JP2000263262A - Method for joining steel band - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for joining a steel band extremely advantageous in welding quality and productivity when producing a steel band used for a tailored blank method by joining steel bands of different kinds. SOLUTION: When continuously welding the edge parts of a plurality of different kinds of steel bands 1, 2, a plurality of steel bands 1, 2 are passed between a welding roll 5 and a plurality of press rolls 3, 4 slantingly arranged so as to apply width direction force to the steel bands, and consequently applying pressing force to the edge part end face of the steel band, a welding position is detected by a position detector 14, and a laser beam emitting tube 6 is moved following the welding position according to the detected value, thus conducting the laser beam welding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining steel strips in which a plurality of steel strips having different thicknesses, strengths or properties are welded at their longitudinal ends to be used for press forming. Things.

[0002]

2. Description of the Related Art Conventionally, in the production of automobile parts, for each automobile part requiring formability such as deep drawing or stretch forming or an automobile part requiring high strength, a steel sheet corresponding to the requirement is press-formed. Automobile parts, but some of the automobile parts have parts that require strict moldability and parts that do not require much formability, or parts that require strict high strength. In addition, there are automobile parts and the like provided with parts that do not require high strength. Conventionally, when manufacturing such an automobile part, an automobile is manufactured by press-forming using a single steel sheet that can withstand the required performance and welding the formed automobile part.

Recently, in the production of automobile parts, in order to provide necessary thickness and strength to necessary parts,
A method called so-called tailored blank, in which steel sheets having different thicknesses or strengths are joined by a laser or the like to form a single steel sheet and then integrally provided for pressing, has been attracting attention. JP 7
-290182 and JP-A-8-174246. A method of butt welding galvanized steel strips with a laser beam is also disclosed in Japanese Examined Patent Publication No. 5-2559.
It is publicly known, for example, from Japanese Patent Application Publication No.

[0004]

However, in a method of forming an automobile part using a single steel sheet of the same material, excellent formability is required even in a part where the formability required for the molded automobile part is not so required. Will have
In other words, there is a problem that the material is over-action and the cost of the material increases accordingly. Further, the tailored blank method known from JP-A-7-290182, JP-A-8-174246, and the like, shears a steel sheet into a small shape, and joins the steel sheet into a single sheet to increase productivity. In addition, it has the drawback that the joining quality is not stable at the welding start end and the end end, and this part must be cut off, resulting in poor product yield. However, the method described in the above-mentioned Japanese Patent Publication No. 5-25596 is not satisfactory in joining, and the emergence of an advantageous joining method is awaited.

[0005]

The basic structure of the method for joining steel strips according to the present invention, which has been completed to meet the above-mentioned demands, is to continuously weld the edges of a plurality of different steel strips. In doing so, a plurality of steel strips, welding rolls,
The welding position is detected by the welding position detector while applying a force in the width direction to the steel strip so that the pressing force acts on the end face of the steel strip by passing it between a plurality of holding rolls arranged at an angle. Then, based on the detected value, the laser emitting tube is made to follow the welding position to perform laser welding. Further, in such a method, an end positioning device is installed at one of the ends on the side where the welding of the steel strip is not performed, and the holding roll is moved in a direction in which each of the steel strips is installed with the above-described end positioning device. The method for joining steel strips according to claim 2, characterized in that the joining faces of the steel strips are pressed on the same plane by inclining so that a pressing force acts on the steel strips. A method according to claim 3 is a method in which a flange roll is disposed upstream of the point so that a gap is provided between the steel strips.

That is, according to the present invention, a steel sheet provided for an automobile part is not made of one sheet of the same material, but a material having a different thickness, strength or property is used as a strip before press forming. This is a method of joining steel strips to obtain a steel sheet having the required formability or strength required by an automobile part to be formed by welding, and then shearing a foreign steel sheet into a small shape. Instead of the method of joining these ends but having low productivity, the ends of a plurality of different steel strips unwound from the coil are continuously welded to each other, so that the productivity is good and the steel An object of the present invention is to provide a method of joining steel strips, which is extremely advantageous in that the joining quality is improved even when the shape accuracy of the end of the strip is poor. In addition, as an automobile part manufactured from the steel strip obtained by the present invention, a part close to a columnar shape such as a skeleton structure part of an automobile or a part that may be used by joining different materials such as a floor in parallel. The method of the present invention makes it possible to dramatically improve the productivity and yield of these parts.

[0007]

DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention
This is a method of joining steel strips in which the edges of steel strips with different sheet thicknesses etc. are continuously and advantageously welded. The major feature of this method is that the presser roll that is inclined is pressed against the steel strip in the width direction of the steel strip. To improve the productivity by applying a force between the edges of the steel strip so that the pressing force acts between the edges of the steel strip. The point is that good bonding is enabled. Hereinafter, the present invention will be described in detail with reference to FIGS. In the present invention, the edges of two types of steel strips 1 and 2 having different materials and plate thicknesses are continuously joined, and these steel strips 1 and 2 are arranged side by side to form upper holding rolls 3 and 4. Then, it passes between the holding rolls 3 and 4 and the welding roll 5 on the lower side of the larger diameter. At this time, the steel strips 1 and 2 are wound around the large-diameter welding roll 5 and pass therethrough.
Reference numeral 4 denotes a welding roll that is disposed so as to be inclined at angles θ ₁ and θ _{2 with} respect to the longitudinal direction of the welding roll 5 so that a force in the width direction is positively applied to the steel strips 1 and 2. Press

As described above, in the present invention, the holding roll 3
4 is inclined so that a force in the width direction is positively applied to the steel strips 1 and 2 to apply a surface pressure between the edges of the steel strips 1 and 2 to be welded. The main feature is that the laser launch tube that irradiates the laser follows the welding position. When the ends of the steel strips 1 and 2 are butt-welded and laser-welded, if a gap is generated between the steel strips 1 and 2 to be welded, poor quality such as undercut is likely to occur after welding. However, when manufacturing a steel strip, usually, in order to ensure the accuracy of the width of the steel strip and the shape quality of the end of the steel strip, shearing of the end such as slitting the center of the steel strip or trimming the end is required. Although it is finished by processing, since small irregularities remain at the ends of the steel strip, some gaps occur when these end faces are abutted, and when performing laser welding, furthermore, when performing laser welding, the steel strip due to heat shrinkage of the welded part A gap is generated near the upstream of the welded portion because a force is applied to push open the butted surface. Therefore, in the present invention, the pressing rolls 3 and 4 are inclined to apply a force in the width direction to the steel strips 1 and 2 to apply a butt force to the ends of the steel strips 1 and 2 to be welded, thereby pressing the gap due to the heat shrinkage. Further, by adding elastic deformation or plastic deformation of the convex portion of the end portion of the steel strip to significantly reduce the gap due to the unevenness, the gap between the ends of the steel strip 1.2 at the welding point is significantly reduced. When the welding position fluctuates due to poor accuracy of the steel strip width,
The laser emitting tube for irradiating the laser is made to follow the welding position, thereby ensuring stable welding quality.

At this time, in order to apply a force in the width direction of the steel strip,
Normally, a method of applying a force from the end of the steel strip such as a side guide roll on the non-welded side is generally considered. However, for a thin steel strip such as used for automobile parts, these methods have a large effect. If force is applied, buckling of the steel strip or roughening of the ends will occur, so a large force cannot be applied, and the gap between the ends of the steel strip to be welded cannot be sufficiently reduced. There was a problem. Therefore, in the present invention, the pressing roll 3 is used to apply a force in the width direction to the steel strips 1 and 2.
By adopting the method of inclining and pressing 4 and properly adjusting the pressing force and the inclination angle of the pressing rolls 3 and 4, the buckling of the steel strips 1 and 2 and the roughening of the edge of the ends are prevented. A sufficient pressing force can be applied to a thin steel strip used for an automobile part.

In the present invention, a steel strip end positioning device is installed at one of the ends of the steel strips 1 and 2 where welding is not performed, and the holding rolls 3 and 4 are attached to the steel strips 1 and 2 respectively. Is inclined so that a pressing force acts in a direction in which the end positioning device is installed. For this purpose, the holding rolls 3 and 4 are also inclined in the same direction.
That is, the steel strip 1 and the steel strip 2 are generally joined by applying a pressing force from both sides toward the bonding face 10, but in the present invention, the steel strip 1 and the steel strip 2 are joined. 2 are designed to apply the pressing force in the same direction,
For this purpose, the pressing rolls 3 and 4 are both inclined by angles θ ₁ and θ _{2 in the} same direction. In order to apply the pressing force from both sides toward the joining surface 10, it is necessary to adjust the pressing force from both sides in a well-balanced manner so that the joining surface 10 does not always change to the welding position, but adjust the pressing force from both sides. It is difficult to do, as in the present invention,
To the steel strip first end positioning apparatus, pressed to the end positioning device end portions of the positioning apparatus side of the steel strip 1 by pressing the pressing roll 3 is inclined theta _1, the width direction position of the steel strip 1 Can be stabilized. Further, although intended to widthwise position of the strip 2 to be pressed against the weld end of the steel strip 1 stable by pressing the pressing roll 4 by tilting theta _2, welding position due to factors such as inaccuracy of the strip width Is slightly fluctuated, it is based on the knowledge that an advantageous joining is possible if the laser irradiation tube for irradiating the laser follows the welding position. Further, the pressing force between the steel strip ends to be welded can be easily controlled by adjusting the pressing force and the inclination angle theta ₂ of the roll 4 retainer furthermore welded steel strip 1 large-diameter Wrapping around the roll 5 allows the steel strips 1 and 2 to have a good butting accuracy in the thickness direction, and if not wound, a space between the steel strips 1 and 2 and the welding roll 5 is easily formed. This is because there is a high possibility that the butting accuracy of the strip 1 and the steel strip 2 in the thickness direction is not sufficient.

According to the present invention, various investigations are performed so that the position of the fixed laser firing tube 6 for irradiating the laser beam 9 and the welding position of the joint surface 10 to be welded coincide with each other.
In order to prevent the welding position of the joint surface 10 to be welded from fluctuating so much, an idea which is greatly different from the usual idea is adopted. Further, even when a slight variation occurs due to factors such as poor width accuracy of the steel strip. The variation is detected, and the laser firing tube 6 follows the welding position based on the detected value. That is, an idea is given that pressing force is applied to the steel strip from both sides to the joint surface 10 so that the position of the joint surface 10 does not fluctuate from the welding position. The idea is to apply a pressing force so that the steel strip moves to one side of 1 and 2. For example, as shown in FIG. 1, an entrance edge guide 7 and an exit edge guide 8 are provided outside the steel strip 1 as an end positioning device, and the steel strip is moved in the direction of the entrance edge guide 7 and the exit edge guide 8. A press roll 3 inclined so that 1 can move is provided above the welding roll 5. The pressing roll 3 applies a pressing force to the welding roll 5 by a cylinder or the like, and moves the steel strip 1 in the direction of the arrow while restraining the steel strip 1. At this time, since the press roll 3 is inclined by the angle θ ₁ , the steel strip 1 is pressed against the entrance edge guide 7 and the exit edge guide 8. The pressing roll 3 can adjust the pressing force and the angle θ ₁ so that the edge of the steel strip 1 is not damaged. When the steel strip 1 is restrained by the entrance edge guide 7 and the exit edge guide 8, the entry edge guide 7 and the exit edge are set so that the welding surface 10 of the steel strip 1 is at the welding position. The guide 8 can be adjusted in the width direction of the steel strip 1.

As described above, the position of the steel strip 1 in the width direction is adjusted. Similarly, the steel strip 2 is moved while being restrained by the pressing roll 4 inclined by the angle θ ₂ , and
By appropriately adjusting θ ₂ and the holding force of the holding roll 4, the joining surface 10 of the steel strip 2 exerts an appropriate pressing force on the joining surface 10 of the steel strip 1, and the gap between the edges of the steel strips 1 and 2 is adjusted. Therefore, welding is performed in a state in which the gap is crushed and the gap is crushed. In other words, butting is performed by a pinch method, and the welding quality is improved, which is extremely advantageous. By doing so, the joining position of the steel strips 1 and 2 can be adjusted with high accuracy only by considering the pressing force in one direction, and welding is performed with a surface pressure between the edges of the steel strips 1 and 2. The welding quality is improved. After the welding position and the welding position of the steel strips 1 and 2 are advantageously adjusted in this way, the steel strips 1 and 2 are joined by irradiating the laser beam 9 from the laser firing tube 6 and welding. The holding rolls 3, 4
As shown in FIG. 3 and FIG. 4, four steel strips may be used for each of the steel strips 1 and 2. Although various arrangements are possible, there is no particular preference.

Next, a method for the laser emitting tube 6 to follow the welding position, which is the joint surface 10, will be described. First, the welding surface 10, which is the welding position of the steel strip 1 and the steel strip 2, is detected by the welding position detector 14. To detect. The welding position detector 14 is a transmission type line sensor (auto wide) type or CC
An image processing type using a D camera may be considered, but the type of the welding position detector 14 is not particularly limited. Then, for example, when the steel strip fluctuates due to factors such as poor accuracy of the steel strip width, the detected value of the welding position detected by the welding position detector 14 is sent to the amplifier 15, and the variation of the fluctuation is sent from the controller 16. The motor 17 rotates the screw shaft 18 by the motor 17 to move the laser emitting tube position adjusting mechanism 19 fixed to the screw shaft 18, and the laser emitting tube 6 fixed to the laser emitting tube position adjusting mechanism 19. Is moved to follow the welding position. Reference numeral 20 denotes a support shaft provided in parallel with the screw shaft 18. The position of the laser emitting tube 6 may be adjusted by other methods such as using a position control cylinder in addition to the above-described method, and the method is not particularly limited.

Further, as shown in FIG. 5, the welding roll 5 is provided with a groove 11 at a position corresponding to a welding position to prevent the welding roll 5 from being damaged by the thermal influence during welding. In FIG. 5, steel strips 1 having different thicknesses are shown.
2, the diameter of the welding roll 5 is the same over the entire length, so that the steel strips 1 and 2 are
Welding is performed according to the lower surface. FIG.
In FIG. 7, the upper surfaces of the steel strips 1 and 2 are welded together, and in FIG. 7, the thin steel strip 2 is welded at the center of the thickness of the thick steel strip 1. Groove 11
This can be easily achieved by using a welding roll 5 having a different diameter on the left and right with respect to. In addition, welding roll 5
In order to change the left and right diameters, the welding roll 5 may be made freely expandable and contractible, and the means is not particularly limited.

Further, in the present invention, as shown in FIG. 8, a flange roll 13 is disposed upstream of the welding point 12 to provide a gap between the steel strips 1 and 2. Further, in the present invention, the steel strips 1 and 2 are passed on the same plane, and are conveyed to the welding point 12.
May be rubbed or steel strip 1 and steel strip 2 may overlap,
To prevent this, a flange roll 1 between steel strips 1 and 2
Provision of 3 is more preferable.

The pressing rolls 3, 4 used in the present invention
Are inclined at angles θ ₁ and θ ₂ respectively.
The angles θ ₁ and θ ₂ are both preferably 2 ° to 25 °, and
The pressing force of the pressing rolls 3 and 4 is 350N to 20,000
N is preferred. The reason is that if the angles θ ₁ and θ ₂ are less than 2 ° or the pressing force is less than 350 N, the pressing force in the width direction of the steel strips 1 and 2 is insufficient, and the welding quality is not preferable, and the angles θ ₁ and θ ₂ Is over 25 ° or holding force is 20,000
If N is exceeded, the pressing force becomes too large, and buckling of the steel strips 1 and 2 may occur. However, the above-described ranges of the angle and the pressing force are merely preferred ranges, and are not limited to these ranges unless buckling occurs.

It should be noted that the present invention has been described so far by using two steel strips 1, 2
Has been described, but the three steel strips may be joined in the same manner as in the case of the two steel strips described above, and the three steel strips may be joined in the traveling direction of the steel strip. The welding may be performed at the same position or at two different welding positions, and the number of steel strips and the welding position are not particularly limited.

Example 1 The thickness of the chemical composition shown in Table 1 was 0.7 in accordance with a conventional method.
mm, steel strip 1 having a width of 250 mm and a plate thickness of 1.4 mm, a width of 6
A 90 mm steel strip 2 was prepared, and the steel strip 1 and the steel strip 2 were joined at a speed of 1.7 m / min with a 2 kW laser welding machine. Note that, in the present invention, the laser emitting tube was joined while following the welding position using a transmission type line sensor as a welding position detector (see FIG. 1). The conditions are shown in Table 1, and the welding results are shown in Tables 2 and 3.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

[Table 3] As is clear from the above table, according to the method of the present invention, no buckling occurs, no undercut occurs, and extremely good welding quality can be obtained.

Example 2 In order to form the steel strip 1 and the steel strip 2 shown in Example 1 into an automobile part (center pillar), each was cut into 1000 mm.
In this case, in the present invention, the steel strips 1 and 2 are joined and then cut. In the comparative example, the steel strips 1 and 2 are cut and then the steel sheets are joined. The required time at that time is shown in Table 4.

[0023]

[Table 4] As shown in Table 4, according to the present invention, it can be seen that productivity is remarkably improved as compared with the cut plate joining method shown in the comparative example.

[0024]

As is apparent from the above description, according to the present invention, when manufacturing automobile parts and the like by the tailored blank method, it is possible to join steel strips having good welding quality and high productivity. The effect is extremely large.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view of the method of the present invention.

FIG. 2 is an explanatory side view of the method of the present invention shown in FIG.

FIG. 3 is an explanatory plan view of the method of the present invention in which the number of press rolls is increased.

FIG. 4 is an explanatory side view of the method of the present invention shown in FIG. 3;

FIG. 5 is an enlarged explanatory view showing the vicinity of welding in the method of the present invention.

FIG. 6 is an enlarged explanatory view showing the vicinity of welding in the method of the present invention.

FIG. 7 is an enlarged explanatory view showing the vicinity of welding in the method of the present invention.

FIG. 8 is an explanatory view of a state in which a flange roll is provided upstream of a welding point in the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel strip 2 Steel strip 3 Holding roll 4 Holding roll 5 Welding roll 6 Laser emitting tube 7 Inlet edge guide 8 Outlet edge guide 9 Laser beam 10 Joining surface 11 Groove 12 Weld point 13 Flange roll 14 Weld position detector 15 Amplifier 16 Controller 17 Motor 18 Screw shaft 19 Laser oscillation tube position adjustment mechanism 20 Support shaft

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Murai 5-3 Tokai-cho, Tokai-shi, Aichi F-term in Nagoya Works, Nippon Steel Corporation (Reference) 4E068 BE00 BE02 CA09 CA14 CC02 CC06 DA14 DB01

Claims (3)

[Claims] When continuously welding the edge portions of a plurality of different steel strips, the plurality of steel strips are passed between a welding roll and a plurality of holding rolls arranged at an angle, thereby forming a plurality of steel strips. Welding position is detected by a welding position detector while applying a pressing force to the edge of the steel strip by applying a force in the width direction to the steel strip, and based on the detected value, the laser firing tube follows the welding position and laser welding is performed. A method for joining steel strips. 2. An end positioning device is installed at one of the ends on the side where the steel strip is not welded, and a pressing force is applied to the holding roll in a direction in which each steel strip is installed with the above-described end positioning device. The method for joining steel strips according to claim 1, wherein the joining faces of the steel strips are pressed on the same plane by inclining so that 働 く works. 3. The joining of steel strips according to claim 1, wherein a flange roll is arranged upstream of a welding point for laser welding to provide a gap between the steel strips. Method.