Steel wire rod for low-carbon welding wire and production method of steel wire rod

Abstract

The steel wire rod for the low-carbon welding wire comprises the following chemical components in percentage by weight: 0.06 to 0.08 percent of C, 0.81 to 0.87 percent of Si, 1.41 to 1.47 percent of Mn, less than or equal to 0.023 percent of P, 0.008 to 0.015 percent of S, less than or equal to 0.010 percent of Al, more than or equal to 1.67 percent of Mn / Si and the balance of Fe and inevitable impurities. The invention further provides a production method of the steel wire rod for the low-carbon welding wire, and the steel wire rod for the low-carbon welding wire is prepared through a molten steel smelting procedure, a refining procedure, a casting procedure, a heating procedure, a temperature control rolling procedure and a slow cooling procedure which are sequentially carried out. The tensile strength of the wire rod is smaller than or equal to 550 Mpa, the percentage elongation after fracture is larger than or equal to 35%, the drawing performance is good, and the gas shielded welding wire with the diameter ranging from 0.8 mm to 1.2 mm can be produced; welding wire seam metal provided by the product is good in mobility, a welding pool is fast to solidify, and welding seam formability is good. In addition, the unique slow cooling process enables metallographic phase transformation to be sufficient, the use aging period of the product is shortened by half, and therefore the production cost of a manufacturer is reduced.

Description

Technical Field

[0001] The invention relates to the field of steel material production, in particular to a steel wire rod for low-carbon welding wire and a production method thereof. Background Art

[0002] Welding is a precise, reliable, low-cost and high-tech method of connecting materials. It can make separated workpieces (same or different) produce atomic (molecular) bonding and achieve permanent connection between workpieces. It is an important processing method in the manufacturing industry.

[0003] In the prior art, the uniformity and purity of molten steel components are mainly improved through research, the macro and micro segregation of the billet is reduced, and the surface defect depth of the wire rod, the uniformity of the wire rod structure and strength, the mechanical peeling property of the iron oxide scale, the plasticity and other aspects are improved, so that the final wire rod has high tensile strength, low wire rod strength difference, high cross-sectional shrinkage, low hard phase structure volume percentage, low iron oxide scale indentation depth, high iron oxide scale thickness and other excellent properties, which can meet the needs of high-speed drawing. However, the slow cooling process involved in the prior art only performs Stelmor slow cooling, and generally requires a 15-day aging cycle treatment afterwards, which takes a long time, occupies storage space and increases costs.

[0004] Therefore, how to shorten the aging cycle of welding wire steel after production while ensuring high-speed drawing during welding, and optimize both cost and efficiency at the same time is a problem that many manufacturers need to consider now. Summary of the invention

[0005] The object of the present invention is to provide a low-carbon steel wire rod for welding wire and a production method thereof, so that the quality and performance of the prepared steel wire rod for welding wire are optimized while shortening the aging period.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A first aspect of the present invention provides a low-carbon steel wire rod for welding wire, wherein the chemical composition of the low-carbon steel wire rod for welding wire is as follows in terms of weight percentage: C: 0.06-0.08%, Si: 0.81-0.87%, Mn: 1.41-1.47%, P: ≤0.023%, S: 0.008-0.015%, Al: ≤0.010%, Mn / Si≥1.67, the balance is Fe and unavoidable impurities.

[0007] Furthermore, the chemical composition of the steel wire rod for low carbon welding wire, measured in weight percentage, also includes: Cr: ≤0.10%, Ni: ≤0.05%, Cu: ≤0.05%, Mo: ≤0.10%, Ti: ≤0.10%, V: ≤0.03%, Ca: ≤0.0010%, As: ≤0.03%.

[0008] The second aspect of the present invention provides a method for producing a low-carbon steel wire rod for welding wire, by sequentially performing a molten steel smelting process, a refining process, a casting process, a heating process, a temperature-controlled rolling process and a slow cooling process to obtain the low-carbon steel wire rod for welding wire.

[0009] Furthermore, the molten steel smelting process includes: adding KR desulfurized molten iron and scrap steel into a converter for smelting to obtain molten steel, adding ferrosilicon alloy and silicon-manganese alloy to the molten steel in sequence during the steel-discharging process, and determining whether to add sulfur-containing slag to the molten steel according to the S content in the molten steel; wherein, the C content of the KR desulfurized molten iron is 4.1-4.5%, and the S content is 0.003-0.008%; and the scrap steel ratio is 15-20%.

[0010] Furthermore, when the S content in the molten steel is 0.010-0.015%, it is not necessary to add the sulfur-containing slag; when the S content in the molten steel is ≤0.010%, the sulfur-containing slag is added before adding the ferrosilicon alloy to the molten steel.

[0011] Furthermore, the refining process includes: adding low-titanium, low-aluminum ferrosilicon and metallic manganese to adjust the composition of the molten steel according to the target composition of the steel grade, and then performing LF refining, wherein the LF refining station entry temperature is ≥1560°C.

[0012] Furthermore, the casting process comprises: performing protective casting on the molten steel obtained in the refining process, the superheat of the molten steel is 18-35° C., and the casting billet drawing speed is 2.2-2.4 m / min.

[0013] Furthermore, the heating process includes: heating the steel billet obtained in the casting process in sections, wherein the temperature of the first heating section is 720-850°C, the temperature of the second heating section is 950-1030°C, the temperature of the soaking section is 1050-1100°C, and the steel tapping temperature is 970-1010°C.

[0014] Furthermore, the temperature-controlled rolling process includes: descaling the steel billet obtained in the heating process with high-pressure water, rolling it into wire rod, and then water-cooling it for spinning, wherein the descaling water pressure is ≥15Mpa; the starting rolling temperature is 970-1000°C, the finishing mill inlet temperature is 900-950°C; and the spinning temperature is 940-960°C.

[0015] Furthermore, the slow cooling process includes: after the wire rod produced in the temperature-controlled rolling process is kept warm and slowly cooled on the Stelmor slow cooling line, a second stage of keeping warm and slowly cooling is performed, wherein the cooling rate of the wire rod in the phase change temperature range is ≤0.8°C / s, and the second stage of keeping warm and slowly cooling is 120-150min.

[0016] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The present invention limits the weight percentages of C, Si, Mn, S and P in the steel wire rod for welding wire and simultaneously controls the content of Al to achieve the deoxidation and purification effects on the weld metal, while ensuring the strength and toughness of the weld metal and the smooth progress of the welding process, so that the weld metal structure is transformed into the required organizational structure. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In one embodiment of the present invention, a low-carbon steel wire rod for welding wire is provided, and the chemical composition of the low-carbon steel wire rod for welding wire is calculated by weight percentage: C: 0.06-0.08%, Si: 0.81-0.87%, Mn: 1.41-1.47%, P: ≤0.023%, S: 0.008-0.015%, Al: ≤0.010%, Mn / Si≥1.67, the balance is Fe and unavoidable impurities.

[0019] In the present invention, by limiting the content of carbon element, the eutectoid ferrite in the steel wire rod for welding wire can be effectively reduced, and the content of acicular ferrite can be increased, thereby improving the strength and hardness of the weld metal. Si element and Mn element, as the main deoxidizing element and strengthening element in the steel wire rod for welding wire, play a role of solid solution strengthening, thereby improving the strength of the weld. In the present invention, the mass ratio of Mn / Si is limited to above 1.67. This is because the content of Mn and Si in steel can affect both the castability of molten steel and the mechanical properties of steel. Limiting the Mn / Si ratio within this range can ensure the generation of the required liquid deoxidation product (MnO·SiO2), whose viscosity is lower than SiO2, thereby improving the fluidity of molten steel, which is beneficial to slag removal and continuous casting production.

[0020] As impurity elements in the steel wire rod for welding wire, S and P elements, if their content is too high, will easily cause component segregation at the end of the solidification of molten steel, which is not conducive to the drawing of the wire rod and the low-temperature thermal properties of welding. However, adding an appropriate amount of S and P elements to the steel wire rod for welding wire can improve the cutting performance of the steel. While adding Al as a deoxidizing element, an appropriate amount of Al is also beneficial to improving the impact absorption energy of the weld metal.

[0021] In addition, the chemical composition of the low-carbon steel wire rod also includes Cr: ≤0.10%, Ni: ≤0.05%, Cu: ≤0.05%, Mo: ≤0.10%, Ti: ≤0.10%, V: ≤0.03%, Ca: ≤0.0010%, As: ≤0.03%. The addition of the above elements not only improves the drawing rate of the wire rod in the drawing process of welding wire, but also improves the weld structure, increases its ferrite content, improves the weld toughness, and improves the welding performance of the welding wire.

[0022] Cr can increase the hardenability of steel and has a secondary hardening effect, thereby improving the hardness and wear resistance of steel without making the steel brittle; Mo can also improve the hardenability and heat strength in steel, prevent temper brittleness, and in addition to the above effects, it can also reduce the tendency of carbides to form a continuous network on the grain boundary in the carburized layer, reduce the residual austenite in the carburized layer, and relatively increase the wear resistance of the surface layer. Ni can increase the strength of steel while maintaining good plasticity and toughness. At the same time, Ni has a high corrosion resistance to acids and alkalis, and has rust and heat resistance at high temperatures. Cu can improve the atmospheric corrosion resistance of steel. Ti is a strong deoxidizer in steel, which can make the internal structure of steel dense, refine the grain strength, and then reduce aging sensitivity and cold brittleness, and improve welding performance. The carbides formed by V and C can improve the resistance to hydrogen corrosion under high temperature and high pressure. The addition of Ca can significantly affect the structure and properties of low alloy high strength steel. By combining controlled rolling technology with calcium microalloying technology, steel with good toughness and excellent weldability can be obtained. As has a certain effect on improving the tensile strength of carbon steel.

[0023] The low carbon welding wire steel wire rod is prepared by sequentially performing a molten steel smelting process, a refining process, a casting process, a heating process, a temperature-controlled rolling process and a slow cooling process. Specifically, each of the above processes is described in detail below.

[0024] (1) Molten steel smelting process: After KR desulfurization, the molten iron has C: 4.1-4.5%, S: 0.003-0.008%, and the temperature is 1300-1360℃; during the KR desulfurization process, the molten iron sample is taken every 3-5 minutes, and the S content is analyzed in real time. When the S content is between 0.003-0.008%, the desulfurization is stopped and the slag is removed immediately, and the slag removal rate is ≥95%; Subsequently, the smelting raw materials consisting of the desulfurized molten iron and scrap steel are sent to a converter for smelting, wherein the scrap steel accounts for 15-20% of the smelting raw materials. The scrap steel selected in the present invention is high-quality scrap steel, for example, the head and tail billets cut off during the smelting of low-carbon steel can be selected, but it is certainly not limited thereto. The S content of the selected high-quality scrap steel is 0.005-0.015%, the P content is ≤0.02%, and the rest is Fe and other inevitable components. In addition, the S content in each bag of molten iron is 0.003-0.008%.

[0025] When the S content in the molten steel in this process is determined to be within the range of 0.010-0.015% and 25% of the converter is tapped, the alloy is added in the order of ferrosilicon and high silicon silicon manganese, and all the alloy is added before the end of tapping; when the S content in the molten steel is ≤0.010%, the sulfur-containing slag and the alloy are added in the order of sulfur-containing slag, ferrosilicon, high silicon silicon manganese, and all the sulfur-containing slag and the alloy are added before the end of tapping, and then calcium silicate synthetic slag is added. The ladle bottom blowing and stirring are opened throughout the tapping process. After the synthetic slag is added, stirring is continued for 3-5 minutes. The obtained slag has a basicity of CaO / SiO2=0.4-0.7 and a T.Fe+MnO content of 3-5%.

[0026] The alloy components added are calculated by mass percentage: Si: 70-75%, P≤0.025%, S≤0.015% in ferrosilicon, and the rest are Fe and other inevitable components; Si: 25-30%, Mn: 62-67%, P≤0.015%, S≤0.01% in high silicon silicon manganese, and the rest are Fe and other inevitable components; S: 2.5-5.5%, CaO / SiO2=0.3-0.5, and other inevitable components in sulfur-containing slag, with a particle size of 3-10mm accounting for ≥90%, and a maximum of no more than 20mm; calcium silicate synthetic slag: CaO: 45-55%, SiO2: 35-45%, MgO: 5-10%, and the rest are inevitable components.

[0027] In the present invention, when 25% of the steel is tapped from the converter in the steel smelting process, it is determined whether to add sulfur-containing slag according to the S content in the molten steel, and ferrosilicon and high-silicon silicon-manganese alloy are added to the molten steel simultaneously. By regulating the order of adding various alloys, the content components and slag formation in the molten steel are adjusted, thereby improving the purity of the molten steel and improving the structure and strength of the wire rod.

[0028] In addition, the amount of ferrosilicon alloy added is controlled at 12.5±0.5kg / t, that is, ferrosilicon alloy is added to the molten steel at a ratio of 12.5±0.5kg per ton of molten steel; similarly, the amount of high-silicon silicon manganese alloy added is 20-22kg / t.

[0029] (2) Refining process Take samples of molten steel and slag in the steel smelting process to measure their chemical composition, and start bottom blowing and stirring of the ladle simultaneously. After the composition of the molten steel and slag is tested, add low-titanium, low-aluminum ferrosilicon and metallic manganese to adjust the composition of the molten steel according to the target composition of the steel grade, so that the composition of the molten steel reaches the target composition, and then add lime and silicon carbide to adjust the slag composition to obtain slag basicity CaO / SiO2=0.9-1.2, T.Fe+MnO content: 2.5-4.5%.

[0030] Then the power is turned on to raise the temperature until the molten steel temperature reaches the target value, and then the ladle bottom blowing is adjusted to the soft stirring mode. After the soft stirring is completed, the molten steel is transported to the continuous casting. In this refining process, the added lime includes more than 95% CaO and other inevitable components; silicon carbide includes more than 98% SiC and other inevitable components.

[0031] In this process, the LF refining station entry temperature is ≥1560℃, and the ladle bottom blowing flow rate is 100-150NL / min in the non-operating stage of the LF refining process; the ladle bottom blowing flow rate is 200-250NL / min in the alloying stage; the ladle bottom blowing flow rate is 150-200NL / min in the stage of adding lime and silicon carbide to adjust the slag composition; the ladle bottom blowing flow rate is 200-250NL / min in the power-on heating stage; the ladle bottom blowing flow rate is 50-100NL / min in the soft stirring stage, and the soft stirring time is ≥20min. By adjusting and limiting the above parameters, the homogenization of molten steel is greatly improved, thereby reducing the macro and micro segregation of the billet, so that the organization and strength of the wire rod finally prepared can be improved.

[0032] (3) Casting process The molten steel obtained in the above refining process is cast with long nozzle argon seal + immersion nozzle protection. The superheat of the molten steel is controlled at 18-35℃, and the casting billet is kept at a constant pulling speed of 2.20-2.40m / min to obtain a billet with a cross-sectional size of 150mm×150mm. Of course, the billet size is not limited to this. In addition, the specific water volume is 0.50L / kg; the crystallizer vibration adopts a small amplitude and high frequency to reduce the depth of the vibration mark; the secondary cooling adopts a mist cooling method: the secondary cooling zone distribution ratio is: 30% in zone one, 35% in zone two, 25% in zone three, and 10% in zone four. By controlling the superheat, pulling speed, etc., the macro and micro segregation of the billet is reduced.

[0033] (4) Heating process The steel billet obtained by the above casting process is heated by a regenerative gas heating furnace, and the present invention adopts a segmented heating method, the temperature of the first heating section is 720-850°C, the temperature of the second heating section is 950-1030°C, the temperature of the equalizing section is 1050-1100°C, and the steel tapping temperature is 970-1010°C.

[0034] (5) Temperature controlled rolling process The steel billet obtained through the heating process is descaled by high-pressure water and rolled into wire rod. The descaling water pressure is ≥15Mpa to effectively remove the iron oxide scale on the surface of the steel billet and prevent the residual iron oxide scale from being pressed into the deep part of the wire rod structure during the rolling process.

[0035] The intermediate rolling mill uses machined grooves to ensure the flatness of the wire rod surface and avoid the increase of wire rod surface defects due to the rough groove surface.

[0036] When the steel billet is rolled after descaling, the starting rolling temperature is 970-1000℃, and the inlet temperature of the finishing mill is 900-950℃. The plasticity of the rolled wire rod can be improved by low-temperature rolling.

[0037] Specifically, the steel billet needs to go through rough rolling (rolling size φ73mm±1mm, rolling temperature 850-950℃); intermediate rolling (8 short stress rolling mills, rolling size φ27~32mm±0.6mm, rolling temperature 920-1000℃); pre-finishing rolling (4 cantilever rolling mills, rolling size φ16.8~24.2mm±0.2mm round rolling, rolling temperature 950-1020℃) and finishing rolling (10-stand top cross 45° twist-free rolling mill, according to different finished product specifications, the future material is rolled into 6.5-15mm wire finished products) to obtain wire rods. The finishing outlet temperature is ≤1020℃.

[0038] After the final rolling, the wire rod is water-cooled before spinning, and the spinning temperature is 940-960℃, that is, water cooling is carried out between the rolling mill and the spinning machine, and three or more water cooling tanks are arranged in sequence between the rolling mill and the spinning machine. When the wire rod passes through the three water cooling tanks after leaving the rolling mill, only one or two water cooling tanks close to the spinning machine are opened, and the other water cooling tanks are closed. Of course, it is not limited to this.

[0039] (6) Slow cooling process The wire rod obtained by the above-mentioned temperature-controlled rolling process is placed on the Stelmor slow cooling line for heat preservation and slow cooling. The insulation cover and the fan tuyere are all closed. The cooling rate of the wire rod in the phase change temperature range is ≤0.8℃ / s, so as to extend the residence time of the wire rod in the phase change temperature range and reasonably control the thickness and structure of the oxide scale on the surface of the wire rod to improve the mechanical releasability of the oxide scale.

[0040] Specifically, the Stellmor slow cooling line is 30m long, with an inlet roller speed of 0.16m / s and an outlet roller speed of 0.25m / s (actually there can be a ±5% deviation). This can further ensure that a lower cooling rate is maintained, prolong the residence time in the phase change temperature range, and reasonably control the thickness and structure of the iron oxide scale on the surface of the wire rod to improve the mechanical stripping of the iron oxide scale, and improve the uniformity of the internal structure of the wire rod, which is conducive to increasing the drawing speed of the wire rod when it is drawn into welding wire.

[0041] The wire rods after slow cooling on the Stelmore line are collected at 830℃, and then enter the insulation corridor at 700~770℃ for the second insulation slow cooling for 120~150min, so that the metallographic transformation of the product is more complete, so as to obtain a coarser ferrite structure, and compared with the existing technology, the aging cycle is reduced by 7 days, and the product obtains the required tensile strength and better elongation performance. In addition, two insulation cover doors are respectively provided at the entrance and exit of the insulation corridor to improve the efficiency of product insulation and slow cooling.

[0042] The specific implementation methods of the present invention are further introduced below by setting Examples 1-6 and Comparative Examples 1-3.

[0043] (I) Molten steel smelting The smelting raw materials consisting of desulfurized molten iron and scrap steel were smelted in a 180t converter, wherein the mass percentage of S in each bag of molten iron was 0.003-0.008%. The total loading amount of the smelting raw materials, the weight percentage of molten iron in the smelting raw materials, the smelting time, the mass percentage of C during steel tapping, and the steel tapping temperature of the above 6 embodiments and 3 comparative examples are shown in Table 1: Table 1 It should also be noted that the scrap steel used in the above six embodiments is the head and tail billets of low-carbon steel scrap, while the three comparative examples use ordinary scrap steel.

[0044] (II) Refining The molten steel obtained from the steelmaking process is refined in the LF furnace. During the refining, deoxidation and desulfurization are carried out by making white slag. Before feeding the titanium-iron wire, the content of other alloys is adjusted to meet the target range, and soft stirring is carried out in the later stage of refining. The soft stirring is based on the operating standard that the slag surface fluctuates slightly and the molten steel is not exposed.

[0045] Among them, the refining time, white slag making time, soft stirring time, and steel tapping temperature of the six embodiments and three comparative examples are shown in Table 2: Table 2 (III) Casting The molten steel obtained from the refining process is cast in full protection, including long nozzle argon sealing + immersion nozzle protection casting. During casting, the casting billet is kept at a constant pulling speed, and the crystallizer electromagnetic stirring current is controlled to be 350A and the frequency is 4Hz, and the end electromagnetic stirring current is 480A and the frequency is 10Hz, and the billet is cast into a cross-sectional size of 150mm×150mm. Among them, the superheat of the molten steel and the pulling speed of the 6 embodiments and 3 comparative examples are shown in Table 3: Table 3 (IV) Heating The obtained steel billet is heated under temperature control in a regenerative gas heating furnace. The first heating stage temperature, the second heating stage temperature, the soaking stage temperature, the soaking stage air-fuel ratio, and the holding time of the six embodiments and three comparative examples are shown in Table 4: Table 4 (V) Temperature controlled rolling The steel billet obtained in the heating process is descaled by high-pressure water and rolled into a wire rod. The descaling water pressure, the amount of steel passed by the tungsten carbide roller ring used in the last two passes of finishing rolling, the start rolling temperature, the finishing mill inlet temperature, and the spinning temperature of the 6 embodiments and 3 comparative examples are shown in Table 5. In addition, three water tanks, 5#, 6#, and 7#, are arranged from front to back between the finishing mill and the spinning mill of the last pass, and the opening conditions of the three water tanks in the 6 embodiments and 3 comparative examples are also shown in Table 5: Table 5 (VI) Slow cooling The wire rod obtained in the temperature-controlled rolling process is kept warm and slowly cooled on the Stelmor slow cooling line, the insulation cover and the fan tuyere are all closed, and the cooling rate of the wire rod in the phase change temperature range is ≤0.8°C / s. In addition, the total length of all insulation covers, the entrance roller speed, and the exit roller speed of the Stelmor slow cooling line of the 6 embodiments and 3 comparative examples are controlled as shown in Table 6. Among them, the cooling rate of the wire rod in the phase change temperature range can be calculated by testing the temperature between the insulation covers of the wire rod with an infrared thermometer.

[0046] Table 6 Then, the wire rods after slow cooling on the Stettelmore line were collected at 830°C, and then the temperature was lowered to a certain level before entering the insulation corridor for the second stage of insulation and slow cooling. The temperature entering the insulation corridor, the insulation time of the insulation corridor, and the temperature leaving the insulation corridor for the six embodiments and three comparative examples are shown in Table 7: Table 7 In the present invention, according to the production methods corresponding to the above 6 embodiments and 3 comparative examples, the finally prepared steel wire rods for welding wire were inspected, wherein the chemical composition and weight percentage of each finished product are shown in Table 8: Table 8 In addition, the organization, mechanical properties, scale penetration depth, mechanical stripping rate and aging time of the wire rod are shown in Table 9: Table 9 It can be seen from the above embodiments and comparative examples that the steel wire rod for welding wire in the embodiments of the present invention and the production method thereof, through the homogenization control of the molten steel composition during smelting and the unique controlled cooling process to control the microstructure type and surface quality of the hot-rolled wire rod, the produced wire rod has excellent mechanical properties, good microstructure uniformity of the same circle of wire rods, very small proportion of abnormal microstructure control, almost no effect on the drawing use of the wire rod, easy peeling of the oxide scale, and the aging period is shortened by half compared with the aging period of the wire rod for welding wire manufactured by the traditional controlled cooling process.

[0047] After implementation and verification, the finished wire rods produced by the corresponding production methods in Examples 1-6 can achieve a drawing speed of 25-30m / s when manufacturing welding wires with a diameter of 1.2mm, while the contents of some elements and key production process parameters in Comparative Examples 1-3 are not within the scope of this embodiment. When manufacturing welding wires with a diameter of 1.2mm, the maximum drawing speed is only about 20m / s. When the drawing speed is further increased for testing, wire breakage is serious and normal production cannot be achieved.

[0048] In summary, based on the reasonable design of the steel wire rod components and their mass percentages for welding wire, the prepared wire rod has a tensile strength of ≤550Mpa, an elongation after fracture of ≥35%, and good drawing performance, and can produce gas shielded welding wire with a diameter of 0.8mm~1.2mm; the welding wire provided by the product has good metal fluidity, fast solidification of the welding molten pool, and good weld formability. In addition, the unique slow cooling process in the present invention makes the metallographic transformation sufficient, reduces the product aging cycle by half, and the production cost of the manufacturer is also reduced.

[0049] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A steel wire rod for low carbon welding wire, characterized in that: The chemical composition of the steel wire rod for low carbon welding wire is calculated as follows by weight percentage: C: 0.06-0.08%, Si: 0.81-0.87%, Mn: 1.41-1.47%, P: ≤0.023%, S: 0.008-0.015%, Al: ≤0.010%, Mn / Si≥1.67, and the balance is Fe and unavoidable impurities.

2. A low carbon steel wire rod for welding wire according to claim 1, characterized in that: The chemical composition of the steel wire rod for low carbon welding wire, measured by weight percentage, also includes: Cr: ≤0.10%, Ni: ≤0.05%, Cu: ≤0.05%, Mo: ≤0.10%, Ti: ≤0.10%, V: ≤0.03%, Ca: ≤0.0010%, As: ≤0.03%.

3. A method for producing a low-carbon steel wire rod for welding wire according to claim 1 or 2, characterized in that: The low-carbon steel wire rod for welding wire is obtained by sequentially performing a molten steel smelting process, a refining process, a casting process, a heating process, a temperature-controlled rolling process and a slow cooling process.

4. The method for producing a low-carbon steel wire rod for welding wire according to claim 3, characterized in that: The molten steel smelting process comprises: adding KR desulfurized molten iron and scrap steel into a converter for smelting to obtain molten steel, adding ferrosilicon alloy and silicon-manganese alloy to the molten steel in sequence during the steel-discharging process, and determining whether to add sulfur-containing slag to the molten steel according to the S content in the molten steel; wherein, the C content of the KR desulfurized molten iron is 4.1-4.5%, and the S content is 0.003-0.008%; and the scrap steel ratio is 15-20%.

5. The method for producing a low-carbon steel wire rod for welding wire according to claim 4, characterized in that: When the S content in the molten steel is 0.010-0.015%, it is not necessary to add the sulfur-containing slag; when the S content in the molten steel is ≤0.010%, the sulfur-containing slag is added before adding the ferrosilicon alloy to the molten steel.

6. The method for producing a low-carbon steel wire rod for welding wire according to claim 3, characterized in that: The refining process includes: adding low-titanium, low-aluminum ferrosilicon and metallic manganese to adjust the composition of the molten steel according to the target composition of the steel grade, and then performing LF refining, wherein the LF refining station entry temperature is ≥1560°C.

7. The method for producing a low-carbon steel wire rod for welding wire according to claim 3, characterized in that: The casting process comprises: performing protective casting on the molten steel obtained in the refining process, the superheat degree of the molten steel is 18-35° C., and the casting billet drawing speed is 2.2-2.4 m / min.

8. The method for producing a low-carbon steel wire rod for welding wire according to claim 3, characterized in that: The heating process includes: heating the steel billet obtained in the casting process in sections, wherein the temperature of the first heating section is 720-850°C, the temperature of the second heating section is 950-1030°C, the temperature of the soaking section is 1050-1100°C, and the steel tapping temperature is 970-1010°C.

9. The method for producing a low-carbon steel wire rod for welding wire according to claim 3, characterized in that: The temperature-controlled rolling process comprises: descaling the steel billet obtained in the heating process with high-pressure water, rolling it into wire rod, and then cooling it with water to spin wire, wherein the descaling water pressure is ≥15Mpa; the starting rolling temperature is 970-1000°C, the finishing mill inlet temperature is 900-950°C; and the spinning temperature is 940-960°C.

10. The method for producing a low-carbon steel wire rod for welding wire according to claim 3, characterized in that: The slow cooling process includes: after the wire rod obtained in the temperature-controlled rolling process is kept warm and slowly cooled on the Stelmor slow cooling line, a second stage of keeping warm and slowly cooling is performed; wherein, the cooling rate of the wire rod in the phase change temperature range is ≤0.8°C / s, and the second stage of keeping warm and slowly cooling is 120-150min.

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