Automobile part high-strength steel plate and manufacturing method thereof

Abstract

The invention relates to a high-strength steel plate for automobile parts and a manufacturing method thereof, and belongs to the technical field of steel for automobiles, and the manufacturing method comprises the following steps: pickling and heating a steel plate, immediately quenching with water, and then carrying out double-phase tempering treatment to obtain a first steel plate; and performing cold rolling and hot stamping forming on the first steel plate at room temperature, and performing laser surface treatment to obtain the high-strength steel plate for the automobile parts. Microalloy elements such as Ti, Nb, V and Zr are added into the raw materials of the steel plate, grains are effectively refined, formation of carbides is enhanced, Ti promotes grain refinement, Nb can further reduce the phase transition temperature, and V and Zr refine grains and form carbides, so that the tensile strength and toughness of steel are improved, and the service life of the steel plate is prolonged. And by means of heating, water quenching, double-phase tempering treatment, cold rolling, hot stamping forming, laser surface treatment and other operations, the high-strength steel plate with high strength and excellent low-temperature performance is cooperatively prepared, and the modern industrial requirements are met.

Description

Technical Field

[0001] The invention belongs to the technical field of automobile steel materials and relates to a high-strength steel plate for automobile parts and a manufacturing method thereof. Background Art

[0002] High-strength steel plate is a kind of steel with high strength and good toughness. It uses special alloy composition design and heat treatment process to make the steel have a strength far higher than ordinary steel while maintaining a certain toughness. It is called high-strength steel because its strength indicators (such as yield strength, tensile strength, etc.) are far higher than ordinary steel. These strength indicators are important parameters to measure the ability of steel to resist deformation and fracture when subjected to stress. Compared with ordinary steel, high-strength steel can remain stable under greater stress and is not prone to plastic deformation or fracture.

[0003] In modern automobile manufacturing, the plates of automobile parts are usually made of high-strength steel, aluminum alloy and composite materials. Due to its excellent strength and toughness, high-strength steel has become an important part of the car body structure and is widely used in automobile parts such as body frames, doors and collision protection systems.

[0004] Although high-strength steel plates play an important role in automobile manufacturing, their toughness is relatively low, especially in low-temperature environments, and they are prone to brittle fracture, affecting the service life and safety of parts. Secondly, the formability of high-strength steel plates is lower than that of traditional steels, and cracks or deformations are prone to occur during the forming process, which limits their use in practical applications and increases manufacturing difficulty and cost. Summary of the invention

[0005] The purpose of the present invention is to provide a high-strength steel plate for automobile parts and a method for manufacturing the same. The present invention adds microalloying elements such as Ti, Nb, V and Zr to the steel plate raw materials to effectively refine the grains and enhance the formation of carbides, thereby improving the tensile strength and toughness of the steel. Then, with the help of heating, water quenching, two-phase tempering treatment, cold rolling, hot stamping, laser surface treatment and other operations, a high-strength steel plate with high strength and excellent low-temperature performance is prepared in a coordinated manner to meet the needs of modern industry.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a high-strength steel plate for automobile parts, the method comprising the following steps:

[0008] (1) pickling the steel plate, quenching it with water immediately after heating, and then performing a duplex tempering treatment to obtain a first steel plate;

[0009] (2) The first steel plate is cold rolled at room temperature, hot stamped, and then subjected to laser surface treatment to obtain a high-strength steel plate for automotive parts.

[0010] Further, by mass percentage, the raw materials of the steel plate in step (1) include C: 0.08 - 0.12%, Mn: 1.2 - 1.3%, Mg: 0.02 - 0.04%, Si: 0.28 - 0.32%, Cr: 0.28 - 0.32%, Ti: 0.06 - 0.1%, Nb: 0.03 - 0.04%, V: 0.05 - 0.07%, Zr: 0.015 - 0.025%, B: 0.001 - 0.003%, and the balance Fe.

[0011] Further, the pickling in step (1) uses a sulfuric acid solution with a concentration of 8 - 12%, and the pickling time is 5 - 15 min.

[0012] Further, immediately quenching in water after heating in step (1) means first heating to 880 - 920 °C and holding for 20 - 30 min, and then quenching into water at 5 °C.

[0013] Further, the duplex tempering treatment in step (1) means tempering the quenched steel plate in the range of 450 - 550 °C, and the tempering time is 30 - 60 min.

[0014] Further, the deformation rate of the cold rolling in step (2) is controlled at 70 - 85%.

[0015] Further, the hot stamping forming in step (2) means heating the cold - rolled steel plate to 850 - 900 °C, heating for 6 - 10 min, then transferring it into a mold pre - heated to 150 - 300 °C for stamping forming, holding the pressure for 6 - 10 s, and then cooling to room temperature at a cooling rate of 30 - 40 °C / s.

[0016] Further, the laser surface treatment in step (2) means using a laser with a power of 900 - 1100 W for surface treatment until the depth reaches 0.2 mm.

[0017] Advantages of the present invention:

[0018] (1) In the present invention, Ti, Nb, V, and Zr are added to the raw materials of the steel plate. Among them, Ti can promote grain refinement, improve the tensile strength and toughness at low temperature of the steel; Nb can further reduce the phase transformation temperature, so that the material can still maintain good toughness under low - temperature conditions; V and Zr further improve the strength of the steel plate by refining grains and forming carbides.

[0019] (2) The present invention rapidly forms a high-strength martensite structure through heating and water quenching steps, and then softens part of the martensite and precipitates fine carbides by means of duplex tempering treatment, which not only reduces the internal stress of the steel but also improves its toughness and ductility. The combination of cold rolling and hot stamping forming steps not only improves the strength and surface quality of the steel but also ensures good processability during the forming process. In addition, the present invention finally adopts laser surface treatment to form a high-hardness hardened layer on the surface, significantly enhancing the wear resistance of the steel plate. Through the collaborative treatment of each step, a high-strength steel plate with high strength, good low-temperature performance, and not easily cracking or deforming is prepared, meeting the requirements of modern industry. Detailed implementation manners

[0020] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in combination with embodiments, details the specific implementation manners, structures, features, and effects according to the present invention as follows.

[0021] Example 1

[0022] A preparation method of a high-strength steel plate for automotive parts. The preparation method of the high-strength steel plate for automotive parts in this example includes the following steps:

[0023] (1) Pickle the steel plate, immediately water quench it after heating, and then perform duplex tempering treatment to obtain the first steel plate;

[0024] (2) Cold roll the first steel plate at room temperature, hot stamp it, and then perform laser surface treatment to obtain the high-strength steel plate for automotive parts.

[0025] In this example, the raw materials of the steel plate in step (1) include, by mass percentage, C: 0.08%, Mn: 1.2%, Mg: 0.02%, Si: 0.28%, Cr: 0.28%, Ti: 0.06%, Nb: 0.03%, V: 0.05%, Zr: 0.015%, B: 0.001%, and the balance Fe.

[0026] In this example, the pickling in step (1) uses a sulfuric acid solution with a concentration of 8%, and the pickling time is 5 min.

[0027] The immediate water quenching after heating in step (1) of this example means heating to 880 °C and holding for 20 min first, and then quenching into water at 5 °C.

[0028] The duplex tempering treatment in step (1) of this example means tempering the water-quenched steel plate within the range of 450 °C, and the tempering time is 30 min.

[0029] In this example, the deformation rate of the cold rolling in step (2) is controlled at 70%.

[0030] The hot stamping forming in step (2) of this embodiment refers to heating the cold-rolled steel plate to 850 °C, transferring it to a die preheated to 150 °C for stamping forming after 6 minutes of heating, maintaining the pressure for 6 seconds, and then cooling it to room temperature at a cooling rate of 30 °C / s.

[0031] The laser surface treatment in step (2) of this embodiment refers to using a 900W laser for surface treatment until the depth reaches 0.2 mm.

[0032] Example 2

[0033] A preparation method of high-strength steel plate for automobile parts. The preparation method of the high-strength steel plate for automobile parts in this embodiment includes the following steps:

[0034] (1) Pickle the steel plate, immediately water quench it after heating, and then perform duplex tempering treatment to obtain the first steel plate;

[0035] (2) Cold roll the first steel plate at room temperature, perform hot stamping forming, and then perform laser surface treatment to obtain the high-strength steel plate for automobile parts.

[0036] The raw materials of the steel plate in step (1) of this embodiment, by mass percentage, include C: 0.12%, Mn: 1.3%, Mg: 0.04%, Si: 0.32%, Cr: 0.32%, Ti: 0.1%, Nb: 0.04%, V: 0.07%, Zr: 0.025%, B: 0.003%, and the balance of Fe.

[0037] The pickling in step (1) of this embodiment uses a sulfuric acid solution with a concentration of 12%, and the pickling time is 15 minutes.

[0038] The immediate water quenching after heating in step (1) of this embodiment refers to first heating to 920 °C and maintaining for 30 minutes, and then quenching into water at 5 °C.

[0039] The duplex tempering treatment in step (1) of this embodiment refers to tempering the water-quenched steel plate within the range of 550 °C, and the tempering time is 60 minutes.

[0040] The deformation rate of the cold rolling in step (2) of this embodiment is controlled at 85%.

[0041] The hot stamping forming in step (2) of this embodiment refers to heating the cold-rolled steel plate to 900 °C, transferring it to a die preheated to 300 °C for stamping forming after 10 minutes of heating, maintaining the pressure for 10 seconds, and then cooling it to room temperature at a cooling rate of 40 °C / s.

[0042] The laser surface treatment in step (2) of this embodiment refers to using an 1100W laser for surface treatment until the depth reaches 0.2 mm.

[0043] Example 3

[0044] A preparation method of high-strength steel plate for automobile parts. The preparation method of the high-strength steel plate for automobile parts in this embodiment comprises the following steps:

[0045] (1) Pickle the steel plate, immediately water-quench it after heating, and then perform duplex tempering treatment to obtain the first steel plate;

[0046] (2) Cold-roll the first steel plate at room temperature, perform hot stamping forming, and then perform laser surface treatment to obtain the high-strength steel plate for automobile parts.

[0047] In terms of mass percentage, the raw materials of the steel plate in step (1) of this embodiment include C: 0.1%, Mn: 1.25%, Mg: 0.03%, Si: 0.3%, Cr: 0.3%, Ti: 0.08%, Nb: 0.035%, V: 0.06%, Zr: 0.02%, B: 0.002%, and the balance is Fe.

[0048] The sulfuric acid solution with a concentration of 10% is used for pickling in step (1) of this embodiment, and the pickling time is 10 min.

[0049] Immediately water-quenching after heating in step (1) of this embodiment means heating to 900 °C first and holding for 25 min, and then quenching into water at 5 °C.

[0050] The duplex tempering treatment in step (1) of this embodiment means tempering the water-quenched steel plate within the range of 500 °C, and the tempering time is 45 min.

[0051] The deformation rate of cold rolling in step (2) of this embodiment is controlled at 77.5%.

[0052] The hot stamping forming in step (2) of this embodiment means heating the cold-rolled steel plate to 875 °C, transferring it to a mold preheated to 225 °C for stamping forming after heating for 8 min, holding the pressure for 8 s, and then cooling to room temperature at a cooling rate of 35 °C / s.

[0053] The laser surface treatment in step (2) of this embodiment means using a laser of 1000 W for surface treatment until the depth reaches 0.2 mm.

[0054] Comparative Example 1

[0055] On the basis of Example 3, Ti in the raw materials of the steel plate is removed and replaced with Fe of equal weight, and the others are the same as in Example 3.

[0056] Comparative Example 2

[0057] On the basis of Example 3, Nb in the raw materials of the steel plate is removed and replaced with Fe of equal weight, and the others are the same as in Example 3.

[0058] Comparative Example 3

[0059] Based on Example 3, V in the steel plate raw material was removed and replaced with an equal weight of Zr, and the others were the same as in Example 3.

[0060] Comparative Example 4

[0061] Based on Example 3, Zr in the steel plate raw material was removed and replaced with an equal weight of V, and the others were the same as in Example 3.

[0062] Comparative Example 5

[0063] Based on Example 3, the temperature and time of the duplex tempering treatment in step (1) were changed to 560 °C and 20 min, and the others were the same as in Example 3.

[0064] Comparative Example 6

[0065] Based on Example 3, the temperature and time of the duplex tempering treatment in step (1) were changed to 430 °C and 20 min, and the others were the same as in Example 3.

[0066] Comparative Example 7

[0067] Based on Example 3, the cold rolling deformation rate in step (1) was controlled at 60%, and the other conditions were the same as in Example 3.

[0068] Comparative Example 8

[0069] Based on Example 3, the cold rolling deformation rate in step (2) was controlled at 90%, and the other conditions were the same as in Example 3.

[0070] Comparative Example 9

[0071] Based on Example 3, the laser surface treatment in step (2) was removed, and the others were the same as in Example 3.

[0072] Taking the high-strength steel plates prepared in Examples 1-3 and Comparative Examples 1-9 as samples, the samples were processed into dumbbell shapes, and the elongation at break of the samples was tested according to GB / T 228.1-2010. The average value was taken after each sample was tested 3 times, and the results are recorded in Table 1 below; the low-temperature impact performance of the samples was tested according to GB / T 229-2020. The samples were processed into long strip samples with a V-notch, with dimensions of approximately 55 mm × 10 mm × 10 mm and a notch depth of 2 mm. The samples were taken out after being pre-cooled to -60 °C in a low-temperature box and were subjected to impact treatment with a pendulum within 5 s, and the fracture conditions of the samples were observed. The results are recorded in Table 1 below.

[0073] Table 1

[0074]

[0075]

[0076] As can be seen from Table 1, the high-strength steel plates prepared in Examples 1-3 of the present invention have excellent mechanical properties, and no fracture occurs under impact at -60°C, having good application prospects.

[0077] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, any indirect modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing high-strength steel plates for automobile parts, characterized in that: The method for preparing the high-strength steel plate for automobile parts comprises the following steps: (1) pickling the steel plate, quenching it with water immediately after heating, and then performing a duplex tempering treatment to obtain a first steel plate; (2) The first steel plate is cold rolled at room temperature, hot stamped, and then subjected to laser surface treatment to obtain a high-strength steel plate for automotive parts.

2. The method for preparing a high-strength steel plate for automobile parts according to claim 1, characterized in that: The raw materials of the steel plate in step (1) include, by mass percentage, C: 0.08-0.12%, Mn: 1.2-1.3%, Mg: 0.02-0.04%, Si: 0.28-0.32%, Cr: 0.28-0.32%, Ti: 0.06-0.1%, Nb: 0.03-0.04%, V: 0.05-0.07%, Zr: 0.015-0.025%, B: 0.001-0.003% and the balance Fe.

3. The method for preparing a high-strength steel plate for automobile parts according to claim 1, characterized in that: The pickling in step (1) uses a sulfuric acid solution with a concentration of 8-12%, and the pickling time is 5-15 minutes.

4. The method for preparing a high-strength steel plate for automobile parts according to claim 1, characterized in that: The immediate water quenching after heating in step (1) means first heating to 880-920° C. and then maintaining for 20-30 minutes, and then quenching in 5° C. water.

5. The method for preparing a high-strength steel plate for automobile parts according to claim 1, characterized in that: The dual-phase tempering treatment in step (1) refers to tempering the water-quenched steel plate in the range of 450-550° C. for 30-60 min.

6. The method for preparing a high-strength steel plate for automobile parts according to claim 1, characterized in that: The deformation rate of the cold rolling in step (2) is controlled at 70-85%.

7. The method for preparing a high-strength steel plate for automobile parts according to claim 1, characterized in that: The hot stamping forming in step (2) refers to heating the cold-rolled steel plate to 850-900°C, heating for 6-10 minutes, transferring it into a mold preheated to 150-300°C for stamping, holding the pressure for 6-10 seconds, and then cooling it to room temperature at a cooling rate of 30-40°C / s.

8. The method for preparing a high-strength steel plate for automobile parts according to claim 1, characterized in that: The laser surface treatment in step (2) refers to using a 900-1100W laser to perform surface treatment to a depth of 0.2mm.

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