Intermediate frequency furnace steelmaking method

Abstract

The invention discloses a steelmaking method of an intermediate frequency furnace, which belongs to the technical field of steelmaking, and comprises the following steps of: A, padding a neutral or alkaline furnace lining and waste steel or steel cuttings into the bottom of the furnace, and selecting return scraps with the same components to be added into the furnace according to the component requirements of castings; b, after charging is completed, a furnace cover is sealed, molten steel is smelted in a full furnace, sampling detection is conducted after charging is completed and basically melting down is conducted, and carbonized rice husks are added for heat preservation; c, a steel ladle is baked, and an argon blowing sliding plate is adopted and used for stirring molten steel obtained after tapping; d, a baked steel ladle is prepared in front of a furnace, and flushing type pre-melting slag is pre-added into the steel ladle; e, tapping to a steel ladle, and after tapping is finished, covering the surface of molten steel with rice hulls for heat preservation; and F, after sedation is completed and the pouring temperature is reached, a crane ladle is used for pouring.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking, and in particular relates to a medium frequency furnace steelmaking method, which ensures the purity of molten steel in the medium frequency furnace and meets the requirements of steel castings. Background Art

[0002] Steel casting products mostly adopt the conventional process of electric furnace + LF refining. This method does not have high requirements for raw materials, but the outstanding problem is that the alloy recovery when the return material is used is small and the cost is high. When the scrap steel return material is very sufficient and the price has a significant advantage, the return material cannot be effectively utilized. This situation will be more prominent, especially when smelting high-alloy materials. The cost reduction advantage of medium-frequency furnace smelting is very obvious, but the requirements for scrap steel composition are also very strict, especially harmful impurity elements such as phosphorus and sulfur. However, from the perspective of cost control and cost production, improving the residual control of return materials to meet the production of medium-frequency furnaces and reduce costs is still the choice of most manufacturers. However, due to the failure of molten steel to be refined and low purity, the promotion and application of medium-frequency furnace smelting is limited. Summary of the invention

[0003] The purpose of the present invention is to provide a medium frequency furnace steelmaking method to improve the purity of molten steel in the medium frequency furnace and meet the needs of steel castings.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is: A medium frequency furnace steelmaking method, characterized by comprising the following steps: Step A: Use neutral or alkaline furnace lining, put scrap steel or steel chips into the furnace bottom, and select return materials with the same composition to add into the furnace according to the casting composition requirements; Step B, after the feeding is completed, the furnace cover is sealed, and the molten steel is smelted in the full furnace. After the feeding is completed and the molten steel is basically melted, sampling is performed for testing, and carbonized rice husks are added for heat preservation; Step C, the ladle is baked and an argon blowing slide is used to stir the molten steel after tapping; Step D, prepare a baked ladle in front of the furnace, and pre-fill the ladle with flushing pre-melted slag; Step E: tapping the steel into the ladle, and after tapping, the surface of the molten steel is covered with rice husks for heat preservation; Step F: After the sedation is completed and the pouring temperature is reached, ladle pouring is performed.

[0005] The further improvement of the technical solution of the present invention is that the raw materials in step A are determined according to the composition of the casting, and the same material return material + scrap steel and alloy elements are selected. When the material contains easily oxidizable elements such as V, alloy elements need to be supplemented.

[0006] A further improvement of the technical solution of the present invention is that a cover is added and sealed in step B to ensure that [O] in the molten steel is reduced during the smelting process, the burnout rate of alloy elements is reduced, and inclusions caused by oxidation of the molten steel are reduced; and 2.5-3.0 kg / t of carbonized rice husk is added after molten steel is smelted for heat preservation, air isolation, and oxidation reduction.

[0007] The further improvement of the technical solution of the present invention is that in step D, an argon blowing slide is installed for the ladle and used after baking to ensure the temperature drop and calming time during the steel tapping process, and 3.0-5.0 kg / t of flushing pre-melted slag is pre-dosed in the ladle.

[0008] A further improvement of the technical solution of the present invention is that after the molten metal sampling in step E meets the composition requirements, the slag is removed from the furnace, the temperature is raised to the required temperature for the casting and then the steel is tapped, and 0.4-0.6 kg / t aluminum beans are added along the flow.

[0009] A further improvement of the technical solution of the present invention is that in step F, rice husks are added to cover the steel, and the calming is based on the slight movement of the molten steel surface, the time is not less than 15 minutes, and after the temperature is measured to be appropriate, the ladle is poured.

[0010] Due to the adoption of the above technical solution, the technical effects achieved by the present invention are as follows: This application adopts sealed smelting and auxiliary material insulation to reduce oxygen absorption of molten steel during the smelting process of the medium frequency furnace and reduce the initial inclusion content in the molten steel; during the steel-making process of the medium frequency furnace, flushing pre-melted slag and aluminum beans are added to achieve deoxidation of the molten steel; when the steel is tapped, argon is blown from the bottom of the ladle to promote the floating of inclusions. Using the method of this application, the return material can be fully utilized, and the medium frequency furnace can be used to melt cast steel at the same time, breaking through the limitation that only electric arc furnaces can be used to refine molten steel. DETAILED DESCRIPTION

[0011] The present invention is further described in detail below in conjunction with embodiments: A medium frequency furnace steelmaking method comprises the following steps: Step A: Use neutral or alkaline furnace lining, put scrap steel or steel chips into the furnace bottom, and select return materials with the same composition to add into the furnace according to the casting composition requirements; Step B, after the feeding is completed, the furnace cover is sealed, and the molten steel is smelted in the full furnace. After the feeding is completed and the molten steel is basically melted, sampling is performed for testing, and carbonized rice husks are added for heat preservation; Step C, the ladle is baked and an argon blowing slide is used to stir the molten steel after tapping; Step D, prepare a baked ladle in front of the furnace, and pre-fill the ladle with flushing pre-melted slag; Step E: tapping the steel into the ladle, and after tapping, the surface of the molten steel is covered with rice husks for heat preservation; Step F: After the sedation is completed and the pouring temperature is reached, ladle pouring is performed.

[0012] The process is: Batching → Cover and melt → Add materials → Melt all the furnace → Take samples (if the composition is appropriate, otherwise fine-tune the alloy) → Add rice husks to the furnace → Prepare the ladle (bake, pre-fill the ladle with flushing type pre-melted slag) → Raise the temperature in the furnace and then remove the slag → Tap out the steel → Calm down → Pouring.

[0013] The smelting and pouring steps are as follows: 1. Ingredients Ingots of the same material should be added first, and the insufficient part should be added with similar material or alloy. When selecting ingots, the surface of the charge should be clean and free of oil stains. When the material contains easily oxidizable elements such as V, alloy elements need to be added.

[0014] 2. Covering and smelting Control the charging and smelting speed during the smelting process, control the charging and melting time within 2.5 hours, and the high-power power transmission time for smelting shall not exceed 5 hours. After the charging is completed and the smelting is completed and the sampling is taken, add carbonized rice husks to completely cover the molten steel surface. In addition to charging and sampling during the smelting process, the furnace charge is covered and smelted before it is melted to reduce the inhalation of gas by the molten steel.

[0015] 3. Ladle preparation Ladle baking time ≥5h, ladle temperature ≥500℃, and firing stop to steel tapping ≤30min.

[0016] 4. Steel tapping and pouring (1) The temperature in front of the furnace is not less than 1680℃, and the steel is tapped after slag removal. Before tapping, 4 kg / t of pre-melting type washing slag is pre-added in the ladle. When 25% of the steel is tapped, aluminum beans are added, and the addition is completed when 75% of the steel is tapped. The total amount of aluminum beans added is 0.5 kg / t.

[0017] (2) Pouring After steel tapping is completed, add 2.0 kg / t of carbonized rice husk into the ladle. After the cooling time is ≥15 min and the temperature reaches the pouring temperature, the ladle is hung for pouring.

[0018] When the above operation is adopted to produce steel casting products, the gas [O] of molten steel in the medium frequency furnace is 45-60ppm, the [O] of the roll blank sampling test is ≤30ppm, and the detected inclusion size is ≤50μm, which is close to the inclusion level of LF refining.

[0019] Example 1 The following is a specific description of the scheme of the present invention by taking the smelting of 10t of molten steel in a medium frequency furnace as an example.

[0020] 1. Ingredients To produce Cr5 steel castings, we are looking for return materials of the same material, including 0.8t of turnings, 9.75t of ingot heads, and a total of 10.55t.

[0021] 2. Smelting production (1) 06:47-07:20 After adding materials, close the cover and supply power.

[0022] (2) 07:21-08:14 Power is supplied for melting.

[0023] (3) There was a power outage from 08:15 to 08:24 to replenish the chips and spindle heads.

[0024] (4) 08:25-09:06 Power supply for melting.

[0025] (5) There was a power outage from 09:07 to 09:21 to replenish the remaining turnings and spindle heads.

[0026] (6) 09:22-11:00: Electricity is supplied for melting.

[0027] (7) 11:01 After all the steel is melted, samples are taken to test the composition and gas (O is 45.4 ppm), and rice husks are added to keep it warm.

[0028] (8) 11:05 After spectral detection of the sample, fine-tune the alloy.

[0029] (9) 11:30-11:41 Sampling and testing, the ingredients are qualified.

[0030] (10) 11:42-12:08 The temperature was raised, the temperature in front of the furnace was measured at 1685°C, and the slag was removed from the furnace.

[0031] (11) At 12:10, the ladle baking temperature was 520℃. The interval from stopping the fire to tapping was 20 minutes. 40 kg of flushing pre-melted slag was pre-placed in the ladle on the tapping side.

[0032] (12) 12:11 Steel was tapped. When the tapped steel reached 2.5 t, aluminum beans were added along the flow. When the tapped steel reached 7.5 t, the addition was completed. The total amount of aluminum beans added was 5.0 kg. The temperature after the furnace was measured at 1630 °C. (13) 12:12:05-12:28:10 After blowing argon into the ladle for 16 minutes to calm it, take samples to test the gas (oxygen [O] is 31.7). The temperature is measured to reach the pouring temperature and the ladle is hung for pouring.

[0033] 3. Roller blank inspection When slicing the roll neck at the casting end of the roll blank, the oxygen [O] in the gas was detected to be 15.0ppm; when slicing the roll neck at the riser end, the oxygen [O] in the gas was detected to be 24.8ppm. According to the A method in the national standard 10561, the 1 / 2R position of the test piece is tested: (1) Casting end roll neck test piece Class C has coarse level 1.0 and fine level 1.0; Class D has coarse level 0.5 and fine level 1.0.

[0034] (2) Test piece for the roll neck of the cap Class C has a coarse level of 0.5 and a fine level of 1.0; Class D has a coarse level of 0.5 and a fine level of 1.0.

[0035] The inclusion size is less than 50μm, close to the refined inclusion level.

Claims

1. A medium frequency furnace steelmaking method, characterized in that The following steps are involved: Step A: Use neutral or alkaline furnace lining, put scrap steel or steel chips into the furnace bottom, and select return materials with the same composition to add into the furnace according to the casting composition requirements; Step B, after the feeding is completed, the furnace cover is sealed, and the molten steel is smelted in the full furnace. After the feeding is completed and the molten steel is basically melted, sampling is performed for testing, and carbonized rice husks are added for heat preservation; Step C, the ladle is baked and an argon blowing slide is used to stir the molten steel after tapping; Step D, prepare a baked ladle in front of the furnace, and pre-fill the ladle with flushing pre-melted slag; Step E: tapping the steel into the ladle, and after tapping, the surface of the molten steel is covered with rice husks for heat preservation; Step F: After the sedation is completed and the pouring temperature is reached, ladle pouring is performed.

2. A medium frequency furnace steelmaking method according to claim 1, characterized in that: In step A, the raw materials are determined according to the composition of the casting, and the same material return material + scrap steel and alloy elements are selected.

3. A medium frequency furnace steelmaking method according to claim 1, characterized in that: In step B, the melting time of the material is controlled within 2.5 hours, the high-power smelting time is not more than 5 hours, the smelting process is sealed with a cover, and 2.5-3.0 kg / t of carbonized rice husk is added after the smelting is complete.

4. A medium frequency furnace steelmaking method according to claim 1, characterized in that: In step D, an argon blowing slide is installed in the ladle, which is used after baking, and 3.0-5.0 kg / t of flushing pre-melted slag is pre-dosed in the ladle.

5. A medium frequency furnace steelmaking method according to claim 1, characterized in that: After the molten metal sampling in step E meets the composition requirements, the slag is removed from the furnace, the temperature is raised to the required temperature for the casting, and the steel is tapped, and 0.4-0.6 kg / t aluminum beans are added along the flow.

6. A medium frequency furnace steelmaking method according to claim 5, characterized in that: Aluminum beans were added when 25% of the steel was tapped and were completely added when 75% of the steel was tapped. The total amount of aluminum beans added was 0.5 kg / t.

7. A medium frequency furnace steelmaking method according to claim 1, characterized in that: In step F, rice husk is added to cover the steel. The calming is based on the slight movement of the molten steel surface. The time is not less than 15 minutes. After the temperature is measured to be appropriate, the ladle is used for pouring.