阅读说明：本技术 一种管线钢的夹杂物控制方法 (Method for controlling inclusions in pipeline steel ) 是由 秦哲 张俊志 王云东 朱志强 李晓冬 刘先同 张万金 蒲锐 张海波 王锃 董光军 于 2020-12-28 设计创作，主要内容包括：本发明涉及钢铁技术领域,具体涉及一种管线钢的夹杂物控制方法,所述控制方法包括如下步骤：S1、转炉冶炼；S2、出钢；S3、LF炉精炼：精炼过程中进行钙前软吹、钙处理和钙后软吹,终渣渣系目标为[CaO]：53％-59％、[Al-2O-3]：26％-34％、[SiO-2]≤10％、[MgO]≤10％、FeO+MnO≤1.2％；S4、连铸机保护浇铸成坯。该控制方法满足生产效率高、产品性能稳定、成本较低的要求,尤其是废钢比较高的生产条件,工艺特点为软吹工艺合适、钢水洁净度高、连铸二次氧化小、操作简单易行等,该控制方法能够起到提高管线钢夹杂物检测合格率,达到减少改判、提高产品质量以及降低成本的技术效果。(The invention relates to the technical field of steel, in particular to a method for controlling inclusions in pipeline steel, which comprises the following steps: s1, smelting in a converter; s2, tapping; s3, refining in an LF furnace: carrying out soft blowing before calcium treatment, soft blowing after calcium treatment and soft blowing after calcium treatment in the refining process, wherein the final slag system is aimed at [ CaO ]]：53％‑59％、[Al 2 O 3 ]：26％‑34％、[SiO 2 ]≤10％、[MgO]Less than or equal to 10 percent, and less than or equal to 1.2 percent of FeO and MnO; and S4, protecting the casting blank by a continuous casting machine. The control method meets the requirements of high production efficiency, stable product performance and lower cost, particularly meets the production conditions of higher scrap steel ratio,the control method has the advantages of improving the detection qualification rate of the inclusion of the pipeline steel, and achieving the technical effects of reducing the judgment, improving the product quality and reducing the cost.)

1. A method for controlling inclusions in pipeline steel, the method comprising the steps of:

s1, smelting in a converter;

s2, tapping;

s3, refining in an LF furnace:

performing soft blowing before calcium, calcium treatment and soft blowing after calcium in the refining process, wherein the soft blowing before calcium is 3-5min, the flow is properly increased, and the argon blowing effect is based on the diameter of argon flower of 200-300 mm;

the calcium treatment wire feeding amount is 120-180 m/furnace, 20-30 m/furnace is properly added for abnormal times, the wire feeding process is protected by argon, and the target of the middle package [ Ca ] is 12-28 ppm;

the soft blowing time after calcium is more than or equal to 15min, the argon blowing effect is based on the slag surface creeping diameter of 100-200mm, and the molten steel is strictly forbidden to be exposed in the process;

the final slag system is targeted at [ CaO ]]：53％-59％、[Al₂O₃]：26％-34％、[SiO₂]≤10％、[MgO]≤10％、FeO+MnO≤1.2％；

S4, protecting and casting a blank by a continuous casting machine:

the tundish baking time for casting the pipeline steel and the yield of the tundish is more than or equal to 500t is 3-3.5h, and the baking temperature is more than or equal to 1100 ℃;

continuously carrying out middle ladle argon replacement from the closing of the ladle baking device to the pouring of the big ladle;

the flow rate of the argon seal blowing of the large ladle is 20-80L/min;

the thickness of the middle ladle slag layer is controlled to be less than or equal to 60 mm;

the argon blowing flow of the stopper rod is controlled according to 4-8 NL/min;

the covering slag adopts black slag operation, the slag consumption is 0.4-0.6kg/t, the thickness of the liquid slag layer is 8-15mm, and the thickness of the total slag layer is 35-45 mm;

the service time of the long nozzle is less than or equal to 4h, the insertion depth of the ladle nozzle is more than or equal to 200mm, and the insertion depth of the immersion nozzle is 120-140 mm;

a steel ladle electromagnetic induction slag discharging detection control system is adopted to control the sliding plate to automatically close when the proportion of the large ladle steel slag reaches 12% -30%, or steel is left for 3 t;

the casting tonnage of the tundish is more than or equal to 10t, so that the casting slag entrapment phenomenon is reduced;

full ladle casting is carried out during normal casting, the ladle weighing fluctuation is less than or equal to 3t, and the ladle weighing is more than or equal to 28 t; during the replacement period of the ladle, the weight of the tundish is more than or equal to 16 t;

the pulling speed is executed according to the standard requirement of steel grade, the pulling speed is constant in continuous casting furnace time except for a water changing port, the pulling speed is strictly prohibited from changing frequently, and the pulling speed change in the process is less than or equal to 0.05 m/min.

2. The control method as claimed in claim 1, wherein the S1 has an end point T.gtoreq.1610 ℃ and T [ O ] of 750ppm or less.

3. The control method of claim 1, wherein the tapping time of S2 is more than or equal to 4min or the tapping frequency is less than or equal to 220, the steel flow has no flow scattering phenomenon, the slag is retained after tapping, and 300kg of top slag lime and 100kg of modifier are added for slag washing during the tapping process.

4. The control method as claimed in claim 1, wherein the refining time of S3 is 40-80min, and the micro positive pressure is controlled in the whole process.

5. The control method of claim 1, wherein the adding of the aluminum-containing alloy is strictly prohibited within 8min before the soft blowing of S3; the soft blowing and calcium treatment process forbids the operations of aluminum supplement, alloy supplement and heating.

6. The control method according to claim 1, wherein the fluctuation > ± 5mm of S4 corresponds to the casting blank judging the low grade steel grade or judging the scrap; and judging the low-grade steel grade or judging the waste of the head and tail billets corresponding to the casting billets due to the abnormal head and tail billets and the abnormal process.

7. The control method according to claim 1, wherein the step S4 is performed by fixing the intermediate package partition wall by using dry-type sintering and dry-type ramming material.

8. The control method as claimed in claim 1, wherein the S4 long nozzle seal is intact, and the long nozzle sleeve is right perpendicular to the tundish liquid level.

9. The control method as claimed in claim 1, wherein the covering agent of S4 uses low-silicon high-alkalinity covering agent, and no molten steel is exposed in the process.

Technical Field

The invention relates to the technical field of steel, in particular to a method for controlling inclusions in pipeline steel.

Background

Pipeline steel has been widely used in the construction of oil and gas transmission pipelines, and in order to meet the ever-increasing toughness requirements of pipeline steel, particularly the requirements for the HIC (hydrogen induced cracking) resistance of acid gas transmission pipelines, technicians have made extensive studies on reducing the S content in steel in the past 60 years. The Ca treatment is a key technology for producing pipeline steel, and aims and functions to spheroidize and modify sulfides (mainly existing in molten steel in a MnS form) in the steel, namely to change the sulfides into spherical high-melting-point non-deformable inclusion CaS so as to improve the crack resistance of the pipeline steel. w ([ Ca ])/w ([ S ]) is 1.5 to 3.0. Since calcium has a very limited solubility in molten steel, the sulfur content of molten steel must be extremely low, and if the sulfur content is less than 15ppm, the calcium-sulfur ratio may not be considered.

However, after calcium treatment, composite inclusions such as low-melting-point calcium aluminate and the like are easily formed, the low-melting-point calcium aluminate is softened at the rolling temperature and is easily crushed, and discontinuous long-strip-shaped inclusions are formed in steel and exceed the standard due to long length.

Therefore, it is necessary to provide a method for controlling inclusions in pipeline steel to solve the problem of excessive length of inclusions in pipeline steel due to calcium treatment.

Disclosure of Invention

The invention provides an inclusion control method of pipeline steel, aiming at the technical problem that the overlength of inclusions exceeds the standard after the pipeline steel is subjected to calcium treatment, the control method meets the requirements of high production efficiency, stable product performance and lower cost, particularly the production condition that scrap steel is higher, the process is characterized by proper soft blowing process, high molten steel cleanliness, small continuous casting secondary oxidation, simple and easy operation and the like, the control method can improve the detection qualification rate of the inclusions in the pipeline steel, achieve the technical effects of reducing the judgment, improving the product quality and reducing the cost, and simultaneously solve the problems that the control difficulty of the inclusions generated when the pipeline steel is smelted at present is large, and the large inclusions are left in the pipeline steel to influence the HIC resistance of the steel.

A method for controlling inclusions in pipeline steel, the method comprising the steps of:

s1, smelting in a converter;

s2, tapping;

s3, refining in an LF furnace:

performing soft blowing before calcium, calcium treatment and soft blowing after calcium in the refining process, wherein the soft blowing before calcium is 3-5min, the flow is properly increased, and the argon blowing effect is based on the diameter of argon flower of 200-300 mm;

the calcium treatment feeding amount is 120-;

the soft blowing time after calcium is more than or equal to 15min, the argon blowing effect is based on the slag surface creeping diameter of 100-;

the final slag system is targeted at [ CaO ]]：53％-59％、[Al₂O₃]：26％-34％、[SiO₂]≤10％、[MgO]≤10％、FeO+MnO≤1.2％；

S4, protecting and casting a blank by a continuous casting machine:

the tundish baking time for casting the pipeline steel and the yield of the tundish is more than or equal to 500t is 3-3.5h, and the baking temperature is more than or equal to 1100 ℃;

continuously carrying out middle ladle argon replacement from the closing of the ladle baking device to the pouring of the big ladle;

the flow rate of the argon seal blowing of the large ladle is 20-80L/min;

the thickness of the middle ladle slag layer is controlled to be less than or equal to 60 mm;

the argon blowing flow of the stopper rod is controlled according to 4-8 NL/min;

the covering slag adopts black slag operation, the slag consumption is 0.4-0.6kg/t, the thickness of a liquid slag layer is 8-15mm, the thickness of a total slag layer is 35-45mm, and unsealed, overdue or wet covering slag is forbidden to be used;

the service time of the long nozzle is less than or equal to 4h, the insertion depth of the ladle nozzle is more than or equal to 200mm, and the insertion depth of the immersion nozzle is 120-140 mm;

a steel ladle electromagnetic induction slag discharging detection control system is adopted to control the sliding plate to automatically close when the proportion of the large ladle steel slag reaches 12% -30%, or steel is left for 3 t;

the casting tonnage of the tundish is more than or equal to 10t, so that the casting slag entrapment phenomenon is reduced;

full ladle casting is carried out during normal casting, the ladle weighing fluctuation is less than or equal to 3t, and the ladle weighing is more than or equal to 28 t; during the replacement period of the ladle, the weight of the tundish is more than or equal to 16 t;

the pulling speed is executed according to the standard requirement of steel grade, the pulling speed is constant in continuous casting furnace time except for a water changing port, the pulling speed is strictly prohibited from changing frequently, and the pulling speed change in the process is less than or equal to 0.05 m/min.

Furthermore, the terminal point T of S1 is not less than 1610 ℃, and T [ O ] is not more than 750 ppm.

Further, the tapping time of S2 is more than or equal to 4min or the tapping frequency is less than or equal to 220 (mainly the tapping time), the steel flow does not have the flow scattering phenomenon, the slag is retained after tapping, and 300kg of top slag lime and 100kg of modifier are added in the tapping process for slag washing.

Further, the refining time of S3 is 40-80min, and the whole process is controlled by micro positive pressure, wherein the refining time of the L245M/L290M series pipeline steel is more than 40min, and the refining time of other series pipeline steel is more than 50 min.

Further, aluminum-containing alloy is strictly forbidden to be supplemented within 8min before the soft blowing of S3, so that the castability of molten steel is ensured;

the soft blowing and calcium treatment process forbids the operations of aluminum supplement, alloy supplement and heating.

Furthermore, the fluctuation > +/-5 mm of S4 is corresponding to the casting blank, and the low-grade steel grade is judged or the waste is judged;

and (4) judging the low-grade steel grade or judging the waste of the head and tail billets corresponding to the casting billets due to abnormal processes (drainage, open casting and the like).

Further, in the step S4, a middle package partition wall is fixed by using dry material sintering and dry ramming material.

Furthermore, the sealing gasket of the long nozzle of the S4 nozzle is intact, and the long nozzle sleeve is just vertical to the liquid level of the tundish.

Furthermore, the covering agent of S4 uses low-silicon high-alkalinity covering agent (slag alkalinity in impact area is more than 1.5, FeO + MnO is less than 3%), no molten steel is exposed in the process, wherein when the pipeline steel is directly cast, the low-silicon high-alkalinity covering agent is selected; when the pipeline steel is mixed and poured after the general steel is poured, the low-silicon high-alkalinity covering agent is uniformly used for the general steel after the same pouring time and before the pipeline steel is mixed and poured.

The beneficial effect of the invention is that,

in order to meet the requirement of the pipeline steel on inclusion, the invention controls the quantity and the size of non-metal inclusion in the steel by measures such as converter process optimization, refining process optimization, accurate calcium treatment, soft blowing time control, tundish slag oxidability control, tundish refractory material moisture (tundish baking time) control, continuous casting process protective casting, ladle slag discharging control and the like, so that the large inclusion can float upwards fully, the rolling-in of the large inclusion in the continuous casting process can be avoided, the size and the number of the large inclusion can be controlled within a certain range, the qualification rate of the produced pipeline steel with inclusion once detected is greatly improved, and the stable production of steel grades can be realized.

The yield is increased by 5 percent, the annual sales of pipeline steel is calculated by 30 ten thousand tons, the judging amount is reduced by 1.5 ten thousand tons, the price is reduced by 300 RMB per ton, and the efficiency can be increased by 450 RMB/year. Meanwhile, other steel grades with strict requirements on inclusions can be produced by adopting the patented technology, the cleanliness of other products is further improved, the market application is expanded, and the product competitiveness is improved.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The pipeline steel controls the inclusions according to the following method, and specifically comprises the following steps:

s1, smelting in a converter: the end point temperature T is 1619 deg.C, and T [ O ] is 594 ppm;

s2, tapping the steel hole well, wherein the tapping time is 4.5min, the tapping frequency is 145 (mainly the tapping time), the steel flow has no flow scattering phenomenon, and the steel flow is tapped to block slag;

adding 300kg of top slag lime and 100kg of modifier in the tapping process for slag washing;

s3, refining in an LF furnace:

(1) controlling the refining time: refining time is 69 min;

(2) whole-process micro-positive pressure control;

(3) aluminum is supplemented in the process: aluminum-containing alloy is not supplemented within 8min before soft blowing;

(4) controlling gas: argon protection is performed in the wire feeding process;

(5) the final slag system is targeted at [ CaO ]]：58.35％、[Al₂O₃]：29.67％、[SiO₂]：3.87％、[MgO]：3.55％、FeO+MnO：0.79％；

(6) Soft blowing and calcium treatment:

a. the soft blowing time before calcium is 4min, and the argon blowing effect is that the diameter of the argon flower is 200-300 mm;

the soft blowing time after calcium is 19min, the argon blowing effect is that the slag surface creeping diameter is 100-;

b. calcium treatment criteria: the wire feeding amount is 121 m/furnace, and the secondary package [ Ca ]: 15 ppm;

c. the soft blowing and calcium treatment processes do not have the operations of aluminum supplement, alloy supplement and heating;

s4, casting and forming a blank under protection of a continuous casting machine

(1) The baking time of the tundish is 3.2h, and the baking temperature is 1125 ℃;

(2) argon replacement: continuously carrying out middle ladle argon replacement from the closing of the ladle baking device to the pouring of the big ladle;

(3) from big bag to middle bag: the flow rate of the argon seal blowing gas of the large ladle is 68L/min;

(4) covering agent: the low-silicon high-alkalinity covering agent has no molten steel exposure in the process;

(5) the thickness of the middle ladle slag layer is controlled to be 45 mm;

(6) blowing argon by using a stopper rod: the argon blowing flow of the stopper rod is controlled according to 5 NL/min;

(7) a long water gap: the sealing gasket is intact, and the long water gap sleeve is right vertical to the liquid level of the tundish;

(8) adding the covering slag: black slag operation, wherein slag consumption is 0.47kg/t, the thickness of a liquid slag layer is 10mm, the thickness of a total slag layer is 42mm, and unsealed, overdue or damp covering slag is not used;

(9) the service time of the long nozzle is 3.7h, the insertion depth of the ladle nozzle is 220mm, and the insertion depth of the submerged nozzle is 135 mm;

(10) controlling the slag discharging of the ladle: steel is left for 3 t;

(11) the casting tonnage of the tundish is 11t, so that the casting and slag entrapment are reduced;

(12) performing full ladle casting during normal casting, wherein the ladle weighing fluctuation is less than or equal to 3t, and the ladle weighing is 29 t; during the replacement of the ladle, weighing 18t of the tundish;

(13) the pulling speed is executed according to the standard requirement of the steel grade, the constant pulling speed of the continuous casting furnace (except for a water changing port) is realized, and the pulling speed is not changed frequently; the pulling speed in the process is changed by 0.01 m/min;

(14) the fluctuation is less than or equal to +/-3 mm;

(15) and (4) judging the low-grade steel grade or judging the waste of the head and tail billets corresponding to the casting billets due to abnormal processes (drainage, open casting and the like).

The furnace line steel casting blank sulfides A, sulfides Ae, oxides B, oxides Be, silicates C, silicates Ce, spherical oxides De and single-particle spherical Ds are all 0 grade, and the spherical oxides D are 0.5 grade, and meet the standard requirements.

Example 2

The pipeline steel controls the inclusions according to the following method, and specifically comprises the following steps:

s1, smelting in a converter: the end temperature T is 1618 ℃, and T [ O ] is 424 ppm;

s2, tapping the steel hole well, wherein the tapping time is 5.1min, the tapping frequency is 29 times (mainly the tapping time), the steel flow has no flow scattering phenomenon, and tapping slag is blocked;

adding 300kg of top slag lime and 100kg of modifier in the tapping process for slag washing;

s3, refining in an LF furnace:

(1) controlling the refining time: refining for 60 min;

(2) whole-process micro-positive pressure control;

(3) aluminum is supplemented in the process: aluminum-containing alloy is not supplemented within 8min before soft blowing;

(4) controlling gas: argon protection is performed in the wire feeding process;

(5) the final slag system is targeted at [ CaO ]]：57.83％、[Al₂O₃]：33.16％、[SiO₂]：3.14％、[MgO]：3.77％、FeO+MnO：0.96％；

(6) Soft blowing and calcium treatment:

a. the soft blowing time before calcium is 3min, and the argon blowing effect is that the diameter of the argon flower is 200-300 mm;

the soft blowing time after calcium is 15min, the argon blowing effect is that the slag surface creeping diameter is 100-;

b. calcium treatment criteria: the wire feeding amount is 120 m/furnace, and the secondary package [ Ca ]: 15 ppm;

c. the soft blowing and calcium treatment processes do not have the operations of aluminum supplement, alloy supplement and heating;

s4, casting and forming a blank under protection of a continuous casting machine

(1) The baking time of the tundish is 3.2h, and the baking temperature is 1125 ℃;

(2) argon replacement: continuously carrying out middle ladle argon replacement from the closing of the ladle baking device to the pouring of the big ladle;

(3) from big bag to middle bag: the flow rate of the argon seal blowing gas of the large ladle is 68L/min;

(4) covering agent: the low-silicon high-alkalinity covering agent has no molten steel exposure in the process;

(5) the thickness of the slag coating is controlled to be 48 mm;

(6) blowing argon by using a stopper rod: the argon blowing flow of the stopper rod is controlled according to 5 NL/min;

(7) a long water gap: the sealing gasket is intact, and the long water gap sleeve is right vertical to the liquid level of the tundish;

(8) adding the covering slag: black slag operation, wherein slag consumption is 0.46kg/t, the thickness of a liquid slag layer is 11mm, the thickness of a total slag layer is 43mm, and unsealed, overdue or wet covering slag is not used;

(9) the service time of the long nozzle is 3.6h, the insertion depth of the ladle nozzle is 220mm, and the insertion depth of the submerged nozzle is 135 mm;

(10) controlling the slag discharging of the ladle: steel is left for 3 t;

(11) the tundish casting tonnage is 10t, so that the casting and slag entrapment are reduced;

(12) performing full ladle casting during normal casting, wherein the ladle weighing fluctuation is less than or equal to 3t, and the ladle weighing is 30 t; during the replacement of the ladle, weighing 17t of the tundish;

(13) the pulling speed is executed according to the standard requirement of the steel grade, the constant pulling speed of the continuous casting furnace (except for a water changing port) is realized, and the pulling speed is not changed frequently; the pulling speed in the process is changed by 0.01 m/min;

(14) the fluctuation is less than or equal to +/-3 mm;

(15) and (4) judging the low-grade steel grade or judging the waste of the head and tail billets corresponding to the casting billets due to abnormal processes (drainage, open casting and the like).

The furnace line steel casting blank sulfides A, sulfides Ae, oxides B, oxides Be, silicates C, silicates Ce, spherical oxides De and single-particle spherical Ds are all 0 grade, and the spherical oxides D are 0.5 grade, and meet the standard requirements.

Example 3

The pipeline steel controls the inclusions according to the following method, and specifically comprises the following steps:

s1, smelting in a converter: the end temperature T is 1646 ℃ and T [ O ] is 576 ppm;

s2, tapping the steel hole well, wherein the tapping time is 4.1min, the tapping frequency is 129 times (mainly the tapping time), the steel flow has no flow scattering phenomenon, and tapping slag is blocked;

adding 300kg of top slag lime and 100kg of modifier in the tapping process for slag washing;

s3, refining in an LF furnace:

(1) controlling the refining time: refining for 77 min;

(2) whole-process micro-positive pressure control;

(3) aluminum is supplemented in the process: aluminum-containing alloy is not supplemented within 8min before soft blowing;

(4) controlling gas: argon protection is performed in the wire feeding process;

(5) the final slag system is targeted at [ CaO ]]：56.77％、[Al₂O₃]：31.52％、[SiO₂]：3.14％、[MgO]：3.38％、FeO+MnO：0.95％；

(6) Soft blowing and calcium treatment:

a. the soft blowing time before calcium is 3min, and the argon blowing effect is that the diameter of the argon flower is 200-300 mm;

the soft blowing time after calcium is 24min, the argon blowing effect is that the slag surface creeping diameter is 100-;

b. calcium treatment criteria: the line feeding amount is 136 m/furnace, and the secondary package [ Ca ]: 23 ppm;

c. the soft blowing and calcium treatment processes do not have the operations of aluminum supplement, alloy supplement and heating;

s4, casting and forming a blank under protection of a continuous casting machine

(1) The baking time of the tundish is 3.45h, and the baking temperature is 1131 ℃;

(2) argon replacement: continuously carrying out middle ladle argon replacement from the closing of the ladle baking device to the pouring of the big ladle;

(3) from big bag to middle bag: the flow rate of the argon seal blowing gas of the large ladle is 65L/min;

(4) covering agent: the low-silicon high-alkalinity covering agent has no molten steel exposure in the process;

(5) the thickness of the middle ladle slag layer is controlled to be 45 mm;

(6) blowing argon by using a stopper rod: the argon blowing flow of the stopper rod is controlled according to 5 NL/min;

(7) a long water gap: the sealing gasket is intact, and the long water gap sleeve is right vertical to the liquid level of the tundish;

(8) adding the covering slag: black slag operation, wherein slag consumption is 0.45kg/t, the thickness of a liquid slag layer is 10mm, the thickness of a total slag layer is 41mm, and unsealed, overdue or wet covering slag is not used;

(9) the service time of the long nozzle is 2.3h, the insertion depth of the ladle nozzle is 210mm, and the insertion depth of the submerged nozzle is 135 mm;

(10) controlling the slag discharging of the ladle: steel is left for 3 t;

(11) the casting tonnage of the tundish is 13t, so that the casting and slag entrapment are reduced;

(12) performing full ladle casting during normal casting, wherein the ladle weighing fluctuation is less than or equal to 3t, and the ladle weighing is 29 t; during the replacement of the ladle, weighing 18t of the tundish;

(13) the pulling speed is executed according to the standard requirement of the steel grade, the constant pulling speed of the continuous casting furnace (except for a water changing port) is realized, and the pulling speed is not changed frequently; the pulling speed in the process is changed by 0.01 m/min;

(14) the fluctuation is less than or equal to +/-3 mm;

(15) and (4) judging the low-grade steel grade or judging the waste of the head and tail billets corresponding to the casting billets due to abnormal processes (drainage, open casting and the like).

The furnace line steel casting blank sulfides A, sulfides Ae, oxides B, oxides Be, silicates C, silicates Ce, spherical oxides De and single-particle spherical Ds are all 0 grade, and the spherical oxides D are 0.5 grade, and meet the standard requirements.

Example 4

The pipeline steel controls the inclusions according to the following method, and specifically comprises the following steps:

s1, smelting in a converter: the end temperature T is 1617 ℃ and T [ O ] is 690 ppm;

s2, tapping the steel hole well, wherein the tapping time is 4.1min, the tapping frequency is 135 (mainly the tapping time), the steel flow has no flow scattering phenomenon, and tapping slag is blocked;

adding 300kg of top slag lime and 100kg of modifier in the tapping process for slag washing;

s3, refining in an LF furnace:

(1) controlling the refining time: refining for 61 min;

(2) whole-process micro-positive pressure control;

(3) aluminum is supplemented in the process: aluminum-containing alloy is not supplemented within 8min before soft blowing;

(4) controlling gas: argon protection is performed in the wire feeding process;

(5) the final slag system is targeted at [ CaO ]]：57.31％、[Al₂O₃]：32.24％、[SiO₂]：4.32％、[MgO]：3.65％、FeO+MnO：0.89％；

(6) Soft blowing and calcium treatment:

a. the soft blowing time before calcium is 4min, and the argon blowing effect is that the diameter of the argon flower is 200-300 mm;

the soft blowing time after calcium is 16min, the argon blowing effect is that the slag surface creeping diameter is 100-;

b. calcium treatment criteria: wire feeding amount 139 m/furnace, including [ Ca ]: 18.7 ppm;

c. the soft blowing and calcium treatment processes do not have the operations of aluminum supplement, alloy supplement and heating;

s4, casting and forming a blank under protection of a continuous casting machine

(1) The baking time of the tundish is 3.45h, and the baking temperature is 1131 ℃;

(2) argon replacement: continuously carrying out middle ladle argon replacement from the closing of the ladle baking device to the pouring of the big ladle;

(3) from big bag to middle bag: the flow rate of the argon seal blowing gas of the large ladle is 66L/min;

(4) covering agent: the low-silicon high-alkalinity covering agent has no molten steel exposure in the process;

(5) the thickness of the intermediate slag layer is controlled to be 47 mm;

(6) blowing argon by using a stopper rod: the argon blowing flow of the stopper rod is controlled according to 5 NL/min;

(7) a long water gap: the sealing gasket is intact, and the long water gap sleeve is right vertical to the liquid level of the tundish;

(8) adding the covering slag: black slag operation, wherein slag consumption is 0.47kg/t, the thickness of a liquid slag layer is 10mm, the thickness of a total slag layer is 44mm, and unsealed, overdue or damp covering slag is not used;

(9) the service time of the long nozzle is 3.2h, the insertion depth of the ladle nozzle is 230mm, and the insertion depth of the submerged nozzle is 135 mm;

(10) controlling the slag discharging of the ladle: steel is left for 3 t;

(11) the casting tonnage of the tundish is 11t, so that the casting and slag entrapment are reduced;

(12) performing full ladle casting during normal casting, wherein the ladle weighing fluctuation is less than or equal to 3t, and the ladle weighing is 30 t; during the replacement of the ladle, weighing 17t of the tundish;

(13) the pulling speed is executed according to the standard requirement of the steel grade, the constant pulling speed of the continuous casting furnace (except for a water changing port) is realized, and the pulling speed is not changed frequently; the pulling speed in the process is changed by 0.01 m/min;

(14) the fluctuation is less than or equal to +/-3 mm;

(15) and (4) judging the low-grade steel grade or judging the waste of the head and tail billets corresponding to the casting billets due to abnormal processes (drainage, open casting and the like).

The furnace line steel casting blank sulfides A, sulfides Ae, oxides B, oxides Be, silicates C, silicates Ce, spherical oxides De and single-particle spherical Ds are all 0 grade, and the spherical oxides D are 0.5 grade, and meet the standard requirements.

S3 and LF furnace refining in the embodiments 1-4 of the invention can avoid molten steel from being exposed in air and secondarily oxidized to form inclusion under the protection of argon in the micro-positive pressure and wire feeding processes, and the precise calcium treatment and soft blowing processes can promote the upward floating removal of a deoxidation product, avoid the enrichment and growth in the continuous casting process to form a nozzle plug which is flushed into a crystallizer to form large inclusion;

s4, when the continuous casting machine protects casting and blank forming, because the refractory material in the tundish can cause secondary oxidation of molten steel if the refractory material contains moisture, the number of large inclusions with the size of more than 30 mu m in the molten steel is increased, and in order to reduce the number of the large inclusions, the moisture in the refractory material of the tundish is removed as much as possible; since the large ladle slag is dropped into the middle ladle, a part of the slag is directly carried into the mold by the steel flow and may remain in the steel as large inclusions, and thus the control of the large ladle slag dropping is necessary.

The pipeline steel produced by the control of the embodiments 1-4 of the invention can meet the technical requirements of petroleum and natural gas transmission pipelines and the demand of maximizing the profit of customers.

Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made on the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and these modifications or substitutions are within the scope of the present invention/any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.