CN113913673B - Method for controlling size and quantity of inclusions in steel by magnesium-containing alloy - Google Patents
Method for controlling size and quantity of inclusions in steel by magnesium-containing alloy Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
- B21B1/463—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting in a continuous process, i.e. the cast not being cut before rolling
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
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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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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Abstract
The application relates to the field of steelmaking, in particular to a method for controlling the size and the number of inclusions in steel by using magnesium-containing alloy. The method comprises the following steps: alloying the molten steel to obtain alloyed molten steel; adding a magnesium-containing alloy into the alloyed molten steel to obtain magnesium-containing molten steel; continuously casting the magnesium-containing molten steel to obtain a continuous casting blank; the addition amount of the magnesium-containing alloy is determined according to the aluminum content of the alloying molten steel, and when the continuous casting starts, the mass concentration of magnesium in the magnesium-containing molten steel is more than or equal to 0.0002ppm, the deoxidizing capacity of the remaining metal element or elements in the magnesium-containing alloy is respectively smaller than that of the iron element; MgO-Al without affecting magnesium to form solid 2 O 3 Spinel is randomly distributed in the steel, a large amount of oxide less than 3 mu m is precipitated, and along with the increase of the amount of the oxide, the fatigue resistance and the corrosion resistance of a steel billet are improved, the nucleation effect of acicular ferrite can be induced, and the welding impact toughness of the thick plate is improved.
Description
Technical Field
The application relates to the field of steelmaking, in particular to a method for controlling the size and the number of inclusions in steel by using magnesium-containing alloy.
Background
Magnesium oxide was first used in steel for high heat input welding and to improve heat affected zone toughness. In the metallurgical process, in laboratory and industrial small batch tests, after the molten steel is treated by the magnesium oxide, the problems of high magnesium activity, low yield, large fluctuation of the quantity of the magnesium oxide and large-size inclusion after the magnesium treatment generally exist.
The patent publication No. CN106399633A, a process for treating liquid magnesium in ship plate steel, adopts Mg-A1 core-spun alloy wire after fine adjustment of LF alloy, the feeding position is opposite to the second air brick of the ladle, the radius of the opposite side from the center of the ladle is 1/3-1/2, and the wire feeding speed is 2.5-4.0 m.s -1 Soft blowing is carried out for more than or equal to 12min after wire feeding; in the refining process of the ship plate steel, molten steel is added in a Mg-Al-Fe alloy mode for molten steel magnesium treatment, the alloy is prepared by utilizing the characteristic that aluminum, magnesium and iron can easily form alloy in any proportion, and the cleanliness of the ship plate steel and the components, the quantity, the granularity and the distribution of inclusions in the steel can be controlled; the method improves the cleanliness of the ship plate steel and the control level of non-metallic inclusions, thereby improving the mechanical property and the stability of the ship plate steel.
In patent publication CN 102181802A, "a preparation method of easily-welded high-toughness X80G pipeline steel treated by magnesium", firstly, magnesium-treated steel is trial-produced in a vacuum induction furnace, and the X80G pipeline steel has good high heat input welding performance by controlling components of Ti/Mg ratio.
In China, the research on the molten steel Mg treatment technology is mainly used in the experimental and basic theory research stages, and the popularization and application of the industrial technology to wheel steel have little application. However, there is no report on how to improve the process for controlling the number and size of particles by using magnesium oxide metallurgy.
Disclosure of Invention
The application provides a method for controlling the size and the quantity of inclusions in steel by using magnesium-containing alloy, which aims to solve the technical problem that the size and the quantity of inclusions in steel cannot be controlled by the existing Mg treatment technology.
In a first aspect, the present application provides a method for controlling the size and amount of inclusions in steel with a magnesium-containing alloy, the method comprising the steps of:
alloying the molten steel to obtain alloyed molten steel;
adding a magnesium-containing alloy into the alloyed molten steel to obtain magnesium-containing molten steel;
continuously casting the magnesium-containing molten steel to obtain a continuous casting blank;
wherein the addition amount of the magnesium-containing alloy is determined according to the aluminum content of the alloying molten steel, and when the continuous casting starts, the mass concentration of magnesium in the magnesium-containing molten steel is more than or equal to 0.0002ppm, the deoxidizing capacity of the remaining metal element or metal elements in the magnesium-containing alloy is respectively less than that of iron elements.
Optionally, the magnesium-containing alloy comprises a Ni-Mg alloy and/or a Cr-Mg alloy, wherein the content of magnesium is 10-30% by mass; the first metal element comprises nickel or chromium.
Optionally, the granularity of the magnesium-containing alloy is less than or equal to 30 mm.
Optionally, the protective atmosphere in the ladle includes an atmospheric atmosphere or an argon-containing atmosphere.
Optionally, the alloying molten steel contains, by mass, 0.0015% -0.003% of oxygen and 0.0015% -0.003% of sulfur.
Optionally, the mass concentration of magnesium in the continuous casting slab is more than or equal to 0.0002 ppm.
Optionally, the sizes of the inclusions in the continuous casting slab are all less than 15 microns.
Optionally, in the continuous casting billet, each 32.1mm 2 The number of inclusions with a size of 1 to 5 μm in the area of (A) is more than 470.
Optionally, the oxygen potential of the slag of the molten steel is 20-30 ppm.
In a second aspect, the application provides a continuous casting billet prepared by the method in the first aspect, and a high-quality steel plate is obtained by rolling, wherein the welding toughness of the steel plate is more than or equal to 280J at-30 ℃; the fatigue limit is more than or equal to 480 MPa.
Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages:
according to the method provided by the embodiment of the application, in the process of treating molten steel by magnesium-containing alloy, the magnesium-containing alloy is added according to the aluminum content to obtain the molten steel meeting the requirement of the target steel grade, and meanwhile, the deoxidation capability of the rest one or more metal elements in the magnesium-containing alloy is ensured to be smaller than that of iron element, so that MgO-Al 2O of magnesium forming solid is not influenced 3 Spinel; when the mass concentration of magnesium is more than or equal to 0.0002ppm, continuously casting the molten steel in the ladle, after the molten steel is treated by magnesium-containing alloy, the magnesium in the steel is gradually attenuated along with the time extension, and when the mass concentration of magnesium is more than or equal to 0.0002ppm, continuously casting is carried out, so that sufficient magnesium element in a continuous casting blank is ensured to form oxides, and MgO and Al are ensured simultaneously 2 O 3 The amount of spinel is not cluster-shaped, and the spinel is randomly distributed in the steel, a large amount of oxide less than 3 mu m is precipitated, and along with the increase of the amount of the oxide, the fatigue resistance and the corrosion resistance of the steel billet are improved, the nucleation effect of acicular ferrite can be induced, and the welding impact toughness of the thick plate is improved.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is a schematic flow chart of a method for controlling the size and quantity of inclusions in steel by using a magnesium-containing alloy according to an embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In a first aspect, the present application provides a method for controlling the size and amount of inclusions in steel using a magnesium-containing alloy, as shown in fig. 1, the method comprising the steps of:
s1, alloying the molten steel to obtain alloyed molten steel;
s2, adding a magnesium-containing alloy into the alloyed molten steel to obtain magnesium-containing molten steel;
s3, continuously casting the magnesium-containing molten steel to obtain a continuous casting blank;
the addition amount of the magnesium-containing alloy is determined according to the aluminum content of the alloying molten steel, and when the continuous casting starts, the mass concentration of magnesium in the magnesium-containing molten steel is more than or equal to 0.0002ppm, the deoxidizing capacity of the remaining one or more metal elements in the magnesium-containing alloy is respectively smaller than that of the iron element.
In the present embodiment, it is preferable to control the deoxidation ability of the first metal element contained less than that of the iron element because more oxygen in the steel forms MgO with the magnesium alloy, and the amount of oxides formed by other elements is reduced, thereby increasing the original amount of small-sized MgO; the passivation treatment is carried out on the activity of pure Mg, and the beneficial effects of safety and higher yield of the alloy by using M are achieved; if Al or Si is selected and the alloy adopts Al-Mg, Si-Mg and other magnesium-containing alloys, a certain amount of A1 or Si participates in the deoxidation reaction, and the amount of MgO is reduced; the deoxidation capability of one or more metal elements in the magnesium-containing alloy can be controlled to be respectively smaller than that of the iron element.
In the embodiment of the application, after the vacuum refining molten steel is treated by the magnesium-containing alloy, the magnesium content in the vacuum refining molten steel after magnesium treatment can reach 0.0002-0.0018%; can also achieve the thermodynamic conditions of low sulfur and low oxygen after the molten steel is alloyed, and can also be subjected to Mg alloying treatment.
In the embodiment of the application, the adding mode comprises a wire feeding method and a throwing method, the wire feeding operation is adopted, the wire feeding depth is about 0.50-0.80H (molten steel depth), the wire feeding speed is 3-6 m/s, argon is blown softly for 3-8 minutes after the wire feeding, and the Mg treatment can achieve a good modification effect; after the magnesium-containing alloy is used for treating vacuum refined molten steel, in order to ensure less splashing, the speed can be reduced when the Mg alloy wire is fed initially, and the speed is gradually increased after the molten steel surface added with the Mg alloy wire is boiled stably; after Mg treatment, proper stirring is necessary, but molten steel cannot be exposed, and meanwhile, the molten steel flow field is ensured to enable Mg alloy to circularly enter the molten steel during stirring and not to move to the surface of the molten steel.
In the embodiment of the application, magnesium-containing alloy is added, the size of inclusions in steel is refined, and Mg oxides in molten steel are modified into a large amount of MgO & Al 2 O 3 And MgO. Al 2 O 3 -S small size particles.
In the embodiment of the application, when the mass concentration of magnesium is more than or equal to 0.0002ppm, the reason for continuously casting the ladle molten steel is that after the ladle molten steel is treated by magnesium-containing alloy, magnesium in the steel gradually attenuates along with the prolonging of time, and the adverse effect of the quantity of small-size inclusions formed by Mg alloying can be caused; when the concentration is more than or equal to 0.0002ppm, the beneficial effect of ensuring a certain amount of MgO is achieved.
In the embodiment of the application, in order to ensure the magnesium treatment effect, the magnesium content in the steel after magnesium treatment can reach 0.0002-0.0018%, small-size inclusions in the steel are formed, the casting operation is completed as soon as possible when the steel is stable, and the number of effective small-size oxide inclusions in the steel is reduced and the number of effective small-size oxide inclusions in the steel is increased after Mg in the steel is further attenuated.
As an optional embodiment, the magnesium-containing alloy comprises a Ni-Mg alloy and/or a Cr-Mg alloy, wherein the magnesium content is 10-30% by mass; the first metal element comprises nickel or chromium.
In the embodiment of the application, the first metal element in the magnesium-containing alloy has the function of not participating in deoxidation, and the effect of increasing the original small-size MgO can be achieved.
As an alternative embodiment, the magnesium-containing alloy has a particle size of 30mm or less.
In the embodiment of the application, the granularity of the magnesium-containing alloy is less than or equal to 30mm, so that the magnesium-containing alloy has the beneficial effects of effectively increasing the yield and safety of Mg alloy, and if the granularity is greater than 30mm, the yield is influenced, and the magnesium-containing alloy has the adverse effects of overhigh local Mg concentration and danger caused by eruption in the steelmaking process; when the alloy cored wire is added, the granularity of the magnesium-containing alloy can be 1-3 mm.
As an alternative embodiment, the protective atmosphere in the ladle comprises an atmospheric atmosphere or an argon-containing atmosphere.
In the embodiment of the application, the magnesium treatment is carried out in the ladle, and the ladle can be in a normal atmosphere or an argon-containing atmosphere, the vacuum degree of argon can be 30-80KPa, and the preferable argon pressure is about 50 KPa.
In an optional embodiment, the alloyed molten steel has an oxygen content of 0.0015% to 0.003% and a sulfur content of 0.0015% to 0.003% by mass fraction.
In the embodiment of the application, before magnesium-containing alloy is added, the reason for controlling the oxygen content and the sulfur content is that the oxygen content is controlled to ensure that certain free oxygen in the steel can form a certain amount of small-size MgO once with the magnesium alloy after being added, when the oxygen content is low and a certain amount of sulfur is available, Mg can directly react with sulfur to generate MgS, and the size of MgS once is larger than that of MgO, so that the method is unfavorable for refining the size of the original oxide inclusion.
In the embodiment of the application, the Mg treated molten steel does not stay for a long time, so that the pollution and secondary oxidation of the furnace lining to the low-oxygen clean molten steel after Mg treatment are reduced. In addition, too high content of S in molten steel before Mg treatment can also influence the modification effect of Mg on oxides, and Mg in the molten steel with lower oxygen content can be combined with S in the steel to form MgS inclusion, thereby influencing Mg to directly form small-size MgO. Relevant experimental data show that higher molten steel temperature is also unfavorable for Mg treatment yield. In summary, the molten steel state before Mg treatment should ensure that all alloying trimming is finished, lower oxygen, sulfur content, proper temperature.
As an alternative embodiment, the mass concentration of magnesium in the continuous casting slab is more than or equal to 0.0002 ppm.
In the embodiment of the application, the reason why the mass concentration of magnesium in the continuous casting billet is controlled to be more than or equal to 0.0002ppm is that a certain amount of Mg forms MgO after the Mg in the steel-making process, and the Mg has a decay tendency along with the time, so that the minimum content of the Mg in the casting billet is regulated, and the beneficial effect of a certain amount of MgO can be ensured.
In an alternative embodiment, the inclusions in the strand have a size of <15 μm.
As an alternative embodiment, the strand is cast every 32.1mm 2 The number of inclusions with a size of 1 to 5 μm in the area of (A) is more than 470.
As an alternative embodiment, the oxygen potential of the slag of the molten steel is 20 to 30 ppm.
In the embodiment of the present application, the reason why the oxygen potential of the molten steel is controlled to be 20-30ppm is that a certain amount of oxygen is contained in the steel, and the oxygen can be provided for forming a certain amount of MgO during Mg treatment. If the alloying treatment is carried out during vacuum refining, before the vacuum refining treatment is carried out on the molten steel, the method also comprises the step of carrying out LF refining treatment on the molten steel to obtain LF refined molten steel, wherein the oxygen potential of the slag of the molten steel is 20-30 ppm.
In a second aspect, the application provides a continuous casting billet prepared by the method in the first aspect, and a high-quality steel plate is obtained by rolling, wherein the welding toughness of the steel plate is more than or equal to 280J at-30 ℃; the fatigue limit is more than or equal to 480MPa, and the alloy has better comprehensive mechanical properties, and is reflected in the corrosion properties of fatigue, welding toughness, acid resistance and the like.
The process of the present invention will be described in detail below with reference to examples, comparative examples and experimental data.
In examples 1 to 3 and comparative examples 1 to 2, the process flow adopted when magnesium-containing alloy is used for treatment is as follows: blast furnace molten iron → molten iron desulphurization → converter top and bottom combined blowing → LF furnace → RH (Mg) treatment → continuous casting. The deoxidation and desulfurization tasks are completed in the steel-making LF furnace, the slag modification is performed on the slag on the top of the steel ladle, the oxidability of the slag is greatly reduced, the content of a gas harmful element N, H, O in steel after vacuum RH treatment is further reduced, and the content of O, S in the steel is 0.0015-0.003%. The process of carrying out the Mg wire feeding operation at the RH wire feeding station comprises the following steps:
firstly, selecting Mg alloy wires, selecting Ni-Mg alloy in examples 1-3, selecting Al-Mg alloy in comparative example 1, and selecting no-treatment in comparative example 2, wherein Al-Mg and no-treatment are comparative examples;
a ladle wire feeding process: and the wire feeding operation is carried out after the vacuum treatment is finished, the cover of the ladle furnace is opened, and the wire feeding machine feeds the Mg-Ni/Al-Mg wire for 400 meters. Soft blowing is started before wire feeding to enable molten steel to flow circularly, argon blowing strength is increased to blow away a slag surface in the center of a steel ladle during wire feeding, a magnesium wire is fed into the molten steel, wire feeding depth is about 0.50-0.80H (molten steel depth), wire feeding speed is 3-6 m/s, argon is blown softly for 3-8 minutes after wire feeding, and a molten steel flow field is ensured to enable Mg alloy to enter the molten steel circularly during argon stirring and not move to the surface of the molten steel directly, so that the metallurgical treatment effect of Mg oxide is promoted.
Table 1 size and number distribution of inclusions in different modified treated steels in examples 1 to 3 and comparative examples 1 to 2.
Table 2 properties of the steel sheets of examples 1 to 3 and comparative examples 1 to 2.
As can be seen from the table, the molten steel after Mg treatment is continuously cast and is heated and rolled to the thickness of a finished product of 12.7mm, and the inclusions in the steel in the rolled state are analyzed, so that the inclusions with the large size of more than or equal to 15 mu m are not seen in the steel, and the inclusions are mainly granular MgO-Al 2 O 3 And granular MgO & Al with enriched sulfide on surface 2 O 3 . The quantitative statistics of the inclusions in the three different types of treatment modes are shown in the table 1, and the table shows that the total amount of the inclusions in the steel is sorted into Ni-Mg alloy Al-Mg alloy, the treatment-free process is adopted, the Ni-Mg content is the largest, and the Ni-Mg serving as the oxide metallurgical alloy can effectively improve the number of oxide particles. As can be seen from Table 2, the continuous casting slabs were rolledThe treatment of Ni-Mg in the later fatigue limit is higher than that of Al-Mg and that of no treatment, and the welding toughness and the H resistance 2 Good S corrosion, steel fatigue, welding toughness and H resistance without any inclusion modification treatment 2 S is the least corrosive.
In examples 4 to 6 and comparative examples 3 to 4, the process flow adopted when producing a certain special steel by an electric furnace is as follows: electric furnace → VIM (vacuum induction furnace)/VD (vacuum degassing) (Mg treatment) → continuous casting/die casting. The aluminum deoxidized killed steel completes the tasks of deoxidation and desulfurization in an electric furnace, and the vacuum treatment is carried out in vacuum to further reduce the gas harmful element N, H, O in the steel. Vacuum Mg treatment is carried out subsequently. Magnesium-containing alloy treatment in examples 4 to 6, a Ni — Mg alloy was used, wherein in the Nil-Mg alloy, in mass fraction, Ni: 90%, Mg: 10 percent, the granularity is 2-20mm, and the mixture is added to the surface of the molten steel by a top feeding method; the comparative example was carried out using an Al — Mg alloy, and comparative example 2 was carried out using an alloy containing no magnesium.
(1) Vacuum refining in a vacuum furnace, wherein the weight of the molten steel is 500kg, the components of the molten steel meet the target requirements, the total oxygen in the steel is less than or equal to 0.003 percent, and then a magnesium-containing alloy treatment process is carried out in a vacuum chamber. Filling protective gas Ar gas of 50KPa before the magnesium-containing alloy is treated, then adding Ni-Mg alloy or A1-Mg alloy, after the alloy is added, raising power, carrying out electromagnetic stirring for 2 minutes to promote the homogenization of the alloy, and then casting into ingots. The content of the finished product in the steel is shown in Table 3.
Table 3 size and number distribution of inclusions in different modified treated steels in examples 4 to 6 and comparative examples 3 to 4.
Table 4 properties of the steel sheets of examples 4 to 6 and comparative examples 3 to 4.
Hot rolling and rolling the steel ingot treated by electric furnace Mg to obtain a finished product with the thickness of 12.7mm, performing surface scanning inclusion statistical analysis on inclusions in the steel in a rolling state,the main impurities in the steel do not have large size larger than or equal to 15 mu m, and the impurities are mainly granular MgO & Al 2 O 3 And granular MgO & Al with enriched sulfide on surface 2 O 3 . And simultaneously carrying out quantitative statistics on the inclusion. From table 3, it can be seen that the total amount of inclusions in the steel are sorted into Ni-Mg alloy Al-Mg alloy, no treatment process, and the Ni-Mg content is the largest, so that the use of Ni-Mg as an oxide metallurgical alloy can effectively increase the number of oxide particles, and from table 4, the comprehensive physical and chemical properties of the rolled steel slab are shown in table 4. The total amount of inclusions in the steel is sorted into Ni-Mg alloy A1-Mg alloy, the treatment process is omitted, the Ni-Mg content is the largest, and the Ni-Mg is used as an oxide metallurgical alloy, so that the number of small-size oxide particles can be effectively increased. As can be seen from Table 4, the fatigue limit of the properties obtained by treating with Ni-Mg was higher than that obtained by treating with Al-Mg and not treated, and the weld toughness and the corrosion resistance against H2S were better, and the fatigue resistance, weld toughness and H resistance of the steel which had not been subjected to any inclusion modification treatment were improved 2 S is the least corrosive.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above description is merely illustrative of particular embodiments of the invention that enable those skilled in the art to understand or practice the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (4)
1. A method for controlling the size and quantity of inclusions in steel using a magnesium-containing alloy, said method comprising the steps of:
alloying the molten steel to obtain alloyed molten steel, wherein the oxygen potential of the slag of the molten steel is 20-30ppm, and the oxygen content and the sulfur content in the alloyed molten steel are respectively 0.0015-0.003% and 0.0015-0.003% by mass fraction;
adding a magnesium-containing alloy into the alloyed molten steel to obtain magnesium-containing molten steel;
continuously casting the magnesium-containing molten steel to obtain a continuous casting blank;
the magnesium-containing alloy is added in a wire feeding mode, the wire feeding depth is 0.50-0.80 times of the depth of molten steel, the wire feeding speed is 3-6 m/s, argon is blown softly for 3-8 minutes after wire feeding, the continuous casting starts when the mass concentration of magnesium in the magnesium-containing molten steel is more than or equal to 0.0002ppm, the deoxidizing capacity of the rest metal element or metal elements in the magnesium-containing alloy is respectively less than that of iron elements, the magnesium-containing alloy is a Cr-Mg alloy, and the content of magnesium is 10-30% in mass fraction; the first metal element is chromium, and the content of the first metal element in the continuous casting billet is 32.1mm per square meter 2 The number of inclusions with a size of 1 to 5 μm in the area of (2) is more than 470.
2. The method of claim 1, wherein the magnesium-containing alloy has a grain size of 30mm or less.
3. Method according to claim 1, characterized in that the inclusions in the slab are all <15 μm in size.
4. A steel plate rolled into a finished thickness from a continuous casting slab produced by the method according to any one of claims 1 to 3, wherein the weld toughness of the steel plate is more than or equal to 280J at-30 ℃; the fatigue limit is more than or equal to 480 MPa.
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| CN105803156B (en) * | 2016-03-25 | 2017-12-26 | 江苏省沙钢钢铁研究院有限公司 | A kind of oxide control method for improving magnesium recovery rate |
| CN106399633B (en) * | 2016-09-30 | 2019-04-26 | 东北大学 | A kind of ship steel molten steel magnesium treatment process |
| CN113088624A (en) * | 2021-02-26 | 2021-07-09 | 武汉钢铁有限公司 | Preparation method of low-inclusion aluminum killed steel |
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