Non-grain oriented electrical steel alloys

Abstract

A non-grain oriented electrical steel alloy composition is provided comprising: 0.05 wt% or less of carbon; 2 wt% to 7 wt% of silicon; 2 wt% to 7 wt% of manganese; 0 wt% to 4 wt% or less of aluminium; and at least 0.2 wt% of the group consisting of nickel, chromium and molybdenum. The alloy composition comprises no more than: 2 wt% of nickel; 3 wt% of chromium; and 2 wt% of molybdenum. The balance of the composition consists of iron and no more than 0.2 wt% total in other alloying elements or impurities.

Description

[0001] Non-Grain Oriented Electrical Steel Alloys

[0002] Technical Field

[0003] This invention relates generally to a non-grain oriented electrical steel alloy composition. More specifically, although not exclusively, this invention relates to a non-grain oriented electrical steel sheet made from the non-grain oriented electrical steel alloy composition.

[0004] Background

[0005] With an ever increasing focus on addressing climate change and the increase in energy prices, recent years have seen a dramatic increase in the production of electric motors. Components made out of electrical steel alloys, such as non-grain oriented electrical steel sheets, are fundamental for the manufacture of the majority of electric motors as part of the core of rotary machines which generate propulsion. Exploring different electrical steel alloy compositions with a view to improving the efficiency of components made from electrical steel is thus of keen interest and is expected to have significant economic and environmental benefits e.g. in the manufacture of electric vehicles.

[0006] Electrical steels have typically used <3.5 wt% silicon, with 3.2 wt% being the most widely used. These materials have been iteratively improved from the pure iron that was the soft magnetic material of choice in the early 20th century. Modern alloys remain predominantly binary alloys (Fe-Si) (with only minor additions for grain pinning (Al, N etc)) and offer a cost effective, mass producible alloy which dominates with around 80% of the soft magnetic materials market.

[0007] Electrical steel with 6.5 wt% silicon has been long observed to offer superior magnetic properties with increased electrical resistivity and reduced coercivity compared to its lower silicon containing counterparts. However, this material exhibits a high degree of brittleness, preventing the conventional production of useable electrical steel sheets. This brittleness has since been attributed to the formation of the ordered BCC structures of the B2 or D03 phases from the less ordered A2 phase during processing. For example, the majority of electrical steel sheets are formed by continuous casting, followed by hot and cold rolling to provide sheets of thicknesses down to, for example, 0.10 - 0.35 mm. Thus, in spite of their superior electrical / magnetic properties, electrical steels with 6.5 wt% silicon are limited in their commercial producibility.

[0008] To address this problem, alternative methods of producing electrical steel sheets have been proposed. For example, siliconization involves the deposition of SiCk onto a 3 wt% silicon electrical steel followed by a range of heat treatments which allows production of an electrical steel having 6.5 wt% silicon. However, subsequent processes such as stamping and stacking remains difficult with these brittle materials. Furthermore, these methods are typically more complex, having additional steps which made their commercial application more limited due to increased cost and reduced production rate.

[0009] Furthermore, applications such as electric vehicles, unmanned aerial vehicles and high performance power tools are starting to demand more from electrical steels used to make components for use therein. For example, with increasing revolutions per minute of motors, higher mechanical loads are being placed on the materials. Increasing loads mean that higher strength electrical steels are desired to avoid exceeding yield strength which would result in increased losses and / or potentially motor failure. Whilst laminate design can be utilised to aid with this, offering a high performing alloy both mechanical and magnetically offers the greatest flexibility for electrical motor design optimisation.

[0010] The object of the present invention is thus to provide an improved non-oriented electrical steel alloy composition that addresses at least some of the aforementioned problems. In particular, the aim of the present invention is to provide a family of non-oriented electrical steel alloy compositions that may be produced economically, via conventional production techniques, but offer improved combination of resistivity, processability and strength with respect to the alloys known in the art. For example, a non-limiting aim of the present invention is to provide an electrical steel alloy composition with electrical / magnetic properties comparable to a 6.5 wt% silicon electrical steel but with vastly improved processability.

[0011] Summary of Invention

[0012] In a first aspect, a non-grain oriented electrical steel alloy composition is provided, the composition comprising:

[0013] 0.05 wt% or less of carbon;

[0014] 7 wt% or less of silicon 0- 7 wt% of manganese

[0015] 2 wt% or less of nickel

[0016] 3 wt% or less of chromium

[0017] 4 wt% or less of aluminium

[0018] 2 wt% or less of molybdenum the balance consisting of iron and no more than 0.2 wt% total in other alloying elements or impurities; wherein the non-grain oriented electrical steel alloy composition has a calculated R- value (R) and a T-value (T) in accordance with the following equations:

[0019] R = 10.11 + 6.20Mn + 11.75Si + 2.98Ni + 5.57Cr + 9.01AZ and

[0020] T = -363.38 + 262.17C + 24.69Mn + 228.77SI + 9.57Ni + 20.26Cr + 177.43AZ + 16.92MO + 16.64C. Mn - 41.33C. Si - 33.57C. Ni + 1.04C. Cr - 24.01C. Al - 22.23C. Mo - 2.16Mn. Si + 0.4 Mn. Ni - 0.68Mn. Cr - 2.11Mn. Al - 0.71Mn. Mo - 1.2Si. Ni - 1.67 Si. Cr - 8.77 Si. Al - 0.98Si. Mo + 0.41NL Cr + 3.03Ni. Al - 0.69Ni. Mo - 1.77 Cr. Al - 0.02Cr. Al + 0.63AI. Mo + 840.78 C2- 0.29 Mn2- 7.95 Si2+ 0.89 Ni2- 0.35 Cr2- 9.14 Al2- 3.16 Mo2; wherein C, Mn, Si, Ni, Cr, Al, Mo are the respective wt% of carbon, manganese, silicon, nickel, chromium, aluminium and molybdenum in the composition; and and wherein the R- and T- values satisfy the following relationship:

[0021] R < (13 X T) - 288.83 .

[0022] The first aspect of the present invention thus aims to provide a family of improved non-grain oriented electrical steel alloy compositions that are both high performing and processable. In particular, the first aspect of the present invention provides a family of alloy compositions that show improved properties and performance compared to predominantly binary Fe-Si alloys. The inventors have surprisingly found that the parameters defined in the first aspect of the invention allow the successful design of improved non-grain orientated electrical steel alloy compositions with predictable performance properties, the performance of which has been verified experimentally. An important part of the design process leading to the compositions of the first aspect is the determination of the R-value and T-value as recited above. The R-value is representative of the resistivity of the composition based on the wt% of the components comprised therein. The T-value is representative of the A2-B2 transformation temperature (T) based on the wt% of the components comprised therein, whereby compositions having a reduced A2-B2 (compared to predominantly binary Fe-Si alloys) would be expected to show improved performance properties. The R-value and the T-value thus provide performance indices by which a composition may be evaluated numerically to assess whether the composition is improved, especially relative to predominantly binary Fe-Si alloys. The inventors have thus surprisingly found that compositions meeting the requirement whereby R<(13xT)-363.83- 75 and having a compositional makeup as defined in the first aspect allows both the prediction and provision of a novel family of improved non-grain oriented electrical steel alloy compositions.

[0023] Optionally, the non-grain oriented electrical steel alloy composition comprises 0.04 wt% or less of carbon, e.g. 0.03 wt% or less of carbon, e.g. 0.02 wt% or less of carbon, e.g. 0.01 wt% or less of carbon, e.g. 0.006 wt% or less of carbon, e.g. 0.0055 wt% or less of carbon, e.g. 0.005 wt% or less of carbon, e.g. 0.0045 wt% or less of carbon, e.g. 0.004 wt% or less of carbon, e.g. 0.0035 wt% or less of carbon, e.g. 0.003 wt% or less of carbon, e.g. 0.0025 wt% or less of carbon, e.g. 0.002 wt% or less of carbon, 0.001 wt% or less of carbon.

[0024] Optionally, the non-grain oriented electrical steel alloy composition comprises 0.001 wt% or more of carbon, e.g. 0.0015 wt% or more of carbon, e.g. 0.002 wt% or more of carbon, e.g. 0.0025 wt% or more of carbon, e.g. 0.003 wt% or more of carbon, e.g. 0.0035 wt% or more of carbon, e.g. 0.0045 wt% or more of carbon, e.g. 0.005 wt% or more of carbon.

[0025] Optionally, the non-grain oriented electrical steel alloy composition comprises 0 wt% or more of manganese, e.g. 0.5 wt% or more of manganese, e.g. 1 wt% or more of manganese, e.g. 1.5 wt% or more of manganese, e.g. 2 wt% or more of manganese, e.g. 2.5 wt% or more of manganese, e.g. 3 wt% or more of manganese. Optionally, the non- grain oriented electrical steel alloy composition comprises 5 wt% or less of manganese, e.g. 4.5 wt% or less of manganese, e.g. 4 wt% or less of manganese. Optionally, the non- grain oriented electrical steel alloy composition comprises from 2 wt% to 5 wt% of mangangese (i.e. inclusive of the end points), e.g. between 2 wt% to 5 wt % of manganese (i.e. exclusive of the end points), e.g. from 2.1 wt% to 4.9 wt% of manganese, e.g. between 2.1 wt% to 4.9 wt% of manganese, e.g. from 2.2 wt% to 4.8 wt% of manganese, e.g. between 2.2 wt% to 4.8 wt% of manganese, e.g. from 2.3 wt% to 4.7 wt% of manganese, e.g. between 2.3 wt% to 4.7 wt% of manganese, e.g. from 2.4 wt% to 4.6 wt% of manganese, e.g. between 2.4 wt% to 4.7 wt% of manganese, e.g. from 2.5 wt% to 4.5 wt% of manganese, e.g. between 2.5 wt% to 4.5 wt% of manganese.

[0026] Optionally, the non-grain oriented electrical steel alloy composition comprises 2 wt% or more of silicon, e.g. 2.5 wt% or more of silicon, e.g. 3 wt% or more of silicon, e.g. 3.1 wt% or more of silicon, e.g. 3.2 wt% or more of silicon, e.g. 3.3 wt% or more of silicon, e.g. 3.4 wt% or more of silicon, e.g. 3.5 wt% or more of silicon, e.g. 3.6 wt% or more of silicon, e.g. 3.7 wt% or more of silicon, e.g. 3.8 wt% or more of silicon, e.g. 3.9 wt% or more of silicon, e.g. 4 wt% or more of silicon, e.g. 4.1 wt% or more of silicon, e.g. 4.2 wt% or more of silicon, e.g. 4.3 wt% or more of silicon, e.g. 4.4 wt% or more of silicon, e.g. 4.5 wt% or more of silicon, e.g. 4.6 wt% or more of silicon, e.g. 4.7 wt% or more of silicon, e.g. 4.8 wt% or more of silicon, e.g. 4.9 wt% or more of silicon.

[0027] Optionally, the non-grain oriented electrical steel alloy composition comprises 6 wt% or less of silicon, e.g. 5.9 wt% or less of silicon, e.g. 5.8 wt% or less of silicon, e.g. 5.7 wt% or less of silicon, e.g. 5.6wt% or less of silicon, e.g. 5.5 wt% or less of silicon, e.g. 5.4 wt% or less of silicon, e.g. 5.3 wt% or less of silicon, e.g. 5.2 wt% or less of silicon, e.g. 5.1 wt% or less of silicon, e.g. 5 wt% or less of silicon, e.g. 4.9 wt% or less of silicon, e.g. 4.8 wt% or less of silicon, e.g. 4.7 wt% or less of silicon, e.g. 4.6 wt% or less of silicon, e.g. 4.5 wt% or less of silicon, e.g. 4.4 wt% or less of silicon, e.g. 4.3 wt% or less of silicon, e.g. 4.2 wt% or less of silicon, e.g. 4.1 wt% or less of silicon, e.g. 4 wt% or less of silicon, e.g. 3.9 wt% or less of silicon, e.g. 3.8 wt% or less of silicon, e.g. 3.7 wt% or less of silicon, e.g. 3.6 wt% or less of silicon, e.g. 3.5 wt% or less of silicon, e.g. 3.4 wt% or less of silicon, e.g. 3.3 wt% or less of silicon, e.g. 3.2 wt% or less of silicon, e.g. 3.1 wt% or less of silicon, e.g. 3 wt% or less of silicon.

[0028] Optionally, the non-grain oriented electrical steel alloy composition comprises from 2 wt% to 6 wt% (inclusive of end points) of silicon, e.g. from 2.5 wt% to 5.5 wt% of silicon, e.g. from 3 wt% to 5 wt% of silicon, e.g. from 3.5 wt% to 5 wt% of silicon, e.g. from 3.5 wt% to 4 wt% of silicon, e.g. from 3.1 wt% to 3.9 wt% of silicon, e.g. from 3.15 wt% to 3.85 wt of silicon, e.g. from 3.2 wt% to 3.8 wt% of silicon, e.g. from 3.25 to 3.75 wt% of silicon, e.g. from 3.1 wt% to 3.5 wt% of silicon, e.g. from 3.15 wt% to 3.45 wt% of silicon, e.g. from 3.15 to 3.4 wt% of silicon, e.g. from 3.15 wt% to 3.35 wt% of silicon, e.g. from 4.1 wt% to 4.9 wt% of silicon, e.g. from 4.2 wt% to 4.8 wt% of silicon, e.g. from 4.25 wt% to 4.75 wt% of silicon, e.g. from 4.3 wt% of silicon to 4.7 wt% of silicon, e.g. from 4.35 to 4.65 wt% of silicon.

[0029] Optionally, the non-grain oriented electrical steel alloy composition comprises 1.95 wt% or less, e.g. 1.9 wt% or less, e.g. 1.8 wt% or less, e.g. 1.7 wt% or less, e.g. 1.6 wt% or less, e.g. 1 .5 wt% or less of nickel, e.g. 1 .4 wt% or less of nickel, e.g. 1 .3 wt% or less of nickel, e.g. 1.2 wt% or less of nickel, e.g. 1.1 wt% or less of nickel, e.g. 1 wt% or less of nickel, e.g. 0.95 wt% or less of nickel, e.g. 0.9 wt% or less of nickel, e.g. 0.85 wt% or less of nickel, e.g. 0.8 wt% or less of nickel, e.g. 0.75 wt% or less of nickel, e.g. 0.7 wt% or less of nickel, e.g. 0.65 wt% or less of nickel, e.g. 0.6 wt% or less of nickel, e.g. 0.55 wt% or less of nickel, e.g. 0.5 wt% or less of nickel, e.g. 0.45 wt% or less of nickel, e.g. 0.4 wt% or less of nickel, 0.35 wt% or less of nickel, e.g. 0.3 wt% or less of nickel, e.g. 0.25 wt% or less of nickel, e.g. 0.2 wt% or less of nickel, e.g. 0.15 wt% or less of nickel, e.g. 0.1 wt% or less of nickel.

[0030] Optionally, the non-grain oriented electrical steel alloy composition comprises 0.005 wt% or more of nickel, e.g. 0.01 wt% or more of nickel, e.g. 0.02 wt% or more of nickel, e.g. 0.03 wt% or more of nickel, e.g. 0.04 wt% or more of nickel, e.g. 0.05 wt% or more of nickel, e.g. 0.1 wt% or more of nickel, e.g. 0.15 wt% or more of nickel, e.g. 0.2 wt% or more of nickel, e.g. 0.25 wt% or more of nickel, e.g. 0.3 wt% or more of nickel, e.g. 0.35 wt% or more of nickel, e.g. 0.4 wt% or more of nickel, e.g. 0.45 wt% or more of nickel, e.g. 0.5 wt% or more of nickel, e.g. 0.55 wt% or more of nickel, e.g. 0.6 wt% or more of nickel, e.g. 0.65 wt% or more of nickel, e.g. 0.7 wt% or more of nickel, e.g. 0.75 wt% of nickel, e.g. 0.8 wt% or more of nickel, e.g. 0.85 wt% or more of nickel, e.g. 0.9 wt% or more of nickel, e.g. 0.95 wt% or more of nickel, e.g. 1 wt% or more of nickel. Optionally, the amount of nickel is non-zero and / or non-negligible ( / .e. the composition comprises an amount of nickel that exceeds that of an impurity amount).

[0031] Optionally, the non-grain oriented electrical steel alloy composition comprises from 0.005 wt% to 1.95 wt% or more of nickel, e.g. 0.01 wt% to 1.9 wt% or more of nickel, e.g. 0.02 wt% to 1.8 wt% or more of nickel, e.g. 0.03 wt% to 1.7 wt% or more of nickel, e.g. 0.04 wt% to 1.6 wt% or more of nickel, 0.05 wt% to 1.5 wt% of nickel, e.g. 0.05 wt% to 1.4 wt% or more of nickel, e.g. 0.05 wt% to 1.3 wt% or more of nickel, e.g. 0.05 wt% to 1.2 wt% or more of nickel, e.g. 0.05 wt% to 1.1 wt% or more of nickel, e.g. 0.05 wt% to 1 wt%, e.g. from 0.1 wt% to 0.9 wt% of nickel, e.g. from 0.1 wt% to 0.8 wt% of nickel, e.g. from 0.2 wt% to 0.7 wt% of nickel, e.g. from 0.3 wt% to 0.7 wt% of nickel, e.g. from 0.35 wt% to 0.65 wt% nickel, e.g. from 0.35 wt% to 0.6 wt% of nickel, e.g. from 0.35 wt% to 0.55 wt% of nickel, e.g. from 0.35 wt% to 0.5 wt% of nickel, e.g. from 0.35 wt% to 0.45 wt% of nickel, e.g. from 0.5 wt% to 0.8 wt% of nickel, e.g. from 0.55 wt% to 0.75 wt% of nickel, e.g. from 0.6 wt% to 0.7 wt% of nickel, e.g from 0.6 wt% to 0.65 wt% of nickel.

[0032] Optionally, the non-grain oriented electrical steel alloy composition comprises 1 wt% or less of chromium, e.g. 0.95 wt% or less of chromium, e.g. 0.9 wt% or less of chromium, e.g. 0.85 wt% or less of chromium, e.g. 0.8 wt% or less of chromium, e.g. 0.75 wt% or less of chromium, e.g. 0.7 wt% or less of chromium. Optionally, the non-grain oriented electrical steel alloy composition comprises 0.1 wt% or more of chromium, e.g. 0.2 wt% or more of chromium, e.g. 0.3 wt% or more of chromium, e.g. 0.4 wt% or more of chromium, e.g. 0.5 wt% or more of chromium, e.g. 0.6 wt% or more of chromium, e.g. 0.7 wt% or more of chromium, e.g. 0.8 wt% or more of chromium. Optionally, the non-grain oriented electrical steel alloy composition comprises from 0.5 wt% to 1 wt% chromium, e.g. from 0.6 wt% to 0.9 wt% of chromium, e.g. from 0.7 wt% to 0.8 wt% of chromium. Optionally, the amount of chromium is non-zero and / or non-negligible ( / .e. the composition comprises an amount of chromium that exceeds that of an impurity amount).

[0033] Optionally, the non-grain oriented electrical steel alloy composition comprises 0.05 wt% or more of aluminium, e.g. 0.1 wt% or more of aluminium, e.g. 0.15 wt% or more of aluminium, e.g. 0.2 wt% or more of aluminium. Optionally, the non-grain oriented electrical steel alloy composition comprises 5 wt% or less of aluminium, e.g. 4.5 wt% or less of aluminium, e.g. 4 wt% or less of aluminium, e.g. 3.5 wt% or less of aluminium, e.g. 3 wt% or less of aluminium, e.g. 2.5 wt% or less of aluminium, e.g. 2 wt% or less of aluminium, e.g. 1.5 wt% or less of aluminium, e.g. 1 wt% or less of aluminium, e.g. 0.9 wt% or less of aluminium, e.g. 0.8 wt% or less of aluminium, e.g. 0.7 wt% or less of aluminium, e.g. 0.7 wt% or less of aluminium, e.g. 0.6 wt% or less of aluminium, e.g. 0.5 wt% or less of aluminium, e.g. 0.4 wt% or less of aluminium, e.g. 0.3 wt% or less of aluminium, e.g. 0.2 wt% or less of aluminium, e.g. 0.15 wt% or less of aluminium. Optionally, the non-grain oriented electrical steel alloy composition comprises from 0.05 to 0.5 wt% of aluminium, e.g. from 0.05 wt% to 0.4 wt% of aluminium, e.g. from 0.05 to 0.3 wt% of aluminium, e.g. from 0.05 to 0.2 wt% of aluminium, e.g. from 0.05 to 0.1 wt% aluminium, e.g. from 0.1 wt% to 0.3 wt% of aluminium.

[0034] Optionally, the non-grain oriented electrical steel alloy composition comprises 1 wt% or less of molybdenum, e.g. 0.9 wt% or less of molybdenum, e.g. 0.8 wt% or less of molybdenum, e.g. 0.7 wt% or less of molybdenum, e.g. 0.6 wt% or less of molybdenum, e.g. 0.5 wt% or less of molybdenum, e.g. 0.45 wt% or less of molybdenum, e.g. 0.4 wt% or less of molybdenum, e.g. 0.35 wt% or less of molybdenum, e.g. from 0.3 wt% or less of molybdenum, e.g. 0.25 wt% or less of molybdenum, e.g. from 0.2 wt% or less of molybdenum, e.g. 0.15 wt% or less of molybdenum, e.g. 0.1 wt% or less of molybdenum, e.g. 0.05 wt% or less of molybdenum.

[0035] Optionally, the amount of molybdenum is non-zero and / or non-negligible ( / .e. the composition comprises an amount of molybdenum that exceeds that of an impurity amount). Optionally, the non-grain oriented electrical steel alloy composition comprises a non-zero wt% amount of molybdenum, e.g. 0.005 wt% or more, e.g. 0.01 wt%, e.g. 0.02 wt%, e.g. 0.03 wt%, e.g. 0.04 wt%, e.g. 0.05 wt% or more, e.g. 0.1 wt% or more, e.g. 0.15 wt% or more, e.g. 0.2 wt% or more, e.g. 0.3 wt% or more, e.g. 0.4 wt% or more, e.g. 0.5 wt% or more, e.g. 0.6 wt% or more, e.g. 0.7 wt% or more, e.g. 0.8 wt% or more, e.g. 0.9 wt% or more. Optionally, the non-grain oriented electrical steel alloy composition comprises from 0.05 to 1 wt% of molybdenum, e.g. from 0.05 wt% to 0.9 wt% of molybdenum, e.g. from 0.05 to 0.8 wt% of molybdenum, e.g. from 0.05 to 0.7 wt% of molybdenum, e.g. from 0.05 to 0.6 wt% molybdenum, e.g. from 0.1 wt% to 0.5 wt% of molybdenum. Optionally, the non-grain oriented electrical steel alloy composition comprises from 0.05 to 1 wt% of molybdenum, e.g. from 0.1 wt% to 1 wt% of molybdenum, e.g. from 0.2 to 1 wt% of molybdenum, e.g. from 0.3 to 1 wt% of molybdenum, e.g. from 0.4 to 1 wt% molybdenum. Optionally, the non-grain oriented electrical steel alloy composition comprises from 0.1 to 0.9 wt% of molybdenum, e.g. from 0.2 wt% to 0.8 wt% of molybdenum, e.g. from 0.3 to 0.7 wt% of molybdenum, e.g. from 0.4 to 0.6 wt% of molybdenum, e.g. from 0.4 to 0.5 wt% molybdenum, e.g. approximately 0.45 wt% molybdenum.

[0036] Optionally, the composition comprises a non-zero wt% amount of the group consisting of nickel, chromium and molybdenum is non-zero ( / .e. the total amount of nickel, chromium and molybdenum exceeds impurity amounts). Optionally, the group (consisting of nickel, chromium and molybdenum) is present in an amount of 0.05 wt% or more, e.g. 0.1 wt% or more, e.g. 0.2 wt% or more, e.g. 0.3 wt% or more, e.g. 0.4 wt% or more, e.g. 0.5 wt% or more, e.g. 0.6 wt% or more, e.g. 0.7 wt% or more, e.g. 0.8 wt% or more, e.g. 0.9 wt% or more, e.g. 1 wt% or more, e.g. 1.5 wt% or more, e.g. 2 wt% or more, e.g. 3 wt% or more, e.g. 4 wt% or more, e.g. 5wt% or more, e.g. 6 wt% or more. Optionally, the group (consisting of nickel, chromium and molybdenum) is present in an amount of 8 wt% or less, e.g. 7.5 wt% or less, e.g. 7 wt% or less, e.g. 6.5 wt% or less, e.g. 6 wt% or less, e.g. 5.5 wt% or less, e.g. 5 wt% or less, e.g. 4.5 wt% or less, e.g. 4 wt% or less, e.g. 3.5 wt% or less, e.g. 3 wt% or less, e.g. 2.5 wt% or less, e.g. 2 wt% or less, e.g. 1 .5 wt% or less. e.g. 1 wt% or less, e.g. 0.9 wt% or less, e.g. 0.8 wt% or less, e.g. 0.7 wt% or less, e.g. 0.5 wt% or less.

[0037] Optionally, the non-grain oriented electrical steel alloy composition comprises from 0.2 wt% to 4 wt% of the group (consisting of nickel, chromium and molybdenum), e.g. from 0.3 wt% to 4 wt%, e.g. from 0.4 wt% to 4 wt%, e.g. from 1 wt% to 3.5 wt%, e.g. from 1 wt% to 3 wt%, e.g. from 1 wt% to 2.5 wt%, e.g. from 1.1 wt% to 2.3 wt%, e.g. from 1.1 wt% to 2.2 wt%, e.g. from 1.2 wt% to 2.1 wt%, e.g. from 1.3 wt% to 2 wt%, e.g. from 1.4 wt% to 1.9 wt%, e.g. from 1.5 wt% to 2 wt%, e.g. from 1.6 wt% to 2 wt%, e.g. from 1.7 wt% to 2 wt%, e.g. from 1.8 wt% to 2 wt%, e.g. from 1.8 wt% to 1.9 wt%, e.g. from 1.8 wt% to 2.2 wt%, e.g. from 1.9 wt% to 2.3 wt%, e.g. from 2 wt% to 3 wt%, e.g. from 2 wt% to 2.5wt%, e.g. from 2 wt% to 2.3 wt%, e.g. from 2.1 wt% to 2.3 wt%, e.g. from 1 wt% to 1.5 wt%, e.g. from 1 wt% to 1.4 wt%, e.g. 1 wt% to 1 .3 wt%, e.g. 1 wt% to 1 .2 wt%, e.g. 1.1 wt% to 1 wt%.

[0038] Optionally, the non-grain oriented electrical steel alloy composition comprises one or more alloying elements and / or impurities that total less than 0.2 wt% of the composition, e.g. less than 0.19 wt% of the composition, e.g. less than 0.18 wt% of the composition, e.g. less than 0.17 wt% of the composition, e.g. less than 0.16 wt% of the composition, e.g. less than 0.15 wt% of the composition, e.g. less than 0.14 wt% of the composition, e.g. less than 0.13 wt% of the composition, e.g. less than 0.12 wt% of the composition, e.g. less than 0.11 wt% of the composition, e.g. less than 0.1 wt% of the composition.

[0039] Optionally, each of the one or more alloying elements and / or impurities does not exceed more than 0.01 wt% of the composition, e.g. not more than 0.005 wt% of the composition, e.g. not more than 0.004 wt% of the composition, e.g. not more than 0.003 wt% of the composition, e.g. not more than 0.002 wt% of the composition, e.g. not more than 0.001 wt% of the composition, e.g. less than 0.0005 wt% of the composition. Within the meaning of the present invention, an impurity is preferably defined as an element that is included in the composition at 0.0005 wt% or less, e.g. 0.0004 wt% or less, e.g. 0.0001 wt% or less.

[0040] Optionally, the non-grain oriented electrical steel alloy composition comprises less than 0.0005 wt% total of gadolinium and germanium. Optionally, the non-grain oriented electrical steel alloy composition comprises substantially no (e.g. less than 0.0001 wt%) gadolinium and / or germanium.

[0041] Optionally, the non-grain oriented electrical steel alloy composition comprises: 0.05 wt.% or less (e.g. 0.006 wt% or less, e.g. 0.0055 wt% or less, e.g. 0.005 wt% or less, e.g. 0.0045 wt%, e.g. from 0.001 wt% to 0.05 wt%) of carbon; more than 2 wt% and no more than 5 wt% (e.g. from 2.1 wt% to 4.9 wt%) of manganese;

[0042] 2 wt% to 6 wt% inclusive (e.g. from 3 wt% to 6 wt%, e.g. from 3.5 wt% to 6 wt%, e.g. from 3.5 wt% to 5 wt%, e.g. from 4.45 wt% to 4.65 wt%, e.g. from 3.15 wt% to 3.35 wt%) of silicon;

[0043] 1.5 wt% or less (e.g. from 0.05 wt% to 1 wt%, e.g. from 0.1 wt% to 0.8 wt%, e.g. from 0.3 wt% to 0.7 wt%, e.g. from 0.35 wt% to 0.45 wt%, e.g. 0.6 wt% to 0.65 wt%) of nickel;

[0044] 1 wt% or less (e.g. from 0.1 wt% to 0.9 wt%, e.g. from 0.5 wt% to 0.9 wt%, e.g. from 0.7 wt% to 0.8 wt%) of chromium;

[0045] 0.05 wt% to 5 wt% inclusive (e.g. from 0.05 wt% to 4 wt%, e.g. from 0.05 wt% to 3 wt%, e.g. from 0.05 wt% to 2 wt%, e.g. from 0.05 wt% to 0.15 wt%, e.g. from 0.05 to 0.1 wt%) of aluminium;

[0046] 0.7 wt% or less (e.g. 0.6 wt% or less, e.g. 0.5 wt% or less, e.g. 0.45 wt% or less, e.g. 0.4 wt% or less, e.g. 0.3 wt% or less, e.g. 0.05 wt% or less) of molybdenum; and 0.0004 wt% or less of gadolinium or germanium; and the balance consisting of iron and no more than 0.2 wt% total in other alloying elements or impurities, optionally, wherein the other alloying elements or impurities are each present in an amount of less than 0.0004 wt%; wherein, preferably the composition comprises at least 0.2 wt% of the group consisting of nickel, chromium and molybdenum, wherein the alloy composition comprises no more than:

[0047] 1.5 wt% (e.g. from 0.05 wt% to 1 wt%, e.g. from 0.1 wt% to 0.8 wt%, e.g. from 0.3 wt% to 0.7 wt%, e.g. from 0.35 wt% to 0.45 wt%, e.g. 0.6 wt% to 0.65 wt%) of nickel;

[0048] 1 wt% (e.g. from 0.1 wt% to 0.9 wt%, e.g. from 0.5 wt% to 0.9 wt%, e.g. from

[0049] 0.7 wt% to 0.8 wt%) of chromium; and

[0050] 0.7 wt% (e.g. 0.6 wt% or less, e.g. 0.5 wt% or less, e.g. 0.45 wt% or less, e.g. 0.4 wt% or less, e.g. 0.3 wt% or less, e.g. 0.05 wt% or less) of molybdenum.

[0051] Optionally, the non-grain oriented electrical steel alloy composition comprises:

[0052] 0.05 wt% or less of carbon;

[0053] 2 wt% to 7 wt% of silicon;

[0054] 2 wt% to 7 wt% of manganese; 4 wt% or less of aluminium; and at least 0.2 wt% of the group consisting of nickel, chromium and molybdenum, wherein the alloy composition comprises no more than:

[0055] 2 wt% of nickel;

[0056] 3 wt% of chromium; and

[0057] 2 wt% of molybdenum.

[0058] Optionally, the non-grain oriented electrical steel alloy composition comprises:

[0059] 0.05 wt.% or less of carbon; more than 2 wt% and no more than 5 wt% of manganese;

[0060] 2 wt% to 6 wt% inclusive of silicon;

[0061] 1 .5 wt% or less of nickel;

[0062] 1 wt% or less of chromium;

[0063] 0.7 wt% to 4 wt% inclusive of aluminium;

[0064] 0.7 wt% or less of molybdenum; and

[0065] 0.0004 wt% or less of gadolinium or germanium; and optionally, wherein the alloy comprises at least 0.2 wt% of the group consisting of nickel, chromium and molybdenum.

[0066] Optionally, the non-grain oriented electrical steel alloy composition comprises:

[0067] 0.05 wt.% or less of carbon; more than 2 wt% and less than or equal to 5 wt% of manganese;

[0068] 2 wt% to 6 wt% inclusive of silicon;

[0069] 1 .5 wt% or less of nickel;

[0070] 1 wt% or less of chromium;

[0071] 0.05 wt% to 4 wt% inclusive of aluminium;

[0072] 0.7 wt% or less of molybdenum; and wherein the other alloying elements or impurities are each present in an amount less than 0.0004 wt%; and optionally, wherein the alloy comprises at least 0.2 wt% of the group consisting of nickel, chromium and molybdenum.

[0073] Optionally, the non-grain oriented electrical steel alloy composition comprises:

[0074] 0.001 wt% or more (e.g. 0.001 wt% to 0.005 wt%) of carbon;

[0075] 3 wt% or more (e.g. 3 wt% to 6 wt%) of silicon;

[0076] 0.05 wt% to 1.5 wt% (e.g. 0.05 wt% to 1 wt%) inclusive of nickel; 0.1 wt% to 1 wt% (e.g. 0.1 wt% to 0.9 wt%) inclusive of chromium;

[0077] 3 wt% or less (e.g. 0.05 wt% to 3 wt%) of aluminium; and

[0078] 0.6 wt% or less of molybdenum; and optionally, wherein the alloy comprises at least 0.2 wt% of the group consisting of nickel, chromium and molybdenum.

[0079] Optionally, the non-grain oriented electrical steel alloy composition comprises:

[0080] 0.005 wt% or less of carbon;

[0081] 3.5 wt% or more (e.g.3.5 wt% to 6 wt%) of silicon;

[0082] 0.1 wt% to 0.8 wt% inclusive of nickel;

[0083] 0.5 wt% to 0.9 wt% inclusive of chromium;

[0084] 2 wt% or less (e.g. 0.05 wt% to 2 wt%) of aluminium; and

[0085] 0.5 wt% or less of molybdenum.

[0086] Optionally, the non-grain oriented electrical steel alloy composition comprises:

[0087] 0.005 wt% or less of carbon;

[0088] 3.5 wt% to 5 wt% inclusive or more of silicon;

[0089] 0.3 wt% to 0.7 wt% inclusive of nickel;

[0090] 0.7 wt% to 0.8 wt% inclusive of chromium;

[0091] 0.5 wt% or less (e.g.0.05 wt% to 0.5 wt%) of aluminium;

[0092] 0.4 wt% or less of molybdenum.

[0093] Optionally, the non-grain oriented electrical steel alloy composition comprises:

[0094] 0.0055 wt% or less of carbon;

[0095] 4.45 wt% to 4.65 wt% inclusive of silicon;

[0096] 0.35 wt% to 0.45 wt% inclusive of nickel;

[0097] 0.70 wt% to 0.80 wt% inclusive of chromium;

[0098] 0.05 wt% to 0.15 wt% inclusive of aluminium;

[0099] 0.05 wt% or less of molybdenum.

[0100] Optionally, the non-grain oriented electrical steel alloy composition comprises:

[0101] 0.0045 wt% or less of carbon;

[0102] 3.15 wt% to 3.35 wt% inclusive of silicon;

[0103] 0.60 wt% to 0.65 wt% inclusive of nickel;

[0104] 0.70 wt% to 0.80 wt% inclusive of chromium;

[0105] 0.10 wt% to 0.20 wt% inclusive of aluminium; 0.45 wt% or less of molybdenum.

[0106] Optionally, the non-grain oriented electrical steel alloy composition comprises:

[0107] 0.004 wt% or less of carbon;

[0108] 2.10 wt% to 2.30 wt% inclusive of silicon;

[0109] 1 .05 wt% to 1 .25 wt% inclusive of nickel;

[0110] 0.85 wt% to 1 .05 wt% inclusive of chromium;

[0111] 1 .85 wt% to 2.05 wt% inclusive of aluminium;

[0112] 0.05 wt% or less of molybdenum.

[0113] In a second aspect, a non-grain oriented electrical steel sheet is provided, wherein the nongrain oriented electrical steel sheet is made from the alloy composition of the first aspect.

[0114] Optionally, the non-grain oriented electrical steel alloy composition, or the non-grain oriented electrical steel sheet made thereof, has a resistivity of 60 pQ.cm or more, e.g. 70 pQ.cm or more, e.g. 75 pQ.cm or more, e.g. from 75 pQ.cm to 90 pQ.cm (i.e. inclusive of end points).

[0115] Optionally, the non-grain oriented electrical steel alloy composition, or the non-grain oriented electrical steel sheet made thereof, has an A2->B2 transformation arising at a temperature of less than 600 °C, e.g. less than 400 °C, e.g. less than 300 °C.

[0116] Optionally, the non-grain oriented electrical steel alloy composition, or the non-grain oriented electrical steel sheet made thereof, has a resistivity of from 45 pQ.cm to 100 pQ.cm, e.g. from 50 pQ.cm to 90 pQ.cm, e.g. from 50 pQ.cm to 85 pQ.cm.

[0117] Optionally, the non-grain oriented electrical steel alloy composition, or the non-grain oriented electrical steel sheet made thereof, has an A2->B2 transformation arising at a temperature of less than 600 °C and a resistivity of from 45 pQ.cm to 100 pQ.cm.

[0118] Optionally, the non-grain oriented electrical steel alloy composition, or the non-grain oriented electrical steel sheet made thereof, has an A2->B2 transformation arising at a temperature of less than 400 °C and a resistivity of from 50 pQ.cm to 90 pQ.cm. Optionally, the non-grain oriented electrical steel alloy composition, or the non-grain oriented electrical steel sheet made thereof, has an A2->B2 transformation arising at a temperature of less than 300 °C and a resistivity of from 50 pQ.cm to 85 pQ.cm.

[0119] Optionally, the non-grain oriented electrical steel sheet has a tensile strength greater than 600 MPa. Optionally, the non-grain oriented electrical steel sheet has a strain of from 0.01 to 0.15. Optionally, the non-grain oriented electrical steel sheet has a tensile strength greater than 600 MPa at a strain of 0.01 to 0.15.

[0120] Optionally, the non-grain oriented electrical steel sheet has a thickness of from 100 pm to 500 pm (i.e. inclusive of end points).

[0121] For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention.

[0122] Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any suitable and / or desirable combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible.

[0123] For the avoidance of doubt, the terms “may”, “and / or”, “e.g.”, “for example” and any similar term as used herein should be interpreted as non-limiting such that any feature so- described need not be present. Indeed, any combination of optional features is expressly envisaged without departing from the scope of the invention, whether or not these are expressly claimed. Similarly, for the avoidance of doubt, all ranges disclosed herein and in the claims are intended to be inclusive of the endpoint values disclosed, regardless as to whether this has been explicitly stated. For example, a range from 2 wt% to 3 wt% is intended to be inclusive of both 2 wt% and 3 wt%, whether or not it has been explicitly stated as such. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner.

[0124] Figures Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0125] Figure 1 shows a schematic of the general relationship between magnetic properties of classical electrical steels and formability;

[0126] Figure 2 shows a flow diagram of an example alloy design methodology;

[0127] Figure 3 shows the resistivity and temperature of the A2->B2 transformation for a plurality of different alloy compositions generated through an alloy design methodology;

[0128] Figure 4 is a photograph showing examples of lab rolled electrical steel sheet products;

[0129] Figure 5 shows the change in iron loss with final annealing treatment for both a Fe-3 wt% Si electrical steel composition and a new alloy composition in accordance with an embodiment of the present invention;

[0130] Figure 6 shows the final cold rolled annealed microstructure for a) a Fe-3 wt% Si electrical steel composition, and b) a new alloy composition in accordance with an embodiment of the present invention;

[0131] Figure 7 shows predicted and measured electrical resistivity for three different electrical steel compositions;

[0132] Figure 8 shows the relationship between loss and frequency for different electrical steel alloy compositions at 1.5T;

[0133] Figure 9 shows the relationship between coercivity and frequency for different electrical steel alloy compositions;

[0134] Figure 10 shows the relationship between loss and frequency for different electrical steel alloy compositions at 1T; Figure 11 shows stress-strain curves for different electrical steel alloy compositions;

[0135] Figure 12a shows the sensitivity of total loss to grain size for a commercially available electrical steel sample and Figure 12b shows the sensitivity of total loss to grain size for a composition in accordance with an embodiment of the invention; and

[0136] Figure 13 shows the loss under tensile stress and compressive stress as a function of frequency for a commercially available electrical steel sample and a composition in accordance with an embodiment of the invention.

[0137] Detailed Description

[0138] The relationship between the magnetic property (specifically iron loss) and the formability of electrical steel compositions can be represented on a “banana diagram" which is schematically represented in Figure 1. As shown, pure iron compositions exhibit excellent processability, but have relatively poor magnetic properties. In contrast, a substantially binary Fe-Si composition (having minor amounts of additional alloying components) with 6.5 wt% silicon (as was commercialised in the 1990’s) exhibits excellent magnetic properties but extremely poor processibility due to its brittle nature.

[0139] As such, the majority of commercial electrical steel products currently on the market comprise of mainly Fe and Si, with minor additions (deviating only slightly from the classical banana curve) with the silicon content ranging from 2.5 to 3.2 wt%.

[0140] One of the aims of the present invention is to identify novel non-grain orientated electrical steel alloy compositions that exist away from the binary curve whilst still being able to be produced by a current conventional commercial hot / cold rolling / annealing production routes and that exhibit improved properties compared to current Fe-Si alloys having 2.5-3.5wt% silicon. These improved properties may include one or more of: increased strength which allows thinner laminations, higher operational frequencies, higher loads and narrower bridge designs for motors, and reduced losses in the motor; higher resistivity which reduces eddy current losses at higher frequencies; improved saturation magnetisation and permeability and / or lower coercivity to minimise hysteretic losses at low frequencies; and comparable or improved magnetic properties under applied elastic compressive / tensile stresses.

[0141] In particular, the present invention aims to investigate and identify electrical steel alloy compositions that are suitable for use in high speed electric motors that exhibit improved resistivity (e.g. comparable to high (e.g. approximately 6.5 wt%) silicon electrical steels) without significant compromise on magnetic properties and / or the formation of the embrittling phase that is typical for electrical steel alloy compositions having more than 3 (e.g. more than 3.2) wt% silicon.

[0142] However, discovery of such alloy compositions is extremely difficult as deviation away from the classical predominantly binary Fe-Si compositions typically results in a reduction in properties (e.g. magnetic properties, mechanical properties, or processability), which makes identifying and optimising promising electrical steel compositions outside of the classical predominantly binary compositions difficult, costly, and time consuming.

[0143] To address this, the present inventors have developed a new protocol with experimental verification, for discovering and designing potential electrical steel alloying compositions by implementing a computer implemented design loop as described below.

[0144] Alloy Design

[0145] To identify and analyse potential electrical steel alloys which exhibit the desired properties outlined above, the inventors employed a combination of Thermocalc 2022b software (TCFelO and MOBFe5 databases) along with Matlab 2022a software to implement the feedback loop that is schematically represented in Figure 3.

[0146] This feedback loop generates an electrical steel alloy composition within the pre-defined input limits, checks to ensure that the alloy is fully ferritic (at room temperature) and then determines specific alloy characteristics used for performance ranking.

[0147] The inventors have surprisingly identified a family of improved electrical steel alloy compositions by limiting the alloying elements to carbon, silicon, manganese, nickel, chromium, aluminium and molybdenum, wherein inter alia’. silicon may increase resistivity; manganese may increase resistivity; nickel may supress the BCC B2 and D03 phases; chromium, aluminium and molybdenum may stabilise ferrite without promoting BCC B2 and D03 phases.

[0148] Taking these considerations into account, the inputs for the alloy design protocol shown in Figure 1 is shown in Table 1.

[0149] Table 1 shows the inputs for design loop shown in Figure 1

[0150] Once an electrical steel alloying composition has been identified, the feedback loop evaluates the composition by calculating the resistivity, BCC B2 fraction, the atomic fraction of Fe, the lattice parameter and the A2->B2 transformation temperature.

[0151] The resistivity (R) of the new alloy was calculated using Equation (1).

[0152] R = 10.11 + 6.20Mn + 11.75Si + 2.98Ni + 5.57Cr + 9.01AZ (1) where C, Mn, Si, Ni, Cr, Al are the respective wt% of carbon, manganese, silicon, nickel, chromium and aluminium in the composition.

[0153] The A2-B2 transition temperature (T) may be represented by the following equation:

[0154] T = -363.38 + 262.17C + 24.69Mn + 228.77Si + 9.57Ni + 20.26Cr + 177.43AZ + 16.92MO + 16.64C. Mn - 41.33C. Si - 33.57C. Ni + 1.04C. Cr - 24.01C. Al - 22.25C. Mo - 2.16Mn. Si + 0.45Mn. Ni - 0.68Mn. Cr - 2.11Mn. Al - 0.71Mn. Mo - 1.2Si. Ni - 1.67 Si. Cr - 8.77 Si. Al - 0.98Si. Mo + OAlNi. Cr + 3.03Ni. Al - 0.69Ni. Mo - 1.77Cr. Al - 0.02Cr. Al + 0.63AI. Mo + 840.78 C2- 0.29 Mn2- 7.95 Si2+ 0.89 Ni2- 0.35 Cr2- 9.14 Al2- 3.16 Mo2 where C, Mn, Si, Ni, Cr, Al, Mo are the respective wt% of carbon, manganese, silicon, nickel, chromium, aluminium and molybdenum in the composition. The A2-B2 transition temperature may also be calculated directly using the Thermo-Calc software.

[0155] It will be appreciated that any composition which exhibits a reduced A2-B2 transformation temperature (T) and / or an increased resistivity (R) with respect to the Fe-Si binary line is expected to show improved properties and performance compared to binary Fe-Si alloys. The R- and T-values (i.e. calculated via equations (1) and (2) respectively) may therefore be used as performance indexes for assessing the compositions generated by the design protocol shown in Figure 2 with respect to the Fe-Si binary characteristics. As such, electrical steel compositions generated by the design protocol that have a high R value and a low T value are predicted to produce a high performing and processable alloy.

[0156] Electrical steel compositions having the relationship defined in equation (3) between the T- and R- value performance indices are found to provide high performing and processable alloy and thus provide embodiments of the present invention.

[0157] T < (13 X R) - 288.83 (3)

[0158] The result of this part of the assessment is shown in Figure 3 where the curve shows the relationship between resistivity and the temperature of the A2-B2 transformation for the classical Fe-Si binary compositions (with the results for a 3 wt% silicon composition and a 6.5 wt% silicon composition indicated thereon). The remaining points shown offset from the binary Fe-Si line show electrical steel alloy compositions in accordance with embodiments of the present invention (e.g. predicted by the design protocol and meeting the requirement of Equation 3).

[0159] As such, the present inventors have been able to identify electrical steel alloy compositions that may be processed using conventional hot / cold rolling / annealing process techniques to generate electrical steels having improved properties with respect to classical predominantly binary Fe-Si compositions. Examples of compositions with associated predicted properties can be seen in Table 2. Table 2: A selection of compositions with associated R and T.

[0160] To demonstrate the viability of the new electrical steel compositions predicted by the feedback loop shown in Figure 2, and to experimentally verify the property predictions, two potential alloy compositions (Example 1 (E1), Example 2 (E2)) were selected for manufacture and testing alongside two different binary Fe-Si compositions (Comparison 1 (C1), Comparison 2 (C2)). The identified compositions of these alloys as output by the feedback loop protocol shown in Figure 2 is shown in Table 3. Table 3 shows the compositions generated by the feedback loop represented in Figure 1

[0161] The results of these experiments are outlined below.

[0162] Experimental To assess the properties of the new alloy compositions in accordance with the present invention, an electrical steel alloy was manufactured in accordance with the composition of Example 1 , Example 2 and Example 3. To demonstrate the improvement, this alloy was compared to two different electrical steel alloy compositions: Comparison 1 and Comparison 2. The composition of Comparison 1 was selected to have approximately 3 wt% silicon content to act as baseline values. The composition of Comparison 2 was selected to represent electrical steels having approximately 6.5 wt% silicon to represent the most currently favourable lowest high frequency losses of electrical steels known. The actual experimentally determined compositions of Example 1 (E1), Example 2 (E2), Comparison 1 (C1) and Comparison 2 (C2) are shown in Table 4.

[0163] E1 , E2, C1 and C2 were cast as 10 kg ingots using a Consarc 30 kW VIM furnace and poured into a 30 x 80 x 210 mm mould.

[0164] Table 4 compositions of electrical steel alloys, all wt%, determined by Oxford Instruments Foundry Master Pro OES

[0165] The ingots were homogenised at 1200°C for 3 hours after which they were rolled to 2.5 mm in 7 passes, reheating to 1050°C after each pass. The resulting strips were pickled in 40% HCI solution for 10 minutes before being cold rolled to 0.35 mm. The 0.35 mm strips were annealed at 1100°C for 1 hour before being furnace cooled to room temperature.

[0166] Examples of the rolled strips are shown in Figure 4. As can be seen, C2 cracked during the process of hot rolling to 3 mm (as expected due to its well-known brittleness) and thus no further cold rolling was applied. This further highlights the limitation of commercially producing this material via hot / cold rolling despite its superior performance (in terms of iron loss) at high frequencies.

[0167] In addition to E1 , E2, E3, C1 and C2, samples of commercially available electrical steels (i.e. M250-35A, NO20 (N020-1200H) and NO10 (N010-1270N) with thicknesses of 0.35, 0.2 and 0.1 mm respectively) were also tested to compare to the new alloys of the present invention.

[0168] Testing Procedures

[0169] High Frequency Magnetic Testing using Single Sheet Tester (SST)

[0170] Magnetic performance measurements were made using the Brockhaus MPG 200 platform with the single sheet tester (SST) configuration. The SST operates in full accordance with the international standard I EC 60404-2. The sample geometry is 300 mm length x 30 mm width, with the thickness dependent on the electrical steel being tested. Tests were performed either to 1 .0 or 1 ,5T. Successive tests were carried out starting at 50 Hz then at subsequent frequencies of 100, 200, 400, 800, 1000, 1500, 2000, 2500, 3000Hz. Measurements of iron loss and coercivity were made.

[0171] Resistivity Measurements

[0172] The resistivity measurements were carried out on the same samples as for SST testing, using a Cropico Microhmmeter D05000 over a length of 200mm.

[0173] Microstructure Analysis

[0174] To analyse the microstructure of the electrical steels, samples were ground and polished to a 0.05 pm finish. Electron Backscatter Diffraction (EBSD) patterns were measured using the JEOL JSM-7800F Field Emission Scanning Electron Microscope (FE-SEM).

[0175] Mechanical Stress-Strain Testing

[0176] Sub-sized dog-bone tensile samples were electro-discharge machined (EDM) from the electrical steel sheets following the ASTM E8 standard (gauge length of 25 mm and gauge width of 6 mm). All samples were taken with the gauge length along the rolling direction. Testing was carried out on an Instron 5985 static machine equipped with a 10 kN load cell and a video extensometer. The crosshead speed used was 1 mm / min before 1 % strain and 5 mm / min afterwards, and the criteria for the end of test was a drop of load by 40%.

[0177] Losses under tensile and compressive loads As with the High Frequency Magnetic Testing, magnetic measurements under tensile and compressive load were made using the Brockhaus MPG 200 platform with the single sheet tester (SST) configuration. The sample geometry is 300 mm length x 30 mm width, with the thickness dependent on the electrical steel being tested. Tests were performed either to 1.0 or 1 ,5T with a compressive or tensile stress of 50 MPa. Successive tests were carried out starting at 50 Hz then at subsequent frequencies of 100, 200, 400, 800, 1000, 1500, 2000, 2500, 3000Hz.

[0178] Experimental Results

[0179] To monitor the effect of annealing on properties, SST testing was conducted after annealing times of 0.5 and 1 hr at 1100 °C. The results of these tests are shown in Figure 5. C1 shows a very flat response to annealing time due to the very little change in grain size during this time. A decrease in iron loss is seen in the first 30mins for E2, suggesting a slightly slower annealing response, however after this, a stable plateau is achieved. All samples were therefore heat treated to 1100 °C for 1 hr to obtain a fully annealed microstructure.

[0180] Figure 6 shows the final cold rolled and annealed microstructures of C1 (Figure 6a) and E2 (Figure 6b).

[0181] Figure 7 shows a comparison of the predicted resistivity values (determined via Equation 1) and the measured electrical resistivities of E1 and C1 after cold rolling and annealing at 1100°C for 1 hr. Good agreement between the measured and predicted values is observed.

[0182] Again, due to the poor processability, electrical resistivity measurement was not possible for C2.

[0183] It can be seen that the resistivity of E1 is much higher than C1 and is only 8% lower than the predicted value of C2. With resistivity values such as these, it is expected that the eddy current losses at high frequencies would be significantly reduced for the alloys of the present invention.

[0184] Figures 8 and 9 shows the Iron loss and Coercivity as a function of frequency tested through SST testing at 1.5T. E2 can be seen to outperform both C1 and M250-35A (which have comparable thicknesses) at frequencies above 900Hz. Compared to M250-35A, E2 has nearly a 30% reduction in loss at frequencies above 2000 Hz. NO10 and NO20 both outperform E2 at high frequencies which is due to the thinner gauge of these products. Therefore, it is expected that even greater improvement to losses would be anticipated in the new presented alloys when rolled to the equivalent thicknesses of the NO10 and NO20 grades.

[0185] Figure 10 shows E1 , E3 and M250-35A tested at 1T with a similar trend to Figure 8 being shown, e.g. at 3000Hz E1 shows around a 32% reduction in loss with respect to M250-35A and at 2500 Hz E3 shows around a 51% reduction in loss with respect to M250-35A and around a 29% reduction in loss with respect to E1.

[0186] Figure 11 shows the tensile stress-strain curves for C1 and E1 compared against the commercial M250-35A electrical steel. E1 shows much greater strength than both the commercial grade M250-35A sample and C1. There is over 220 MPa improvement in the mean ultimate tensile strength (UTS) values of E1 with respect to the commercial grade M250-35A sample. The majority of this difference is expected to be due to the additional solid solution strengthening from the Mn and additional Si content (equating to around 152 MPa increase compared to C1). There is also an additional strengthening increment coming from the finer 80 pm grain size in E1 compared to C1. N010 and NO20 have product specification UTS values of 430 and 500 MPa respectively, both consistency lower than E1.

[0187] Figure 12 shows the sensitivity of total loss to grain size for the commercial grade M250- 35A sample (Figure 12a) and a sample of E2 (Figure 12b). The data shown in Figure 12 has been normalised to 100pm for ease of comparison, with Tables 5 and 6 showing the raw data) The results show that E2 exhibits a much lower sensitivity to grain size than M250-35A.

[0188] Figure 13 shows the loss under tensile stress (50 MPa) and compressive stress (50 MPa) as a function of frequency for the commercially available M250-35A electrical steel and E2 tested in the SST. It can be seen that both steels show an increase in loss under the compressive load, with the losses in the new alloy being less than in the commercial steel. Under tensile stress E2 shows better performance (i.e. a greater decrease in losses compared to the no stress condition) compared to M250-35A, particularly at higher frequencies. Table 5 shows M250-35A W10 loss (W / kg) with respect to grain size Table 6 shows E2 W10 loss (W / kg) with respect to grain size

[0189] The above results therefore validate the results from the alloy feedback design program used to identify promising alloy compositions for non-grain oriented electrical steels. Indeed, E1 and E2 validate that compositions (selected based on having similar A2-B2 transformations to a 3wt% silicon steel, but similar resistivity to that of a 6-6.5wt%Si steel) output from the feedback design loop exhibits improved properties with respect to classical binary systems as well as commercially available electrical steels currently on the market.

[0190] The present invention therefore provides electrical steel alloy compositions which exhibit improved properties over known electrical steels in the art. It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and / or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

Claims

CLAIMS1. A non-grain oriented electrical steel alloy composition comprising:0.05 wt% or less of carbon;2 wt% to 7 wt% inclusive of silicon;2 wt% to 7 wt% inclusive of manganese;0 wt% to 4 wt% inclusive of aluminium; and at least 0.2 wt% of the group consisting of nickel, chromium and molybdenum, wherein the alloy composition comprises no more than:2 wt% of nickel;3 wt% of chromium; and2 wt% of molybdenum; and wherein the balance of the composition consists of iron and no more than 0.2 wt% total in other alloying elements or impurities; wherein the non-grain oriented electrical steel alloy composition has a calculated R- value (R) and a T-value (T) in accordance with the following equations:R = 10.11 + 6.20Mn + 11.75SZ + 2.98Ni + 5.57Cr + 9.01AZ andT = -363.38 + 262.17C + 24.69Mn + 228.77SI + 9.37Ni + 20.26Cr + 177.43AZ + 16.92MO + 16.64C. Mn - 41.33C. Si - 33.57C. Ni + 1.04C. Cr - 24.01C. Al - 22.25C. Mo - 2.16Mn. Si + 0.45Mn. Ni - 0.68Mn. Cr - 2.11Mn. Al - 0.71Mn. Mo - 1.2SL Ni - 1.67 Si. Cr - 8.77 Si. Al - 0.98Si. Mo + O.AlNi. Cr + 3.03Ni. Al - 0.69Ni. Mo - 1.77Cr.Al - 0.02Cr. Al + 0.63AI. Mo + 840.78 C2- 0.29 Mn2- 7.95 Si2+ 0.89 Ni2- 0.35 Cr2- 9.14 AZ2- 3.16 Mo2wherein C, Mn, Si, Ni, Cr, Al, Mo are the respective wt% of carbon, manganese, silicon, nickel, chromium, aluminium and molybdenum in the composition; and and wherein the R- and T- values satisfy the following relationship:R < (13 X T) - 288.83 .

2. The non-grain oriented electrical steel alloy composition of Claim 1 , comprising: 0.05 wt.% or less of carbon;2 wt% to 5 wt% inclusive of manganese;2 wt% to 6 wt% inclusive of silicon;1.5 wt% or less of nickel;1 wt% or less of chromium;0.05 wt% to 4 wt% inclusive of aluminium;0.7 wt% or less of molybdenum; and0.0004 wt% or less of gadolinium or germanium.

3. The non-grain oriented electrical steel alloy composition of Claim 1 or Claim 2, comprising:0.05 wt.% or less of carbon;2 wt% to 5 wt% inclusive of manganese;2 wt% to 6 wt% inclusive of silicon;1.5 wt% or less of nickel;1 wt% or less of chromium;0.05 wt% to 4 wt% inclusive of aluminium;0.7 wt% or less of molybdenum; and wherein the other alloying elements or impurities are each present in an amount less than 0.0004 wt%.

4. The non-grain oriented electrical steel alloy composition of any one of the preceding Claims, comprising:0.001 wt% to 0.05 wt% of carbon;3 wt% to 6 wt% of silicon;0.05 wt% to 1.5 wt% inclusive of nickel;0.1 wt% to 1 wt% inclusive of chromium;0.05 wt% to 3 wt% inclusive of aluminium;0.6 wt% or less of molybdenum.

5. The non-grain oriented electrical steel alloy composition of any one of the preceding Claims, comprising:0.005 wt% or less of carbon;3.5 wt% to 6 wt% inclusive of silicon;0.1 wt% to 0.8 wt% inclusive of nickel;0.5 wt% to 0.9 wt% inclusive of chromium;0.05 wt% to 2 wt% inclusive of aluminium;0.5 wt% or less of molybdenum.

6. The non-grain oriented electrical steel alloy composition of any one of the preceding Claims, comprising:0.005 wt% or less of carbon;3.5 wt% to 5 wt% inclusive or more of silicon;0.3 wt% to 0.7 wt% inclusive of nickel;0.7 wt% to 0.8 wt% inclusive of chromium;0.05 wt% to 0.5 wt% inclusive of aluminium;0.4 wt% or less of molybdenum.

7. The non-grain oriented electrical steel alloy composition of any one of the preceding Claims, comprising:0.0055 wt% or less of carbon;4.45 wt% to 4.65 wt% inclusive of silicon;0.35 wt% to 0.45 wt% inclusive of nickel;0.70 wt% to 0.80 wt% inclusive of chromium;0.05 wt% to 0.15 wt% inclusive of aluminium;0.05 wt% or less of molybdenum.

8. The non-grain oriented electrical steel alloy composition of any one of Claims 1 to 6, comprising:0.0045 wt% or less of carbon;3.15 wt% to 3.35 wt% inclusive of silicon;0.60 wt% to 0.65 wt% inclusive of nickel;0.70 wt% to 0.80 wt% inclusive of chromium;0.10 wt% to 0.20 wt% inclusive of aluminium;0.45 wt% or less of molybdenum.

9. The non-grain oriented electrical steel alloy composition of any one of Claims 1 to 4, comprising:0.004 wt% or less of carbon;2.10 wt% to 2.30 wt% inclusive of silicon;1.05 wt% to 1.25 wt% inclusive of nickel;0.85 wt% to 1.05 wt% inclusive of chromium;1.85 wt% to 2.05 wt% inclusive of aluminium;0.05 wt% or less of molybdenum.

10. The non-grain oriented electrical steel alloy composition of any one of the preceding Claims, having a resistivity of 60 pQ.cm or more, optionally 70 pQ.cm or more, optionally 75 pQ.cm or more, optionally 75 pQ.cm to 90 pQ.cm.

11. A non-grain oriented electrical steel sheet made from the alloy composition of any one of the preceding Claims, wherein the thickness of the non-grain oriented electrical steel sheet is from 100 pm to 500 pm.

12. The non-grain oriented electrical steel sheet of Claim 11 , having an A2->B2 transformation arising at a temperature of less than 600 °C and a resistivity of from 45 pQ.cm to 100 pQ.cm.

13. The non-grain oriented electrical steel sheet of Claim 11 or 12, having an A2->B2 transformation arising at a temperature of less than 400 °C and a resistivity of from 50 pQ.cm to 90 pQ.cm.

14. The non-grain oriented electrical steel sheet of any one of Claims 11 or 12, having an A2->B2 transformation arising at a temperature of less than 300 °C and a resistivity of from 50 pQ.cm to 85 pQ.cm.

15. The non-grain oriented electrical steel sheet of any one of Claims 11 to 14, wherein the tensile strength of the non-oriented electrical steel sheet is greater than 600 MPa.

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