A method for increasing phosphorus in a weathering steel

Abstract

This invention discloses a method for increasing phosphorus content in weathering steel, comprising: converter smelting using scrap steel and molten iron as furnace charge, with a phosphorus content of 0.06%–0.200% in the molten iron; adding quicklime at the beginning of blowing, followed by adding lightly calcined dolomite in batches; employing a low lance position and high oxygen flow rate for blowing; achieving a final phosphorus content of 0.06%–0.100%; after the final test, adding coke particles through a high-level silo and adjusting the bottom blowing flow rate; adding silicon-manganese alloy, ferrosilicon alloy, and aluminum alloy sequentially according to the target chemical composition of the steel grade 30–60 seconds after tapping for alloying; subsequently adding quicklime for modification; using slag-blocking tapping at the end of tapping; increasing phosphorus content in the molten steel by transferring low-carbon, high-phosphorus molten steel into the ladle after tapping; and sending it to LF refining treatment, whereby it is cast after meeting the required composition and temperature specifications. This invention achieves a phosphorus increase of 0.005%–0.0200% in molten steel, saving on phosphorus and iron consumption, reducing iron loss, and lowering the production cost of weathering steel.

Description

Technical Field

[0001] This invention relates to the fields of materials and metallurgy, and more specifically, to a method for phosphorus enrichment in weathering steel. Background Technology

[0002] Weathering steel reacts with air and rainwater in the natural environment, forming a stable and dense protective rust layer on its surface. Compared with ordinary carbon steel, it has higher corrosion resistance and is therefore widely used in structures with harsh environments and certain requirements for corrosion resistance, such as oil drilling, containers, and railway vehicles.

[0003] Weathering steel requires a phosphorus content in the range of 0.07% to 0.12%. In order to meet the composition requirements, the converter smelting adopts decarburization and dephosphorization operation, and then phosphorus is precisely controlled by adding ferrophosphorus in the refining process to meet the composition control requirements. The disadvantage of this method is that the final phosphorus content control is unstable, which requires an additional large amount of ferrophosphorus consumption and increases the smelting cost of copper-phosphorus steel. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects in the existing technology and provide a method for phosphorus enrichment of weathering steel. The method uses molten iron for phosphorus enrichment, and the weathering steel is smelted in a converter. The blowing process adopts low oxidation control. After tapping, according to the final phosphorus content, low carbon high phosphorus molten steel is added for phosphorus enrichment. This method can save phosphorus iron consumption and reduce iron loss. At the same time, the method is safe, practical and easy to implement on site.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for phosphorus enrichment in weathering steel includes the following steps:

[0007] In the converter smelting process, scrap steel and molten iron are used as furnace charge, with scrap steel accounting for 12% to 20% by mass fraction; the phosphorus content in the molten iron is 0.06% to 0.200%.

[0008] Slag formation control: lime is added at the beginning of blowing, followed by lightly calcined dolomite in batches;

[0009] Gun position control: adopt a low gun position and high oxygen flow rate method for smelting;

[0010] The converter endpoint is controlled with an oxygen value of 200ppm to 500ppm and a phosphorus content of 0.06% to 0.100%. After the endpoint test, coke particles are added through the high-level silo.

[0011] During the tapping process, argon blowing is initiated at the bottom of the molten steel ladle. 30-60 seconds after tapping, silicon-manganese alloy, ferrosilicon alloy, and aluminum alloy are added sequentially according to the target chemical composition of the steel grade for alloying. Subsequently, quicklime for modification is added. Slag-blocking is used for tapping at the end of the tapping process.

[0012] Phosphorus enrichment of molten steel involves transferring 50 kg / t to 80 kg / t of low-carbon, high-phosphorus molten steel into a ladle after tapping.

[0013] The LF furnace refining process involves sending the phosphorus-enhanced molten steel into the LF refining process. Once the composition and temperature meet the requirements, the steel is then cast into the furnace.

[0014] Optionally, the weathering steel comprises the following components by mass percentage: C: 0.08%–0.10%, Si: 0.4%–0.5%, Mn: 0.5%–0.6%, P: 0.08%–0.12%, S≤0.01%, Als: 0.01%–0.05%, Ni: 0.045%–0.10%, Cu: 0.25%–0.3%, Cr: 0.3%–0.35%, with the remainder being Fe and unavoidable impurities.

[0015] Optionally, the slag control involves adding 15 kg / t steel to 30 kg / t steel quicklime at the start of blowing, followed by adding lightly calcined dolomite in batches. The first batch of lightly calcined dolomite accounts for 60% to 80% of the total amount of lightly calcined dolomite added, and the remaining lightly calcined dolomite is added in batches, with each batch containing ≤0.5 tons. The total amount of lightly calcined dolomite added is controlled at 10 kg / t steel to 15 kg / t steel.

[0016] Optionally, the oxygen lance position control allows for an oxygen supply intensity of 3.5 Nm³. 3 / min·t~3.8Nm 3 / min·t, the oxygen lance position is controlled within the range of 1.8m to 2.5m, and the carbon extraction time is 2min to 5min.

[0017] Optionally, the converter endpoint control has an endpoint temperature ≥1680℃.

[0018] Optionally, the converter endpoint control includes a coke particle addition rate of 1 kg / t steel to 2 kg / t steel and a bottom blowing flow rate of 16 Nm³. 3 / min~30Nm 3 / min.

[0019] Optionally, in the steel tapping process control, the amount of silicon-manganese alloy added is 6 kg / t steel to 7 kg / t steel, the amount of silicon-iron alloy added is 5 kg / t steel to 6 kg / t steel, and the amount of aluminum alloy added is 1 kg / t steel to 3 kg / t steel; the amount of quicklime added for modification is 2 kg / t steel to 3 kg / t steel.

[0020] Optional, during the tapping process, the argon flow rate is 60 Nm³. 3 / min~90Nm 3 / min, argon blowing time ≥3min.

[0021] Optionally, the low-carbon, high-phosphorus molten steel comprises the following components by mass percentage: C ≤ 0.30%, Si ≤ 0.01%, Mn ≤ 0.5%, P: 0.08%–0.20%, S: 0.005%–0.06%.

[0022] Implementing the embodiments of the present invention will have the following beneficial effects:

[0023] This invention provides a method for increasing phosphorus content in weathering steel. The method involves smelting weathering steel in a converter, controlling the oxidation level during the blowing process, and then adding low-carbon, high-phosphorus molten steel after tapping, based on the final phosphorus content, to increase phosphorus content in the molten steel by 0.005% to 0.0200%. This method can save on phosphorus and iron consumption, reduce iron loss, and lower the production cost of weathering steel. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0025] This invention discloses a method for phosphorus enrichment in weathering steel, comprising the following steps:

[0026] S1. Converter smelting uses scrap steel and molten iron as furnace charge, with scrap steel accounting for 12% to 20% by mass fraction; the P content in the molten iron is 0.06% to 0.200%.

[0027] S2. Slag control: Add quicklime at the start of blowing, followed by lightly calcined dolomite in batches.

[0028] In one specific embodiment, during slag control, at the start of blowing, 15 kg / t steel to 30 kg / t steel of quicklime is added, followed by batches of lightly calcined dolomite. The first batch of lightly calcined dolomite accounts for 60% to 80% of the total amount added, with the remaining lightly calcined dolomite added in batches of ≤0.5 tons each. The total amount of lightly calcined dolomite added is controlled at 10 kg / t steel to 15 kg / t steel. The timing of addition depends on the slag condition; it is added when the slag is active to reduce FeO formation in the slag and create favorable conditions for decarburization and phosphorus retention.

[0029] S3. Gun position control: adopt a low gun position and high oxygen flow rate method for smelting.

[0030] In one specific embodiment, during lance position control, the oxygen supply intensity of the oxygen lance is 3.5 Nm. 3 / min·t~3.8Nm 3 The oxygen lance position is controlled within the range of 1.8m to 2.5m, and the carbon removal time is 2min to 5min. The purpose is to achieve low oxidizability of the final slag and increase the final phosphorus content.

[0031] S4. Converter endpoint control: endpoint oxygen value is 200ppm to 500ppm, and endpoint phosphorus content is controlled at 0.06% to 0.100%. After the endpoint test, coke particles are added through the high-level silo.

[0032] In one specific embodiment, the endpoint temperature in the converter endpoint control is ≥1680℃.

[0033] In one specific embodiment, during converter endpoint control, the coke particle addition rate is 1 kg / t steel to 2 kg / t steel, and the bottom blowing flow rate is 16 Nm³. 3 / min~30Nm 3 / min. The aim is to further reduce the oxidizing properties of the final slag.

[0034] S5. Steel tapping process control: Start bottom argon blowing in the molten steel ladle. 30s to 60s after tapping, add silicon-manganese alloy, ferrosilicon alloy, and aluminum alloy in sequence according to the target value of the steel grade's chemical composition for alloying. Then add quicklime for modification. At the end of the tapping process, use slag-blocking tapping to avoid slag from falling into the molten steel.

[0035] In one specific embodiment, during the steel tapping process control, the amount of silicon-manganese alloy added is 6 kg / t steel to 7 kg / t steel, the amount of silicon-iron alloy added is 5 kg / t steel to 6 kg / t steel, and the amount of aluminum alloy added is 1 kg / t steel to 3 kg / t steel; the amount of quicklime added for modification is 2 kg / t steel to 3 kg / t steel.

[0036] In one specific embodiment, during the steel tapping process control, the argon gas flow rate during argon blowing is 60 Nm³. 3 / min~90Nm 3 / min, argon blowing time ≥3min.

[0037] S6. Phosphorus Addition to Molten Steel: After tapping, 50kg / t to 80kg / t of low-carbon, high-phosphorus molten steel is poured into the ladle for phosphorus addition.

[0038] In one specific embodiment, the low-carbon, high-phosphorus molten steel comprises the following components by mass percentage: C ≤ 0.30%, Si ≤ 0.01%, Mn ≤ 0.5%, P: 0.08%–0.20%, S: 0.005%–0.06%.

[0039] S7 and LF furnace refining: The phosphorus-enhanced molten steel is sent to the LF refining process, and after the composition and temperature meet the requirements, it is cast into the furnace.

[0040] In one specific embodiment, the weathering steel comprises the following components by mass percentage: C: 0.08%–0.10%, Si: 0.4%–0.5%, Mn: 0.5%–0.6%, P: 0.08%–0.12%, S≤0.01%, Als: 0.01%–0.05%, Ni: 0.045%–0.10%, Cu: 0.25%–0.3%, Cr: 0.3%–0.35%, with the remainder being Fe and unavoidable impurities.

[0041] The following are specific embodiments.

[0042] Example 1

[0043] The method for phosphorus enrichment of weathering steel in this embodiment uses a 260-ton converter to smelt weathering steel. The weathering steel comprises the following components by mass percentage: C: 0.08%, Si: 0.42%, Mn: 0.55%, P: 0.095%, S: 0.008%, Al: 0.025%, Ni: 0.06%, Cu: 0.28%, Cr: 0.32%, with the remainder being Fe and unavoidable impurities. The specific steps include:

[0044] S1. Converter smelting: Weathering steel is produced in the converter and fed directly into the furnace without pretreatment. The P content in the molten iron is 0.12%. Scrap steel and molten iron are used as furnace charge. 40 tons of scrap steel are added, and 15 tons of molten iron are added at a lower rate. The total charge is 285 tons.

[0045] S2. Slag control: At the start of blowing, 25 kg / t steel of quicklime is added to the furnace at once, followed by batches of lightly calcined dolomite. The first batch of lightly calcined dolomite accounts for 65% of the total amount of lightly calcined dolomite added. The remaining lightly calcined dolomite is added in batches, with each batch containing 0.2 tons. The total amount of lightly calcined dolomite added is controlled at 15 kg / t steel.

[0046] S3. Oxygen lance position control: A low lance position and high oxygen flow rate are used for smelting. The oxygen supply intensity of the oxygen lance is 3.6 Nm. 3 / min·t, the oxygen lance position is controlled within the range of 1.8m to 2.5m, and the carbon extraction time is 4min.

[0047] S4. Converter endpoint control: endpoint temperature 1685℃, endpoint oxygen value 425ppm, endpoint phosphorus content controlled at 0.075%; after endpoint testing, coke particles are added through the high-level silo at a rate of 1.5 kg / t steel, with a bottom blowing flow rate of 16 Nm³. 3 / min.

[0048] S5. Steel tapping process control: Initiate argon blowing at the bottom of the molten steel ladle; during argon blowing, the argon flow rate is 60 Nm³. 3 / min, argon blowing time 3min, when 1 / 3 of the steel is tapped, the following are added sequentially according to the target values ​​of the steel grade chemical composition: 6kg / t steel for silicon-manganese alloy, 6kg / t steel for ferrosilicon alloy, and 3kg / t steel for aluminum alloy; the amount of quicklime used for modification is 2kg / t steel. Slag-blocking tapping is adopted at the end of the tapping process.

[0049] S6. Phosphorus Addition to Molten Steel: After tapping, 15 tons of low-carbon, high-phosphorus molten steel (containing the following components by mass percentage: C: 0.25%, Si: 0.01%, Mn: 0.35%, P: 0.085%, S: 0.06%) are poured into a ladle for phosphorus addition, with an average phosphorus addition of 0.005%.

[0050] S7 and LF furnace refining: The phosphorus-enhanced molten steel is sent to the LF refining process, and after the composition and temperature meet the requirements, it is cast into the furnace.

[0051] Example 2

[0052] This embodiment of the method for phosphorus enrichment in weathering steel involves smelting weathering steel in a 120-ton converter. The weathering steel comprises the following components by mass percentage: C: 0.09%, Si: 0.45%, Mn: 0.55%, P: 0.100%, S: 0.008%, Al: 0.025%, Ni: 0.06%, Cu: 0.28%, Cr: 0.32%, with the remainder being Fe and unavoidable impurities. The specific steps include:

[0053] S1. Converter smelting: Weathering steel is produced in the converter and fed directly into the furnace without pretreatment. The P content in the molten iron is 0.12%. Scrap steel and molten iron are used as furnace charge. The amount of scrap steel added is 15 tons, the amount of molten iron is 85 tons, and the total amount of charge is 100 tons.

[0054] S2. Slag control: At the start of blowing, 15 kg / t steel of quicklime is added to the furnace at once, followed by batches of lightly calcined dolomite. The first batch of lightly calcined dolomite accounts for 75% of the total amount of lightly calcined dolomite added. The remaining lightly calcined dolomite is added in batches, with each batch containing 0.1 tons. The total amount of lightly calcined dolomite added is controlled at 12 kg / t steel.

[0055] S3. Oxygen lance position control: A low lance position and high oxygen flow rate are used for smelting. The oxygen supply intensity of the oxygen lance is 3.8 Nm. 3 / min·t, the oxygen lance position is controlled within the range of 1.8m to 2.0m, and the carbon extraction time is 3.5min.

[0056] S4. Converter endpoint control: endpoint temperature 1695℃, endpoint oxygen value 425ppm, endpoint phosphorus content controlled at 0.082%; after endpoint testing, coke particles are added through the high-level silo at a rate of 1.2 kg / t steel, with a bottom blowing flow rate of 20 Nm³. 3 / min.

[0057] S5. Steel tapping process control: Start bottom argon blowing in the molten steel ladle; during argon blowing, the argon flow rate is 70 Nm³. 3 / min, argon blowing time 3.5min, when 1 / 3 of the steel is tapped, according to the target values ​​of the steel grade chemical composition, the following are added in sequence: 6.8kg / t steel for silicon-manganese alloy, 5.5kg / t steel for ferrosilicon alloy, and 2.5kg / t steel for aluminum alloy; the amount of quicklime for modification is 2kg / t steel. Slag-blocking tapping is adopted at the end of the tapping process.

[0058] S6. Phosphorus Addition to Molten Steel: After tapping, 6 tons of low-carbon, high-phosphorus molten steel (containing the following components by mass percentage: C: 0.3%, Si: 0.01%, Mn: 0.18%, P: 0.095%, S: 0.05%) are poured into a ladle for phosphorus addition, with an average phosphorus increase of 0.006%.

[0059] S7 and LF furnace refining: The phosphorus-enhanced molten steel is sent to the LF refining process, and after the composition and temperature meet the requirements, it is cast into the furnace.

[0060] Example 3

[0061] This embodiment of the method for phosphorus enrichment in weathering steel uses a 220-ton converter to smelt weathering steel. The weathering steel comprises the following components by mass percentage: C: 0.095%, Si: 0.46%, Mn: 0.585%, P: 0.105%, S: 0.005%, Als: 0.025%, Ni: 0.07%, Cu: 0.28%, Cr: 0.32%, with the remainder being Fe and unavoidable impurities. The specific steps include:

[0062] S1. Converter smelting: Weathering steel is produced in the converter and fed directly into the furnace without pretreatment. The P content in the molten iron is 0.125%. Scrap steel and molten iron are used as furnace charge. 32 tons of scrap steel are added, and the total charge is 188 tons.

[0063] S2. Slag control: At the start of blowing, 26 kg / t steel of quicklime is added to the furnace at once, followed by batches of lightly calcined dolomite. The first batch of lightly calcined dolomite accounts for 72% of the total amount of lightly calcined dolomite added. The remaining lightly calcined dolomite is added in batches, with each batch containing 0.3 tons. The total amount of lightly calcined dolomite added is controlled at 17 kg / t steel.

[0064] S3. Oxygen lance position control: A low lance position and high oxygen flow rate are used for smelting. The oxygen supply intensity of the oxygen lance is 3.65 Nm. 3 / min·t, the oxygen lance position is controlled within the range of 1.8m to 2.5m, and the carbon extraction time is 3min.

[0065] S4. Converter endpoint control: endpoint temperature 1692℃, endpoint oxygen value 498ppm, endpoint phosphorus content controlled at 0.079%; after endpoint testing, coke particles are added through the high-level silo at a rate of 1.0 kg / t steel, with a bottom blowing flow rate of 20 Nm³. 3 / min.

[0066] S5. Steel tapping process control: Start bottom argon blowing in the molten steel ladle; during argon blowing, the argon flow rate is 80 Nm. 3 / min, argon blowing time 3.5min, when 1 / 3 of the steel is tapped, according to the target values ​​of the steel grade chemical composition, the following are added in sequence: silicon manganese alloy 6.2kg / t steel, silicon ferrosilicon alloy 6.0kg / t steel, and aluminum alloy 2.8kg / t steel; the amount of quicklime for modification is added 2.5kg / t steel. Slag-blocking tapping is used at the end of the tapping process.

[0067] S6. Phosphorus Addition to Molten Steel: After tapping, 13 tons of low-carbon, high-phosphorus molten steel (containing the following components by mass percentage: C: 0.28%, Si: 0.01%, Mn: 0.32%, P: 0.075%, S: 0.045%) are added to the ladle for phosphorus addition, with an average phosphorus addition of 0.0045%.

[0068] S7 and LF furnace refining: The phosphorus-enhanced molten steel is sent to the LF refining process, and after the composition and temperature meet the requirements, it is cast into the furnace.

[0069] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for phosphorus enrichment in weathering steel, characterized in that, Includes the following steps: In the converter smelting process, scrap steel and molten iron are used as furnace charge, with scrap steel accounting for 12% to 20% by mass fraction; the phosphorus content in the molten iron is 0.06% to 0.200%. Slag formation control: Add quicklime at the beginning of blowing, followed by lightly calcined dolomite in batches; Gun position control: adopt a low gun position and high oxygen flow rate method for smelting; The converter endpoint is controlled with an oxygen value of 200ppm to 500ppm and a phosphorus content of 0.06% to 0.100%. After the endpoint test, coke particles are added through the high-level silo. During the tapping process, argon blowing is initiated at the bottom of the molten steel ladle. 30-60 seconds after tapping, silicon-manganese alloy, ferrosilicon alloy, and aluminum alloy are added sequentially according to the target chemical composition of the steel grade for alloying. Subsequently, quicklime for modification is added. Slag-blocking is used for tapping at the end of the tapping process. Phosphorus enrichment of molten steel involves transferring 50 kg / t to 80 kg / t of low-carbon, high-phosphorus molten steel into a ladle after tapping. The LF furnace refining process involves sending the phosphorus-enhanced molten steel into the LF refining process. Once the composition and temperature meet the requirements, the steel is then cast into the furnace.

2. The method for phosphorus enrichment of weathering steel according to claim 1, characterized in that, The weathering steel comprises the following components in weight percentage: C: 0.08%–0.10%, Si: 0.4%–0.5%, Mn: 0.5%–0.6%, P: 0.08%–0.12%, S≤0.01%, Als: 0.01%–0.05%, Ni: 0.045%–0.10%, Cu: 0.25%–0.3%, Cr: 0.3%–0.35%, with the remainder being Fe and unavoidable impurities.

3. The method for phosphorus enrichment of weathering steel according to claim 1, characterized in that, The slag control involves adding 15 kg / t steel to 30 kg / t steel quicklime at the start of blowing, followed by adding lightly calcined dolomite in batches. The first batch of lightly calcined dolomite accounts for 60% to 80% of the total amount of lightly calcined dolomite added, and the remaining lightly calcined dolomite is added in batches, with each batch ≤ 0.5 tons. The total amount of lightly calcined dolomite added is controlled at 10 kg / t steel to 15 kg / t steel.

4. The method for phosphorus enrichment of weathering steel according to claim 1, characterized in that, The lance position control, oxygen lance oxygen supply intensity is 3.5Nm 3 / min·t~3.8Nm 3 / min·t, oxygen lance lance position control in 1.8m~2.5m range, carbon time is 2min~5min.

5. The method for phosphorus enrichment of weathering steel according to claim 1, characterized in that, The converter endpoint control has an endpoint temperature ≥1680℃.

6. The method for phosphorus enrichment of weathering steel according to claim 1, characterized in that, The converter endpoint control includes a coke particle addition rate of 1 kg / t steel to 2 kg / t steel and a bottom blowing flow rate of 16 Nm³. 3 / min~30Nm 3 / min.

7. The method for phosphorus enrichment of weathering steel according to claim 1, characterized in that, The steel tapping process control includes adding 6 kg / t steel to 7 kg / t steel of silicon-manganese alloy, 5 kg / t steel to 6 kg / t steel of silicon-iron alloy, and 1 kg / t steel to 3 kg / t steel of aluminum alloy; the addition of quicklime for modification is 2 kg / t steel to 3 kg / t steel.

8. The method for phosphorus enrichment of weathering steel according to claim 1, characterized in that, During the steel tapping process control, the argon flow rate during argon blowing is 60 Nm. 3 / min~90Nm 3 / min, argon blowing time ≥3min.

9. The method for phosphorus enrichment of weathering steel according to claim 1, characterized in that, The low-carbon, high-phosphorus molten steel comprises the following components by mass percentage: C ≤ 0.30%, Si ≤ 0.01%, Mn ≤ 0.5%, P: 0.08%–0.20%, S: 0.005%–0.06%.