Cold rolled steel strip for flux cored wire and method of manufacturing the same
By designing a low-carbon aluminum deoxidation composition and controlling the process rationally, the problems of high cost and poor production stability of cold-rolled steel for flux-cored welding wire have been solved, and cold-rolled steel strip with excellent plasticity and stability has been prepared, which is suitable for the efficient production of flux-cored welding wire.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUNAN HUALING LIANYUAN STEEL SPECIAL NEW MATERIAL CO LTD
- Filing Date
- 2026-03-19
- Publication Date
- 2026-06-09
AI Technical Summary
The addition of precious metals and copper to cold-rolled steel used in existing flux-cored welding wires results in high costs and poor drawing performance. Continuous annealing production lines require large investments, are complex to operate, have poor production stability, and are prone to wire breakage during drawing.
By employing a low-carbon, aluminum-deoxidized composition design, combined with reasonable hot rolling, cold rolling, and bell-type annealing processes, and controlling chemical composition and process parameters, including appropriate cooling rates and annealing temperatures, cold-rolled steel strips with excellent plasticity and stability are produced.
It achieves high elongation, appropriate hardness and good drawing performance of cold-rolled steel strip for flux-cored welding wire, reduces production costs, improves production efficiency and yield, and is suitable for small-batch multi-specification production.
Smart Images
Figure CN122168841A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the technical field, and in particular relates to a cold-rolled steel strip for flux-cored welding wire and its manufacturing method. Background Technology
[0002] Flux-cored welding wire, also known as powder-cored welding wire or tubular welding wire, is divided into two main categories: gas-shielded and non-gas-shielded. Like solid welding wire, the surface of flux-cored welding wire is made of materials with good plasticity, such as low-carbon steel or low-alloy steel. The manufacturing process involves first rolling a steel strip into a U-shaped cross-section, then adding the pre-mixed welding powder to the U-shaped steel strip, pressing it tightly with a press, and finally drawing it into flux-cored welding wires of different specifications.
[0003] Flux-cored welding wire has many advantages. For example, firstly, it is highly adaptable to welding various types of steel, and the composition and ratio of the flux can be easily adjusted to provide the required chemical composition of the weld. Secondly, it has good process performance, produces aesthetically pleasing welds, and achieves good weld formation with combined gas and slag protection. The addition of an arc stabilizer stabilizes the arc and ensures uniform droplet transfer. Thirdly, it has a fast deposition rate and high production efficiency. Under the same welding current, flux-cored welding wire has a higher current density and faster melting rate, with a deposition rate of approximately 85% to 90%, which is about 3 to 5 times higher than that of shielded metal arc welding. Fourthly, it can be used for all-position welding with a larger welding current.
[0004] The finished cold-rolled steel strips used for flux-cored welding wire are mainly 0.5mm to 1.2mm thick, requiring high material performance and surface quality. Generally, an elongation of ≥38% is required to meet the drawing requirements of the welding wire: tensile strength 280MPa to 350MPa, hardness HV80 to 120. While ensuring formability, it is crucial to avoid materials that are too soft, which could lead to uneven wire thickness and breakage during the drawing process, reducing production efficiency and yield.
[0005] Most existing flux-cored welding wires use cold-rolled steel that requires the addition of precious metals, increasing steel costs. Furthermore, the addition or absence of copper is detrimental to the drawing process of the flux-cored wire. In addition, most existing flux-cored welding wires are produced using continuous annealing, but continuous annealing production lines require significant investment, involve complex annealing processes, and are difficult to operate. Summary of the Invention
[0006] This application provides a cold-rolled steel strip for flux-cored welding wire and its manufacturing method. The resulting cold-rolled steel strip for flux-cored welding wire has excellent plasticity, appropriate hardness, stable properties and drawing performance, and the product has excellent performance.
[0007] In a first aspect, this application provides a method for manufacturing cold-rolled steel strip for flux-cored welding wire, comprising: providing molten steel; and continuously casting the molten steel to obtain a continuously cast slab with a chemical composition meeting requirements, wherein the continuously cast slab comprises the following components by mass percentage: C: 0.01wt.%~0.025wt.%, Si: ≤0.01wt.%, Mn: 0.20wt.%~0.40wt.%, P: ≤0.015wt.%, S: ≤0.012wt.%, Al: 0.06wt.%~0.1wt.%. N: ≤0.005wt.%, Cu: ≤0.03wt.%, balance being Fe and unavoidable inclusions; the continuously cast slab is heated and hot-rolled to obtain hot-rolled steel coils; the hot-rolled steel coils are re-coiled and pickled to remove the iron oxide scale on the surface of the hot-rolled steel coil strip to obtain clean strip; the clean strip is rolled in a cold continuous rolling mill at a cold rolling reduction rate of 60% to 80% to obtain cold-rolled steel coils; the cold-rolled steel coils are placed in a full hydrogen bell furnace for annealing, and the annealing temperature is controlled at 650℃ to 700℃ to obtain annealed steel coils; the annealed steel coils are leveled and oiled to obtain cold-rolled steel strips for flux-cored welding wire.
[0008] According to an embodiment of the first aspect of this application, providing molten steel includes: pre-desulfurizing blast furnace molten iron to obtain desulfurized molten iron; placing the desulfurized molten iron in a top-and-bottom combined blowing converter for converter smelting to obtain converter molten steel; and refining the converter molten steel in an RH furnace to obtain RH refined molten steel.
[0009] According to an embodiment of the first aspect of this application, the composition of the molten steel, by mass percentage, needs to meet the following content: C: 0.01wt.%~0.025wt.%, Si: ≤0.01wt.%, Mn: 0.20wt.%~0.40wt.%, P: ≤0.015wt.%, S: ≤0.012wt.%, Al: 0.06wt.%~0.1wt.%, N: ≤0.005wt.%, Cu: ≤0.03wt.%, with the balance being Fe and unavoidable inclusions.
[0010] According to an embodiment of the first aspect of this application, the continuous casting slab is heated and hot-rolled, including: heating the continuous casting slab to 1200℃~1250℃ to obtain a heated slab; performing multi-pass roughing rolling on a reversible roughing mill with ≥5 rolling passes to obtain a rough-rolled slab; performing multi-pass finishing rolling on a finishing continuous rolling mill with ≥7 rolling passes and a finishing temperature of 880℃~930℃ to obtain finished steel; laminar cooling the finished steel to 660℃~730℃ to obtain finished steel to be coiled; and coiling the finished steel to be coiled to obtain a hot-rolled steel coil.
[0011] According to an embodiment of the first aspect of this application, the finished rolled steel is subjected to laminar flow cooling to 660°C to 730°C, using a cooling rate of 20°C / s to 30°C / s.
[0012] According to an embodiment of the first aspect of this application, the annealed steel coil is leveled and oiled, including: leveling the annealed steel coil with a leveling reduction rate of 0.8% to 1.5%, and oiling the coil to obtain cold-rolled steel strip for flux-cored welding wire.
[0013] According to an embodiment of the first aspect of this application, the thickness difference between the cold-rolled steel strip used for flux-cored welding wire and the plate is ≤10μm.
[0014] According to an embodiment of the first aspect of this application, the annealing time for cold-rolled steel coils in a full-hydrogen bell-type furnace is 6h to 10h.
[0015] Secondly, this application provides a cold-rolled strip steel for flux-cored welding wire, which is prepared by the manufacturing method of cold-rolled steel strip for flux-cored welding wire provided in the embodiments of the first aspect.
[0016] According to an embodiment of the second aspect of this application, the cold-rolled steel strip for flux-cored welding wire has a yield strength of 180MPa to 240MPa, a tensile strength of 280MPa to 350MPa, a hardness of HV80 to 120, and an elongation A≥40.
[0017] The method for manufacturing cold-rolled steel strip for flux-cored welding wire in this application adopts a bell-type annealing process. Through appropriate composition design and reasonable process control, the steel strip for flux-cored welding wire has excellent plasticity, appropriate hardness, stable performance and drawing performance. The product has excellent performance and can meet the requirements of flux-cored welding wire. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a schematic flowchart of the manufacturing method of cold-rolled steel strip for flux-cored welding wire provided in the embodiments of this application.
[0020] Figure 2 This is a product drawing of cold-rolled steel strip for flux-cored welding wire provided in Embodiment 1 of this application.
[0021] Figure 3 This is a product drawing of cold-rolled steel strip for flux-cored welding wire provided in Embodiment 2 of this application.
[0022] Figure 4This is a product drawing of cold-rolled steel strip for flux-cored welding wire provided in Comparative Example 1.
[0023] Figure 5 This is a product drawing of cold-rolled steel strip for flux-cored welding wire provided in Comparative Example 2.
[0024] It should be noted that, Figures 2 to 5 All images are metallographic structures of cold-rolled steel strips used for flux-cored welding wire in the corresponding embodiments or comparative examples, magnified 500 times. Detailed Implementation
[0025] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.
[0026] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.
[0027] As mentioned in the background section, existing technologies include methods that do not add copper or the precious metal Ni to cold-rolled flux-cored wire steel. However, adding a large amount of Ni significantly increases the cost of cold-rolled flux-cored wire steel. Other existing technologies include adding Cu and precious rare earth elements to cold-rolled flux-cored wire steel. However, a high Cu content is detrimental to the drawing process of cold-rolled flux-cored wire steel, while adding a large amount of precious rare earth elements significantly increases the cost of cold-rolled flux-cored wire steel.
[0028] Furthermore, the most critical issue in the manufacturing process of flux-cored welding wire is production stability, i.e., preventing wire breakage during drawing, which would affect production efficiency and yield. This requires the cold-rolled strip steel used for flux-cored welding wire production to have excellent plasticity, i.e., high elongation; secondly, it must have a certain hardness, neither too soft nor too hard. If too soft, the diameter of the drawn wire cannot be kept constant, and uneven thickness will easily lead to wire breakage; if too hard, the formability is poor. Thirdly, the steel strip used for flux-cored welding wire must have good performance stability; large fluctuations will easily lead to uneven thickness during drawing, affecting subsequent use. Finally, excessively high Cu content in the steel plate will lead to poor drawing performance. Cu's melting point is 1083℃, which is relatively low, and it is easy to accumulate and precipitate in the steel plate, affecting the plasticity of the strip steel. Existing technologies either do not control the Cu content of the steel strip or have a high content, both of which have an adverse effect on the drawing performance of the welding wire.
[0029] To address the problems of the prior art, embodiments of this application provide a cold-rolled steel strip for flux-cored welding wire and a method for manufacturing the same. The method for manufacturing the cold-rolled steel strip for flux-cored welding wire provided in this application embodiment will be described below.
[0030] Figure 1 A schematic flowchart illustrating the manufacturing method of cold-rolled steel strip for flux-cored welding wire provided in an embodiment of this application is shown. Figure 1 As shown, the manufacturing method of cold-rolled steel strip for flux-cored welding wire includes: providing molten steel; continuously casting the molten steel to obtain a continuously cast slab with a chemical composition meeting the requirements, wherein the continuously cast slab includes the following contents by mass percentage: C: 0.01wt.%~0.025wt.%, Si: ≤0.01wt.%, Mn: 0.20wt.%~0.40wt.%, P: ≤0.015wt.%, S: ≤0.012wt.%, Al: 0.06wt.%~0.1wt.%. N: ≤0.005wt.%, Cu: ≤0.03wt.%, balance being Fe and unavoidable inclusions; the continuously cast slab is heated and hot-rolled to obtain hot-rolled steel coils; the hot-rolled steel coils are re-coiled and pickled to remove the iron oxide scale on the surface of the hot-rolled steel coil strip to obtain clean strip; the clean strip is rolled in a cold continuous rolling mill at a cold rolling reduction rate of 60% to 80% to obtain cold-rolled steel coils; the cold-rolled steel coils are placed in a full hydrogen bell furnace for annealing, and the annealing temperature is controlled at 650℃ to 700℃ to obtain annealed steel coils; the annealed steel coils are leveled and oiled to obtain cold-rolled steel strips for flux-cored welding wire.
[0031] The method for manufacturing cold-rolled steel strip for flux-cored welding wire in this application adopts a bell-type annealing process. Through appropriate composition design and reasonable process control, the steel strip for flux-cored welding wire has excellent plasticity, appropriate hardness, stable performance and drawing performance. The product has excellent performance and can meet the requirements of flux-cored welding wire.
[0032] Compared to existing continuous annealing production lines for producing steel strips, which involve complex annealing processes and high operational difficulty, the cold-rolled steel strip manufacturing method for flux-cored welding wire in this application uses a bell-type furnace for annealing, offering greater flexibility and suitability for small-batch, multi-specification production.
[0033] The method for manufacturing cold-rolled steel strip for flux-cored welding wire in this application uses low-carbon and aluminum deoxidation as grain refining elements, and combines reasonable hot rolling, cold rolling and annealing process control to make its hardness and elongation meet the specified requirements, thereby achieving high elongation, suitable hardness, excellent processing performance and good welding performance, and integrating these properties into one.
[0034] In some embodiments, providing molten steel includes: pre-desulfurizing blast furnace molten iron to obtain desulfurized molten iron; placing the desulfurized molten iron in a top-and-bottom combined blowing converter for converter smelting to obtain converter molten steel; and refining the converter molten steel in an RH furnace to obtain RH refined molten steel.
[0035] In some embodiments, the composition of molten steel, by mass percentage, needs to meet the following content: C: 0.01wt.%~0.025wt.%, Si: ≤0.01wt.%, Mn: 0.20wt.%~0.40wt.%, P: ≤0.015wt.%, S: ≤0.012wt.%, Al: 0.06wt.%~0.1wt.%, N: ≤0.005wt.%, Cu: ≤0.03wt.%, with the balance being Fe and unavoidable inclusions.
[0036] In some embodiments, the continuous casting slab is heated and hot-rolled, including: heating the continuous casting slab to 1200°C~1250°C to obtain a heated slab; performing multi-pass roughing rolling on a reversible roughing mill with ≥5 passes to obtain a rough-rolled slab; performing multi-pass finishing rolling on a finishing continuous rolling mill with ≥7 passes and a finishing temperature of 880°C~930°C to obtain finished steel; laminar cooling the finished steel to 660°C~730°C to obtain finished steel to be coiled; and coiling the finished steel to be coiled to obtain a hot-rolled steel coil.
[0037] The manufacturing method of cold-rolled strip steel of flux-cored welding wire in this application adopts a bell-type annealing furnace and a return process. Compared with the continuous annealing process, the bell-type annealing equipment has lower investment costs, higher production flexibility, and no need for transition materials.
[0038] In some embodiments, the finished steel is laminar cooled to 660°C to 730°C using a cooling rate of 20°C / s to 30°C / s.
[0039] The method for manufacturing cold-rolled strip steel for flux-cored welding wire according to the embodiments of this application involves laminar cooling of the finished steel to 660°C to 730°C. Using a cooling rate of 20°C / s to 30°C / s for laminar cooling can make the microstructure of the finished steel finer, thereby improving its flexibility and preventing wire breakage during the drawing process of flux-cored welding wire preparation, which would affect the production efficiency and quality stability of the welding wire.
[0040] In some embodiments, the thickness difference between the cold-rolled steel strip used for flux-cored welding wire and the plate is ≤10μm.
[0041] In some embodiments, the annealing time for cold-rolled steel coils in a full-hydrogen bell furnace is 6 to 10 hours.
[0042] In some embodiments, the annealed steel coil is leveled and oiled, including: leveling the annealed steel coil with a leveling reduction rate of 0.8% to 1.5%, and oiling the coil to obtain cold-rolled steel strip for flux-cored welding wire.
[0043] The second aspect of this application provides a cold-rolled strip steel for flux-cored welding wire, which is prepared according to the manufacturing method for cold-rolled steel strip for flux-cored welding wire provided in the first aspect.
[0044] In some embodiments, the cold-rolled strip steel of flux-cored welding wire comprises, by weight percentage, the following components: C: 0.01wt.%~0.025wt.%, Si: ≤0.01wt.%, Mn: 0.20wt.%~0.40wt.%, P: ≤0.015wt.%, S: ≤0.012wt.%, Al: 0.06wt.%~0.1wt.%, N: ≤0.005wt.%, Cu: ≤0.03wt.%, with the balance being Fe and unavoidable inclusions.
[0045] The cold-rolled strip steel with flux-cored welding wire in this application improves the drawing stability of the flux-cored welding wire strip steel by reasonably controlling the Cu element content, and ultimately improves production efficiency and yield.
[0046] The cold-rolled strip steel with flux-cored welding wire in this application adopts the following principles for steel composition design and process design control: Considering the drawing stability of flux-cored welding wire during processing, this application adopts a low-carbon design concept, using a certain amount of carbon and aluminum to form cementite and AlN precipitation to inhibit grain growth, thereby giving the strip steel a certain hardness; secondly, this application improves the stability of strip steel performance through narrow-range composition control, thereby improving drawing stability; furthermore, this application avoids Cu agglomeration and precipitation in the steel strip by strictly controlling the Cu element content, thereby avoiding the deterioration of the strip steel's drawing performance.
[0047] The key chemical composition ratios and key process steps of the steel plates used in this application play the following roles: 1) Key chemical composition ratios and their functions C: Carbon content affects the strength and plasticity of the product. High carbon content results in low elongation and the formation of uneven deformation zones after deformation. During recrystallization, these deformation zones promote the nucleation of randomly oriented recrystallized grains, which in turn reduces the texture {111} and decreases formability. Low carbon content, after cold rolling and annealing, cannot meet the strength and hardness requirements. Based on the strength and hardness requirements of the material, the carbon content is designed to be between 0.01 wt.% and 0.025 wt.%.
[0048] Si: Si is both a deoxidizing element and a solid solution strengthening element, increasing the yield strength of the product and decreasing the elongation. Furthermore, high Si content easily leads to the formation of iron oxide scale that is difficult to pickle, affecting the surface quality of the steel plate. Therefore, the lower the Si content, the better; hence, this application designs the Si content to be ≤0.01 wt.%.
[0049] Mn: The main role of manganese in steel is to strengthen and further eliminate the adverse effects of sulfur. To achieve the desired hardness of strip steel, the Mn range is designed to be 0.2wt.% to 0.4wt.%.
[0050] P: Phosphorus is a harmful element in steel, which can cause cold brittleness and reduce toughness. Therefore, it is desirable to control the P content in steel as low as possible. In this application, the P content is designed to be ≤0.015wt.
[0051] S: Sulfur is a harmful element in steel. The compounds formed by S with Mn and Fe elements can cause edge cracking defects in steel during hot rolling. Sulfide inclusions can also deteriorate the deep drawing performance of steel plates. Therefore, the S content is designed to be ≤0.012wt.%.
[0052] Al: Aluminum is added as a deoxidizer during steelmaking. When the content is less than 0.06 wt.%, the inclusions in the steel increase and the stamping performance deteriorates. However, too much Al will lead to increased production costs. Therefore, Al should be controlled between 0.06 wt.% and 0.1 wt.%.
[0053] Nitrogen (N): Like carbon (C), nitrogen (N) is an interstitial atom. When present in a solid solution state, it has a significant strengthening effect, increasing the strength of the steel plate while decreasing its plasticity. Ti needs to be added to bind with N and precipitate to eliminate its adverse effects. Therefore, excessive nitrogen content is detrimental to cost control and should be as low as possible. Thus, this application designs the nitrogen content to be ≤0.005 wt.%.
[0054] Cu: Copper has a low melting point of only 1083℃, and it tends to accumulate and precipitate in steel, reducing the formability of the steel sheet. Therefore, the lower its content, the better. Hence, this application designs the Cu content to be ≤0.03wt.%.
[0055] In some embodiments, the cold-rolled steel strip used for flux-cored welding wire has a yield strength of 180MPa to 240MPa, a tensile strength of 280MPa to 350MPa, a hardness of HV80 to 120, and an elongation A≥40.
[0056] 2) Key process steps and their functions Slab heating temperature: Excessive heating temperature will result in coarse microstructure and reduced hardness. Insufficient heating temperature will prevent the final hot rolling temperature from being completed within the austenitic single-phase region, leading to uneven microstructure. Therefore, the slab heating temperature should be controlled between 1200℃ and 1250℃.
[0057] Hot rolling final rolling temperature: The hot rolling final rolling temperature is set at an austenitic zone temperature higher than Ar3. If the temperature is too high, the iron oxide scale will be severe and difficult to pickle, affecting the surface quality of the steel plate; if the temperature is too low, entering the two-zone rolling will result in mixed crystals of the material, producing snowflake-like defects during stamping, affecting the appearance of the product. Therefore, the final rolling temperature is generally controlled between 880℃ and 930℃.
[0058] Hot-rolled coiling temperature: A coiling temperature greater than 660℃ is beneficial for AlN precipitation and inhibits grain growth during annealing. However, excessively high coiling temperatures can lead to severe iron oxide scale on the steel plate surface, making pickling difficult and affecting the quality of the steel plate. Therefore, the coiling temperature control range is 660℃~730℃.
[0059] Cold rolling deformation: Smaller deformation reduces the nucleation rate of the steel sheet, resulting in larger grain size and lower hardness. Excessive cold rolling deformation increases rolling difficulty and also causes uneven grain size, worsening formability. Therefore, cold rolling deformation should be controlled between 60% and 80%.
[0060] Annealing temperature: The purpose of annealing is to eliminate the work hardening effect of cold rolling, giving the steel sheet excellent plastic forming properties. However, excessively high temperatures increase energy consumption. Therefore, the annealing temperature is controlled within the range of 650℃ to 700℃.
[0061] Leveling elongation: The purpose of leveling is to eliminate the yield plateau in the steel plate, avoiding tensile strain mark defects during stamping, which affect the product's appearance quality, and preventing wire breakage due to uneven deformation. If the leveling elongation is too low, the yield plateau cannot be eliminated; if it is too high, work hardening will occur, the elongation will decrease, and the material's plasticity will be reduced. Therefore, the leveling elongation should be controlled within the range of 0.8% to 1.5%.
[0062] The technical solution of this application will be further described in detail below through specific embodiments and comparative examples.
[0063] Example 1 A method for manufacturing cold-rolled steel strip for flux-cored welding wire, comprising: Provide molten steel; The molten steel is continuously cast to obtain a continuously cast slab. By mass percentage, the continuously cast slab contains the following components: C: 0.017 wt.%, Si: 0.006 wt.%, Mn: 0.29 wt.%, P: 0.0102 wt.%, S: 0.0051 wt.%, Al: 0.084 wt.%, N: 0.0025 wt.%, Cu: 0.026 wt.%, with the remainder being iron and unavoidable impurities. The continuously cast slab is fed into a heating furnace for heating, and exits the furnace at 1234°C to obtain a heated slab. After roughing, the heated slab enters the finishing mill. The roughing temperature is 1062℃, and the roughing is done in 5 passes. The finishing is done in 7 passes, and the finishing temperature is 907℃. The finished steel is cooled to 670℃ using cooling water at a cooling rate of 22℃ / s and then coiled at a coiling temperature of 678℃ to form a 3.3mm thick hot-rolled coil. The hot-rolled coil is then transferred to cold rolling. The cold rolling roll shifting is -26 / -26 on stand 0, -17 / -17 on stand 1, and -12 / -12 on stand 2. The work roll bending force is 35.4 tons on stand 0, 25.7 tons on stand 1, and 24.1 tons on stand 2. The steel plate was acid-rolled into a 1.0 mm thick hard-rolled coil with a cold rolling reduction rate of 69.7%. The hard-rolled coil was then placed in a bell-type annealing furnace and annealed at 670℃ for 8 hours. After cooling, it was leveled on a leveling unit with a leveling reduction rate of 1.0%, and then spun and oiled on a rewinding line. The steel plate has a yield strength of 212 MPa, a tensile strength of 308 MPa, an elongation of 43.5%, and an HV of 103. The thickness difference between plates is 7 μm. No wire breakage occurred during the drawing process of the flux-cored welding wire.
[0064] Example 2 A method for manufacturing cold-rolled steel strip for flux-cored welding wire, comprising: Provide molten steel; The molten steel is continuously cast to obtain a continuously cast slab. By mass percentage, the continuously cast slab contains the following components: C: 0.023 wt.%, Si: 0.0074 wt.%, Mn: 0.33 wt.%, P: 0.0131 wt.%, S: 0.0097 wt.%, Al: 0.0837 wt.%, N: 0.0042 wt.%, Cu: 0.015 wt.%, with the remainder being iron and unavoidable impurities. The continuously cast slab is heated in a heating furnace and removed from the furnace at 1215°C to obtain a heated slab. After roughing, the heated slab enters the finishing mill. The roughing temperature is 1076℃, and the roughing is done in 5 passes. The finishing is done in 7 passes, and the finishing temperature is 921℃. The finished steel is cooled to 710℃ using cooling water at a cooling rate of 27℃ / s and then coiled at a coiling temperature of 705℃ to form a 3.4mm thick hot-rolled coil. The hot-rolled coil is then transferred to cold rolling. The cold rolling roll shifting is -26 / -26 on stand 0, -17 / -17 on stand 1, and -12 / -12 on stand 2. The work roll bending force is 34.5 tons on stand 0, 26.3 tons on stand 1, and 23.8 tons on stand 2. The steel plate was acid-rolled into a 0.8mm thick hard-rolled coil with a cold rolling reduction rate of 76.5%. The hard-rolled coil was then placed in a bell-type annealing furnace and annealed at 695℃ for 9 hours. After cooling, it was leveled on a leveling unit with a leveling reduction rate of 1.2%, and then spun and oiled on a rewinding line. The steel plate has a yield strength of 198MPa, a tensile strength of 297MPa, an elongation of 45.5%, an HV of 96, and a thickness difference of 8μm between plates. No wire breakage occurred during the drawing process of the flux-cored welding wire.
[0065] Example 3 A method for manufacturing cold-rolled steel strip for flux-cored welding wire, comprising: Provide molten steel; The molten steel is continuously cast to obtain a continuously cast slab. By mass percentage, the continuously cast slab contains the following components: C: 0.011 wt.%, Si: 0.0079 wt.%, Mn: 0.228 wt.%, P: 0.0079 wt.%, S: 0.0057 wt.%, Al: 0.0671 wt.%, N: 0.0024 wt.%, Cu: 0.022 wt.%, with the remainder being iron and unavoidable inclusions. The continuously cast slab is heated in a heating furnace and exits the furnace at 1188°C to obtain a heated slab. After roughing, the heated slab enters the finishing mill. The roughing temperature is 1069℃, and the roughing is done in 5 passes. The finishing is done in 7 passes, and the finishing temperature is 914℃. The finished steel is cooled to 675℃ using cooling water at a cooling rate of 21℃ / s and then coiled at 668℃ to form a 3.4mm thick hot-rolled coil. The hot-rolled coil is then transferred to cold rolling. The cold rolling roll shifting is -26 / -26 on stand 0, -17 / -17 on stand 1, and -12 / -12 on stand 2. The work roll bending force is 36.3 tons on stand 0, 25.1 tons on stand 1, and 25.4 tons on stand 2. The steel plate was acid-rolled into a 1.0 mm thick hard-rolled coil with a cold rolling reduction rate of 70.6%. The hard-rolled coil was then placed in a bell-type annealing furnace and annealed at 685℃ for 8 hours. After cooling, it was leveled on a leveling unit with a leveling reduction rate of 0.8%, and then spun and oiled on a rewinding line. The steel plate has a yield strength of 206 MPa, a tensile strength of 311 MPa, an elongation of 42%, and an HV of 110. The thickness difference between plates is 5 μm. No wire breakage occurred during the drawing process of the flux-cored welding wire.
[0066] Example 4 A method for manufacturing cold-rolled steel strip for flux-cored welding wire, comprising: Provide molten steel; The molten steel is continuously cast to obtain a continuously cast slab. By mass percentage, the continuously cast slab contains the following components: C: 0.0143 wt.%, Si: 0.0072 wt.%, Mn: 0.334 wt.%, P: 0.0112 wt.%, S: 0.0085 wt.%, Al: 0.0637 wt.%, N: 0.0027 wt.%, Cu: 0.0117 wt.%, with the remainder being iron and unavoidable impurities. The continuously cast slab is heated in a heating furnace and exits the furnace at 1219°C to obtain a heated slab. After roughing, the heated slab enters the finishing mill. The roughing temperature is 1058℃, and the roughing is done in 5 passes. The finishing is done in 7 passes, and the finishing temperature is 911℃. The finished steel is cooled to 700℃ using cooling water at a cooling rate of 25℃ / s and then coiled at a coiling temperature of 695℃ to form a 3.3mm thick hot-rolled coil. The hot-rolled coil is then transferred to cold rolling. The cold rolling roll shifting is -26 / -26 on stand 0, -17 / -17 on stand 1, and -12 / -12 on stand 2. The work roll bending force is 34.3 tons on stand 0, 24.9 tons on stand 1, and 25.7 tons on stand 2. The steel plate was acid-rolled into a 0.8mm thick hard-rolled coil with a cold rolling reduction rate of 75.8%. The hard-rolled coil was then placed in a bell-type annealing furnace and annealed at 676℃ for 10 hours. After cooling, it was leveled on a leveling unit with a leveling reduction rate of 1.1%, and then spun and oiled on a rewinding line. The steel plate has a yield strength of 199MPa, a tensile strength of 307MPa, an elongation of 43%, an HV of 97, and a thickness difference of 7μm between plates. No wire breakage occurred during the drawing process of the flux-cored welding wire.
[0067] Example 5 A method for manufacturing cold-rolled steel strip for flux-cored welding wire, comprising: Provide molten steel; The molten steel is continuously cast to obtain a continuously cast slab. By mass percentage, the continuously cast slab contains the following components: C: 0.019 wt.%, Si: 0.0054 wt.%, Mn: 0.271 wt.%, P: 0.0083 wt.%, S: 0.0047 wt.%, Al: 0.0772 wt.%, N: 0.0031 wt.%, Cu: 0.0235 wt.%, with the remainder being iron and unavoidable impurities. The continuously cast slab is heated in a heating furnace and exits the furnace at 1233°C to obtain a heated slab. After roughing, the heated slab enters the finishing mill. The roughing temperature is 1060℃, and the roughing process is repeated 5 times. The finishing process is repeated 7 times, and the finishing temperature is 889℃. The finished steel is then cooled to 678℃ using laminar flow cooling water at a cooling rate of 23℃ / s before being coiled at 672℃ to form a 3.3mm thick hot-rolled coil. The hot-rolled coil is then transferred to cold rolling. The cold rolling roll shifting is -26 / -26 on stand 0, -17 / -17 on stand 1, and -12 / -12 on stand 2. The work roll bending force is 35.3 tons on stand 0, 27.2 tons on stand 1, and 22.5 tons on stand 2. The steel plate was acid-rolled into a 0.8mm thick hard-rolled coil with a cold rolling reduction rate of 75.8%. The hard-rolled coil was then placed in a bell-type annealing furnace and annealed at 682℃ for 9 hours. After cooling, it was leveled on a leveling unit with a leveling reduction rate of 1.3%, and then spun and oiled on a rewinding line. The steel plate has a yield strength of 207MPa, a tensile strength of 334MPa, an elongation of 42.5%, an HV of 103, and a thickness difference of 6μm between plates. No wire breakage occurred during the drawing process of the flux-cored welding wire.
[0068] Comparative Example 1 A method for manufacturing cold-rolled steel strip for flux-cored welding wire, comprising: Provide molten steel; The molten steel is continuously cast to obtain a continuously cast slab. By mass percentage, the continuously cast slab contains the following components: C: 0.017 wt.%, Si: 0.0071 wt.%, Mn: 0.312 wt.%, P: 0.0103 wt.%, S: 0.0052 wt.%, Al: 0.0818 wt.%, N: 0.0024 wt.%, Cu: 0.0186 wt.%, with the remainder being iron and unavoidable impurities. The continuously cast slab is fed into a heating furnace for heating, and exits the furnace at 1227°C to obtain a heated slab. After roughing, the heated slab enters the finishing mill. The roughing temperature is 1064℃, and the roughing is done in 5 passes. The finishing is done in 7 passes, and the finishing temperature is 902℃. The finished steel is cooled to 690℃ using cooling water at a cooling rate of 18℃ / s and then coiled at a coiling temperature of 685℃ to form a 3.3mm thick hot-rolled coil. The hot-rolled coil is then transferred to cold rolling. The cold rolling roll shifting is -26 / -26 on stand 0, -17 / -17 on stand 1, and -12 / -12 on stand 2. The work roll bending force is 47.3 tons on stand 0, 35.8 tons on stand 1, and 31.2 tons on stand 2. The steel plate was acid-rolled into a 0.8mm thick hard-rolled coil with a cold rolling reduction rate of 75.8%. The hard-rolled coil was then placed in a bell-type annealing furnace and annealed at 677℃ for 10 hours. After cooling, it was leveled on a leveling unit with a leveling reduction rate of 1.1%, and then spun and oiled on a rewinding line. The steel plate has a yield strength of 198MPa, a tensile strength of 331MPa, an elongation of 44%, an HV of 99, and a thickness difference of 13μm between plates (not meeting customer requirements). No wire breakage occurred during the drawing process of the flux-cored welding wire.
[0069] Comparative Example 2 A method for manufacturing cold-rolled steel strip for flux-cored welding wire, comprising: Provide molten steel; The molten steel is continuously cast to obtain a continuously cast slab. By mass percentage, the continuously cast slab contains the following components: C: 0.022 wt.%, Si: 0.0055 wt.%, Mn: 0.283 wt.%, P: 0.0096 wt.%, S: 0.0061 wt.%, Al: 0.0798 wt.%, N: 0.0027 wt.%, Cu: 0.0513 wt.%, with the remainder being iron and unavoidable impurities. The continuously cast slab is heated in a heating furnace and exits the furnace at 1233°C to obtain a heated slab. After roughing, the heated slab enters the finishing mill. The roughing temperature is 1056℃, and the roughing is done in 5 passes. The finishing is done in 7 passes, and the finishing temperature is 889℃. The finished steel is cooled to 710℃ using cooling water at a cooling rate of 35℃ / s and then coiled at a coiling temperature of 702℃ to form a 3.3mm thick hot-rolled coil. The hot-rolled coil is then transferred to cold rolling. The cold rolling roll shifting is -26 / -26 on stand 0, -17 / -17 on stand 1, and -12 / -12 on stand 2. The work roll bending force is 35.7 tons on stand 0, 25.4 tons on stand 1, and 24.8 tons on stand 2. The steel plate was acid-rolled into 0.8mm thick hard-rolled coils with a cold rolling reduction rate of 75.8%. The hard-rolled coils were then placed in a bell-type annealing furnace and annealed at 686℃ for 10 hours. After cooling, they were leveled on a leveling unit with a leveling reduction rate of 1.2%, and then spun and oiled on a rewinding line. The steel plate has a yield strength of 211MPa, a tensile strength of 341MPa, an elongation of 43.5%, an HV of 109, and a thickness difference of 8μm between plates. Occasionally, wire breakage occurred during the drawing process of the flux-cored welding wire, failing to meet product requirements.
[0070] Table 1 The cold-rolled steel strips for flux-cored welding wire prepared by the methods of Examples 1-5 and Comparative Examples 1-2 show little difference in yield strength, tensile strength, elongation, and Vickers hardness. However, the cold-rolled steel strips for flux-cored welding wire prepared in this application have a relatively lower thickness variation with the plate, indicating better thickness consistency. Figure 2 and 3 As shown, the metallographic structure of the flux-cored welding wire prepared in this embodiment, magnified 500 times, shows relatively small grain size, resulting in virtually no wire breakage during the drawing process. Figure 4 and Figure 5 As shown, the metallographic structure of the cold-rolled steel strip for flux-cored welding wire in Comparative Examples 1 and 2, magnified 500 times, shows that the grains are generally coarse. Furthermore, the thickness difference between the cold-rolled steel strip and the sheet material prepared by the manufacturing method of Comparative Example 2 does not meet the target requirements, significantly impacting the drawing performance during processing and leading to uneven thickness of the drawn flux-cored wire, i.e., excessive fluctuations. The cold-rolled steel strip for flux-cored welding wire prepared by the manufacturing method of Comparative Example 2 occasionally breaks during the drawing process, indicating that the manufacturing method of the cold-rolled steel strip for flux-cored welding wire in this application can produce a cold-rolled steel strip with superior performance. Therefore, not only do the mechanical properties of the cold-rolled steel strip for flux-cored welding wire meet the requirements, but there is also no breakage during the drawing process.
[0071] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.
Claims
1. A method for manufacturing cold-rolled steel strip for flux-cored welding wire, characterized in that, include: Provide molten steel; The molten steel is subjected to continuous casting to obtain a continuously cast slab with a chemical composition that meets the requirements. By mass percentage, the continuously cast slab includes the following components: C: 0.01wt.%~0.025wt.%, Si: ≤0.01wt.%, Mn: 0.20wt.%~0.40wt.%, P: ≤0.015wt.%, S: ≤0.012wt.%, Al: 0.06wt.%~0.1wt.%, N: ≤0.005wt.%, Cu: ≤0.03wt.%, with the balance being Fe and unavoidable inclusions. The continuously cast slab is heated and hot-rolled to obtain a hot-rolled steel coil. The hot-rolled steel coil is re-coiled and pickled to remove the iron oxide scale on the surface of the hot-rolled steel coil strip, resulting in clean strip. The clean strip steel is rolled in a cold rolling mill at a cold rolling reduction rate of 60% to 80% to obtain cold-rolled steel coils; The cold-rolled steel coil is placed in a full-hydrogen bell furnace for annealing, and the annealing temperature is controlled at 650℃~700℃ to obtain an annealed steel coil. The annealed steel coil is flattened and oiled to obtain cold-rolled steel strip for flux-cored welding wire.
2. The method for manufacturing cold-rolled steel strip for flux-cored welding wire according to claim 1, characterized in that, The provision of molten steel includes: Pre-desulfurization of blast furnace molten iron yields desulfurized molten iron; The desulfurized molten iron is placed in a top-and-bottom blown converter for converter smelting to obtain converter steel; The molten steel from the converter is refined in an RH furnace to obtain RH refined molten steel.
3. The method for manufacturing cold-rolled steel strip for flux-cored welding wire according to claim 1, characterized in that, The heating and hot rolling process of the continuously cast slab includes: The continuously cast slab is heated to 1200℃~1250℃ to obtain a heated slab. The heated slab is subjected to multiple passes of rough rolling on a reversible roughing mill, with ≥5 passes, to obtain a rough rolled slab. The rough-rolled slab is subjected to multiple passes of finishing rolling on a finishing continuous rolling mill, with ≥7 rolling passes and a final finishing rolling temperature of 880℃~930℃, to obtain finished steel. The finished steel is subjected to laminar flow cooling to 660°C~730°C to obtain finished steel to be coiled. The fine-rolled steel to be coiled is coiled to obtain a hot-rolled steel coil.
4. The method for manufacturing cold-rolled steel strip for flux-cored welding wire according to claim 1, characterized in that, The molten steel shall have the following composition by mass percentage: C: 0.01wt.%~0.025wt.%, Si: ≤0.01wt.%, Mn: 0.20wt.%~0.40wt.%, P: ≤0.015wt.%, S: ≤0.012wt.%, Al: 0.06wt.%~0.1wt.%, N: ≤0.005wt.%, Cu: ≤0.03wt.%, with the balance being Fe and unavoidable inclusions.
5. The method for manufacturing cold-rolled steel strip for flux-cored welding wire according to claim 3, characterized in that, The rolled steel is then subjected to laminar flow cooling to 660°C to 730°C at a cooling rate of 20°C / s to 30°C / s.
6. The method for manufacturing cold-rolled steel strip for flux-cored welding wire according to claim 1, characterized in that, The annealed steel coil is leveled and oiled, including: The annealed steel coil is leveled with a leveling reduction rate of 0.8% to 1.5%, then slit and coated with oil to obtain cold-rolled steel strip for flux-cored welding wire.
7. The method for manufacturing cold-rolled steel strip for flux-cored welding wire according to claim 1, characterized in that, The thickness difference between the cold-rolled steel strip used for the flux-cored welding wire and the plate is ≤10μm.
8. The method for manufacturing cold-rolled steel strip for flux-cored welding wire according to claim 1, characterized in that, The annealing time for placing the cold-rolled steel coil in the all-hydrogen bell furnace is 6h to 10h.
9. A cold-rolled steel strip for flux-cored welding wire, characterized in that, It is prepared by the method of manufacturing cold-rolled steel strip for flux-cored welding wire according to any one of claims 1-8.
10. The cold-rolled steel strip for flux-cored welding wire according to claim 9, characterized in that, The cold-rolled steel strip used for the flux-cored welding wire has a yield strength of 180MPa~240MPa, a tensile strength of 280MPa~350MPa, a hardness of HV80~120, and an elongation A≥40.