Smelting method of low-aluminum high-titanium welding wire steel

Abstract

The invention discloses a smelting method of low-aluminum high-titanium welding wire steel. The smelting method comprises a converter smelting stage, an LF refining stage and a continuous casting stage. In the converter smelting stage, the converter smelting end point molten steel temperature, the P content, the C content and the [O] content are controlled, then converter turning-down tapping is carried out, and alloying is carried out in the tapping process; in the LF refining stage, lime and fluorite are added into a steel ladle for slagging, calcium carbide is adopted for deoxidation, and the target alkalinity, the content of dissolved [O] in steel and the temperature of molten steel are controlled; titanium wires are fed multiple times in stages according to different titanium targets, when the titanium wires are fed every time, the temperature of molten steel is correspondingly increased, and dissolved [O] in calcium carbide deoxidation control steel is correspondingly reduced. According to the scheme, generation of titanium inclusions in the smelting process can be reduced, the production stability of the low-aluminum high-titanium welding wire steel is improved, and the production cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel metallurgy, and particularly relates to a smelting method of low-aluminum high-titanium welding wire steel. BACKGROUND

[0002] Low-aluminum high-titanium welding steel is based on ordinary welding steel and adds titanium elements, which can reduce spatter by 30%-50%, the plasticity and toughness of the welding metal are good, the arc is easy to start and restart, the arc is stable and soft, and the welding appearance is beautiful. With the continuous progress of the welding wire market, the demand for high-end welding wire materials such as titanium-containing welding wire is increasing, among which high-titanium special welding (Ti>0.16%) is used as welding material for automobiles and high-rise buildings, and becomes the mainstream product in the market.

[0003] The production difficulty of low-aluminum high-titanium special welding mainly lies in the high titanium content and the low aluminum content. The aluminum deoxidization process cannot be used, and titanium is a relatively active element, which is easy to react with oxygen and nitrogen. If the molten steel is not fully deoxidized or the protection casting is not good, the titanium in the steel is easy to oxidize and nitride, generating a large amount of titanium inclusions, which deteriorates the purity of the molten steel, causing problems such as nozzle clogging and crystallizer clogging in the subsequent casting process.

[0004] At present, the low-aluminum high-titanium welding steel is produced by the traditional process, and titanium or titanium wire is fed during the refining process. The oxygen content is high before the wire feeding, and a large amount of titanium inclusions are produced, resulting in a titanium recovery rate of only about 30%. At the same time, during the casting process, the titanium inclusions in the steel enter the protective slag, affecting the viscosity and crystallization behavior of the protective slag, and thus destroying the metallurgical function of the protective slag, causing the continuous casting billet to be prone to defects such as depression, cracks and slag inclusion.

[0005] After searching, the invention with the publication number CN112011718A uses high-purity alloy and feeds titanium wire in the late refining process, which has high production cost and low titanium recovery rate. The invention with the publication number CN104278197A uses an electric furnace to remove slag, and a new slag-making process, which has low titanium recovery rate and realizes smooth continuous casting of more than 3 furnaces.

[0006] In summary, the current process for producing low-aluminum high-titanium welding steel cannot guarantee stable production, and there are problems such as high production cost and poor quality of the casting billet. In order to promote the stable production of low-aluminum high-titanium welding steel and solve the problem of high production cost, it is necessary to explore a suitable smelting method for low-aluminum high-titanium welding steel.

[0007] The above information disclosed in the background of the present application is only used to increase the understanding of the background of the present application, and therefore, it can include prior art known by those skilled in the art. SUMMARY

[0008] In view of the problems pointed out in the background art, the present application proposes a smelting method of low-aluminum high-titanium welding wire steel, which can reduce the generation of titanium inclusions in the smelting process, improve the production stability of low-aluminum high-titanium welding wire steel, and reduce the production cost.

[0009] To achieve the above-mentioned application purposes, the present application adopts the following technical solutions:

[0010] In some embodiments of the present application, a smelting method of low-aluminum high-titanium welding wire steel is provided, which includes a converter smelting stage, an LF refining stage, and a continuous casting stage.

[0011] In the converter smelting stage, the converter smelting endpoint molten steel temperature, P content, C content, and [O] content are controlled, and then the furnace is tapped, and alloying is performed during the tapping process.

[0012] In the LF refining stage, lime and fluorite are added to the ladle for slagging, calcium carbide is used for deoxidation, the target basicity, dissolved [O] content in the steel, and molten steel temperature are controlled, and titanium wire is fed multiple times according to different titanium targets in stages. When titanium wire is fed each time, the molten steel temperature is correspondingly raised, and the calcium carbide deoxidation controls the dissolved [O] in the steel to correspondingly decrease.

[0013] In some embodiments of the present application, in the LF refining stage, the initial control of the dissolved [O] in the steel is ≤0.0020%, and the molten steel temperature is controlled to be 1550-1570℃; the titanium wire is fed according to the titanium target of 0.10%, the temperature is raised to 1560-1580℃, and the calcium carbide deoxidation controls the dissolved [O] in the steel to be ≤0.0015%; the titanium wire is fed according to the titanium target of 0.15%, the temperature is raised to 1570-1590℃, and the calcium carbide deoxidation controls the dissolved [O] in the steel to be ≤0.0010%; the titanium wire is fed according to the titanium target of 0.20%, the temperature is raised to 1580-1600℃, and the calcium carbide deoxidation controls the dissolved [O] in the steel to be ≤0.0005%; the titanium wire is fed according to the titanium target of 0.25-0.30%, the temperature is raised to 1590-1610℃, soft blowing is performed for 5-10 minutes, carbonized rice husk is added for heat preservation, and the ladle is lifted to the continuous casting station.

[0014] In some embodiments of the present application, in the LF refining stage, the composition is fine-tuned according to the target composition of the molten steel after entering the LF station, then 800-1000kg of lime and 200-300kg of fluorite are added to the ladle for slagging, and the target basicity is controlled to be 2.0-2.5.

[0015] In some embodiments of the present application, in the LF refining stage, the process argon flow is controlled at 120-180NL / min, and the molten steel surface is not exposed.

[0016] In some embodiments of the present application, in the converter smelting stage, the converter smelting endpoint molten steel temperature is controlled to be 1580-1600℃, the P content is ≤0.030%, the C content is 0.03%-0.05%, and the [O] is ≤0.060%.

[0017] In some embodiments of the present application, during the tapping of the converter, high-silicon silicon-manganese and low-carbon ferromanganese are added to the molten steel at 1 / 2 of the tapping to perform alloying according to the target components of silicon and manganese of the converter steel.

[0018] In some embodiments of the present application, in the converter smelting stage, no post-blowing operation is performed, and a front and middle stage tapping hole is used.

[0019] In some embodiments of the present application, in the continuous casting stage, the cross section of the casting blank is 150*150mm-200*200mm, full-process protective casting is used, the superheat is 25-40℃, the pulling speed is 1.5-2.5m / min, the crystallizer water quantity is 140-180m 3 / h, the secondary cooling specific water quantity is 1.00-1.40L / kg, the crystallizer electromagnetic stirring current is 180-220A, the frequency is 3-5Hz, the terminal electromagnetic stirring current is 300A, and the frequency is 8Hz.

[0020] In some embodiments of the present application, in the continuous casting stage, the protective casting measures such as full-steel liquid surface covering of covering agent and rice husk and use of an integrated water gap are used.

[0021] In some embodiments of the present application, in the continuous casting stage, the [N] is controlled to be ≤0.0040%.

[0022] Compared with the prior art, the present application has the following advantages and positive effects:

[0023] The smelting method of the low-titanium high-aluminum welding wire steel can stably control the titanium content to be 0.20-0.30%, and the titanium recovery rate is ≥80%.

[0024] The smelting method of the low-titanium high-aluminum welding wire steel generates Ti2O3 and Ti3O5 under different [O] content conditions, adjusts the titanium content by using a refining segmented titanium wire feeding, gradually reduces the oxygen content in the steel, avoids the generation conditions of Ti2O3 and Ti3O5, effectively controls the generation of titanium oxide inclusions, solves the problems of nozzle clogging, crystallizer clogging, and low titanium recovery rate, and the continuous casting furnace number can reach 12.

[0025] The smelting method of the low-titanium high-aluminum welding wire steel is a smelting method with simple process and easy control, realizes stable control of the components of the low-aluminum high-titanium welding wire steel, greatly improves the stable casting performance and titanium element recovery rate of the low-aluminum high-titanium welding wire steel, and reduces the production cost.

[0026] The smelting method of the low-titanium high-aluminum welding wire steel of the present application needs only conventional smelting equipment, without additional process and equipment.

[0027] Other features and advantages of the present application will become more apparent from the following detailed description of the application when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0029] Figure 1 Gibbs free energy change calculation for Ti2O3, Ti3O5 formation of Ti at [O]=15ppm;

[0030] Figure 2 Gibbs free energy change calculation for Ti2O3, Ti3O5 formation of Ti at [O]=10ppm;

[0031] Figure 3 Gibbs free energy change calculation for Ti2O3, Ti3O5 formation of Ti at [O]=5ppm;

[0032] Figure 4 Calculation of [N] content in steel for TiN inclusion precipitation temperature. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0034] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0035] The terms "first", "second", etc. are used to describe various components only and do not imply or suggest relative importance or a specific number of the technical features indicated. Thus, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0036] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0037] In the present application, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "upper", "above" and "on" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The "lower", "below" and "under" of the first feature to the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0038] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. For the purpose of simplifying the present application, the components and arrangements of specific examples are described in the following. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to numbers and / or letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or arrangements discussed. In addition, the present application provides various specific examples of processes and materials, but those skilled in the art can realize the application of other processes and / or the use of other materials.

[0039] In some embodiments of the present application, a smelting method of low-aluminum high-titanium welding wire steel is provided, and the chemical composition of the low-aluminum high-titanium welding wire steel is as follows in terms of mass percentage: C: 0.05%-0.10%, Si: 0.50%-0.80%, Mn: 1.40%-1.80%, P: 0.010%-0.030%, S: 0.010%-0.030%, Ti: 0.20%-0.30%, Al: ≤0.010%, N: ≤0.004%, and the balance is Fe and inevitable impurities.

[0040] The smelting method of the low-aluminum high-titanium welding wire steel comprises a converter smelting stage, an LF refining stage and a continuous casting stage.

[0041] In the converter smelting stage, the converter smelting end-point molten steel temperature, P content, C content and [O] content are controlled, and then the molten steel is tapped, and alloying is performed during the tapping process.

[0042] In the LF refining stage, lime and fluorite are added into a ladle for slagging, calcium carbide is used for deoxidation, and the target basicity, dissolved [O] content in the steel and molten steel temperature are controlled; titanium wires are fed in multiple stages and multiple times according to different titanium targets, and the molten steel temperature is correspondingly increased and the dissolved [O] content in the steel is correspondingly decreased each time the titanium wire is fed.

[0043] The smelting method of the low-titanium high-aluminum welding wire steel can stably control the titanium content to be 0.20-0.30% and the titanium recovery rate to be greater than or equal to 80%.

[0044] The smelting method of the low-titanium high-aluminum welding wire steel generates Ti2O3 and Ti3O5 under different [O] content conditions, adjusts the titanium content by using a refining segmented titanium wire feeding process, gradually reduces the oxygen content in the steel, avoids the generation conditions of Ti2O3 and Ti3O5, effectively controls the generation of titanium oxide inclusions, solves the problems of nozzle clogging, mold clogging and low titanium recovery rate, and the continuous casting furnace number can reach 12.

[0045] The smelting method of the low-titanium high-aluminum welding wire steel is a smelting method with simple process and easy control, realizes stable control of the composition of the low-aluminum high-titanium welding wire steel, greatly improves the stable casting performance and titanium element recovery rate of the low-aluminum high-titanium welding wire steel, and reduces the production cost.

[0046] The smelting method of the low-titanium high-aluminum welding wire steel requires only conventional smelting equipment without additional process and equipment.

[0047] Compared with the prior art, the advantages and positive effects of the present application are as follows:

[0048] The titanium element recovery rate is greatly improved, and the production cost is reduced. In the prior art, the low-aluminum high-titanium welding wire steel production has a high oxygen content before feeding the wire, titanium is easily reacted with oxygen to generate a large amount of inclusions, the titanium recovery rate is only about 30%, the titanium-iron or titanium wire consumption is large, and the production cost is high. The smelting method of the low-titanium high-aluminum welding wire steel of the present application adopts a segmented titanium wire feeding process in the LF refining stage, cooperates with a stepwise temperature increase and a gradual reduction of the dissolved oxygen content in the steel, avoids the generation conditions of Ti2O3, Ti3O5 and other titanium inclusions, and makes the titanium element recovery rate increase to more than 80%. This improvement significantly reduces the consumption of titanium alloy, directly reduces the cost of raw materials, reduces the scrap rate caused by inclusions, and further reduces the comprehensive production cost.

[0049] Effectively control the generation of titanium inclusions, improve the purity of molten steel and the quality of the billet. In the prior art, the oxidation and nitridation reaction of titanium generates a large number of inclusions, which not only deteriorates the purity of molten steel, but also causes nozzle clogging, mold clogging during continuous casting, and defects such as concave, crack, and slag inclusion in the billet. The present application solves this problem by the following measures:

[0050] (1) Strictly control the oxygen content at the end of the converter to reduce the oxidation of titanium by initial oxygen;

[0051] (2) Adopt calcium deoxidation instead of traditional aluminum deoxidation in the LF refining stage to avoid the problem of insufficient deoxidation under low aluminum conditions;

[0052] (3) Precisely match the temperature and oxygen content when feeding titanium wire in sections to fundamentally inhibit the reaction of titanium with oxygen and nitrogen.

[0053] The above measures effectively reduce the generation of titanium inclusions, significantly improve the purity of molten steel, avoid continuous casting failures such as nozzle clogging and mold clogging, greatly reduce the defect rate of continuous casting billet, and significantly improve the stability of product quality.

[0054] Improve production stability and continuity, and improve production efficiency. In the prior art, continuous casting is prone to interruption due to excessive inclusions, making it difficult to achieve stable continuous casting (such as some processes can only continuously cast more than 3 furnaces). The present application controls the generation of inclusions and optimizes the continuous casting protection measures (full protection casting, full liquid surface coverage of covering agent, etc.), improves the flowability of molten steel and the stability of the continuous casting process, and the number of continuous casting furnaces can reach more than 12. The improvement of production continuity greatly reduces the downtime and start-up cost caused by interrupted casting, improves equipment utilization and production efficiency

[0055] Simple and easy to control process, no additional equipment, easy to popularize and apply: In the prior art, some processes need to use high-purity alloy or additional slagging process, which not only increases the cost, but also increases the process complexity. The present application is based on the conventional smelting equipment of converter, LF refining and continuous casting, without the need for additional processes or equipment, and only by optimizing the process parameters of each link (such as end composition, temperature, deoxidation method, wire feeding system, etc.) can realize stable production. The process is simple and easy to control, and has strong adaptability to existing production lines, which is convenient for steel enterprises to quickly popularize and apply.

[0056] In some embodiments of the present application, during the LF refining stage, the initial control of the dissolved [O] in the steel is ≤0.0020%, and the temperature of the molten steel is controlled at 1550-1570℃;

[0057] Titanium wire is fed according to the titanium target of 0.10%, the temperature is raised to 1560-1580℃, and the calcium deoxidation controls the dissolved [O] in the steel to be ≤0.0015%, according to Figure 1 ;

[0058] Ti target 0.15%, Ti wire feeding, temperature rising to 1570-1590℃, calcium deoxidation to control dissolved [O] in steel ≤0.0010%, reference Figure 2 ;

[0059] Ti target 0.20%, Ti wire feeding, temperature rising to 1580-1600℃, calcium deoxidation to control dissolved [O] in steel ≤0.0005%, reference Figure 3 ;

[0060] Ti target 0.25-0.30%, Ti wire feeding, temperature rising to 1590-1610℃, soft blowing for 5-10 minutes, adding carbonized rice husk, holding and hanging the ladle to the continuous casting station.

[0061] In the LF refining stage of the present application, the above-mentioned segmented Ti wire feeding and the matching stepwise temperature and oxygen control process design are the core links to realize the efficient smelting of low-aluminum high-titanium welding wire steel.

[0062] The initial deoxidation and temperature regulation have the following effects: after entering the LF refining station, first, lime (800-1000 kg) and fluorite (200-300 kg) are added to form slag, and the slag basicity is controlled at 2.0-2.5 to provide a good slag system basis for deoxidation and inclusion absorption. Calcium deoxidation is used to control the initial dissolved oxygen in steel to ≤0.0020%, and the molten steel temperature is stabilized at 1550-1570℃. First, a low-basicity slag system can enhance the adsorption capacity of oxide inclusions in steel, reducing the risk of secondary oxidation of titanium elements by oxygen in the slag after adding titanium; second, calcium deoxidation avoids the problem of excessive aluminum content caused by traditional aluminum deoxidation, while creating a low-oxygen environment for the stable addition of titanium elements in the future; in addition, the initial temperature of 1550-1570℃ can ensure good fluidity of the molten steel, facilitating composition homogenization, and can also avoid the absorption of the molten steel due to high temperature (especially nitrogen absorption), reducing the generation of titanium nitride inclusions.

[0063] The synergistic effect of segmented Ti wire feeding and stepwise temperature and oxygen control has the following effects:

[0064] (1) When the Ti target is 0.10%, the temperature of the molten steel is raised to 1560-1580℃, and the dissolved oxygen is further controlled to ≤0.0015% by calcium deoxidation. The role of this stage is to:

[0065] A lower initial titanium target (0.10%) combined with appropriate temperature increase (10-30℃ higher than the initial temperature) can promote the rapid melting and uniform diffusion of the Ti wire in the molten steel, reducing the oxidation caused by excessive local titanium concentration;

[0066] The decrease of oxygen content from ≤0.0020% to ≤0.0015% can avoid the large amount of reaction between titanium and residual oxygen in the molten steel to generate Ti ·O3, preliminary improve the recovery rate of titanium.

[0067] (2) When feeding titanium wire according to the titanium target of 0.15%, the temperature is raised to 1570-1590℃, and the oxygen content is controlled to ≤0.0010%. The key role of this step is:

[0068] With the increase of titanium content target, further increase the temperature of molten steel (increase by 10-30℃ compared with the previous stage), which can reduce the viscosity of molten steel, promote the mixing of titanium elements and molten steel, and facilitate the floating of fine inclusions generated in the early stage;

[0069] The oxygen content is reduced to ≤0.0010%, which can avoid the main generation interval of Ti3O5, reduce the invalid consumption of titanium, and steadily improve the recovery rate of titanium.

[0070] (3) When feeding titanium wire according to the titanium target of 0.20%, the temperature is raised to 1580-1600℃, and the oxygen content is controlled to ≤0.0005%. The core effect of this stage is:

[0071] Higher temperature (1580-1600℃) ensures the fluidity of molten steel under high titanium content, avoiding the increase of molten steel viscosity caused by the increase of titanium elements;

[0072] Further reducing the oxygen content to ≤0.0005% can maximize the inhibition of titanium oxidation reaction (at this time, the driving force of titanium and oxygen reaction is very low), laying the foundation for the final titanium content of 0.25-0.30%, and reducing the generation of titanium oxide inclusions.

[0073] (4) After feeding titanium wire according to the titanium target of 0.25-0.30%, the temperature is raised to 1590-1610℃ and soft blowing for 5-10 minutes. The effect of this operation is reflected in:

[0074] The highest temperature (1590-1610℃) ensures the fluidity of molten steel under the final titanium content, meeting the requirements of subsequent continuous casting on the temperature of molten steel;

[0075] 5-10 minutes of soft blowing (weak argon stirring) can promote the aggregation and floating of small inclusions in molten steel, which are absorbed by slag, further purifying the molten steel;

[0076] Adding carbonized rice husk insulation can reduce the temperature loss of molten steel from LF to continuous casting, ensuring the stability of the superheat degree during continuous casting.

[0077] Through the above-mentioned coordinated operation of the segmented titanium feeding, the stepped temperature control and the gradual oxygen reduction, the titanium recovery rate can be increased from about 30% in the traditional process to ≥80%, greatly reducing the titanium wire consumption and directly reducing the production cost; effectively avoiding the main generation interval of titanium oxide inclusions such as Ti2O3 and Ti3O5, significantly reducing the content of titanium inclusions in the molten steel, solving the problems of nozzle clogging and crystallizer clogging in the traditional process; the purity of the molten steel is improved, the defect rate of the continuous casting billet such as depression, crack and slag inclusion is reduced, and the product quality stability is improved; combined with full-process protective casting and other measures, the continuous casting furnace number can be stably reached more than 12 furnaces, and the production efficiency is significantly improved.

[0078] In some embodiments of the present application, in the LF refining stage, after entering the LF, the composition is first adjusted according to the target composition of the molten steel, then 800-1000 kg of lime and 200-300 kg of fluorite are added to the ladle for slagging, and the target basicity is controlled at 2.0-2.5.

[0079] After entering the LF, the composition is first adjusted according to the target composition of the molten steel, which can ensure that the content of basic alloy elements such as silicon and manganese in the molten steel is close to the target value before entering the slagging and titanium feeding link, avoiding the interference of the subsequent slagging or titanium feeding process due to the fluctuation of the basic composition, laying a uniform composition foundation for the stable addition and precise control of titanium elements, and reducing the problem of titanium reaction stability caused by composition deviation.

[0080] As the main slagging agent, lime with high CaO content can provide sufficient basic oxides, which can neutralize the acidic oxides in the molten steel on the one hand, reducing the risk of secondary oxidation of the molten steel; on the other hand, it can provide a carrier for the adsorption of titanium inclusions in the steel, and through the slag-steel interface reaction, the inclusions are transferred to the slag.

[0081] As a fluxing agent, fluorite can effectively reduce the melting point of lime and improve the fluidity of the slag, ensuring that lime can fully participate in the slagging reaction and avoiding the decrease of the deoxidation and inclusion adsorption capacity caused by the over-thickening of the slag. At the same time, the addition amount of fluorite is controlled at 200-300 kg, which can avoid the excessive addition of fluorite leading to the excessive slagging caused by the sharp decrease of the viscosity of the slag, and prevent the excessive erosion of the slag to the ladle lining.

[0082] The slag basicity is controlled in the range of 2.0-2.5, which is a precise design for the smelting requirements of low-aluminum high-titanium welding wire steel. First, the slag with this basicity range has strong desulfurization and deoxidation capacity, which can further reduce the dissolved oxygen content in the molten steel in cooperation with the calcium carbide deoxidation. Secondly, the basicity of 2.0-2.5 can make the slag maintain appropriate surface tension and viscosity, which can not only capture the fine titanium inclusions generated in the steel through physical adsorption, but also stabilize them in the slag through chemical action, preventing the inclusions from re-entering the molten steel. This effect can significantly reduce the problems of nozzle clogging and crystallizer clogging caused by inclusions in the subsequent continuous casting process.

[0083] In some embodiments of the present application, during the LF refining stage, the process argon flow rate is controlled at 120-180 NL / min, without exposing the molten steel surface.

[0084] The setting of this argon flow rate range is based on the precise matching requirements of the low-aluminum high-titanium welding wire steel for molten steel stirring intensity and protection effect. The argon flow rate of 120-180 NL / min can form a moderate bottom blowing stirring effect, which can not only promote the full contact of molten steel and slag, accelerate the escape of calcium deoxidation products, and accelerate the adsorption reaction of lime-fluorite slag system on inclusions, but also ensure the rapid melting and diffusion of the titanium wire fed in sections in the molten steel, avoiding the selective oxidation caused by excessive local titanium concentration, and providing kinetic guarantee for stabilizing the titanium content at 0.20-0.30%.

[0085] In some embodiments of the present application, during the converter smelting stage, the molten steel temperature at the end of the converter smelting is controlled at 1580-1600℃, the P content is ≤0.030%, the C content is 0.03%-0.05%, and the [O] is ≤0.060%.

[0086] The end temperature is controlled at 1580-1600℃, and this temperature range is the optimal choice considering the molten steel fluidity, subsequent process adaptability and element reaction stability. The temperature of 1580-1600℃ can ensure that the molten steel has appropriate viscosity when the converter is tapped, so that the high-silicon silicon manganese, low-carbon ferromanganese and other alloys added during the tapping process can be quickly melted and uniformly diffused, avoiding incomplete dissolution of the alloys and composition segregation due to too low temperature, and reducing the burden of subsequent LF refining composition fine tuning.

[0087] Phosphorus is a harmful element in welding wire steel, which can easily form low-melting eutectic in the weld, causing hot cracking during welding, and seriously affecting the toughness and plasticity of the weld. Strictly controlling the P content at the end of the converter smelting to ≤0.030% can reduce the residual amount of phosphorus from the source. The converter stage is the main link for dephosphorization, and by controlling the end phosphorus content, the limited dephosphorization capacity of the subsequent LF refining can be avoided, and the welding performance of the welding wire can be ensured.

[0088] The C content is controlled at 0.03%-0.05%, and the setting of this carbon content range is closely related to the composition requirements of low-aluminum high-titanium welding wire steel and the deoxidation process. The present application uses calcium deoxidation, and appropriate carbon content can inhibit the excessive oxidation of carbon during the deoxidation process, ensuring that the calcium deoxidation can steadily reduce the oxygen content in the steel to the target value.

[0089] Titanium is a strong deoxidizing element, and excessive oxygen content at the end of the converter will cause the titanium to react violently with oxygen at the beginning of the LF refining, generating a large amount of titanium oxide inclusions, reducing the titanium recovery rate. Controlling the end point [O]≤0.060%, can significantly reduce the initial oxygen consumption of titanium. This oxygen content level provides a lower initial oxygen basis for the calcium deoxidation in the LF stage, so that the oxygen in the steel can gradually decrease to ≤0.0005% during the subsequent segmented titanium feeding process, effectively avoiding the formation of TiO, Ti3O5, and ensuring the titanium recovery rate to be ≥80%. · The generation conditions of O3 and Ti3O5 lay the key foundation for improving the titanium recovery rate to ≥80%.

[0090] In some embodiments of the present application, during the tapping process, high-silicon silicon manganese and low-carbon ferromanganese are added to the molten steel at 1 / 2 of the tapping process to perform alloying according to the target components of silicon and manganese in the furnace steel.

[0091] At the middle stage of the tapping process, there is a certain amount of molten steel in the ladle. At this time, the high-silicon silicon manganese and low-carbon ferromanganese are added, which can take advantage of the impact and stirring action of the tapping flow to make the alloy quickly disperse in the molten steel, accelerate melting and dissolution. Compared with the initial stage of the tapping process (the amount of molten steel is small, and the alloy is easy to accumulate at the bottom of the ladle) or the final stage (the impact of the molten steel is weakened, and the alloy dissolution efficiency is low), this timing can minimize the undissolved inclusions of the alloy and ensure the uniform distribution of silicon and manganese elements.

[0092] During the tapping process, the molten steel from the converter into the ladle will contact with air, there is a risk of secondary oxidation. Adding alloy at 1 / 2 of the tapping process can take advantage of the high temperature and fluidity of the molten steel at this time to make silicon and manganese elements quickly form a stable solid solution in the molten steel, reduce the element burning loss caused by the subsequent cooling and oxidation of the molten steel, and improve the alloy utilization rate.

[0093] The silicon in high-silicon silicon manganese has a certain deoxidizing ability, which can assist in reducing the oxygen content in the molten steel during the addition process, reduce the pressure of subsequent LF refining calcium deoxidation, and provide supplementary support for the deoxidation process under low aluminum conditions.

[0094] In some embodiments of the present application, during the converter smelting stage, no post-blowing operation is performed, and a front and middle tapping hole is used.

[0095] The post-blowing in the converter smelting refers to the additional oxygen blowing operation performed after the molten steel has reached the end point composition for further carbon reduction or temperature rise. By canceling the post-blowing, the present application can stably control the converter end point [O] to be ≤0.060%, create a low-oxygen basis for the gradual oxygen reduction and segmented titanium feeding in the LF stage, and directly ensure that the titanium recovery rate is improved to ≥80%. Canceling the post-blowing can also significantly reduce the degree of over-oxidation of the molten steel, reduce the deoxidation burden of the subsequent refining, avoid the deterioration of the inclusions to the purity of the molten steel, and lay the foundation for reducing the nozzle clogging and mold clogging during the continuous casting process.

[0096] The converter tapping hole gradually expands with the increase of the use frequency (the tapping hole diameter is larger in the later stage), the front and middle stage tapping hole can reduce the amount of slag entrainment by stable tapping flow state, reduce the risk of molten steel rephosphorization, and reduce the oxidizing substances brought in by the slag, and cooperate with non-back blowing to further reduce the oxygen content of the molten steel.

[0097] In some embodiments of the application, in the continuous casting stage, the casting blank cross section is 150*150mm-200*200mm, full-process protective casting, superheat is 25-40℃, drawing speed is 1.5-2.5m / min, crystallizer water volume is 140-180m 3 / h, secondary cooling specific water volume is 1.00-1.40L / kg, crystallizer electromagnetic stirring current is 180-220A, frequency is 3-5Hz, end electromagnetic stirring current is 300A, frequency is 8Hz.

[0098] The application sets the casting blank cross section to 150*150mm-200*200mm, compared with larger cross section casting blank, the improved size can shorten the solidification time of molten steel in the crystallizer, reduce the aggregation of titanium inclusions at the solidification front (titanium inclusions are easy to float or sink due to density difference in the solidification process), and reduce the risk of center segregation of the casting blank; at the same time, smaller cross section is more conducive to uniform cooling in the secondary cooling zone, reducing thermal stress cracks caused by uneven cooling.

[0099] Full-process protective casting can completely avoid the contact of molten steel with O2 and N2 in the air, prevent the secondary oxidation or nitriding of titanium elements during casting, ensure that the titanium recovery rate is stably ≥80%, and reduce the damage of new inclusions to the purity of molten steel. In addition, protective casting can reduce the fluctuation of molten steel liquid level, avoid the slag inclusion defects caused by slag entrapment (protective slag is entrained into molten steel), and ensure uniform growth of the billet shell in the crystallizer, providing a stable foundation for subsequent cooling and stirring process.

[0100] The superheat of 25-40℃ can ensure good flowability of molten steel in the tundish and nozzle, avoid nozzle blockage (titanium inclusions are easy to adhere to the inner wall of the nozzle at low temperature) caused by insufficient superheat (<25℃). If the superheat is too high (>40℃), the cooling speed of molten steel in the crystallizer slows down, columnar crystals grow quickly and penetrate the casting blank cross section, resulting in center porosity and intensified segregation; and the superheat of 25-40℃ can promote the formation of equiaxed crystals, reduce the enrichment of titanium elements at the grain boundary, and improve the toughness of the casting blank.

[0101] For a cross section of 150*150mm-200*200mm, a drawing speed of 1.5-2.5m / min can ensure the avoidance of the risk of leakage. The crystallizer water volume is 140-180m 3The water amount can ensure that the heat exchange intensity between the copper plate of the crystallizer and the surface of the cast blank is moderate, so that the blank shell is quickly and uniformly formed. If the water amount is insufficient, the blank shell will be thin and the surface temperature will be too high, which will easily cause bulging or longitudinal cracking. If the water amount is too large, the surface temperature of the cast blank will suddenly drop, which will cause transverse cracking or angular cracking, especially for the titanium-containing steel.

[0102] The secondary cooling specific water amount is 1.00-1.40 L / kg. The water mist cooling in the secondary cooling zone further strengthens the solidification of the cast blank. The specific water amount can reasonably distribute the temperature gradient of the cast blank from the surface to the center, so as to avoid too large temperature difference between the surface and the center caused by excessive cooling or delayed center solidification caused by insufficient cooling.

[0103] In some embodiments of the present application, in the continuous casting stage, the covering agent and the rice husk fully cover the molten steel surface, and a whole water gap is used for protection pouring. By constructing a closed oxygen-free environment throughout the whole process, the oxidation and nitridation paths of titanium elements are cut off from the pouring link, and the oxygen and titanium control process in the LF refining stage is cooperated to jointly ensure the stable improvement of titanium recovery rate and the improvement of molten steel purity. At the same time, this measure effectively solves the problems of water gap clogging and crystallizer clogging caused by titanium inclusions in the traditional process, provides a key protection for realizing stable continuous casting of more than 12 heats, and finally reduces the production cost and improves the stability of the cast blank quality.

[0104] In some embodiments of the present application, reference is made to Figure 4 In the continuous casting stage, [N] is controlled to be less than or equal to 0.0040%. By inhibiting the reaction of titanium and nitrogen, the generation of titanium nitride inclusions is fundamentally reduced, which not only ensures the purity of molten steel and the performance of welding wire, but also cooperates with the protection pouring measure to improve the stability of continuous casting, and is an important guarantee for realizing efficient and high-quality production of low-aluminum high-titanium welding wire steel.

[0105] Embodiment 1

[0106] A smelting method of low-titanium high-aluminum welding wire steel, the composition of the welding wire steel is as follows in percentage by mass: 0.06% C, 0.65% Si, 1.50% Mn, 0.015% P, 0.013% S, 0.26% Ti, 0.0032% N,

[0107] 0.0023% Al, and the rest is Fe and inevitable impurities. The smelting method is as follows:

[0108] (1) Converter smelting

[0109] Through 100 t top and bottom combined blowing converter smelting, the end point temperature is 1599 ℃, the P content is 0.015%, the C content is 0.06%, and the [O] content is 0.0568%. Then the molten steel is poured out and according to the target composition of silicon and manganese of the steel, high-silicon silicon manganese and low-carbon ferromanganese are added into the molten steel at 1 / 2 of the tapping time for alloying (the silicon and manganese recovery rates are calculated as 85% and 95% respectively).

[0110] (2) LF refining

[0111] After the LF entry, the composition is first adjusted according to the target composition of the molten steel, then 950 kg of lime and 256 kg of fluorite are added to the ladle for slagging, the refining slag basicity is 2.3, the calcium carbide is used for deoxidation, the dissolved [O] in the steel is ≤0.00198%, the molten steel temperature is 1553°C, 500 m of titanium wire is fed, and the Ti content is 0.110%; the temperature is raised to 1565°C, the calcium carbide is deoxidized, the dissolved [O] in the steel is ≤0.0013%, 250 m of titanium wire is fed, and the Ti content is 0.152%; the temperature is raised to 1571°C, the calcium carbide is deoxidized, the dissolved [O] in the steel is ≤0.009%, 250 m of titanium wire is fed, and the Ti content is 0.201%; the temperature is raised to 1585°C, the calcium carbide is deoxidized, the dissolved [O] in the steel is ≤0.004%, 300 m of titanium wire is fed, and the Ti content is 0.26%; the temperature is raised to 1608°C, soft blowing for 7 minutes, carbonized rice husk is added for holding and the ladle is lifted to the continuous casting position.

[0112] (3) Continuous casting

[0113] The cross section of the casting blank is 150x150 mm, the tundish temperature is 1540°C (TL=1513°C), the withdrawal speed is 2.1 m / min, the crystallizer water quantity is 140 m3 / h, the secondary cooling specific water quantity is 1.00 L / kg, the crystallizer electromagnetic stirring current is 180 A, and the frequency is 5 Hz.

[0114] Technical effect of Example 1: The Ti element recovery rate of the furnace is 83%, 12 furnaces are produced in the pouring process, and no nozzle clogging and crystallizer clogging occurs in the casting process.

[0115] Example 2

[0116] A smelting method of a low-titanium high-aluminum welding wire steel, the composition of the welding wire steel is as follows in mass percent: 0.06% C, 0.67% Si, 1.53% Mn, 0.014% P, 0.015% S, 0.27% Ti, 0.0029% N,

[0117] 0.0033% Al, and the rest is Fe and unavoidable impurities. The smelting method is as follows:

[0118] (1) Converter smelting

[0119] Through 100 t top and bottom combined blowing converter smelting, the end point temperature is 1594°C, the P content is 0.014%, the C content is 0.06%, and the [O] content is 0.0589%. Then the furnace is poured and the steel is tapped, and according to the silicon and manganese target composition of the steel, high-silicon silicon manganese and low-carbon ferromanganese are added to the molten steel at 1 / 2 of the tapping to perform alloying (the silicon and manganese recovery rates are calculated as 85% and 95% respectively).

[0120] (2) LF refining

[0121] After the LF entry, the composition is first adjusted according to the target composition of the molten steel, then 953 kg of lime and 261 kg of fluorite are added to the ladle for slagging, the refining slag basicity is 2.2, calcium carbide is used for deoxidation, the dissolved [O] in the steel is ≤0.00193%, the molten steel temperature is 1555℃, 500 m of titanium wire is fed, and the Ti content is 0.107%; the temperature is raised to 1563℃, calcium carbide is used for deoxidation, the dissolved [O] in the steel is ≤0.0014%, 250 m of titanium wire is fed, and the Ti content is 0.149%; the temperature is raised to 1576℃, calcium carbide is used for deoxidation, the dissolved [O] in the steel is ≤0.0092%, 250 m of titanium wire is fed, and the Ti content is 0.198%; the temperature is raised to 1582℃, calcium carbide is used for deoxidation, the dissolved [O] in the steel is ≤0.0032%, 300 m of titanium wire is fed, and the Ti content is 0.27%; the temperature is raised to 1605℃, soft blowing is carried out for 8 minutes, carbonized rice husk is added for holding, and the ladle is lifted to the continuous casting position.

[0122] (3) Continuous casting

[0123] The cross section of the casting blank is 150x150 mm, the tundish temperature is 1545℃ (TL=1513℃), the withdrawal speed is 2.1 m / min, the crystallizer water quantity is 140 m3 / h, the secondary cooling specific water quantity is 1.00 L / kg, the crystallizer electromagnetic stirring current is 180 A, and the frequency is 5 Hz.

[0124] Technical effect of Example 2: The Ti element recovery rate of the furnace is 85%, 12 furnaces are produced in the pouring process, and no nozzle clogging and crystallizer clogging occurs in the casting process.

[0125] Example 3

[0126] A smelting method of a low-titanium high-aluminum welding wire steel, the composition of the welding wire steel is as follows in terms of mass percentage: 0.06% C, 0.66% Si, 1.51% Mn, 0.015% P, 0.012% S, 0.26% Ti, 0.0035% N,

[0127] 0.0028% Al, and the rest is Fe and unavoidable impurities. The smelting method is as follows:

[0128] (1) Converter smelting

[0129] Through 100 t top and bottom combined blowing converter smelting, the end point temperature is 1598℃, the P content is 0.015%, the C content is 0.06%, and the [O] content is 0.0551%. Then the furnace is tapped and according to the target composition of silicon and manganese of the steel, high-silicon silicon manganese and low-carbon ferromanganese are added to the molten steel at 1 / 2 of the tapping for alloying (the silicon and manganese recovery rates are calculated as 85% and 95% respectively).

[0130] (2) LF refining

[0131] After the LF entry, the composition is first adjusted according to the target composition of the molten steel, then 950 kg of lime and 232 kg of fluorite are added to the ladle for slagging, the refining slag basicity is 2.1, the calcium carbide is used for deoxidation, the dissolved [O] in the steel is ≤0.00191%, the molten steel temperature is 1551℃, 500 m titanium wire is fed, the Ti content is 0.105%; the temperature is raised to 1562℃, the calcium carbide is deoxidized, the dissolved [O] in the steel is ≤0.0014%, 250 m titanium wire is fed, the Ti content is 0.151%; the temperature is raised to 1572℃, the calcium carbide is deoxidized, the dissolved [O] in the steel is ≤0.0089%, 250 m titanium wire is fed, the Ti content is 0.196%; the temperature is raised to 1586℃, the calcium carbide is deoxidized, the dissolved [O] in the steel is ≤0.0039%, 300 m titanium wire is fed, the Ti content is 0.26%; the temperature is raised to 1606℃, soft blowing for 7 minutes, carbonized rice husk is added, the ladle is kept and hung to the continuous casting position.

[0132] (3) Continuous casting

[0133] The cross section of the casting blank is 150x150 mm, the tundish temperature is 1543℃ (TL=1513℃), the pulling speed is 2.1 m / min, the crystallizer water amount is 140 m3 / h, the secondary cooling specific water amount is 1.00 L / kg, the crystallizer electromagnetic stirring current is 180 A, and the frequency is 5 Hz.

[0134] Technical effect of example 3: the Ti element recovery rate of the furnace is 82%, 12 furnaces are produced in the pouring process, and no nozzle clogging and crystallizer clogging occurs in the casting process.

[0135] In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0136] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of smelting a low-aluminum high-titanium welding wire steel, characterized in that, Comprise: Converter smelting stage, control converter smelting end molten steel temperature, P content, C content and [O] content, then pour furnace tapping, alloying is carried out in the tapping process; LF refining stage, add lime and fluorite to the ladle for slagging, adopt calcium carbide deoxidation, control target basicity, dissolved [O] content in steel and molten steel temperature; According to different titanium target, multiple times of titanium wire feeding is carried out in stages, and the molten steel temperature is correspondingly increased each time the titanium wire is fed, and the dissolved [O] in steel is correspondingly decreased by calcium carbide deoxidation control; Continuous casting stage.

2. The smelting method of the low-aluminum high-titanium welding wire steel according to claim 1, characterized in that, In the LF refining stage, the initial control of the dissolved [O] in steel is ≤0.0020%, and the molten steel temperature is controlled to be 1550-1570℃; According to the titanium target 0.10%, the titanium wire is fed, the temperature is raised to 1560-1580℃, and the dissolved [O] in steel is controlled to be ≤0.0015% by calcium carbide deoxidation; According to the titanium target 0.15%, the titanium wire is fed, the temperature is raised to 1570-1590℃, and the dissolved [O] in steel is controlled to be ≤0.0010% by calcium carbide deoxidation; According to the titanium target 0.20%, the titanium wire is fed, the temperature is raised to 1580-1600℃, and the dissolved [O] in steel is controlled to be ≤0.0005% by calcium carbide deoxidation; According to the titanium target 0.25-0.30%, the titanium wire is fed, the temperature is raised to 1590-1610℃, soft blowing is carried out for 5-10 minutes, carbonized rice husk is added for heat preservation, and the ladle is lifted to the continuous casting station.

3. The smelting method of the low-aluminum high-titanium welding wire steel according to claim 2, characterized in that, In the LF refining stage, after entering the LF, the composition is fine-tuned according to the target composition of the molten steel, then 800-1000 kg of lime and 200-300 kg of fluorite are added to the ladle for slagging, and the target basicity is controlled to be 2.0-2.

5.

4. The smelting method of the low-aluminum high-titanium welding wire steel according to claim 1, characterized in that, In the LF refining stage, the process argon flow is controlled to be 120-180 NL / min, and the bare liquid surface is not exposed.

5. The smelting method of the low-aluminum high-titanium welding wire steel according to claim 1, characterized in that, In the converter smelting stage, the molten steel temperature at the end of converter smelting is controlled to be 1580-1600℃, the P content is ≤0.030%, the C content is 0.03%-0.05%, and the [O] is ≤0.060%.

6. The smelting method of the low-aluminum high-titanium welding wire steel according to claim 5, characterized in that, When pouring furnace tapping, high-silicon silicon manganese and low-carbon ferromanganese are added to the molten steel at 1 / 2 of the tapping to perform alloying according to the silicon and manganese target composition of the furnace steel.

7. The smelting method of the low-aluminum high-titanium welding wire steel according to claim 1, characterized in that, In the converter smelting stage, no post-blowing operation is carried out, and the front and middle tapping holes are adopted.

8. The smelting method of the low-aluminum high-titanium welding wire steel according to claim 1, characterized in that, In the continuous casting stage, the casting blank section is 150x150mm-200x200mm, the whole process is protected casting, the superheat is 25-40℃, the pulling speed is 1.5-2.5m / min, the crystallizer water quantity is 140-180m 3 / h, the secondary cooling specific water quantity is 1.00-1.40L / kg, the crystallizer electromagnetic stirring current is 180-220A, the frequency is 3-5Hz, the terminal electromagnetic stirring current is 300A, and the frequency is 8Hz.

9. The smelting method of the low-aluminum high-titanium welding wire steel according to claim 1, characterized in that, In the continuous casting stage, the whole liquid surface is covered with covering agent and rice husk, and whole nozzle is adopted to protect the casting measures.

10. The method of smelting a low-aluminum high-titanium welding wire steel according to claim 1, characterized in that, during the continuous casting phase, [N] is controlled < 0.0040%.

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