CN111139407A - Optimized production method of low-iron-loss high-magnetic-induction oriented electrical steel - Google Patents

Abstract

The invention discloses an optimized production method of low-iron-loss high-magnetic-induction oriented electrical steel, which comprises the following steps of: forming a strip steel by molten iron after steel making, hot rolling, acid pickling and primary cold rolling, and performing nitriding treatment during annealing of the strip steel, and then performing secondary cold rolling including high-temperature annealing, stretching thermal leveling annealing and finished product shearing laser-containing nicking processes to obtain a finished product; the composition of sol-Al in the molten iron is 0.010-0.035%, and the composition of C is 0.030-0.070%. The production process has low control difficulty relative to the inhibitor obtained in the next day, the product performance is close to that of Hi-B steel, and partial products have high magnetic induction. The method is stable, easy to implement and convenient to control, is suitable for the manufacturing process of products with excellent performance, and has the comprehensive advantages of low cost and high performance.

Description

Optimized production method of low-iron-loss high-magnetic-induction oriented electrical steel

Technical Field

The invention relates to a production method of electrical steel, in particular to an optimized production method of low-iron-loss high-magnetic-induction oriented electrical steel.

Background

Oriented Silicon Steel is classified into two types, namely common oriented Silicon Steel (CGO) and High Magnetic induction oriented Silicon Steel (High-B), according to the difference between the {110} <001> orientation degree and the Magnetic property. The requirements of low iron loss, high magnetic induction strength, small magnetostriction and other electromagnetic functions are pursued.

Comparison of CGO and Hi-B Performance

The core goal of technological process and parameter control is to utilize the secondary recrystallization process to form good {110} <001> orientation texture at high temperature annealing, needs Gaussian orientation crystal grains with enough strength in the primary recrystallization structure as crystal nuclei of secondary recrystallization, create environmental conditions which can promote the abnormal growth of the primary crystal nuclei of the Gaussian orientation crystal grains, such as fine primary crystallization crystal grains and the like, simultaneously utilize inhibitors (such as ALN, MnS, Cu2S and the like) with proper quantity and size in dispersion distribution to keep the primary recrystallization crystal grains, remove the inhibition of crystal grain growth at 1150 ℃ of high temperature annealing, and finish the abnormal growth of the secondary recrystallization of the Gaussian orientation crystal grains by taking the deformation energy and surface energy of the steel plate as power to obtain a product with good electromagnetic performance.

The function of the inhibitor in the production of the oriented silicon steel is extremely critical. In order to obtain a single Gaussian texture and have excellent magnetic performance, fine dispersed second phase particles and single element solute are generally used as inhibitors, primary recrystallized grains are kept fine before secondary recrystallization starts through pinning effect and grain boundary segregation effect, primary grains (secondary crystal nuclei) with {110} <001> orientation can be swallowed by other surrounding primary grains in the final high-temperature annealing and temperature rising stage, secondary recrystallization occurs, and the primary grains grow abnormally to form an excellent Gaussian oriented crystal structure.

At present, according to different inhibitor forming modes and slab soaking temperatures, industrial production technologies are divided into 3 production technologies, namely an inherent inhibitor method high-temperature slab heating technology, an inherent inhibitor method medium-temperature slab heating technology and an acquired inhibitor method low-temperature slab heating technology, wherein the slab soaking temperatures adopted by the 3 production technologies are 1350-.

In the production process by adopting the inherent inhibitor method, enough inhibitor forming elements are added during smelting, the slab needs to be heated at high temperature or medium temperature to ensure that coarse precipitated phases (AlN, MnS, MnSe, Cu2S and the like) precipitated during solidification are completely dissolved or fully dissolved as far as possible, and then are re-precipitated in a fine dispersed state in the subsequent hot rolling or normalizing process, so that the required inhibitor strength is achieved.

In the process of producing Hi-B steel by adopting the acquired inhibitor method, the content of inhibitor forming elements in the steel can be adjusted during smelting, the slab does not require inhibitor solid solution after being heated at low temperature, but hot rolled plate normalizing heat treatment is required, and the steel plate needs to be subjected to nitriding treatment before final high-temperature annealing, so that a new fine and dispersed nitride inhibitor is obtained to enhance the inhibition capability.

The existing industrial production adopts the high-temperature slab heating technology of the inherent inhibitor method, the product performance is best, but the energy consumption is high, the cost is high, the method is rarely adopted, the acquired inhibitor method for producing the Hi-B steel has excellent comprehensive performance and excellent comprehensive cost, but the process control difficulty is high, the performance of the inherent inhibitor method for producing the Hi-B steel is lower than that of the acquired inhibitor method for producing the Hi-B steel, but the process control is relatively easy, easy and stable to produce, and the comprehensive cost is low.

Disclosure of Invention

It is to be understood that both the foregoing general description and the following detailed description of the present disclosure are exemplary and explanatory and are intended to provide further explanation of the disclosure as claimed.

Aiming at the problems, the method mainly uses the inherent inhibitor which is easy to stably operate and control, increases the acquired nitriding to obtain the inhibitor, forms the inhibitor capability which is mainly compounded and stable and can be sufficiently used by ALN, and can produce the aluminum-based composite material by adopting medium-temperature plate blank heating below 1300 ℃ and common heating furnace equipment. Meanwhile, the intermediate annealing has partial normalizing function, low iron loss and high magnetic induction are obtained, the difficulty of Hi-B steel cold rolling is reduced by twice cold rolling and annealing, the overall performance of the product is close to the level of Hi-B steel, the product is more stable and easy to produce, and the comprehensive benefit is good.

In order to achieve the above object, the present invention provides an optimized method for producing a low-iron-loss high-magnetic-induction oriented electrical steel, comprising:

forming a strip steel by molten iron after steel making, hot rolling, acid pickling and primary cold rolling, and performing nitriding treatment during annealing of the strip steel, and then performing secondary cold rolling including high-temperature annealing, stretching thermal leveling annealing and finished product shearing laser-containing nicking processes to obtain a finished product;

the composition of sol-Al in the molten iron is 0.010-0.035%, and the composition of C is 0.030-0.070%.

Preferably, the invention further provides an optimized production method of the low-iron-loss high-magnetic-induction oriented electrical steel, which is characterized in that,

and between the processes of the primary cold rolling and the high-temperature annealing, the strip steel is subjected to intermediate decarburization annealing and nitriding at the same time, and then is subjected to secondary cold rolling and coating of a separating agent.

Preferably, the invention further provides an optimized production method of the low-iron-loss high-magnetic-induction oriented electrical steel, which is characterized in that,

and (3) performing intermediate annealing on the strip steel between the primary cold rolling process and the high-temperature annealing process, and performing decarburization annealing and nitriding coating with a separant during the secondary cold rolling.

Preferably, the invention further provides an optimized production method of the low-iron-loss high-magnetic-induction oriented electrical steel, which is characterized in that,

adding an innate inhibitor into the molten iron, wherein the innate inhibitor comprises ALN, Cu2S, MnS and BN, and the acquired inhibitor is added in the nitriding process.

Preferably, the invention further provides an optimized production method of the low-iron-loss high-magnetic-induction oriented electrical steel, which is characterized in that,

the temperature range during nitriding is 700-900 ℃.

Preferably, the invention further provides an optimized production method of the low-iron-loss high-magnetic-induction oriented electrical steel, which is characterized in that,

the heating temperature during hot rolling is 1270-1290 ℃.

Preferably, the invention further provides an optimized production method of the low-iron-loss high-magnetic-induction oriented electrical steel, which is characterized in that,

the reduction rate range of the secondary cold rolling is 60-75%.

Preferably, the invention further provides an optimized production method of the low-iron-loss high-magnetic-induction oriented electrical steel, which is characterized in that,

the components further comprise:

si: 2.5-3.5%; mn: 0.05-0.45%; 0.020 to 0.055 percent of Cu; s is less than or equal to 0.015 percent; s is less than or equal to 0.015 percent; n is less than or equal to 0.010 percent; ni: 0.02-0.15%; cr: 0.03-0.20%, and the balance of Fe and inevitable impurities.

The invention adopts a medium-temperature slab heating technology, and a composite inhibitor method which takes the inherent inhibitor as the main part and takes the acquired inhibitor as the auxiliary part, thereby reducing the iron loss of the product. The high magnetic induction of the product is obtained in a partial normalizing temperature range obtained by secondary cold rolling intermediate annealing without the need of normalizing treatment of a hot rolled plate.

The production process has low control difficulty relative to the inhibitor obtained in the later day, the product performance is close to that of Hi-B steel, and partial products have ultrahigh magnetic induction. The method is stable, easy to implement and convenient to control, is suitable for the manufacturing process of products with excellent performance, and has the comprehensive advantages of low cost and high performance.

Detailed Description

This specification discloses one or more embodiments that incorporate the features of this invention. The disclosed embodiments are merely illustrative of the invention. The scope of the invention is not limited to the disclosed embodiments. The invention is defined by the appended claims.

References in the specification to "one embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but all embodiments do not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

Moreover, it should be understood that the spatial descriptions used herein (e.g., above, below, above, left, right, below, top, bottom, vertical, horizontal, etc.) are for purposes of illustration only, and that an actual implementation of the structures described herein may be spatially arranged in any orientation or manner.

The production method of the present invention is explained in detail as follows:

the slab is composed of the following chemical components:

c: 0.030-0.070%; si: 2.5-3.5%; mn: 0.05-0.45%; 0.020 to 0.055 percent of Cu; s is less than or equal to 0.015 percent; al: 0.010-0.035%; s is less than or equal to 0.015 percent; n is less than or equal to 0.010 percent; ni: 0.02-0.15%; cr: 0.03-0.20%, and the balance of Fe and inevitable impurities.

The specific process flow comprises the following steps:

the plate blank is subjected to iron making, steel making, hot rolling, acid pickling, primary cold rolling, annealing (nitriding), secondary cold rolling, separant coating high-temperature annealing, stretching and hot leveling annealing and finished product shearing or laser scoring.

In the process, the plate blank is heated at the temperature below 1300 ℃ and then is subjected to hot rolling for 2.3-2.5 mm without being normalized, is subjected to acid cleaning and then is subjected to cold rolling to the thickness of 0.6-1.5 mm, is subjected to decarburization annealing at the temperature of 800-850 ℃, is subjected to NH3 nitriding treatment, is subjected to secondary cold rolling to the thickness of a finished product, and then is coated with an annealing separant and is subjected to high-temperature annealing.

The slab is heated at a temperature of 1300 ℃ or lower, and inhibitor elements such as AlN and CuS in the steel are in a completely solid-solution state, but a certain amount of free Al is present, and the slab is nitrided into the steel before secondary recrystallization occurs, thereby forming an auxiliary inhibitor.

The method can stably produce the oriented electromagnetic steel plate with the specification of 0.20-0.35 mm.

In a preferred embodiment, the steel is produced by smelting in a converter or an electric furnace, followed by vacuum degassing and continuous casting, and the strand is electromagnetically stirred. And hot rolling into a hot coil, pickling, and performing cold rolling twice and intermediate annealing and nitriding to obtain a 0.18-0.35 mm steel strip.

The same slab composition is adopted, and the process flow has another mode: the plate blank is heated at the temperature below 1300 ℃, then is hot-rolled for 2.3-2.5 mm without being normalized, is cold-rolled to the thickness of 0.6-1.5 mm after being acid-washed, is subjected to intermediate annealing at the temperature of 800-950 ℃, is secondarily cold-rolled to the thickness of a finished product, is subjected to decarburization annealing at the temperature of 800-850 ℃, is subjected to nitriding treatment by introducing NH3, and then is coated with an annealing separant and is subjected to high-temperature annealing.

In the process production process of the invention, the high manganese component is adopted to enlarge the gamma phase region, so that the carbon content can be reduced, the primary crystal grains are fine and uniform, and the decarburization annealing pressure is reduced. If the C content is increased, the gamma phase may be increased, but the intermediate decarburization annealing pressure may be increased. The copper is added to improve the gamma phase and reduce the solid solution temperature of AIN, and simultaneously, the AIN can be subjected to solid solution by adopting low S and heating at 1250-1300 ℃, fine and uniform ALN is precipitated after cooling in a hot rolling phase change region, and a main inherent solid solution ALN inhibitor is formed.

Secondly, Al is combined with N to generate AlN, and the AlN is nitrided into the steel to form (Al & Si) N after primary recrystallization is finished, so that a certain amount of free-state Al is required, and the AlN/SiN is converted into ALN/SiN serving as a supplement auxiliary inhibitor in a high-temperature annealing stage after nitridation.

Third, the production method of the present invention improves sol.al in order to obtain high magnetic induction and low core loss, but too high ALs causes non-uniform magnetic properties of the finished product.

In addition, Ni and Cr make primary crystal grains finer and more uniform, and expand the hot rolling temperature range.

Addition of a small amount of B can form a BN auxiliary inhibitor.

The secondary cold rolling reduction rate of 50-75% generates enough deformation energy to obtain good performance of the finished product. The intermediate annealing temperature is at partial gamma phase transition temperature, and ALN is used for solid solution and re-precipitation.

Example 1 the composition of the test material of this example is given in table 1 below:

table 1:

the process comprises the following steps:

the slabs of the above composition were each rolled to a hot rolled plate of 2.3mm thickness, acid-washed, and cold-rolled twice to the final plate thickness, as shown in table 2.

Table 2:

and (2) decarburization annealing after cold rolling, wherein the process is 830 ℃ for 330 seconds, the atmosphere is a wet protective atmosphere, nitriding treatment is carried out next, the process conditions are 800 ℃ for 60 seconds, the atmosphere is H2+ N2+ NH3 mixed gas, then secondary cold rolling is carried out, an isolation coating taking MgO as a main agent is coated, and high-temperature annealing is carried out at 1170-1190 ℃ for 24 hours, and the results are shown below.

In the production method of the present invention, the grain growth process when the oriented electrical steel sheet is secondarily recrystallized is such that the gaussian crystal nuclei of the surface layer of the steel sheet swallow other grains toward the center layer and penetrate the surface. In order to obtain secondary recrystallized grains having excellent orientation, the final cold rolling reduction is within a proper range, the deformation energy generated is matched with the effective inhibitor capability, and the surface layer and the central layer of the steel sheet after decarburization annealing are different. Therefore, it is possible to produce a thin gauge grain-oriented electrical steel sheet excellent in magnetic properties by selecting an appropriate pre-cooling reduction and final cold rolling reduction and matching them with an appropriate effective inhibitor.

In this case, if the secondary reduction ratio is more than 75%, the {110} <001> orientation component in the primary recrystallized texture is reduced, and the secondary recrystallization is not complete.

During nitriding, ALN and CuS as inherent inhibitors are stably produced in large batch for a long time, so that the control condition is stable, the control of the subsequent process is facilitated, and the stability is greatly superior to that of the acquired inhibitor method. The method adopts the inherent inhibitor as the main part, the acquired inhibitor is used as the auxiliary supplement, and the subsequent process basically does not produce the waste product without the brand number performance. And the influence of the fluctuation of the nitriding amount on the final performance is small, and the production control is easy. The matching of the nitriding amount is the key point.

The grain size of primary recrystallization is adjusted before nitriding treatment, so that products with excellent magnetic performance can be obtained only when the grain size reaches a certain size range.

The nitriding temperature should be 700-900 deg.C, preferably about 800 deg.C, and once it exceeds 900 deg.C, the texture of the steel sheet will be changed, so that the secondary recrystallization is not good, and the nitriding time is not particularly limited, preferably within 30-60 seconds. The protective atmosphere is H2+ N2 with NH3 added, and is a dry atmosphere with low dew point.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. An optimized production method of low-iron-loss high-magnetic-induction oriented electrical steel is characterized by comprising the following steps of:

forming a strip steel by molten iron after steel making, hot rolling, acid pickling and primary cold rolling, and performing nitriding treatment during annealing of the strip steel, and then performing secondary cold rolling including high-temperature annealing, stretching thermal leveling annealing and finished product shearing laser-containing nicking processes to obtain a finished product;

the composition of sol-Al in the molten iron is 0.010-0.035%, and the composition of C is 0.030-0.070%.

2. The optimized low-core-loss high-magnetic-induction oriented electrical steel production method according to claim 1,

and between the processes of the primary cold rolling and the high-temperature annealing, the strip steel is subjected to intermediate decarburization annealing and nitriding at the same time, and then is subjected to secondary cold rolling and coating of a separating agent.

3. The optimized low-core-loss high-magnetic-induction oriented electrical steel production method according to claim 1,

and (3) performing intermediate annealing on the strip steel between the primary cold rolling process and the high-temperature annealing process, and performing decarburization annealing and nitriding coating with a separant during the secondary cold rolling.

4. The optimized low-core-loss high-magnetic-induction oriented electrical steel production method according to claim 2 or 3,

adding an innate inhibitor into the molten iron, wherein the innate inhibitor comprises ALN, Cu2S, MnS and BN, and the acquired inhibitor is added in the nitriding process.

5. The optimized low-core-loss high-magnetic-induction oriented electrical steel production method according to claim 4,

the temperature range during nitriding is 700-900 ℃.

6. The optimized low-core-loss high-magnetic-induction oriented electrical steel production method according to claim 5,

the heating temperature during hot rolling is 1270-1290 ℃.

7. The optimized low-core-loss high-magnetic-induction oriented electrical steel production method according to claim 5,

the reduction rate range of the secondary cold rolling is 60-75%.

8. The optimized low-core-loss high-magnetic-induction oriented electrical steel production method according to claim 6,

the components further comprise:

si: 2.5-3.5%; mn: 0.05-0.45%; 0.020 to 0.055 percent of Cu; s is less than or equal to 0.015 percent; s is less than or equal to 0.015 percent; n is less than or equal to 0.010 percent; ni: 0.02-0.15%; cr: 0.03-0.20%, and the balance of Fe and inevitable impurities.