RU2550440C2 - Method of production of random-orientation electrotechnical steel plates without rising defect - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to metallurgy, particularly to production of random-orientation electrotechnical steel plates. The slab is made out of steel with the following chemical composition in wt %: C < 0.005, Si from 1.2 to 2.2, Mn from 0.2 to 0.4, P < 0.2, S < 0.005, Al from 0.2 to 0.6, N < 0.005, O < 0.005, Fe and inevitable admixtures - rest, by melting in the converter, pre-treatment of hot metal by circulating affinage and continuous casting, at that cooling water quantity during secondary cooling is monitored ensuring its flow rate 100-190 l/min, and average level of liquid steel overheating during continuous casting is monitored at level 10-45°C. The slab is heated and subjected to hot rolling, including roughing and burnishing, at that the slab heating temperature is 1050-1150°C, temperature difference between two any points along the slab length during its heating is below 25°C, and input temperature of the burnishing process is at least 970°C. Etching by acid, cold rolling, annealing and coating application are performed.

EFFECT: produced steel plates have excellent magnetic properties and are not prone to rising defects.

5 dwg

Description

Field of Invention

The present invention relates to a method for the production of electrotechnical sheet steel, in particular a non-textured middle-class electrotechnical sheet steel without a defect of riser having excellent magnetic properties.

State of the art

In the production of non-textured electrical steel sheets with a high silicon content, uneven waves appear on the surface of the finished strip in the rolling direction, resembling corrugation, which is usually called a “defect in height”. This defect significantly reduces the stacking coefficient of the finished strip, worsens the magnetic properties of the finished strip and reduces the electrical resistance between the layers of the insulating film, which reduces the performance and service life of the final products. Therefore, almost all consumers clearly require the prevention of riser defects in the finished strip.

The mechanism of the formation of growth defects can be explained as follows: the coefficient of equiaxed crystals in the slab is low, while the columnar crystal is large and continues to grow. The growth direction of the columnar crystal <001>, which is the normal direction (001), is the direction of the largest heat flux gradient. During the hot rolling process, a large columnar crystal cannot break to the end due to dynamic return and slow recrystallization. However, columnar crystals of the slab easily grow in the direction of the heat flux and form large columnar crystals with a certain orientation, which leads to inhomogeneous deformations during the rolling process, the center of the sheet thickness after hot rolling has a mainly fibrous texture, and austenite and ferrite in the subsequent process do not have phase transitions and cannot recrystallize in subsequent processes of cold rolling and annealing, which does not eliminate the heterogeneity of the texture, which goes into the final product, as a result of formed on the uneven defective riser.

The traditional methods for dealing with defects of growth are mainly as follows: by using electromagnetic stirring, the coefficient of equiaxed crystals in a slab can be improved, for example, according to Japanese patent application JP 49-39526; by adding carbon and manganese to the steel, it is possible to lower the phase transition temperature during hot rolling, for example, according to Japanese patent application JP 48-49617, Chinese patent applications CN 10127519, CN 1548569 and CN 101139681, etc .; due to the use of casting at low temperature, the coefficient of equiaxed crystals in the slab can be improved, for example, according to Japanese patent applications JP 53-14609 and JP 2-192853; by increasing the temperature of the outlet of the furnace for the slab, adjusting the rate of heating of the slab, controlling the temperature of the final rolling during smoothing and controlling the degree of decrease in the first and last pass of the hot rolling process, sufficient strip recrystallization can be achieved, for example, according to Japanese patent applications JP 49-27420 , JP 49-38813, JP 53-2332 and JP 61-69923, as well as Chinese patent applications CN 1611616 and CN 1548569; by applying the normalization process, sufficient recrystallization of the strip can be achieved, for example according to Japanese Patent Application JP 61-127817, etc.

The above methods can be used individually or together depending on the technology, costs and requirements for the magnetic properties of the final product and surface. The characteristics and requirements of these methods are described below.

By using electromagnetic stirring, the coefficient of equiaxed crystals in the slab can be improved. This method uses electromagnetic stirring, columnar crystals can break under the influence of electromagnetic force, and therefore this method is most effective. It significantly reduces the coefficient of columnar crystals in the slab and improves the coefficient of equiaxed crystals in the slab, especially when using electromagnetic stirring twice or more times, and also effectively prevents the formation of a secondary columnar crystal in the central region. The main disadvantage of this method is that the mixing effect depends on the silicon content in the steel and on the number of electromagnetic mixing. In the case of a steel grade with a low silicon content, after primary electromagnetic stirring, equiaxed crystals in a slab are relatively easy to combine, grow and again form a large columnar crystal, and thus it is necessary to use electromagnetic stirring twice or more times and strictly control the solidification effect of liquid steel. In addition, the manufacturing costs of electromagnetic stirring are very high.

By adding carbon and manganese to the steel, the phase transition temperature in the hot rolling process can be reduced. This method is mainly performed by adding carbon and manganese to steel, while in the slab a phase transition occurs during heating and hot rolling, dynamic return and recrystallization are accelerated, which avoids large deformed crystalline grains. The main disadvantage of this method is the need to perform decarburization during the annealing process, as a result of which the inner oxide layer and the inner nitrided layer are easily formed, worsening the magnetic properties of steel.

By using casting at low temperature, the coefficient of equiaxed crystals in the slab can be improved. This method allows to reduce the coefficient of columnar crystals in the slab and improves the coefficient of equiaxed crystals, mainly by reducing the overheating of molten steel during the casting process. The main disadvantage of this method is that it requires a very low range of overheating of liquid steel, which is difficult to effectively control, and this also affects the normal control during continuous casting.

By increasing the temperature of the output of the furnace for the slab, adjusting the rate of heating of the slab, controlling the temperature of the final rolling during smoothing and controlling the degree of decrease in the first and last pass of the hot rolling process, it is possible to achieve sufficient recrystallization of the strip. This method is mainly performed by increasing the temperature of the outlet of the furnace for the slab, adjusting the rate of heating of the slab, controlling the temperature of the final rolling during smoothing and controlling the degree of decrease in the first and last pass of the hot rolling process, while large columnar crystals in the slab can break, which helps prevent the formation of large deformed crystalline grains and achieve sufficient recrystallization of the strip. The main disadvantage of this method is that with an increase in the outlet temperature of the furnace for the slab, intensive dissolution of such impurities as MnS, AlN, etc. occurs, which impairs the magnetic properties of the finished strip. At the same time, to ensure the effect of recrystallization of the strip, strict requirements are imposed on the content of impurity elements such as sulfur S, nitrogen N, etc. in the steel. In addition, the improvement in the degree of reduction in the first and last pass of the hot rolling process is limited by the capabilities of the rolling mill.

By using the normalization process, sufficient recrystallization of the strip can be achieved. When using the single cold rolling method for a class of steel with a high silicon content, it is necessary to carry out the normalization process, and one of the goals is to increase the recrystallization coefficient of the hot-rolled sheet to prevent the occurrence of riser defects. The main disadvantage of this method is the very high production costs, which is not applicable for low and medium grade electrical steel, the additional surplus value of which is relatively small.

Disclosure of invention

The invention is faced with the task of creating a non-textured electrical steel sheet without a defect of risers, as well as a method for its production. The production of medium-grade non-textured electrical steel sheet without a defect of growth, which has such advantages as simplicity of processes, low cost, energy saving and environmental protection, as well as excellent magnetic properties of steel can be achieved by exercising strict control over the cooling rate of the slab during continuous casting and pouring over the temperature difference along the length of the slab inside the heating furnace, as well as due to the control over the temperature difference before ironing iem slab. At the same time, the speed of slab casting during continuous casting and casting is normal, which allows us to maintain a relatively high level of overheating of liquid steel and a relatively low temperature of the furnace output for the slab, as well as the normal temperature of the final rolling, the temperature of coiling, etc. in the process of hot rolling and heating of steel, so that it is not necessary to perform the process of normalizing the strip when performing hot rolling.

The problem in the present invention is solved by the technical solution described below.

Non-textured electrical steel sheet without a defect of risers, the chemical composition of which includes, wt.%: C: <0.005, Si: 1.2-2.2, Mn: 0.2-0.4, P: <0.2, S : <0.005, Al: 0.2-0.6, N: <0.005, O: <0.005, Fe and unrecoverable impurities - the rest.

In embodiments of the present invention, the proportion of carbon C is not more than 0.005 wt.%. Element C actively inhibits the growth of crystalline grains, which easily leads to an increase in iron loss in the strip, causing significant magnetic aging. At the same time, carbon C can additionally expand the γ phase, increase the number of transitions between the α and γ phases during normalization, which significantly reduces the ACl point and increases the fine-grained crystalline structure. Therefore, the carbon content C must be controlled at a level of not more than 0.005 wt.%.

The proportion of silicon Si is 1.2-2.2 wt.%. The Si element effectively increases the electrical resistance of steel. When the silicon Si content is less than 1.2 wt.%, The electromagnetic properties of the steel turn out to be poor, and when the silicon Si content is more than 2.2 wt.% During the hot rolling process, no phase transition occurs and the properties of the steel during cold processing are poor.

The proportion of aluminum Al is 0.2-0.6 wt.%. The Al element effectively increases the electrical resistance of steel. When the content of aluminum Al is less than 0.2 wt.%, The electromagnetic properties are unstable, and when the content of aluminum Al is more than 0.6 wt.%, The process of smelting and pouring is complicated, which leads to an increase in production costs.

The proportion of manganese Mn is 0.2-0.4 wt.%. Like the Si and Al elements, the Mn element can increase the electrical resistance of steel, as well as improve the surface condition of electrical steel, so it is necessary to add at least 0.2 wt.% Manganese Mn. When the manganese content of Mn is more than 0.4 wt.%, The smelting and pouring process is complicated, which leads to an increase in production costs.

The proportion of phosphorus P is not more than 0.2 wt.%. The addition of phosphorus to steel can improve the machinability of the steel sheet, however, when the phosphorus content is more than 0.2 wt.%, The machinability of the steel strip during cold rolling, on the contrary, worsens.

The proportion of sulfur S is not more than 0.005 wt.%. When the sulfur content S is more than 0.005 wt.%, The volume of sulfide deposition, for example, manganese sulfide MnS, sharply increases, which actively inhibits the growth of crystalline grains and increases iron loss.

The proportion of nitrogen N is not more than 0.005 wt.%. When the nitrogen content N is more than 0.005 wt.%, The precipitation of nitrides, for example, aluminum nitride AlN, sharply increases, which actively inhibits the growth of crystalline grains and increases iron loss.

The proportion of oxygen O is not more than 0.005 wt.%. When the oxygen content of O more than 0.005 wt.% Sharply increases the content of impurities of oxidation products, such as aluminum oxide Al ₂ O ₃ that actively inhibits the growth of crystalline grains and increases iron loss.

Proposed in the present invention, a method for the production of non-textured electrical steel sheet without defect risers includes the following steps:

1) the content of elements in the chemical compositions of non-textured electrical steel sheet is as follows, wt.%: C <0.005, Si from 1.2 to 2.2, Mn from 0.2 to 0.4, P <0.2, S <0.005 , Al from 0.2 to 0.6, N <0.005, O <0.005, Fe and fatal impurities - the rest; first, a slab is obtained by pretreating hot metal, smelting in a converter, circulating refining and continuous casting and pouring, while controlling the amount of water in the secondary cooling, the flow of cooling water being controlled at 100-190 l / min, and the average level of overheating of liquid steel in the process of continuous casting is controlled at a level of 10-45 ° C;

2) the slab is heated and subjected to hot rolling; the outlet temperature of the furnace for the slab is 1050-1150 ° C, the temperature difference between two randomly selected points in the longitudinal direction of the slab when it is heated is less than 25 ° C, and the hot rolling process involves rough rolling and smoothing, and the inlet temperature for the process smoothing not lower than 970 ° C;

3) the final sheet of non-textured electrical steel is obtained after acid pickling, cold rolling, annealing and coating.

A method for the production of a non-textured medium grade non-textured electrical steel sheet of the present invention comprises the following steps.

The average level of overheating of molten steel during casting is controlled at 10-45 ° C. In the process of continuous casting and pouring, the flow rate of cooling water is regulated at the level of 100-190 l / min in order to improve the coefficient of equiaxed crystals in the slab and to avoid the appearance of large and growing columnar crystals in the slab.

Avoid low temperatures that affect the surface temperature of the slab, leading to insufficient recrystallization of the strip. Thus, the temperature difference between two randomly selected points in the longitudinal direction of the slab when it is heated is controlled so that it is below 25 ° C; the temperature difference between the slab water level marks is limited to 25 ° C, while the slab stay in the zone after firing should be at least 45 minutes to ensure uniform heating, as a result of which the temperatures of both surfaces of the slab take close values.

The outlet temperature of the furnace for the slab can be reduced to a value not exceeding 1150 ° C to prevent the intensive dissolution of impurities such as MnS, AlN, etc., which would otherwise impair the magnetic properties of the finished strip. A hot-rolled sheet is rolled to a thickness of 2.0 mm to 2.8 mm. Before performing rough rolling and smoothing, profits are used to insulate the slab and intermediate bar, while the inlet temperature for the smoothing process is regulated at a level not lower than 970 ° C to ensure sufficient recrystallization, the temperature of the final rolling is regulated at about 850 ° C, and the temperature Roll-up - at around 600 ° C.

By hot rolling, a thick strip with a thickness of 0.5 mm is obtained, and then continuous annealing is performed in a dry atmosphere. In the process of continuous annealing, the electromagnetic properties of the steel are further improved by quickly heating the finished strip in the preheating zone, in which the heating rate is at least 1000 ° C / min, as well as by controlling the atmospheric regime in the furnace.

In accordance with the requirements for the regulation of the composition in the present invention, after the silicon content in the steel exceeds 2.2 wt.%, When not using electromagnetic stirring or using weak electromagnetic stirring, due to the relatively high silicon content, the columnar crystal in the slab will be large and growing and the forces of electromagnetic mixing will not be enough to destroy columnar crystals, while part of the broken columnar crystals will polymerize and grow s back, resulting in small equiaxed crystal ratio in the slab will be relatively low, and the ratio of large and growing columnar crystals - is relatively high. Therefore, it is necessary to increase the intensity of electromagnetic mixing in order to control the appearance of riser defects on the surface of the finished strip.

In the present invention, when the silicon content is less than 2.2 wt.%, The volume of silicon does not affect the growth of columnar crystals as much as the cooling rate of the slab, so that the flow rate of cooling water during continuous casting can be adjusted so as to reduce the gradient of heat flow of the slab in the direction of growth of columnar crystals, which allows to effectively reduce the coefficient of large and growing columnar crystals. In addition, since during the heating of the slab its temperature at the point of contact with the roller table is relatively low, which affects the recrystallization of the fibrous texture inside the slab and does not eliminate the heterogeneity of the texture that goes into the final product, it is necessary to strictly control the temperature of the slab at the water level mark. The inlet temperature for the smoothing process is improved mainly in order to facilitate the destruction and disappearance of columnar crystals during the rolling process and to improve the recrystallization coefficient of the fibrous texture in the hot rolled strip.

In addition, since the silicon content does not exceed 1.2 wt.%, The phase transition from phase γ to phase α during hot rolling is sufficient and there are no riser defects on the surface of the finished product.

Also, when using two or three pairs of rollers for electromagnetic mixing, it is possible to achieve the destruction of columnar crystals in the slab due to the high intensity of electromagnetic mixing, as well as their transition into small equiaxed crystals, which will significantly improve the coefficient of equiaxed crystals in the slab; either there is a phase transition from phase γ to phase α inside the slab with a significant increase in the temperature of the outlet of the furnace for the slab during heating, and the recrystallization of the slab is improved by using high temperature to increase the structure of the recrystallization inside the slab. In addition to a significant increase in equipment costs and energy consumption, it is more important that the technology of electromagnetic mixing is difficult to accurately combine with overheating of liquid steel, and if the overheating of liquid steel is not properly controlled, the regulatory effect of electromagnetic mixing is unstable, as a result of which it is difficult to achieve the expected effect; with an increase in the outlet temperature of the furnace for the slab, the distribution of the heat load in the heating furnace is redirected, making the temporary high temperature zone relatively long, which affects the magnetic properties of the finished strip. This method easily leads to mass defects along the edge of the strip for a class of steel with a high silicon content.

Provided that a special chemical composition is used in accordance with the present invention, the flow rate of cooling water during continuous casting can be adjusted to reduce the heat flux gradient of the slab in the direction of growth of columnar crystals, which can effectively reduce the coefficient of large and growing columnar crystals. More importantly, this method significantly affects the change in the overheating of liquid steel, so the scope is relatively wide. Moreover, the correction of the cooling water flow is a very simple and easily adjustable operation, therefore, the complexity of implementation is low, the stability is good. In addition, the load on the equipment can be reduced by using a lower outlet temperature of the furnace for the slab, which prevents the precipitation of small impurities in steel and affects the magnetic properties of the final product. If a low temperature is used to heat the slab, it is possible to adjust the slab temperature at water level marks to increase the coefficient of recrystallization of the fibrous structure of the slab during hot rolling and to improve the uniformity of the texture of the slab in the hot rolled strip, which helps to eliminate the defects of growth on the surface of the finished strip.

Brief Description of the Drawings

Figure 1 schematically shows the relationship between the flow rate of cooling water and the coefficient of equiaxed crystals in the slab.

Figure 2 schematically shows the relationship between the inlet temperature for the hot rolling process and smoothing and the frequency of occurrence of riser defects in the final product.

Figure 3 schematically shows the relationship between the temperature of the release of the furnace for the slab and the magnetic properties of the final product.

Figure 4 shows the image of the metallographic structure of the strip during hot rolling at a temperature at the water level mark of 20 ° C.

Figure 5 shows the image of the metallographic structure of the strip during hot rolling at a temperature at the water level mark of 35 ° C.

The best embodiment of the invention

Further, the present invention is described with specific examples of its implementation with reference to the drawings.

Option 1.

The chemical composition of the liquid steel in the tundish during continuous casting is regulated as follows: C 0.001 wt.%, Si 1.22 wt.%, Mn 0.25 wt.%, P 0.02 wt.%, S 0.003 wt.%, Al wt / 0.33%, N 0.001 wt.%, About 0.004 wt.%, And a residue consisting of iron Fe and fatal impurities. The average superheat of liquid steel is 34.6 ° C, the casting speed is 1.07 m / min, the cooling water flow rate is 185 l / min, the rate of decrease in slab temperature is 11.6 min / ° C, the surface temperature of the slab at the exit of the foundry machines - 710 ° C, the coefficient of equiaxed crystals - 43%. In a heating furnace, the temperature difference between the water level marks is 22 ° C; the slab remains in the zone after firing for 46 minutes. The rolling process is carried out after heating for 3 hours at a temperature of 1125 ° C, the inlet temperature for the smoothing process is 978 ° C, the temperature of the final rolling is 856 ° C, and the temperature of the coiling is 567 ° C. The hot-rolled sheet is rolled to obtain a strip with a thickness of 0.5 mm by a single cold rolling method, and then continuous annealing is performed in a dry atmosphere. No surface defects are formed on the surface of the finished strip, iron loss is 4.743 W / kg, and magnetic induction is 1.727 T.

Option 2

The chemical composition of the molten steel in the tundish during continuous casting is controlled as follows: C 0.002 wt.%, Si 1.42 wt.%, Mn 0.30 wt.%, P 0.06 wt.%, S 0.002 wt.%, Al 0.25 wt.%, N 0.002 wt.%, O 0.002 wt.%, And a residue consisting of iron Fe and fatal impurities. The average superheat of liquid steel is 31.4 ° C, the casting speed is 1.04 m / min, the cooling water flow rate is 175 l / min, the rate of decrease in slab temperature is 9.6 min / ° C, the surface temperature of the slab at the exit of the foundry machines - 680 ° C, the coefficient of equiaxed crystals - 57%. In a heating furnace, the temperature difference between the water level marks is 22 ° C, and the slab remains in the zone after firing for 48 minutes. The rolling process is carried out after heating for 3 hours at a temperature of 1135 ° C, the inlet temperature for the smoothing process is 973 ° C, the temperature of the final rolling is 853 ° C, and the temperature of coiling is 563 ° C. The hot-rolled sheet is rolled to obtain a strip with a thickness of 0.5 mm by a single cold rolling method, and then continuous annealing is performed in a dry atmosphere. No surface defects are formed on the surface of the finished strip, iron loss is 3.130 W / kg, and magnetic induction is 1.741 T.

Option 3

The chemical composition of the liquid steel in the tundish during continuous casting is controlled as follows: C 0.002 wt.%, Si 1.49 wt.%, Mn 0.49 wt.%, P 0.02 wt.%, S 0.003 wt.%, Al 0.59 wt.%, N 0.001 wt.%, O 0.002 wt.%, And a residue consisting of iron Fe and fatal impurities. The average overheating of liquid steel is 28.7 ° C, the casting speed is 0.99 m / min, the cooling water flow rate is 189 l / min, the rate of decrease in slab temperature is 8.7 min / ° C, the surface temperature of the slab at the exit of the foundry machines - 660 ° C, the coefficient of equiaxed crystals - 63%. In a heating furnace, the temperature difference between the water level marks is 24 ° C, the residence time of the slab in the zone after firing is 53 minutes. The rolling process is carried out after heating for 3 hours at a temperature of 1102 ° C, the inlet temperature for the smoothing process is 983 ° C, the temperature of the final rolling is 854 ° C, and the roll-up temperature is 575 ° C. The hot-rolled sheet is rolled to obtain a strip with a thickness of 0.5 mm by a single cold rolling method, and then continuous annealing is performed in a dry atmosphere. No surface defects are formed on the surface of the finished strip, iron loss is 3,559 W / kg, and magnetic induction is 1,737 T.

Option 4

The chemical composition of the molten steel in the tundish during continuous casting is controlled as follows: C 0.001 wt.%, Si 2.12 wt.%, Mn 0.25 wt.%, P 0.01 wt.%, S 0.002 wt.%, Al 0.36 wt.%, N 0.001 wt.%, O 0.004 wt.%, And a residue consisting of iron Fe and fatal impurities. The average superheat of liquid steel is 31.2 ° C, the casting speed is 0.95 m / min, the cooling water flow rate is 173 l / min, the rate of decrease in slab temperature is 13.2 min / ° C, the surface temperature of the slab at the exit of the foundry machines - 680 ° C, coefficient of equiaxed crystals - 59%. In a heating furnace, the temperature difference between the water level marks is 20 ° C, the residence time of the slab in the zone after firing is 48 minutes. The rolling process is carried out after heating for 3 hours at a temperature of 1097 ° C, the inlet temperature for the smoothing process is 972 ° C, the temperature of the final rolling is 844 ° C, and the temperature of coiling is 583 ° C. The hot-rolled sheet is rolled to obtain a strip with a thickness of 0.5 mm by a single cold rolling method, and then continuous annealing is performed in a dry atmosphere. No riser defects are formed on the surface of the finished strip, the iron loss is 2.833 W / kg, and the magnetic induction is 1.726 T.

Comparative example.

The chemical composition of the liquid steel in the tundish during continuous casting is controlled as follows: C 0.001 wt.%, Si 1.47 wt.%, Mn 0.32 wt.%, P 0.02 wt.%, S 0.003 wt.%, Al 0.25 wt.%, N 0.002 wt.%, O 0.002 wt.%, And a residue consisting of iron Fe and fatal impurities. The average superheat of liquid steel is 28.9 ° C, the casting speed is 1.03 m / min, the cooling water flow rate is 257 l / min, the rate of decrease in slab temperature is 17.4 min / ° C, the surface temperature of the slab at the exit of the foundry machines - 580 ° C, coefficient of equiaxed crystals - 28%. In a heating furnace, the temperature difference between the water level marks is 37 ° C, the slab in the zone after firing is 41 minutes. The rolling process is carried out after heating for 3 hours at a temperature of 1153 ° C, the inlet temperature for the smoothing process is 947 ° C, the temperature of the final rolling is 847 ° C, the temperature of the coiling is 567 ° C. The hot-rolled sheet is rolled to obtain a strip with a thickness of 0.5 mm by a single cold rolling method, and then continuous annealing is performed in a dry atmosphere. The percentage of defect formation on the surface of the finished strip is at least 90%, iron loss is 3.273 W / kg, and magnetic induction is 1.736 T.

Figure 1 shows the relationship between the flow rate of cooling water and the coefficient of equiaxed crystals in the slab. As can be seen from Figure 1, provided that the electromagnetic stirring is not used due to the reduction of the cooling water flow and its regulation strictly at the level of not more than 190 l / min, the coefficient of equiaxed crystals in the slab can be significantly improved. In embodiments, the coefficient of equiaxed crystals in the slab can be adjusted with a sufficiently large overheating of molten steel. In the fourth of these embodiments, with a cooling water flow of 173 l / m, the coefficient of equiaxed crystals in the slab reaches 59%, and in the comparative example, with a cooling water flow of 257 l / min, the coefficient of equiaxed crystals in the slab is only 28%. Also, the regulation of the coefficient of equiaxed crystals is improved in the third embodiment and reaches 63%.

Figure 2 shows the relationship between the inlet temperature for the hot rolling and ironing process and the frequency of occurrence of riser defects in the final product. According to the statistical results, the frequency of occurrence of riser defects in the finished strip can be significantly reduced by increasing the inlet temperature for the hot rolling process and smoothing over 970 ° C, because the recrystallization coefficient of the fibrous texture of the slab during hot rolling increases significantly. In a comparative example, the inlet temperature for the hot rolling and ironing process for most of the strips is less than 970 ° C, and the percentage of formation of riser defects on the surface of the final strip is at least 90%. In several embodiments, the inlet temperature for the hot rolling process and the smoothing of the strips exceeds 970 ° C, and there are no riser defects on the surface of the finished strip.

Figure 3 shows the relationship between the temperature of the release of the furnace for the slab and the magnetic properties of the final product. The higher the temperature of the release of the furnace for the slab, the worse the magnetic properties of the final product.

Figures 4 and 5 show the metallographic structures of the strips during hot rolling at different temperatures at the water level mark. The temperature at the water level mark is everywhere less than 25 ° C, from the first to fourth embodiments, therefore, the strip recrystallization structures during hot rolling are very uniform, the fibrous textures completely disappear, while in the comparative example the temperature at the water level mark is 37 ° C , the fibrous texture of the strip during hot rolling is clearly present, which leads to the difficulty of recrystallization during subsequent cold rolling and annealing, the inability to eliminate structural heterogeneity ur, which proceeds to the final product, resulting in formation of uneven defect riser.

Claims (1)

A method for the production of non-textured electrical steel sheet without a defect of risers, in which:
- get a slab of steel having a chemical composition, wt.%: C <0.005, Si from 1.2 to 2.2, Mn from 0.2 to 0.4, P <0.2, S <0.005, Al from 0.2 to 0.6, N <0.005, O <0.005, Fe and unavoidable impurities - the rest, by smelting in a converter, pre-treatment of hot metal by circulating refining and continuous casting, while controlling the amount of cooling water in the secondary cooling with its flow rate is at the level of 100-190 l / min, and the average level of overheating of molten steel during continuous casting is controlled at 10-45 ° C;
- the slab is heated and hot rolled, including rough rolling and smoothing, while the heating temperature of the slab is 1050-1150 ° C, the temperature difference between any two points along the length of the slab when it is heated is less than 25 ° C, and the inlet temperature for the process smoothing is not lower than 970 ° C;
- then carry out acid etching, cold rolling, annealing and coating.

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