CN105714039B - The annealing process and its control method of the low-temperature oriented silicon steel containing niobium - Google Patents

Abstract

The present invention provides an annealing process and control method for niobium-containing low-temperature oriented silicon steel. The process parameters of the decarburization annealing process are controlled as follows: put the cold-rolled sheet into an annealing furnace, and control the atmosphere in the furnace to 85% H ₂ + 15% N ₂ , the dew point is controlled at 30-65°C, the temperature of the water bath is 60-70°C; then the heating rate is greater than 50°C/s to 900-1180°C, the holding time is 7-30min, and the atmosphere in the furnace is adjusted to After 100% N ₂ , the samples were taken out and cooled to room temperature in air. Aiming at the chemical composition and inhibitor composition of niobium-containing low-temperature oriented silicon steel, the present invention provides the heating system, holding time and cooling system for high-temperature annealing of niobium-containing low-temperature oriented silicon steel, that is, provides the high-temperature annealing process system and its Control Method.

Description

Annealing process and control method of low temperature grain oriented silicon steel containing niobium

technical field

The invention belongs to the technical field of metal material preparation, and in particular relates to an annealing process of low-temperature oriented silicon steel containing niobium and a control method thereof.

Background technique

Silicon steel sheet, also known as electromagnetic steel sheet or electrical steel sheet, is known as "artwork in steel" and is an indispensable and important soft magnetic alloy in electric power, electronics and military industry. According to different scopes of use, silicon steel can be divided into two categories: oriented silicon steel suitable for oriented magnetic fields of transformers and non-oriented silicon steel suitable for rotating magnetic fields of motors. The strong Goss texture (namely {110}<001> texture) results in extremely excellent magnetic properties in the rolling direction of the steel plate. It can be seen that oriented silicon steel is the core material for making iron cores of various transformers, ballasts, amplifiers, voltage stabilizers, relays, rectifiers, electromagnetic switches and other oriented magnetic field electrical products. Oriented silicon steel mainly reduces the eddy current loss by means of its specific composition, and utilizes the excellent magnetization performance of Goss oriented grains in the rolling direction to reduce the magnetic loss and greatly increase the magnetic induction level.

At present, the production of grain-oriented silicon steel is mainly based on the traditional process, and the inhibitors used mainly include MnS and AlN. Due to the high solid solution temperature of MnS and AlN, the heating temperature of the slab is usually above 1350°C, resulting in coarse grains, segregation of silicon at the grain boundaries, serious edge cracks, low yield, high energy consumption, and high manufacturing costs. Compared with the silicon steel with AlN or MnS as the inhibitor, the silicon steel with niobium carbonitride as the main inhibitor has a higher degree of orientation Gaussian texture and better magnetic properties. Compared with traditional inhibitors (AlN or MnS), the solid solution temperature of niobium carbonitride Nb(C, N) is lower, and niobium carbonitride can reduce the solid solution temperature of AlN, thereby realizing the low temperature heating system of the slab , has the advantages of saving energy, increasing the yield and prolonging the life of the furnace. During hot rolling, the precipitated Nb(C,N) is fine and dispersed in the steel. The coarsening rate of Nb(C,N) after precipitation is very small, no aggregation or growth occurs, and the fine size can be maintained, and the ability to inhibit the growth of primary recrystallized grains is stronger. However, the microalloying element niobium is a strong carbide forming element, which will make the decarburization of silicon steel difficult during decarburization annealing. At the same time, there are few reports on the decarburization annealing process and high temperature annealing process of niobium-containing low-temperature oriented silicon steel. Therefore, there is an urgent need Developed the decarburization annealing and high temperature annealing process and control method of niobium-containing oriented silicon steel.

Contents of the invention

The present invention aims to solve the problem of difficult decarburization in the decarburization annealing process of niobium-containing low-temperature oriented silicon steel, and provides an annealing process and control method for niobium-containing low-temperature oriented silicon steel, which is suitable for the decarburization of niobium-containing low-temperature oriented silicon steel in actual production. The carbon annealing and high-temperature annealing process and its control method improve the magnetic properties of niobium-containing silicon steel.

The technical solution adopted by the present invention to solve the problems of the technologies described above is:

A niobium-containing low-temperature oriented silicon steel annealing process and its control method, the process parameters of the decarburization annealing process are controlled as follows: put the cold-rolled sheet into an annealing furnace, and the atmosphere in the furnace is controlled to 85% _H2 +15%N _2. The dew point is controlled at 30-65°C, and the temperature of the water bath is 60-70°C; then it is heated to 900-1180°C with a heating rate greater than 50°C/s, and the holding time is 7-30 minutes, and the atmosphere in the furnace is adjusted to 100%N After ₂ , take out the sample and air cool to room temperature.

The process parameters of the high-temperature annealing process in the present invention are controlled as follows: before high-temperature annealing, coat MgO on the surface of the steel plate, control the atmosphere in the furnace to 85%H ₂ +15%N ₂ , and first rapidly raise the temperature to 500°C in 1 hour; Heat up to 600-680°C at a rate of 65°C/h and keep warm for 3-4 hours; then heat up to 900°C at a rate of 55-65°C/h and keep warm for 3-4 hours; then heat up at a rate of 10-14°C/h to 1100°C; then adjust the atmosphere in the furnace to 100% H2, then raise the temperature to 1180-1240°C at a rate of 10°C/h, and keep it for 7-10 hours; then cool it to 550°C at a rate of 55°C/h, and finally put the After the atmosphere was adjusted to 100% _N2 , it was cooled to room temperature with the furnace.

The chemical composition of niobium-containing low-temperature grain-oriented silicon steel in the present invention is as follows according to weight percentage: C: 0.04-0.06%, Si: 2.8-3.40%, Mn: 0.04-0.05%, Nb: 0.04-0.10%, S: 0.013- 0.018%, N: 0.0085～0.014%, Als: 0.015～0.025%, Cu: 0.07～0.08%, Cr≤0.03%, P≤0.012%, the balance is Fe and unavoidable impurities.

The niobium-containing low-temperature grain-oriented silicon steel of the present invention, its main inhibitor is Nb (C, N), the auxiliary inhibitor is AlN, Cu ₂ S, (Cu, Mn) S and grain boundary segregation element Cr, and the precipitate size is 5 ~ 55nm, and dispersed in the matrix.

The production method of niobium-containing low-temperature oriented silicon steel of the present invention mainly includes smelting, continuous casting, hot rolling, normalization, cold rolling, decarburization annealing and high-temperature annealing processes, wherein: the slab thickness in the continuous casting process is 180 ~220mm; in the hot rolling process, after the slab is heated at a low temperature of 1150-1230°C, it is hot-rolled into a hot-rolled plate with a thickness of 1.7-2.4mm; in the normalization process, the hot-rolled plate is subjected to normalization treatment, and the The hot-rolled sheet is heated to 1100°C, kept for 2.5 minutes, cooled to 940°C with the furnace, held for 3 minutes, and then quenched with boiling water to cool; in the cold rolling process, the normalized hot-rolled sheet (i.e. Normalized plate) for cold rolling, the thickness of the cold rolled plate is 0.3mm.

Design idea of the present invention:

The decarburization annealing process parameters and control methods of niobium-containing low-temperature oriented silicon steel are provided. The present invention uses Nb (C, N) as the main inhibitor of low-temperature oriented silicon steel. Since niobium is a strong carbide forming element, the low-temperature oriented silicon steel containing niobium Decarburization is difficult during decarburization annealing, so it is necessary to determine the annealing process parameters and control methods for the chemical composition and inhibitor composition of niobium-containing low-temperature grain-oriented silicon steel. In the present invention, the temperature is raised rapidly at a heating rate greater than 50°C/s, mainly to obtain fine primary recrystallized grains, and to make a sufficient number of Goss grains in the matrix, so as to facilitate the formation of fronts in the subsequent secondary recrystallization process. Sharp Goss{110}<001> texture. According to the chemical composition and inhibitor composition of niobium-containing low-temperature oriented silicon steel, increasing the decarburization annealing temperature and holding time is to ensure that the weight percentage of C is reduced to less than 0.003% during the decarburization annealing process to ensure the magnetic properties of the finished product.

According to the chemical composition and inhibitor composition of niobium-containing low-temperature oriented silicon steel, the heating system, holding time and cooling system of high-temperature annealing of niobium-containing low-temperature oriented silicon steel are provided, that is, the high-temperature annealing process system and control method of niobium-containing low-temperature oriented silicon steel are provided . During the high-temperature annealing process, the temperature is raised to 600-680°C at a rate of 55-65°C/h, and the temperature is kept for 3-4 hours. Raise the temperature to 900°C at a rate of 65°C/h and keep it warm for 3-4 hours, mainly to coarsen the inhibitor selection and start secondary recrystallization; then raise the temperature to 1100°C at a rate of 10-14°C/h, mainly to In order to complete the secondary recrystallization during this heating process, a sharp Goss{110}<001> texture is formed; then the atmosphere in the furnace is adjusted to 100%H ₂ , and the temperature is raised to 1180-1240 at a rate of 10℃/h ℃, keep warm for 7-10 hours, this process is mainly to clean the substrate, through the chemical reaction between magnesium oxide and the surface silicon dioxide film to form the bottom layer of magnesium silicate, and remove sulfur and nitrogen in the steel during high-temperature purification and annealing, so that The steel is purified; it is then cooled to 550°C at a rate of 55°C/h, mainly to remove residual precipitates.

The beneficial effects produced by adopting the above-mentioned technical scheme are: 1. The present invention adopts Nb (C, N) as the main inhibitor of low-temperature oriented silicon steel, and solves the problem of niobium-containing low-temperature oriented silicon steel by controlling the decarburization annealing process parameters of niobium-containing low-temperature oriented silicon steel. The problem of difficult decarburization in the decarburization annealing process of oriented silicon steel; 2. The present invention aims at the chemical composition and inhibitor composition of niobium-containing low-temperature oriented silicon steel, and provides the heating system, holding time and cooling system for high-temperature annealing of niobium-containing low-temperature oriented silicon steel, That is, the high-temperature annealing process system and control method of niobium-containing low-temperature oriented silicon steel are provided; 3. The magnetic property test results show that the average magnetic properties of the niobium-containing low-temperature oriented silicon steel produced by the method of the present invention all reach the 30Q140 specified in the national standard GB2521-1996 Performance.

detailed description

The present invention will be described in further detail below in conjunction with specific examples.

Example 1

According to the chemical composition of niobium-containing low-temperature oriented silicon steel of the present invention, it is smelted and cast into a slab, and its chemical composition is as follows according to weight percentage: C: 0.04%, Si: 2.8%, Mn: 0.05%, Nb: 0.04%, S : 0.018%, N: 0.014%, Als: 0.025%, Cu: 0.08%, Cr: 0.03%, P: 0.012%, and the balance is Fe and unavoidable impurities.

After the slab is heated at a low temperature of 1230°C, it is hot-rolled into a hot-rolled plate with a thickness of 2.4mm; then the hot-rolled plate is subjected to normalization treatment, the hot-rolled plate is heated to 1100°C, kept for 2.5 minutes, cooled to 940°C with the furnace, and kept warm 3min, and then quenched with boiling water to cool; cold-rolled the normalized hot-rolled sheet (that is, the normalized sheet) by a cold-rolling method, and the thickness of the cold-rolled sheet is 0.3mm. Put the cold-rolled sheet into the annealing furnace, the atmosphere in the furnace is controlled at 85%H ₂ +15%N ₂ , the dew point is controlled at 45°C, and the temperature of the water bath is 60°C; then heated to 900°C at a heating rate of 51°C/s , keep warm for 30min, adjust the atmosphere in the furnace to 100% _N2 , take out the sample and air cool to room temperature. Before high-temperature annealing, coat MgO on the surface of the steel plate. The atmosphere in the furnace is controlled to 85%H ₂ +15%N ₂ . First, it takes 1 hour to quickly heat up to 500°C; Raise the temperature to 900°C at a rate of 55°C/h and hold for 4 hours; then raise the temperature to 1100°C at a rate of 10°C/h; then adjust the atmosphere in the furnace to 100% hydrogen, and then raise the temperature to 1180°C at a rate of 10°C/h. Insulate for 10 hours; then cool to 550°C at a rate of 55°C/h, and finally adjust the atmosphere in the furnace to 100% N ₂ , then cool to room temperature with the furnace. The tested product has iron loss P _1.7 =1.389w/kg and magnetic induction B ₈ =1.805T.

Example 2

According to the chemical composition of niobium-containing low-temperature grain-oriented silicon steel of the present invention, it is smelted and cast into a slab, and its chemical composition is as follows according to weight percentage: C: 0.06%, Si: 3.40%, Mn: 0.04%, Nb: 0.10%, S : 0.013%, N: 0.0085%, Als: 0.015%, Cu: 0.07%, Cr: 0.02%, P: 0.010%, and the balance is Fe and unavoidable impurities.

After the slab is heated at a low temperature of 1150°C, it is hot-rolled into a hot-rolled sheet with a thickness of 2.2 mm; then the hot-rolled sheet is subjected to normalization treatment, the hot-rolled sheet is heated to 1100°C, kept for 2.5 minutes, cooled to 940°C with the furnace, and kept 3min, and then quenched with boiling water to cool; cold-rolled the normalized hot-rolled sheet (that is, the normalized sheet) by a cold-rolling method, and the thickness of the cold-rolled sheet is 0.3mm. Put the cold-rolled sheet into the annealing furnace, the atmosphere in the furnace is controlled at 85%H ₂ +15%N ₂ , the dew point is controlled at 30°C, and the temperature of the water bath is 65°C; then heated to 1180°C at a heating rate of 55°C/s , keep warm for 7 minutes, adjust the atmosphere in the furnace to 100% N ₂ , take out the sample and air cool to room temperature. Before high-temperature annealing, coat MgO on the surface of the steel plate. The atmosphere in the furnace is controlled at 85%H ₂ +15%N ₂ . First, the temperature is rapidly raised to 500°C in 1 hour; Raise the temperature to 900°C at a rate of 65°C/h and hold for 3 hours; then raise the temperature to 1100°C at a rate of 14°C/h; then adjust the atmosphere in the furnace to 100% hydrogen, and then raise the temperature to 1240°C at a rate of 10°C/h. Keep warm for 7 hours; then cool down to 550°C at a rate of 55°C/h, and finally adjust the atmosphere in the furnace to 100% N ₂ , then cool down to room temperature with the furnace. The iron loss P _1.7 =1.378w/kg and the magnetic induction B ₈ =1.816T of the tested product.

Example 3

According to the chemical composition of niobium-containing low-temperature oriented silicon steel of the present invention, it is smelted and cast into a slab, and its chemical composition is as follows according to weight percentage: C: 0.047%, Si: 3.05%, Mn: 0.047%, Nb: 0.045%, S : 0.016%, N: 0.0095%, Als: 0.016%, Cu: 0.074%, Cr: 0.022%, P: 0.009%, and the balance is Fe and unavoidable impurities.

After the slab is heated at a low temperature of 1200°C, it is hot-rolled into a hot-rolled sheet with a thickness of 1.7 mm; then the hot-rolled sheet is subjected to normalization treatment, the hot-rolled sheet is heated to 1100°C, kept for 2.5 minutes, cooled to 940°C with the furnace, and kept 3min, and then quenched with boiling water to cool; cold-rolled the normalized hot-rolled sheet (that is, the normalized sheet) by a cold-rolling method, and the thickness of the cold-rolled sheet is 0.3mm. Put the cold-rolled sheet into the annealing furnace, the atmosphere in the furnace is controlled at 85%H ₂ +15%N ₂ , the dew point is controlled at 65°C, and the temperature of the water bath is at 70°C; then heated to 950°C at a heating rate of 56°C/s , keep warm for 16min, adjust the atmosphere in the furnace to 100% _N2 , take out the sample and air cool to room temperature. Before high-temperature annealing, coat MgO on the surface of the steel plate. The atmosphere in the furnace is controlled at 85%H ₂ +15%N ₂ . First, the temperature is rapidly raised to 500°C in 1 hour; Heat up to 900°C at a rate of 57°C/h and hold for 3.5 hours; then heat up to 1100°C at a rate of 12°C/h; then adjust the atmosphere in the furnace to 100% hydrogen, and then heat up to 1200°C at a rate of 10°C/h , keep warm for 9h; then cool down to 550°C at a rate of 55°C/h, and finally adjust the atmosphere in the furnace to 100% N ₂ , then cool down to room temperature with the furnace. The tested product has iron loss P _1.7 =1.361w/kg and magnetic induction B ₈ =1.827T.

Example 4

According to the chemical composition of niobium-containing low-temperature oriented silicon steel of the present invention, it is smelted and cast into a slab, and its chemical composition is proportioned as follows in terms of weight percentage: C: 0.052%, Si: 3.22%, Mn: 0.043%, Nb: 0.055%, S : 0.015%, N: 0.010%, Als: 0.020%, Cu: 0.076%, Cr: 0.023%, P: 0.011%, and the balance is Fe and unavoidable impurities.

After the slab is heated at a low temperature of 1230°C, it is hot-rolled into a hot-rolled plate with a thickness of 2.4mm; then the hot-rolled plate is subjected to normalization treatment, the hot-rolled plate is heated to 1100°C, kept for 2.5 minutes, cooled to 940°C with the furnace, and kept warm 3min, and then quenched with boiling water to cool; cold-rolled the normalized hot-rolled sheet (that is, the normalized sheet) by a cold-rolling method, and the thickness of the cold-rolled sheet is 0.3mm. Put the cold-rolled sheet into the annealing furnace, the atmosphere in the furnace is controlled at 85%H ₂ +15%N ₂ , the dew point is controlled at 47°C, and the temperature of the water bath is 62°C; then heated to 960°C at a heating rate of 53°C/s , keep warm for 13min, adjust the atmosphere in the furnace to 100% _N2 , take out the sample and air cool to room temperature. Before high-temperature annealing, coat MgO on the surface of the steel plate. The atmosphere in the furnace is controlled to 85%H ₂ +15%N ₂ . First, the temperature is rapidly raised to 500°C in 1 hour; Then raise the temperature to 900°C at a rate of 62°C/h and keep it warm for 3.5 hours; then raise the temperature to 1100°C at a rate of 12°C/h; then adjust the atmosphere in the furnace to 100% hydrogen, and then raise the temperature to 1220°C at a rate of 10°C/h ℃, heat preservation for 8.5h, then cooled to 550℃ at a rate of 55℃/h, and finally adjusted the atmosphere in the furnace to 100% N ₂ , then cooled to room temperature with the furnace. The iron loss P _1.7 =1.357w/kg and the magnetic induction B ₈ =1.836T of the tested product.

Example 5

According to the chemical composition of niobium-containing low-temperature grain-oriented silicon steel of the present invention, it is smelted and cast into a slab, and its chemical composition is as follows according to weight percentage: C: 0.054%, Si: 3.08%, Mn: 0.044%, Nb: 0.056%, S : 0.014%, N: 0.0092%, Als: 0.021%, Cu: 0.074%, Cr: 0.026%, P: 0.008%, and the balance is Fe and unavoidable impurities.

After the slab is heated at a low temperature of 1230°C, it is hot-rolled into a hot-rolled plate with a thickness of 2.4mm; then the hot-rolled plate is subjected to normalization treatment, the hot-rolled plate is heated to 1100°C, kept for 2.5 minutes, cooled to 940°C with the furnace, and kept warm 3min, and then quenched with boiling water to cool; cold-rolled the normalized hot-rolled sheet (that is, the normalized sheet) by a cold-rolling method, and the thickness of the cold-rolled sheet is 0.3mm. Put the cold-rolled sheet into the annealing furnace, the atmosphere in the furnace is controlled at 85%H ₂ +15%N ₂ , the dew point is controlled at 48°C, and the temperature of the water bath is 62°C; then heated to 1020°C at a heating rate of 52°C/s , keep warm for 10min, adjust the atmosphere in the furnace to 100% _N2 , take out the sample and air cool to room temperature. Before high-temperature annealing, coat MgO on the surface of the steel plate. The atmosphere in the furnace is controlled at 85%H ₂ +15%N ₂ . First, it takes 1 hour to rapidly raise the temperature to 500°C; Then raise the temperature to 900°C at a rate of 56°C/h and keep it warm for ₃ hours; then raise the temperature to 1100°C at a rate of 11°C/h; ℃, holding for 9.5h; then cooling to 550℃ at a rate of 55℃/h, and finally adjusting the atmosphere in the furnace to 100% N ₂ , then cooling to room temperature with the furnace. The tested product has iron loss P _1.7 =1.328w/kg and magnetic induction B ₈ =1.831T.

The test results of the magnetic properties of the finished product of the embodiment of the present invention show that the average magnetic properties of the niobium-containing low-temperature oriented silicon steel produced by the method of the present invention all reach the performance index of 30Q140 stipulated in the national standard GB2521-1996.

Claims (2)

1. The annealing process and control method of niobium-containing low-temperature oriented silicon steel, characterized in that the chemical composition of the niobium-containing low-temperature oriented silicon steel is proportioned as follows according to weight percentage: C: 0.04-0.06%, Si: 2.8-3.40%, Mn : 0.04～0.05%, Nb: 0.04～0.10%, S: 0.013～0.018%, N: 0.0085～0.014%, Als: 0.015～0.025%, Cu: 0.07～0.08%, Cr≤0.03%, P≤0.012% , the balance is Fe and unavoidable impurities, the main inhibitor is Nb(C,N), the auxiliary inhibitors are AlN, Cu ₂ S, (Cu,Mn)S and the grain boundary segregation element Cr, the precipitate size 5-55nm, and dispersed in the matrix; it includes smelting, continuous casting, hot rolling, normalization, cold rolling, decarburization annealing and high temperature annealing process, the process parameters of the decarburization annealing process are controlled as follows: Put the rolled plate into the annealing furnace, the atmosphere in the furnace is controlled at 85%H ₂ +15%N ₂ , the dew point is controlled at 30-65°C, the temperature of the water bath is 60-70°C; and then heated at a heating rate greater than 50°C/s To 900~1180℃, the holding time is 7~30min, after adjusting the atmosphere in the furnace to 100% _N2 , take out the sample and air cool to room temperature. 2. The annealing process and control method thereof for niobium-containing low-temperature oriented silicon steel according to claim 1, characterized in that the process parameters of the high-temperature annealing process are controlled as follows: before high-temperature annealing, the surface of the steel plate is coated with MgO, and the atmosphere in the furnace is controlled For 85%H ₂ +15%N ₂ , first take 1 hour to rapidly heat up to 500°C; then heat up to 600-680°C at a rate of 55-65°C/h, keep warm for 3-4 hours; Raise the temperature to 900°C at a speed of 10°C/h, keep it warm for 3-4 hours; then raise the temperature to 1100°C at a speed of 10-14°C/h; then adjust the atmosphere in the furnace to 100% H ₂ , and then raise the temperature to 1180~100°C/h 1240°C, keep warm for 7-10h; then cool down to 550°C at a rate of 55°C/h, and finally adjust the atmosphere in the furnace to 100% _N2 , then cool down to room temperature with the furnace.