Non-oriented silicon steel added with rare earth as well as preparation method and evaluation method of non-oriented silicon steel

Abstract

The invention relates to the technical field of steel performance improvement, and discloses rare earth-added non-oriented silicon steel and a preparation method and evaluation method thereof.The rare earth-added non-oriented silicon steel comprises the following chemical components in percentage by weight: less than or equal to 0.005% of C, 1.0-4.0% of Si, 0.1-0.5% of Mn, 0.1-0.5% of Al, less than or equal to 0.005% of P, less than or equal to 0.005% of N, less than or equal to 0.0050% of O, less than or equal to 0.0050% of S, rare earth elements Ce and / or La and the balance of Fe; performing visual analysis on the three-dimensional evolution process of the rare earth modified inclusion induced cracks in the necking area in the tensile deformation process by adopting X-ray microscopy ct (XRM); the result shows that after 0.0035 wt.% of Ce is added, Al2O3 inclusions and MnS inclusions are respectively modified into CeAlO3 inclusions and Ce2S3 inclusions; after 0.0033 wt.% of La is added, the inclusions are modified into LaAlO3 inclusions and La2O2S inclusions respectively; the average volume of cracks of a sample added with Ce is 1057.81 [mu] m < 3 > and is smaller than 1802.51 [mu] m < 3 > of a sample added with La and 3653.13 [mu] m < 3 > of a sample without rare earth, after 0.0035 wt% of Ce is added, the tensile strength, the yield strength and the percentage elongation after fracture of the samples are all improved, and the steel improves the machinability, reduces rolling cracks and improves the energy efficiency.

Description

Technical Field

[0001] This invention relates to the field of steel performance improvement technology, and in particular to a non-oriented silicon steel with added rare earth elements, its preparation method, and its evaluation method. Background Technology

[0002] Non-oriented silicon steel is the core electrical substrate for motors and transformers, and its performance directly determines the operating efficiency, long-term stability, and service life of the equipment. To meet the development needs of high-efficiency and lightweight motors, the thinning of non-oriented silicon steel has become an inevitable trend in the industry. As the thickness of motor cores continues to decrease, more stringent requirements are being placed on the processing performance of non-oriented silicon steel.

[0003] Non-oriented silicon steel requires multiple processing steps such as cold rolling, cutting, and coiling during production and application. Defects such as burrs and edge cracks are easily generated during processing, and these problems are difficult to completely avoid. More importantly, local cracking not only reduces the processing qualification rate, but also further causes significant degradation of the magnetic properties of local areas of the steel, directly weakening the core performance of motors and transformers.

[0004] To address the cracking issue during the cold rolling process of non-oriented silicon steel, existing research primarily focuses on two approaches to reduce edge cracking: "optimizing the rolling process" or "adjusting the chemical composition of the steel matrix." For example, the Müler team used a twin-roll casting combined with warm rolling to produce crack-free non-oriented silicon steel, which significantly suppressed the formation of rolling cracks, but resulted in a significant increase in the steel's iron loss index, sacrificing magnetic properties. The Pan team, however, successfully obtained crack-free non-oriented silicon steel by increasing the silicon content to 6.5 wt.%. <100> and <001> While optimizing magnetic properties through selective texturing is a fundamental approach, this method lacks in-depth research into the machinability of the steel, thus failing to meet the demands of practical processing scenarios. Currently, the problem of crack initiation and propagation induced by brittle inclusions in non-oriented silicon steel remains unresolved. Summary of the Invention

[0005] The purpose of this invention is to provide a non-oriented silicon steel with added rare earth elements, its preparation method, and its evaluation method, thereby solving the problem of crack initiation and propagation induced by brittle inclusions in non-oriented silicon steel mentioned in the background art.

[0006] The technical solution adopted in this invention is as follows: a non-oriented silicon steel with added rare earth elements, the chemical composition of which, by weight percentage, is: C ≤0.005%, Si 1.0~4.0%, Mn 0.1~0.5%, Al 0.1~0.5%, P ≤0.005%, N ≤0.005%, O ≤0.0050%, S ≤0.0050%, and further includes rare earth elements Ce and / or La, wherein the content of Ce is ≤0.0050%, the content of La is ≤0.0050%, and the balance is Fe;

[0007] As a preferred embodiment of the present invention, the non-oriented silicon steel with added rare earth elements has a chemical composition further optimized by weight percentage as follows: C 0.0001~0.003%, Si 2.0~4.0%, Mn 0.2~0.4%, Al 0.2~0.4%, P 0.001~0.003%, N 0.001~0.003%, O ≤0.0030%, S ≤0.0030%, and the balance Fe.

[0008] A method for preparing non-oriented silicon steel with added rare earth elements includes the following steps:

[0009] Step (1) The raw materials are smelted and cast to obtain steel ingots; the smelting temperature is 1600℃, the smelting time is 50~70min, the smelting vacuum degree is 10~15 Pa, and rare earth elements are added during the smelting process.

[0010] Step (2) Heat the billet to 1150~1200 ℃ and hold for 1~2 h; hot roll 5 times, each time with a reduction rate of 25%, and air cool to room temperature.

[0011] An evaluation method for non-oriented silicon steel with rare earth elements, including...

[0012] (1) Mechanical performance evaluation: Using non-oriented silicon steel without rare earth as the control steel, tensile tests were conducted on the test steel of this invention to evaluate its three core mechanical performance indicators: tensile strength, yield strength and elongation after fracture, so as to quantitatively analyze the improvement effect of rare earth addition on the processing performance of steel.

[0013] The dimensions of the specimens used in the tensile test strictly comply with the provisions of the Chinese national standard GB / T 228.1-2021, with specific parameters as follows: gauge length diameter d0 = 8 mm, gauge length L0 = 40 mm, and gauge length cross-sectional area S0 = 50.24 mm². During the test, the tensile tension is controlled at 5 kN and the tensile rate is 0.1 mm / min to ensure uniform test conditions and guarantee the standardization and comparability of the data.

[0014] (2) Three-dimensional morphology evaluation method of non-oriented silicon steel: Non-oriented silicon steel without rare earth is used as the control steel. High-resolution X-ray micro-ct (XRM) technology is used for observation. The spatial characteristics of inclusions inside the steel and the necking area pores after stretching are analyzed.

[0015] The three-dimensional morphology of inclusions and necking-out pores after tensile deformation includes the following steps:

[0016] ① The sample to be evaluated was processed into a cylindrical specimen with a diameter of φ2 mm × 10 mm; the XRM observation parameters were set as follows: test voltage 140 kV, working mode Bin2, objective lens magnification 4x, and color filter HE3; during the observation process, the sample was rotated 360° to obtain continuous two-dimensional tomographic images, which were then processed by a preset three-dimensional reconstruction algorithm to generate a three-dimensional topography of inclusions and necking pores;

[0017] ② The above three-dimensional morphology model was processed using Dragonfly professional image processing software, and a corresponding structural analysis network model was established. Then, cylindrical observation samples with a diameter of φ2 mm × 10 mm were cut from the necking region of the intact tensile specimen. The differences in the morphology, size and spatial distribution characteristics of inclusions between the test steel of this invention and the control steel after tensile deformation were compared and analyzed.

[0018] The beneficial effects of this invention are as follows: By adding rare earth elements Ce and / or La to modify inclusions in non-oriented silicon steel, this invention transforms irregular large-sized inclusions such as Al2O3 and MnS in the steel into fine, near-spherical rare earth composite inclusions, significantly reducing the number of inclusions, shrinking the average volume, and optimizing the uniformity of distribution. This effectively inhibits the initiation and propagation of necking cracks after tensile deformation, reducing the average crack volume by more than 40%. At the same time, it improves the tensile strength, yield strength, and elongation after fracture of the steel, improves the crack resistance and formability during cold rolling, and simultaneously reduces iron loss and improves magnetic induction. This achieves synergistic optimization of the machinability and magnetic properties of non-oriented silicon steel, meeting the stringent requirements of lightweight and high-efficiency motors for steel. Attached Figure Description

[0019] Figure 1 The FE-SEM morphology and elemental distribution of inclusions in sample #1 are shown.

[0020] Figure 2 The FE-SEM morphology and elemental distribution of inclusions in sample #2 are shown.

[0021] Figure 3 The FE-SEM morphology and elemental distribution of inclusions in sample #3 are shown.

[0022] Figure 4 The statistical results of inclusions in the sample are: (a) average number, (b) average area.

[0023] Figure 5 To show the three-dimensional morphology and spatial distribution of inclusions, (a1)(a2) 1# sample, (b1)(b2) 2# sample, (c1)(c2) 3# sample.

[0024] Figure 6To show the three-dimensional morphology and spatial distribution deformation of the crack after tension, specimens are (a1, a2) 1#, (b1, b2) 2#, and (c1, c2) 3#.

[0025] Figure 7 The morphology of inclusions in the tensile specimens is shown; (a1-a3) 1# specimen, (b1-b3) 2# specimen, (c1-c3) 3# specimen. Detailed Implementation

[0026] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0027] The present invention provides a non-oriented silicon steel with added rare earth elements, the chemical composition of which, by weight percentage, is as follows: Example 1 (without added rare earth elements) steel chemical composition: C 0.0001~0.003%, Si 2.0~4.0%, Mn 0.2~0.4%, Al 0.2~0.4%, P 0.001~0.003%, N 0.001~0.003%, O ≤0.0030%, S ≤0.0030%, and balance Fe.

[0028] The comparative example 2 (containing rare earth steel) provided by the present invention has the following chemical composition by weight percentage: C 0.0001~0.003%, Si 2.0~3.2%, Mn 0.2~0.4%, Al 0.15~0.35%, P 0.0012~0.0031%, N 0.001~0.003%, O ≤0.0035%, S ≤0.0025%, Ce≤0.0050%, and the balance Fe.

[0029] The comparative example 3 (containing rare earth steel) provided by the present invention has the following chemical composition by weight percentage: C 0.0001~0.003%, Si 2.0~3.2%, Mn 0.2~0.4%, Al 0.15~0.35%, P 0.0012~0.0031%, N 0.001~0.003%, O ≤0.0035%, S ≤0.0025%, La ≤0.0050%, and the balance Fe.

[0030] Preferably, the Ce content is 0.0020~0.0040% and the La content is 0.0020~0.0040%. In this invention, the rare earth elements Ce / La can combine with oxygen and sulfur in steel to form high-melting-point compounds, reduce the number of inclusions, control the morphology of inclusions, and improve the purity of steel; thereby improving the machinability of the steel.

[0031] Preferably, in the non-oriented silicon steel, the O content does not exceed 0.0030% and the S content does not exceed 0.0030%; more preferably, O ≤ 0.0025% and S ≤ 0.00025%. In this invention, by strictly controlling the content of impurity elements O and S, the purity and comprehensive performance of the steel can be further improved. Therefore, in this invention, by controlling the steel composition and optimizing the control of rare earth elements, the inhibition of crack initiation and propagation in rare earth non-oriented silicon steel can be effectively improved.

[0032] A method for preparing non-oriented silicon steel with added rare earth elements includes the following steps:

[0033] Step (1) Smelting and Casting: The raw materials are smelted and cast to obtain steel ingots;

[0034] Step (2) Hot rolling: The steel ingot obtained in step (1) is heated to 1150~1200 ℃ and held for 1~2 h, and then hot rolled multiple times to obtain the finished steel product.

[0035] Preferably, in step (1), the melting temperature is 1600 ℃, the melting time is 50~70 min, and the melting vacuum degree is 10~15 Pa.

[0036] Preferably, the hot rolling process in step (2) is as follows: a total of 5 hot rollings, each with a reduction rate of 25%, and finally air cooling to room temperature.

[0037] Through the above preparation process, rare earth elements can fully combine with impurity elements in steel to form high-melting-point rare earth inclusions, thereby controlling the morphology of inclusions, refining grains, and thus improving the mechanical properties of steel and inhibiting the initiation and propagation of cracks.

[0038] The technical solution and effects of the present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0039] The non-oriented silicon steel of Example 1 did not contain rare earth elements, and its chemical composition by weight percentage was: C 0.0024%, Si 2.98%, Mn 0.31%, Al 0.29%, P 0.0019%, N 0.0018%, O 0.0025%, S 0.0018%, and the balance Fe.

[0040] The non-oriented silicon steel of Comparative Example 2, with the addition of rare earth element Ce, has the following chemical composition by weight percentage: C 0.0027%, Si 3.02%, Mn 0.30%, Al 0.29%, P 0.0017%, N 0.0018%, O ≤0.0022%, S ≤0.0016%, Ce 0.0035%, and the balance Fe.

[0041] The non-oriented silicon steel of Comparative Example 3 was supplemented with rare earth element La, and its chemical composition by weight percentage was: C 0.0026%, Si 3.00%, Mn 0.32%, Al 0.31%, P 0.0018%, N 0.0022%, O 0.0023%, S 0.0016%, La 0.0033%, and the balance Fe.

[0042] Performance testing

[0043] The test steels of Example 1, Comparative Example 2 and Comparative Example 3 were subjected to inclusion characterization, tensile testing and high-resolution X-ray micro-ct (XRM) observation.

[0044] (1) Characterization of inclusions

[0045] Figure 1 The images show the FE-SEM morphology and surface element distribution of the inclusions in Example 1. The inclusions in non-oriented silicon steel are mainly Al2O3, AlN, and MnS inclusions and their composite inclusions. Figure 1 (a) The Al2O3 inclusion is triangular in shape, with a long side of about 6 μm and a short side of about 2 μm. Figure 1 (b) shows a slender MnS inclusion with a major axis length of about 2 μm, which is raindrop-shaped. Figure 1 (c) shows a composite inclusion of Al2O3, AlN, and MnS, with a maximum planar length of approximately 3 μm and an irregular shape. During the solidification of molten steel, Al2O3 inclusions precipitate first, AlN inclusions nucleate and grow around Al2O3 inclusions, and MnS inclusions grow on the outermost layer. In the sample without rare earth elements, the inclusions are larger and have irregular shapes.

[0046] Figure 2 The FE-SEM morphology and surface element distribution of inclusions in sample #2 are shown. Figure 2 (a) shows a composite inclusion of CeAlO3 and MnS, with the inclusions being quadrilaterals approximately 1 μm in size. During the solidification of molten steel, Ce reacts with Al and O in the molten steel to form CeAlO3 inclusions, while MnS inclusions nucleate and grow around the CeAlO3 inclusions. After the addition of Ce, the irregular, pointed Al2O3 inclusions are modified into regular-shaped CeAlO3 inclusions, and the inclusion size is also significantly reduced. Figure 2(b) shows Al2O3 and Ce-Mn-S composite inclusions, which are circular with a diameter of approximately 1 μm. The central black area corresponds to Al2O3 inclusions, and the outer white area corresponds to Ce-Mn-S inclusions. During the solidification process of molten steel, Al2O3 precipitates first, and Ce2S3 adheres to its surface and grows. Since the enthalpy of formation of CeAlO3 inclusions is lower than that of Ce2S3 inclusions, the addition of rare earth elements will first modify the Al2O3 inclusions into CeAlO3 inclusions. The remaining Ce will modify the MnS inclusions into Ce2S3 inclusions. However, due to insufficient Ce content, the MnS inclusions cannot be completely modified into Ce2S3 inclusions.

[0047] Figure 3 The FE-SEM morphology and surface element distribution of rare earth inclusions in sample #3 are shown. Figure 3 (a) Image of LaAlO3-MnS composite inclusions. The inclusions are spherical with a diameter of approximately 1 μm. After the addition of La, the Al2O3 inclusions are modified into LaAlO3 inclusions, which are smaller and more regularly shaped. During the solidification of molten steel, the LaAlO3 inclusions nucleate and grow first, with MnS adhering around them. Figure 3 (b) is an image of the Al2O3-La2O2S composite inclusion. The inclusion is circular with a diameter of approximately 2 μm. The central black circular area represents Al2O3, the bright white arc corresponds to the modified La2O2S inclusion, and the gray area corresponds to the unmodified MnS inclusion.

[0048] Figure 4 Statistical results of inclusions using the OTS statistical system are presented. Figure 4 (a) shows the average number of various inclusions in the samples. It can be seen that sample #1 has the highest number of Al2O3 inclusions, because rare earth elements can react with Al2O3 inclusions to form REA1O3 inclusions. During the solidification process of molten steel, O element first reacts with rare earth elements to form REA1O3 inclusions. Among the samples, sample #3 has the lowest number of Al2O3 inclusions, because the addition of La can generate La2O2S inclusions, thereby reducing the O content in the sample, allowing the remaining Al to combine with N to form AlN inclusions. This is also the reason why sample #3 has the highest number of AlN inclusions. Adding Ce to sample #2 generates a small number of CeAlO3-MnS composite inclusions and Al2O3-Ce2S3 composite inclusions with similar average numbers, and the latter has a smaller average area than the former. Adding La to sample #3 generates a small number of LaAlO3-MnS composite inclusions and La2O2S inclusions, the latter having a significantly larger average area than other inclusions. Figure 4(b) shows the average area of ​​inclusions in the samples. It can be seen that the average area of ​​Al2O3 and AlN inclusions is significantly larger than that of MnS inclusions, and the average area of ​​Al2O3 inclusions in sample #2 is significantly smaller than that in sample #1. This is because the addition of Ce significantly lowers the nucleation temperature of Al2O3 inclusions, preventing them from growing large enough. After the addition of rare earth elements, large, irregular inclusions are modified into smaller, regularly shaped rare earth inclusions.

[0049] (2) X-ray microscopic CT characterization image

[0050] Figure 5 It shows the three-dimensional morphology and spatial distribution of the inclusions. Figure 5 (a1, b1, c1) is a three-dimensional topographic image, where different colors from purple to red represent inclusions of different volumes from small to large. Figure 5 (a2, b2, c2) represents the volume of the inclusions. Figure 5 (a) shows the three-dimensional morphology of sample #1. It can be seen that the inclusions are irregular in shape and uneven in size and distribution. The largest inclusion is 6247.05 μm. 3 The smallest is 11.41 μm. 3 The average value is 3129.23 μm. 3 . Figure 5 (b) shows the three-dimensional morphology of sample #2. The largest inclusion is 1553.82 μm. 3 The smallest is 11.17 μm. 3 The average value is 782.49 μm. 3 . Figure 5 (c) shows the three-dimensional morphology of sample #3. The maximum inclusion size is 2656.42 μm. 3 The smallest is 17.10 μm. 3 The average value is 1336.76 μm. 3 The addition of rare earth elements reduces the average volume of inclusions, makes their shape closer to spherical, and results in a more uniform distribution. The addition of Ce has a more significant effect than the addition of La.

[0051] (3) Three-dimensional morphology of cracks after tensile deformation

[0052] Figure 6 The three-dimensional morphology of the necking crack after tensile deformation. Figure 6 (a) shows the three-dimensional morphology of the crack in sample #1. It can be seen that the maximum crack volume is 7295.53 μm. 3 The minimum crack volume is 10.71 μm. 3 The average crack volume is 3653.13 μm. 3The crack size distribution is uneven, and the overall direction of the crack is consistent with the direction of tension during tensile deformation. Figure 6 (b) shows the three-dimensional morphology of the crack in specimen #2. The maximum crack volume is 2086.99 μm. 3 The minimum crack volume is 28.63 μm. 3 The average crack volume is 1057.81 μm. 3 . Figure 6 (c) shows the three-dimensional morphology of the crack in sample #3. The maximum crack volume is 3590.7 μm. 3 The minimum crack volume is 14.32 μm. 3 The average crack volume is 1802.51 μm. 3 After adding Ce, the average crack volume was minimized and the crack distribution was relatively uniform.

[0053] Figure 7 The image shows the morphology of the inclusions after tensile deformation. (From...) Figure 7 (a1-a3) shows that there are obvious cracks around the Al2O3 inclusions, obvious pores exist between the AlN inclusions and the matrix, and the MnS inclusions grow along the tensile direction of the sample; the direction of the cracks or pores is consistent with the direction of the applied force. Figure 7 (b1-b3) No obvious cracks were found around the modified CeAlO3 inclusions and Al2O3 inclusions, and no obvious pores were found between the CeAlO3 inclusions and the matrix. Figure 7 In (c1-c3), there are no obvious cracks around the LaAlO3 inclusions, but there are fine pores, and the pores around the La2O2S inclusions are smaller than those around the MnS inclusions before rare earth modification. Overall, the addition of rare earth elements improves the crack resistance around the Al2O3 inclusions, inhibits the formation of pores around the MnS inclusions, and prevents the separation of the inclusions from the matrix.

[0054] Table 1 shows the mechanical and magnetic properties of the test steel.

[0055]

[0056] Overall effect

[0057] The above experimental results show that the rare earth-containing steel of this invention exhibits advantages over the control steel without rare earth addition in terms of inclusion characteristics, mechanical properties, and three-dimensional morphology. Specifically:

[0058] (1) After adding 0.0035 wt.% Ce, Al2O3 and MnS inclusions were modified into CeAlO3 and Ce2S3, respectively, and the average crack volume increased from 3129.23 μm. 3 Reduced to 782.49 μm 3 .

[0059] (2) After adding 0.0033 wt. %La, the Al2O3 and MnS inclusions were modified into LaAlO3 and La2O2S inclusions, respectively, and the average crack volume was reduced to 1336.76 μm. 3 .

[0060] (3) The specimens with added Ce have smaller cracks, better mechanical properties, and higher tensile and yield strength.

[0061] Although the present invention has been described in detail with reference to the foregoing examples, those skilled in the art can still make and modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A non-oriented silicon steel with added rare earth elements, characterized in that, Its chemical composition by weight percentage is as follows: C ≤0.0050%, Si 1.0~4.0%, Mn 0.1~0.5%, Al 0.1~0.5%, P≤0.0050%, N≤0.0050%, O ≤0.0050%, S ≤0.0050%, and also includes rare earth elements Ce and / or La, wherein the content of Ce is ≤0.0050%, the content of La is ≤0.0050%, and the balance is Fe.

2. The non-oriented silicon steel with added rare earth elements according to claim 1, characterized in that, The chemical composition by weight percentage is as follows: C 0.0001~0.003%, Si 2.0~4.0%, Mn 0.2~0.4%, Al 0.2~0.4%, P 0.001~0.003%, N 0.001~0.003%, O ≤0.0030%, S ≤0.0030%, with the balance being Fe.

3. The non-oriented silicon steel with added rare earth elements according to claim 1, characterized in that, The content of Ce is 0.0020~0.0040%, and the content of La is 0.0020~0.0040%.

4. The non-oriented silicon steel with added rare earth elements according to claim 1, characterized in that, O≤0.0025%, S≤0.00025%.

5. The non-oriented silicon steel with added rare earth elements according to claim 1, characterized in that, The rare earth elements Ce and / or La can transform Al2O3 and MnS inclusions in steel into CeAlO3, Ce2S3 or LaAlO3, La2O2S composite inclusions, wherein the average size of the composite inclusions is ≤2μm and the morphology is nearly spherical.

6. A method for preparing the rare-earth-added non-oriented silicon steel according to any one of claims 1-5, characterized in that, Includes the following steps: Step (1) The steel sample is smelted in a ZG-0.01 vacuum melting furnace, and raw materials are added sequentially for smelting and casting to obtain steel ingots; Step (2) The steel ingot obtained in step (1) is hot rolled, normalized, cold rolled and annealed to obtain non-oriented silicon steel with added rare earth.

7. The preparation method according to claim 6, characterized in that, The smelting conditions in step (1) are: smelting temperature 1600℃, smelting time 50~70 min, and smelting vacuum degree 10~15 Pa.

8. The preparation method according to claim 6, characterized in that, In step (2), the hot rolling conditions are as follows: the billet is heated to 1150~1200 ℃, held for 1~2 h, and hot rolled 5 times, with a reduction rate of 25% each time, and finally air-cooled to room temperature.

9. A method for evaluating the rare-earth-added non-oriented silicon steel according to any one of claims 1-5, characterized in that, The evaluation includes mechanical property assessment and three-dimensional morphology assessment of inclusions and necking-off pores after tensile deformation. The specific steps are as follows: (1) Mechanical property evaluation: Using non-oriented silicon steel without rare earth as the control steel, tensile tests were conducted on the test steel with added rare earth to evaluate the tensile strength, yield strength and elongation after fracture of the test steel; the specimen size of the tensile test conformed to the Chinese national standard GB / T 228.1-2021, where d0=8 mm, L0=40 mm, S0=50.24 mm², the tensile tension was 5 kN and the tensile rate was 0.1 mm / min; (2) Three-dimensional morphology evaluation: Using non-oriented silicon steel without rare earth as the control steel, the test steel was observed by high-resolution X-ray micro-CT. Specifically, the sample was processed into a φ2×10 mm cylinder. Under the conditions of test voltage 140 kV, working mode Bin2, objective lens magnification 4x, and color filter HE3, the sample was rotated 360° and photographed. The two-dimensional image was processed by the preset three-dimensional reconstruction algorithm to generate a three-dimensional terrain. The image was processed by Dragonfly to generate a network model. The φ2×10 mm cylinder was cut from the necking area of ​​the intact tensile specimen. The three-dimensional morphology of the inclusions and the holes in the necking area generated after the tensile deformation of the test steel was compared.

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