Non-vacuum melting method of martensitic stainless steel

Abstract

The invention relates to the technical field of alloy smelting, in particular to a martensitic stainless steel non-vacuum smelting method which comprises the steps of raw material preparation, primary feeding, smelting, secondary feeding, slagging, slagging-off, raw material supplementation, deoxidation and tapping. According to the method, through process improvement, smelting in a non-vacuum medium-frequency induction furnace is achieved, smelting in a vacuum state is not needed, the equipment replacement cost is saved, through process improvement, burning loss of some elements in the smelting process can be avoided, chemical components are controllable, spectral analysis is conducted in the smelting process, and the smelting efficiency is improved. And missing metal elements are added in the process, so that the smelting finished product degree can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of alloy smelting, and in particular to a non-vacuum melting method for martensitic stainless steel. Background Art

[0002] The opening of the Arctic route is gradually opening the door to the stainless steel propeller market for ice-cold ships, and martensitic stainless steel materials are gradually entering the historical stage of manufacturing propellers for ice-cold ships. The martensitic stainless steel materials used to manufacture propellers for ice-cold ships are high-purity steels with extremely low carbon content, which have very high requirements for molten steel liquid, and conventional smelting methods cannot achieve this at all. Traditional martensitic stainless steel smelting usually adopts out-of-furnace refining processes, such as AOD, VOD, VODC, LF method, etc. The basic principle is to blow oxygen, blow argon, and evacuate; it is used to decarbonize, degas, and remove inclusions, and it needs to be done in a vacuum environment. At present, most casting product manufacturers choose to use ordinary non-vacuum medium-frequency induction furnaces to melt martensitic stainless steel because vacuum melting furnaces are expensive. In this non-vacuum environment, some elements are severely burned, especially C elements, and it is very difficult to control the chemical composition during the smelting process. Summary of the invention

[0003] In order to overcome the technical problems in the prior art of difficult smelting and difficult control of elements of martensitic stainless steel, the present invention provides a non-vacuum smelting method for martensitic stainless steel.

[0004] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: a non-vacuum melting method of martensitic stainless steel, comprising the following steps:

[0005] S1: prepare 0Cr13Ni4Mo alloy ingot, industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum, ferrosilicon, limestone, slag collector, covering agent, and silicon-calcium alloy according to the mass ratio of 0-150:10:2:36:2:2:4:1:1:1 for use;

[0006] S2: evenly spread limestone accounting for 80% of the total limestone mass in the raw materials on the bottom of the medium frequency induction furnace, put all the 0Cr13Ni4Mo alloy ingots into the middle of the furnace chamber, and then add industrial pure iron accounting for 80% of the total industrial pure iron mass in the raw materials, micro-carbon soldering iron accounting for 80% of the total micro-carbon soldering iron mass in the raw materials, ferromolybdenum accounting for 80% of the total ferromolybdenum mass in the raw materials, and electrolytic nickel accounting for 80% of the total electrolytic nickel mass in the raw materials in sequence;

[0007] S3: raising the temperature of the medium frequency induction furnace to 1000°C and maintaining the furnace at 1000°C;

[0008] S4: Continue to raise the temperature until the charge is melted and molten steel is visible or the charge sinks, then add the remaining industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum and ferrosilicon;

[0009] S5: adding a slag collecting agent to cover the surface of the molten steel until all the raw materials are melted, and then slag making and slag removal are performed, and this step is repeated until no slag is discharged;

[0010] S6: maintaining the temperature after heating and taking samples for spectral analysis, comparing the spectral analysis results with the target composition, and adding metal raw materials corresponding to the elements that do not reach the target composition into the furnace until the chemical composition of the molten steel reaches the target composition;

[0011] S7: adding the remaining limestone and silicon-calcium alloy for deoxidation in the furnace;

[0012] S8: Raise the furnace temperature to 1680-1700℃ and tap the steel at this temperature. After the molten steel fills the ladle, add a covering agent on the surface of the molten steel to complete the smelting.

[0013] Preferably, in step 1, the mass of the 0Cr13Ni4Mo alloy ingot is 90% of the total planned smelting amount.

[0014] Preferably, in step S3, the smelting is maintained at 1000° C. for 2 hours.

[0015] Preferably, the mass fraction of each element in the target composition described in step S6 is: C≤0.06%, Si≤1.0%, Mn≤2.0%, P≤0.035%, S≤0.030%, Ni: 3.5%~5.0%, Cr: 11.5%~17.0%, Mo≤1.0%.

[0016] Preferably, in step S6, the metal ingots corresponding to the elements that do not reach the target composition are added into the furnace, and the mass of the added metal raw material is calculated as: the product of the total planned smelting amount and the difference between the mass fraction of the element in the sample and the mass fraction of the target composition.

[0017] Compared with the prior art, the beneficial effect of the present invention lies in that, through the improvement of the process, smelting can be carried out in a non-vacuum medium frequency induction furnace without the need to carry out smelting in a vacuum state, thus saving the cost of equipment replacement. Through the improvement of the process, the burning of some elements in the smelting process can be avoided, the chemical composition can be controlled, spectral analysis can be carried out during the smelting process, and the missing metal elements can be added in this process, which can improve the smelting finished product. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0019] A specific implementation of a non-vacuum melting method for martensitic stainless steel of the present invention comprises the following steps:

[0020] Embodiment 1: S1: prepare 0Cr13Ni4Mo alloy ingot, industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum, ferrosilicon, limestone, slag collector, covering agent, and silicon-calcium alloy in a mass ratio of 150:10:2:36:2:2:4:1:1:1 for standby use, and the mass of the 0Cr13Ni4Mo alloy ingot is 90% of the total planned smelting amount;

[0021] S2: evenly spread limestone accounting for 80% of the total limestone mass in the raw materials on the bottom of the medium frequency induction furnace, put all the 0Cr13Ni4Mo alloy ingots into the middle of the furnace chamber, and then add industrial pure iron accounting for 80% of the total industrial pure iron mass in the raw materials, micro-carbon soldering iron accounting for 80% of the total micro-carbon soldering iron mass in the raw materials, ferromolybdenum accounting for 80% of the total ferromolybdenum mass in the raw materials, and electrolytic nickel accounting for 80% of the total electrolytic nickel mass in the raw materials in sequence;

[0022] S3: raising the temperature of the medium frequency induction furnace to 1000°C and maintaining the temperature at 1000°C for 2 hours;

[0023] S4: Continue to raise the temperature until the charge is melted and molten steel is visible or the charge sinks, then add the remaining industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum and ferrosilicon;

[0024] S5: After all the raw materials are melted, a slag collecting agent is added to cover the surface of the molten steel, slag is made, slag is removed, and this step is repeated until no slag is discharged;

[0025] S6: Maintain the temperature after heating and take samples for spectral analysis, compare the spectral analysis results with the target composition, add the metal raw materials corresponding to the elements that have not reached the target composition into the furnace until the chemical composition of the molten steel reaches the target composition. The mass fraction of each element in the target composition is: C≤0.06%, Si≤1.0%, Mn≤2.0%, P≤0.035%, S≤0.030%, Ni: 3.5%~5.0%, Cr: 11.5%~17.0%, Mo≤1.0%, and the mass of the added metal raw materials is calculated as: the product of the total planned smelting amount and the difference between the mass fraction of the element in the sample and the mass fraction of the target composition;

[0026] S7: adding the remaining limestone and silicon-calcium alloy for deoxidation in the furnace;

[0027] S8: Raise the furnace temperature to 1680°C and tap the steel at this temperature. After the molten steel fills the ladle, add a covering agent on the surface of the molten steel to complete the smelting.

[0028] The chemical composition of the martensitic stainless steel obtained in this embodiment is shown in Table 1:

[0029] Table 1

[0030]

[0031] Embodiment 2: S1: prepare 0Cr13Ni4Mo alloy ingot, industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum, ferrosilicon, limestone, slag collector, covering agent, and silicon-calcium alloy in a mass ratio of 0:10:2:36:2:2:4:1:1:1 for standby use, and the mass of the 0Cr13Ni4Mo alloy ingot is 90% of the total planned smelting amount;

[0032] S2: evenly spread limestone accounting for 80% of the total limestone mass in the raw materials on the bottom of the medium frequency induction furnace, put all the 0Cr13Ni4Mo alloy ingots into the middle of the furnace chamber, and then add industrial pure iron accounting for 80% of the total industrial pure iron mass in the raw materials, micro-carbon soldering iron accounting for 80% of the total micro-carbon soldering iron mass in the raw materials, ferromolybdenum accounting for 80% of the total ferromolybdenum mass in the raw materials, and electrolytic nickel accounting for 80% of the total electrolytic nickel mass in the raw materials in sequence;

[0033] S3: raising the temperature of the medium frequency induction furnace to 1000°C and maintaining the temperature at 1000°C for 2 hours;

[0034] S4: Continue to raise the temperature until the charge is melted and molten steel is visible or the charge sinks, then add the remaining industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum and ferrosilicon;

[0035] S5: After all the raw materials are melted, a slag collecting agent is added to cover the surface of the molten steel, and slag is made and removed, and this step is repeated until no slag is discharged;

[0036] S6: Maintain the temperature after heating and take samples for spectral analysis, compare the spectral analysis results with the target composition, add the metal raw materials corresponding to the elements that have not reached the target composition into the furnace until the chemical composition of the molten steel reaches the target composition. The mass fraction of each element in the target composition is: C≤0.06%, Si≤1.0%, Mn≤2.0%, P≤0.035%, S≤0.030%, Ni: 3.5%~5.0%, Cr: 11.5%~17.0%, Mo≤1.0%, and the mass of the added metal raw materials is calculated as: the product of the total planned smelting amount and the difference between the mass fraction of the element in the sample and the mass fraction of the target composition;

[0037] S7: adding the remaining limestone and silicon-calcium alloy for deoxidation in the furnace;

[0038] S8: Raise the furnace temperature to 1680°C and tap the steel at this temperature. After the molten steel fills the ladle, add a covering agent on the surface of the molten steel to complete the smelting.

[0039] The chemical composition of the martensitic stainless steel obtained in this embodiment is shown in Table 2:

[0040] Table 2

[0041]

[0042] Example 3: S1: prepare 0Cr13Ni4Mo alloy ingot, industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum, ferrosilicon, limestone, slag collector, covering agent, and silicon-calcium alloy in a mass ratio of 75:10:2:36:2:2:4:1:1:1 for standby use, and the mass of the 0Cr13Ni4Mo alloy ingot is 90% of the total planned smelting amount;

[0043] S2: evenly spread limestone accounting for 80% of the total limestone mass in the raw materials on the bottom of the medium frequency induction furnace, put all the 0Cr13Ni4Mo alloy ingots into the middle of the furnace chamber, and then add industrial pure iron accounting for 80% of the total industrial pure iron mass in the raw materials, micro-carbon soldering iron accounting for 80% of the total micro-carbon soldering iron mass in the raw materials, ferromolybdenum accounting for 80% of the total ferromolybdenum mass in the raw materials, and electrolytic nickel accounting for 80% of the total electrolytic nickel mass in the raw materials in sequence;

[0044] S3: raising the temperature of the medium frequency induction furnace to 1000°C and maintaining the temperature at 1000°C for 2 hours;

[0045] S4: Continue to raise the temperature until the charge is melted and molten steel is visible or the charge sinks, then add the remaining industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum and ferrosilicon;

[0046] S5: After all the raw materials are melted, a slag collecting agent is added to cover the surface of the molten steel, and slag is made and removed, and this step is repeated until no slag is discharged;

[0047] S6: Maintain the temperature after heating and take samples for spectral analysis, compare the spectral analysis results with the target composition, add the metal raw materials corresponding to the elements that have not reached the target composition into the furnace until the chemical composition of the molten steel reaches the target composition. The mass fraction of each element in the target composition is: C≤0.06%, Si≤1.0%, Mn≤2.0%, P≤0.035%, S≤0.030%, Ni: 3.5%~5.0%, Cr: 11.5%~17.0%, Mo≤1.0%, and the mass of the added metal raw materials is calculated as: the product of the total planned smelting amount and the difference between the mass fraction of the element in the sample and the mass fraction of the target composition;

[0048] S7: adding the remaining limestone and silicon-calcium alloy for deoxidation in the furnace;

[0049] S8: Raise the furnace temperature to 1690°C and tap the steel at this temperature. After the molten steel fills the ladle, add a covering agent on the surface of the molten steel to complete the smelting.

[0050] The chemical composition of the martensitic stainless steel obtained in this embodiment is shown in Table 3:

[0051] Table 3

[0052]

[0053]

[0054] Example 4: S1: Prepare 0Cr13Ni4Mo alloy ingot, industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum, ferrosilicon, limestone, slag collector, covering agent, and silicon-calcium alloy in a mass ratio of 150:10:2:36:2:2:4:1:1:1 for standby use, and the mass of the 0Cr13Ni4Mo alloy ingot is 90% of the total planned smelting amount;

[0055] S2: evenly spread limestone accounting for 80% of the total limestone mass in the raw materials on the bottom of the medium frequency induction furnace, put all the 0Cr13Ni4Mo alloy ingots into the middle of the furnace chamber, and then add industrial pure iron accounting for 80% of the total industrial pure iron mass in the raw materials, micro-carbon soldering iron accounting for 80% of the total micro-carbon soldering iron mass in the raw materials, ferromolybdenum accounting for 80% of the total ferromolybdenum mass in the raw materials, and electrolytic nickel accounting for 80% of the total electrolytic nickel mass in the raw materials in sequence;

[0056] S3: raising the temperature of the medium frequency induction furnace to 1000°C and maintaining the temperature at 1000°C for 2 hours;

[0057] S4: Continue to raise the temperature until the charge is melted and molten steel is visible or the charge sinks, then add the remaining industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum and ferrosilicon;

[0058] S5: After all the raw materials are melted, a slag collecting agent is added to cover the surface of the molten steel, slag is made, slag is removed, and this step is repeated until no slag is discharged;

[0059] S6: Maintain the temperature after heating and take samples for spectral analysis, compare the spectral analysis results with the target composition, add the metal raw materials corresponding to the elements that have not reached the target composition into the furnace until the chemical composition of the molten steel reaches the target composition. The mass fraction of each element in the target composition is: C≤0.06%, Si≤1.0%, Mn≤2.0%, P≤0.035%, S≤0.030%, Ni: 3.5%~5.0%, Cr: 11.5%~17.0%, Mo≤1.0%, and the mass of the added metal raw materials is calculated as: the product of the total planned smelting amount and the difference between the mass fraction of the element in the sample and the mass fraction of the target composition;

[0060] S7: adding the remaining limestone and silicon-calcium alloy for deoxidation in the furnace;

[0061] S8: Raise the furnace temperature to 1700℃ and tap the steel at this temperature. After the molten steel fills the ladle, add a covering agent on the surface of the molten steel to complete the smelting.

[0062] The chemical composition of the martensitic stainless steel obtained in this embodiment is shown in Table 4:

[0063] Table 4

[0064]

[0065] The present invention is described by way of embodiments, and those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the protection scope of the present invention.

Claims

1. A non-vacuum melting method for martensitic stainless steel, characterized in that: The following steps are involved: S1: prepare 0Cr13Ni4Mo alloy ingot, industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum, ferrosilicon, limestone, slag collector, covering agent, and silicon-calcium alloy according to the mass ratio of 0-150:10:2:36:2:2:4:1:1:1 for use; S2: evenly spread limestone accounting for 80% of the total limestone mass in the raw materials on the bottom of the medium frequency induction furnace, put all the 0Cr13Ni4Mo alloy ingots into the middle of the furnace chamber, and then add industrial pure iron accounting for 80% of the total industrial pure iron mass in the raw materials, micro-carbon soldering iron accounting for 80% of the total micro-carbon soldering iron mass in the raw materials, ferromolybdenum accounting for 80% of the total ferromolybdenum mass in the raw materials, and electrolytic nickel accounting for 80% of the total electrolytic nickel mass in the raw materials in sequence; S3: raising the temperature of the medium frequency induction furnace to 1000°C and maintaining the furnace at 1000°C; S4: Continue to raise the temperature until the charge is melted and molten steel is visible or the charge sinks, then add the remaining industrial pure iron, electrolytic nickel, electrolytic manganese, micro-carbon soldering iron, ferromolybdenum and ferrosilicon; S5: After all the raw materials are melted, a slag collecting agent is added to cover the surface of the molten steel, slag is made, slag is removed, and this step is repeated until no slag is discharged; S6: maintaining the temperature after heating and taking samples for spectral analysis, comparing the spectral analysis results with the target composition, and adding metal raw materials corresponding to the elements that do not reach the target composition into the furnace until the chemical composition of the molten steel reaches the target composition; S7: adding the remaining limestone and silicon-calcium alloy for deoxidation in the furnace; S8: Raise the furnace temperature to 1680-1700℃ and tap the steel at this temperature. After the molten steel fills the ladle, add a covering agent on the surface of the molten steel to complete the smelting.

2. The non-vacuum melting method of martensitic stainless steel according to claim 1, characterized in that: In the step 1, the mass of the 0Cr13Ni4Mo alloy ingot is 90% of the total planned smelting amount.

3. The non-vacuum melting method of martensitic stainless steel according to claim 1, characterized in that: In step S3, the melting is maintained at 1000° C. for 2 hours.

4. The non-vacuum melting method of martensitic stainless steel according to claim 1, characterized in that: The mass fraction of each element in the target composition described in step S6 is: C≤0.06%, Si≤1.0%, Mn≤2.0%, P≤0.035%, S≤0.030%, Ni: 3.5%~5.0%, Cr: 11.5%~17.0%, Mo≤1.0%.

5. The non-vacuum melting method of martensitic stainless steel according to claim 1, characterized in that: In step S6, metal ingots corresponding to elements that do not reach the target composition are added into the furnace, and the mass of the added metal raw material is calculated as: the product of the total planned smelting amount and the difference between the mass fraction of the element in the sample and the mass fraction of the target composition.

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