A deep-drawn steel plate and its production process

Abstract

The invention relates to the technical field of steel smelting, and proposes a low-cost deep-drawing steel plate and a production process thereof. The composition of the low-cost deep-drawing steel plate is as follows by mass percentage: C 0.02% to 0.07%, Si≤0.03%, Mn 0.08% to 0.20%, P≤0.025%, S≤0.020%, Als 0.015% to 0.055%, the balance is Fe and inevitable impurities, the production process includes the following steps: S1, converter smelting: add the raw materials into the converter for blowing; S2, LF refining; S3, continuous casting into slabs; S4, hot rolling; S5, cold rolling pickling; S6, annealing: heating to 480-500℃ at 70-90℃ / h, keeping warm for 5-6h; heating to 680-700℃ at 70-110℃ / h, keeping warm for 8-10h; air cooling to 200-250℃, then water cooling to 50-60℃, and finally cooling at room temperature for 5-6h; S7, flattening treatment to obtain the low-cost deep-drawing steel plate. Through the above technical solution, the problem that the cost and quality of deep-drawing steel plates in the prior art cannot be taken into account is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and in particular to a deep-drawn steel plate and a production process thereof. Background Art

[0002] As an intermediate product of cold-rolled sheet, SPHC has a wide range of uses, such as cold-rolled pickled sheet, cold hardened coil, raw material for color coating and galvanizing, low-level stamping parts, structural parts, and 0.16mm ultra-thin sheet, etc., and its usage is relatively large. In recent years, under the fierce market competition, downstream manufacturing users have higher and higher quality requirements for ordinary SPCC cold-rolled sheets, not only requiring ordinary SPCC cold-rolled sheets to have certain stamping performance, but also putting forward higher requirements for the appearance and surface quality of ordinary SPCC cold-rolled sheets. In addition to the cold rolling production process, the quality of hot-rolled SPHC raw materials also has a decisive influence on the quality of the final cold-rolled products.

[0003] With the deteriorating steel market, the steel industry has entered an era of losses. High added value and are the two major goals that the steel industry has been pursuing. Creating the most value with the lowest cost and the highest quality is the basis for the survival and development of steel companies. Under the premise of ensuring quality, further reducing process costs is the significance of the invention. Summary of the invention

[0004] The present invention provides a deep-drawing steel plate and a production process thereof, which solves the problem in the related art that the cost and quality of the deep-drawing steel plate cannot be taken into consideration at the same time.

[0005] The technical solution of the present invention is as follows:

[0006] A deep-drawing steel sheet, wherein the composition of the deep-drawing steel sheet is, by mass percentage, C 0.02% to 0.07%, Si ≤0.03%, Mn 0.08% to 0.20%, P ≤0.025%, S ≤0.020%, Als 0.015% to 0.055%, and the balance is Fe and unavoidable impurities.

[0007] As a further technical solution, the composition of the deep drawing steel sheet is, by mass percentage, C 0.06%, Si≤0.02%, Mn 0.12%, P≤0.015%, S≤0.015%, Als 0.02%, and the balance is Fe and unavoidable impurities.

[0008] As a further technical solution, when the thickness of the deep-drawn steel plate is 4-5 mm, the yield strength is 290-310 MPa, the tensile strength is 340-360 MPa, and the elongation is 42%-44%.

[0009] The present invention also provides a production process for deep drawing steel plates, comprising the following steps:

[0010] S1. Converter smelting: adding raw materials into the converter for blowing;

[0011] S2, LF refining;

[0012] S3, continuous casting into slab;

[0013] S4, hot rolling;

[0014] S5, cold rolling and pickling;

[0015] S6, Annealing:

[0016] Raise the temperature to 480-500℃ at 70-90℃ / h and keep warm for 5-6h;

[0017] Raise the temperature to 680~700℃ at 70~110℃ / h and keep warm for 8~10h;

[0018] Air cooling to 200~250℃, then water cooling to 50~60℃, and finally cooling to room temperature for 5~6h;

[0019] S7, leveling treatment;

[0020] S8, repairing the rollers to obtain the deep-drawn steel plate.

[0021] As a further technical solution, in step S2, the argon blowing station blows argon for ≥10 minutes, and aluminum-manganese-iron is added for alloying.

[0022] As a further technical solution, in step S2, the feeding amount of aluminum wire is 1.8 m / t, the feeding amount of calcium wire is 1.4 m / t, and the soft blowing time after wire feeding is ensured to be ≥ 5 minutes.

[0023] As a further technical solution, the hot rolling in step S4 is as follows:

[0024] Finishing rolling start temperature: 1020~1060℃, finishing rolling final temperature: 840~940℃, coiling temperature: 600~680℃.

[0025] As a further technical solution, the annealing process in step S6 is:

[0026] Raise the temperature to 480-500℃ at 70-90℃ / h and keep warm for 5h;

[0027] Raise the temperature to 680~700℃ at 70~110℃ / h and keep warm for 10h;

[0028] Air cool to 250℃, then water cool to 50℃, and finally cool at room temperature for 5h.

[0029] As a further technical solution, during the annealing in step S6, the first heating rate is greater than the second heating rate.

[0030] As a further technical solution, in step S7, the flattening elongation is controlled to be 0.7% to 1.3%.

[0031] As a further technical solution, in step S7, the surface roughness is controlled to be 0.9-1.9 μm.

[0032] When the thickness of the steel plate is ≥4.5mm, the start temperature of finishing rolling is 1040±20℃, the final rolling temperature is 860±20℃, and the coiling temperature is 620±20℃;

[0033] When 4.5mm>steel plate thickness≥4mm, finishing rolling start temperature: 1040±20℃, finishing rolling final rolling temperature: 900±20℃, coiling temperature: 630±20℃;

[0034] When 4mm>steel plate thickness≥3.5mm, finishing rolling start temperature: 1040±20℃, finishing rolling final rolling temperature: 920±20℃, coiling temperature: 640±20℃;

[0035] When 3.5mm>steel plate thickness≥3mm, finishing rolling start temperature: 1040±20℃, finishing rolling final rolling temperature: 920±20℃, coiling temperature: 650±20℃;

[0036] When the steel plate thickness is less than 3.0 mm, the start temperature of finishing rolling is 1040±20°C, the final temperature of finishing rolling is 920±20°C, and the coiling temperature is 660±20°C.

[0037] The beneficial effects of the present invention are:

[0038] 1. In the present invention, by optimizing the composition of the steel plate, the C content is controlled at 0.02% to 0.07%, and the Mn content is controlled at 0.08% to 0.20%. Increasing carbon and reducing manganese can both ensure the carbon equivalent and reduce it. The traditional process requires the carbon content to be below 0.05%, while the carbon content in the present invention is below 0.07%. The increase in carbon content, on the one hand, expands the converter endpoint range, increases the one-time carbon drawing rate, and reduces the difficulty of converter operation, and on the other hand, reduces converter blowing loss and refractory loss. When the silicon content in the steel is greater than 0.03%, the yield strength and tensile strength of the steel will increase, and the stamping formability of the cold-rolled plate and the adhesion of zinc will be seriously affected. The silicon content is strictly controlled to be below 0.03%.

[0039] 2. In order to promote the precipitation of dispersed AlN, obtain a stronger {111} favorable texture, and improve its forming performance, the present invention reduces the heating rate in the first stage, prolongs the heating time in the first stage, and further allows the steel coil to be evenly heated in the annealing furnace, so that the structure undergoes recrystallization and refinement, and a finer and more uniform structure is obtained. At the same time, the growth of austenite grains caused by overheating is avoided, and a brittle and coarse needle-like structure, namely, Widmanstatten structure, is formed along a certain direction during subsequent rapid cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0041] Figure 1 This is a metallographic micrograph of Example 1 of the present invention. DETAILED DESCRIPTION

[0042] 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 described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] A deep drawn steel plate:

[0045] The composition is: C 0.07%, Si 0.03%, Mn 0.08%, P 0.025%, S 0.020%, Als 0.055%, the balance is Fe and unavoidable impurities;

[0046] The production process includes the following steps:

[0047] S1. Converter smelting: adding raw materials into the converter for blowing;

[0048] S2, LF refining: argon blowing station blows argon for 10 minutes, aluminum-manganese-iron is added for alloying, the aluminum wire feeding amount is 1.8m / t, the calcium wire feeding amount is 1.4m / t, and the soft blowing time is guaranteed to be 5 minutes after wire feeding;

[0049] S3, continuous casting into slab;

[0050] S4, hot rolling: finishing rolling start temperature: 1040℃, finishing rolling final rolling temperature: 860℃, coiling temperature: 620℃;

[0051] S5, cold rolling and pickling;

[0052] S6, Annealing:

[0053] Raise the temperature to 480℃ at 80℃ / h and keep it at that temperature for 5h;

[0054] Raise the temperature to 680℃ at 100℃ / h and keep it at that temperature for 10h;

[0055] Air cooling to 250℃, then water cooling to 50℃, and finally cooling at room temperature for 5h;

[0056] S7. Flattening treatment is performed to obtain a deep-drawn steel sheet with a flattening elongation of 1% and a surface roughness of 1 μm.

[0057] Example 2

[0058] A deep drawn steel plate:

[0059] The composition is: C 0.06%, Si 0.02%, Mn 0.12%, P 0.015%, S 0.015%, Als 0.02%, the balance is Fe and unavoidable impurities;

[0060] The production process includes the following steps:

[0061] S1. Converter smelting: adding raw materials into the converter for blowing;

[0062] S2, LF refining: argon blowing station blows argon for 12 minutes, aluminum-manganese-iron is added for alloying, the aluminum wire feeding amount is 1.8m / t, the calcium wire feeding amount is 1.4m / t, and the soft blowing time is guaranteed to be 6 minutes after wire feeding;

[0063] S3, continuous casting into slab;

[0064] S4, hot rolling: finishing rolling start temperature: 1040℃, finishing rolling final rolling temperature: 900℃, coiling temperature: 630℃;

[0065] S5, cold rolling and pickling;

[0066] S6, Annealing:

[0067] Raise the temperature to 500°C at 90°C / h and keep it at that temperature for 5h;

[0068] Raise the temperature to 690℃ at 110℃ / h and keep it at that temperature for 10h;

[0069] Air cool to 200℃, then water cool to 60℃, and finally cool to room temperature for 5h;

[0070] S7. Flattening treatment is performed to obtain a deep-drawn steel sheet with a flattening elongation of 0.8% and a surface roughness of 1.2 μm.

[0071] Example 3

[0072] A deep drawn steel plate:

[0073] The composition is: C 0.02%, Si 0.03%, Mn 0.20%, P 0.025%, S 0.010%, Als 0.015%, the balance is Fe and unavoidable impurities;

[0074] The production process includes the following steps:

[0075] S1. Converter smelting: adding raw materials into the converter for blowing;

[0076] S2, LF refining: argon blowing station blows argon for 15 minutes, aluminum-manganese-iron is added for alloying, the aluminum wire feeding amount is 1.8m / t, the calcium wire feeding amount is 1.4m / t, and the soft blowing time is guaranteed to be 8 minutes after wire feeding;

[0077] S3, continuous casting into slab;

[0078] S4, hot rolling: finishing rolling start temperature: 1030℃, finishing rolling final rolling temperature: 930℃, coiling temperature: 660℃;

[0079] S5, cold rolling and pickling;

[0080] S6, Annealing:

[0081] Raise the temperature to 500°C at 70°C / h and keep it at that temperature for 5h;

[0082] Raise the temperature to 700℃ at 90℃ / h and keep it at that temperature for 10h;

[0083] Air cool to 200℃, then water cool to 60℃, and finally cool to room temperature for 5h;

[0084] S7. Flattening treatment to obtain a deep-drawn steel sheet with a flattening elongation of 1.3% and a surface roughness of 1.9 μm.

[0085] Example 4

[0086] The difference from Example 1 is that the annealing process is different:

[0087] Raise the temperature to 480℃ at 80℃ / h and keep it at that temperature for 5h;

[0088] Raise the temperature to 680℃ at 80℃ / h and keep it at that temperature for 10h;

[0089] Air cool to 250℃, then water cool to 50℃, and finally cool at room temperature for 5h.

[0090] Example 5

[0091] The difference from Example 1 is that the annealing process is different:

[0092] Raise the temperature to 480℃ at 100℃ / h and keep it for 5h;

[0093] Raise the temperature to 680℃ at 80℃ / h and keep it at that temperature for 10h;

[0094] Air cool to 250℃, then water cool to 50℃, and finally cool at room temperature for 5h.

[0095] Example 6

[0096] The difference from Example 1 is that the coiling temperature is 660°C.

[0097] Comparative Example 1

[0098] The difference from Example 1 is that

[0099] The composition is: C 0.05%, Si 0.03%, Mn 0.3%, P 0.025%, S 0.020%, Als 0.055%, and the balance is Fe and inevitable impurities.

[0100] Comparative Example 2

[0101] The difference from Example 1 is that the steel plate with a surface roughness of 0.8 μm is obtained through flattening treatment.

[0102] Table 1 Properties of the steel plates of Examples 1-6 and Comparative Example 1

[0103]

[0104] Compared with comparative example 1, the yield strength and tensile strength of the embodiment of the present invention are reduced, and the sub-dark green is increased, thereby improving the stamping forming performance of the material.

[0105] Table 2 Stamping pass rate of Example 1 and Comparative Example 2

[0106]

[0107] The embodiment of the present invention optimizes the roller repair process of the leveling roller, and improves the original surface roughness of ≤0.9μm to between 0.9-1.9μm. By revising the surface roughness parameter value, the stamping forming performance of the steel plate is effectively improved, and the stamping qualification rate is improved to a certain extent.

[0108] The steel plate obtained in Example 1 was observed under a metallographic microscope. The metallographic structure was fine and uniform ferrite grains, with little pearlite and no obvious banded structure. Figure 1 shown.

[0109] The ferrite grains of the steel plate are fine, and the grain size is evaluated according to GB / T 6394-2017, meeting the requirements for the grain size range of steel for stamping processing to be within the range of 8 to 10, as shown in Table 3.

[0110] Table 3 Microstructure test results

[0111]

[0112] Through metallographic observation (observing inclusions at 500 times magnification), it is difficult to find inclusions such as long strips of MnS that are easy to form material directionality, as well as oxide and silicate inclusions, indicating that the product has a high degree of cleanliness and meets high cleanliness requirements.

[0113] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A deep drawn steel sheet, characterized in that: The composition of the deep drawing steel sheet is as follows, by mass percentage: C 0.02% to 0.07%, Si≤0.03%, Mn 0.08% to 0.20%, P≤0.025%, S≤0.020%, Als 0.015% to 0.055%, and the balance is Fe and unavoidable impurities; The production process of the deep-drawn steel plate comprises the following steps: S1. Converter smelting: adding raw materials into the converter for blowing; S2, LF refining; S3, continuous casting into slab; S4, hot rolling; S5, cold rolling and pickling; S6, Annealing: Raise the temperature to 480-500℃ at 70-90℃ / h and keep warm for 5-6h; Raise the temperature to 680-700℃ at 70-110℃ / h and keep warm for 8-10h; Air cool to 200-250℃, then water cool to 50-60℃, and finally cool to room temperature for 5-6h; S7, flattening to obtain the deep-drawn steel plate; The hot rolling in step S4 is as follows: finishing rolling start temperature: 1020-1060°C, finishing rolling final temperature: 840-940°C, coiling temperature: 600-680°C; In the step S7, the surface roughness is controlled to be 0.9-1.9 μm.

2. A deep drawn steel sheet according to claim 1, characterized in that: Measured by mass percentage, the deep-drawing steel sheet has the following components: C 0.06%, Si≤0.02%, Mn 0.12%, P≤0.015%, S≤0.015%, Als 0.02%, and the remainder is Fe and unavoidable impurities.

3. The deep-drawn steel sheet according to claim 1, characterized in that: When the thickness is 4-5mm, the yield strength is 290-310MPa, the tensile strength is 340-360MPa, and the elongation is 42%-44%.

4. A production process for deep drawing steel sheet according to claim 1, characterized in that: The following steps are involved: S1. Converter smelting: adding raw materials into the converter for blowing; S2, LF refining; S3, continuous casting into slab; S4, hot rolling; S5, cold rolling and pickling; S6, Annealing: Raise the temperature to 480-500℃ at 70-90℃ / h and keep warm for 5-6h; Raise the temperature to 680-700℃ at 70-110℃ / h and keep warm for 8-10h; Air cool to 200-250℃, then water cool to 50-60℃, and finally cool to room temperature for 5-6h; S7, flattening to obtain the deep-drawn steel plate; The hot rolling in step S4 is as follows: finishing rolling start temperature: 1020-1060°C, finishing rolling final temperature: 840-940°C, coiling temperature: 600-680°C; In the step S7, the surface roughness is controlled to be 0.9-1.9 μm.

5. A production process for deep drawing steel sheet according to claim 4, characterized in that: In step S2, the argon blowing station blows argon for ≥10 minutes, and aluminum, manganese and iron are added for alloying.

6. A production process for deep drawing steel sheet according to claim 5, characterized in that: In the step S2, the feeding amount of aluminum wire is 1.8 m / t, the feeding amount of calcium wire is 1.4 m / t, and the soft blowing time after wire feeding is ensured to be ≥ 5 minutes.

7. A production process for deep drawing steel sheet according to claim 4, characterized in that: The annealing process in step S6 is: Raise the temperature to 480-500℃ at 70-90℃ / h and keep warm for 5h; Raise the temperature to 680-700℃ at 70-110℃ / h and keep warm for 10h; Air cool to 250℃, then water cool to 50℃, and finally cool at room temperature for 5h.

8. The production process of deep drawing steel sheet according to claim 4, characterized in that: In the step S7, the flattening elongation is controlled to be 0.7% to 1.3%.

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