Method for improving pickling quality of CGO oriented silicon steel

Abstract

The invention provides a method for improving the pickling quality of CGO oriented silicon steel, and belongs to the field of hot rolling. Comprising the steps that a plate blank with set chemical components is obtained; the plate blank is heated under set parameters; carrying out rough rolling on the heated plate blank, and carrying out rough descaling under set descaling pressure by adopting a double-row descaling mode to obtain an intermediate blank; carrying out finish rolling on the intermediate billet, and carrying out finish descaling by adopting a double-row descaling mode to obtain strip steel; and adopting a front-section dense mode, cooling the strip steel, and then coiling at a set coiling temperature to obtain a hot-rolled coil. The thickness of the iron sheet is optimized and reduced through a hot rolling heating process, a descaling process, a finish rolling speed, water between finish rolling racks, rolling lubrication, laminar cooling mode adjustment, coiling temperature control and other methods, so that the proportion of a phase easy to pickle and a phase easy to withdraw and straighten in the iron sheet is increased, and the pickling efficiency and the pickling quality are improved.

Description

Technical Field

[0001] The present application relates to the field of hot rolling technology, and in particular to a method for improving the pickling quality of CGO oriented silicon steel. Background Art

[0002] The manufacturing equipment and process of oriented silicon steel are complex, the composition is strictly controlled, the impurity content is required to be extremely low, the manufacturing process is long and there are many influencing factors. Therefore, its product quality is often considered an important indicator of a country's special steel manufacturing level. Oriented silicon steel is divided into high magnetic induction oriented silicon steel (HIB) and ordinary oriented silicon steel (CGO). Among them, high magnetic induction oriented silicon steel (HIB) usually requires normalization treatment, and after normalization treatment, there are shot blasting and pickling processes. After the steel coil of high magnetic induction oriented silicon steel is shot blasted, the surface oxide scale has been broken and loose, and pickling is easier. Ordinary oriented silicon steel (CGO) does not require normalization treatment, and the pickling unit basically does not have shot blasting equipment. Therefore, the oxide scale on the surface of ordinary oriented silicon steel is dense, and pickling is more difficult.

[0003] In order to ensure the magnetic properties, ordinary grain-oriented silicon steel (CGO) has a high furnace temperature, a long furnace time, thick hot-rolled iron sheet, and strong adhesion. The heating temperature and heating time of ordinary grain-oriented silicon steel (CGO) in the hot rolling process are longer than those of other steel types. Therefore, the iron sheet is thicker. At the same time, the characteristics of high silicon make the iron sheet very adhesive, the iron sheet is relatively dense, and pickling is difficult. After pickling, black ash and iron sheet are likely to remain on the surface, which will cause color difference defects during subsequent rolling and decarburization annealing, reduce the adhesion between the coating and the steel plate, damage the coating quality, and bring great economic losses to production. The existing technology generally solves the problem of poor pickling quality by shot blasting pickling, secondary pickling, reducing the pickling speed, increasing the acid concentration, and adding accelerators. Shot blasting pickling requires increased equipment investment, and secondary pickling and reducing the pickling speed affect the pickling efficiency. Summary of the invention

[0004] The present application provides a method for improving the pickling quality of CGO-oriented silicon steel to solve the following technical problem: how to improve the pickling quality of CGO-oriented silicon steel.

[0005] The present application provides a method for improving the pickling quality of CGO-oriented silicon steel, the method comprising:

[0006] A slab with a set chemical composition is obtained;

[0007] heating the slab under set parameters;

[0008] The heated slab is subjected to rough rolling, and rough descaling is performed by a double descaling method with a set descaling pressure to obtain an intermediate slab;

[0009] The intermediate billet is finish rolled and descaled by double descaling to obtain a steel strip; the parameters of the descaling include: a water opening ratio between F1 racks, a belt threading speed between F7 racks, and a lubricating fluid flow rate between F2-F6 racks;

[0010] The steel strip is cooled by adopting the front-end intensive mode, and then coiled at a set coiling temperature to obtain a hot-rolled coil.

[0011] Optionally, heating the slab under set parameters includes:

[0012] The slab is sequentially subjected to preheating, first heating, second heating and even heating; the air excess coefficient of the second heating and the even heating is 0.9-1, and the even heating time is ≥40min.

[0013] Optionally, the heating furnace exit temperature is 1280°C-1310°C, and the heating furnace time is 250min-310min.

[0014] Optionally, the descaling pressure is set to be ≥180 bar.

[0015] Optionally, during the rough descaling process, the first descaling water of R1 and R2 is turned on.

[0016] Optionally, the water opening ratio between the F1 racks is 30%-80%, the belt threading speed between the F7 racks is 10m / s-11m / s, and the lubricating fluid flow rate of the F2-F6 racks is 120mL / min-144mL / min.

[0017] Optionally, the final rolling temperature of the refining is 920°C-940°C.

[0018] Optionally, the cooling adopts water cooling, and the cooling rate of the water cooling is 40℃ / S-70℃ / S.

[0019] Optionally, the set coiling temperature is 540°C-560°C.

[0020] Optionally, the set chemical composition includes, by mass fraction: C: 0.025%-0.045%, Si: 3.05%-3.25%, Mn: 0.18%-0.25%, P≤0.018%, S≤0.01%, Als: 0.016%-0.025%, N: 0.008%-0.0115%, Cu: 0.48%-0.52%.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] The present application provides a method for improving the pickling quality of CGO oriented silicon steel, comprising: obtaining a slab with a set chemical composition; heating the slab under set parameters; rough rolling the heated slab, and adopting a double descaling method to perform rough descaling with a set descaling pressure to obtain an intermediate slab; finishing rolling the intermediate slab, and adopting a double descaling method to perform fine descaling to obtain a strip; the parameters of the fine descaling include: the water opening ratio between F1 stands, the belt threading speed between F7 stands, and the lubricating liquid flow rate of F2-F6 stands; adopting a front-end intensive mode, cooling the strip, and then coiling at a set coiling temperature to obtain a hot-rolled coil. The thickness of the iron sheet is optimized and reduced by hot rolling heating process, descaling process, finishing rolling speed, water between finishing rolling stands, rolling lubrication, layer cooling mode adjustment, and coiling temperature control, so that the proportion of easy pickling phase and easy straightening phase in the iron sheet composition is increased, and the pickling efficiency and pickling quality are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0024] In order to more clearly illustrate the embodiments of the present application 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, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 A schematic flow chart of a method for improving the pickling quality of CGO-oriented silicon steel provided in an embodiment of the present application;

[0026] Figure 2 This is a scanning electron microscope image of the CGO oriented silicon steel prepared from the hot rolled coil provided in Example 1 of the present application;

[0027] Figure 3 This is a scanning electron microscope image of the CGO oriented silicon steel prepared from the hot rolled coil provided in Comparative Example 1 of the present application;

[0028] Figure 4 A schematic diagram of the surface of a hot-rolled coil after pickling provided in Example 1 of the present application;

[0029] Figure 5 A schematic diagram of the surface of a hot-rolled coil after pickling provided in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0031] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0032] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0033] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0034] Figure 1A schematic flow chart of a method for improving the pickling quality of CGO-oriented silicon steel provided in an embodiment of the present application.

[0035] See also Figure 1 The present application provides a method for improving the pickling quality of CGO oriented silicon steel, the method comprising:

[0036] S1. Obtaining a slab with a set chemical composition;

[0037] In some embodiments, the set chemical composition includes, by mass fraction: C: 0.025%-0.045%, Si: 3.05%-3.25%, Mn: 0.18%-0.25%, P≤0.018%, S≤0.01%, Als: 0.016%-0.025%, N: 0.008%-0.0115%, Cu: 0.48%-0.52%.

[0038] S2, heating the slab under set parameters;

[0039] In some embodiments, heating the slab under set parameters comprises:

[0040] The slab is sequentially subjected to preheating, first heating, second heating and even heating; the air excess coefficient of the second heating and the even heating is 0.9-1, and the even heating time is ≥40min.

[0041] In some embodiments, the heating furnace temperature is 1280° C.-1310° C., and the heating furnace time is 250 min-310 min.

[0042] The furnace temperature is controlled at 1280℃-1310℃, and the furnace time is 250min-310min. On the one hand, the high temperature furnace and long furnace time are to ensure that MnS is fully dissolved to ensure the magnetic properties of the silicon steel product. On the other hand, the furnace temperature does not exceed 1310℃, and the furnace time does not exceed 310min, mainly to avoid long-term high-temperature heating and serious iron oxide scale, which affects the pickling quality. Exemplarily, the heated furnace temperature can be 1280℃, 1285℃, 1290℃, 1295℃, 1300℃, 1305℃, 1310℃, etc., and the heated furnace time is 250min, 260min, 270min, 280min, 290min, 300min, 310min, etc.

[0043] S3, rough rolling the heated slab, and performing rough descaling with a set descaling pressure in a double descaling method to obtain an intermediate slab;

[0044] It should be noted that the double row descaling method refers to the use of double rows of headers or nozzles for high-pressure water spraying during the descaling process, and the two rows of nozzles are arranged crosswise to increase the descaling effect.

[0045] In some embodiments, the set descaling pressure is ≥ 180 bar.

[0046] In some embodiments, during the rough descaling process, the first descaling water of R1 and R2 is turned on.

[0047] Rough descaling is double-row, and the rough descaling pressure is not less than 180 bar, in order to ensure that the raw iron scale is completely removed. The first descaling water of R1 and R2 is turned on to ensure that the secondary iron scale formed in the rough rolling area is completely removed. Exemplarily, the dephosphorization pressure of rough descaling can be 180 bar, 181 bar, 182 bar, 183 bar, 184 bar, 185 bar, 187 bar, 189 bar, etc.

[0048] It should be noted that the first pass of R1 and R2 in rough rolling is an important part of the rough rolling process. The R1 mill is mainly responsible for reducing the thickness of the slab and laying the foundation for the subsequent rolling process, while the R2 mill further rolls and adjusts the slab. The two mills work together to ensure the continuity and efficiency of the rolling process.

[0049] S4, finishing rolling the intermediate billet and performing finish descaling by double descaling to obtain a steel strip; the parameters of the finish descaling include: a water opening ratio between F1 racks, a belt threading speed between F7 racks, and a lubricating liquid flow rate between F2-F6 racks;

[0050] It should be noted that the F1 to F7 stands in the finishing mill are important components of the finishing process. They work together to roll the intermediate billet that has been rough rolled and cut into finished strip steel. The main function of the F1 to F7 stands is to continuously roll and deform the intermediate billet through the gradually decreasing roll gap, thereby reducing its thickness and increasing its length. During the rolling process, each stand needs to coordinate and cooperate to ensure the stable transmission of rolling force and the precise control of rolling speed to obtain finished strip steel that meets the requirements.

[0051] In some embodiments, the water opening ratio between the F1 racks is 30%-80%, the belt threading speed between the F7 racks is 10m / s-11m / s, and the lubricating fluid flow rate of the F2-F6 racks is 120mL / min-144mL / min.

[0052] In some embodiments, the finishing rolling temperature of the refining is 920°C-940°C.

[0053] Double rows of fine descaling are turned on to remove the secondary iron scale formed in the rough rolling area before fine rolling. The water opening ratio between F1 stands is 30%-80%. The strip threading speed of F7 stand is 10m / s-11m / s to reduce the contact between the strip and the air between stands and further oxidation to generate tertiary iron scale. F2-F6 rolling lubrication is turned on and the flow rate is controlled at 120mL / min-144mL / min to prevent the pressure of oxide scale and improve the quality of oxide scale formation on the strip surface, making the iron scale easier to pickle. The final rolling temperature is controlled between 920℃-940℃ to ensure the magnetic properties of the final product. For example, the water opening ratio between F1 stands can be 30%, 40%, 50%, 60%, 70%, 80%, etc., the belt threading speed between F7 stands can be 10m / s, 10.2m / s, 10.4m / s, 10.6m / s, 10.8m / s, 11m / s, etc., the lubricating fluid flow rate of F2-F6 stands is 120mL / min, 124mL / min, 128mL / min, 132mL / min, 138mL / min, 142mL / min, 144mL / min, etc. The finishing rolling temperature of the refining can be 920℃, 925℃, 930℃, 935℃, 940℃, etc.

[0054] S5. Using the front-end intensive mode, the strip steel is cooled, and then coiled at a set coiling temperature to obtain a hot-rolled coil.

[0055] In some embodiments, the cooling is performed by water cooling, and the cooling rate of the water cooling is 40°C / S-70°C / S.

[0056] The purpose of adopting the front-end intensive mode is to cool the finishing outlet quickly, avoid further oxidation in the high-temperature section in contact with air, reduce the thickness of the iron sheet, and increase the proportion of the iron sheet that is easy to pickle, thereby improving the pickling quality. Exemplarily, the cooling rate of water cooling can be 40℃ / S, 45℃ / S, 50℃ / S, 55℃ / S, 60℃ / S, 65℃ / S, 70℃ / S, etc.

[0057] In some embodiments, the set coiling temperature is 540°C-560°C.

[0058] The coiling temperature is controlled at 540°C-560°C. The purpose of low-temperature coiling is to avoid the eutectoid transformation temperature of 570°C, reduce the eutectoid structure of iron scale, and improve the pickling quality. For example, the coiling temperature can be 540°C, 545°C, 550°C, 555°C, 560°C, etc.

[0059] In summary, the present application provides a hot rolling production method for improving the pickling quality of CGO oriented silicon steel. Aiming at the problem that the pickling of hot-rolled iron sheets is difficult due to the high silicon content, high temperature of the furnace and long time in the furnace of CGO, work is carried out from the improvement of the hot rolling process. The hot rolling process is optimized and the thickness of the iron sheet is thinned, so that the proportion of the easy-to-pickling phase and the easy-to-stretch phase in the iron sheet structure is increased, and the pickling efficiency and pickling quality are improved. The pickling does not require equipment modification and process adjustment. Therefore, the pickling efficiency is greatly improved and the equipment investment cost is reduced.

[0060] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0061] The present application provides a method for improving the pickling quality of CGO-oriented silicon steel, the method comprising:

[0062] S11, obtaining a slab with a set chemical composition;

[0063] S21, heating the slab under set parameters;

[0064] S31, rough rolling the heated slab, and performing rough descaling with a set descaling pressure in a double descaling method to obtain an intermediate slab;

[0065] S41, finishing rolling the intermediate billet and performing finish descaling by double descaling to obtain a steel strip; the parameters of the finish descaling include: a water opening ratio between F1 racks, a belt threading speed between F7 racks, and a lubricating liquid flow rate between F2-F6 racks;

[0066] S51. The front-end intensive mode is adopted to cool the strip steel, and then the strip steel is coiled at a set coiling temperature to obtain a hot-rolled coil. The specific parameters of the method for improving the pickling quality of CGO oriented silicon steel are shown in Table 1.

[0067] Table 1 Specific parameters of the method for improving the pickling quality of CGO oriented silicon steel

[0068]

[0069]

[0070] The surface quality of the hot rolled coils obtained in Example 1 and Comparative Example after pickling was tested, and the results are shown in Table 2. At the same time, the iron scale phase ratio of the CGO oriented silicon steel obtained from the hot rolled coils of Example 1 and Comparative Example 1 was tested, and the results are shown in Table 3.

[0071] Table 2 Surface quality of hot rolled coils obtained in the examples and comparative examples after pickling

[0072] Group Surface quality after pickling Example 1 Silvery white, no obvious yellow rust spots, no black ash or iron residue when wiped with white gloves Example 2 Silvery white, no obvious yellow rust spots, no black ash or iron residue when wiped with white gloves Comparative Example 1 There is obvious black and gray when wiping with gloves, and the surface color difference is obvious Comparative Example 2 There is a small amount of black ash when wiping with gloves, and the surface color difference is quite obvious Comparative Example 3 There is a small amount of black ash when wiping with gloves, and the surface color difference is quite obvious

[0073] Table 3 Iron scale phase ratio of CGO oriented silicon steel of Example 1 and Comparative Example 1

[0074] phase of matter Example 1 Comparative Example 1 <![CDATA[Fe3O4]]> 49.8％ 100％ <![CDATA[Fe2O3]]> 40.8％ -- FeO 9.4％ --

[0075] As can be seen from Table 3, this embodiment optimizes the thickness of the thinned iron sheet through methods such as hot rolling heating process, descaling process, finishing rolling speed, finishing mill inter-stand water, rolling lubrication, layer cooling mode adjustment and coiling temperature control, and the proportion of the easy pickling phase and the easy straightening phase in the iron sheet composition is increased, thereby improving the pickling efficiency and pickling quality.

[0076] Figure 2 This is a scanning electron microscope image of the CGO oriented silicon steel prepared from the hot rolled coil provided in Example 1 of the present application; Figure 3 is a scanning electron microscope image of CGO oriented silicon steel prepared from the hot rolled coil provided in Comparative Example 1 of the present application; Figure 2 and Figure 3 It can be seen that the iron sheet thickness of the CGO oriented silicon steel in Example 1 is 2μm-4μm, and the iron sheet thickness of the CGO oriented silicon steel in Comparative Example 1 is 6μm-8μm. The iron sheet thickness is optimized and reduced by hot rolling heating process, descaling process, finishing rolling speed, finishing mill inter-stand water, rolling lubrication, layer cooling mode adjustment and coiling temperature control.

[0077] Figure 4 A schematic diagram of the surface of a hot-rolled coil after pickling provided in Example 1 of the present application; Figure 5 The surface diagram of the hot rolled coil after pickling provided in Comparative Example 1 of the present application is shown in FIG. Figure 4 and Figure 5 It can be seen that the surface of the hot-rolled coil of Example 1 is silvery white after pickling, without obvious yellow rust spots, and no black ash or iron sheet remains when wiped with white gloves. After pickling, the hot-rolled coil of Comparative Example 1 has obvious black ash when wiped with gloves, and the surface color difference is relatively obvious.

[0078] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0079] In the embodiment of the present invention, the thickness of the iron sheet is optimized and reduced through methods such as hot rolling heating process, descaling process, finishing rolling speed, water between finishing rolling stands, rolling lubrication, layer cooling mode adjustment and coiling temperature control, so that the proportion of the easy pickling phase and the easy straightening phase in the iron sheet structure is increased, thereby improving the pickling efficiency and pickling quality.

[0080] In the embodiment of the present invention, pickling does not require equipment modification and process adjustment, thereby greatly improving the pickling efficiency and reducing the equipment investment cost.

[0081] In the embodiment of the present invention, in order to solve the problem that the hot-rolled iron sheet is difficult to pickle due to the high silicon content, high temperature and long furnace time of CGO, work is carried out from the perspective of improving the hot rolling process. The hot rolling process is optimized to reduce the thickness of the iron sheet, so that the proportion of the easy-to-pickling phase and the easy-to-draw-straighten phase in the iron sheet structure is increased, thereby improving the pickling efficiency and pickling quality.

[0082] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for improving the pickling quality of CGO oriented silicon steel, characterized in that: The method comprises: A slab with a set chemical composition is obtained; heating the slab under set parameters; The heated slab is subjected to rough rolling, and rough descaling is performed by a double descaling method with a set descaling pressure to obtain an intermediate slab; The intermediate billet is finish rolled and descaled by double descaling to obtain a steel strip; the parameters of the descaling include: a water opening ratio between F1 racks, a belt threading speed between F7 racks, and a lubricating fluid flow rate between F2-F6 racks; The steel strip is cooled by adopting the front-end intensive mode, and then coiled at a set coiling temperature to obtain a hot-rolled coil.

2. The method according to claim 1, characterized in that The step of heating the slab under set parameters comprises: The slab is sequentially subjected to preheating, first heating, second heating and even heating; the air excess coefficient of the second heating and the even heating is 0.9-1, and the even heating time is ≥40min.

3. The method according to claim 2, characterized in that The heating furnace exit temperature is 1280° C.-1310° C., and the heating furnace time is 250 min-310 min.

4. The method according to claim 1, characterized in that: The set descaling pressure is ≥180 bar.

5. The method according to claim 1, characterized in that During the rough descaling process, the first descaling water of R1 and R2 is turned on.

6. The method according to claim 1, characterized in that The water opening ratio between the F1 frames is 30%-80%, the belt threading speed between the F7 frames is 10m / s-11m / s, and the lubricating fluid flow rate of the F2-F6 frames is 120mL / min-144mL / min.

7. The method according to claim 1, characterized in that The final rolling temperature of the refining is 920°C-940°C.

8. The method according to claim 1, characterized in that The cooling is carried out by water cooling, and the cooling rate of the water cooling is 40°C / S-70°C / S.

9. The method according to claim 1, characterized in that: The set coiling temperature is 540°C-560°C.

10. The method according to claim 1, characterized in that In terms of mass fraction, the set chemical composition includes: C: 0.025%-0.045%, Si: 3.05%-3.25%, Mn: 0.18%-0.25%, P≤0.018%, S≤0.01%, Als: 0.016%-0.025%, N: 0.008%-0.0115%, and Cu: 0.48%-0.52%.

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