CN115161535B - Manufacturing method for smelting low-nitrogen stainless steel ingot by vacuum induction furnace - Google Patents
Manufacturing method for smelting low-nitrogen stainless steel ingot by vacuum induction furnace Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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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
- C21C5/005—Manufacture of stainless steel
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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
- C21C7/0006—Adding metallic additives
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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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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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Abstract
The invention discloses a manufacturing method for smelting a low-nitrogen stainless steel ingot by a vacuum induction furnace, which comprises the following steps: adding a steelmaking raw material into a vacuum induction furnace for smelting, wherein the smelting sequentially comprises the following steps of: melting, refining and casting, wherein in the melting step, raw material metal chromium is not added, and metal raw materials iron, nickel and molybdenum are added into a vacuum induction furnace in batches to be melted; in the refining step, the molten steel which is melted is refined, then metal chromium is added into the molten steel in batches and melted, and then the alloy element content of the molten steel is finely adjusted after the nitrogen element content in the molten steel is qualified so as to ensure that the component content of the molten steel meets the requirement. The chemical components of the low-nitrogen stainless steel ingot manufactured by the method meet the requirements, the nitrogen content is low, and the smelting time is short.
Description
Technical Field
The invention relates to a manufacturing method of a metal material, in particular to a manufacturing method of a vacuum induction furnace smelting low-nitrogen stainless steel ingot.
Background
With the rapid development of industrialization at present, the requirements on metal materials are higher and higher, and particularly in special environments such as ocean, plateau and low-temperature environments, metal materials with corrosion resistance, high toughness and high strength are often involved, and among the common steel materials, only high-strength, high-toughness and corrosion resistance stainless steel can meet the use requirements, but the stainless steel has strict requirements on chemical components, and particularly has lower nitrogen content.
At present, the stainless steel is smelted by a vacuum induction furnace in the world and in the domestic, and the standard of the steel generally requires the chemical component Cr:12-14%, mo:2-4%, C less than or equal to 0.04%, ni 8-12%, N less than or equal to 0.001%, S less than or equal to 0.003%, P less than or equal to 0.004%, and in order to ensure high strength and toughness of the steel, the contents of carbon and nitrogen are limited in the steel: c is less than or equal to 0.04 percent, N is less than or equal to 0.001 percent, and meanwhile, in order to ensure that the steel has higher corrosion resistance, the chromium content in the steel is higher: 12-14% of Cr.
Because the binding capacity of chromium element and nitrogen element is stronger, the nitrogen content of the raw material metal chromium for increasing chromium element is between 0.008 percent and 0.015 percent when the vacuum induction furnace is used for smelting the stainless steel, and the main denitrification element carbon content of the stainless steel is lower in the vacuum induction furnace smelting process, so that the stainless steel has great difficulty in denitrification in the vacuum induction furnace smelting process.
At present, domestic enterprises adopt molten steel to smelt under high vacuum degree (less than or equal to 5 pa) for a long time when producing the stainless steel, and utilize molten steel to smelt and denitrify under vacuum environment, the smelting manufacturing method generally takes 25-30h, and because the smelting time of the manufacturing method is longer, a large amount of energy sources are consumed, and the quality of steel is also at risk.
Therefore, a manufacturing method capable of shortening the smelting time of the low-nitrogen stainless steel ingot in the vacuum induction furnace is needed.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provides a manufacturing method for smelting a low-nitrogen stainless steel ingot by a vacuum induction furnace, so as to shorten the smelting time for smelting the low-nitrogen stainless steel ingot by the vacuum induction furnace in the conventional process.
The inventor of the invention has found through intensive research that metal chromium is not added in the melting period of vacuum induction furnace smelting, other metal materials are slowly added in batches for melting denitrification, metal chromium is added and melted in a specific mode in the refining period of vacuum induction furnace smelting, molten steel is poured in a specific mode in the pouring period of vacuum induction furnace smelting, and finally, stainless steel ingots with qualified components and lower nitrogen elements are obtained in a shorter time.
In order to achieve the above object, the following technical scheme is adopted.
The manufacturing method of the vacuum induction furnace smelting low-nitrogen stainless steel ingot comprises the following components in percentage by mass: 12-14%, mo:2-4%, C is less than or equal to 0.04%, ni:8-12%, N less than or equal to 0.001%, S less than or equal to 0.003%, P less than or equal to 0.004%, and the balance Fe and unavoidable impurities, wherein the manufacturing method comprises the steps of: adding a steelmaking raw material into a vacuum induction furnace for smelting, wherein the smelting sequentially comprises the following steps of: melting treatment, refining treatment and casting molding, wherein,
in the melting treatment step, raw material metal chromium is not added, and metal raw materials iron, nickel and molybdenum are added into a vacuum induction furnace in batches to be melted;
in the refining treatment step, refining treatment is carried out on molten steel (molten steel) of full melting after the melting treatment, then metal chromium is added into the molten steel in batches and melted, and then the alloy element content of the molten steel is finely adjusted after the nitrogen element content in the molten steel is qualified so as to ensure that the component content of the molten steel meets the requirement.
In the above manufacturing method, as a preferred embodiment, in the melting treatment step, pure iron is added to be melted, then metallic nickel is added to be melted, and finally metallic molybdenum is added to be melted.
In the above manufacturing method, as a preferable embodiment, in the melting treatment step, the conditions of the melting treatment are: the melting power is 400-600kW and is not equal to 600kW, the vacuum degree is less than or equal to 5Pa, and the melting treatment time is 6-8h.
In the invention, the purpose of controlling the melting power in the melting treatment is to ensure that the metal raw material can be completely melted.
In the above manufacturing method, as a preferred embodiment, in the melting treatment step, the same metal raw material is added to the molten steel in 3 to 5 times in a bin, and the amount of each addition is 1/5 to 1/3 of the total weight of the same metal raw material in the bin.
In the prior art, the melting power of the furnace body is generally set to 600-1000kW. In the present invention, the use of low power and small batch feeds ensures adequate removal of gases during the melting stage.
In the above production method, in the melting treatment step, the smelting raw material is brought into a fully molten state at a later stage of the melting treatment, and the temperature of the fully molten steel is preferably controlled to be in a range of 1500 to 1600 ℃ (e.g., 1510 ℃, 1520 ℃, 1550 ℃, 1570 ℃, 1580 ℃, 1590 ℃), more preferably 1580 to 1590 ℃ (e.g., 1582 ℃, 1585 ℃, 1587 ℃, 1588 ℃, 1589 ℃).
In the above manufacturing method, as a preferred embodiment, the steelmaking material includes metallic nickel, metallic chromium, metallic molybdenum, and pure iron; the metallic nickel, metallic chromium, metallic molybdenum, pure iron may be various metals conventionally used in the art for refining stainless steel, for example, the metallic nickel is 1#ni, etc.;
preferably, the pure iron is a metal material which is smelted and purified by EAF+LF+VOD to remove C, si, mn, S, P and other harmful elements; more preferably, in terms of mass percent, N <0.015%, S <0.003%, P <0.005%, mn <0.03%, si <0.05% in the pure iron;
preferably, the metallic chromium is conventional metallic chromium, and the nitrogen content in the metallic chromium is 0.008-0.015-wt%. The raw material cost of the low-nitrogen stainless steel ingot can be reduced by adopting conventional metal chromium.
In the above-described production method, as a preferred embodiment, in the refining step, the refining conditions are as follows: the power is 200-400kW, (for example, 220kW, 250kW, 280 kW, 300kW, 350kW, 370 kW and 390 kW), the vacuum degree is less than or equal to 3Pa (for example, 1.5Pa, 1.2Pa, 1Pa, 0.5Pa and 0.1 Pa), the vacuum degree is less than or equal to 2Pa, the temperature is 1580-1590 ℃, and the time under power frequency stirring is 10-20min.
In the present invention, the purpose of controlling power in refining treatment is to control refining temperature.
In the above production method, as a preferred embodiment, in the refining treatment, metallic chromium is added to the molten steel when the vacuum degree of refining is not more than 2 Pa.
In the above manufacturing method, as a preferred embodiment, in the refining treatment step, the metal chromium is divided into 2 parts in average, each part of metal chromium is added into the refined molten steel 3 to 4 times, and 1/4 to 1/3 of the total weight of each part of metal chromium is added each time; preferably, after the first part of metal chromium is added for smelting for 1 hour, the second part of metal chromium is added for continuing smelting for 1 hour; still more preferably, the power is 300-400kW (e.g., 310 kW, 320 kW, 350kW, 370 kW, 380kW, 390 kW), the smelting temperature is 1580-1590 ℃ (e.g., 1582 ℃, 1585 ℃, 1587 ℃, 1588 ℃, 1589 ℃), and the vacuum degree is less than or equal to 5Pa (e.g., 4Pa, 3Pa, 2Pa, 1 Pa), more preferably less than or equal to 3Pa.
The invention adopts high smelting temperature (i.e. high refining temperature) to slowly feed under high vacuum, so as to ensure the sufficient removal of nitrogen element in the chromium metal.
In the prior art, metallic chromium is added in the melting treatment stage, and the smelting temperature during the addition of the metallic chromium is 1540-1560 ℃.
In the above production method, as a preferable embodiment, in the refining step, after each part of the metal chromium is added, the metal is smelted for 10 to 20 minutes (for example, 12 minutes, 15 minutes, 18 minutes) under stirring at the power frequency.
In the above production method, as a preferable embodiment, the total refining time in the refining treatment is 5 to 10 hours (for example, 6 hours, 7 hours, 8 hours, 9 hours).
In the above manufacturing method, as a preferable embodiment, in the casting molding step, inert gas is simultaneously filled into the vacuum chamber and the mold injection chamber of the vacuum induction furnace so that the pressures of the vacuum chamber and the mold injection chamber are uniform, and then casting is performed to obtain a stainless steel ingot; preferably, the inert gas is argon, and more preferably, argon with the pressure of 20-50Pa is filled into a vacuum chamber and a mold injection chamber of the vacuum induction furnace at the same time, so that the liquid level of steel is stabilized during casting, and molten steel is prevented from splashing and blocking; it is further preferable that the tapping temperature at the time of casting is 1540 to 1560 ℃.
In the above production method, as a preferred embodiment, the total time of the melting is 15 to 20 hours.
The method for manufacturing the low-nitrogen stainless steel ingot by smelting in the vacuum induction furnace can obtain the high-strength, high-toughness and corrosion-resistant stainless steel ingot with qualified chemical components, low nitrogen content and short smelting time, and the gas nitrogen content of the high-strength, high-toughness and corrosion-resistant stainless steel ingot smelted by adopting the method is less than or equal to 0.0010 percent, the chemical components meet the requirements, and the smelting time is 15-20 hours.
In the invention, the technical characteristics can be freely combined to form a new technical scheme under the condition of no conflict.
Compared with the prior art, the invention has the following beneficial technical effects:
the chemical components of the low-nitrogen stainless steel ingot manufactured by the method meet the requirements, the nitrogen content is low, and the smelting time is shortened greatly.
Detailed Description
The present invention will be described in detail with reference to examples thereof. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention. Indeed, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features illustrated or described as part of one embodiment can be used on another embodiment to yield still a further embodiment. Accordingly, it is intended that the present invention encompass such modifications and variations as fall within the scope of the appended claims and their equivalents.
A manufacturing method for smelting a low-nitrogen stainless steel ingot by a vacuum induction furnace comprises the following steps: adding a steelmaking raw material into a vacuum induction furnace for smelting, wherein the smelting comprises sequentially carrying out melting treatment, refining treatment and casting molding,
the ingredients of the steelmaking raw materials lead the obtained steel ingot to contain: cr:12-14%, mo:2-4%, C less than or equal to 0.04%, ni 8-12%, N less than or equal to 0.001%, S less than or equal to 0.003%, P less than or equal to 0.004%;
the melting process includes: the metal chromium is reserved completely, the pure iron, the metal molybdenum and the metal nickel are added and melted in batches, the adding amount of each time is 1/5-1/3 of the total weight of the metal materials in the storage bin, the melting power of the melting period is 400-600kW and is not equal to 600kW (for example, 420kW, 450kW, 500kW, 550kW and 580 kW), the pure iron is added and melted firstly, the metal nickel is added and melted secondly, and finally the metal molybdenum is added and melted;
the refining process includes: after all the metal materials in the melting period are melted, adding metal chromium, wherein the metal chromium is added in two parts in average, each part of metal chromium is added into molten steel for 3-4 times, and the weight of each part of metal chromium is added by 1/4-1/3 of the weight of each part of metal chromium; after the first part of metal chromium is added and smelted for 1 hour, a second part of metal chromium is added, wherein the adding mode of the second part of metal chromium is the same as that of the first part of metal chromium; smelting temperature during adding metal chromium is 1580-1590 ℃ (e.g. 1582 ℃, 1585 ℃, 1586 ℃, 1588 ℃);
the casting molding comprises the following steps: and after the chemical components and the nitrogen content meet the requirements, simultaneously filling argon into a vacuum chamber and a mold injection chamber of the vacuum induction furnace to ensure that the air pressure is 20-50Pa, and finally casting into a required steel ingot.
According to the invention, the steelmaking raw materials comprise metallic nickel, metallic chromium, metallic molybdenum and pure iron. The metallic nickel, metallic chromium, metallic molybdenum, pure iron may be various metals conventionally used in the art for refining stainless steel, for example, the metallic nickel is 1#ni, etc.; the pure iron is a metal material from which C, si, mn, S, P and other harmful elements are removed through smelting and purifying of EAF+LF+VOD; the steelmaking material is dosed such that the final ingot obtained contains: cr:12-14%, mo:2-4%, C less than or equal to 0.04%, ni 8-12%, N less than or equal to 0.001%, S less than or equal to 0.003%, P less than or equal to 0.004%.
According to the invention, the melting treatment in the vacuum induction furnace refers to the process of melting and mixing the steelmaking raw materials in batches by adjusting a certain vacuum degree and melting power after adding the steelmaking metal materials except metal chromium into the vacuum induction furnace; preferably, the conditions of the melting process include: the chemical material power is 400-600kW (for example, 420kW, 450kW, 500kW, 550kW and 580 kW), the vacuum degree is less than or equal to 5Pa (for example, 4Pa, 3Pa, 2Pa and 1 Pa), and the time is 6-8h (for example, 6.5h, 7h and 7.5 h); the addition amount of the metal materials is 1/5-1/3 of the total weight of the metal materials in the bin, and the metal materials are added for 3-5 times; the smelting raw material reaches a fully molten state at the late stage of the melting treatment, and the temperature of the molten steel is preferably controlled within a range of 1500-1600 ℃ (e.g., 1510 ℃, 1520 ℃, 1550 ℃, 1570 ℃, 1580 ℃, 1590 ℃), more preferably 1580-1590 ℃ (e.g., 1582 ℃, 1585 ℃, 1586 ℃, 1588 ℃).
And refining the fully melted molten steel after the melting treatment is completed.
Preferably, the conditions of the refining treatment include: the power is 200-400kW (e.g., 220kW, 250kW, 300kW, 350kW, 380 kW), the vacuum degree is less than or equal to 3Pa, preferably less than or equal to 2Pa, the temperature is 1580-1590 ℃ (e.g., 1582 ℃, 1585 ℃, 1586 ℃, 1588 ℃), and the power frequency stirring time is 10-20min (e.g., 12min, 15min, 17min, 19 min).
The components of the refined molten steel (namely, molten steel) are more uniform, and metal chromium is added into the refined molten steel in a specific adding mode, wherein the metal chromium is added into the molten steel in an average mode in two parts, each part of metal chromium is added into the molten steel for 3-4 times, and the weight of each part of metal chromium is added into the molten steel for 1/4-1/3 of the weight of each part of metal chromium. After the first part of metal chromium is added and smelted for 1 hour, the second part of metal chromium is added and then smelted for 1 hour continuously, and the adding mode is the same as that of the first part of metal chromium.
And casting the refined molten steel into a steel ingot mould. The casting conditions preferably include: the tapping temperature is 1540-1560 ℃ (e.g. 1545 ℃, 1550 ℃, 1555 ℃, 1558 ℃). In the invention, in order to obtain lower gas nitrogen content and qualified chemical components, argon is generally filled into a vacuum chamber and a mold injection chamber of a vacuum induction furnace at the same time, so that the air pressure is 20-50Pa (for example, 25Pa, 30Pa, 35Pa, 40Pa and 45 Pa), thereby ensuring that molten steel can be stably injected into an ingot mold and avoiding splashing and blockage of the molten steel.
The chemical components of the low-nitrogen stainless steel ingot manufactured by the method meet the requirements, the nitrogen content is low, and the smelting time is short.
Example 1
In this example, the method for manufacturing a low-nitrogen stainless steel ingot by smelting 0Cr13Ni8Mo in a 6 ton vacuum induction furnace is described.
Melting period (melting treatment): the metal nickel, the metal chromium, the metal molybdenum and the pure iron are mixed according to the following steps: ni:8.5%, cr:12.5%, mo:2.0%, C:0.03%, S:0.002%, P:0.005% of the mixture is prepared, wherein the metal chromium is fully reserved; under the vacuum degree of 5Pa and the electric power of 400KW, firstly adding pure iron, adding 4500kg of pure iron in total, putting the pure iron into a vacuum induction furnace bin three times, putting 1500kg each time, adding the pure iron in the bin 3 times into a crucible of the vacuum induction furnace to form molten iron, and adding 500kg each time; adding 600kg of total metal nickel after pure iron is completely melted, adding the total metal nickel into a vacuum induction furnace bin once, adding the total metal nickel into molten steel for three times, adding 200kg of total metal molybdenum and 200kg of total molybdenum plate each time, adding the total metal nickel into the vacuum induction furnace bin once, and adding the total metal nickel into the molten steel for three times. After molten steel is melted, the temperature is controlled to be 1580-1590 ℃ and the melting period time is 8 hours.
Refining stage (refining treatment): refining molten steel under the condition that the high vacuum degree is less than or equal to 3Pa, wherein the power in the refining period is 300kW, and the refining temperature is 1580-1590 ℃; when the vacuum degree is less than or equal to 2Pa, 800kg of metal chromium is added at the temperature of 1580-1590 ℃ and refined at the temperature, the metal chromium is divided into two parts, each part of 400kg, firstly, the first 400kg of metal chromium is added into a feed bin, the 400kg of metal chromium is added into molten steel for three times, 140kg is added for the first time, 130kg is added again after melting, and smelting is carried out for 10-20min under the condition of power frequency stirring after each part of metal chromium is added; stirring the first 400kg of metal chromium after melting for 1h, and adding the second 400kg of metal chromium in the same manner as the first part; stirring for 1 hour after all the materials are added, and sampling; and after the gas nitrogen element is qualified, finely adjusting the alloy element, and reducing the temperature to 1550 ℃, and preparing for pouring, wherein the refining period time is 8 hours.
Casting period (casting molding): argon is simultaneously filled into a vacuum chamber and a mold injection chamber of the vacuum induction furnace in the casting period to ensure that the air pressure reaches 20-50Pa, and after the pressure of the vacuum chamber and the mold injection chamber is consistent, an ingot mold vehicle is opened for casting; the casting period time is 1h, and the components and smelting time of the obtained steel ingot are shown in table 1.
Table 1 chemical composition and melting time of steel ingot obtained in example 1
| C | S | P | Cr | Ni | Mo | N | Smelting time |
| 0.03 | 0.002 | 0.005 | 12.5 | 8.5 | 2.0 | 0.0009 | 17h |
Comparative example 1
This comparative example, which is a method for producing a steel ingot for low nitrogen stainless steel by a conventional smelting method, is described by taking a 6-ton vacuum induction furnace smelting 0Cr13Ni8Mo as an example, and differs from example 1 in that: 1) Adding metal chromium in the melting period, and not adding metal chromium in the refining period; 2) The metallic nickel and the metallic molybdenum are added into molten steel at one time; 3) Refining temperature is controlled according to 1540-1560 ℃; 4) Argon is not filled in the casting period, and vacuum casting is adopted; in particular, the method comprises the steps of,
melting period: the metal nickel, the metal chromium, the metal molybdenum and the pure iron are mixed according to the following proportion of the steel ingot: ni:8.5%, cr:12.5%, mo:2.0%, C:0.03%, S:0.002%, P:0.005% of the mixture was blended. Under the vacuum degree of 5Pa and the electric power of 900kW, firstly adding pure iron, adding 4500kg of pure iron in total, putting the pure iron into a vacuum induction furnace bin, adding into a crucible of a vacuum induction furnace for 3 times to form molten iron, and adding 1500kg each time; adding 600kg of metal nickel after pure iron is completely melted, adding the metal nickel into a vacuum induction furnace bin once, adding the metal chromium into molten steel once, adding the metal chromium into the vacuum induction furnace bin once, adding the metal chromium into the molten steel for 2 times, adding 400kg each time, adding 200kg of metal molybdenum at last, adding the metal chromium into the vacuum induction furnace bin once, and adding the metal chromium into the molten steel once; after molten steel is melted, the temperature is controlled to be 1540-1560 ℃ and the melting period time is 6 hours.
Refining period: refining and denitrifying molten steel under the condition that the high vacuum degree is less than or equal to 3pa, wherein the power of the refining period is 300kW, the nitrogen element is reduced by 0.0003-0.0005 wt% per hour, the alloy element is finely adjusted after the gas nitrogen element is qualified, casting is prepared, and the time of the refining period is 22 hours.
Casting period: pouring the vacuum chamber of the vacuum induction furnace and the mold injection chamber under vacuum in the casting period; the casting period time was 2 hours due to the splashing and clogging of the molten steel, and the composition of the obtained steel ingot was shown in table 2.
Table 2 chemical composition and melting time of steel ingot obtained in comparative example 1
Comparative example 2
This comparative example illustrates the method for manufacturing a low nitrogen stainless steel ingot by smelting 0Cr13Ni8Mo in a 6 ton vacuum induction furnace according to the present invention, which differs from example 1 in that a lower refining temperature is used in the refining process. In particular, the method comprises the steps of,
melting period (melting treatment): the metal nickel, the metal chromium, the metal molybdenum and the pure iron are mixed according to the following steps: ni:8.5%, cr:12.5%, mo:2.0%, C:0.03%, S:0.002%, P:0.005% of the mixture is prepared, wherein the metal chromium is fully reserved; under the vacuum degree of 5Pa and the electric power of 400kW, firstly adding pure iron, adding 4500kg of pure iron in total, putting the pure iron into a vacuum induction furnace bin three times, putting 1500kg each time, adding the pure iron in the bin into a crucible of the vacuum induction furnace 3 times to form molten iron, and adding 500kg each time; adding 600kg of total metal nickel after pure iron is completely melted, adding the total metal nickel into a vacuum induction furnace bin once, adding the total metal nickel into molten steel for three times, adding 200kg of total metal molybdenum and 200kg of total molybdenum plate each time, adding the total metal nickel into the vacuum induction furnace bin once, and adding the total metal nickel into the molten steel for three times. The temperature is controlled to 1520-1530 ℃ after the molten steel is melted, and the melting period time is 10h.
Refining stage (refining treatment): refining molten steel under the condition that the high vacuum degree is less than or equal to 3Pa, wherein the power in the refining period is 300kW, and the refining temperature is 1520-1530 ℃; when the vacuum degree is less than or equal to 2Pa, 800kg of metal chromium is added at 1520-1530 ℃ and refined at the temperature, the metal chromium is divided into two parts, each part of 400kg, firstly, the first 400kg of metal chromium is added into a feed bin, the 400kg of metal chromium is added into molten steel for three times, 140kg is added for the first time, 130kg is added again after melting, and smelting is carried out for 10-20min under the condition of power frequency stirring after each part of metal chromium is added; stirring the first 400kg of metal chromium after melting for 1h, and adding the second 400kg of metal chromium in the same manner as the first part; stirring for 1 hour after all the materials are added, and sampling; refining and denitrifying the molten steel with nitrogen content of 0.003ppm, wherein the power of the refining period is 300kW, the nitrogen element is reduced by 0.0003-0.0005 wt% per hour, the alloy element is finely adjusted after the gas nitrogen element is qualified, the temperature is increased to 1550 ℃, casting is prepared, and the refining period time is 14h.
Casting period (casting molding): argon is simultaneously filled into a vacuum chamber and a mold injection chamber of the vacuum induction furnace in the casting period to ensure that the air pressure reaches 20-50Pa, and after the pressure of the vacuum chamber and the mold injection chamber is consistent, an ingot mold vehicle is opened for casting; the casting period time was 1h, and the composition and the smelting time of the obtained steel ingot are shown in Table 3.
Table 3 chemical composition and melting time of steel ingot obtained in comparative example 2
| C | S | P | Cr | Ni | Mo | N | Smelting time |
| 0.031 | 0.002 | 0.005 | 12.46 | 8.48 | 2.17 | 0.0010 | 25h |
Comparative example 3
This comparative example illustrates a method for manufacturing a low nitrogen stainless steel ingot by smelting 0Cr13Ni8Mo in a 6 ton vacuum induction furnace according to the present invention, which differs from example 1 in that chromium metal is added at one time during refining.
Melting period (melting treatment): the metal nickel, the metal chromium, the metal molybdenum and the pure iron are mixed according to the following steps: ni:8.5%, cr:12.5%, mo:2.0%, C:0.03%, S:0.002%, P:0.005% of the mixture is prepared, wherein the metal chromium is fully reserved; under the vacuum degree of 5Pa and the electric power of 400kW, firstly adding pure iron, adding 4500kg of pure iron in total, putting the pure iron into a vacuum induction furnace bin three times, putting 1500kg each time, adding the pure iron in the bin into a crucible of the vacuum induction furnace 3 times to form molten iron, and adding 500kg each time; adding 600kg of total metal nickel after pure iron is completely melted, adding the total metal nickel into a vacuum induction furnace bin once, adding the total metal nickel into molten steel for three times, adding 200kg of total metal molybdenum and 200kg of total molybdenum plate each time, adding the total metal nickel into the vacuum induction furnace bin once, and adding the total metal nickel into the molten steel for three times. After molten steel is melted, the temperature is controlled to be 1580-1590 ℃ and the melting period time is 8 hours.
Refining stage (refining treatment): refining molten steel under the condition that the high vacuum degree is less than or equal to 3Pa, wherein the power in the refining period is 300kW, and the refining temperature is 1580-1590 ℃; when the vacuum degree is less than or equal to 2Pa, 800kg of metallic chromium is added at a time at the temperature of 1580-1590 ℃ and refined at the temperature, and the mixture is stirred for 1 hour and sampled after the complete addition; refining and denitrifying molten steel with nitrogen content of 0.0045ppm, refining period power of 300kW, nitrogen element drop of 0.0003-0.0005 wt% per hour, fine-tuning alloy element after qualified gas nitrogen element, temperature reduction to 1550 deg.C, preparation for casting, refining period time of 24h.
Casting period (casting molding): argon is simultaneously filled into a vacuum chamber and a mold injection chamber of the vacuum induction furnace in the casting period to ensure that the air pressure reaches 20-50Pa, and after the pressure of the vacuum chamber and the mold injection chamber is consistent, an ingot mold vehicle is opened for casting; the casting period time was 1h, and the composition and the smelting time of the obtained steel ingot are shown in Table 4.
Table 4 chemical composition and melting time of steel ingots obtained in comparative example 3
| C | S | P | Cr | Ni | Mo | N | Smelting time |
| 0.034 | 0.002 | 0.005 | 12.47 | 8.46 | 2.1 | 0.0010 | 33h |
Claims (6)
1. The manufacturing method of the vacuum induction furnace smelting low-nitrogen stainless steel ingot is characterized in that the stainless steel ingot comprises the following components in percentage by mass: 12-14%, mo:2-4%, C is less than or equal to 0.04%, ni:8-12%, N less than or equal to 0.001%, S less than or equal to 0.003%, P less than or equal to 0.004%, and the balance Fe and unavoidable impurities, wherein the manufacturing method comprises the steps of: adding a steelmaking raw material into a vacuum induction furnace for smelting, wherein the smelting sequentially comprises the following steps of: melting treatment, refining treatment and casting molding, wherein,
in the melting treatment step, raw material metal chromium is not added, and metal raw materials iron, nickel and molybdenum are added into a vacuum induction furnace in batches to be melted; the steelmaking raw materials comprise metallic nickel, metallic chromium, metallic molybdenum and pure iron; the pure iron is a metal material from which C, si, mn, S, P and other harmful elements are removed through smelting and purifying of EAF+LF+VOD;
in the refining treatment step, refining treatment is carried out on molten steel (molten steel) of full melting after the melting treatment, then metal chromium is added into the molten steel in batches and melted, and then the alloy element content of the molten steel is finely adjusted after the nitrogen element content in the molten steel is qualified so as to ensure that the component content of the molten steel meets the requirement;
in the melting treatment step, firstly adding pure iron for melting, then adding metallic nickel for melting, and finally adding metallic molybdenum for melting; the conditions of the melting treatment are as follows: the melting power is 400-600kW and is not equal to 600kW, the vacuum degree is less than or equal to 5Pa, and the melting treatment time is 6-8h;
in the refining step, the refining conditions are as follows: vacuum degree is less than or equal to 3Pa, power is 200-400kW, temperature is 1580-1590 ℃, and time under power frequency stirring is 10-20min;
when the vacuum degree of refining is less than or equal to 2Pa, adding metal chromium into the molten steel;
dividing the metal chromium into 2 parts, adding 3-4 times of each part of metal chromium into refined molten steel, and adding 1/4-1/3 of the total weight of each part of metal chromium each time;
adding a second part of metal chromium after the first part of metal chromium is added to smelt for 1 hour;
during the adding of the metal chromium, the vacuum degree is less than or equal to 5Pa, the power is 300-400kW, and the smelting temperature is 1580-1590 ℃;
after each part of metal chromium is added, smelting is carried out for 10-20min under the stirring of power frequency;
in the casting molding step, inert gas is filled into a vacuum chamber and a mold injection chamber of a vacuum induction furnace at the same time so as to ensure that the pressure of the vacuum chamber and the pressure of the mold injection chamber are consistent, and then casting is carried out to obtain a stainless steel ingot; the inert gas is argon, and argon with the pressure of 20-50Pa is filled into a vacuum chamber and a mold injection chamber of the vacuum induction furnace at the same time; the tapping temperature in casting is 1540-1560 ℃;
in the manufacturing method, the total time of smelting is 15-20 hours.
2. The method for manufacturing a low nitrogen stainless steel ingot by vacuum induction furnace smelting according to claim 1, wherein in the melting treatment step, the same metal raw material is added to the molten steel in 3-5 times in a bin, and the addition amount of each time is 1/5-1/3 of the total weight of the same metal raw material in the bin.
3. The method for manufacturing a low nitrogen stainless steel ingot by vacuum induction furnace according to claim 1, wherein in the melting treatment step, the melting raw material reaches a full melting state at a later stage of the melting treatment, and the temperature of the molten steel of the full melting is controlled within a range of 1500-1600 ℃.
4. The method for manufacturing a low nitrogen stainless steel ingot by vacuum induction furnace smelting according to claim 1, wherein the pure iron comprises N <0.015%, S <0.003%, P <0.005%, mn <0.03%, and Si <0.05% by mass.
5. The method for manufacturing a low nitrogen stainless steel ingot by vacuum induction furnace smelting according to claim 1, wherein the nitrogen content in the chromium metal is 0.008-0.015-wt%.
6. The method for manufacturing a low-nitrogen stainless steel ingot smelted by a vacuum induction furnace according to claim 1, wherein in the refining treatment, the total refining time is 5-10 hours.
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| JPH11140530A (en) * | 1997-11-10 | 1999-05-25 | Nippon Steel Corp | Production of ultra-low nitrogen stainless steel |
| JP2002161306A (en) * | 2000-11-24 | 2002-06-04 | Kawasaki Steel Corp | Refining process with decarburization for chromium- containing molten ferrous alloy |
| CN105970074A (en) * | 2016-05-30 | 2016-09-28 | 河北钢铁股份有限公司 | Method for quickly smelting low-nitrogen stainless steel through vacuum induction furnace |
| CN114032441A (en) * | 2021-10-21 | 2022-02-11 | 重庆大学 | Method for smelting ultra-low carbon stainless steel in vacuum induction furnace |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11140530A (en) * | 1997-11-10 | 1999-05-25 | Nippon Steel Corp | Production of ultra-low nitrogen stainless steel |
| JP2002161306A (en) * | 2000-11-24 | 2002-06-04 | Kawasaki Steel Corp | Refining process with decarburization for chromium- containing molten ferrous alloy |
| CN105970074A (en) * | 2016-05-30 | 2016-09-28 | 河北钢铁股份有限公司 | Method for quickly smelting low-nitrogen stainless steel through vacuum induction furnace |
| CN114032441A (en) * | 2021-10-21 | 2022-02-11 | 重庆大学 | Method for smelting ultra-low carbon stainless steel in vacuum induction furnace |
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