Alloy, magnet core and method for producing a strip from an alloy

1. An alloy having a composition consisting of

Fe 100-a-b-c-d-x-y-z Cu a Nb b M c T d Si x B y Z z and up to 1 atomic % impurities, wherein M is Mo and/or Ta, T is one or more of the elements V, Cr, Co or Ni and Z is one or more of the elements C, P or Ge, and wherein 0.0 atomic %≤a<1.5 atomic %, 0.0 atomic %≤b<3.0 atomic %, 0.2 atomic %≤c≤4.0 atomic %, 0.0 atomic %≤d<5.0 atomic %, 12.0 atomic %<x<18.0 atomic %, 5.0 atomic %<y<12.0 atomic %, 0.0 atomic %≤z<2.0 atomic % and 2.0 atomic %≤(b+c)≤4.0 atomic %,

wherein the alloy is in the form of a strip,

wherein the alloy comprises a nanocrystalline structure, at least 50% by volume of the grains having an average size of less than 100 nm,

wherein the alloy has a remanence ratio J r /J s <0.02, J r being the remanent polarisation and J s being the saturation polarisation,

wherein the alloy has a coercitive field strength H c which is less than 1% of the anisotropic field strength H a ,

wherein the strip is heat-treated in a continuous process at a annealing temperature between 450° C. and 750° C. under a tension of 5 MPa to 1000 MPa with a dwell time of 2 seconds to 2 minutes, and

wherein the remanent polarisation J r , the saturation polarization J s , the coercitive field strength H c and/or the anisotropic field strength H a or permittivity of the strip are continuously measured as the strip leaves a continuous furnace, and if a deviation from a permitted deviation range of the remanent polarisation J r , the saturation polarization J s , the coercitive field strength H c , and/or the anisotropic field strength H a or permittivity is detected, the tension applied to the strip is adjusted to bring the remanent polarisation J r , the saturation polarization J s , the coercitive field strength H c , and/or the anisotropic field strength H a or permittivity measured to be outside the permitted deviation range within the permitted deviation range.

2. The alloy according to claim 1 , wherein the remanence ratio J r /J s is <0.01.

3. The alloy according to claim 1 , wherein the hysteresis loop of the alloy has a nonlinearity factor NL, NL being <0.5%, and

NL=100/2(δJ auf +δJ ab )/J s

wherein δJ auf is the standard deviation of the magnetic polarisation from a regression line through the ascending branch of the hysteresis loop between polarisation values of ±75% of the saturation polarisation J s and δJ ab is the standard deviation of the magnetic polarisation from a regression line through the descending branch of the hysteresis loop between polarisation values of ±75% of the saturation polarisation J s .

4. The alloy according to claim 1 , wherein the alloy has a permeability μ between 40 and 10000.

5. The alloy according to claim 1 , wherein the alloy has a saturation magnetostriction of less than 1 ppm.

6. The alloy according to claim 1 , wherein the alloy has a saturation polarisation J s that is ≥1.22 T and the coercitive field strength H c is ≤8 A/m.

7. The alloy according to claim 1 , wherein 0.0 atomic %≤b<2.5 atomic %.

8. The alloy according to claim 1 , wherein 2.1 atomic %≤(b+c)≤3.0 atomic %.

9. The alloy according to claim 1 , wherein 0.0 atomic %≤d<2.0 atomic %.

10. The alloy according to claim 1 , wherein 14.0 atomic %<x<17 atomic % and 5.5 atomic %<y<8.0 atomic %.

11. The alloy according to claim 1 , wherein the strip is heat-treated in the continuous process under a tension of 10 MPa to 250 MPa with a dwell time of 2 seconds to 2 minutes.

12. The alloy according to claim 1 , wherein the strip is heat-treated in the continuous process under a tension of 250 MPa to 1000 MPa with a dwell time of 2 seconds to 2 minutes.

13. A magnet core made from an alloy according to claim 1 .

14. The magnet core according to claim 13 , having the form of a wound strip.

15. The magnet core according to claim 13 , wherein the strip has an oxide layer with a thickness of <0.2 μm on its surface.

16. The magnet core according to claim 13 , wherein the strip is coated with an additional insulating layer.

17. The alloy according to claim 1 , wherein the minimum niobium content is 1.8 atomic % and the minimum Mo content is 0.2 atomic %.

18. The alloy according to claim 1 , wherein the alloy does not contain any tantalum, except as a possible impurity.

19. The alloy according to claim 1 , wherein M is Mo and 1.8 atomic %≤b<3.0 atomic %.

20. The alloy according to claim 1 , wherein 0.0 atomic %<b<2.5 atomic % and 2.1 atomic %≤(b+c)<3.0 atomic %.

21. The alloy according to claim 1 , wherein the alloy has a permeability μ in the range of 50 to 200.

22. The alloy according to claim 1 , wherein the alloy has a coercitive field strength H c which is less than 10 A/m.

23. A method for producing a strip, comprising the following:

providing a strip from an amorphous alloy with a composition consisting of Fe 100a-b-c-d-x-y-z Cu a Nb b M c T d Si x B y Z z and up to 1 atomic % impurities, wherein M is Mo and/or Ta, T is one or more of the elements V, Cr, Co or Ni and Z is one or more of the elements C, P or Ge, and wherein 0.0 atomic %≤a<1.5 atomic %, 0.0 atomic %≤b<3.0 atomic %, 0.2 atomic %≤c≤4.0 atomic %, 0.0 atomic %≤d<5.0 atomic %, 12.0 atomic %<x<18.0 atomic %, 5.0 atomic %<y<12.0 atomic %, 0.0 atomic %≤z<2.0 atomic % and 2.0 atomic %≤(b+c)≤4.0 atomic %, wherein the alloy has a remanence ratio J r /J s <0.02, J r being the remanent polarisation and J s being the saturation polarisation, and the alloy has a coercitive field strength H c which is less than 1% of the anisotropic field strength H a ,

heat treating the strip under a tension of 5 MPa to 1000 MPa with a dwell time of 2 seconds to 2 minutes in a continuous process at an annealing temperature T a , wherein 450° C.≤T a ≤750° C.,

continuously measuring the remanent polarisation J r , the saturation polarization J s , the coercitive field strength H c and/or the anisotropic field strength H a or permittivity of the strip as the strip leaves a continuous furnace, and if a deviation from a permitted deviation range of the remanent polarisation J r , the saturation polarization J s , the coercitive field strength H c and/or the anisotropic field strength H a or permittivity is detected, adjusting the tension applied to the strip to bring the remanent polarisation J r , the saturation polarization J s , the coercitive field strength H c and/or the anisotropic field strength H a or permittivity measured to be outside the permitted deviation range within the permitted deviation range.

24. The method according to claim 23 , wherein the strip is heat-treated in the continuous furnace.

25. The method according to claim 24 , wherein the strip is pulled through the continuous furnace with a speed s, so that a dwell time of the strip in a temperature zone of the continuous furnace at the temperature T a is between 2 seconds and 2 minutes.

26. The method according to claim 23 , wherein the strip is heat-treated in the continuous furnace under a tension of 5 MPa to 1000 MPa.

27. The method according to claim 26 , wherein the strip is heat-treated in the continuous furnace under a tension of 10 MPa to 250 MPa.

28. The method according to claim 26 , wherein the strip is heat-treated in the continuous furnace under a tension of 250 MPa to 1000 MPa.

29. The method according to claim 23 , further comprising: predetermining a desired value of the anisotropic field strength H a or the permeability and/or a maximum value of the remanence ratio J r /J s of less than 0.02 and/or a maximum value of the coercitive field strength H c which is less than 1% of the anisotropic field strength H a and/or less than 10 A/m, as well as the permitted deviation range for each of these values.