TWI487796B - Non - directional electromagnetic strip annealing method - Google Patents

Description

Non-directional electromagnetic steel strip annealing cooling method

The invention relates to a steel piece annealing cooling method, in particular to a non-directional electromagnetic steel strip annealing cooling method.

The iron loss of the conventional non-directional electromagnetic steel sheet includes eddy current loss and magnetic hysteresis loss, the former is related to the resistivity and the thickness of the steel, and the latter is related to the grain size, the aggregate structure, the inclusions, the lattice defects and the residual stress. It is conventional to reduce the eddy current loss of steel, generally adding a high amount of alloy, mainly bismuth alloy, to increase the electrical resistivity. However, the addition of high amount of niobium alloy system will lead to the deterioration of the thermal conductivity of the steel, so that the steel strip is easily controlled due to the cooling rate (referred to as the cooling rate) during the final annealing process, resulting in the formation of residual stress, which in turn causes the magnetic hysteresis to rise. .

In addition, since the conventional steel strip is annealed and cooled, the variation effect of the steel niobium content is not taken into consideration. Therefore, after the steel strips with different niobium content are treated under the same annealing and cooling conditions, residual stress is often formed inside the steel strip.

Therefore, it is necessary to provide an innovative and progressive non-directional electromagnetic steel strip annealing cooling method to solve the above problems.

The invention provides a non-directional electromagnetic steel strip annealing cooling method, the annealing cooling method comprising the following steps: (a) providing a steel embryo, the steel embryo composition comprising less than 0.01% by weight of carbon, x% by weight of niobium, 0.1 To 2.0% by weight of aluminum, 0.1 to 1.5% by weight of manganese, 0.005 to 0.2% by weight of phosphorus, less than 0.01% by weight of sulfur, less than 0.01% by weight of nitrogen and the balance being substantially iron and unavoidable impurities; (b Heating the steel embryo; (c) hot rolling the steel blank to form a hot rolled sheet; (d) performing an annealing treatment step on the hot rolled sheet; (e) cold rolling the hot rolled sheet to a final thickness, To form an electromagnetic steel strip; (f) performing a temperature equalizing annealing step on the electromagnetic steel strip at a soaking temperature T; and (g) cooling the electromagnetic steel strip, the cooling step comprising: a first stage cooling Cooling from the soaking temperature T to a first temperature T1 at a first cooling rate V1, the first temperature T1 and the first cooling rate V1 satisfying the following conditions: T1≦T-(100+14x)- x ^2; and V1 ≦ (6 + 5 / x ); and a second cooling stage, a second cooling system with a cooling rate V2 T1 from the first temperature to a second temperature T2, the second And the second temperature T2, the cooling rate V2 satisfy the following condition: T2 ≦ T1- (200 + 18x ) -x 2: and V2 ≦ (8 + 5 / x ).

The invention designs different final annealing cooling temperature intervals and cooling speeds according to the change of the bismuth content of the electromagnetic steel strip. If the strontium content is lowered, the cooling rate is increased, and the strontium content is increased, and the cooling rate is decreased. The annealing cooling method of the invention can automatically adjust the cooling temperature interval and the cooling speed for the electromagnetic steel strips with different bismuth contents, so that in addition to reducing the residual stress and iron loss of the electromagnetic steel strip, the production efficiency of the steel strip can be greatly improved. . In addition, the cooling rate designed by the present invention is the upper limit of the boundary, and is not an average value. Therefore, the production line is easy to implement and adjust.

The above description is only an overview of the technical solutions of the present invention, and the technical means of the present invention can be more clearly understood, and the objects, features, and advantages of the present invention can be more clearly understood. The preferred embodiment is described in detail with reference to the accompanying drawings. under.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the annealing method of the non-directional electromagnetic steel strip of the present invention. Referring to step S11 of FIG. 1 , a steel embryo is provided, the composition of which includes less than 0.01% by weight of carbon, x% by weight of bismuth, 0.1 to 2.0% by weight of aluminum, 0.1 to 1.5% by weight of manganese, and 0.005 to 0.2% by weight of phosphorus, less than 0.01% by weight of sulfur, less than 0.01% by weight of nitrogen and the balance being substantial iron and unavoidable impurities. In the present embodiment, the ruthenium content x is preferably from 0.1 to 4.0.

Referring to step S12, the steel embryo is heated. The heating temperature for this step is 1200 to 1250 ° C, and preferably, the heating time is 2 to 4 hours.

Referring to step S13, the steel blank is hot rolled to form a hot rolled sheet. In this step, the thickness of the hot rolled sheet is 1.5 to 2.5 mm.

Referring to step S14, the hot rolled sheet is subjected to an annealing treatment step. In the present embodiment, the annealing treatment step is performed at a temperature ranging from 700 to 1100 ° C, and the annealing time is from 3 minutes to 30 hours. Preferably, the hot rolled sheet is subjected to a pickling process prior to the annealing step.

Referring to step S15, the hot rolled sheet is cold rolled to a final thickness to form an electromagnetic steel strip. In this embodiment, the final thickness is from 0.1 to 0.7 mm.

Referring to step S16, the electromagnetic steel strip is subjected to a temperature equalization annealing step at a soaking temperature T. In the present embodiment, the soaking temperature T is 900 to 1100 ° C, and the annealing time is 30 seconds to 10 minutes.

Referring to step S17, the electromagnetic steel strip is cooled, and the cooling step includes: A first stage of cooling and a second stage of cooling.

The first stage cooling system is cooled by the soaking temperature T to a first temperature T1 at a first cooling rate V1. In the embodiment, the first temperature T1 and the first cooling rate V1 satisfy the following conditions, respectively.

T1≦T-(100+14x)-x ² (1)

V1≦(6+5/x) (2)

The second stage cooling system is cooled from the first temperature T1 to a second temperature T2 by a second cooling rate V2. In the embodiment, the second temperature T2 and the second cooling rate V2 satisfy the following conditions, respectively.

T2≦T1-(200+18x)-x ² (3)

V2≦(8+5/x) (4)

The invention designs different final annealing cooling temperature intervals (T~T1, T1~T2) and cooling speed (V1, V2) according to the change of the bismuth content x of the electromagnetic steel strip, and if the strontium content is lowered, the cooling rate is improved. While the strontium content is increased, the cooling rate is lowered. The annealing cooling method of the invention can automatically adjust the cooling temperature interval and the cooling speed for the electromagnetic steel strips with different bismuth contents, so that in addition to reducing the residual stress and iron loss of the electromagnetic steel strip, the production efficiency of the steel strip can be greatly improved. . In addition, the cooling rate designed by the present invention is the upper limit of the boundary, and is not an average value. Therefore, the production line is easy to implement and adjust.

The invention is illustrated by the following examples, which are not intended to be limited to the scope of the invention.

Invention examples and comparative examples:

The steel composition of the invention examples and comparative examples are listed in Table 1, and the unit is % by weight. As listed in Table 1, the invention examples and comparative examples use four types: A, B, C, and D. The composition of different steel materials, wherein the strontium content is 0.51, 1.68, 2.78 and 3.51% by weight respectively; the manganese content is 0.55, 0.53, 0.56 and 0.55 wt%, respectively; the aluminum contents are 0.21, 0.22, 0.21 and 0.21% by weight, respectively; and phosphorus The contents were 0.038, 0.037, 0.037 and 0.040% by weight, respectively. The carbon, sulfur and nitrogen contents not shown in Table 1 were both about 0.004% by weight, and the rest were substantial iron and unavoidable impurities.

The steel embryo produced by agglomeration or continuous casting is heated in an oven at 1220 ° C for 2 hours; then, hot rolled into a hot rolled sheet having a thickness of about 2 mm; after hot-rolled sheet is pickled, Hot rolling annealing is performed at a temperature of 700 ° C for 30 hours; after the hot rolled sheet is cooled, it is cold rolled to a final sheet thickness of 0.35 mm to form an electromagnetic steel strip; after that, the electromagnetic steel strip is heated to 800 to 1000 ° C, and both Heat for 90 seconds to grow the final grain size of the steel; finally, the electromagnetic steel strip is cooled according to the first-stage cooling conditions and the second-stage cooling conditions described above. The detailed cooling conditions are listed in Table 2.

The cooled electromagnetic steel strip is measured for iron loss (W15/50) and magnetic flux density (B50), where W15/50 indicates that the excitation frequency is 50 Hz and is excited to 1.5 Tesla. Iron loss value; B50 represents the magnetic flux density obtained when the excitation frequency is 50 Hz and the magnetic field strength is 5000 A/m. The measurement results of W15/50 and B50 are listed in Table 3.

The measurement results of Table 3 showed that the iron loss values of the inventive examples A-1, B-1, B-3, C-1 and D-1 whose cooling conditions were in conformity with (1) to (4) were significantly decreased. Further, comparing the results of Inventive Example C-1 with the results of Comparative Examples D-2 and D-3, it was found that the electromagnetic characteristics of the electromagnetic steel strip using a lower niobium content after being cooled by the annealing cooling method of the present invention It is similar or even better than the high bismuth content steel strip which is not cooled by the same method, and it proves that the annealing cooling method of the present invention can further achieve the effect of saving the cost of adding the bismuth alloy.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Changes remain without departing from the spirit of the invention. The scope of the invention should be as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing the annealing method of the non-directional electromagnetic steel strip of the present invention.

Claims (10)

A non-directional electromagnetic steel strip annealing cooling method comprises the following steps: (a) providing a steel embryo, the steel embryo comprising less than 0.01% by weight of carbon, x% by weight of niobium, 0.1 to 2.0% by weight of aluminum, 0.1 to 1.5% by weight of manganese, 0.005 to 0.2% by weight of phosphorus, less than 0.01% by weight of sulfur, less than 0.01% by weight of nitrogen and the balance being substantially iron and unavoidable impurities; (b) heating the steel embryo; c) hot rolling the steel blank to form a hot rolled sheet; (d) performing an annealing treatment step on the hot rolled sheet; (e) cold rolling the hot rolled sheet to a final thickness to form an electromagnetic steel strip; (f) performing a temperature equal annealing step on the electromagnetic steel strip at a soaking temperature T; and (g) cooling the electromagnetic steel strip, the cooling step comprising: (g1) a first stage of cooling, The first cooling rate V1 is cooled by the soaking temperature T to a first temperature T1, and the first temperature T1 and the first cooling rate V1 satisfy the following conditions: T1≦T-(100+14x)-x ² ; V1≦(6+5/x); and (g2) a second stage cooling, which is cooled by the first temperature T1 to a second temperature T2 at a second cooling rate V2, the second temperature T2 and the first Second cooling speed V 2 The following conditions are respectively satisfied: T2≦T1-(200+18x)-x ² ; and V2≦(8+5/x). The non-directional electromagnetic steel strip annealing cooling method according to claim 1, wherein x of the step (a) is 0.1 to 4.0. The non-directional electromagnetic steel strip annealing cooling method according to claim 1, wherein the heating temperature of the step (b) is 1200 to 1250 °C. The non-directional electromagnetic steel strip annealing cooling method according to claim 1, wherein the heating time of the step (b) is 2 to 4 hours. The non-directional electromagnetic steel strip annealing cooling method according to claim 1, wherein the hot rolled sheet of the step (c) has a thickness of 1.5 to 2.5 mm. The non-directional electromagnetic steel strip annealing cooling method according to claim 1, wherein the annealing treatment step of the step (d) is performed at a temperature ranging from 700 to 1100 °C. The non-directional electromagnetic steel strip annealing cooling method according to claim 1, wherein the annealing time of the step (d) is from 3 minutes to 30 hours. The non-directional electromagnetic steel strip annealing cooling method according to claim 1, wherein the final thickness of the step (e) is 0.1 to 0.7 mm. The non-directional electromagnetic steel strip annealing cooling method according to claim 1, wherein the soaking temperature T of the step (f) is 900 to 1100 °C. The non-directional electromagnetic steel strip annealing cooling method according to claim 1, wherein the annealing time of the step (f) is from 30 seconds to 10 minutes.