Production method of steel for cold-rolled galvanized filter

Abstract

The invention relates to the technical field of steel and iron materials, and provides a production method of steel for a cold-rolled galvanized filter, which comprises the following steps: molten iron is subjected to converter smelting, LF refining, RH refining, continuous casting, heating, rough rolling, finish rolling, laminar cooling, cold rolling, annealing and galvanizing to obtain the steel for the cold-rolled galvanized filter, during RH refining, when the carbon content is smaller than or equal to 0.04%, the vacuum degree ranges from 50 Pa to 133Pa, and the oxygen supply intensity ranges from 3 m < 3 > / (tmin) to 3.5 m < 3 > / (tmin); when the carbon content is larger than or equal to 0.01% and smaller than 0.04%, the vacuum degree is 10-30 Pa, and the oxygen supply intensity is 4.5-5 m < 3 > / (tmin); when the carbon content is smaller than 0.01%, the vacuum degree is 4-8 Pa, and the oxygen supply intensity is 2-2.5 m < 3 > / (tmin). According to the technical scheme, the problem that the strength of the steel for the cold-rolled galvanized filter is poor due to the fact that the capacity of accurately controlling carbon to improve the purity is insufficient in the related technology is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel materials, and in particular to a production method of cold-rolled galvanized filter steel. Background Art

[0002] Cold-rolled galvanized filter steel is a steel material widely used in filter manufacturing for the automotive and other industries. Filters are typically manufactured through forming processes such as deep drawing, which requires the steel to possess excellent deep-drawing properties. Ultra-low carbon steel, compared to conventional steel, offers advantages such as resistance to cracking during deep drawing and a high forming yield, making it the mainstream steel grade for cold-rolled galvanized filter steel. Currently, filter housings primarily utilize traditional interstitial-free ultra-low carbon steel (IF steel), such as DX53D and DX54D. This type of IF steel generally has low strength despite its thickness. The market urgently needs to develop a high-strength ultra-low carbon steel for filters.

[0003] To ensure good strength in ultra-low carbon steel, precise carbon control and improved purity are essential. However, in the current ultra-low carbon steel production process, how to precisely control carbon and improve purity is a difficult problem that companies have to face. Summary of the Invention

[0004] The present invention proposes a production method for cold-rolled galvanized filter steel, which solves the problem in the related art that the strength of cold-rolled galvanized filter steel is poor due to insufficient ability to accurately control carbon to improve purity.

[0005] The technical solutions of the present invention are as follows: The present invention provides a production method for cold-rolled galvanized filter steel, comprising the following steps: molten iron is subjected to converter smelting, LF refining, RH refining, continuous casting, heating, rough rolling, finish rolling, laminar cooling, cold rolling, annealing and galvanizing to obtain cold-rolled galvanized filter steel; During the RH refining, the relationship between carbon content, vacuum degree, and oxygen supply intensity is specifically as follows:

[0006] As a further technical solution, the endpoint of the converter smelting is controlled to be: C 0.05%~0.07%, P≤0.008%, S≤0.016%, in weight percentage.

[0007] In the present invention, by strictly controlling the end point of converter smelting, the influence of harmful elements such as P and S is reduced, and the purity in the production process is improved.

[0008] As a further technical solution, during the LF refining, the white slag holding time is ≥20 minutes, and the soft blowing time is ≥8 minutes.

[0009] In the present invention, during the LF refining stage, the white slag holding time and the soft blowing time are coupled to control the directional floating of inclusions, thereby improving the purity of the production process.

[0010] As a further technical solution, during the continuous casting, the casting speed fluctuation is controlled to be ≤±0.05m / min, and the liquid level fluctuation is controlled to be ≤±3mm.

[0011] In the present invention, by controlling the fluctuation of the drawing speed to ≤±0.05m / min and the fluctuation of the liquid level to ≤±3mm, the stability of the solidification process of the molten steel is ensured and the microstructure of the ingot is made uniform.

[0012] As a further technical solution, during the heating, the temperature of the heating section is 1200~1220℃, and the heating time is 150~180min; the temperature of the soaking section is 1205~1215℃, and the soaking time is 50~60min.

[0013] In the present invention, by strictly controlling the temperature of the heating section, the heating time, the temperature of the soaking section and the soaking time during heating, the surface and core temperatures of the steel material are made uniform, and the structure and properties are made uniform.

[0014] As a further technical solution, during the rough rolling, the starting rolling temperature is 1090~1150℃, the finishing rolling temperature is 1050~1080℃, and the total reduction rate is 65%~75% based on the thickness deformation degree.

[0015] In the present invention, precise temperature control and an appropriate total reduction ratio contribute to improved stability and processing efficiency during the rough rolling process. At a starting rolling temperature of 1090-1150°C, the slab's excellent plasticity ensures uniform rolling deformation, reducing uneven wear between the rolls and the slab and extending the roll's service life. At a finishing rolling temperature of 1050-1080°C, the slab can successfully complete rolling deformation in the final stage. Furthermore, a total reduction ratio of 65%-75% ensures sufficient deformation during the rough rolling stage, providing the appropriate slab thickness and microstructure for the subsequent finishing process.

[0016] As a further technical solution, during the finish rolling, the starting rolling temperature is 960-980°C, the final rolling temperature is 910-940°C, and the total reduction rate is 70%-75% based on the thickness deformation degree.

[0017] In the present invention, the start temperature of the finishing rolling is below 1000°C, which prevents the oxide film on the roller surface from being damaged and causing iron scale that affects the surface quality. The final finishing rolling temperature is above 900°C, ensuring that the finishing rolling is completed in the austenite phase, promoting uniform microstructure and deformation, preventing coarse grains on the plate surface, and reducing the orange peel effect on the plate surface.

[0018] As a further technical solution, during the laminar cooling, when the steel temperature is greater than 760°C, the cooling rate is 20-25°C / s; When the steel temperature is ≤760℃, the cooling rate is 5~10℃ / s.

[0019] In this invention, a "fast-first, slow-later" cooling strategy is employed during laminar cooling to improve the elongation at break of cold-rolled galvanized filter steel by both grain refinement and internal defect reduction. When the steel temperature exceeds 760°C, a high cooling rate of 20-25°C / s promotes rapid austenite transformation, refines ferrite and pearlite grains, and lays the structural foundation for improving the elongation at break of cold-rolled galvanized filter steel. When the steel temperature is ≤760°C, a lower cooling rate of 5-10°C / s is used to avoid thermal stress caused by rapid cooling and prevent the formation of defects such as microcracks.

[0020] As a further technical solution, during the cold rolling, the total reduction rate is 80% to 83% based on the thickness deformation degree.

[0021] In the present invention, under the condition that the total cold rolling reduction is 80% to 83%, the defects inside the steel can be improved to a certain extent, and the steel can be guaranteed to have a suitable organizational state in the subsequent annealing process.

[0022] As a further technical solution, during the annealing, the termination temperature of the heating section is 740~760°C, and the heating time is 15~20 minutes; the temperature of the soaking section is 755~770°C, and the time is 10~15 minutes; the termination temperature of the rapid cooling section is 470~490°C, and the time is 5~10 minutes.

[0023] As a further technical solution, before galvanizing, the temperature of the steel is 455-465°C.

[0024] As a further technical solution, the cold-rolled galvanized filter steel is composed of the following components in weight percentage: C ≤0.005%, Mn 0.28%~0.5%, Si 0.01%~0.03%, Al 0.04%~0.08%, Ti 0.07%~0.08%, P≤0.012%, S≤0.008%, and the rest is Fe and unavoidable impurities.

[0025] The working principle and beneficial effects of the present invention are: In this invention, the "gradient vacuum + carbon-oxygen balance control" technology is used to control the relationship between carbon content, vacuum degree and oxygen supply intensity, so as to ensure that the carbon content of cold-rolled galvanized filter steel can be accurately controlled to improve the purity, so that the cold-rolled galvanized filter steel has good strength. When the carbon content is 0.04% or less, by ensuring the vacuum degree is 50~133Pa and the oxygen supply intensity is 3~3.5m3 / (t•min), avoiding the splashing caused by the violent reaction in the early stage of decarburization; when the carbon content is 0.01%≤<0.04%, by ensuring the vacuum degree is 10~30Pa and the oxygen supply intensity is 4.5~5m 3 / (t•min), accelerate deoxidation, and through the coordination of vacuum degree and oxygen supply intensity, enhance the carbon-oxygen reaction kinetics and prevent the phenomenon of decarbonization stagnation; when the carbon content is less than 0.01%, by ensuring the vacuum degree is 4~8Pa and the oxygen supply intensity is 2~2.5m 3 / (t•min), which avoids the oxidation of alloy elements during oxygen decarburization and reduces the purity of cold-rolled galvanized filter steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Figure 1 This is a metallographic image of the cold-rolled galvanized filter steel before galvanizing produced in Example 1; Figure 2 This is the metallographic image of the cold-rolled galvanized filter steel before galvanizing produced in Example 2. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 any creative efforts are within the scope of protection of the present invention.

[0029] Example 1 A production method for cold-rolled galvanized filter steel, comprising the following steps: molten iron is subjected to converter smelting, LF refining, RH refining, continuous casting, heating, rough rolling, finish rolling, laminar cooling, cold rolling, annealing and galvanizing to obtain cold-rolled galvanized filter steel. The metallographic diagram of the cold-rolled galvanized filter steel before galvanizing is as follows: Figure 1 As shown; The cold-rolled galvanized filter steel is composed of the following components in weight percentage: C 0.005%, Mn 0.28%, Si 0.01%, Al 0.04%, Ti 0.07%, P 0.012%, S 0.008%, and the remainder is Fe and unavoidable impurities; In terms of weight percentage, the endpoint control of converter smelting is: C 0.07%, P 0.008%, S 0.016%; During LF refining, the white slag holding time is 20 minutes and the soft blowing time is 8 minutes; During RH refining, the relationship between carbon content, vacuum degree and oxygen supply intensity is as follows:

[0030] During continuous casting, the casting speed fluctuation is controlled to be ±0.05m / min, and the liquid level fluctuation is controlled to be ±3mm; During heating, the temperature of the heating section is 1200°C and the heating time is 180 minutes; the temperature of the soaking section is 1205°C and the soaking time is 60 minutes; During rough rolling, the starting rolling temperature is 1090℃, the finishing rolling temperature is 1050℃, and the total reduction rate is 65% based on the thickness deformation degree; During finishing rolling, the starting rolling temperature is 960℃, the final rolling temperature is 910℃, and the total reduction rate is 70% based on the thickness deformation degree; During laminar cooling, the cooling rate was 15°C / s and the temperature was cooled to 590°C. During cold rolling, the total reduction is 80% based on the thickness deformation degree; During annealing, the end temperature of the heating section is 740°C and the heating time is 20 minutes; the temperature of the soaking section is 755°C and the time is 15 minutes; the end temperature of the rapid cooling section is 490°C and the time is 5 minutes; Before galvanizing, the temperature of the steel is 465℃. The zinc solution consists of the following components in weight percentage: Fe 1%, Al 1.6%, and the rest is Zn and inevitable impurities. The zinc coating amount is 120g / m 2 .

[0031] Example 2 A production method for cold-rolled galvanized filter steel, comprising the following steps: molten iron is subjected to converter smelting, LF refining, RH refining, continuous casting, heating, rough rolling, finish rolling, laminar cooling, cold rolling, annealing and galvanizing to obtain cold-rolled galvanized filter steel. The metallographic diagram of the cold-rolled galvanized filter steel before galvanizing is as follows: Figure 2 As shown; The cold-rolled galvanized filter steel is composed of the following components in weight percentage: C 0.004%, Mn 0.5%, Si 0.03%, Al 0.08%, Ti 0.08%, P 0.01%, S 0.006%, and the remainder is Fe and unavoidable impurities; In terms of weight percentage, the endpoint control of converter smelting is: C 0.05%, P 0.006%, S 0.015%; During LF refining, the white slag holding time is 25 minutes and the soft blowing time is 10 minutes; During RH refining, the relationship between carbon content, vacuum degree and oxygen supply intensity is as follows:

[0032] During continuous casting, the casting speed fluctuation is controlled to be ±0.03m / min, and the liquid level fluctuation is controlled to be ±1mm; During heating, the temperature of the heating section is 1220°C and the heating time is 150 minutes; the temperature of the soaking section is 1215°C and the soaking time is 50 minutes; During rough rolling, the starting rolling temperature is 1150℃, the finishing rolling temperature is 1080℃, and the total reduction rate is 75% based on the thickness deformation degree; During finishing rolling, the starting rolling temperature is 980℃, the final rolling temperature is 940℃, and the total reduction rate is 74% based on the thickness deformation degree; During laminar cooling, the cooling rate was 15°C / s and the temperature was cooled to 630°C. During cold rolling, the total reduction is 83% based on the thickness deformation degree; During annealing, the heating section temperature is 760°C and the heating time is 15 minutes; the soaking section temperature is 770°C and the time is 10 minutes; the fast cooling section temperature is 470°C and the time is 10 minutes; Before galvanizing, the temperature of the steel is 455℃. The zinc solution consists of the following components in weight percentage: Fe 1%, Al 1.6%, and the rest is Zn and unavoidable impurities. The zinc coating amount is 120g / m 2 .

[0033] Example 3 The only difference between this embodiment and embodiment 1 is that in this embodiment, when the steel temperature is greater than 760°C, the cooling rate is 5°C / s; when the steel temperature is less than or equal to 760°C, the cooling rate is 25°C / s.

[0034] Example 4 The only difference between this embodiment and embodiment 1 is that in this embodiment, when the steel temperature is greater than 760°C, the cooling rate is 25°C / s; when the steel temperature is less than or equal to 760°C, the cooling rate is 5°C / s.

[0035] Example 5 The only difference between this embodiment and embodiment 1 is that in this embodiment, when the steel temperature is greater than 760°C, the cooling rate is 20°C / s; when the steel temperature is less than or equal to 760°C, the cooling rate is 10°C / s.

[0036] Comparative Example 1 The only difference between this comparative example and Example 1 is that in this comparative example, during RH refining, the relationship between carbon content, vacuum degree, and oxygen supply intensity is as follows:

[0037] Comparative Example 2 The only difference between this comparative example and Example 1 is that in this comparative example, during RH refining, the relationship between carbon content, vacuum degree, and oxygen supply intensity is as follows:

[0038] Comparative Example 3 The only difference between this comparative example and Example 1 is that in this comparative example, during RH refining, the relationship between carbon content, vacuum degree, and oxygen supply intensity is as follows:

[0039] Comparative Example 4 The only difference between this comparative example and Example 1 is that in this comparative example, during RH refining, the relationship between carbon content, vacuum degree, and oxygen supply intensity is as follows:

[0040] Comparative Example 5 The only difference between this comparative example and Example 1 is that in this comparative example, during RH refining, the relationship between carbon content, vacuum degree, and oxygen supply intensity is as follows:

[0041] Comparative Example 6 The only difference between this comparative example and Example 1 is that in this comparative example, during RH refining, the relationship between carbon content, vacuum degree, and oxygen supply intensity is as follows:

[0042] Experimental Example 1 Tensile Strength Test With reference to GB / T 228.1-2021 “Tensile tests on metallic materials - Part 1: Room temperature test methods”, the tensile strength of the steels before galvanizing in Examples 1-2 and Comparative Examples 1-6 was tested, and the test results are shown in Table 1 below.

[0043] Table 1 Tensile strength test results

[0044] Comparison between Example 1 and Comparative Examples 1 to 6 shows that by regulating the relationship between carbon content, vacuum degree, and oxygen supply intensity, the cold-rolled galvanized filter steel has good tensile strength.

[0045] Experimental Example 2 Elongation at break test With reference to GB / T 228.1-2021 “Tensile tests on metallic materials - Part 1: Room temperature test methods”, the tensile strength of the steel before galvanizing in Example 1 and Examples 3 to 5 was tested. The test results are shown in Table 2 below.

[0046] Table 2 Elongation at break test results

[0047] Comparison between Examples 1 and 3 and Examples 4 to 5 shows that the laminar cooling strategy of "fast at first and slow later" can improve the elongation at break of cold-rolled galvanized filter steel.

[0048] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, 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 producing cold-rolled galvanized filter steel, characterized in that: The following steps are involved: The molten iron is subjected to converter smelting, LF refining, RH refining, continuous casting, heating, rough rolling, finish rolling, laminar cooling, cold rolling, annealing and galvanizing to obtain cold-rolled galvanized filter steel; During the RH refining, the relationship between carbon content, vacuum degree, and oxygen supply intensity is specifically as follows:

2. The method for producing cold-rolled galvanized filter steel according to claim 1, wherein: Calculated in weight percentage, the endpoint of the converter smelting is controlled to be: C 0.05%-0.07%, P≤0.008%, and S≤0.016%.

3. The method for producing cold-rolled galvanized filter steel according to claim 1, characterized in that: During the LF refining, the white slag holding time is ≥20min, and the soft blowing time is ≥8min; During the continuous casting, the casting speed fluctuation is controlled to be ≤±0.05m / min, and the liquid level fluctuation is controlled to be ≤±3mm.

4. The method for producing cold-rolled galvanized filter steel according to claim 1, characterized in that: During the heating, the temperature of the heating section is 1200-1220° C., and the heating time is 150-180 min; the temperature of the soaking section is 1205-1215° C., and the soaking time is 50-60 min.

5. The method for producing cold-rolled galvanized filter steel according to claim 1, characterized in that: During the rough rolling, the starting rolling temperature is 1090-1150°C, the finishing rolling temperature is 1050-1080°C, and the total reduction rate is 65%-75% based on the thickness deformation degree; During the finish rolling, the starting rolling temperature is 960-980° C., the final rolling temperature is 910-940° C., and the total reduction rate is 70%-75% based on the thickness deformation degree.

6. The method for producing cold-rolled galvanized filter steel according to claim 1, characterized in that: During the laminar cooling, when the steel temperature is greater than 760°C, the cooling rate is 20-25°C / s; When the steel temperature is ≤760℃, the cooling rate is 5~10℃ / s.

7. The method for producing cold-rolled galvanized filter steel according to claim 1, characterized in that: During the cold rolling, the total reduction rate is 80% to 83% based on the thickness deformation degree.

8. The method for producing cold-rolled galvanized filter steel according to claim 1, characterized in that: During the annealing, the heating section has a termination temperature of 740-760° C. and a heating time of 15-20 minutes; the soaking section has a temperature of 755-770° C. and a time of 10-15 minutes; and the rapid cooling section has a termination temperature of 470-490° C. and a time of 5-10 minutes.

9. The method for producing cold-rolled galvanized filter steel according to claim 1, characterized in that: Before galvanizing, the temperature of the steel is 455-465°C.

10. The method for producing cold-rolled galvanized filter steel according to claim 1, wherein: The cold-rolled galvanized filter steel is composed of the following components in weight percentage: C ≤ 0.005%, Mn 0.28% to 0.5%, Si 0.01% to 0.03%, Al 0.04% to 0.08%, Ti 0.07% to 0.08%, P ≤ 0.012%, S ≤ 0.008%, and the remainder is Fe and unavoidable impurities.

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