CN118291852A - Method for preparing non-oriented silicon steel ultrathin strip by using plane casting - Google Patents

Abstract

The present invention relates to a method for preparing non-oriented silicon steel ultra-thin strip by plane flow casting, which belongs to the technical field of soft magnetic metal material preparation, and solves the problems of difficult forming and poor spreading when preparing non-oriented silicon steel ultra-thin strip by plane flow casting in the prior art. The chemical composition of the non-oriented silicon steel ultra-thin strip is Si: 2.8-3.8%, Al: 0.2-0.5%, B: 0.1-0.3%, P: 0.04-0.12%, C: 0.002-0.005%, Mn: 0.08-0.24%, Sn: 0.02-0.06%, Cu≤0.003%, S≤0.004%, and the rest is Fe and unavoidable impurities. The formability and medium-high frequency magnetic properties of the non-oriented silicon steel ultra-thin strip in the plane flow casting process are improved.

Description

A method for preparing non-oriented silicon steel ultra-thin strip by plane flow casting

Technical Field

The invention relates to the technical field of soft magnetic metal material preparation, and in particular to a method for preparing non-oriented silicon steel ultra-thin strips by plane flow casting.

Background technique

Non-oriented silicon steel has excellent magnetic properties. It is mainly used to manufacture motor cores and is an indispensable and important magnetic material in the fields of electricity and electronics. For high-speed motors, there are high requirements for iron loss at 1000Hz. Improving the iron loss at a power frequency of 50Hz or a medium frequency of 400Hz has certain limitations on improving the efficiency of the motor.

At present, the production of conventional non-oriented silicon steel mainly adopts the traditional process of continuous casting and rolling, cold rolling and annealing technology. Due to the large hot rolling reduction and cold rolling reduction, the {111} texture in the final strip steel structure is very strong, which is not conducive to the improvement of the magnetic induction strength of non-oriented silicon steel.

Planar flow casting is a short-process rapid solidification technology. The typical manufacturing process is: melt the metal raw materials of specific composition, and then let the molten steel flow through a nozzle slit with a width of less than 1mm to a high-speed rotating metal cooling roller with good thermal conductivity. The molten steel spreads into a stable molten pool on the outer circumferential surface of the cooling roller. The melt at the bottom of the molten pool contacts the roller surface and cools rapidly at a high rate to form a continuous metal thin strip. Compared with traditional casting technology, planar flow casting technology has great advantages in short process and high efficiency. However, due to the characteristics of high melting point, high viscosity and poor fluidity of the melt, its formability and spreadability are difficult to guarantee when prepared by planar flow casting, which to a certain extent limits the high-frequency application of ultra-thin and large-width strips.

Summary of the invention

In view of the above analysis, the embodiments of the present invention aim to provide a method for preparing non-oriented silicon steel ultra-thin strip by plane flow casting and optimizing its formability, so as to solve the problems of poor fluidity and poor spreadability of existing silicon steel melt.

On the one hand, an embodiment of the present invention provides a method for preparing an ultra-thin strip of non-oriented silicon steel by plane flow casting, wherein the chemical composition of the non-oriented silicon steel is, in percentage by mass, Si: 2.8-3.8%, Al: 0.2-0.5%, B: 0.1-0.3%, P: 0.04-0.12%, C: 0.002-0.005%, Mn: 0.08-0.24%, Sn: 0.02-0.06%, Cu≤0.003%, S≤0.004%, and the rest is Fe and unavoidable impurities.

Preferably, the Si+Al content is 3.2-4.2%.

Preferably, the non-oriented silicon steel ultra-thin strip has a Mn/S of ≥50.

Furthermore, in the non-oriented silicon steel ultra-thin strip, the content of coarse columnar crystals is ≥60%, and the content ratio of {100}/{111} oriented grains is ≥3.

Specifically, the non-oriented silicon steel ultra-thin strip has a width of 10-15 mm, a thickness of 0.06-0.12 mm, a magnetic induction intensity B ₅₀₀₀ ≥1.65 T, and an iron loss P _1.0/1000 ≤42 W/kg.

Furthermore, the non-oriented silicon steel ultra-thin strip is prepared by plane flow casting.

On the other hand, an embodiment of the present invention provides a method for preparing non-oriented silicon steel ultra-thin strip by planar flow casting, wherein the planar flow casting method includes melting alloy raw materials, the alloy melt flows through a straight slit onto a high-speed rotating copper roller, rapidly cools and throws out the alloy thin strip, flat rolling, annealing in a protective atmosphere, and air cooling to room temperature.

It should be noted that the chemical composition of the master alloy ingot is, in mass percentage, Si: 2.8-3.8%, Al: 0.2-0.5%, B: 0.1-0.3%, P: 0.04-0.12%, C: 0.002-0.005%, Mn: 0.08-0.24%, Sn: 0.02-0.06%, Cu≤0.003%, S≤0.004%, and the rest is Fe and unavoidable impurities.

Specifically, the alloy raw materials are melted in a melting furnace to 1465-1600° C., and alloy thin strips are thrown out through a high-speed rotating copper roller.

Preferably, the material used for the straight slit for controlling the melt flow out is high-density boron nitride.

Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

1. The present invention reduces melt viscosity and solidus-liquidus temperature by regulating the content of alloy elements such as Si, Al, B, P, C, Mn, Sn, etc. in the casting melt;

The reduction of melt viscosity can reduce the movement resistance in the rapid solidification process, effectively improve the wettability and spreadability of molten steel, thereby solving the problem of difficult casting caused by poor melt fluidity and spreadability, and help to obtain uniform thin strips, improve the stability of the prepared steel strip in terms of forming ability, width and thickness, and at the same time make it unnecessary to specially control the subsequent flattening reduction rate, saving the preparation cost;

The lowering of the solid-liquid phase temperature can, on the one hand, moderately reduce the heating melting temperature and further save energy; on the other hand, it can obtain a higher superheat at the same melting temperature, increase the columnar crystal ratio in the solidified structure, reduce the thickness of the thin strip and obtain good magnetic properties.

2. The present invention controls the content of alloy elements in the melt and adopts a planar flow casting preparation method to form columnar crystals with a strong {100} texture in the flow casting strip, reduce the proportion of {111} oriented grains, and form coarse columnar crystals accounting for ≥60%. The grain size is relatively uniform and not too small, and this strong {100} texture is effectively retained in the subsequent process to obtain a non-oriented silicon steel ultra-thin strip with high magnetic induction intensity and low high-frequency iron loss at 1000Hz, with a width of 10-15mm, a thickness of 0.06-0.12mm, a magnetic induction intensity B ₅₀₀₀ ≥1.65T, and P _1.0/1000Hz ≤42W/kg.

In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents particularly pointed out in the description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are only for the purpose of illustrating specific embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

FIG. 1 is a grain structure diagram of the non-oriented silicon steel ultra-thin strip of the present invention.

Detailed ways

The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

A specific embodiment of the present invention discloses a method for preparing an ultra-thin strip of non-oriented silicon steel by plane flow casting, wherein the chemical composition of the non-oriented silicon steel is, in mass percentage, Si: 2.8-3.8%, Al: 0.2-0.5%, B: 0.1-0.3%, P: 0.04-0.12%, C: 0.002-0.005%, Mn: 0.08-0.24%, Sn: 0.02-0.06%, Cu≤0.003%, S≤0.004%, and the rest is Fe and unavoidable impurities.

Preferably, the Si+Al content is 3.2-4.2%.

Preferably, the non-oriented silicon steel ultra-thin strip has a Mn/S of ≥50.

The present invention improves the formability and the magnetic properties of the finished product by regulating the content of alloy elements in the melt. The reasons for limiting the composition are explained below:

Control Si+Al: 3.2~4.2%. Silicon can effectively improve the resistivity of non-oriented silicon steel and reduce hysteresis loss. However, excessive silicon will reduce the processing quality of non-oriented silicon steel and its magnetic induction. The effect of aluminum on magnetic properties is similar to that of silicon. It increases the resistivity of steel plates, grows grains, and reduces iron loss of finished products. In addition, the appropriate addition of aluminum helps to increase the columnar crystal ratio in the casting structure of non-oriented silicon steel. Therefore, the content of Si and Al is controlled within 3.2~4.2%.

B: The content is 0.1-0.3%. B will exist in the form of precipitation phase in non-oriented silicon steel, which can significantly reduce the anisotropy of magnetic induction and iron loss of non-oriented silicon steel, but excessive B will destroy the magnetic properties. The addition of B lowers the solid-liquid phase line, improves formability, and saves its preparation cost.

P: The content is 0.04-0.12%. P is generally considered to be a harmful impurity element in steel, which will lead to grain refinement and increased iron loss, and its content needs to be reduced as much as possible. However, an appropriate amount of P can improve the magnetic properties of the strip, and the increase in P content can significantly reduce the viscosity and solid-liquid phase temperature of the non-oriented silicon steel melt, so the present invention adds P but controls its content upper limit to 0.10%.

C: The content is 0.002-0.005%. C is generally considered to damage the magnetic properties of non-oriented silicon steel, but C can also effectively reduce its viscosity. And too low a C content is also difficult to achieve, so its content is controlled to 0.002-0.005%.

Mn: The content is 0.08-0.24%. Mn plays a role of solid solution strengthening in steel, improving the resistivity of electrical steel and reducing iron loss. However, manganese and sulfur in steel will form MnS. Too high Mn can coarsen MnS, hinder grain growth, increase the strength of harmful {111} texture components, and damage the magnetic properties of non-oriented silicon steel.

Control Mn/S ≥ 50. The addition of Mn can inhibit the hot brittleness caused by S, and Mn/S ≥ 50 can significantly control its hot brittleness.

Sn: The content is 0.02-0.06%. Sn can significantly change the texture of silicon steel. Sn is concentrated on the surface and grain boundaries, which increases the texture strength of the {100} plane, reduces the texture strength of the {111} component, and improves the magnetic properties of silicon steel. However, too high Sn content will cause surface nodules on the finished product during high-temperature annealing, so its content is controlled at 0.02-0.06%.

S: content ≤ 0.004%. Sulfur exists in steel mainly in the form of sulfide inclusions, which reduces the formability of steel. S should be reduced as much as possible, so S is controlled at 0.004% and below.

Cu: content ≤ 0.003%. The presence of Cu will have an adverse effect on the magnetic properties of silicon steel, but it is difficult to remove it by chemical metallurgical methods. Its segregation can be used to reduce its effect on the magnetic properties of silicon steel, so its content is controlled at 0.003% and below.

Furthermore, the content of coarse columnar crystals in the non-oriented silicon steel ultra-thin strip is ≥60%; because the long axis direction of the columnar crystals in the BCC structure metal tends to be parallel to the crystallographic <100> direction, a higher columnar crystal ratio ensures a higher {100} grain ratio; wherein, the {100} surface texture is beneficial to improving the magnetic properties of the non-oriented silicon steel, while the {111} surface texture is difficult to magnetize and should be avoided as much as possible; the {100}/{111} oriented grain content ratio is ≥3, which significantly improves the material magnetic induction intensity B ₅₀₀₀ value;

Specifically, the non-oriented silicon steel ultra-thin strip has a thickness of 0.06-0.12 mm, a width of 10-15 mm, a magnetic induction intensity B ₅₀₀₀ ≥1.65 T, and an iron loss P _1.0/1000 ≤42 W/kg.

Furthermore, the non-oriented silicon steel ultra-thin strip is prepared by plane flow casting.

On the other hand, an embodiment of the present invention provides a method for preparing non-oriented silicon steel ultra-thin strip by planar flow casting, wherein the planar flow casting method comprises heating and melting a master alloy ingot - spraying the master alloy melt onto a rotating copper roller through a nozzle - natural cooling - flattening - annealing in a nitrogen atmosphere - air cooling to room temperature.

It should be noted that the chemical composition of the master alloy ingot is Si: 2.8-3.8%, Al: 0.2-0.5%, B: 0.1-0.3%, P: 0.04-0.12%, C: 0.002-0.005%, Mn: 0.08-0.24%, Sn: 0.02-0.06%, Cu≤0.003%, S≤0.004%, and the rest is Fe and unavoidable impurities.

In a possible design, Si: 2.9-3.7%, Al: 0.3-0.45%, B: 0.15-0.25%, P: 0.045-0.10%, Sn: 0.025-0.055%.

Specifically, the master alloy raw material is melted at 1465-1600° C. and then cast into a master alloy ingot.

Exemplarily, the alloy raw material is placed in a heating device for heating and melting, and the superheat of the alloy melt is controlled at 20 to 80° C., and then the melt flows through a slit onto a high-speed rotating copper roller to throw out an alloy thin strip;

Among them, the slit width is 10-15 mm, the roller mouth spacing is 0.05-0.4 mm, the pressure applied to the melt is 20-60 kPa, and the copper roller speed is 15-30 m/s;

The non-oriented silicon steel ultra-thin strip with a thickness of 0.06-0.12 mm is thrown out by the rotating copper roller;

The plane flow casting strip is flattened. Since the melt fluidity of the selected alloy system is significantly improved, the ultra-thin non-oriented silicon steel prepared is very thin and uniform in thickness. It does not need to be significantly pressed down during the flattening treatment, but it can be pressed down to no more than 30% deformation according to the needs to ensure the effective retention of the {100} texture.

Then, annealing treatment is carried out at 700-950℃ in a nitrogen atmosphere for 0.5-1h, and nitrogen is introduced into the protective atmosphere to prevent oxidation of the non-oriented silicon steel ultra-thin strip; finally, air cooling is carried out to room temperature;

For example, the nozzle material is made of high-density boron nitride, which can effectively adapt to the melt temperature; the density of the high-density boron nitride is 2.17 g/cm ³

In a possible design, the preparation process includes the following steps: placing the mother alloy ingot raw material in a heating device for heating and melting, the superheat of the mother alloy melt is 60°C; then spraying the melt onto a high-speed rotating copper roller through a nozzle, the nozzle width is 10-15mm, the roller nozzle spacing is 0.25mm, the nozzle pressure during spraying is 50kPa, and the copper roller speed is 20m/s; after natural cooling, a non-oriented silicon steel ultra-thin strip with a thickness of 0.06-0.12mm is formed; and flattening treatment is performed without significant pressure reduction during flattening; then annealing treatment is performed in a nitrogen atmosphere at 900°C*1h; and finally air cooling to room temperature.

The present invention effectively improves the formability of the preparation process by regulating the alloy elements in the melt and combining the plane flow casting method, and develops an ultra-thin non-oriented silicon steel strip with a thickness of 0.06-0.12 mm and a width of more than 10 mm, wherein the proportion of coarse columnar crystals exceeds 60%, the ratio of {100}/{111} oriented grains is ≥3, the magnetic induction intensity B ₅₀₀₀ is ≥1.65T, and the iron loss P _1.0/1000 is ≤42W/kg.

The method for controlling the alloy elements in the melt and optimizing the formability of the present invention will be described below with reference to specific embodiments.

This embodiment discloses 8 non-oriented silicon steel ultra-thin strips prepared by the planar flow casting method (Examples 1-5 and Comparative Examples 1-3);

The main difference between the non-oriented silicon steel ultra-thin strips prepared in Examples 1-5 and Comparative Examples 1-3 is the different contents of various alloy elements; the mass percentages of the elemental components in Examples 1-5 all meet the requirements of the present invention; the non-oriented silicon steel ultra-thin strip prepared in Comparative Example 1 does not have Sn added, and the other elements are within the composition range of the non-oriented silicon steel ultra-thin strip provided by the present invention; the P content of the non-oriented silicon steel ultra-thin strip prepared in Comparative Example 2 is 0.20%, which exceeds the P content of 0.04-0.12% provided by the present invention; the B content of the non-oriented silicon steel ultra-thin strip prepared in Comparative Example 3 is 0.50%, which exceeds the B content of 0.1-0.3% provided by the present invention;

The chemical composition of the non-oriented silicon steel ultra-thin strip melt is shown in Table 1, and the test results of various properties of the non-oriented silicon steel ultra-thin strip are shown in Table 2.

Examples 1-5 and Comparative Examples 1-3 are all prepared by the same method, and the preparation process includes the following steps: placing the master alloy ingot raw material in a heating device for heating and melting, and the superheat of the master alloy melt is 60°C; then spraying the melt onto a high-speed rotating copper roller through a nozzle, the nozzle width is 10-15mm, the roller mouth spacing is 0.25mm, the pressure during nozzle spraying is 50kPa, and the copper roller rotation speed is 20m/s; after natural cooling, a non-oriented silicon steel ultra-thin strip with a thickness of 0.06-0.12mm is formed; and a flattening treatment is performed without significant pressure reduction during flattening; then annealing treatment is performed in a nitrogen atmosphere at 900°C*1h; and finally air cooling to room temperature.

Table 1 List of chemical composition values of various embodiments and comparative examples of the present invention (wt.%)

serial number Si Al B P C Mn Sn Cu S Example 1 3.34 0.41 0.15 0.055 0.0025 0.095 0.055 0.0025 0.0018 Example 2 3.04 0.28 0.20 0.060 0.003 0.125 0.052 0.0021 0.0022 Example 3 3.12 0.36 0.21 0.083 0.004 0.114 0.046 0.0018 0.0018 Example 4 3.40 0.25 0.23 0.062 0.0038 0.189 0.043 0.0022 0.0025 Example 5 2.90 0.35 0.20 0.045 0.0029 0.197 0.038 0.0013 0.0029 Comparative Example 1 3.21 0.28 0.17 0.090 0.0028 0.179 0 0.0012 0.0032 Comparative Example 2 3.26 0.38 0.18 0.200 0.0028 0.118 0.037 0.0008 0.0016 Comparative Example 3 3.10 0.38 0.50 0.085 0.004 0.116 0.045 0.0024 0.0020

Table 2 Performance test results of various embodiments of the present invention and comparative examples

It can be seen from Table 2 that the {100}/{111} oriented grain ratio of the non-oriented silicon steel ultra-thin strip prepared in Comparative Example 1 is 2.1, P _1.0/1000 is 40.8 W/kg, and B ₅₀₀₀ is 1.57 T, and each performance is significantly lower than that of Examples 1-5, indicating that the addition of Sn element provided by the present invention can effectively improve the magnetic properties of the non-oriented silicon steel ultra-thin strip; the viscosity of the non-oriented silicon steel ultra-thin strip prepared in Comparative Example 2 is 0.0058 mPas, and P _1.0/1000 is 53.4 W/kg. Compared with Examples 1-5 that meet the P content value provided by the present invention, the viscosity is significantly reduced, but the iron loss is high, exceeding the P _1.0/1000 provided by the present invention. ≤42W/kg, indicating that the addition of P can significantly reduce the viscosity of the non-oriented silicon steel ultra-thin strip prepared by the present invention, but excessive addition will also increase its iron loss and reduce its magnetic properties; the non-oriented silicon steel ultra-thin strip prepared in Comparative Example 3 has a width of 15mm, a thickness of 0.07mm, a P _1.0/1000 of 50.3W/kg, and a B ₅₀₀₀ of 1.61T. Compared with Examples 1-5 which meet the B content value provided by the present invention, the iron loss is relatively high, exceeding the P _1.0/1000 ≤42W/kg provided by the present invention, and the magnetic induction is relatively low, indicating that the addition of B is helpful to obtain a wide and thin strip, but excessive addition will destroy the magnetic properties.

It can be seen that the present invention provides a method for optimizing the formability and magnetic properties of an ultra-thin strip of non-oriented silicon steel prepared by plane flow casting, and reduces the viscosity of the melt by regulating the alloy elements of the melt, solves the problems of difficult forming and poor spreadability when preparing an ultra-thin strip of non-oriented silicon steel by plane flow casting, and smoothly obtains a more uniform, thin and wider strip; the regulation of the content of alloy elements in the melt is combined with the plane flow casting method to form a coarse columnar crystal ratio of ≥60%, a {100}/{111} oriented grain content ratio of ≥3, and the strong {100} texture is effectively retained in the subsequent process, so as to obtain an ultra-thin strip of non-oriented silicon steel with high magnetic induction intensity and low high-frequency iron loss at 1000Hz, with a width of 10-15mm, a thickness of 0.06-0.12mm, a magnetic induction intensity B5000≥1.65T, and P1.0/1000Hz≤42W/kg.

The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims (10)

1. A planar flow casting method for preparing an ultra-thin strip of non-oriented silicon steel, characterized in that the chemical composition of the ultra-thin strip of non-oriented silicon steel is, in terms of mass percentage, Si: 2.8-3.8%, Al: 0.2-0.5%, B: 0.1-0.3%, P: 0.04-0.12%, C: 0.002-0.005%, Mn: 0.08-0.24%, Sn: 0.02-0.06%, Cu≤0.003%, S≤0.004%, and the rest is Fe and unavoidable impurities. 2. The non-oriented silicon steel ultra-thin strip according to claim 1, characterized in that the Si+Al content is 3.2-4.2%. 3 . The non-oriented silicon steel ultra-thin strip according to claim 1 , wherein Mn/S of the non-oriented silicon steel ultra-thin strip is ≥50. 4. The non-oriented silicon steel ultra-thin strip according to claim 3, characterized in that the content of coarse columnar crystals in the non-oriented silicon steel ultra-thin strip is ≥ 60%, and the content ratio of {100}/{111} oriented grains is ≥ 3. 5. The non-oriented silicon steel ultra-thin strip according to claim 3, characterized in that the non-oriented silicon steel ultra-thin strip has a width of 10-15 mm, a thickness of 0.06-0.12 mm, a magnetic induction intensity B ₅₀₀₀ ≥1.65 T, and an iron loss P _1.0/1000 ≤42 W/kg. 6. The non-oriented silicon steel ultra-thin strip according to any one of claims 1 to 5, characterized in that it is prepared by plane flow casting. 7. A method for preparing non-oriented silicon steel ultra-thin strip by plane flow casting, characterized in that the non-oriented silicon steel ultra-thin strip according to any one of claims 1 to 6 is prepared by plane flow casting; the plane flow casting method includes melting silicon steel alloy raw material, the alloy steel liquid flows through a straight slit onto a high-speed rotating copper roller, and is rapidly cooled and thrown out of the alloy thin strip, flat rolling, annealing in a protective atmosphere, and air cooling to room temperature. 8. The method according to claim 7 is characterized in that the chemical composition of the alloy raw material is, in mass percentage, Si: 2.8-3.8%, Al: 0.2-0.5%, B: 0.1-0.3%, P: 0.04-0.12%, C: 0.002-0.005%, Mn: 0.08-0.24%, Sn: 0.02-0.06%, Cu≤0.003%, S≤0.004%, and the rest is Fe and unavoidable impurities. 9. The method according to claim 7 is characterized in that the alloy raw materials are melted in a melting furnace to 1465-1600°C and the alloy thin strips are thrown out through a high-speed rotating copper roller. 10. The optimization method according to claim 7, characterized in that the material used for the straight slit for controlling the outflow of the alloy steel liquid is high-density boron nitride.