# Patent

## Title
Method for detecting electromagnetic property of oriented silicon steel

## Abstract

A method for detecting electromagnetic property of oriented silicon steel, the method comprises: measuring Euler angles of each of crystal grains in a specimen by use of metallographic etch-pit method; calculating orientation deviation angle θi (degree) of the crystal grain; combining area Si (mm2) of the crystal grain and correction coefficient X of element Si (X=0.1 ̃10 T/degree); correcting on the basis of the magnetic property B0 (saturation magnetic induction, T) of single-crystal material by using these parameters (θi, Si, X), formula for correcting is




  
    
      
        
          B
          8
        
        =
        
          
            
              -
              0.015
            
            ×
            X
            ×
            
              
                
                  ∑
                  
                    n
                    =
                    1
                  
                  i
                
                ⁢
                
                  
                    S
                    i
                  
                  ⁢
                  
                    
                    
                      θ
                      i
                    
                    
                  
                
              
              
                
                  ∑
                  
                    n
                    =
                    1
                  
                  i
                
                ⁢
                
                  S
                  i
                
              
            
          
          +
          
            (
            
              
                B
                0
              
              -
              0.04
            
            )
          
        
      
    
    
      
        (
        1
        )
      
    
  




    
    
        obtaining electromagnetic property B8 of the oriented silicon steel by the above calculations. The present invention can implement detection of electromagnetic property of a specimen under the circumstances that there is no magnetizm measuring device or that magnetizm measuring devices cannot be used due to reasons such as weight and size of the specimen being too small or surface quality of the specimen being poor.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application represents the national stage entry of PCT International Application No. PCT/CN2011/072644 filed on Apr. 12, 2011 and claims the benefit of Chinese Patent Application No. 201010207498.0 filed Jun. 22, 2010. The contents of both of these applications are hereby incorporated by reference as if set forth in their entirety herein.
FIELD OF THE INVENTION
This invention relates generally to a detection method, and particularly to a method for detecting electromagnetic property of oriented silicon steel.
BACKGROUND
Epstein's square and circle method is stipulated by Chinese national standard (GB/T 3655-2000) as a method for detecting magnetic property of electric steel, which has strict requirements on weight, surface quality and so on of specimens. In the case that a specimen has too small weight and poor surface quality, it is impossible to use the Epstein's square and circle method to measure magnetic property (GB/T 3655-2000 requirements: effective mass of a specimen shall be at least 240 g, length of a specimen is recommended to be 300 mm, mass is about 1 kg; shear requirements of a specimen lie in that the shear shall be orderly, flat, being of good right-angle, and having no obvious burrs on the edge).
Etch pits are formed by preferential corrosion performed on crystal face of specimen surface. By use of this characteristic, it is possible to use metallographic etch-pit method to directly calculate crystallographic orientation of each crystal grain in the specimen (see “FORMATION CONDITIONS AND GEOMETRIC DIVERSITY OF ETCHED PITS”, Y. Luo, Acta metall Sin, 1982, 18 (4), p 472; “A STUDY ON THE DEFORMATION AND PRIMARY RECRYSTALLIZATION TEXTURE IN A MnS—AlN-INHIBITED 3% SILICON STEEL”, Q. C. Lv, R. J. Shuai, X. Y. Zhou et. al., Acta Metall Sin, 1981, 17 (1), p 58); “The application of the etch-pit method to quantitative texture analysis”, K. T. LEE, G. de WIT, A. MORA WIEC, J. A. SZPUNAR, JOURNAL OF MATERIAL SCIENCE, 1995, 30, p 1327-1332), and then to calculate orientation deviation angle θi of the crystal grain (see “ODF Determination of the Recrystallization Texture of Grain Oriented Silicon Steel from the Etch Figure”, G. Liu, F. Wang et. al., Journal of Northeastern University (Natural Science), 1997, 18 (6), p 614; “The application of the etch-pit method to quantitative texture analysis”, K. T. LEE, G. de WIT, A. MORA WIEC, J. A. SZPUNAR, JOURNAL OF MATERIAL SCIENCE, 1995, 30, p 1327-1332).
Magnetocrystalline anisotropy is a phenomenon due to a coupling effect between electron orbit and magnetic moment as one party and crystal lattice as another party, which makes magnetic moment have an optimum-choosing arrangement along a certain crystallographic axis, so as to result in difference of magnetization characteristics in various crystallographic axis directions. Crystallographic axis <100> is an easy magnetization direction, crystallographic axis <111> is a hard magnetization direction, and crystallographic axis <110> falls in between. As to oriented silicon steel, its electromagnetic property is closely related to crystal grain orientation <100> of a specimen (see “Electric Steel”, H E Zhongzhi, Metallurgical Industry Press, Beijing, 1996; “Mechanism of Orientation Selectivity of Secondary Recrystallization in Fe-3% Si Alloy”, Yoshiyuki USHIGAMI, Takeshi KUBOTA and Nobuyuki TAKAHASHI, Textures and Microstructures, vol. 32, p 137-151; “The Relationship between Primary and Secondary Recrystallization Texture of Grain Oriented Silicon Steel”, Tomoji KUMANO, Tsutomu HARATANI and Yoshiyuki USHIGAMI, ISIJ International, 2002, 42(4) 440). In view of the above, it is possible to use the metallographic pit-etching method plus calculation formula to take the place of magnetism-measuring devices to detect electromagnetic property of oriented silicon steel, as an innovative solution, which has the advantage that it can detect electromagnetic property in the cases that Epstein's square and circle method is not applicable thereto, such as specimen's weight being too small or its surface quality being poor.
In Chinese patent (Publication No.: CN101216440A), this invention utilizes a unsymmetrical X-ray diffraction method by using a fixed angle 2θ to perform ω can, in order to determine distribution of lattice orientation in the easy magnetization direction [001] of oriented silicon steel. A shortcoming of this patent, however, lies in that only deviation angle of lattice orientation [001] of the finished oriented silicon steel product is measured, but not further studying relativity between deviation angle of lattice orientation [001] and magnetism of the oriented silicon steel product.
In Chinese patent (Publication No.: CN101210947A), this invention measures three Euler angles of lattice orientation at every point of a specimen by use of EBSD system and accounts ratio X in every same or similar lattice orientation, and then calculates reckoned thickness coefficient fH, composition fC and influence coefficient e of orientation difference on performance. Magnetic property B of the specimen is obtained by correcting these coefficients based on pure iron performance Bθ. However, this patent has the following shortcomings: firstly, since EBSD device is expensive and is cumbersome in operation, many enterprises, especially small and medium-sized ones, are not able to apply this technique; secondly, with regards to calculation model for magnetic property of a finished product, it has been found from experimental data (oriented silicon steel with thickness 0.2 ̃0.3 mm) that thickness has little impact on magnetic property of the finished product, and it has been found from researches on chemical compositions that Si is a predominant influencing factor, and other chemical compositions have a little or basically no influence.
SUMMARY
The object of the invention is to provide a method to detect electromagnetic property of oriented silicon steel, which can implement detection of electromagnetic property of a specimen under the circumstances that there is no magnetism measuring device or that magnetism measuring devices cannot be used due to reasons such as weight and size of the specimen being too small or surface quality of the specimen being poor.
In order to attain the object, solution of the invention is as follows.
The present invention utilizes metallographic etch-pit method to measure Euler angles (α, β, γ) of each of crystal grains in a specimen of a finished product. Euler angles (α, β, γ) are a group of three independent angle parameters used to determine position of a fixed-point rotation rigid body, which consists of angle of nutation α, angle of precession β and angle of rotation γ. An orientation deviation angle θi of the crystal grain is then converted out from the Euler angles (α,β,γ), and finally, the electromagnetic property of the specimen can be calculated by use of other related parameters.
In particular, the invention provides a method for detecting electromagnetic property of oriented silicon steel, which comprises: measuring Euler angles of each of crystal grains in a specimen by use of metallographic etch-pit method; calculating orientation deviation angle θi (degree) of the crystal grain; combining area Si (mm2) of the crystal grain and correction coefficient X of element Si (X=0.1 ̃10 T/degree); correcting on the basis of magnetic property B0 (saturation induction density, T) of single crystal material, by using these parameters (θi, Si, X), formula for correcting is




  
    
      
        
          B
          8
        
        =
        
          
            
              -
              0.015
            
            ×
            X
            ×
            
              
                
                  ∑
                  
                    n
                    =
                    1
                  
                  i
                
                ⁢
                
                  
                    S
                    i
                  
                  ⁢
                  
                    
                    
                      θ
                      i
                    
                    
                  
                
              
              
                
                  ∑
                  
                    n
                    =
                    1
                  
                  i
                
                ⁢
                
                  S
                  i
                
              
            
          
          +
          
            (
            
              
                B
                0
              
              -
              0.04
            
            )
          
        
      
    
    
      
        (
        1
        )
      
    
  




The electromagnetic property B8 of the oriented silicon steel is obtained by the above calculations.
For specimens of a finished oriented silicon steel product with the same thickness, it can be calculated from formula (1) that an interrelation illustrated by formula 2 exists between average deviation angle θ and electromagnetic property B8 of the finished sheet product. The average deviation angle θ is a weighted average of degree of orientation θi of each macrograin (plus or minus sign merely denotes deviation of [001] lattice orientation to rolling direction from left side or right side) and area Si (see formula (2)).




  
    
      
        θ
        =
        
          
            
              ∑
              
                n
                =
                1
              
              i
            
            ⁢
            
              
                S
                i
              
              ⁢
              
                
                
                  θ
                  i
                
                
              
            
          
          
            
              ∑
              
                n
                =
                1
              
              i
            
            ⁢
            
              S
              i
            
          
        
      
    
    
      
        (
        2
        )
      
    
  




The present invention can implement detection of magnetic property of a specimen under the circumstances that there is no magnetism measuring device or that magnetism measuring devices cannot be used due to reasons such as weight and size of the specimen being too small or surface quality of the specimen being poor. At the same time, the method is capable to precisely detect magnetic property of any small region and thus is very suitable for laboratory research on magnetic materials, such as oriented silicon steels, and especially is representative for data of the same compositions.
Comparison of the Present Invention with the Prior Art:
the present invention utilizes a metallographic method that is more convenient to detect [001] crystal orientation deviation angle of finished oriented silicon steel sheet product, further studies relativity between the [001] crystal orientation deviation angle of the finished oriented silicon steel sheet product and magnetic property of the finished product, and finally obtains relational model of the deviation angle and the magnetic property of the finished product. And, the present invention might determine magnetic property of the finished product based on the deviation angle detected by the metallographic method.
By using the metallographic etch-pit method, the present invention overcomes shortcomings of EBSD technique, e.g., expensive devices and cumbersome operations, i.e., the invention is inexpensive and easy to use, as it might detect magnetic property of a specimen only with a metallographic microscope. Secondly, the present invention establishes a more suitable relational model between the deviation angle and the magnetic property of the finished product through experiments, so as to eliminate inoperative thickness coefficient and find out Si in chemical compositions has predominant effect on magnetic property of the finished product.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of Euler angles.
FIG. 2 illustrates relationship between average deviation angle θ and magnetic property B8 of a specimen of a finished product of oriented silicon steel.
FIG. 3 is a photo of typical etch pits.
FIG. 4 illustrates the particulars and result of a specimen of embodiment 1 of the present invention (numbers labeled on crystal grains of the specimen are deviation angle θi thereof).
FIG. 5 illustrates the particulars and result of a specimen of embodiment 2 of the present invention (numbers labeled on crystal grains of the specimen are deviation angle θi thereof).



DETAILED DESCRIPTION
The invention provides a method for detecting electromagnetic property of oriented silicon steel, which utilizes a metallographic etch-pit method to measure Euler angles of each of crystal grains in a specimen of a finished product, and then utilizes the measured Euler angles to calculate comprehensive deviation angle θi of orientation <100> of various crystal grains {110} in respect to rolling plane and rolling direction of the specimen, and meanwhile counts area Si to which each of the crystal grains corresponds.
Electromagnetic property of oriented silicon steel with 2.8% Si content is measured by using Epstein's square and circle method, and then electromagnetic properties of specimens, average deviation angles of which is identical to that of the specimen with 2.8% Si content but Si contents of which are 3.0%, 3.2%, 3.4%, 3.6% and 4.0%, are measured. Suppose that correction coefficient of electromagnetic property of the specimen with 2.8% Si content is 1, specimens with other Si contents, by comparing magnetic property thereof with that of the supposed specimen, obtain chemical composition correction coefficients X of different Si contents. Finally, a correction coefficient X for all compositions can be reckoned by fitting.
Electromagnetic property B8 of a specimen can be calculated in accordance with following equation, in which B0 is magnetic induction property of a single-crystal material:




  
    B
    8
  
  =
  
    
      
        -
        0.015
      
      ×
      X
      ×
      
        
          
            ∑
            
              n
              =
              1
            
            i
          
          ⁢
          
            
              S
              i
            
            ⁢
            
              
              
                θ
                i
              
              
            
          
        
        
          
            ∑
            
              n
              =
              1
            
            i
          
          ⁢
          
            S
            i
          
        
      
    
    +
    
      (
      
        
          B
          0
        
        -
        0.04
      
      )
    
  




Embodiment 1
(1) An oriented silicon steel with 2.8% Si content is selected, which has thickness h=0.30 mm. SST (single sheet testing) detection is performed for electromagnetic property B8(T).
(2) After the detection of the electromagnetic property B8, insulated coating on surface and bottom layer of the specimen is removed; then the specimen is etched by use of special etch-pit process so as to enable each of crystal grains to have a clear etched pit (refer to FIG. 3 for photo of typical etch pits); and based on parameters (shape, deviation angle of rolling direction, ratio of both sides of the etched pit, etc.) of respective etched pit of the crystal grains, Euler angles (α,β,γ) of the crystal grain are calculated.
(3) Miller index {HKL}<UVW> of the crystal grain is reckoned by use of the Euler angles (α,β,γ) (calculation formulas are given in equations (3) and (4));

H:K:L=−sin β cos γ:sin β sin γ:cos β  (3)

U:V:W=(cos β cos α cos γ−sin α sin γ):(−cos β cos α sin γ−sin α cos γ):sin β cos α   (4)

Based on the Miller index, deviation angle θi with respect to (110)[001] is calculated (refer to equation (5));




  
    
      
        
          COS
          ⁢
          
            
          
          ⁢
          θ
        
        =
        
          
            
              
                h
                1
              
              ⁢
              
                h
                2
              
            
            +
            
              
                k
                1
              
              ⁢
              
                k
                2
              
            
            +
            
              
                l
                1
              
              ⁢
              
                l
                2
              
            
          
          
            
              
                (
                
                  
                    h
                    1
                    2
                  
                  +
                  
                    k
                    1
                    2
                  
                  +
                  
                    l
                    1
                    2
                  
                
                )
              
              ⁢
              
                (
                
                  
                    h
                    2
                    2
                  
                  +
                  
                    k
                    2
                    2
                  
                  +
                  
                    l
                    2
                    2
                  
                
                )
              
            
          
        
      
    
    
      
        (
        5
        )
      
    
  




(4) Based on the deviation angle θi and corresponding area Si of the respective crystal grains in the specimen (refer to table 1), an average deviation angle of the specimen is calculated, and magnetic property B8 of the specimen is reckoned from the equation 1 and FIG. 1, which is then compared to actual measured value (refer to the particulars in table 2).







TABLE 1







deviation angle θi (degree) and corresponding area Si (mm2) of


2# specimen











No.
Angle
Area















1
11
50



2
5
1320



3
0
141



4
9
30



5
16
25



6
3
450



7
−11
99



8
0
120



9
4
44



10
4
1500



11
−2
30



12
3
1000



13
12
200



14
0
1210



15
−3
216



16
9
500



17
9
140



18
6
2750



19
0
196



20
10
35



21
2
96



22
3
121



23
0
30



24
0
56



25
−2
1750



26
2
1080



27
3
90



28
−2
1400



29
−9
60



30
8
324



31
2
225



32
10
52



33
0
2000



34
2
660













  
    θ
    =
    
      
        
          ∑
          
            n
            =
            1
          
          i
        
        ⁢
        
          
            S
            i
          
          ⁢
          
            
            
              θ
              i
            
            
          
        
      
      
        
          ∑
          
            n
            =
            1
          
          i
        
        ⁢
        
          S
          i
        
      
    
  




  
    θ
    =
    3.3
  



See FIG. 4 and Table 2, the figure shows the particulars and result of the specimen of the embodiment 1 (numbers labeled on the crystal grains of the specimen are deviation angle θi of the crystal grains).










TABLE 2









Measured value B8 (T)
1.95



Calculated value B8 (T)
1.9405



Deviation (%)
0.5










As can be seen from the Table 2, deviation of magnetic property data detected by the present invention over magnetic property data detected by SST is 0.5%, which fully satisfies requirements for high precision detection.
Embodiment 2
(1) A specimen of an oriented silicon steel with 2.8% Si content and thickness h=0.27 mm is selected. An SST (single sheet testing) detection for electromagnetic property B8 (T) is performed.
(2) After the detection of the electromagnetic property B8, insulated coating and bottom layer on the surfaces of the specimen is removed; then the specimen is etched by use of special etch-pit process so as to enable each of crystal grains to have a clear etched pit (refer to FIG. 3 for photo of typical etch pits); and based on parameters (shape, deviation angle of rolling direction, ratio of both sides of the etched pit, etc.) of respective etched pit of the crystal grains, Euler angles (α,β,γ) of the crystal grain are calculated.
(3) Miller index {HKL}<UVW> of the crystal grain is reckoned by use of the Euler angles (α,β,γ) (calculation formulas are given in equations (2) and (3));

H:K:L=−sin β cos γ:sin β sin γ:cos β  (2)

U:V:W=(cos β cos α cos γ−sin α sin γ):(−cos β cos α sin γ−sin α cos γ):sin β cos α   (3)

Based on the Miller index, deviation angle θi with respect to (110)[001] is reckoned (refer to equation (4));




  
    
      
        
          COS
          ⁢
          
            
          
          ⁢
          θ
        
        =
        
          
            
              
                h
                1
              
              ⁢
              
                h
                2
              
            
            +
            
              
                k
                1
              
              ⁢
              
                k
                2
              
            
            +
            
              
                l
                1
              
              ⁢
              
                l
                2
              
            
          
          
            
              
                (
                
                  
                    h
                    1
                    2
                  
                  +
                  
                    k
                    1
                    2
                  
                  +
                  
                    l
                    1
                    2
                  
                
                )
              
              ⁢
              
                (
                
                  
                    h
                    2
                    2
                  
                  +
                  
                    k
                    2
                    2
                  
                  +
                  
                    l
                    2
                    2
                  
                
                )
              
            
          
        
      
    
    
      
        (
        4
        )
      
    
  




(4) Based on the deviation angle θi and corresponding area Si of the respective crystal grains in the specimen (refer to Table 3), an average deviation angle of the specimen is calculated, and magnetic property B8 of the specimen is reckoned from the equation (1) and FIG. 1, which is then compared to actual measured value (refer to the particulars in table 3).







TABLE 3







deviation angle θi (degree) and corresponding area Si (mm2) of the


specimen











No.
Angle
Area















1
−3
10



2
5
35



3
0
30



4
5
100



5
7
128



6
7
400



7
9
100



8
7
132



9
−6
400



10
−4
70



11
7
300



12
−3
90



13
3
600



14
0
440



15
−5
50



16
11
80



17
9
9



18
7
30



19
5
300



20
−6
144



21
−23
16



22
−6
36



23
0
100



24
18
40



25
29
35



26
−9
575



27
17
1200



28
7
91



29
3
125



30
10
40



31
−10
20



32
2
18



33
0
50



34
4
124



35
0
40



36
12
120



37
0
255



38
22
144



39
17
15



40
−4
300



41
17
63



42
5
230



43
6
450



44
−42
48



45
−8
28



46
42
15



47
27
50



48
0
300



49
38
274



50
10
51



51
7
78



52
20
226



53
0
150



54
14
144



55
12
80



56
13
140



57
11
70



58
−1
180



59
−2
90



60
6
280



61
12
440



62
7
375



63
20
62



64
−24
24



65
−4
56



66
0
700



67
−2
1200



68
14
9



69
0
120



70
0
400



71
10
205



72
8
150



73
16
60



74
−6
35



75
13
360



76
11
20



77
0
140



78
4
1600



79
8
200



80
16
80



81
14
16



82
−1
850



83
14
63



84
−2
54



85
7
580



86
10
42



87
0
20



88
7
56



89
−3
56



90
3
225



91
11
25



92
0
30



93
−38
12



94
7
6













  
    θ
    =
    
      
        
          ∑
          
            n
            =
            1
          
          i
        
        ⁢
        
          
            S
            i
          
          ⁢
          
            
            
              θ
              i
            
            
          
        
      
      
        
          ∑
          
            n
            =
            1
          
          i
        
        ⁢
        
          S
          i
        
      
    
  




  
    θ
    =
    7
  



See FIG. 5 and Table 4, the figure shows the particulars and result of the specimen of the embodiment 2 (numbers labeled on the crystal grains of the specimen are deviation angle θi of the crystal grains). As can be seen from the Table 4, deviation of magnetic property data detected by the present invention over magnetic property data detected by SST is merely 0.4%, which fully satisfies requirements for high precision detection.










TABLE 4









Measured value B8 (T)
1.878



Calculated value B8 (T)
1.885



Deviation (%)
0.4

## Claims

1. A method for detecting an electromagnetic property, B8, of an oriented silicon steel, the oriented silicon steel having a Si percentage content of 2.8 ̃4.0%, the oriented silicon steel comprising crystal grains, the method comprising:
etching an etched pit into each of the crystal grains of the oriented silicon steel;
measuring, using a metallographic microscope and the etched pits, Euler angles of each of the crystal grains in the oriented silicon steel;
calculating an orientation deviation angle θi of each of the crystal grains using the respective Euler angles of each of the crystal grains;
calculating the electromagnetic property, B8, using the following equation:





  
    
      
        
          B
          8
        
        =
        
          
            
              -
              0.015
            
            ×
            X
            ×
            
              
                
                  ∑
                  
                    n
                    =
                    1
                  
                  i
                
                ⁢
                
                  
                    S
                    i
                  
                  ⁢
                  
                    
                    
                      θ
                      i
                    
                    
                  
                
              
              
                
                  ∑
                  
                    n
                    =
                    1
                  
                  i
                
                ⁢
                
                  S
                  i
                
              
            
          
          +
          
            (
            
              
                B
                0
              
              -
              0.04
            
            )
          
        
      
    
    
      
        (
        1
        )
      
    
  



where Si is an area of each of the crystal grains, X is a correction coefficient of the element silicon, where X ranges from 0.1 T/degree to 10 T/degree and B0 is a magnetic induction property of a single-crystal material.