Half door ring ultrahigh strength steel hot stamping process

Abstract

The invention discloses a half-door ring ultrahigh strength steel hot stamping process, and belongs to the technical field of hot stamping forming. According to the technical scheme, the method comprises the following steps that S1, a pseudo door ring blank is obtained; s2, heat treatment; and S3, cutting. The production process of the semi-door ring is optimized, the production procedure of hot stamping forming of the semi-door ring is simplified, production energy consumption is greatly reduced, production cost is effectively reduced, the anti-impact strength and precision of the semi-door ring product are remarkably improved, the percent of pass and quality of the semi-door ring product are improved, and riding safety is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of hot stamping, and in particular relates to a hot stamping process of ultra-high-strength steel for a half door ring. Background Art

[0002] With the development of society, the requirements for automobile collision safety are getting higher and higher, and at the same time, the restrictions on automobile carbon dioxide emissions are becoming more and more stringent. Under such a background, hot stamping forming technology, which is beneficial to automobile safety, automobile lightweight, and automobile energy conservation and emission reduction, is highly favored. Hot stamping forming technology is a forming method in which the blank is heated to an austenitized state, then quickly transferred to a mold for high-speed stamping, and quenched for a period of time under a certain pressure to obtain ultra-high-strength steel parts with uniform martensitic structure.

[0003] Reducing the weight of the vehicle body as much as possible while ensuring safety has become the top priority of the automotive industry. The mainstream of high-strength automotive body parts currently produced has gradually changed from late-stage finished product welding to early-stage welding. The market demand for half door rings and door rings is increasing, but the hot forming of half door rings is still a more difficult one in hot stamping forming technology. This part combines the upper half of the A-pillar, the upper half of the B-pillar, the upper side beam, the lower half of the A-pillar and the lower half of the B-pillar. Its shape is very complex and its size is large, making it difficult to form. It is a typical multi-component integrated part, especially the lower half of the A-pillar, which has the most difficult hot stamping forming technology. In current production, the hot forming of half door rings still has the problems of high production cost, high energy consumption and low production efficiency. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a half door ring hot stamping production process which can significantly reduce the production cost of the half door ring, effectively improve the production efficiency of the half door ring, and effectively reduce carbon emissions.

[0005] In order to solve the above technical problems, the technical solutions applied by the present invention are as follows: A hot stamping process of ultra-high strength steel for a half door ring, the steps of which are as follows: S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is carried out on high-speed tool steel plates of different thicknesses to obtain A-pillar upper section blanks, upper side beam blanks, B-pillar upper section blanks, B-pillar lower section blanks and A-pillar lower section blanks; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blanks and B-pillar lower section blanks of the half door ring blanks are connected by connecting parts to obtain pseudo door ring blanks.

[0006] Preferably, the high-speed tool steel plate is 22MnB5.

[0007] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to a certain temperature, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, no gasket or a gasket of a certain thickness is placed on the upper surface of the groove before hot stamping, after the pseudo door ring blank is placed at the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank downward into the groove of the lower die insert, and hot stamping is performed to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0008] Preferably, the dummy door ring blank is heated to a temperature of 150° C. to 250° C. before being fed into the die of the hot stamping device.

[0009] Preferably, the number of pillars is greater than or equal to 4.

[0010] Preferably, the number of auxiliary columns is greater than or equal to 2.

[0011] Preferably, the thickness of the gasket is 0 to 0.15 mm.

[0012] Preferably, the gasket is a silicon steel sheet.

[0013] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0014] Through the above design scheme, the present invention can bring the following beneficial effects: (1) The production process of the half door ring was optimized, the production process of the half door ring hot stamping was simplified, the production energy consumption was greatly reduced, and the production cost was effectively reduced.

[0015] (2) The impact resistance, shock resistance and precision of the semi-door ring products have been significantly improved, the qualified rate and product quality of the semi-door ring products have been greatly improved, the safety of passengers has been improved, and the market competitiveness has been significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0017] Figure 1This is a schematic diagram of a pseudo door ring blank before heat treatment by hot stamping process of ultra-high strength steel for a half door ring of the present invention.

[0018] Figure 2 The microstructure diagrams of 22MnB5 of Example 1, Example 2, Example 3, and Example 4 under an optical microscope.

[0019] Figure 3 This is the microstructure diagram of 22MnB5 of Comparative Example 1 under an optical microscope.

[0020] Figure 4 The fracture morphology of 22MnB5 of Example 4 and Example 5 under SEM electron microscope.

[0021] Figure 5 Fracture morphology of 22MnB5 of Comparative Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 5 under SEM electron microscope.

[0022] Among them, 1-the material piece of the upper section of the A-pillar, 2-the material piece of the upper side beam, 3-the material piece of the upper section of the B-pillar, 4-the material piece of the lower section of the B-pillar, 5-the material piece of the lower section of the A-pillar. DETAILED DESCRIPTION

[0023] The technical solution of the hot stamping process of the ultra-high strength steel of the half door ring of the present invention is further described below in conjunction with the specific implementation methods. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0024] Embodiment 1:

[0025] S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0026] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 150° C., the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove has a groove for limiting A pillar for determining the position of the pseudo door ring blank and an auxiliary pillar for assisting in determining the position of the pseudo door ring blank, no silicon steel sheet is placed on the upper surface of the groove before hot stamping, after the pseudo door ring blank is placed on the designated position on the lower die insert, the upper die insert presses the pseudo door ring blank downward into the groove of the lower die insert, and hot stamping is performed to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device by the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0027] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0028] Embodiment 2:

[0029] S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0030] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 150°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, a silicon steel sheet with a thickness of 0.05mm is placed on the upper surface of the groove before hot stamping, and after the pseudo door ring blank is placed on the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank into the groove of the lower die insert for hot stamping to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0031] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0032] Embodiment 3:

[0033] S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0034] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 150°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, a silicon steel sheet with a thickness of 0.10mm is placed on the upper surface of the groove before hot stamping, and after the pseudo door ring blank is placed at the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank into the groove of the lower die insert for hot stamping to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0035] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0036] Embodiment 4:

[0037] S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0038] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 150°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, a silicon steel sheet with a thickness of 0.15mm is placed on the upper surface of the groove before hot stamping, and after the pseudo door ring blank is placed on the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank into the groove of the lower die insert for hot stamping to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0039] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0040] Comparative Example 1: S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0041] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 150°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, a silicon steel sheet with a thickness of 0.20mm is placed on the upper surface of the groove before hot stamping, and after the pseudo door ring blank is placed on the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank into the groove of the lower die insert for hot stamping to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0042] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0043] The mechanical properties of 22MnB5 were compared for the half door knockers obtained in Example 1, Example 2, Example 3, Example 4 and Comparative Example 1. The comparative data are shown in Table 1. The fracture strength reflects the maximum stress that the steel can withstand under tension and is an important criterion for measuring its bearing capacity. The elongation reflects the full extension degree of the steel during the stretching process and is an important basis for evaluating its plastic deformation capacity. The automotive industry's requirements for half door knockers are: fracture strength ≥ 1300MPa, elongation ≥ 5%.

[0044] Table 1 Mechanical properties of 22MnB5 at the same heating temperature and different silicon steel sheet thickness

[0045] Observing the half door rings obtained in Example 1, Example 2, Example 3, Example 4 and Comparative Example 1 under an optical microscope, it can be observed that the 22MnB5 in Example 1, Example 2, Example 3 and Example 4 is almost a full martensitic structure. Figure 2 As shown, ferrite and bainite appear in 22MnB5 of Comparative Example 1, as shown in Figure 3 As shown, ferrite and bainite cause the elongation of the material to deteriorate abnormally.

[0046] Embodiment 5: S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0047] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 250°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, a silicon steel sheet with a thickness of 0.15mm is placed on the upper surface of the groove before hot stamping, and after the pseudo door ring blank is placed on the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank into the groove of the lower die insert for hot stamping to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0048] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0049] Comparative Example 2: S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0050] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 300°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, a silicon steel sheet with a thickness of 0.15mm is placed on the upper surface of the groove before hot stamping, and after the pseudo door ring blank is placed on the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank into the groove of the lower die insert for hot stamping to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0051] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0052] Comparative Example 3: S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0053] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 350°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, a silicon steel sheet with a thickness of 0.15mm is placed on the upper surface of the groove before hot stamping, and after the pseudo door ring blank is placed on the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank into the groove of the lower die insert for hot stamping to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0054] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0055] Comparative Example 4: S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0056] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 400°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the groove depth is the same as the half door ring thickness required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, a silicon steel sheet with a thickness of 0.15mm is placed on the upper surface of the groove before hot stamping, and after the pseudo door ring blank is placed on the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank into the groove of the lower die insert for hot stamping to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0057] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0058] Comparative Example 5: S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel 22MnB5 plates of different thicknesses to obtain A-pillar upper section blank 1, upper side beam blank 2, B-pillar upper section blank 3, B-pillar lower section blank 4 and A-pillar lower section blank 5; these blanks are laser welded to obtain half door ring blanks, and the A-pillar lower section blank 5 and the B-pillar lower section blank 4 of the half door ring blank are connected by a connector to obtain a pseudo door ring blank, such as Figure 1 shown.

[0059] S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 450°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the groove depth is the same as the half door ring thickness required by the design. The lower surface of the upper mold insert is a protrusion that fits the groove of the lower mold insert, and the outer surface of the groove is used to limit the pseudo door ring blank. The support for the material position and the auxiliary column for assisting in limiting the position of the pseudo door ring blank, a silicon steel sheet with a thickness of 0.15mm is placed on the upper surface of the groove before hot stamping, and after the pseudo door ring blank is placed on the specified position on the lower die insert, the upper die insert presses the pseudo door ring blank into the groove of the lower die insert for hot stamping to obtain a half door ring semi-finished product, and then the half door ring semi-finished product is removed from the mold of the hot stamping device through the loading and unloading device, which can avoid damage to the half door ring semi-finished product caused by direct clamping and ensure the yield rate of the half door ring.

[0060] S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

[0061] The mechanical properties of the half door rings obtained in Example 4, Example 5, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 5 were compared with each other. The comparative data are shown in Table 2, where the yield strength refers to the yield limit of the material when the yield phenomenon occurs, that is, the stress for resisting a small amount of plastic deformation. For materials without obvious yield phenomenon, the stress value that produces 0.2% residual deformation is usually used as its yield limit. The requirements for half door rings in the automotive industry are: breaking strength ≥ 1300MPa, elongation ≥ 5%, and yield strength ≥ 950MPa.

[0062] Table 2 Mechanical properties of 22MnB5 at different heating temperatures and the same gasket thickness

[0063] Observe the fracture morphology of 22MnB5 of Example 4 and Example 5 under SEM electron microscope Figure 4 , and the fracture morphology of 22MnB5 of Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 under SEM electron microscope Figure 5 It can be seen that when the mold heating temperature is 300-450℃, the 22MnB5 fracture dimple is shallow and there are more holes. The holes cause stress concentration and further promote the rapid extension of cracks, which eventually leads to the deterioration of plasticity.

Claims

1. A hot stamping process for ultra-high strength steel of a half door ring, characterized in that: Here are the steps: S1: Acquisition of pseudo door knocker blanks: According to the design requirements and specifications of the automobile, blanking is performed on high-speed tool steel plates of different thicknesses to obtain an A-pillar upper section blank (1), an upper side beam blank (2), a B-pillar upper section blank (3), a B-pillar lower section blank (4) and an A-pillar lower section blank (5); these blanks are laser welded to obtain a half door ring blank, and the A-pillar lower section blank (5) and the B-pillar lower section blank (4) of the half door ring blank are connected by a connector to obtain a pseudo door ring blank; S2: Heat treatment: After the pseudo door ring blank obtained in step S1 is heated to 150°C to 250°C, the pseudo door ring blank is placed at a designated position on a hot stamping device through a loading and unloading device. The hot stamping part of the hot stamping device includes a mold, a pillar, and an auxiliary pillar. The mold includes an upper mold insert and a lower mold insert. The upper surface of the lower mold insert has a groove that is the same as the half door ring shape required by the design, and the depth of the groove is the same as the thickness of the half door ring required by the design. The lower surface of the upper mold insert is a convex groove that fits the groove of the lower mold insert. The outer side of the groove is provided with a pillar for limiting the position of the pseudo door ring blank and an auxiliary pillar for assisting in limiting the position of the pseudo door ring blank. Before hot stamping, no gasket is placed on the upper surface of the groove or a gasket with a thickness of 0 to 0.15 mm is placed. After the pseudo door ring blank is placed at a designated position on the lower die insert, the upper die insert presses the pseudo door ring blank downward into the groove of the lower die insert to perform hot stamping to obtain a semi-finished door ring, and then the semi-finished door ring is removed from the die of the hot stamping device by a loading and unloading device. S3: Cutting: The semi-finished half door knocker is cut to obtain a finished half door knocker.

2. The hot stamping process of ultra-high strength steel for half door ring according to claim 1, characterized in that: The number of the pillars is greater than or equal to 4.

3. The hot stamping process of ultra-high strength steel for half door ring according to claim 1, characterized in that: The number of the auxiliary columns is greater than or equal to 2.

4. The hot stamping process of ultra-high strength steel for half door ring according to claim 1, characterized in that: The gasket is a silicon steel sheet.

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