EP4656761A1

EP4656761A1 - High-magnetic-induction oriented silicon steel and manufacturing method therefor

Info

Publication number: EP4656761A1
Application number: EP24756115.2A
Authority: EP
Inventors: Huande Sun; Guobao Li; Yongjie Yang; Huabing ZHANG; Meihong Wu; Desheng Liu; Zipeng Zhao; Qi Xu
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2023-02-17
Filing date: 2024-02-05
Publication date: 2025-12-03
Also published as: CN118516602A; WO2024169741A1; JP2026507562A; KR20250143350A

Abstract

The present disclosure provides an oriented silicon steel comprising, in addition to Fe and inevitable impurities, the following chemical elements in percentage by mass as follows: C: 0.035-0.120%, Si: 2.5-4.5%, Mn: 0.05-0.20%, P: 0.005-0.05%, S: 0.005-0.012%, Als: 0.015-0.045%, N: 0.003-0.010%, Sn: 0.03-0.30%, and Mo: 0.01-0.03%. The oriented silicon steel of the present disclosure has excellent magnetic induction properties. In addition, the present disclosure also provides a method for manufacturing the oriented silicon steel. In the method of the present disclosure, by using appropriate steel component ratios in combination with specific normalizing annealing, decarburization, and nitriding processes, a stable and ultra-high-magnetic-induction oriented silicon steel product is obtained, edge cracking is avoided, and a product yield is greatly improved.

Description

TECHNICAL FIELD

The present disclosure relates to a steel plate and a manufacturing method therefor, and in particular to an oriented silicon steel and a manufacturing method therefor.

BACKGROUND ART

There are two main production processes for traditional oriented silicon steel: high-temperature process (using MnS+AlN as inhibitors) and low-temperature process (A1N+nitriding treatment).
In the high-temperature process, MnS and AlN are used as inhibitors, and normalizing and single-stage cold rolling are employed to produce high-temperature HiB steel. This production process is characterized by the requirement for a slab heating temperature as high as 1400°C during the hot rolling, such that MnS and AlN in the steel plate are fully dissolved into solid solution, then precipitated as fine and dispersed second-phase particles during subsequent normalization process. These particles serve as inhibitors for primary grain growth, facilitating the formation of large Goss grains through secondary recrystallization during high-temperature annealing, so as to obtain a high-magnetic-induction oriented silicon steel product with high orientation and low iron loss. However, high-temperature slab heating suffers from multiple drawbacks, including low yield rate, serious slag accumulation at the bottom of the furnace, reduced production output, high energy consumption, shortened furnace lifespan, high manufacturing cost, frequent surface defects, and unstable magnetic properties.
In the low-temperature HiB production process, the temperature for heating the slab can be reduced to 1150 °C. Only trace amounts of Al are added in the steelmaking process, and nitriding is performed after decarbonizing annealing. A main feature of the process lies in that, when the decarbonizing annealing is performed at a low temperature, since coarse sulfides and nitrides cannot be dissolved into solid solution, inhibitors cannot be formed during hot rolling and normalization; instead, inhibitor AlN is formed in a nitrifying atmosphere after decarbonizing annealing. However, when the low-temperature slab heating process is used, since the AlN cannot completely dissolve into solid solution in the heating phase, a quantity of inhibitors is insufficient, and therefore secondary recrystallization cannot be fully achieved. For this reason, many manufacturers have studied various methods for strengthening inhibitors, improving secondary recrystallization, and/or improving magnetic induction intensity of oriented silicon steel.
In addition, in order to shorten the production process, the thin slab continuous casting and rolling process may be used to produce the oriented silicon steel. In this process, the casted slab is hot rolled directly, thereby shortening the production process and saving energy. The production of oriented silicon steel by thin slab continuous casting and rolling process has the advantages such as rapid slab solidification, low segregation, and fine and dispersed inhibitors (MnS, AlN, etc.). However, the hot-rolled silicon steel plate often exhibits defects at the edges, such as hard non-metallic slags and micro cracks at the edges. In addition, during the subsequent cold rolling process, the steel plate not only bears the tensile force and bending force, but also has a large plastic deformation amount. The defects can be extended under such complicated stress deformation, resulting in a more severe cold rolling edge crack and even a broken strip.
For this reason, in a traditional hot rolling process, in order to prevent a hot rolling edge from cracking, measures including controlling a mass fraction of oxygen in a protective atmosphere and a retention time during slab reheating, and adjusting rough rolling reduction rate and rolling temperature are often adopted, so as to reduce grain boundary oxidation and refine steel plate grains, thereby achieving the purpose of reducing the occurrence of edge cracks.
In addition, it is disclosed in Publication No. CN113058998A, published on July 2, 2021 , entitled "A method for preventing edge cracking in hot-rolled oriented silicon steel under low-temperature heating" that, after the orientation silicon steel cast slab enters the second heating section, rapid heating is used with a heating rate of 15-30 °C/min; the furnace gas temperature in the soaking section is controlled within the range of 1150-1180°C; in the rough rolling stage, the number of rolling passes does not exceed 5; the side-pressing amount during the rough rolling is ≥ 75mm, wherein the side-pressing amount of the vertical roller mill is 40mm or more. In this method, a large side-pressing amount is selected, and the rolling of the edge is strengthened, and the stress and strain degree of the edge is improved, recrystallization of the edge is promoted, and grains are refined, thereby effectively reducing hot-rolled edge cracks.
However, for the thin slab continuous casting and continuous rolling process, since the thickness of the slab is thin, the deformation amount in rough rolling is relatively small, no vertical roller mill is configured, and the side-pressing amount at the edge is very small. Therefore, the quality of the hot-rolled edge is relatively poor, and edge trimming is often required before the cold rolling, which still seriously affects production efficiency and yield rate.

SUMMARY

In view of the above-mentioned disadvantages in the prior art, one of the objects of the present disclosure is to provide a high-magnetic-induction oriented silicon steel, which has excellent magnetic induction performance while having a low cracking rate of hot-rolled coil, thereby greatly improving a yield rate.
In order to achieve the above object, the present disclosure provides an oriented silicon steel comprising, in addition to Fe and inevitable impurities, the following chemical elements in percentage by mass as follows:
C: 0.035-0.120%, Si: 2.5-4.5%, Mn: 0.05-0.20%, P: 0.005-0.05%, S: 0.005-0.012%, Als: 0.015-0.045%, N: 0.003-0.010%, Sn: 0.03-0.30%, and Mo: 0.01-0.03%.
In another aspect, the present disclosure also provides an oriented silicon steel, wherein the content of chemical elements in percentage by mass is as follows:
C: 0.035-0.120%, Si: 2.5-4.5%, Mn: 0.05-0.20%, P: 0.005-0.05%, S: 0.005-0.012%, Als: 0.015-0.045%, N: 0.003-0.010%, Sn: 0.03-0.30%, Mo: 0.01-0.03%, and the balance being Fe and inevitable impurities.
Preferably, the oriented silicon steel according to the present disclosure further comprises at least one of the following chemical elements in percentage by mass as follows: $0 < Cr \leq 0.30 %;$ $0 < Cu \leq 0.3 %;$ $0 < Nb \leq 0.01 %;$ $0 < Bi \leq 0.05 % .$
Preferably, the inevitable impurities include V element and Ti element, and V≤0.01% \ and Ti≤0.01%.
Preferably, in the oriented silicon steel according to the present disclosure, the content of chemical elements in percentage by mass satisfies at least one of the following:

C: 0.04-0.08%,
Si: 3.0-4.0%,
Mn: 0.08-0.18%,
P: 0.005-0.040%,
S: 0.006-0.010%,
Als: 0.02-0.04%,
N: 0.004-0.009%,
Sn: 0.03-0.20%,
Mo: 0.015-0.025%.

Preferably, the oriented silicon steel according to the present disclosure has secondary recrystallisation grains with an average grain size (an average grain diameter D of secondary recrystallisation grains) of 20 mm or more.
Preferably, the oriented silicon steel according to the present disclosure has a magnetic induction B₈ of ≥ 1.95 T.
Preferably, the oriented silicon steel according to the present disclosure has a ratio (B₈/Bs) of magnetic induction B₈ to saturation magnetic induction value Bs of 0.98 or more.
Preferably, the oriented silicon steel according to the present disclosure has an iron loss P_17/50 of <1.00 W/kg.
Preferably, the oriented silicon steel according to the present disclosure has an untrimmed cold rolling ratio η of ≥ 90%.
In a further aspect, the present disclosure further provides a method for manufacturing the above-mentioned oriented silicon steel, comprising the following steps:

(1) smelting;
(2) thin slab continuous casting and rolling: the slab having a thickness of 60-70 mm, soaking the slab at a temperature of 1100-1200 °C, and soaking in a furnace for a time period of 20-40 min;
(3) normalizing annealing: heating from room temperature to 900-1020°C and holding for a time period of 60s or less; then cooling to 900-930°C within 15s and holding for a time period of 60-120s; then water quenching with a cooling rate of 30-100 °C/s;
(4) cold rolling;
(5) decarburization annealing and nitriding treatment: adopting a two-stage decarbonization annealing, wherein in a first decarbonization annealing stage, decarbonization annealing is performed at a temperature of 800-900°C for a time period of 80s-160s, with pH₂O/pH₂ = 0.4-0.75; in a second decarbonization annealing stage, decarbonization annealing is performed at a temperature of 800-950°C for a time period of 40-60s, with pH₂O/pH₂ < 0.4; and performing nitriding treatment during the decarburization annealing process, wherein nitriding is performed at a temperature of 750-900°C for a time period of 5-50s, a nitriding atmosphere is NH₃+H₂+N₂, and a volume percentage of NH₃ in the nitriding atmosphere is 0.1-15%, such that a molar ratio (Als/[N]) of an acid-soluble aluminum content to a nitrogen content of a steel plate before second recrystallization satisfies: 1≤Als/[N]≤1.8;
(6) applying MgO coating and performing high temperature annealing;
(7) applying an insulating coating on a surface of the annealed plate, and conducting hot stretching and levelling annealing to obtain the oriented silicon steel.

Preferably, in step (2), a molten steel has a superheat of 20-40 °C, with a casting speed of 3-5 mpm.
Preferably, in step (2), a start rolling temperature for hot rolling is 1000-1150 °C, and a finishing rolling temperature for hot rolling is 850-1050 °C.
Preferably, in step (2), a laminar cooling is performed after rolling, and then coiling is performed, wherein the coiling is performed at a temperature of 650 °C or less. When the coiling is performed at a temperature of 650 °C or less, it can be further ensured that no coarse precipitates will be formed.
Preferably, in step (4), the cold rolling further includes an intermediate annealing.
The oriented silicon steel of the present disclosure is obtained based on the thin slab continuous casting and rolling process, effectively avoiding a problem of a hot-rolled coil cracking.
The inventors have found through studies that the thickness of the slab had a significant influence on the size of precipitates after continuous casting and rolling. When the thickness of the slab is 60-70 mm, the equivalent diameter of the precipitate is relatively small. The slab of the oriented silicon steel prepared by the method of the present disclosure is thin, and the cooling speed for casting is fast, and precipitates are relatively small. The method of the present disclosure can effectively reduce the cracking of the hot-rolled coil and improve yield rate.
In addition, the specific normalizing annealing process of the present disclosure can result in the precipitation of fine inhibitors such as AlN, thereby increasing the quantity of recrystallized grains in the hot-rolled plate, and making the texture distribution more reasonable.
The inventors have found that in a decarburization annealing process in the prior art, when pH₂O/pH₂ is < 0.4, a SiO₂-rich oxide film will be formed, which prevents decarburization. When pH₂O/pH₂ is 0.30-0.65, the decarbonization effect is good, but the magnetic properties and glass film quality are not good. After extensive research, in the method of this disclosure, a two-stage decarbonized annealing process is used, where the first stage adopts 800-900°C × 80s-160s, with pH₂O/pH₂ = 0.4-0.75; and the second stage adopts 800-950°C × 40s-60s, with pH₂O/pH₂ <0.4. By using the two-stage decarburization annealing process of the present disclosure, decarburization is sufficiently achieved, glass film quality is improved, secondary recrystallization is stable, and secondary recrystallization grains are fine, thereby improving the magnetic properties.
In the method of this disclosure, nitriding is performed during or after the decarburization annealing process to form advantageous inclusions. According to the specific nitriding method of this disclosure (the nitriding temperature is 750-900 °C, the nitriding time is 5-50 s, the nitriding atmosphere is NH₃+H₂+N₂, and the volume percentage of NH₃ in the nitriding atmosphere is 0.1-15%), after the nitriding is completed, nitrogen infiltrated into the surface of the steel plate diffuses and forms advantageous inclusions mainly composed of (Al,Si)N, which inhibits the growth of the primary grain and prepares for secondary recrystallization, such that the molar ratio Als/[N] of an acid dissolved aluminum content to a nitrogen content of the steel plate before secondary recrystallization satisfies: 1≤Als/[N]≤1.8. Therefore, an ultra-high-magnetic-induction oriented silicon steel product with B₈ ≥ 1.95 T can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG.1 shows the effect of the slab thickness on precipitate size in the oriented silicon steel of the present disclosure.
FIG.2 shows the effect of a molar ratio (Als/[N]) of an acid-soluble aluminum content to a nitrogen content on the magnetic induction B₈ of the oriented silicon steel of the present disclosure before the secondary recrystallization.

DETAILED DESCRIPTION

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms used in the description of the present disclosure are for the purpose of describing particular embodiments only and are not intended to limit the invention.
In this description, an average grain size of secondary recrystallisation grains is measured as described in the Examples section. Specifically, a single magnetic test sample is subjected to acid pickling to remove the surface coating and display macro grains, and photographed to obtain an image. The image of the secondary recrystallized grains is then processed by using an image processing software, and the equivalent circular diameter of secondary recrystallized grains in the image is obtained via the area method so as to calculate an average value of the equivalent circular diameter of secondary recrystallized grains, that is, an average grain size of secondary recrystallization grains.
In this description, the magnetic induction B₈ and B₂₅ are measured according to GB/T 13789-2008 "Methods of Measurement of the Magnetic Properties of Magnetic Sheet and Strip by Means of a Single Sheet Tester"; and B₂₅ is defined as a saturation magnetic induction value Bs.
In this description, an iron loss P_17/50 is measured using a 0.3 mm thick sample in accordance with GB/T 13789-2008 "Methods of Measurement of the Magnetic Properties of Magnetic Sheet and Strip by Means of a Single Sheet Tester".
In this description, an untrimmed cold rolling ratio η refers to a ratio of the number of hot-rolled coils for direct use without trimming to the total number of hot-rolled coils during cold rolling.
In this description, pH₂O/pH₂ refers to a partial pressure ratio of water to hydrogen in the atmosphere, obtained by measuring a dew point in the atmosphere, determining a water content, and calculating according to the hydrogen content.
In this description, when calculating the molar ratio (Als/[N]) of the acid-soluble aluminum to the nitrogen content of the steel plate before second recrystallization occurs, the nitrogen content is expressed as [N] because the nitrogen content of the steel plate has changed compared to the smelting component.
In the oriented silicon steel of this disclosure, a design principle of each chemical element is described as follows:
C: In the oriented silicon steel of this disclosure, the main function of the C element is as follows: during the hot rolling process, the steel contains 20% - 30% of γ phase, and the hot-rolled steel plate structure can be refined through the γ↔α phase transformation, and the microstructure of hot-rolled steel plate exhibits a specific structural gradient along the thickness direction of the steel plate. That is, in the center of the steel plate, the C content is relatively high, and the grain structure is fine, while near the surface of the steel plate, due to decarburization, the C content is low, and the ferrite grains are coarse, which makes it easy to form coarse and accurately oriented Goss grains along the rolling direction. However, the content of C element in steel should not be too high. If the content of the C element in the steel is too high, it will not only be difficult to decarbonize, but also lead to the presence of coarse carbides and troostites along the grain boundary, resulting in uneven structure and even the inability of secondary recrystallization to occur. In addition, C is also a main factor causing magnetic aging. If the C element content in the steel is too high and the decarburization is incomplete, the C in the finished product will be interstitially dissolved in ferrite lattice, which will generate a large stress field around the carbon atoms and significantly increase the magnetic hysteresis loss. Therefore, in the oriented silicon steel of this disclosure, the mass percentage of the C element is controlled to be 0.035-0.120%.
In some preferred embodiments, the mass percentage of the C element is controlled to be 0.04-0.08%.
Si: In the oriented silicon steel of this disclosure, the Si element can effectively reduce iron loss of a finished steel plate. However, the content of the Si element in steel should not be too high. If the content of the Si element in the steel is too high, the content of γ phase will be reduced sharply, such that the material processing is difficult, and the microstructure of the hot-rolled steel plate is coarse. As such, the precipitated inhibitors are coarse, the amount of inhibitors is reduced, the inhibiting force is reduced, the primary recrystallization grains are coarse, the {110} pole density in the primary recrystallization structure is decreased, and secondary recrystallization is difficult. In addition, if the content of the Si element in the steel is too high, carbide particles precipitated after the normalization step are coarse, which affects cold rolling aging and decarburization annealing. Therefore, in the oriented silicon steel of this disclosure, the mass percentage of the Si element is controlled to be 2.5-4.5%.
In some preferred embodiments, the mass percentage of the Si element is controlled to be 3.0-4.0%.
Mn: In the oriented silicon steel of this disclosure, the Mn element can play a role of preventing hot brittleness of the hot-rolled plate, and can also be combined with the S element to form an MnS precipitate, such that the primary recrystallized grains are fine and uniform, and the development of a secondary recrystallization is promoted. In addition, the Mn element can also expand the γ phase region in the steel, such that an amount of the C element added in the steel can be effectively reduced, thereby reducing the burden of decarburization in the subsequent process. However, the Mn content in steel should not be too high. If the content of the Mn element in the steel is too high, it will cause γ phase to appear in the subsequent processes, interfering with the secondary recrystallization process. Therefore, in the oriented silicon steel of the present disclosure, the mass percentage of the Mn element is controlled to be 0.05-0.20%.
In some preferred embodiments, the mass percent of the Mn element is controlled to be 0.08-0.18%.
P: In the oriented silicon steel of this disclosure, the P element can effectively promote finer and more uniform primary recrystallized grains, while also increasing the proportion of the {111} texture within the primary recrystallized grains and improving the secondary recrystallization. However, if the content of P element in the steel is too high, the steel will be brittle. Therefore, in the oriented silicon steel of this disclosure, the mass percentage of the P element is controlled to be 0.005-0.050%.
In some preferred embodiments, the mass percentage of the P element is controlled to be 0.005-0.040%.
S: It is generally believed that the content of the S element in oriented silicon steel produced by the nitriding process should be controlled to be 0.007% or less. However, the present inventors have found through research that, in the oriented silicon steel of the present disclosure, when the content of the S element is <0.005%, not only steelmaking becomes difficult, but also the magnetic properties of the finished steel plate are also affected. This is likely due to insufficient amount of formed (Cu,Mn)S and affected AlN precipitation. This is because there is a certain orientation relationship between AlN and (Cu,Mn)S: {2110}AIN//{110}(Cu,Mn)S, wherein excessive or insufficient S content may affect the AlN precipitation morphology. Furthermore, the content of S element in steel should not be too high. When the S content in steel is >0.012%, secondary recrystallization is not incomplete, and linear crystals are likely to occur. Based on this, in the grain- oriented silicon steel of this disclosure, the mass percentage of the S element is controlled to be 0.005-0.012%.
In some preferred embodiments, the mass percentage of the S element is controlled to be 0.006-0.010%.
Als and N: In the oriented silicon steel of this disclosure, Als (acid-soluble aluminum) in the steel may be combined with the N element to form AlN. AlN is a major inhibitor in the oriented silicon steel. From the perspective of ensuring sufficient magnetic properties, the content of the acid-soluble aluminum should be 0.015-0.045%, and the content of the nitrogen should be 0.003% or more. Furthermore, when the nitrogen content exceeds 0.010%, casting is prone to swelling, resulting in peeling and blistering defects in the product.
In some preferred embodiments, the mass percentage of Als is controlled to be 0.02-0.04%, and the N content is controlled to be 0.004-0.009%.
Mo: In the oriented silicon steel of this disclosure, the Mo element is a core element for controlling edge cracking of a hot-rolled plate. The addition of Mo can reduce the cracking of the hot-rolled plate. The enrichment of Mo in the surface of the hot-rolled plate can suppress the grain boundary oxidation, form Mo₃S₃ near the surface, and prevent FeS formation, such that primary grain refinement is promoted, and the crack at grain boundary is prevented. In addition, the addition of Mo can also increase secondary nucleation sites, improve orientation accuracy, and improve magnetic induction intensity.
In some preferred embodiments, the mass percent of the Mo element is controlled to be 0.015-0.025%.
Sn: In the oriented silicon steel of this disclosure, Sn is a grain boundary segregation element. The appropriate amount of the Sn element added in the steel can strengthen the inhibitory effect on the grain growth, prevent premature denitriding and nitrogen uptake during high-temperature annealing, promote complete secondary recrystallization, and improve the magnetic properties of the steel. In addition, in the oriented silicon steel of the present disclosure, the Sn element occupies the grain boundary, the diffusion of the O element in the steel is hindered, and the formation of the underlying embedded structure is affected, which may cause the quality of the underlying layer to deteriorate. Therefore, the quality of the underlying layer can be compensated by adding Cr and Cu elements. Based on this, in the oriented silicon steel of this disclosure, the mass percentage of the Sn element is controlled to be 0.03-0.30%.
In some preferred embodiments, the mass percent of the Sn element is controlled to be 0.03-0.20%.
In some preferred embodiments, the oriented silicon steel of this disclosure further comprises at least one of the following chemical elements in percentage by mass as follows: $0 < Cr \leq 0.30 %;$ $0 < Cu \leq 0.3 %;$ $0 < Nb \leq 0.01 %;$ $0 < Bi \leq 0.05 % .$
Cr: In the grain- oriented silicon steel disclosed herein, adding an appropriate amount of the Cr element can effectively promote oxidation during decarburization annealing, improve an oxygen adhesion amount, and improve the quality of the underlying layer. Based on this, in the oriented silicon steel of this disclosure, the mass percentage of Cr is controlled to be 0.05-0.30%.
In some preferred embodiments, the mass percentage of Cr element is controlled to be 0.08-0.28%.
Cu: In the oriented silicon steel of this disclosure, the addition of Cu can increase the content of γ phase, appropriately reduce the content of C, and reduce the heating temperature of the slab. In addition, the addition of Cu can precipitate (Cu,Mn)_xS or Cu_xS particles. The precipitation temperature of (Cu,Mn)_xS or Cu_xS is 80°C-100°C lower than that of MnS, thereby helping to reduce the heating temperature of the slab. In addition, the precipitated (Cu,Mn)_xS or Cu_xS is finer and more dispersed than the MnS, and the precipitation amount is also significantly increased. Therefore, an inhibiting force on grain growth is enhanced, and the second cold rolling reduction rate and the magnetic properties of the finished product are improved. In addition, the addition of Cu can enhance the {110}<001>-oriented grains in the hot-rolled plate and after decarburization annealing, reduce the {100}<001>-oriented grains, and promote secondary recrystallization. The addition of Cu can also mitigate the deterioration of the glass film due to the addition of Sn or Sb. Based on this, in the oriented silicon steel of this disclosure, the mass percentage of the Cu element is controlled to be 0<Cu≤0.3%.
In some preferred embodiments, in the oriented silicon steel of this disclosure, inevitable impurities include V and Ti, and V≤0.01% and Ti≤0.01%.
In the oriented silicon steel of this disclosure, inevitable impurities are mainly V and Ti. V and Ti are strong carbides or oxide-forming elements. When the V and Ti contents are high, the decarbonization annealing process will be affected. Therefore, the V and Ti contents must be controlled. Therefore, in the oriented silicon steel of this disclosure, V≤0.01%, Ti≤0.01%.
In some preferred embodiments, V≤0.008%, Ti≤0.008%.
In addition, in some preferred embodiments, by adding Nb and Bi and controlling the contents of impurity elements V and Ti, the number of coarse MnS+AlN composite precipitates in the slab with TiN, TiC and VN as the core can be greatly reduced.
In some preferred embodiments, the average grain size of the second recrystallization grains in the oriented silicon steel of the present disclosure is 20 mm or more.
In the oriented silicon steel of this disclosure, the obtained magnetic properties of the finished product of the oriented silicon steel rely on a principle of secondary recrystallization, forming a single Goss texture {110}<001>. The secondary recrystallization refers to a phenomenon in which, after deformation, the metal is restricted by certain conditions (such as inhibitors and texture), such that most grains cannot grow normally during heating and recrystallization of metal, and only a few grains (Goss grains) abnormally grow by consuming grains with other orientations. Only those Goss nuclei with more accurate orientations can grow and utilize size effects to consume grains of other orientations. The number of the secondary recrystallization grains is decreased, and the size of the secondary recrystallization grains is increased, resulting in better magnetic properties for the steel.
The oriented silicon steel of the present disclosure and a manufacturing method therefor have the following advantages and beneficial effects:
In the orientation silicon steel of the present disclosure, by optimizing the chemical composition design of the steel, especially adding an appropriate amount of the Mo element, the hot-rolled coil cracking is effectively reduced, such that the untrimmed cold rolling ratio is 90% or more, and the yield rate is improved.
In the present disclosure, the normalizing annealing, decarburization, and nitriding processes are adjusted, such that a molar ratio of an acid-soluble aluminum content to a nitrogen content in the oriented silicon steel before second recrystallization occurs satisfies: 1≤Als/[N]≤1.8, the inhibiting capability on primary grains is enhanced, an average grain diameter D of the secondary recrystallization grains in the finished product is ≥ 20mm, and finally the product with stable and ultra-high magnetic induction is obtained, wherein the product has a magnetic induction of B₈≥1.95T, a ratio of magnetic induction B₈ to saturation magnetic induction value Bs, B8/Bs, of ≥ 0.98, and an iron loss of P_17/50 < 1.00 W/kg for a 0.3 mm thick finished product.

Examples

Hereinafter, the oriented silicon steel and the manufacturing method therefor according to the present disclosure will be further explained and described with reference to the specific examples and accompanying figures, however, the explanation and description do not constitute inappropriate limitation to the technical solution of the present disclosure. The experimental methods, in which specific conditions were not specified in the examples, were implemented in accordance with conventional conditions known in the art or the conditions recommended by the manufacturer.

Examples 1-18 and Comparative Examples 1-8

Table 1 lists the mass percentages of various chemical elements in the oriented silicon steels in Examples 1-18 and the comparative steels in Comparative Examples 1-8.

Table 1. (wt %, the balance being Fe and other inevitable impurities except V and Ti)

	C	Si	Mn	P	S	Als	N	Sn	Mo	V	Ti	Cr	Cu	Nb	Bi
Example 1	0.051	3.24	0.099	0.008	0.0087	0.027	0.0086	0.047	0.015	0.0006	0.0012	-	-	-	-
Example 2	0.064	3.19	0.20	0.040	0.0070	0.028	0.008	0.067	0.010	0.0008	0.0021	-	-	-	-
Example 3	0.053	3.22	0.098	0.050	0.0079	0.038	0.0079	0.200	0.012	0.0012	0.0012	-	-	-	-
Example 4	0.052	3.22	0.11	0.023	0.0050	0.034	0.0081	0.300	0.027	0.0007	0.0012	-	-	-	-
Example 5	0.083	3.45	0.098	0.032	0.0120	0.032	0.009	0.09	0.019	0.0009	0.0013	-	-	-	-
Example 6	0.035	3.35	0.10	0.045	0.0093	0.029	0.0087	0.05	0.025	0.0009	0.0012	-	-	-	-
Example 7	0.094	4.50	0.08	0.005	0.008	0.045	0.0075	0.030	0.028	0.0012	0.0025	-	-	-	-
Example 8	0.120	3.30	0.12	0.008	0.0065	0.033	0.0100	0.055	0.030	0.0007	0.0028	-	-	-	-
Example 9	0.051	3.00	0.11	0.024	0.006	0.027	0.0077	0.048	0.015	0.005	0.0021	-	-	-	-
Example 10	0.04	3.25	0.11	0.040	0.0070	0.020	0.0086	0.047	0.020	0.0012	0.0025	0.08	-	-	-
Example 11	0.055	3.22	0.11	0.040	0.010	0.029	0.0080	0.060	0.015	0.0012	0.0025	-	0.1	-	0.045
Example 12	0.053	4.00	0.11	0.050	0.0070	0.029	0.0079	0.046	0.018	0.0012	0.0025	-	0.2	-	-
Example 13	0.052	3.22	0.11	0.050	0.0070	0.040	0.0081	0.052	0.013	0.0012	0.0025	0.15	-	-	-
Example 14	0.053	3.25	0.05	0.050	0.0070	0.029	0.0080	0.052	0.015	0.0010	0.0025	-	-	0.008	-
Example 15	0.055	3.35	0.18	0.045	0.0070	0.029	0.0030	0.050	0.025	0.0010	0.0025	-	0.3	-	0.040
Example 16	0.053	2.50	0.11	0.005	0.0070	0.035	0.0080	0.050	0.020	0.0012	0.0025	0.12	-	0.005	-
Example 17	0.053	3.30	0.12	0.050	0.0070	0.015	0.0080	0.050	0.028	0.0012	0.0022	0.30	-	-	-
Example 18	0.053	3.22	0.11	0.050	0.0070	0.027	0.0040	0.050	0.013	0.0012	0.0022	-	-	-	0.035
Comparative Example 1	0.062	3.20	0.11	0.033	0.0062	*0.048*	0.0077	0.049	*0.005*	0.005	0.0016	-	-	-	-
Comparative Example 2	0.053	3.27	0.13	0.025	*0.0167*	0.027	0.0079	0.052	*0.005*	0.005	0.0022	-	-	-	-
Comparative Example 3	0.055	3.28	0.089	*0.065*	0.0068	0.028	0.0077	0.047	*0.005*	0.005	0.0024	-	-	-	-
Comparative Example 4	0.060	3.20	0.11	0.035	0.0062	*0.014*	0.0078	0.049	*0.005*	0.005	0.0016	-	-	-	-
Comparative Example 5	0.054	3.17	0.13	*0.070*	0.0077	0.027	0.0079	0.052	*0.005*	0.005	0.0026	-		-	-
Comparative Example 6	0.055	3.22	0.092	0.015	0.0070	0.028	0.0077	0.047	*0.005*	0.005	0.0023	-	-	-	-
Comparative Example 7	0.053	3.32	0.11	0.050	0.0068	0.028	0.0080	0.050	*0.005*	0.0012	0.0022	-	-	-	-
Comparative Example 8	0.053	3.20	0.10	0.050	0.0068	0.028	0.0080	0.052	*0.003*	0.0012	0.0022	-	-	-	-

The oriented silicon steels in Examples 1-18 and the comparative steels in Comparative Examples 1-8 were prepared by the following steps (specific process parameters are shown in Tables 2-1, 2-2, and 2-3):

(1) Steelmaking with a converter or electric furnace, and subjecting the molten steel to secondary refining;
(2) Thin slab continuous casting and rolling, performing laminar cooling after rolling, and then performing coiling to obtain 2.6 mm hot-rolled plate;
(3) Normalizing annealing;
(4) Cold rolling: a cumulative rolling reduction rate in the cold rolling ≥ 88%, obtaining a cold-rolled plate with a thickness of 0.3 mm;
(5) Decarburization annealing and nitriding treatment;
(6) Applying MgO coating, and performing high-temperature annealing in a bell-type furnace or annular furnace in an atmosphere of 100% H₂ at a temperature of 1200°C for 20 hours;
(7) Applying an insulating coating on the surface of the annealed plate, and conducting hot stretching and levelling annealing to obtain the oriented silicon steel coil.

Tables 2-1, 2-2, and 2-3 list specific process parameters for the oriented silicon steels in Examples 1-18 and the comparative steels in Comparative Examples 1-8.

Table 2-1

	Slab thickness (mm)	Superheat in continuous casting (°C)	Casting speed (mpm)	Slab soaking temperature (°C)	Soaking time in furnace (min)	Start rolling temperature for hot rolling (°C)	Finishing rolling temperature for hot rolling (°C)	Coiling temperature (°C)
Example 1	68	20	3.2	1200	23	1145	1043	649
Example 2	68	20	3.2	1200	23	1148	1050	615
Example 3	68	23	3.2	1200	23	1150	1048	628
Example 4	70	23	3.2	1180	25	1110	1033	634
Example 5	70	23	3.0	1180	23	1115	1035	568
Example 6	70	23	3.1	1170	23	1100	1030	566
Example 7	65	25	4.1	1170	23	1110	1042	563
Example 8	65	25	4.1	1160	20	1120	1040	564
Example 9	65	25	4.1	1160	20	1110	1032	566
Example 10	60	36	4.8	1100	20	1005	852	566
Example 11	60	36	5.0	1100	20	1069	905	570
Example 12	60	36	4.8	1100	20	1070	906	645
Example 13	62	36	4.5	1120	30	1071	909	573
Example 14	62	39	4.6	1120	30	1072	910	568
Example 15	62	39	4.5	1120	30	1068	907	570
Example 16	69	40	4.1	1180	40	1066	907	566
Example 17	69	39	4.1	1180	40	1067	892	566
Example 18	69	39	4.1	1190	40	1095	894	563
Comparative Example 1	*230*	39	3.0	1190	40	1095	890	565
Comparative Example 2	*230*	39	3.0	1190	40	1100	1035	558
Comparative Example 3	*230*	25	3.2	1170	40	1085	910	558
Comparative Example 4	*230*	25	3.2	1170	40	1090	913	563
Comparative Example 5	*230*	25	4.0	1150	35	1070	905	561
Comparative Example 6	*230*	25	4.0	1150	35	1100	1012	562
Comparative Example 7	*230*	25	5.0	1110	25	1020	885	559
Comparative Example 8	*230*	25	5.0	1110	25	1030	890	569

Table 2-2

	Heating temperature for normalization (°C)	Holding time after heating for normalization (s)	Cooling temperature within 15s for normalization (°C)	Holding time after cooling for normalization (s)	Cooling rate of water quenching for normalization (°C/s)	Cumulative rolling reduction rate for cold rolling (%)
Example 1	940	10	910	120	100	89
Example 2	900	55	900	120	100	89
Example 3	960	9	915	120	100	90
Example 4	980	9	925	80	80	89
Example 5	980	9	905	80	80	89
Example 6	1000	5	930	80	80	89
Example 7	1020	5	930	80	70	89
Example 8	980	10	925	80	70	89
Example 9	980	10	930	60	70	88
Example 10	960	8	920	60	30	88
Example 11	980	8	925	60	30	88
Example 12	940	8	930	60	30	88
Example 13	920	35	920	60	50	88
Example 14	1000	6	925	60	50	88
Example 15	975	6	920	60	50	88
Example 16	975	7	915	100	30	88
Example 17	965	7	910	100	30	88
Example 18	965	8	900	100	30	88
Comparative Example 1	*1050*	9	900	60	30	88
Comparative Example 2	*1100*	9	900	60	20	88
Comparative Example 3	*1110*	6	900	60	25	89
Comparative Example 4	*1120*	9	900	60	30	89
Comparative Example 5	*1070*	7	920	60	25	89
Comparative Example 6	*1025*	5	920	60	30	89
Comparative Example 7	*1030*	5	920	60	40	89
Comparative Example 8	*1040*	5	920	60	28	89

Table 2-3

No.	First decarburization annealing stage			Second decarburization annealing stage			Nitriding treatment (nitriding atmosphere: NH₃ +H₂ +N₂)
No.	Decarburization annealing temperature (°C)	Decarburization annealing time (s)	pH₂O / pH₂	Decarburization annealing temperature (°C)	Decarburizatio n annealing time (s)	pH₂O / pH₂	Nitriding temperature (°C)	Nitriding time (s)	Volume percentage of NH₃ (%)	Als/[N] molar ratio before secondary crystallization
Example 1	810	160	0.75	950	45	0.30	770	40	13.00	1.35
Example 2	810	160	0.75	950	45	0.30	770	40	13.30	1.43
Example 3	810	160	0.75	950	45	0.30	770	40	13.25	1.38
Example 4	800	160	0.75	950	45	0.30	770	40	13.00	1.27
Example 5	800	160	0.75	800	60	0.32	750	45	15.00	1.36
Example 6	820	120	0.70	800	60	0.32	750	45	14.30	1.75
Example 7	820	120	0.70	800	60	0.32	750	45	14.30	1.25
Example 8	830	120	0.65	900	40	0.32	900	45	3.40	1.23
Example 9	830	120	0.65	900	40	0.32	900	45	3.40	1.22
Example 10	860	120	0.40	860	40	0.32	860	50	3.40	1.20
Example 11	860	120	0.40	860	40	0.32	860	50	0.10	1.80
Example 12	860	80	0.40	860	40	0.32	860	50	0.12	1.16
Example 13	900	80	0.40	900	40	0.32	900	5	0.12	1.04
Example 14	900	80	0.40	900	40	0.32	900	5	0.12	1.15
Example 15	850	100	0.65	850	50	0.38	770	10	10.50	1.65
Example 16	850	100	0.65	850	50	0.38	770	10	10.50	1.55
Example 17	830	100	0.65	850	50	0.38	770	10	10.50	1.44
Example 18	830	100	0.65	860	50	0.38	820	10	3.60	1.47
Comp. Example 1	830	100	0.65	860	50	*0.42*	820	40	3.60	*0.87*
Comp. Example 2	830	100	0.65	830	50	*0.42*	820	40	3.60	*0.89*
Comp. Example 3	820	120	0.70	830	50	*0.42*	820	40	10.50	*0.89*
Comp. Example 4	820	120	0.70	830	50	0.35	850	40	10.50	*0.88*
Comp. Example 5	820	120	0.70	830	50	0.35	850	30	10.50	*0.86*
Comp. Example 6	860	110	*0.77*	830	45	0.32	850	30	12.36	*0.87*
Comp. Example 7	860	110	*0.77*	860	45	0.32	850	30	12.36	*0.84*
Comp. Example 8	860	110	*0.77*	860	45	0.32	850	30	12.36	*0.83*

The finally obtained oriented silicon steels in Examples 1-18 and the comparative steels in Comparative Examples 1-8 were sampled, observed and subjected to various relevant performance tests. The obtained observation and test results are listed in Table 3.
The average grain size of the secondary recrystallisation grains was measured as follows: a single magnetic test sample was subjected to acid pickling to remove the surface coating and display macro grains, and photographed to obtain an image. The image of the secondary recrystallized grains was then processed with the image processing software, and the equivalent circular diameter of the secondary recrystallized grains in the image was obtained via the area method so as to calculate the average value of the equivalent circle diameter of the secondary recrystallized grains, that is, an average grain size of secondary recrystallization grains.
The parameters for magnetic properties were measured according to GB/T 13789-2008 "Methods of Measurement of the Magnetic Properties of Magnetic Sheet and Strip by Means of a Single Sheet Tester".
Untrimmed cold rolling ratio η: a ratio of the number of hot-rolled coils directly used without trimming to the total number of hot-rolled coils during cold rolling.

Table 3 lists the observation and performance test results of the oriented silicon steels in Examples 1-18 and the comparative steels in Comparative Examples 1-8.

Table 3

	Average grain diameter D of secondary recrystallization grains for finished product (mm)	B₈ (T)	B₈/Bs	P_17/50 (W/kg)	η (%)
Example 1	21.5	1.976	0.99	0.897	92
Example 2	21.5	1.975	0.99	0.903	90
Example 3	21.2	1.970	0.99	0.919	91
Example 4	21.1	1.969	0.99	0.922	92
Example 5	21.1	1.968	0.99	0.926	90
Example 6	21.0	1.967	0.98	0.930	91
Example 7	21.0	1.967	0.98	0.930	91
Example 8	20.9	1.965	0.98	0.938	90
Example 9	21.2	1.963	0.98	0.942	90
Example 10	20.6	1.960	0.98	0.955	91
Example 11	20.3	1.956	0.98	0.968	90
Example 12	20.2	1.955	0.98	0.955	91
Example 13	20.1	1.952	0.98	0.970	92
Example 14	20.5	1.951	0.98	0.961	90
Example 15	20.8	1.959	0.99	0.951	91
Example 16	21.0	1.967	0.99	0.923	91
Example 17	21.4	1.977	0.99	0.915	90
Example 18	21.2	1.976	0.99	0.915	90
Comparative Example 1	18.7	1.931	0.97	1.084	88
Comparative Example 2	18.2	1.922	0.96	1.115	85
Comparative Example 3	18.5	1.922	0.97	1.085	87
Comparative Example 4	17.5	1.910	0.96	1.127	89
Comparative Example 5	16.4	1.893	0.97	1.186	88
Comparative Example 6	15.5	1.877	0.96	1.240	87
Comparative Example 7	14.7	1.867	0.96	1.276	88
Comparative Example 8	14.5	1.864	0.95	1.287	87

As shown in Table 3, the magnetic induction B₈ of the oriented silicon steels in Examples 1-18 was significantly higher than that of the comparative steels in Comparative Examples 1-8, and the iron loss P_17/50 of the oriented silicon steels in Examples 1-18 was significantly lower than that of the comparative steels in Comparative Examples 1-8. In the oriented silicon steels in Examples 1-18, the average grain size of secondary recrystallization grains was 20 mm or more, the magnetic induction B₈ was ≥ 1.95 T, the ratio B₈/Bs of magnetic induction B₈ to saturation magnetic induction value Bs was ≥ 0.98, and the iron loss P_17/50 of the finished product with a thickness of 0.3 mm was <1.00 W/kg. Furthermore, the untrimmed cold rolling ratio η for the oriented silicon steels in Examples 1-18 was ≥ 90%, while the untrimmed cold rolling ratio η for the comparative steels in Comparative Examples 1-8 was all below 90%.
It can be seen that the oriented silicon steels in Examples 1-18 not only achieve excellent magnetic properties but also avoid the problem of edge cracking.
FIG.2 shows the effect of the molar ratio (Als/[N]) of the acid-soluble aluminum content to the nitrogen content on the magnetic induction B₈ of the oriented silicon steel of the present disclosure before the secondary recrystallization.
It can be seen from FIG.2 that when the molar ratio of the acid-soluble aluminum to the nitrogen content of the steel plate before secondary recrystallization satisfies: 1≤Als/[N]≤1.8, a relatively high magnetic induction can be obtained.
It should be noted that the combination mode of the technical features in the present disclosure is not limited to the combination modes described in the claims or the combination modes described in the embodiments. All the technical features described in present disclosure can be combined or integrated in any way, unless there is a contradiction between them.
It should also be noted that the foregoing embodiments merely are specific embodiments of the present disclosure. It is obvious that the present disclosure is not limited to the above embodiments, and similar variations or modifications, which can be directly obtained or easily conceived by those skilled in the art accordingly from the contents disclosed in the present disclosure, all shall fall within the scope of the present disclosure.

Claims

An oriented silicon steel, wherein the oriented silicon steel comprises, in addition to Fe and inevitable impurities, the following chemical elements in percentage by mass as follows:
C: 0.035-0.120%, Si: 2.5-4.5%, Mn: 0.05-0.20%, P: 0.005-0.05%, S: 0.005-0.012%, Als: 0.015-0.045%, N: 0.003-0.010%, Sn: 0.03-0.30%, and Mo: 0.01-0.03%.
The oriented silicon steel according to claim 1, wherein the content of chemical elements in percentage by mass in the oriented silicon steel is as follows:
C: 0.035-0.120%, Si: 2.5-4.5%, Mn: 0.05-0.20%, P: 0.005-0.05%, S: 0.005-0.012%, Als: 0.015-0.045%, N: 0.003-0.010%, Sn: 0.03-0.30%, Mo: 0.01-0.03%, and the balance being Fe and inevitable impurities.
The oriented silicon steel according to claim 1 or 2, wherein the oriented silicon steel further comprises at least one of the following chemical elements in percentage by mass as follows: $0 < Cr \leq 0.30 %;$ $0 < Cu \leq 0.3 %;$ $0 < Nb \leq 0.01 %;$ $0 < Bi \leq 0.05 % .$
The oriented silicon steel according to claim 1 or 2, wherein the inevitable impurities include V element and Ti element, and V≤0.01% and Ti≤0.01%.
The oriented silicon steel according to claim 1 or 2, wherein the content of chemical elements in percentage by mass satisfies at least one of the following:
C: 0.04-0.08%;

Si: 3.0-4.0%;

Mn: 0.08-0.18%;

P: 0.005-0.040%;

S: 0.006-0.010%;

Als: 0.02-0.04%;

N: 0.004-0.009%;

Sn: 0.03-0.20%;

Mo: 0.015-0.025%.
The oriented silicon steel according to claim 1 or 2, wherein the oriented silicon steel has secondary recrystallisation grains with an average grain size of 20 mm or more.
The oriented silicon steel according to claim 1 or 2, wherein the oriented silicon steel has a magnetic induction Bs of ≥ 1.95 T, a ratio of magnetic induction B₈ to saturation magnetic induction value Bs, B₈/Bs, of ≥ 0.98, and an iron loss P_17/50 of < 1.00 W/kg.
The oriented silicon steel according to claim 1 or 2, wherein the oriented silicon steel has an untrimmed cold rolling ratio η of ≥ 90%.
A method for manufacturing the oriented silicon steel according to any one of claims 1 to 8, comprising the following steps:
(1) smelting;

(2) thin slab continuous casting and rolling: the slab having a thickness of 60-70 mm, soaking the slab at a temperature of 1100-1200 °C, and soaking in a furnace for a time period of 20-40 min;

(3) normalizing annealing: heating from room temperature to 900-1020°C and holding for a time period of 60s or less; then cooling to 900-930°C within 15s and holding for a time period of 60-120s; then water quenching with a cooling rate of 30-100 °C/s;

(4) cold rolling;

(5) decarburization annealing and nitriding treatment: adopting a two-stage decarbonization annealing, wherein in a first decarbonization annealing stage, decarbonization annealing is performed at a temperature of 800-900°C for a time period of 80s-160s, with pH₂O/pH₂ = 0.4-0.75; in a second decarbonization annealing stage, decarbonization annealing is performed at a temperature of 800-950°C for a time period of 40-60s, with pH₂O/pH₂ < 0.4; and performing nitriding treatment during the decarburization annealing process, wherein nitriding is performed at a temperature of 750-900°C for a time period of 5-50s, a nitriding atmosphere is NH₃+H₂+N₂, and a volume percentage of NH₃ in the nitriding atmosphere is 0.1-15%, such that a molar ratio of an acid-soluble aluminum content to a nitrogen content of a steel plate before second recrystallization satisfies: 1≤Als/[N]≤1.8;

(6) applying MgO coating and performing high temperature annealing;

(7) applying an insulating coating on a surface of an annealed plate, and conducting hot stretching and levelling annealing to obtain the oriented silicon steel.
The method according to claim 9, wherein in step (2), a molten steel has a superheat of 20-40 °C, with a casting speed of 3-5 mpm.
The method according to claim 9, wherein in step (2), a start rolling temperature for hot rolling is 1000-1150 °C, and a finishing rolling temperature for hot rolling is 850-1050 °C.
The method according to claim 11, wherein in step (2), a laminar cooling is performed after rolling, and then coiling is performed, wherein the coiling is performed at a temperature of 650 °C or less.
The method according to claim 9, wherein in step (4), the cold rolling further includes an intermediate annealing.