CN114350881A - Method for producing low-carbon medium-alloy round pipe billet by LD-LF-VD-MCC system through double refining process - Google Patents
Method for producing low-carbon medium-alloy round pipe billet by LD-LF-VD-MCC system through double refining process Download PDFInfo
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Abstract
The invention discloses a method for producing a low-carbon medium-alloy CrMo circular tube blank by adopting an LD-LF-VD-MCC system.
Description
Technical Field
The invention relates to the field of ferrous metal metallurgy, in particular to a method for producing a low-carbon medium-alloy round pipe blank by an LD-LF-VD-MCC system through a double refining process.
Background
With the development of the metallurgical field, the steel industry makes remarkable progress, the converter steelmaking method, the open hearth steelmaking method and the electric arc furnace steelmaking method develop nearly two hundred years due to respective advantages and disadvantages and technology upgrading, however, with the popularization and application of the continuous casting technology, the open hearth smelting gradually fades out of the black metallurgical field, and the two sets of metallurgical systems which are most widely applied at present are top-bottom combined blown converter smelting and high-power electric arc furnace smelting. The converter steelmaking generally adopts blast furnace molten iron and a small amount of scrap steel, and no additional heating is needed due to the temperature of the incoming molten iron and the heat release of the oxidation reaction during steelmaking, so that the energy consumption is reduced. The heat source of the electric arc furnace steel making is electric energy, namely an electrode made of graphite in the electric arc furnace, and strong electric arc can be emitted between the end of the electrode and furnace burden, so that the furnace burden is melted by increasing the temperature, the electric arc furnace consumes the electric energy, but the components of molten steel are relatively stable. In recent years, with the localization of high alloy steel for special purposes, the advantages of electric arc furnaces are fully exerted. However, for some low-carbon medium-alloy steels, the manufacturing cost caused by smelting energy loss and production period extension of an electric arc furnace is adopted, so that the popularization and application of the products in the boiler field, the oil and gas exploitation field and the petrochemical refining field are very difficult, and the production of low-carbon medium-alloy steel circular tube blanks by adopting an economic and efficient LD-LF-VD-MCC system becomes a hot topic in recent years.
Through search, three patents in the literature are found to be most relevant to the technology, and the specific contents are as follows:
document 1 is a converter smelting method of a low-phosphorus high-alloy steel (patent application No. 201310230260.3), which provides a converter smelting method of a low-phosphorus high-alloy steel, wherein a duplex method of smelting a first semi-steel in a dephosphorization furnace and smelting a second semi-steel in a decarburization furnace is adopted, the first semi-steel is alloyed in the smelting process, and the high-alloy element is mainly metallic nickel. The alloying of the technology is mainly an oxygen-philic alloy element chromium, if a duplex method is adopted, chromium is added into the first half steel and evolved, and oxide is formed in the oxygen blowing and decarburization process of the second half steel and enters a steel slag system, so that the expected alloying effect cannot be achieved.
Document 2 is an alloy preheating process for smelting high alloy steel in a converter steelmaking process (patent application No. 202010708366.X), which discloses an alloy preheating process for smelting high alloy steel in a converter steelmaking process, characterized in that a metal or iron alloy to be alloyed is baked in a roaster to 634 to 651 ℃, solving the problem of sharply lowering the tapping temperature due to the addition of a large amount of alloy into the converter. The patent shortens the alloying time and ensures continuous operation. However, the alloy baking period of the patent is 48-52 hours, which is not beneficial to the continuous operation of the same material in large batch and brings difficulty for the flexible scheduling production on site.
Document 3 is a smelting method (patent application No. 201610113192.6) for producing low-phosphorus high-alloy steel by alloying in a converter, and discloses a smelting method for producing low-phosphorus high-alloy steel by alloying in a converter, which is characterized in that low-phosphorus steel is produced by duplex smelting of a molten iron washing tank, a molten steel tank, a converter and a converter, slag removal operation of first half steel, and smelting end point of second half steel is carried out and evolved, and meanwhile, point blowing is adopted to increase tapping temperature. The patent adopts aerobic soft blowing, and the added oxygen-philic alloy elements of manganese and chromium cause oxidation loss, so that the yield of the alloy elements is reduced.
Disclosure of Invention
The invention aims to provide a method for producing a low-carbon medium-alloy round pipe blank by an LD-LF-VD-MCC system through a double refining process, wherein the round pipe blank produced by the method is low in inclusion content, low in oxyhydrogen and nitrogen gas content, low in residual harmful elements and low in production cost, and can realize continuous operation.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for producing a low-carbon medium-alloy round pipe blank by an LD-LF-VD-MCC system by adopting a double refining process comprises the following steps:
the method comprises the following steps of (1) molten iron pretreatment, wherein a blast furnace tapping hook is sprayed with calcium oxide, fluorite, limestone powder, soda ash and converter slag complexing agent for desiliconization, the silicon in the molten iron is reduced to be not more than 0.15%, so that a top-bottom combined blown converter can be subjected to good decarburization, dephosphorization and desulfurization treatment are performed in a molten iron tank by a powder injection stirring method, the sulfur content in the molten iron can be reduced to be below 0.015%, the dephosphorization efficiency in the converter smelting process is improved, the sulfur content is reduced to be below 0.05%, the desulfurization pressure in the refining process is relieved, the tapping temperature of the molten iron in the blast furnace is guaranteed to be at 1400-class 1500 ℃, and the temperature of the molten iron to the converter is 1200-class 1300 ℃ due to heat loss in the transportation process;
smelting in a top-bottom combined blowing converter, adding the pretreated blast furnace molten iron and high-quality waste steel into the top-bottom combined blowing converter for smelting according to the mass ratio of 12-8:1, building a furnace lining by adopting an alkaline refractory material in the top-bottom combined blowing converter, adding lime for slagging, blowing high-speed oxygen into the top, blowing inert gas argon into the bottom for stirring and combined blowing smelting, oxidizing the oxygen-philic elements such as iron, silicon and manganese and the like in the initial blowing stage to a large extent, wherein the silicon and manganese content is close to a trace amount, the temperature of the molten iron is 1400 ℃ and 1500 ℃, the carbon content in the molten iron begins to generate a severe oxidation reaction, when the blowing is close to the end point, realizing the transformation of the molten steel after the decarburization of the molten iron, the temperature of the molten steel is 1550 ℃ and 1650 ℃, and in order to share the alloying pressure of the furnace, adding ferrosilicon, ferromanganese for deoxidation and alloying, and adding ferromolybdenum and ferrochrome before tapping of the converter for final deoxidation, and adopting aluminum;
LF refining, wherein the tasks of the LF refining 1 are mainly to ensure the temperature of molten steel and mainly add elements for alloying, molten iron is poured into a ladle and transferred to an LF refining station to be heated by a graphite electrode, argon is blown in the whole smelting process, ferrochrome is added, the molten iron enters a second LF refining station for refining after alloying is completed, and the purpose of the LF refining 2 is mainly to further desulfurize and adjust the chemical components and temperature of the molten steel;
VD vacuum treatment aims at the shape control of non-metallic inclusions and the addition of degassing and other microalloy elements, the VD vacuum treatment requires that the vacuum degree is less than or equal to 0.10KPa, the deep vacuum time is more than or equal to 20 minutes, a proper amount of iron-calcium wires are fed after the vacuum treatment is finished, and the soft blowing time is more than or equal to 15 minutes after the wire feeding;
and (2) MCC continuous casting, wherein molten steel is solidified into a solid round pipe blank through a crystallizer, a secondary cooling zone and an air cooling zone, the MCC continuous casting adopts constant-pulling-speed low-pulling-speed control, an electromagnetic stirring process is adopted, the superheat degree of the molten steel is controlled to be less than or equal to 30 ℃, the continuous casting round pipe blank is cooled in a slow cooling pit after being sawed according to requirements, and the slow cooling time is more than or equal to 48 hours.
Further, the powder spraying comprises soda ash, calcium carbide powder, lime powder and a metal magnesium system desulfurizer.
Compared with the prior art, the invention has the beneficial technical effects that:
the round pipe billet produced by the invention has the advantages of low inclusion content, low oxyhydrogen nitrogen gas content, less residual harmful elements and low production cost, and can realize continuous operation.
Drawings
The invention is further illustrated in the following description with reference to the drawings.
FIG. 1 is a macroscopic structure diagram of casting blank hot acid detection.
Detailed Description
The following embodiments are further illustrated by reference to the following specific examples:
the LD-LF-VD-MCC system adopts a double refining process to produce low-carbon medium-alloy round tube billets 10Cr5MoVRE, and realizes the low-carbon alloy 10Cr5MoVRE steel with the finished products of 0.08-0.012 percent of C, 0.25-0.30 percent of Si, 0.4-0.5 percent of Mn, less than or equal to 0.010 percent of P, less than or equal to 0.003 percent of S, 5.0-5.2 percent of Cr, 0.45-0.50 percent of Mo, 0.04-0.06 percent of V and 0.0010-0.0030 percent of RE through molten iron pretreatment, LD top and bottom combined blown converter smelting, LF external refining (double refining), VD vacuum treatment and MCC round tube billet continuous casting process methods; the method comprises the following specific steps:
the method comprises the steps of pretreating molten iron, blowing a complexing agent such as calcium oxide, fluorite, limestone powder, soda ash, converter slag and the like on a blast furnace tapping hook for desiliconization treatment, wherein the silicon content in the molten iron is 0.10-0.15%, carrying out dephosphorization and desulfurization treatment in a molten iron tank by a powder spraying (soda ash, calcium carbide powder, lime powder and a metal magnesium desulfurizer) stirring method, controlling the sulfur content in the molten iron to be 0.012-0.015%, reducing the sulfur content to 0.03-0.05%, tapping the molten iron in a blast furnace to 1350-1450 ℃, and controlling the temperature of the molten iron to the converter to be 1200-1250 ℃.
Smelting in a top-bottom combined blowing converter, adding 80 tons of pretreated blast furnace molten iron and 8 tons of high-quality scrap steel into the top-bottom combined blowing converter for smelting, adding lime for slagging, blowing high-speed oxygen into the top, blowing inert gas argon into the bottom for stirring and combined blowing smelting, wherein the carbon content after decarburization is 0.09-0.11%, the molten steel temperature is 1600-1625 ℃, stopping blowing oxygen after decarburization is finished, continuously blowing argon into the converter for stirring, adding 0.37 ton of 75% ferrosilicon, 0.74 ton of 68% ferromanganese, 0.87 ton of 60% ferromolybdenum, and 3 tons (parts) of 55% ferrochromium for alloying, wherein aluminum deoxidation is adopted for final deoxidation, and the smelting period of the converter is 40 minutes.
Pouring molten iron into a ladle, transferring to an LF refining 1 station, heating by adopting a graphite electrode, blowing argon in the whole smelting process, adding 7.1 tons of ferrochrome, wherein the smelting period of the refining 1 is 40 minutes, after the ferrochrome is melted, refining in an LF refining 2 station, adding 0.11 ton of 50% ferrovanadium, adjusting the temperature of molten steel to 1625-1650 ℃, and performing the LF refining 2 for 40 minutes.
The VD vacuum treatment requires the vacuum degree of 0.06KPa and the deep vacuum time of 20 minutes, 200 meters of iron-calcium wires are fed after the vacuum treatment is finished, 10 percent rare earth alloy 50KG is added, the soft blowing time is 15 minutes after wire feeding, the standing is carried out for 5 minutes, and the temperature of the molten iron is 1580-1600 ℃ after the vacuum pumping.
The MCC continuous casting adopts a constant drawing speed and a low drawing speed, the drawing speed is controlled to be 1.0m/min, a crystallizer electromagnetic stirring and tail end electromagnetic stirring process is adopted, the superheat degree of molten steel is controlled to be 20-25 ℃, the outer diameter specification of a continuous casting blank is phi 210mm, the blank is cooled in a slow cooling pit after the continuous casting round tube blank is sawed, and the slow cooling time is 48 hours.
Effects of the implementation
The chemical component test results of the low-carbon medium alloy 10Cr5MoVRE round pipe billet manufactured by the implementation method are shown in table 1, the casting blank sulfur mark test results are shown in table 2, and the macrostructure of the casting blank hot acid test results is shown in table 1.
TABLE 110 chemical composition test results wt/% of Cr5MoVRE round tube blank
TABLE 210 Cr5MoVRE circular tube blank sulfur print test result/grade
| Center crack | Median crack | Cracks under the skin | Inclusions | |
| Example 1 | 0 | 0 | 0 | 1 |
| Example 2 | 0 | 0 | 0 | 0 |
| Embodiment 3 | 0 | 0 | 0 | 1 |
| Example 4 | 0 | 0 | 0 | 1 |
| Example 5 | 0 | 0 | 0 | 0 |
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (2)
1. A method for producing a low-carbon medium-alloy round pipe blank by an LD-LF-VD-MCC system by adopting a double refining process is characterized by comprising the following steps of: the method comprises the following steps:
the method comprises the following steps of (1) molten iron pretreatment, wherein a blast furnace tapping hook is sprayed with calcium oxide, fluorite, limestone powder, soda ash and converter slag complexing agent for desiliconization, the silicon in the molten iron is reduced to be not more than 0.15%, so that a top-bottom combined blown converter can be subjected to good decarburization, dephosphorization and desulfurization treatment are performed in a molten iron tank by a powder injection stirring method, the sulfur content in the molten iron can be reduced to be below 0.015%, the dephosphorization efficiency in the converter smelting process is improved, the sulfur content is reduced to be below 0.05%, the desulfurization pressure in the refining process is relieved, the tapping temperature of the molten iron in the blast furnace is guaranteed to be at 1400-class 1500 ℃, and the temperature of the molten iron to the converter is 1200-class 1300 ℃ due to heat loss in the transportation process;
smelting in a top-bottom combined blowing converter, adding the pretreated blast furnace molten iron and high-quality waste steel into the top-bottom combined blowing converter for smelting according to the mass ratio of 12-8:1, building a furnace lining by adopting an alkaline refractory material in the top-bottom combined blowing converter, adding lime for slagging, blowing high-speed oxygen into the top, blowing inert gas argon into the bottom for stirring and combined blowing smelting, oxidizing the oxygen-philic elements such as iron, silicon and manganese and the like in the initial blowing stage to a large extent, wherein the silicon and manganese content is close to a trace amount, the temperature of the molten iron is 1400 ℃ and 1500 ℃, the carbon content in the molten iron begins to generate a severe oxidation reaction, when the blowing is close to the end point, realizing the transformation of the molten steel after the decarburization of the molten iron, the temperature of the molten steel is 1550 ℃ and 1650 ℃, and in order to share the alloying pressure of the furnace, adding ferrosilicon, ferromanganese for deoxidation and alloying, and adding ferromolybdenum and ferrochrome before tapping of the converter for final deoxidation, and adopting aluminum;
LF refining, wherein the tasks of the LF refining 1 are mainly to ensure the temperature of molten steel and mainly add elements for alloying, molten iron is poured into a ladle and transferred to an LF refining station to be heated by a graphite electrode, argon is blown in the whole smelting process, ferrochrome is added, the molten iron enters a second LF refining station for refining after alloying is completed, and the purpose of the LF refining 2 is mainly to further desulfurize and adjust the chemical components and temperature of the molten steel;
VD vacuum treatment aims at the shape control of non-metallic inclusions and the addition of degassing and other microalloy elements, the VD vacuum treatment requires that the vacuum degree is less than or equal to 0.10KPa, the deep vacuum time is more than or equal to 20 minutes, a proper amount of iron-calcium wires are fed after the vacuum treatment is finished, and the soft blowing time is more than or equal to 15 minutes after the wire feeding;
and (2) MCC continuous casting, wherein molten steel is solidified into a solid round pipe blank through a crystallizer, a secondary cooling zone and an air cooling zone, the MCC continuous casting adopts constant-pulling-speed low-pulling-speed control, an electromagnetic stirring process is adopted, the superheat degree of the molten steel is controlled to be less than or equal to 30 ℃, the continuous casting round pipe blank is cooled in a slow cooling pit after being sawed according to requirements, and the slow cooling time is more than or equal to 48 hours.
2. The LD-LF-VD-MCC system of claim 1, which adopts a double refining process to produce low-carbon medium-alloy round tube billets, and is characterized in that: the powder spraying comprises soda ash, calcium carbide powder, lime powder and a metal magnesium system desulfurizer.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103131950A (en) * | 2013-03-22 | 2013-06-05 | 内蒙古包钢钢联股份有限公司 | Rear-earth-containing seamless steel tube material for high-pressure fertilizer and preparation method thereof |
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