Welding method, welding part, frame structure and vehicle

Abstract

The invention provides a welding method, a welding part, a frame structure and a vehicle, and belongs to the technical field of vehicle parts, and the welding method comprises the steps that tempering treatment is conducted on at least part of the area on a to-be-welded part, and a tempering area is formed; wherein the tempering area comprises an area to be welded; and welding is conducted in the to-be-welded area, so that a nugget area, a heat affected area and a tempered base metal area which is not covered by the nugget area and the heat affected area are formed in the tempered area. Wherein the tempering base metal area is distributed on the periphery of the heat affected area in the circumferential direction. According to the welding method provided by the embodiment of the invention, the plastic deformation area on the welded part can be widened, the phenomenon that stress is concentrated in a heat affected area in the related technology is improved, the risk that the welded part is broken in the collision process is reduced, and the safety is improved.

Description

Technical Field

[0001] The present application relates to the technical field of vehicle parts, and in particular to a welding method, welding parts, a frame structure and a vehicle. Background Art

[0002] When resistance spot welding is used to weld hot-formed steel parts together, a softened heat-affected zone (HAZ) typically forms around the weld. The microstructure of hot-formed steel is martensite, and the nugget of the resistance spot weld also has a martensite structure, resulting in high hardness in both the base metal and the nugget. The base metal region near the nugget undergoes a transition from melting temperature to room temperature during welding, and hot-formed steel exhibits a variety of phase transformations that depend on the temperature path. This results in a variety of microstructures in the HAZ of the hot-formed steel weld. The HAZ's microstructure, from the nugget side to the room-temperature base metal side, is characterized by coarse-grained martensite, fine-grained martensite, ferrite + martensite, and tempered martensite. Ferrite + martensite has the lowest hardness. This variability in microstructure within a small area, the sudden change in hardness, and the presence of a softened HAZ easily lead to significant stress concentration in the HAZ.

[0003] In vehicle safety assemblies such as the A-pillar and B-pillar that use hot-formed steel, the softened heat-affected zone around the weld point is prone to cracking during a collision, causing the weld point to crack, and then causing the strong hot-formed steel parts to break, increasing the risk of intrusion into the passenger compartment. Summary of the Invention

[0004] The embodiments of the present application provide a welding method, welding parts, a frame structure and a vehicle, which can improve the stress concentration phenomenon in the heat-affected zone around the weld core area, reduce the risk of fracture of the welded parts during a collision, and improve safety.

[0005] In order to achieve the above object, according to a first aspect of the present application, a welding method is provided, comprising:

[0006] Tempering at least a portion of the part to be welded to form a tempered area; wherein the tempered area includes the area to be welded;

[0007] Welding is performed in the area to be welded so that a nugget zone, a heat-affected zone, and a tempered base material area not covered by the nugget zone and the heat-affected zone are formed in the tempered area;

[0008] Among them, the tempered base material area is distributed in the peripheral circumference of the heat affected zone.

[0009] Optionally, the parts to be welded comprise hot-formed steel parts.

[0010] Optionally, the minimum hardness in the heat-affected zone is H1, and the hardness of the tempered base material zone is H2, satisfying: 0.8H2≤H1≤H2.

[0011] Optionally, the microstructure of the tempered base material region is tempered martensite.

[0012] Optionally, the hardness of the tempered base material zone is 200 HV-350 HV.

[0013] Optionally, the minimum hardness in the heat-affected zone is 200 HV-350 HV.

[0014] Optionally, hot-formed steel parts are positioned in critical crash paths in the vehicle frame structure.

[0015] Optionally, the hot-formed steel part includes a B-pillar inner panel and / or a B-pillar reinforcement panel.

[0016] Optionally, the area of the tempering zone is less than or equal to 40 cm 2 .

[0017] Optionally, welding is performed on the area to be welded, including:

[0018] Resistance spot welding is used to weld the area to be welded to form a weld spot.

[0019] Optionally, the circumscribed circle diameter D of the nugget zone is ≤8 mm.

[0020] Optionally, the heat-affected zone is distributed in the peripheral circumferential direction of the nugget zone, and the width W of the heat-affected zone along the radial direction of the nugget zone is ≤1.5 mm.

[0021] Optionally, the area on the hot part area not covered by the tempered area forms a basic parent material area, and the hardness of the basic parent material area is 480HV-550HV.

[0022] According to a second aspect of the present application, there is also provided a welding part, wherein the welding part is connected by welding;

[0023] The nugget zone, heat-affected zone and tempered base metal zone are formed on the welded parts;

[0024] Among them, the tempered base material zone is distributed in the outer circumference of the heat affected zone, the minimum hardness in the heat affected zone is H1, and the hardness of the tempered base material zone is H2, satisfying: 0.8H2≤H1≤H2.

[0025] According to a third aspect of the present application, a vehicle frame structure is further provided, comprising the welding parts as described above, and / or being welded using the welding method as described above.

[0026] According to a fourth aspect of the present application, a vehicle is also provided, comprising the above-mentioned frame structure.

[0027] The welding method provided in an embodiment of the present application includes: tempering at least a portion of the area on the part to be welded to form a tempered area, wherein the tempered area includes the area to be welded. Then welding is performed in the area to be welded, so that the tempered area forms a nugget zone, a heat-affected zone, and a tempered base material area not covered by the nugget zone and the heat-affected zone. Wherein, the tempered base material area is distributed in the outer circumference of the heat-affected zone. By tempering at least a portion of the area of the part to be welded and forming a tempered area before welding, the hardness of the tempered area can be reduced to achieve a softening effect. Wherein, the tempered area includes the area to be welded, that is, the tempered area is set corresponding to the welding position. Then welding is performed in the area to be welded, and the nugget zone formed after welding has a higher hardness, and because the hot-formed steel base material near the nugget zone undergoes a change from melting temperature to room temperature, a heat-affected zone with lower hardness is formed. At the same time, the tempered base material area not covered by the molten core area and the heat-affected zone is not affected by the welding process and maintains a lower hardness. The tempered base material area is distributed in the outer circumference of the heat-affected zone, which widens the plastic deformation area on the welded part. This improves the phenomenon of stress concentration in the heat-affected zone in related technologies, reduces the risk of fracture of the welded part during collision, and improves safety.

[0028] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0030] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings, wherein the same drawing numbers represent the same parts in the following description.

[0031] Figure 1 This is a schematic diagram of the hardness distribution of the weld spot area of the parts after welding in the prior art;

[0032] Figure 2 1 is a schematic flow chart of the welding method provided in the embodiment of the present application;

[0033] Figure 3 Schematic diagram of the position distribution of the tempering area, the nugget zone, the heat-affected zone and the tempered base material zone in the embodiment of the present application;

[0034] Figure 4 This is a schematic diagram of the force transmission path and the distribution area of hot-formed steel parts during a vehicle side collision;

[0035] Figure 5 This is a schematic diagram of the force transmission path and the distribution area of hot-formed steel parts during a head-on collision.

[0036] Figure 6 Schematic diagram of the tempering area on the B-pillar inner panel and the B-pillar reinforcement plate in an embodiment of the present application;

[0037] Figure 7 3 is a comparison chart of the microhardness test results in the embodiment and the comparative example.

[0038] Description of reference numerals:

[0039] 1. Tempering area; 2. Nut zone; 3. Heat-affected zone; 4. Tempering base material area. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0041] In the related art, when the parts to be welded are welded by resistance spot welding, a softened heat-affected zone is easily generated around the weld. Figure 1 As shown in (a), after welding, a nugget and a heat-affected zone are formed on the base material, and the heat-affected zone is distributed around the outer circumference of the nugget. Figure 1 Samples were taken from the black spots of the bricks shown in (a) and the hardness of each sample was tested. The results are shown in Figure 2. Figure 1 As shown in (b).

[0042] from Figure 1 As can be seen in (b), the hardness decreases sharply and then increases from the weld nugget to the heat-affected zone (HAZ) and then to the parent material. The HAZ has the lowest hardness, significantly lower than other areas, resulting in significant stress concentration in the HAZ. In vehicles, hot-formed steel parts are welded in safety assemblies such as the A-pillar and B-pillar. In side impacts or 25% offset collisions, stress concentration in the HAZ can easily lead to cracking, causing the hot-formed steel parts to break during the collision and increasing intrusion into the passenger compartment.

[0043] First, as Figure 2 As shown, an embodiment of the present application provides a welding method, comprising:

[0044] Step S1, tempering at least a portion of a hot-formed steel part to be welded to form a tempered region 1; wherein the tempered region 1 includes the area to be welded; the area to be welded is tempered to form the tempered region 1;

[0045] Step S2: welding the area to be welded in the tempering area 1 to form a weld spot, so that the tempering area 1 forms a nugget zone 2, a heat-affected zone 3, and a tempered base material area 4 not covered by the nugget zone 2 and the heat-affected zone 3;

[0046] The tempered base material zone 4 is distributed in the peripheral direction of the heat-affected zone 3 .

[0047] By tempering at least part of the area of the part to be welded and forming a tempered area 1 before welding, the hardness of the tempered area 1 can be reduced to achieve a softening effect. The tempered area 1 includes the area to be welded. That is, the tempered area 1 is set corresponding to the welding position. Welding is then performed in the area to be welded. The nugget zone 2 formed after welding has a higher hardness. However, since the hot-formed steel base material near the nugget zone 2 undergoes a change from melting temperature to room temperature, a heat-affected zone 3 with lower hardness is formed. At the same time, the tempered base material area 4 not covered by the nugget zone 2 and the heat-affected zone 3 maintains a lower hardness because it is not affected by the welding process. The tempered base material area 4 is distributed in the outer circumference of the heat-affected zone 3, which widens the plastic deformation area on the welded part, improves the phenomenon of stress concentration in the heat-affected zone 3 in the related art, reduces the risk of fracture of the welded part during a collision, and improves safety.

[0048] Specifically, by tempering at least a portion of the part to be welded, the overall hardness of the resulting tempered region 1 is reduced, remaining in a softened state. The area to be welded is then welded within the tempered region 1, forming a weld spot. A nugget zone 2 is formed near the weld spot. Because the nugget zone 2 undergoes a process of melting and rapid cooling, its microstructure is martensite, resulting in a relatively high hardness. The heat-affected zone 3, formed circumferentially around the nugget zone 2, undergoes a complex thermal cycle, resulting in a variety of microstructures within the heat-affected zone 3. From the side closest to the nugget zone 2 to the direction away from the nugget zone 2, the microstructures are coarse-grained martensite, fine-grained martensite, ferrite + martensite, and tempered martensite. The ferrite + martensite microstructure has the lowest hardness, resulting in stress concentration in the area with the lowest hardness. The tempered base material region 4, not covered by the nugget zone 2 and the heat-affected zone 3, is not affected by the welding process because it was tempered prior to welding and is located away from the nugget zone 2, maintaining a relatively low hardness. The tempered base material zone 4 is distributed in the outer circumference of the heat-affected zone 3, thereby increasing the width of the softened area after welding, dispersing the stress in the heat-affected zone 3, and the tempered base material zone 4 distributed in the outer circumference of the heat-affected zone 3 improves the phenomenon of stress concentration in the heat-affected zone 3, thereby reducing the risk of fracture of the welded parts during collision and improving safety.

[0049] In some embodiments, the parts to be welded include hot-formed steel parts. Hot-formed steel parts have high mechanical properties and play a vital role in ensuring the mechanical properties of the overall structure. However, the heat-affected zone (3) formed after welding can cause stress concentration in the hot-formed steel parts, making them susceptible to cracking at the weld location during collisions. The welding methods provided in the embodiments of the present application can reduce stress concentration, thereby lowering the risk of cracking in hot-formed steel parts during welding.

[0050] For example, the hot-formed steel parts in the embodiment of the present application may be ultra-high-strength hot-formed steel parts. Ultra-high-strength hot-formed steel is obtained by austenitizing the steel plate at high temperature (usually above 900°C), then quickly transferring it to a mold for stamping, and quenching the steel plate using the cooling system of the mold to transform the steel plate structure into martensite. The tensile strength of ultra-high-strength hot-formed steel can reach 1400MPa-1600MPa. It has high strength and impact resistance and is widely used in door anti-collision beams, front and rear bumpers, A-pillars, B-pillars, center channels, etc. When welding ultra-high-strength hot-formed steel parts, the hardness of the heat-affected zone 3 is significantly reduced, and stress concentration is likely to occur. The risk of cracking can be reduced by treating it with the method for reducing cracking of welds of hot-formed steel parts provided in the embodiment of the present application.

[0051] in, Figure 3Schematic diagram of the positional relationship between the tempering region 1, the nugget region 2, the heat-affected zone 3, and the tempered base metal region 4 in the embodiment of the present application. The nugget region 2, the heat-affected zone 3, and the tempered base metal region 4 are all located within the tempering region 1. The heat-affected zone 3 is distributed circumferentially around the nugget region 2, and the tempered base metal region 4 is distributed circumferentially around the heat-affected zone 3.

[0052] It is understandable that the size and shape of the tempering zone 1 can be set according to actual needs. The shape of the tempering zone 1 can be set to be long, circular, triangular or polygonal, as long as the formed tempered base material zone 4 can be distributed in the outer circumference of the heat-affected zone 3. No specific limitation is made here.

[0053] In some embodiments, the minimum hardness in the heat-affected zone 3 is H1, and the hardness of the tempered base material zone 4 is H2, satisfying: 0.8H2≤H1≤H2.

[0054] The hardness of the heat-affected zone 3 gradually decreases as it moves away from the nugget zone 2, reaching its lowest hardness on the side of the heat-affected zone 3 closest to the tempered base metal zone 4. By ensuring that the minimum hardness value H1 in the heat-affected zone 3 and the hardness H2 of the tempered base metal zone 4 satisfy the relationship 0.8H2≤H1≤H2, the problem of a sharp drop in hardness followed by a rapid rebound in the welded parts can be alleviated. This also minimizes the hardness fluctuation range in the area adjacent to the heat-affected zone 3 and the tempered base metal zone 4, thereby alleviating stress concentration.

[0055] During the welding process, the tempered base metal zone 4 is unaffected by the welding heat and maintains the hardness of the tempered zone 1. To ensure that the minimum hardness value in the heat-affected zone 3 satisfies the aforementioned relationship with the hardness of the tempered base metal zone 4, a suitable tempering method can be employed, with appropriate tempering temperature and time settings, to soften the hardness of the tempered base metal zone 1 to within a suitable range. This allows the minimum hardness value in the heat-affected zone 3 formed after welding to satisfy the aforementioned relationship with the hardness of the tempered base metal zone 4. For example, laser heat treatment or induction heat treatment can be employed for tempering.

[0056] In some embodiments, the microstructure of the tempered base material region 4 is tempered martensite. Tempered martensite is a microstructure obtained after a metal material undergoes a tempering treatment. During the tempering process, supersaturated carbon in the martensite precipitates as carbides, resulting in a decrease in hardness. By making the microstructure of the tempered base material region 4 tempered martensite, the hardness of the tempered base material region 4 can be reduced, maintaining the difference between the minimum hardness of the tempered base material region 4 and the heat-affected zone 3 within a certain fluctuation range, thereby reducing the stress concentration in the heat-affected zone 3.

[0057] It is understandable that the tempered martensite has a wide hardness range. During the tempering process, by setting and adopting a suitable tempering method, setting a suitable tempering temperature and tempering time, the tempered martensite in the tempered base material area 4 is within a suitable hardness range.

[0058] In some embodiments, the hardness of the tempered base material region 4 is 200 HV-350 HV. By controlling the hardness of the tempered base material region 4 within the range of 200 HV-350 HV, the difference between the hardness of the tempered base material region 4 and the lowest hardness in the heat-affected zone 3 can be reduced, avoiding the problem of a sharp drop in hardness followed by a rapid increase in hardness. This allows stress to be dispersed to the heat-affected zone 3 and the tempered base material region 4 located circumferentially outside the heat-affected zone 3, thereby reducing stress concentration.

[0059] Illustratively, the hardness of the tempered base material zone 4 may be 200 HV, 210 HV, 220 HV, 230 HV, 240 HV, 250 HV, 260 HV, 270 HV, 280 HV, 290 HV, 300 HV, 310 HV, 320 HV, 330 HV, 340 HV, or 350 HV.

[0060] Among them, HV is the Vickers hardness unit, which is defined as pressing a regular square pyramid diamond indenter with an angle of 136° between the opposite faces into the sample surface with a certain load and maintaining the test force for a certain period of time before removing it. The ratio of the load used at this time to the area of the indentation formed on the sample surface is the Vickers hardness value.

[0061] In some embodiments, the minimum hardness in the heat-affected zone 3 is between 200 HV and 350 HV. As previously mentioned, the heat-affected zone 3 is subjected to a relatively complex thermal cycle, resulting in the presence of various microstructures, and the hardness of the heat-affected zone 3 decreases as it moves away from the nugget zone 2. By setting the minimum hardness in the heat-affected zone 3 between 200 HV and 350 HV, the difference between the minimum hardness in the heat-affected zone 3 and the hardness of the tempered base metal zone 4 can be minimized, thereby providing a wider plastic deformation zone in the welded part after welding. This, in turn, improves stress concentration, reduces the risk of fracture of the welded part during a collision, and enhances safety.

[0062] In some embodiments, hot-formed steel parts are positioned in critical crash paths within the vehicle frame structure.

[0063] like Figure 4 and Figure 5As shown, in both side and head-on collision conditions, a force transmission path exists after a collision, known as the critical collision path. Placing hot-formed steel parts along this critical collision path ensures structural strength. The method for reducing weld cracking in hot-formed steel parts, as provided in the embodiments of this application, can improve stress concentration in hot-formed steel parts, thereby reducing the risk of hot-formed steel parts breaking at welds during a collision and improving safety.

[0064] It should be noted that Figure 4 is the force transmission path of the vehicle under side collision conditions, Figure 5 The force transmission path of the vehicle under head-on collision conditions is shown in Figure 1. The arrows indicate the force transmission path, and the black shadows indicate the distribution area of the hot-formed steel parts.

[0065] In some embodiments, the hot-formed steel parts include B-pillar inner panels and / or B-pillar reinforcement panels. Among them, the B-pillar inner panel is an important component of the frame structure, mainly responsible for supporting the vehicle body, and can also play a role in protecting the passenger compartment in side collisions. When the vehicle collides from the side, the B-pillar inner panel can effectively disperse and absorb the impact force, thereby reducing the deformation of the passenger compartment and protecting the safety of the occupants. The B-pillar reinforcement panel is usually installed on the outside or inside of the B-pillar inner panel to further enhance the strength and rigidity of the B-pillar. Its main function is to improve the B-pillar's ability to resist deformation in a collision, thereby more effectively protecting the passenger compartment.

[0066] The method for reducing cracking of welds of hot-formed steel parts provided in the embodiment of the present application can improve the stress concentration phenomenon at the weld between the B-pillar inner panel and the B-pillar reinforcement plate, reduce the risk of hot-formed steel parts breaking at the weld during a collision, and improve safety.

[0067] It is understandable that hot-formed steel parts are not limited to B-pillar inner panels and B-pillar reinforcement panels, but can also be other components arranged on the critical collision path, such as A-pillars, B-pillars, C-pillars and roof crossbeams, etc., which are hot-formed steel parts located on the critical collision path.

[0068] In some embodiments, the area of the tempering zone 1 is less than or equal to 40 cm 2 Tempering area 1 will reduce the hardness after tempering treatment. By controlling the area of tempering area 1 to 40cm 2 In the following, on the basis of improving the stress concentration phenomenon, the structural strength of the parts to be welded can be guaranteed.

[0069] It can be understood that the area of the tempering zone 1 can be specifically set according to the structure, installation position, and welding method of the part to be welded. On the basis of satisfying the circumferential distribution of the tempering base material zone 4 outside the heat-affected zone 3, reducing the area of the tempering zone 1 can improve the overall structural strength of the hot-formed part.

[0070] In some embodiments, welding parts to be welded to form welds includes:

[0071] Resistance spot welding is used to weld the parts to be welded to form weld spots.

[0072] Resistance spot welding offers high production efficiency, meeting the needs of high-volume processing and improving production efficiency. Furthermore, heat is concentrated and the heating range is small during resistance spot welding, resulting in a smaller heat-affected zone (HAZ) and weld deformation. This helps ensure the overall strength of the welded parts and reduces the impact of welding on performance. Resistance spot welding does not require the use of filler materials or shielding gas, resulting in lower welding costs. Furthermore, the resistance spot welding process is relatively simple and easily automated and mechanized, meeting the needs of automated vehicle production.

[0073] In some embodiments, as Figure 3 As shown, the diameter D of the circumscribed circle of the nugget zone 2 is ≤ 8 mm. When the parts to be welded are welded by resistance spot welding, the diameter of the circumscribed circle of the nugget zone 2 is formed to be less than 8 mm. This means that the heat generated during the welding process is more concentrated, reducing the range of heat exposure to the surrounding materials and thus reducing the risk of weld deformation. A smaller nugget zone 2 also helps reduce defects such as cracks and pores that may occur during the welding process, thereby improving the strength and reliability of the weld. Furthermore, the smaller diameter of the circumscribed circle of the nugget zone 2 also reduces the heat and time required for welding, improving welding efficiency and reducing energy consumption.

[0074] It is understood that the diameter of the circumscribed circle of the nugget zone 2 can be affected by the welding temperature and time. The higher the temperature during welding, the more dispersed the heat is, and the longer the welding time is, the larger the nugget zone 2 is. By controlling the welding temperature, welding time, and heat concentration, the diameter of the nugget zone 2 can be controlled within the above range.

[0075] In some embodiments, as Figure 3 As shown, the heat-affected zone 3 is distributed in the peripheral circumferential direction of the nugget zone 2 , and the width W of the heat-affected zone 3 along the radial direction of the nugget zone 2 is ≤1.5 mm.

[0076] The heat-affected zone 3 is an area distributed circumferentially around the nugget zone 2. The heat-affected zone 3 does not melt during the welding process, but is subjected to the effects of thermal cycling, resulting in a solid-phase transformation. Because the heat-affected zone 3 has undergone the effects of the welding thermal cycle, phenomena such as grain coarsening and decreased mechanical properties may occur. Different parameters during the welding process will cause a certain variation in the width of the heat-affected zone 3. In the embodiment of the present application, the width of the heat-affected zone 3 along the radial direction of the nugget zone 2 is less than 1.5 mm, which reduces the changes in structure and performance caused by thermal effects, helps maintain the original properties of the base material, and improves the overall quality of the weld.

[0077] It can be understood that the heat affected zone 3 is located between the weld core zone 2 and the tempered base metal zone 4, and the width of the heat affected zone 3 refers to the shortest distance between the boundary between the heat affected zone 3 and the weld core zone 2 and the boundary between the heat affected zone 3 and the tempered base metal zone 4.

[0078] In some embodiments, the area on the part to be welded that is not covered by the tempered area 1 forms a basic parent material area, and the hardness of the basic parent material area is 480HV-550HV.

[0079] That is to say, the hardness of the parts to be welded is 480HV-550HV. By setting the hardness of the base material area within the above range, the structural strength can be guaranteed and the structural reinforcement effect can be improved.

[0080] According to a second aspect of the present application, a welded part is provided, wherein the welded part is connected by welding. A nugget zone 2, a heat-affected zone 3, and a tempered base metal zone 4 are formed on the welded part. The tempered base metal zone 4 is distributed circumferentially around the heat-affected zone 3. The minimum hardness of the heat-affected zone 3 is H1, and the hardness of the tempered base metal zone 4 is H2, satisfying the following conditions: 0.8H2≤H1≤H2.

[0081] In the welded part provided in the embodiment of the present application, a nugget zone 2, a heat-affected zone 3, and a tempered base metal zone 4 are formed, and the tempered base metal zone 4 is distributed circumferentially around the heat-affected zone 3. Since the minimum hardness value in the heat-affected zone 3 is H1, and the hardness of the tempered base metal zone 4 is H2, the following condition is satisfied: 0.8H2≤H1≤H2. That is, the difference between the minimum hardness value in the heat-affected zone 3 and the hardness of the tempered base metal zone 4 is small. This can expand the width of the region with lower hardness in the welded part, thereby reducing the problem of stress concentration in the welded part and lowering the risk of cracking of the welded part during collision.

[0082] According to a third aspect of the present application, a vehicle frame structure is also provided, comprising welded parts, and / or welded using the welding method described above.

[0083] By processing the welded parts in the frame structure using the welding method described above, the risk of the frame structure breaking during a collision can be reduced, the amount of intrusion into the passenger compartment when the vehicle is hit can be reduced, and safety can be improved.

[0084] According to a fourth aspect of the present application, a vehicle is further provided, comprising the frame structure described above. The vehicle provided in the present application has all the advantages of the frame structure described above, which will not be described in detail here.

[0085] The following examples are further described in conjunction with specific embodiments. It should be understood that these embodiments are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. The experimental methods in the following examples where specific conditions are not specified are generally based on the conditions recommended by the manufacturer.

[0086] Example

[0087] like Figure 6 As shown in the figure, in the frame structure of a certain vehicle model, the B-pillar inner panel and the B-pillar reinforcement plate are both made of hot-formed steel parts with a tensile strength of 1500MPa.

[0088] right Figure 6 The black shaded areas of the center B-pillar inner panel and B-pillar reinforcement are tempered using local laser heat treatment to form a tempered area. The hardness of the tempered area formed by laser heat treatment is 270HV.

[0089] The treated B-pillar inner plate and B-pillar reinforcement plate are subjected to resistance spot welding to form a nugget zone, a heat-affected zone, and a tempered base material zone not covered by the nugget zone and the heat-affected zone within the tempered area; wherein the tempered base material zone is distributed in the outer circumference of the heat-affected zone.

[0090] Comparative Example

[0091] like Figure 6 As shown in the figure, in the frame structure of a certain vehicle model, the B-pillar inner panel and the B-pillar reinforcement plate are both made of hot-formed steel parts with a tensile strength of 1500MPa.

[0092] wrong Figure 6 The middle black shaded portion is tempered and directly subjected to resistance spot welding.

[0093] That is, the comparative example was not subjected to laser heat treatment before welding, and other conditions were the same as those of the example.

[0094] according to Figure 1 The micro Vickers hardness of the B-pillar inner plate and the B-pillar reinforcement plate in Example 1 and Comparative Example 1 was tested at the point shown in (a). The results are as follows: Figure 7 It should be noted that Figure 7 The data shown in the examples and comparative examples are for Figure 6 The sampling is obtained at the middle dotted box, and the sampling range and position remain consistent.

[0095] like Figure 7As shown, the hardness of the nugget zone in the embodiment and the comparative example is basically the same, indicating that the tempering treatment of the welding area in this application will not affect the hardness of the nugget zone. The hardness of the heat-affected zone in both the embodiment and the comparative example shows a sharp downward trend, but because the base material near the heat-affected zone in the embodiment has been tempered, the hardness is relatively low, which is basically consistent with the lowest value of the hardness in the heat-affected zone, and there is no rapid recovery phenomenon, so that the stress can be dispersed to the heat-affected zone and the tempered base material area in the circumferential direction of the heat-affected zone, improving the phenomenon of stress concentration in the heat-affected zone. Since the comparative example has not been tempered before welding, the base material near the heat-affected zone still maintains a relatively high hardness, resulting in a problem of a sharp drop in hardness followed by a rapid recovery on the transition path of the nugget zone-heat-affected zone-base material, resulting in stress concentration in the heat-affected zone with the lowest hardness, increasing the risk of cracking during collision.

[0096] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0097] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0098] The embodiments, implementation methods and related technical features of the present application can be combined and replaced with each other without conflict.

[0099] The above are merely preferred embodiments of the present application and do not constitute any form of limitation to the present application. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are still within the scope of the technical solution of the present application.

Claims

1. A welding method, characterized in that: include: Tempering at least a portion of the area on the part to be welded to form a tempered area; wherein the tempered area includes the area to be welded; Welding is performed in the area to be welded, so that the tempered area forms a nugget zone, a heat-affected zone, and a tempered base material area not covered by the nugget zone and the heat-affected zone; Wherein, the tempered base material zone is distributed in the peripheral circumference of the heat-affected zone.

2. The welding method according to claim 1, characterized in that The parts to be welded include hot-formed steel parts.

3. The welding method according to claim 2, characterized in that The minimum hardness value in the heat-affected zone is H1, and the hardness of the tempered base material zone is H2, satisfying: 0.8H2≤H1≤H2.

4. The welding method according to claim 3, characterized in that The microstructure of the tempered base material region is tempered martensite.

5. The welding method according to claim 4, characterized in that The hardness of the tempered base material zone is 200HV-350HV.

6. The welding method according to claim 5, characterized in that The minimum hardness in the heat-affected zone is 200 HV-350 HV.

7. The welding method according to claim 2, characterized in that The hot-formed steel parts are positioned on critical collision paths in the vehicle frame structure.

8. The welding method according to claim 7, characterized in that: The hot-formed steel part includes a B-pillar inner panel and / or a B-pillar reinforcement panel.

9. The welding method according to any one of claims 1 to 8, characterized in that: The area of the tempering zone is less than or equal to 40 cm 2 .

10. The welding method according to any one of claims 1 to 8, characterized in that: The welding is performed in the area to be welded, comprising: The area to be welded is welded by resistance spot welding to form welding spots.

11. The welding method according to claim 10, characterized in that: The diameter D of the circumscribed circle of the nugget zone is ≤8 mm.

12. The welding method according to claim 11, characterized in that: The heat-affected zone is distributed in the peripheral circumferential direction of the nugget zone, and the width W of the heat-affected zone along the radial direction of the nugget zone is ≤1.5 mm.

13. The welding method according to claim 1, wherein: The area on the part to be welded that is not covered by the tempering area forms a basic parent material area, and the hardness of the basic parent material area is 480HV-550HV.

14. A welding part, characterized in that: The welding parts are connected by welding; A nugget zone, a heat-affected zone and a tempered base metal zone are formed on the welded part; The tempered base material zone is distributed in the outer circumference of the heat-affected zone, the lowest hardness value in the heat-affected zone is H1, and the hardness of the tempered base material zone is H2, satisfying: 0.8H2≤H1≤H2.

15. A vehicle frame structure, characterized in that: The welding part comprises the welding part according to claim 14, and / or is welded using the welding method according to any one of claims 1 to 13.

16. A vehicle, characterized in that: Including the frame structure described in claim 15.

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