Vacuum smelting method for smelting cerium-containing stainless steel and accurately controlling cerium

Abstract

The invention provides a precise cerium control vacuum smelting method for smelting cerium-containing stainless steel, which adopts a vacuum induction furnace for smelting and comprises the following steps: 1) proportioning according to components; 2) charging and melting steel and iron materials; 3) carrying out bottom argon blowing refining after melting down; (4) after refining is finished, protective gas is introduced, and then an alloy material is added; the method comprises the steps of (1) smelting, (2) smelting, (3) smelting, (4) smelting, (5) sampling, detecting and analyzing, and carrying out fine adjustment according to the result, (6) firstly adding aluminum particles after the components are qualified, then shaking the furnace to enable a surface slag film to be adhered to the furnace wall, and then adding rare earth, and (7) sampling, tapping and detecting the rare earth content after melting down The method is simple in process and wide in applicability, and not only can reduce the loss of rare earth, but also can realize accurate control on the rare earth Ce content in the steel.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and particularly relates to a vacuum smelting method for precisely controlling cerium in the smelting of cerium-containing stainless steel. Background Art

[0002] As an active element, rare earth cerium has a strong affinity with oxygen and sulfur elements, and thus has an important impact on the structure and properties of steel materials. Cerium element is not only an excellent deoxidizer and desulfurizer for steel, but also can modify the inclusions in steel (composition, morphology, size and distribution) and play a purification role at the grain boundaries. Especially in recent years, it has shown remarkable performance in improving the oxidation resistance, corrosion resistance (intergranular corrosion, pitting corrosion) performance and high-temperature creep plasticity of steel.

[0003] At present, developed countries such as those in Europe and America have obtained stainless steel parts with excellent performance by adding rare earths to stainless steel, such as high-end bearings, pipeline structure parts, chemical oil well pipelines and aerospace industries. Many scientific and technological workers in China have done a lot of research on the application of rare earth elements in stainless steel and heat-resistant steel, and great progress has also been made in the research on the action mechanism and law of rare earths in steel.

[0004] Vacuum induction furnaces have received extensive attention due to their functions such as refining, sampling, alloying, temperature measurement, and bottom blowing gas (N2, Ar) under vacuum conditions, and have now become the main equipment for high-end steel grades such as superalloys, stainless steels, and corrosion-resistant alloys. During the induction smelting process, oxygen enters the molten steel through raw materials, the atmosphere, crucible materials, etc. The oxygen entering the molten steel will bring great harm to the workability and service performance of the steel. The forms of oxygen existing in the steel are mainly dissolved oxygen and combined oxygen, among which dissolved oxygen is the most likely to participate in oxidation-reduction reactions, so it needs to be removed during the refining period. However, if the parameters and processes during the refining process are unreasonable, not only can oxygen not be removed, but also oxygen increase will be caused. Therefore, deoxidation during the refining period is of great significance for the precise control of the subsequent rare earth content. The research progress in this field in China is particularly slow. In order to completely reverse this situation, it is very necessary to develop a process method that can stably control the rare earth recovery rate under vacuum conditions. Summary of the Invention

[0005] The purpose of the present invention is to provide a vacuum smelting method for precisely controlling cerium in the smelting of cerium-containing stainless steel, which can precisely and uniformly control the content of rare earth Ce.

[0006] To solve the above technical problems, the present invention adopts the following technical scheme: A vacuum smelting method for precisely controlling cerium in the smelting of cerium-containing stainless steel, and the control steps of the vacuum smelting method are as follows:

[0007] 1) Charge materials according to the composition;

[0008] 2) Charge the furnace and melt the iron and steel materials;

[0009] 3) After melting to liquid steel, argon blowing from bottom is carried out for refining;

[0010] 4) After the refining is completed, protective gas is filled and then alloy materials are added. The oxygen content in the steel before alloying is 10 - 15 ppm;

[0011] 5) Sampling and testing analysis are carried out, and component fine-tuning is performed according to the test results;

[0012] 6) After the components are qualified, aluminum grains are first added, then the furnace is rocked to make the surface slag film adhere to the furnace wall, and then rare earth is added. The oxygen content in the steel before adding rare earth is maintained at 6 - 10 ppm;

[0013] 7) After melting to liquid steel, sampling, tapping, and testing the rare earth Ce content are carried out.

[0014] In step 3) of the present invention, the bottom blowing pressure is maintained at 0.25 - 0.35 MPa, the flow rate is controlled at 2 - 3 L / min, the vacuum degree is maintained within 4 - 8 Pa throughout the process, and the refining time is determined according to the empirical formula where d: crucible diameter, cm; h: molten steel height, cm; [Ce%]: target cerium content, %.

[0015] In step 6) of the present invention, the addition amount of aluminum grains is controlled between 0.01% and 0.02% of the total smelting weight.

[0016] In step 6) of the present invention, the rare earth is ferrosilicon cerium alloy with a cerium content of 20 - 30%.

[0017] The applicable rare earth range of the vacuum smelting method of the present invention is 0.005% - 0.015%, and the control accuracy can reach within 5%.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: The loss of rare earth elements in the steel is mainly due to the fact that rare earth elements are extremely easy to combine with oxygen in the steel to form oxides or oxysulfides. The present invention can control the oxygen in the steel within an extremely low range before and after alloying through the double-channel control process of refining + deep deoxidation with aluminum. Therefore, the present invention can achieve stable control of the rare earth content and the content distribution is uniform without obvious segregation. Detailed Embodiment

[0019] The present invention will be further described in detail below in conjunction with specific embodiments.

[0020] Embodiment 1

[0021] A 50 Kg vacuum induction furnace with a rated power of 100 KW and an ultimate vacuum degree of 6.67×10 -2 Pa is adopted.

[0022] 1) Calculate and weigh carbon powder, metallic silicon, electrolytic manganese, metallic chromium, molybdenum bar, nickel plate, and pure iron based on the target composition of the steel grade and the loading amount of 40 kg.

[0023] 2) Put pure iron, nickel plate, molybdenum bar and metallic chromium into a crucible for smelting.

[0024] 3) After melting, refining begins. The bottom blowing pressure is maintained at 0.30 MPa, the flow rate is controlled at 2.5 L / min, and the vacuum is maintained at 4 Pa ​​throughout the process. Substitute the data d = 18 cm, h = 25 cm, Ce% = 0.005 into the formula It is calculated that the refining time is 27.1 min, the actual refining time is 28 min, and the oxygen content in the steel before alloying is 12 ppm.

[0025] 4) After refining, fill with 35000Pa protective gas argon and then add the remaining alloy material.

[0026] 5) Take samples for testing and analysis, and make fine adjustments to the ingredients based on the results.

[0027] 6) After the ingredients are qualified, add 4g of aluminum particles, then shake the furnace to make the surface slag film adhere to the furnace wall, and then add 10.3g of rare earth alloy (30% content), and the oxygen content in the steel is maintained at 8ppm before adding rare earth;

[0028] 7) After melting, stir at high power, then take samples and tap steel, and test the rare earth content after the sample cools down.

[0029] Table 1 Chemical composition of Example 1 (%)

[0030] Element C Si Mn P S Cr Ti V Ni Ce Target value 0.385 0.5 0.8 ＜0.01 ＜0.01 16.5 0.02 0.03 0.6 0.0050 Measured value 0.388 0.502 0.798 0.004 0.002 16.48 0.018 0.031 0.598 0.0048

[0031] Take one piece from the top, middle and bottom of the ingot for testing. Use the diagonal sampling method to take samples for ICP testing.

[0032] Table 2 Detection results of rare earth content at various locations of ingot in Example 1 (%)

[0033]

[0034]

[0035] Example 2

[0036] A 50Kg vacuum induction furnace is used, with a rated power of 100KW and an ultimate vacuum degree of 6.67×10 -2 Pa.

[0037] 1) Calculate and weigh carbon powder, metallic silicon, electrolytic manganese, metallic chromium, molybdenum bar, nickel plate, and pure iron based on the target composition of the steel grade and the loading amount of 40 kg.

[0038] 2) Put pure iron, nickel plates, molybdenum bars, and metallic chromium into a crucible for melting.

[0039] 3) After melting is complete, start refining. Keep the bottom blowing pressure at 0.35 MPa, the flow rate controlled at 3 L / min, and maintain a vacuum degree of 8 Pa throughout the process. Substitute the data d = 18 cm, h = 25 cm, and Ce% = 0.01 into the formula It can be calculated that the refining time is 39.6 min, and the actual refining time is 40 min. The oxygen content in the steel before alloying is 10 ppm.

[0040] 4) After the refining is completed, fill with protective gas argon at 35000 Pa, and then add the remaining alloy materials.

[0041] 5) Take samples for testing and analysis, and make fine adjustments to the composition according to the results.

[0042] 6) After the composition is qualified, first add 7 g of aluminum pellets, then rock the furnace to make the surface slag film adhere to the furnace wall, and then add 29.4 g of rare earth alloy (20% content). The oxygen content in the steel before adding rare earth is kept at 6 ppm;

[0043] 7) After melting is complete, stir at high power, then take samples and tap the steel. After the samples cool down, detect the rare earth content.

[0044] Table 3 Chemical composition of Example 2 (%)

[0045] Element C Si Mn P S Cr Ti V Ni Ce Target value 0.01 0.4 0.8 ＜0.01 ＜0.01 17 0.02 0.05 13 0.01 Measured value 0.0098 0.399 0.798 0.0035 0.0018 17.01 0.018 0.048 12.98 0.097

[0046] Take one piece each from the top, middle, and bottom of the ingot for testing. Use the diagonal sampling method and take samples for ICP testing respectively.

[0047] Table 4 Detection results of rare earth Ce content at various parts of the ingot in Example 2 (%)

[0048]

[0049]

[0050] Example 3

[0051] Use a 500 Kg vacuum induction furnace with a rated power of 300 KW and an ultimate vacuum degree of 6.67×10 -2 Pa.

[0052] 1) Calculate and weigh carbon powder, metallic silicon, electrolytic manganese, metallic chromium, molybdenum bars, nickel plates, and pure iron in combination with the target composition of the steel grade and the charged amount of 400 kg.

[0053] 2) Put pure iron, nickel plates, molybdenum bars, and metallic chromium into a crucible for melting.

[0054] 3) After melting is complete, start refining. The bottom blowing pressure is maintained at 0.25 MPa, the flow rate is controlled at 2 L / min, and the vacuum degree is maintained at 5 Pa throughout the process. Substitute the data d = 35 cm, h = 45 cm, and Ce% = 0.02 into the formula and it can be calculated that the refining time is 65.4 min, and the actual refining time is 66 min. The oxygen content in the steel before alloying is 15 ppm.

[0055] 4) After the refining is completed, fill with protective gas argon at 50000 Pa and then add the remaining alloy materials.

[0056] 5) Take samples for testing and analysis, and make fine adjustments to the composition according to the results.

[0057] 6) After the composition is qualified, first add 80 g of aluminum pellets, then rock the furnace to make the surface slag film adhere to the furnace wall, and then add 450.7 g of rare earth alloy (25% content). The oxygen content in the steel before adding rare earth is maintained at 10 ppm.

[0058] 7) After melting is complete, stir at high power, then take samples and tap the steel. After the sample cools, detect the rare earth content.

[0059] Table 5 Chemical composition of Example 3 (%)

[0060] Element C Si Mn P S Cr Ti V Ni Ce Target value 0.25 0.4 0.6 ＜0.01 ＜0.01 18 0.03 0.05 5 0.02 Measured value 0.254 0.401 0.602 0.0036 0.0017 18.01 0.028 0.0502 5.03 0.0195

[0061] Table 4 Detection results of rare earth Ce content at various parts of the ingot in Example 3 (%)

[0062]

[0063]

[0064] It is not difficult to know from the above examples that by using this method, the deviation of the rare earth content in the steel can be controlled within 5%, so as to achieve precise control of the rare earth Ce content in stainless steel.

[0065] The above examples are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above examples, those of ordinary skill in the art should understand that: the present invention can still be modified or equivalently replaced, and any modification or partial replacement without departing from the spirit and scope of the present invention should be covered by the scope of the claims of the present invention.

Claims

1. A vacuum smelting method for smelting cerium-containing stainless steel with precise cerium control, characterized in that: The control steps of the vacuum smelting method are as follows: 1) Mix ingredients according to their composition; 2) Loading the furnace to melt steel materials; 3) After melting, bottom blowing argon refining is carried out; 4) After refining, a protective gas is filled in and then alloying materials are added. The oxygen content in the steel before alloying is 10-15 ppm; 5) Take samples for testing and analysis, and make fine adjustments to the ingredients based on the test results; 6) After the ingredients are qualified, add aluminum particles first, then shake the furnace to make the surface slag film adhere to the furnace wall, and then add rare earth. The oxygen content in the steel is maintained at 6-10ppm before adding rare earth; 7) After melting, take samples, tap steel, and test the rare earth Ce content.

2. A vacuum smelting method for smelting cerium-containing stainless steel with precise cerium control according to claim 1, characterized in that: In step 3), the bottom blowing pressure is maintained at 0.25-0.35 MPa, the flow rate is controlled at 2-3 L / min, the vacuum is maintained at 8-10 Pa throughout the process, and the refining time is based on the empirical formula to determine, d: crucible diameter, cm; h: molten steel height, cm; [Ce%]: target cerium content, %.

3. A vacuum smelting method for smelting cerium-containing stainless steel with precise cerium control according to claim 1, characterized in that: In the step 6), the amount of aluminum particles added is controlled between 0.01% and 0.02% of the total smelting weight.

4. A vacuum smelting method for smelting cerium-containing stainless steel with precise cerium control according to claim 1, characterized in that: In the step 6), the rare earth is ferrocerium alloy, and the cerium content is 20-30%.

5. A vacuum smelting method for smelting cerium-containing stainless steel with precise cerium control according to any one of claims 1 to 4, characterized in that: The vacuum smelting method is applicable to rare earths in the range of 0.005% to 0.02%, and the accuracy can be controlled within ±5%.

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