Laboratory normalizing process for non-oriented silicon steel

Abstract

The invention discloses a non-oriented silicon steel laboratory normalizing process which is characterized in that five muffle furnaces are adopted for heating, the five muffle furnaces are connected in series and are respectively marked as 1-5 # furnaces for normalizing: the normalizing annealing speed is set to be 20 + / -2 m / min, the set temperature of 1 # furnace is 800 DEG C, the set temperature of 2 # furnace is 980-1050 DEG C, the set temperature of 3 # furnace is 920-970 DEG C, the 4 # furnace is a soaking and holding furnace, and the furnace is a furnace with the thickness of 1-5 mm; the normalizing heat preservation temperature is set to be 900 DEG C, 930 DEG C and 950 DEG C, the heat preservation time is 80-100 s, the 5 # furnace is a cooling furnace, and the temperature is set to be 650 DEG C. By means of the normalizing process, the banded structure of the core of the hot-rolled plate can be obviously eliminated, the hot-rolled structure, the inclusion size and the texture orientation are improved, and the high-grade non-oriented silicon steel with the excellent magnetic performance is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of non-oriented silicon steel, and in particular relates to a laboratory normalization process for non-oriented silicon steel. Background Art

[0002] At present, application number 202310455735.2 has announced a normalization method for improving the magnetic properties of high-grade non-oriented silicon steel. It focuses on controlling the normalization temperature and cooling rate to make the hot-rolled plate structure more uniform and increase the number of recrystallized grains. The present invention focuses on the laboratory normalization process method. Through normalization at different temperatures, it is determined that the hot-rolled plate grains have completed recrystallization, in preparation for subsequent cold rolling, and more shear bands can be formed.

[0003] Application No. 202311362452.X discloses a method for preparing non-oriented silicon steel and a high-grade non-oriented electrical steel, focusing on the use of an oriented silicon steel normalizing furnace to normalize non-oriented silicon steel to obtain non-oriented silicon steel that meets performance requirements. The present invention focuses on the laboratory normalizing process methods and steps, simulates the on-site normalizing process as much as possible, completes the recrystallization of the hot-rolled structure, and makes technical reserves for industrial normalization.

[0004] High-grade non-oriented silicon steel has high silicon and aluminum content. Generally, the silicon content is greater than 1.7%. There is no phase change during the heating and hot rolling process of the ingot. The (100) columnar crystal size in the ingot is well developed. During the hot rolling process, due to the slow dynamic recovery and recrystallization, it cannot be completely broken. Coarse and elongated deformed grains will be produced in the core of the hot-rolled plate, mainly {100} <011> The fiber texture is difficult to recrystallize during cold rolling and annealing, which will cause corrugation defects. Corrugation defects seriously affect the surface quality and stacking coefficient of silicon steel products, and will also cause many problems when the product is used. Summary of the invention

[0005] The purpose of the present invention is to provide a laboratory normalizing process for non-oriented silicon steel, so as to provide technical reserves for the industrial mass production of high-grade non-oriented silicon steel. By adding the normalizing process, the banded structure in the core of the hot-rolled plate can be significantly eliminated, the hot-rolled structure, inclusion size and texture orientation can be improved, and high-grade non-oriented silicon steel with excellent magnetic properties can be obtained.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention discloses a laboratory normalizing process for non-oriented silicon steel, which adopts 5 muffle furnaces for heating. The 5 muffle furnaces are connected in series and marked as furnaces #1 to #5 respectively, to carry out the normalizing process:

[0008] The normalizing annealing speed is set to 20±2m / min, the temperature of furnace 1# is set to 800℃, the temperature of furnace 2# is set to 980-1050℃, the temperature of furnace 3# is set to 920-970℃, furnace 4# is a heat-saturating and holding furnace, the normalizing and holding temperatures are set to 900℃, 930℃ and 950℃, the holding time is 80-100s, and furnace 5# is a cooling furnace with a set temperature of 650℃.

[0009] Furthermore, every two muffle furnaces are separated by an insulating plate, and a thermocouple is set above each muffle furnace to measure the temperature inside the furnace. The thermometer is externally connected to a temperature display device to monitor the temperature inside the furnace at all times. The power of the heating rod is controlled according to the temperature setting to ensure that each heating furnace is stably controlled at the set temperature.

[0010] Furthermore, the bottom of the muffle furnace is prevented from sliding by rollers, and the operation of the rollers is controlled by 5 small drive motors. After the specified insulation time is met, the partitions between the heating furnaces are opened, the rollers are operated, and the samples are sent to the next heating furnace.

[0011] Furthermore, after the non-oriented silicon steel is smelted in a converter, RH refined, continuously cast, and 7-line hot rolled, the thickness of the hot rolled plate is 2.0 mm, wherein the heating temperature is 1130-1150°C, the holding time final rolling temperature is 850-870°C, and the coiling temperature is 620-640°C; a shearing machine is used to cut a sample with a size of thickness × transverse × rolling direction: 2.0 mm × 180 mm × 550 mm, and a normalizing process is carried out.

[0012] Furthermore, after the sample plate is normalized, it is taken out and air-cooled, cooled to room temperature, and left to stand for 24 hours. A 20 mm transverse × 15 mm rolling sample is cut and the metallographic structure is observed.

[0013] Furthermore, the chemical composition of the non-oriented silicon steel in terms of mass percentage is: C: <0.0025%, Si: 2.0-3.0%, Mn: 0.4-0.6%, P: <0.020, S: ≤0.002%, Als: 0.45-0.55%, and the rest is Fe and unavoidable impurities.

[0014] Normalizing process parameters and functions of non-oriented silicon steel and oriented silicon steel are different. Oriented silicon steel is normalized in two stages. The first stage normalizing temperature is about 1120℃. The purpose is to dissolve Si3N4 and part of AlN in the steel. At this time, the steel contains the most γ and the solid solubility of N is the largest. When cooled to the second stage normalizing temperature of 900-920℃, due to the occurrence of γ→α phase transition, 10-50nm AlN precipitates. Finally, quenching in water at 100℃ can precipitate the largest number of fine AlN. AlN, as an inhibitor, can effectively inhibit the growth of other oriented grains and promote the growth of Goss-oriented grains in the high-temperature annealing stage, so that the final Goss orientation reaches the maximum, achieving the anisotropy of oriented silicon steel, only ensuring the Goss orientation, and improving the magnetic induction. The normalization effect of non-oriented silicon steel is just the opposite of that of oriented silicon steel. The normalization temperature of non-oriented silicon steel is 900-950℃. The normalization temperature is different according to the content of elements such as Si and Al, because it is necessary to ensure that all hot-rolled structures are fully recrystallized, in order to make the hot-rolled plate structure more uniform, to recrystallize the deformation structure in the core, and to transform the structure into a recrystallized structure to prevent corrugation defects. At the same time, it is the coarsening of grains and precipitates, preventing the inhibitory effect of precipitates in the later annealing process, promoting the nucleation of {110} grains in the deformation zone, and inhibiting the formation of {111} grains nucleated along the grain boundary, because {111} oriented grains are unfavorable to magnetic induction, promoting the formation and growth of {100} and {110} easily magnetized oriented grains, and achieving isotropy of non-oriented silicon steel.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are:

[0016] The present invention adopts a five-stage muffle furnace for normalization, provides an effective process reference for on-site batch production, shortens the number of on-site process debugging times and the scrap rate and defective rate, and reduces the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below in conjunction with the accompanying drawings.

[0018] Figure 1 The metallographic structure of the non-oriented silicon steel normalized at 900°C in Example 1 (left and right are thickness directions);

[0019] Figure 2 The metallographic structure of the non-oriented silicon steel normalized at 930°C in Example 2 (left and right are thickness directions);

[0020] Figure 3 The metallographic structure of the non-oriented silicon steel normalized at 950°C in Example 3 (left and right are thickness directions);

[0021] Figure 4 This is the metallographic structure of the non-oriented silicon steel normalized at 780°C in Comparative Example 1 (left and right are thickness directions). DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with specific embodiments.

[0023] Embodiment 1:

[0024] 1) Sampling

[0025] After converter smelting, RH refining, continuous casting, and 7-line hot rolling, the thickness of the hot-rolled plate is 2.0 mm, the heating temperature is 1135 ° C, the holding time final rolling temperature is 865 ° C, and the coiling temperature is 628 ° C. The sample size of thickness × transverse × rolling direction: 2.0 mm × 180 mm × 550 mm is cut by a shearing machine for normalization test.

[0026] 2) Normalization

[0027] The normalizing annealing speed is set to 18m / min, the temperature of furnace 1 is set to 800℃, and the insulation time is 90s, the temperature of furnace 2 is set to 980℃, and the insulation time is 45s, the temperature of furnace 3 is set to 920℃, and the insulation time is 60s, the temperature of furnace 4 is set to 900℃, and the insulation time is 100s, and the temperature of furnace 5 is set to 650℃, and the insulation time is 67s.

[0028] 3) Organizational Observation

[0029] After normalization, the sample plate was taken out and air-cooled to room temperature, and left to stand for 24 h. A 20 mm (transverse) × 15 mm (rolling direction) sample was cut and the metallographic structure was observed.

[0030] Embodiment 2:

[0031] 1) Sampling

[0032] After converter smelting, RH refining, continuous casting, and 7-line hot rolling, the thickness of the hot-rolled plate is 2.0 mm, the heating temperature is 1141 ° C, the holding time final rolling temperature is 862 ° C, and the coiling temperature is 627 ° C. The sample size of thickness × transverse × rolling direction: 2.0 mm × 180 mm × 550 mm is cut by a shearing machine for normalization test.

[0033] 2) Normalization

[0034] The normalizing annealing speed is set to 20m / min, the temperature of furnace #1 is set to 800℃, and the insulation time is 80s, the temperature of furnace #2 is set to 1000℃, and the insulation time is 40s, the temperature of furnace #3 is set to 950℃, and the insulation time is 55s, the temperature of furnace #4 is set to 930℃, and the insulation time is 90s, and the temperature of furnace #5 is set to 650℃, and the insulation time is 60s.

[0035] 3) Organizational Observation

[0036] After normalization, the sample plate was taken out and air-cooled to room temperature, and left to stand for 24 h. A 20 mm (transverse) × 15 mm (rolling direction) sample was cut and the metallographic structure was observed.

[0037] Embodiment 3:

[0038] 1) Sampling

[0039] After converter smelting, RH refining, continuous casting, and 7-line hot rolling, the thickness of the hot-rolled plate is 2.0 mm, the heating temperature is 1133 ° C, the holding time final rolling temperature is 868 ° C, and the coiling temperature is 634 ° C. The sample size is cut by a shearing machine with the size of thickness × transverse × rolling direction: 2.0 mm × 180 mm × 550 mm, and the normalization test is carried out.

[0040] 2) Normalization

[0041] The normalizing annealing speed is set to 22m / min, the temperature of furnace 1 is set to 800℃, and the insulation time is 75s, the temperature of furnace 2 is set to 1050℃, and the insulation time is 35s, the temperature of furnace 3 is set to 970℃, and the insulation time is 50s, the temperature of furnace 4 is set to 950℃, and the insulation time is 80s, and the temperature of furnace 5 is set to 650℃, and the insulation time is 55s.

[0042] 3) Organizational Observation

[0043] After normalization, the sample plate was taken out and air-cooled to room temperature, and left to stand for 24 h. A 20 mm (transverse) × 15 mm (rolling direction) sample was cut and the metallographic structure was observed.

[0044] Comparative Example 1:

[0045] 1) Sampling

[0046] After converter smelting, RH refining, continuous casting, and 7-line hot rolling, the thickness of the hot-rolled plate is 2.0 mm, of which the heating temperature is 1141 ° C, the holding time final rolling temperature is 862 ° C, and the coiling temperature is 637 ° C. The sample size is cut by a shearing machine with the thickness × transverse × rolling direction: 2.0 mm × 180 mm × 550 mm, and the normalization test is carried out.

[0047] 2) Normalization

[0048] The normalizing annealing speed is set to 18m / min, the temperature of furnace #1 is set to 700℃, and the insulation time is 95s, the temperature of furnace #2 is set to 870℃, and the insulation time is 48s, the temperature of furnace #3 is set to 850℃, and the insulation time is 64s, the temperature of furnace #4 is set to 780℃, and the insulation time is 106s, and the temperature of furnace #5 is set to 650℃, and the insulation time is 69s.

[0049] 3) Organizational Observation

[0050] After normalization, the sample plate was taken out and air-cooled to room temperature, and left to stand for 24 h. A 20 mm (transverse) × 15 mm (rolling direction) sample was cut and the metallographic structure was observed.

[0051] Compared with the embodiment, the comparative example structure has not completed all recrystallization, and there is still a certain amount of deformed structure in the core structure, which means that recrystallization has started at 780°C, but the recrystallization has not ended. A higher temperature or time is required to completely transform the deformed structure into a recrystallized structure.

[0052] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A laboratory normalizing process for non-oriented silicon steel, characterized in that: Five muffle furnaces are used for heating. The five muffle furnaces are connected in series and marked as 1-5# furnaces respectively for normalizing process: The normalizing annealing speed is set to 20±2m / min, the temperature of furnace 1# is set to 800℃, the temperature of furnace 2# is set to 980-1050℃, the temperature of furnace 3# is set to 920-970℃, furnace 4# is a heat-saturating and holding furnace, the normalizing and holding temperatures are set to 900℃, 930℃ and 950℃, the holding time is 80-100s, and furnace 5# is a cooling furnace with a set temperature of 650℃.

2. The laboratory normalization process of non-oriented silicon steel according to claim 1, characterized in that: Every two muffle furnaces are separated by an insulation board. A thermocouple is set above each muffle furnace to measure the temperature inside the furnace. The thermometer is connected to a temperature display device to monitor the temperature inside the furnace at all times. The power of the heating rod is controlled according to the temperature setting to ensure that each heating furnace is stably controlled at the set temperature.

3. The laboratory normalization process for non-oriented silicon steel according to claim 1 or 2, characterized in that: The bottom of the muffle furnace is protected by a roller conveyor to prevent sliding. Five small drive motors are used to control the operation of the roller conveyor. After the specified insulation time is met, the partitions between the heating furnaces are opened, the roller conveyor runs, and the sample is sent to the next heating furnace.

4. The laboratory normalization process of non-oriented silicon steel according to claim 1, characterized in that: After converter smelting, RH refining, continuous casting and 7-line hot rolling, the thickness of the hot-rolled plate is 2.0 mm, wherein the heating temperature is 1130-1150°C, the holding time final rolling temperature is 850-870°C, and the coiling temperature is 620-640°C; the sample size is thickness × transverse × rolling direction: 2.0 mm × 180 mm × 550 mm cut by a shearing machine, and the normalization process is carried out.

5. The laboratory normalization process of non-oriented silicon steel according to claim 1, characterized in that: After normalization, the sample plate was taken out and air-cooled to room temperature, and left to stand for 24 hours. A 20 mm transverse × 15 mm rolling sample was cut for metallographic structure observation.

6. The laboratory normalization process of non-oriented silicon steel according to claim 1, characterized in that: The chemical composition of the non-oriented silicon steel by mass percentage is: C: <0.0025%, Si: 2.0-3.0%, Mn: 0.4-0.6%, P: <0.020, S: ≤0.002%, Als: 0.45-0.55%, and the rest is Fe and unavoidable impurities.

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