Manufacturing method of grain-oriented magnetic steel sheet
View Patent ↗A nitriding treatment (Step S 6 ) in which an N content of a decarburization-annealed steel strip is increased is performed between start of a decarburization annealing (Step S 4 ) and occurrence of secondary recrystallization in a finish annealing (Step S 5 ). In hot rolling (Step S 1 ), a silicon steel material is held in a temperature range between 1000° C. and 800° C. for 300 seconds or longer, and then finish rolling is performed.
1. A manufacturing method of a grain-oriented electrical steel sheet, comprising:
hot rolling a silicon steel material so as to obtain a hot-rolled steel strip, the silicon steel material containing Si: 0.8 mass % to 7 mass %, acid-soluble Al: 0.01 mass % to 0.065 mass %, N: 0.004 mass % to 0.012 mass %, Mn: 0.05 mass % to 1 mass %, Ti: 0.004 mass % or less and B: 0.0005 mass % to 0.0080 mass %, the silicon steel material further containing at least one element selected from a group consisting of S and Se being 0.003 mass % to 0.015 mass % in total amount, a C content being 0.085 mass % or less, and a balance being composed of Fe and inevitable impurities;
annealing the hot-rolled steel strip so as to obtain an annealed steel strip;
cold rolling the annealed steel strip one time or more so as to obtain a cold-rolled steel strip;
decarburization annealing the cold-rolled steel strip so as to obtain a decarburized-annealed steel strip in which primary recrystallization is caused;
coating an annealing separating agent containing MgO as its main component on the decarburized-annealed steel strip; and
causing secondary recrystallization by finish annealing the coated decarburized-annealed steel strip, wherein
the method further comprises performing a nitriding treatment in which an N content of the decarburized-annealed steel strip is increased between start of the decarburization annealing and occurrence of the secondary recrystallization in the finish annealing,
wherein the hot rolling comprises:
holding the silicon steel material in a temperature range from 1000° C. to 800° C. for 300 seconds or longer; and
then performing finish rolling.
2. The manufacturing method of the grain-oriented electrical steel sheet according to claim 1 , further comprising heating the silicon steel material at a predetermined temperature which is a temperature T 1 (° C.) or lower before the hot rolling, in a case when no Se is contained in the silicon steel material, the temperature T 1 is expressed by equation (1) below
T 1=14855/(6.82−log([Mn]×[S]))−273 (1)
wherein, [Mn] represents a Mn content (mass %) of the silicon steel material, and [S] represents an S content (mass %) of the silicon steel material.
3. The manufacturing method of the grain-oriented electrical steel sheet according to claim 1 , further comprising heating the silicon steel material at a predetermined temperature which is a temperature T 2 (° C.) or lower before the hot rolling, in a case when no S is contained in the silicon steel material, the temperature T 2 is expressed by equation (2) below
T 2=10733/(4.08−log([Mn]×[Se]))−273 (2)
wherein, [Mn] represents a Mn content (mass %) of the silicon steel material, and [Se] represents an Se content (mass %) of the silicon steel material.
4. The manufacturing method of the grain-oriented electrical steel sheet according to claim 1 , further comprising heating the silicon steel material at a predetermined temperature which is lower than each of a temperature T 1 (° C.) and a temperature T 2 (° C.) or lower before the hot rolling, in a case when S and Se are contained in the silicon steel material, the temperature T 1 is being expressed by equation (1) below, and the temperature T 2 is expressed by equation (2) below
T 1=14855/(6.82−log([Mn]×[S]))−273 (1)
T 2=10733/(4.08−log([Mn]×[Se]))−273 (2)
wherein, [Mn] represents a Mn content (mass %) of the silicon steel material, [S] represents an S content (mass %) of the silicon steel material, and [Se] represents an Se content (mass %) of the silicon steel material.
5. The manufacturing method of the grain-oriented electrical steel sheet according to claim 1 , wherein the nitriding treatment is performed under a condition that an N content [N] of a steel strip obtained after the nitriding treatment satisfies equation (3) below
[N]≧14/27[Al]+14/11[B]+14/47[Ti] (3)
wherein, [N] represents the N content (mass %) of the steel strip obtained after the nitriding treatment, [Al] represents an acid-soluble Al content (mass %) of the steel strip obtained after the nitriding treatment, [B] represents a B content (mass %) of the steel strip obtained after the nitriding treatment, and [Ti] represents a Ti content (mass %) of the steel strip obtained after the nitriding treatment.
6. The manufacturing method of the grain-oriented electrical steel sheet according to claim 2 , wherein the nitriding treatment is performed under a condition that an N content [N] of a steel strip obtained after the nitriding treatment satisfies equation (3) below
[N]≧14/27[Al]+14/11[B]+14/47[Ti] (3)
wherein, [N] represents the N content (mass %) of the steel strip obtained after the nitriding treatment, [Al] represents an acid-soluble Al content (mass %) of the steel strip obtained after the nitriding treatment, [B] represents a B content (mass %) of the steel strip obtained after the nitriding treatment, and [Ti] represents a Ti content (mass %) of the steel strip obtained after the nitriding treatment.
7. The manufacturing method of the grain-oriented electrical steel sheet according to claim 3 , wherein the nitriding treatment is performed under a condition that an N content [N] of a steel strip obtained after the nitriding treatment satisfies equation (3) below
[N]≧14/27[Al]+14/11[B]+14/47[Ti] (3)
wherein, [N] represents the N content (mass %) of the steel strip obtained after the nitriding treatment, [Al] represents an acid-soluble Al content (mass %) of the steel strip obtained after the nitriding treatment, [B] represents a B content (mass %) of the steel strip obtained after the nitriding treatment, and [Ti] represents a Ti content (mass %) of the steel strip obtained after the nitriding treatment.
8. The manufacturing method of the grain-oriented electrical steel sheet according to claim 4 , wherein the nitriding treatment is performed under a condition that an N content [N] of a steel strip obtained after the nitriding treatment satisfies equation (3) below
[N]≧14/27[Al]+14/11[B]+14/47[Ti] (3)
wherein, [N] represents the N content (mass %) of the steel strip obtained after the nitriding treatment, [Al] represents an acid-soluble Al content (mass %) of the steel strip obtained after the nitriding treatment, [B] represents a B content (mass %) of the steel strip obtained after the nitriding treatment, and [Ti] represents a Ti content (mass %) of the steel strip obtained after the nitriding treatment.
9. The manufacturing method of the grain-oriented electrical steel sheet according to claim 1 , wherein the nitriding treatment is performed under a condition that an N content [N] of a steel strip obtained after the nitriding treatment satisfies equation (4) below
[N]≧2/3[Al]+14/11[B]+14/47[Ti] (4)
wherein, [N] represents the N content (mass %) of the steel strip obtained after the nitriding treatment, [Al] represents an acid-soluble Al content (mass %) of the steel strip obtained after the nitriding treatment, [B] represents a B content (mass %) of the steel strip obtained after the nitriding treatment, and [Ti] represents a Ti content (mass %) of the steel strip obtained after the nitriding treatment.
10. The manufacturing method of the grain-oriented electrical steel sheet according to claim 2 , wherein the nitriding treatment is performed under a condition that an N content [N] of a steel strip obtained after the nitriding treatment satisfies equation (4) below
[N]≧2/3[Al]+14/11[B]+14/47[Ti] (4)
wherein, [N] represents the N content (mass %) of the steel strip obtained after the nitriding treatment, [Al] represents an acid-soluble Al content (mass %) of the steel strip obtained after the nitriding treatment, [B] represents a B content (mass %) of the steel strip obtained after the nitriding treatment, and [Ti] represents a Ti content (mass %) of the steel strip obtained after the nitriding treatment.
11. The manufacturing method of the grain-oriented electrical steel sheet according to claim 3 , wherein the nitriding treatment is performed under a condition that an N content [N] of a steel strip obtained after the nitriding treatment satisfies equation (4) below
[N]≧2/3[Al]+14/11[B]+14/47[Ti] (4)
wherein, [N] represents the N content (mass %) of the steel strip obtained after the nitriding treatment, [Al] represents an acid-soluble Al content (mass %) of the steel strip obtained after the nitriding treatment, [B] represents a B content (mass %) of the steel strip obtained after the nitriding treatment, and [Ti] represents a Ti content (mass %) of the steel strip obtained after the nitriding treatment.
12. The manufacturing method of the grain-oriented electrical steel sheet according to claim 4 , wherein the nitriding treatment is performed under a condition that an N content [N] of a steel strip obtained after the nitriding treatment satisfies equation (4) below
[N]≧2/3[Al]+14/11[B]+14/47[Ti] (4)
wherein, [N] represents the N content (mass %) of the steel strip obtained after the nitriding treatment, [Al] represents an acid-soluble Al content (mass %) of the steel strip obtained after the nitriding treatment, [B] represents a B content (mass %) of the steel strip obtained after the nitriding treatment, and [Ti] represents a Ti content (mass %) of the steel strip obtained after the nitriding treatment.
13. The manufacturing method of the grain-oriented electrical steel sheet according to claim 1 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
14. The manufacturing method of the grain-oriented electrical steel sheet according to claim 2 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
15. The manufacturing method of the grain-oriented electrical steel sheet according to claim 3 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
16. The manufacturing method of the grain-oriented electrical steel sheet according to claim 4 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
17. The manufacturing method of the grain-oriented electrical steel sheet according to claim 5 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
18. The manufacturing method of the grain-oriented electrical steel sheet according to claim 6 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
19. The manufacturing method of the grain-oriented electrical steel sheet according to claim 7 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
20. The manufacturing method of the grain-oriented electrical steel sheet according to claim 8 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
21. The manufacturing method of the grain-oriented electrical steel sheet according to claim 9 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
22. The manufacturing method of the grain-oriented electrical steel sheet according to claim 10 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
23. The manufacturing method of the grain-oriented electrical steel sheet according to claim 11 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
24. The manufacturing method of the grain-oriented electrical steel sheet according to claim 12 , wherein the silicon steel material further contains at least one element selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.
25. The manufacturing method of the grain-oriented electrical steel sheet according to claim 1 , wherein BN precipitates during the hot rolling.