Method for improving re-annealing performance of non-oriented silicon steel

Abstract

The invention discloses a method for improving re-annealing performance of non-oriented silicon steel. The non-oriented silicon steel comprises the following chemical components in percentage by mass: 0.4-3.0% of Si, 0.15-0.8% of Als, less than or equal to 0.0025% of C, less than or equal to 0.0025% of S, less than or equal to 0.0025% of N, less than or equal to 0.0020% of Ti, less than or equal to 0.0020% of Nb, less than or equal to 0.0020% of V, 0.2-0.5% of Mn, 0.001-0.06% of P, 0.02-0.15% of Sn and / or Sb, 0.015-0.120% of La and / or Ce, 0.0006-0.0050% of B and the balance of Fe and uncontrollable residual elements. A casting blank is smelted according to the chemical components, and then the non-oriented silicon steel is obtained through hot rolling, acid pickling, cold rolling, continuous annealing and recoiling. Normal production can be achieved on an existing production line, and equipment does not need to be added for producing semi-processed products.

Description

Technical Field

[0001] The invention belongs to the field of silicon steel production, relates to a production method of cold-rolled non-oriented electrical steel products under a metallurgical process, and specifically relates to a method for improving the re-annealing performance of non-oriented silicon steel. Background Art

[0002] Cold-rolled non-oriented electrical steel is the most widely used functional metal material, usually used to prepare various motor and electrical appliance cores. In the production of the motor industry, non-oriented electrical steel strips are usually cut, punched, and stacked to obtain the required stator and rotor cores of the main components.

[0003] During the stacking process from electrical steel strips to iron cores, the electromagnetic properties of the electrical steel matrix are affected due to the influence of processing stress, resulting in reduced operating efficiency after further assembly into a motor. With the development of low-carbon green manufacturing, the energy efficiency rating standards of the industrial motor industry and the household appliance motor industry are gradually improving. On the one hand, relevant motor manufacturers use higher-grade silicon steel products to design and produce motor stators and rotors. On the other hand, they combine traditional processes to heat treat silicon steel chips or iron cores to soften burrs, eliminate stress, and coarsen the structure, which can also improve electromagnetic properties, which is equivalent to improving the electromagnetic properties of 1 to 3 grades of silicon steel products with the same composition, thereby improving the motor energy efficiency indicators.

[0004] In the development history of non-oriented electrical steel, one of the branch products is the "semi-process" product. In the production of steel strip in the later process, the annealing + leveling process is used, combined with the chip or core re-annealing process in the user's processing process, so as to achieve "double excellence" cooperation in the industrial chain process. Here, the main function of leveling is to increase the energy storage of the matrix after recrystallization. In the heat treatment process of the user, it promotes the crystal organization to break through the pinning effect of the original inclusions and precipitates, coarsen the second phase particles, promote grain growth, reduce hysteresis loss, improve the electromagnetic performance of the product, and improve the operating efficiency of the stator and rotor.

[0005] Nowadays, with the large-scale and specialized production of electrical steel product manufacturers, there are no dedicated leveling units, and basically all products are full-process products. When users purchase such products, even if they perform chip or core heat treatment, it can only eliminate processing stress and restore lattice defects caused by processing, and cannot further improve the electromagnetic performance of the product. Therefore, in motor design and manufacturing, only relatively higher-grade products can be purchased. Summary of the invention

[0006] In order to solve the problems of the prior art, the present invention provides a method for improving the re-annealing performance of non-oriented silicon steel. Under the conditions of conventional non-oriented silicon steel grades and production tooling, under certain steel cleanliness control conditions, the present invention adds elements that improve beneficial inclusions and precipitates, and seeks to perform "energy storage" of the matrix without adding a flattening process in the production of finished products, thereby replacing traditional semi-process products, improving the electromagnetic performance of the user's re-annealing core, forming a close cooperative relationship with users with personalized products, and promoting the healthy development of low-carbon manufacturing of upstream and downstream enterprises in the industrial chain.

[0007] A method for improving the reannealing performance of non-oriented silicon steel. The chemical composition of the non-oriented silicon steel is calculated by mass percentage as follows: Si: 0.4-3.0%, Als: 0.15-0.8%, C≤0.0025%, S≤0.0025%, N≤0.0025%, Ti≤0.0020%, Nb≤0.0020%, V≤0.0020%, Mn: 0.2-0.5%, P: 0.001-0.06%, Sn and / or Sb: 0.02-0.15%, rare earth RE (La and / or Ce): 0.015-0.120%, B: 0.0006-0.0050% (i.e., the sum ratio of boron to oxygen and nitrogen is controlled to be 0.5-1.2, i.e., B / O+N is 0.5-1.2), and the rest is Fe and uncontrollable residual elements.

[0008] The process route is the same as that of conventional non-oriented silicon steel products: the ingot is smelted according to the chemical composition of the above non-oriented silicon steel, and the ingot is subjected to hot rolling, pickling, annealing in a multi-functional continuous furnace, and re-coiling to obtain the non-oriented silicon steel.

[0009] The chemical composition of the steel of the present invention includes the main alloy elements and the elements added to improve the process performance, which are the same as the original non-oriented silicon steel series grades. The steel cleanliness control requirements are: C, S, N are all ≤0.0025%; Ti, Nb, V are all ≤0.0020%, ensuring that the addition of trace elements obtains beneficial effects and reduces the usage. Add and control trace elements Sn and / or Sb: utilize their grain boundary segregation characteristics to reduce the pinning of tiny precipitates on the grain boundary, and they can be added in combination or separately, and control Sn and / or Sb: 0.02-0.15%. Add rare earth RE: purify steel, coarsen inclusions and precipitates, La series or Ce series or La-Ce series can be used, mainly to control the addition amount of molten steel, and control RE: 0.015-0.120%. Add B: 0.0006-0.0050% (i.e. control the sum ratio of boron to oxygen and nitrogen to 0.5-1.2, i.e. B / O+N to 0.5-1.2), and use the affinity of boron to oxygen and nitrogen to form coarsening inclusions and precipitate aggregation core points, and lay the foundation for increasing the cooling rate for subsequent heat treatment of the finished product.

[0010] In the circulating jet cooling section (RJC nitrogen spray cooling section, RJC section) of continuous annealing, the running speed of the strip is 100-150m / min, the inlet temperature is 800-890℃, the cooling speed is 60~150℃ / s, and the outlet temperature is 60-110℃. The finished product heat treatment is the same as the multifunctional continuous annealing unit widely equipped today. The process section temperature, speed, protective atmosphere and other process requirements required for original structure recovery, crystallization and grain growth are the same as the original products of the same brand. The present invention mainly controls the heat treatment cooling speed, the temperature mark of the last section of the steel strip soaking section SF is mainly used, and enters the RJC nitrogen spray cooling section, controls the cooling speed of the middle part of the RJC to 60~150℃ / s, and increases the internal stress of the matrix under the condition that the operating tension of the unit is guaranteed and the steel strip does not undergo serious deformation.

[0011] Furthermore, the unit tension of the rewound steel strip is 0.15~0.5Rp 0.2 , Rp 0.2 It is the yield strength of the strip after continuous annealing; by controlling the operating tension of the rewinding unit during production, the stress in the matrix is ​​increased under the condition of product plate shape.

[0012] Furthermore, when the Si content is ≥1.7%, the pickling is normalized pickling.

[0013] Furthermore, the process of smelting the ingot includes molten iron desulfurization, converter smelting, RH refining, and continuous casting.

[0014] Furthermore, the thickness of the strip steel is 0.35 to 0.50 mm.

[0015] Furthermore, the re-annealing conditions of the non-oriented silicon steel are: temperature 730°C to 850°C, time 1 to 2.5 hours, atmosphere H 2 and N 2 The mixed atmosphere contains H 2 The volume fraction is 0 to 30%, for example, 100% N 2 , or 30% H 2 +70%N 2 Atmosphere. Motor and refrigeration compressor manufacturing enterprises have the heat treatment conditions for re-annealing of silicon steel core or chip.

[0016] The present invention, under the conditions of conventional non-oriented silicon steel grades and production tooling, adds appropriate amounts of trace elements such as rare earth in the original grade design to purify the steel and coarsen inclusions; adds grain boundary segregation elements to hinder the aggregation of precipitates at grain boundaries and pinning of grain boundaries, and hinders the growth of re-annealing grains; and controls the cooling conditions during the annealing of the finished product, increases the operating tension in the finished product trimming and rolling process, promotes the increase of internal stress in the matrix, combines the stress caused in the user's iron core chip processing process and the comprehensive effect of partial lattice distortion energy, and replaces the flattening energy storage of semi-process products; superimposes steel purification and inclusion modification, so as to achieve the condition without adding processes, and further promotes grain growth and improves electromagnetic performance in the heat treatment processing and manufacturing of the full-process product of the motor user without adding processes, so as to achieve the purpose of preparing high-efficiency motors with relatively low-cost raw materials (without flattening process flow).

[0017] Beneficial effects of the present invention:

[0018] (1) The present invention can be produced normally on the existing production line, and there is no need to add equipment (such as a leveling unit, etc.) for the production of semi-process products.

[0019] (2) The products produced by the present invention are controlled by technical parameters. According to different user needs, the present invention can deliver full-process products of the same brand, personalized semi-process coated products, and uncoated semi-process products (after continuous annealing and cooling, the coating unit is passed through without subsequent coating process), which is convenient for production organization.

[0020] (3) After the implementation of the front-end technology of the present invention, due to the modification of inclusions and precipitates and the weakening of their ability to pin grain boundaries, the iron loss of the full-process product is reduced by 0.2-0.5 W / Kg, and the magnetic induction is increased by 0.01-0.04 T compared with the original brand product, thereby improving the market competitiveness; the product is delivered as a semi-process product or a special semi-process special product (the parameters of the present invention are optimized according to the use requirements), and after annealing by the user, the iron loss is reduced by 0.3-1.5 W / Kg, and the magnetic induction is increased by 0.01-0.03 T compared with the original product.

[0021] (4) The present invention has fully considered the safe operation of the entire production process and can ensure production safety under the same original steel grade and process conditions. DETAILED DESCRIPTION

[0022] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0023] Example 1. Comparison between the original low-grade typical product 50W1000 and the technical implementation test product

[0024] Original typical product: Chemical composition of steel grade, calculated by mass percentage: C: 0.0027%, Si: 0.45%, Als: 0.18%, Mn: 0.35%, P: 0.055%, S: 0.0035%, N: 0.0025%, Ti: 0.0025%, V: 0.0021%, Nb: 0.0014%, the rest is Fe and uncontrollable residual elements. After continuous casting, billet heating, hot rolling, pickling and cold rolling, the steel grade has a continuous annealing process speed of 150m / min, RJC section inlet temperature of 800℃, RJC section outlet temperature of 80℃, and RJC nitrogen injection cooling speed is controlled at 52℃ / s. The finished product electromagnetic properties are P 15 5.6W / Kg, magnetic induction B 5000 1.73T, Rp 0.2 205Mpa; normal unit tension for rewinding is 15MPa, user re-annealing temperature is 750℃, 100%N 2 Atmosphere protection, heat preservation for 2h, electromagnetic properties of annealed steel sheet P 15 5.32W / Kg, magnetic induction B 5000 It is 1.716T.

[0025] Technical implementation product: The chemical composition of the steel grade is calculated by mass percentage as follows: Si: 0.45%, Als: 0.18%, Mn: 0.35%, P: 0.055%, C: 0.0024%, S: 0.0021%, N: 0.0018%, Ti: 0.0018%, V: 0.0015%, Nb: 0.0015%, Sn: 0.025%, Ce: 0.038%, B: 0.003%, and the rest are Fe and uncontrollable residual elements. After continuous casting, billet heating, hot rolling and cold rolling, the steel grade has a continuous annealing process speed of 150m / min, an RJC section inlet temperature of 800℃, an RJC section outlet temperature of 80℃, and a nitrogen injection cooling rate of 71℃ / s in the middle of the RJC. The electromagnetic properties of the finished product are P 15 5.45W / Kg, magnetic induction B 5000 1.736T, Rp 0.2 210MPa; rewinding control unit tension 30MPa, user reannealing temperature 750℃, 100%N 2 Atmosphere protection, heat preservation for 2h, electromagnetic properties of annealed steel sheet P 15 4.83W / Kg, magnetic induction B 5000 It is 1.741T.

[0026] Example 2. Comparison between the original low-grade typical product 50W800 and the technical implementation test product

[0027] Original typical product: Chemical composition of steel, calculated by mass percentage: C: 0.0031%, Si: 0.85%, Als: 0.28%, Mn: 0.31%, P: 0.015%, S: 0.0038%, N: 0.0023%, Ti: 0.0026%, V: 0.0021%, Nb: 0.0018%, others are Fe and uncontrollable residual elements. After continuous casting, billet heating, hot rolling, pickling and cold rolling, the steel is annealed at a speed of 135m / min, the inlet temperature of the RJC section is 830℃, the outlet temperature of the RJC section is 95℃, the nitrogen injection cooling speed in the middle of the RJC is controlled at 50℃ / s, and the electromagnetic properties of the finished product are P 15 5.1W / Kg, magnetic induction B 5000 1.725T, Rp 0.2 235MPa; normal unit tension for rewinding is 18MPa, user re-annealing temperature is 750℃, 100%N 2 Atmosphere protection, heat preservation for 2h, electromagnetic properties of annealed steel sheet P 15 4.82W / Kg, magnetic induction B 5000 It is 1.728T.

[0028] Technical implementation product: Steel chemical composition, calculated by mass percentage: Steel chemical composition: Si: 0.83%, Als: 0.31%, Mn: 0.27%, P: 0.017%, C: 0.0021%, S: 0.0022%, N: 0.0018%, Ti: 0.0017%, V: 0.0016%, Nb: 0.0013%, Sn: 0.048%, Ce: 0.058%, B: 0.0041%, the rest are Fe and uncontrollable residual elements. After continuous casting, billet heating, hot rolling, pickling and cold rolling, the steel is subjected to continuous annealing process speed of 135m / min, RJC section inlet temperature of 830℃, RJC section outlet temperature of 95℃, and the RJC nitrogen middle blowing cooling speed is controlled at 75℃ / s. The finished product electromagnetic properties P 15 4.87W / Kg, magnetic induction B 5000 1.733T, Rp 0.2 240MPa; rewinding control unit tension 94MPa, user reannealing temperature 750℃, 100%N 2 Atmosphere protection, heat preservation for 2h, electromagnetic properties of annealed steel sheet P 15 3.88W / Kg, magnetic induction B 5000 It is 1.738T.

[0029] Example 3. Comparison between typical medium grade product 50W600 and technical implementation test product

[0030] Original typical product: Chemical composition of steel, calculated by mass percentage: C: 0.0032%, Si: 1.35%, Als: 0.36%, Mn: 0.26%, P: 0.009%, S: 0.0036%, N: 0.0022%, Ti: 0.0024%, V: 0.0023%, Nb: 0.0021%, others are uncontrollable residual elements. After continuous casting, billet heating, hot rolling, pickling and cold rolling, the steel is annealed at a speed of 130m / min, the inlet temperature of the RJC section is 850℃, the outlet temperature of the RJC section is 70℃, the nitrogen injection cooling speed in the middle of the RJC is controlled at 51℃ / s, and the electromagnetic properties of the finished product are P 15 4.31W / Kg, magnetic induction B 5000 1.695T, Rp 0.2 275MPa; normal unit tension for rewinding is 18MPa, user re-annealing temperature is 750℃, 100%N 2 Atmosphere protection, heat preservation for 2h, electromagnetic properties of annealed steel sheet P 15 4.12W / Kg, magnetic induction B 5000 It is 1.697T.

[0031] Technical implementation product: The chemical composition of the steel grade is calculated by mass percentage as follows: C: 0.0025%, Si: 1.33%, Als: 0.34%, Mn: 0.29%, P: 0.007%, S: 0.0021%, N: 0.0016%, Ti: 0.0017%, V: 0.0016%, Nb: 0.0019%, Sn: 0.05%, Ce: 0.033%, B: 0.0039%, and the rest are Fe and uncontrollable residual elements. After continuous casting, billet heating, hot rolling and cold rolling, the steel grade has a continuous annealing process speed of 130m / min, an RJC section inlet temperature of 850℃, an RJC section outlet temperature of 70℃, and a nitrogen injection cooling rate of 81℃ / s in the middle of the RJC section. The finished product has an electromagnetic property of P 15 3.95W / Kg, magnetic induction B 5000 1.705T, Rp 0.2 280MPa; normal unit tension for rewinding is 82MPa, user re-annealing temperature is 760℃, 100%N 2 Atmosphere protection, heat preservation for 2h, electromagnetic properties of annealed steel sheet P 15 3.42W / Kg, magnetic induction B 5000 It is 1.699T.

[0032] Example 4. Comparison of high-grade typical product 50W350 and technical implementation test product

[0033] Original typical product: Chemical composition of steel, calculated by mass percentage: C: 0.0028%, Si: 2.65%, Als: 0.51%, Mn: 0.21%, P: 0.007%, S: 0.0031%, N: 0.0022%, Ti: 0.0031%, V: 0.0024%, Nb: 0.0021%, the rest are Fe and uncontrollable residual elements. After continuous casting, billet heating, hot rolling, normalizing pickling and cold rolling, the steel is annealed at a speed of 100m / min, the inlet temperature of RJC section is 890℃, the outlet temperature of RJC section is 100℃, the nitrogen injection cooling speed in the middle of RJC is controlled at 42℃ / s, and the electromagnetic properties of the finished product are P 15 3.01W / Kg, magnetic induction B 5000 1.675T, Rp 0.2 335MPa; the normal unit tension of rewinding is 15MPa, the user's re-annealing temperature is 770℃, 30%H 2 +70%N 2 Atmosphere protection, heat preservation for 2h, electromagnetic properties of annealed steel sheet P 15 2.89W / Kg, magnetic induction B 5000 It is 1.677T.

[0034] Technical implementation product: The chemical composition of the steel grade is calculated by mass percentage as follows: C: 0.0021%, Si: 2.69%, Als: 0.48%, Mn: 0.23%, P: 0.005%, S: 0.0020%, N: 0.0015%, Ti: 0.0016%, V: 0.0018%, Nb: 0.0013%, Sn: 0.065%, Ce: 0.068%, B: 0.0035%, and the rest are Fe and uncontrollable residual elements. After continuous casting, billet heating, hot rolling, normalizing pickling and cold rolling, the steel grade has a continuous annealing process speed of 100m / min, an RJC section inlet temperature of 890℃, an RJC section outlet temperature of 100℃, and a nitrogen injection cooling speed of 85℃ / s in the middle of the RJC section. The electromagnetic properties of the finished product are P 15 3.95W / Kg, magnetic induction B 5000 1.701T, Rp 0.2 345MPa, rewinding control unit tension 85MPa; user re-annealing temperature 770℃, 30%H 2 +70%N 2 Atmosphere protection, heat preservation for 2h, electromagnetic properties of annealed steel sheet P 15 2.42W / Kg, magnetic induction B 5000 It is 1.689T.

Claims

1. A method for improving the reannealing performance of non-oriented silicon steel, characterized in that: The chemical composition of the non-oriented silicon steel is calculated by mass percentage as follows: Si: 0.4-3.0%, Als: 0.15-0.8%, C≤0.0025%, S≤0.0025%, N≤0.0025%, Ti≤0.0020%, Nb≤0.0020%, V≤0.0020%, Mn: 0.2-0.5%, P: 0.001-0.06%, Sn and / or Sb: 0.02-0.15%, La and / or Ce: 0.015-0.120%, B: 0.0006-0.0050%, and the rest are Fe and uncontrollable residual elements; The method comprises: smelting a casting billet according to the chemical composition of the non-oriented silicon steel, and subjecting the casting billet to hot rolling, pickling, cold rolling, continuous annealing, and re-coiling to obtain the non-oriented silicon steel; In the circulating jet cooling section of continuous annealing, the strip running speed is 100-150m / min, the inlet temperature is 800-890℃, the cooling rate is 60~150℃ / s, and the outlet temperature is 60~110℃.

2. The method according to claim 1, characterized in that The unit tension of rewinding is 0.15~0.5Rp 0.2 , Rp 0.2 It is the yield strength of the strip after continuous annealing.

3. The method according to claim 1, characterized in that When the Si content is ≥1.7%, the pickling is normalized pickling.

4. The method according to claim 1, characterized in that: The process of smelting ingots includes molten iron desulfurization, converter smelting, RH refining and continuous casting.

5. The method according to claim 1, characterized in that The thickness of the strip steel is 0.35 to 0.50 mm.

6. The method according to claim 1, characterized in that The re-annealing conditions of non-oriented silicon steel are: temperature 730°C to 850°C, time 1 to 2.5 hours, atmosphere is a mixed atmosphere of H2 and N2, and the volume fraction of H2 in the mixed atmosphere is 0 to 30%.