A method for producing low-temperature high-magnetic-induction oriented silicon steel based on grain homogenization control

Abstract

The present application provides a method for producing low-temperature and high-magnetic induction oriented silicon steel based on grain homogenization control, and the process steps include steelmaking, continuous casting, billet heating, hot rolling, normalization, primary cold rolling, decarburization and nitriding, high-temperature annealing and stretching and flattening of oriented silicon steel. The present invention determines the heating temperature according to the chemical composition, determines the normalization temperature by the heating temperature and the actual chemical composition, determines the decarburization annealing temperature by the normalization temperature, and determines the hot rolling and cold rolling processes according to the grain homogenization principle. In the production of high-magnetic induction oriented silicon steel, the processes between each process affect each other. The advantage of the present invention is that the process of the latter process is formulated according to the process of the former process, and through multiple grain recrystallization controls of processes such as hot rolling, normalization, and annealing, the primary recrystallized grains of the decarburization annealing tend to be homogenized, and finally good magnetic properties are obtained.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a method for producing low-temperature high-magnetic-induction oriented silicon steel based on grain homogenization control. Background Art

[0002] The production process of low-temperature high-magnetic induction oriented silicon steel mainly includes smelting, hot rolling, normalizing, cold rolling, decarburization, nitriding, high-temperature annealing and stretching and flattening. The processes of each process are interrelated and affect each other. The recrystallization that occurs during decarburization annealing is called primary recrystallization, and the abnormal growth of GOSS grains during high-temperature annealing is called secondary recrystallization. In the production of high-magnetic induction oriented silicon steel, the grain size and uniformity of the primary recrystallization have an important influence on the secondary recrystallization. Uniform and appropriate primary recrystallization grains are conducive to obtaining more precisely oriented grains in secondary recrystallization, thereby obtaining higher magnetic induction intensity. This has been clearly explained in many literatures. However, steelmaking, continuous casting, hot rolling, normalizing, cold rolling and decarburization annealing processes will affect the homogenization of the primary recrystallization grains. Therefore, in order to control the homogenization of the primary recrystallization grains and improve the magnetic properties of the product, it is necessary to design the processes of the above processes in a linked manner.

[0003] The Chinese patent document with patent application number 201110295909.0 discloses "a method for producing oriented silicon steel with excellent magnetic properties", and describes a method of controlling the value and proportion of the primary recrystallization grain size of the surface layer and the center layer of the primary recrystallization plate within a suitable range by adjusting the friction force (shear stress) on the surface of the steel plate during cold rolling, so as to achieve the purpose of affecting the distribution of the primary recrystallization along the plate thickness direction, realize the uniformity of the primary recrystallization grain size along the thickness direction, and finally realize the optimization of the magnetic properties of the finished product. However, the method of improving the uniformity of grains by adjusting the friction force through rolling oil has high requirements on the cold rolling equipment and requires precise detection equipment; on the other hand, its improvement ability has certain limitations.

[0004] The Chinese patent document with patent application number 201910348330.2 discloses "a method for producing thin-gauge low-temperature high-magnetic induction oriented silicon steel strip", which describes a method for improving the poor performance stability of low-temperature thin-gauge high-magnetic induction oriented silicon steel, improving the magnetic properties of thin-gauge high-magnetic induction oriented silicon steel, and improving the uniformity of performance in the width direction of the plate. It takes into account the effects of Al, N, Si and hot rolling final rolling temperature in the decarburization annealing process, and has achieved certain results. However, this method ignores the effects of elements such as Mn, S, Cu, which form another important inhibitor, and the normalization process on the decarburization annealing temperature. There are great limitations in both the control of inhibitors and the homogenization control of primary recrystallization grains. At the same time, the difference in its nitriding temperature is not conducive to mass production, and it is also not conducive to the stability of the atmosphere in the furnace. For this reason, we propose a method for producing low-temperature high-magnetic induction oriented silicon steel based on grain homogenization control to solve the above problems. Summary of the invention

[0005] The main purpose of the present invention is to provide a low-temperature high magnetic induction oriented silicon steel production method based on grain homogenization control. The method is a production method that promotes the homogenization of primary recrystallization grains and improves the magnetic properties of the final product through the linkage design of steelmaking, continuous casting, hot rolling, normalizing, cold rolling and decarburization annealing processes.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for producing low-temperature high-magnetic induction oriented silicon steel based on grain homogenization control comprises: homogenizing the primary recrystallized grains through the linkage design of process parameters of each process, and the steps are as follows:

[0008] Step 1: The control range of chemical composition mass percentage is: C: 0.05-0.07%; Si: 2.9-3.5%; Mn: 0.05-0.15%; P: ≤0.030%; S: 0.005-0.010%; Als: 0.02-0.035%; N: 0.0060-0.010%; Sn: 0.05-0.10%; Cr: ≤0.30%; Cu: ≤0.60%; the rest are Fe and unavoidable impurity elements;

[0009] Step 2: The continuous casting adopts a high-speed strong cooling process and electromagnetic stirring, thereby reducing the proportion of coarse columnar crystals, controlling the proportion of equiaxed crystals at 30-50%, and the thickness of the ingot is 200-250 mm;

[0010] Step 3: The slab obtained after continuous casting enters a heating furnace at a temperature above 500°C for a heating time of 200 to 300 minutes;

[0011] Step 4: After the slab is heated, it is rolled into a 2.1-2.5 mm steel strip through a continuous rolling mill, wherein a large reduction rate is used in the rough rolling pass to promote grain recrystallization, the deformation rate of the rough rolling pass is controlled at 40-50%, and the reduction rate of the finishing rolling pass is reduced from 50% to 20%, and the final rolling temperature is 900-1000°C;

[0012] Step 5: The hot-rolled steel strip undergoes two-stage normalization, where the first stage normalization temperature is determined according to the chemical composition of the steel strip, the second stage normalization temperature is 900°C, and the total furnace time is 4.5 minutes. After leaving the furnace, water cooling is used, and the cooling rate is 40°C / s;

[0013] Step 6: After normalization, the steel strip is rolled through a twenty-roll cold rolling mill, and cold rolled to a finished product thickness of 0.27 mm in one pass, wherein the total reduction rate is 87-90%, and the pass reduction rate is controlled from large to small, and the aging rolling temperature is controlled at 150-250°C;

[0014] Step 7: After cold rolling, the steel strip is decarburized and nitrided in the annealing process, and is coiled into a steel coil after being coated with magnesium oxide. The heating rate of the steel strip entering the furnace is controlled at 20-50°C / s, the decarburization annealing temperature is determined according to the normalizing temperature, and the nitriding is carried out in two stages. The first stage nitriding temperature is 850°C, and the second stage nitriding temperature is 800°C. The total time in the furnace is 3 minutes.

[0015] Step 8: heating to 700°C at full speed in N2 atmosphere, then keeping warm for 20 hours in nitrogen-hydrogen mixed gas atmosphere with a hydrogen volume fraction of 40%, then heating to 1200°C at a heating rate of 18°C / h in an atmosphere of ammonia decomposition gas, then keeping warm for 25h in pure H2 atmosphere, and finally cooling down in N2 atmosphere;

[0016] Step nine: After applying the insulating layer, stretching and flattening annealing are performed, and the elongation is 0.03-0.15%.

[0017] Preferably, in step 3, the heating temperature follows the following relationship:

[0018] T R =1100+(7.1[Mn][S]+0.51[Cu][S])×106, (T R : Heating temperature);

[0019] Preferably, in step 5: the first normalization heating temperature follows the following relationship: T C =T R -34.05ln(([Als]-1.93[N])×104)-56Tz[Mn][S], (T C : The first stage normalizing temperature).

[0020] Preferably, in step seven, the annealing temperature follows the following relationship: T A =930000 / T C , (T A : decarburization annealing temperature).

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] In the production of high magnetic induction oriented silicon steel, the processes of various steps influence each other. The advantage of the present invention is that the process of the latter step is formulated according to the process of the former step, and through multiple grain recrystallization controls in the processes of hot rolling, normalizing, annealing, etc., the primary recrystallized grains of decarburization annealing are made uniform, and finally good magnetic properties are obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A primary recrystallization grain diagram of a method for producing low-temperature high magnetic induction oriented silicon steel based on grain homogenization control according to the present invention;

[0024] Figure 2 This is a primary recrystallization grain diagram of a comparative example of a low-temperature high magnetic induction oriented silicon steel production method based on grain homogenization control of the present invention. DETAILED DESCRIPTION

[0025] In the following, the heating temperature is determined according to the chemical composition in combination with the attached drawings, the normalizing temperature is determined by the heating temperature and the actual chemical composition, the decarburization annealing temperature is determined by the normalizing temperature, and the hot rolling and cold rolling processes are determined according to the principle of grain homogenization. Through the process linkage design of the previous and next steps, the primary recrystallized grains are further homogenized, thereby improving the orientation degree of the secondary recrystallization and achieving the purpose of improving the magnetic properties of the finished product.

[0026] Example 1

[0027] A method for producing low-temperature high-magnetic induction oriented silicon steel based on grain homogenization control, wherein the production process includes steelmaking, continuous casting, hot rolling, normalizing, cold rolling, decarburization, nitriding, high-temperature annealing and stretching and leveling, and the steps are as follows:

[0028] Step 1: The control range of chemical composition mass percentage during smelting is: C: 0.05-0.07%; Si: 2.9-3.5%; Mn: 0.05-0.15%; P: ≤0.030%; S: 0.005-0.010%; Als: 0.02-0.035%; N: 0.0060-0.010%; Sn: 0.05-0.10%; Cr: ≤0.30%; Cu: ≤0.60%; the rest are Fe and unavoidable impurity elements;

[0029] Step 2: The continuous casting billet drawing speed is 0.95m / min, the billet thickness is 230mm, and the chemical composition of the billet is C: 0.061%; Si: 3.27%; Mn: 0.08%; P: 0.011%; S: 0.008%; Als: 0.024%; N: 0.0073%; Sn: 0.066%; Cu: 0.21% and the rest is Fe and unavoidable impurity elements;

[0030] Step 3: The slab obtained after continuous casting enters the heating furnace at 570℃ for 223min. The heating temperature is calculated as follows: T R =1100+(7.1[Mn][S]+0.51[Cu][S])×106=1154℃;

[0031] Step 4: After the slab is heated, it is rolled into a 2.3 mm steel strip through a continuous rolling mill. The rough rolling pass uses a large reduction rate to promote grain recrystallization. The rough rolling pass deformation rate is controlled at 40-50%, and the finishing pass reduction rate decreases from 50% to 20%. The final rolling temperature T Z =946℃, coiling temperature is 550℃;

[0032] Step 5: The hot-rolled steel strip is subjected to two-stage normalization, wherein the first stage normalization temperature is calculated according to the formula T C =T R -34.05ln(([Als]-1.93[N])×104)-56Tz[Mn][S]=1121℃, the second stage normalizing temperature is 900℃, the total furnace time is 4.5min, and water cooling is adopted after the furnace is taken out, and the cooling rate is 40℃ / s;

[0033] Step 6: After normalization, the steel strip is rolled through a twenty-roll cold rolling mill, and cold rolled to a finished product thickness of 0.27 mm, wherein the total reduction rate is controlled at 88.3%, and 5 rolling passes are adopted, and the reduction rates of the passes are 40%, 39.1%, 36.8%, 33.9%, and 23.1% respectively. The second and third passes are aging rolled, and the aging temperature of the second pass is 171°C, and the aging temperature of the third pass is 218°C;

[0034] Step 7: After cold rolling, the steel strip is decarburized and nitrided in the annealing process, and then coated with magnesium oxide and coiled into a steel coil. The heating rate of the steel strip entering the furnace is controlled at 27°C / s, and the decarburization annealing temperature is determined according to the normalizing temperature. A =930000 / T C =830℃, nitriding adopts two-stage nitriding, the first stage nitriding temperature is 850℃, the second stage nitriding temperature is 800℃, after nitriding [N] = 205ppm, the total time in the furnace is 3min;

[0035] Step 8: heating to 700°C at full speed in N2 atmosphere, then keeping warm for 20 hours in nitrogen-hydrogen mixed gas atmosphere with a hydrogen volume fraction of 40%, then heating to 1200°C at a heating rate of 18°C / h in ammonia decomposition gas atmosphere, then keeping warm for 25h in pure hydrogen atmosphere, and finally cooling down in nitrogen atmosphere;

[0036] Step 9: After applying the insulating layer, stretching and flattening annealing are performed with an elongation of 0.07%.

[0037] Take samples for square circle test, P 1.7 = 1.08W / kg or less: 63.3%; B 800 =The proportion above 1.90T is 69.5%.

[0038] Example 2

[0039] The present embodiment provides a method for producing low-temperature high magnetic induction oriented silicon steel based on grain homogenization control, and the production steps are as follows:

[0040] Step 1: The control range of chemical composition mass percentage during smelting is: C: 0.05-0.07%; Si: 2.9-3.5%; Mn: 0.05-0.15%; P: ≤0.030%; S: 0.005-0.010%; Als: 0.02-0.035%; N: 0.0060-0.010%; Sn: 0.05-0.10%; Cr: ≤0.30%; Cu: ≤0.60%; the rest are Fe and unavoidable impurity elements;

[0041] Step 2: The continuous casting billet drawing speed is 0.95m / min, the billet thickness is 230mm, and the chemical composition of the billet is C: 0.051%; Si: 3.25%; Mn: 0.10%; P: 0.013%; S: 0.006%; Als: 0.027%; N: 0.0068%; Sn: 0.069%; Cu: 0.02% and the rest is Fe and unavoidable impurity elements;

[0042] Step 3: The slab obtained after continuous casting enters the heating furnace at 570℃ for 235min. The heating temperature is calculated as follows: T R =1100+(7.1[Mn][S]+0.51[Cu][S])×106=1143℃;

[0043] Step 4: After the slab is heated, it is rolled into a 2.18 mm steel strip through a continuous rolling mill. The rough rolling pass uses a large reduction rate to promote grain recrystallization. The rough rolling pass deformation rate is controlled at 40-50%, and the finishing pass reduction rate decreases from 50% to 20%. The final rolling temperature T Z =941℃, coiling temperature is 550℃;

[0044] Step 5: The hot-rolled steel strip is subjected to two-stage normalization, wherein the first stage normalization temperature is calculated according to the formula T C =T R -34.05ln(([Als]-1.93[N])×104)-56Tz[Mn][S]=1102℃, the second stage normalizing temperature is 900℃, the total furnace time is 4.5min, and water cooling is adopted after the furnace is taken out, and the cooling rate is 45℃ / s;

[0045] Step 6: After normalization, the steel strip is rolled through a twenty-roll cold rolling mill, and cold rolled to a finished product thickness of 0.27 mm, wherein the total reduction rate is controlled at 87.6%, and 5 passes are used for rolling, and the pass reduction rates are 36.7%, 39.1%, 36.8%, 33.9%, and 23.1% respectively. The second and third passes are aging rolled, and the aging temperature of the second pass is 167°C, and the aging temperature of the third pass is 211°C;

[0046] Step 7: After cold rolling, the steel strip is decarburized and nitrided in the annealing process, and then coated with magnesium oxide and coiled into a steel coil. The heating rate of the steel strip entering the furnace is controlled at 27°C / s, and the decarburization annealing temperature is determined according to the normalizing temperature. A =930000 / T C =846℃, nitriding adopts two-stage nitriding, the first stage nitriding temperature is 850℃, the second stage nitriding temperature is 800℃, after nitriding [N] = 213ppm, the total time in the furnace is 3min;

[0047] Step 8: heating to 700°C at full speed in N2 atmosphere, then keeping warm for 20 hours in nitrogen-hydrogen mixed gas atmosphere with a hydrogen volume fraction of 40%, then heating to 1200°C at a heating rate of 18°C / h in an atmosphere of ammonia decomposition gas, then keeping warm for 25h in pure H2 atmosphere, and finally cooling down in N2 atmosphere;

[0048] Step 9: After applying the insulating layer, stretching and flattening annealing are performed with an elongation of 0.07%.

[0049] Take samples for square circle test, P 1.7 = 1.08W / kg or less: 73.3%; B 800 =The proportion above 1.90T is 87.8%.

[0050] Example 3

[0051] The present embodiment provides a method for producing low-temperature high magnetic induction oriented silicon steel based on grain homogenization control, and the production steps are as follows:

[0052] Step 1: The control range of chemical composition mass percentage during smelting is: C: 0.05-0.07%; Si: 2.9-3.5%; Mn: 0.05-0.15%; P: ≤0.030%; S: 0.005-0.010%; Als: 0.02-0.035%; N: 0.0060-0.010%; Sn: 0.05-0.10%; Cr: ≤0.30%; Cu: ≤0.60%; the rest are Fe and unavoidable impurity elements;

[0053] Step 2: The continuous casting billet drawing speed is 0.95m / min, the billet thickness is 230mm, and the chemical composition of the billet is C: 0.053%; Si: 3.25%; Mn: 0.13%; P: 0.016%; S: 0.007%; Als: 0.0308%; N: 0.0095%; Sn: 0.061%; Cu: 0.02% and the rest is Fe and unavoidable impurity elements;

[0054] Step 3: The slab obtained after continuous casting enters the heating furnace at 570℃ for 226min. The heating temperature is calculated as follows: T R =1100+(7.1[Mn][S]+0.51[Cu][S])×106=1165℃;

[0055] Step 4: After the slab is heated, it is rolled into a 2.46 mm steel strip through a continuous rolling mill. The rough rolling pass uses a large reduction rate to promote grain recrystallization. The rough rolling pass deformation rate is controlled at 40-50%, and the finishing pass reduction rate decreases from 50% to 20%. The final rolling temperature T Z =937℃, coiling temperature is 556℃;

[0056] Step 5: The hot-rolled steel strip is subjected to two-stage normalization, wherein the first stage normalization temperature is calculated according to the formula T C =T R -34.05ln(([Als]-1.93[N])×104)-56Tz[Mn][S]=1109℃, the second normalizing temperature is 900℃, and the total furnace time is 4.5min. After leaving the furnace, water cooling is adopted, and the cooling rate is 45℃ / s;

[0057] Step 6: After normalization, the steel strip is rolled through a twenty-roll cold rolling mill, and cold rolled to a finished product thickness of 0.27 mm in one pass, wherein the total reduction rate is controlled at 89.02%, and 5 passes are used for rolling, and the pass reduction rates are 40.2%, 39.5%, 37.1%, 35.7%, and 25% respectively. The second and third passes are aging rolled, and the aging temperature of the second pass is 180°C, and the aging temperature of the third pass is 212°C;

[0058] Step 7: After cold rolling, the steel strip is decarburized and nitrided in the annealing process, and then coated with magnesium oxide and coiled into a steel coil. The heating rate of the steel strip entering the furnace is controlled at 27°C / s, and the decarburization annealing temperature is determined according to the normalizing temperature. A =930000 / T C =838℃, nitriding adopts two-stage nitriding, the first stage nitriding temperature is 850℃, the second stage nitriding temperature is 800℃, after nitriding [N] = 190ppm, the total time in the furnace is 3min;

[0059] Step 8: heating to 700°C at full speed in N2 atmosphere, then keeping warm for 20 hours in nitrogen-hydrogen mixed gas atmosphere with a hydrogen volume fraction of 40%, then heating to 1200°C at a heating rate of 18°C / h in an atmosphere of ammonia decomposition gas, then keeping warm for 25h in pure H2 atmosphere, and finally cooling down in N2 atmosphere;

[0060] Step 9: After applying the insulating layer, stretching and flattening annealing are performed with an elongation of 0.07%.

[0061] Take samples for square circle test, P 1.7 = 1.08W / kg or less: 69.2%; B 800 =1.90T and above: 72.6%

[0062] Comparative Example

[0063] The process flow of the comparative example is: smelting → continuous casting → heating → hot rolling → normalizing → cold rolling → decarburization → nitriding → high temperature annealing → stretching and leveling. The processes of smelting, continuous casting, hot rolling, cold rolling, nitriding, high temperature annealing and leveling and leveling are the same as those in the embodiment, while the three processes of heating, normalizing and decarburization adopt conventional processes, that is, the heating temperature is 1160°C, the first normalizing temperature in the normalizing process is 1100°C, and the denitrification annealing temperature is 830°C.

[0064] Sampling was carried out for square circle test, and the proportion below P1.7=1.08W / kg was 45.6%; the proportion above B800=1.90T was 38.3%.

[0065] In summary: In the production of high magnetic induction oriented silicon steel, the processes of each process affect each other. The advantage of the present invention is that the process of the latter process is formulated according to the process of the former process, and the primary recrystallization grains of the decarburization annealing are uniformed through multiple grain recrystallization control of the processes such as hot rolling, normalizing, and annealing, so as to finally obtain good magnetic properties.

[0066] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for producing low-temperature high-magnetic induction oriented silicon steel based on grain homogenization control, It is characterized in that The primary recrystallization grains are homogenized through the linkage design of process parameters of each process. The steps are as follows: Step 1: The control range of chemical composition mass percentage is: C: 0.05-0.07%; Si: 2.9-3.5%; Mn: 0.05-0.15%; P: ≤0.030%; S：0 .005～0 .010％； Als: 0.02~0.035%; N：0 .0060～0 .010％； Sn: 0.05~0.10%; Cr: ≤0.30%; Cu: ≤0.60%; the rest are Fe and unavoidable impurity elements; Step 2: The continuous casting adopts a high-speed strong cooling process and electromagnetic stirring, thereby reducing the proportion of coarse columnar crystals, controlling the proportion of equiaxed crystals at 30-50%, and the thickness of the ingot is 200-250 mm; Step 3: The slab obtained after continuous casting enters the heating furnace at above 500℃ for 200-300min, and the heating temperature follows the following relationship: T R =1100+(7.1[Mn][S]+0.51[Cu][S])×106, where T R is the slab heating temperature, [Mn], [S], [Cu] are the mass percentages of the corresponding alloys; Step 4: After the slab is heated, it is rolled into a 2.1-2.5 mm steel strip through a continuous rolling mill. A large reduction rate is used in the rough rolling pass to promote grain recrystallization. The deformation rate of the rough rolling pass is controlled at 40-50%. The reduction rate of the finishing rolling pass decreases from 50% to 20%, and the final rolling temperature is 900-1000°C. Step 5: The hot-rolled steel strip undergoes two-stage normalization, where the first stage normalization temperature is determined according to the chemical composition of the steel strip, following the following relationship: T C =T R -34.05ln(([Als]-1.93[N])×104)-56Tz[Mn][S], where Tc is the first normalizing temperature, T R is the slab heating temperature, T Z is the final rolling temperature during hot rolling, [Als], [N], [Mn], [S] are the mass percentages of the corresponding alloys; the second stage normalizing temperature is 900℃, the total furnace time is 4.5min, and water cooling is used after leaving the furnace, with a cooling rate of 40℃ / s; Step 6: After normalization, the steel strip is rolled through a twenty-roll cold rolling mill, and cold rolled to a finished product thickness of 0.27 mm in one pass, wherein the total reduction rate is 87-90%, and the pass reduction rate is controlled from large to small, and the aging rolling temperature is controlled at 150-250°C; Step 7: After cold rolling, the steel strip is decarburized and nitrided in the annealing process, and then coated with magnesium oxide and coiled into a steel coil. The heating rate of the steel strip entering the furnace is controlled at 20-50℃ / s. The decarburization annealing temperature is determined according to the normalizing temperature. The annealing temperature follows the following relationship: T A =930000 / T C , where T A is the decarburization annealing temperature, T C The normalizing temperature is 850℃, the second nitriding temperature is 800℃, and the total furnace time is 3min. Step 8: heating to 700°C at full speed in N2 atmosphere, then keeping warm for 20 hours in nitrogen-hydrogen mixed gas atmosphere with a hydrogen volume fraction of 40%, then heating to 1200°C at a heating rate of 18°C / h in an atmosphere of ammonia decomposition gas, then keeping warm for 25h in pure H2 atmosphere, and finally cooling down in N2 atmosphere; Step nine: After applying the insulating layer, stretching and flattening annealing is performed, and the elongation is 0.03 to 0.15%.

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