Hot stamping die and manufacturing method thereof

Abstract

The present application relates to hot forming steel hot stamping technical field, especially to a kind of hot stamping die and its manufacturing method.The water cooling system is opened in the hot stamping die, water cooling system is close to the die face of hot stamping die and is arranged, water cooling system includes the multiple cooling water channels of interval arrangement, die face includes the first working surface of cooperation with the sidewall of part and is arranged, cooling water channel close to first working surface is configured as first cooling water channel, first working surface is opened with first cooling water channel one-to-one and is arranged water jet unit, water jet unit is communicated with corresponding first cooling water channel, to spray the cooling water in corresponding first cooling water channel.This application provides a kind of hot stamping die and its manufacturing method, realizes the water quenching of part sidewall, to ensure that martensite at part sidewall is fully converted, ensure that part performance is uniform.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hot stamping of hot-formed steel, and particularly relates to a hot stamping die and a manufacturing method thereof. BACKGROUND

[0002] Hot stamping technology is an important way to realize automobile lightweighting, and the application of hot-formed steel can improve the strength of automobile parts while reducing the thickness of automobile parts. However, hot stamping technology also has certain defects, such as the problem of uneven performance of the parts after hot stamping. The reason why the hot-formed steel has high strength after hot stamping is that the austenitic structure in the part is transformed into martensitic structure in the quenching stage of the hot stamping die of the hot stamping process. One condition for realizing this transformation is that the cooling rate of the part needs to reach a certain value, and the cooling rate usually needs to be not less than 27℃ / s. In the pressure-maintaining cooling quenching stage of the hot stamping die, the side wall of the part cannot be pressed to death at the side wall of the hot stamping die due to the gap of the hot stamping die, so that the temperature drop rate of the side wall of the part is low, thereby causing the martensitic transformation of the side wall of the part to be insufficient compared with other parts, especially for parts with steep side walls, which leads to uneven performance of the part. SUMMARY

[0003] The hot stamping die and the manufacturing method thereof provided by the present application solve the technical problem of insufficient martensitic transformation of the side wall of the part in the prior art, which leads to uneven performance of the part.

[0004] In one aspect, the present application provides a hot stamping die for hot stamping and forming of a part, wherein a water cooling system is arranged in the hot stamping die, the water cooling system is arranged close to a die face of the hot stamping die, the water cooling system comprises a plurality of cooling water channels arranged at intervals, the die face comprises a first working face arranged in cooperation with a side wall of the part, the cooling water channels arranged close to the first working face are configured as first cooling water channels, the first working face is provided with a plurality of water spraying units arranged one-to-one corresponding to the first cooling water channels, each water spraying unit comprises a plurality of water spraying holes, and the plurality of water spraying holes are in communication with the corresponding first cooling water channel to spray cooling water in the corresponding first cooling water channel.

[0005] In some embodiments, the cooling water channels are arranged obliquely, and the distance between the top of the pipe wall of the outlet of the cooling water channel and the corresponding die face is smaller than the distance between the top of the pipe wall of the inlet of the cooling water channel and the corresponding die face.

[0006] In some embodiments, the plurality of cooling water channels are arranged in parallel.

[0007] In some embodiments, the diameter of the cooling water channel is 8-14mm.

[0008] In some embodiments, the die surface of the hot stamping die comprises two first working surfaces arranged oppositely, and the die surface of the hot stamping die further comprises a second working surface arranged in cooperation with the bottom of the part and two third working surfaces arranged in cooperation with the edge of the part, the second working surface is arranged between the bottoms of the two first working surfaces, the two third working surfaces are arranged on the tops of the two first working surfaces, and the third working surface is arranged on the side of the first working surface away from the second working surface.

[0009] In some embodiments, the water spraying unit comprises a plurality of water spraying holes arranged side by side, the water spraying holes are in communication with the corresponding first cooling water channel, and the plurality of water spraying holes are arranged at intervals along the length direction of the corresponding cooling water channel.

[0010] In some embodiments, the diameter of the water spraying hole is 1-5 mm.

[0011] In some embodiments, the water spraying unit is arranged on the side of the corresponding first cooling water channel close to the second working surface.

[0012] In another aspect, the embodiments of the present application provide a hot stamping die manufacturing method, characterized in that the method is the above-mentioned hot stamping die manufacturing method, comprising:

[0013] S1: designing the die surface of the hot stamping die so that the die surface is consistent with the outer contour of the target part;

[0014] S2: designing a plurality of cooling water channels along the die surface so that the local temperature of the part at the inlet of the cooling water channel is the same as the local temperature of the part at the outlet of the cooling water channel;

[0015] S3: opening a water spraying unit on the first working surface in one-to-one correspondence with the first cooling water channel and in communication with the first cooling water channel to obtain a design model of the hot stamping die;

[0016] S4: processing the hot stamping die according to the design model of the hot stamping die.

[0017] In some embodiments, step S2 specifically comprises:

[0018] S21: designing a plurality of cooling water channels along the die surface to form a water cooling system, the distance between the top of the pipe wall at the inlet of the cooling water channel and the corresponding die surface is the same as the distance between the top of the pipe wall at the outlet of the cooling water channel and the corresponding die surface;

[0019] S22: performing numerical simulation of the pressure maintaining process of the water cooling system to obtain the local temperature T1 of the part at the inlet of the cooling water channel and the local temperature T2 of the part at the outlet of the cooling water channel, T2>T1.

[0020] S23: Obtain the distance D1 between the top of the tube wall at the inlet of the cooling water channel and the corresponding die surface in step S21, and obtain the corrected distance D2 between the top of the tube wall at the outlet of the cooling water channel and the corresponding die surface according to formula 1):

[0021] In formula 1), A is a correction coefficient, 0

[0022] S24: Correct the distance between the top of the tube wall at the outlet of the cooling water channel and the corresponding die surface in step S21 according to the value of D2 obtained in step S23.

[0023] The present application has the following advantages:

[0024] The hot stamping die and the manufacturing method thereof provided by the present application have the following advantages: the water spraying unit is arranged on the first working surface of the hot stamping die for cooperation with the side wall of the part, the water spraying unit can spray the cooling water in the corresponding first cooling water channel, when the part is pressed against the hot stamping die during the pressure maintaining process and the side wall of the part is arranged in cooperation with the first working surface of the hot stamping die, the water spraying unit sprays the cooling water in the corresponding first cooling water channel to the side wall of the part, thereby realizing water quenching of the side wall of the part, the cooling effect and efficiency of the water quenching are obviously superior to those of die quenching, thereby ensuring full transformation of the martensite at the side wall of the part and ensuring uniform performance of the part, and the cooling efficiency of the water quenching is also superior to that of the die quenching, so that the martensite transformation at the side wall of the part is completed prior to the transformation at other positions, and therefore the quenching time is no longer limited by the degree of martensite transformation at the side wall, thereby improving the quenching efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application.

[0026] Figure 1 A perspective view of the hot stamping die provided by the present embodiment;

[0027] Figure 2 A sectional view of Figure 1 ;

[0028] Figure 3 A schematic view of the cooling water channel before correction;

[0029] Figure 4 A schematic view of the cooling water channel after correction.

[0030] Explanation of reference signs:

[0031] 100-Hot stamping die, 110-Water cooling system, 111-Cooling water channel, 1111-Inlet, 1112-Outlet, 1113-First cooling water channel, 120-Die surface, 121-First working surface, 122-Second working surface, 123-Third working surface, 130-Water spray unit, 131-Water spray hole. Detailed Implementation

[0032] 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.

[0033] The traditional hot stamping process mainly consists of the following steps: 1. Austenitizing heat treatment of sheet metal: The sheet metal is placed in a heating furnace for austenitizing heat treatment. The heating temperature range for austenitizing heat treatment is usually 880-950℃, and the austenitizing holding time is usually 3-8 minutes. After austenitizing heat treatment, the sheet metal structure is transformed into an austenitic structure.

[0034] 2. Sheet metal is hot stamped: After the sheet metal has been heat-treated to austenitic shape, it is transferred to a hot stamping die. The die surface of the hot stamping die matches the shape of the part. The hot stamping die gradually presses the sheet metal into the target part until the die is closed. At this time, the part is compacted.

[0035] 3. Pressure holding and quenching: After the parts are compacted, they enter the pressure holding and quenching stage. The significant temperature drop of the parts mainly occurs in this stage. The water cooling system in the hot stamping die cools the sheet metal, and the austenitic structure in the parts is transformed into martensite structure, thus completing the hot stamping.

[0036] The water cooling system in hot stamping dies is usually located near the die surface. During the holding and quenching stage, after the outer contour of the part is compacted with the die surface of the hot stamping die, a high cooling rate can be achieved for the part. However, the sidewalls of the part are difficult to be compacted by the hot stamping die. Therefore, the martensitic transformation in the sidewalls of the part is not sufficient compared with other parts, resulting in uneven part performance.

[0037] Based on this, combined Figures 1-4The embodiment of the present application provides a hot stamping die 100 for hot stamping forming of a part. A water cooling system 110 is arranged in the hot stamping die 100, and the water cooling system 110 is used for flowing cooling water in the hot stamping process, so that the temperature of the sheet metal is reduced in the pressure holding quenching stage, and the material organization is changed to martensite; the water cooling system 110 is arranged close to a die surface 120 of the hot stamping die 100, the water cooling system 110 comprises a plurality of cooling water channels 111 arranged at intervals, and each cooling water channel 111 can flow cooling water; the die surface 120 of the hot stamping die 100 is matched with the outer contour of the part, wherein the die surface 120 comprises a first working surface 121 matched with the side wall of the part, the cooling water channel 111 arranged close to the first working surface 121 is configured as a first cooling water channel 1113, the first working surface 121 is provided with a water spraying unit 130 corresponding to the first cooling water channel 1113, the water spraying unit 130 comprises a plurality of water spraying holes 131, and the plurality of water spraying holes 131 are communicated with the corresponding first cooling water channel 1113 to spray the cooling water in the corresponding first cooling water channel 1113.

[0038] The hot stamping die 100 provided by the embodiment of the present application is arranged with the water spraying unit 130 on the first working surface 121 matched with the side wall of the part on the hot stamping die 100, the water spraying unit 130 can spray the cooling water in the corresponding first cooling water channel 1113, therefore, when the part is pressed with the hot stamping die 100 in the pressure holding process, the side wall of the part is matched with the first working surface 121 of the hot stamping die 100, the water spraying unit 130 sprays the cooling water in the corresponding first cooling water channel 1113 to the side wall of the part, water quenching of the side wall of the part is realized, the cooling effect and efficiency of the water quenching are obviously better than those of die quenching, so that the martensite transformation of the side wall of the part is ensured to be sufficient, the performance of the part is ensured to be uniform, and the cooling efficiency of the water quenching is also better than that of the die quenching, so that the martensite transformation of the side wall of the part is completed earlier than that of other positions, and therefore the quenching time is no longer limited by the martensite transformation degree of the side wall, so that the quenching efficiency can be improved.

[0039] Further, the plurality of water spraying holes 131 are arranged at intervals and side by side along the length direction of the corresponding cooling water channel 111, that is, the cooling water in the first cooling water channel 1113 is sprayed to the side wall of the part through the plurality of water spraying holes 131. The size of the water spraying hole 131 needs to be determined through calculation and simulation, so that the performance of the side wall of the part is ensured, and the water spraying is not too much. Specifically, the diameter of the water spraying hole 131 in the embodiment is 1-5mm.

[0040] Each cooling water channel 111 has an inlet 1111 and an outlet 1112, cooling water enters the cooling water channel 111 through the inlet 1111, absorbs the heat of the part, and then is discharged through the outlet 1112. Since the cooling water absorbs the heat of the part during the flow process in the cooling water channel 111, the temperature of the outlet 1112 of each cooling water channel 111 is greater than that of the inlet 1111. Different temperatures of the cooling water have different cooling effects, which leads to that the local temperature of the part corresponding to the outlet 1112 of the cooling water channel 111 is greater than that of the part corresponding to the inlet 1111 of the cooling water channel 111, thereby causing the uneven temperature of the part and affecting the overall performance of the part.

[0041] Therefore, in the embodiment, the cooling water channel 111 is inclined, and the distance between the top of the pipe wall of the outlet 1112 of the cooling water channel 111 and the corresponding die surface 120 is less than the distance between the top of the pipe wall of the inlet 1111 of the cooling water channel 111 and the corresponding die surface 120, in other words, the distance between the top of the pipe wall of the outlet 1112 of the cooling water channel 111 and the corresponding local part is less than the distance between the top of the pipe wall of the inlet 1111 of the cooling water channel 111 and the corresponding local part. The part is better cooled on the part closer to the cooling water channel 111. In the embodiment, the distance between the top of the pipe wall of the outlet 1112 of the cooling water channel 111 and the corresponding die surface 120 is less than that of the inlet 1111, thereby to a certain extent, the influence caused by the higher temperature of the cooling water at the outlet 1112 of the cooling water channel 111 is compensated for, and the cooling of the part is more uniform.

[0042] Further, in the embodiment, a plurality of cooling water channels 111 are arranged in parallel, which can further enhance the uniformity of cooling of each part on the part. Specifically, in the embodiment, the diameter of the cooling water channel 111 can be 8-14mm.

[0043] As described above, the die surface 120 of the hot stamping die 100 is matched with the outer contour of the part. Specifically, in the embodiment, the part has side walls on both sides, so the die surface 120 of the hot stamping die 100 includes two oppositely arranged first working surfaces 121, and the die surface 120 of the hot stamping die 100 further includes a second working surface 122 arranged in cooperation with the bottom of the part and two third working surfaces 123 arranged in cooperation with the edge pressing portions of the part. The second working surface 122 is arranged between the bottoms of the two first working surfaces 121, and the two third working surfaces 123 are arranged on the tops of the two first working surfaces 121, and the third working surface 123 is arranged on the side of the first working surface 121 away from the second working surface 122.

[0044] It should be noted that, in addition to the first cooling water channel 1113, other cooling water channels 111 are kept water throughout the production process to ensure the temperature and cooling capacity of the hot stamping die 100, and the cooling effect of the part edge and bottom, while the first cooling water channel 1113 is only water in the holding quenching stage to achieve rapid cooling of the side wall of the part.

[0045] Further, the water spraying unit 130 is arranged on the side of the corresponding first cooling water channel 1113 close to the second working surface 122, that is, the water spraying unit 130 is arranged at the downward position of the corresponding first cooling water channel 1113, so that under the influence of gravity, the spraying effect of the cooling water can be enhanced, thereby improving the water quenching effect.

[0046] Based on the same inventive concept, the application also provides a hot stamping die manufacturing method, which is the manufacturing method of the above hot stamping die 100, comprising:

[0047] S1: design the die surface 120 of the hot stamping die 100, so that the die surface 120 is consistent with the outer contour of the target part;

[0048] The shape of the hot stamping die 100 is preliminarily designed, and the die surface 120 of the hot stamping die 100 is obtained according to the shape of the part.

[0049] S2: design multiple cooling water channels 111 along the die surface 120, so that the local temperature of the part corresponding to the inlet 1111 of the cooling water channel 111 and the local temperature of the part corresponding to the outlet 1112 of the cooling water channel 111 are the same;

[0050] By designing the cooling water channel 111, the local temperature of the part corresponding to the inlet 1111 of the cooling water channel 111 and the local temperature of the part corresponding to the outlet 1112 of the cooling water channel 111 are the same, so that the cooling effect and rate of each part of the part are the same, and the performance uniformity of the part is improved.

[0051] S3: a water spraying unit 130 corresponding to the first cooling water channel 1113 is arranged and communicated on the first working surface 121 to obtain a design model of the hot stamping die 100;

[0052] The size of the water spraying unit 130 and the water speed in the first cooling water channel 1113 need to be determined through calculation and simulation to ensure the performance of the side wall of the part without causing excessive cooling water spraying.

[0053] S4: according to the design model of the hot stamping die 100, the physical processing is carried out.

[0054] Steps S1-S3 are all processes of designing the model of the hot stamping die 100 in three-dimensional software. After the design, the physical processing is carried out according to the design model of the hot stamping die 100 for actual hot stamping production. This method can reduce the strength unevenness of the parts to a certain extent.

[0055] Further, in combination with Figure 3 and Figure 4 , step S2 specifically includes:

[0056] S21: conformally design a plurality of cooling water channels 111 along the die surface 120 to form a water cooling system 110, the distance between the top of the pipe wall of the inlet 1111 of the cooling water channel 111 and the corresponding die surface 120 is the same as the distance between the top of the pipe wall of the outlet 1112 of the cooling water channel 111 and the corresponding die surface 120;

[0057] That is, in this step, each cooling water channel 111 is horizontally arranged (see Figure 3 ), and the distance between the top of the pipe wall of the inlet 1111 and the corresponding die surface 120 and the distance between the top of the pipe wall of the outlet 1112 and the corresponding die surface 120 are both D1.

[0058] S22: simulate the pressure maintaining process of the water cooling system 110 to obtain the local temperature T1 of the part corresponding to the inlet 1111 of the cooling water channel 111 and the local temperature T2 of the part corresponding to the outlet 1112 of the cooling water channel 111, T2>T1;

[0059] According to the foregoing, in the case of horizontally arranging the cooling water channel 111, the distance between the top of the pipe wall of the inlet 1111 and the corresponding die surface 120 and the distance between the top of the pipe wall of the outlet 1112 and the corresponding die surface 120 are the same, since the cooling water absorbs the heat of the part during the flow process in the cooling water channel 111, the temperature T2 of the outlet 1112 of each cooling water channel 111 will be greater than the temperature T1 of the inlet 1111;

[0060] S23: obtain the distance D1 between the top of the pipe wall of the inlet 1111 of the cooling water channel 111 and the corresponding die surface 120 in step 21, and obtain the corrected distance D2 between the top of the pipe wall of the outlet 1112 of the cooling water channel 111 and the corresponding die surface 120 according to formula 1), formula 1) is:

[0061] In formula 1), A is a correction coefficient, 0

[0062] The correction coefficient of the distance between the cooling water channel 111 and the corresponding die surface 120 can be obtained preliminarily through the temperature distribution difference of the two ends of the hot stamping die, and a new correction coefficient of the distance between the cooling water channel 111 and the die surface 120 can be obtained by adjusting the coefficient according to the material properties of the die.

[0063] S24: The distance between the top of the pipe wall at the outlet 1112 of the cooling water channel 111 and the corresponding die surface 120 in step S21 is corrected according to the value of D2 obtained in step 23.

[0064] The value of D2 obtained in step 23 is smaller than the value of Dl, and the closer to the cooling water channel 111 the part is, the better the cooling effect is. After the distance between the top of the pipe wall at the outlet 1112 of the cooling water channel 111 and the corresponding die surface 120 is corrected, the cooling water channel 111 changes from horizontal to inclined (see Fig. 6), i.e. the distance compensates for the influence of the higher cooling water temperature at the outlet 1112 of the cooling water channel 111, and the part is cooled more uniformly. Figure 4

[0065] Although preferred embodiments of the application have been described herein, changes and modifications can be suggested to one skilled in the art, and it is intended that the application encompass such changes and modifications as fall within the scope of the appended claims.

[0066] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.​​

Claims

1. A hot stamping die for hot stamping forming of parts, characterized in that, The hot stamping die is provided with a water cooling system, which is located close to the die surface of the hot stamping die. The water cooling system includes multiple cooling water channels arranged at intervals. The die surface includes a first working surface that is configured to cooperate with the side wall of the part. The cooling water channel located close to the first working surface is configured as a first cooling water channel. The first working surface is provided with a water spraying unit that corresponds to the first cooling water channel. The water spraying unit includes multiple water spraying holes, which are connected to the corresponding first cooling water channel to spray out the cooling water in the corresponding first cooling water channel. The cooling water channel is inclined, and the distance between the top of the pipe wall at the outlet of the cooling water channel and the corresponding mold surface is less than the distance between the top of the pipe wall at the inlet of the cooling water channel and the corresponding mold surface.

2. The hot stamping die as described in claim 1, characterized in that, Multiple cooling water channels are arranged in parallel.

3. The hot stamping die as described in claim 1, characterized in that, The diameter of the cooling water channel is 8–14 mm.

4. The hot stamping die as described in claim 1, characterized in that, The hot stamping die has two opposing first working surfaces, and the hot stamping die also has a second working surface that mates with the bottom of the part and two third working surfaces that mate with the pressing edge of the part. The second working surface is located between the bottoms of the two first working surfaces, and the two third working surfaces are located at the tops of the two first working surfaces, and the third working surfaces are located on the side of the first working surfaces away from the second working surfaces.

5. The hot stamping die as described in claim 4, characterized in that, The plurality of water spray holes are spaced apart and arranged side by side along the length of the corresponding cooling water channels.

6. The hot stamping die as described in claim 5, characterized in that, The diameter of the water spray hole is 1-5mm.

7. The hot stamping die as described in claim 5, characterized in that, The water spray unit is located on the side of the corresponding first cooling water channel near the second working surface.

8. A method for manufacturing a hot stamping die, characterized in that, The method is the method for manufacturing a hot stamping die according to any one of claims 1-7, comprising: S1: Design the die surface of the hot stamping die so that the die surface matches the outer contour of the target part; S2: Design multiple cooling channels along the mold surface so that the local temperature of the part corresponding to the inlet of the cooling channel is the same as the local temperature of the part corresponding to the outlet. S3: A water spray unit is set on the first working surface and connected to the first cooling water channel to obtain the design model of the hot stamping die. S4: Perform physical machining based on the design model of the hot stamping die; Specifically, step S2 includes: S21: Multiple cooling channels are designed along the mold surface to form a water cooling system. The distance between the top of the pipe wall at the inlet of the cooling channel and the corresponding mold surface is the same as the distance between the top of the pipe wall at the outlet of the cooling channel and the corresponding mold surface. S22: Perform a numerical simulation of the pressure holding process of the water cooling system to obtain the local temperature T1 of the part at the inlet of the cooling water channel and the local temperature T2 of the part at the outlet, where T2 > T1. S23: Obtain the distance D1 between the top of the pipe wall at the cooling water channel inlet and the corresponding mold surface as described in step S21, and calculate the corrected distance D2 between the top of the pipe wall at the cooling water channel outlet and the corresponding mold surface according to formula 1). Formula 1) is: Formula 1), where A is a correction coefficient, 0 < A < 1; S24: Based on the value of D2 obtained in step S23, correct the distance between the top of the pipe wall at the outlet of the cooling water channel in step S21 and the corresponding mold surface.

Images