Process for smelting rare earth-containing neodymium steel

Abstract

The invention relates to a process for smelting rare earth neodymium-containing steel, a process route of an alkaline electric furnace, an induction furnace, external refining, vacuum degassing and die casting forming is adopted, furnace charge of the alkaline electric furnace is composed of waste steel and steelmaking pig iron, a carburant and a ton of lime are added into the furnace in advance before charging, and the steel is discharged into a steel mixing ladle after the steel discharging condition is met; transferring the steel ladle to an external refining station, feeding an aluminum wire, adding silicon iron powder and silicon-calcium powder for deoxidation, transferring to a vacuum degassing station for vacuum degassing after the task is completed, introducing argon after the steel ladle is in place at the vacuum degassing station, keeping for a certain time under the vacuum degree of less than or equal to 0.7 mbar, and carrying out vacuum degassing on the steel ladle; after fluorite and rare earth metal neodymium alloy are added, pumping is continued for a certain time, vacuum breaking is carried out, weak stirring is started, and ladle hoisting pouring is carried out after the temperature is proper; after pouring, the steel ingot is solidified and demoulded, and the steel ingot is thermally sent to a forging workshop to be forged or annealed for standby application; and the recovery rate of the rare earth neodymium element can be stably controlled to be more than 80%.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking, and relates to a process for smelting steel containing rare earth neodymium, which can stably control the recovery rate of rare earth neodymium elements to be above 80%. Background Art

[0002] The application of rare earth in steel materials has a history of about 100 years. Trace rare earth elements can reduce the oxygen and sulfur content in steel, reduce the harmful effects of phosphorus and low melting point. A large number of experimental studies have shown that rare earth has the following effects on the organization and performance of steel: 1) Improve the impact toughness of steel; 2) Reduce the brittle transition temperature of steel; 3) Improve the anisotropy of steel; 4) Improve the fluidity of molten steel; 5) Improve the cast structure; 6) Inhibit the tendency of grain growth; 7) Influence the transformation of the organization; 8) Improve the hot plasticity; 9) Reduce the tendency of quenching cracking; 10) Inhibit temper brittleness; 11) Improve thermal strength; 12) Improve wear resistance; 13) Improve fatigue performance; 14) Improve welding performance; 15) Improve resistance to hydrogen embrittlement; 16) Improve low temperature performance; 17) Improve oxidation resistance; 18) Improve the corrosion resistance of the atmosphere and other media; 19) Improve surface quality, etc.

[0003] At present, there are two common ways to add rare earth elements into molten steel: 1) feeding wire after VD or RH; 2) adding rare earth alloys or metals directly into the molten steel using special containers after VD or RH. The recovery rate of rare earth alloy elements in the above addition methods is generally less than 50%, the utilization rate is generally low, the cost is high, and the operation is complicated. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a smelting process for smelting rare earth neodymium steel which can improve the utilization rate of rare earth alloy elements.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A smelting process for smelting rare earth neodymium steel, adopting a process route of "alkaline electric furnace + refining outside the furnace + vacuum degassing + die casting", wherein the composition is controlled as follows according to mass percentage: [C]: 0.25-0.35%, [Mn]: 0.40-0.80%, [Si]: 0.15-0.35%, [P]≤0.015%, [S]≤0.003%, [Nd]: 0.01-0.04%, and the rest is Fe. The specific smelting process steps are as follows: Step 1), the basic electric furnace charge includes 900kg / t of scrap steel and 200kg / t of pig iron for steelmaking. Before charging, 30-40kg / t of carburizer and 10-20kg / t of lime are added to the furnace in advance; sampling is performed when the temperature is ≥1580℃ after melting; the conditions for tapping from the electric arc furnace are as follows: [C] mass percentage ≤0.10%, [P] mass percentage ≤0.004%, tapping temperature ≥1650℃, and 2-4kg / t of aluminum blocks and 5-10kg / t of lime are added to the steel ladle during 1 / 4 to 3 / 4 of the tapping process; Step 2), after the ladle is transferred to the refining station outside the furnace, argon gas is connected for stirring, 4-6 m / t of aluminum wire is fed into the molten steel using a wire feeder for deep deoxidation, 10-20 kg / t of lime is added for slag making, 4-6 kg / t of ferrosilicon and 10-15 kg / t of high carbon ferromanganese are added, 2-4 kg / t of ferrosilicon powder and 1-2 kg / t of calcium silicon powder are added during refining to maintain a reducing atmosphere and perform slag deoxidation; the mass percentage of aluminum in the steel is controlled at 0.03-0.05%, and the temperature is 1680-1700°C and transferred to a vacuum degassing station; Step 3), after the ladle is in place, the temperature is measured, and argon is connected. After the vacuum degree is maintained at ≤0.7mbar for more than 15 minutes, fluorite 1.5kg / t and neodymium iron alloy 1.3kg / t are added through the vacuum feeding system, and the air is pumped for 5 minutes. After breaking the air, argon is used for weak stirring for more than 15 minutes to hang the ladle for pouring. The temperature of the mold casting ladle is 1550-1570℃; Step 4) After pouring, the ingot is demoulded after solidification, and the ingot is sent to the forging workshop for hot forging or annealing for standby use. The positive effects of the technical solution of the present invention are as follows: (1) The recovery rate of the rare earth neodymium element is stably controlled to be above 80%. The recovery rate of the present invention is shown in Table 1. DETAILED DESCRIPTION

[0006] A process for smelting rare earth neodymium steel, using a process route of "alkaline electric furnace + refining outside the furnace + vacuum degassing + die casting", the composition is controlled as follows according to mass percentage: [C]: 0.25-0.35%, [Mn]: 0.40-0.80%, [Si]: 0.15-0.35%, [P] ≤ 0.015%, [S] ≤ 0.003%, [Nd]: 0.01-0.04%, and the rest is Fe. The specific smelting process steps are as follows: Step 1), the basic electric furnace charge consists of 900kg / t of scrap steel and 200kg / t of pig iron for steelmaking. Before charging, 30-40kg / t of carburizer and 10-20kg / t of lime are added to the furnace in advance; after melting, the temperature is ≥1580℃ for sampling. Electric arc furnace tapping conditions: [C] mass percentage ≤0.10%, [P] mass percentage ≤0.004%, tapping temperature ≥1650℃, and 2-4kg / t of aluminum blocks and 5-10kg / t of lime are added to the steel ladle during 1 / 4 to 3 / 4 of the tapping process.

[0007] Step 2), transfer the ladle to the refining station outside the furnace and connect argon gas for stirring, use a wire feeder to feed 4-6m / t of aluminum wire into the molten steel for deep deoxidation, add 10-20kg / t of lime to make slag, add 4-6kg / t of ferrosilicon, 10-15kg / t of high carbon ferromanganese, add 2-4kg / t of ferrosilicon powder and 1-2kg / t of calcium silicon powder during refining to maintain a reducing atmosphere and perform slag deoxidation. The mass percentage of aluminum in the steel is 0.03-0.05%, and the temperature is 1680-1700℃ and transferred to the vacuum degassing station.

[0008] Step 3), after the ladle is in place, measure the temperature and connect argon gas. After keeping the vacuum degree ≤0.7mbar for more than 15 minutes, add fluorite 1.5kg / t and neodymium iron alloy 1.3kg / t through the vacuum feeding system, continue to evacuate for 5 minutes, and use argon gas weak stirring for more than 15 minutes after breaking the air for hanging ladle pouring. The temperature of the mold casting hanging ladle is 1550-1570℃.

[0009] Step 4) After the pouring is completed and the steel ingot is solidified, it is demoulded and sent hot to the forging workshop for forging or annealing for standby use.

[0010] Two groups of smelting examples were carried out according to this smelting process. The chemical composition contents of the products obtained from the two groups of smelting examples are shown in Table 1, and both meet the target requirements. Table 1 Chemical composition m% element Target ingredients This embodiment 1 This embodiment 2 C 0.25～0.35 0.30 0.28 Si 0.15～0.35 0.25 0.30 Mn 0.40～0.80 0.60 0.58 P ≤0.015 0.010 0.008 S ≤0.003 0.003 0.001 Nd 0.01～0.04 0.022 0.023 Nd recovery rate 85% 88%

Claims

1. A process for smelting steel containing rare earth neodymium, characterized in that: The process route of "alkaline electric furnace + refining outside the furnace + vacuum degassing + mold casting" is adopted, and the composition is controlled as follows according to mass percentage: [C]: 0.25-0.35%, [Mn]: 0.40-0.80%, [Si]: 0.15-0.35%, [P] ≤ 0.015%, [S] ≤ 0.003%, [Nd]: 0.01-0.04%, and the rest is Fe. The specific smelting process steps are as follows: Step 1), the basic electric furnace charge includes 900kg / t of scrap steel and 200kg / t of pig iron for steelmaking. Before charging, 30-40kg / t of carburizer and 10-20kg / t of lime are added to the furnace in advance; sampling is performed when the temperature is ≥1580℃ after melting; the conditions for tapping from the electric arc furnace are as follows: [C] mass percentage ≤0.10%, [P] mass percentage ≤0.004%, tapping temperature ≥1650℃, and 2-4kg / t of aluminum blocks and 5-10kg / t of lime are added to the steel ladle during 1 / 4 to 3 / 4 of the tapping process; Step 2), after the ladle is transferred to the refining station outside the furnace, argon gas is connected for stirring, 4-6 m / t of aluminum wire is fed into the molten steel using a wire feeder for deep deoxidation, 10-20 kg / t of lime is added for slag making, 4-6 kg / t of ferrosilicon and 10-15 kg / t of high carbon ferromanganese are added, 2-4 kg / t of ferrosilicon powder and 1-2 kg / t of calcium silicon powder are added during refining to maintain a reducing atmosphere and perform slag deoxidation; the mass percentage of aluminum in the steel is controlled at 0.03-0.05%, and the temperature is 1680-1700°C and transferred to a vacuum degassing station; Step 3), after the ladle is in place, the temperature is measured, and argon is connected. After the vacuum degree is maintained at ≤0.7mbar for more than 15 minutes, fluorite 1.5kg / t and neodymium iron alloy 1.3kg / t are added through the vacuum feeding system, and the air is pumped for 5 minutes. After breaking the air, argon is used for weak stirring for more than 15 minutes to hang the ladle for pouring. The temperature of the mold casting ladle is 1550-1570℃; Step 4) After the pouring is completed and the steel ingot is solidified, it is demoulded and sent hot to the forging workshop for forging or annealing for standby use.