Method for preparing steel plate for flux-cored welding wire

Abstract

The present invention discloses a method for preparing a steel plate for flux-cored welding wire. The method comprises: subjecting a steel billet to hot rolling, pickling, and cold rolling to obtain a cold-rolled steel coil; subjecting the cold-rolled steel coil to step-by-step annealing and cooling under a protective gas atmosphere to obtain an annealed cold-rolled steel coil, wherein the flow rate of the protective gas is regulated according to the temperature of the step-by-step annealing; and leveling the annealed cold-rolled steel coil to obtain the flux-cored welding wire steel plate. The flux-cored welding wire steel plate prepared by the present invention achieves improved surface quality, drawing performance, and strength by strictly controlling the hydrogen blowing process, annealing temperature process, and the original roughness of the leveling work rolls. This method can better meet the requirements of high-end flux-cored welding wire steel with high surface quality requirements, while also improving the pass rate of flux-cored welding wire steel plates.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical production of metal materials, in particular to a method for preparing a steel plate for flux-cored welding wire. Background Art

[0002] Flux-cored welding wire is a new type of welding material that can be used for welding carbon steel, low-alloy structural steel, heat-resistant steel, high-tensile steel, high-strength quenched and tempered steel, stainless steel, and hard-faced wear-resistant steel. Due to the special preparation method of flux-cored welding wire, the steel plate used to prepare the flux-cored welding wire must have high tensile properties and strength.

[0003] CN102676917A discloses a method for preparing a cold-rolled sheet for flux-cored welding wire. The method involves hot-rolling, pickling, and cold-rolling a steel billet to obtain a cold-rolled steel coil, which is then subjected to continuous annealing and smoothing to prepare the cold-rolled sheet for flux-cored welding wire. The cold-rolled sheet for flux-cored welding wire prepared by this method has low yield strength, high tensile strength, and excellent cold forming and drawing properties. However, this method does not analyze the qualification rate of the cold-rolled steel coil. The heating time, cooling time, and gas flow rate of the cold-rolled steel coil during annealing may have a significant impact on the performance of the cold-rolled steel coil, resulting in a decrease in the product qualification rate, product degradation, or even direct scrapping.

[0004] Therefore, it is necessary to optimize the annealing process in the preparation of steel plates for flux-cored welding wires, improve the qualified rate of flux-cored welding wire steels, and improve economic efficiency. Summary of the Invention

[0005] The present invention improves the drawing performance and strength of the steel plate for flux-cored welding wire by controlling heating time, annealing temperature, cooling speed, hydrogen blowing process and flattening process, and improves the qualified rate of the steel plate for flux-cored welding wire.

[0006] In order to achieve the above object, the present invention provides a method for preparing a steel plate for flux-cored welding wire, the method comprising:

[0007] The steel billet is subjected to hot rolling, pickling and cold rolling to obtain a cold-rolled steel coil;

[0008] Under a protective gas, the cold-rolled steel coil is subjected to step-by-step annealing and cooling to obtain an annealed cold-rolled steel coil, wherein the flow rate of the protective gas needs to be controlled according to the temperature of the step-by-step annealing;

[0009] The annealed cold-rolled steel coil is flattened to obtain steel plates for flux-cored welding wire.

[0010] Furthermore, the cold-rolled steel coil is subjected to step-wise annealing and cooling under a protective gas to obtain an annealed cold-rolled steel coil, wherein the flow rate of the protective gas needs to be regulated according to the temperature of the step-wise annealing, including:

[0011] With a flow rate of 10 to 15 m 3 / h to pass protective gas for 2 to 3 hours. At the same time, heat the cold rolled steel coil from room temperature to 350 to 510℃ in 2.5 to 5 hours, keep it warm for 3 to 5 hours and keep it at a flow rate of 20 to 30m 3 / h to introduce protective gas for 3 to 5 hours;

[0012] After keeping warm for 3 to 5 hours, 3 / h to introduce protective gas for 2-3h, and at the same time, heat the 350-510℃ cold-rolled steel coil to 680-710℃ in 5-8h;

[0013] Keep the cold rolled steel coil at 680-710℃ for 9-19h. After the heat preservation is completed, 3 / h to introduce protective gas for 2h, and at the same time, cool to room temperature to obtain annealed cold-rolled steel coil.

[0014] Furthermore, the process of flattening the annealed cold-rolled steel coil to obtain a steel plate for flux-cored welding wire comprises:

[0015] Controls the elongation of cold rolled coils after annealing.

[0016] Furthermore, the elongation of the cold-rolled steel coil after controlled annealing is,

[0017] The elongation of the cold-rolled steel coil after annealing is adjusted to 1.0% to 1.1%.

[0018] Furthermore, the steel billet is subjected to hot rolling, pickling and cold rolling to obtain a cold-rolled steel coil, and the cold-rolled steel coil does not have defects such as loose coil, flat coil and heart-shaped coil.

[0019] Furthermore, the steel billet is subjected to hot rolling, pickling and cold rolling to obtain a cold-rolled steel coil, and the thickness of the cold-rolled steel coil is 0.8 to 1.0 mm.

[0020] Furthermore, the cooling includes air cooling and spraying.

[0021] Furthermore, the steel billet is subjected to hot rolling, pickling and cold rolling to obtain a cold-rolled steel coil. The specific parameters of hot rolling, pickling and cold rolling include:

[0022] Hot rolling parameters: heating temperature 1200-1270℃, finishing temperature 870-900℃, coiling temperature 530-570℃;

[0023] Pickling parameters: acid concentration is controlled at 65-75g / L, and pickling temperature is 75-85℃;

[0024] Cold rolling parameters: cold rolling reduction rate is 70-80%.

[0025] Furthermore, the protective gas includes nitrogen and / or hydrogen.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The flux-cored welding wire steel plate produced by the method of the present invention achieves improved surface quality, drawing performance, and strength by strictly controlling the hydrogen blowing process, annealing temperature process, and smoothing the original roughness of the work rolls. This method can better meet the requirements of high-end flux-cored welding wire steel for use with high surface quality, while also improving the pass rate of flux-cored welding wire steel plates. The method accurately controls the heating process and adjusts the holding time to achieve uniform performance of the flux-cored welding wire steel plate, resulting in excellent cold forming and drawing properties for the flux-cored welding wire steel plate, which can better meet the requirements of multiple drawing passes for flux-cored welding wire steel.

[0028] Other features and advantages of the invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the invention. The purpose and other advantages of the invention can be realized and obtained by the steps or processes indicated in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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 work.

[0030] Figure 1 A flow chart showing a method for preparing a steel plate for flux-cored welding wire according to the present invention is shown;

[0031] Figure 2 A schematic diagram showing an annealing process according to an embodiment of the present invention is shown;

[0032] Figure 3 The metallographic structure diagram of the steel plate for flux-cored welding wire prepared in the embodiment of the present invention is shown;

[0033] Figure 4 The metallographic structure of the steel plate for flux-cored welding wire prepared in the comparative example of the present invention is shown. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the specific embodiments of the present invention and the accompanying drawings. Obviously, the embodiments described 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 are within the scope of protection of the present invention.

[0035] The heating time, cooling time and gas flow rate of cold-rolled steel coils for flux-cored welding wire during annealing may have a significant impact on their performance, resulting in a decrease in product qualification rate, product degradation, or even direct scrapping. Figure 1 As shown, the present invention provides a method for preparing a steel plate for flux-cored welding wire, comprising the following steps:

[0036] S101, hot rolling, pickling and cold rolling the steel billet to obtain a cold-rolled steel coil;

[0037] S102, subjecting the cold-rolled steel coil to step-annealing and cooling under a protective gas to obtain an annealed cold-rolled steel coil, wherein the flow rate of the protective gas needs to be controlled according to the temperature of the step-annealing;

[0038] S103, flattening the annealed cold-rolled steel coil to obtain a steel plate for flux-cored welding wire.

[0039] More specifically, step S102 includes: 3 / h to pass protective gas for 2 to 3 hours. At the same time, heat the cold rolled steel coil from room temperature to 350 to 510℃ in 2.5 to 5 hours, keep warm for 3 to 5 hours and pass the protective gas at a flow rate of 20 to 30m 3 / h to pass protective gas for 3 to 5 hours; after keeping warm for 3 to 5 hours, 3 / h to pass protective gas for 2 to 3 hours, and at the same time, heat the 350-510℃ cold-rolled steel coil to 680-710℃ in 5 to 8 hours; keep the cold-rolled steel coil at 680-710℃ for 9 to 19 hours, and then, at a flow rate of 5 to 10m 3 / h is supplied with protective gas for 2 hours, and the steel is cooled to room temperature to obtain annealed cold-rolled steel coils. The protective gas includes nitrogen and / or hydrogen.

[0040] The present invention improves the surface quality and performance of steel plate products for flux-cored welding wire by precisely regulating the temperature process of cold-rolled steel coil annealing, strictly controlling the flow rate of shielding gas, and smoothing the original roughness of the working roll.

[0041] It should be noted that the steel billet used in the embodiment of the present invention is PHS1, and the mass percentages of its elemental components are shown in Table 1.

[0042] Table 1 Elemental composition of steel billets used in the examples

[0043] element C Si Mn P S Alt Fe Mass percentage (%) 0.019 0.01 0.19 0.010 0.010 0.040 margin

[0044] Specific process parameters include: hot rolling process parameters: heating temperature of 1270°C, finishing temperature of 880°C, and coiling temperature of 550°C; pickling parameters: total iron ion concentration in the 0# acid tank controlled at 110 g / L, free acid concentration of 70 g / L, pickling temperature of 80°C, and pickling speed of 160 m / min; cold rolling parameters: a 4-stand, 6-roller HC continuous rolling mill with a cold rolling reduction of 75%. The steel slabs were hot rolled, pickled, and cold rolled to produce cold-rolled coils. The resulting cold-rolled coils had a thickness of 1.0 mm and were free of loose coils, flat coils, and heart-shaped coils. These details will not be further detailed in the specific examples.

[0045] Example

[0046] A method for preparing a steel plate for flux-cored welding wire comprises the following steps:

[0047] T1, hot rolling, pickling and cold rolling the steel billet to obtain a cold-rolled steel coil;

[0048] T2: Place the cold-rolled steel coil obtained in step T1 into a bell-type annealing furnace, introduce nitrogen gas so that the oxygen content in the bell-type annealing furnace is less than 1%, ignite and heat, and heat the cold-rolled steel coil from room temperature 25°C to 510°C in 4.5 hours. During the first 3 hours of the 4.5 hours of heating, heat the cold-rolled steel coil at a flow rate of 15m / s. 3 / h hydrogen was introduced for purging, and the cold rolled steel coil was kept at 510℃ for 5h. During the 5h of keeping warm, the flow rate was 30m 3 / h continuous introduction of hydrogen for purging;

[0049] T3, after the cold rolled steel coil is kept at 510℃ for 5 hours, it is heated again and heated to 710℃ in 5 hours. The flow rate is 15m3 / s for the first 2 hours of the heating period. 3 / h hydrogen purging was introduced, and after the temperature was raised to 710℃, the cold rolled steel coil was kept at 710℃ for 14.5h;

[0050] T4, cold rolled steel coil after 14.5h of heat preservation at 710℃, with a flow rate of 5m 3 / h to purge hydrogen for 2h, and at the same time use cooling hood for air cooling and spray cooling. When the gas temperature in the bell-type annealing furnace drops to 120℃, nitrogen purge flow rate reaches 50m 3 Finally, the cooling cover and the inner cover are removed, and the cold-rolled steel coil after the insulation is completed is hung on the final cooling table and blown to cool it to room temperature 25°C to obtain the annealed cold-rolled steel coil.

[0051] T5. The annealed cold-rolled steel coil obtained in step T4 is smoothed using a work roll with a roughness of 2.0 μm, and the elongation is controlled to be 1.1%, thereby obtaining a steel plate for flux-cored welding wire.

[0052] Figure 2The schematic diagram of the annealing process of this embodiment is shown, and the heating rate, heating temperature, holding time and hydrogen purge conditions of the annealing process of this embodiment are summarized. It can be seen that the heating time is 4.5 hours from room temperature 25℃ to 510℃, and the flow rate of 15m3 / s in the first 3 hours is 15m3 / s. 3 / h to pass hydrogen purge; keep warm at 510℃ for 5h, with a flow rate of 30m 3 / h continuously introduced hydrogen purge; then the temperature was raised to 710℃ within 5h, with a flow rate of 15m 3 / h to pass hydrogen purge; heat to 710℃ and keep warm for 14.5h, then 2h at a flow rate of 5m 3 It can also be seen that hydrogen is not always introduced for purging during the continuous heating and heat preservation process in this embodiment, which can also save the cost of hydrogen injection.

[0053] Comparative Example

[0054] A method for preparing a steel plate for flux-cored welding wire comprises the following steps:

[0055] T1, hot rolling, pickling and cold rolling the steel billet to obtain a cold-rolled steel coil;

[0056] T2: The cold-rolled steel coil obtained in step T1 is placed in a bell-type annealing furnace, and nitrogen is introduced to make the oxygen content in the bell-type annealing furnace less than 1%. The ignition is started and the temperature of the cold-rolled steel coil is raised from room temperature 25°C to 350°C in 2.5 hours, and the temperature is heated at a flow rate of 10m 3 / h hydrogen is introduced for continuous purging;

[0057] T3, after the temperature of the cold rolled steel coil is raised to 350℃, it is heated again and raised to 680℃ within 8 hours. The flow rate is 30m3 / s for the first 3 hours of the 8 hours of heating. 3 / h to pass hydrogen for purging, and then for 3h at a flow rate of 20m 3 / h hydrogen purging was introduced, and after the temperature was raised to 680℃, the cold rolled steel coil was kept at 680℃ for 12h;

[0058] T4, cold rolled steel coil after 12h of heat preservation at 680℃ with a flow rate of 5m 3 / h to purge hydrogen for 2h, and at the same time use cooling hood for air cooling and spray cooling. When the gas temperature in the bell-type annealing furnace drops to 120℃, nitrogen purge flow rate reaches 50m 3 Finally, the cooling cover and the inner cover are removed, and the cold-rolled steel coil after the insulation is completed is hung on the final cooling table and blown to cool to room temperature 25°C to obtain the annealed cold-rolled steel coil;

[0059] T5. The annealed cold-rolled steel coil obtained in step T4 is smoothed using a work roll with a roughness of 3.0 μm, and the elongation is controlled to be 1.0%, thereby obtaining a steel plate for flux-cored welding wire.

[0060] Test Case

[0061] A batch of steel billets was prepared using the methods of the embodiment and the comparative example to obtain 10 batches of flux-cored steel plates for welding wire, and the yield strength, tensile strength, elongation, surface smoothness and HRB hardness of the 10 batches of flux-cored steel plates for welding wire of the embodiment and the comparative example were tested. Tables 2 and 3 show the performance test results of the flux-cored steel plates for welding wire obtained by the methods of the embodiment and the comparative example, respectively. It should be noted that the comparative example is the original production process of the flux-cored steel plates for welding wire, and the technical agreement requirements are the requirements put forward by the customer for the quality of the flux-cored steel plates for welding wire. When the produced flux-cored steel plates for welding wire do not meet any of the parameter requirements in the technical agreement requirements, the produced flux-cored steel plates for welding wire are unqualified products and need to be reworked, downgraded or scrapped.

[0062] Table 2 Performance test results of steel plates for flux-cored welding wire prepared by the method of embodiment

[0063]

[0064]

[0065] It can be seen from the test results in Table 2 that all properties of the flux-cored welding wire steel plate prepared in the embodiment can meet the requirements, and the qualified rate calculated according to the requirements reaches 100%. These results show that the flux-cored welding wire steel plate prepared in the embodiment has excellent cold forming performance and drawing performance, can better meet the requirements of flux-cored welding wire steel, and improves the economic efficiency of the preparation of the flux-cored welding wire steel plate.

[0066] Table 3 Performance test results of steel plates for flux-cored welding wire prepared by the comparative example method

[0067]

[0068] From the test results in Table 3, it can be seen that the steel plate for flux-cored welding wire prepared in the comparative example has a large change in yield strength, while the elongation A 80 Poor, almost at elongation A 80 The requirements fluctuate up and down, and the qualified rate calculated based on the requirements is only 70%. These results show that the preparation method of the comparative example is unstable and is not suitable for application production line production.

[0069] At the same time, surface measurements were also performed, and it was found that the steel plate for flux-cored welding wire prepared in the embodiment had lower frequencies of surface oxidation color, black spots, and color difference problems than those in the comparative example. Figure 3 The metallographic structure diagram of the steel plate for flux-cored welding wire prepared in the embodiment is shown. Figure 4 The metallographic structure diagram of the steel plate for flux-cored welding wire prepared in the comparative example is shown. Figure 3 and Figure 4 The scale bars are all 50 μm. Figure 3 and Figure 4 By comparison, it can be seen that the steel plate for flux-cored welding wire prepared in the embodiment of the present invention has a complete recrystallized structure, less granular cementite, uniform grain size, and better organizational structure and cold forming performance.

[0070] The differences in surface properties and quality of the flux-cored welding wire steel plates prepared in the examples and comparative examples are directly caused by the differences in the heating rate, holding time, and hydrogen purge flow rate during the annealing process, as well as the differences in the roughness of the work rolls used for leveling. The method of the embodiment of the present invention achieves better surface quality, drawing performance, and strength by strictly controlling the hydrogen blowing process, the annealing temperature process, and the original roughness of the leveling work rolls. It can better meet the use requirements of high-end flux-cored welding wire steel with high surface quality requirements, and at the same time improve the pass rate of flux-cored welding wire steel plates. The present invention accurately controls the heating process and adjusts the holding time to achieve uniformity in the performance of the flux-cored welding wire steel plates; it enables the flux-cored welding wire steel plates to have excellent cold forming and drawing properties, which can better meet the requirements of multiple drawing passes of flux-cored welding wire steel.

[0071] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. 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 method for preparing a steel plate for flux-cored welding wire, characterized in that: The method comprises, The steel billet is subjected to hot rolling, pickling and cold rolling to obtain a cold-rolled steel coil; Under a protective gas, the cold-rolled steel coil is subjected to step-by-step annealing and cooling to obtain an annealed cold-rolled steel coil, wherein the flow rate of the protective gas needs to be controlled according to the temperature of the step-by-step annealing; The annealed cold-rolled steel coil is flattened to obtain a steel plate for flux-cored welding wire; The cold-rolled steel coil is subjected to step-wise annealing and cooling under protective gas to obtain annealed cold-rolled steel coil, wherein the flow rate of protective gas needs to be controlled according to the temperature of the step-wise annealing, including: With flow rate of 10~15m 3 / h to introduce protective gas for 2~3h. At the same time, heat the cold rolled steel coil from room temperature to 350~510℃ in 2.5~5h, keep it warm for 3~5h and keep it at a flow rate of 20~30m 3 / h to introduce protective gas for 3~5h; After keeping warm for 3~5h, 3 / h to introduce protective gas for 2~3h, and at the same time, heat the 350~510℃ cold-rolled steel coil to 680~710℃ in 5~8h; Keep the cold rolled steel coil at 680~710℃ for 9~19h. After the heat preservation, 3 / h to introduce protective gas for 2h, and at the same time, cool to room temperature to obtain annealed cold-rolled steel coil.

2. The method according to claim 1, characterized in that The process of flattening the annealed cold-rolled steel coil to obtain a steel plate for flux-cored welding wire comprises: Controls the elongation of cold rolled coils after annealing.

3. The method according to claim 2, characterized in that The elongation of the cold-rolled steel coil after controlled annealing is, The elongation of the cold-rolled steel coil after annealing is adjusted to 1.0%~1.1%.

4. The method according to claim 1, wherein The steel billet is subjected to hot rolling, pickling and cold rolling to obtain a cold-rolled steel coil, and the cold-rolled steel coil does not have defects such as loose coil, flat coil and heart-shaped coil.

5. The method according to claim 1, wherein The steel billet is subjected to hot rolling, pickling and cold rolling to obtain a cold-rolled steel coil, and the thickness of the cold-rolled steel coil is 0.8-1.0 mm.

6. The method according to claim 1, characterized in that The cooling includes air cooling and spraying.

7. The method according to claim 1, characterized in that The steel billet is hot rolled, pickled and cold rolled to obtain cold rolled steel coil. The specific parameters of hot rolling, pickling and cold rolling include: Hot rolling parameters: heating temperature 1200~1270℃, finishing temperature 870~900℃, coiling temperature 530~570℃; Pickling parameters: acid concentration is controlled at 65~75g / L, pickling temperature is 75~85℃; Cold rolling parameters, cold rolling reduction rate is 70~80%.

8. The method according to claim 1, characterized in that The protective gas includes nitrogen and / or hydrogen.

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