CN112458368A - Rare earth-titanium microalloyed high-strength medium plate and manufacturing method thereof - Google Patents
Rare earth-titanium microalloyed high-strength medium plate and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a rare earth-titanium microalloyed high-strength medium plate and a manufacturing method thereof. Steel grade Q390CTi, comprising: 0.10 to 0.18 percent of carbon, 0.10 to 0.30 percent of silicon, 0.60 to 1.10 percent of manganese, 0.04 to 0.08 percent of titanium, less than or equal to 0.05 percent of nickel, less than or equal to 0.15 percent of copper, 0.010 to 0.050 percent of aluminum, less than or equal to 0.020 percent of phosphorus, less than or equal to 0.020 percent of sulfur and 0 to 0.05 percent of rare earth Re. According to the invention, the steel is subjected to microalloying treatment by rare earth and titanium, so that the high-strength medium and heavy plate Q390CTi is ensured to have higher strength, higher surface quality, more stable performance and longer service life.
Description
Technical Field
The invention relates to the technical field of high-strength medium plates, in particular to a rare earth-titanium microalloyed high-strength medium plate and a manufacturing method thereof.
Background
The high-strength medium plate is mainly applied to building engineering, machine manufacturing, container manufacturing, shipbuilding, bridge construction and the like. It can also be used for manufacturing various containers, furnace shells, furnace plates, bridges, automobile steel plates and the like.
In the use process of the medium plate, the plasticity and the toughness are influenced to a greater or lesser extent along with the improvement of the strength requirement. Particularly, in a low-temperature environment, the requirement on the low-temperature toughness of a high-strength medium plate is more strict, and the most economical method for improving the strength is to increase the content of C, but the increase of the content of C brings adverse effects on the welding performance, the plasticity and the toughness of the medium plate. When the condition of a continuous casting machine is not good, the produced casting blank has large-level internal defect, and the performance of the common high-strength medium plate is not enough or even seriously layered, so that the safety of engineering after the material is used is seriously threatened.
The steel for the rare earth alloying grinding ball has the patent number of CN201810573584.X, and is a bar product, which belongs to different steel types from the rare earth-titanium alloying medium plate in the application and has completely different component systems; the invention is not practical according to the original component system, and the expected performance is achieved, so that the problem to be solved by the invention is how to design a new high-strength medium plate material with higher strength, higher surface quality, more stable performance and longer service life.
Disclosure of Invention
The invention provides a rare earth-titanium microalloyed high-strength medium plate and a manufacturing method thereof aiming at the defects. The grade Q390CTi of steel, through adding titanium and tombarthite Re and carrying out the alloying and optimizing key process control point, the effectual Q390CTi of guaranteeing has higher intensity, higher surface quality, more stable performance, higher life.
The technical scheme of the invention is as follows:
a rare earth-titanium microalloyed high-strength medium plate is a steel mark Q390CTi, and comprises the following components in percentage by mass: 0.10 to 0.18 percent of carbon, 0.10 to 0.30 percent of silicon, 0.60 to 1.10 percent of manganese, 0.04 to 0.08 percent of titanium, less than or equal to 0.05 percent of nickel, less than or equal to 0.15 percent of copper, 0.010 to 0.050 percent of aluminum, less than or equal to 0.020 percent of phosphorus, less than or equal to 0.020 percent of sulfur, 0 to 0.05 percent of rare earth Re, and the balance of iron and inevitable elements.
As preferred function of Ti: the solid solubility of titanium in steel is very small, the solid solution strengthening effect can not be generated basically, the microalloying effect is mainly embodied in fine crystal strengthening and precipitation strengthening, TiN or Ti (NC) below 100nm can prevent austenite grains from growing in the heating and hot rolling processes, and the dispersed and precipitated Ti (C) in the cooling and coiling processes can obviously improve the strength of the steel. The titanium is combined with sulfur in the steel to form Ti4C2S2 which is difficult to deform, thereby avoiding the reaction of manganese and sulfur to generate MnS which extends into a strip shape along the rolling direction and reducing the anisotropy of the steel performance. In addition, Ti can significantly improve the strength and toughness of the weld and the heat affected zone.
As a preferred rare earth Re element: the rare earth is called as 'industrial monosodium glutamate', and trace rare earth can play a role in obviously improving the performance of steel. The rare earth element has extremely strong chemical activity due to a unique electronic shell structure, the energy valence state of the 4f shell structure is variable, the size of a large atom is large, the rare earth element is an extremely strong purifying agent for steel and an effective modifier for clean steel inclusion, and the rare earth element is a strong inhibitor for effectively controlling a weakening source in steel and reducing the energy state of a local area and local weakening of the steel. The concrete functions are as follows:
1. deep purification, control of the weakening source: the main points are as follows: can deeply reduce the content of oxygen and sulfur, and reduce the harmful effects of low-melting-point elements such as phosphorus, sulfur, hydrogen, arsenic, antimony, bismuth, lead, tin and the like. The segregation of sulfur and rare earth elements on the grain boundary of high-speed steel is studied by Auger spectroscopy and an ion probe. The rare earth elements reduce the segregation of the grain boundary P, eliminate the harmful effect of weakening the grain boundary caused by Fe3P, and improve the state of the grain boundary, thereby strengthening the grain boundary, hindering intergranular fracture and increasing the transgranular fracture fraction.
2. Coagulation "tissue control": the size of the secondary dendrite spacing will affect microsegregation, inclusion and porosity, thus affecting the mechanical properties. The rare earth forms a compound with a higher melting point in steel, and is precipitated before the molten steel is solidified, and the compound is distributed in the molten steel in a fine particle form and serves as a heterogeneous nucleation center, so that the supercooling degree of the molten steel crystal is reduced, the solidification structure of the steel can be refined, the segregation is reduced, and the solidification structure control is realized.
3. Micro-alloying action: rare earth has purification and obvious modification effects in steel. The cleanliness of steel is continuously improved, and the microalloy strengthening effect of rare earth elements is increasingly prominent. The microalloying of the rare earth comprises solid solution strengthening of trace rare earth elements, interaction of the rare earth elements and other solute elements or compounds, size, shape and distribution of existing states (atoms, inclusions or compounds) of rare earth atoms, particularly segregation in grain boundaries, influence of the rare earth on the steel surface and matrix structure and the like.
[ TO ] as a high-strength medium-thickness plate preferably microalloyed with rare earth-titanium]The content is controlled to be less than or equal to 25 multiplied by 10-6The content of N is controlled to be less than or equal to 50 multiplied by 10-6。
The rare earth-titanium microalloyed high-strength medium plate is characterized in that the nonmetallic inclusions of the rare earth-titanium microalloyed high-strength medium plate are rated according to GBT10561, and are controlled to be less than or equal to 1.5 grade of A-type inclusions, less than or equal to 1.0 grade of B-type inclusions, less than or equal to 0.5 grade of C-type inclusions, less than or equal to 1.0 grade of D-type inclusions and less than or equal to 1.0 grade of Ds-type inclusions, so that the medium plate has longer service life.
The preferable rare earth-titanium microalloyed high-strength medium plate is characterized in that the yield strength ReH of the rare earth-titanium microalloyed high-strength medium plate is more than or equal to 390MPa, and the tensile strength Rm: 500 MPa-650 MPa, transverse elongation A is more than or equal to 22%, and impact energy KV2 at 0 ℃ is more than or equal to 40J, so that the medium plate can have more balanced mechanical properties, namely, good plasticity index can be considered under the condition of high strength.
The invention also provides a method for manufacturing the rare earth-titanium microalloyed high-strength medium plate, which comprises the following steps:
s1, adding a preformed dephosphorization agent into the converter before smelting and charging the converter, (wherein the preformed dephosphorization agent is prepared from the raw materials of the company, and the specific components are lime CaO and iron scale Fe2O3According to the mass ratio of 3: 2), ensuring the dephosphorization capability of converter smelting, adding a deoxidizer aluminum block at one time during tapping, and feeding the deoxidizer aluminum block into a refining aluminum feeding wire for 50-200 m;
s2, refining the slag system with medium and high alkalinity, adding refined lime according to 5-8 kg/t, adding 300 kg of premelted slag refined slag into a furnace, adding 10-50 kg of fluorite into the furnace for slag regulation, adding ferrotitanium and pure rare earth alloy under the condition of good molten steel deoxidation and desulfurization, and feeding Ca-Si wire 200 m/furnace at the final stage of LF refining;
s3, casting a wide and thick slab blank with a cross section of 250 x 2100mm in the continuous casting process, wherein the continuous casting process ensures low superheat degree casting, the superheat degree is controlled to be less than or equal to 25 ℃, electromagnetic stirring is adopted in the continuous casting process, and the control parameter of the electromagnetic stirring is current: 500A frequency: 6 HZ; and the dynamic soft reduction technology, adopt two cold dynamic water distribution, the specific water content is controlled in 0.7L/kg, make the central equiaxial crystal area obviously improve, the grain size is obviously refined, the macrostructure of casting blank is obviously improved, has dispelled the middle crackle; the segregation index is reduced;
s4, controlling the heating time of the rolling heating furnace for 2.5-4.5 h, ensuring the high-temperature diffusion of segregation elements, reducing the segregation index, controlling the soaking temperature at 1240 ℃, preventing the crystal grains from being coarse, controlling the heating furnace to control the neutral atmosphere, preventing the decarburization of steel, controlling the high-pressure water descaling pressure at 18-20 MPa, the descaling rate at 95% or more, controlling the tapping temperature at 1120-1150 ℃, controlling the thickness of the intermediate billet to be 2.0-3.5 times of the thickness of the finished billet, controlling the rolling temperature at 1000 ℃, controlling the finish rolling temperature at 880-920 ℃, and controlling the return-to-red temperature of ACC effluent at 680-720 ℃.
In S1, the pre-prepared dephosphorizing agent comprises the specific components of lime CaO and iron scale Fe2O3According to the mass ratio of 3:2After the dephosphorizing agent is used, the phosphorus can be rapidly dephosphorized in the earlier stage of smelting in the converter, the phosphorus content in the steel tapping is controlled to be less than or equal to 0.015 percent, the proportion of the scrap steel is controlled to be more than or equal to 20 percent, the steel tapping temperature is controlled to 1610 and 1660 ℃, and the deoxidizer aluminum block is added for one time in the steel tapping at 1.0 kg/t.
In S2, the addition of ferrotitanium can deoxidize and desulfurize molten steel well in the refining process, namely [ S ]]Less than or equal to 0.01 percent; the adding time of the rare earth is good for molten steel deoxidation in the final stage of refining, [ Al ]]0.01-0.04% of content, T [ O ]]≤10×10-6When the method is used, pure rare earth is rapidly added, and the addition of the rare earth is controlled to be 0-30 kg/furnace.
In S3, the equiaxed crystal rate reaches 65-75%, and the median crack is less than or equal to 0.5 grade.
The invention has the beneficial effects that:
the invention provides a rare earth-titanium microalloyed high-strength medium plate (steel mark Q390CTi) and a manufacturing method thereof, which effectively ensure the excellent comprehensive performance of a new material Q390CTi of the high-strength medium plate by reasonably controlling the proportion of various alloy elements, key process control points and a scientific heat treatment system, and ensure that the material has higher strength, higher surface quality, more stable performance and longer service life.
The specific implementation mode is as follows:
in order to make those skilled in the art better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and 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 invention.
Example 1
The rare earth-titanium microalloyed high-strength medium plate designed in the embodiment, steel brand Q390CTi, specifically comprises the following components:
0.10 to 0.18 percent of carbon, 0.10 to 0.30 percent of silicon, 0.60 to 1.10 percent of manganese, 0.04 to 0.08 percent of titanium, less than or equal to 0.05 percent of nickel, less than or equal to 0.15 percent of copper, 0.010 to 0.050 percent of aluminum, less than or equal to 0.020 percent of phosphorus, less than or equal to 0.020 percent of sulfur, 0 to 0.05 percent of rare earth Re, and the balance of iron and inevitable elements such as tin, antimony, bismuth and the like.
Based on the above component design, the measured values of component control in the implementation process are shown in table 1:
TABLE 1 internal control Range/% of chemical composition
In the process of manufacturing the rare earth-titanium microalloyed high-strength medium and heavy plate Q390CTi, the process capability control index Cpk of actually controlling the components is more than or equal to 1.80, reaches the A + level and meets the design requirements, and the specific test furnace number components are shown in Table 2.
TABLE 2 actually measured chemical composition control values
| Furnace number | C | Si | Mn | P | S | Al | Ti | Cu | Ni | Re |
| 1 | 0.14 | 0.20 | 0.80 | 0.008 | 0.002 | 0.016 | 0.055 | 0.05 | 0.010 | 0.02 |
| 2 | 0.13 | 0.22 | 0.79 | 0.009 | 0.004 | 0.020 | 0.060 | 0.06 | 0.015 | 0.03 |
| 3 | 0.15 | 0.21 | 0.80 | 0.005 | 0.003 | 0.022 | 0.064 | 0.07 | 0.011 | 0.02 |
Example 2
In this example, the method for manufacturing the rare earth-titanium microalloyed high strength medium plate Q390CTi according to the charging amount of the example 1 is provided:
s1, adding a preformed dephosphorization agent into the converter before smelting and charging the converter, (wherein the preformed dephosphorization agent is prepared from the raw materials of the company, and the specific components are lime CaO and iron scale Fe2O3According to the mass ratio of 3: 2), the dephosphorization capability of converter smelting is ensured, the phosphorus content in the steel tapping is controlled to be less than or equal to 0.015 percent, the scrap steel proportion is controlled to be 21 percent, the steel tapping temperature is controlled to be 1650 ℃, and a deoxidizer aluminum block is added into the steel tapping at one time for 1.0 kg/t;
s2, adopting a refining slag system with medium and high alkalinity, and adopting slag binary alkalinity R (CaO/SiO)2) Adding refined lime according to 6.0kg/t, adding 300 kg/furnace premelted slag refining slag, adding 50 kg/furnace fluorite for slag regulation, and adding ferrotitanium and pure rare earth alloy under the condition of good molten steel deoxidation and desulfurization; the supply unit of the pure rare earth alloy is a metal institute of Chinese academy of sciences, and the Ca-Si wire is fed into a furnace at the last stage of LF refining at 200 m/furnace;
s3, casting a wide and thick slab blank with a cross section of 250 x 2100mm in the continuous casting process, wherein the continuous casting process ensures low superheat degree casting, the superheat degree is controlled to be 23 ℃, electromagnetic stirring is adopted in the continuous casting process, and the control parameters are current: 500A frequency: the 6HZ and dynamic soft reduction technology adopts secondary cooling dynamic water distribution, and the specific water amount is controlled to be 0.7L/kg, so that the central equiaxial crystal area is obviously increased, the crystal grain size is obviously refined, the macrostructure of a casting blank is obviously improved, and intermediate cracks are eliminated; the segregation index is reduced;
s4, controlling the heating time of the rolling heating furnace for 3.5h, ensuring the high-temperature diffusion of segregation elements, reducing the segregation index, controlling the soaking temperature to 1240 ℃, preventing the crystal grains from being coarse, controlling the neutral atmosphere of the rolling heating furnace, preventing the steel from being decarburized, controlling the high-pressure water descaling pressure to 19MPa, controlling the descaling rate to 98 percent, controlling the tapping temperature to 1140 ℃, controlling the thickness of an intermediate billet to be 3.0 times of that of a finished billet, controlling the initial rolling temperature to 1100 ℃, controlling the finish rolling temperature to 900 ℃ and controlling the ACC effluent re-reddening temperature to.
By examining the final mechanical properties of the product obtained in example 2: the yield strength ReH is 420MPa, the tensile strength Rm is 580MPa, the transverse elongation A is 24 percent, and the impact energy KV2 is 80J at 0 ℃. The mechanical properties of the conventional Q390C product are compared with those of the example in Table 3.
TABLE 3 comparison of the Performance of conventional Q390C with that of Q390CTi from example 2
| ReH/MPa | Rm/MPa | A/％ | KV2/J | |
| Generic Q390C | 405 | 560 | 20 | 45 |
| Example 2 | 420 | 580 | 24 | 80 |
As can be seen from Table 3, the newly designed rare earth-titanium microalloyed steel has higher performance, better plasticity and higher toughness.
Example 3
Based on the preparation process of the embodiment 2, in the step (4), the heating time of the rolling heating furnace is controlled for 3.5 hours, the high-temperature diffusion of segregation elements is guaranteed, the segregation index is reduced, the soaking temperature is controlled to be 1240 ℃, coarse grains are prevented, the neutral atmosphere of the heating furnace is controlled, the decarburization of steel is prevented, the high-pressure water descaling pressure is controlled to be 19MPa, the descaling rate is 99%, the tapping temperature is controlled to be 1130 ℃, the thickness of an intermediate billet is 2.9 times of that of a finished billet, the rolling temperature is 1100 ℃, the finish rolling temperature is 880 ℃, and the temperature for returning water to red is 720 ℃ for ACC.
By checking the final mechanical properties of the product obtained in example 3: yield strength ReH 410MPa, tensile strength Rm 565MPa, transverse elongation a 25%, and impact power KV2 at 0 ℃ 88J. The results of the performance of example 3 compared to conventional Q390C are shown in Table 4.
Table 4 comparison of example 3 with conventional Q390C performance
| ReH/MPa | Rm/MPa | A/％ | KV2/J | |
| Generic Q390C | 405 | 560 | 20 | 45 |
| Example 3 | 410 | 565 | 25 | 88 |
As can be seen from Table 4, the plate made in example 3 has higher performance, better plasticity and higher toughness than the conventional Q390C.
Example 4
Different feed compositions were used, the ingredients being shown in table 5.
TABLE 5 chemical composition control Range/% ]
| Furnace number | C | Si | Mn | P | S | Al | Ti | Cu | Ni | Re |
| 1 | 0.15 | 0.23 | 0.84 | 0.009 | 0.005 | 0.018 | 0.056 | 0.02 | 0.011 | 0.03 |
| 2 | 0.16 | 0.24 | 0.86 | 0.010 | 0.005 | 0.023 | 0.062 | 0.04 | 0.013 | 0.03 |
| 3 | 0.16 | 0.25 | 0.83 | 0.009 | 0.003 | 0.025 | 0.063 | 0.04 | 0.012 | 0.03 |
By checking the final mechanical properties of the product obtained in example 4: the yield strength ReH is 439MPa, the tensile strength Rm is 595MPa, the transverse elongation A is 23 percent, and the impact energy KV2 is 65J at 0 ℃. The results of the performance of example 4 compared to example 2 are shown in Table 6.
Table 6 comparison of example 4 with example 2
| ReH/MPa | Rm/MPa | A/％ | KV2/J | |
| Generic Q390C | 405 | 560 | 20 | 45 |
| Example 4 | 439 | 595 | 23 | 65 |
As can be seen from Table 6, the plate of the medium plate produced in example 4 has higher performance, better plasticity and higher toughness than the conventional Q390C.
Example 5
Different feed compositions were used, the compositions being shown in table 7.
TABLE 7 chemical composition control Range/% ]
| Furnace number | C | Si | Mn | P | S | Al | Ti | Cu | Ni | Re |
| 1 | 0.12 | 0.20 | 0.78 | 0.008 | 0.005 | 0.015 | 0.052 | 0.03 | 0.010 | 0.02 |
| 2 | 0.14 | 0.20 | 0.76 | 0.011 | 0.004 | 0.020 | 0.060 | 0.03 | 0.010 | 0.02 |
| 3 | 0.13 | 0.20 | 0.76 | 0.009 | 0.003 | 0.023 | 0.054 | 0.02 | 0.012 | 0.03 |
By checking the final mechanical properties of the product obtained in example 5: the yield strength ReH is 410MPa, the tensile strength Rm is 583MPa, the transverse elongation A is 26 percent, and the impact energy KV2 is 100J at 0 ℃. The results of the performance of example 5 compared to example 2 are shown in Table 7.
Table 7 comparison of the properties of example 4 with example 2
| ReH/MPa | Rm/MPa | A/％ | KV2/J | |
| Generic Q390C | 405 | 560 | 20 | 45 |
| Example 5 | 410 | 583 | 26 | 100 |
As can be seen from Table 7, the plate of the medium plate produced in example 5 has higher performance, better plasticity and higher toughness than the conventional Q390C.
According to the rare earth-titanium microalloyed high-strength medium plate, the steel mark Q390CTi is formed by alloying trace element titanium and rare earth and various control measures in the manufacturing process, so that the manufactured high-strength medium plate has higher strength, higher surface quality, more stable performance and longer service life.
Claims (8)
1. The rare earth-titanium microalloyed high-strength medium plate is characterized in that the steel grade Q390CTi comprises the following components in percentage by mass: 0.10 to 0.18 percent of carbon, 0.10 to 0.30 percent of silicon, 0.60 to 1.10 percent of manganese, 0.04 to 0.08 percent of titanium, less than or equal to 0.05 percent of nickel, less than or equal to 0.15 percent of copper, 0.010 to 0.050 percent of aluminum, less than or equal to 0.020 percent of phosphorus, less than or equal to 0.020 percent of sulfur, 0 to 0.05 percent of rare earth Re, and the balance of iron and other inevitable elements.
2. The rare earth-titanium microalloyed high strength medium plate according to claim 1, wherein the rare earth-titanium microalloyed high strength medium plate has T [ O ]]The content is controlled to be less than or equal to 25 multiplied by 10-6The content of N is controlled to be less than or equal to 50 multiplied by 10-6。
3. The rare earth-titanium microalloyed high strength medium plate according to claim 1, wherein the nonmetallic inclusions of the rare earth-titanium microalloyed high strength medium plate reach class A inclusion less than or equal to 1.5, class B inclusion less than or equal to 1.0, class C inclusion less than or equal to 0.5, class D inclusion less than or equal to 1.0 and class Ds inclusion less than or equal to 1.0 according to GBT10561 rating.
4. The rare earth-titanium microalloyed high-strength medium plate as claimed in claim 1, wherein the yield strength ReH of the rare earth-titanium microalloyed high-strength medium plate is not less than 390MPa, and the tensile strength Rm: 500 MPa-650 MPa, transverse elongation A is more than or equal to 22%, and impact energy KV2 at 0 ℃ is more than or equal to 40J.
5. The method for manufacturing a rare earth-titanium microalloyed high-strength medium plate according to claim 1, comprising the steps of:
s1, adding a prefabricated dephosphorization agent into the converter before the converter smelting feeding to ensure the dephosphorization capability of the converter smelting, adding a deoxidant aluminum block at one time during tapping, and feeding a refined aluminum feeding wire for 50-200m in a matching manner;
s2, refining the slag system with medium and high alkalinity, adding refined lime according to 5-8 kg/t, adding 300 kg of premelted slag refined slag into a furnace, adding 10-50 kg of fluorite into the furnace for slag regulation, adding ferrotitanium and pure rare earth alloy under the condition of good molten steel deoxidation and desulfurization, and feeding Ca-Si wire 200 m/furnace at the final stage of LF refining;
s3, casting a slab with a width and thickness of 250 x 2100mm in the continuous casting process, wherein the continuous casting process ensures low superheat degree casting, the superheat degree is controlled to be less than or equal to 25 ℃, the continuous casting process adopts electromagnetic stirring and dynamic soft reduction technology, secondary cooling dynamic water distribution is adopted, and the specific water amount is controlled to be 0.7L/kg, so that the central equiaxial crystal area is obviously increased, the crystal grain size is obviously refined, the macrostructure of a casting blank is obviously improved, and middle cracks are eliminated; the segregation index is reduced;
s4, controlling the heating time of the rolling heating furnace for 2.5-4.5 h, ensuring the high-temperature diffusion of segregation elements, reducing the segregation index, controlling the soaking temperature at 1240 ℃, preventing the crystal grains from being coarse, controlling the heating furnace to control the neutral atmosphere, preventing the decarburization of steel, controlling the high-pressure water descaling pressure at 18-20 MPa, the descaling rate at least equal to 95%, controlling the tapping temperature at 1120-1150 ℃, controlling the thickness of the intermediate billet at 2.0-3.5 times of the thickness of the finished plate, controlling the rolling temperature at more than 1000 ℃, controlling the finish rolling temperature at 880-920 ℃, and controlling the return-to-red temperature of ACC effluent at 680-720 ℃.
6. The method for manufacturing a rare earth-titanium microalloyed high-strength medium plate as claimed in claim 5, wherein the pre-prepared dephosphorization agent in S1 comprises CaO lime and Fe scale2O3According to the mass ratio of 3:2, the phosphorus content in the steel tapping is controlled to be less than or equal to 0.015 percent, the proportion of the scrap steel is controlled to be more than or equal to 20 percent, the steel tapping temperature is controlled to 1610 and 1660 ℃, and a deoxidizer aluminum block is added for 1.0kg/t once in the steel tapping.
7. The method of claim 6, wherein the addition of Ti-Fe in S2 is performed at a timing such that deoxidation and desulfurization of molten steel during refining are good [ S ]]Less than or equal to 0.01 percent; re was added at a timing such that molten steel was well deoxidized at the final stage of refining, [ Al ]]0.01-0.04% of content, T [ O ]]≤10×10-6When the method is used, pure rare earth is rapidly added, and the addition of the rare earth is controlled to be 0-30 kg/furnace.
8. The method for manufacturing a rare earth-titanium microalloyed high-strength medium plate according to claim 7, wherein the equiaxed grain ratio in S3 is 65 to 75 percent, and the median crack is less than or equal to 0.5 grade.
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