A sheet of non-textured electrical steel with low iron loss at high frequencies and corresponding fatigue properties and a method for its manufacture

Claims

1. A sheet of non-oriented electrical steel which, in addition to Fe and inevitable impurities, additionally contains the following chemical elements in mass percent: 0 <C≤0,0045%, Si: 2,65-3,75%, Mn: 0,10-1,04%, Al: 0,10-1,85%; причём количество включений Al2O3размером 2,0 мкм или более в листе из нетекстурированной электротехнической стали составляет не более 4 частиц / мм 2 , preferably no more than 2 particles / mm 2 .

2. A sheet of non-oriented electrical steel according to paragraph 1, which includes the following chemical elements in mass percent: 0 <C≤0,0045%, Si: 2,65-3,75%, Mn: 0,10-1,04%, Al: 0,10-1,85%; остальное составляют Fe железо и неизбежные примеси.

3. A sheet of non-oriented electrical steel according to claim 1 or 2, which additionally includes Ca and / or REE, in mass percent Ca: 0.0005-0.0060%, and / or REE: 0.0005-0.0120%.

4. A sheet of non-oriented electrical steel according to any one of claims 1 to 3, which further comprises at least one element from Nb, V, Cu, Mo, Ni, Co, Cr, Sn, Sb and Zr in a total amount of 0.0095-1.05% by weight.

5. A sheet of non-oriented electrical steel according to claim 4, which includes Sn, in mass percent: 0.0035-0.25%.

6. A non-oriented electrical steel sheet according to any one of claims 1 to 5, wherein the unavoidable impurities include P, S, N and Ti, in mass percentages of P≤0.02%, S≤0.0055%, N≤0.0035% and Ti≤0.0025%.

7. A sheet of non-oriented electrical steel according to any of paragraphs 1-6, with a thickness of 0.15-0.35 mm.

8. A sheet of non-oriented electrical steel according to any one of paragraphs 1-7, in which the average grain size is 45-165 µm.

9. A sheet of non-oriented electrical steel according to any one of paragraphs 1-8, in which the iron loss P 1,0 / 600are ≤ 36−([Si]+1.2×[Al]) / 5t, where t denotes the thickness of the steel sheet in mm, and [Si] and [Al] are replaced by numerical values ​​preceding the % symbol, denoting the mass percentage of Si and Al, respectively, in the steel sheet.

10. A sheet of non-oriented electrical steel according to any one of paragraphs 1-9, wherein the sheet of non-oriented electrical steel has a fatigue limit of S 25 at 25ºС ≥ 365 MPa and fatigue limit S 150 at 150ºС ≥ 294 MPa, and preferably the ratio S 150 to S 25 , S 150 / S 25 , satisfies the condition 0.80 ≤ S 150 / S 25 ≤ 1.

0.

11. A method for producing a non-oriented electrical steel sheet according to any one of claims 1 to 10, comprising the following steps performed sequentially: melting, RH refining, casting, hot rolling, normalizing annealing, cold rolling, final annealing, and applying an insulating coating, wherein in the RH refining step, the purging gas flow rate V1 during decarburization and the purging gas flow rate V0 at the end of decarburization satisfy the following relationships: V1≥ V0+12[Al], where [Al] is the Al content in the molten steel (replaced by the numerical value before the symbol % of the mass percentage of the Al element in the molten steel), and V0≥ 140 Nm³ / h; and after decarburization, the ratio of the free oxygen content [O] to the carbon content [C], [O] / [C], in the molten steel is set to 21.5 or less.

12. The method according to claim 11, in which single-pass or two-pass cold rolling is performed.

13. The method according to item 11 or 12, wherein the final annealing is carried out at a temperature of 830-990ºC.