Method for smelting ZG06Cr13Ni4Mo martensitic stainless steel through argon-oxygen mixed blowing in oxidation period by adopting alkaline electric arc furnace return method

Abstract

The invention discloses a method for smelting ZG06Cr13Ni4Mo martensitic stainless steel through argon-oxygen mixed blowing in the oxidation period by adopting a basic electric arc furnace return method, and relates to the field of martensitic stainless steel smelting. The invention aims to solve the technical problems that the smelting cost of a ZG06Cr13Ni4Mo martensitic stainless steel return method is high, and the quality of molten steel is difficult to guarantee. The method comprises the following steps: adding carbon into returned furnace charge carbon steel scrap, and smelting in a melting period, an oxidation period and a reduction period in a basic electric arc furnace. According to the method, selective oxidation of VOD and AOD refining is achieved, the purposes of carbon removal and chromium protection are achieved, the operations of degassing, inclusion removal and the like are achieved, the yield of return scrap alloy entering the furnace is increased, the production cost is reduced, the smelting operation difficulty is reduced, and the quality of molten steel is guaranteed. The method disclosed by the invention is used for smelting the ZG06Cr13Ni4Mo martensitic stainless steel.

Description

Technical Field

[0001] The invention relates to the field of martensitic stainless steel smelting. Background Art

[0002] ZG06Cr13Ni4Mo martensitic stainless steel material is widely used in hydropower and atomic power station castings. Under the condition of high prices of raw materials such as nickel plate and micro-carbon ferrochrome, it is an economical process route to use return materials such as ZG06Cr13Ni4Mo casting riser, ZG06Cr13Ni4Mo casting runner and low-phosphorus carbon scrap steel return material to smelt ZG06Cr13Ni4Mo martensitic stainless steel by return method.

[0003] The return smelting process of ZG06Cr13Ni4Mo martensitic stainless steel currently mainly adopts the medium frequency furnace smelting process which only carries out the melting period and the reduction period, or adopts the smelting process which cooperates the electric arc furnace with the VOD and AOD refining furnace equipment for the melting period, the oxidation period and the reduction period.

[0004] The medium frequency furnace smelting process flow only carries out the melting period and the reduction period to smelt ZG06Cr13Ni4Mo martensitic stainless steel by the return method, and the molten steel alloy recovery rate is high. Since the molten steel smelting does not go through the oxidation period, the chemical composition requirements of the returned scrap steel such as P and S are strict, the production cost is high, and the molten steel degassing and inclusion removal operations cannot be achieved, which seriously affects the molten steel quality.

[0005] The ZG06Cr13Ni4Mo martensitic stainless steel is smelted by the return method using the smelting process flow of the arc furnace with VOD and AOD refining furnace equipment during the melting period, oxidation period and reduction period, and the molten steel alloy recovery rate is high. The molten steel smelting is carried out through the melting period, oxidation period and reduction period to achieve the degassing and inclusion removal of the molten steel, thereby ensuring the quality of the molten steel. However, the smelting process flow of the arc furnace with VOD and AOD refining furnace equipment has high equipment cost and high smelting operation requirements. Summary of the invention

[0006] The invention aims to solve the technical problems that the return process smelting cost of ZG06Cr13Ni4Mo martensitic stainless steel is high and it is difficult to ensure the quality of molten steel.

[0007] A method for smelting ZG06Cr13Ni4Mo martensitic stainless steel by argon-oxygen mixed blowing during oxidation period using a basic arc furnace return method, using ZG06Cr13Ni4Mo casting riser and ZG06Cr13Ni4Mo casting runner return furnace charge with a total addition amount of 95% and carbon scrap steel addition amount of 5% for subsequent smelting (by mass), using a basic arc furnace, using ZG06Cr13Ni4Mo casting runner return furnace charge and carbon scrap steel The scrap steel is carbonized and the smelting process flow of melting period, oxidation period and reduction period is carried out in the alkaline electric arc furnace. Oxygen blowing is used for decarburization and fluxing in the early stage of the oxidation period. Argon and oxygen ratio are adjusted for mixed blowing in the middle stage of the oxidation period for decarburization and chromium preservation. Argon and oxygen ratio are adjusted for mixed blowing at the end of the oxidation period for degassing. Argon exhaust and oxygen blowing pipe are used for argon and oxygen mixed blowing for decarburization in the oxidation period. At the temperature of 1650℃-1720℃, the CO partial pressure in the molten steel smelting process is reduced to achieve decarburization and chromium preservation.

[0008] Furthermore, the alkaline electric arc furnace lining used is a low-carbon magnesia-chrome brick refractory material, and a smelting process flow of a melting period, an oxidation period, and a reduction period is carried out.

[0009] Furthermore, 5% of carbon scrap steel is added to carbonize the molten steel, so that the C content in the molten steel after molten steel is cleared is higher than the upper limit of the finished product specification of 0.06-0.10%.

[0010] Furthermore, oxygen blowing is used in the early stage of oxidation period to decarburize and assist fluxing.

[0011] Furthermore, oxygen blowing is used in the early stage of oxidation to decarburize and assist melting, so as to achieve a molten steel temperature of over 1650°C.

[0012] Furthermore, after the temperature of the molten steel is above 1650°C, the first stage of the middle stage of the oxidation period is carried out by using an argon exhaust and an oxygen blowing pipe in a 1:3 argon-oxygen ratio to carry out smelting decarburization and chromium preservation; the carbon is reduced to about 0.08%, and the temperature of the molten steel reaches 1680°C.

[0013] Furthermore, in the second stage of the middle oxidation process, argon exhaust and oxygen blowing pipe are used to carry out mixed blowing smelting to remove carbon and retain chromium in the argon-oxygen volume ratio of 1:2; the carbon is reduced to about 0.05%, and the molten steel temperature reaches 1700°C.

[0014] Furthermore, in the third stage of the middle oxidation process, argon exhaust and oxygen blowing pipe are used to carry out mixed blowing in a 1:1 argon-oxygen volume ratio to decarburize and preserve chromium; the carbon is reduced to below 0.03%, and the molten steel temperature is used to reach 1720°C.

[0015] Furthermore, during the oxidation period, argon exhaust and oxygen blowing pipe are used to carry out argon-oxygen mixed blowing decarburization.

[0016] Furthermore, in the middle of the oxidation period, argon exhaust and oxygen blowing pipe are used to carry out mixed blowing smelting in the argon-oxygen volume ratio of (1:3), (1:2) and (1:1) to decarburize and retain chromium; argon-oxygen mixed blowing smelting reduces the CO partial pressure in the smelting process of the molten steel during the oxidation period, realizes the selective oxidation of VOD and AOD refining from the metallurgical dynamics, achieves the purpose of "decarburization and chromium retention", realizes the degassing and removal of impurities in the molten steel, improves the alloy recovery rate of the return material into the furnace, reduces production costs, reduces the difficulty of smelting operations, and ensures the quality of the molten steel.

[0017] The chemical composition of ZG06Cr13Ni4Mo martensitic stainless steel is shown in Table 1. Its outstanding features are low carbon and high chromium, which brings great difficulty to molten steel smelting.

[0018] Table 1: Chemical composition (mass fraction%)

[0019]

[0020] The invention aims to solve the problem of ZG06Cr13Ni4Mo martensitic stainless steel return process for hydropower and atomic power station castings in the absence of VOD and AOD refining furnace equipment, using a large proportion of ZG06Cr13Ni4Mo casting riser, ZG06Cr13Ni4Mo casting runner return material and a small proportion of carbon scrap steel, using a basic arc furnace lining of a low-carbon magnesia-chrome brick refractory material, using carbon scrap steel as the return charge, carrying out a smelting process flow of a melting period, an oxidation period and a reduction period in the basic arc furnace, using oxygen blowing to smelt decarburization and fluxing in the early oxidation period, using argon-oxygen ratio mixed blowing to smelt decarburization and chromium preservation in the middle oxidation period, using argon-oxygen ratio mixed blowing to smelt degassing in the late oxidation period, using argon exhaust and oxygen blowing pipe in the oxidation period to carry out argon-oxygen mixed blowing decarburization, reducing the CO partial pressure in the molten steel smelting process at a high temperature of 1650°C-1720°C, and from the perspective of metallurgical thermodynamics ( Figure 1 ) and metallurgical dynamics, the selective oxidation of VOD and AOD refining is realized, the purpose of "decarbonization and chromium preservation" is achieved, the degassing and inclusion removal operations are realized, the alloy recovery rate of the return material into the furnace is improved, the production cost is reduced, the difficulty of smelting operation is reduced, and the quality of molten steel is guaranteed.

[0021] Beneficial effects of the present invention:

[0022] The invention uses a large proportion of ZG06Cr13Ni4Mo casting risers, ZG06Cr13Ni4Mo casting runner return materials and a small proportion of carbon scrap steel, an alkaline arc furnace whose lining adopts low-carbon magnesia-chrome brick refractory materials, adopts carbon scrap steel as return charge, carries out smelting process flow of melting period, oxidation period and reduction period in the alkaline arc furnace, adopts oxygen mixed blowing smelting decarburization in the early stage of oxidation period, adjusts argon oxygen ratio mixed blowing smelting decarburization and chromium preservation in the middle stage of oxidation period, adjusts argon oxygen ratio mixed blowing smelting degassing in the late stage of oxidation period, adopts argon oxygen ratio mixed blowing smelting degassing by argon exhaust and oxygen blowing pipe in oxidation period, reduces CO partial pressure in molten steel smelting process at high temperature of 1650°C-1720°C, and reduces CO partial pressure in metallurgical thermodynamics ( Figure 1 ) and metallurgical dynamics, the selective oxidation of VOD and AOD refining is realized, the purpose of "decarbonization and chromium preservation" is achieved, the degassing and inclusion removal operations are realized, the alloy recovery rate of the return material into the furnace is improved, the production cost is reduced, the difficulty of smelting operation is reduced, and the quality of molten steel is guaranteed.

[0023] The method of the invention is used for smelting ZG06Cr13Ni4Mo martensitic stainless steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a graph showing the relationship between the oxidation free energy ΔGθ of elements in molten steel and temperature. DETAILED DESCRIPTION

[0025] Specific implementation method 1: This implementation method uses a basic arc furnace return method to smelt ZG06Cr13Ni4Mo martensitic stainless steel in an argon-oxygen mixed blowing oxidation period, using a ZG06Cr13Ni4Mo casting riser and a ZG06Cr13Ni4Mo casting runner to return the total amount of the charge to be added to 95% and a carbon scrap steel addition amount of 5% for subsequent smelting, using a basic arc furnace, using a ZG06Cr13Ni4Mo casting runner to return the charge It is mixed with carbon steel scrap and the smelting process flow of melting period, oxidation period and reduction period is carried out in an alkaline electric arc furnace. Oxygen blowing is used for decarburization and fluxing in the early stage of the oxidation period. Argon and oxygen ratio is adjusted for mixed blowing in the middle stage of the oxidation period for decarburization and chromium preservation. Argon and oxygen ratio is adjusted for mixed blowing at the end of the oxidation period for degassing. In the oxidation period, argon exhaust and oxygen blowing pipe are used for argon and oxygen mixed blowing for decarburization. At a temperature of 1650℃-1720℃, the CO partial pressure in the process of molten steel smelting is reduced to achieve decarburization and chromium preservation.

[0026] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the lining of the basic arc furnace used is low-carbon magnesia-chrome brick refractory material, and the smelting process flow of the melting period, oxidation period and reduction period is carried out. The rest is the same as specific embodiment 1.

[0027] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that: 5% carbon scrap steel is added to carbonize the molten steel, so that the C content in the molten steel after molten steel is higher than the upper limit of the finished product specification of 0.06-0.10%. Other aspects are the same as specific implementation method 1 or 2.

[0028] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that oxygen blowing is used in the early stage of oxidation period for smelting decarburization and fluxing. The rest is the same as specific embodiments 1 to 3.

[0029] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that oxygen blowing is used in the early stage of oxidation period to decarburize and flux the molten steel to a temperature above 1650° C. The rest is the same as specific embodiments 1 to 4.

[0030] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that: after the molten steel temperature is above 1650°C, an argon exhaust and an oxygen blowing pipe are used in the first stage of the middle stage of the oxidation period to carry out smelting decarburization and chromium preservation in accordance with an argon-oxygen ratio of 1:3; the carbon is reduced to about 0.08%, and the molten steel temperature is used to reach 1680°C. Others are the same as specific embodiments 1 to 5.

[0031] Specific embodiment 7: This embodiment is different from specific embodiments 1 to 6 in that: in the second stage of the oxidation middle stage, argon gas exhaust and oxygen blowing pipe are used to mix argon and oxygen in a volume ratio of 1:2 to smelt decarburization and retain chromium; carbon is reduced to about 0.05%, and the molten steel temperature is used to reach 1700°C. Others are the same as specific embodiments 1 to 6.

[0032] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that: in the third stage of the oxidation intermediate stage, argon exhaust and oxygen blowing pipe are used to carry out smelting decarburization and chromium preservation in a volume ratio of 1:1; carbon is reduced to below 0.03%, and the molten steel temperature is used to reach 1720°C. Other aspects are the same as specific embodiments 1 to 7.

[0033] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that an argon exhaust and an oxygen blowing pipe are used to carry out argon-oxygen mixed blowing decarburization during the oxidation period. The rest is the same as specific embodiments 1 to 8.

[0034] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that: in the middle of the oxidation period, argon exhaust and oxygen blowing pipe are used to carry out mixed blowing smelting according to the argon-oxygen volume ratio of (1:3), (1:2) and (1:1) to decarburize and preserve chromium; argon-oxygen mixed blowing smelting reduces the CO partial pressure during the oxidation period of molten steel, realizes the selective oxidation of VOD and AOD refining from the perspective of metallurgical dynamics, achieves the purpose of "decarburization and chromium preservation", realizes the degassing and inclusion removal of molten steel, improves the alloy recovery rate of the return material into the furnace, reduces production costs, reduces the difficulty of smelting operations, and ensures the quality of molten steel. Others are the same as specific embodiments 1 to 9.

[0035] The content of the present invention is not limited to the content of the above-mentioned embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0036] Example:

[0037] In this embodiment, a process for smelting ZG06Cr13Ni4Mo martensitic stainless steel by argon-oxygen mixed blowing during oxidation period using a basic arc furnace return method is specifically carried out in the following steps:

[0038] 1. The C content of ZG06Cr13Ni4Mo martensitic stainless steel is required to be ≤0.06%. In a process for smelting ZG06Cr13Ni4Mo martensitic stainless steel by argon-oxygen mixed blowing during the oxidation period using an alkaline arc furnace return method, the alkaline arc furnace lining uses low-carbon magnesia-chrome brick refractory materials.

[0039] 2. The alkaline arc furnace return method is used to smelt ZG06Cr13Ni4Mo martensitic stainless steel to produce alkaline slag.

[0040] 3. Use 95% of the same material ZG06Cr13Ni4Mo casting riser and ZG06Cr13Ni4Mo casting runner return material whose chemical composition meets Table 1, and use carbon scrap steel for the rest.

[0041] 4. Carbon steel scrap is used for carbon mixing.

[0042] 5. The smelting process flow of the melting period, oxidation period and reduction period is carried out in an alkaline arc furnace.

[0043] 6. The amount of oxidative decarburization during the smelting oxidation period was 0.06-0.10%.

[0044] 7. Blow oxygen to decarburize and assist melting in the early low-temperature stage of the oxidation period.

[0045] 8. When the temperature of molten steel reaches above 1650℃, in the first stage of oxidation period, argon exhaust and oxygen blowing pipe are used to mix argon and oxygen in a ratio of 1:3 to smelt decarburization and retain chromium, reduce carbon to about 0.08%, and use molten steel temperature to reach 1680℃.

[0046] 9. In the second stage of oxidation period, argon exhaust and oxygen blowing pipe are used to mix argon and oxygen in the ratio of 1:2 to decarburize and retain chromium. The carbon content is reduced to about 0.05%, and the temperature of molten steel reaches 1700℃.

[0047] 10. In the third stage of the oxidation period, argon exhaust and oxygen blowing pipe are used to mix argon and oxygen in a ratio of 1:1 to smelt decarburization and retain chromium. The carbon content is reduced to below 0.03%, and the molten steel temperature is used to reach 1720℃.

[0048] 11. In the middle of the oxidation period, argon exhaust and oxygen blowing pipe are used to mix and blow argon and oxygen in a ratio of 1:3, 1:2 and 1:1 to smelt decarburization and retain chromium.

[0049] 12. When the carbon content drops below 0.03%, use argon to purge for more than 15 minutes at the end of the oxidation period.

[0050] 13. When the carbon content is between 0.02 and 0.03, stop the argon blowing operation and take a full analysis sample to analyze the C, P, Cr, Ni, Mn, and Mo components.

[0051] 14. When the components of C, P, Cr, Ni, Mn and Mo meet the process requirements and the temperature meets the requirements, the reduction period is entered. During the reduction period, aluminum is inserted for pre-deoxidation, and then reducing slag FeSi powder and CaSi powder are added in batches for deoxidation and reduction.

Claims

1. A method for smelting ZG06Cr13Ni4Mo martensitic stainless steel by using a basic arc furnace return method and argon-oxygen mixed blowing during the oxidation period, characterized in that The total amount of ZG06Cr13Ni4Mo casting riser and ZG06Cr13Ni4Mo casting runner return charge is 95%, and the amount of carbon scrap steel added is 5% for subsequent smelting. An alkaline arc furnace is used, and ZG06Cr13Ni4Mo casting runner return charge and carbon scrap steel are used for carbon matching. The smelting process flow of melting period, oxidation period and reduction period is carried out in the alkaline arc furnace. Oxygen blowing is used for decarburization and fluxing in the early stage of the oxidation period. Argon and oxygen ratio are adjusted in the middle stage of the oxidation period for mixed blowing to decarburize and retain chromium. Argon and oxygen ratio are adjusted in the late stage of the oxidation period for mixed blowing to degas. Argon exhaust and oxygen blowing are used in the oxidation period for argon oxygen mixed blowing decarburization. At a temperature of 1650°C-1720°C, the CO partial pressure in the molten steel smelting process is reduced to achieve decarburization and chromium retention.

2. The method of smelting ZG06Cr13Ni4Mo martensitic stainless steel by using alkaline arc furnace return method oxidation period argon oxygen mixed blowing according to claim 1, characterized in that The alkaline electric arc furnace lining used is a low-carbon magnesia-chrome brick refractory material, and the smelting process flow includes the melting period, oxidation period and reduction period.

3. The method for smelting ZG06Cr13Ni4Mo martensitic stainless steel by using a basic arc furnace return method during an oxidation period with argon-oxygen mixed blowing according to claim 1, characterized in that 5% carbon scrap steel is added to carbonize the molten steel, so that the C content in the molten steel after molten steel is cleared is higher than the upper limit of the finished product specification of 0.06-0.10%.

4. A method for smelting ZG06Cr13Ni4Mo martensitic stainless steel by using a basic arc furnace return method during an oxidation period with argon and oxygen mixed blowing according to claim 1 or 3, characterized in that Oxygen blowing is used in the early stage of oxidation to decarburize and assist fluxing.

5. A method for smelting ZG06Cr13Ni4Mo martensitic stainless steel by using a basic arc furnace return method during an oxidation period with argon and oxygen mixed blowing according to claim 1 or 4, characterized in that Oxygen blowing is used in the early stage of oxidation to decarburize and assist melting, so that the molten steel temperature can reach above 1650℃.

6. The method of smelting ZG06Cr13Ni4Mo martensitic stainless steel by using alkaline arc furnace return method oxidation period argon oxygen mixed blowing according to claim 1, characterized in that When the temperature of the molten steel is above 1650℃, the first stage of the middle oxidation period uses argon exhaust and oxygen blowing pipe in a 1:3 argon-oxygen ratio to smelt decarburization and chromium preservation; the carbon is reduced to about 0.08%, and the molten steel temperature reaches 1680℃.

7. The method of smelting ZG06Cr13Ni4Mo martensitic stainless steel by using alkaline arc furnace return method oxidation period argon oxygen mixed blowing according to claim 1, characterized in that In the second stage of the middle oxidation period, argon exhaust and oxygen blowing pipe are used in a mixed blowing process with an argon-oxygen volume ratio of 1:2 to decarburize and preserve chromium; the carbon content is reduced to about 0.05%, and the molten steel temperature reaches 1700°C.

8. The method of smelting ZG06Cr13Ni4Mo martensitic stainless steel by using alkaline arc furnace return method oxidation period argon oxygen mixed blowing according to claim 1, characterized in that In the third stage of the middle oxidation period, argon exhaust and oxygen blowing pipe are used in a mixed blowing process with a volume ratio of argon and oxygen of 1:1 to decarburize and preserve chromium; the carbon is reduced to below 0.03% and the molten steel temperature reaches 1720°C.

9. A method for smelting ZG06Cr13Ni4Mo martensitic stainless steel by using a basic arc furnace return method during an oxidation period with argon and oxygen mixed blowing according to claim 6, 7 or 8, characterized in that During the oxidation period, argon exhaust and oxygen blowing pipe are used to carry out argon-oxygen mixed blowing decarburization.

10. The method of smelting ZG06Cr13Ni4Mo martensitic stainless steel by using alkaline arc furnace return method oxidation period argon oxygen mixed blowing according to claim 9, characterized in that In the middle of the oxidation period, argon exhaust and oxygen blowing pipe are used in accordance with the argon-oxygen volume ratio of (1:3), (1:2) and (1:1) for mixed smelting to remove carbon and retain chromium; argon-oxygen mixed blowing reduces the CO partial pressure during the oxidation period of molten steel, realizes the selective oxidation of VOD and AOD refining from the metallurgical dynamics, achieves the purpose of "removing carbon and retaining chromium", realizes the degassing and removal of inclusions in molten steel, improves the alloy recovery rate of the return material into the furnace, reduces production costs, reduces the difficulty of smelting operations, and ensures the quality of molten steel.

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