Annealing-free special welding wire rod and production method thereof

Abstract

The invention discloses a special annealing-free welding wire rod and a production method thereof. The special annealing-free welding wire rod comprises the following chemical components in percentage by mass: 0.02 to 0.08 percent of C, 0.65 to 0.95 percent of Si, 1.50 to 1.90 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.0045 percent of N, 0.010 to 0.025 percent of S, 0.40 to 0.80 percent of Cr, 0.16 to 0.30 percent of Ti, 0.05 to 0.30 percent of Mo, 0.020 to 0.060 percent of V and the balance of Fe and inevitable impurity elements. The casting blank is heated at a low temperature for less than 2.2 hours, so that large-size particles such as TiC and the like are prevented from being dissolved into austenite, and dispersed precipitation in the subsequent cooling process is reduced; through heat preservation and slow cooling at the temperature of 830 + / -50 DEG C, aggregation and growth of small-size particles such as TiC are achieved, and wire rod strength increase caused by fine grain strengthening and precipitation strengthening is relieved; and due to the formation of particles such as large-size TiC, a large amount of C, N, Ti and V elements are consumed, the solid solution strengthening effect is reduced, annealing-free drawing is achieved, the production process is simplified, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to an annealing-free special welding wire rod and a production method thereof. Background Art

[0002] With the increasingly fierce competition in the steel industry, low-carbon microalloying composition systems have been widely used in many industries such as coal machinery and engineering machinery in the welding industry.

[0003] At present, the 80kg-grade high-strength special gas shielded welding wire steel produced in China generally improves the strength of the weld by adding alloying elements such as nickel (Ni), molybdenum (Mo), and chromium (Cr). However, these alloying elements significantly increase the production cost. In addition, after rolling, a large amount of martensite and bainite structure will be formed in the wire rod using the traditional Stelmor controlled cooling process, which makes the tensile strength of the wire rod higher. It must undergo offline annealing treatment after rolling to ensure that the welding wire will not have serious wire breakage problems during the drawing process. In view of this, how to design a technology that can simplify the production process of wire rods and reduce the production cost of wire rods is the technical problem to be solved by the present invention. Summary of the Invention

[0004] The purpose of the present invention is to provide an annealing-free special welding wire rod and a production method thereof, so as to simplify the production process of the wire rod and reduce the production cost of the wire rod.

[0005] In order to solve the above technical problems, the present invention is mainly achieved through the following technical solutions: In a first aspect, the present invention provides an annealing-free special welding wire rod, whose chemical composition, by mass percentage, includes: C 0.02~0.08%, Si 0.65~0.95%, Mn 1.50~1.90%, P≤0.015%, N≤0.0045%, S0.010~0.025%, Cr 0.40~0.80%, Ti 0.16~0.30%, Mo 0.05~0.30%, V 0.020~0.060%, and the rest is Fe and unavoidable impurity elements.

[0006] In some embodiments of the present application, the mass percentage relationship between the elements C, N, S, V, and Ti is as follows: (C / 12+N / 14+S / 32)<(V-0.01%) / 51+(Ti-0.02%) / 48.

[0007] In some embodiments of the present application, the chemical composition includes, by mass percentage, C 0.04%, Si 0.75%, Mn 1.79%, P 0.007%, N 0.0032%, S 0.015%, Cr 0.48%, Ti 0.22%, Mo 0.14%, V 0.035%, and the rest is Fe and unavoidable impurity elements.

[0008] In some embodiments of the present application, the chemical composition includes, by mass percentage, C 0.05%, Si 0.77%, Mn 1.75%, P 0.005%, N 0.0026%, S 0.013%, Cr 0.55%, Ti 0.24%, Mo 0.09%, V 0.028%, and the rest is Fe and unavoidable impurity elements.

[0009] In a second aspect, the present invention provides a method for producing the annealing-free special welding wire rod as described in any one of the embodiments of the first aspect above, comprising the following steps: S1. Converter smelting: The molten iron entering the furnace is pre-treated and desulfurized using the KR method; S2. Refining: After the refining furnace enters the station, slag material is added. During the refining process, titanium-iron wire is fed once and the Ti weight percentage is adjusted to 0.21~0.28%. After the refining furnace leaves the station, the molten steel is soft-blown with argon gas; S3. Casting the ingot: The ingot is cast using a continuous casting machine. During the casting process, the target superheat is controlled at 70-85°C and the casting speed is controlled at 0.8-1.2 m / min. The crystallizer is electromagnetically stirred. The current intensity of the electromagnetic stirring at the head end of the crystallizer is 250-300 A and the frequency is 3-4 Hz; the current intensity of the electromagnetic stirring at the end end is 100-150 A and the frequency is 8-10 Hz. The secondary cooling water flow rate is 0.8-1.0 L / kg. S4. Heat the slab in a hot heating furnace: Maintain the surface temperature of the slab at >550°C, control the temperature of the heating section and the soaking section at 920-960°C, and control the heating section and the soaking section time at 90-120 minutes; S5, rolling: the rolling line is equipped with online induction heating, the starting rolling temperature is 850~890℃, the finishing rolling temperature is 900~960℃, and the wire laying temperature is 890~950℃; S6. After the wire rod is laid out, it is hot rolled and the hot rolling temperature is controlled to be ≥880℃. After hot rolling, it enters the insulation corridor for slow cooling: the slow cooling temperature is 830±50℃, and it is kept in the insulation section of the insulation corridor for 20-40 minutes. Then it enters the insulation corridor slow cooling section, and the cooling rate is controlled to be less than 0.05℃ / s. It is slowly cooled to below 550℃ in the insulation corridor. S7. The wire rods are inspected and qualified, and then packed and put into storage.

[0010] In some embodiments of the present application, in S1, the end point composition of converter smelting is controlled as follows: C≤0.03%, P≤0.010%, and the tapping temperature is ≥1660°C.

[0011] In some embodiments of the present application, in S1, before steel is tapped, silicon manganese and ferromanganese are added to control deoxidation and alloying.

[0012] In some embodiments of the present application, in S2, the slag-making material includes low-carbon ferrochrome (C < 0.10%), ferromolybdenum and ferrovanadium alloy.

[0013] In some embodiments of the present application, in S3, the size of the ingot is 180 mm×240 mm.

[0014] In some embodiments of the present application, in S3, the front roller is used to lightly press down 8 to 14 mm in four passes.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are as follows: through a unique composition design, the molar number of C+N+S elements is made smaller than the molar number of V+Ti atoms; during the continuous casting process, a light reduction technology for low-carbon steel rectangular billets is adopted to improve the center segregation of the billet, thereby avoiding the generation of black heart after rolling, reducing the size of the billet, and avoiding the problem of high motor load during rough rolling; and when heating the billet, a low heating temperature of less than 980°C and a heating time of less than 2.2 hours are adopted, which is conducive to avoiding and reducing the solid solution of large-sized particles such as TiC, V(CN) and Ti(CN), and can also reduce or avoid dispersion precipitation during the subsequent cooling process.

[0016] After rolling, the use of a high temperature range of 830±50℃ for holding and slow cooling is conducive to the aggregation and growth of small-sized particles such as TiC, V(CN) and Ti(CN), reducing the increase in wire rod strength caused by fine grain strengthening and precipitation strengthening. At the same time, the formation of large-sized compound particles such as TiC, V(CN) and Ti(CN) consumes a large amount of C, N, Ti, and V elements, reducing the solid solution strengthening effect brought by C, N, Ti, and V elements, and correspondingly reducing the hardenability of the wire rod. By combining with a higher Si element, the CCT curve is significantly shifted to the left, ensuring that more than 95% of the wire rod structure is iron, reducing the generation of cementite, reducing the formation of martensite and bainite, and realizing annealing-free drawing of the wire rod, simplifying the production process; During the carbon dioxide gas shielded welding process, the temperature of the weld pool of the finished welding wire of the wire rod of the present application ranges from 1700°C to 2900°C, and large particles of TiC, V (CN) and Ti (CN) are completely dissolved, and are rapidly precipitated as extremely small particles at a relatively high cooling rate. The effects of fine grain strengthening and precipitation strengthening are significant, thereby achieving refinement of the weld structure and a substantial improvement in strength, ensuring that the tensile strength of the weld deposited metal is greater than 810 MPa and the elongation after fracture is greater than 18%, meeting the mechanical property requirements of 80kg-level high-strength special welding; avoiding the existing practice of increasing weld strength by adding alloying elements such as nickel (Ni), molybdenum (Mo), and chromium (Cr), which is beneficial to reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0018] Figure 1 This is a metallographic image of the φ5.5 mm wire rod of Example 1 of the present invention; Figure 2 This is a metallographic image of the φ5.5 mm wire rod of Example 2 of the present invention; Figure 3 This is a metallographic image of the φ5.5 mm wire rod of Comparative Example 1 of the present invention; Figure 4 This is a metallographic image of the φ5.5 mm wire rod of Comparative Example 2 of the present invention; Figure 5 This is a graph showing the through-loop tensile strength of a φ5.5 mm wire rod according to Example 1 of the present invention; Figure 6 This is a cross-sectional shrinkage diagram of a φ5.5 mm wire rod according to Example 1 of the present invention; Figure 7 This is a graph showing the through-loop tensile strength of a φ1.2 mm welding wire drawn from a φ5.5 mm wire rod according to Example 1 of the present invention; Figure 8 This is a graph showing the through-loop tensile strength of a φ5.5 mm wire rod according to Example 2 of the present invention; Figure 9 This is a cross-sectional shrinkage diagram of a φ5.5 mm wire rod according to Example 2 of the present invention; Figure 10 This is a graph showing the through-loop tensile strength of a φ1.2 mm welding wire drawn from a φ5.5 mm wire rod according to Example 2 of the present invention; Figure 11This is a graph showing the through-loop tensile strength of a φ5.5 mm wire rod of Comparative Example 1 of the present invention; Figure 12 This is a cross-sectional shrinkage diagram of the φ5.5 mm wire rod of Comparative Example 1 of the present invention; Figure 13 This is a graph showing the through-loop tensile strength of a φ1.2mm welding wire drawn from a φ5.5mm wire rod in Comparative Example 1 of the present invention; Figure 14 This is a graph showing the through-loop tensile strength of a φ5.5 mm wire rod of Comparative Example 2 of the present invention; Figure 15 This is a cross-sectional shrinkage diagram of the φ5.5 mm wire rod of Comparative Example 2 of the present invention; Figure 16 This is a diagram of the through-loop tensile strength of φ1.2mm welding wire drawn from φ5.5mm wire rod in comparative example 2 of the present invention. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0020] It should be noted that in the description of the present invention, terms such as "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. These are merely for ease of description and do not indicate or imply that the device or component described must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integral connection; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0022] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0023] The disclosure below provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0024] In a first aspect, an embodiment of the present disclosure provides an annealing-free special welding wire rod, whose chemical composition, calculated by mass percentage, includes: C 0.02~0.08%, Si 0.65~0.95%, Mn 1.50~1.90%, P≤0.015%, N≤0.0045%, S 0.010~0.025%, Cr 0.40~0.80%, Ti 0.16~0.30%, Mo 0.05~0.30%, V 0.020~0.060%, and the rest is Fe and unavoidable impurity elements.

[0025] In some embodiments of the present application, the mass percentage relationship between the elements C, N, S, V, and Ti is as follows: (C / 12+N / 14+S / 32)<(V-0.01%) / 51+(Ti-0.02%) / 48.

[0026] Specifically, through a unique composition setting, the molar number of C+N+S elements is made smaller than the molar number of V+Ti elements; this is beneficial to reducing the formation of cementite and can effectively improve the plasticity of the wire rod; while ensuring that the microalloying elements (V, Ti) can fully form precipitation phases such as TiC and VC, achieving fine grain and precipitation strengthening.

[0027] In a second aspect, an embodiment of the present disclosure provides a method for producing an annealing-free special welding wire rod as described in any one of the embodiments of the first aspect above, comprising the following steps: S1. Converter smelting: First, the molten iron entering the furnace is pre-treated and desulfurized using the KR method.

[0028] In some embodiments of the present application, in S1, the end point composition of the converter smelting is controlled as follows: C≤0.03%, P≤0.010%, and the tapping temperature is ≥1660°C.

[0029] In some embodiments of the present application, in S1, before steel is tapped, silicon manganese and ferromanganese are added to perform deoxidation and alloying control, which can effectively reduce the oxygen content in the steel, reduce inclusions, increase the purity of the steel, and improve the performance of the steel.

[0030] S2. LF furnace refining: slag material is added after entering the station, and titanium-ferrowire is fed once during the refining process to adjust the Ti weight percentage in the molten steel to 0.21~0.28%. After leaving the LF furnace refining station, the molten steel is soft-blown with argon to make the various components in the molten steel more evenly mixed.

[0031] In some embodiments of the present application, in S2, the slag-making material includes low-carbon ferrochrome (C < 0.10%), ferromolybdenum and ferrovanadium alloy.

[0032] S3. Casting of ingots: Molten steel is put into continuous casting machine for casting. During the casting process, the target superheat is controlled at 70~85℃, and the casting speed is controlled at 0.8~1.2m / min. Through electromagnetic stirring of the crystallizer, the water flow of the crystallizer is 1110~1180L / min, the current intensity of electromagnetic stirring at the head end of the crystallizer is 250~300A, and the frequency is 3~4Hz; the current intensity of electromagnetic stirring at the end end is 100~150A, and the frequency is 8~10Hz. The secondary cooling water flow rate is 0.8~1.0L / kg.

[0033] In some embodiments of the present application, in S3 , the size of the casting billet is 180 mm×240 mm.

[0034] In some embodiments of the present application, in S3, the front roller is used to lightly press down 8 to 14 mm in four passes.

[0035] Specifically, during the continuous casting process, the use of light reduction technology for low-carbon steel rectangular slabs can improve centerline segregation and porosity, preventing the formation of black heart after rolling. This also reduces slab size and avoids excessive motor load during rough rolling.

[0036] S4. Heat the slab in a hot furnace: Keep the surface temperature of the slab > 550°C, control the temperature of the heating section and the soaking section to 920-960°C, and control the time of the heating section and the soaking section to 90-120 minutes.

[0037] Specifically, when heating the ingot, a heating temperature below 980°C and a heating time of less than 2.2 hours are used, which is beneficial to avoiding and reducing the solid solution of large-sized particles such as TiC, V(CN) and Ti(CN), and at the same time can reduce or avoid dispersion precipitation in the subsequent cooling process.

[0038] S5. Controlled rolling: The rolling line is equipped with online induction heating, with the starting rolling temperature at 850~890℃, ensuring the final rolling temperature at 900~960℃, and the wire laying temperature at 890~950℃; Specifically, the final rolling temperature is ≤ the dissolution temperature of particles such as TiC, V(CN), and Ti(CN) to avoid dissolution.

[0039] In some embodiments of the present application, the size of the wire rod is controlled at φ5.5 mm.

[0040] S6. After the wire rod is spun, it is quickly hot-coiled within 15 seconds, and the hot-coil temperature is controlled to be ≥880℃; after hot-coiled, it enters the insulation corridor for slow cooling: the slow cooling temperature of the pile is 830±50℃, and it is kept warm in the insulation section of the insulation corridor for 20~40min, and then enters the slow cooling section of the insulation corridor, controlling the cooling rate to <0.05℃ / s, and slowly cooling to below 550℃ in the insulation corridor.

[0041] Specifically, the hot coiling is performed quickly within 15 seconds, which reduces the time that the hot coiled wire rod is in contact with the outside air, avoids the rapid drop in the surface temperature of the hot coiled wire rod, and is conducive to ensuring quality consistency; through the above operation, the tensile strength of the wire rod can be achieved to be less than 680MPa and the cross-sectional shrinkage rate can be greater than 70%.

[0042] Specifically, by adopting a special post-rolling controlled cooling method, the temperature is kept at 830±50℃ for 20~40min, which is conducive to the aggregation and growth of small-sized particles such as TiC, V(CN) and Ti(CN), thereby further reducing the significant increase in wire rod strength caused by fine grain strengthening and precipitation strengthening of elements such as Ti and V.

[0043] At the same time, the formation of large-sized compound particles such as TiC, V (CN) and Ti (CN) consumes a large amount of C, N, Ti, and V elements, reduces the solid solution strengthening effect brought by C, N, Ti, and V elements, and correspondingly reduces the hardenability of the wire rod. By combining with a higher Si element, the CCT curve is significantly shifted to the left, ensuring that more than 95% of the wire rod structure is iron, and basically no cementite is produced, which reduces the formation of martensite and bainite, realizes annealing-free drawing of the wire rod, and simplifies the production process.

[0044] Specifically, after rolling, the φ5.5mm wire rod of the present application is stably drawn to form a φ1.2mm welding wire, and carbon dioxide gas shielded welding is adopted. During the welding process, the temperature range of the weld pool is between 1700℃ and 2900℃, and large particles such as TiC, V(CN) and Ti(CN) are all dissolved, and are quickly precipitated as extremely small particles at a large cooling rate. The fine grain strengthening and precipitation strengthening effects are significant, achieving the refinement of the weld structure and a significant improvement in strength, ensuring that the tensile strength of the weld cladding metal is greater than 810MPa and the elongation after fracture is greater than 18%, meeting the mechanical formation requirements of 80Kg-level high-strength special welding.

[0045] S7. The wire rods are inspected and qualified, and then packed and put into storage.

[0046] In addition, the wire rod of the present application avoids the prior art practice of increasing weld strength by adding alloy elements such as nickel (Ni), molybdenum (Mo), and chromium (Cr), which helps reduce production costs.

[0047] Example 1: A special annealing-free welding wire rod with a specification of φ5.5 mm, whose chemical composition, by mass percentage, includes: C 0.04%, Si 0.75%, Mn 1.79%, P 0.007%, N 0.0032%, S 0.015%, Cr 0.48%, Ti 0.22%, Mo 0.14%, V 0.035%, and the rest is Fe and unavoidable impurity elements.

[0048] The production method of annealing-free special welding wire rod includes the following steps: S1. Converter smelting: First, the molten iron is pre-treated and desulfurized using the KR method; the final composition of converter smelting is controlled as follows: C ≤ 0.03%, P ≤ 0.010%, and the tapping temperature is ≥ 1660°C; before tapping, silicon manganese and ferromanganese are added for deoxidation and alloying control.

[0049] S2. Refining: After the refining furnace enters the station, slag making materials are added. The slag making materials include low-carbon ferrochrome (C < 0.10%), ferromolybdenum and ferrovanadium alloy. In the later stage of refining, titanium-ferrowire is fed once and for all to adjust the Ti weight percentage to 0.21~0.28%. After the refining furnace leaves the station, the molten steel is soft-blown with argon.

[0050] S3. Casting of ingots: A continuous casting machine is used to cast ingots with a size of 180 mm × 240 mm. During the casting process, the target superheat is controlled at 75°C and the pulling speed is controlled at 0.9 m / min. The crystallizer is electromagnetically stirred, the water flow rate of the crystallizer is 1130 L / min, the current intensity of the electromagnetic stirring at the head end of the crystallizer is 260 A, and the frequency is 3 Hz; the current intensity of the electromagnetic stirring at the end end is 120 A, the frequency is 10 Hz, and the secondary cooling water flow rate is 0.9 L / kg. The front roller is used to lightly press down 12 mm in 4 passes.

[0051] S4. Heat the slab in a hot furnace: Keep the surface temperature of the slab > 550°C, control the temperature of the heating section and the soaking section to 920-960°C, and control the time of the heating section and the soaking section to 90-120 minutes.

[0052] S5, rolling: the rolling line is equipped with online induction heating, the starting rolling temperature is 850~890℃, the finishing rolling temperature is 910~960℃, and the wire laying temperature is 920~950℃; S6. After the wire rod is spun, it is hot-coiled within 15 seconds, and the hot-coil temperature is controlled at 910℃. After hot-coiled, it enters the insulation corridor for slow cooling: the slow cooling temperature of the pile is 830±30℃, and it is kept warm in the insulation section of the insulation corridor for 35 minutes. Then it enters the slow cooling section of the insulation corridor, and the cooling rate is controlled to be less than 0.05℃ / s. It is slowly cooled to below 550℃ in the insulation corridor.

[0053] S7, the wire rod is inspected and packed for storage, and its metallographic structure is as follows Figure 1 shown.

[0054] Trial 760t: φ5.5mm wire rod was mechanically bent, sanded, and drawn in 14 passes to φ1.2mm, cleaned, and copper-plated. Wire breakage was ≤0.8 per ton of steel, achieving annealing-free drawing.

[0055] Example 2: A special annealing-free welding wire rod with a specification of φ5.5 mm, whose chemical composition, by mass percentage, includes: C 0.05%, Si 0.77%, Mn 1.75%, P 0.005%, N 0.0026%, S 0.013%, Cr 0.55%, Ti 0.24%, Mo 0.09%, V 0.028%, and the rest is Fe and unavoidable impurity elements.

[0056] A method for producing annealing-free special welding wire rod comprises the following steps: S1. Converter smelting: First, the molten iron is pre-treated and desulfurized using the KR method; the final composition of converter smelting is controlled as follows: C ≤ 0.04%, P ≤ 0.003%, and the tapping temperature is ≥ 1664°C; before tapping, silicon manganese and ferromanganese are added for deoxidation and alloying control.

[0057] S2. Refining: After the refining furnace enters the station, slag making materials are added. The slag making materials include low-carbon ferrochrome (C < 0.10%), ferromolybdenum and ferrovanadium alloy. In the later stage of refining, titanium-ferrowire is fed once and for all to adjust the Ti weight percentage to 0.25~0.28%. After the refining furnace leaves the station, the molten steel is soft-blown with argon.

[0058] S3. Casting of ingots: A continuous casting machine is used to cast ingots with a size of 180 mm × 240 mm. During the casting process, the target superheat is controlled at 72°C and the pulling speed is controlled at 0.9 m / min. The crystallizer is electromagnetically stirred, the water flow rate of the crystallizer is 1150 L / min, the current intensity of the electromagnetic stirring at the head end of the crystallizer is 260 A, and the frequency is 3 Hz; the current intensity of the electromagnetic stirring at the end end is 120 A, the frequency is 10 Hz, and the secondary cooling water flow rate is 0.9 L / kg. The front roller is used to lightly press down 12 mm in 4 passes.

[0059] S4. Heat the slab in a hot furnace: Keep the surface temperature of the slab > 550°C, control the temperature of the heating section and the soaking section to 925-955°C, and control the time of the heating section and the soaking section to 90-120 minutes.

[0060] S5, rolling: the rolling line is equipped with online induction heating, the starting rolling temperature is 850~890℃, the finishing rolling temperature is 920~960℃, and the wire laying temperature is 930~950℃; S6. After the wire rod is spun, it is hot-coiled within 15 seconds, and the hot-coil temperature is controlled at 900℃. After hot-coiled, it enters the insulation corridor for slow cooling: the slow cooling temperature is 830±50℃, and it is kept warm in the insulation section of the insulation corridor for 30 minutes. Then it enters the slow cooling section of the insulation corridor, and the cooling rate is controlled to be less than 0.05℃ / s. It is slowly cooled to below 550℃ in the insulation corridor.

[0061] S7, the wire rod is inspected and packed for storage, and its metallographic structure is as follows Figure 2 shown.

[0062] Trial 225t: φ5.5mm wire rod was mechanically bent, sanded, and drawn in 14 passes to φ1.2mm, cleaned, and copper-plated. Wire breakage was ≤0.7 per ton of steel, achieving annealing-free drawing.

[0063] Example 3: A special annealing-free welding wire rod with a specification of φ5.5 mm, whose chemical composition, by mass percentage, includes: C 0.02%, Si 0.65%, Mn 1.50%, P 0.005%, N 0.0030%, S 0.010%, Cr 0.40%, Ti 0.16%, Mo 0.05%, V 0.020%, and the rest is Fe and unavoidable impurity elements.

[0064] The production method of annealing-free special welding wire rod includes the following steps: S1. Converter smelting: First, the molten iron is pre-treated and desulfurized using the KR method; the final composition of converter smelting is controlled as follows: C ≤ 0.04%, P ≤ 0.010%, and the tapping temperature is ≥ 1660°C; before tapping, silicon manganese and ferromanganese are added for deoxidation and alloying control.

[0065] S2. Refining: After the refining furnace enters the station, slag making materials are added. The slag making materials include low-carbon ferrochrome (C < 0.10%), ferromolybdenum and ferrovanadium alloy. In the later stage of refining, titanium-ferrowire is fed once and for all to adjust the Ti weight percentage to 0.16~0.28%. After the refining furnace leaves the station, the molten steel is soft-blown with argon.

[0066] S3. Casting of ingots: A continuous casting machine is used for casting ingots with a size of 180 mm × 240 mm. During the casting process, the target superheat is controlled at 75°C and the pulling speed is controlled at 0.9 m / min. The crystallizer is electromagnetically stirred, the water flow rate of the crystallizer is 1150 L / min, the current intensity of the electromagnetic stirring at the head end of the crystallizer is 260 A, and the frequency is 3 Hz; the current intensity of the electromagnetic stirring at the end end is 120 A, the frequency is 10 Hz, and the secondary cooling water flow rate is 0.9 L / kg. The front roller is used to lightly press down 8 mm in 4 passes.

[0067] S4. Heat the slab in a hot furnace: Keep the surface temperature of the slab > 550°C, control the temperature of the heating section and the soaking section to 920-960°C, and control the time of the heating section and the soaking section to 90-120 minutes.

[0068] S5, rolling: the rolling line is equipped with online induction heating, the starting rolling temperature is 850~890℃, the finishing rolling temperature is 910~960℃, and the wire laying temperature is 920~950℃; S6. After the wire rod is spun, it is hot-coiled within 15 seconds, and the hot-coil temperature is controlled at 910℃. After hot-coiled, it enters the insulation corridor for slow cooling: the slow cooling temperature of the pile is 830±50℃, and it is kept warm in the insulation section of the insulation corridor for 20 minutes. Then it enters the slow cooling section of the insulation corridor, and the cooling rate is controlled to be less than 0.05℃ / s. It is slowly cooled to below 550℃ in the insulation corridor.

[0069] S7. The wire rods are inspected and qualified, and then packed and put into storage.

[0070] Trial test: 450t: φ5.5mm wire rod was mechanically bent, sanded, and drawn in 14 passes to φ1.2mm, cleaned, and copper-plated. Wire breakage was ≤0.7 per ton of steel, achieving annealing-free drawing.

[0071] Example 4: A special annealing-free welding wire rod with a specification of φ5.5 mm, whose chemical composition, by mass percentage, includes: C 0.08%, Si 0.95%, Mn 1.90%, P 0.015%, N 0.0045%, S 0.025%, Cr 0.80%, Ti 0.30%, Mo 0.30%, V 0.060%, and the rest is Fe and unavoidable impurity elements.

[0072] A method for producing annealing-free special welding wire rod comprises the following steps: S1. Converter smelting: First, the molten iron is pre-treated and desulfurized using the KR method; the final composition of converter smelting is controlled as follows: C ≤ 0.04%, P ≤ 0.003%, and the tapping temperature is ≥ 1664°C; before tapping, silicon manganese and ferromanganese are added for deoxidation and alloying control.

[0073] S2. Refining: After the refining furnace enters the station, slag making materials are added. The slag making materials include low-carbon ferrochrome (C < 0.10%), ferromolybdenum and ferrovanadium alloy. In the later stage of refining, titanium-ferrowire is fed once and for all to adjust the Ti weight percentage to 0.27~0.30%. After the refining furnace leaves the station, the molten steel is soft-blown with argon.

[0074] S3. Casting of ingots: A continuous casting machine is used for casting ingots with a size of 180 mm × 240 mm. During the casting process, the target superheat is controlled at 72°C and the pulling speed is controlled at 0.9 m / min. The crystallizer is electromagnetically stirred, the water flow rate of the crystallizer is 1130 L / min, the current intensity of the electromagnetic stirring at the head end of the crystallizer is 260 A, and the frequency is 3 Hz; the current intensity of the electromagnetic stirring at the end end is 120 A, the frequency is 10 Hz, and the secondary cooling water flow rate is 0.9 L / kg. The front roller is used to lightly press down 14 mm in 4 passes.

[0075] S4. Heat the slab in a hot furnace: Keep the surface temperature of the slab > 550°C, control the temperature of the heating section and the soaking section to 925-955°C, and control the time of the heating section and the soaking section to 90-120 minutes.

[0076] S5, rolling: the rolling line is equipped with online induction heating, the starting rolling temperature is 850~890℃, the finishing rolling temperature is 920~960℃, and the wire laying temperature is 930~950℃; S6. After the wire rod is spun, it is hot-coiled within 15 seconds, and the hot-coil temperature is controlled at 900℃. After hot-coiled, it enters the insulation corridor for slow cooling: the slow cooling temperature is 830±50℃, and it is kept warm in the insulation section of the insulation corridor for 30 minutes. Then it enters the slow cooling section of the insulation corridor, and the cooling rate is controlled to be less than 0.05℃ / s. It is slowly cooled to below 550℃ in the insulation corridor.

[0077] S7. The wire rods are inspected and qualified, and then packed and put into storage.

[0078] Trial test: 375t: φ5.5mm wire rod was mechanically bent, sanded, and drawn in 14 passes to φ1.2mm, cleaned, and copper-plated. Wire breakage was ≤0.7 per ton of steel, achieving annealing-free drawing.

[0079] Comparative Example 1: annealing-free 76kg grade welding wire rod, whose chemical composition, by mass percentage, includes: C 0.08%, Si 0.59%, Mn 1.69%, P ≤ 0.010%, N ≤ 0.0025%, S ≤ 0.010%, Cr 0.25%, Ni 0.81%, Cu ≤ 0.15%, Mo 0.22%, Ti 0.10%, B 0.0025%, and the rest is Fe and unavoidable impurity elements.

[0080] The production method of welding wire rod comprises the following steps: (1) During preparation, the smelting method is converter + LF furnace + continuous casting billet 150×150mm + rolled wire rod.

[0081] (2) BOF tapping conditions: the tapping carbon content is 0.05%, the tapping phosphorus content is 0.006%, and the tapping temperature is 1635°C. The order of charging during the tapping process is: deoxidizer → alloy → modified refined slag → lime. The bottom blowing of the BOF adopts argon blowing throughout the process. During the BOF tapping process, silicon-manganese alloy, 5.5 kg / t of lime, and 3.5 kg / t of modified refined slag are added.

[0082] (3) The LF furnace is supplemented with a small amount of lime based on the slag condition and sulfur content. The target alkalinity is controlled below 3.0. Ti and B alloying is performed after the white slag. The static stirring time is ≥10 min. The superheat of the continuous casting billet of 150×150 mm is 24°C, the casting speed is 2.1 m / min, the specific water volume adopts weak cooling mode, the continuous casting adopts protective pouring, and the pouring operation is open argon.

[0083] (4) Rolling wire rod: walking beam heating furnace, preheating section temperature 600℃, heating section temperature 900℃, heating section temperature 1010℃, soaking section temperature 1100℃, starting rolling temperature 1030℃, finishing rolling temperature 860℃, spinning temperature 860℃, after delayed cooling on Stelmor wire, φ5.5mm wire rod is obtained, its metallographic structure is as follows Figure 3 shown.

[0084] (5) Trial use: The wire breaks ≤ 2 times per ton of steel drawn.

[0085] Comparative Example 2: A high-strength welding wire steel, composed of the following components in weight percentage: C 0.08%, Cr 0.40%, Si 0.44%, Ni 0.50%, Mo 0.35%, N 0.06%, Nb 0.04%, V 0.08%, Mn 1.65%; Ti 0.04%, P 0.015%, S 0.004%, with the balance being iron and unavoidable impurities.

[0086] (1) Molten steel smelting: deoxidation and alloying in converter, steelmaking and tapping composition control requirements: C content is 0.08%, P content is ≤0.020%, and tapping temperature is 1620℃.

[0087] (2) Refining: In the early stage of refining, aluminum particles and silicon carbide are used for deoxidation and desulfurization; the content of the following components in the molten steel is controlled: Cr 0.40%, Ni 0.50%, N 0.06%, Nb 0.04%, V 0.08%, Mn 1.65%, Ti 0.04%, P 0.015%, S 0.008%; LF refining produces white slag and maintains it for 25 minutes, and the basicity of the refined slag is controlled at 3; VD vacuum degassing, vacuum degree 65Pa, maintenance time 25 minutes; after LF leaves the station, the molten steel is soft-blown with argon; the argon pressure does not exceed 0.2MPa, the flow rate is 15NL / min, and the soft-blowing time is 20 minutes.

[0088] (3) Casting: Molten steel is poured on a continuous casting machine. Protective casting is used throughout the continuous casting process to avoid contamination of the molten steel. The target superheat is 25°C and the casting speed is controlled at 1.8 m / min. The secondary cooling water volume is 0.8 L / kg. Electromagnetic stirring of the crystallizer and electromagnetic stirring of the end are used. The electromagnetic stirring current of the crystallizer is 300 A and the frequency is 4 Hz. The electromagnetic stirring current of the end is 400 A and the frequency is 10 Hz.

[0089] (4) Controlled rolling and controlled cooling: the rolling start temperature is 960℃, the temperature entering the finishing mill is 880℃, and the temperature entering the sizing and reducing mill is 900℃; the finishing rolling is repeated for 5 passes and the wire drawing temperature is 845℃; the wire is collected after drawing.

[0090] (5) Annealing treatment: Heat the wire to 720℃, keep it warm for 4h, then cool it to 680℃ at a rate of 10℃ / min, keep it warm for 2h, then cool it to 280℃ at a rate of 25℃ / min and keep it warm for 1.5h, and finally slowly cool it to 160℃ before taking it out of the furnace.

[0091] (6) Inspection, packaging and storage, its metallographic structure is as follows Figure 4 shown.

[0092] (7) Trial use: The number of wire breakages per ton of steel drawn is ≤1.5 times.

[0093] Experiment 1: Samples of finished wire rod materials of Examples 1-2 and Comparative Examples 1-2 were taken respectively, and the metallographic structures were observed under an optical microscope at 500X. The results are as follows: Figures 1 to 4 .

[0094] Combine Figure 1 It can be seen that the metallographic structure of the wire rod of Example 1 is mainly ferrite + granular bainite + a very small amount of cementite; Figure 2 The metallographic structure of the wire rod of Example 2 is ferrite + a small amount of cementite; Figure 3 The metallographic structure of the wire rod of comparative example 1 is ferrite + martensite + granular bainite; Figure 4The metallographic structure of the wire rod of comparative example 2 is ferrite + a small amount of cementite; The wire rod prepared in the present application can reduce the bainite structure and basically eliminate the martensite structure, which is beneficial to reducing the tensile strength of the wire rod and realizing annealing-free drawing.

[0095] Experiment 2: The φ5.5 mm wire rods obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were subjected to performance tests on the through-loop tensile strength and through-loop cross-sectional shrinkage. The results are shown in Table 1 below: Table 1 is the performance comparison results of φ5.5mm wire rod of Examples 1 to 4 and Comparative Examples 1 to 2

[0096] Combine Figures 5 to 14 As can be seen from Table 1, the through-loop tensile strength of the wire rods after rolling using Example 1, Example 2, Example 3 and Example 4 of the method of the present invention are 604 MPa, 612 MPa, 565 MPa and 650 MPa, respectively, that is, the through-loop tensile strength of the wire rods is 565~650 MPa; while the through-loop tensile strength of Comparative Example 1 and Comparative Example 2 is 910 MPa and 760 MPa, that is, it exceeds 750 MPa. It can be seen that the through-loop tensile strength of the wire rods prepared by the method of the present invention is much lower than the through-loop tensile strength of the wire rods prepared in the comparative examples.

[0097] Combine Figures 6 to 15 As shown in the figure, the cross-sectional shrinkage of the wire rod after rolling by the method of the present invention is greater than 75%, while the cross-sectional shrinkage of the wire rod after rolling by Comparative Example 1 and Comparative Example 2 is 61%~73%. No annealing treatment is required after rolling by the method of the present invention, and wire breakage is not likely to occur during the drawing process, thereby realizing annealing-free drawing, simplifying the production process, and helping to reduce costs.

[0098] Experiment 3: The φ5.5 mm wire rods obtained in Examples 1-4 and Comparative Examples 1-2 were drawn to form φ1.2 mm welding wires. The wires were tested for their through-loop tensile strength and welded using CO2 gas shielded welding. The test results for the tensile strength and elongation of the weld deposited metal are shown in Table 2 below: Table 2 is the performance comparison results of the wire rods corresponding to φ1.2mm welding wires of Examples 1 to 4 and Comparative Examples 1 to 2

[0099] Combine Figure 7 、 Figure 10 、 Figure 13 and Figure 16As can be seen from Table 2, the wire rods prepared by Example 1, Example 2, Example 3 and Example 4 of the method of the present invention are drawn into φ1.2 mm welding wires, and their tensile strengths are in the range of 1180-1230 MPa, which are relatively uniform overall. However, the dispersion of the tensile strengths of the welding wires of Example 1 and Example 2 is relatively large, and the tensile strength is relatively high at around 1500 MPa. The die loss during the wire drawing process is serious, and the conductive nozzle is easily aggravated during the wire feeding process, resulting in unsmooth wire feeding. The tensile strength of the deposited metal of the welding wire in Example 1, Example 2, Example 3 and Example 4 is 810~920MPa, and the elongation after fracture is 25%~33%, that is, the elongation after fracture is above 25%, and the plasticity is good; while the wire rods prepared in Comparative Example 1 and Comparative Example 2, the tensile strength of the deposited metal of the drawn φ1.2mm welding wire is 760~810MPa, and the elongation after fracture is 15%~23%, and wire breakage is very likely to occur. It can be seen that the wire rods prepared in Example 1, Example 2, Example 3 and Example 4 using the method of the present invention meet the mechanical performance requirements of 80kg-level high-strength special welding.

[0100] The welding wires processed in Comparative Examples 1 and 2 have higher strengths and poorer overall uniformity. It can be seen that the welding wire formed by drawing the wire rod prepared by the method of the present invention can improve the smoothness of wire feeding during welding; and the unique formula components of the present invention and the presence of particles such as TiC, V (CN) and Ti (CN) in the wire rod ensure that the tensile strength of the weld deposited metal during the welding process of the welding wire is greater than 810 MPa, and the elongation after fracture is greater than 18%, which meets the mechanical performance requirements of 80 kg-level high-strength special welding.

[0101] Therefore, compared with the prior art, the beneficial effects of the present invention are as follows: through a unique composition design, the molar number of C+N+S elements is made smaller than the molar number of V+Ti atoms; in the continuous casting process, a light reduction technology for low-carbon steel rectangular billets is adopted to improve the center segregation of the billet, avoid the generation of black heart after rolling, reduce the size of the billet, avoid the problem of high motor load during rough rolling, and adopt a low heating temperature below 980°C and a heating time of less than 2.2h when heating the billet, which is beneficial to avoid and reduce the solid solution of large-sized particles such as TiC, V(CN) and Ti(CN), and at the same time can reduce or avoid dispersion precipitation in the subsequent cooling process.

[0102] After rolling, the use of a high temperature range of 830±50℃ for holding and slow cooling is conducive to the aggregation and growth of small-sized particles such as TiC, V(CN) and Ti(CN), reducing the increase in wire rod strength caused by fine grain strengthening and precipitation strengthening. At the same time, the formation of large-sized compound particles such as TiC, V(CN) and Ti(CN) consumes a large amount of C, N, Ti, and V elements, reducing the solid solution strengthening effect brought by C, N, Ti, and V elements, and correspondingly reducing the hardenability of the wire rod. By combining with a higher Si element, the CCT curve is significantly shifted to the left, ensuring that more than 95% of the wire rod structure is iron, reducing the generation of cementite, reducing the formation of martensite and bainite, and realizing annealing-free drawing of the wire rod, simplifying the production process; During the carbon dioxide gas shielded welding process, the temperature of the weld pool of the finished welding wire of the wire rod of the present application ranges from 1700°C to 2900°C, and large particles of TiC, V (CN) and Ti (CN) are completely dissolved, and are rapidly precipitated as extremely small particles at a relatively high cooling rate. The effects of fine grain strengthening and precipitation strengthening are significant, thereby achieving refinement of the weld structure and a substantial increase in strength, ensuring that the tensile strength of the weld deposited metal is greater than 810 MPa and the elongation after fracture is greater than 18%, meeting the mechanical property requirements of 80kg-level high-strength special welding; avoiding the existing technique of increasing weld strength by adding alloying elements such as nickel (Ni), molybdenum (Mo), and chromium (Cr), which is beneficial to reducing production costs.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A special welding wire rod without annealing, characterized in that: Its chemical composition, by mass percentage, includes: C 0.02~0.08%, Si 0.65~0.95%, Mn 1.50~1.90%, P≤0.015%, N≤0.0045%, S 0.010~0.025%, Cr 0.40~0.80%, Ti 0.16~0.30%, Mo 0.05~0.30%, V 0.020~0.060%, and the rest are Fe and unavoidable impurity elements.

2. The annealing-free special welding wire rod according to claim 1, characterized in that: The mass percentage relationship between elements C, N, S, V, and Ti is as follows: (C / 12+N / 14+S / 32)<(V-0.01%) / 51+(Ti-0.02%) / 48.

3. The annealing-free special welding wire rod according to claim 1, characterized in that: Its chemical composition, by mass percentage, includes: C 0.04%, Si 0.75%, Mn 1.79%, P 0.007%, N 0.0032%, S 0.015%, Cr 0.48%, Ti0.22%, Mo 0.14%, V 0.035%, and the rest are Fe and unavoidable impurity elements.

4. The annealing-free special welding wire rod according to claim 1, characterized in that: Its chemical composition, by mass percentage, includes: C 0.05%, Si 0.77%, Mn 1.75%, P 0.005%, N 0.0026%, S 0.013%, Cr 0.55%, Ti 0.24%, Mo 0.09%, V 0.028%, and the rest are Fe and unavoidable impurity elements.

5. A method for producing an annealing-free special welding wire rod according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Converter smelting: The molten iron entering the furnace is pre-treated and desulfurized using the KR method; S2. Refining: After the refining furnace enters the station, slag material is added. During the refining process, titanium-iron wire is fed once and the Ti weight percentage is adjusted to 0.21~0.28%. After the refining furnace leaves the station, the molten steel is soft-blown with argon gas; S3. Casting the ingot: The ingot is cast using a continuous casting machine. During the casting process, the target superheat is controlled at 70-85°C and the casting speed is controlled at 0.8-1.2 m / min. The crystallizer is electromagnetically stirred. The current intensity of the electromagnetic stirring at the head end of the crystallizer is 250-300 A and the frequency is 3-4 Hz; the current intensity of the electromagnetic stirring at the end end is 100-150 A and the frequency is 8-10 Hz. The secondary cooling water flow rate is 0.8-1.0 L / kg. S4. Heat the slab in a hot heating furnace: Maintain the surface temperature of the slab at >550°C, control the temperature of the heating section and the soaking section at 920-960°C, and control the heating section and the soaking section time at 90-120 minutes; S5, rolling: the rolling line is equipped with online induction heating, the starting rolling temperature is 850~890℃, the finishing rolling temperature is 900~960℃, and the wire laying temperature is 890~950℃; S6. After the wire rod is laid out, it is hot rolled and the hot rolling temperature is controlled to be ≥880℃. After hot rolling, it enters the insulation corridor for slow cooling: the slow cooling temperature is 830±50℃, and it is kept in the insulation section of the insulation corridor for 20-40 minutes. Then it enters the insulation corridor slow cooling section, and the cooling rate is controlled to be less than 0.05℃ / s. It is slowly cooled to below 550℃ in the insulation corridor. S7. The wire rods are inspected and qualified, and then packed and put into storage.

6. The method for producing annealing-free special welding wire rod according to claim 5, characterized in that: In S1, the final composition of the converter smelting is controlled as follows: C≤0.03%, P≤0.010%, and the tapping temperature is ≥1660°C.

7. The method for producing annealing-free special welding wire rod according to claim 6, characterized in that: In S1, before steel is tapped, silicon manganese and ferromanganese are added to control deoxidation and alloying.

8. The method for producing annealing-free special welding wire rod according to claim 5, characterized in that: In the above S2, the slag-making material includes low-carbon ferrochrome (C < 0.10%), ferromolybdenum and ferrovanadium alloy.

9. The method for producing annealing-free special welding wire rod according to claim 5, characterized in that: In the above-mentioned S3, the size of the ingot is 180 mm×240 mm.

10. The method for producing annealing-free special welding wire rod according to claim 5, characterized in that: In the above-mentioned S3, the front roller is used to lightly press down 8 to 14 mm in four passes.

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