Hot forming steel and parts prepared from same

Abstract

The invention relates to hot forming steel and a part prepared from the hot forming steel. The hot forming steel comprises the following components in percentage by mass: 0.002% < = C < = 0.15%; 0.05% < = Mn < = 1.8%; p is less than or equal to 0.04%; less than or equal to 0.05% of S; si < = 0.8%; ni < = 0.6%; and the balance of Fe and inevitable impurities. The hot forming steel disclosed by the invention can be used for processing parts with relatively low strength and relatively high ductility through a hot forming process, and meanwhile, the material utilization rate can reach about 75%.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy steel. Specifically, the present invention relates to a hot-forming steel and components prepared therefrom. Background Art

[0002] Among body components, different components have different strength requirements. Not all components use high-strength steel. It is necessary to consider the combination of different strength materials to play an energy absorption role and effectively improve safety.

[0003] For automotive components such as car doors and hoods, their strength requirements are lower than those of automotive safety components. Therefore, cold stamping forming is usually used, and the strength can reach 500 MPa.

[0004] However, there are the following problems with the cold stamping of current vehicles (such as B-pillar reinforcement plates, connection plates, etc.):

[0005] First, limited by the cold stamping forming process, the material utilization rate is low, generally 55-60%;

[0006] Second, there are many processes in cold stamping, including blanking, stretching, trimming, forming, flanging, shaping, and punching;

[0007] Third, each process requires corresponding molds, so many processes lead to complex tooling;

[0008] Fourth, cold stamping parts need to be split into multiple parts and then manufactured.

[0009] In summary, the existing steel plates have disadvantages such as low material utilization rate, many processes, and many types of molds during cold stamping.

[0010] In addition, the strength of parts processed by existing hot stamping forming methods can reach 1500 MPa. Usually, high-strength steel materials have poor plasticity, and the elongation rate is generally about 5%. Due to insufficient toughness and poor formability, many parts cannot be manufactured.

[0011] Therefore, there has always been a desire in the art to develop a new steel material with good processing performance and capable of being hot-formed into low-strength components. Summary of the Invention

[0012] One object of the present invention is to provide a steel material with good processing performance and capable of being hot-formed into low-strength components.

[0013] Therefore, according to one aspect of the present invention, there is provided a hot-forming steel, characterized in that, by mass percentage, it comprises:

[0014] 0.002% ≤ C ≤ 0.15%;

[0015] 0.05% ≤ Mn ≤ 1.8%;

[0016] P ≤ 0.04%;

[0017] S ≤ 0.05%;

[0018] Si ≤ 0.8%;

[0019] Ni ≤ 0.6%;

[0020] The balance is Fe and inevitable impurities.

[0021] According to the second aspect of the present invention, there is provided a component, characterized in that it is prepared from the above-mentioned hot-formed steel.

[0022] According to the third aspect of the present invention, there is provided a vehicle, characterized in that it includes the above-mentioned component.

[0023] The hot-formed steel of the present invention can be processed by a hot-forming process to produce components with a tensile strength in the range of 450 - 650 Mpa, a yield strength in the range of 350 - 500 MPa, and an elongation rate ≥ 15%, and the material utilization rate can reach about 75%. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be described in conjunction with the accompanying drawings to enable those skilled in the art to better understand the various features and advantages of the present invention, wherein:

[0025] Figure 1 Shows the metallographic diagram of the component obtained in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0026] In the following, various aspects of the present invention, as well as further objects, features, and advantages, will be more fully embodied in conjunction with some specific embodiments.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. When the definitions in this specification conflict with the commonly understood meanings of those skilled in the art to which the present invention belongs, the definitions described herein shall apply.

[0028] In the following and unless otherwise specified, the upper and lower limits of a numerical range are included within the range, especially in the expressions "between... and..." and "... to...".

[0029] In this application, the term "comprising / including" shall be construed to cover all specifically mentioned features as well as any optional, additional, unspecified features. As used herein, the use of the term "comprising / including" also discloses embodiments in which there are no features other than the specifically mentioned features (i.e., "consisting of...").

[0030] In the present application, the use of "preferably" means that the features following it bring benefits for the purposes of the present invention.

[0031] Unless otherwise specified, all numerical values representing amounts of components, etc. used in the specification and claims should be understood to be modified by the term "about". Accordingly, unless indicated to the contrary, the numerical values and parameters described herein are approximate values that can vary as required for the desired purpose.

[0032] Hot-formed steel

[0033] According to one aspect of the present invention, there is provided a hot-formed steel, characterized in that, by mass percentage, it contains:

[0034] 0.002% ≤ C ≤ 0.15%;

[0035] 0.05% ≤ Mn ≤ 1.8%;

[0036] P ≤ 0.04%;

[0037] S ≤ 0.05%;

[0038] Si ≤ 0.8%;

[0039] Ni ≤ 0.6%;

[0040] The balance is Fe and unavoidable impurities.

[0041] In the hot-formed steel of the present invention, by mass percentage, the carbon element content is 0.002% - 0.15%, preferably 0.01% - 0.15%, more preferably 0.01% - 0.12%.

[0042] For example, in the hot-formed steel of the present invention, by mass percentage, the carbon element content is 0.002%, 0.003%, 0.005%, 0.008%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14% or 0.15%.

[0043] In the hot-formed steel of the present invention, by mass percentage, the manganese element content is 0.05% - 1.8%, preferably 0.08% - 1.6%, more preferably 0.09% - 1.5%.

[0044] For example, in the hot-formed steel of the present invention, by mass percentage, the manganese element content is 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7% or 1.8%.

[0045] In the hot-formed steel of the present invention, by mass percentage, the phosphorus element content does not exceed 0.04%, preferably 0.01% - 0.04%, and more preferably 0.012% - 0.04%.

[0046] For example, in the hot-formed steel of the present invention, by mass percentage, the phosphorus element content is 0.01%, 0.011%, 0.012%, 0.013%, 0.014%, 0.015%, 0.016%, 0.017%, 0.018%, 0.019%, 0.02%, 0.03% or 0.04%.

[0047] In the hot-formed steel of the present invention, by mass percentage, the sulfur element content does not exceed 0.05%, preferably 0.005% - 0.04%, and more preferably 0.007% - 0.04%.

[0048] For example, in the hot-formed steel of the present invention, by mass percentage, the sulfur element content is 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.015%, 0.02%, 0.03%, 0.04% or 0.05%.

[0049] In the hot-formed steel of the present invention, by mass percentage, the silicon element content does not exceed 0.8%, preferably 0 - 0.6%, and more preferably 0.01% - 0.5%.

[0050] For example, in the hot-formed steel of the present invention, by mass percentage, the silicon element content is 0, 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6% or 0.7%.

[0051] In the hot-formed steel of the present invention, by mass percentage, the nickel element content does not exceed 0.6%, preferably 0 - 0.4%, more preferably 0.01% - 0.2%, and even more preferably 0.01% - 0.1%.

[0052] For example, in the hot-formed steel of the present invention, the nickel content is 0, 0.01%, 0.02%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or 0.6% by mass.

[0053] In some embodiments, the hot-formed steels of the present invention do not contain silicon and / or nickel.

[0054] Preferably, in the hot-formed steel of the present invention, the contents of carbon, silicon and manganese satisfy the following relationship:

[0055] 0.005%≤0.8×C C +0.1×C Si +0.05×C Mn +2.0×C Ni ≤0.3%

[0056] in:

[0057] C C Indicates the mass percentage of carbon;

[0058] C Si Indicates the mass percentage of carbon;

[0059] C Mn Indicates the mass percentage of carbon;

[0060] C Ni Indicates the mass percentage of carbon.

[0061] The microstructure of the hot-formed steel of the present invention includes ferrite and martensite.

[0062] Preferably, the structure of the hot-formed steel of the present invention is substantially composed of ferrite and martensite.

[0063] Preferably, the martensite content of the hot-formed steel of the present invention is in the range of 5-60%.

[0064] The hot-formed steel of the present invention takes into account the toughness and plasticity, processing performance, product strength, elongation and other properties of the material through the combination of element types and contents.

[0065] The hot-formed steel of the present invention can be prepared by using the steelmaking and rolling techniques commonly used in the art.

[0066] For example, the preparation of hot-formed steel can be carried out as follows:

[0067] 1) Smelting process: The mixed raw materials are prepared according to the composition ratio and smelted to obtain molten steel;

[0068] 2) Continuous casting process: continuously casting the molten steel treated in step 1) into slabs;

[0069] 3) Hot rolling process: After heating the slab obtained in step 2), carry out descaling, rough rolling, and finish rolling processes to obtain a hot rolled coil;

[0070] 4) Pickling and cold rolling process: After uncoiling the hot rolled coil obtained in step 3), adjusting the strip shape and pickling to remove the surface oxide layer, cold roll it into a cold rolled thin strip coil;

[0071] 5) Continuous annealing process: Continuously anneal the cold rolled thin strip coil obtained in step 4) to obtain a cold rolled sheet that can be used for subsequent processing and forming.

[0072] The hot forming steel of the present invention belongs to low-strength hot forming steel.

[0073] The low strength described herein means that the tensile strength is in the range of 450 - 650 Mpa and the yield strength is in the range of 350 - 500 MPa.

[0074] The elongation of the hot forming steel of the present invention is not less than 15%.

[0075] In some embodiments, the tensile strength of the hot forming steel of the present invention is in the range of 480 - 650 Mpa, the yield strength is in the range of 380 - 500 MPa, and the elongation ≥ 15%.

[0076] In some embodiments, the tensile strength of the hot forming steel of the present invention is in the range of 500 - 650 Mpa, the yield strength is in the range of 380 - 450 MPa, and the elongation ≥ 20%.

[0077] In some embodiments, the tensile strength of the hot forming steel of the present invention is in the range of 515 - 630 Mpa, the yield strength is in the range of 380 - 430 MPa, and the elongation ≥ 20%.

[0078] In some embodiments, by mass percentage, the hot forming steel of the present invention contains 0.003% - 0.12% of carbon, 0.09% - 1.5% of manganese, 0.01 - 0.04% of phosphorus, 0.005 - 0.04% of sulfur, 0 - 0.5% of silicon, 0 - 0.02% of nickel, and the balance is Fe and unavoidable impurities, with a tensile strength in the range of 500 - 650 MPa, a yield strength in the range of 380 - 450 MPa, and an elongation ≥ 20%.

[0079] In some embodiments, by mass percentage, the hot forming steel of the present invention comprises 0.01%-0.12% of carbon, 0.15%-1.5% of manganese, 0.01-0.04% of phosphorus, 0.005-0.04% of sulfur, 0.02-0.5% of silicon, 0.01-0.02% of nickel, with the balance being Fe and inevitable impurities, and its tensile strength is in the range of 515-630 MPa, yield strength is in the range of 380-430 MPa, and elongation rate ≥ 22%.

[0080] Components and vehicles

[0081] According to the second aspect of the present invention, there is provided a component, characterized in that it is prepared from the above-mentioned hot forming steel.

[0082] The hot forming steel of the present invention can be used to produce low-strength components.

[0083] By using the hot forming steel of the present invention, components with a tensile strength in the range of 450-650 Mpa, a yield strength in the range of 350-500 MPa, and an elongation rate not less than 15% can be obtained.

[0084] The components may be inner and outer front door rings, integral roof, front floor, rear floor, front panel, trunk, etc. of the component.

[0085] Specifically, the hot forming steel of the present invention can be processed into components by a hot forming process, such as a hot stamping forming process.

[0086] The hot forming steel of the present invention can be hot stamped at a heating temperature in the range of 800-1000 °C, preferably in the range of 850-960 °C. The heating time can be 2-8 minutes, such as 3-6 minutes.

[0087] For example, the following procedures can be used to prepare components:

[0088] i) Uncoiling process: Uncoil the coil stock to form square plates, facilitating subsequent blanking;

[0089] ii) Blanking process: Blank the square plate stock into the shape stock for final production, preparing for stamping;

[0090] iii) Hot stamping: Heat the shape stock and stamp it into parts;

[0091] iv) Cutting: Process the edges and holes through laser cutting or a die to produce the final product.

[0092] Compared with cold stamping in the prior art, hot forming has the following advantages:

[0093] In the heated state, the sheet metal has a higher formability, so deep-formed parts can be stamped in one step, avoiding the need for multiple steps.

[0094] It can realize multi-part integration, reduce the number of parts, and reduce the production process;

[0095] Since thermoforming tooling can realize the production mode of one mold with multiple cavities and one cavity with multiple parts, it can realize nesting of multiple parts and improve material utilization.

[0096] Therefore, when the hot-formed steel of the present invention is used for processing vehicle parts, it can achieve the unification of vehicle body parts, modularization of components, and reduction of assembly parts, thereby significantly reducing the total cost.

[0097] The hot-formed steel of the present invention can also undergo processes such as heating, stamping and quenching, shot blasting, and cold punching on a continuous production line to achieve one-step processing from raw materials to finished products, saving intermediate inventory.

[0098] In addition, hot-formed steels (including the hot-formed steel of the present invention) of different strengths can be welded together through a welding process (such as a laser splicing process) and then hot-formed to achieve a combination of different strengths on the same component.

[0099] According to a third aspect of the present invention, a vehicle is provided, characterized by comprising the above-mentioned components.

[0100] The component of the present invention has a tensile strength within the range of 450-650 MPa, a yield strength within the range of 350-500 MPa, and an elongation of not less than 15%, and therefore can be used as a component of a vehicle.

[0101] Example

[0102] The following will further illustrate the concept of the present invention and the technical effects produced in conjunction with the embodiments so that those skilled in the art can fully understand the purpose, features and effects of the present invention. It will be readily understood by those skilled in the art that the embodiments herein are for illustrative purposes only and the scope of the present invention is not limited thereto. Unless otherwise specified, the raw materials used in the embodiments are those commonly used in the art.

[0103] Example 1

[0104] This embodiment provides a hot-formed steel, which comprises, by mass percentage, the following: C: 0.003%; Mn: 0.09%; P: 0.014%; S: 0.005%; and the balance being Fe and unavoidable impurities.

[0105] The preparation process of hot-formed steel is as follows:

[0106] 1) Smelting process: The mixed raw materials are prepared according to the composition ratio and smelted to obtain molten steel;

[0107] 2) Continuous casting process: The molten steel processed in step 1) is continuously cast into slab billets, with the casting temperature being 1450 - 1550 °C and the slab thickness being 120 - 240 mm;

[0108] 3) Hot rolling process: After heating the slab billets obtained in step 2), descaling, rough rolling, and finish rolling processes are carried out to obtain hot rolled coils; among them, the hot rolling heating temperature is 1200 - 1300 °C; the start rolling temperature of finish rolling is 1000 - 1150 °C, the finish rolling temperature is 850 - 950 °C; the intermediate temperature is 740 - 800 °C; the thickness of the hot rolled coils is 2 - 4.0 mm;

[0109] 4) Pickling and cold rolling process: The hot rolled coils obtained in step 3) are uncoiled, the strip shape is adjusted, and the surface oxide layer is removed by pickling, and then cold rolled into cold rolled thin strip coils;

[0110] 5) Continuous annealing process: The cold rolled thin strip coils obtained in step 4) are continuously annealed; among them, the soaking temperature is 900 - 950 °C; the slow cooling end temperature is 750 - 800 °C, the fast cooling end temperature is 330 - 360 °C; the over - aging temperature is 340 - 360 °C; the unit speed is 40 - 60 m / min, and the cold rolled sheets obtained can be used for subsequent processing and forming.

[0111] The obtained hot - formed steel is processed into parts according to the following processes:

[0112] i) Uncoiling process: The coiled material is uncoiled to form square plates, facilitating subsequent blanking.

[0113] Parameters: Power: 3000 W; Pulse: 5000 HZ; Nozzle height: 0.5 - 1 mm.

[0114] ii) Blanking process: The square plate material is blanked into shape materials for final production, preparing for stamping, and the material utilization rate reaches 75%.

[0115] Parameters: Power: 2500 - 3000 W; Pulse: 4000 - 5500 HZ; Nozzle height: 0.5 - 1 mm

[0116] iii) Hot stamping: The shape materials are heated and stamped into parts.

[0117] Parameters are: Heating temperature: 900 °C, Heating time: 5 min.

[0118] iv) Cutting: The edges and holes are processed by laser cutting or die to produce the final finished product.

[0119] Parameters: Pressure: 2000 KN.

[0120] Figure 1 The metallographic diagram of the manufactured components is shown.

[0121] As Figure 1 shown, the structure in the component is mainly composed of ferrite and martensite, and the martensite content is approximately 7%.

[0122] Examples 2-4 and Comparative Examples 1-3

[0123] A series of steels and components were prepared using a process substantially the same as that of Example 1, and the specific components and contents are shown in Table 1 (the balance is iron and unavoidable impurities, not shown).

[0124] Table 1

[0125] C(％) Mn (%) P(％) S(％) Si (%) Ni (%) Value A* (%) Example 1 0.003 0.09 0.014 0.005 0 0 0.007 Example 2 0.01 0.5 0.04 0.04 0.02 0.02 0.075 Example 3 0.06 0.15 0.019 0.007 0.02 0.01 0.078 Example 4 0.12 1.5 0.02 0.02 0.5 0.02 0.261 Comparative example 1 0.15 2 0.03 0.01 0.9 0.5 1.31 Comparative example 2 0.14 2 0.02 0.03 0.6 0 0.272

[0126] *: A = 0.8 × C C + 0.1 × C Si + 0.05 × C Mn + 2.0 × C Ni

[0127] where C C 、C Si 、C Mn 、C Ni is as defined previously.

[0128] Mechanical property test

[0129] The mechanical properties of the components prepared in Examples 1-4 and Comparative Examples 1-2 were tested in accordance with GB228.1-2021, and the results are shown in Table 2.

[0130] Table 2

[0131]

[0132]

[0133] It can be seen from Table 2 that the hot-formed steel of the present invention can be processed to obtain components with a tensile strength in the range of 450-650 Mpa, a yield strength in the range of 350-500 MPa, and an elongation rate ≥ 15%.

[0134] Although some aspects of the present invention have been shown and discussed, those skilled in the art should realize that changes can be made to the above aspects without departing from the principles and spirit of the present invention. Therefore, the scope of the present invention will be defined by the claims and their equivalents.

Claims

1. A hot-formed steel, characterized in that, By mass percentage, it contains: 0.002％≤C≤0.15％； 0.05% ≤ Mn ≤ 1.8%; P≤0.04％； S≤0.05％； Si ≤ 0.8%; Ni ≤ 0.6%; The balance is Fe and unavoidable impurities.

2. The hot forming steel according to claim 1, wherein By mass percentage, the carbon element content is 0.01% - 0.15%, preferably 0.01% - 0.12%.

3. The hot-formed steel according to claim 1 or 2, characterized in that, By mass percentage, the manganese element content is 0.08% - 1.6%, preferably 0.09% - 1.5%.

4. The hot forming steel according to any one of claims 1-3, characterized in that, By mass percentage, the phosphorus element content is 0.01% - 0.04%, preferably 0.012% - 0.04%.

5. The hot-formed steel according to any one of claims 1-4, characterized in that, By mass percentage, the sulfur element content is 0.005% - 0.04%, preferably 0.007% - 0.04%.

6. The hot forming steel according to any one of claims 1-5, characterized in that, By mass percentage, the silicon element content is 0 - 0.6%, preferably 0.01% - 0.5%.

7. The hot forming steel according to any one of claims 1-6, characterized in that, By mass percentage, the nickel element content is 0% - 0.4%, preferably 0.01% - 0.2%, more preferably 0.01% - 0.1%.

8. The hot-formed steel according to any one of claims 1-7, characterized in that, The carbon, silicon, and manganese element contents satisfy the following relationship: 0.005% ≤ 0.8 × C C + 0.1 × C Si + 0.05 × C Mn + 2.0 × C Ni ≤ 0.3% Wherein: C C represents the mass percentage of carbon; C Si represents the mass percentage of carbon; C Mn represents the mass percentage of carbon; C Ni Indicates the mass percentage of carbon.

9. The hot-formed steel according to any one of claims 1-8, characterized in that, The structure includes ferrite and martensite. Preferably, the martensite content is in the range of 5 - 60%.

10. The hot forming steel according to any one of claims 1-9, characterized in that, Its tensile strength is in the range of 450 - 650 Mpa, the yield strength is in the range of 350 - 500 MPa, and the elongation rate ≥ 15%.

11. A component, characterized in that, It is prepared by using the hot - formed steel described in claims 1 - 10.

12. The component according to claim 11, characterized in that, It is selected from the inner and outer front door rings, the integral roof, the front floor, the rear floor, the front panel, and the trunk of components.

13. A vehicle, characterized in that, It includes the components of claim 11 or 12.

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