CN113699429A - Smelting process for reducing TP321 stainless steel seamless tube layering defects - Google Patents
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Abstract
The invention relates to the technical field of stainless steel smelting, and provides a smelting process for reducing the layering defect of a TP321 stainless steel seamless tube, which comprises the steps of providing crude molten steel by an electric arc furnace, blowing oxygen for decarburization by AOD, reducing AOD ferrosilicon, deeply deoxidizing AOD aluminum, alloying AOD titanium, then tapping,the steel ladle is stirred softly and treated with calcium, and die casting and casting are carried out. The invention adopts the process route of 'electric arc furnace +20t AOD refining furnace + ladle treatment + die casting', and the Al element content in the molten steel is strictly controlled to carry out deep deoxidation before Ti alloying of the AOD refining furnace; after AOD tapping, feeding a calcium-silicon wire into a steel ladle to melt high-melting-point Al in molten steel2O3‑MgO‑TiOxModifying the inclusions into low-melting-point inclusions; effectively reduce large-size SiO in stainless steel2‑Al2O3MnO-CaO and TiOxThe content of MnO inclusions is reduced, the layering defects in the stainless steel seamless tube are reduced, and the ultrasonic flaw detection qualification rate of the stainless steel seamless tube is improved.
Description
Technical Field
The invention relates to the technical field of stainless steel smelting, in particular to a smelting process for reducing the layering defect of a TP321 stainless steel seamless tube.
Background
The austenitic stainless steel has the advantages of excellent corrosion resistance, formability, toughness in a wide temperature range and the like, is widely applied to industrial departments such as petroleum, nuclear industry, transportation, aerospace and the like and living goods industry, and the yield of the austenitic stainless steel accounts for about 70 percent of the total weight of the stainless steel. The Ti element is widely applied to the stainless steel, and mainly realizes the effects of stabilization, pinning, dispersion strengthening and the like by separating out TiN (C, N) particles with different sizes and uniform distribution, thereby further improving the corrosion resistance and the obdurability of the stainless steel. The TP321 is typical titanium-containing austenitic stainless steel, has more excellent high-temperature corrosion resistance than the conventional 304 austenitic stainless steel, does not need heat treatment after welding, and can be used for a long time at the temperature of a stainless steel sensitization area, thereby being widely applied to heat-resistant pressure-resistant pipelines of petroleum, natural gas, nuclear power and the like.
However, because Ti element has strong binding ability with O, S, N, C elements in molten steel, Al can be generated in the smelting process of the titanium-containing stainless steel2O3-MgO-TiOx、CaO·TiO2And a great variety of inclusions such as TiN and the like, wherein most of the inclusions are harmful, and the adverse effects are brought to the smelting and the quality of the stainless steel, including agglomeration in a crystallizer, blockage of a continuous casting nozzle, scale defects on the surface of a stainless steel plate, improper ultrasonic flaw detection caused by layering defects and the like. Researches find that the layering defect of TP321 stainless steel is mainly large-size SiO in the steel2-Al2O3MnO-CaO and TiOxThe MnO inclusion cluster is formed after rolling.
In order to control harmful impurities generated in the titanium-containing stainless steel smelting process and reduce adverse effects caused by titanium alloying, Chinese patent CN103225008A discloses a method for preventing agglomeration and nozzle nodulation in a crystallizer in the titanium-containing stainless steel smelting process, the process route is electric smelting crude molten steel, AOD furnace refining, LF ladle refining and continuous casting, and favorable conditions are created for reduction mainly by improving the carbon content and the temperature of molten steel in an electric furnace; the aim of full deoxidation is achieved through reduction, and the yield of titanium is improved and stabilized; the flow of blowing and stirring is increased in the LF furnace, so that impurities in molten steel fully float upwards, secondary oxidation of continuous casting tundish is prevented, the temperature of molten steel in the tundish is increased, the molten steel is prevented from secondary pollution, caking and nozzle nodulation in a crystallizer are reduced, the continuous casting operation rate is effectively increased, and on-site and rolled waste products are reduced. However, the method has specific requirements on equipment, is difficult to implement without an LF furnace, does not refer to a calcium treatment process, and can cause the problem that high-melting-point inclusions block a nozzle in the steel casting process. Chinese patent CN104294005A discloses a method for smelting titanium-containing stainless steel, which is to carry out ladle treatment on molten steel after refining, mainly comprising slagging-off and re-slagging, Ti alloying after Al deep deoxidation and calcium treatment, aiming at carrying out secondary deep deoxidation on the molten steel, improving the yield of titanium, reducing the oxygen content in the molten steel, and reducing TiO in the molten steel2、CaO·TiO2And the impurities are contained, so that the nozzle nodulation probability in the continuous casting process is reduced, and the surface quality of the stainless steel in the rolling process is improved. However, the alloy addition amount is too large in the ladle treatment process, and molten steel may have a uniformity problem.
Disclosure of Invention
The invention aims to overcome at least one of the defects of the prior art, and provides a smelting process for reducing the layering defect of a TP321 stainless steel seamless tube aiming at the problem of unstable control of the layering defect of the current TP321 stainless steel seamless tube.
The invention adopts the following technical scheme:
a smelting process for reducing the layering defect of a TP321 stainless steel seamless tube comprises the following steps:
s1, providing crude molten steel by an electric arc furnace: controlling the components of the AOD molten steel entering the furnace and the temperature of the molten steel to set values;
s2, AOD oxygen blowing decarburization: adding lime and magnesia, controlling the end point w C not more than 0.06%; supplementing high-carbon ferrochrome and electrolytic manganese during the period;
s3, AOD ferrosilicon reduction: adding lime and ferrosilicon, introducing argon, and stirring; after reduction, slagging-off is thorough in the AOD furnace, and the residue amount is less than 20kg of ton steel;
s4, deep deoxidation of AOD aluminum; adding lime, fluorite and aluminum ingot, introducing argon, stirring, and controlling w [ Al ] in the molten steel to be 0.05-0.06%;
s5, tapping after AOD titanium alloying: adding ferrotitanium alloy, and controlling w [ Ti ] in the molten steel to be 0.40-0.45%; after the components are qualified, mixing the AOD slag steel;
s6, steel ladle soft stirring and calcium treatment: feeding a calcium-silicon wire to the molten steel;
s7, die casting: argon is adopted for protection in the whole process, and die casting protective slag is added to prevent secondary oxidation.
In step S1, w [ C ] in the AOD charged molten steel is controlled to be equal to or greater than 2.0%, w [ Si ] is 0.4 to 0.5%, w [ Mn ] is 0.8 to 0.9%, w [ Cr ] is 16.0 to 16.5%, w [ Ni ] is 9.5 to 10.0%, and the temperature of the molten steel is not lower than 1470 ℃, so as to create favorable conditions for the subsequent AOD oxygen decarburization and reduction.
In any of the above possible implementation manners, there is further provided an implementation manner, when the 20t AOD refining furnace is adopted, in step S2, 1500 ± 100kg of lime and 200 ± 50kg of magnesium oxide are added; during the period, 800 plus or minus 50kg of high-carbon ferrochrome and 60 plus or minus 5kg of electrolytic manganese are supplemented, so that the pressure for supplementing alloy and adjusting components in the reduction period is reduced.
In any of the above possible implementations, there is further provided an implementation that in step S3, lime 300 ± 50kg, ferrosilicon 450 ± 50kg and argon gas flow rate are controlled to 10-15Nm3Min, stirring for 8-12min, controlling W [ Si ] in molten steel](0.3-0.5)%, promotes the reaction between ferrosilicon and slag and molten steel, and promotes SiO2Floating removal of MnO inclusions; after the ferrosilicon reduction is finished, slagging-off in the AOD furnace needs to be thorough, and the residue is less than 20kg of steel per ton.
In any of the above possible implementation manners, there is further provided an implementation manner that in step S4, lime 300 ± 50kg, fluorite 140 ± 10kg, aluminum ingot 150 ± 10kg, and argon gas flow rate is controlled to be 10-15Nm3Min, stirring for 8-12min to speed the smelting of aluminum ingot and the homogenization of molten steel components and control W [ Al ] in molten steel]0.05-0.06% of SiO in steel2MnO inclusion content is reduced, total oxygen content in molten steel is reduced, and TiO content after Ti alloying is reducedxPossibility of occurrence of inclusion of MnO type.
In step S6, a calcium silicate wire is fed into the molten steel by a wire feeder, wherein the feeding amount of pure calcium is 0.2-0.8 kg per ton of steel, and the high-melting-point Al in the modified molten steel is2O3-MgO-TiOxImpurities; the flow rate of argon gas is controlled to be 0.1-0.2 Nm3And/min, soft stirring to promote floating removal of the inclusion.
In step S7, when the temperature of the molten steel is reduced to 1510 ± 10 ℃, casting is started, and during the casting process, the whole process of the nozzle is protected by argon gas; the method adopts a lower pouring method die casting mode, and die casting protective slag is added at the bottom of the die, so that the secondary oxidation caused by the direct contact of molten steel and air is prevented.
In any of the possible implementations described above, there is further provided an implementation that in step S2, w [ Cr ] is ≥ 52%, w [ C ] is ≤ 10.0%, and w [ Si ] is ≤ 5.0%.
In any of the above possible implementations, there is further provided an implementation in which, in step S3, w [ Si ] in the ferrosilicon is 72.0 to 80.0%, and w [ Al ] is 2.0% or less.
In any of the possible implementations described above, there is further provided an implementation that, in step S5, w [ Ti ] ≦ 65.0-75.0%, w [ Si ] ≦ 3.50%, and w [ Al ] ≦ 6.0% in the ferrotitanium alloy.
The invention has the beneficial effects that: the invention adopts the process route of 'electric arc furnace +20t AOD refining furnace + ladle treatment + die casting', and reduces the peroxidation degree of the molten steel in the oxygen blowing and decarbonization process and the addition of the later-stage reducing agent by strictly controlling the components and the temperature of the AOD molten steel entering the furnace; adding aluminum ingot for deep deoxidation before Ti alloying in AOD refining furnace to reduce SiO in steel2MnO inclusion content is reduced, total oxygen content in molten steel is reduced, and TiO content after Ti alloying is reducedxThe possibility of the occurrence of inclusions of MnO type; ti alloying is carried out before AOD steel tapping, and the homogenization of Ti element in molten steel is promoted in the slag steel mixing process; after AOD tapping, feeding a calcium-silicon wire into a steel ladle to melt high-melting-point Al in molten steel2O3-MgO-TiOxModifying the inclusions into low-melting-point inclusions; effectively reduces large-size SiO in stainless steel2-Al2O3MnO-CaO and TiOxThe content of MnO inclusions reduces the layering defects in the stainless steel seamless tube, improves the ultrasonic flaw detection qualification rate of the stainless steel seamless tube, and provides technical support for improving the quality of the stainless steel seamless tube.
Drawings
FIG. 1 is a schematic diagram showing the delamination defect of a TP321 stainless steel seamless tube.
FIG. 2 is a diagram showing a layered defect inclusion of a TP321 stainless steel seamless pipe; (a) the side surface of the delamination defect, and (b) the surface of the delamination defect.
Detailed Description
Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that technical features or combinations of technical features described in the following embodiments should not be considered as being isolated, and they may be combined with each other to achieve better technical effects. In the drawings of the embodiments described below, the same reference numerals appearing in the respective drawings denote the same features or components, and may be applied to different embodiments.
The embodiment of the invention provides a smelting process for reducing the layering defect of a TP321 stainless steel seamless tube, which comprises the following steps:
s1, providing crude molten steel by an electric arc furnace: controlling the components of the AOD molten steel entering the furnace and the temperature of the molten steel to set values;
s2, AOD oxygen blowing decarburization: adding lime and magnesia, controlling the end point w C not more than 0.06%; supplementing high-carbon ferrochrome and electrolytic manganese during the period;
s3, AOD ferrosilicon reduction: adding lime and ferrosilicon, introducing argon, and stirring; after reduction, slagging-off is thorough in the AOD furnace, and the residue amount is less than 20kg of ton steel;
s4, deep deoxidation of AOD aluminum; adding lime, fluorite and aluminum ingot, introducing argon, stirring, and controlling w [ Al ] in the molten steel to be 0.05-0.06%;
s5, tapping after AOD titanium alloying: adding ferrotitanium alloy, and controlling w [ Ti ] in the molten steel to be 0.40-0.45%; after the components are qualified, mixing the AOD slag steel;
s6, steel ladle soft stirring and calcium treatment: feeding a calcium-silicon wire to the molten steel;
s7, die casting: argon is adopted for protection in the whole process, and die casting protective slag is added to prevent secondary oxidation.
Preferably, in step S1, the AOD is controlled to be charged into the molten steel w [ C ] > 2.0%, w [ Si ] > 0.4-0.5%, w [ Mn ] > 0.8-0.9%, w [ Cr ] > 16.0-16.5%, w [ Ni ] > 9.5-10.0%, and the temperature of the molten steel is not lower than 1470 ℃, which provides favorable conditions for the subsequent AOD oxygen decarburization and reduction.
Preferably, when a 20t AOD refining furnace is adopted, 1500 plus or minus 100kg lime and 200 plus or minus 50kg magnesium oxide are added in the step S2; during the period, 800 plus or minus 50kg of high-carbon ferrochrome and 60 plus or minus 5kg of electrolytic manganese are supplemented, so that the pressure for supplementing alloy and adjusting components in the reduction period is reduced.
Preferably, in step S3, lime 300 + -50 kg and ferrosilicon 450 + -50 kg are added, and the argon flow rate is controlled to 10-15Nm3Min, stirring for 8-12min, controlling W [ Si ] in molten steel](0.3-0.5)%, promotes the reaction between ferrosilicon and slag and molten steel, and promotes SiO2Floating removal of MnO inclusions; after the ferrosilicon reduction is completed, AODThe slag skimming in the furnace needs to be thorough, and the residual slag amount is less than 20kg of ton steel.
Preferably, in step S4, lime 300 + -50 kg, fluorite 140 + -10 kg, aluminum ingot 150 + -10 kg and argon gas flow rate is controlled to 10-15Nm3Min, stirring for 8-12min to speed the smelting of aluminum ingot and the homogenization of molten steel components and control W [ Al ] in molten steel]0.05-0.06% of SiO in steel2MnO inclusion content is reduced, total oxygen content in molten steel is reduced, and TiO content after Ti alloying is reducedxPossibility of occurrence of inclusion of MnO type.
Preferably, in step S6, a wire feeder is used for feeding calcium silicate wire into molten steel, the feeding amount of pure calcium is 0.2-0.8 kg per ton of steel, and high-melting-point Al in modified molten steel2O3-MgO-TiOxImpurities; the flow rate of argon gas is controlled to be 0.1-0.2 Nm3And/min, soft stirring to promote floating removal of the inclusion.
Preferably, in step S7, casting is started when the temperature of the molten steel is reduced to 1510 ± 10 ℃, and in the casting process, the whole process of the nozzle is protected by argon gas; the method adopts a lower pouring method die casting mode, and die casting protective slag is added at the bottom of the die, so that the secondary oxidation caused by the direct contact of molten steel and air is prevented.
Preferably, in step S2, w [ Cr ] is not less than 52%, w [ C ] is not more than 10.0%, and w [ Si ] is not more than 5.0%.
Preferably, in step S3, w [ Si ] in the ferrosilicon is 72.0 to 80.0%, and w [ Al ] is 2.0% or less.
Preferably, in step S5, w [ Ti ] ≦ 65.0 to 75.0%, w [ Si ] ≦ 3.50%, and w [ Al ] ≦ 6.0% in the ferrotitanium alloy.
The present invention will be further described below by way of comparative examples and specific examples. The comparative example and the embodiment both adopt the process route of 'electric arc furnace +20t AOD refining furnace + ladle treatment + die casting' to produce TP321 stainless steel cast ingots, and the stainless steel seamless tubes are obtained through subsequent forging and tube penetration.
Comparative example
(1) The electric arc furnace provides crude molten steel: the raw materials of the electric arc furnace comprise scrap steel and return materials, and the components of crude molten steel obtained by melting before tapping are shown in table 1, namely the components of AOD molten steel entering the furnace; after the AOD is put into the furnace, the temperature of the molten steel is detected to be 1480 ℃.
(2) AOD oxygen blowing decarburization: adding 300kg of lime and 50kg of magnesium oxide at the bottom of the AOD furnace, and slagging off after molten steel is put into the furnace and oxygen is blown for 3 min; adding 1500kg of lime and 200kg of magnesium oxide into the furnace, continuously adjusting the flow of oxygen-argon, blowing oxygen for decarburization, and supplementing 920kg of high-carbon ferrochrome during decarburization; after the completion of decarburization, the molten steel had the composition shown in Table 1.
(3) AOD reduction slagging-off: continuously blowing oxygen for decarburization for 6 min; then adding 250kg of ferrosilicon, 120kg of aluminum ingot, 85kg of electrolytic manganese and 300kg of lime into the furnace, and controlling the argon flow to be 15Nm3The melting of the alloy and the homogenization of the molten steel components are accelerated, the reaction between the ferrosilicon and the aluminum ingot and between the slag and the molten steel is promoted, and the floating removal of inclusions is promoted; and after 15min, slagging off in an AOD furnace.
(4) Tapping after AOD titanium alloying: after slagging off is finished, 42kg of micro-carbon ferrochrome, 30kg of ferrosilicon, 30kg of aluminum ingot, 40kg of ferrotitanium, 300kg of lime and 140kg of fluorite are added into the furnace, and the argon flow is controlled to be 15Nm3Min, accelerating the melting of the alloy and the homogenization of the components of the molten steel, and accelerating the slagging; after 4min, 360kg of ferrotitanium is added, AOD slag steel is mixed out after the component detection is qualified, and the components of AOD tapping molten steel are shown in Table 1.
(5) Steel ladle soft stirring: on the die casting platform, argon is blown into the ladle, and the flow of the argon is controlled to be 0.1-0.2 Nm3And/min, soft stirring to promote floating removal of the inclusion.
(6) Die casting and casting: when the temperature of the steel ladle molten steel is reduced to about 1510 ℃, casting is started; in the casting process, the whole process of the water gap is protected by argon; a lower pouring method die casting mode is adopted, and die casting protective slag is added at the bottom of the die, so that secondary oxidation caused by direct contact of molten steel and air is prevented; the composition of the molten steel before the end of casting is shown in Table 1.
Table 1 example 1 molten steel composition change in the smelting process,% by mass
| C | Si | Mn | P | S | Cr | Ni | Ti | Al | Ca | O | N | |
| AOD furnace | 0.96 | 0.88 | 0.85 | 0.03 | 0.012 | 15.6 | 9.5 | |||||
| After AOD decarburization | 0.11 | - | 0.52 | 0.03 | 0.01 | 16.6 | 10.4 | 0.048 | 0.016 | |||
| Before AOD tapping | 0.059 | 0.37 | 1.12 | 0.03 | 0.001 | 18.3 | 9.6 | 0.51 | 0.026 | 0.0007 | 0.0022 | 0.016 |
| Before the steel casting is finished | 0.057 | 0.4 | 1.12 | 0.03 | 0.002 | 18.5 | 9.6 | 0.46 | 0.023 | 0.0005 | 0.002 | 0.013 |
Examples
(1) The electric arc furnace provides crude molten steel: raw materials of the electric arc furnace comprise scrap steel and return materials, and the components of crude molten steel obtained after melting are shown in table 2, namely the components of AOD molten steel entering the furnace; the composition of the molten steel after the AOD is charged is detected to be 1475 ℃.
(2) AOD oxygen blowing decarburization: after molten steel is put into a furnace, adding 1500kg of lime, 200kg of magnesium oxide and oxygen-argon mixed blowing for decarburization, gradually adjusting the flow of the oxygen-argon and reducing the burning loss of Cr element in the decarburization process; during the period, 800kg of high carbon ferrochrome and 60kg of electrolytic manganese are supplemented; after the completion of decarburization, the molten steel had the composition shown in Table 2.
(3) AOD ferrosilicon reduction: adding 300kg of lime and 450kg of ferrosilicon into the furnace, and controlling the flow of argon to be 15Nm3Stirring for 10min to speed the smelting of ferrosilicon and the homogenization of molten steel components, promote the reaction between ferrosilicon and slag and molten steel and promote SiO reaction2Floating and removing the similar impurities; and after the ferrosilicon reduction is finished, slagging off in the AOD furnace.
(4) Deep deoxidation of AOD aluminum: after slagging off is finished, 300kg of lime, 140kg of fluorite and 150kg of aluminum ingot are added into the furnace, and the argon flow is controlled to be 15Nm3Stirring for 10min to accelerate the melting of aluminum ingot and the homogenization of molten steel components, promote the reaction between the aluminum ingot and the molten steel and promote Al2O3Removing impurities floating upward to reduce the content of O element in molten steelAmount of the compound (A).
(5) Tapping after AOD titanium alloying: after the deep deoxidation is finished, 200kg of ferrotitanium alloy is added into the furnace; and after the components are detected to be qualified, AOD slag steel is mixed out, and the components of AOD molten steel are shown in Table 2.
(6) Steel ladle soft stirring and calcium treatment: on a die casting platform, a wire feeder is used for feeding calcium-silicon wires into steel ladle molten steel, the feeding amount of pure calcium is 0.2-0.8 kg per ton of steel, and the flow rate of argon is controlled to be 0.1-0.2 Nm3And/min, soft stirring to promote floating removal of the inclusion.
(7) Die casting and casting: when the temperature of the steel ladle molten steel is reduced to about 1510 ℃, casting is started; in the casting process, the whole process of the water gap is protected by argon; a lower pouring method die casting mode is adopted, and die casting protective slag is added at the bottom of the die, so that secondary oxidation caused by direct contact of molten steel and air is prevented; the composition of the molten steel before the end of casting is shown in Table 2.
Table 2 example 2 molten steel composition change in the smelting process,% by mass
| C | Si | Mn | P | S | Cr | Ni | Ti | Al | Ca | O | N | |
| AOD furnace | 2.1 | 0.48 | 0.83 | 0.03 | 0.015 | 16.3 | 9.8 | |||||
| After AOD decarburization | 0.05 | - | 0.79 | 0.03 | 0.012 | 17.6 | 10.1 | 0.042 | 0.012 | |||
| Before AOD tapping | 0.051 | 0.42 | 1.08 | 0.03 | 0.002 | 18.5 | 9.8 | 0.45 | 0.058 | 0.0006 | 0.0025 | 0.011 |
| Before the steel casting is finished | 0.05 | 0.43 | 1.08 | 0.03 | 0.002 | 18.6 | 9.8 | 0.43 | 0.052 | 0.0023 | 0.0018 | 0.0098 |
Example the invention is adopted to reduce the layering defect of the TP321 stainless steel seamless tubeThe smelting process. Comparing the comparative example with the example, it is found that before Ti alloying, Al element content in the molten steel is low, molten steel deoxidation is insufficient, yield of ferrotitanium in the titanium alloying process is low, and SiO with high melting point generated in the molten steel2-Al2O3MnO-CaO and TiOxMnO inclusions are difficult to remove, and layering defects are formed in the processes of forging and tube penetrating, so that the ultrasonic flaw detection yield of the seamless tube is low. In the embodiment, the composition and the temperature of the AOD molten steel entering the furnace are strictly controlled, so that the pressure of the AOD in the processes of oxygen blowing, decarburization and reduction is reduced; the Al element content in the molten steel is reasonably controlled by deep deoxidation, the O element content in the molten steel is reduced, and the yield of ferrotitanium during titanium alloying is improved; the Ca content in the molten steel is reasonably controlled by the calcium treatment of the steel ladle, the quantity of high-melting-point inclusions is reduced, the possibility of occurrence of large-size inclusion clusters and layering defects is reduced, and the qualification rate of ultrasonic flaw detection of the stainless steel seamless pipe is improved from about 80 percent to over 95 percent.
On one hand, aluminum is utilized for deep deoxidation before Ti alloying in the AOD refining furnace, the deep deoxidation of the aluminum element content in molten steel is strictly controlled, and the content of large-size SiO2-Al2O3-MnO-CaO and TiOx-MnO inclusions is reduced; on one hand, the steel ladle is fed with calcium-silicon wires to reduce the content of high-melting-point Al2O3-MgO-TiOx inclusions.
While several embodiments of the present invention have been presented herein, it will be appreciated by those skilled in the art that changes may be made to the embodiments herein without departing from the spirit of the invention. The above examples are merely illustrative and should not be taken as limiting the scope of the invention.
Claims (10)
1. A smelting process for reducing the layering defects of a TP321 stainless steel seamless tube is characterized by comprising the following steps:
s1, providing crude molten steel by an electric arc furnace: controlling the components of the AOD molten steel entering the furnace and the temperature of the molten steel to set values;
s2, AOD oxygen blowing decarburization: adding lime and magnesia, controlling the end point w C not more than 0.06%; supplementing high-carbon ferrochrome and electrolytic manganese during the period;
s3, AOD ferrosilicon reduction: adding lime and ferrosilicon, introducing argon, and stirring; after reduction, slagging-off is thorough in the AOD furnace, and the residue amount is less than 20kg of ton steel;
s4, deep deoxidation of AOD aluminum; adding lime, fluorite and aluminum ingot, introducing argon, stirring, and controlling w [ Al ] in the molten steel to be 0.05-0.06%;
s5, tapping after AOD titanium alloying: adding ferrotitanium alloy, and controlling w [ Ti ] in the molten steel to be 0.40-0.45%; after the components are qualified, mixing the AOD slag steel;
s6, steel ladle soft stirring and calcium treatment: feeding a calcium-silicon wire to the molten steel;
s7, die casting: argon is adopted for protection in the whole process, and die casting protective slag is added to prevent secondary oxidation.
2. A smelting process for reducing the delamination defect of a TP321 stainless steel seamless tube as claimed in claim 1, wherein in step S1, the AOD is added into the molten steel, w [ C ] is not less than 2.0%, w [ Si ] is 0.4-0.5%, w [ Mn ] is 0.8-0.9%, w [ Cr ] is 16.0-16.5%, w [ Ni ] is 9.5-10.0%, and the temperature of the molten steel is not lower than 1470 ℃.
3. A smelting process for reducing the delamination defect of a TP321 stainless steel seamless tube according to claim 1, wherein when a 20t AOD refining furnace is used, in step S2, 1500 ± 100kg of lime and 200 ± 50kg of magnesium oxide are added; during the period, 800 plus or minus 50kg of high-carbon ferrochrome and 60 plus or minus 5kg of electrolytic manganese are supplemented.
4. The Ti alloying process for reducing the delamination defect of a TP321 stainless steel seamless tube according to claim 3, wherein in the step S3, lime 300 + -50 kg, ferrosilicon 450 + -50 kg and argon gas flow rate are controlled to 10-15Nm3Min, stirring for 8-12min, controlling W [ Si ] in molten steel]＝(0.3-0.5)％。
5. The Ti alloying process for reducing the delamination defect of the TP321 stainless steel seamless tube as claimed in claim 3, wherein in the step S4, lime 300 + -50 kg, fluorite 140 + -10 kg, aluminum ingot 150 + -10 kg and argon gas flow rate is controlled to 10-15Nm3The stirring time is 8-12minControlling w [ Al ] in molten steel]＝0.05～0.06％。
6. The Ti alloying process for reducing the delamination defect of the TP321 stainless steel seamless tube as claimed in claim 3, wherein in step S6, Si-Ca wire is fed into the molten steel by a wire feeder, and the feeding amount of pure calcium is 0.2-0.8 kg per ton of steel; the flow rate of argon gas is controlled to be 0.1-0.2 Nm3/min。
7. The Ti alloying process for reducing the delamination defect of a TP321 stainless steel seamless tube as claimed in claim 3, wherein in step S7, the casting is started after the temperature of the molten steel is decreased to 1510 ± 10 ℃.
8. A Ti alloying process for reducing the delamination defect of TP321 stainless steel seamless tube according to claim 1 or 3 wherein in step S2 w [ Cr ] ≦ 52%, w [ C ] ≦ 10.0%, w [ Si ] ≦ 5.0%.
9. A Ti alloying process for reducing the delamination defect of a seamless tube of TP321 stainless steel as claimed in claim 1 or 4 wherein in step S3, w [ Si ] in Si-Fe is 72.0-80.0%, w [ Al ] is 2.0% or less.
10. A Ti alloying process for reducing the delamination defect of a TP321 stainless steel seamless tube as claimed in claim 1, wherein in step S5, w [ Ti ] ≦ 3.50% w [ Si ] ≦ 6.0% w [ Al ] ≦ 65.0-75.0%.
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