1. A production method for improving cold rolling processability of oriented silicon steel comprises the following process flows: smelting, continuous casting, hot rolling, normalizing, acid washing, cold rolling, decarburization and nitridation, MgO coating, high-temperature annealing, insulating layer coating and hot stretching flattening; the method is characterized by comprising the following steps:

1) the oriented silicon steel comprises the chemical components with the mass percentage of C0.040% -0.060%; si3.10% -3.30%; 0.150 to 0.200 percent of Mn0; 0.010-0.030% of P; 0.0050% -0.0070% of S; al0.0250% -0.0300%; 0.0060% -0.0090% of N;

2) smelting and continuous casting: smelting according to the chemical components of the oriented silicon steel, and then continuously casting by adopting the thickness of 200 plus 250mm casting blank;

3) hot rolling: after the casting blank is subjected to heat preservation at 1120-1250 ℃ for 200-300min, the thickness of the rough rolling intermediate blank is 35-45mm, the rough rolling is performed until the thickness of a hot rolled plate is 1.80-2.30mm, the finish rolling temperature is 945-965 ℃, and the hot rolled plate is coiled after laminar cooling to 560-600 ℃;

4) normalizing: adopting a two-stage normalizing process system, wherein the first-stage normalizing temperature is 1080-1120 ℃, the time is 40-60s, the second-stage normalizing temperature is 880-920 ℃, the time is 120-250s, the transverse sectional cooling water distribution of the strip steel is started at 800-830 ℃ to refine edge tissues and inhibit the cold rolling edge crack of the oriented silicon steel, the middle part of the strip steel is a middle section, the two lateral edges of the strip steel of the middle section are an outer section and an edge section in sequence, and the cooling water quantity of the middle section is 50-85m³The cooling water amount of the outer section is 25-50m³The amount of cooling water in the edge section is 0 to 25m³/h；

5) Cold rolling: performing five-pass rolling, and cold-rolling the steel plate to the thickness of a finished product;

6) decarburization and nitridation: h₂+N₂Mixed and humidified atmosphere is subjected to decarburization treatment at 800-900 ℃ for 5-10min, and NH is carried out at 820-910 DEG C₃Coating MgO coating liquid after nitriding treatment;

7) high-temperature annealing: carrying out high-temperature annealing in an annular furnace to finish secondary recrystallization and purification annealing;

8) hot stretching and flattening: and (5) preparing an oriented silicon steel finished product through processes of stretching, flattening and coating an insulating layer, and detecting the magnetic property.

2. The production method for improving the cold rolling workability of the oriented silicon steel according to claim 1, wherein the width of the middle section in the step 4) is 3/10-4/10 of the width of the strip steel, and the width of the side sections is 1/10-2/10 of the width of the strip steel.

Background

The grain-oriented silicon steel generally contains 3.0 to 3.4% of silicon element, and its cold rolling workability is deteriorated due to the solid solution strengthening effect of silicon. Production practices show that the ductile-brittle transition of the oriented silicon steel is extremely sensitive to the rolling temperature, brittle failure accidents are easy to happen 3 times before cold rolling or in the starting moment, and the cold rolling stability and the production efficiency are improved to be adversely affected, so that the cold rolling process becomes one of the technical bottlenecks in quality improvement and efficiency improvement of the oriented silicon steel. Besides external factors such as the cold rolling process conditions of the oriented silicon steel, the cold rolling processing performance of the oriented silicon steel is a main internal factor influencing the improvement of the yield. Therefore, the technical key of breaking through the cold rolling bottleneck is to improve the cold rolling processing performance by regulating and controlling the structure state before rolling to improve the intercrystalline bonding strength and inhibit the crack initiation condition.

After hot rolling and normalizing treatment are carried out on oriented silicon steel produced by the traditional method, coarse surface grains and pearlite hard phases are easily formed on the structure (particularly the edge of a strip steel) before cold rolling, the inter-crystalline bonding force is weakened, the structure is unevenly deformed, cracks are initiated and expanded, and further the cold rolling processability and the yield are reduced. The invention provides a production method for improving cold rolling processability of oriented silicon steel, which realizes differentiated regulation and control of tissues before rolling and tissues at edges by controlling a normalizing temperature system and a cooling process, improves cold rolling processability of the oriented silicon steel, inhibits the formation and expansion of edge cracks, and ensures good product magnetic performance while improving cold rolling yield.

Disclosure of Invention

The invention aims to solve the technical problem of providing a production method for improving the cold rolling processability of oriented silicon steel, improving the cold rolling processability of the oriented silicon steel, inhibiting the edge crack initiation and expansion to improve the cold rolling yield, and simultaneously ensuring the stability and reliability of the product quality.

In order to achieve the purpose, the invention adopts the following technical scheme:

a production method for improving cold rolling processability of oriented silicon steel comprises the following process flows: smelting, continuous casting, hot rolling, normalizing, acid washing, cold rolling, decarburization and nitridation, MgO coating, high-temperature annealing, insulating layer coating and hot stretching flattening; the method specifically comprises the following steps:

1) the chemical components of the oriented silicon steel are shown in the table 1;

table 1: chemical composition of oriented silicon steel (wt.%)

2) Smelting and continuous casting: smelting according to the chemical components of the oriented silicon steel, and then continuously casting by adopting the thickness of 200 plus 250mm casting blank;

3) hot rolling: after the casting blank is subjected to heat preservation at 1120-1250 ℃ for 200-300min, the thickness of the rough rolling intermediate blank is 35-45mm, the rough rolling is performed until the thickness of a hot rolled plate is 1.80-2.30mm, the finish rolling temperature is 945-965 ℃, and the hot rolled plate is coiled after laminar cooling to 560-600 ℃;

4) normalizing: a two-stage normalizing process system is adopted, wherein the first-stage normalizing temperature is 1080-1120 ℃, the time is 40-60s, the second-stage normalizing temperature is 880-920 ℃,starting to distribute and refine edge tissues of the strip steel in a transverse sectional type by cooling water at 800-830 ℃ for 250 seconds, inhibiting cold rolling edge cracks of the oriented silicon steel, wherein the middle part of the strip steel is a middle section, two sides of the middle section are an external section and an edge section in sequence towards the edge of the strip steel, and the cooling water quantity of the middle section is 50-85m³The cooling water amount of the outer section is 25-50m³The amount of cooling water in the edge section is 0 to 25m³/h；

5) Cold rolling: performing five-pass rolling, and cold-rolling the steel plate to the thickness of a finished product;

6) decarburization and nitridation: h₂+N₂Mixed and humidified atmosphere is subjected to decarburization treatment at 800-900 ℃ for 5-10min, and NH is carried out at 820-910 DEG C₃Coating MgO coating liquid after nitriding treatment;

7) high-temperature annealing: carrying out high-temperature annealing in an annular furnace to finish secondary recrystallization and purification annealing;

8) hot stretching and flattening: and (5) preparing an oriented silicon steel finished product through processes of stretching, flattening and coating an insulating layer, and detecting the magnetic property.

The width of the middle section in the step 4) is 3/10-4/10 strip steel width, and the width of the side section is 1/10-2/10 strip steel width.

Compared with the prior art, the invention has the beneficial effects that:

0.040-0.060% of C and 3.10-3.30% of Si are adopted, and the formation of an inhibitor is controlled by combining 0.150-0.200% of Mn, 0.0050-0.0070% of S and 0.0250-0.0300% of Als of inhibitor elements so as to ensure the performance of a finished product, and meanwhile, the magnetism is ensured and the strip steel is prevented from being embrittled by 0.010-0.030% of P.

The method is characterized in that the surface grain size and the second phase structure volume fraction of a hot rolling structure are regulated and controlled by reducing the thickness of a medium billet and increasing the finish rolling temperature and the coiling temperature, the grain size of the surface grain is refined to inhibit the grain-oriented expansion of cracks, and the microcracks generated by uneven deformation between ferrite and pearlite are reduced, so that the condition for inhibiting the initiation of the cracks in the cold rolling process is realized.

The coarse ferrite structure and the pearlite volume fraction of the surface layer of the normalizing plate are regulated and controlled by controlling the starting temperature of strip steel water cooling and controlling the transverse cooling water quantity in a segmented mode. The water cooling starting temperature of the strip steel is reduced, so that the crystal grain size of the ferrite on the surface layer can be effectively reduced, the volume fraction of pearlite is reduced, and the formation of micro cracks in the strip steel can be inhibited. Through a sectional type cooling regulation and control mode, the volume fraction of pearlite at the edge of the strip steel is further reduced, so that the inhibiting effect of the material structure condition on crack formation and expansion is enhanced.

The invention reduces the grain size of the surface layer before rolling by 5-10 mu m, reduces the volume fraction of pearlite by 6 percent, obviously improves the cold rolling processability of rolled materials and can improve the yield by more than 8 percent by regulating and controlling the thickness of a hot rolling medium blank, the finish rolling temperature, the coiling temperature, the normalized cooling water quantity and the control mode. Through the subsequent processes of cold rolling, decarburization annealing, high-temperature annealing and the like, the perfect secondary recrystallization texture and good magnetic performance can be ensured.

Drawings

In FIG. 1, a is a microstructure diagram of a hot rolled surface layer of example 2, corresponding to a grain size of 23.71 μm and a pearlite volume fraction of 5.26%; b is the microstructure of the hot rolled subsurface layer of example 2, corresponding to a grain size of 16.46 μm and a pearlite volume fraction of 8.15%; c is the hot rolled core microstructure of example 2, corresponding to a grain size of 9.75 μm and a pearlite volume fraction of 10.25%.

FIG. 2A is a microstructure diagram of a hot rolled surface layer of comparative example 3, corresponding to a grain size of 25.47 μm and a pearlite volume fraction of 11.83%; b is a microstructure diagram of a hot-rolled subsurface layer of comparative example 3, corresponding to a grain size of 23.48 μm and a pearlite volume fraction of 13.54%; c is a hot-rolled core microstructure of comparative example 3, corresponding to a grain size of 21.87m and a pearlite volume fraction of 18.27%.

In FIG. 3, a is a view of the normalized surface microstructure of example 2, corresponding to a grain size of 39.30 μm and a pearlite volume fraction of 2.15%; b is the normalized sub-surface microstructure of example 2, corresponding to a grain size of 22.88 μm and a pearlite volume fraction of 10.53%; c is the normalized core microstructure of example 2, corresponding to a grain size of 22.12m and a pearlite volume fraction of 13.89%.

In FIG. 4, a is a fibrous structure diagram of the normalized surface layer of comparative example 3, corresponding to a grain size of 40.57 μm and a pearlite volume fraction of 4.78%; b is the normalized sublayer fiber structure of comparative example 3, corresponding to a grain size of 25.31 μm and a pearlite volume fraction of 10.96%; c is the fibrous structure diagram of the normalized core layer of comparative example 3, corresponding to a grain size of 10.79m and a pearlite volume fraction of 17.19%.

FIG. 5 is the texture map of the product of example 2, which has undergone complete secondary recrystallization and magnetic properties of AG 100.

FIG. 6 is a structural diagram of the product of comparative example 3, which has undergone complete secondary recrystallization and magnetic properties of AG 100.

Detailed Description

The invention is further illustrated by the following examples:

the following examples describe the invention in detail. These examples are merely illustrative of the best embodiments of the present invention and do not limit the scope of the invention.

A production method for improving cold rolling workability of oriented silicon steel comprises the following steps:

1. process flow

Smelting → continuous casting → hot rolling → normalizing → iron scale removing → cold rolling → decarburization and nitriding → coating MgO → high temperature annealing → hot stretch leveling and coating insulating film

2. Process parameters

(1) Smelting and continuous casting: the thickness of a casting blank smelted according to the conventional high magnetic induction oriented silicon steel component is 230 mm. The ingredients of the examples are shown in Table 2.

Table 2: examples oriented silicon steel chemistry (wt.%)

Scheme(s)	C	Si	Mn	P	S	Als	N
								Example 1	0.043	3.13	0.152	0.013	0.0053	0.0255	0.0065
Example 2	0.048	3.18	0.157	0.019	0.0058	0.0265	0.0071
								Example 3	0.053	3.20	0.166	0.018	0.0061	0.0272	0.0075
Example 4	0.056	3.24	0.177	0.023	0.0062	0.0279	0.0078
								Example 5	0.055	3.26	0.173	0.025	0.0068	0.0283	0.0084
Example 6	0.058	3.28	0.198	0.025	0.0068	0.0297	0.0088

(2) Hot rolling: heating the casting blank to 1150 ℃, preserving the heat for 200-.

(3) Normalizing: after normalizing treatment at 1080 ℃ multiplied by 35s +900 ℃ multiplied by 80s and 1100 ℃ multiplied by 32s +900 ℃ multiplied by 72s, the strip steel is slowly cooled to 800 ℃ multiplied by 830 ℃, the transverse sectional type cooling water distribution of the strip steel is carried out to refine edge tissues, the cold rolling edge crack of the oriented silicon steel is inhibited, the middle part of the strip steel is a middle section, and the two sides of the middle section to the strip steel edge parts are an external section and an edge in sequenceThe cooling water quantity of the middle section is 50-85m³The cooling water amount of the outer section is 25-50m³The amount of cooling water in the edge section is 0 to 25m³/h；

The example strip was wide (1070mm), mid-section wide (320mm), outer section wide (215mm), and edge section wide (160 mm). Examples hot rolling and normalization process parameters are shown in table 3.

Table 3: hot rolling and normalizing process parameters

(4) And (5) cold rolling. The cold rolling is performed by 5-pass reversible rolling with a total reduction of 87%, wherein the pass reductions are evenly distributed, and the steel plate is rolled to 0.27 mm.

(5) And (4) decarburization and nitridation. Heating the decarburization annealing to 850 ℃ at the speed of 900 ℃/min and keeping the temperature at 25% H₂+75％N₂、P_H2O/P_H2Keeping the temperature for 8min under the annealing and humidifying atmosphere of 0.6, and decarburizing and annealing the carbon to be less than 30 ppm. By NH₃Nitriding the medium at 840 ℃, coating MgO coating liquid on the surface of the steel strip, heating to 550 ℃ and drying.

(6) And (6) high-temperature annealing. Annealing at high temperature in N₂Heating to 650 ℃ at the speed of 50 ℃/H in the protective atmosphere, preserving the temperature for 9H, and then keeping the temperature at 25% H₂+75％N₂Heating to 1200 ℃ at a speed of 16 ℃/h under the mixed atmosphere, preserving heat for 24h, completing secondary recrystallization, cooling to 300 ℃ along with the furnace, discharging, purifying and removing impurities.

(7) And (4) hot stretching and flattening. And (3) carrying out hot drawing leveling annealing, coating the insulating coating liquid, drying, carrying out annealing treatment at 850 ℃, and testing the magnetic property of the product.

Comparative example

The production method of the cold rolling processability of the oriented silicon steel comprises the following process flows: smelting → continuous casting → hot rolling → normalizing → iron scale removing → cold rolling → decarburization annealing → nitriding → coating MgO → high temperature annealing → hot stretch leveling and coating insulating film. The ingredients of the comparative examples are shown in Table 4.

Table 4: comparative example ingredients (wt.%)

Scheme(s)	C	Si	Mn	P	S	Als	N
								Comparative example 1	0.050	3.20	0.185	0.012	0.0055	0.0263	0.0065
Comparative example 2	0.055	3.25	0.173	0.018	0.0062	0.0282	0.0073
								Comparative example 3	0.057	3.22	0.167	0.027	0.0068	0.0300	0.0085

Comparative example hot rolling and normalization processes are shown in table 5.

Table 5: comparative examples Hot Rolling and normalizing Process parameters

The embodiment provided by the invention can effectively improve the cold rolling yield and ensure good product magnetic performance while improving the cold rolling processability of the oriented silicon steel. The results of the comparison of the cold rolling yield and the magnetic properties of the examples and comparative examples are shown in Table 6.

Table 6: cold rolling yield and magnetic property comparison of examples and comparative examples

Example 2 the hot rolled microstructure is shown in figure 1.

Comparative example 3 the hot rolled microstructure is shown in figure 2.

The grain size and pearlite volume fraction of the hot rolled surface layer are compared in Table 7.

Table 7: grain size and pearlite volume fraction comparison of hot rolled surface layer

As can be seen from fig. 1, fig. 2 and table 7, the method of the present invention is effective in reducing the grain size and pearlite volume fraction of the hot rolled surface layer.

Example 2 normalized microstructure is shown in figure 3.

Comparative example 3 normalized microstructure is shown in fig. 4.

The grain size and pearlite volume fraction of the surface layer of the structures of examples and comparative examples are compared in Table 6.

Table 6: comparison of superficial grain size and pearlite volume fraction of structures of examples and comparative examples

As can be seen from fig. 3, fig. 4 and table 6, the method of the present invention can effectively reduce the surface grain size and the pearlite volume fraction of the normalized (before rolling) structure, thereby achieving the effect of inhibiting crack initiation and propagation.

The microstructure of the product of example 2 is shown in figure 5.

The microstructure of the product of comparative example 3 is shown in FIG. 6.

As can be seen from FIGS. 5 and 6, perfect secondary recrystallization can occur in both the examples and the comparative examples.