CN108480587B - Production method of low-inclusion-defect-rate high-magnetic-induction oriented silicon steel - Google Patents

Abstract

The invention relates to a production method of high magnetic induction oriented silicon steel with low inclusion defect rate, which comprises the following steps: argon blowing is carried out in the whole smelting process of the converter, and the end point control is carried out after the converter is smelted: c is less than or equal to 0.040%; p is less than or equal to 0.011 percent; s is less than or equal to 0.005 percent; the alkalinity of the slag in the converting process is 3.0-3.5; the thickness of the slag is less than or equal to 80 mm; stopping slag when tapping is finished; calculating the liquidus width of the actual smelting components of the high magnetic induction oriented silicon steel; controlling the superheat degree of molten steel in the tundish by using the calculated liquidus width result, and controlling the temperature in the solidification process to be 90-130 ℃; electromagnetic stirring is put into the continuous casting process, a casting blank is delivered in a hot way after continuous casting, and the temperature of the casting blank is controlled to be more than or equal to 700 ℃. The advantages are that: the method can realize the rapid and accurate calculation of the width of the liquid phase line of the smelting components, reasonably design the technological parameters of continuous casting according to the calculation result, effectively control the quantity of impurities in the steel plate, improve the yield, save the cost and reduce the waste.

Description

Production method of low-inclusion-defect-rate high-magnetic-induction oriented silicon steel

Technical Field

The invention relates to a production method of high-magnetic-induction oriented silicon steel with low inclusion defect rate.

Background

Oriented silicon steel is divided into two main categories according to the magnetic induction intensity: the general oriented silicon steel CGO has the magnetic induction of less than 1.88T; the magnetic induction of the high-magnetic-induction oriented silicon steel HGO is more than or equal to 1.88T. The high magnetic induction grain-oriented silicon steel has the characteristics of high magnetic induction and low iron loss, and the manufactured transformer has low noise, is widely used for manufacturing high-capacity power transformers with voltage levels of more than 220KV and high-efficiency energy-saving distribution transformer cores, and has wider and wider application range due to the improvement of energy-saving and consumption-reducing requirements.

The high magnetic induction grain-oriented silicon steel was invented by Nippon Nissan iron company in the last 60 th century, and the company named ORIENTCORE Hi-B, HiB steel for short. The method is mainly characterized in that the plate blank is hot-rolled after being heated at high temperature, and the highest magnetic induction product can be produced by one-time cold rolling under high pressure.

Thereafter, the RGH high magnetic induction grain-oriented silicon steel was developed by kawasaki corporation in japan by the double cold rolling method.

High magnetic induction oriented silicon Steel (SL) produced by low-temperature slab heating and nitriding treatment in a later process developed by iron companies in the new era of the last 80 th century has the characteristics of low hot rolling heating temperature and high yield compared with HiB steel.

The domestic production of high magnetic induction grain-oriented silicon steel mainly adopts two technologies, one is HiB type HGO produced by taking MnS + AlN as a main inhibitor and hot rolling a slab at a high temperature; and the other method is to produce the SL-type HGO by taking AlN as a main inhibitor, heating a hot-rolled plate blank at low temperature and nitriding the hot-rolled plate blank in a post-process nitriding treatment mode.

No matter which way is adopted to produce the high magnetic induction oriented silicon steel, the precise control of the liquid phase line width is the main factor influencing the inclusion defects on the surface of the product. At present, the liquid phase line temperature is calculated by large oriented silicon steel manufacturers in China by adopting empirical formulas, the liquid phase line width cannot be accurately calculated, the control of the solidification process is directly fuzzy, when the liquid phase line width of actual casting components is narrow, a near liquid phase line temperature casting technology is used, as a result, the molten steel viscosity is high, inclusions are not easy to float, a large amount of macroscopic inclusions exist from the surfaces of a hot rolled plate and a normalized plate to the surface of a finished plate, the defects of finished products are many, the material rate is low, and a large amount of waste is caused.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a production method of oriented silicon steel with low inclusion defect rate and high magnetic induction, which eliminates inclusions in an oriented silicon steel hot rolled plate, a normalizing plate, a decarburization plate and a finished plate, improves the yield and reduces waste by accurately controlling a continuous casting process.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a production method of low inclusion defect rate high magnetic induction oriented silicon steel comprises the following steps:

1) smelting: argon blowing is carried out in the whole smelting process of the converter, and the end point control is carried out after the converter is smelted: c is less than or equal to 0.040%; p is less than or equal to 0.011 percent; s is less than or equal to 0.005 percent; the alkalinity of the slag in the converting process is 3.0-3.5; the thickness of the slag is less than or equal to 80 mm; stopping slag when tapping is finished; calculating the liquidus width of the actual smelting components of the high magnetic induction oriented silicon steel; the liquidus width of the actual smelting components of the high magnetic induction oriented silicon steel is calculated by Thermo-Calc software.

2) Continuous casting: controlling the superheat degree of molten steel in the tundish by using the calculated liquidus width result, and controlling the temperature in the solidification process to be 90-130 ℃; if the width of the liquidus is large, the ratio of isometric crystals is improved by adopting near liquidus pouring, and if the width of the liquidus is small, the superheat degree needs to be improved, and the temperature interval of the solidification process is enlarged to lead to the inclusion of a sufficient floating process;

determining the casting blank pulling speed according to the calculated liquidus width result, and controlling the casting blank pulling speed to be 0.80-1.30 m/min if the liquidus width is 80-130 ℃; when the liquid line width is lower than 80 ℃, the casting blank pulling speed is controlled to be 0.4-0.80 m/min;

electromagnetic stirring is put into the continuous casting process, a casting blank is delivered in a hot way after continuous casting, and the temperature of the casting blank is controlled to be more than or equal to 700 ℃;

3) hot rolling:

if the high magnetic induction oriented silicon steel comprises the following chemical components in percentage by weight:

0.02 to 0.05 percent of C, 2.8 to 3.8 percent of Si, 0.10 to 0.16 percent of Mn, less than or equal to 0.008 percent of S, 0.02 to 0.04 percent of Als, 0.006 to 0.012 percent of N, 0.08 to 0.4 percent of Cu, 0.03 to 0.15 percent of Sn, and the balance of Fe and inevitable impurities; when the temperature of the soaking section of the plate blank reaches 1200 ℃, the temperature is kept for more than 80 minutes, the temperature difference between the upper surface and the lower surface is less than or equal to 50 ℃, the tapping temperature is 1190-1220 ℃, the thickness range of the intermediate blank is 38-45 mm, the outlet temperature range of the finish rolling is 920 +/-20 ℃, and the coiling temperature is 550 +/-20 ℃;

if the high magnetic induction oriented silicon steel comprises the following chemical components in percentage by weight:

0.03 to 0.08 percent of C, 3.1 to 3.4 percent of Si, 0.06 to 0.16 percent of Mn, less than or equal to 0.03 percent of P, 0.02 to 0.03 percent of S, 0.02 to 0.03 percent of Als, 0.004 to 0.013 percent of N, and the balance of Fe and inevitable impurities; when the temperature of the soaking section of the plate blank reaches 1300 ℃, the temperature is kept for more than 120 minutes, the temperature difference between the upper surface and the lower surface is less than or equal to 50 ℃, the tapping temperature is 1310-1280 ℃, the thickness range of the intermediate blank is 38-45 mm, the temperature range of the outlet of the finish rolling is 1050 +/-20 ℃, and the coiling temperature is less than 600 ℃;

finally, the product is manufactured by the process of cold rolling and subsequent processes.

Compared with the prior art, the invention has the beneficial effects that:

the method can realize the fast and accurate calculation of the width of the liquid phase line of the smelting components, reasonably design the technological parameters of continuous casting according to the calculation result, effectively control the quantity of inclusions in the steel plate, improve the yield, save the cost and reduce the waste. The calculation of Thermo-Calc software provides theoretical basis for reasonable design of pouring process parameters, and the impurities in the oriented silicon steel hot rolled plate, the normalizing plate, the decarburization plate and the finished plate are eliminated by realizing the accurate control of the continuous casting process, so that the yield is improved, and the waste is reduced.

Detailed Description

The present invention is described in detail below, but it should be noted that the practice of the present invention is not limited to the following embodiments.

A production method of low inclusion defect rate and high magnetic induction oriented silicon steel adopts Thermo-Cal software to accurately calculate the width of a liquid phase line of smelting components, reasonably designs continuous casting process parameters according to a calculation result, effectively controls the inclusion amount in a steel plate, and has the following process flows: smelting → continuous casting → hot rolling → normalizing → acid washing → one-time cold rolling → decarburization annealing (nitriding) coating MgO → high temperature annealing → coating insulating layer and hot stretching flattening, which comprises the following steps:

1) smelting:

the high magnetic induction oriented silicon steel comprises the following components:

the SL type HGO comprises the following chemical components in percentage by weight:

0.02 to 0.05 percent of C, 2.8 to 3.8 percent of Si, 0.10 to 0.16 percent of Mn, less than or equal to 0.008 percent of S, 0.02 to 0.04 percent of Als, 0.006 to 0.012 percent of N, 0.08 to 0.4 percent of Cu, 0.03 to 0.15 percent of Sn, and the balance of Fe and inevitable impurities;

the HiB type HGO comprises the following chemical components in percentage by weight:

0.03 to 0.08 percent of C, 3.1 to 3.4 percent of Si, 0.06 to 0.16 percent of Mn, less than or equal to 0.03 percent of P, 0.02 to 0.03 percent of S, 0.02 to 0.03 percent of Als, 0.004 to 0.013 percent of N, and the balance of Fe and inevitable impurities;

blowing argon in the whole converter smelting process, and controlling the C to be less than or equal to 0.040% at the end point after the converter is smelted; p is less than or equal to 0.011 percent; s is less than or equal to 0.005 percent; the alkalinity of the slag in the converting process is 3.0-3.5; the thickness of the slag is less than or equal to 80 mm; stopping slag when tapping is finished, and preventing converter slag from falling into a steel ladle; fine adjustment of components is carried out in the RH refining process, so that the component requirements of the high-magnetic-induction oriented silicon steel are met; calculating the liquidus width of the actual smelting components of the high-magnetic induction oriented silicon steel by adopting Thermo-Cal software;

2) continuous casting

a, controlling the superheat degree of molten steel in a tundish according to a liquidus width result calculated by Thermo-Calc software, ensuring that the temperature interval of a solidification process is 90-130 ℃, adopting near-liquidus pouring to improve the isometric crystal proportion if the liquidus width is large, and increasing the superheat degree if the liquidus width is small, so that a sufficient floating process is included in the temperature interval of the solidification process;

b, designing the casting blank pulling speed according to the liquid phase line width calculated by Thermo-Calc software, wherein the liquid phase line width is large, the casting blank pulling speed is large, and when the liquid phase line width is small, the pulling speed is reduced in order to enable inclusions in molten steel to float sufficiently; wherein, the liquidus width is liquidus temperature-solidus temperature; the values for liquidus and solidus temperatures were calculated by Thermo-Calc software.

c, in order to reduce the proportion of columnar crystals, electromagnetic stirring is required to be put into the continuous casting process;

d, after continuous casting, the casting blank must be hot-fed, and the temperature of the casting blank must be guaranteed to be more than or equal to 700 ℃.

3) Hot rolling

HGO of SL type

When the temperature of the soaking section of the plate blank reaches 1200 ℃, the temperature is kept for more than 80 minutes, the temperature difference between the upper surface and the lower surface is less than or equal to 50 ℃, the tapping temperature is 1190-1220 ℃, the thickness range of the intermediate blank is 38-45 mm, the temperature range of the outlet of the finish rolling is 920 +/-20 ℃, and the coiling temperature is 550 +/-20 ℃;

HiB type HGO

When the temperature of the soaking section of the plate blank reaches 1300 ℃, the temperature is preserved for more than 120 minutes, the temperature difference between the upper surface and the lower surface is less than or equal to 50 ℃, the tapping temperature is 1310-1280 ℃, the thickness range of the intermediate blank is 38-45 mm, the temperature range of the outlet of the finish rolling is 1050 +/-20 ℃, and the coiling temperature is less than 600 ℃.

4) Normalizing cold rolling and subsequent process

After normalizing the hot rolled plate, cold rolling the plate to a thickness close to the thickness of a finished product by one-time high reduction rate, decarburizing and annealing the cold rolled plate, nitriding the cold rolled plate, coating MgO separant on the cold rolled plate, then carrying out high-temperature annealing in an annular furnace, and carrying out hot drawing and flattening annealing on the high-temperature annealed plate and coating a stress coating on the high-temperature annealed plate to prepare the finished oriented silicon steel.

And (3) performance detection:

(1) and detecting that the surfaces of the hot rolled plate, the normalizing plate, the decarburization annealing plate and the finished plate have no impurities.

(2) And detecting the magnetic property of the finished plate.

Example 1

The production method of the oriented silicon steel with low inclusion defect rate and high magnetic induction comprises the following steps:

1) smelting

a) Smelting an SL type HGO in one tank, wherein the chemical components in percentage by weight are as follows:

0.05% of C, 3.3% of Si, 0.12% of Mn, 0.005% of S, 0.028% of Als, 0.007% of N, 0.2% of Cu, 0.06% of Sn and the balance of Fe and inevitable impurities;

b) argon is blown in the whole smelting process of the converter, and the end points C, P and S are controlled to be 0.035%, 0.008% and 0.004% after the converter is smelted;

c) the alkalinity of slag in the converting process is 3.2; the slag thickness is 70mm, slag blocking is carried out after tapping, and no converter slag falls into a steel ladle;

d) fine adjustment of components in an RH refining furnace to obtain the chemical components of the SL-type HGO in the step a;

e) and (3) calculating the liquidus width of the SL type HGO in the step a to be 60 ℃ from 1487 ℃ to 1427 ℃ by using Thermo-Cal software.

2) Continuous casting

a) Calculating the liquidus width of smelting components by Thermo-Calc software to be 60 ℃, controlling the superheat degree of molten steel in the tundish to be 45 ℃, namely the pouring temperature to be 1532 ℃, ensuring the temperature interval of the solidification process to be 105 ℃, and enabling the inclusion of a sufficient floating process;

b) the liquid line width calculated by Thermo-Calc software is 60 ℃, and the casting blank pulling speed is 0.7m/min in order to ensure that inclusions in molten steel are fully floated;

c) electromagnetic stirring is added in the continuous casting process, and a casting blank is delivered in a hot manner after continuous casting, wherein the temperature of the casting blank is 720 ℃.

3) Hot rolling

And (3) keeping the temperature of the soaking section of the plate blank at 1200 ℃ for 100 minutes, discharging the plate blank, wherein the temperature difference between the upper surface and the lower surface is 20 ℃, the thickness of the intermediate blank is 40mm, the outlet temperature of the finish rolling is 940 ℃, and the coiling temperature is 560 ℃.

4) Normalized cold rolling and performance testing

After normalizing the hot rolled plate, cold rolling the plate to a thickness close to the thickness of a finished product by one-time high reduction rate, decarburizing and annealing the cold rolled plate, nitriding the cold rolled plate, coating MgO separant on the cold rolled plate, then carrying out high-temperature annealing in an annular furnace, and carrying out hot drawing and flattening annealing on the high-temperature annealed plate and coating a stress coating on the high-temperature annealed plate to prepare the finished oriented silicon steel.

1) And detecting that the surfaces of the hot rolled plate, the normalizing plate, the decarburization annealing plate and the finished plate have no impurities.

2) Average magnetic property of the finished plate was measured to be J₈₀₀＝1.888T，P_1.7＝1.05W/kg。

Example 2

The production method of the oriented silicon steel with low inclusion defect rate and high magnetic induction comprises the following steps:

1) smelting

a) Smelting a HiB type HGO in one tank, wherein the chemical components in percentage by weight are as follows:

0.055% of C, 3.2% of Si, 0.08% of Mn, 0.010% of P, 0.023% of S, 0.022% of Als, 0.008% of N, and the balance of Fe and inevitable impurities;

b) argon is blown in the whole smelting process of the converter, and the end points C, P and S are controlled to be 0.03%, 0.01% and 0.005% respectively after the converter is smelted;

c) the alkalinity of slag in the converting process is 3.2; the slag thickness is 60mm, slag blocking is carried out after tapping, and no converter slag falls into a steel ladle;

d) fine adjustment of components in an RH refining furnace to obtain the HiB type HGO chemical components in the step a;

e) the width of the liquid phase line of the HiB type HGO in step a was calculated to be 109 ℃ from 1489 ℃ to 1380 ℃ using Thermo-Cal software.

2) Continuous casting

a) The Thermo-Calc software calculates the liquidus width of smelting components to be 109 ℃, controls the superheat degree of molten steel in the tundish to be 11 ℃, namely the pouring temperature to be 1500 ℃, the temperature interval of the solidification process to be 120 ℃, and is mixed with a sufficient floating process;

b) the liquid line width calculated by Thermo-Calc software is 109 ℃, and the casting blank pulling speed is 1.05 m/min;

c) electromagnetic stirring is added in the continuous casting process, and a casting blank is delivered in a hot way after continuous casting, wherein the temperature of the casting blank is 700 ℃.

3) Hot rolling

And (3) keeping the temperature of the soaking section of the plate blank at 1200 ℃ for 100 minutes, discharging the plate blank, wherein the temperature difference between the upper surface and the lower surface is 20 ℃, the thickness of the intermediate blank is 40mm, the outlet temperature of the finish rolling is 940 ℃, and the coiling temperature is 560 ℃.

4) Normalized cold rolling and performance testing

After normalizing the hot rolled plate, cold rolling the plate to a thickness close to the thickness of a finished product by one-time high reduction rate, decarburizing and annealing the cold rolled plate, nitriding the cold rolled plate, coating MgO separant on the cold rolled plate, then carrying out high-temperature annealing in an annular furnace, and carrying out hot drawing and flattening annealing on the high-temperature annealed plate and coating a stress coating on the high-temperature annealed plate to prepare the finished oriented silicon steel.

1) And detecting that the surfaces of the hot rolled plate, the normalizing plate, the decarburization annealing plate and the finished plate have no impurities.

2) Average magnetic property of the finished plate was measured to be J₈₀₀＝1.883T，P_1.7＝1.08W/kg。

And (4) comparing the results:

the magnetic properties and surface quality of high magnetic induction grain-oriented silicon steel produced by the casting process designed by the empirical formula calculation liquidus method were compared with the examples, as shown in table 1.

Table 1: comparison of results

As can be seen from table 1:

(1) the magnetic properties of examples 1 and 2 are very different from those of comparative examples 1 and 2;

(2) the surface of example 1 had no inclusions, while the surface of comparative example 1, in which the casting process was designed using an empirical formula, had a large amount of inclusions;

(3) the surface of example 2 and comparative example 2 had no inclusions;

by adopting the method, the surface defect rate of the high-magnetic-induction oriented silicon steel can be effectively reduced.

Claims (1)

1. A production method of oriented silicon steel with low inclusion defect rate and high magnetic induction is characterized by comprising the following steps:

1) smelting: argon blowing is carried out in the whole smelting process of the converter, and the end point control is carried out after the converter is smelted: c is less than or equal to 0.040%; p is less than or equal to 0.011 percent; s is less than or equal to 0.005 percent; the alkalinity of the slag in the converting process is 3.0-3.5; the thickness of the slag is less than or equal to 80 mm; stopping slag when tapping is finished; calculating the liquidus width of the actual smelting components of the high magnetic induction oriented silicon steel; the liquidus width of the actual smelting components of the high magnetic induction oriented silicon steel is calculated by Thermo-Calc software.

2) Continuous casting: controlling the superheat degree of molten steel in the tundish by using the calculated liquidus width result, and controlling the temperature in the solidification process to be 90-130 ℃; if the width of the liquidus is large, the ratio of isometric crystals is improved by adopting near liquidus pouring, and if the width of the liquidus is small, the superheat degree needs to be improved, and the temperature interval of the solidification process is enlarged to lead to the inclusion of a sufficient floating process;

determining the casting blank pulling speed according to the calculated liquidus width result, and controlling the casting blank pulling speed to be 0.80-1.30 m/min if the liquidus width is 80-130 ℃; when the liquid line width is lower than 80 ℃, the casting blank pulling speed is controlled to be 0.4-0.80 m/min;

electromagnetic stirring is put into the continuous casting process, a casting blank is delivered in a hot way after continuous casting, and the temperature of the casting blank is controlled to be more than or equal to 700 ℃;

3) hot rolling:

if the high magnetic induction oriented silicon steel comprises the following chemical components in percentage by weight:

0.02 to 0.05 percent of C, 2.8 to 3.8 percent of Si, 0.10 to 0.16 percent of Mn, less than or equal to 0.008 percent of S, 0.02 to 0.04 percent of Als, 0.006 to 0.012 percent of N, 0.08 to 0.4 percent of Cu, 0.03 to 0.15 percent of Sn, and the balance of Fe and inevitable impurities; when the temperature of the soaking section of the plate blank reaches 1200 ℃, the temperature is kept for more than 80 minutes, the temperature difference between the upper surface and the lower surface is less than or equal to 50 ℃, the tapping temperature is 1190-1220 ℃, the thickness range of the intermediate blank is 38-45 mm, the outlet temperature range of the finish rolling is 920 +/-20 ℃, and the coiling temperature is 550 +/-20 ℃;

if the high magnetic induction oriented silicon steel comprises the following chemical components in percentage by weight:

0.03 to 0.08 percent of C, 3.1 to 3.4 percent of Si, 0.06 to 0.16 percent of Mn, less than or equal to 0.03 percent of P, 0.02 to 0.03 percent of S, 0.02 to 0.03 percent of Als, 0.004 to 0.013 percent of N, and the balance of Fe and inevitable impurities; when the temperature of the soaking section of the plate blank reaches 1300 ℃, the temperature is kept for more than 120 minutes, the temperature difference between the upper surface and the lower surface is less than or equal to 50 ℃, the tapping temperature is 1310-1280 ℃, the thickness range of the intermediate blank is 38-45 mm, the temperature range of the outlet of the finish rolling is 1050 +/-20 ℃, and the coiling temperature is less than 600 ℃;

finally, the product is manufactured by the process of cold rolling and subsequent processes.