A smelting method for improving the recovery rate of refined calcium treatment

Abstract

The invention discloses a smelting method for improving the yield of refined calcium treatment, which includes reducing the oxidizability of slag before wire feeding and accurately controlling wire feeding, wherein in reducing the oxidizability of slag before wire feeding, the refined slag before wire feeding is ensured to be white slag, and FeO+MnO in the slag is less than 1%, and in accurately controlling wire feeding, the wire feeding argon flow rate, wire feeding conduit length, wire feeding conduit diameter, wire feeding speed and soft blowing argon flow rate after wire feeding are controlled. The method provided by the invention can effectively improve the yield of calcium wire in the refining process.

Description

Technical Field

[0001] The present invention belongs to the field of iron and steel metallurgy and relates to a smelting method for improving the recovery rate of refining calcium treatment. Background Art

[0002] The low recovery rate of calcium wire seriously affects the quality of molten steel and the castability of molten steel. With the continuous decline of steel prices, it is urgent to improve the recovery rate of calcium wire to reduce costs and improve the quality of molten steel.

[0003] The main purpose of calcium treatment is to feed calcium into the molten steel in the form of a wire, react with high-melting-point chain-like molten steel deoxidation products Al 2 O 3 and sulfide inclusions to produce low-melting-point spherical aluminate complexes. Through the soft blowing effect of calcium treatment, the inclusions float up and are adsorbed by the refining slag to improve the cleanliness of the molten steel and avoid the formation of Al 2 O 3 nodules at the nozzle to cause nozzle blockage and ensure the normal progress of the casting process. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a smelting method for improving the recovery rate of refining calcium treatment, which includes the following operations:

[0005] (S1) Reducing the oxidability of the slag before wire feeding

[0006] By making a reducing slag with low oxidability, it is possible to effectively reduce the reduction of the recovery rate due to the reaction of the calcium wire with the oxygen in the slag during wire feeding. Ensure that the refining slag before wire feeding is white slag. By making a reducing slag with low oxidability, it is possible to effectively reduce the reduction of the recovery rate due to the reaction of the calcium wire with the oxygen in the slag during wire feeding. Specifically: During the heating process of the LF furnace, quicklime is added in batches for slag making, and 45 - 55 kg of aluminum pellets are added during the first heating process to remove the oxygen in the slag. During the subsequent stirring deoxidation and desulfurization process after the heating is completed, observe the change of the slag and timely add slag deoxidizer to maintain white slag, ensuring that FeO + MnO in the slag < 1%;

[0007] (S2) Precise control of wire feeding

[0008] 1) Wire feeding argon gas flow rate: During wire feeding, it is strictly prohibited to feed wire with a large amount of argon gas to avoid secondary oxidation caused by molten steel splashing and ensure soft blowing wire feeding. Specifically: The argon gas flow rate in the early stage of wire feeding is controlled at 100 - 150 L / min for two wires, and the argon gas is controlled at 30 - 80 L / min in the later stage of wire feeding;

[0009] 2) Wire feeding catheter length: Standardize the upper line standard of the catheter. The length of the newly installed catheter needs to be ≥ 1.7 m, and the length of the middle catheter during production needs to be ≥ 1.4 m. If the catheter length < 1.4 m, a new catheter must be replaced;

[0010] 3) Wire feeding conduit diameter: Reducing the diameter of the wire feeding conduit can reduce the deflection, knotting, and coiling of the calcium wire during wire feeding. Specifically, to standardize the wire standard on the conduit, the conduit diameter should be within 0.1 m - 0.15 m;

[0011] 4) Wire feeding speed: Establish a wire feeding speed standard. The wire feeding speed of high-calcium wire is 1.4 - 1.6 m / s, and that of iron-calcium wire is 1.8 - 2.2 m / s. Avoid splashing during wire feeding due to too fast wire feeding speed, and reduce secondary oxidation during wire feeding; at the same time, reduce the consumption of calcium wire. For low-silicon steel, the high-calcium wire feeding is 250 - 350 m, the iron-calcium wire feeding is 300 - 400 m. For silicon-containing steel, the high-calcium wire feeding is 150 - 250 m, and the iron-calcium wire feeding is 200 - 300 m;

[0012] 5) Soft blowing control after wire feeding: Establish a soft blowing standard, with the standard that the slag surface slightly moves and the molten steel is not exposed, to avoid the loss of calcium in the steel due to too large soft blowing argon after wire feeding; the soft blowing argon flow rate is 16 - 200 L / min for double wires; standardize the fixed soft blowing time to 7 - 9 minutes.

[0013] Based on the above technical solutions, the smelting method for improving the refining calcium treatment recovery rate can improve the recovery rate of calcium wire during refining. Actual production shows that using the method provided by the present invention can increase the average from 33.51% before improvement to more than 44.72%, effectively saving the consumption of calcium wire and reducing production costs. And through the improvement of the process, the cleanliness of molten steel can be effectively improved, and the secondary oxidation of molten steel during wire feeding can be reduced. Specific embodiments

[0014] The content of the present invention will be described in detail below through specific embodiments. The embodiments are intended to help understand the present invention, rather than limiting the content of the present invention.

[0015] Example 1

[0016] Steel grade SPCC, the type of wire feeding is high-calcium wire, the length of the wire feeding conduit is 1.8 m, the diameter is 0.15 m, the argon flow rate in the early stage of wire feeding is 120 L / min for double wires, the argon flow rate in the later stage of wire feeding is 50 L / min for double wires, the wire feeding speed is 1.5 m / s, the wire feeding amount is 300 m, the soft blowing time is 8 min, the soft blowing argon flow rate is 30 L / min for double wires, the FeO + MnO in the slag before wire feeding < 0.7% (During the heating process of the LF furnace, quicklime is added in batches for slag making, and 50 kg of aluminum pellets are added during the first heating process to remove oxygen in the slag. During the subsequent stirring, deoxidation, and desulfurization process after the heating ends, observe the change of the furnace slag and timely add slag deoxidizer to maintain white slag), the calcium content in the steel after wire feeding is 0.0021%, and the calcium wire recovery rate is 45.31%.

[0017] Example 2

[0018] Steel grade: SPCC, wire feeding type: high calcium wire, wire feeding duct length: 1.8 m, diameter: 0.15 m, argon flow rate in the early stage of wire feeding: 130 L / min for two lines, argon flow rate in the later stage of wire feeding: 60 L / min for two lines, wire feeding speed: 1.5 m / s, wire feeding amount: 280 m, soft blowing time: 8 min, soft blowing argon flow rate: 40 L / min for two lines, FeO + MnO in the slag before wire feeding < 0.5% (During the heating process of the LF furnace, lime is added in batches for slag making, and 50 kg of aluminum pellets are added during the first heating process to remove oxygen in the slag. During the subsequent stirring deoxidation and desulfurization process after heating, the change of the slag is observed, and the slag deoxidizer is added in time to maintain white slag), calcium content in the steel after wire feeding: 0.0020%, calcium wire recovery rate: 44.72%.

[0019] Example 3

[0020] Steel grade: SPCC, wire feeding type: high calcium wire, wire feeding duct length: 1.8 m, diameter: 0.15 m, argon flow rate in the early stage of wire feeding: 100 L / min for two lines, argon flow rate in the later stage of wire feeding: 50 L / min for two lines, wire feeding speed: 1.5 m / s, wire feeding amount: 330 m, soft blowing time: 8 min, soft blowing argon flow rate: 20 L / min for two lines, FeO + MnO in the slag before wire feeding < 0.5% (During the heating process of the LF furnace, lime is added in batches for slag making, and 50 kg of aluminum pellets are added during the first heating process to remove oxygen in the slag. During the subsequent stirring deoxidation and desulfurization process after heating, the change of the slag is observed, and the slag deoxidizer is added in time to maintain white slag), calcium content in the steel after wire feeding: 0.0026%, calcium wire recovery rate: 46.53%.

[0021] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A smelting method for improving the recovery rate of refined calcium treatment, which includes the following operations: (S1) Reduce the oxidability of the slag before wire feeding Ensure that the refined slag before wire feeding is white slag, and FeO + MnO in the slag < 1%; (S2) Precise control of wire feeding 1) Argon flow rate for wire feeding: The argon flow rate in the early stage of wire feeding is controlled at 100 - 150 L / min for double lines, and the argon is controlled at 30 - 80 L / min in the later stage of wire feeding; 2) Length of the wire feeding conduit: Standardize the upper line standard of the conduit. The length of the newly installed conduit needs to be ≥ 1.7 m, the length of the middle conduit during production needs to be ≥ 1.4 m, and the conduit with a length < 1.4 m must be replaced with a new one; 3) Diameter of the wire feeding conduit: Standardize the upper line standard of the conduit. The diameter of the conduit needs to be within 0.1 m - 0.15 m; 4) Wire feeding speed: Establish a wire feeding speed standard. The wire feeding speed of the high-calcium wire is 1.4 - 1.6 m / s or the wire feeding speed of the iron-calcium wire is 1.8 - 2.2 m / s, to avoid splashing during wire feeding due to too fast wire feeding speed, reduce secondary oxidation during wire feeding; at the same time, reduce the consumption of calcium wire. For low-silicon steel: the wire feeding amount of the high-calcium wire is 250 - 350 m or the wire feeding amount of the iron-calcium wire is 300 - 400 m; 5) Soft blowing control after wire feeding: Establish a soft blowing standard, with the criterion that the molten steel is not exposed when the slag surface is slightly moving, to avoid the loss of calcium in the steel due to too large soft blowing argon after wire feeding ends; the soft blowing argon flow rate is 16 - 200 L / min for double lines; standardize the fixed soft blowing time to be 7 - 9 minutes; The calcium wire recovery rate of the smelting method is above 44.72%.

2. According to the smelting method described in claim 1, the specific operation in step (S1) is as follows: During the heating process of the LF furnace, add quicklime in batches for slag making, and add 45 - 55 kg of aluminum pellets during the first heating process to remove the oxygen in the slag. Observe the change of the slag during the subsequent stirring deoxidation and desulfurization process after the heating ends, and timely add slag deoxidizer to maintain white slag, ensuring that FeO + MnO in the slag < 1%.