A hot formed component segmented quenching organisation modification process

Abstract

The application discloses a sectional quenching organization modification process of a hot forming component and relates to the technical field of metal piece heat treatment. The process heats and keeps the steel plate blank, and then the steel plate blank is transferred into a stamping die without cooling water channels arranged on the punch and the die, is formed by closing the die and is kept pressure; after the die is opened, the formed piece is placed into a sectional quenching clamp outside the stamping die, the first contact cooling block contacts the high-strength area, the second contact cooling block keeps a gap with the energy absorption area, and the transition area is supported by the small-area supporting of the heat insulation fulcrum; the second contact cooling block contacts the energy absorption area and is cooled; no cooling medium is sprayed or atomized to the formed piece in the sectional quenching process, and then laser cutting is carried out. The process can simplify the structure of the stamping die, and the high-strength area, the energy absorption area and the continuous transition area are formed by the sectional contact cooling outside the die, so that the matching stability of the organizations and the hardness between different functional areas is improved.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for metal parts, and specifically to a segmented quenching and microstructure modification process for hot-formed components. Background Technology

[0002] Hot stamping typically involves heating a hardenable steel slab to its austenitizing temperature, transferring it to a stamping die, and then cooling it in the die or in a subsequent process to obtain a high-strength martensitic structure. For automotive safety structural components, load-bearing members, and connecting components, while a single high-strength structure is beneficial for improving intrusion resistance, it may lead to insufficient plasticity and toughness, a higher risk of edge cracking, or localized performance mismatches near connection ends, energy-absorbing areas, or subsequent cutting holes.

[0003] Existing technologies already include various methods for localized softening or segmented strengthening. For example, some technologies use zoned heating, localized die clearance, die insert temperature control, or post-forming secondary heating to create hard and soft areas in thermoformed parts. Other technologies perform intermediate cooling on localized areas before forming, allowing them to form a mixed martensite and bainite structure during subsequent pressure quenching. Still other technologies use in-mold hydraulic cylinders, die blanking cores, or localized die pressure control to achieve different cooling rates in different areas. Furthermore, some technologies employ gas or atomized media to rapidly cool thermoformed parts, followed by subsequent cutting or punching.

[0004] While the above solutions can achieve a certain degree of regional microstructure control, the following problems still exist: First, some solutions rely on forming dies with water-cooling channels, resulting in complex die structures and high manufacturing and maintenance costs; Second, some solutions simultaneously perform forming, shape retention, and main quenching functions within the stamping die, leading to long in-die holding times and limited process cycle time; Third, local softening or segmented strengthening solutions are prone to abrupt hardness changes between hard and soft areas, making it difficult to stably control the hardness gradient in the transition zone; Fourth, when using spray or atomized cooling media, cooling uniformity, surface condition, and adaptability to subsequent laser cutting require additional control; Fifth, if ordinary laser cutting is only performed after forming without considering the relationship between hole positions and microstructure areas, it is difficult to demonstrate the synergistic effect with previous microstructure modification.

[0005] Therefore, there is a need for a segmented quenching structure modification process that can simplify the structure of stamping die while enabling hot-formed components to form high-strength zones, energy-absorbing zones, and continuous transition zones. Summary of the Invention

[0006] The purpose of this invention is to provide a segmented quenching microstructure modification process for hot-formed components, which solves the technical problem in the prior art of needing a segmented quenching microstructure modification process to form a high-strength zone, an energy-absorbing zone, and a continuous transition zone in hot-formed components.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A segmented quenching process for modifying the microstructure of hot-formed components includes the following steps: 22MnB5 steel slabs with a thickness of 1.0 to 2.2 mm are heated to 890 to 930°C and held at that temperature for 240 to 360 seconds. Within 5 seconds, they are transferred into a stamping die with no cooling channels in either the punch or the die. The die is closed at 720 to 820°C and held under pressure for 1.5 to 3 seconds. Within 2 seconds after mold opening, the formed part with a surface temperature of 620-760℃ is placed into the segmented quenching fixture outside the mold, so that the first contact cooling block contacts the high-strength area with 0.20-0.60MPa, the second contact cooling block maintains a gap of 2-6mm with the energy absorption area, and the transition area is only supported by the heat insulation support point and the contact area of ​​the support point is less than or equal to 10% of the projected area of ​​the transition area; The first contact cooling block lowers the high-strength zone to 190–230°C; the energy-absorbing zone continues to cool while maintaining a 2–6 mm gap with the second contact cooling block. When the energy-absorbing zone drops to 430–520°C, the second contact cooling block contacts the energy-absorbing zone at 0.15–0.50 MPa and cools it to below 150°C, followed by laser cutting; the hardness difference between adjacent zones in the resulting transition zone, measured at a 5 mm interval, is ≤30HV0.5.

[0008] Furthermore, the 22MnB5 steel slab comprises the following elements by mass percentage: C 0.22%–0.25%, Si 0.15%–0.30%, Mn 1.15%–1.40%, Cr 0.10%–0.25%, Ti 0.02%–0.05%, B 0.0020%–0.0035%, Al 0.02%–0.06%, P≤0.020%, S≤0.008%, with the balance being Fe and unavoidable impurities.

[0009] Furthermore, the 22MnB5 steel slab is an Al-Si coated steel slab with a coating thickness of 10–35 μm on one side.

[0010] Furthermore, both the first contact cooling block and the second contact cooling block have conformal contact surfaces and built-in heat exchange channels, wherein the cooling medium in the built-in heat exchange channels does not contact the surface of the formed part.

[0011] Furthermore, the heat insulation support is made of alumina ceramic, silicon nitride ceramic, or graphite material, and the contact area between a single heat insulation support and the transition zone is 20–200 mm². 2 The distance between adjacent insulation support points is 30-100mm.

[0012] Furthermore, after the first contact cooling block comes into contact with the high-strength zone, the high-strength zone is cooled to 190-230°C at a rate of 40-75°C / s; while the second contact cooling block maintains a gap with the energy-absorbing zone, the energy-absorbing zone is cooled to 430-520°C at a rate of 5-18°C / s; after the second contact cooling block comes into contact with the energy-absorbing zone, the energy-absorbing zone is cooled to 120-180°C at a rate of 15-30°C / s.

[0013] Furthermore, the external segmented quenching fixture is equipped with infrared thermometers or thermocouples corresponding to the high-strength zone and the energy-absorbing zone, respectively, with a sampling frequency of 5 to 20 Hz; when the difference between the measured temperature and the target temperature in any zone is ≥20℃, the contact pressure or contact time of the corresponding contact cooling block is adjusted.

[0014] Furthermore, the martensite area fraction of the high-strength region is 85%–98%, and the Vickers hardness is 450–540 HV0.5; the martensite area fraction of the energy-absorbing region is 15%–45%, and the Vickers hardness is 280–360 HV0.5; the width of the transition region is 25–60 mm.

[0015] Furthermore, the laser cutting is performed after the surface temperature of the formed part is ≤80℃, the connecting hole formed by the laser cutting is located in the energy absorption zone or transition zone, and the minimum distance between the edge of the connecting hole and the high-intensity zone is ≥12mm.

[0016] Furthermore, the thermoformed component is a B-pillar reinforcing plate, the high-strength zone is located in the middle section of the B-pillar reinforcing plate, and the energy-absorbing zone is located in the upper connecting section, the lower connecting section, or the upper connecting section and the lower connecting section of the B-pillar reinforcing plate.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: This invention, under the condition that the stamping die does not have a cooling water channel and laser cutting is subsequently used, controls the cooling process of different functional areas of the hot-formed component through an external segmented quenching process, so that the component forms a high-strength area, an energy-absorbing area and a transition area with continuously changing hardness, thereby improving the stability of the microstructure and hardness matching between different functional areas.

[0018] This invention separates the forming process from the main quenching and microstructure modification process by using an external segmented quenching fixture for primary cooling and microstructure control after forming. Through preferential contact cooling in the high-strength zone, delayed contact cooling in the energy-absorbing zone, and small-area support at the heat-insulating fulcrum in the transition zone, a high-strength zone, an energy-absorbing zone, and a transition zone with continuously varying hardness can be formed. The non-spraying and non-atomizing contact cooling method avoids direct application of liquid or atomized cooling media to the surface of the formed part. By setting laser-cut connecting holes in the energy-absorbing zone or transition zone, the edges of the holes can avoid the high-hardness, high-strength zone. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the process for segmented quenching and structural modification of thermoformed components according to the present invention.

[0021] Figure 2 This is a schematic diagram of the stamping die structure of the present invention without cooling water channels.

[0022] Figure 3 This is a schematic diagram of the external segmented quenching fixture structure of the present invention.

[0023] Figure 4 This is a schematic diagram showing the relative positions of the first contact cooling block, the second contact cooling block, and the heat insulation support point of the present invention.

[0024] Figure 5 This is a schematic diagram of the hardness test points in the transition zone of the present invention.

[0025] Figure 6 This is a schematic diagram of the metallographic sampling locations in the high-strength region, energy-absorbing region, and transition region of this invention.

[0026] Figure 7 This is a schematic diagram showing the relative positions of the laser-cut connecting hole, the high-intensity zone, the energy-absorbing zone, and the transition zone of the present invention.

[0027] Figure 8 This is a schematic diagram showing the arrangement of the high-strength zone, energy-absorbing zone, and transition zone in the B-pillar reinforcement plate of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In this specification, the high-strength zone, energy-absorbing zone, and transition zone are all areas pre-determined before segmented quenching based on the functional position of the component and the corresponding relationship of the segmented quenching fixture outside the mold; the high-strength zone is the area corresponding to and preferentially contacted by the first contact cooling block for cooling; the energy-absorbing zone is the area that maintains a gap with the second contact cooling block in the first stage and is subsequently contacted and cooled by the second contact cooling block; the transition zone is the area located between the high-strength zone and the energy-absorbing zone and supported by a small area of ​​heat-insulating support points; the microstructure and hardness of each zone are the test results after segmented quenching and are not used as the basis for identifying the zone during the quenching process.

[0030] The absence of cooling channels in stamping dies refers to the absence of water-cooling channels inside the punches and dies that are in contact with the hot-formed steel slab or the formed part, which are used to introduce cooling water and perform the main function of extracting quenching heat.

[0031] External segmented quenching fixtures are fixtures set outside the stamping die, which receive the formed parts that are still in a high-temperature state after the die is opened, and apply different cooling processes to different areas through contact cooling blocks and heat insulation support points.

[0032] During the segmented quenching process, liquid water, oil, polymer quenching liquid, liquid nitrogen, water mist, oil mist or other atomized droplets are not sprayed directly onto the surface of the formed part; the cooling medium in the heat exchange channel inside the contact cooling block can be water, oil, gas or other heat exchange medium, but the medium does not directly contact the surface of the formed part.

[0033] See Figure 1 As shown, the process flow of segmented quenching and microstructure modification of thermoformed components of the present invention includes, in sequence, slab heating, waterless mold forming, mold opening and transfer, external segmented quenching, laser cutting and partitioned components. By separating the forming process from the main quenching and microstructure modification process, the stamping die mainly undertakes the geometric forming function, and the external segmented quenching fixture undertakes the regional microstructure control function.

[0034] This process setup avoids the need for complex cooling channels in the punch and die, reducing the difficulty of mold processing, sealing, and maintenance. On the other hand, since the external clamping fixture is dedicated to cooling process control, the contact states of the high-strength zone, energy-absorbing zone, and transition zone can be designed separately, so that the cooling process of each zone is no longer completely limited by the forming mold surface and the in-mold holding time.

[0035] See Figure 2As shown, the stamping die includes a mating punch and a die, which are used for hot forming of the austenitized 22MnB5 steel slab. Unlike traditional hot stamping water-cooled dies, neither the punch nor the die of this invention has cooling water channels for introducing cooling water and undertaking the main function of extracting quenching heat. The necessity of this structural design is that the stamping die no longer bears the main task of cooling control for forming the high-strength zone, energy-absorbing zone, and transition zone, thereby providing a temperature basis for subsequent external segmented quenching.

[0036] Because hot-formed steel slabs are molded at 720–820℃ and held under pressure for only 1.5–3 seconds, the formed parts retain a relatively high surface temperature of 620–760℃ after mold opening. This temperature range allows the subsequent external mold fixtures to still control the cooling rate through contact pressure, contact time, and thermal insulation supports. In other words, Figure 2 The waterless cooling stamping die shown is not simply an omission of cooling channels, but rather... Figure 3 , Figure 4 The external segmented quenching fixtures shown together constitute a continuous thermal process control system that first forms the shape and then performs sectional quenching.

[0037] See Figure 3 As shown, the external segmented quenching fixture includes a first contact cooling block corresponding to the high-strength zone, a second contact cooling block corresponding to the energy-absorbing zone, and a heat-insulating support point located between the two. Both the first and second contact cooling blocks have conformal contact surfaces that match the surface of the formed part, and heat exchange channels are provided inside. The cooling medium flows inside the contact cooling blocks without directly contacting the surface of the formed part.

[0038] The necessity of this structure lies in the fact that the first contact cooling block makes contact with the high-strength region earlier and applies contact pressure, so that the high-strength region can quickly pass through the cooling zone required for martensitic transformation; the second contact cooling block maintains a gap with the energy-absorbing region in the first stage, so that the energy-absorbing region is prevented from being rapidly quenched simultaneously; the heat insulation support only provides small-area support for the transition region, so as to prevent the transition region from being rapidly heated by the continuous metal surface.

[0039] Existing technologies include methods that achieve localized softening through temperature control in the mold area, and methods that achieve rapid overall cooling through gas and atomized droplets; the present invention... Figure 3 The structure adopts a combination of external conformal contact cooling blocks and heat insulation support points, and explicitly excludes surface spraying or atomized cooling media for the formed parts, thus forming a heat extraction path different from existing pneumatic atomized quenching or localized in-mold cooling.

[0040] See Figure 4As shown, in the first stage of segmented quenching, the first contact cooling block contacts the high-strength area of ​​the formed part, the second contact cooling block maintains a gap of 2-6 mm with the energy-absorbing area, and the transition zone is supported by a small area of ​​heat-insulating fulcrum. The necessity of this relative positional relationship lies in ensuring that the three regions have different heat transfer boundary conditions within the same time period: the high-strength area undergoes pressurized contact heat transfer, the energy-absorbing area experiences slow heat dissipation under void isolation, and the transition zone undergoes weak contact heat transfer supported by heat-insulating fulcrum. Through this relative positional arrangement, the high-strength area can achieve a greater interfacial heat transfer intensity, the energy-absorbing area can avoid directly forming a high martensite proportion structure in the first stage, and the transition zone avoids localized rapid cooling points due to continuous metal support. The first and second contact cooling blocks are preferably made of H13 hot work die steel, copper alloy inserts, or embedded copper alloy heat exchange layers, with a contact surface roughness Ra≤1.6μm and a gap with the theoretical surface of the formed part≤0.2mm; the circulating water temperature in the built-in heat exchange channel is 15~30℃ and the flow rate is 5~20L / min; the heat insulation supports are staggered along the width of the transition zone, and the total contact area of ​​the supports accounts for 3~10% of the projected area of ​​the transition zone.

[0041] Existing localized quenching or softening solutions typically adjust performance by adjusting the contact time within the mold area, the mold temperature, or localized secondary heating. This invention utilizes three boundary conditions—contact, gap, and hot spot support—in the external mold fixture to simultaneously act on different areas, resulting in a more defined distribution of regional thermal history.

[0042] See Figure 7 As shown, the laser-cut connecting holes are located in the energy-absorbing zone or transition zone, and the minimum distance between the edge of the connecting hole and the high-intensity zone is not less than 12mm. The necessity of this hole position relationship lies in the fact that laser cutting is not a normal post-processing step, but rather a step that complements the preceding zoning design: the high-intensity zone is used to bear the functions of anti-intrusion or load-bearing and has high hardness; the energy-absorbing zone or transition zone has lower hardness and relatively higher plasticity, making it more suitable as a connecting hole, mounting hole, or local grooving area.

[0043] Existing pneumatic thermoforming-atomizing quenching solutions also include subsequent cutting and punching operations, but their focus is on obtaining uniform and rapid quenching and overall martensitic structure through atomizing cooling; the present invention, on the other hand, clearly defines the laser cutting hole position in the energy absorption zone or transition zone, and specifies the minimum distance between the hole edge and the high-intensity zone, thereby forming a synergistic relationship between the subsequent cutting position and the preceding structural partition.

[0044] The above hole design can reduce the risk of brittle cracking at the hole edge, hardness concentration in the heat-affected zone, or defects at the connection edge caused by directly drilling holes in the high-hardness and high-strength zone; at the same time, it can preserve the continuous load-bearing area of ​​the high-strength zone, so that the high-strength zone mainly undertakes the function of anti-intrusion, while the energy-absorbing zone or transition zone undertakes the functions of connection, installation, and coordination of local deformation.

[0045] See Figure 8As shown, when the thermoformed component is a B-pillar reinforcement plate, the high-strength zone is located in the middle section of the B-pillar reinforcement plate, the energy-absorbing zone is located in the upper and lower connecting sections, or the upper and lower connecting sections, and the transition zone is located between the middle high-strength zone and the end energy-absorbing zone. The necessity of this arrangement lies in the fact that the middle section of the B-pillar reinforcement plate usually requires high resistance to intrusion, while the end connecting section needs to take into account the functions of connection assembly, local deformation coordination, and energy absorption.

[0046] By placing the high-strength zone in the middle section of the B-pillar reinforcement plate, the load-bearing capacity and resistance to lateral intrusion of the middle section can be improved; by placing the energy-absorbing zone in the end connection section, the plastic coordination of the connection area can be improved; by setting a continuous transition zone between the high-strength zone and the energy-absorbing zone, the local stress concentration caused by abrupt changes in hardness can be reduced. Example 1:

[0047] In this embodiment, an Al-Si coated 22MnB5 steel slab with a thickness of 1.6 mm and a single-sided coating thickness of 20 μm is selected. The 22MnB5 steel slab includes the following elements by mass percentage: C 0.235%, Si 0.22%, Mn 1.28%, Cr 0.16%, Ti 0.035%, B 0.0028%, Al 0.040%, P 0.012%, S 0.004%, with the balance being Fe and unavoidable impurities.

[0048] The steel slab is placed in a heating furnace, heated to 910°C and held for 300 seconds to austenitize it. Within 4 seconds after exiting the furnace, the steel slab is transferred to a stamping die, the punch and die of which are not equipped with cooling channels. The steel slab is formed at 770°C with a forming time of 1.2 seconds and a holding time of 2.0 seconds. Within 1.5 seconds after opening the die, the formed part with a surface temperature of 690°C is placed into an external segmented quenching fixture.

[0049] The external segmented quenching fixture includes a first contact cooling block, a second contact cooling block, and an alumina ceramic heat insulation support; the first contact cooling block has a conformal contact surface and an internal heat exchange channel, through which 20°C circulating water is introduced, and the circulating water does not directly contact the surface of the formed part; the second contact cooling block has a conformal contact surface and an internal heat exchange channel, through which 20°C circulating water is introduced, and the circulating water does not directly contact the surface of the formed part.

[0050] In the first stage of segmented quenching, the first contact cooling block is brought into contact with the high-strength zone at a contact pressure of 0.40 MPa, while the second contact cooling block maintains a 4 mm gap with the energy-absorbing zone. The transition zone is supported by alumina ceramic heat insulation supports, with a contact area of ​​80 mm² between each heat insulation support and the transition zone. 2The spacing between adjacent heat-insulating support points is 60mm, and the total contact area of ​​the heat-insulating support points accounts for 8% of the projected area of ​​the transition zone. When the temperature of the energy-absorbing zone drops to 480℃, the second contact cooling block is brought into contact with the energy-absorbing zone at a contact pressure of 0.30MPa, and the energy-absorbing zone is cooled to below 150℃. No liquid cooling medium or atomized cooling medium is sprayed onto the surface of the formed part throughout the entire process.

[0051] After the surface temperature of the formed part drops to 75℃, laser cutting is performed to form the outer contour and connecting hole. The connecting hole is located in the energy absorption zone, and the minimum distance between the edge of the connecting hole and the high-strength zone is 15mm. Example 2:

[0052] This embodiment is basically the same as Embodiment 1, except that: the 22MnB5 steel slab includes the following elements by mass percentage: C 0.221%, Si 0.25%, Mn 1.27%, Cr 0.18%, Ti 0.030%, B 0.0025%, Al 0.023%, P 0.016%, S 0.005%, with the balance being Fe and unavoidable impurities; the steel slab thickness is 1.0 mm, and the Al-Si coating thickness on one side is 18 μm; the steel slab is heated to 900℃ and held for 260 s; after exiting the furnace, it is transferred to the stamping die within 3.5 s, and the steel slab is formed by closing the die at 750℃, with a forming time of 1.0 s and a holding time of 1.8 s; after opening the die, the formed part with a surface temperature of 670℃ is placed into the external segmented quenching fixture within 1.4 s.

[0053] The first contact cooling block contacts the high-strength zone with a contact pressure of 0.35 MPa, while the second contact cooling block maintains a 5 mm gap with the energy-absorbing zone. The transition zone is supported by alumina ceramic thermal insulation supports, with a contact area of ​​60 mm² between each thermal insulation support and the transition zone. 2 The spacing between adjacent heat insulation support points is 50mm, and the total contact area of ​​the heat insulation support points accounts for 7% of the projected area of ​​the transition zone. When the temperature of the energy absorption zone drops to 465℃, the second contact cooling block is brought into contact with the energy absorption zone with a contact pressure of 0.25MPa, and the energy absorption zone is cooled to below 150℃. After the surface temperature of the formed part drops to 72℃, laser cutting is performed. The connecting hole is located in the energy absorption zone, and the minimum distance between the edge of the connecting hole and the high-strength zone is 14mm. Example 3:

[0054] This embodiment is basically the same as Embodiment 1, except that: the 22MnB5 steel slab includes the following elements by mass percentage: C 0.234%, Si 0.26%, Mn 1.19%, Cr 0.18%, Ti 0.037%, B 0.0028%, Al 0.031%, P 0.015%, S 0.004%, with the balance being Fe and unavoidable impurities; the steel slab thickness is 2.2mm, and the thickness of the Al-Si coating on one side is 24μm; the steel slab is heated to 925℃ and held for 360s; after exiting the furnace, it is transferred to the stamping die within 4.5s, and the steel slab is formed by closing the die at 800℃, with a forming time of 1.5s and a holding time of 2.8s; after opening the die, the formed part with a surface temperature of 730℃ is placed into the external segmented quenching fixture within 1.8s.

[0055] The first contact cooling block contacts the high-strength zone with a contact pressure of 0.55 MPa, while the second contact cooling block maintains a 3 mm gap with the energy-absorbing zone. The transition zone is supported by alumina ceramic thermal insulation supports, with each thermal insulation support having a contact area of ​​100 mm² with the transition zone. 2 The spacing between adjacent heat insulation support points is 70mm, and the total contact area of ​​the heat insulation support points accounts for 9% of the projected area of ​​the transition zone. When the temperature of the energy absorption zone drops to 500℃, the second contact cooling block is brought into contact with the energy absorption zone with a contact pressure of 0.45MPa, and the energy absorption zone is cooled to below 150℃. After the surface temperature of the formed part drops to 78℃, laser cutting is performed. The connecting hole is located in the transition zone, and the minimum distance between the edge of the connecting hole and the high-strength zone is 16mm. Example 4:

[0056] This embodiment is basically the same as Embodiment 1, except that: the 22MnB5 steel slab includes the following elements by mass percentage: C 0.242%, Si 0.26%, Mn 1.19%, Cr 0.16%, Ti 0.033%, B 0.0024%, Al 0.042%, P 0.012%, S 0.004%, with the balance being Fe and unavoidable impurities; the steel slab thickness is 1.6mm, and the Al-Si coating thickness on one side is 20μm; the steel slab is heated to 890℃ and held for 240s; within 4s after exiting the furnace, it is transferred to the stamping die, and the steel slab is formed at 720℃ with a forming time of 1.0s and a holding time of 1.5s; within 1.5s after opening the die, the formed part with a surface temperature of 620℃ is placed into the external segmented quenching fixture.

[0057] The first contact cooling block contacts the high-strength zone with a contact pressure of 0.30 MPa, while the second contact cooling block maintains a 6 mm gap with the energy-absorbing zone. The transition zone is supported by alumina ceramic thermal insulation supports, with a contact area of ​​70 mm² between each thermal insulation support and the transition zone. 2The spacing between adjacent heat insulation support points is 60mm, and the total contact area of ​​the heat insulation support points accounts for 7% of the projected area of ​​the transition zone. When the temperature of the energy absorption zone drops to 430℃, the second contact cooling block is brought into contact with the energy absorption zone with a contact pressure of 0.25MPa, and the energy absorption zone is cooled to below 150℃. Laser cutting is performed after the surface temperature of the formed part drops to 70℃. Example 5:

[0058] This embodiment is basically the same as Embodiment 1, except that: the 22MnB5 steel slab includes the following elements by mass percentage: C 0.237%, Si 0.17%, Mn 1.36%, Cr 0.24%, Ti 0.046%, B 0.0022%, Al 0.043%, P 0.011%, S 0.004%, with the balance being Fe and unavoidable impurities; the steel slab thickness is 1.6mm, and the Al-Si coating thickness on one side is 22μm; the steel slab is heated to 930℃ and held for 360s; within 5s after exiting the furnace, it is transferred to the stamping die, and the steel slab is formed at 820℃ with a forming time of 1.5s and a holding time of 3.0s; within 2s after opening the die, the formed part with a surface temperature of 760℃ is placed into the external segmented quenching fixture.

[0059] The first contact cooling block contacts the high-strength zone with a contact pressure of 0.55 MPa, while the second contact cooling block maintains a 2 mm gap with the energy-absorbing zone. The transition zone is supported by alumina ceramic thermal insulation supports, with a contact area of ​​110 mm² between each thermal insulation support and the transition zone. 2 The spacing between adjacent heat insulation support points is 80mm, and the total contact area of ​​the heat insulation support points accounts for 9% of the projected area of ​​the transition zone. When the temperature of the energy absorption zone drops to 520℃, the second contact cooling block is brought into contact with the energy absorption zone with a contact pressure of 0.45MPa, and the energy absorption zone is cooled to below 150℃. Laser cutting is performed after the surface temperature of the formed part drops to 80℃. Example 6:

[0060] This embodiment is basically the same as Embodiment 1, except that: the 22MnB5 steel slab includes the following elements by mass percentage: C 0.223%, Si 0.18%, Mn 1.33%, Cr 0.17%, Ti 0.036%, B 0.0027%, Al 0.047%, P 0.009%, S 0.003%, with the balance being Fe and unavoidable impurities; the thermal insulation support is made of silicon nitride ceramic, and the contact area between a single thermal insulation support and the transition zone is 120 mm². 2The distance between adjacent heat insulation support points is 80mm, and the total contact area of ​​the heat insulation support points accounts for 9% of the projected area of ​​the transition zone. The first contact cooling block contacts the high-strength zone with a pressure of 0.42MPa, and the second contact cooling block maintains a 4mm gap with the energy absorption zone. When the temperature of the energy absorption zone drops to 485℃, the second contact cooling block contacts the energy absorption zone with a contact pressure of 0.32MPa and cools the energy absorption zone to below 150℃. Example 7:

[0061] This embodiment is basically the same as Embodiment 1, except that: the external segmented quenching fixture is equipped with K-type thermocouples corresponding to the high-strength zone and the energy-absorbing zone respectively, and an infrared thermometer is used to verify the surface temperature with a sampling frequency of 10Hz. When the difference between the measured temperature and the target temperature in any region reaches 20℃, the control system adjusts the contact pressure of the corresponding contact cooling block, with a single pressure adjustment of 0.10MPa; in this embodiment, the initial contact pressure of the first contact cooling block is 0.38MPa, and the initial contact pressure of the second contact cooling block is 0.28MPa. Example 8:

[0062] See Figure 8 As shown, this embodiment uses the process of Embodiment 1 to prepare the B-pillar reinforcement plate. The high-strength zone of the B-pillar reinforcement plate is located in the middle section of the B-pillar reinforcement plate, the energy-absorbing zone is located in the upper and lower connecting sections of the B-pillar reinforcement plate, and the transition zone is located between the middle section and the end connecting section. The laser-cut connecting holes are set in the energy-absorbing zones of the upper and lower connecting sections, and the minimum distance between the edge of the connecting hole and the high-strength zone is 15mm.

[0063] Comparative Example 1: The comparative example uses the same steel slab as in Example 1, which is heated to 910°C and held for 300 seconds. It is then transferred to a stamping die with cooling channels within 4 seconds and formed at 770°C. The forming time is 1.2 seconds and the holding time is 10 seconds. The overall pressure quenching is completed in the die without using external segmented quenching fixtures.

[0064] Comparative Example 2: This comparative example uses the same steel slab as Example 1, and the heating, transfer, mold forming, and pressure holding conditions are the same as in Example 1. After mold opening, the part is not transferred to the external segmented quenching fixture, and is allowed to cool to below 150°C in still air at 25°C.

[0065] Comparative Example 3: This comparative example uses the same steel slab as Example 1, and the heating, transfer, mold forming, and pressure holding conditions are the same as in Example 1. After mold opening, it is transferred to an external segmented quenching fixture, so that the first contact cooling block and the second contact cooling block simultaneously contact the high-strength zone and the energy-absorbing zone, respectively, without setting an initial gap for the energy-absorbing zone.

[0066] Comparative Example 4: This comparative example uses the same steel slab as Example 1, and the heating, transfer, mold forming, and pressure holding conditions are the same as in Example 1. After mold opening, it is transferred to an external segmented quenching fixture, and the transition zone is contacted by a continuous metal support surface, without the use of small-area support points for heat insulation.

[0067] Comparative Example 5: This comparative example uses the same steel slab as Example 1, and the heating, transfer, mold closing, and pressure holding conditions are the same as in Example 1. After mold opening, the formed part is cooled by spray cooling, instead of using the internal heat exchange contact cooling method of the first and second contact cooling blocks.

[0068] Comparative Example 6: This comparative example uses the same steel slab and preparation process as Example 7, but does not set up temperature acquisition feedback, and does not adjust the contact pressure or contact time according to the temperature deviation.

[0069] Comparative Example 7: This comparative example uses the same B-pillar reinforcement plate preparation process as Example 8, but the laser-cut connecting hole is set in the high-strength zone, and the minimum distance between the edge of the connecting hole and the high-strength zone is 6mm.

[0070] Test example: Vickers hardness testing was conducted according to GB / T 4340.1-2024, with a test force of HV0.5 and a holding time of 10s. Five measuring points were taken in each of the high-strength and energy-absorbing zones, and the average value was calculated. In the transition zone, measuring points were arranged at 5mm intervals along the direction from the high-strength zone to the energy-absorbing zone, and the hardness difference between adjacent measuring points was recorded. (See reference...) Figure 5 As shown, the hardness test points in the transition zone are arranged at 5mm intervals along the direction from the high-strength zone to the energy-absorbing zone. The necessity of this arrangement is that measuring the average hardness of the high-strength zone and the energy-absorbing zone separately can only indicate that there is a performance difference between the two, but cannot prove whether a continuous transition has been formed between them. By arranging hardness test points at equal intervals in the transition zone and limiting the hardness difference between adjacent test points to no more than 30HV0.5, it is possible to directly evaluate whether there is a sudden change in hardness in the transition zone.

[0071] The continuity of hardness in the transition zone is a key technical advantage of this invention compared to conventional partitioned hardening or localized softening schemes. If the hardness abrupt change between the high-strength zone and the energy-absorbing zone is too large, strain concentration points are easily formed under service deformation or impact loads. By using small-area support with heat-insulating fulcrums and avoiding continuous metal cooling surface contact, the transition zone can obtain a cooling process between the high-strength zone and the energy-absorbing zone, thereby forming a hardness distribution that gradually changes along the length direction.

[0072] The room temperature tensile test was conducted according to GB / T 228.1-2021. Samples were taken along the length of the component, with the original plate thickness, a parallel section width of 12.5 mm, and an initial gauge length of 50 mm. A strain rate control method was used, with a strain rate of 0.00025 s⁻¹ before yielding.-1 The strain rate after yielding is 0.0067 s⁻¹. -1 .

[0073] Microstructure was prepared, etched, and observed according to GB / T 13298-2015. Metallographic image analysis software was used to statistically analyze the area fractions of martensite, bainite, ferrite, and pearlite. At least five fields of view were selected for each sampling location, and the average value was taken. (See reference...) Figure 6 As shown, metallographic sampling positions are set in the high-strength zone, energy-absorbing zone, and transition zone, with the sampling position preferably located at one-quarter of the plate thickness from the component surface. The necessity of this sampling method lies in the fact that there may be a difference in heat flow between the surface and the core of the thermoformed component during the contact cooling process; selecting a plate thickness position for microstructure observation helps to eliminate the influence of sampling depth differences on the judgment of microstructure proportions.

[0074] The high-strength zone corresponds to the priority contact area of ​​the first contact cooling block, and its microstructure is mainly martensite; the energy-absorbing zone corresponds to the first stage delayed contact area, and its microstructure can include various microstructures such as martensite, bainite, ferrite and pearlite; the transition zone is located between the two, and its microstructure gradually changes along the direction from the high-strength zone to the energy-absorbing zone.

[0075] The quality evaluation of laser-cut edges was carried out by observing the edges of the connecting holes with a 50x optical microscope to record whether there were through cracks, continuous slag, and obvious ablation. At the same time, an HV0.5 hardness test was performed at 0.2mm outside the edge of the hole, and the width of the heat-affected zone of the hole edge was measured.

[0076] The following test results are listed for the corresponding samples according to the test purpose. Tables 1 and 2 are used to evaluate the segmented quenching thermal history and hardness zoning results; Tables 3 and 4 are used to list representative metallographic structures and representative room temperature tensile properties; Table 5 is used to evaluate the influence of the laser-cut connecting hole location and the distance from the hole edge to the high-strength zone on the hole edge quality; Table 6 is used to evaluate the influence of temperature acquisition feedback on batch stability. Comparative Example 7, except for the connecting hole location and the distance from the hole edge to the high-strength zone, has the same B-pillar reinforcing plate preparation process as Example 8, therefore it is only listed in Table 5 and not repeated in Tables 1 to 4.

[0077] The thermal history and cooling rate parameters of the embodiments and comparative examples are shown in Table 1 below. In Table 1, the cooling rate of the first stage of the high-intensity zone, the cooling rate of the delayed stage of the energy-absorbing zone, and the cooling rate of the second stage of the energy-absorbing zone are the average cooling rates of the corresponding regions within the corresponding cooling intervals, and do not indicate that the high-intensity zone and the energy-absorbing zone reach their respective target temperatures at the same time. Table 1. Thermal history and cooling rate parameters Example 1 1.6 910 300 770 690 57.5 10.8 22.0 Example 2 1.0 900 260 750 670 68.2 12.6 26.5 Example 3 2.2 925 360 800 730 44.8 7.9 17.2 Example 4 1.6 890 240 720 620 50.3 8.5 20.4 Example 5 1.6 930 360 820 760 61.0 15.4 28.3 Example 6 1.6 910 300 770 692 55.8 10.2 21.4 Example 7 1.6 910 300 770 688 56.9 10.6 21.8 Example 8 1.6 910 300 770 690 57.1 10.7 22.1 Comparative Example 1 1.6 910 300 770 710 65.0 63.5 62.8 Comparative Example 2 1.6 910 300 770 690 8.6 7.9 7.4 Comparative Example 3 1.6 910 300 770 690 57.8 55.4 54.6 Comparative Example 4 1.6 910 300 770 690 57.2 10.6 21.7 Comparative Example 5 1.6 910 300 770 690 49.5 26.8 31.2 Comparative Example 6 1.6 910 300 770 690 52.0 13.8 24.5

[0078] The Vickers hardness test results are shown in Table 2 below: Table 2. Vickers hardness test results Example 1 498 326 172 42 24 Example 2 512 338 174 38 27 Example 3 482 312 170 46 22 Example 4 468 304 164 45 25 Example 5 522 356 166 36 29 Example 6 494 322 172 48 20 Example 7 501 328 173 41 21 Example 8 500 329 171 43 23 Comparative Example 1 506 492 14 28 18 Comparative Example 2 318 296 22 55 16 Comparative Example 3 502 462 40 30 19 Comparative Example 4 499 328 171 31 48 Comparative Example 5 486 386 100 34 42 Comparative Example 6 488 342 146 39 36 The results of the metallographic area fraction test are shown in Table 3 below: Table 3. Results of area fraction test of representative metallographic structures Example 1 High-strength area 92.6 5.4 1.2 0.8 Example 1 Energy absorption zone 32.8 43.6 15.4 8.2 Example 1 transition zone 61.5 25.8 8.4 4.3 Example 2 High-strength area 94.8 3.8 0.9 0.5 Example 2 Energy absorption zone 36.5 41.2 14.6 7.7 Example 3 High-strength area 89.6 7.0 2.0 1.4 Example 3 Energy absorption zone 28.4 45.8 17.2 8.6 Example 6 transition zone 58.2 27.6 9.4 4.8 Comparative Example 1 Energy absorption zone 90.5 6.5 2.0 1.0 Comparative Example 2 High-strength area 22.6 39.5 25.8 12.1 Comparative Example 3 Energy absorption zone 82.4 12.8 3.2 1.6 Comparative Example 4 The transition zone is located near the high-intensity zone. 86.8 9.4 2.5 1.3 Comparative Example 4 The transition zone is located on the side of the energy-absorbing zone. 36.2 40.0 15.6 8.2 The results of the room temperature tensile properties test are shown in Table 4 below: Table 4. Representative room temperature tensile property test results Example 1 High-strength area 1185 1530 5.8 Middle of the gauge length Example 1 Energy absorption zone 665 920 11.6 Middle of the gauge length Example 2 High-strength area 1210 1565 5.5 Middle of the gauge length Example 2 Energy absorption zone 690 955 10.8 Middle of the gauge length Example 3 High-strength area 1140 1485 6.1 Middle of the gauge length Example 3 Energy absorption zone 640 890 12.4 Middle of the gauge length Comparative Example 1 Energy absorption zone 1135 1490 5.9 Middle of the gauge length Comparative Example 2 High-strength area 610 835 13.5 Middle of the gauge length Comparative Example 3 Energy absorption zone 1060 1395 6.5 Middle of the gauge length The results of the laser-cut hole edge quality test are shown in Table 5 below: Table 5. Test Results of Laser Cut Hole Edge Quality Example 1 Energy absorption zone 75 15 342 0.18 The hole edges are continuous, with no through cracks and minimal slag buildup. Example 3 transition zone 78 16 382 0.20 The hole edges are continuous, with no through cracks and minimal slag buildup. Example 8 Energy absorption zone 76 15 348 0.19 The hole edges are continuous, with no through cracks and minimal slag buildup. Comparative Example 7 High-strength area 75 6 505 0.31 There are localized micro-cracks around the hole, and the slag buildup is quite noticeable. The batch stability test results are shown in Table 6 below: Table 6. Batch stability test results Example 7 5 8.2 7.5 21.4 2.1 Comparative Example 6 5 18.6 20.2 36.8 6.7 Analysis of experimental results: As shown in Table 1, in Examples 1-8, the cooling rate in the first stage of the high-strength zone is 44.8-68.2℃ / s, falling within the range of 40-75℃ / s; the cooling rate in the delayed stage of the energy-absorbing zone is 7.9-15.4℃ / s, falling within the range of 5-18℃ / s; and the cooling rate in the second stage of the energy-absorbing zone is 17.2-28.3℃ / s, falling within the range of 15-30℃ / s. These results indicate that by having the first contact cooling block preferentially contact the high-strength zone, and the second contact cooling block maintaining a gap with the energy-absorbing zone before subsequently contacting it, a differentiated cooling process can be formed between the high-strength zone and the energy-absorbing zone.

[0079] As shown in Table 2, the hardness of the high-strength zone in Examples 1-8 is 468-522 HV0.5, and the hardness of the energy-absorbing zone is 304-356 HV0.5, both falling within the range of 450-540 HV0.5 for the high-strength zone and 280-360 HV0.5 for the energy-absorbing zone. The hardness difference between the high-strength zone and the energy-absorbing zone is 164-174 HV0.5, forming a clear functional zoning. The maximum hardness difference between adjacent 5mm sections in the transition zone of Examples 1-8 is 20-29 HV0.5, none exceeding 30 HV0.5, indicating that the hardness change in the transition zone is continuous.

[0080] Comparative Example 1 uses a stamping die with cooling channels for integral press quenching. The hardness of its high-strength zone and energy-absorbing zone are 506 HV0.5 and 492 HV0.5 respectively, with a hardness difference of only 14 HV0.5 between the two zones, failing to form a low-hardness energy-absorbing zone. Comparative Example 2 uses a stamping die without cooling channels followed by air cooling. Its high-strength zone hardness is 318 HV0.5, which does not meet the high-strength zone hardness requirement. This demonstrates that neither integral press quenching nor natural air cooling alone can simultaneously achieve the desired combination of high-strength and energy-absorbing zones.

[0081] In Comparative Example 3, the high-strength region and the energy-absorbing region were simultaneously cooled in contact. The hardness of the energy-absorbing region was 462 HV0.5, significantly higher than that of Example 1 (326 HV0.5); its martensite area fraction was 82.4%, also significantly higher than that of Example 1 (32.8%). This result indicates that maintaining a 2–6 mm gap between the energy-absorbing regions and delaying contact cooling in the first stage is beneficial for reducing the martensite ratio and hardness of the energy-absorbing region.

[0082] In Comparative Example 4, the transition zone uses a continuous metal support surface. The maximum hardness difference between adjacent 5mm sections in the transition zone is 48HV0.5, which is higher than 24HV0.5 in Example 1 and 20HV0.5 in Example 6. This result indicates that a continuous metal contact surface is prone to causing localized rapid cooling in the transition zone, while the small-area support of the thermal insulation fulcrum helps to reduce sudden changes in hardness in the transition zone.

[0083] Comparative Example 5, which employed spray cooling, exhibited a hardness of 386 HV0.5 in its energy-absorbing zone and a maximum hardness difference of 42 HV0.5 between adjacent 5 mm sections in the transition zone, both higher than the corresponding values ​​in Example 1. This result demonstrates that, in the component and region design defined by this invention, avoiding spraying or atomizing cooling media onto the surface of the formed part and instead employing heat exchange within the contact cooling block is beneficial for controlling the hardness of the energy-absorbing zone and the hardness gradient in the transition zone.

[0084] As shown in Table 3, the martensite area fraction in the high-strength region of Example 1 is 92.6%, and the martensite area fraction in the energy-absorbing region is 32.8%. Examples 2 and 3 also show a microstructure distribution with a high proportion of martensite in the high-strength region and a low proportion of martensite in the energy-absorbing region. This result corresponds to the hardness results in Table 3, indicating that preferential contact cooling in the high-strength region can form a high-hardness region dominated by martensite, while delayed contact cooling in the energy-absorbing region can form a lower-hardness region where martensite, bainite, ferrite, and pearlite coexist.

[0085] Table 4 shows that in Example 1, the tensile strength of the high-strength zone is 1530 MPa, the tensile strength of the energy-absorbing zone is 920 MPa, and the elongation after fracture of the energy-absorbing zone is 11.6%, which is higher than the 5.8% of the high-strength zone. This result indicates that the segmented quenching microstructure modification process can make the high-strength zone focus on load-bearing capacity, and the energy-absorbing zone focus on reshaping and energy absorption capacity. In Comparative Example 1, the tensile strength of the energy-absorbing zone is 1490 MPa and the elongation after fracture is 5.9%, indicating that integral pressure quenching is not conducive to forming a low-strength, high-ductility energy-absorbing zone. In Comparative Example 2, the tensile strength of the high-strength zone is 835 MPa, indicating that natural air cooling cannot form a high-strength zone with sufficient strength.

[0086] Table 5 shows that in Examples 1, 3, and 8, the connecting hole is located in the energy-absorbing zone or the transition zone, respectively. The distance from the hole edge to the high-strength zone is 15–16 mm, the hole edge hardness is 342–382 HV0.5, the heat-affected zone width is 0.18–0.20 mm, and the hole edge is continuous without penetrating cracks. In Comparative Example 7, the connecting hole is located in or near the high-strength zone, the hole edge hardness is 505 HV0.5, the heat-affected zone width is 0.31 mm, and local microcracks exist at the hole edge. These results indicate that placing the laser-cut connecting hole in the energy-absorbing zone or the transition zone and maintaining a distance of not less than 12 mm between the hole edge and the high-strength zone helps reduce the risk of cutting defects caused by the high hardness of the hole edge.

[0087] As shown in Table 6, in Example 7, after temperature acquisition and pressure regulation, the standard deviation of hardness in the high-strength zone of the five samples was 8.2HV0.5, and the standard deviation of hardness in the energy-absorbing zone was 7.5HV0.5. In Comparative Example 6, without temperature feedback regulation, the standard deviation of hardness in the high-strength zone was 18.6HV0.5, and the standard deviation of hardness in the energy-absorbing zone was 20.2HV0.5. These results indicate that temperature acquisition and pressure regulation are beneficial to improving the batch stability of the segmented quenching process.

[0088] In summary, this invention achieves short-time forming through a non-cooling-channel stamping die, completes the main microstructure control through an external segmented quenching fixture, and realizes the combination of high-strength zone, energy-absorbing zone, and continuous transition zone through priority contact in the high-strength zone, delayed contact in the energy-absorbing zone, small-area support for heat insulation in the transition zone, and laser-cut hole arrangement after cooling.

[0089] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0090] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described above. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A segmented quenching process for modifying the microstructure of hot-formed components, characterized in that, Includes the following steps: 22MnB5 steel slabs with a thickness of 1.0 to 2.2 mm are heated to 890 to 930°C and held at that temperature for 240 to 360 seconds. Within 5 seconds, they are transferred into a stamping die with no cooling channels in either the punch or the die. The die is closed at 720 to 820°C and held under pressure for 1.5 to 3 seconds. Within 2 seconds after mold opening, the formed part with a surface temperature of 620-760℃ is placed into the segmented quenching fixture outside the mold, so that the first contact cooling block contacts the high-strength area with 0.20-0.60MPa, the second contact cooling block maintains a gap of 2-6mm with the energy absorption area, and the transition area is only supported by the heat insulation support point and the contact area of ​​the support point is less than or equal to 10% of the projected area of ​​the transition area; The first contact cooling block lowers the high-strength zone to 190–230°C; the energy-absorbing zone continues to cool while maintaining a 2–6 mm gap with the second contact cooling block. When the energy-absorbing zone drops to 430–520°C, the second contact cooling block contacts the energy-absorbing zone at 0.15–0.50 MPa and cools it to below 150°C, followed by laser cutting; the hardness difference between adjacent zones in the resulting transition zone, measured at a 5 mm interval, is ≤30HV0.

5.

2. The segmented quenching and microstructure modification process for hot-formed components according to claim 1, characterized in that, The 22MnB5 steel slab comprises the following elements by mass percentage: C 0.22%~0.25%, Si 0.15%~0.30%, Mn 1.15%~1.40%, Cr 0.10%~0.25%, Ti 0.02%~0.05%, B 0.0020%~0.0035%, Al 0.02%~0.06%, P≤0.020%, S≤0.008%, with the balance being Fe and unavoidable impurities.

3. The segmented quenching and microstructure modification process for hot-formed components according to claim 1, characterized in that, The 22MnB5 steel slab is an Al-Si coated steel slab with a coating thickness of 10-35 μm on one side.

4. The segmented quenching and microstructure modification process for hot-formed components according to claim 1, characterized in that, Both the first contact cooling block and the second contact cooling block have conformal contact surfaces and built-in heat exchange channels, wherein the cooling medium in the built-in heat exchange channels does not contact the surface of the formed part.

5. The segmented quenching and microstructure modification process for hot-formed components according to claim 1, characterized in that, The thermal insulation support is made of alumina ceramic, silicon nitride ceramic, or graphite material, and the contact area between a single thermal insulation support and the transition zone is 20–200 mm². 2 The distance between adjacent insulation support points is 30-100mm.

6. The segmented quenching and microstructure modification process for hot-formed components according to claim 1, characterized in that, After the first contact cooling block comes into contact with the high-strength zone, the high-strength zone is cooled to 190-230°C at a rate of 40-75°C / s; while the second contact cooling block maintains a gap with the energy-absorbing zone, the energy-absorbing zone is cooled to 430-520°C at a rate of 5-18°C / s; after the second contact cooling block comes into contact with the energy-absorbing zone, the energy-absorbing zone is cooled to 120-180°C at a rate of 15-30°C / s.

7. The segmented quenching and microstructure modification process for hot-formed components according to claim 1, characterized in that, The external segmented quenching fixture is equipped with infrared thermometers or thermocouples corresponding to the high-strength zone and the energy-absorbing zone, respectively, with a sampling frequency of 5 to 20 Hz; when the difference between the measured temperature and the target temperature in any zone is ≥20℃, the contact pressure or contact time of the corresponding contact cooling block is adjusted.

8. The segmented quenching and microstructure modification process for hot-formed components according to claim 1, characterized in that, The high-strength region has a martensite area fraction of 85%–98% and a Vickers hardness of 450–540 HV0.5; the energy-absorbing region has a martensite area fraction of 15%–45% and a Vickers hardness of 280–360 HV0.5; and the transition region has a width of 25–60 mm.

9. The segmented quenching and microstructure modification process for hot-formed components according to claim 1, characterized in that, The laser cutting is performed after the surface temperature of the formed part is ≤80℃. The connecting hole formed by the laser cutting is located in the energy absorption zone or transition zone, and the minimum distance between the edge of the connecting hole and the high-intensity zone is ≥12mm.

10. The segmented quenching and microstructure modification process for hot-formed components according to claim 1, characterized in that, The thermoformed component is a B-pillar reinforcement plate. The high-strength zone is located in the middle section of the B-pillar reinforcement plate, and the energy-absorbing zone is located at the upper and lower connecting sections or the upper and lower connecting sections of the B-pillar reinforcement plate.

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