Manufacture method of high-efficiency non-oriented silicon steel with excellent magnetic performance

Abstract

A manufacture method of high-efficiency non-oriented silicon steel with excellent magnetic property includes the steps of smelting a chemical composition of non-oriented silicon steel, by weight percent, is: C≤0.0040%, Si:0.1˜0.8%, Al:0.002˜1.0%, Mn:0.10˜1.50%, P:≤0.2%, Sb:0.04˜0.08%, S≤0.0030%, N≤0.0020%, Ti≤0.0020%, and the rest is Fe and unavoidable inclusions. The molten steel is then cast into billets which are hot-rolled into a hot-rolled product. The heating temperature for the billet is 1100°˜1150° and the finish-rolling temperature is 860°˜920°. The hot-rolled product is then air cooled for a period of time within a range determined by air cooling time t: (2+30×Sb%)s≤t≤7 s. The hot-rolled product is reeled at a temperature ≥720° and cold-rolled to form cold-rolled plate with a target thickness at a reduction ratio of 70˜78% followed by heating up the cold-rolled plate to 800˜1000° at heating rate of ≥15°/s, and holding time of 10s˜25s.

Claims

1. A manufacture method of non-oriented silicon steel, said method comprising: smelting a chemical composition of non-oriented silicon steel, which by weight percent, comprising: C≤0.0040%, Si:0.1-0.8%, Al:0.45-1.0%, Mn:0.10-1.50%, P:≤0.2%, Sb:0.055-0.08%, S≤0.0030%, N≤0.0020%, Ti≤0.0020%, and the rest is Fe and unavoidable impurities; casting said composition into a billet; hot rolling said billet into a hot-rolled product, wherein heating temperature for said billet is 1100° C.-1150° C. and finish-rolling temperature is 860° C.-920° C.; air cooling said hot-rolled product for a period of time within a range determined by air cooling time t: (2+30xSb %)s<t<7 s; reeling at a temperature ≥720° C.; cold rolling said hot-rolled product to form cold-rolled plates with a target thickness at a reduction ratio of 70-78%; and heating up the cold-rolled plates to 800-1000° C. at a heating rate of ≥15° C./s, with a holding time of 10-25 s.

2. The manufacture method of non-oriented silicon steel of claim 1, in which said step of heating up is in an annealing atmosphere of (volume ratio 30%-70%)H.sub.2+(volume ratio 70%-30%)N.sub.2, and dew point is controlled at −25° C.-−40° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates relation between air cooling time and magnetic property after hot-rolling process in the case of 0.26% Si and 0.055% Sb.

(2) FIG. 2 illustrates relation between air cooling time and magnetic property after hot-rolling process in the case of 0.26% Si and 0.055% Sb.

(3) FIG. 3 is a photo of metallographic structure of a hot-rolled plate with contents of 0.26% Si and 0.055% Sb under reeling temperature of 650° C.; and

(4) FIG. 4 is a photo of metallographic structure of a hot-rolled plate with contents of 0.26% Si and 0.055% Sb under reeling temperature of 720° C.

DETAILED DESCRIPTION

(5) The invention is described in detail below in connection with embodiments.

(6) After being smelted, a casted billet in accordance with compositions given in Table 1 undergoes through heating, rough rolling, finish rolling, high temperature reeling, pickling, single cold-rolling at a reduction ratio of 70-78% to form a strip steel with thickness of 0.5 mm, and thereafter the cold-rolled strip steel is final-annealed at different temperatures to form finished product. Table 2 represents manufacture method of the present invention for types of steels with the chemical compositions in Table 1 and results of finished products measured by Epstein's square and circle method.

(7) TABLE-US-00001 TABLE 1 Chemical compositions of embodiments (%)* C Si Mn P S Al N Ti Sb Embodiment 1 0.0009 0.23 0.60 0.071 0.0020 0.45 0.0019 0.0010 0.055 Embodiment 2 0.0015 0.43 1.34 0.110 0.0015 0.69 0.0016 0.0009 0.042 Embodiment 3 0.0028 0.61 0.82 0.052 0.0020 0.88 0.0024 0.0017 0.061 Embodiment 4 0.0025 0.74 0.44 0.005 0.0012 1.06 0.0018 0.0016 0.079 Embodiment 5 0.0030 0.80 1.02 0.03 0.0018 0.002 0.0013 0.0015 0.025 Comparative 0.0010 0.22 0.54 0.073 0.0024 0.45 0.0018 0.0006 — Object 1 Comparative 0.0012 0.44 1.2 0.110 0.0018 0.61 0.0019 0.0008 — Object 2 Comparative 0.0018 0.68 0.78 0.055 0.0015 0.79 0.0025 0.0015 — Object 3 Comparative 0.0026 0.75 0.42 0.005 0.0012 0.98 0.0012 0.0012 — Object 4 Comparative 0.0017 0.80 1.06 0.034 0.0020 0.002 0.0023 0.0017 — Object 5 *the rest is Fc and unavoidable impurities.

(8) TABLE-US-00002 TABLE 2 Manufacture method embodiments and magnetic property results Air cooling time in air Re-crystal- Finish-rolling after Reeling lization Temperature hot-rolling Temperature annealing P15/50 B50 FDT (° C.) s ° C. ° C. × S W/Kg T Embodiment 1 880 4 720 820 4.38 1.796 Embodiment 2 860 5.5 720 820 3.62 1.787 Embodiment 3 920 6 720 880 4.07 1.793 Embodiment 4 900 6.5 720 860 3.43 1.782 Embodiment 5 870 7 720 880 3.82 1.794 Comparative 880 0 720 820 4.63 1.765 Object 1 Comparative 860 0 720 820 3.79 1.759 Object 2 Comparative 920 0 720 880 4.46 1.776 Object 3 Comparative 900 0 720 860 3.84 1.753 Object 4 Comparative 870 0 720 880 4.24 1.768 Object 5

(9) As can be seen from the Table 2, under the circumstance of the same finish-rolling temperature, reeling temperature and annealing temperature, in comparison with comparative objects without adding Sb and without air cooling after being rolled, magnetic properties of compositions of the embodiments are relatively superior, iron loss thereof is 0.1-0.4 W/kg lower and B50 thereof is 0.2 T or more higher than the ones of the comparative objects.

(10) By measuring magnetic properties of the compositions of embodiments in Table 1 processed in accordance with Table 3, magnetic detection results are shown in Table 3.

(11) TABLE-US-00003 TABLE 3 Manufacture methods and results of magnetic properties of the embodiments Air cooling time in air Re-crystal- Finish-rolling after Reeling lization Temperature hot-rolling Temperature annealing P15/50 B50 FDT (° C.) s ° C. ° C. × S W/Kg T Embodiment 1 860 4 720 820 4.38 1.796 Embodiment 2 870 5.5 720 820 3.62 1.785 Embodiment 3 880 6 720 880 4.07 1.792 Embodiment 4 900 6.5 720 860 3.43 1.784 Embodiment 5 920 7 720 880 3.79 1.790 Comparative 860 4 570 820 4.57 1.754 Object 1 Comparative 870 5.5 600 820 3.91 1.742 Object 2 Comparative 880 6 580 870 4.78 1.763 Object 3 Comparative 900 6.5 570 860 4.15 1.749 Object 4 Comparative 920 7 610 880 4.63 1.760 Object 5

(12) As can be seen from the above Table, the magnetic properties of comparative objects 1-4, which do not undergo high temperature reeling, are significantly lower than the ones of types of steel of the embodiments, which undergoes high temperature reeling.

(13) By measuring magnetic properties of the compositions of embodiment 1 in Table 1 processed in accordance with Table 4, magnetic detection results are shown in Table 4.

(14) TABLE-US-00004 TABLE 4 Manufacture methods and results of magnetic properties of the embodiment Air cooling time in air Reeling Re-crystal- after Temper- lization Sb hot-rolling ature annealing P15/50 B50 % s ° C. ° C. × S W/Kg T Remarks Embodiment 1 0.055 0 740 820 × 16 4.66 1.77 Comparative 1 4.58 1.772 Object 2 4.52 1.774 3 4.50 1.774 4 4.33 1.79 The present 5 4.28 1.796 invention 6 4.2 1.792 7 4.16 1.79 8 4.33 1.788

(15) As can be seen from the above Table, control of air cooling time after hot-rolling is an important factor that affects magnetic properties of finished products. Both of a too short air cooling time and a too long air cooling time are adverse to the magnetic properties of the finished products. In the present invention, the air cooling time t after rolling is controlled within a range of (2+30xSb %)s≤t≤7 s, and so magnetic properties of the finished products are the best.

(16) In summary, the present invention refers to a manufacture method of high-efficiency non-oriented silicon steel with good magnetic properties, characteristics of which lie in adding a certain content of Sb, a grain boundary segregation element, during steel-making process; controlling air cooling process of hot-rolled plate by controlling air cooling time after hot-rolling to be (2+30xSb %)s≤t≤7 s; and meanwhile replacing normalization of hot-rolled plate with high temperature reeling, so as to obtain high efficiency electric steel of high performance and therefore to problems of conventional process for manufacture of high efficiency non-oriented electric steel, such as high cost and long manufacturing cycle etc.