CN116673453A - Method for controlling nonmetallic inclusion liquid separation in continuous casting process - Google Patents
Method for controlling nonmetallic inclusion liquid separation in continuous casting process Download PDFInfo
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- 238000009749 continuous casting Methods 0.000 title claims abstract description 70
- 239000007788 liquid Substances 0.000 title claims abstract description 31
- 238000000926 separation method Methods 0.000 title claims abstract description 24
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 117
- 239000010959 steel Substances 0.000 claims abstract description 117
- 229910000861 Mg alloy Inorganic materials 0.000 claims abstract description 39
- 238000007711 solidification Methods 0.000 claims abstract description 25
- 230000008023 solidification Effects 0.000 claims abstract description 25
- 238000009826 distribution Methods 0.000 claims abstract description 19
- 238000005266 casting Methods 0.000 claims abstract description 17
- 229910052751 metal Inorganic materials 0.000 claims abstract description 11
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- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 7
- 239000001301 oxygen Substances 0.000 claims abstract description 7
- 239000011777 magnesium Substances 0.000 claims description 34
- 239000012535 impurity Substances 0.000 claims description 17
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 14
- 229910052717 sulfur Inorganic materials 0.000 claims description 14
- 239000011593 sulfur Substances 0.000 claims description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 13
- 238000002386 leaching Methods 0.000 claims description 10
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 6
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 6
- 239000011575 calcium Substances 0.000 claims description 6
- 229910052791 calcium Inorganic materials 0.000 claims description 6
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 2
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- 229910052742 iron Inorganic materials 0.000 claims description 2
- 238000012986 modification Methods 0.000 abstract description 2
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- 229910052749 magnesium Inorganic materials 0.000 description 25
- 238000001556 precipitation Methods 0.000 description 20
- CADICXFYUNYKGD-UHFFFAOYSA-N sulfanylidenemanganese Chemical compound [Mn]=S CADICXFYUNYKGD-UHFFFAOYSA-N 0.000 description 19
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- 239000010936 titanium Substances 0.000 description 11
- 229910052719 titanium Inorganic materials 0.000 description 8
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 7
- 238000005520 cutting process Methods 0.000 description 7
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- 229910000915 Free machining steel Inorganic materials 0.000 description 6
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- 238000005070 sampling Methods 0.000 description 5
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 4
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 4
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
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Classifications
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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
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/116—Refining the metal
-
- 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
- B22D11/12—Accessories for subsequent treating or working cast stock in situ
- B22D11/1226—Accessories for subsequent treating or working cast stock in situ for straightening strands
-
- 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
- C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The invention relates to a method for controlling nonmetallic inclusion liquid separation in a continuous casting process, which comprises the following steps: in the continuous casting process, after molten steel is injected into a continuous casting tundish, the superheat degree of the molten steel in a molten metal state in the continuous casting tundish is maintained to be 20-45 ℃, and the total oxygen content of the molten steel is 5-45 ppm; in a continuous casting tundish, magnesium alloy is utilized to treat molten steel in a molten state, and nonmetallic inclusion in the molten steel is modified; the molten steel is injected into a crystallizer, the molten steel is gradually changed from a molten metal state to a solidification state, a casting blank in the crystallizer is pulled out by a withdrawal and straightening machine, and the pulling speed is controlled to be 1.3-2.5 m/min, so that the non-metallic inclusion after modification becomes a liquid separation core in the solidification process of the molten steel, and the granularity and the distribution of the liquid separation inclusion are controlled. In the continuous casting process, the molten steel in a molten state is treated before the molten steel is solidified, so that the problem that the liquid separation behavior of nonmetallic inclusion in the molten steel solidification process is difficult to effectively control is solved.
Description
Technical Field
The invention belongs to the technical field of metal casting, and particularly relates to a method for controlling nonmetallic inclusion liquid separation in a continuous casting process.
Background
Typical liquid separation phenomena are: the phenomenon of liquation of titanium nitride in the titanium microalloy steel and the phenomenon of liquation of manganese sulfide in the free cutting steel. Liquid separation generally refers to the precipitation behavior of nonmetallic inclusions caused by segregation of solute elements in the solidification process of molten metal, the precipitated nonmetallic inclusions have no opportunity to float up and be removed and remain in steel, and the granularity is generally larger, so that the performance of the steel is adversely affected.
The micro-alloy steel is formed by adding trace alloying elements (carbon nitride forming elements such as Ti, V and Nb) into common carbon steel or low alloy steel, and the micro-alloy steel regulates and controls the precipitation behavior of the carbon nitride by controlling rolling and cooling in the hot working process, so as to control the steel structure, thereby achieving the aim of improving the strength, the toughness and the welding performance of the steel and realizing multi-performance coordination matching. Titanium is a typical microalloying element that can act both as a fine grain strengthening and as a precipitation strengthening in steel. Titanium is a strong carbonitride forming element, and can separate out a large number of dispersed TiN/TiC/Ti (CN) fine particles in the processes of Austenite phase transformation, heat preservation after phase transformation and cooling, and the fine particles can interact with dislocation, pin or block dislocation movement, so that the stress required by plastic deformation of steel materials is improved, and the yield strength and the tensile strength of the materials are improved. The grain size, the quantity and the distribution of the carbonitrides are critical for the strengthening function of the titanium microalloy steel, but the TiN and the Ti can not occur in the solidification and the subsequent cooling stages of the titanium microalloy steel 4 C 2 S 2 Particle liquid and solid phase precipitation behavior, but liquid TiN and Ti 4 C 2 S 2 The particles can reach several micrometers or even tens of micrometers and are easy to accumulate at grain boundaries, so that the strengthening effect is not achieved, and the performance of the high-strength steel is deteriorated.
The cutting performance of the sulfur free-cutting steel is mainly determined by MnS inclusions in the steel, and the MnS can cut the continuity of a matrix and play a role of a stress concentration source in the cutting process, so that the cutting process is easier to break chips, and meanwhile, the MnS has lower hardness and can play a role of lubrication so as to reduce the abrasion of a cutter. However, sulfur is extremely easy to segregate in the solidification process, so that the sizes and the distribution of MnS inclusions in steel are uneven, mnS is easy to deform and mingle, and is easy to deform and distributed in a strip shape along with steel in the rolling process, so that the anisotropy of the mechanical properties of the steel and the deterioration of the cutting performance are caused. The cutting performance and mechanical performance of the sulfur-based free-cutting steel are closely related to the size, morphology and distribution of MnS in the steel, and it is generally considered that the high-quality sulfur-based free-cutting steel should control the sulfide in the steel to be spherical or spindle-shaped and be dispersed and distributed in a proper particle size. To achieve a coordinated match of mechanical properties and workability, the morphology, particle size and distribution of sulfides in the sulfur free-cutting steel must be controlled. However, the existing method has no remarkable control effect on the particle size and distribution of the inclusions.
Chinese patent CN110385412a relates to a continuous casting method for controlling the liquid separation of TiN from titanium-containing alloy steel, which reduces the generation of large-particle TiN particles, but cannot solve the problem of uniform division of TiN. Similarly, chinese patent CN116140578A relates to a continuous casting method for improving center segregation of high-carbon steel billets, which controls the cross section of molten steel at the center of the solidification end of a continuous casting billet to be a specific morphology by ensuring a higher equiaxed crystal rate of the billets, so that the cross section is matched with a soft reduction process, and finally, the center segregation of the continuous casting billet is effectively improved and the segregation index is reduced, but the problem of uniform distribution of segregated nonmetallic inclusions cannot be solved.
In summary, controlling the leaching behavior of nonmetallic inclusions during continuous casting is a highly desirable problem.
Disclosure of Invention
The invention provides a method for controlling the liquid precipitation of nonmetallic inclusion in a continuous casting process, which aims to treat molten steel in a molten state before the molten steel is solidified in the continuous casting process so as to solve the problem that the liquid precipitation behavior of nonmetallic inclusion in the molten steel solidification process is difficult to control effectively.
The invention provides a method for controlling nonmetallic inclusion liquid separation in a continuous casting process, which comprises the following steps:
s1: in the continuous casting process, after molten steel is injected into a continuous casting tundish, the superheat degree of the molten steel in a molten metal state in the continuous casting tundish is maintained to be 20-45 ℃, and the total oxygen content of the molten steel is 5-45 ppm;
s2: in a continuous casting tundish, magnesium alloy is utilized to treat molten steel in a molten state, and nonmetallic inclusion in the molten steel is modified;
s3: and (2) injecting the molten steel treated in the step (S2) into a crystallizer, gradually changing the molten steel from a molten metal state to a solidification state, pulling out a casting blank in the crystallizer by a withdrawal and straightening machine, and controlling the pulling speed to be 1.3-2.5 m/min, so that the non-metallic inclusion after deterioration becomes a liquid separation core in the solidification process of the molten steel, and controlling the granularity and the distribution of the liquid separation inclusion.
Further, in step S2, the molten steel is treated by: in the pouring area of the continuous casting tundish, the magnesium alloy is fed into molten steel in a cored wire mode and in an interval mode, and the content of the magnesium alloy in the molten steel is controlled to be in a range of 0.0010% -0.0100% through the wire feeding speed, the wire feeding interval duration and the wire feeding duration.
Further, the wire feeding speed is 0.5-4 m/s, the wire feeding interval duration is 10-400 s, and the wire feeding duration is 5-30 s.
Furthermore, the iron sheet material of the cored wire is prepared from a low-carbon material, and the mass fraction of carbon in the low-carbon material is not higher than 0.2%.
Further, the wire diameter of the cored wire is 8-15 mm, the core weight of the cored wire is 100-450 g/m, and the wire weight of the cored wire is 200-750 g/m.
Further, the magnesium alloy comprises the following components in percentage by mass: 0.1-50% of Si, 0.1-45% of Al, 1-40% of Mg and the balance of Fe and impurity elements.
Optionally, the magnesium alloy comprises the following components in percentage by mass: 0.1-50% of Si, 1-40% of Mg, and the balance of Fe and impurity elements.
Optionally, the magnesium alloy comprises the following components in percentage by mass: 0.1-45% of Al, 1-40% of Mg and the balance of Fe and impurity elements.
Further, the impurity elements include sulfur, phosphorus and calcium, and the impurity elements are as follows in mass percent: the sulfur content is less than 0.03%, the phosphorus content is less than 0.03%, and the calcium content is less than 0.05%.
The invention provides a method for controlling nonmetallic inclusion liquid separation in a continuous casting process, which utilizes the stage that molten steel is in a molten state before solidification in the continuous casting process, and processes molten steel in the molten state by combining technical means such as magnesium, molten steel superheat degree, molten steel total oxygen content and the like, so that nonmetallic inclusion is modified before solidification of the molten steel, and the pulling speed is controlled in the process of pulling out a casting blank by a subsequent withdrawal and straightening machine, so that nonmetallic inclusion is fully modified, the modified nonmetallic inclusion becomes a liquid separation core in the solidification process of the molten steel, and the granularity and distribution of liquid separation inclusion are controlled.
The invention utilizes the treatment process of combining magnesium with other parameters to treat molten steel in a molten state before solidification in a continuous casting process to realize the functionalization of nonmetallic inclusion, namely, the beneficial effect of nonmetallic inclusion is exerted. The functionalization of nonmetallic inclusions requires, on the one hand, that the nonmetallic inclusions have a suitable composition and are finely dispersed in the steel, and, on the other hand, that the nonmetallic inclusions have a sufficient quantity. According to the invention, the magnesium alloy is fed into the molten steel in a continuous casting tundish in a spaced mode, so that the magnesium content in the molten steel is ensured, and further, the modified nonmetallic inclusion (Mg-Al-O) can be used as a precipitation core of delta ferrite, thereby promoting the formation of equiaxed crystals and being beneficial to improving the performance uniformity of the finished steel.
The invention realizes the functionalization of the magnesium nonmetallic inclusion by developing a new continuous casting process, controls the liquid separation behavior of other nonmetallic inclusions by using the modified magnesium nonmetallic inclusion, and further changes the granularity and the distribution state of other nonmetallic inclusions so as to realize the purpose of reducing the harm of the nonmetallic inclusions. The invention solves the problems of continuous maintenance of magnesium content in molten steel, continuous supply of nonmetallic inclusion cores and the like, and nonmetallic inclusion (Mg-Al-O) can provide a proper amount of precipitation cores for the precipitation of nonmetallic inclusion such as manganese sulfide, titanium nitride and the like, thereby controlling the precipitation granularity and distribution state of the nonmetallic inclusion for the precipitation so as to inhibit or even eliminate the harm of the nonmetallic inclusion.
In addition, when the invention is applied to aluminum deoxidization sulfur-containing free-cutting steel, the deformation of the manganese sulfide is effectively inhibited in the hot rolling process by depending on the precipitated Mg-Al-O core of the manganese sulfide, the slenderness ratio of nonmetallic inclusion is obviously reduced, and the cooperative control of cutting performance and mechanical performance is realized.
Drawings
FIG. 1 is a schematic flow chart of the method;
FIG. 2 is a photograph of an original process typical nonmetallic inclusion in example 1;
FIG. 3 is a photograph of typical nonmetallic inclusion of the present invention in example 1;
FIG. 4 is a photograph of an original process typical nonmetallic inclusion in example 2;
FIG. 5 is a photograph of typical nonmetallic inclusion of the present invention in example 2;
FIG. 6 is a typical form of manganese sulfide present in raw as-rolled steel in example 2;
FIG. 7 is a typical form of manganese sulfide present in the rolled steel of the invention in example 2.
Detailed Description
The invention will be better explained by the following detailed description of the embodiments with reference to the drawings.
The magnesium alloy is a typical active metal, has excellent nonmetallic inclusion control function in steel, the molten steel magnesium treatment technology is gradually developed and applied, in the existing magnesium treatment technology, the magnesium alloy is added in the refining technology, and before the continuous casting technology, the magnesium alloy is subjected to refining and casting, the final aim is to control the granularity and distribution of nonmetallic inclusion, and the aim is to concentrate on harmless control of nonmetallic inclusion, but the functionalization of nonmetallic inclusion cannot be realized. On the one hand, the existing magnesium treatment process is characterized in that a large amount of nonmetallic inclusion in steel floats upwards to be removed, so that the nonmetallic inclusion is in a lack of enough cores for liquid separation; on the other hand, the content of dissolved magnesium in steel gradually decreases, and the control capability on nonmetallic inclusion is weakened, and the functionalization of nonmetallic inclusion is difficult to realize in both aspects. The invention creatively combines the continuous casting process and the magnesium treatment process, and the magnesium alloy added in the continuous casting process changes the quality of Al 2 O 3 The cluster inclusions are Mg-Al-O inclusions, the Mg-Al-O inclusions are finely dispersed and distributed in steel, and in the solidification process, the nonmetallic clampThe Mg-Al-O inclusion formed after the sundries (carbonitride or sulfide) are subjected to depending on the deterioration is separated out and distributed in the steel in a fine dispersion state, so that the harm to the performance of the steel is reduced, and the functionalization of the magnesium nonmetallic inclusion is realized. The modified magnesium inclusion is utilized to control the liquid precipitation behavior of other inclusions, change the granularity and the distribution state of other inclusions, further reduce the harm of the other inclusions, solve the problems of continuous maintenance of magnesium content in molten steel, continuous supply of nonmetallic inclusion cores and the like, and the Mg-Al-O inclusion provides a proper amount of precipitation cores for the liquid precipitation of the inclusions such as manganese sulfide, titanium nitride and the like, so as to control the precipitation granularity and the distribution state of the liquid precipitation inclusions, and inhibit or even eliminate the harm of the liquid precipitation inclusions.
The invention provides a method for controlling nonmetallic inclusion liquid separation in a continuous casting process, which is shown in figure 1 and comprises the following steps:
s1: in the continuous casting process, after molten steel is injected into a continuous casting tundish, the superheat degree of the molten steel in a molten metal state in the continuous casting tundish is maintained to be 20-45 ℃, and the total oxygen content of the molten steel is 5-45 ppm; in the continuous casting process, the superheat degree and the total oxygen content of the molten steel in the tundish are strictly controlled, so that the influence on the cleanliness of the molten steel is avoided. And is beneficial to the uniformity and stability of the magnesium alloy content in the molten steel. The superheat degree and the total oxygen content of the specific molten steel are determined according to the different steel components.
S2: in a continuous casting tundish, magnesium alloy is utilized to treat molten steel in a molten state, and nonmetallic inclusion in the molten steel is modified; in the pouring area of the continuous casting tundish, magnesium alloy is fed into molten steel in a cored wire mode and in an interval mode, and the content of the magnesium alloy in the molten steel is controlled to be within the range of 0.0010% -0.0100% by the feeding speed, the feeding interval duration, the feeding duration and the total length of the feeding.
The magnesium alloy comprises the following components in percentage by mass: 0.1-50% of Si, 0.1-45% of Al, 1-40% of Mg and the balance of Fe and impurity elements. Or the magnesium alloy comprises the following components in percentage by mass: 0.1-50% of Si, 1-40% of Mg, and the balance of Fe and impurity elements. Or the magnesium alloy comprises the following components in percentage by mass: 0.1-45% of Al, 1-40% of Mg and the balance of Fe and impurity elements. The magnesium alloy is required to strictly control the content of impurity elements, wherein the content of sulfur in the impurity elements is less than 0.03%, the content of phosphorus in the impurity elements is less than 0.03%, and the content of calcium in the impurity elements is less than 0.05% in percentage by mass. The magnesium alloy is wrapped in the cored wire in the form of alloy powder and added to inhibit the occurrence of naked molten steel surface and splash caused by gasification of the magnesium alloy, thereby preventing secondary oxidation of molten steel and protecting working environment. The magnesium alloy is prepared according to the target component range of the cast steel, the content of impurity elements such as phosphorus, sulfur, calcium and the like is strictly controlled, and the influence on the molten steel components is avoided. In this embodiment, the content of magnesium alloy in the molten steel is preferably in the range of 0.0020% -0.0050%, so that the content of magnesium alloy in the molten steel is uniform and stable in time and space (space contained in a tundish molten pool).
S3: and (2) injecting the molten steel processed in the step (S2) into a crystallizer, gradually pulling the casting blank in the crystallizer from a molten metal state to a solidification state by a withdrawal and straightening machine, controlling the pulling speed to be 1.3-2.5 m/min, strictly controlling the pulling speed in the continuous casting process, avoiding the influence on the cleanliness of the molten steel due to the fact that the pulling speed is fast and slow, ensuring that metal magnesium is gradually and uniformly mixed with the molten steel in a pouring area of a continuous casting tundish and in the flowing process to the pouring area by controlling the pulling speed, and deteriorating nonmetallic inclusions in the molten steel so as to ensure that the nonmetallic inclusions are finely and dispersedly distributed in the molten steel. Further, the non-metallic inclusion after deterioration becomes a liquid separation core in the solidification process of molten steel, so that the granularity and the distribution of the liquid separation inclusion are controlled.
Example 1:
as shown in fig. 1, a method for controlling the precipitation behavior of titanium nitride in a titanium microalloyed steel during continuous casting,
the steel type supported by the embodiment is X70 pipeline steel, and the smelting process route adopted by the steel type is BOF-LF-RH-CC. The industrial production of two heats is carried out, the converter, LF refining and RH refining processes are the same, the production is carried out on the same double-flow slab continuous casting machine, and the basic continuous casting process parameters are kept consistent, and are shown in the table 1. One of the furnace runs adopts the original process, namely no magnesium alloy wire is fed, and the other furnace run adopts the continuous casting process, wherein main process parameters are shown in table 2, and the adopted magnesium alloy parameters are shown in table 3.
TABLE 1 basic continuous casting process parameters
TABLE 2 Process parameters of the invention
Table 3 chemical compositions of magnesium alloy (mass percent,%)
In the casting process, steel water samples are taken in the pouring area and the casting area respectively, and after casting, steel samples are taken at the 1/4 wide and 1/4 thick positions of the continuous casting billet, and the analysis results of magnesium content are shown in table 4. It can be seen from the table that the magnesium content in the steel is significantly higher than in the prior art after the invention is adopted. From the point of view of the variation of magnesium content, the magnesium content gradually decreases from the main flow area of the tundish to the casting area to the continuous casting slab over time, mainly due to the escape of magnesium alloy and the floating removal of magnesium-containing inclusions.
Table 4 magnesium content (mass%, percent) in steel
Sampling at the 1/4 width and 1/4 rear thickness of the continuous casting billet, detecting the existence form and the granularity distribution of TiN, and sampling 1/2 thickness of the continuous casting billet at the 1/4 width to detect solidification structure. Figures 2 and 3 are pictures of typical nonmetallic inclusions in steel under the conditions of the original process and the present invention, respectively. Under the original technological conditions, the inclusions mainly exist in three types, namely Al 2 O 3 TiN inclusion and depending on Al 2 O 3 Precipitating TiN complex inclusions, wherein the number of TiN inclusions is the largest, the number of complex inclusions is the next time, al 2 O 3 The inclusion quantity is minimum, and under the condition of the invention, the inclusion is equally divided into three types, namely magnesia-alumina spinel and TiN and composite inclusion of TiN precipitated by taking magnesia-alumina spinel as core, and modified Al 2 O 3 The cluster inclusions are Mg-Al-O inclusions, and the fine inclusions are distributed in steel in a dispersed manner, so that the damage to the performance of the steel is reduced. In the solidification process, the inclusions (carbon nitride or sulfide) are precipitated by virtue of the modified Mg-Al-O inclusions and are distributed in the steel in a fine dispersion state, and the modified Mg-Al-O inclusions can be used as a precipitation core of delta ferrite, so that the formation of equiaxed crystals is promoted, and the performance uniformity of the finished steel product is improved. The solidification structure detection result shows that compared with the original process, the equiaxial crystal rate of the casting blank center is improved by 5.6 percent. The proportion of the composite inclusions is obviously higher than that of the prior art, and the types and the distribution of the inclusions are shown in the table 5.
TABLE 5 comparison of inclusion quantity distribution
Example 2:
as shown in figure 1, a method for controlling the leaching behavior of manganese sulfide in aluminum deoxidized sulfur-containing steel in a continuous casting process.
The steel supported by the embodiment is CrMnTi sulfur-containing gear steel, and the smelting process route adopted by the steel is EAF-LF-VD-CC. The industrial production of two heats is carried out, the electric furnace, LF refining and VD refining processes are the same, the production is carried out on the same four-flow billet continuous casting machine, and the basic continuous casting process parameters are kept consistent, and are shown in the table 6. One of the heats adopts the original process, namely no magnesium alloy wire is fed, and the other heats adopts the continuous casting process, wherein main process parameters are shown in table 7, and the adopted magnesium alloy parameters are shown in table 8.
TABLE 6 basic continuous casting process parameters
TABLE 7 Process parameters of the invention
Table 8 chemical compositions of magnesium alloy (mass percent,%)
In the casting process, molten steel samples are respectively taken in the casting area above the pouring area and the end side water inlet, and after casting, steel samples are taken at the 1/4 wide and 1/4 thick positions of the square billet, and the analysis results of magnesium content are shown in table 9. It can be seen from the table that the magnesium content in the steel is significantly higher than in the prior art after the invention is adopted. From the point of view of the change in magnesium content, the magnesium content gradually decreases from the main flow area of the tundish to the casting area to the continuous casting slab over time, which is caused by the escape of magnesium alloy and the floating removal of magnesium-containing inclusions.
Table 9 magnesium content (mass%, percent) in steel
Sampling at the 1/4 width and 1/4 rear thickness of the continuous casting billet, detecting the existence form and the granularity distribution of manganese sulfide, and sampling 1/2 thick plate blank at the 1/4 width of the continuous casting billet for solidification structure detection. Fig. 4 and 5 show the main forms of manganese sulphide in as-cast steel in the original process and under the conditions of the invention, respectively. Under the original technological conditions, manganese sulfide exists mainly in a single form, while under the conditions of the invention, manganese sulfide exists mostly in the form of magnesia-alumina spinel as a core, and Al is modified 2 O 3 The cluster inclusions are Mg-Al-O inclusions, and the fine inclusions are distributed in steel in a dispersed manner, so that the harm to the performance of the steel is reduced. In the solidification process, the inclusions (carbon nitride or sulfide) are precipitated by virtue of the modified Mg-Al-O inclusions and are distributed in the steel in a fine dispersion state, and the modified Mg-Al-O inclusions can be used as a precipitation core of delta ferrite, so that the formation of equiaxed crystals is promoted, and the performance uniformity of the finished steel product is improved. The solidification structure detection result shows that compared with the original process, the equiaxial crystal rate of the casting blank center is improved by 7.4 percent.
Sampling in the rolled bar, detecting the deformation condition of the rolled manganese sulfide, and respectively obtaining the existence form of the manganese sulfide in the rolled bar under the conditions of the original process and the invention in the figures 6 and 7. The graph shows that under the original technological condition, the manganese sulfide exists mainly in a long-strip state, the average length-diameter ratio exceeds 9.0, and under the condition of the invention, the deformation of the manganese sulfide is effectively inhibited in the hot rolling process by depending on the precipitated Mg-Al-O core of the manganese sulfide, the length-diameter ratio of the inclusion is obviously reduced, and the cooperative control of the cutting performance and the mechanical performance is realized. In the invention, the length-diameter ratio of the manganese sulfide is almost less than 5.0, and more than 85 percent is less than 3.0, so that the shape control effect of the manganese sulfide is obvious.
Although the embodiments of the present invention have been described above, the above embodiments are exemplary and should not be construed as limiting the present invention. Alterations, modifications, substitutions and variations of the above described embodiments within the scope of the invention should be regarded as being within the scope of the invention by those of ordinary skill in the art.
Claims (9)
1. A method for controlling nonmetallic inclusion liquid separation in a continuous casting process is characterized in that: the method comprises the following steps:
s1: in the continuous casting process, after molten steel is injected into a continuous casting tundish, the superheat degree of the molten steel in a molten metal state in the continuous casting tundish is maintained to be 20-45 ℃, and the total oxygen content of the molten steel is 5-45 ppm;
s2: in a continuous casting tundish, magnesium alloy is utilized to treat molten steel in a molten state, and nonmetallic inclusion in the molten steel is modified;
s3: and (2) injecting the molten steel treated in the step (S2) into a crystallizer, gradually changing the molten steel from a molten metal state to a solidification state, pulling out a casting blank in the crystallizer by a withdrawal and straightening machine, and controlling the pulling speed to be 1.3-2.5 m/min, so that the non-metallic inclusion after deterioration becomes a liquid separation core in the solidification process of the molten steel, and controlling the granularity and the distribution of the liquid separation inclusion.
2. A method of controlling the leaching of nonmetallic inclusions in a continuous casting process as defined in claim 1, wherein: in step S2, the molten steel is treated by: in the pouring area of the continuous casting tundish, the magnesium alloy is fed into molten steel in a cored wire mode and in an interval mode, and the content of the magnesium alloy in the molten steel is controlled to be in a range of 0.0010% -0.0100% through the wire feeding speed, the wire feeding interval duration and the wire feeding duration.
3. A method for controlling the leaching of nonmetallic inclusions in a continuous casting process according to claim 2, wherein: the wire feeding speed is 0.5-4 m/s, the wire feeding interval duration is 10-400 s, and the wire feeding duration is 5-30 s.
4. A method for controlling the leaching of nonmetallic inclusions in a continuous casting process according to claim 2, wherein: the iron sheet material of the cored wire is prepared from a low-carbon material, and the mass fraction of carbon in the low-carbon material is not higher than 0.2%.
5. The method for controlling the leaching of nonmetallic inclusions in a continuous casting process according to claim 4, wherein: the diameter of the cored wire is 8-15 mm, the core weight of the cored wire is 100-450 g/m, and the wire weight of the cored wire is 200-750 g/m.
6. A method for controlling the leaching of nonmetallic inclusions in a continuous casting process according to claim 2, wherein: the magnesium alloy comprises the following components in percentage by mass: 0.1-50% of Si, 0.1-45% of Al, 1-40% of Mg and the balance of Fe and impurity elements.
7. A method for controlling the leaching of nonmetallic inclusions in a continuous casting process according to claim 2, wherein: the magnesium alloy comprises the following components in percentage by mass: 0.1-50% of Si, 1-40% of Mg, and the balance of Fe and impurity elements.
8. A method for controlling the leaching of nonmetallic inclusions in a continuous casting process according to claim 2, wherein: the magnesium alloy comprises the following components in percentage by mass: 0.1-45% of Al, 1-40% of Mg and the balance of Fe and impurity elements.
9. A method for controlling the leaching of nonmetallic inclusions in a continuous casting process according to any one of claims 6-8, wherein: the impurity elements comprise sulfur, phosphorus and calcium, and the mass percentages are as follows: the sulfur content is less than 0.03%, the phosphorus content is less than 0.03%, and the calcium content is less than 0.05%.
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