CN111763800B - Preparation method of 18Ni steel intermediate alloy - Google Patents
Preparation method of 18Ni steel intermediate alloy Download PDFInfo
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- CN111763800B CN111763800B CN202010568829.7A CN202010568829A CN111763800B CN 111763800 B CN111763800 B CN 111763800B CN 202010568829 A CN202010568829 A CN 202010568829A CN 111763800 B CN111763800 B CN 111763800B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
- C21C5/527—Charging of the electric furnace
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/56—Manufacture of steel by other methods
- C21C5/562—Manufacture of steel by other methods starting from scrap
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0025—Adding carbon material
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/064—Dephosphorising; Desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/068—Decarburising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
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Abstract
The invention relates to the technical field of metallurgy and pressure processing, and discloses a preparation method of an 18Ni steel intermediate alloy. The method comprises the following steps: s1, placing lime on the bottom of the electric arc furnace, loading the metal return material into the electric arc furnace, blowing oxygen to assist melting after a molten pool is formed, slagging to remove impurities in molten steel, and tapping and discharging slag; s2, after the molten steel is put into a tank, stirring by adopting large-flow Ar gas, then stirring by adopting low-flow Ar gas, adding Al blocks, lime, fluorite and steel slag, heating to melt slag, removing the steel slag, and then adding a carburant to carry out recarburization; s3, pre-blowing oxygen after molten steel is put into a tank, then blowing main oxygen, blowing Ar gas after oxygen blowing for stirring, vacuum carbon deoxidation, air breaking, adding Al ingots, fluorite powder and lime, closing a cover, stirring by adopting large-flow Ar gas, stirring by adopting low-flow Ar gas for vacuumization slag, feeding Al wires, and tapping after Ar gas stirring; and S4, casting. The intermediate alloy prepared by using the return material as the raw material can be used for smelting 18Ni maraging steel.
Description
Technical Field
The invention relates to the technical field of metallurgy and pressure processing, in particular to a preparation method of an 18Ni steel intermediate alloy.
Background
The 18Ni maraging steel is formed by adopting modes of smelting in a vacuum induction furnace and a vacuum consumable furnace, forging, rolling or extruding and the like, a plurality of metal materials such as crop ends, turning scraps and the like can appear in the whole production process, and the steel is smelted by pure metals such as pure iron, metal Ni, metal Mo, sponge Ti and the like in one-step smelting (smelting in the vacuum induction furnace) for ensuring the final performance of the product. Because the crop and the turning scraps contain a large amount of impurities such as oxide skin, oil stain, mixed materials and the like, the impurities cannot be directly smelted and used in the vacuum induction furnace, and the steel contains a large amount of Co and Ni and cannot be used in other steel types. According to understanding, can get rid of impurity through ultrasonic cleaning means, but ultrasonic cleaning produces the line construction cost higher, and the technical degree of difficulty is big, can't distinguish the compounding, economic nature is relatively poor. In order to solve the problem, the special intermediate alloy for the 18Ni steel with low C, Si, S and P is smelted by adopting EBT + LF + VOD smelting to smelt the scrap ends and the scrap irons in the production process. The intermediate alloy is used as a metal material to smelt the 18Ni maraging steel ingot by adopting a vacuum induction furnace and a vacuum consumable electrode furnace. The method recycles a large amount of crop ends and turning scraps, not only greatly reduces the manufacturing cost, but also recycles important strategic resources such as Co, Ni and the like. At present, the method is used, and the product performance of the intermediate alloy smelting product is equivalent to that of the pure metal smelting product.
Disclosure of Invention
The invention aims to overcome the defect that the 18Ni maraging steel in the prior art contains a large amount of impurities such as oxide skin, oil stain, mixed materials and the like in crop ends, scrap reports and turning scraps and can not be directly used in the smelting of a vacuum induction furnace, and the problems of higher impurity removal cost, great technical difficulty, incapability of distinguishing mixed materials and poorer economy by an ultrasonic cleaning means are solved, the preparation method of the 18Ni steel intermediate alloy is provided, the method adopts an EBT + LF + VOD smelting mode to smelt the return material produced in the production process into the special intermediate alloy of 18Ni steel with low C, Si, S and P content, the 18Ni steel intermediate alloy can be used as a metal material for smelting 18Ni maraging steel ingots, not only recycles a large amount of crop, scrap and turning scraps, greatly reduces the manufacturing cost, but also recycles important strategic resources such as Co, Ni and the like.
In order to achieve the above object, the present invention provides a method for preparing an 18Ni steel master alloy, comprising the steps of:
s1, electric arc furnace smelting
After lime is filled on the bottom of the electric arc furnace, the metal return material is filled into the electric arc furnace and is electrified and melted, after a molten pool is formed, oxygen is blown to assist melting, slag is formed to remove impurities in molten steel, and steel and slag are discharged;
s2 smelting in LF furnace
After molten steel obtained by smelting in an electric arc furnace is fed into an LF furnace, stirring by adopting large-flow Ar gas, then stirring by adopting low-flow Ar gas, then adding an Al block for precipitation deoxidation, adding lime, fluorite and steel slag, heating to melt slag for reduction desulfurization reaction, removing the steel slag, then adding a carburant for recarburization, and feeding the molten steel into a VOD furnace;
s3, smelting in a VOD furnace
After molten steel obtained by smelting in an LF furnace is fed into a VOD furnace, pre-oxygen blowing is carried out, then main oxygen blowing is used, Ar gas is blown for stirring after oxygen blowing is finished, then a vacuum pump is started for vacuum carbon deoxidation reaction, air breaking is carried out, then Al ingots, fluorite powder and lime are added, a cover is closed, after stirring by adopting large-flow Ar gas, low-flow Ar gas is adopted for stirring for vacuum slag melting, then Al wires are fed for adjusting the Al content in the molten steel, and after stirring by adopting Ar gas, steel is discharged;
and S4, casting.
Preferably, in step S1, the metal returns are crop ends, scrap and turnings of the 18Ni maraging steel.
Preferably, in step S1, the impurity elements P, Cr, and Si in the molten steel are removed by oxygen blowing for fluxing and slagging so that the impurity elements P, Cr, and Si in the molten steel satisfy: p is less than or equal to 0.003 weight percent, Cr is less than or equal to 0.15 weight percent, and Si is less than or equal to 0.05 weight percent.
Preferably, in step S1, the oxygen blowing temperature is 1540 ℃.
Preferably, in step S1, the tapping is performed using a carbon-free ladle.
Preferably, in step S2, the conditions for stirring with the large flow rate of Ar gas are: the flow rate is more than or equal to 120L/min, and the stirring time is more than or equal to 3 minutes.
Preferably, in step S2, the conditions for stirring with the low flow rate of Ar gas are: the flow rate is 20-40L/min, and the stirring time is more than or equal to 3 minutes.
Preferably, in step S2, the temperature of the temperature-rising slagging is more than or equal to 1650 ℃.
Preferably, in step S2, the steel slag is removed, and then a carburant is added to carburize the molten steel by 0.35 to 0.5 wt%, and the molten steel is introduced into the VOD furnace.
Preferably, in step S3, the molten steel obtained by the LF furnace is poured into the tank under the following conditions: the temperature is more than or equal to 1550 ℃; 0.35-0.50 wt% of C, less than or equal to 0.005 wt% of P, less than or equal to 0.003 wt% of S and less than or equal to 0.08 wt% of Si; the slag thickness is less than or equal to 40 mm; the free space is more than or equal to 800 mm.
Preferably, in step S3, the oxygen lance is started to perform pre-oxygen blowing when the vacuum degree of the VOD furnace reaches 20-25 KPa.
Preferably, in step S3, the conditions of the pre-blowing of oxygen are: flow rate of 330 and 390m3/h, the time is 2-5 min.
Preferably, in step S3, the conditions of the main oxygen blowing are: the flow rate is 490-610m3The over-blown oxygen amount is 150-3/h。
Preferably, in step S3, the conditions for blowing Ar gas after the oxygen blowing are: the flow rate is 30-50L/min.
Preferably, in step S3, the vacuum carbon deoxygenation reaction conditions are: the ultimate vacuum degree is less than or equal to 350Pa, and the time is more than or equal to 10 min.
Preferably, in step S3, Al ingot, fluorite powder and lime are added, after the cover is closed and the holding time is not less than 4min, large flow Ar gas is used for stirring, and low flow Ar gas is used for stirring for vacuum slagging.
Preferably, in step S3, the conditions for stirring with the large flow rate of Ar gas are: the flow rate is more than or equal to 120L/min, and the time is 2-5 min.
Preferably, in step S3, the conditions for stirring with the low flow rate of Ar gas are: the flow rate is 20-40L/min.
Preferably, in the step S3, the slagging time of the vacuum slagging is more than or equal to 15 min.
Preferably, in step S3, the Al content in the molten steel is adjusted by feeding an Al wire under the conditions: the temperature is more than or equal to 1600 ℃, and the Al content in the molten steel is adjusted to 0.03-0.05 weight percent.
Preferably, in step S3, the conditions for tapping after stirring with Ar gas are: the Ar gas flow is 15-25L/min, and the stirring time is more than or equal to 5 min.
The method adopts an EBT + LF + VOD smelting mode to smelt the return materials (scrap, scrap and turning scraps) generated in the production process into the special 18Ni steel intermediate alloy with low C, Si, S and P, and the 18Ni steel intermediate alloy can be used as a metal material for smelting 18Ni maraging steel ingots.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The preparation method of the 18Ni steel intermediate alloy comprises the following steps:
s1, electric arc furnace smelting
After lime is filled on the bottom of the electric arc furnace, the metal return material is filled into the electric arc furnace and is electrified and melted, after a molten pool is formed, oxygen is blown to assist melting, slag is formed to remove impurities in molten steel, and steel and slag are discharged;
s2 smelting in LF furnace (ladle refining furnace)
After molten steel obtained by smelting in an electric arc furnace is fed into an LF furnace, stirring by adopting large-flow Ar gas, then stirring by adopting low-flow Ar gas, then adding an Al block for precipitation deoxidation, adding lime, fluorite and steel slag, heating to melt slag for reduction desulfurization reaction, removing the steel slag, then adding a carburant for recarburization, and feeding the molten steel into a VOD furnace;
s3, smelting in a VOD furnace
After molten steel obtained by smelting in an LF furnace is fed into a VOD furnace, pre-oxygen blowing is carried out, then main oxygen blowing is used, Ar gas is blown for stirring after oxygen blowing is finished, then a vacuum pump is started for vacuum carbon deoxidation reaction, air breaking is carried out, then Al ingots, fluorite powder and lime are added, a cover is closed, after stirring by adopting large-flow Ar gas, low-flow Ar gas is adopted for stirring for vacuum slag melting, then Al wires are fed for adjusting the Al content in the molten steel, and after stirring by adopting Ar gas, steel is discharged;
and S4, casting.
In the method of the present invention, in step S1, the metal returns are crop ends, scrap and turnings of 18Ni maraging steel. When the metal returning material is insufficient, pure iron can be matched and used in a proper amount.
In the method, the main functions of the electric arc furnace smelting are to melt the crop ends, the scrap reports and the scrap metal returns into molten steel, and remove the impurity elements of P, Cr and Si in the molten steel through oxygen blowing oxidation and slagging. Oxygen is blown to melt the metal immediately after the molten pool is formed, so that the melting speed of the metal is accelerated, and P in the molten steel can be removed through oxidation reaction. When P is more than 0.003 weight percent, the steel slag needs to flow out again, lime and fluorite are added again for slagging again, and oxygen is blown after the slag is melted, and the P is removed by continuous oxidation. The lime used in the present invention is preferably activated lime unless otherwise specified.
In one embodiment, in step S1, the impurity elements P, Cr, and Si in the molten steel are removed by oxygen blowing for fluxing and slagging so that the impurity elements P, Cr, and Si in the molten steel satisfy: p is less than or equal to 0.003 weight percent, Cr is less than or equal to 0.15 weight percent, and Si is less than or equal to 0.05 weight percent. In step S1, the oxygen blowing temperature is more than or equal to 1540 ℃, preferably, the oxygen blowing temperature is more than or equal to 1550 ℃; more preferably, the oxygen blowing temperature is 1560 ℃. In a preferred embodiment, the tapping is performed with a carbon-free ladle.
In the method, the LF furnace smelting mainly has the functions of heating and desulfurizing, and S in the molten steel is controlled to be less than 0.003 weight percent.
In the method of the present invention, in step S2, the conditions for stirring with a large flow of Ar gas are: the flow rate is more than or equal to 120L/min, preferably, the flow rate is more than or equal to 122L/min, and more preferably, the flow rate is more than or equal to 125L/min; the stirring time is 3 minutes or more, preferably 5 minutes or more, and more preferably 7 minutes or more.
In the method of the present invention, in step S2, the conditions for stirring with the low flow rate of Ar gas are: the flow rate is 20-40L/min, specifically, for example, 20L/min, 25L/min, 30L/min, 35L/min, 40L/min and any value in the range formed by any two of these points, preferably, the flow rate is 30L/min; the stirring time is 3 minutes or more, preferably 5 minutes or more, and more preferably 7 minutes or more.
In the method, in step S2, the temperature of the temperature rise and slag melting is more than or equal to 1650 ℃; preferably, the temperature of the temperature rise slagging is more than or equal to 1660 ℃; more preferably, the temperature of the temperature rise slagging is more than or equal to 1670 ℃. In a preferred embodiment, in step S2, the steel slag is removed, and then the steel slag is carburized by adding a carburizer to 0.35 to 0.5 wt.% (specifically, for example, 0.35 wt.%, 0.37 wt.%, 0.39 wt.%, 0.41 wt.%, 0.43 wt.%, 0.45 wt.%, 0.47 wt.%, 0.49 wt.%, or 0.50 wt.%) before entering the VOD furnace.
The main function of VOD furnace smelting is to remove elements such as C, oxygen, nitrogen and the like in steel through vacuum carbon deoxidation reaction, and the C in the steel is controlled to be less than or equal to 0.004 weight percent.
In the method, in step S3, the molten steel obtained by the LF furnace is put into the tank under the following conditions: temperature is more than or equal to 1550 ℃, preferably more than or equal to 1560 ℃, more preferably more than or equal to 1570 ℃; 0.35-0.50 wt% of C, less than or equal to 0.005 wt% of P, less than or equal to 0.003 wt% of S and less than or equal to 0.08 wt% of Si; the slag thickness is less than or equal to 40mm, preferably less than or equal to 39mm, and more preferably less than or equal to 38 mm; the free space is more than or equal to 800mm, preferably the free space is more than or equal to 820mm, more preferably the free space is more than or equal to 850 mm.
In the method, in step S3, when the vacuum degree of the VOD furnace reaches 20-25KPa, starting an oxygen lance to pre-blow oxygen; specifically, when the vacuum degree of the VOD furnace can be 20KPa, 21KPa, 22KPa, 23KPa, 24KPa or 25KPa, starting the oxygen lance to perform pre-oxygen blowing; preferably, the oxygen lance is started to perform pre-oxygen blowing when the vacuum degree of the VOD furnace reaches 23 KPa.
In the method of the present invention, in step S3, the flow rate of the pre-blown oxygen is 330-3H; specifically, it may be 330m, for example3/h、340m3/h、350m3/h、360m3/h、370m3/h、380m3H or 390m3H; preferably, the flow rate of the pre-blowing oxygen is 360m3H is used as the reference value. In step S3, the time of pre-oxygen blowing is 2-5 min; specifically, for example, it may be 2min, 3min, 4min or 5 min; preferably, the time of pre-oxygen blowing is 4 min.
In the method of the present invention, in step S3, the flow rate of the main oxygen blast is 490-610m3H; specifically, it may be 490m, for example3/h、500m3/h、510m3/h、520m3/h、530m3/h、540m3/h、550m3/h、560m3/h、570m3/h、580m3/h、590m3/h、600m3H or 610m3H; preferably, the flow rate of the main oxygen blowing is 555m3H is used as the reference value. In step S3, the oxygen blowing amount is made excessive by main oxygen blowing, and the over-blown oxygen amount is 150-350m3H; specifically, it may be, for example, 150m3/h、200m3/h、250m3/h、300m3H or 350m3H; preferably, the amount of oxygen blown is 250m3/h。
In the method of the invention, in step S3, the flow rate of blowing Ar gas is 30-50L/min after oxygen blowing is finished; specifically, for example, it may be 30L/min, 35L/min, 40L/min, 45L/min or 50L/min; preferably, the flow rate of the Ar gas after the oxygen blowing is finished is 40L/min.
In the method of the present invention, in step S3, the vacuum carbon deoxidation reaction conditions are as follows: the ultimate vacuum degree is less than or equal to 350Pa, preferably, the ultimate vacuum degree is less than or equal to 330Pa, and more preferably, the ultimate vacuum degree is less than or equal to 300 Pa; the time is more than or equal to 10min, preferably more than or equal to 12min, and more preferably more than or equal to 15 min.
In the method, in step S3, Al ingot, fluorite powder and lime are added, after the cover is closed and the holding time is more than or equal to 4min, large-flow Ar gas is adopted for stirring, and low-flow Ar gas is adopted for stirring and vacuum slagging. In step S3, the flow rate of stirring by adopting large-flow Ar gas is more than or equal to 120L/min; preferably, the flow rate of stirring by adopting large-flow Ar gas is more than or equal to 125L/min; more preferably, the flow rate of the stirring by adopting the large-flow Ar gas is more than or equal to 130L/min. In step S3, stirring with large flow Ar gas for 2-5 min; specifically, for example, it may be 2min, 3min, 4min or 5 min; preferably, the stirring time with a large flow of Ar gas is 3.5 min.
In the method, in step S3, the flow rate of stirring by using low-flow Ar gas is 20-40L/min; specifically, for example, it may be 20L/min, 25L/min, 30L/min, 35L/min or 40L/min; preferably, the flow rate of stirring with the low-flow Ar gas is 30L/min.
In the method, in the step S3, the slagging time of the vacuum slagging is more than or equal to 15 min; preferably, the slagging time of the vacuum slagging is more than or equal to 18 min; more preferably, the slagging time of the vacuum slagging is more than or equal to 20 min.
In the method of the present invention, in step S3, Al wire is fed to adjust the Al content in the molten steel to a temperature of 1600 ℃ or higher, and the Al content in the molten steel is adjusted to 0.03 to 0.05 wt% (e.g., 0.03 wt%, 0.04 wt%, or 0.05 wt%).
In the method of the present invention, in step S3, the conditions for tapping after stirring with Ar gas are: the Ar gas flow rate is 15-25L/min, specifically, for example, 15L/min, 17L/min, 19L/min, 21L/min, 23L/min or 25L/min, preferably, the Ar gas flow rate is 20L/min; the stirring time is more than or equal to 5min, preferably more than or equal to 7min, and more preferably more than or equal to 10 min.
The method takes the return materials (crop ends, scrap reports and car scraps) generated in the production process as raw materials, and adopts an EBT + LF + VOD smelting mode to prepare the special intermediate alloy for the 18Ni steel with low C, Si, S and P, wherein the 18Ni intermediate alloy meets the requirements of enterprise standards CJX-TJ031-2014 and can be used as a metal material for smelting 18Ni maraging steel ingots.
The present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto.
Example 1
S1, electric arc furnace smelting
After lime is added at the position of 700-900Kg (and lime is added at the position of 750-950Kg) on the bottom cushion of the electric arc furnace after secondary feeding is adopted, the cut ends, the scrap reports and the scraps of 18Ni maraging steel are put into the electric arc furnace and are electrified to be melted, after a molten pool is formed, oxygen is blown immediately to assist melting and accelerate the metal melting speed, and P in molten steel can be removed through oxidation reaction, the oxygen blowing temperature is required to be more than or equal to 1540 ℃, when P is more than 0.003 percent, the molten steel needs to flow out again, lime and fluorite are added to re-form slag, after the slag is melted, oxygen is blown, and the oxidation and the P removal are continued, the components of the molten steel meet the requirements shown in table 1, the slag is completely secreted after the tapping, and a carbon-free steel ladle is adopted for the tapping;
s2 smelting in LF furnace (ladle refining furnace)
After molten steel obtained by smelting in an electric arc furnace is put into an LF furnace, large-flow Ar gas is adopted for stirring, the flow is more than or equal to 120L/min, the stirring time is controlled to be more than or equal to 3 minutes, then, after the low-flow Ar gas with the flow of 30L/min is adopted for stirring, 50-80Kg of Al blocks are added for precipitation and deoxidation, 500Kg of lime 300-containing materials, 300Kg of fluorite 150-containing materials and 200Kg of steel slag-containing materials are added, the temperature is controlled to be more than or equal to 1650 ℃, all the steel slag is removed, and 0.4 percent of carburant is added for recarburization and then enters a VOD furnace;
s3, smelting in a VOD furnace
The molten steel obtained by smelting in the LF furnace enters the VOD furnace under the following conditions: the temperature is more than or equal to 1550 ℃, C: 0.35-0.50 percent of oxygen lance, less than or equal to 0.005 percent of P, less than or equal to 0.003 percent of S, less than or equal to 0.08 percent of Si, less than or equal to 40mm of slag thickness, more than or equal to 800mm of free space, starting the oxygen lance to pre-blow when the vacuum degree reaches 23KPa, and controlling the flow of oxygen blowing to be 360m3H, pre-blowing for 4min, then changing main blowing to 550m oxygen flow3H, controlling the over-blown oxygen amount to be 250m3H is used as the reference value. And after the oxygen blowing is finished, blowing Ar gas for stirring, controlling the flow of the blown Ar gas at 40L/min, starting a vacuum pump to perform vacuum carbon deoxidation reaction, and breaking the air after the holding time is more than or equal to 10min under the condition that the ultimate vacuum degree is less than or equal to 350 Pa. After the air is broken, 200Kg of Al ingot, 200Kg of fluorite powder, 100 Kg of fluorite powder and 800Kg of lime are addedAfter the cover is closed, keeping the flow rate for more than or equal to 4min, blowing Ar gas for stirring for 4min, wherein the flow rate is more than or equal to 120L/min, then stirring for vacuum slagging by using low-flow 30L/min Ar gas, and the slagging time is more than or equal to 15 min. Good slag, the temperature is more than or equal to 1600 ℃, Al wire is fed to adjust the Al component to 0.04 percent, 20L/min Ar gas is adopted to stir for 5min, and then steel is discharged;
and S4, casting without adding auxiliary materials such as casting powder, a heating agent and the like, and directly casting.
TABLE 1 electric arc furnace molten steel composition requirements/%)
| Element(s) | Mn | Si | S | P | Ni | Co | Mo |
| Standard of merit | ≤0.02 | ≤0.02 | ≤0.01 | ≤0.003 | / | / | / |
Example 2
S1, electric arc furnace smelting
After lime is added at the position of 700-900Kg (and lime is added at the position of 750-950Kg) on the bottom cushion of the electric arc furnace after secondary feeding is adopted, the crop, the scrap reporting and the turning of the 18Ni maraging steel are put into the electric arc furnace and are electrified to be melted, after a molten pool is formed, oxygen is blown immediately to assist melting and accelerate the metal melting speed, and P in molten steel can be removed through oxidation reaction, the oxygen blowing temperature is required to be not less than 1590 ℃, when P is more than 0.003 percent, the molten steel needs to flow out again, lime and fluorite are added to re-form slag, the oxygen is blown after the slag is melted, the oxidation and the P removal are continued, the components of the molten steel meet the requirements shown in the table 1, the slag is completely secreted after the tapping, and a carbon-free steel ladle is adopted;
s2 smelting in LF furnace (ladle refining furnace)
After molten steel obtained by smelting in an electric arc furnace is put into an LF furnace, large-flow Ar gas is adopted for stirring, the flow is more than or equal to 125L/min, the stirring time is controlled to be more than or equal to 3 minutes, then, after the low-flow Ar gas with the flow of 20L/min is used for stirring, 50-80Kg of Al blocks are added for precipitation and deoxidation, 500Kg of lime 300-containing materials, 300Kg of fluorite 150-containing materials and 200Kg of steel slag-containing materials are added, the temperature is controlled to be more than or equal to 1670 ℃, the reduction and desulfurization reaction is carried out on the slag, all the steel slag is removed, and 0.5 percent of carburant is added for recarburization and then the molten steel enters a VOD furnace;
s3, smelting in a VOD furnace
The molten steel obtained by smelting in the LF furnace enters the VOD furnace under the following conditions: the temperature is more than or equal to 1560 ℃, C: 0.35-0.50 percent of oxygen lance, less than or equal to 0.005 percent of P, less than or equal to 0.003 percent of S, less than or equal to 0.08 percent of Si, less than or equal to 37mm of slag thickness, more than or equal to 840mm of free space, starting the oxygen lance to pre-blow when the vacuum degree reaches 25KPa, and controlling the flow of oxygen blowing to be 330m3H, pre-blowing for 5min, then changing main blowing, with oxygen blowing flow of 490m3H, controlling the over-blown oxygen amount to be 150m3H is used as the reference value. And after the oxygen blowing is finished, blowing Ar gas for stirring, controlling the flow of the blown Ar gas at 50L/min, starting a vacuum pump to perform vacuum carbon deoxidation reaction, and breaking the air after the limiting vacuum degree is less than or equal to 330Pa and the holding time is more than or equal to 15 min. After breaking the cavity, adding 350Kg of Al ingot 200-The time is more than or equal to 16 min. Good slag, the temperature is more than or equal to 1650 ℃, Al wire is fed to adjust the Al component to 0.04 percent, 15L/min Ar gas is adopted to stir for 5min, and then steel is tapped;
and S4, casting without adding auxiliary materials such as casting powder, a heating agent and the like, and directly casting.
Example 3
S1, electric arc furnace smelting
After lime is added at the position of 700-900Kg (and lime is added at the position of 750-950Kg) on the bottom cushion of the electric arc furnace after secondary feeding is adopted, the cut ends, the scrap reports and the scraps of 18Ni maraging steel are put into the electric arc furnace and are electrified to be melted, after a molten pool is formed, oxygen is blown immediately to assist melting and accelerate the metal melting speed, and P in molten steel can be removed through oxidation reaction, the oxygen blowing temperature is required to be more than or equal to 1560 ℃, when P is more than 0.003 percent, the molten steel needs to flow out again, lime and fluorite are added to re-form slag, after the slag is melted, oxygen is blown, and the oxidation is continued to remove P, the components of the molten steel meet the requirements shown in table 1, slag is completely secreted after tapping, and a carbon-free steel ladle is adopted for tapping;
s2 smelting in LF furnace (ladle refining furnace)
After molten steel obtained by smelting in an electric arc furnace is put into an LF furnace, large-flow Ar gas is adopted for stirring, the flow is more than or equal to 122L/min, the stirring time is controlled to be more than or equal to 5 minutes, then, after the low-flow Ar gas with the flow of 40L/min is adopted for stirring, 50-80Kg of Al blocks are added for precipitation and deoxidation, 500Kg of lime 300-containing materials, 300Kg of fluorite 150-containing materials and 200Kg of steel slag-friendly materials are added, the temperature is controlled to be more than or equal to 1680 ℃, all steel slag is removed, and 0.35 percent of carburant is added for recarburization and then the molten steel enters a VOD furnace;
s3, smelting in a VOD furnace
The molten steel obtained by smelting in the LF furnace enters the VOD furnace under the following conditions: the temperature is more than or equal to 1580 ℃, C: 0.35-0.50 percent of oxygen lance, less than or equal to 0.005 percent of P, less than or equal to 0.003 percent of S, less than or equal to 0.08 percent of Si, less than or equal to 38mm of slag thickness, more than or equal to 830mm of free space, starting the oxygen lance to pre-blow when the vacuum degree reaches 20KPa, and controlling the flow of oxygen blowing to 390m3H, pre-blowing for 2min, then changing main blowing, with the oxygen flow of 610m3H, controlling the over-blown oxygen amount to be 350m3H is used as the reference value. Blowing Ar gas for stirring after oxygen blowing is finished, controlling the flow of the blown Ar gas at 30L/min, starting a vacuum pump for vacuum carbon deoxidation reaction, and breaking after the ultimate vacuum degree is less than or equal to 340Pa and the holding time is more than or equal to 13minAnd (4) is empty. After the air is broken, 350Kg of Al ingot, 200Kg of fluorite powder and 500Kg of lime are added, after the cover is closed, the Ar gas is blown for 5min and the large flow rate is more than or equal to 123L/min for stirring after the cover is kept for more than or equal to 6min, then the vacuum slag melting is carried out by stirring with 20L/min of low flow rate, and the slag melting time is more than or equal to 18 min. Good slag, the temperature is more than or equal to 1630 ℃, Al wires are fed to adjust the Al content to 0.04%, 25L/min Ar gas is adopted to stir for 5min, and then steel is discharged;
and S4, casting without adding auxiliary materials such as casting powder, a heating agent and the like, and directly casting.
Test example
The 18Ni steel master alloy finished materials prepared in examples 1 to 3 were tested for chemical composition and the results are shown in table 2.
TABLE 218 chemical composition/% of Ni master alloy
The results in the table 2 show that the 18Ni intermediate alloy prepared by using the crop ends, the scrap and the turning scraps of the 18Ni maraging steel as the raw materials meets the requirements of the enterprise standard CJX-TJ031-2014, and can be used as a metal material for smelting 18Ni maraging steel ingots.
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.
Claims (8)
1. A preparation method of an 18Ni steel intermediate alloy is characterized by comprising the following steps:
s1, electric arc furnace smelting
After lime is filled on the bottom of the electric arc furnace, the metal return material is filled into the electric arc furnace and is electrified and melted, after a molten pool is formed, oxygen is blown to assist melting, slag is formed to remove impurities in molten steel, and steel and slag are discharged;
s2 smelting in LF furnace
After molten steel obtained by smelting in an electric arc furnace is fed into an LF furnace, stirring by adopting large-flow Ar gas, then stirring by adopting low-flow Ar gas, then adding an Al block for precipitation deoxidation, adding lime, fluorite and steel slag, heating to melt the slag for reduction desulfurization reaction, removing the steel slag, then adding a carburant for recarburization, and feeding the molten steel into a VOD furnace;
s3, smelting in a VOD furnace
After molten steel obtained by smelting in an LF furnace is fed into a VOD furnace, pre-oxygen blowing is carried out, then main oxygen blowing is used, Ar gas is blown for stirring after oxygen blowing is finished, then a vacuum pump is started for vacuum carbon deoxidation reaction, air breaking is carried out, then Al ingots, fluorite powder and lime are added, a cover is closed, after stirring by adopting large-flow Ar gas, low-flow Ar gas is adopted for stirring for vacuum slag melting, then Al wires are fed for adjusting the Al content in the molten steel, and after stirring by adopting Ar gas, steel is discharged;
s4, pouring;
in step S2, the conditions for stirring with a large flow of Ar gas are: the flow rate is more than or equal to 120L/min, and the stirring time is more than or equal to 3 minutes; the stirring conditions with low flow of Ar gas are as follows: the flow rate is 20-40L/min, and the stirring time is more than or equal to 3 minutes;
in step S3, the temperature of molten steel obtained by smelting in the LF furnace in a tank is 1550-;
in step S3, when the vacuum degree of the VOD furnace reaches 20-25KPa, starting an oxygen lance to pre-blow oxygen; the conditions of pre-oxygen blowing are as follows: flow rate of 330 and 390m3/h, the time is 2-5 min; the main oxygen blowing conditions are as follows: the flow rate is 490-610m3The over-blown oxygen amount is 150-3H; the conditions of blowing Ar gas after the oxygen blowing are as follows: the flow rate is 30-50L/min; the conditions of the vacuum carbon deoxidation reaction are as follows: the ultimate vacuum degree is less than or equal to 350Pa, and the time is more than or equal to 10 min;
in step S3, adding Al ingots, fluorite powder and lime, covering and keeping for more than or equal to 4min, stirring by adopting high-flow Ar gas, and stirring by adopting low-flow Ar gas to carry out vacuum slagging; the conditions for stirring by adopting large-flow Ar gas are as follows: the flow rate is more than or equal to 120L/min, and the time is 2-5 min; the stirring conditions with low flow Ar gas are as follows: the flow rate is 20-40L/min; the slagging time of the vacuum slagging is more than or equal to 15 min; the Al wire is fed to adjust the Al content in the molten steel under the following conditions: adjusting the Al content in the molten steel to 0.03-0.05 wt% at a temperature of more than or equal to 1600 ℃; the tapping conditions after stirring by Ar gas are as follows: the Ar gas flow is 15-25L/min, and the stirring time is more than or equal to 5 min.
2. The method of claim 1, wherein in step S1, the metal returns are crop ends, scrap and turnings of 18Ni maraging steel.
3. The method of claim 1, wherein in step S1, the impurity elements of P, Cr and Si in the molten steel are removed by oxygen blowing for fluxing and slagging so that the impurity elements of P, Cr and Si in the molten steel satisfy the following requirements: p is less than or equal to 0.003 weight percent, Cr is less than or equal to 0.15 weight percent, and Si is less than or equal to 0.05 weight percent.
4. The method according to claim 1, wherein in step S1, the oxygen blowing temperature is 1540 ℃.
5. The method of claim 1, wherein tapping is performed with a carbon-free ladle in step S1.
6. The method according to claim 1, wherein the temperature of the temperature-raised slagging is 1650 ℃ or higher in step S2.
7. The method as claimed in claim 1, wherein the steel slag is removed and then carburized 0.35 to 0.5 wt% by adding a carburizer to the steel slag, and then introduced into the VOD furnace in step S2.
8. The method of claim 1, wherein in the step S3, the molten steel obtained by smelting in the LF furnace is put into the tank under the following conditions: 0.35-0.50 wt% of C, less than or equal to 0.005 wt% of P, less than or equal to 0.003 wt% of S and less than or equal to 0.08 wt% of Si; the slag thickness is less than or equal to 40 mm; the free space is more than or equal to 800 mm.
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