A production method for realizing annealing-free drawing of Ti-containing high-strength special welding steel wire rod

Abstract

The application discloses a production method for realizing annealing-free drawing of high-strength special welding steel wire rod containing Ti, belongs to the technical field of steel smelting, and discloses the following technical scheme: the wire rod is φ6.5 mm, the component control is C≤0.10%, Ti 0.17-0.35% and appropriate Si, Mn, Cr, Mo and B. According to the thermodynamic law of TiC precipitation and dissolution, high superheat continuous casting and φ180 mm round billet are adopted to promote TiC aggregation and growth; after the billet is hot sent, low-temperature short-time heating is adopted to avoid TiC dissolution, online induction temperature compensation is adopted during rolling, and rapid hot coiling is adopted after wire drawing and then the wire rod is kept and slowly cooled. The obtained wire rod has a tensile strength of 480-530 MPa, can be directly drawn into φ1.2 mm welding wire without annealing, abnormal structures are eliminated, processing hardening and die loss are reduced, cost reduction and benefit increase and green production are realized.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, specifically to a production method for anneal-free drawing of high-strength special welding steel wire rod containing Ti. Background Technology

[0002] With the continuous progress of my country's steel and welding industries, low-carbon micro-alloying composition systems are increasingly being adopted in many fields such as automobiles, coal mining machinery, and construction machinery, aiming to achieve both heavy load-bearing capacity and lightweight design. Therefore, the demand for steel used in alloy welding is growing daily.

[0003] In the field of high-strength special gas-shielded welding wire steel, countries such as South Korea and Japan have generally adopted a strategy of adding more than 0.15% titanium to replace rare and expensive metallic elements such as nickel (Ni) and molybdenum (Mo). Currently, my country has also followed this approach in the field of high-strength gas-shielded welding wire steel, gradually achieving the replacement of precious alloys and developing products such as Cr-Ti series, Mo-Ti series, and Ti-B series. The purpose of this strategy is to reduce the production cost of welding wire and improve production efficiency by increasing the heat input during the welding process, thereby effectively enhancing market competitiveness. However, the high content of titanium has a dual impact: on the one hand, its precipitation strengthening and grain refinement strengthening effects will change the strength and toughness of welding steel wire rods; on the other hand, the introduction of these elements will cause the C-curve of welding steel to shift to the right, making it easy to form supercooled structures such as granular bainite during cooling, which will lead to excessively high material strength and reduced toughness.

[0004] Given the high alloy content of high-strength special welding steel, especially the precipitation strengthening and grain refinement effects of titanium alloys, the strength and work hardening rate of high-strength special welding steel wire rods are significantly improved. Therefore, high-strength special welding steel wire rods must undergo annealing before or during drawing to ensure they can be drawn to specifications of φ1.2mm and below. This process undoubtedly reduces the production efficiency of welding wire manufacturers and increases their production costs, resulting in an increase of approximately 300 yuan per ton of steel cost for welding wire, thus affecting market competitiveness. Therefore, improving the microstructure and properties of high-strength special welding steel wire rods is of paramount importance for improving the efficiency of subsequent production processes and reducing production costs.

[0005] Currently, the main high-strength special welding materials in China are Cr and Ti series, Mo and Ti series, and Ti and B series, with an annual market demand of around 80,000 tons. However, traditional high-strength welding wire production methods, such as patents CN 110983176 B (titled: A hot-rolled wire rod for 70 kg welding wire and its production method), CN 114293107 B (titled: A gas-shielded welding alloy wire rod and its production method), and CN 116657042 A (titled: A high-alloy welding wire rod and its preparation method), all employ techniques such as increasing heating temperature, controlling rolling process temperature, lowering wire exit temperature, and slow cooling. For example, the heating section is 1080-1120℃, the soaking section is 1120-1160℃; the finishing mill inlet temperature is 900-940℃; the wire exit temperature is 780-820℃; the air-cooled roller speed is 0.09-0.12 m / s; and all insulation covers are used to cool the hot-rolled wire rod within a temperature range of 725-550℃ at a speed ≤0. Processes such as 0.07℃ / s only consider the direction of reducing bainite and martensite structures, without taking into account the form of Ti in the steel, and thus neglecting the effects of titanium compounds on grain refinement and precipitation strengthening. Therefore, although abnormal structures such as martensite and bainite in the wire rod microstructure are effectively controlled, the tensile strength of the wire rod is generally high, the work hardening rate during drawing is significantly increased, the grinding wheel wear is severe, and insufficient plasticity is also present. Simultaneously, the strength of the finished welding wire generally exceeds 1500MPa, leading to severe wear of the contact tip and poor wire feeding during welding.

[0006] On the other hand, publications such as CN 117025889 A, entitled "A Drawing Annealing Process for High-Strength Welding Wire Steel," require annealing of high-strength special welding steel wire rods containing Ti before or during the drawing process for welding wires with specifications of φ1.2mm and below. This results in increased production costs and reduced processing efficiency.

[0007] In summary, traditional processes for producing high-strength Ti-containing special welding steel wire rods only consider reducing martensite and bainite structures during controlled rolling and cooling, neglecting the precipitation strengthening and grain refinement effects of Ti precipitates. This leads to excessively high welding wire strength, severe mold wear, and deteriorated welding performance of the finished wire during subsequent processing. Furthermore, high-strength welding wires produced using annealing processes have long production cycles and high annealing costs, resulting in insufficient market competitiveness. Summary of the Invention

[0008] The purpose of this invention is to provide a production method for high-strength special welding steel wire rod containing Ti that does not require annealing during drawing, so as to overcome the defects of existing technologies such as poor microstructure compatibility, high annealing energy consumption, difficulty in decarburization control, and low spheroidization efficiency.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A method for producing high-strength special welding steel wire rod containing Ti without annealing, wherein the chemical composition of the high-strength special welding steel wire rod containing Ti is as follows by weight percentage: C≤0.10%, Si: 0.50-1.20%, Mn: 1.10-2.00%, P≤0.025%, S: 0.005-0.025%, Cr≤0.70%, Ti: 0.17-0.35%, Mo≤0.50%, B≤0.0080%, with the balance being iron and unavoidable impurities; The method sequentially includes the steps of converter smelting, LF refining, continuous casting, billet heating, rolling, wire rod coiling, hot coiling, and online heat preservation corridor slow cooling. The continuous casting adopts high superheat and is matched with φ180mm continuous casting round billets to achieve smooth continuous casting and agglomeration and growth of Ti-containing compounds. The billet heating adopts low temperature heating below 970℃ and heating time within 2 hours to avoid the re-dissolution of Ti-containing compounds and reduce the impact of fine grain strengthening and precipitation strengthening. During the rolling process, online induction heating at the decoupling roller table position is used to ensure uniform temperature of the rolled material. After wire rod coiling, the wire rod is hot-coiled within 1 minute at a temperature above 750℃, and then rapidly cooled in a heat preservation corridor for 1-2 hours. After the temperature drops below 350℃, the wire rod is removed from the heat preservation corridor and allowed to cool naturally to room temperature.

[0010] The precipitation reaction of TiC in the liquid phase or solid-liquid two-phase region is as follows: [Ti] + [C] = TiC(s) Its standard Gibbs free energy is related to temperature as follows: ΔG θ / RT = 12.08 - 22142.17 / T The expression for the actual precipitation Gibbs free energy is: ΔG=ΔG θ +RTln(a TiC / a Ti ·a C )=ΔG θ +RTlna TiC / (w Ti ·f Ti )·(w C ·f C ) In the formula: a TiC The activity of TiC is always equal to 1 when TiC precipitates in steel; a Ti a C These represent the activities of Ti and C in molten steel / austenite, respectively, w Ti w C f is the mass fraction. Ti fC This is the activity coefficient.

[0011] Thermodynamic calculations show that, under the conditions of C ≤ 0.10% and Ti 0.17-0.35%, TiC begins to precipitate in the solid-liquid two-phase region when the temperature is reduced to around 1396℃, and gradually accumulates and grows as the temperature decreases further and the holding time is extended.

[0012] Under the conditions of C ≤ 0.10% and Ti: 0.17-0.35%, the solubility product formula was used to calculate... lg[Ti][C]=-7000 / T+2.75, The temperature at which TiC begins to dissolve is approximately 980℃. That is, TiC tends to dissolve when the temperature is above approximately 980℃; it is more likely to precipitate stably when the temperature is below this.

[0013] This invention increases the Ti content in steel to 0.17% or higher through analysis of TiC precipitation, aggregation, growth, and dissolution. It improves the superheat during continuous casting, matching the φ180mm round billet to achieve the aggregation and growth of Ti-containing compounds such as TiC. Low-temperature heating (below 970℃) and a heating time of less than 2 hours avoid the dissolution of TiC and other compounds, mitigating the effects of fine-grain strengthening and precipitation strengthening. The formation of higher levels of TiC and TiC2S2 compounds consumes a certain amount of C and Ti elements, correspondingly reducing the hardenability of the wire rod and decreasing the solid solution strengthening effect of C and Ti elements, resulting in a significant leftward shift of the CCT curve. Combined with a hot-rolled coil slow-cooling process, the tensile strength of the wire rod is significantly reduced while eliminating bainite and martensite, enabling anneal-free drawing of high-strength Ti-containing special welding steel wire rod. This also reduces work hardening during drawing and decreases wear on drawing tools. Furthermore, the increased Ti content in the welding wire enables high heat input welding, improving welding efficiency.

[0014] Preferably, the molten steel is cast on a continuous casting machine with a target superheat of 60-80°C. This high superheat ensures a stable and smooth continuous casting process, prevents nozzle clogging, and facilitates the aggregation and growth of Ti-containing compounds such as TiC.

[0015] Preferably, the steel billet is heated in a hot furnace to ensure that the surface temperature of the billet is greater than 500°C. This effectively avoids the problems of cooling bending and delayed cracking of Ti-containing high-alloy special welding steel billets, and ensures that the core temperature is slightly higher than the edge temperature during the billet rolling process, effectively guaranteeing the deformation of the core during the rolling process and ensuring the transformation of the core microstructure.

[0016] Preferably, the temperature of the heating section and the soaking section of the heating furnace is 930-970℃, and the heating section and soaking section time is controlled at 1.5-2.0h. This avoids the re-dissolution of compounds such as TiC, reducing the impact of fine grain strengthening and precipitation strengthening; the formation of higher concentrations of compounds such as TiC and TiC2S2 consumes a certain amount of C and Ti elements, correspondingly reducing the hardenability of the wire rod and reducing the solid solution strengthening effect brought by C and Ti elements, causing the CCT curve to shift significantly to the left.

[0017] Preferably, the spinning process uses a temperature of 900°C or higher, combined with a roller speed of not less than 0.6 m / s, to achieve hot coiling of the wire rod within 1 minute, ensuring that the hot coiling temperature is above 750°C.

[0018] Preferably, the bottom of the hot coil drum in the hot coiling process is equipped with a heater to prevent the temperature at the beginning of the coiling process from being lower than the overall coiling temperature.

[0019] Preferably, the high-strength special welding steel wire rod containing Ti has a tensile strength of 480-530 MPa and a reduction of area of ​​≥75%, meeting the requirement of direct drawing to φ1.2 mm without annealing.

[0020] Compared with the prior art, the beneficial effects of the present invention are: High superheat in continuous casting + large round billet: ensures smooth continuous casting, avoids nozzle clogging, achieves stable production of thousands of tons per casting, and promotes the coarsening and growth of precipitates such as TiC, laying the foundation for strength reduction; φ180mm round billet ensures rolling compression ratio and solves the defect of iron oxide scale embedding.

[0021] Hot delivery of billet + low-temperature short-time heating: reduces heating energy consumption and avoids billet bending and delayed cracking; heating below 970℃ for ≤2h effectively prevents TiC re-dissolution, significantly weakens fine grain strengthening and precipitation strengthening, reduces solid solution strengthening and hardenability, and shifts the CCT curve to the left.

[0022] Uniform rolling temperature control: Online induction stepped temperature compensation is adopted on the decoupling roller table to eliminate the temperature difference and tension fluctuation between the head and tail, improve the uniformity of size and structure, and avoid local mixed crystals.

[0023] Hot coiling + precise slow cooling: The coiling temperature is 750-830℃ and the overall temperature difference is ≤40℃. Combined with slow cooling through the heat-insulating corridor, the bainite and martensite structures are completely eliminated.

[0024] Performance meets standards and requires no annealing: The wire rod has a strength of 480-530MPa and excellent plasticity. It can be directly drawn into φ1.2mm welding wire, eliminating the need for annealing. This reduces the cost per ton by about 300 yuan. It also has low work hardening, low die wear, moderate welding wire strength, smooth wire feeding, and excellent welding performance.

[0025] Green and efficient: Simplified process, reduced energy consumption, Ti microalloying replaces precious alloys, while also supporting high heat input welding, thus enhancing market competitiveness. Attached Figure Description

[0026] Figure 1 Example 1: Schematic diagram of tensile strength and reduction of area of ​​φ6.5mm hot-rolled wire rod; Figure 2 Example 1: Schematic diagram of the metallographic structure of φ6.5mm hot-rolled wire rod; Figure 3 Example 1: Schematic diagram of the strength of φ6.5mm hot-rolled wire rod drawn into φ1.2mm welding wire; Figure 4 Example 2: Schematic diagram of tensile strength and reduction of area of ​​φ6.5mm hot-rolled wire rod; Figure 5 Example 2: Schematic diagram of the metallographic structure of φ6.5mm hot-rolled wire rod; Figure 6 Example 2: Schematic diagram of the strength of φ6.5mm hot-rolled wire rod drawn into φ1.2mm welding wire; Figure 7 Example 3: Schematic diagram of tensile strength and reduction of area of ​​φ6.5mm hot-rolled wire rod; Figure 8 Example 3: Schematic diagram of the metallographic structure of φ6.5mm hot-rolled wire rod; Figure 9 Example 3: Schematic diagram of the strength of φ6.5mm hot-rolled wire rod drawn into φ1.2mm welding wire; Figure 10 Comparative Example 1: Tensile strength and reduction of area of ​​φ6.5mm hot-rolled wire rod; Figure 11 Schematic diagram of the metallographic structure of a φ6.5mm hot-rolled wire rod (comparative example); Figure 12 Comparative Example 1: Schematic diagram of the strength of φ6.5mm hot-rolled wire rod drawn into φ1.2mm welding wire; Figure 13 Comparative Example 2: Tensile strength and reduction of area of ​​φ6.5mm hot-rolled wire rod; Figure 14 Comparative Example 2: Schematic diagram of the metallographic structure of φ6.5mm hot-rolled wire rod; Figure 15 Comparative Example 2: Schematic diagram of the strength of φ6.5mm hot-rolled wire rod drawn into φ1.2mm welding wire. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below through examples.

[0028] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments. Example 1:

[0030] See Figure 1-3 This embodiment provides a production method for anneal-free drawing of high-strength special welding steel wire rod containing Ti. The specific implementation steps include: converter smelting, LF refining, continuous casting (round billet), billet heating, rolling, wire drawing, hot coiling, and slow cooling in an online heat preservation corridor.

[0031] The specific operating steps are as follows: A type of high-strength special welding steel wire rod containing Ti has a specification of φ6.5mm. Its chemical composition by weight percentage is C: 0.07%, Si: 0.75%, Mn: 1.53%, Cr: 0.45%, Mo: 0.14%, Ti: 0.23%, B: 0.0035%, with the remainder being Fe and unavoidable impurities.

[0032] (1) Converter: Deoxidation and alloying are carried out in the converter. The composition control requirements for the steel tapped from the converter are: C≤0.025%, P≤0.011%, and the tapping temperature is 1663℃. Slag is added after the furnace to form the refining primary slag. (2) Refining: After entering the LF refining furnace, slag-forming materials are added, and low-carbon ferrochrome and ferromolybdenum alloys are selected to adjust the composition; titanium iron wire is fed in once before soft blowing argon; the weight percentage of Ti is adjusted to 0.27%, and then boron iron wire is fed in, and the weight percentage of boron B is adjusted to 0.0042%. After leaving the LF, soft blowing argon is performed on the molten steel. (3) Casting of φ180mm round billet: Casting is carried out on a continuous casting machine with a superheat of 75℃, a casting speed of 1.05m / min, a crystallizer water flow rate of 1200L / min, a crystallizer electromagnetic stirring parameter of 220A current intensity and 4Hz frequency, a terminal electromagnetic stirring parameter of 170A current intensity and 10Hz frequency, a secondary cooling water flow rate of 0.8L / kg, and continuous casting is carried out under full protection. (4) Steel billet hot delivery heating furnace heating: the surface temperature of the billet is 540℃, the temperature of the heating section of the heating furnace is 930-950℃, the temperature of the soaking section is 940-960℃, the total heating time of the heating section and the soaking section is 1.85h, and the rolling start temperature is 875℃; (5) Controlled rolling: Using the de-rolling roller table, the No. 1 rolling inlet speed is 0.5m / s to realize the rapid deformation of φ180mm round billet into φ140mm round billet. The online induction heating at the position of the de-rolling roller table is used to ensure uniform rolling temperature. The final rolling temperature is controlled at 935℃ and the wire drawing temperature is 922℃. (6) Slow cooling in the heat preservation corridor after the wire rod is spun out: the speed of the Stellmore roller is 0.75m / s, and the hot coiling is completed in 95s. The heater at the bottom of the hot coil is set with 3 heating intensity levels, and the temperature of the hot coil is 780-820℃. After that, it enters the heat preservation corridor for slow cooling for 50s, and the cooling rate is controlled to be less than 0.05℃ / s. It is slow cooled in the heat preservation corridor for 1.6h, so that the temperature of the heat preservation corridor is 332℃. (7) Inspect the wire rods and pack them into the warehouse. Example 2:

[0033] See Figure 4-6 This embodiment provides a production method for anneal-free drawing of high-strength special welding steel wire rod containing Ti. The specific implementation steps include converter smelting, LF refining, continuous casting (round billet), billet heating, rolling, wire drawing, hot coiling, and slow cooling in an online heat preservation corridor.

[0034] The specific operating steps are as follows: A type of high-strength special welding steel wire rod containing Ti has a specification of φ6.5mm and a chemical composition by weight percentage of C: 0.06%, Si: 0.66%, Mn: 1.67%, Cr: 0.38%, Mo: 0.22%, Ti: 0.26%, with the remainder being Fe and unavoidable impurities.

[0035] (1) Converter: Converter smelting deoxidation and alloying, converter tapping steel composition control requirements: C≤0.033%, P≤0.009%, tapping temperature: 1659℃, slag is added after the furnace to form refining primary slag; (2) Refining: After entering the LF refining furnace, slag-forming materials are added, and low-carbon ferrochrome and ferromolybdenum alloys are selected to adjust the composition; titanium-iron wire is fed in once before soft argon blowing; the weight percentage of Ti is adjusted to 0.29%; after leaving the LF furnace, soft argon is blown into the molten steel. (3) Casting of φ180mm rectangular billet: Casting is carried out on a continuous casting machine with a target superheat of 68℃, a casting speed of 1.05m / min, a crystallizer water flow rate of 1200L / min, a crystallizer electromagnetic stirring parameter of 210A current intensity and 4Hz frequency, a terminal electromagnetic stirring parameter of 175A current intensity and 10Hz frequency, a secondary cooling water flow rate of 0.8L / kg, and continuous casting is carried out under full protection. (4) Steel billet hot delivery heating furnace heating: billet surface temperature 510℃, heating furnace heating section temperature 930-945℃, soaking section temperature 935-955℃, total heating section and soaking section time 1.9h, rolling start temperature 860℃; (5) Controlled rolling: Using the de-rolling roller table, the No. 1 rolling inlet speed is 0.5m / s to realize the rapid deformation of φ180mm round billet into φ140mm round billet. The online induction heating at the position of the de-rolling roller table is used to ensure uniform rolling temperature. The final rolling temperature is controlled at 929℃ and the wire drawing temperature is 925℃. (6) Slow cooling in the heat preservation corridor after the wire rod is spun out: the speed of the Stellmore roller is 0.70m / s, and the hot coiling is completed in 92s. The heater at the bottom of the hot coil is set with 3 heating intensity levels, and the temperature of the hot coil is 770-810℃. After that, it enters the heat preservation corridor for slow cooling for 50s, and the cooling rate is controlled to be less than 0.05℃ / s. It is slow cooled in the heat preservation corridor for 1.7h, so that the temperature of the heat preservation corridor is 325℃. (7) Inspect the wire rods and pack them into the warehouse. Example 3:

[0036] See Figure 7-9 This embodiment provides a production method for anneal-free drawing of high-strength special welding steel wire rod containing Ti. The specific implementation steps include converter smelting, LF refining, continuous casting (round billet), billet heating, rolling, wire drawing, hot coiling, and slow cooling in an online heat preservation corridor.

[0037] The specific operating steps are as follows: A type of high-strength special welding steel wire rod containing Ti has a specification of φ6.5mm. Its chemical composition by weight percentage is C: 0.07%, Si: 0.78%, Mn: 1.52%, Cr: 0.46%, Mo: 0.15%, Ti: 0.24%, B: 0.0036%, with the remainder being Fe and unavoidable impurities.

[0038] (1) Converter: Converter smelting deoxidation and alloying, converter steel output composition control requirements: C≤0.024%, P≤0.012%, steel output temperature: 1668℃, slag is added after the furnace to form refining primary slag; (2) Refining: After entering the LF refining furnace, slag-forming materials are added, and low-carbon ferrochrome and ferromolybdenum alloys are selected to adjust the composition; titanium iron wire is fed in once before soft blowing argon; the weight percentage of Ti is adjusted to 0.28%, and then boron iron wire is fed in, and the weight percentage of boron B is adjusted to 0.0043%. After leaving the LF station, soft blowing argon is performed on the molten steel. (3) Casting of φ180mm round billet: Casting is carried out on a continuous casting machine with a superheat of 74℃, a casting speed of 1.05m / min, a crystallizer water flow rate of 1200L / min, a crystallizer electromagnetic stirring parameter of 220A current intensity and 4Hz frequency, a terminal electromagnetic stirring parameter of 170A current intensity and 10Hz frequency, a secondary cooling water flow rate of 0.8L / kg, and continuous casting is carried out under full protection. (4) Steel billet hot delivery heating furnace heating: the surface temperature of the billet is 542℃, the temperature of the heating section of the heating furnace is 930-950℃, the temperature of the soaking section is 940-960℃, the total time of the heating section and the soaking section is 1.82h, and the rolling start temperature is 874℃; (5) Controlled rolling: Using the de-rolling roller table, the No. 1 rolling inlet speed is 0.5m / s to realize the rapid deformation of φ180mm round billet into φ140mm round billet. The online induction heating at the position of the de-rolling roller table is used to ensure uniform rolling temperature. The final rolling temperature is controlled at 933℃ and the wire drawing temperature is 920℃. (6) Slow cooling in the heat preservation corridor after the wire rod is spun out: the speed of the Stellmore roller is 0.80m / s, and the hot coiling is completed in 92s. The bottom heater of the hot coil is set with 3 heating intensity levels, and the temperature of the hot coil is 780-818℃. After that, it enters the heat preservation corridor for slow cooling for 50s, and the cooling rate is controlled to be less than 0.05℃ / s. It is slow cooled in the heat preservation corridor for 1.7h, so that the temperature of the heat preservation corridor is 327℃. (7) Inspect the wire rods and pack them into the warehouse.

[0039] Comparative Example 1 See Figure 10-12 A 70 kg grade Ti-containing high-strength special welding steel wire rod with a specification of φ6.5 mm has a chemical composition by weight percentage as follows: C: 0.091%, Si: 0.37%, Mn: 1.43%, Mo: 0.21%, Cr: 0.17%, Ti: 0.11%, B: 0.004%, with the balance being Fe.

[0040] (1) Using scrap steel as raw material, after electric arc furnace smelting, LF refining and continuous casting, a continuous casting billet with a specification of 150x150mm is obtained; in the continuous casting process, electromagnetic stirring in the crystallizer and electromagnetic stirring at the solidification end are adopted. Two electromagnetic stirrers are set at the solidification end, respectively at 3 / 5 of the total length of the liquid core and at 1 / 10 of the total length of the liquid core from the solidification end. The parameters of the electromagnetic stirring in the crystallizer are: stirring current 305A, frequency 7.8Hz, counterclockwise stirring; the parameters of the electromagnetic stirring at the solidification end are: stirring current 340A, frequency 8.5Hz, clockwise stirring. (2) The continuously cast billet is heated in an annular furnace at a temperature of 1042°C and held for 2.5 hours. (3) The continuous casting square ball is rolled at an initial rolling temperature of 1010℃ and a final rolling temperature of 995℃. After the final rolling, the wire is immediately spun out and collected to obtain a hot-rolled coil. (4) The insulation channel is divided into 5 temperature zones along the roller conveyor direction and the temperature is controlled separately. The temperature of each temperature zone decreases sequentially along the roller conveyor direction, and the temperature difference between adjacent temperature zones is the same: the temperature of the first temperature zone is 725-690℃, and the temperature of the last temperature zone is 585-550℃. After the insulation channel temperature is heated to the set temperature, the hot-rolled coil with a temperature >725℃ is placed on the roller conveyor of the insulation channel. When the temperature of the hot-rolled coil drops to 725℃, the roller conveyor is started and the roller conveyor running speed is set to 1.37m / min, so that the cooling rate of the hot-rolled coil in the temperature range of 725-550℃ is constant at 0.04℃ / s. The coil is air-cooled to room temperature below 550℃ to obtain the 70 kg grade hot-rolled wire rod.

[0041] Comparative Example 2 See Figure 13-15 This embodiment provides a production method for anneal-free drawing of high-strength special welding steel wire rod containing Ti. Comparative Example 2 is the same as Example 1 in general, but the main difference is that the steel billet is cold-charged, the heating section temperature of the heating furnace is 1060-1120℃, the soaking section temperature is 1100-1160℃, the total time of the heating section and the soaking section is 2.2h, and the rolling start temperature is 990℃.

[0042] As shown in Figures 1-15, the φ6.5mm high-strength Ti-containing welding steel wire rods produced in Examples 1-3 of this invention have a tensile strength of 480–530 MPa, a reduction of area ≥75%, and a uniform ferrite + pearlite microstructure without abnormal structures such as bainite or martensite. After being drawn into φ1.2mm finished welding wires, their strength stabilizes at 1150–1250 MPa. Compared with Comparative Example 1 (traditional controlled cooling process) and Comparative Example 2 (high-temperature heating process), the wire rods of this invention have lower strength, better plasticity, and more uniform microstructure. The finished welding wires have moderate strength, fully meeting the requirements for direct drawing without annealing. They also exhibit less work hardening, lower die wear, and smoother welding wire feeding, demonstrating significantly better overall performance than traditional processes.

[0043] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for producing high-strength special welding steel wire rod containing Ti without annealing, the method comprising the steps of converter smelting, LF refining, continuous casting, billet heating, rolling, wire drawing, hot coiling, and online heat preservation corridor slow cooling, characterized in that, The chemical composition of the high-strength special welding steel wire rod containing Ti, by weight percentage, is C≤0.10%, Si: 0.50-1.20%, Mn: 1.10-2.00%, P≤0.025%, S: 0.005-0.025%, Cr≤0.70%, Ti: 0.17-0.35%, Mo≤0.50%, B≤0.0080%, with the balance being iron and unavoidable impurities; The continuous casting employs high superheat and is matched with a φ180mm continuous casting round billet to achieve smooth continuous casting and agglomeration and growth of Ti-containing compounds. The billet heating adopts low temperature heating below 970℃ and heating time within 2 hours to avoid the re-dissolution of Ti-containing compounds and reduce the impact of fine grain strengthening and precipitation strengthening. During the rolling process, online induction heating at the decoupling roller table position is used to ensure uniform temperature of the rolled material. After the wire rod is finished, it is controlled to be hot-coiled within 1 minute, with a hot-coil temperature above 750℃, and then rapidly subjected to slow cooling in a heat preservation corridor for 1-2 hours. After the temperature drops below 350℃, it is removed from the heat preservation corridor and allowed to cool naturally to room temperature.

2. The production method for anneal-free drawing of Ti-containing high-strength special welding steel wire rod according to claim 1, characterized in that, The molten steel is cast on a continuous casting machine with a target superheat of 60-80℃.

3. The production method for anneal-free drawing of Ti-containing high-strength special welding steel wire rod according to claim 1, characterized in that, The billet is heated in a hot-feeding furnace to ensure that the surface temperature of the billet is greater than 500°C.

4. The production method for anneal-free drawing of Ti-containing high-strength special welding steel wire rod according to claim 3, characterized in that, The temperature of the heating section and the soaking section of the heating furnace is 930-970℃, and the time of the heating section and the soaking section is controlled at 1.5-2.0h.

5. The production method for anneal-free drawing of Ti-containing high-strength special welding steel wire rod according to claim 1, characterized in that, The spinning process uses a temperature of over 900℃, combined with a roller speed of not less than 0.6m / s, to achieve hot coiling of the wire rod within 1 minute, ensuring that the hot coiling temperature is above 750℃.

6. The production method for anneal-free drawing of Ti-containing high-strength special welding steel wire rod according to claim 1, characterized in that, The bottom of the hot coil drum in the hot coiling process is equipped with a heater to prevent the temperature at the beginning of the coiling process from being lower than the overall coiling temperature.

7. The production method for anneal-free drawing of Ti-containing high-strength special welding steel wire rod according to any one of claims 1-6, characterized in that, The high-strength special welding steel wire rod containing Ti has a tensile strength of 480-530MPa and a reduction of area of ​​≥75%, meeting the requirement of direct drawing to φ1.2mm without annealing.

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