CN113122679A - Calcium treatment method for molten steel and steel prepared by using calcium treatment method - Google Patents
Calcium treatment method for molten steel and steel prepared by using calcium treatment method Download PDFInfo
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- CN113122679A CN113122679A CN202110416965.9A CN202110416965A CN113122679A CN 113122679 A CN113122679 A CN 113122679A CN 202110416965 A CN202110416965 A CN 202110416965A CN 113122679 A CN113122679 A CN 113122679A
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/0006—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
- C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
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Abstract
The invention discloses a calcium treatment method of molten steel, which comprises the following steps: (1) tapping by a converter, and deoxidizing the molten steel to 10-30 ppm; (2) in the refining process of an LF refining furnace, adding aluminum slag balls into deoxidized molten steel to deoxidize the slag surface until the color of the steel slag is white and the oxygen content in the molten steel is 3-5 ppm; (3) and feeding a calcium wire into the molten steel after the deoxidation of the slag surface. According to the invention, the oxygen content of the molten steel is lower by controlling the converter tapping and the deoxidation degree of the LF furnace, and the yield of calcium is improved by matching with proper calcium line introducing conditions, namely the effective rate of calcium elements in the calcium line retained in the molten steel is improved; this increase can promote the addition of calcium and Al2O3Together, the chain-like or strip-like inclusions are made into a spherical shape and then floated up to be removed.
Description
Technical Field
The invention belongs to the technical field of smelting and manufacturing, and particularly relates to a calcium treatment method for molten steel and a steel prepared by using the same.
Background
Obtaining products with higher purity and higher uniformity is a hot spot of steel production and research at present, and is a development direction of metallurgical technology. With the further reduction of the content of impurity elements in the molten steel, the adverse effect of the inclusions in the steel on steel products is more obvious, so that the control and improvement of the properties of the inclusions in the molten steel according to different quality requirements of the products are more important.
Oxygen blowing smelting is carried out on the top of the converter, so that carbon, silicon, manganese, phosphorus and other elements in the molten steel are oxidized to produce oxides of carbon monoxide, silicon dioxide and the like, and the oxides are discharged out of the liquid level of the molten steel or float upwards to enter smelting slag. A large amount of free oxygen and oxides still remain in the molten steel, and ferroaluminum is added in the tapping process for deoxidation and purification, and Al is generated after deoxidation2O3The inclusion floats upwards to the molten steel surface along with the stirring of the molten steel to be removed.
But Al generated after deoxidation2O3The inclusion often can not float up to the molten steel surface completely, and the remaining remains in the steel with the form of impurity, especially to the steel that has the extension demand, the existence of impurity causes the reduction of ductility ability more easily, leads to the extension in-process, the fracture of steel. For some steels, certain amount of Al element, Al, is added2O3Inclusions are more easily formed and more difficult to remove.
The calcium wire is usually introduced in the field to remove Al in the steel2O3However, in the feeding process of the calcium wire, calcium element is easy to volatilize, the effective calcium element entering molten steel is low, and the method capable of improving the calcium yield of the molten steel needs to be developed in the field.
Disclosure of Invention
In view of the defects of the prior art, one of the purposes of the invention is to provide a method for treating calcium in molten steel, which is characterized by comprising the following steps:
(1) tapping by a converter;
(2) in the refining process of an LF refining furnace, adding aluminum slag balls into deoxidized molten steel to deoxidize the slag surface until the color of the steel slag is white and the oxygen content in the molten steel is 3-5 ppm (such as 3.3ppm, 3.8ppm, 4.2ppm, 4.7ppm and the like);
(3) feeding a calcium wire into the molten steel after deoxidation of the slag surface, wherein the feeding method of the calcium wire comprises the following steps:
the calcium wire is straightened through a guide pipe, the guide pipe is provided with a first section in the horizontal direction, a second section of an arc line and a third section in the vertical direction, and the calcium wire is led out from the third section and then is output vertically downwards; the length of the third section is 0.3-0.5 m; the distance between the outlet of the third section and the slag surface of the molten steel is 0.4-0.6 m, the outlet speed (feeding speed) of the calcium line is 100-150 m/min, and the depth of the calcium line penetrating into the molten steel is 0.3-0.5 m.
In the field of deoxidation treatment of molten steel, particularly deoxidation by using an aluminum deoxidizer, a small amount of inclusions still remain in the molten steel, and when the molten steel is subsequently poured into a steel, the inclusions exist in a chain or strip shape, so that the anisotropy of the steel is increased, and the inclusions are easy to break in the extension process of the steel, thereby affecting the ductility of the steel. The method carries out slag surface deoxidation after the smelting of the converter, controls the oxygen content in molten steel to be 3-5 ppm, and adds an aluminum deoxidizer into the molten steel to react with oxygen in the molten steel to generate Al2O3Impurities are removed by stirring through bottom blowing argon, and Al in molten steel is reduced at the end of LF refining2O3The content of the inclusions is increased, the conversion of calcium elements of the calcium wires in the molten steel is improved, and the calcium elements in the molten steel can form spherical compounds with the inclusions to promote the floating of the spherical compounds. In addition, the invention also defines the feeding mode of the calcium wire, the conduit with the first section in the horizontal direction, the second end of the arc line of 90 degrees and the third section in the vertical direction can guide the calcium wire which is placed in a coiling way to a certain extent, and can be ensured to be within the height range of 0.4-0.6 m through the guidance of a third section of 0.3-0.5 m, feeding calcium wire into the molten steel in a vertical direction, and controlling the feeding speed of the calcium wire at 100-150 m/min to ensure that the calcium wire smoothly passes through the steel slag, and can not cause excessive volatilization of calcium element due to overhigh temperature of the molten steel surface, reduce the yield of calcium, on the other hand, the verticality of the calcium line (the length of the third section and the distance from the liquid level of the molten steel) and the feeding speed of the calcium line are controlled, so that the calcium line can be smoothly inserted into the molten steel by 0.3-0.5 m, and the calcium line can be kept vertical at the depth, so that more calcium elements enter the molten steel. Too low depth of insertion of the calcium wire (less than 0.3m) is such thatThe calcium is volatilized more, so that the yield of the calcium is reduced; the excessively high insertion depth (more than 0.5m) of the calcium wire causes the calcium wire to bend, the end part of the calcium wire is turned upwards, the volatilization of calcium is increased, and the yield of calcium is reduced.
Preferably, the molten steel in the step (1) is deoxidized to 10 to 30ppm (for example, 12ppm, 15ppm, 18ppm, 22ppm, 26ppm, 29ppm, etc.).
As a preferable technical scheme, the molten steel deoxidation in the step (1) comprises the step of adding an aluminum deoxidizer for deoxidation during molten steel tapping, and specifically comprises the following steps:
adding 3-3.6 kg/t of aluminum iron when the end point carbon range is 0-0.08%;
when the end point carbon range is 0.08-0.15%, adding 2.4-3 kg/t of aluminum and iron;
when the end point carbon range is more than 0.15 percent, 2kg/t of aluminum iron is added.
In this preferred embodiment, the aluminum deoxidizer is added during tapping to promote oxidation reaction in molten steel to produce Al2O3Impurities are removed by stirring through bottom blowing argon; and different aluminum iron addition amounts are selected as aluminum deoxidizers according to different end point carbon contents. Adding 3-3.6 kg/t of aluminum iron when the end point carbon range is 0-0.08%; when the end point carbon range is 0.08-0.15%, adding 2.4-3 kg/t of aluminum and iron; when the end point carbon range is more than 0.15%, adding ferroaluminum within the range of 2kg/t ", and deeply removing oxygen in molten steel to more rapidly reduce the oxygen to 10-30 ppm.
As a preferred technical scheme, the deoxidation of the slag surface in the step (2) specifically comprises the following steps:
when Als of a steel water sample entering the LF furnace is less than or equal to 0.005%, adding 2-3 kg/t of aluminum slag balls;
adding 1.6-2 kg/t of aluminum slag balls when Als of the molten steel sample entering the LF furnace is 0.005-0.015%;
adding 1.2-1.6 kg/t of aluminum slag balls when Als of the molten steel sample entering the LF furnace is 0.015-0.025%;
when Als of a steel water sample entering the LF furnace is more than 0.025 percent, 0.8kg/t of aluminum slag balls are added.
And (2) in order to further deoxidize the molten steel, adding the aluminum slag balls into the ladle through a feeding system, deoxidizing the dross, and further promoting the oxygen in the molten steel to float upwards for removal (diffusion deoxidation). In the preferred technical scheme, different aluminum slag balls are added according to the different aluminum contents of the molten steel sample entering the LF furnace, so that the oxygen content in the molten steel is lower, if the aluminum slag balls are added too little, oxygen in the molten steel is not thoroughly removed, if the aluminum slag balls are added too much, the aluminum slag balls sink into the molten steel, slagging and floating are carried out again, the smelting time is prolonged, and more impurities can be brought to the molten steel.
After tapping of the converter, molten steel firstly enters an argon station for argon low blowing and then enters an LF furnace. The molten steel composition detection is usually performed by sampling at an argon station, and therefore, the molten steel sample entering the LF furnace includes but is not limited to an argon station sample.
In another preferable technical scheme, before the refining of the LF refining furnace in the step (2) is started, silicon carbide is added into the LF refining furnace for deoxidation.
Preferably, the silicon carbide is added in an amount of 0.10 to 0.15kg/t, such as 0.11kg/t, 0.12kg/t, 0.13kg/t, 0.14kg/t, and the like.
The silicon carbide deoxidation is used for better reducing the oxygen content of molten steel and improving the yield of calcium.
In another preferred technical scheme, the feeding amount of the calcium wire is calculated by adding 0.0010 to 0.0014 weight percent of calcium to 1 meter of calcium wire fed per ton of steel.
The specific feeding length of the calcium wire is not specifically limited in the invention, and a person skilled in the art can select the feeding length according to the actual situation, wherein the selection is based on that "the calcium wire is added by 0.0010 wt% -0.0014 wt% according to 1 meter of calcium wire fed into each ton of steel", namely if 0.0010 wt% -0.0014 wt% of calcium is required to be added into molten steel, the calcium wire is required to be fed into each ton of molten steel by 1 meter.
The type of the calcium wire is not particularly limited, and typical but non-limiting examples of the calcium wire include a pure calcium wire, an aluminum-clad calcium wire, a steel-clad calcium wire and the like.
The second purpose of the invention is to provide a preparation method of steel, which comprises the following steps:
(A) providing molten steel treated by the calcium treatment method according to one of the purposes;
(B) controlling the flow rate of the stirring gas of the molten steel to be 5-11 m3/h；
(C) And pouring the molten steel to obtain the steel.
The dissolving speed and uniformity of the calcium line can be improved by the stirring airflow, but too high stirring airflow can cause great fluctuation of molten steel, lead to slag surface fracture and bare molten steel and increase oxidation of the molten steel, namely, the stirring airflow is only 5-11 m3The stirring airflow can ensure the contact of calcium element and molten steel and avoid the oxidation of the molten steel.
Preferably, when steel inclusion particles need to reach that B-type inclusions are less than 1.5e, the stirring gas introducing time of the molten steel is 20-30 min.
When steel inclusion particles need to reach the B-type inclusion less than 1.5e, the calcium wire and the molten steel can be fully mixed only by introducing stirring gas for more than 20min, so that the inclusions are changed into spheres from chain or cuboid shapes and smoothly float to a slag layer.
Preferably, when steel inclusion particles need to reach that B-type inclusions are less than 2.0e, the stirring gas introducing time of the molten steel is 10-15 min.
When steel inclusion particles need to reach the condition that B-type inclusions are smaller than 2.0e, only introducing stirring gas for 10-15 min can enable calcium wires to be fully mixed with molten steel, so that the inclusions are changed into spheres from a chain or cuboid shape and smoothly float to a slag layer, wherein the stirring time is more than 15min, and the calcium aluminate composite compound after calcification is denatured and the dissolubility is improved, but the inclusions are not favorably floated and retained in the molten steel, and the stirring time is less than 10min, so that part of the inclusions are not absorbed by the slag layer of the molten steel and are still retained in the molten steel due to the too short stirring time.
The third object of the present invention is to provide a steel product obtained by casting the calcium-treated molten steel of the second object.
Preferably, the steel material comprises cold heading steel.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention controls the deoxidation degree of the LF furnace to ensure that the oxygen content of the molten steel is lower, and the invention is matched withThe yield of calcium is improved by combining proper calcium line introducing conditions (angle, distance, speed, depth and the like), namely the effective rate of the calcium element in the calcium line retained in molten steel is improved; this increase can promote the addition of calcium and Al2O3Together, the chain-like or strip-like inclusions are made into a spherical shape and then floated up to be removed.
(2) The calcium treatment method provided by the invention has higher calcium yield, can increase 0.0010-0.0014 wt% of calcium for each ton of steel by 1m calcium line, is higher than the calcium yield of the prior art, and reduces the cost.
(3) The calcium treatment method provided by the invention has the advantages of high calcium yield, high controllability on the amount of calcium transferred into molten steel, reduced fluctuation of molten steel components and improved quality stability of steel.
Drawings
FIG. 1 is a schematic view showing the structure of a calcium wire feeding apparatus according to an embodiment;
wherein, 10-calcium wire coil wire, 20-guide tube, 21-horizontal first section, 22-arc second section, 23-vertical third section, 30 steel ladle, 31-molten steel slag surface, H1Length of third section 23, H2Height H of the outlet of the third section 23 from the slag surface 312，H3The depth of penetration of the calcium wire into the molten steel.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to specific embodiments. The following examples are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of the invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
Example 1
A cold heading steel (SWRCH18A) prepared by the method comprising:
(1) tapping the steel in a converter, measuring the end point carbon of the molten steel to be 0.06 wt%, adding 3.3kg40 ferro-aluminum (containing 40% of aluminum) as an aluminum deoxidizer to deoxidize in the process of tapping to a 120-ton ladle 30, and deoxidizing the molten steel to 15 ppm;
(2) placing a steel ladle 30 in an argon station, blowing argon at a low rate, measuring Als of a molten steel sample to be 0.004%, then placing the steel ladle 30 in an LF refining furnace for refining, and adding 2.5kg of aluminum slag balls into deoxidized molten steel for slag surface deoxidation until the color of steel slag is white and the oxygen content in the molten steel is 4 ppm;
(3) feeding a 100-meter pure calcium wire into the molten steel after deoxidation of the slag surface, wherein the feeding method of the calcium wire comprises the following steps:
a calcium wire at one end of the calcium wire coil wire 10 is straightened through a guide pipe 20, the guide pipe 20 is provided with a first section 21 in the horizontal direction, a second section 22 of an arc line and a third section 23 in the vertical direction, and the calcium wire is led out from the third section 23 and then is output vertically downwards; length H of said third section 231Is 0.4 m; the height H of the outlet of the third section 23 from the molten steel slag surface 3120.5m, the discharge speed (feeding speed) of the calcium line is 120m/min, and the depth H of the calcium line penetrating into the molten steel3Is 0.4 m;
(4) controlling the flow rate of the molten steel stirring gas to be 7m3/h；
(5) And pouring the molten steel to obtain the steel.
FIG. 1 is a schematic structural diagram of a calcium wire feeding apparatus according to an embodiment.
Comparative example 1
A cold heading steel (SWRCH18A), the preparation method differing from example 1 only in that:
and (3) feeding a calcium wire into the molten steel after deoxidation of the slag surface, wherein the feeding method of the calcium wire comprises the following steps:
a calcium wire at one end of the calcium wire coil wire 10 is straightened through a guide pipe 20, the guide pipe 20 is provided with a first section 21 in the horizontal direction, a second section 22 of an arc line and a third section 23 in the vertical direction, and the calcium wire is led out from the third section 23 and then is output vertically downwards; length H of said third section 231Is 0.3 m; the height H of the outlet of the third section 23 from the molten steel slag surface 3120.3m, the discharge speed (feed speed) of the calcium wire is 160m/min, and the depth H of the calcium wire penetrating into the molten steel3Is 0.6 m.
Comparative example 2
A cold heading steel (SWRCH18A), the preparation method differing from example 1 only in that:
and (3) feeding a calcium wire into the molten steel after deoxidation of the slag surface, wherein the feeding method of the calcium wire comprises the following steps:
a calcium wire at one end of the calcium wire coil wire 10 is straightened through a guide pipe 20, the guide pipe 20 is provided with a first section 21 in the horizontal direction, a second section 22 of an arc line and a third section 23 in the vertical direction, and the calcium wire is led out from the third section 23 and then is output vertically downwards; length H of said third section 231Is 0.7 m; the height H of the outlet of the third section 23 from the molten steel slag surface 3120.7m, the discharge speed (feeding speed) of the calcium line is 100m/min, and the depth H of the calcium line penetrating into the molten steel3Is 0.2 m.
Comparative example 3
A cold heading steel (SWRCH18A), the preparation method differing from example 1 only in that:
(2) placing the ladle 30 in an argon station, blowing argon gas at a low rate, measuring Als of a molten steel sample to be 0.004%, then placing the ladle 30 in an LF refining furnace for refining, and adding 1.8kg of aluminum slag balls into the deoxidized molten steel for deoxidizing the slag surface until the color of the steel slag is white and the oxygen content in the molten steel is 6 ppm.
Example 2
A cold heading steel (SWRCH18A), the preparation method differing from example 1 only in that:
controlling the flow rate of the stirring gas of the molten steel to be 15m in the step (4)3/h。
Example 3
A cold heading steel (SWRCH18A), the preparation method differing from example 1 only in that:
controlling the flow rate of the stirring gas of the molten steel to be 3m in the step (4)3/h。
Example 4
A cold heading steel (SWRCH18A) prepared by the method comprising:
(1) tapping the steel by a converter, measuring the end point carbon of the molten steel to be 0.10 wt%, adding 2.8kg40 ferro-aluminum (containing 40% of aluminum) as an aluminum deoxidizer to deoxidize in the process of tapping to a 120-ton ladle 30, and deoxidizing the molten steel to be 30 ppm;
(2) placing a steel ladle 30 in an argon station, blowing argon at a low rate, measuring Als of a molten steel sample to be 0.010%, then placing the steel ladle 30 in an LF refining furnace for refining, and adding 2.0kg of aluminum slag balls into the deoxidized molten steel for slag surface deoxidation until the color of the steel slag is white and the oxygen content in the molten steel is 3 ppm;
(3) feeding a 100-meter calcium wire into the molten steel after deoxidation of the slag surface, wherein the feeding method of the calcium wire comprises the following steps:
a calcium wire at one end of the calcium wire coil wire 10 is straightened through a guide pipe 20, the guide pipe 20 is provided with a first section 21 in the horizontal direction, a second section 22 of an arc line and a third section 23 in the vertical direction, and the calcium wire is led out from the third section 23 and then is output vertically downwards; length H of said third section 231Is 0.3 m; the height H of the outlet of the third section 23 from the molten steel slag surface 3120.4m, the discharge speed (feeding speed) of the calcium line is 100m/min, and the depth H of the calcium line penetrating into the molten steel3Is 0.3 m.
(4) Controlling the flow rate of the molten steel stirring gas to be 5m3/h；
(5) And pouring the molten steel to obtain the steel.
Example 5
A cold heading steel (SWRCH18A) prepared by the method comprising:
(1) tapping the steel by a converter, measuring the end point carbon of the molten steel to be 0.15 wt%, adding 2.4kg40 ferro-aluminum (containing 40% of aluminum) as an aluminum deoxidizer to deoxidize in the process of tapping to a 120-ton ladle 30, and deoxidizing the molten steel to be 30 ppm;
(2) placing a steel ladle 30 in an argon station, blowing argon at a low rate, measuring Als of a molten steel sample to be 0.015%, then placing the steel ladle 30 in an LF refining furnace for refining, and adding 1.6kg of aluminum slag balls into the deoxidized molten steel for deoxidizing the slag surface until the color of the steel slag is white and the oxygen content in the molten steel is 5 ppm;
(3) feeding a 120-meter calcium wire into the molten steel after deoxidation of the slag surface, wherein the feeding method of the calcium wire comprises the following steps:
a calcium wire at one end of the calcium wire coil wire 10 is straightened through a guide pipe 20, the guide pipe 20 is provided with a first section 21 in the horizontal direction, a second section 22 of an arc line and a third section 23 in the vertical direction, and the calcium wire is led out from the third section 23 and then is output vertically downwards; the above-mentionedLength H of third section 231Is 0.4 m; the height H of the outlet of the third section 23 from the molten steel slag surface 3120.5m, the discharge speed (feeding speed) of the calcium line is 120m/min, and the depth H of the calcium line penetrating into the molten steel3Is 0.4 m.
(4) Controlling the flow rate of the molten steel stirring gas to be 8m3/h；
(5) And pouring the molten steel to obtain the steel.
Example 6
A cold heading steel (SWRCH18A), the preparation method differing from example 1 only in that:
(1) tapping the steel by a converter, measuring the end point carbon of the molten steel to be 0.25 wt%, adding 1.2kg40 ferro-aluminum (containing 40% of aluminum) as an aluminum deoxidizer to deoxidize in the process of tapping to a 120-ton ladle 30, and deoxidizing the molten steel to 8 ppm;
(2) placing the ladle 30 in an argon station, blowing argon gas in a low pressure mode, measuring Als of a molten steel sample to be 0.025%, then placing the ladle 30 in an LF refining furnace for refining, and adding 1.2kg of aluminum slag balls into the deoxidized molten steel for slag surface deoxidation until the color of the steel slag is white and the oxygen content in the molten steel is 5 ppm.
Example 7
A cold heading steel (SWRCH18A), the preparation method differing from example 1 only in that:
(2) placing the ladle 30 in an argon station, blowing argon gas at a low rate, measuring Als of a molten steel sample to be 0.030%, then placing the ladle 30 in an LF refining furnace for refining, and adding 0.8kg of aluminum slag balls into the deoxidized molten steel for deoxidizing the slag surface until the color of the steel slag is white and the oxygen content in the molten steel is 4 ppm.
Example 8
A cold heading steel (SWRCH18A), the preparation method differing from example 1 only in that:
(1) tapping the steel by a converter, measuring the end point carbon of the molten steel to be 0.06 wt%, adding 2.8kg40 ferro-aluminum (containing 40% of aluminum) as an aluminum deoxidizer to deoxidize in the process of tapping to a 120-ton ladle 30, and deoxidizing the molten steel to 35 ppm;
and (3) performance testing:
the molten steels or steel products obtained in the examples and comparative examples were subjected to the following performance tests:
(1) measuring the calcium content in the molten steel by a method of spectral assay analysis of a molten steel sample;
(2) the yield strength of the steel is measured by the method of GB/T228.1-2010 metallic material tensile test part 1: room temperature test method;
(3) the tensile strength of the steel is measured by the method of GB/T228.1-2010 metallic material tensile experiment part 1: room temperature test method.
The test results are shown in table 1.
TABLE 1
As can be seen from table 1, the cold heading steel prepared in the examples of the present invention has excellent yield strength and tensile strength (calcium content is above 0.0010%, yield strength is above 315MPa, and tensile strength is above 458 MPa), which may be due to the fact that the yield of calcium is increased, impurities are more thoroughly removed, and the yield strength and tensile strength just before are increased by controlling the deoxidation degree in the molten steel before being fed to the calcium wire and the suitable conditions (angle, distance, speed, depth, etc.) for feeding the calcium wire.
From the results of example 1 and comparative examples 1-2, it can be seen that if the calcium wire introducing conditions (angle, distance, speed, depth, etc.) are not within the limits of the present application, the yield of the calcium wire is reduced, and if 100m calcium wire is introduced, the calcium content is only 0.0008% and 0.0006%, and meanwhile, impurities in the molten steel cannot be effectively removed in a floating manner, and the yield strength and tensile strength are affected. From the results of comparative example 3, it can be seen that the final oxygen removal degree of the LF furnace also affects the calcium line yield, i.e. when the oxygen content is higher than 5ppm, the calcium yield is reduced, and the yield strength and tensile strength are reduced, which may be caused by that excessive oxygen in the molten steel consumes excessive calcium element, reduces the calcium yield, and cannot effectively remove impurities.
The oxygen content of the molten steel is lower through the control of the converter tapping and the deoxidation degree of the LF furnace, and the yield of calcium is improved by matching with proper calcium line introduction conditions (angle, distance, speed, depth and the like), so that the calcium yield is improved, and the calcium element and Al are promoted to be mixed with each other2O3And the chain-shaped or strip-shaped inclusions are made into balls and then float upwards to remove the balls, and the cold forging steel with the yield strength and the tensile strength which are both relatively different is obtained.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A calcium treatment method for molten steel, characterized by comprising the steps of:
(1) tapping by a converter, and deoxidizing the molten steel;
(2) in the refining process of an LF refining furnace, adding aluminum slag balls into deoxidized molten steel to deoxidize the slag surface until the color of the steel slag is white and the oxygen content in the molten steel is 3-5 ppm;
(3) feeding a calcium wire into the molten steel after deoxidation of the slag surface, wherein the feeding method of the calcium wire comprises the following steps:
the calcium wire is straightened through a guide pipe, the guide pipe is provided with a first section in the horizontal direction, a second section of an arc line and a third section in the vertical direction, and the calcium wire is led out from the third section and then is output vertically downwards; the length of the third section is 0.3-0.5 m; the distance between the outlet of the third section and the slag surface of the molten steel is 0.4-0.6 m, the outlet speed (feeding speed) of the calcium line is 100-150 m/min, and the depth of the calcium line penetrating into the molten steel is 0.3-0.5 m.
2. The calcium treatment method according to claim 1, wherein the molten steel in the step (1) is deoxidized to 10 to 30 ppm;
preferably, the molten steel deoxidation in the step (1) includes adding an aluminum deoxidizer for deoxidation when molten steel is tapped, and specifically includes:
adding 3-3.6 kg/t of aluminum iron when the end point carbon range is 0-0.08%;
when the end point carbon range is 0.08-0.15%, adding 2.4-3 kg/t of aluminum and iron;
when the end point carbon range is more than 0.15 percent, 2kg/t of aluminum iron is added.
3. The calcium treatment method according to claim 1 or 2, wherein the deoxidation of the slag surface in step (2) is carried out by:
when Als of a steel water sample entering the LF furnace is less than or equal to 0.005%, adding 2-3 kg/t of aluminum slag balls;
adding 1.6-2 kg/t of aluminum slag balls when Als of the molten steel sample entering the LF furnace is 0.005-0.015%;
adding 1.2-1.6 kg/t of aluminum slag balls when Als of the molten steel sample entering the LF furnace is 0.015-0.025%;
when Als of a steel water sample entering the LF furnace is more than 0.025 percent, 0.8kg/t of aluminum slag balls are added.
4. The calcium treatment method of claim 1 or 2, wherein before the refining of the LF refining furnace in the step (2) is started, silicon carbide is added into the LF refining furnace for deoxidation;
preferably, the addition amount of the silicon carbide is 0.10-0.15 kg/t.
5. A calcium treatment process according to claim 1 or 2, wherein the amount of calcium wire fed is calculated as 0.0010 to 0.0014% by weight of calcium per ton of steel fed by 1 meter of calcium wire.
6. A method of producing a steel material, the method comprising the steps of:
(A) providing molten steel treated by the calcium treatment method according to any one of claims 1 to 5;
(B) controlling the flow rate of the stirring gas of the molten steel to be 5-11 m3/h；
(C) And pouring the molten steel to obtain the steel.
7. The method according to claim 6, wherein the molten steel is stirred with a gas for 20-30 min when steel inclusion particles are required to achieve less than 1.5e of B-inclusions.
8. The method according to claim 6, wherein the molten steel is supplied with the stirring gas for 10 to 15min when the steel inclusion particles are required to have less than 2.0e of B-type inclusions.
9. A steel product obtained by casting the calcium-treated molten steel according to claim 6 or 7.
10. The steel product as claimed in claim 9 wherein the steel product comprises cold heading steel.
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| CN115232917A (en) * | 2022-07-18 | 2022-10-25 | 中天钢铁集团有限公司 | Smelting deoxidation process of aluminum-containing cold forging steel |
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