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CN-122013028-A - No. 20 steel for fluid pipe and production method thereof

CN122013028ACN 122013028 ACN122013028 ACN 122013028ACN-122013028-A

Abstract

The invention relates to a production method of a No. 20 steel for a fluid pipe, which comprises the working procedures of converter smelting, LF refining and continuous casting, wherein the working procedure of the converter adopts CO 2 /Ar sectional dynamic bottom blowing, CO2 is blown in the earlier stage and is switched to Ar in the later stage, and the alloying operation of primary carbon pulling, double slag blocking tapping and accurate aluminum ingot adding amount matching based on the terminal carbon content are matched, the LF refining working procedure forms and maintains white slag for a long time through aluminum particle and calcium carbide collaborative slagging, the acid-soluble aluminum content is regulated in the earlier stage of refining, the middle-stage and later-stage aluminum supplementing is strictly forbidden, and then calcium treatment and long-time soft argon blowing are carried out. The continuous casting process adopts whole argon protection casting, including long nozzle sealing, submerged nozzle black level operation and full ladle casting slag discharge control, and through the cooperation of the whole process, the invention can stably produce high purity No. 20 steel with total oxygen content less than or equal to 30ppm, nitrogen content less than or equal to 80ppm and excellent inclusion rating, thereby fundamentally solving the problems of reduced mechanical property, welding property and corrosion resistance of the pipe caused by excessive oxide inclusion.

Inventors

  • ZHAO YUNLONG
  • YANG PENGHUI
  • WANG YONGLIANG
  • MAO RENJIE
  • REN GENZHU

Assignees

  • 江苏省镔鑫钢铁集团有限公司

Dates

Publication Date
20260512
Application Date
20260212

Claims (6)

  1. 1. A production method of a No. 20 steel for a fluid pipe is characterized by sequentially comprising a converter smelting process, an LF furnace refining process and a continuous casting process; Wherein the mass percentage of the chemical components of the No. 20 steel for the fluid pipe is that C is 0.18-0.23%, si is 0.17-0.37%, mn is 0.40-0.65%, P is less than or equal to 0.025%, S is less than or equal to 0.015%, alt is less than or equal to 0.015%, O is less than or equal to 30ppm, N is less than or equal to 80ppm, and the balance is Fe and unavoidable impurities; The converter smelting process specifically comprises the following steps of; 1) The bottom blowing stirring is adopted, the bottom blowing gas is CO 2 at the stage before the blowing starts and the total oxygen supply reaches 75%, the air supply intensity is 0.04-0.10Nm3/(min.t), then Ar is switched to be used as the bottom blowing gas, and the air supply intensity is 0.06-0.12Nm3/(min.t); 2) Controlling the end point by adopting one-time carbon pulling operation, wherein the carbon content C in the end point molten steel is more than or equal to 0.08%; 3) The method comprises the steps of carrying out deoxidization alloying in the tapping process, starting to add aluminum ingots, silicon-manganese alloy, silicon-iron alloy and aluminum ingots when the tapping amount reaches 1/4, and adding all materials in sequence before the tapping amount reaches 3/4, wherein the amount of the aluminum ingots added for the first time is 0.2-0.4kg/t steel, the amount of the aluminum ingots added for the last time is 0.6-0.8kg/t steel, the adding amount is matched according to the carbon content of the end point of a converter, and the slag layer thickness flowing into a ladle is controlled to be less than 50mm by adopting double slag blocking operation in tapping; The LF furnace refining process specifically comprises the following steps: 4) After entering a station, aluminum particles and calcium carbide are adopted for slagging, the aluminum particles are firstly added to quickly form white slag, and the calcium carbide is synchronously added to ensure the submerged arc effect, wherein the retention time of the white slag is not less than 10 minutes, if the acid-soluble aluminum content Alt of the entering station molten steel is less than 0.010%, the aluminum is adjusted to 0.010-0.018% in the early stage of refining, and aluminum supplementation is forbidden in the middle and later stages of refining, calcium treatment is carried out after power transmission and before soft argon blowing, and pure calcium wire 0.5m/t steel is fed; 5) Performing soft argon blowing treatment after calcium treatment, wherein the steel liquid level is not exposed in the soft blowing process, and the soft blowing time is longer than 10 minutes; 6) Measuring the oxygen content in molten steel before the molten steel is discharged, and controlling the oxygen content to be less than or equal to 15ppm; The continuous casting process specifically comprises the following steps: 7) The ladle to the tundish adopts long nozzle protection pouring, the long nozzle and the ladle drain nozzle are sealed and argon is introduced for protection, the long nozzle is inserted into the tundish 200-300mm below the molten steel surface, the tundish to the crystallizer adopts immersion nozzle pouring, the nozzle centering and the insertion depth of 70-110mm are ensured, the black liquid level operation is carried out, the full ladle pouring is adopted, and slag discharge is carried out when the tundish covering agent thickness is more than 80 mm.
  2. 2. The method for producing a steel grade 20 for a fluid pipe according to claim 1, wherein in the step 1), sectional bottom blowing is adopted for bottom blowing CO 2 and Ar; The gas supply intensity of CO 2 at the beginning of bottom blowing is 0.08Nm 3/(min.t), and the gas supply intensity of the bottom blowing CO 2 at the beginning of 5 minutes is adjusted to be 0.05Nm 3/(min.t); The bottom blowing gas was switched to Ar in 8 minutes, the supplied gas strength was 0.06Nm 3/(min. T), and the bottom blowing Ar supplied gas strength was adjusted to 0.09Nm 3/(min. T) in 10 minutes.
  3. 3. The method for producing a steel grade 20 for a fluid pipe according to claim 1, wherein in the step 3), the matching relationship between the amount of the aluminum ingot added for the first time and the amount of the aluminum ingot added for the last time and the carbon content at the end point of the converter is: when the final carbon content C is 0.08% -0.10%, adding 0.4kg/t steel for the first time and adding 0.8kg/t steel for the last time; when the final carbon content C is 0.11% -0.13%, adding 0.3kg/t steel for the first time and adding 0.7kg/t steel for the last time; when the final carbon content C is greater than 0.13%, 0.2kg/t of steel is added for the first time, and 0.6kg/t of steel is added for the last time.
  4. 4. The method of producing a steel grade 20 for a fluid pipe according to claim 1, wherein in step 3), a circulating ladle is used for receiving molten steel, and the circulating ladle is directly used for receiving molten steel in the next furnace after being cast into an empty ladle.
  5. 5. A method for producing steel No. 20 for a fluid pipe according to claim 1, wherein in step 4), when adding aluminum particles for slagging, aluminum particles are added first after entering a station, the addition amount of each time is 0.1kg/t of steel, the addition is carried out at intervals of 10 seconds, 4 times are continuously carried out, the color of slag is observed after heating for 5 minutes, if the slag is not changed into white slag, 0.1kg/t of steel is added, and after 2 minutes, the slag is confirmed again until the slag becomes white.
  6. 6. The method of producing steel No. 20 for a fluid pipe according to claim 1, wherein in step 4), when calcium carbide is added, 0.5kg/t of the calcium carbide is added for the first time when the refining is brought into the station, and then 0.1kg/t of the steel is added every 5 minutes until the power transmission is completed.

Description

No. 20 steel for fluid pipe and production method thereof Technical Field The invention relates to the technical field of steel industry, in particular to a production method of No. 20 steel for a fluid pipe. Background No. 20 steel belongs to high-quality carbon structural steel, and is widely applied to manufacturing of low-pressure fluid conveying pipelines due to good plasticity, toughness and welding performance. However, the high-pressure fluid pipe has higher purity requirement on the used No. 20 steel round steel, the oxygen content, inclusion content and chemical component stability in the steel need to be strictly controlled, otherwise, potential safety hazards such as corrosion, leakage and the like are easy to occur in the use process of the pipeline; In the existing No. 20 steel steelmaking production process, the phenomenon of converter process post-blowing is easy to cause the oxidation enhancement of molten steel, the follow-up refining deoxidization is not thorough, the slag discharging problem in the tapping process brings impurities to influence the purity of the molten steel, the problems of poor slag forming effect, irregular soft argon blowing and the like in the refining process are easy to cause the problems that the oxygen content in steel is higher, the inclusions cannot float up sufficiently, the secondary oxidation is caused when the continuous casting process is not properly protected, and the steel quality is further reduced. All these problems can influence the quality of the No. 20 steel round steel for the fluid pipe, and the use requirement of the high-end fluid pipe can not be met. Therefore, there is a need for a method for producing a steel rod of No. 20 for a fluid pipe, which can precisely control various process parameters and improve purity and quality stability of molten steel. Disclosure of Invention The invention aims to solve the technical problem of providing a production method for stably producing the No. 20 steel for the fluid pipe with high cleanliness, low gas content and ultralow inclusion level aiming at the defects of the prior art. The technical problem to be solved by the invention is realized by the following technical scheme, namely a production method of a No. 20 steel for a fluid pipe, which sequentially comprises a converter smelting process, an LF furnace refining process and a continuous casting process; Wherein the mass percentage of the chemical components of the No. 20 steel for the fluid pipe is that C is 0.18-0.23%, si is 0.17-0.37%, mn is 0.40-0.65%, P is less than or equal to 0.025%, S is less than or equal to 0.015%, alt is less than or equal to 0.015%, O is less than or equal to 30ppm, N is less than or equal to 80ppm, and the balance is Fe and unavoidable impurities; The converter smelting process specifically comprises the following steps of; 1) The bottom blowing stirring is adopted, the bottom blowing gas is CO 2 at the stage before the blowing starts and the total oxygen supply reaches 75%, the air supply intensity is 0.04-0.10Nm3/(min.t), then Ar is switched to be used as the bottom blowing gas, and the air supply intensity is 0.06-0.12Nm3/(min.t); 2) Controlling the end point by adopting one-time carbon pulling operation, wherein the carbon content C in the end point molten steel is more than or equal to 0.08%; 3) The method comprises the steps of carrying out deoxidization alloying in the tapping process, starting to add aluminum ingots, silicon-manganese alloy, silicon-iron alloy and aluminum ingots when the tapping amount reaches 1/4, and adding all materials in sequence before the tapping amount reaches 3/4, wherein the amount of the aluminum ingots added for the first time is 0.2-0.4kg/t steel, the amount of the aluminum ingots added for the last time is 0.6-0.8kg/t steel, the adding amount is matched according to the carbon content of the end point of a converter, and the slag layer thickness flowing into a ladle is controlled to be less than 50mm by adopting double slag blocking operation in tapping; The LF furnace refining process specifically comprises the following steps: 4) After entering a station, aluminum particles and calcium carbide are adopted for slagging, the aluminum particles are firstly added to quickly form white slag, and the calcium carbide is synchronously added to ensure the submerged arc effect, wherein the retention time of the white slag is not less than 10 minutes, if the acid-soluble aluminum content Alt of the entering station molten steel is less than 0.010%, the aluminum is adjusted to 0.010-0.018% in the early stage of refining, and aluminum supplementation is forbidden in the middle and later stages of refining, calcium treatment is carried out after power transmission and before soft argon blowing, and pure calcium wire 0.5m/t steel is fed; 5) Performing soft argon blowing treatment after calcium treatment, wherein the steel liquid level is not exposed in the soft blowing process, and the sof