CN116024419A - High-temperature annealing method of low-temperature high-magnetic induction oriented silicon steel - Google Patents

Abstract

The invention discloses a high-temperature annealing method for low-temperature high-magnetic-induction oriented silicon steel. The specific steps are as follows: a steel strip with a finished thickness is obtained through the processes of smelting, continuous casting, heating, hot rolling, normalization and cold rolling; the steel strip is decarburized Annealing, the annealed steel strip is coated with magnesium oxide, and coiled into a steel coil; the sample is tested and the average value of [C], [N], [O] and grain size is calculated; calculated according to a given formula High temperature annealing parameters Perform high temperature annealing. The invention provides a high-temperature annealing method for low-temperature high-magnetic-inductive oriented silicon steel, that is, the temperature rise rate in the high-temperature annealing process is determined by the composition and the oxygen, nitrogen and primary recrystallized grain size in the steel after decarburization annealing, and the furnace atmosphere, thereby achieving the purpose of improving the magnetic properties and facilitating the precise control of the high-temperature annealing process.

Description

A high temperature annealing method for low temperature high magnetic induction grain oriented silicon steel

technical field

The invention belongs to the technical field of iron and steel smelting, in particular to a high-temperature annealing method for low-temperature high-magnetic induction oriented silicon steel.

Background technique

Silicon alloy steel with a silicon content of 1.0 to 4.5% and a carbon content of less than 0.08% is called silicon steel. It has the characteristics of high magnetic permeability, low coercivity, and large resistivity, so hysteresis loss and eddy current loss are small. It is mainly used as magnetic material in motors, transformers, electrical appliances and electrical instruments. In order to meet the needs of punching and shearing processing in the manufacture of electrical appliances, a certain degree of plasticity is also required. In order to improve the magnetic induction performance and reduce the hysteresis loss, it is required that the content of harmful impurities is as low as possible, and the plate shape is required to be flat and the surface quality is good.

The production process of low temperature high magnetic induction grain oriented silicon steel mainly includes smelting, hot rolling, normalization, cold rolling, decarburization, nitriding, high temperature annealing and stretching and tempering, and the processes of each process are interrelated and affect each other. The recrystallization that occurs during decarburization annealing is called primary recrystallization, and the abnormal growth of GOSS grains during high temperature annealing is called secondary recrystallization. In the production of high magnetic induction grain-oriented silicon steel, the grain size of the primary recrystallization has an important influence on the secondary recrystallization. When the primary recrystallization grains are fine, the driving force for secondary recrystallization of the grains becomes larger, and the secondary recrystallization temperature decreases; when the primary recrystallization grains are larger, the driving force for secondary recrystallization of the grains becomes smaller, The secondary recrystallization temperature increases. Under a certain inhibitor condition, both cases are prone to imperfect secondary recrystallization. In addition, during the high-temperature annealing process, the atmosphere in the furnace has an important impact on the secondary recrystallization, and an inappropriate atmosphere in the furnace will cause the secondary recrystallization to be imperfect or even impossible. Therefore, different composition control and primary recrystallization grain size require a suitable atmosphere and heating rate for high temperature annealing to ensure the perfection of secondary recrystallization.

The Chinese patent document of Chinese invention patent 201910938854.7, which discloses "a method for preparing high magnetic induction oriented silicon steel", the Chinese patent document of patent application number 200910273458.3, which discloses "a method for preparing high magnetic induction oriented silicon steel", The above-mentioned documents all describe in detail the high-temperature annealing of grain-oriented silicon steel. However, only a range of atmosphere and heating rate has been determined, and the corresponding relationship between the main influencing factors has not been established, which is not conducive to the precise control of the high-temperature annealing process.

Therefore, we propose a high temperature annealing method for low temperature high magnetic induction grain-oriented silicon steel.

Contents of the invention

The purpose of the present invention is to overcome the defects of the prior art, and provide a high-temperature annealing method for low-temperature high-magnetic-induction grain-oriented silicon steel.

To achieve the above object, the present invention adopts the following technical solutions:

A high temperature annealing method for low temperature high magnetic induction oriented silicon steel, the specific steps of the high temperature annealing method are as follows:

(S1), smelting according to the set composition and obtaining the billet through the continuous casting process, the billet is heated, hot-rolled, normalized, and cold-rolled to obtain a steel strip with a finished thickness;

(S2), decarburization annealing is carried out to the steel strip material after cold rolling, and the steel strip after annealing is coated with magnesia and then coiled into a steel coil;

(S3), sampling detection [C], [N], [O] and grain size after decarburization annealing of the steel strip;

(S4), performing high-temperature annealing on the steel coil after decarburization annealing.

Preferably, the chemical composition of the finished thickness steel strip obtained in the step (S1) is: C: 0.05-0.09%; Si: 2.9-3.5%; Mn: 0.05-0.15%; P: ≤0.030 %; S: 0.005～0.010%; Als: 0.02～0.035%; N: 0.0060～0.011%; Sn: 0.05～0.10%; Cr: ≤0.30%; Cu: ≤0.60%; the rest is Fe and unavoidable impurities element.

Preferably, the process flow in the step (S1) is billet→heating→hot rolling→normalization→cold rolling, wherein the heating temperature of the billet is 1120-1200°C, the finishing temperature of the hot rolling is 900-1000°C, normal The total deformation rate of 1100℃+900℃ two-stage normalization and one-time cold rolling is 86-90%.

Preferably, [C]: ≤30ppm; [N]: 150-300ppm; [O]: 450-1200ppm in the steel after decarburization annealing in the step (S2), while detecting the primary recrystallized grain size.

Preferably, in the step (S3), samples are taken at the head, middle and tail of each coil of steel strip, and then the data average values of [C], [N], [O] and grain size are obtained by detection.

Preferably, in the step (S4), the steel coil is subjected to high-temperature annealing, and _{the temperature is raised to 650-750° C. for 20-30 hours in an atmosphere of N 2 , and} then the temperature is raised to 1200°C, the percentage of _H2 in the nitrogen-hydrogen mixture is calculated according to the formula (1), the heating rate of the 650-1000 °C heating section is calculated according to the (2) formula, and the heating rate of the 1000-1200 °C heating section is calculated according to the (3) formula calculate. Then keep it warm for 20-30 hours under pure H ₂ atmosphere, and then cool with the furnace under N ₂ atmosphere.

Wherein A: the percentage of _H in the nitrogen-hydrogen mixture;

d: Primary recrystallized grain size.

v ₁ , v ₂ : heating rate;

[Als], [N], [O]: The unit is ppm.

The design basis of the present invention is:

(1) The main inhibitor of low temperature high magnetic induction grain oriented silicon steel is AlN, its size and quantity have an important impact on the perfection of secondary recrystallization, and its size and quantity require reasonable composition control, hot rolling and normalization process Guarantee, the inhibitory ability of the inhibitor directly affects the starting temperature of the secondary recrystallization, so the formulation of the high-temperature annealing process needs to consider the influence of the inhibitory ability. When the inhibitory ability is large, the GOSS grains and other orientations The grains will be restricted, so it is necessary to accelerate the decomposition of the inhibitor to a certain extent through the atmosphere in the furnace. On the contrary, when the inhibition ability of the inhibitor is weak, it is necessary to slow down the decomposition of the inhibitor by adjusting the atmosphere in the furnace. Therefore, with the increase of [Als], [N], [O], the proportion of hydrogen in the atmosphere of high temperature annealing should be increased.

(2) The primary recrystallized grain size is affected by factors such as composition, hot rolling process, normalization process, cold rolling deformation and annealing process, so its size cannot always remain stable. In order to improve the development of secondary recrystallization, when the primary recrystallization grains are finer, the secondary recrystallization temperature is lowered, and high temperature annealing needs to accelerate the decomposition of inhibitors, weaken the inhibitor's inhibitory effect on Goss grains, and promote the development of secondary recrystallization Complete. On the contrary, it is necessary to slow down the decomposition of the inhibitor to ensure the inhibitory effect of the inhibitor on other oriented grains during the secondary recrystallization. Therefore, with the increase of the primary recrystallized grain size, the proportion of hydrogen in the high temperature annealing atmosphere should decrease.

(3) Enter the secondary recrystallization temperature range at around 1000°C. In order to prevent premature coarsening of the inhibitor, a higher heating rate is used below 1000°C, and a lower heating rate is used above 1000°C.

Compared with the prior art, a high-temperature annealing method for low-temperature high-magnetic-induction grain-oriented silicon steel according to the present invention has the following beneficial effects:

The invention discloses a high-temperature annealing method for low-temperature high-magnetic-sensitivity oriented silicon steel, that is, the heating rate in the high-temperature annealing process is determined by the composition, oxygen, nitrogen and primary recrystallized grain size in the steel after decarburization annealing, and the temperature inside the furnace atmosphere, thereby achieving the purpose of improving the magnetic properties and facilitating the precise control of the high-temperature annealing process.

Description of drawings

Fig. 1 is a schematic diagram of the overall process of the present invention.

Fig. 2 is a schematic diagram of the high temperature annealing of the present invention

Detailed ways

A specific embodiment of a high-temperature annealing method for low-temperature high-magnetic-sensitivity grain-oriented silicon steel of the present invention will be further described below in conjunction with accompanying drawings 1-2. The high-temperature annealing method of a low-temperature high-magnetic-sensitivity grain-oriented silicon steel of the present invention is not limited to the description of the following examples.

Example 1:

A high temperature annealing method for low temperature high magnetic induction oriented silicon steel. The specific steps of the high temperature annealing method are as follows:

(S1), obtain finished product thickness steel strip:

The technological process is smelting→continuous casting→heating→hot rolling→normalization→cold rolling, and its composition is calculated by mass percentage: C: 0.058%; Si: 3.11%; Mn: 0.13%; P: 0.012%; S: 0.008 %; Als: 0.023%; N: 0.0075%; Sn: 0.060%; Cr: 0.21%; Cu: 0.02%; the rest is Fe and unavoidable impurity elements. The heating temperature of the billet is 1158°C, the finishing temperature of hot rolling is 953°C, the normalization adopts 1100°C + 900°C two-stage normalization, and the total deformation rate of one cold rolling is 89.5%.

(S2), performing decarburization annealing on the cold-rolled steel strip, coiling it into a steel coil after coating magnesium oxide and sampling.

(S3) Sampling and inspecting [C], [N], [O] and grain size d at the beginning, middle and end of each roll, and finally calculating the average values are: [C]: 13.6ppm, [N]: 230ppm , [O]: 511ppm, primary recrystallized grain size: d=21.2μm.

In (S4), perform high-temperature annealing on the steel coil, raise the temperature to 650-750°C for 20-30 hours in the atmosphere of N ₂ , and then raise the temperature to 1200°C at a certain heating rate in the atmosphere of N ₂ and H ₂ . The percentage A of _H2 in the mixed gas is calculated according to the formula (1), the heating rate v ₁ of the 700-1000 °C heating section is calculated according to the (2) formula, and the heating rate V ₂ of the 1000-1200 °C heating section is calculated according to the (3) formula . Then keep it warm for 20-30 hours under pure H ₂ atmosphere, and then cool with the furnace under N ₂ atmosphere.

Substituting the data in formula (1), the percentage A of H ₂ in the nitrogen-hydrogen mixed gas is 52%, that is, the mixed gas adopts 48% N ₂ +52% H ₂ .

Substituting the data into the formula (2), the heating rate v ₁ of the heating section from 700 to 1000°C is 18°C/h.

Substitute the data into the formula (3), and the heating rate v ₂ in the heating section from 1000 to 1200°C is 10°C/h.

Example 2:

A high temperature annealing method for low temperature high magnetic induction oriented silicon steel. The specific steps of the high temperature annealing method are as follows:

(S1), obtain finished product thickness steel strip:

The technological process is smelting→continuous casting→heating→hot rolling→normalization→cold rolling, and its composition is calculated by mass percentage: C: 0.053%; Si: 3.09%; Mn: 0.14%; P: 0.010%; S: 0.007 %; Als: 0.029%; N: 0.0079%; Sn: 0.061%; Cr: 0.22%; Cu: 0.02%; the rest is Fe and unavoidable impurity elements. The heating temperature of the billet is 1153°C, the finishing temperature of hot rolling is 956°C, the normalization adopts 1100°C + 900°C two-stage normalization, and the total deformation rate of one cold rolling is 89.5%.

(S2), performing decarburization annealing on the cold-rolled steel strip, coiling it into a steel coil after coating magnesium oxide and sampling.

(S3) Sampling and inspecting [C], [N], [O] and grain size d at the beginning, middle and end of each roll, and finally calculating the average values are: [C]: 13.6ppm, [N]: 230ppm , [O]: 511ppm, primary recrystallized grain size: d=21.2μm.

In (S4), high-temperature annealing is performed on the steel coil, and the temperature is raised to 700°C in the atmosphere of N ₂ and kept for 20-30 hours, and then the temperature is raised to 1200°C at a certain heating rate in the atmosphere of N ₂ and H ₂ . The percentage A of _H2 is calculated according to formula (1), the heating rate v ₁ of the 700-1000 °C heating section is calculated according to (2), and the heating rate V ₂ of the 1000-1200 °C heating section is calculated according to (3). Then keep it warm for 20-30 hours under pure H ₂ atmosphere, and then cool with the furnace under N ₂ atmosphere.

Substituting the data in formula (1), the percentage A of H ₂ in the nitrogen-hydrogen mixed gas is 76%, that is, the mixed gas adopts 24% N ₂ +76% H ₂ .

Substituting the data into formula (2), the heating rate v ₁ of the heating section from 700 to 1000°C is 17°C/h.

Substitute the data into the formula (3), and the temperature rise rate v ₂ in the temperature rise section from 1000 to 1200°C is 8°C/h.

comparative example

The result of process control before high temperature annealing of Comparative Example 1 is completely consistent with that of Example 1.

The result of process control before high temperature annealing of Comparative Example 2 is completely consistent with that of Example 2.

The high-temperature annealing process of the comparative example: heat up to 700°C for 25 hours under _N2 atmosphere, then heat up to 1200°C at 17°C/h under ammonia decomposition gas atmosphere, then hold for 25h under pure _H2 atmosphere, and then cool with the furnace .

After warm annealing, flattening and sampling inspection were carried out. The inspection results are shown in Table 1.

<![CDATA[P_1.7/50(W/kg)]]> <![CDATA[B₈₀₀(T)]]> Example 1 1.05 1.89 Comparative example 1 1.28 1.86 Example 2 0.93 1.92 Comparative example 2 1.12 1.89

The invention discloses a high-temperature annealing method for low-temperature high-magnetic-sensitivity oriented silicon steel, that is, the heating rate in the high-temperature annealing process is determined by the composition, oxygen, nitrogen and primary recrystallized grain size in the steel after decarburization annealing, and the temperature inside the furnace atmosphere, thereby achieving the purpose of improving the magnetic properties and facilitating the precise control of the high-temperature annealing process.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be assumed that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deduction or replacement can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (8)

1. A high temperature annealing method for low temperature high magnetic induction oriented silicon steel, characterized in that: the specific steps of the high temperature annealing method are as follows: (S1), smelting according to the set composition and obtaining the billet through the continuous casting process, the billet is heated, hot-rolled, normalized, and cold-rolled to obtain a steel strip with a finished thickness; (S2), decarburization annealing is carried out to the steel strip material after cold rolling, and the steel strip after annealing is coated with magnesia and then coiled into a steel coil; (S3), sampling detection [C], [N], [O] and grain size after decarburization annealing of the steel strip; (S4), carrying out high-temperature annealing to steel coil; Among them, first raise the temperature to 700°C for 20-30 hours under N2 atmosphere, then raise the temperature to 1200°C at a certain heating rate in the atmosphere of a certain proportion of N2 and H2 mixture, and then keep it for 20-30 hours under pure H2 atmosphere. Then cool with the furnace under N2 atmosphere. 2. the high-temperature annealing method of a kind of low-temperature high-magnetic induction oriented silicon steel as claimed in claim 1, is characterized in that: the finished product thickness steel strip obtained in the described step (S1), its chemical composition is according to mass percent: C: 0.05～0.09%; Si: 2.9～3.5%; Mn: 0.05～0.15%; P: ≤0.030%; S: 0.005～0.010%; Als: 0.02～0.035%; 0.10%; Cr: ≤0.30%; Cu: ≤0.60%; the rest is Fe and unavoidable impurity elements. 3. A high temperature annealing method for low temperature high magnetic induction oriented silicon steel as claimed in claim 1, characterized in that: the finished thickness steel strip obtained in the step (S1) has a technological process of blank→heating→hot rolling →Normalization→Cold rolling, where the heating temperature of the billet is 1120-1200°C, the finishing temperature of hot rolling is 900-1000°C, the normalization adopts 1100°C+900°C two-stage normalization, and the total deformation of one-time cold rolling The rate is 86-90%. 4. A high-temperature annealing method for low-temperature high-magnetic-sensitivity grain-oriented silicon steel as claimed in claim 1, characterized in that: [C] in the steel annealed in the step (S2): ≤ 30 ppm; [N]: 150 ～300ppm; [O]: 450～1200ppm, while detecting the primary recrystallized grain size. 5. the high-temperature annealing method of a kind of low-temperature high-magnetic induction grain-oriented silicon steel as claimed in claim 1, is characterized in that: in described step (S3), take samples respectively at the head, middle and tail of each roll of steel strip, and then Detect and obtain the average value of [C], [N], [O] and grain size data. 6. A high-temperature annealing method for low-temperature high-magnetic-sensitivity grain-oriented silicon steel as claimed in claim 1, characterized in that: in the step (S4), the percentage of H2 in the nitrogen-hydrogen mixture in the heating section of 700-1200°C is as follows formula calculation:

A: The percentage of _H2 in the nitrogen-hydrogen mixture; [Als], [N], [O]: The unit is ppm. d: Primary recrystallized grain size. 7. A high-temperature annealing method for low-temperature high-magnetic-sensitivity grain-oriented silicon steel as claimed in claim 6, characterized in that: the heating rate in the 650-1000°C heating section in the step (S4) is calculated by the following formula:

V1: heating rate. 8. A high-temperature annealing method for low-temperature high-magnetic-sensitivity grain-oriented silicon steel as claimed in claim 7, characterized in that: the heating rate in the 1000-1200°C heating section in the step (S7) is calculated according to the following formula:

V1: heating rate.

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