Aluminum-containing plated hot-formed tailor-welded blank and method of manufacturing the same

Abstract

The application relates to the technical field of hot forming part preparation, in particular to an aluminum-containing plated hot forming tailor-welded part and a preparation method thereof. The method comprises the following steps: preheating the edge of the first blank plate on the side to be welded under a set temperature; rolling the edge of the first blank plate on the side to be welded after preheating, so that the thickness of the edge of the first blank plate on the side to be welded after rolling is the same as the thickness of the second blank plate; under the action of high-frequency current, melting the contact part between the first blank plate and the second blank plate, extruding the molten metal to the weld under the action of pressure, and forming a surplus height on the upper and lower surfaces of the weld, then removing the surplus height to obtain a tailor-welded plate; and performing heat treatment on the tailor-welded plate, then performing forming and quenching to obtain the aluminum-containing plated hot forming tailor-welded part. The application solves the technical problem that the weld formed in the laser welding process of the existing aluminum-containing plated hot forming steel has poor performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hot forming part preparation, and particularly relates to an aluminum-containing plated hot forming tailor-welded part and a preparation method thereof. BACKGROUND

[0002] Due to environmental protection and energy saving requirements, automobile lightweight has become a trend of the world automobile development. Aluminum-silicon plated hot forming steel is a main way to realize lightweight, and especially aluminum-silicon plated products after tailor-welding and hot stamping forming are widely used. At present, the welding method used for hot forming steel tailor-welding is laser welding or laser filler wire welding.

[0003] At present, in the process of laser welding of hot forming steel with aluminum or aluminum alloy plating, aluminum enters the molten pool, and high-temperature ferrite is formed after hot forming, the hardness of the high-temperature ferrite is much lower than that of martensite, which reduces the tensile strength of the weld. In addition, the welds of unequal-thickness tailor-welded plates are located at the interface of the two plates. On the one hand, the weld position is located in the geometric shape change area, and the stress concentration at this position is outstanding during service; on the other hand, compared with the base material, the weld is more prone to various defects. Therefore, the weld and the stress concentration area are superimposed, which increases the damage risk of fatigue, collision and the like during the later service of the tailor-welded part. SUMMARY

[0004] The present application provides an aluminum-containing plated hot forming tailor-welded part and a preparation method thereof, to solve the technical problem of poor performance of the weld formed in the process of laser welding of the existing aluminum-containing plated hot forming steel.

[0005] In a first aspect, the present application provides a preparation method of an aluminum-containing plated hot forming tailor-welded part, and the method comprises the following steps:

[0006] Preheating the edge of the first blank on the side to be welded under a set temperature;

[0007] Rolling the edge of the first blank on the side to be welded after preheating, so that the thickness of the edge of the first blank on the side to be welded after rolling is the same as the thickness of the second blank;

[0008] Melting the contact part between the first blank and the second blank under the action of high-frequency current to obtain an initial weld;

[0009] Extruding the molten metal in the initial weld under the action of pressure to form a weld, and forming a excess height on the upper and lower surfaces of the weld, and then removing the excess height to obtain a tailor-welded plate;

[0010] Performing heat treatment on the tailor-welded plate, and then performing forming and quenching to obtain an aluminum-containing plated hot forming tailor-welded part.

[0011] Optionally, the set temperature is <600℃.

[0012] Optionally, the set temperature is ≤500℃.

[0013] Optionally, the preheating the edge of the first slab to be welded at the set temperature comprises:

[0014] preheating the edge of the first slab to be welded at the set temperature; wherein the width of the preheated edge of the first slab to be welded is controlled to be ≥4mm.

[0015] the width of the preheated edge of the first slab to be welded is ≥4mm.

[0016] the width of the preheated edge of the first slab to be welded is ≥4mm.

[0017] Optionally, the rolling the preheated edge of the first slab to be welded to make the thickness of the rolled edge of the first slab to be welded same as the thickness of the second slab comprises:

[0018] rolling the preheated edge of the first slab to be welded to make the thickness of the rolled edge of the first slab to be welded same as the thickness of the second slab; wherein the width of the preheated edge of the first slab to be welded is controlled to be ≥2mm.

[0019] the width of the preheated edge of the first slab to be welded is ≥2mm.

[0020] Optionally, the aluminum content in the weld is <1wt%.

[0021] Optionally, the coating of the first slab is attached to at least one side of the base material of the first slab, and the coating of the second slab is attached to at least one side of the base material of the second slab.

[0022] Optionally, the coating of the first slab and the coating of the second slab are both aluminum-silicon coatings.

[0023] In a second aspect, the present application provides an aluminum-containing coating hot-formed tailor-welded part, which is prepared by the method of any one of the embodiments of the first aspect.

[0024] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages:

[0025] The preparation method of the hot formed tailor welded blank with aluminum coating provided by the embodiment of the present application changes the position of the weld in the welded structure by the way of heating and rolling the thick plate edge to thin. The weld in the method is located in the equal thickness area, and the weld position has no stress concentration caused by geometric shape when subjected to external force. Finally, the weld performance is improved by reducing the stress concentration in the weld area. The method uses the way of high-frequency current heating combined with molten pool extrusion. The molten metal formed under the action of extrusion force moves to the outside of the molten pool (the upper and lower sides of the weld) under the action of the extrusion force, and forms the excess height. In this process, the molten aluminum coating is also driven into the excess height area by the molten metal, thereby avoiding the aluminum entering the weld between the two blanks. Then the excess height is removed by the scraper, thereby eliminating the influence of aluminum element on the weld performance, thereby optimizing the weld structure of the hot formed part, solving the negative influence of aluminum in the coating into the molten pool, improving the weld performance, and having the characteristics of low cost and high efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0026] The accompanying drawings, which are incorporated into and form part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0028] Figure 1 A flowchart of a preparation method of a hot formed tailor welded blank with aluminum coating provided by the embodiment of the present application;

[0029] Figure 2 A schematic diagram of a preparation method of a hot formed tailor welded blank with aluminum coating provided by the embodiment of the present application;

[0030] Figure 3 A schematic diagram of a first blank provided by the embodiment 1 of the present application;

[0031] Figure 4 A schematic diagram of the edge rolling of the first blank provided by the embodiment 1 of the present application;

[0032] Figure 5 A schematic diagram of the initial weld provided by the embodiment 1 of the present application;

[0033] Figure 6 A schematic diagram of the weld after extrusion provided by the embodiment 1 of the present application;

[0034] Figure 7 A schematic diagram of the tailor welded blank provided by the embodiment 1 of the present application;

[0035] 1 - first blank, 101 - first blank base body, 102 - first blank cladding, 103 - first blank rolling zone, 104 - first blank excess zone, 2 - second blank, 201 - second blank base body, 202 - second blank cladding, 3 - edge heating device, 4 - rolling device, first roll 401, second roll 402, 5 - current generator, 6 - extrusion roll, 7 - weld, 701 - initial weld, 702 - post-extrusion weld, 703 - excess height, 8 - hanging knife, 9 - tailor-welded blank, 10 - heating furnace, 11 - hot-formed part. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions, and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings for the embodiments of the present application to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0037] The various embodiments of the present application can exist in a range of forms; it should be understood that the description in a range of forms is merely for convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single values in the described range, such as 1, 2, 3, 4, 5, and 6, which is applicable to any range. In addition, whenever a numerical range is indicated in the present application, it refers to any cited number (fraction or integer) in the indicated range.

[0038] In the present application, the orientation words such as "upper" and "lower" are specific to the drawing surface direction in the accompanying drawings. In addition, in the description of the specification of the present application, the terms "include", "contain", etc. mean "include but are not limited to".

[0039] In this document, relational terms such as“first” and“second”, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. In this document, the term“and / or” covers the possibilities of a single entity or action and a combination of entities or actions. In this document, the term“at least one” means one or more, and the term“multiple” means two or more. In this document, the term“at least one of’ means any combination of the items listed, including single items or combinations of two or more items. For example, “at least one of a, b, or c” or “at least one of a, b, and c” can mean a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, where a, b, and c can be single items or multiple items.

[0040] Unless otherwise specified, the various materials, reagents, instruments and equipment and the like used in the present application can be purchased on the market or can be prepared by existing methods.

[0041] In a first aspect, the present application provides a method for preparing an aluminum-containing plated hot-formed tailor-welded blank, please refer to Figure 1 and Figure 2 , the method comprises:

[0042] S1, preheat the edge of the first blank to be welded under a set temperature;

[0043] In some embodiments, the set temperature is < 600℃.

[0044] In some embodiments, the set temperature is ≤ 500℃.

[0045] In the embodiments of the present application, the“set temperature” refers to the temperature of the above-mentioned preheating, and the positive effect of controlling this temperature is to reduce the difficulty of subsequent rolling, which can be completed under small pressure. However, if the preheating temperature is too high, (1) it will cause the aluminum alloy to melt and cause sticking when it comes into contact with the rolling device 4; (2) it will cause the edge of the first blank 1 to deform, affecting subsequent welding. Here, the preheating width should be greater than the subsequent rolling width and leave a certain amount of surplus. Specifically, the temperature can be 550℃, 500℃, 450℃, etc., and more preferably, the temperature is ≤ 500℃.

[0046] S2, roll the edge of the first blank to be welded after preheating so that the thickness of the edge of the first blank to be welded after rolling is the same as the thickness of the second blank;

[0047] In some embodiments, the preheating the edge of the first blank to be welded under the condition of a set temperature includes:

[0048] preheating the edge of the first blank to be welded under the condition of a set temperature; wherein the width of the preheating the edge of the first blank to be welded is controlled;

[0049] The width of the preheating the edge of the first blank to be welded is ≥4mm.

[0050] In some embodiments, the rolling the preheated edge of the first blank to be welded to make the thickness of the rolled edge of the first blank to be welded equal to the thickness of the second blank includes:

[0051] rolling the preheated edge of the first blank to be welded to make the thickness of the rolled edge of the first blank to be welded equal to the thickness of the second blank; wherein the width of the rolling the preheated edge of the first blank to be welded is controlled;

[0052] The width of the rolling the preheated edge of the first blank to be welded is ≥2mm.

[0053] In the embodiment of the present application, the first blank 1 with the preheated edge is immediately put into the rolling device 4 to roll the preheated edge. The rolling device 4 is composed of a pair of first roller 401 and second roller 402. In the embodiment, the width of the first roller 401 is smaller than the width of the second roller 402, the second roller 402 is flush with the lower surface of the first blank 1, and the edge of the first roller 401 is designed with an arc-shaped transition zone. After rolling, the first blank rolling zone 103 and the first blank transition zone 104 are formed on the edge of the first blank 1. By controlling the gap between the first roller 401 and the second roller 402, the thickness of the first blank rolling zone 103 formed after rolling is equal to the thickness 1.6mm of the second blank 2. The width of the first blank transition zone 104 formed finally is 2mm, and the width of the first blank rolling zone is 4mm. That is, by the edge rolling process, the connection between the different-thickness plates is converted into the connection between the equal-thickness plates. In the rolling process, the width of the first roller 401 is smaller than the width of the second roller 402, and the second roller 402 is flush with the lower surface of the first blank 1, which aims to make the first blank rolling zone 103 formed after rolling located on one side of the thickness direction of the first blank 1. The edge of the first roller 401 is designed with a transition zone, which aims to reduce the stress concentration problem caused by geometric size in the thickness change process. The transition zone can be a circular arc transition or a gradual transition. Here, the width of the first blank edge rolling is required to be ≥2mm, the main reason is that the rolling width is too narrow, the stability of the rolling process is poor, and an effective transition zone cannot be formed. Please refer to Figure 4This is a schematic diagram of the edge rolling of the first billet provided in Embodiment 1 of this application.

[0054] In summary, by setting the preheating width of the edge of the first blank to be welded side to be ≥4mm and the rolling width of the edge of the first blank to be welded side after preheating to be ≥2mm, and in combination with the design of the roll shape in the rolling device, a transition zone can be formed between the thick plate rolling zone and the thick plate after rolling. The shape of the transition zone can be controlled to be a gradual or smooth transition, thereby reducing stress concentration during the thickness change process.

[0055] S3. Under the action of high-frequency current, the contact area between the first blank plate and the second blank plate is melted to obtain an initial weld.

[0056] S4. Under pressure, the molten metal in the initial weld is extruded into a weld, and excess height is formed on the upper and lower surfaces of the weld. Then, the excess height is removed to obtain a welded plate.

[0057] In this embodiment of the application, a high-frequency current is applied between the first blank plate 1 and the second blank plate 2. The current flows through the contact point of the first blank plate 1 and the second blank plate 2 to generate resistance heat and form melting. At the same time, under pressure, the molten metal is squeezed out of the weld 7, and the excess height 703 is formed on the upper and lower surfaces of the weld 7.

[0058] Please see Figure 2 This is a schematic diagram illustrating a method for preparing a hot-formed welded part with an aluminum coating according to an embodiment of this application. In step S3, the high-frequency current is provided by a current generator 5, which can be a high-frequency induction welding device, a high-frequency resistance welding device, etc. In embodiment 1, the current generator 5 is a high-frequency resistance welding device with a frequency of 300kHz. The two electrodes of the current generator 5 are placed on the surfaces of the first blank slab 1 and the second blank slab 2. The welding current flows in through one electrode, passes through the V-shaped opening angle to the other side of the weld, and then flows back to the current generator 5.

[0059] The pressure of the molten metal extrusion weld 7 is provided by extrusion rollers 6 located on the upper and lower sides of the billet. The paired extrusion rollers 6, located on the upper and lower sides of the first billet 1 and the second billet 2 respectively, provide extrusion force to the area to be joined, causing the two billets to form a tight contact at the junction. Under the influence of the skin effect and proximity effect, the current applied between the first billet 1 and the second billet 2 flows along the edge to be welded and passes through the junction, generating a large amount of resistance heat at the junction, causing the edges of the first billet 1 and the second billet 2 to melt and form the initial weld 701. (See [link to previous section]). Figure 5An initial weld schematic provided for the embodiment 1 of the present application. Under the extrusion force of the extrusion roller 6, the molten metal in the initial weld 701 is extruded from the middle of the weld 7 thickness direction to the upper and lower surfaces respectively, and finally forms a excess height 703 on the surface of the weld 7, and forms an extruded weld 702 between the two blanks. Please refer to Figure 6 An extruded weld schematic provided for the embodiment 1 of the present application. Under the extrusion force, the flow of the molten pool brings the plated metal in the weld area into the excess height 703, and does not enter the extruded weld 702. Thus, the aluminum element in the plating layer is prevented from entering the extruded weld 702.

[0060] The excess height 703 will affect the subsequent hot forming, and must be removed before hot forming. In the embodiment of the present application, the excess height 703 is scraped off immediately after welding by the scraper 8 located on the upper and lower surfaces of the weld, so that the surface of the weld is flat, and the preparation of the tailor-welded blank 9 is completed. Please refer to Figure 7 The scraping of the excess height 703 under the hot state will reduce the stress on the scraper 8 and improve the service life of the scraper 8.

[0061] S5, heat treating the tailor-welded blank, then forming and quenching to obtain an aluminum-plated hot-formed tailor-welded part.

[0062] Specifically, the step S5 includes: moving the tailor-welded blank 9 into the heating furnace 10 for heat treatment to achieve complete austenitization; moving the austenitized tailor-welded blank 9 into a hot forming die for forming and quenching, and finally completing the preparation of the hot-formed part 11.

[0063] In the embodiment of the present application, the tailor-welded blank 9 is immediately placed into the hot forming die after being taken out of the furnace. The hot-formed part 9 is stamped, and in the embodiment of the present application, a U-shaped die is used, which contains cooling water channels. After stamping, the part is quenched through a holding stage, and finally the hot-formed part 11 is formed.

[0064] In some embodiments, the aluminum content in the weld is <1 wt%.

[0065] The aluminum content in the weld is <1 wt%, which reduces the aluminum content in the molten pool and ensures the performance of the weld.

[0066] In some embodiments, the plating layer of the first blank is attached to at least one side of the base material of the first blank, and the plating layer of the second blank is attached to at least one side of the base material of the second blank.

[0067] In some embodiments, the plating layer of the first blank and the plating layer of the second blank are both aluminum-silicon plating layers.

[0068] The aluminum-silicon plating layer has excellent heat resistance and corrosion resistance, and is in line with green environmental protection.

[0069] In a second aspect, the present application provides an aluminum plated hot formed tailor-welded blank, which is prepared by the method of any one of the embodiments of the first aspect.

[0070] The aluminum plated hot formed tailor-welded blank is achieved based on the preparation method of the aluminum plated hot formed tailor-welded blank described above. The specific steps of the preparation method of the aluminum plated hot formed tailor-welded blank can be referred to the above embodiments. Since the aluminum plated hot formed tailor-welded blank adopts part or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0071] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods not specified in the following examples are generally determined according to national standards. If there is no corresponding national standard, it is determined according to the general international standard, the conventional condition, or the condition suggested by the manufacturer.

[0072] Example 1

[0073] S1, preheat the edge of the first blank to be welded under a set temperature;

[0074] S2, roll the preheated edge of the first blank to be welded so that the thickness of the rolled edge of the first blank to be welded is the same as the thickness of the second blank;

[0075] S1, melt the contact part between the first blank and the second blank under the action of high-frequency current to obtain an initial weld;

[0076] S3, extrude the molten metal in the initial weld under the action of pressure to form a weld, and form a excess height on the upper and lower surfaces of the weld, and then remove the excess height to obtain a tailor-welded blank;

[0077] S4, heat treat the tailor-welded blank, and then form and quench to obtain an aluminum plated hot formed tailor-welded blank.

[0078] Wherein,

[0079] The first blank 1 includes a first blank base body 101 and a first blank plating layer 102. The thickness of the first blank 1 is 1.8 mm. The first blank base body 101 is 22MnB5, and the first blank plating layer 102 is on both sides of the first blank base body 101. The weight of the single-sided first blank plating layer 102 is 75 g / m 2 The first blank plating layer 102 is an AlSi plating layer, wherein the content of Al is 90 wt%, and the content of Si is 10 wt%. Please refer toFigure 3 The schematic diagram of the first blank provided in Embodiment 1 of the present application.

[0080] The second blank 2 comprises a second blank base body 201 and a second blank coating layer 202. The second blank 2 has a thickness of 1.6 mm, wherein the second blank base body 201 is 22MnB5, and the second blank coating layer 202 is arranged on both sides of the second blank base body 201, and the weight of the single-sided second blank coating layer 202 is 75 g / m 2 The second blank coating layer 202 is an AlSi coating layer, wherein the content of Al is 90 wt%, and the content of Si is 10 wt%.

[0081] The preheating is performed by an induction heating method, the preheating temperature is 300℃, and the heating width is 10 mm;

[0082] The width of the first blank excessive area is 2 mm, and the width of the first blank rolling area is 4 mm;

[0083] The camber removal width is 7 mm,

[0084] Detection: by performing element analysis on the weld of the tailor-welded blank 9, it is detected that the content of Al element does not increase compared with the base material.

[0085] The heat treatment temperature is 930℃, and the heat treatment time is 5 minutes,

[0086] Detection: the hardness of the weld position of the hot formed part 11 is tested, which is 503HV, and is equivalent to that of the base material. The tensile specimen prepared at the weld is stretched, and the fracture position is located at the base material on the thin plate side.

[0087] In the embodiment of the present application, the unequal-thickness material is used to prepare the hot formed part. For the first blank 1 and the second blank 2 with equal thickness, the S1 and S2 procedures can be skipped, that is, the power of the edge heating device 3 in the S1 procedure is set to 0, and the gap of the rolling device 4 in the S2 procedure is set to the thickness of the blank. The other procedures are the same as those in the embodiment.

[0088] In the embodiment of the present application, the process parameters are only for better illustration, and do not limit the technology.

[0089] The above description is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a hot-formed welded part with an aluminum coating, characterized in that, The method includes: Under the set temperature conditions, the edge of the first blank plate to be welded is preheated; The edge of the first blank plate to be welded after preheating is rolled so that the thickness of the edge of the first blank plate to be welded after rolling is the same as the thickness of the second blank plate. Under the action of high-frequency current, the contact area between the first blank plate and the second blank plate is melted to obtain the initial weld. Under pressure, the molten metal in the initial weld is extruded into the weld, and excess height is formed on the upper and lower surfaces of the weld. Then the excess height is removed to obtain the welded plate. The welded plate is heat-treated, then formed and quenched to obtain a hot-formed welded part with an aluminum coating.

2. The method according to claim 1, characterized in that, The set temperature is <600℃.

3. The method according to claim 2, characterized in that, The set temperature is ≤500℃.

4. The method according to claim 1, characterized in that, The step of preheating the edge of the first blank plate to be welded under a set temperature condition includes: Under a set temperature condition, the edge of the first blank plate to be welded is preheated; wherein, the width of the edge of the first blank plate to be welded is controlled. The preheating width of the edge of the first blank plate on the side to be welded is ≥4mm.

5. The method according to claim 1, characterized in that, The step of rolling the edge of the preheated first billet on the side to be welded, so that the thickness of the edge of the first billet on the side to be welded is the same as the thickness of the second billet, includes: The edge of the first billet to be welded after preheating is rolled so that the thickness of the edge of the first billet to be welded after rolling is the same as the thickness of the second billet; wherein, the width of the edge of the first billet to be welded after preheating is controlled. The width of the edge rolled on the side to be welded of the first preheated billet is ≥2mm.

6. The method according to claim 1, characterized in that, The aluminum content in the weld is <1% by weight.

7. The method according to claim 1, characterized in that, The coating of the first blank is attached to at least one side of the substrate of the first blank, and the coating of the second blank is attached to at least one side of the substrate of the second blank.

8. The method according to claim 1 or 7, characterized in that, Both the first blank and the second blank have aluminum-silicon coatings.

9. A thermoformed welded part with an aluminum coating, characterized in that, The aluminum-coated thermoformed welded part is prepared by the method described in any one of claims 1-8.

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