CN1403241A - Weld joint movement control method and device in laser tailor-welded blank forming - Google Patents

Abstract

The present invention relates to a method and device for controlling the movement of welds during the forming process of laser-welded plates, and is mainly used in situations where laser-welded plates are used to stamp and form vehicle body panels. The present invention uses three methods to control the movement of welds during the stamping process of laser-welded plates: 1) The combined blank holder and the forming part of the punch have step surfaces, so that the thin side sheet of the laser-welded plate has sufficient blank holder force to reduce the movement of the welds; 2) The clamping force generated by the nitrogen cylinder is used to clamp the weld during the stamping process of the laser-welded plate to reduce the movement of the welds; 3) The draw ribs are reasonably arranged on the die pressing surface to control the deformation and flow of the thick and thin side sheets of the laser-welded plate. The use of this method and device can well control the movement of the welds during the forming process and the resulting rupture and wrinkling of the sheet.

Description

Weld seam movement control method and device in laser tailor welded blank forming

Technical field

The invention relates to the field of mechanical processing, in particular to a method and a device for controlling weld seam movement in laser tailor welded blank forming, and is mainly used in occasions where laser tailor welded blanks are used to stamp and form vehicle body panels. The method and the device thereof can well control the movement of the welding seam during the forming process and the cracking and wrinkling of the sheet metal caused thereby.

Background technique

Traditionally, there are two stamping forming methods for automotive body panels: separate forming and integral forming. The separate forming method is flexible and easy to implement, but the number of parts is large, which increases the stamping cost and the weight of the vehicle body; the cover parts obtained by the integral forming method have good rigidity, but cause excessive material selection in some parts and increase the weight and cost of the vehicle body. High difficulty. Tailored welded blank stamping method inherits the advantages of traditional separate forming method and integral forming method, and overcomes the shortcomings of both, and has been paid more and more attention to and widely used in the field of body panel manufacturing.

The so-called tailor-welded blank is welded together by two or more sheets after blanking and before stamping. These sheets may be identical or have different thicknesses, mechanical properties and plating types.

The use of laser welded blanks can not only reduce the number of parts, but also provide many additional benefits, including reduced body weight, improved structural integrity and rigidity, improved dimensional accuracy, improved component and sub-assembly accuracy; reduced stamping parts, number of tooling and tooling step, reduce the amount of spot welding, simplify the input system, thereby simplifying the manufacturing process and greatly reducing the cost; during the impact process, more energy can be controlled to be absorbed, thereby enhancing the crashworthiness; avoiding the use of some such as reinforcing ribs The structure and fixtures simplify the overall structure of the vehicle; the integration of reinforcements avoids lap joints, thereby improving corrosion resistance; laser welding can reduce design scraps, and waste materials can be recycled for subsequent stamping, thereby saving materials; for It is important in an era of environmental protection that automakers offer greater flexibility in body design and provide customers with lighter, stronger vehicles that consume less fuel and perform better.

Although the use of tailor-welded blanks has brought many benefits, there are also many technically difficult problems to solve, the most important of which is the decline in formability caused by factors such as weld zone microstructure changes and weld movement. Compared with the base metal, the forming limit strain of the tailored welded blank is reduced by more than 50%. Since the stamping forming of body panels is a large deformation mechanical problem with nonlinear geometry, material nonlinearity and process boundary conditions, the application of laser tailor welded blanks increases the complexity of the problem and the difficulty of forming. Among them, the degradation of stamping performance caused by the shift of weld position is the main problem faced by laser welded blanks. Due to the unequal thickness of the base metal of tailor-welded blanks, the mold used does not compress the thin-side sheet metal, resulting in wrinkling of the sheet metal. When using a combined rigid blankholder with a stepped surface, the thin side sheet will crack when the weld moves toward the thin side, and the sheet will wrinkle when the weld moves toward the thick side.

Jian Cao and Brad L. Kinsey of Northwestern University in the United States applied for a patent "Adaptive method and apparatus for forming tailor welded blanks" (Patent No. 5,941,110) to the US Patent Office in 1999. This patent uses a hydraulic cylinder to provide weld clamping force. Through the signals generated by the pressure sensor and the displacement sensor, the hydraulic directional valve and the servo valve are controlled by the computer to change the pressure of the oil cylinder, so as to generate the welding seam clamping force required by different positions of the punch during the tailor welded blank forming process. The advantage of Jian Cao’s patent is that it can provide the weld clamping force at different positions of the punch. The disadvantage is that there is no step surface on the binder surface and the surface of the convex model, resulting in wrinkling due to the lack of compression of the thin side of the tailored welded blank.

Werner Munzen applied for the patent "Stretch controlled forming mechanism and method for forming multiple gauge welded blanks" (Patent No. 5,600,991) to the US Patent Office in 1997. The clamping force of the weld seam is generated by the compression of polyurethane rubber. The method is relatively simple and practical, but the clamping It is difficult to adjust the clamping force, and with the increase of polyurethane rubber compression, the clamping force increases from small to large, which is exactly the opposite of the initial clamping force required for sheet metal forming, which is then gradually reduced.

Youngmoo Heo et al. used the method of arranging drawbeads to control the weld seam movement during the stamping process of tailor-welded blanks. The specific method was mainly to control the weld seam movement by changing the length and section size of the drawbeads (Youngmoo Heo, Youho Choi, Heon Young Kim, Daegyo Seo, Characteristics of weld line movements for the deep drawing with drawbeads of tailor-welded blanks, Journal of Materials Processing Technology 111(2001):164-169). Due to the thickness difference (1.6mm×0.8mm, 1.2mm×0.8mm) of the base metal of laser tailor welded blank, the mold used in this method does not compress the thin side sheet, and the sheet wrinkling phenomenon occurs.

Contents of the invention

The purpose of the present invention is to provide a method and device that can effectively control the movement of the weld seam in the laser tailor welded blank stamping forming, so as to overcome the problem of the drop of formability caused by the weld seam movement in the laser tailor welded blank stamping forming.

The object of the present invention adopts following technical scheme to realize:

A combined blank holder and punch with a stepped surface is adopted, which is characterized in that the blank holder and a part of the punch are made detachable, and the height difference of the step surface can be adjusted according to the thickness of the base material of the laser tailor welded blank; and set There is a welding seam clamping device that uses the pressure of the nitrogen cylinder to generate clamping force; different drawing beads are arranged on the pressing surface of the die to produce different drawing resistances for different sheets.

The device for realizing the welding seam movement control method in the forming process of laser tailor welded blanks according to the present invention includes a combined blank holder with a stepped surface and a punch, a backing plate for the punch, a backing plate for the blank holder, and a place for laser welding. The concave die of the welding plate is characterized in that the punch and a part of the blank holder are detachable. The punch is composed of the left punch and the right punch, and the left blank holder and the blank holder right are composed of the blank holder. Under the plate, there is a height difference adjustment piece of the edge ring step surface and a height difference adjustment piece of the convex mold step surface; the welding seam clamping device is set to directly limit the movement of the welding seam, and a layer of polyurethane rubber is applied to the front end of the clamping rod to increase the friction coefficient and produce Greater friction; height-adjustable drawbeads are arranged on the binder surface of the mold.

The height difference of the step surface can be adjusted according to the thickness of the base metal of the tailor-welded blank, so that the thick side and the thin side sheet can get the required blank-holding force respectively, so as to control the deformation of the thick side and thin side base metal and control the movement of the weld seam amount; through the clamping force generated by the nitrogen cylinder, the weld seam is clamped during the forming process of the laser welded blank to reduce the movement of the weld seam, and the pressure of the nitrogen cylinder can be adjusted to produce different clamping forces; the drawbead The arrangement can make the thin-side sheet receive greater drawing resistance than the thick-side sheet, thereby reducing the inflow of the thin-side sheet and increasing the inflow of the thick-side sheet, thereby controlling the size of the weld movement.

Compared with the prior art, the present invention has the following advantages:

1) Using a combined punch and blank holder with a stepped surface can meet the pressing requirements of sheets of different thicknesses at the same time, which not only controls the movement of the weld, but also prevents the sheet from wrinkling;

2) The nitrogen cylinder is used to provide the welding seam clamping force, the clamping force is large and constant;

3) The use of drawbeads can conveniently control the deformation and flow of the thick and thin side sheets of tailor-welded blanks, and supplementary adjustments can be made to the weld movement control functions of nitrogen cylinders, combined punches and blank holders.

Description of drawings

Figure 1 Schematic diagram of the welding seam movement control method and device in the laser tailor welded blank forming process

1 Punch left 2 Punch backing plate 3 Binder ring backing plate 4 Binder ring step surface height difference adjustment piece 5 Punch step surface height difference adjustment piece 6 Punch right 7 Binder ring right 8 Tailored welded blank thin side 9 Drawbead 10 Die 11 Nitrogen Cylinder 12 Weld Seam Clamping Rod 13 Tailored Welded Blank Thick Side 14 Blank Holder Left

Detailed ways

The invention is used for single-action press forming, and can also be used for double-action press forming. Taking the stamping forming of a double-action press as an example, the details of the welding seam movement control method and device proposed by the present invention will be described in conjunction with accompanying drawing 1 . The mold is installed on a double-action press, and consists of a punch, a die 10, a binder ring, a punch backing plate 2, a blank holder backing plate 3, a weld clamping device, and a drawbead 9, among which The punch is composed of the punch left 1, the punch right 6 and the height difference adjusting piece 5 of the step surface of the punch, and the blank holder is composed of the left 14 of the binder ring, the right 7 of the binder ring and the height difference adjusting piece 5 of the step surface of the blank holder The welding seam clamping device is composed of a welding seam clamping rod 12 and a nitrogen cylinder 11; the laser tailor welded blank formed by welding the thick side 13 and the thin side 8 is placed on the die 10.

There is a stepped surface on the working surface between the punch left 1 and the punch right 6, and there is also a stepped surface on the working surface between the blank holder left 14 and the blank holder right 7, and the height difference of the stepped surface depends on The thickness difference between the thick side 13 and the thin side 8 of the tailor-welded blank is adjusted by the height difference adjustment piece 4 of the step surface of the blank holder and the height difference adjustment piece 5 of the step surface of the punch. The clamping force of the welding seam clamping rod 12 is provided by the nitrogen cylinder 11, and the pressure of the nitrogen cylinder can be adjusted as required. The drawbead 9 is arranged according to the shape of the tailor-welded blank and the formed part, and the height of the drawbead can be adjusted.

The working process of the present invention is:

1) Put the tailor-welded blank on the die 10, and position the sheet according to its thickness;

2) The blank holders 7 and 14 go down and come into contact with the die 10 to clamp the tailor-welded blank and form the blank holder. At the same time, the drawbeads on the die 10 and the current limiting Grooves for metal flow control in tailor welded blank forming;

3) Punches 1 and 6 start to descend and come into contact with the weld clamping rod 12, which presses the weld against the left 1 of the punch;

4) The punch continues to descend, and the stamping of the tailor-welded blank is completed in the state where the weld seam is clamped;

5) The punch goes up and is separated from the tailor-welded blank first;

6) The blank holder goes up and separates from the tailor welded blank;

7) The stamping parts are ejected, and the stamping process ends.

This embodiment is only used to illustrate the present invention, not to limit it.

Claims (6)

1. The welding seam movement control method in the laser tailor welded blank forming process adopts a combined blank holder and punch with a stepped surface. Tailored welded blanks adjust the height difference of the step surface with different base metal thicknesses. 2. The welding seam movement control method in the laser tailor welded blank forming process according to claim 1, characterized in that there is a welding seam clamping device that uses the pressure of nitrogen cylinder to generate clamping force. 3. The welding seam movement control method in the laser tailor welded blank forming process according to claim 1 or 2, characterized in that different drawbeads are arranged on the pressing surface of the die to produce different drawing forces for different sheets resistance. 4. The device for realizing the welding seam movement control method in the laser tailor welded blank forming process according to claim 1, comprising a combined blank holder (14, 7) with a stepped surface and a punch (1, 6), a punch Die backing plate (2), blank holder backing plate (3) and the die (10) for placing the laser welded blank are characterized in that the punch and part of the blank holder are detachable, and the punch left (1 ) and the punch right (6) form the punch, the blank holder left (14) and the blank holder right (7) form the blank holder, and the blank holder step surface height difference adjustment piece (4) is arranged under the backing plate , Punch step surface height difference adjustment piece (5). 5. The weld seam movement control device in tailor welded blank forming according to claim 4, characterized in that a weld seam clamping rod (12) of a nitrogen cylinder (11) is provided in the die (10), The front end of the seam clamping rod (12) is covered with one deck of polyurethane rubber. 6. The weld seam movement control device in tailor-welded blank forming according to claim 5, characterized in that height-adjustable drawbeads (9) are provided on the binder surface of the die (10).