A vacuum consumable melting method for high nitrogen martensitic heat-resistant steel

Abstract

The present invention relates to the field of metallurgy technology and specifically discloses a vacuum consumable melting method for high-nitrogen martensitic heat-resistant steel, comprising the following steps: S110, preparing a consumable electrode and loading it into an electric vacuum consumable furnace; S120, evacuating the electric vacuum consumable furnace and then filling it with a protective gas; S130, energizing and arcing to form a molten pool, and starting the first stage of melting; S140, when 20% to 30% of the consumable electrode remains, in terms of weight percentage, starting the second stage of melting, wherein the second stage of melting is filling melting; S150, cooling and stripping the ingot after the smelting is completed to obtain a consumable ingot. This method reduces nitrogen loss during the smelting process of high-nitrogen martensitic heat-resistant steel by controlling the protective atmosphere of the vacuum consumable melting, thereby achieving high-quality and stable production of high-nitrogen martensitic heat-resistant steel.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a vacuum consumable melting method for high-nitrogen martensitic heat-resistant steel. Background Art

[0002] High-nitrogen martensitic heat-resistant steel is a key material for manufacturing components operating at high temperatures in industries such as boilers, steam turbines, power machinery, industrial furnaces, and aviation and petrochemicals. It must exhibit high strength and good chemical stability at high temperatures, sufficient toughness, good machinability and weldability, and a certain degree of structural stability. To ensure a long service life, extremely high requirements are placed on the purity of the material and the uniformity of the solidified structure.

[0003] Currently, all methods for producing high-end, high-nitrogen martensitic heat-resistant steels require secondary refining through vacuum consumable smelting. The vacuum consumable smelting (VAR) process melts consumable electrodes in a vacuum environment, utilizing arc heat to melt the steel layer by layer, effectively removing impurities (such as O, H, and S) while precisely controlling the content of gases (such as N). Nitrogen plays a crucial role in improving the high-temperature performance of this high-end, high-nitrogen martensitic heat-resistant steel. However, during conventional vacuum consumable smelting, nitrogen segregation and loss are significant, creating significant pores in the consumable ingots and severely reducing the steel's performance. Furthermore, due to the high alloy content in the steel, segregation and porosity are prone to occur during the smelting process.

[0004] Therefore, how to improve the quality of high nitrogen martensitic heat-resistant steel ingots has become a technical problem that needs to be solved urgently in the metallurgical field. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the main purpose of the present invention is to provide a vacuum consumable melting method for high-nitrogen martensitic heat-resistant steel, so as to solve the problems of high purity, composition uniformity, porosity and loose shrinkage cavities of the material under industrial preparation.

[0006] In order to solve at least one of the above technical problems, the present invention adopts the following technical solutions:

[0007] According to the present invention, a vacuum consumable melting method for high-nitrogen martensitic heat-resistant steel is provided, comprising the following steps: S110, preparing a consumable electrode and loading it into an electric vacuum consumable furnace; S120, evacuating the electric vacuum consumable furnace and then filling it with a protective gas; S130, forming a molten pool after power is turned on and arc is struck, and the first stage of melting is started; S140, when the consumable electrode remains at 20% to 30% by weight, the second stage of melting is started, wherein the second stage of melting is filling melting; S150, cooling and stripping the ingot after the melting is completed to obtain a consumable ingot.

[0008] According to one embodiment of the present invention, in step S110, the consumable electrode is obtained by electric furnace melting+argon oxygen decarburization+ladle refining or vacuum induction melting, wherein the consumable electrode is composed of the following chemical components in weight percentage: 0.08%-0.15% C, 0.5%-1.4% Mn, 2%-4% Ni, 9%-12% Cr, 1.5%-3% Mo, 0.2%-1% V, 0.06%-0.1% N, 0.11%-0.14% Si, 0.0032%-0.0045% P, 0.0019%-0.002% S, and the remainder is Fe and unavoidable impurities.

[0009] According to an embodiment of the present invention, in step S110, the consumable electrode is subjected to cap cutting and surface peeling treatment before being loaded into the electric vacuum consumable furnace.

[0010] According to one embodiment of the present invention, in step S120, the electric vacuum consumable furnace is first evacuated to a pressure below 1 Pa, and then filled with dry nitrogen.

[0011] According to one embodiment of the present invention, in step S120 , the pressure of the dry nitrogen gas charged is 5-20 Pa.

[0012] According to one embodiment of the present invention, in step S130, the first stage of smelting adopts a control system of melting rate + number of droplets.

[0013] According to one embodiment of the present invention, in step S130 , the melting rate is controlled to be 4.0-6.5 kg / min, and the number of droplets is controlled to be 1-15 (1 / s).

[0014] According to one embodiment of the present invention, in step S140 , the second stage of smelting adopts a melting rate + voltage control system.

[0015] According to one embodiment of the present invention, in step S140, the second stage smelting is divided into multi-stage filling, the current is controlled at 8.0~4.0A, the voltage is controlled at 24.0~21.0V, the melting rate is controlled at 4.0~1.0kg / min, the voltage and current are reduced step by step, the voltage is reduced by 0.1~0.8V each time, the current is reduced by 0.1~0.8A, and the heat is kept for 5~25min.

[0016] According to one embodiment of the present invention, in step S150, the electric vacuum consumable furnace is vacuumed again after power outage, and the ingot is removed to obtain the consumable ingot after the cooling time in the furnace is ≥2h.

[0017] By adopting the above technical solution, the vacuum consumable melting method of high-nitrogen martensitic heat-resistant steel according to the present invention reduces nitrogen loss during the smelting process of high-nitrogen martensitic heat-resistant steel by controlling the vacuum consumable protective atmosphere. At the same time, by designing the control system of melting rate + droplet and melting rate + voltage, the molten pool is stabilized during the normal melting process, and good thermal sealing can be achieved during the filling melting process, effectively avoiding component segregation, pores, and loose shrinkage cavities at the head of the consumable ingot, thereby improving the solidification quality and yield rate of the consumable ingot. The method is simple and efficient, and can achieve high-quality and stable production of high-nitrogen martensitic heat-resistant steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 Schematic diagram of the steps of a vacuum consumable melting method for high nitrogen martensitic heat-resistant steel according to one embodiment of the present invention;

[0020] Figure 2 This is a metallographic diagram of the consumable ingot obtained according to Example 1 of the present invention;

[0021] Figure 3 This is the metallographic diagram of the consumable ingot obtained in the comparative example. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0023] It should be understood that the embodiments of the present invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in the present invention, it is readily apparent to those skilled in the art that various modifications are feasible without departing substantially from the teachings of the subject matter of the present invention. Accordingly, all such modifications should be included within the scope of the present invention. Without departing from the gist of the present invention, other replacements, modifications, variations, and deletions may be made to the design, operating conditions, and parameters of the following exemplary embodiments.

[0024] The present invention provides a vacuum consumable melting method for high nitrogen martensitic heat-resistant steel. Figure 1 As shown, the vacuum consumable melting method of high nitrogen martensitic heat-resistant steel according to one embodiment of the present invention generally includes the following steps:

[0025] Step S110, preparing a consumable electrode and placing it into an electric vacuum consumable furnace;

[0026] Step S120, evacuating the electric vacuum consumable furnace and then filling it with protective gas;

[0027] Step S130, after power is turned on and arc is struck, a molten pool is formed and the first stage of smelting begins;

[0028] Step S140, when the consumable electrode remains at 20% to 30% by weight, the second stage of smelting is started, wherein the second stage of smelting is filling smelting;

[0029] Step S150: After smelting is completed, the ingot is cooled and removed to obtain a consumable ingot.

[0030] Step S110 can produce a consumable electrode through electric furnace melting, argon oxygen decarburization (AOD), ladle refining (LF), or vacuum induction melting. In an embodiment of the present invention, the consumable electrode may be composed of the following chemical composition by weight: 0.05%-0.15% C, 0.5%-1.4% Mn, 0.5%-4% Ni, 9%-13% Cr, 0.5%-3% Mo, 0.1%-1% V, 0.01%-0.08% N, 0.1%-0.8% Si, 0.002%-0.005% P, 0.001%-0.003% S, with the remainder being Fe and unavoidable impurities. The specific composition design of the consumable electrode requires comprehensive consideration of material properties, process characteristics, and final application requirements. In other embodiments, those skilled in the art can utilize the teachings disclosed herein to achieve desired properties and appropriately vary the values ​​of each element. It should be understood that the use of numerical ranges expressed as endpoints includes all numbers within that range and any range within that range. Taking C as an example, 0.05%~0.15% may include 0.05%, 0.10%, 0.12%, 0.13%, 0.15%, etc.

[0031] Preferably, the consumable electrode can be capped and surface peeled before being loaded into the electric vacuum consumable furnace to prevent molten pool instability and oxygenation of the consumable ingot during vacuum consumable smelting, thereby reducing the solidification quality and cleanliness of the consumable ingot.

[0032] Step S120 first evacuates the electric vacuum consumable furnace to below 1 Pa, and then fills it with dry nitrogen to prevent air from adding oxygen and hydrogen to the consumable ingots. This also inhibits nitrogen volatilization during the smelting process, improving nitrogen yield and composition uniformity. In actual operation, excessive dry nitrogen filling will lead to instability in the molten pool during normal smelting, affecting smelting quality, while insufficient dry nitrogen filling will fail to effectively control the nitrogen content of the consumable ingots. In an embodiment of the present invention, based on the composition of the molten steel and the characteristics of the consumable furnace smelting, the dry nitrogen pressure preferably ranges from 5 to 20 Pa.

[0033] In step S130, the first stage of smelting utilizes a control system combining melt rate and droplet number. The melt rate refers to the melting rate of the consumable electrode during vacuum consumable smelting, which directly affects the molten pool depth, solidification behavior, and composition distribution. Excessively high melt rates lead to excessively deep molten pools, increasing the risk of segregation; while excessively low melt rates can reduce production efficiency. In embodiments of the present invention, the melt rate is preferably controlled between 4.0 and 6.5 kg / min. The droplet number refers to the number of droplets per unit time during vacuum consumable smelting, which influences the molten pool temperature distribution and solidification behavior. Excessively high droplet numbers can cause molten pool temperature fluctuations, while excessively low droplet numbers can affect molten pool fluidity. In embodiments of the present invention, the droplet number is preferably controlled between 1 and 10 (1 / s). By synergistically controlling the melt rate and droplet number, the present invention achieves a stable melt rate, an active molten pool, and a stable molten pool state during the smelting process. This helps prevent segregation of molten steel components, improves inclusion removal, avoids the formation of pores in consumable ingots, and improves the solidification quality of consumable ingots.

[0034] In step S140, the second stage of smelting adopts a melting rate + voltage control system, using low voltage, low current and low melting rate. The melting current can directly affect the molten pool temperature, melting rate and arc stability. The appropriate current can maintain a stable arc and molten pool depth, promote molten pool convection to reduce element segregation, and at the same time avoid excessive volatilization of nitrogen and retain the required nitrogen content. The voltage affects the arc length, molten pool shape and energy input. In an embodiment of the present invention, the second stage can be divided into multiple filling stages, with the current controlled at 8.0~4.0A, the voltage controlled at 24.0~21.0V, and the melting rate controlled at 4.0~1.0kg / min. The voltage and current are gradually reduced, each time reducing the voltage by 0.1~0.6V and the current by 0.2~0.8A, and the temperature is kept at 5~25min. The second stage of smelting can effectively improve the loose shrinkage cavity at the head of the consumable ingot and improve the yield rate by coordinating the current and voltage and adopting a reasonable filling smelting process.

[0035] In an embodiment of the present invention, in step S150, the electric vacuum consumable furnace is vacuumed again after power failure, and the ingot is removed to obtain the consumable ingot after the cooling time in the furnace is ≥2h.

[0036] The following are specific embodiments of the vacuum consumable melting method for high nitrogen martensitic heat-resistant steel according to the present invention and their specific process parameters.

[0037] The specific chemical compositions of the consumable electrodes prepared in Examples 1-5 are shown in Table 1:

[0038] Table 1 Chemical composition of consumable electrodes in various examples, the remainder being iron (wt.%)

[0039]

[0040] Example 1:

[0041] This embodiment discloses a vacuum consumable melting method for high nitrogen martensitic heat-resistant steel, comprising the following steps:

[0042] Step S110: First, the consumable electrode required for vacuum consumables is obtained by vacuum induction smelting, and then the cap is cut off and the surface is peeled before being loaded into an electric vacuum consumable furnace.

[0043] Step S120: evacuate the vacuum consumable furnace to below 1 Pa, and then fill it with 15 Pa of dry nitrogen;

[0044] Step S130: After the arc is energized and a molten pool is formed, normal smelting begins, with the melting rate controlled at 4.0-5.5 kg / min and the number of droplets at 1-10 (1 / s);

[0045] Step S140: When the weight of the remaining consumable electrode ingots reaches 25%, filling smelting begins;

[0046] Step S150: After the smelting is completed, the furnace is cooled for 2.5 hours and then the ingot is removed to obtain a Φ400mm consumable ingot.

[0047] Among them, step S140 can be divided into 6 stages for filling and melting, with the melting rate controlled at 3.0-1.0 kg / min, and the voltage and current reduced step by step. Specifically:

[0048] Step S141: reduce the current to 23.5V, 7A, and maintain for 5 minutes;

[0049] Step S142: reduce the current to 22.8V, 6.3A, and maintain for 10 minutes;

[0050] Step S143: reduce the current to 22.2V, 5.7A, and maintain for 15 minutes;

[0051] Step S144: reduce the current to 21.6V, 5.1A, and maintain for 20 minutes;

[0052] Step S145: reduce the current to 21.2V, 4.7A, and maintain for 20 minutes;

[0053] Step S146: Reduce the current to 21.0 V, 4.5 A, and maintain for 10 minutes.

[0054] Example 2:

[0055] This embodiment discloses a vacuum consumable melting method for high nitrogen martensitic heat-resistant steel, comprising the following steps:

[0056] Step S110: First, the consumable electrode required for vacuum consumables is obtained by smelting in an electric furnace, AOD, and LF, and then the cap is cut off and the surface is peeled before being loaded into an electric vacuum consumable furnace;

[0057] Step S120: evacuate the vacuum consumable furnace to below 1 Pa, and then fill it with 18 Pa of dry nitrogen;

[0058] Step S130: After the arc is energized and a molten pool is formed, normal smelting begins, with the melting rate controlled at 4.5-6.0 kg / min and the number of droplets at 2-12 (1 / s);

[0059] Step S140: When the weight of the remaining consumable electrode ingots reaches 25%, filling smelting begins;

[0060] Step S150: After the smelting is completed, the furnace is cooled for 2.5 hours and then the ingot is removed to obtain a Φ450mm consumable ingot.

[0061] Among them, step S140 can be divided into 6 stages for filling and melting, with the melting rate controlled at 3.5~1.5kg / min, and the voltage and current reduced step by step. Specifically:

[0062] Step S141: reduce the current to 23.3V, 6.8A, and maintain for 5 minutes;

[0063] Step S142: reduce the current to 22.7V, 6.2A, and maintain for 10 minutes;

[0064] Step S143: reduce the current to 22.2V, 5.7A, and maintain for 15 minutes;

[0065] Step S144: reduce the current to 21.7V, 5.2A, and maintain for 20 minutes;

[0066] Step S145: reduce the current to 21.3V, 4.8A, and maintain for 20 minutes;

[0067] Step S146: Reduce the current to 21.0 V, 4.5 A, and maintain for 10 minutes.

[0068] Example 3:

[0069] This embodiment discloses a vacuum consumable melting method for high nitrogen martensitic heat-resistant steel, comprising the following steps:

[0070] Step S110: First, the consumable electrode required for vacuum consumables is obtained by smelting in an electric furnace, AOD, and LF, and then the cap is cut off and the surface is peeled before being loaded into an electric vacuum consumable furnace;

[0071] Step S120: evacuate the vacuum consumable furnace to below 1 Pa, and then fill it with 20 Pa of dry nitrogen;

[0072] Step S130: After the arc is energized and a molten pool is formed, normal smelting begins, with the melting rate controlled at 5.0-6.5 kg / min and the number of droplets at 1-13 (1 / s);

[0073] Step S140: When the remaining weight of the consumable electrode ingots is 28%, filling smelting begins;

[0074] Step S150: After the smelting is completed, the furnace is cooled for 3 hours and then the ingot is removed to obtain a Φ500mm consumable ingot.

[0075] Among them, step S140 can be divided into 6 stages for filling and melting, with the melting rate controlled at 4.0-1.5 kg / min, and the voltage and current reduced step by step. Specifically:

[0076] Step S141: reduce the current to 24.0V, 7.8A, and maintain for 10 minutes;

[0077] Step S142: reduce the current to 23.2V, 7.0A, and maintain for 15 minutes;

[0078] Step S143: reduce the current to 22.5V, 6.3A, and maintain for 20 minutes;

[0079] Step S144: reduce the current to 21.9V, 5.7A, and maintain for 25 minutes;

[0080] Step S145: reduce the current to 21.4V, 5.2A, and maintain for 15 minutes;

[0081] Step S146: Reduce the current to 21.1 V, 5.0 A, and maintain for 7 minutes.

[0082] Example 4:

[0083] This embodiment discloses a vacuum consumable melting method for high nitrogen martensitic heat-resistant steel, comprising the following steps:

[0084] Step S110: First, the consumable electrode required for vacuum consumables is obtained by smelting in an electric furnace, AOD, and LF, and then the cap is cut off and the surface is peeled before being loaded into an electric vacuum consumable furnace;

[0085] Step S120: evacuate the vacuum consumable furnace to below 1 Pa, and then fill it with 12 Pa of dry nitrogen;

[0086] Step S130: After the arc is energized and a molten pool is formed, normal smelting begins, with the melting rate controlled at 4.0-6.0 kg / min and the number of droplets at 1-12 (1 / s);

[0087] Step S140: When the remaining weight of the consumable electrode ingots is 20%, filling smelting begins;

[0088] Step S150: After the smelting is completed, the furnace is cooled for 2 hours and then the ingot is removed to obtain a Φ450mm consumable ingot.

[0089] Among them, step S140 can be divided into 5 stages for filling and melting, with the melting rate controlled at 3.5~1.5kg / min, and the voltage and current reduced step by step. Specifically:

[0090] Step S141: reduce the current to 23.0V, 7.0A, and maintain for 5 minutes;

[0091] Step S142: reduce the current to 22.4V, 6.5A, and maintain for 10 minutes;

[0092] Step S143: reduce the current to 21.8V, 6.0A, and maintain for 15 minutes;

[0093] Step S144: reduce the current to 21.4V, 5.5A, and maintain for 15 minutes;

[0094] Step S145: reduce the current to 21.0 V, 5.0 A, and maintain for 10 minutes.

[0095] Example 5:

[0096] This embodiment discloses a vacuum consumable melting method for high nitrogen martensitic heat-resistant steel, comprising the following steps:

[0097] Step S110: First, the consumable electrode required for vacuum consumables is obtained by smelting in an electric furnace, AOD, and LF, and then the cap is cut off and the surface is peeled before being loaded into an electric vacuum consumable furnace;

[0098] Step S120: evacuate the vacuum consumable furnace to below 1 Pa, and then fill it with 8 Pa of dry nitrogen;

[0099] Step S130: After the arc is energized and a molten pool is formed, normal smelting begins, with the melting rate controlled at 5.0-6.5 kg / min and the number of droplets at 1-15 (1 / s);

[0100] Step S140: When the remaining weight of the consumable electrode ingots reaches 30%, filling smelting begins;

[0101] Step S150: After the smelting is completed, the furnace is cooled for 3.5 hours and then the ingot is removed to obtain a Φ580mm consumable ingot.

[0102] Among them, step S140 can be divided into 7 stages for filling and melting, with the melting rate controlled at 4.0-1.0 kg / min, and the voltage and current reduced step by step. Specifically:

[0103] Step S141: reduce the current to 24.0V, 7.0A, and maintain for 10 minutes;

[0104] Step S142: reduce the current to 23.4V, 6.4A, and maintain for 10 minutes;

[0105] Step S143: reduce the current to 23.8V, 5.8A, and maintain for 15 minutes;

[0106] Step S144: reduce the current to 23.2V, 5.3A, and maintain for 25 minutes;

[0107] Step S145: reduce the current to 22.6V, 4.8A, and maintain for 20 minutes;

[0108] Step S146: reduce the current to 22.1V, 4.4A, and maintain for 20 minutes;

[0109] Step S147: Reduce the current to 21.7 V, 4.0 A, and maintain for 10 minutes.

[0110] Comparative Example:

[0111] First, the consumable electrode required for vacuum consumable electrode is obtained by smelting in an electric furnace + AOD + LF, and then the cap is cut off and the surface is peeled before being loaded into an electric vacuum consumable furnace. The vacuum consumable furnace is evacuated to below 1Pa, and after the arc is powered on to form a molten pool, normal smelting begins, and the melting rate is controlled at 6.5~7.5kg / min. When the weight of the remaining consumable electrode ingot is 32%, filling smelting begins, and the melting rate is controlled at 2~4 kg / min during filling. After the smelting is completed, the furnace is cooled for 2h and the ingot is removed to obtain a Φ450mm consumable ingot.

[0112] The main chemical components of the A-end and H-end of the high nitrogen martensitic heat-resistant steel consumable ingots obtained in Examples 1-5 were detected, and the main chemical components of the two ends of the high nitrogen martensitic heat-resistant steel ingot obtained in the comparative example were detected. The results are shown in Table 2:

[0113] Table 2 Chemical composition (wt.%) of the electrode rods of various embodiments and the consumable ingots of the comparative examples

[0114]

[0115] in conclusion

[0116] The inclusion rating of the high nitrogen martensitic heat-resistant steel ingots obtained in Examples 1-5 and the comparative example is shown in Table 3:

[0117] Table 3 Inclusion rating results

[0118]

[0119] contrast Figure 2 The metallographic diagram of the consumable ingot obtained in Example 1 of the present invention is shown in FIG. Figure 3 The metallographic diagram of the consumable ingot obtained in the comparative example is shown. The structure obtained in the embodiment is dense and has no solidification defects, while the structure obtained in the comparative example is loose and has serious shrinkage defects.

[0120] The present invention controls the protective atmosphere of vacuum consumable smelting and optimizes the smelting system, thereby reducing nitrogen escape during the smelting process, effectively improving the component segregation and solidification quality of the consumable ingot, and improving the cleanliness of the alloy. At the same time, it reduces shrinkage cavities and loose areas at the feeding end, improves the alloy yield rate, and can achieve high-quality and stable production of high-nitrogen martensitic heat-resistant steel.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. If the present invention is modified or replaced with equivalents without departing from the spirit and scope of the present invention, it should be included in the scope of protection of the claims of the present invention.

[0122] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the disclosure of the embodiments of the present invention is limited to these examples. Within the spirit of the embodiments of the present invention, the technical features of the above embodiments or different embodiments may be combined, and there are many other variations of the various aspects of the embodiments of the present invention described above, which are not provided in detail for the sake of clarity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention shall be included within the scope of protection of the embodiments of the present invention.

Claims

1. A vacuum consumable melting method for high nitrogen martensitic heat-resistant steel, characterized in that: The following steps are involved: S110, preparing a consumable electrode and loading it into an electric vacuum consumable furnace; S120, evacuating the electric vacuum consumable furnace and then filling it with a protective gas; S130, after power is turned on and arc is struck, a molten pool is formed and the first stage of smelting begins. The first stage of smelting adopts a control system of melting rate + number of droplets, with the melting rate controlled to be 4.0-6.5 kg / min and the number of droplets controlled to be 1-15 (1 / s); S140, when the consumable electrode remains at 20% to 30% by weight, the second stage smelting is started, wherein the second stage smelting is a multi-stage filling smelting, wherein the second stage smelting adopts a melting rate + voltage control system, wherein the current is controlled at 8.0 to 4.0 A, the voltage is controlled at 24.0 to 21.0 V, and the melting rate is controlled at 4.0 to 1.0 kg / min, and the voltage and current are gradually reduced, each time by 0.1 to 0.6 V and the current is reduced by 0.2 to 0.8 A, and the temperature is kept at this temperature for 5 to 25 minutes; S150, after the smelting is completed, the ingot is cooled and removed to obtain a consumable ingot.

2. The method according to claim 1, characterized in that In step S110, the consumable electrode is obtained by electric furnace melting + argon oxygen decarburization + ladle refining or vacuum induction melting; The consumable electrode is composed of the following chemical components in weight percentage: 0.08% to 0.15% C, 0.5% to 1.4% Mn, 2% to 4% Ni, 9% to 12% Cr, 1.5% to 3% Mo, 0.2% to 1% V, 0.06% to 0.1% N, 0.11% to 0.14% Si, 0.0032% to 0.0045% P, 0.0019% to 0.002% S, and the remainder is Fe and unavoidable impurities.

3. The method according to claim 1, characterized in that In step S110, the consumable electrode is subjected to cap cutting and surface peeling treatment before being loaded into the electric vacuum consumable furnace.

4. The method according to claim 1, wherein In step S120, the electric vacuum consumable furnace is first evacuated to a pressure below 1 Pa, and then filled with dry nitrogen.

5. The method according to claim 4, characterized in that In step S120, the pressure of the dry nitrogen gas charged is 5-20 Pa.

6. The method according to claim 1, characterized in that In step S150, the electric vacuum consumable furnace is evacuated again after power is turned off, and the ingot is removed to obtain a consumable ingot after the cooling time in the furnace is ≥2h.

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