CN101049669A - Preparation method for cold rolling sheet of duriron - Google Patents

Abstract

The invention discloses a cold-rolling preparation method of a high-silicon steel thin plate, which belongs to the technical field of metal material preparation. The content of Fe in the thin plate is 85-96%, the content of Si is 4-15%, both are weight ratio; the process is: raw material preparation, the range of silicon content is 4-15%, the content of boron is 100-5000ppm, and the rest is Iron; smelting, casting; forging into a slab with a thickness of 10-20mm; hot rolling to a thickness of 1-2mm; 0.05mm high silicon steel plate. The advantage is that the alloy is produced by cold rolling, which was previously considered impossible to produce high-silicon steel due to the room temperature brittleness of the material. The prepared cold-rolled thin strip has good shape and metallic luster on the surface. The production process has universal applicability and low cost; due to the excellent soft magnetic properties of the high-silicon steel, it has broad market application prospects.

Description

Cold rolling preparation method of high silicon steel sheet

technical field

The invention belongs to the technical field of metal material preparation, and relates to a method for preparing boron-containing high-silicon steel by cold rolling.

technical background

Silicon steel is the most widely used soft magnetic alloy, and its silicon content is generally 1.5-3.5% (by weight, the same below). It is an important magnetic material for the electric power and telecommunications industry to manufacture generators, motors, transformers, transformers, relays and other electrical instruments.

High silicon steel generally refers to silicon steel with a silicon content exceeding 3.5%. With the increase of silicon content, the soft magnetic properties of silicon steel are improved, which is manifested in the increase of resistivity and magnetic permeability, and the decrease of coercive force and magnetocrystalline anisotropy. When the silicon content is 6.5%, the performance of silicon steel is the best. In 1928, Schulze found that the hysteresis constant (λ _s ) of Fe-6.5% Si alloy was close to zero. In 1942, Ruder pointed out that compared with Fe-3.5% Si alloy, the magnetocrystalline anisotropy constant K _I and magnetostrictive constant λ _s of Fe-6.5% Si alloy were lower, and the resistivity ρ was higher, so the iron loss P lower. In 1964, Brown et al. proved that Fe-6.5% Si single crystal was 0.2W/kg lower than Fe-3.5% Si single crystal P _15/50 , λ _s was 90% lower, and K _I was 1/3 lower. Therefore, compared with ordinary silicon steel, high silicon steel has excellent magnetic properties, can obtain low iron loss and small magnetostriction, and plays an important role in saving energy and reducing noise.

However, with the increase of Si content, the processing performance of iron-silicon alloy becomes worse, and 4.0% Si is generally the upper limit of silicon steel products. Beyond this range, an ordered phase of iron and silicon appears in the alloy, which greatly increases the brittleness of the material, making it difficult to produce high-silicon steel sheets by traditional rolling methods. Due to the serious brittleness of high-silicon steel, developed countries have successively adopted special processes to prepare this alloy sheet. Y. Takada mentioned in Journal of Applied Physics, 64(10): 5367-5369, 1988, Commercial scale production of Fe-6.5wt.%Si sheet and its magnetic properties that this alloy was produced by CVD (Chemical Vapor Deposition) method. The process includes two steps. In the first step, common silicon steel is rolled to a certain thickness. In the second step, chemical vapor deposition is performed on the steel plate to deposit silicon on the surface, and then diffusion annealing is performed. Although the process is basically mature, the production process is complicated, the production cycle is long, the production cost is high, and the raw material SiCl4 used pollutes the environment. G.E.Fish et al reported in Journal of Applied Physics, 64 (10): 5370, 1988, Frequency dependence of core loss inrapidly quenched Fe-6.5wt.% Si, that the alloy strip was prepared by rapid solidification. Its characteristic is that it directly throws off the strip from the liquid alloy, avoids its brittle zone, and directly obtains a thin and narrow alloy thin strip. However, the size of the resulting thin ribbon is limited, which is not conducive to large-scale production and application. T. Ros-Yanez et al. reported in Journal of Materials Processing Technology, 143-144: 916-921, 2003, Production of high silicon steel for electrical application by thermomechanical processing, that the alloy was prepared by traditional hot rolling and cold rolling methods. However, before cold rolling, the rolling direction must be adjusted and rotated 90° along the hot rolling direction, that is, cold rolling is carried out along the transverse direction of the hot rolled plate, so this process is not suitable for mass production of this alloy.

Contents of the invention

The object of the present invention is to provide a cold-rolled preparation method for high-silicon steel sheets. For high-silicon steels containing 4-15% silicon, use forging, hot-rolling, warm-rolling, and cold-rolling methods in combination with corresponding heat treatment processes to prepare 0.03-15% silicon steel. 0.05mm thin strip. The thin strip has a good shape and a metallic luster on the surface. The production process has universal applicability and can be carried out on traditional rolling mills without major modification of existing equipment. At the same time, the cold-rolling direction is the same as the hot-rolling direction, so the hot-rolled plate can continue to be cold-rolled along the rolling direction, maintaining the continuity of the plate and strip.

Concrete technological process (referring to Fig. 1) is:

(1) Raw material preparation: take industrial pure iron (industrial pure iron DT0, iron content 99.5%), crystalline silicon (purity is 99.9%), boron iron (containing boron 20.43%) as raw material, according to silicon content 4～15%, Proportional mixing with a boron content of 100-5000ppm;

(2) Smelting: smelting pure iron, silicon and ferroboron as raw materials in an intermediate frequency vacuum induction furnace, casting at 1300-1530°C;

(3) Forging: Air hammer free forging is used to forge the ingot into a slab with a thickness of 10-20mm at 1250°C-750°C. Forging can not only provide a raw material shape suitable for hot rolling, but also break grains and inclusions to improve the plasticity of the material;

(4) Hot rolling: hot rolling at 1250～500℃ to 1～2mm, during which the material undergoes large deformation, dynamic recrystallization occurs at the same time, and grain refinement;

(5) Heat treatment of hot-rolled sheet: cooling in water or brine after heat preservation at 700-1000°C for 1-3 hours. Heat treatment causes recovery and recrystallization of the material, eliminating work hardening, and rapid cooling reduces the order of the material.

(6) Warm rolling: Warm rolling at 700-150°C to obtain a plate of 0.2-0.3 mm. Rolling below the recrystallization temperature obtains a fibrous rolling structure and increases the plasticity of the material.

(7) Heat treatment of warm-rolled sheet: keep warm at 700-1000°C for 1-3 hours, then cool in water or brine. This heat treatment is carried out in a protective atmosphere to prevent surface oxidation of the plate and affect the subsequent cold rolling process. This heat treatment eliminates work hardening, and rapid cooling reduces the order of the material;

(8) Cold rolling: cold rolling at room temperature, the reduction in the first pass is 20-70%, the reduction in the second pass is 10-50%, and then repeated cold rolling until the thickness reaches 0.03-0.05mm. After cold rolling, an extremely thin plate is obtained, and the plate shape is neat, the surface quality is good, and it has a metallic luster.

The heat treatment of the warm-rolled sheet of the present invention is carried out in a protective atmosphere, under argon or nitrogen.

In the present invention, the reduction in the first pass of cold rolling is 20-70%, the reduction in the second pass is 10-50%, and then the cold rolling is repeated until the thickness reaches 0.03-0.05mm.

The advantages of the present invention are:

The invention proposes the technology of preparing high silicon steel by traditional rolling method. However, due to the room temperature brittleness of the material, this traditional method was previously considered impossible to prepare high-silicon steel. Therefore, using this method, the alloy thin plate can be prepared by using traditional forging machines and rolling mills, and has wide applicability. Moreover, the raw materials used are simple, the purity is not high, and the cost is low.

There is an ordered phase of iron-silicon in high-silicon steel, which has a great influence on the plasticity of the material. At the same time, the non-metallic impurities contained in the material, such as carbon, oxygen, nitrogen, etc., have a great influence on the magnetic properties of the material. Therefore, from the preparation process Starting from each link, on the one hand, reduce the content of iron-silicon ordered phase, improve plasticity, and on the other hand, reduce impurity content, improve the magnetic properties of the alloy.

Vacuum induction furnace smelting is used during smelting, which can reduce the content of impurities and improve the plasticity and magnetic properties of the alloy. The addition of boron can refine the crystal grains of the casting structure and ensure the smooth progress of forging. Forging and hot rolling process can provide thinner plate and refine the grain. The warm rolling process is the key step to achieve cold rolling. Warm rolling below the recrystallization temperature can obtain elongated fiber structure and improve the plasticity of the material. In the first and second passes of cold rolling, large reductions are used to cause intense reorganization of atomic sites and promote the disordering of ordered alloys. At the same time, the deformation heat in the large deformation process is used to increase the temperature of the material , cold rolling can be carried out smoothly. The appropriate heat treatment system adopted in this preparation process can not only make the material recover and recrystallize, eliminate work hardening, improve plasticity, but also quench the alloy from a disordered state, reduce the order degree of the alloy, and greatly improve plasticity.

The present invention starts research from raw material control and process route, can save costs, has realistic popularization and application value, and has incomparable advantages over other preparation methods. At the same time, because this kind of high-silicon steel has excellent soft magnetic properties, it has a broad market Application prospects.

Description of drawings

Fig. 1 is the preparation process flowchart of the present invention.

Fig. 2 is the warm-rolled 0.3mm thin plate of the present invention.

Fig. 3 is the cold-rolled 0.05mm sheet of the present invention,

Figure 4 is a bending experiment of the thin strip of the present invention.

Detailed ways

For high-silicon steel with a silicon content of 4-15% and a boron content of 100-5000ppm, the thin plate is prepared by rolling. The specific implementation is as follows:

Example 1

For high-silicon steel containing 4.5% silicon and 200ppm boron, the raw material is smelted in an intermediate frequency vacuum induction furnace, and the casting temperature is 1530°C. The ingot is then free forged, the initial forging temperature is 1200°C, and the final forging temperature is 900°C. The ingot is heated up with the furnace to prevent cracks from thermal stress.

After forging, the thickness of the slab is 20mm, followed by hot rolling, the hot rolling start temperature is 1200°C, and the finish rolling temperature is 700°C. The slab is hot rolled to 1.5mm. The obtained hot-rolled sheet is subjected to heat treatment, the heat treatment temperature is 900° C., the holding time is 1 hour, and the water is cooled.

After the treated hot-rolled sheet was pickled, it was subjected to steady rolling, the rolling start temperature was 500° C., the final rolling temperature was 150° C., and the reduction was 30% per pass to obtain a 0.3 mm warm-rolled sheet.

The warm-rolled plate is subjected to 900°C, 1h heat preservation treatment, water cooling, and cold rolling after surface treatment. The first pass of cold rolling is 40%, the second pass is 30%, and then the roll gap is continuously reduced, and the cold rolling is repeated to 0.05mm.

Example 2

For high-silicon steel containing 5.8% silicon and 600ppm boron, the raw material is smelted in an intermediate frequency vacuum induction furnace, and the casting temperature is 1500°C. The ingot is then free forged, with an initial forging temperature of 1200°C and a final forging temperature of 850°C. The ingot is heated up with the furnace to prevent cracks from thermal stress.

After forging, a slab with a thickness of 20mm is obtained, and then hot rolled, the hot rolling start temperature is 1200°C, the finish rolling temperature is 650°C, and the slab is hot rolled to 1.5mm. The obtained hot-rolled sheet is subjected to heat treatment, the heat treatment temperature is 900° C., the holding time is 2 hours, and the water is cooled.

After the treated hot-rolled sheet is pickled, it is warm-rolled. The rolling start temperature was 650°C, the final rolling temperature was 200°C, and the reduction was 25% per pass to obtain a 0.3mm warm rolled sheet.

The warm-rolled plate is subjected to 850°C, 1h heat preservation treatment, water cooling, and cold rolling after surface treatment. The first pass of cold rolling is 35%, the second pass is 30%, and then the roll gap is continuously reduced, and the cold rolling is repeated to 0.03mm.

Example 3

For high-silicon steel containing 6.5% silicon and 1000ppm boron, the raw material is smelted in an intermediate frequency vacuum induction furnace, and the casting temperature is 1480°C. The ingots are then free forged, with a starting forging temperature of 1100°C and a final forging temperature of 850°C. The forged ingots are heated up with the furnace to prevent cracks from thermal stress.

After forging, a slab with a thickness of 20mm was obtained, and then hot rolled, the hot rolling start temperature was 1150°C, and the finish rolling temperature was 650°C. The slab is hot rolled to 1mm. The obtained hot-rolled plate is subjected to heat treatment, the heat treatment temperature is 900° C., the holding time is 2 hours, and the brine is cooled.

After the treated hot-rolled sheet is pickled, it is warm-rolled. The rolling start temperature was 650°C, the final rolling temperature was 250°C, and the reduction was 25% per pass to obtain a 0.3mm warm rolled sheet. The warm-rolled plate is subjected to heat preservation treatment at 900°C for 1 hour, cooled with brine, and cold-rolled after surface treatment.

The first pass of cold rolling is 40%, the second pass is 30%, and then the roll gap is continuously reduced, and the cold rolling is repeated to 0.03mm.

Example 4

For high-silicon steel containing 7.5% silicon and 2000ppm boron, the raw material is smelted in an intermediate frequency vacuum induction furnace, and the casting temperature is 1460°C. The ingot is then free forged, with a starting forging temperature of 1100°C and a final forging temperature of 800°C. The ingot is heated up with the furnace to prevent cracks from thermal stress.

After forging, a slab with a thickness of 15mm is obtained, followed by hot rolling. The starting temperature of hot rolling is 1100° C., the finishing temperature is 700° C., and the slab is hot rolled to 1 mm. The obtained hot-rolled plate is subjected to heat treatment, the heat treatment temperature is 900° C., the holding time is 3 hours, and the brine is cooled.

After the treated hot-rolled sheet is pickled, it is warm-rolled. The rolling start temperature was 700°C, the final rolling temperature was 300°C, and the reduction was 25% per pass to obtain a 0.3mm warm rolled sheet. The warm-rolled plate is subjected to heat preservation treatment at 900°C for 2 hours, cooled by brine, and cold-rolled after surface treatment.

The first pass of cold rolling is 45%, the second pass is 30%, and then the roll gap is continuously reduced, and the cold rolling is repeated to 0.05mm.

Example 5

For high-silicon steel containing 12% silicon and 4000ppm boron, the raw material is smelted in an intermediate frequency vacuum induction furnace, and the casting temperature is 1400°C. The ingots are then free forged, with a starting forging temperature of 1050°C and a final forging temperature of 800°C. The forged ingots are heated up with the furnace to prevent cracks from thermal stress.

After forging, a slab with a thickness of 15 mm is obtained, and then hot rolled, the hot rolling start temperature is 1000° C., the finish rolling temperature is 700° C., and the slab is hot rolled to 1 mm. The obtained hot-rolled plate is subjected to heat treatment, the heat treatment temperature is 900° C., the holding time is 3 hours, and the brine is cooled.

After the treated hot-rolled sheet is pickled, it is warm-rolled. The rolling start temperature was 700°C, the final rolling temperature was 400°C, and the reduction was 25% per pass to obtain a 0.3mm warm rolled sheet. The warm-rolled plate is subjected to heat preservation treatment at 900°C for 2 hours, cooled by brine, and cold-rolled after surface treatment.

The first pass of cold rolling is 50%, the second pass is 35%, and then the roll gap is continuously reduced, and the cold rolling is repeated to 0.05mm.

Claims (3)

1. a cold-rolled preparation method of high-silicon steel sheet, Fe content is 85～96% in the sheet, and Si content is 4～15%, all are percentage by weight; Its technology is: (1) Raw material preparation: industrial pure iron, crystalline silicon, and ferroboron are raw materials, the silicon content to be obtained ranges from 4 to 15%, the boron content is 100 to 5000 ppm, and the rest is iron; (2) Smelting: smelting pure iron, silicon and ferroboron as raw materials in an intermediate frequency vacuum induction furnace, casting at 1300-1530°C; (3) Forging: forging a slab with a thickness of 10-20mm at 1250°C-750°C; (4) Hot rolling: 1250～500℃ hot rolling to 1～2mm; (5) Annealing of hot-rolled sheet: cooling in water or brine after heat preservation at 700-1000°C for 1-3 hours; (6) Warm rolling: Warm rolling at 700-150°C to obtain a plate of 0.2-0.3mm; (7) Heat treatment of warm-rolled plate: cooling in water or brine after heat preservation at 700-1000°C for 1-3 hours; (8) Cold rolling: cold rolling at room temperature to obtain a high-silicon steel plate with a thickness of 0.03 to 0.05 mm; 2. The method for preparing high-silicon steel according to claim 1, characterized in that the heat treatment of the warm-rolled sheet is carried out in a protective atmosphere, using argon or nitrogen to carry out. 3. The preparation method of high-silicon steel according to claim 1, the reduction in the first pass of cold rolling is 20-70%, the reduction in the second pass is 10-50%, and then the cold rolling is repeated until the thickness Reach 0.03 ~ 0.05mm.

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