JPS6054837B2 - How to join metal strips - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a CO that can perform three consecutive types of thermal processing: cutting, welding, and post-welding heat treatment of metal strips.

The present invention relates to a joining method that reduces downtime in the joining process and improves welding accuracy by making the metal strip joining process one stage using a laser processing device.
In various process lines of steelmaking machinery, such as pickling, annealing, plating, and coil building lines, metal strips of carbon steel, low alloy steel, stainless steel, etc. are processed continuously, so the ends of the metal strips are connected to each other. Joining is performed.

FIG. 1 shows an outline of continuous pickling equipment as an example of these metal strip connection processes. 1 is a strip coil,
2 is a coil opener, 3 is a top cutter, 4 is an arc welder or resistance welder, 5 is an entry looper, 6
is a loop car, and 7 is a pickling tank.

After the strip coil 1 is rewound by a coil opener 2 and its starting and ending ends are cut into straight lines by an up-cut shear 3, the front and rear ends of the strip are sequentially butted together by a resistance welder or an arc welder 4. or lap welded into a continuous strip. The continuous strip passes through an entry looper 5, a loop car 6, etc., and is pickled in a pickling tank 7. The loop equipment such as the entry looper 5 and the loop car 6 is used to advance the strip in the pickling tank at a constant speed even during downtime during strip joining. Further, when the material of the metal strip is thermally hardened by welding, for example, in the case of low alloy steel, martensitic stainless steel, etc., an annealing equipment such as gas flame annealing is installed behind the welding machine 4. In the above-mentioned conventional joining method, the joining process of metal strip coils made of thermosetting material consists of three stages including a cutting process, a welding process, and a post-welding heat treatment (annealing) process, as described above. This results in a long downtime, hindering improvement in line efficiency, and furthermore, this requires a very large looper capacity, resulting in an increase in the size of the equipment. In addition, the welded portion has a large amount of backing plate, excess material, etc., which tends to reduce the durability of the roll, and therefore requires equipment such as a grinder or a trimming process to remove the excess material. The present invention is a C
By using O2 laser processing equipment to create a one-stage joining process for metal strips made of heat-hardened materials,
This method aims to reduce the downtime associated with the welding process and improve the welding quality, and its structure is such that the preceding strip is used in the process of connecting metal strips made of materials that harden when welded. The terminal end of the trailing strip and the starting end of the trailing strip are overlapped by the required amount and overlapped and cut using a focused laser beam.Then, the cut parts are brought together and butt welded using a focused laser beam, and the welded part is then welded with a laser beam. It is characterized by applying a beam absorption coating treatment, and irradiating the welded part with a non-focused laser beam to soften it by heating. The present invention will be described in detail below based on embodiments shown in the drawings.

The present invention performs a metal strip bonding process in one stage using a CO2 laser beam, and an example of the configuration of an apparatus used to carry out this method is shown in FIG. 8 in Figure 2 is CO2
The laser oscillator, 9 is a guide shaft provided perpendicular to the plane of the paper, and 10 is a laser processing head equipped with a laser beam focusing optical system, which moves along the guide axis 9 in the direction perpendicular to the plane of the paper. 11 is a laser beam, 12a is a leading strip, 12b is a trailing strip, 13a, 13b
14 is a clamp that fixes the leading strip 12a1 and the trailing strip 12b at predetermined positions in the vertical and horizontal directions, and 14 is a drive mechanism for moving the clamps 13a and 13b in the vertical and horizontal directions.

The laser beam oscillated by the CO2 laser oscillator 8 is conveyed to the laser processing head 10 along the guide axis 9 through an optical system mainly consisting of a plane reflecting mirror that changes the direction of the laser beam, and then is transported to the laser processing head 10 along the guide axis 9. A high energy density laser beam 1 is focused by a mirror or lens within the
1 and irradiates the strips 12a and 12b. The processing head 10 moves at an arbitrary speed along the guide shaft 9 in a direction perpendicular to the plane of the drawing, and performs laser cutting, welding, and the like. The processing head 10 is also movable in the vertical direction so that the focal position of the laser beam 11 can be set above or below the metal strip, so that the laser beam 11 can bring the metal strip to an appropriate temperature without melting it. It can be heated. An outline of the vertical movement mechanism of the processing head 10 is shown in FIG. In FIG. 3, 10 is a processing head, and 11 is a laser beam. The processing head 10 includes a support part 31 fixed to the main body of the apparatus, and a movable part 32 supported by the support part 31 and movable up and down. The support portion 31 is provided with a frame 37 that protrudes downward, the frame 37 is provided with a screw shaft 34 connected to the drive motor 33 and a bearing 35 of the screw shaft 34, and the screw shaft 34 is connected to the movable portion. 32 flanges 38 are screwed together,
The movable part 32 moves up and down by the rotation of the screw shaft 34.
Further, an optical device such as a convex lens 36 for focusing the laser beam 11 is incorporated inside the movable part 32, and the laser beam 11 sent through the inside of the support part 31 is focused on the metal strip. In this case, by moving the movable part 32 up and down, the focusing position of the laser beam 11 can be moved up and down to accurately align it on the metal strip. In addition, when the position of the focal point F of the laser beam is to be moved up or down significantly, for example, when the position of the focal point F of the laser beam is to be moved upward for post-heat treatment after welding, a fourth drive mechanism is used separately from the drive mechanism shown in FIG. As shown in the figure, a plurality of irradiation mechanisms with different focal positions of laser beams 11 are provided inside the processing head 10. The irradiation mechanism will be explained based on FIG.
is sent to the second reflecting mirror 42, and the path of the laser beam 11 is switched as necessary. Each of these reflecting mirrors 41
, 42 have convex lenses 4 each having a different focal length.
3 and 44 to focus and irradiate the reflected laser beam 11 onto or above the metal strip. still,
The laser beam 11 irradiates the laser in response to cutting, welding, and post-processing, and at other times the laser processing head 1
A shutter is provided in the path of the laser beam 11 so that the laser beam 11 is not irradiated from zero, and the opening/closing mechanism of the shutter is linked to the processing step. On the other hand, below the processing head 10, clamps 13a and 13b are provided for fixing the metal strips 12a and 12b.
can be moved vertically and horizontally by a drive mechanism 14,
Conveyance state and cutting of metal strips 12a, 12b,
The metal strips 12a and 12b are fixed in position during processing such as welding. Next, a joining method using the above processing device will be specifically explained. First, the cutting process will be explained with reference to FIG.

The rear end of the leading strip 12a and the trailing strip 1
2b start end portions are overlapped by the required amount, and clamps 13a, 1
3b. Next, the laser processing head 10 is moved in a direction perpendicular to the plane of the paper to cross the metal strips 12a, 12b, and the laser beam 11 is irradiated to overlap and cut the metal strips 12a, 12b. After cutting, unnecessary material 1
5a and 15b are removed, and the drive mechanism 14 raises the outlet clamp 13a by the thickness of the metal strip 12b. After that, in order to fill the width of the groove cut by the laser, the drive mechanism 14 moves the clamp 13b to the metal strip 12a,
12b is moved by a minute amount in the direction of movement, and on the other hand, similarly, the clamp 13a is moved a minute amount in the opposite direction to make the root gap 0.
Tf0! Form an L I-shaped groove butt joint. As a result, if the laser beam 11 scans this area, butt welding becomes possible without the need for a special copying device.
Note that when cutting steel with the laser beam 11, a method is generally adopted in which the oxygen jet 16 is sprayed onto the laser irradiation part to burn the steel and blow away the slag. Here, the nozzle that supplies the oxygen jet 16 is the cutting nozzle 17. On the other hand, when cutting stainless steel with a laser, there is a concern that the fluidity of the cutting slag is poor compared to when cutting mild steel with a laser, and even if it is blown away by oxygen gas, it does not completely separate from the base material, resulting in a decrease in cutting accuracy. Therefore, even when the present invention is applied to stainless steel strip, the laser cutting of stainless steel can be made with high precision and a cut part that can be used as a welding groove can be obtained. In this method, a certain proportion of iron powder is mixed into the oxygen jet. In other words, poor slag fluidity when cutting stainless steel is caused by chromic acid compounds produced when chromium in the base metal is oxidized, and if the ratio of iron oxides, which have excellent fluidity, increases, the fluidity will significantly improve. improves. The precision of stainless steel laser cutting is therefore significantly improved and is comparable to that of mild steel cutting. Of course, the cutting nozzle 17 is attached to the laser processing head 10 and is moved to the same position and at the same speed as the laser beam 11. Next, the welding process will be explained with reference to FIG.

After the above-mentioned welding groove setting is completed, laser welding is performed using the same laser processing head 10 used in the cutting process. In this case, the welding line is exactly the same as the cutting line described above, so there is no need for a welding line copying device, and the laser processing head 10
All you have to do is drive in exactly the same place as when cutting above. Therefore, the laser beam 11 is irradiated while the processing head 10 is moved along the guide shaft 9 so as to cross the metal strips 12a and 12b, and the metal strip 12 is
Butt weld a and 12b. In this case, when performing shield gas welding, a gas supply nozzle 18 is provided that follows the processing head 10 in the same manner as the cutting nozzle 16, and from here a shield gas 19 such as N or He is blown out to the welding location. Do it like this. Next, the heat treatment process after welding is carried out in the seventh step.
This will be explained using figures.

Since the metal strip that is the object of the present invention is made of a material whose welded part hardens, this process is performed to soften the welded part, but most materials other than mild steel, such as high-strength steel, , low alloy steel, ferritic stainless steel, martensitic stainless steel, etc. require softening heat treatment after welding. The heat treatment or annealing process in the present invention is extremely simple; the laser processing head 10 used in the welding process described above is moved upward, the focus F of the laser beam 11 is removed from the surface position of the metal strips 12a, 12b, and the laser beam is The power density on the beam irradiation surface is reduced to heat the metal strip to an appropriate temperature without melting it.
In this state, if the laser processing head 10 is run perpendicular to the plane of the drawing as in the case of cutting and welding, the laser beam 11 heats the weld bead 20 and its vicinity, softening the welded part. Note that during the post-weld heat treatment, the laser beam 11 is reflected by the metal strips 12a, 12b, so after welding, the laser beam absorbing coating is applied to the metal strips 12a, 1.
2b, post-weld heat treatment is performed. This laser beam absorption coating treatment may include metal or nonmetal powder coating, paint coating, chemical conversion coating treatment, etc., but in the present invention, the coating treatment must be performed online in a short time.
Paint application is ideal for this purpose. In this case, if the paint is applied to the welded part by spraying or the like immediately after welding, the film can be coated online in a short time. As shown in Figure 8, spraying can be carried out over the entire length of the weld line at once, or as shown in Figure 9, spraying can be performed on the processing bed 1 during laser welding.
The spray gun 21 may be made to run following 0. In addition, the type of paint is at high temperature (700-800°C).
In order to maintain a stable coating film, inorganic paints such as silicate are suitable. Furthermore, when the thickness of the plate is thick, the method of heating only the surface of the welded part
The front and back sides of b cannot be uniformly annealed. Therefore, in this case, as shown in FIG. 10, the laser beam 11 may be irradiated from both the front and back sides. In addition, when adopting the annealing method as shown in FIG. 10, in addition to the processing head 10 shown in FIG. 2, another processing head is added below the metal strip, thus providing two heads. In order to send laser beams generated by laser oscillators to these two heads, a splitter for dividing the laser beam 11 and a passage leading to the lower processing head are provided. The joining method of the present invention described above has the following effects. Through the cutting process, the laser cut portion becomes a welding groove to form a butt weld. In this case conventional resistance welding (
Compared to arc welding (spot welding, seam welding, etc.), the strength of the joint is higher than that of arc welding, etc., and there is less excess wall of the weld bead, so it has the effect of reducing the amount of weld bead scraping (trimming).

Furthermore, since laser cutting is used to obtain a highly accurate cut, there are no problems such as adhesion of dross, and it can be used as is as a welding groove. In this case, since there are some irregularities, there is also the effect that the excess thickness of the weld bead is reduced. Furthermore, as mentioned above, since the joint is completely butt welded, the mechanical properties (tensile strength, bending ductility, etc.) of the joint are also good. Furthermore, since it has a high energy density, welding can be performed with lower heat input than conventional welding methods, and even wide strips can be easily restrained with the clamps 13a and 13b, and high-quality welding can be performed with less deformation after welding. As described above, since two-layer stack cutting and butt welding can be performed using only one CO2 laser processing device, the strip connecting process, which was conventionally performed in three stages, can be reduced to one stage. We can expect an increase in production volume due to the reduction of the above-mentioned process time, and a reduction in equipment costs due to the reduction in looper volume.

In addition, in the case of low-alloy steel, ferritic stainless steel, and martensitic stainless steel, the laser beam can be defocused by changing the focal position as described above to prevent heat-affected parts due to welding, significant heat hardening of the welded part, and a decrease in bending ductility. When the beam is irradiated onto the welded part at a predetermined rate, the hardened welded part is heated and softened below the austenite transformation temperature. As a result, the bending ductility of the metal strip can also be improved. Next, examples of the present invention will be shown.

The joining method according to the present invention was carried out on martensitic stainless steel plates having a thickness of 47 m and a width of 1300 m.

First, two metal strips were set one on top of the other, and cut in layers using a 5KW laser beam at a cutting speed of 2 m'min. Oxygen jet is used as cutting gas and oxygen pressure is 5.0kt1C.
1 t, and the jet velocity was 200 to 300 rn/sec. Further, iron powder was mixed into the oxygen jet at a supply rate of 1509 min. Next, the cut portion was set as a groove and welded with a 5KW laser beam. Here, the shielding gas is HeO
e′ Minl speed is 3rn, 1 min. Further, as the welding progressed, a silicate inorganic paint was applied by spray simultaneously with the welding. In addition, inorganic heat-resistant paint is 1
A material capable of maintaining a healthy coating film up to 000°C was used. Thereafter, annealing and softening treatment was performed by post-weld heat treatment. first,
The laser processing head is moved upward to move the laser beam focus upward from the metal strip surface. Laser beam irradiation diameter is approximately 10W0! It should be about l. At this diameter, the laser beam power density is low, so the surface of the metal strip can be heated without melting. In this state, the laser processing head is run along the welding line at a speed of 107 nImin, and heated with a 5KW laser beam. Incidentally, the head is moved back and forth several times as necessary. In this example, 3
I ran it twice. If the laser beam is irradiated from both the front and back sides, it will be more effective. As a result of the above, by using an oxygen jet containing iron powder, the cutting accuracy of the lap cut section is improved to the same level as that of mild steel sheets, and it can be used as a welding groove as is. A welded part with extremely little excess metallization can be obtained. The joint strength was also good, with properties equal to or higher than those of the base metal. The weld metal and heat-affected zone were hardened to a Vickers hardness of 450 or higher, and needed to be softened and annealed to a Vickers hardness of 300, which is appropriate for passing through the process line. The welded part was softened to a Vickers hardness of about 290 by annealing, and a sound welded part with bending ductility was obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic explanatory diagram of continuous pickling equipment, Figures 2 to 1
Figure 0 is an explanatory diagram showing the joining method according to the present invention, and the second
The figure is an explanatory diagram showing the outline of the processing device, FIG. 3 is an explanatory diagram of the processing head portion of the processing device, FIG. 4 is a schematic diagram showing the focusing mechanism of the processing head portion, and FIG. 5 is a cutting process. Figure 6 is an explanatory diagram of the welding process, Figure 7 is an explanatory diagram of the heat treatment process after welding, Figure 8 is an explanatory diagram showing an example of a film coating method, and Figure 9 is an explanatory diagram of another method of film application. Explanatory diagram showing the method, 1st
FIG. 0 is an explanatory diagram showing an example in which the front and back surfaces of a metal strip are heat-treated at the same time.

Claims (1)

[Claims] 1. In the process of connecting metal strips made of materials whose welds harden when welded, the terminal end of the leading strip and the starting end of the trailing strip are overlapped by the required amount and cut with a focused laser beam, The cut portions are then butt-welded using a focused laser beam, the welded portion is further treated with a laser beam absorption coating, and the welded portion is irradiated with a non-focused laser beam to heat and soften. A method for joining metal strips.