CN112077531A - Process method for manufacturing automobile parts through hot stamping forming - Google Patents

Abstract

The invention discloses a process method for manufacturing an automobile part by hot stamping forming, which comprises the following steps: blanking welded blanks, heating and austenitizing the blanks, feeding the hot blanks into a die, stamping, quenching in the die and performing subsequent treatment on a formed part, wherein the single product plates are linked by using a tailor-welded blank technology to form an integral plate. By the method, a combined structure product can be produced by one stroke of the press, so that the aims of saving time, labor and process are fulfilled.

Description

Process method for manufacturing automobile parts through hot stamping forming

Technical Field

The invention relates to the technical field of hot forming, in particular to a process method for manufacturing an automobile part by hot stamping forming.

Background

Hot stamping, also called press hardening, is a new technology specially used for stamping and forming parts of high-strength steel plates of automobiles in recent years, and is also one of key technical processes for realizing light-weight production of automobiles. The hot forming product has almost no resilience after forming and has high forming precision. The strength of the stamping part manufactured by adopting the hot stamping forming technology can reach 1500MPa, the stamping part can better absorb vehicle collision energy, the vehicle collision deformation is reduced, the safety of personnel in a vehicle is protected to the greatest extent, and the light weight of a vehicle body is realized. Therefore, the method attracts general attention in the industry and rapidly becomes a hot door technology in the field of automobile manufacturing, and is widely applied to the production of safety parts such as a door anti-collision beam, a front bumper and a rear bumper, and vehicle body structural parts such as an A column, a B column, a C column, a middle channel and the like.

With the continuous improvement of the design and manufacturing level of automobile sheet parts in China, the application of the hot stamping technology is concentrated on the sheet parts, and the standards and specifications of all aspects of the hot stamping technology are improved in the product design and production manufacturing links through practical inspection and correction. In the past, the plate adopted by the steel plate hot forming technology is generally a common single plate, and all formed parts are welded into a whole.

The existing laser tailor-welded blank technology is a new concept appearing in the design and manufacture of automobile bodies. The laser tailor-welding is to adopt laser energy to automatically piece and weld a plurality of steel materials, stainless steel materials, aluminum alloy materials and the like with different materials, different thicknesses and different coatings to form an integral plate, a section bar, a sandwich plate and the like so as to meet different requirements of parts on material performance, and realize light weight of equipment by using the lightest weight, the optimal structure and the optimal performance.

At present, the laser tailor-welded blank is mainly applied to the automobile manufacturing industry. In laser welding, the materials are butted rather than lapped, which results in the following weld characteristics:

(1) reducing the volume of the welding seam area, for example, the width of the welding seam is not more than 0.5-1 mm;

(2) the height of the welding seam is not increased;

(3) the impact on the stamping forming performance is small;

(4) after the zinc plating is added to the welding seam, the cathode protection function of the welding seam can be kept;

(5) the heat affected zone is small during welding.

After welding is completed, the static and dynamic strength of the weld zone is a very important indicator, and therefore, the weld zone needs to be sampled and subjected to a destructive tensile strength test (cupping test) to check the stretch formability of the weld zone. Generally, the tensile strength of the weld is higher than that of the base material.

Compared with the products of the traditional spot welding lap joint process, the laser tailor-welded blank process has the following advantages: the manufacturing cost, the logistics cost, the whole vehicle weight, the assembly tolerance, the oil consumption and the rejection rate of the whole vehicle are reduced, the number of peripheral reinforcing parts is reduced, the assembly steps and the assembly process are simplified, the collision capacity of the vehicle is enhanced, and the punch forming rate and the corrosion resistance are improved. In addition, the use of sealant is avoided, so that benefits are brought to environmental protection.

The laser tailor-welded blank technology is urgently needed to be utilized, the traditional process of independently producing each part is changed, and due to the special production process of the thermal forming product, a great deal of research, development, manufacturing, production and time for marketing of the product are wasted, and a great deal of manpower, financial resources and material resources are consumed.

Disclosure of Invention

The invention aims to provide a method for splicing plates by using a laser welding plate technology and then sequentially carrying out thermal forming on the plates to obtain a product, so as to solve the defects in the technology.

In order to achieve the above purpose, the invention provides the following technical scheme:

a process method for manufacturing automobile parts by hot stamping forming comprises the following steps: blanking and splicing blanks, heating and austenitizing the blanks, putting the hot blanks into a die, stamping, quenching in the die and performing subsequent treatment on a formed part, and is characterized in that:

splicing each single product plate into a whole by utilizing a laser tailor-welded blank technology;

step two, heating the plate material of the heating furnace to 930-950 ℃, and converting the plate material into austenite and quickly transferring the austenite into the die body;

step three, rapidly closing the die, forming, maintaining the pressure, cooling to 200 ℃, and completely converting the plate structure into martensite;

step four, laser cutting and punching;

and step five, cooling at room temperature.

Further, the mold of the second step is used for hot forming a rough product without hole-like features.

Further, the plate removed from the heating furnace in the second step is grabbed and transferred into a stamping die, the time of the hot blank in the air is controlled to be 4-6 seconds, and the die-entering temperature of the hot blank is controlled to be 700-750 ℃;

in the steps of stamping and pressure-maintaining quenching in the die, a blank with the thickness of 4-7 mm is put into the die and then is rapidly molded, pressure-maintaining quenching is carried out in the die, the pressure-maintaining time is 20-40 seconds, the water temperature in a water circulation cavity of the die is 6-10 ℃, the flow rate is 100-140L/min, and the demolding temperature of a molded part is 100-200 ℃.

In the technical scheme, the invention provides the process method for manufacturing the automobile parts by hot stamping forming, which is characterized in that the individual product plate materials are connected by using the tailor-welded blank technology to form an integral plate material. By the method, a combined structure product can be produced by one stroke of the press, so that the aims of saving time, labor and process are fulfilled.

Drawings

In order to more clearly illustrate the embodiments of the present application or technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings can be obtained by those skilled in the art according to the drawings.

FIG. 1 is a schematic structural diagram of a panel material for an automotive door panel;

fig. 2 is a schematic product structure diagram of an automobile door panel.

Detailed Description

In order to make the technical solutions of the present invention better understood, those skilled in the art will now describe the present invention in further detail with reference to the accompanying drawings.

The method needs to develop a stamping process flow suitable for safe production of products according to the characteristics of the products.

(1) Selecting a boron alloy steel plate with the tensile strength of about 600 Mpa.

(2) Uncoiling and cutting blanking. As shown in fig. 1, each door panel in the prior art is assembled by welding after being processed by a plurality of hot-formed parts, and compared with the prior art, the method only changes the splicing sequence and comprises the steps of splicing the panels and then carrying out one-time hot forming. The determination method of the size, material, shape and the like of each spliced plate refers to the determination method of the plate used for independently forming each part, belongs to the prior art, and is not described in detail here.

Wherein, the hot forming die who processes whole product includes: the upper die and the lower die are respectively a pressing plate capable of forcing the plate to be formed. The hot forming technology is characterized in that the hot forming technology is formed in one step, the shapes of the die surfaces of the upper die and the lower die are matched with the upper surface and the lower surface of a product, but the die is not subjected to punching operation, namely the product processed in the step is a rough product to be subjected to subsequent punching operation. Compared with the integral product, the rough-processed product has no various hole shapes along the outer edge of the integral product, and all shape areas needing to be punched are filled. The determination of the upper die and the lower die is a technique that can be determined by those skilled in the art. The selection of the upper die and the lower die of the pressing plate is mainly based on the upper surface and the lower surface of a product numerical model, and how to select the upper die and the lower die is related to the shape, the difficulty degree and the heating mode of the heating furnace of the product. The forming insert is generally rigid, and the pressing plate is divided into elastic control and gap control and is selected according to forming requirements.

(3) The furnace was heated to 930 deg.C and 950 deg.C to transform it into austenite and transfer it rapidly into the mold body.

(4) The temperature of the die is 50-75 ℃ (different according to the beat), the transfer time of the plate is 8-10s, the stroke and the pressure of the pressing plate need to be actually adjusted according to the molding state of the product when CAE software is used for simulation analysis, and the pressure maintaining time is as follows: and ensuring that the part demolding temperature is within the range of 150-.

(4) And (4) quickly closing the die, forming, maintaining the pressure, cooling to 200 ℃, and completely converting the plate structure into martensite.

(5) And (3) laser cutting and punching, wherein the hot-formed product is subjected to punching operation to obtain an accurate product shape because no punching is performed in the step (2).

(6) Cooling at room temperature and post-processing, if the plate is a bare plate, shot blasting is needed to remove surface scale. And (3) subsequent treatment of the formed part: after the hot formed part is cooled to room temperature, surface treatment such as acid washing, shot blasting and the like, laser trimming and punching shaping treatment are carried out according to the design requirements of the part. Finally, a finished product is debugged on site to obtain the part with the tensile strength of about 1500 Mpa.

The hot forming process for the medium plate automobile parts with the thickness higher than 3.5mm is preferably as follows: firstly, a boron alloy steel plate with the strength of 500-600 MPa at normal temperature is heated to the temperature of about 900 ℃ above the outside and the core part is 810-930 ℃ (the lowest heating temperature and time can be calculated and tested according to the corresponding thickness and conditions), at the moment, the material is completely austenitized, then the material is quickly transferred from a heating furnace to a hot forming press machine and sent into a die with a cooling system inside, and the press machine performs stamping and forming. And (3) rapidly cooling the plate in a die (preferably water cooling), converting austenite into martensite at the temperature below 200 ℃, wherein the cooling speed is generally-40-100 ℃/s so as to ensure the hardenability of the part, hardening the stamping part and greatly improving the strength.

The technology for hot forming the thick plate material of the automobile part is based on the technological process of the thin plate material. Firstly, the step of controlling the heating of the plate is changed, the heating time is reduced, the temperature of the plate core entering a die is lower, the pressure maintaining time is reduced, and the cooling rate is improved. The whole plate is not heated to more than 900 ℃. But in order to improve the rapid cooling rate of the part in the die, reduce the heating temperature and the heating time of the plate, ensure that the plate is completely austenitized after being heated and completely avoid the result that the part can not be completely transformed into martensite due to the high temperature of the core part of the plate caused by the high thickness and the slow cooling before the die is closed.

Mold-entering temperature: the cooling speed of the thick plate in the air is slow, the mold-entering temperature is controlled to 750 ℃, then the mold-entering temperature is tried to be reduced continuously, the cooling speed of the thick plate is slow, and the lower the mold-entering temperature is, the shorter the obtained pressure maintaining time is;

pressure maintaining time: there are several necessary preconditions to obtain the final dwell time, 1. stable production takt, after 10 pieces of mould continuous production, the temperature will be maintained to a equilibrium temperature, the dwell time obtained on this basis is accurate; 2. stable cooling water temperature and flow, fixed feeding time; 3. the mold stripping temperature is controlled to be more than 100 ℃ and less than 200 ℃.

The invention has the advantages that:

(1) the number of parts is reduced. Because the tailor-welded blank can be integrated into one piece, the precision of automobile body panel has been improved, has reduced a large amount of stamping process's equipment and process. The automobile body of an automobile is composed of more than 300 parts, and the number of the parts can be reduced by 66% by adopting the laser tailor-welded blank technology, so that the number of dies is greatly reduced, and the utilization rate of materials is improved.

(2) The quality of the structural part is reduced. The different steel plates are adopted for splicing, so that the service life of the easy-to-corrode part can be prolonged by adopting the plated steel plate, and the plates with different thicknesses are welded together according to the strength requirements of different parts and then are subjected to one-step punch forming without welding reinforcing ribs, so that the consumption and the production cost of steel are reduced, and the quality of a vehicle body is reduced.

(3) The quality and the reliability of the structural part are improved. The adoption of the laser tailor-welded blank not only improves the stability of the quality of the finished product of the vehicle door component, but also makes the adjustment of the vehicle door component no longer a difficult problem, and simultaneously can reduce the weight of the component, and the omission of the sealing measure of the original seam position also makes the vehicle door component more environment-friendly. In addition, the application of the tailor welded blank to the vehicle door also enables the rigidity of the hinge region to be integrally enhanced, and the fitting tolerance of the vehicle door is greatly improved. The weight is reduced, and the production process is optimized, so that the cost is necessarily reduced.

While certain exemplary embodiments of the present invention have been described above by way of illustration only, it will be apparent to those of ordinary skill in the art that the described embodiments may be modified in various different ways without departing from the spirit and scope of the invention. Accordingly, the drawings and description are illustrative in nature and should not be construed as limiting the scope of the invention.

Claims (2)

1. A process method for manufacturing automobile parts by hot stamping forming comprises the following steps: blanking and splicing blanks, heating and austenitizing the blanks, putting the hot blanks into a die, stamping, quenching in the die and performing subsequent treatment on a formed part, and is characterized in that:

splicing each single product plate into a whole by utilizing a laser tailor-welded blank technology;

step two, heating the plate material of the heating furnace to 930-950 ℃, and converting the plate material into austenite and quickly transferring the austenite into the die body;

step three, rapidly closing the die, forming, maintaining the pressure, cooling to 200 ℃, and completely converting the plate structure into martensite;

step four, laser cutting and punching;

and step five, cooling at room temperature.

2. The process for manufacturing automobile parts by hot stamping forming according to claim 1, wherein the sheet removed from the heating furnace in the second step is grabbed and transferred into the stamping die step, the time of the hot blank in the air is controlled to be 4-6 seconds, and the die-entering temperature of the hot blank is controlled to be 700-750 ℃;

in the steps of stamping and pressure-maintaining quenching in the die, a blank with the thickness of 4-7 mm is put into the die and then is rapidly molded, pressure-maintaining quenching is carried out in the die, the pressure-maintaining time is 20-40 seconds, the water temperature in a water circulation cavity of the die is 6-10 ℃, the flow rate is 100-140L/min, and the demolding temperature of a molded part is 100-200 ℃.

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