CN1743128A - Method for producing oriented silicon steel band by direct rolling of continuous cast plate slab - Google Patents

Abstract

The invention relates to a method for producing oriented silicon steel strips by direct rolling of continuous casting slabs. The production process steps are: continuous casting slabs, compensation heating, hot rolling, normalized annealing, cold rolling, decarburization annealing, high temperature annealing, the most important The feature is that after the continuous casting slab is produced, it is directly compensated for heating and hot rolling, the compensation heating temperature is 1150-1220° C., and the time is 210-240 minutes. The characteristics and effects of the present invention are: the cooling process after the production of the continuous casting slab in the prior art is omitted, and the problem of inhibitor precipitation caused by the cooling of the slab is solved; the compensation heating solves the problem of low temperature at the edge of the slab and high temperature heating , Reduced burning loss, prolongs the life of the heating furnace, reduces energy consumption, reduces production costs, improves production efficiency, and improves product quality.

Description

Method for producing oriented silicon steel strip by direct rolling of continuous casting slab

technical field

The invention relates to a method for rolling silicon steel, in particular to a method for directly rolling continuous casting slabs to produce oriented silicon steel strips.

Background technique

At present, oriented silicon steel is generally produced by continuous casting slabs. The process steps are to produce continuous casting slabs first, after cooling, heat them at high temperature before entering the hot rolling mill, and then carry out hot rolling, normalized annealing, cold rolling, stripping Carbon annealing and high temperature annealing.

In order to obtain an excellent Goss-oriented texture, reduce iron loss and improve the magnetic properties of grain-oriented silicon steel, inhibitor-forming elements such as Mn, S, Al and N need to be added to the continuous casting slab.

In order to ensure that the coarse MnS and AlN inhibitors are completely dissolved in the heating process of the continuous casting slab, the heating temperature of the ordinary grain-oriented silicon steel casting slab must be guaranteed at 1350-1370 ° C, while the high magnetic induction grain-oriented silicon steel is due to Mn and With high S content, the heating temperature of the slab is higher, reaching 1380-1400°C.

In order to solve the problem of solid solution and dispersed precipitation of MnS and AlN inhibitors, the continuous casting slab needs to be heated at high temperature in the conventional production process. High temperature heating causes the disadvantages of slab burning, high fuel consumption and short life of the heating furnace. After high-temperature heating, the processing methods of grain-oriented silicon steel become extremely complicated in the subsequent steps of rolling, cooling and annealing. For different production equipment, it is necessary to formulate different production processes for grain-oriented silicon steel. The grain orientation and size of oriented silicon steel produced by different production processes are very different, resulting in great differences in iron loss and magnetic induction level. It is very difficult to produce high-quality grain-oriented silicon steel, and the production cost is relatively high.

Contents of the invention

Aiming at the defects existing in the existing production technology of oriented silicon steel strips, the present invention provides a method for producing oriented silicon steel strips by direct rolling of continuous casting slabs, which can simplify the process flow, greatly reduce energy consumption, reduce production costs, and produce high-quality oriented silicon steel strips. Silicon steel belt.

The technical scheme that realizes the object of the present invention is: process step comprises continuous casting slab, hot rolling, normalization degradation, cold rolling, decarburization annealing, high-temperature annealing, main point is that process step and process condition are:

First, design the composition of grain-oriented silicon steel matrix elements and inhibitor elements, in terms of mass percentage: C0.025～0.08%, Si2.8～4.0%, Mn0.03～0.14%, S0.01～0.06%, Al0.016～ 0.07%, N0.004-0.012%, Cu0.03-0.14%, Sn0.07-0.15%, Se0.01-0.05%, and the balance is Fe.

With the composition designed in this way, molten steel is smelted, and continuous casting slabs are produced. The temperature of the casting slab is 800-1100°C, and the casting speed of the slab is 2-3m/min;

After that, the continuous casting slab is directly subjected to compensation heating, the compensation heating temperature is 1150-1220°C, and the time is 210-240 minutes;

Hot rolling is carried out after compensatory heating. The entrance temperature of hot rolling rough rolling is 1130-1200°C, the entrance temperature of finish rolling is 950-1100°C, and the final rolling temperature is 850-1000°C. After that, the hot-rolled steel strip is cooled and the cooling speed is controlled. 10-100°C/s, and then the hot-rolled steel strip is coiled, and the coiling temperature is 550-650°C;

For normalizing annealing of strip steel, it is divided into two stages of normalizing treatment. The temperature of the first stage is controlled at 990-1100°C for 20-60s, the temperature of the second stage is controlled at 920-950°C for 60-120s, and then at 90 ～99℃ water cooling;

Cold-roll the normalized steel strip with a total deformation of 80% to 95%, and coat the surface of the strip with Na ₂ CO ₃ aqueous solution during the third and fourth passes of cold rolling to maintain the temperature of the strip. 200～250℃;

Decarburization annealing is carried out on the steel strip after cold rolling. Before annealing, alkali washing is carried out and the surface of the steel strip is dried. Two-stage decarburization annealing is adopted. The temperature of the first stage is controlled at 850-880°C for 120-240s, and the temperature of the second stage is controlled at 880°C. ~910°C, the time is 10~60s, using a wet atmosphere, the volume ratio is 75~80% nitrogen + 20~25% hydrogen, the dew point is 30~50°C, the cooling section is dry, the volume ratio is 75~80% nitrogen +20～25% hydrogen;

Finally, high-temperature annealing is carried out. Before high-temperature annealing, MgO is coated on the surface of the steel strip. In an atmosphere with a volume ratio of 55-60% hydrogen + 40-45% nitrogen, the temperature is first raised to 840-870°C, kept for 4 hours, and then heated in 100% hydrogen. Heat to 1190-1220°C in the atmosphere, and keep warm for 15-25 hours.

The continuous casting slab mentioned above is to use the continuous casting machine to produce the continuous casting slab of 90mm-260mm from the melted steel. After the continuous casting slab is heated by compensation, it is directly hot-rolled. The thickness of the hot-rolled rough rolling is 25-45 mm, and the thickness of the final rolling is 2.0-4.0 mm.

The hot-rolled coil steel is subjected to normalizing annealing and then cold-rolled. The thickness of the strip steel before cold rolling is 2.0-4.0mm, and the thickness of the strip steel after cold-rolling is 0.2-0.4mm.

The coiled steel after cold rolling is decarburized and annealed, and finally high-temperature annealing is performed by high-temperature bell furnace annealing.

The obvious advantages and positive effects of the present invention are:

Because the present invention adopts the technical scheme of smelting molten steel, producing continuous casting slabs, through direct compensation heating and hot rolling, it saves the cooling process of the slabs after producing the continuous casting slabs in the prior art like this, Solved the problem of precipitation of inhibitors caused by slab cooling;

Edge compensation heating is used before hot rolling to solve the problem of low temperature at the edge of the slab; due to the technical solution of compensation heating, the problem of high temperature heating of the slab is solved, burning loss is reduced, the life of the heating furnace is extended, and production is reduced Energy consumption during the process reduces production costs, increases production efficiency, and improves product quality.

Detailed ways

Example 1

According to this technological process, the matrix element and inhibitor element composition design of grain-oriented silicon steel is carried out. The composition of grain-oriented silicon steel in terms of mass percentage is: C0.04%, Si3.0%, Mn0.1%, S0.03%, Al0.04 %, N0.008%, Cu0.08%, Sn0.11%, Se0.03%, and the balance is Fe.

The specific rolling process of grain-oriented silicon steel is as follows.

(1) Using the above-mentioned design composition and smelting molten steel, a thin slab continuous casting machine is used to produce a 90mm continuous casting thin slab, the casting speed of the thin slab is 2.0m/min, and the casting temperature is 800°C.

(2) Compensation heating the cast slab in the heating furnace, the heating temperature is 1220° C., and the heating time is 210 minutes.

(3) The heated slab is subjected to rough rolling, the rough rolling entrance temperature is 1200°C, the rolled thickness is 25mm, the finish rolling entrance temperature is 950°C, the final rolling temperature is 850°C, and the rolled thickness is 2.0mm. The hot-rolled strip enters the laminar flow cooling zone for cooling, and the cooling rate is controlled to be 10°C/s. After rolling, the hot-rolled strip enters the coiler for coiling, and the coiling temperature is 550°C.

(4) The steel coil is subjected to two-stage normalization treatment before cold rolling. The temperature of the first stage is controlled at 1000°C for 40s, the temperature of the second stage is controlled at 935°C for 90s, and cooled in 95°C water.

(5) Cold rolling the normalized steel strip, the thickness before rolling is 3.0mm, the thickness after rolling is 0.3mm, the total deformation is 90.0%, and the third and fourth passes of cold rolling are coated on the surface of the steel strip Na ₂ CO ₃ aqueous solution, keep the strip temperature at 200°C.

(6) Carry out decarburization annealing on strip steel after cold rolling, alkali wash and dry the surface of the steel plate before annealing, then rapidly raise the temperature, adopt two-stage decarburization annealing, control the temperature of the first stage to 865°C, the time is 180s, and control the second stage The temperature is 895°C, the time is 35s, the atmosphere used is wet 78% nitrogen + 22% hydrogen (volume ratio), the dew point is 43°C, and the cooling section is dry 78% nitrogen + 22% hydrogen (volume ratio).

(7) Carry out the high-temperature annealing of strip steel at last, before high-temperature annealing, coat MgO on strip steel surface, adopt high-temperature bell-type furnace annealing then, the atmosphere that adopts is 58%H ₂ +42%N ₂ (volume ratio), at first be heated up to 855°C, heat preservation for 5h, then heated to 1205°C in 100% _H2 atmosphere, heat preservation for 20h.

Example 2

According to this technological process, the matrix element and inhibitor element composition design of grain-oriented silicon steel is carried out. The composition of grain-oriented silicon steel in terms of mass percentage is: C0.025%, Si4.0%, Mn0.03%, S0.01%, Al0.07 %, N0.012%, Cu0.03%, Sn0.07%, Se0.05%, and the balance is Fe.

The specific rolling process of grain-oriented silicon steel is as follows.

(1) Using the above-mentioned design composition and smelted steel, a thin slab continuous casting machine is used to produce a 175mm continuous casting thin slab, the casting speed of the thin slab is 2.5m/min, and the casting temperature is 950°C.

(2) Compensation heating the cast slab in the heating furnace, the heating temperature is 1180° C., and the heating time is 220 minutes.

(3) The heated slab is subjected to rough rolling, the rough rolling entrance temperature is 1160°C, the rolled thickness is 35mm, the finish rolling entrance temperature is 1000°C, the finish rolling temperature is 920°C, and the rolled thickness is 3.0mm. The hot-rolled strip steel enters the laminar flow cooling zone for cooling, and the cooling rate is controlled at 50°C/s. After rolling, the hot-rolled strip steel enters the coiler for coiling, and the coiling temperature is 600°C.

(4) The steel coil is subjected to two-stage normalization treatment before cold rolling. The temperature of the first stage is controlled at 990°C for 20s, the temperature of the second stage is controlled at 920°C for 120s, and cooled in 99°C water.

(5) Cold rolling the normalized steel strip, the thickness before rolling is 2.0mm, the thickness after rolling is 0.4mm, the total deformation is 80%, the third and fourth passes of cold rolling are on the surface of the strip surface Coat Na ₂ CO ₃ aqueous solution and keep the strip temperature at 210°C.

(6) Carry out decarburization annealing on strip steel after cold rolling, alkali wash and dry the surface of the steel plate before annealing, then rapidly raise the temperature, adopt two-stage decarburization annealing, control the temperature of the first stage to 850°C, the time is 120s, and control the second stage The temperature is 880°C, the time is 60s, the atmosphere used is wet 75% nitrogen + 25% hydrogen (volume ratio), the dew point is 45°C, and the cooling section is dry 75% nitrogen + 25% hydrogen (volume ratio).

(7) Carry out the high-temperature annealing of strip steel at last, before high-temperature annealing, coat MgO on the surface of strip steel, adopt high-temperature bell-type furnace annealing then, the atmosphere that adopts is 55%H ₂ +45%N ₂ (volume ratio), at first be heated up to 840°C, keep warm for 6h, then heat to 1190°C in 100% _H2 atmosphere, keep warm for 15h.

Example 3

According to this technological process, the composition of grain-oriented silicon steel matrix elements and inhibitor elements is designed, and the composition of grain-oriented silicon steel in terms of mass percentage is: C0.08%, Si2.8%, Mn0.14%, S0.06%, Al0.016% , N0.004%, Cu0.14%, Sn0.15%, Se0.01%, and the balance is Fe.

The specific rolling process of grain-oriented silicon steel is as follows.

(1) Using the above-mentioned design composition and smelted steel, the thin slab continuous casting machine is used to produce 260mm continuous casting thin slab, the thin slab casting speed is 3m/min, and the casting slab temperature is 1100°C.

(2) The slab is compensated and heated in a heating furnace at a heating temperature of 1150° C. for 240 minutes.

(3) The heated slab is subjected to rough rolling, the rough rolling entrance temperature is 1130°C, the rolled thickness is 45mm, the finish rolling entrance temperature is 1100°C, the final rolling temperature is 950°C, and the rolled thickness is 4.0mm. The hot-rolled strip enters the laminar flow cooling zone for cooling, and the cooling rate is controlled at 100°C/s. After rolling, the hot-rolled strip enters the coiler for coiling, and the coiling temperature is 650°C.

(4) Steel coils need to undergo two-stage normalization treatment before cold rolling. The temperature of the first stage is controlled at 1100°C for 60s, the temperature of the second stage is controlled at 950°C for 60s, and cooled in 90°C water.

(5) Cold rolling the strip after normalization treatment, the thickness before rolling is 4.0mm, the thickness after rolling is 0.2mm, the total deformation is 95%, the third and fourth passes of cold rolling are on the surface of the strip Coat Na ₂ CO ₃ aqueous solution and keep the strip temperature at 250°C.

(6) Carry out decarburization annealing on strip steel after cold rolling, alkali wash and dry the surface of the steel plate before annealing, and then rapidly raise the temperature, adopt two-stage decarburization annealing, control the temperature of the first stage to 880°C, the time is 240s, and control the second stage The temperature is 910°C, the time is 10s, the atmosphere used is wet 80% nitrogen + 20% hydrogen (volume ratio), dew point 50°C, and 80% nitrogen + 20% hydrogen (volume ratio) in the cooling section.

(7) Carry out the high-temperature annealing of strip steel at last, coat MgO on the strip steel surface before high-temperature annealing, adopt high-temperature bell-type furnace annealing then, the atmosphere that adopts is 60%H ₂ +40%N ₂ (volume ratio), at first be heated up to 870°C, keep warm for 4h, then heat to 1210°C in 100% _H2 atmosphere, keep warm for 25h.

Claims (5)

1. A method for producing oriented silicon steel strips by direct rolling of continuous casting slabs, the process steps comprising continuous casting slabs, hot rolling, normalized annealing, cold rolling, decarburization annealing, high temperature annealing, characterized in that process steps and process requirement is: Design oriented silicon steel matrix element and inhibitor element composition, by mass percentage: C 0.025～0.08%, Si2.8～4.0%, Mn 0.03～0.14%, S 0.01～0.06%, Al 0.016～0.07%, N 0.004～0.012%, Cu 0.03～0.14%, Sn 0.07～0.15%, Se 0.01～0.05%, the balance is Fe; Design composition, smelting molten steel, producing continuous casting slab, casting slab temperature is 800~1100℃, slab casting speed is 2~3m/min; after that The continuous casting slab is directly subjected to compensation heating, the compensation heating temperature is 1150-1220°C, and the time is 210-240 minutes; after compensation heating Carry out hot rolling, the hot rolling rough rolling entrance temperature is 1130～1200℃, the finishing rolling entrance temperature is 950～1100℃, the finish rolling temperature is 850～1000℃, after that, the hot rolled steel strip is cooled, and the cooling rate is controlled to be 10～100℃. 100°C/s, and then coil the hot-rolled steel strip at a coiling temperature of 500-650°C; Coil strip normalization annealing is divided into two stages of normalization treatment, the temperature of the first stage is controlled at 990-1100°C for 20-60s, the temperature of the second stage is controlled at 920-950°C for 60-120s, and then 90 ~ 99 ℃ water cooling; Cold-roll the normalized steel strip with a total deformation of 80% to 95%, and coat the surface of the strip with Na ₂ CO ₃ aqueous solution during the third and fourth passes of cold rolling to maintain the temperature of the strip. 200～250℃; After cold rolling, the steel strip is decarburized and annealed. Before annealing, it is washed with alkali and the surface of the steel strip is dried. Two-stage decarburization annealing is adopted. The first stage controls the temperature at 850-880°C for 120-240s, and the second stage controls the temperature at 880-880°C. 910°C, the time is 10-60s, using a wet atmosphere, the volume ratio is 75-80% nitrogen + 20-25% hydrogen, the dew point is 30-50°C, the cooling section is dry, the volume ratio is 75-80% nitrogen+ 20-25% hydrogen; finally Carry out high-temperature annealing. Before high-temperature annealing, coat MgO on the surface of the steel strip. In an atmosphere with a volume ratio of 55-60% hydrogen + 40-45% nitrogen, first raise the temperature to 840-870°C, keep it for 4 hours, and then heat it up in a 100% hydrogen atmosphere. Heating to 1190-1220°C in medium temperature and keeping warm for 15-25 hours. 2. The method for producing oriented silicon steel strips by direct rolling of continuous casting slabs according to claim 1, characterized in that: said continuous casting slabs are produced by using a slab continuous casting machine to produce 90mm-260mm molten steel. continuous casting slabs. 3. The method for producing oriented silicon steel strips by direct rolling of continuous casting slabs according to claim 1, characterized in that the thickness of the continuous casting slabs is 25-45mm after hot rolling and rough rolling, and the thickness after hot rolling and final rolling is 2.0 ~ 4.0mm, after hot rolling, the strip enters the laminar flow cooling zone for cooling, and finally enters the coiler for coiling. 4. The method for producing oriented silicon steel strip by direct rolling of continuous casting slabs according to claim 1, characterized in that the thickness before cold rolling is 2.0-4.0 mm, and the thickness of the strip after cold rolling is 0.2-0.4 mm. 5. The method for producing oriented silicon steel strip by direct rolling of continuous casting slabs according to claim 1, characterized in that the high temperature annealing of the strip steel is performed by using a high temperature bell furnace for annealing.