JP2013515166A - Non-oriented electrical steel sheet having relatively high magnetic induction and high strength, and method for producing the same - Google Patents

Abstract

  A non-oriented electrical steel sheet having a relatively high magnetic induction and high strength, and its manufacturing method includes 1) smelting and casting, and the weight percentage of the components of the electrical steel sheet is: C ≦ 0.0040%, Si is 2.50% to 4.00%, Al is 0.20% to 0.80%, Cr is 1.0 to 8.0%, Ni is 0.5 to 5.0% Yes, Mn ≦ 0.50%, P ≦ 0.30%, S ≦ 0.0020%, N ≦ 0.0030%, Ti ≦ 0.0030%, Nb ≦ 0.010%, V ≦ 0.010% , C + S + N + Ti ≦ 0.010%, and the balance being substantially Fe and inevitable impurities; smelting, RH vacuum process and casting, and further including 2) hot rolling and 3) normalization The temperature is 850-950 ° C., the time is 0.5-3 minutes, , Gradually cooled to 650 to 750 ° C. at 5 to 15 ° C./s, and further rapidly cooled to 100 ° C. or less at 20 to 70 ° C./s; and 4) including pickling and cold rolling, and the total screw down rate is 5) Including annealing, the temperature is 800-1000 ° C., held for 5-60 s, then slowly cooled to 650-750 ° C. at 3-10 ° C./s, and 20 It is rapidly cooled to 100 ° C or lower at -70 ° C / s. The present invention can produce a non-oriented electrical steel sheet having high strength and high magnetic induction without increasing difficulty during production.

Description

  The present invention applies to devices that require high starting torque and impact resistance performance, such as electric vehicle motors and drive electric machines, the addition of solid solution strengthening elements such as Ni, Cr, etc., and C, N, By controlling the elements that impair the magnetic properties such as S, Ti, etc., the magnetic properties of the electrical steel sheet are ensured to improve the yield strength of the electrical steel sheet, and the heat is improved to improve the magnetic induction of the product. The present invention relates to the field of electrical steel sheet manufacturing performed by simultaneously performing an appropriate annealing annealing step on a hot-rolled steel sheet, and more particularly to a non-oriented electrical steel sheet having a relatively high magnetic induction and high strength and a method for manufacturing the same.

  As non-renewable resources such as oil and coal are depleted every day, the harmfulness of the greenhouse effect in the environment becomes more severe every day, and electric vehicles and hybrid power vehicles are less environmentally friendly vehicles with less pollution. Has gained more and more attention, and it is undoubtedly widely applied. The stator core and rotor core of electric motors and electric motors of hybrid power vehicles are formed from non-oriented electrical steel sheets, and when the car starts and accelerates, the motors need high torque and the electric steel plates need to have high magnetic induction And Furthermore, the rotor core of the motor withstands extreme loads due to centrifugal forces at high speeds and is momentarily exposed to strong impacts when the car starts, thus the core material needs to have high strength and toughness. .

  In the current non-oriented silicon steel products, as the Si content improves, the strength of the products improves, and the yield strength of some of the top level high steel grade products reaches 450 MPa, and the iron loss of the products also increases. Relatively low, it meets application in normal industrial electrical machinery and electrical generators. However, there is a tendency to squeeze, the toughness and plasticity of this type of product is poor, and the magnetic induction is also relatively low, which is not applicable in the use of driving electric machines such as electric vehicle motors, and thus high strength And there is a need to develop non-oriented electrical steel sheets with high magnetic induction.

  “High-strength electrical steel sheet, its processed parts, and its manufacturing method” is disclosed in Chinese patent application CN 1863934, where strengthening such as Mn, Cu, etc. to improve the yield strength and tensile strength of electrical steel sheet The element is added in its composition, but the problem is that when the product is manufactured according to this method, cold rolling is difficult and the magnetic properties of the electrical steel sheet are also affected, so Magnetic induction is relatively low. In order to improve the strength of the product, it is necessary to cool the cold-rolled sheet at a high cooling rate from the high temperature to the intermediate temperature after being annealed. It occurs on the inside, which adversely affects the shape of the steel strip and affects the magnetic properties and fatigue resistance of the product. Furthermore, in this patent application, it is necessary to hold a long time in an intermediate temperature zone and to perform a curing process in annealing and cooling for cold rolling, which is a set of conventional industrial annealing machines Is disadvantageous to achieve. Another aspect of this application is to manufacture electrical steel sheets, the material of which is relatively flexible before being pierced, so that the manufactured components achieve the objectives of strength improvement and wear resistance. It undergoes several heat treatment processes that are applied in customer use.

  In the application WO 2009/128428 A1, it is necessary to cool at a cooling rate in excess of 50 ° C./s in the temperature range from 900 ° C. to 500 ° C. after the product is finally annealed. However, in this method, a strong stress is generated in the steel strip, which has a strong influence on the shape and magnetic properties of the steel strip, which is disadvantageous for being applied in actual industrial production.

  An object of the present invention is to manufacture a non-oriented electrical steel sheet having high strength, wear resistance, and high magnetic properties from an existing apparatus in a stable manner without increasing production difficulties. It is possible to provide a non-oriented electrical steel sheet having relatively high magnetic induction and high strength, and a method for producing the same.

To achieve the above objective, the technical solution of the present invention is a non-oriented electrical steel sheet having a relatively high magnetic induction and high strength, the weight percentage of its chemical composition being:
C: ≦ 0.0040%
Si: 2.50% to 4.00%
Al: 0.20% to 0.80%
Cr: 1.0-8.0%
Ni: 0.5-5.0%
Mn: ≦ 0.50%
P: ≦ 0.30%
S: ≦ 0.0020%
N: ≦ 0.0030%
Ti: ≦ 0.0030%
Nb: ≦ 0.010%
V: ≦ 0.010%
C + S + N + Ti: ≦ 0.010%
And the balance is substantially Fe and inevitable impurities.

Furthermore, the non-oriented electrical steel sheet of the present invention contains Cu ≦ 3% by weight.
Furthermore, the non-oriented electrical steel sheet of the present invention contains Sb and / or Sn having a total content of 0.5% or less by weight%.

  Preferably, in the non-oriented electrical steel sheet according to the present invention, by weight%, C ≦ 0.002% or C ≦ 0.0015%; the Si content is 2.8 to 3.3%; The Al content is 0.4% to 0.6%; the Cr content is 2.5% to 6%; the Ni content is 1.0% to 3.5%; The content of S is 0.1% or less, the content of S is 0.0015% or less; the content of N is 0.002% or less; the content of Ti is 0.0015% or less. is there.

A method for producing a non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to the present invention comprises:
1) including smelting and casting steps,
The weight percentage of chemical components of the non-oriented electrical steel sheet is C ≦ 0.0040%, Si is 2.50% to 4.00%, Al is 0.20% to 0.80%, Cr Is 1.0 to 8.0%, Ni is 0.5 to 5.0%, Mn ≦ 0.50%, P ≦ 0.30%, S ≦ 0.0020%, N ≦ 0.0. 0030%, Ti ≦ 0.0030%, Nb ≦ 0.010%, V ≦ 0.010%, C + S + N + Ti ≦ 0.010%, and the balance is substantially Fe and inevitable impurities, smelting, RH vacuum The process is performed and poured into the slab according to the above composition;
2) including a hot rolling step,
The heating temperature of the slab is 1050 ° C. to 1200 ° C., the holding time is 30 minutes or more, the initial rolling temperature in the rolling smoothing process is controlled to 940 ° C. to 1000 ° C., the final rolling temperature is 850 ° C. or more, and the final The stand screw down rate is controlled to 10 to 15%, the coiling temperature is controlled to 500 to 700 ° C., and the thickness of the rolled steel sheet is 2.0 to 2.6 mm;
3) including a hot rolled steel plate normalizing step,
The normalizing temperature is 850 to 950 ° C., the holding time is 0.5 to 3 minutes, then gradually cooled to 650 to 750 ° C. at a cooling rate of 5 to 15 ° C./s, and further 20 to 70 ° C. Quenching to 100 ° C. or less at a cooling rate of / s;
4) including pickling and cold rolling steps;
Cold rolled in a single cold rolling process, the total screw down rate is 70% or more;
5) including annealing in a continuous furnace,
Annealing is performed in a continuous furnace, the annealing temperature is 800-1000 ° C., holding it for 5-60 s, then slowly cooling to 650-750 ° C. at a cooling rate of 3-10 ° C./s, It is rapidly cooled to 100 ° C. or lower at a cooling rate of 20 to 70 ° C./s.

Furthermore, the non-oriented electrical steel sheet of the present invention contains Cu ≦ 3% by weight.
Furthermore, the non-oriented electrical steel sheet of the present invention contains Sb and / or Sn having a total content of 0.5% or less by weight%.

  In the composition design of the present invention, C can improve the strength of the steel sheet, but fine carbonization greatly reduces the magnetic properties, and if the content of C is larger, magnetic aging occurs in the electrical steel sheet, and therefore the percentage of C In this invention, it is 0.004% or less, and when the C content is 0.002% or less, the deterrent effect on magnetic aging is significant, and non-metallic precipitation such as carbonization occurs. In order to improve the strength without causing it, ≦ 0.0015% is more preferable.

  Si can improve the electrical resistance of the steel and reduce iron loss, and when improving the Si content, the strength can be improved while the iron loss can be reduced, so the Si content is It can take as much as 2.5% and can be improved as high as possible, but if the Si content is improved to some extent, the product becomes brittle while the magnetic induction is reduced, so the Si content is 4 0.0% or less, and more preferably 2.8 to 3.3%.

  The effect of Al is similar to that of Si, which can reduce iron loss, and if the Al content is improved, AlN may become coarser, which improves the magnetic properties of the steel to improve the magnetic properties of the steel. Easy to grow, but with increasing Al, the viscosity of the liquid steel increases, making steelmaking more difficult, while also reducing magnetic induction, so the Al content is between 0.2% and 0.8%. %, Preferably 0.4% to 0.6%.

  Cr and Ni are essential elements in the present invention, added as strengthening elements, and a metal phase based on Cr and Ni is formed in the steel sheet, aiming at high strength without deterioration in magnetic properties. When the Cr content is low, the effect of high strength is reduced, and in order to improve the strength of the steel sheet, the technical requirements in the subsequent processes are high and the degree of freedom of adjustment in manufacturing is low, but the Cr content If the amount is high, the magnetic properties are reduced, and cracks are likely to occur in the hot rolling process, so the Cr content is 1.0% to 8.0%, more preferably 2.5% to 6%. Is needed.

  Ni can improve the strength of the steel sheet and improve magnetic induction, has little effect on iron loss and is added as a useful element, but if Ni is added too much, cracks are likely to occur in the hot rolling process. In this invention, the content of Ni is 0.5% to 5.0%, more preferably 1.0% to 3.5%. It is necessary to be.

  Although Mn can improve the strength of the steel, in this invention, Mn is not added for that purpose, but is added to improve resistivity or roughen the sulfides to reduce iron loss. Adding too much results in a reduction in magnetic induction, so the Mn content is required to be 0.5% or less.

  P is an element for remarkably improving the tensile stress. However, it is easy to separate and accumulate at the crystal grain boundary, making the steel sheet extremely brittle. Therefore, the P content is 0.3% or less, preferably 0.8. It is required to be 1% or less.

  S is an element that impairs magnetic properties, and the formed fine sulfide suppresses the growth of crystal grains and increases the iron loss. Therefore, the S content is 0.002% or less, preferably 0.8. It is required to be 0015% or less.

  N is similar to S and impairs magnetic properties, and therefore the N content is required to be 0.003% or less, preferably 0.002% or less.

  Ti can improve the strength of the steel sheet, but it has a strong influence on the magnetic properties, and its fine precipitation like TiC and TiN will settle at the grain boundaries, which suppresses the growth of the grains and iron The loss is increased and magnetic induction is reduced, so the Ti content is required to be 0.003% or less, preferably 0.0015% or less.

  In this invention, the total content of C + N + S + Ti is controlled within 0.01% so as to guarantee the magnetic properties of the steel sheet.

  Nb and V are required to be controlled to 0.01% or less as elements that impair the magnetic properties.

  Cu is selectively added as an element for improving the strength, and Sn and Sb are selectively added as elements for improving the magnetic properties.

  Steel containing the composition described above uses a continuous casting process with smelting to decarburize in a converter, ladle refining to remove oxygen and alloying to resemble ordinary electrical steel sheets Slabs are manufactured by processes such as hot rolling, normalizing, pickling, cold rolling and final annealing.

  In the manufacturing method, the cooling phase and the final annealing process in the normalization process are controlled as follows in order to generate a characteristic metal phase in the steel sheet and to ensure manufacturability and magnetic properties.

  After the hot rolled steel sheet has been normalized, cooling is performed in the segment, slow cooling is used in the high temperature stage, rapid cooling is performed in the low temperature stage, and after the steel strip comes from the normalized soaking section, The steel strip is gradually cooled to 650 to 750 ° C. at a cooling rate of 5 to 15 ° C./s, and then rapidly cooled to 100 ° C. or less at a cooling rate of 20 to 70 ° C./s. Reducing the cooling rate in the high temperature stage sufficiently restores the grain structure, which reduces stress in the steel sheet, improves the flatness and shape of the normalized steel sheet, and improves the efficiency of cold rolling. In addition, reducing the cooling rate in the high temperature stage after normalizing sufficiently forms solid solution carbonized and nitride deposits, forms coarse impurities of carbonized and nitride, and reduces grain growth. Prevents the formation of fine impurities to suppress and forms an advantageous structure within the finished steel sheet, resulting in improved magnetic properties of the steel sheet.

  After the steel strip has been annealed last, cooling takes place in the segment, the steel strip is first slowly cooled to 650-750 ° C. at a cooling rate of 3-10 ° C./s and then 20-70 ° C./s. It is rapidly cooled to 100 ° C. or lower at a cooling rate of In the high temperature annealing period, Cr and Ni metal phases characterized in composition, size and number density are efficiently formed, and solid solutions or sulfides with low strengthening ability that greatly deteriorate the magnetic properties are not formed. On the other hand, gradual cooling in the high temperature stage further reduces internal stress in the finished steel strip, improves the magnetic properties of the finished product, and improves the fatigue resistance of the product.

  In the non-oriented electrical steel sheet having high magnetic induction and high strength according to the present invention, strengthening elements such as Ni and Cr are added to the components, and elements that impair magnetic properties such as C, N, S, and Ti are relatively Controlled to a low level, the strength of the electrical steel sheet is improved without significant degradation in magnetic properties. The cooling process can be controlled in the normalizing and annealing processes, which ensures the shape of the steel strip, stabilizes the magnetic properties of the product, and solves the problems of cold rolling difficult.

In the following, the invention will be described with reference to examples.
The ingredients in the examples can be seen in Table 1.

  The manufactured slab was heated to 1120 ° C., and this temperature was maintained for 60 minutes. Then, the manufactured slab was hot-rolled to a steel strip having a thickness of 2.3 mm, and the final rolling temperature was 860 ° C. The taking temperature is 570 ° C. After the hot-rolled steel sheet is normalized at a normalizing temperature of 900 ° C. for a heat storage time of 60 s, the hot-rolled steel sheet is rolled into a cold-rolled steel sheet having a thickness of 0.5 mm. . After the cold rolled steel sheet is annealed at an annealing temperature of 900 ° C. for a heat storage time of 15 s, the cold rolled steel sheet is cooled from 900 ° C. to 500 ° C. at different cooling rates and then at room temperature at 70 ° C./s. The magnetic properties of the manufactured samples were measured by an EPSTIN frame, and the mechanical performance and high cycle fatigue performance of the samples were measured by JIS5 tension (average load is 172 MPa, amplitude is 156 MPa). The performance measurement results corresponding to the process can be understood in Table 2.

  The slab was manufactured with the ingredients according to Example 11 in Table 1, and after heating the slab to 1120 ° C. and holding this temperature for 60 minutes, the slab was hot rolled into a steel strip having a thickness of 2.3 mm, The final rolling temperature is 860 ° C. and the winding temperature is 570 ° C. After the hot-rolled steel sheet is normalized at a normalizing temperature of 900 ° C. for a heat storage time of 60 s, the hot-rolled steel sheet is rolled into a cold-rolled steel sheet having a thickness of 0.5 mm. . After the cold rolled steel sheet is annealed at an annealing temperature of 900 ° C. for a heat storage time of 15 s, the cold rolled steel sheet is heated from 900 ° C. to 500-600 ° C. at different cooling rates (1 # -5 #). Cooled and the cooling process can be seen in Table 3.

  The magnetic properties of the manufactured samples were measured by an EPSTIN frame, and the mechanical performance and high cycle fatigue performance of the samples were measured by JIS5 tension (average load is 172 MPa, amplitude is 156 MPa). 4 can be understood.

  As can be seen in Tables 3 and 4, if the annealing cooling temperature is too rapid, the magnetic performance of the steel sheet becomes worse, resulting in increased iron loss, decreased magnetic induction, and fatigue resistance. It gets worse.

Claims (14)

A non-oriented electrical steel sheet having a relatively high magnetic induction and high strength, the weight percentage of its chemical composition is:
C: ≦ 0.0040%
Si: 2.50% to 4.00%
Al: 0.20% to 0.80%
Cr: 1.0-8.0%
Ni: 0.5-5.0%
Mn: ≦ 0.50%
P: ≦ 0.30%
S: ≦ 0.0020%
N: ≦ 0.0030%
Ti: ≦ 0.0030%
Nb: ≦ 0.010%
V: ≦ 0.010%
C + S + N + Ti: ≦ 0.010%
And a non-oriented electrical steel sheet, the balance being substantially Fe and inevitable impurities.   The non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 1, wherein the non-oriented electrical steel sheet has a relatively high magnetic induction and high strength.   The non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 1 or 2, comprising Sb and / or Sn having a total content of 0.5% or less by weight.   The non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 1, wherein C ≦ 0.002% or C ≦ 0.0015% by weight.   The non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 1, having a Si content of 2.8 to 3.3% by weight.   The non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 1, having an Al content of 0.4 to 0.6% by weight.   The non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 1, having a Cr content of 2.5 to 6% by weight.   The non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 1, having a Ni content of 1.0 to 3.5% by weight.   2. Non-directional with relatively high magnetic induction and high strength according to claim 1, wherein the content of P is 0.1% or less and the content of S is 0.0015% or less by weight%. Electrical steel sheet.   The non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 1, having a content of N of 0.002% or less by weight.   The non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 1, having a Ti content of 0.0015% or less by weight. A method for producing a non-oriented electrical steel sheet having a relatively high magnetic induction and high strength comprising:
1) including smelting and casting steps,
The weight percentage of chemical components of the non-oriented electrical steel sheet is C ≦ 0.0040%, Si is 2.50% to 4.00%, Al is 0.20% to 0.80%, Cr Is 1.0 to 8.0%, Ni is 0.5 to 5.0%, Mn ≦ 0.50%, P ≦ 0.30%, S ≦ 0.0020%, N ≦ 0.0. 0030%, Ti ≦ 0.0030%, Nb ≦ 0.010%, V ≦ 0.010%, C + S + N + Ti ≦ 0.010%, and the balance is substantially Fe and inevitable impurities; smelting, RH vacuum The process is performed and poured into the slab according to the above composition;
2) including a hot rolling step,
The heating temperature of the slab is 1050 ° C. to 1200 ° C., the holding time is 30 minutes or more, the initial rolling temperature in the rolling smoothing process is controlled to 940 ° C. to 1000 ° C., the final rolling temperature is 850 ° C. or more, and the final The stand screw down rate is controlled to 10 to 15%, the coiling temperature is controlled to 500 to 700 ° C., and the thickness of the rolled steel sheet is 2.0 to 2.6 mm;
3) including a hot rolled steel plate normalizing step,
The normalizing temperature is 850 to 950 ° C., the holding time is 0.5 to 3 minutes, then gradually cooled to 650 to 750 ° C. at a cooling rate of 5 to 15 ° C./s, and further 20 to 70 ° C. Quenching to 100 ° C. or less at a cooling rate of / s;
4) including pickling and cold rolling steps;
Cold rolled in a single cold rolling process, the total screw down rate is 70% or more;
5) including an annealing step in a continuous furnace,
Annealing is performed in a continuous furnace, the annealing temperature is 800-1000 ° C., holding it for 5-60 s, then slowly cooling to 650-750 ° C. at a cooling rate of 3-10 ° C./s, A method of rapidly cooling to 100 ° C. or lower at a cooling rate of 20 to 70 ° C./s.   The method of manufacturing a non-oriented electrical steel sheet having a relatively high magnetic induction and high strength according to claim 12, wherein the non-oriented electrical steel sheet further comprises Cu ≦ 3% by weight.   The non-oriented electrical steel sheet further comprises Sb and / or Sn having a total content of 0.5% or less by weight, and having no relative high magnetic induction and high strength according to claim 12 or 13. A method for producing a grain-oriented electrical steel sheet.