4 include rinsing water temperature and fresh water flow rate, and the rinsing water temperature range is 20-60°C, and the fresh water flow rate range is 0.5-5m 3 / h. However, if the rinse water flow rate is greater than 2m 3 / h, it increases the capacity of wastewater treatment or acid regeneration, which is not economical. If it is less than 0.5m 3 / h, it is easy to cause the rinsing to be not clean, making the surface of the strip steel plate 1 dark or light yellow. The preferred control range of the rinsing water flow rate is 0.5-1m 3 / h, and the rinsing water temperature is preferably 50°C.

[0033] Of course, since the strip steel plate 1 is sequentially pickled and rinsed, the strip steel plate 1 after rinsing needs to be dried, that is, a dryer 5 should be provided at the outlet side of the last group of rinsing tanks 4, through which the strip steel plate 1 is dried, and a squeeze roller 6 should be provided at the inlet side of the dryer 5. A squeeze roller 6 is also provided at the outlet side of each group of rinsing tanks 4, and a squeeze roller 6 is also provided at the inlet side of the first group of rinsing tanks 4. Correspondingly, three groups of pickling tanks 2 are also provided, and each pickling tank 2 is provided sequentially. The strip steel plate 1 passes through the three groups of pickling tanks 2 sequentially, and a squeeze roller 6 is provided at the inlet of each group of pickling tanks 2, and a squeeze roller 6 is also provided at the outlet side of the third group of pickling tanks 2. The squeeze roller 6 can generate linear pressure on the steel strip 1, and if the linear pressure value is greater than 0.8kg / cm, it is easy to cause the steel strip 1 to deviate, reducing the operating stability of the unit. If it is less than 0.1kg / cm, the liquid on the surface of the steel strip 1 is not effective, so that the surface liquid enters the next pickling tank 2 or rinsing tank 4 or dryer 5, affecting the pickling, rinsing or drying effect. The preferred range of the linear pressure value is 0.15-0.65kg / cm.

[0034] The following is an experimental comparison between three groups of embodiments and comparative examples provided according to the above pickling method, specifically:

[0035]

[0036]

[0037] Through the above three embodiments and comparative examples, the pickling process parameters are adjusted according to the surface roughness. Under the premise of ensuring the pickling effect, not only the pickling speed is improved, but also the acid consumption and energy consumption of strip pickling are reduced.

[0038] The embodiment of the present invention further provides a steel plate pickling unit, comprising a plurality of groups of pickling tanks 2, wherein a roughness detector 3 is provided at the entrance of the first group of pickling tanks 2, and the roughness detector 3 is used to detect the surface roughness of the steel plate 1 entering the pickling tank 2, and adjust the parameters of each pickling tank 2 according to the roughness. The pickling unit provided in this embodiment corresponds to the above-mentioned pickling method, that is, the above-mentioned pickling method is used to pickle the steel plate 1 after shot blasting and dephosphorization, and the parameters of the pickling tank 2 are adjusted by detecting the surface roughness of the steel plate 1 entering the pickling tank 2, thereby reducing the pickling time and reducing the acid consumption under the premise of ensuring the pickling effect.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for pickling a strip steel plate, characterized in that: After removing the iron oxide scale on the surface of the strip steel plate, the parameters of each pickling tank are adjusted according to the surface roughness of the strip steel plate at the entrance of the pickling tank. The larger the roughness value, the higher the free acid concentration in the pickling solution and the higher the acid solution temperature. The hydrochloric acid concentration of each pickling tank is: ； Where: i—the i-th pickling tank, i=1, 2, 3, ...; C i —free hydrochloric acid concentration in the i-th pickling tank, in g / L; C i，min —Minimum concentration of free hydrochloric acid in the i-th pickling tank, in g / L; C i，max —The maximum concentration of free hydrochloric acid in the i-th pickling tank, in g / L; R—Surface roughness of the strip at the inlet of the pickling tank, in μm; R min —Minimum roughness of the strip surface at the pickling tank entrance, in μm; R max —Minimum roughness of the strip surface at the pickling tank entrance, in μm; t—pickling time, in s; t min —Minimum pickling time, unit: s; t max —The longest pickling time, in seconds; k1—coefficient; The range of free hydrochloric acid concentration is 40-150g / L, the range of acid solution temperature is 55-85°C, and the range of pickling time is 20-120s.

2. The method for pickling a steel strip according to claim 1, characterized in that: A roughness detector is provided at the inlet side of the first pickling tank, and the surface roughness of the strip steel plate is detected by the roughness detector.

3. The method for pickling a steel strip according to claim 1, characterized in that: The roughness of the upper and lower surfaces of the strip steel plate is detected at the entrance side of the first pickling tank, and the higher roughness value is taken as the actual roughness of the strip steel plate.

4. The method for pickling a steel strip according to claim 1, characterized in that: There are three pickling tanks, each of which is arranged in sequence, and a squeezing roller is arranged at the entrance of each pickling tank.

5. The method for pickling a steel strip according to claim 1, characterized in that: After pickling, the strip steel plate enters multiple groups of rinsing tanks for water washing in sequence, and a squeezing roller is provided at the exit of each group of rinsing tanks.

6. The method for pickling a steel strip according to claim 5, characterized in that: The process parameters of the rinsing tank include rinsing water temperature and new water flow rate, and the rinsing water temperature range is 20-60°C, and the new water flow rate range is 0.5-5m³ / h.

7. The method for pickling a steel strip according to claim 5, characterized in that: A dryer is also provided at the outlet side of the last set of rinsing tanks.

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