Method for reducing converter tapping oxygen of ultra-low carbon anti-corrosion pipeline steel

Abstract

The invention discloses a method for reducing converter tapping oxygen of ultra-low carbon anti-corrosion pipeline steel, which relates to the technical field of steel production and comprises the following steps: controlling the unit consumption of molten iron to be greater than 910kg / t; slagging by adopting a single-slag method calcium slagging path; a'high-low-high-low 'bottom blowing mode is adopted; lime accounting for 90% of the total amount of the lime and all the magnesium balls are added within two minutes of blowing in the blowing process, and the remaining lime is added after process measurement is finished. According to the method, the converter charging amount system and the converter operation are optimized, the converter tapping oxygen qualification rate of the ultra-low carbon corrosion-resistant carbon pipeline steel can reach 95% or above, the Fe content in converter slag is effectively reduced, the furnace production is improved, and the purity of the molten ultra-low carbon pipeline steel is improved. Meanwhile, the slag splashing effect is improved, the adhesion rate of the slag is greatly increased, the erosion degree of a furnace lining is reduced, the dosage of a slag regulator is reduced, the furnace protection quality is improved, the smelting period is shortened, the production efficiency is improved, and the productivity of the converter is released.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, in particular to a method for reducing oxygen in converter tapping of ultra-low carbon corrosion-resistant pipeline steel. Background Art

[0002] Ultra-low carbon corrosion-resistant pipeline steel is the most difficult type of steel used in oil pipelines and petroleum pipelines to produce. It has extremely high requirements for the cleanliness of molten steel and the control of the center segregation of continuous casting billets. The control of oxygen and sulfur content in molten steel in converter smelting and the compliance rate of molten steel temperature have extremely high requirements for acid-resistant pipeline steelmaking process. Therefore, the production process of ultra-low carbon corrosion-resistant pipeline steel is highly demanding, especially the optimization of oxygen and temperature control in steelmaking process.

[0003] Although the high oxygen content in molten steel is beneficial to the RH decarburization process, the excessively high oxygen content causes part of the oxygen in the molten steel to enter the slag. When the LF furnace is deoxidizing and slagging, the oxygen content in the slag is relatively high, which is reduced to the molten steel during the static stirring process, resulting in an increase in CaO and Al2O3 inclusions in the molten steel, which is not conducive to the control of the purity of the molten steel. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the disadvantages of the prior art and provide a method for reducing oxygen in converter tapping of ultra-low carbon corrosion-resistant pipeline steel.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows: A method for reducing oxygen in ultra-low carbon corrosion-resistant pipeline steel converter tapping, comprising: Control the molten iron consumption to be greater than 910kg / t; The slag is made by using the single slag method and the calcium slag forming path; Adopt "high-low-high-low" bottom blowing mode; 90% of the total lime and all the magnesium balls are added within two minutes of the start of blowing process, and the remaining lime is added after the process measurement is completed.

[0006] As a preferred solution of the method for reducing oxygen in converter tapping of ultra-low carbon corrosion-resistant pipeline steel described in the present invention, the proportion of scrap steel in the molten steel is less than 20%.

[0007] As a preferred solution of the method for reducing oxygen in ultra-low carbon corrosion-resistant pipeline steel converter tapping according to the present invention, after slagging by adopting the single slag method calcium slagging path, the method further comprises: Control the magnesium oxide content in the slag to be greater than 5% and the slag basicity to be greater than 3.5.

[0008] As a preferred embodiment of the method for reducing oxygen in converter tapping of ultra-low carbon corrosion-resistant pipeline steel of the present invention, wherein: 90% of the total amount of lime and all magnesium balls are added within two minutes of the start of blowing during the blowing process, and after the remaining lime is added after the process measurement is completed, the method further comprises: The smelting gun positions are controlled as follows: the lowest gun position for blowing is 1700mm, and the highest gun position for slag forming process is 2200mm.

[0009] As a preferred solution of the method for reducing oxygen in ultra-low carbon corrosion-resistant pipeline steel converter tapping according to the present invention, after controlling the smelting gun position to: the lowest gun position for opening blowing is 1700mm, and the highest gun position for process slag is 2200mm, it also includes: The oxygen flow rate during the blowing process is set to 37000~42000Nm 3 / h, set the oxygen flow rate during process measurement to 41000~42000Nm 3 / h.

[0010] As a preferred solution of the method for reducing the oxygen content of ultra-low carbon corrosion-resistant pipeline steel converter tapping according to the present invention, the oxygen flow rate is set to 37000-42000 Nm during the blowing process. 3 / h, set the oxygen flow rate during process measurement to 41000~42000Nm 3 After / h, it also includes: The TSC process temperature is controlled at 1600-1630°C, the carbon content is 0.2-0.35%, and the phosphorus content is <0.025%.

[0011] As a preferred embodiment of the method for reducing oxygen content in converter tapping of ultra-low carbon corrosion-resistant pipeline steel of the present invention, after controlling the TSC process temperature to 1600-1630° C., the carbon content to 0.2-0.35%, and the phosphorus content to less than 0.025%, the method further comprises: The endpoint temperature is controlled at 1680±10℃, the endpoint oxygen content is controlled at 700-800ppm, and the oxygen content of steel is controlled to be more than 95% in the range of 500-650ppm.

[0012] As a preferred embodiment of the method for reducing oxygen content in ultra-low carbon corrosion-resistant pipeline steel converter tapping according to the present invention, after the endpoint temperature is controlled to be 1680±10°C, the endpoint oxygen content is controlled to be 700-800ppm, and the tapping oxygen content is controlled to be more than 95% of the range of 500-650ppm, the method further comprises: After steel tapping, the amount of slag remaining is controlled to be less than 5 tons.

[0013] The beneficial effects of the present invention are: The present invention optimizes the converter charging system and converter operation, and reduces the oxygen qualified rate of ultra-low carbon corrosion-resistant carbon pipeline steel converter steel to more than 95%, effectively reduces the Fe content in converter slag, increases furnace production, and improves the purity of ultra-low carbon pipeline steel liquid. At the same time, the slag splashing effect is improved, the adhesion rate of slag is greatly improved, the degree of lining erosion is reduced, the amount of slag regulator is reduced, the furnace protection quality is improved, the smelting cycle is shortened, the production efficiency is improved, and the converter capacity is released. DETAILED DESCRIPTION

[0014] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific implementation methods.

[0015] This embodiment provides a method for reducing the oxygen content of ultra-low carbon corrosion-resistant pipeline steel converter tapping, the method specifically comprising the following steps: Step S101: Control the molten iron consumption to be greater than 910kg / t, and use self-produced scrap steel, with the scrap steel proportion in the molten steel being less than 20%.

[0016] Specifically, the scrap steel used in this embodiment is the scrap steel produced by the steel plant, weighing 25.3 tons, the liquid level visibility after molten iron slag removal is 97%, the sulfur content at the end of molten iron pretreatment is 10ppm, the molten iron temperature is 1345℃, the weight is 155.6t, the high-level crushing material is 7 tons / furnace (which can be adjusted according to the smelting heat balance), and the composition design is shown in Table 1.

[0017]

[0018] Table 1 Composition of ultra-low carbon corrosion-resistant pipeline steel Step S102: Slag material control: Use the single slag method calcium slag formation path, magnesium oxide in the slag>5%, and slag basicity>3.5.

[0019] Specifically, the raw materials used were lime, dolomite, light-burned magnesium balls and pellets. The results of component analysis of the lime used are shown in Table 2.

[0020]

[0021] Table 2 Lime composition Step S103: bottom blowing mode control: adopt the "high-low-high-low" bottom blowing mode, and the bottom blowing pipeline is controlled in sections and grades. The specific flow rate is shown in Table 3.

[0022]

[0023] Table 3 Bottom blowing flow rate Step S104: blowing control. This step specifically includes the following steps: Step S104a: adopt a slag structure mode with large slag volume and low magnesium oxide, add part of the lime and all the magnesium balls within two minutes of blowing, reserve 10% of the total lime amount to be added after the process measurement is completed, do not add raw materials during the smelting process, ensure the process temperature coordination, and add raw materials appropriately when it exceeds 1640°C. See Table 4 for the auxiliary material structure ratio.

[0024]

[0025] Table 4 Excipient structure ratio Step S104b: Use high lance position for blowing. The lance position in the early stage of blowing is 1700mm, and the lance position in the middle stage of blowing is controlled between 1800 and 2200mm. Smelting to 7000Nm 3 When the oxygen supply is increased, slowly lower it to the carbon pulling gun position of 1400mm.

[0026] Step S104c: The oxygen flow rate during the blowing process is set to 38000-40000 Nm 3 / h, the flow rate is set to 42222Nm during process measurement 3 / h.

[0027] Step S104d: Control the TSC process temperature to 1623°C, the carbon content to 0.25%, and the phosphorus content to 0.023%, meeting the target requirements.

[0028] Step S104e: In this embodiment, the endpoint control refers to the secondary dynamic calculated value. After the calculated value reaches 1700°C, the blowing is stopped. The endpoint component C content is 0.025%, the P content is 0.010%, the sulfur content is 0.004%, the endpoint oxygen content is 756ppm, and the oxygen content is set to 645ppm before steelmaking, which meets the composition requirements. The RH arrival temperature is 1621°C, which meets the temperature requirements.

[0029] Step S105: The steel-making process adopts the composite double-blocking technology of "slide plate slag blocking + slag blocking cone", combined with the intelligent control means of slag detection. The ladle has one vertical and two horizontal clearances. The hourly molten steel weight of the ladle is 175 tons. There is no slag and no phosphorus reversion during steel-making.

[0030] Step S106: After the steel is tapped, the slag is firstly poured, the slag pouring angle is 108, and about 4 tons of slag is left.

[0031] See Table 5 for slag sample analysis:

[0032] Table 5 It can be seen from the above embodiments that, after adjusting the converter charging amount system and converter operation, the converter tapping oxygen meets the requirements, while the molten steel weight is significantly increased, the converter output is effectively improved, and the Fe content in the slag is reduced.

[0033] In addition to the above embodiments, the present invention may also have other implementation modes; any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A method for reducing oxygen in ultra-low carbon corrosion-resistant pipeline steel converter tapping, characterized in that: include: Control the molten iron consumption to be greater than 910kg / t; The slag is made by using the single slag method and the calcium slag forming path; Adopt "high-low-high-low" bottom blowing mode; 90% of the total lime and all the magnesium balls are added within two minutes of the start of blowing process, and the remaining lime is added after the process measurement is completed.

2. The method for reducing oxygen in converter tapping of ultra-low carbon corrosion resistant pipeline steel according to claim 1, characterized in that: The scrap steel accounts for less than 20% of the molten steel.

3. The method for reducing oxygen in converter tapping of ultra-low carbon corrosion-resistant pipeline steel according to claim 1, characterized in that: After slag making by adopting the single slag method calcium slag forming path, the method further comprises: Control the magnesium oxide content in the slag to be greater than 5% and the slag basicity to be greater than 3.

5.

4. The method for reducing oxygen in converter tapping of ultra-low carbon corrosion-resistant pipeline steel according to claim 1, characterized in that: The blowing process includes adding 90% of the total amount of lime and all magnesium balls within two minutes of the start of blowing, and adding the remaining lime after the process measurement is completed, and further comprising: The smelting gun positions are controlled as follows: the lowest gun position for blowing is 1700mm, and the highest gun position for slag forming process is 2200mm.

5. The method for reducing oxygen in converter tapping of ultra-low carbon corrosion-resistant pipeline steel according to claim 4, characterized in that: After the smelting gun position is controlled to be: the lowest gun position for blowing is 1700mm, and the highest gun position for process slag is 2200mm, it also includes: The oxygen flow rate during the blowing process is set to 37000~42000Nm 3 / h, set the oxygen flow rate during process measurement to 41000~42000Nm 3 / h.

6. The method for reducing oxygen in converter tapping of ultra-low carbon corrosion resistant pipeline steel according to claim 5, characterized in that: In the blowing process, the oxygen flow rate is set to 37000-42000 Nm 3 / h, set the oxygen flow rate during process measurement to 41000~42000Nm 3 After / h, it also includes: The TSC process temperature is controlled at 1600-1630°C, the carbon content is 0.2-0.35%, and the phosphorus content is <0.025%.

7. The method for reducing oxygen in converter tapping of ultra-low carbon corrosion resistant pipeline steel according to claim 6, characterized in that: After controlling the TSC process temperature to be 1600-1630° C., the carbon content to be 0.2-0.35%, and the phosphorus content to be less than 0.025%, the method further comprises: The endpoint temperature is controlled at 1680±10℃, the endpoint oxygen content is controlled at 700-800ppm, and the oxygen content of steel is controlled to be more than 95% in the range of 500-650ppm.

8. The method for reducing oxygen in converter tapping of ultra-low carbon corrosion resistant pipeline steel according to claim 7, characterized in that: After the endpoint temperature is controlled to be 1680±10°C, the endpoint oxygen content is controlled to be 700-800ppm, and the oxygen content of the steel is controlled to be more than 95% of the range of 500-650ppm, the process further includes: After steel tapping, the amount of slag remaining is controlled to be less than 5 tons.

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