TWI579092B - Laser welded shaped steel - Google Patents

Description

Laser welded steel

The present invention relates to a welded steel obtained by forming a T-weld joint by a laser welding method using laser light as a heat source.

In recent years, in the method of manufacturing a profile steel such as a T-shaped steel or an H-shaped steel that is used for a beam of a building structure or the like, a T-shaped connecting member for a flange steel and a web steel has been proposed, and laser welding is performed to perform laser welding. Methods.

For example, Japanese Laid-Open Patent Publication No. 2005-21912 (hereinafter referred to as "Patent Document 1") discloses that after the two metal plates are vertically adhered to each other, the closely bonded metal plates are respectively formed from the front and back sides. Two methods of laser light, the opposite position, along the joint, and the simultaneous illumination.

According to the above method, it is necessary to irradiate laser light from the opposite sides of the web from the front and back sides of the web steel, and it is not efficient from the viewpoint of improving productivity.

For this reason, the applicant of the present invention has proposed a method of irradiating the laser beam to the joint position from the one side of the web material, and the Japanese Patent Laid-Open Publication No. 2007-307591 (hereinafter referred to as "Patent Document 2").

The method is characterized in that the edge of the second metal plate is vertically adhered to the first metal plate, and when the building material forming the T-shaped welded joint is manufactured, the laser welding method using laser light irradiation is used as the welding method. And irradiating the laser light at an inclination angle of 30 degrees or less with the first metal plate to face the entire edge portion of the metal plate in a thickness direction toward the edge portion of the second metal plate Melt.

Prior art

Patent Document 1: JP-A-2005-21912

Patent Document 2: JP-A-2007-307591

According to the welding method proposed in Patent Document 2, since the laser beam is irradiated and the web material of the edge portion of the web material on the joint side is melted in the entire thickness direction, the melting range can be made narrower and deeper. Therefore, the welding joining method can not only obtain more excellent shape accuracy, but even if the flange steel and the web steel (the welded steel plate) are gold-plated steel sheets, the portion of the gold plating layer which may be damaged by evaporation can be greatly reduced. Further, it is possible to reduce the amount of repair coating applied after welding. Moreover, since the melting range can be further deepened, the profile having the required weld strength can be produced in a simple manner even if welding is performed from only one side.

However, in the welding method described in Patent Document 2, since the welded portion is irradiated with the laser light, it is necessary to completely melt the thickness direction of the welded portion. However, with the angle of incidence of the laser light on the flange steel, the position of the edge of the web steel, and the energy of the laser itself, it is possible to change the forming condition of the welded portion, and the desired joint may not be obtained. strength. In addition, when a gold-plated steel sheet is used as a material, in particular, when a galvanized steel sheet is used, the evaporation state of the gold-plated layer changes depending on the molding state of the molten portion, and the corrosion resistance of the welded steel obtained may be Deterioration.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a laser welded steel. The steel is a T-shaped connector, and the formed welded portion can be formed into a proper and correct shape and ensure It is enough to achieve the desired joint strength and corrosion resistance.

In order to solve the above problems, the laser welded steel of the present invention is such that the edge of the web steel is closely attached to the flange steel at a vertical angle to form a T-shaped joint, and the laser is used for one time from one side of the web steel. Irradiation, melting and welding to form steel. The utility model is characterized in that: when the flange steel and the web steel are both steel plates, the shape of the welded portion along the longitudinal direction of the profile steel forms a>0, b>0, c≧0.14Tw, d≧0, e≧0.

If the flange steel and the web steel are all made of galvanized steel, it is better to form a>0, b>0, c≧0.14Tw, d≧0, e≧0, a+d≦2, b+e. The situation of ≦2.

The above a is the melting width of the front surface of the web steel (the laser light irradiation surface), b is the melting width of the back surface of the web steel (non-laser light irradiation surface), c is the maximum melting depth in the thickness direction of the flange steel, and d is the wing. The melting width of the front side of the edge steel (the laser irradiation surface), e is the melting width of the flange steel back surface (non-laser light irradiation surface), and Tw is the thickness of the sheet material of the web steel. The above units are all mm.

Further, when the melting area of the flange steel of the welded portion is expressed by sf and the melting area of the web steel is represented by Su, the ratio of Sf/Su is preferably Sf/Su < 0.75.

Where Sf is approximately (d + Tw + e) × c / 2, and Su is approximately (a + b) × Tw / 2.

The welded steel formed by the invention is characterized in that the edge of the web steel is vertically adhered to the flange steel material to form a T-shaped connecting member, and the T-shaped connecting member portion is irradiated with laser light from a single side for a single time. The connector is made by fusion welding and defines a shape formed in the welded portion of the connector.

Therefore, the laser welded steel provided by the present invention has stable joint strength, and more particularly, even if a welded steel is made of a galvanized steel sheet, the corrosion resistance of the welded portion is not lowered, so It is possible to manufacture welded steel with high strength and high corrosion resistance at low cost.

The edge of the web steel is closely attached to the flange steel at a vertical angle to form a T-shaped joint, and the single side of the T-shaped joint (one side of the front and back of the web steel) is irradiated with laser light for a single time. When welding is performed, as shown in Fig. 1, if the irradiation angle θ of the laser light with respect to the flange steel and the irradiation position of the edge of the web steel are not properly adjusted, the desired joint strength cannot be obtained. . Further, in the case of using a gold-plated steel sheet as a material, if the irradiation angle θ and the irradiation position are not properly set, the gold plating layer on the joint surface of the flange steel and the web steel may be damaged.

For example, if the irradiation angle θ of the above-described laser light is adjusted to be small, as shown in FIG. 2, in the upper and lower regions of the contact point (blocking position) between the web steel and the flange steel, the front side melt width d of the flange steel material is d. Further, the back surface melt width e of the flange steel material is increased, resulting in deterioration of the corrosion resistance of the welded portion.

On the other hand, if the irradiation angle θ is increased, the melting width d and e of the flange steel become small, and the melting range of the edge of the web steel is also reduced. As a result, some of the steel cannot be melted, and sufficient strength cannot be ensured. Further, in the case where the irradiation angle θ is increased, the melting depth c of the flange steel material also becomes large, and if the flange steel is a thin plate, the amount of thermal deformation is increased. Furthermore, if a galvanized steel sheet is used at this time, the degree of damage of the gold plating layer on the opposite side of the web steel may also be increased.

Therefore, the inventors of the present invention irradiate the laser beam with respect to the flange steel with an angle θ, And the position of the laser light irradiation on the edge of the web is finely adjusted so that the size of each part as shown in Fig. 2 can achieve the desired characteristics, and the most appropriate method is obtained.

The following is a detailed description of the invention.

First, in order to clarify the above-described laser light irradiation angle θ with respect to the flange steel, and the distance between the web steel and the flange steel joining position and the laser light irradiation position, the influence of the profile steel characteristics has been performed many times by the inventors. Prepare for the experiment. During the experiment, the irradiation angle θ and the irradiation position were variously changed, and the manner is as shown in FIG. 1 . The measured irradiation position refers to measuring the coordinates of the laser light on the laser light irradiation surface of the web steel along the direction away from the blocking position with the blocking position as the origin.

A steel plate with a width of 200 mm and a length of 2,000 mm, a steel plate having a thickness of 2.3 mm and a tensile strength of 400 N/mm ² was applied with a 6% Zn/3% Al/alloy plating layer on the front side, and the single-sided adhesion amount was set to 90 g/ m ² . Laser welding was carried out under the conditions shown in Table 1 to obtain a T-shaped steel. The argon gas is used as a shielding gas, and the laser light is irradiated from the oblique side to the point of the jet, and is used as a side gas.

Thereafter, the obtained T-type laser welded steel was observed for the cross section of the welded portion, photographed, and the size of each portion as shown in Fig. 2 was measured according to the photograph, and the joint strength was also measured. In addition, the non-blocking surface of the flange steel and the web steel is visually observed.

Thereafter, the tensile strength test was carried out in accordance with JIS G 3353. When the base material of the web steel material is broken, if the tensile strength under the breaking load is 400 N/mm ² or more, the joint strength is judged to be good. Further, if the breaking position is in the welded portion and the value obtained by dividing the breaking load by the sectional area of the web steel is 400 N/mm ² or more, the joint strength can be judged to be good. Further, when the non-joining surface of the flange steel was observed, it was found that the damage was caused by remelting of the plating layer, and the width of the damage was measured.

The above experimental results are shown in Tables 2 to 12.

In Tables 2 to 12, the value indicated by the bottom line is the portion of the tensile test result judged to be insufficient in strength. The numerical unit in each table is mm.

In order to ensure the welding strength of the T-joints in which the web steel and the flange steel are combined, it is necessary to melt the vicinity of the joint surface between the flange steel and the web steel to integrate the two. That is, although welding is performed by a single laser welding from one side, it is necessary to have a melting width (front bead and back bead of the flange steel) on the front and back sides of the web steel, that is, a> 0, b>0, and the flange steel must be melted inward. Referring to the results of Table 4 above, it can be known that the melting depth c of the flange steel must be 0.33 mm or more. Since Table 4 is a result of a test for a steel plate having a thickness of 2.3 mm, in general, since c/Tw = 0.33 / 2.3 = 0.14, the melting width c of the flange steel should be 0.14 × Tw (mm) or more.

Because the laser light is incident from above the flange steel at an oblique angle, if the incident angle is too large, or the irradiation position is too far from the position where the flange steel and the web steel are in contact with each other, the front side melt width and back surface of the web steel The melt width does not exist, and as a result, an unmelted portion is formed between the end face of the web steel and the flange steel, which may lower the strength. That is to say, the melting widths d and e of the front side and the back side of the flange steel must be d ≧ 0 (mm) and e ≧ 0 (mm), respectively.

In addition, if the flange steel is a thin plate of gold-plated steel, the melting amount of the flange steel will increase, so that the damage of the gold plating layer on the opposite side surface of the web steel is increased, and thermal deformation occurs at the same time. Therefore, the amount of melting of the flange steel should not be excessive.

Furthermore, it is preferable to reduce the melting area as much as possible in the vicinity of the contact point between the web steel and the flange steel. On the edge of the section of the galvanized steel sheet, generally only the outer part of 2.3 mm can provide a sacrificial use as a corrosion prevention effect. Considering that during laser welding, the gold plating layer around the welding position portion will evaporate, and if the melting width caused by laser welding is controlled within 2 mm, the welded portion can be ensured even if it is not coated and repaired. Corrosion resistance. Therefore, it is more appropriate to control the melting zone range within 2 mm.

That is, in the case where the flange steel is a galvanized steel sheet, in order to suppress deterioration of corrosion resistance in the vicinity of the intersection of the web steel and the flange steel, the conditions required are a + d ≦ 2 mm and b + e ≦ 2 mm.

From the viewpoint of preventing corrosion of the gold-plated steel sheet, it is preferable that the damage width of the flange steel is controlled to 2 mm or less. However, although in Table 7, when the irradiation angle θ is 10° or 15°, the alignment position is 0.2 mm, and a+d is also 2 mm or less, it is still shown in Table 12, under the same conditions. The damage width of the lower flange steel is still more than 2mm.

The damaged part of the flange steel is not irradiated by the laser light, so the gold plating layer does not completely disappear due to evaporation, so it is not necessary to control it below 2 mm. However, in order to make the galvanized steel sheet exhibit good corrosion resistance without coating repair work, it is necessary to control the width of the damaged portion of the flange steel to 2 mm or less. At the same time, it is also necessary to suppress the thermal deformation of the flange steel. Therefore, it is preferable to control the ratio of Sf/Su<0.75. Where Sf is the melting area of the flange steel of the welded part, and Su is the melting area of the web steel. The flanged steel melting area refers to the section along the length of the section steel, which appears in the flange steel and the area where the metal once melted. The melting area of the web steel refers to the section along the length of the section steel, which appears in the web steel and the area where the metal once melted.

In addition, considering the strength of the welded portion, it is more desirable to control the ratio of Sf/Su ≧ 0.15.

Wherein Sf is approximately (d + Tw + e) × c / 2, and Su is approximately (a + b) × Tw / 2.

In order to prove that in the case of using galvanized steel sheets as materials, it is necessary to control a+d≦2mm, b+e≦2mm, and Sf/Su<0.75 is preferable, so the brine which is widely used in the known technology is used. The spray-drying-wet repeated operation test (CCT test) was carried out to confirm the accelerated test for corrosion resistance. (This test condition was: spraying with a 5% NaCl aqueous solution at 35 ° C for 2 hours → drying at 60 ° C and 30% RH (relative humidity) for 4 hours → wetting at 50 ° C and 95% RH for 2 hours, and repeated. )

The result of the test of 200 cycles is that the laser welding part of the T-connector made by the condition of a+d≦2mm and b+e≦2mm has not been found to have covered white rust or has been produced since the beginning. Red rust. On the heat affected zone of the flange steel, it was found that the damaged portion of the gold plating layer was not covered with white rust and no red rust was generated. In addition, no thermal deformation of the flange steel portion was observed.

Incidentally, in order to obtain a melting range of a generally narrow width as described above, it is necessary to melt all of the side edges of the web steel with a preferable efficiency. Therefore, in order to obtain a melting range of a narrow width as described above, the present invention is self-geographically considered to weld a T-shaped connector from a single side with a single laser irradiation. When welding, it is better to align the intersection of the web steel and the flange steel on the back side of the web steel than the alignment of the web and the flange steel on the front side of the web steel.

The position X from the flange steel to the front side of the web steel is obtained by "X = Tw‧ tan θ" (Tw: thickness of the web steel, θ: angle of incidence of the laser beam and the flange steel). If the alignment position X is controlled above the laser beam radius (D/2), it can be known from the geometry, because The laser does not pass through the contact point of the web front and the flange steel, resulting in an unmelted portion.

However, in reality, the laser beam path is also affected by heat (heat conduction), and the part outside the beam range will still melt. The region where this melting occurs is located in the region of the beam range of about 1.1 to 2.5 times depending on the conditions. Therefore, the upper limit value of the alignment position X is "2.5 × (D/2)", that is, Tw‧tan θ < X ≦ 2.5 × (D/2). The illumination angle θ obtained by this method is in the range of 0 &lt; θ ≦ tan ^-1 ((2.5 × D / 2) / Tw.

When the T-shaped connector is welded by a single laser irradiation from one side by using the irradiation angle θ and the alignment position X as described above, a welded portion having a predetermined shape can be obtained.

Fig. 1 is a schematic view showing a method of performing laser welding by irradiating a single-side irradiated light to a T-shaped connecting member.

Figure 2 is a schematic illustration of the shape of the melt welded portion of the T-shaped connector along the lengthwise section of the section steel.

Fig. 3 is a schematic diagram showing the relationship between the laser irradiation angle θ and the edge irradiation position of the web steel when the T-connector is irradiated from one side and the laser beam is irradiated with a single shot.

Claims (3)

A laser-welded steel is formed by vertically bonding the edge of the web steel to the flange steel to form a T-shaped connecting member, and is irradiated and welded from a single side of the web steel by laser light; The flange steel and the web steel are steel plates, and the shape of the welded portion along the length direction of the steel is formed: a>0, b>0, c≧0.14Tw, d≧0, e≧0; wherein a is The melting width of the front side of the web steel (the surface illuminated by the laser light), b is the melting width of the back side of the web steel (non-laser light irradiation surface), c is the maximum melting depth in the thickness direction of the flange steel, and d is the front side of the flange steel ( The melting width of the laser light irradiation surface, e is the melting width of the flange steel back surface (non-laser light irradiation surface), and Tw is the thickness of the sheet material of the web steel; the above units are all mm. A laser-welded steel is formed by vertically bonding the edge of the web steel to the flange steel to form a T-shaped connecting member, and is irradiated with a single shot from a single side by laser light, and the flange steel is melted and welded; The web steel is galvanized steel, and the shape of the welded portion perpendicular to the longitudinal direction of the steel is formed: a>0, b>0, c≧0.14Tw, d≧0, e≧0, a+d≦ 2, b + e ≦ 2; where a is the melting width of the front side of the web steel (laser light irradiation surface), b is the melting width of the back side of the steel plate (non-laser light irradiation surface), c is the thickness of the flange steel The maximum melting depth, d is the melting width of the flange steel front surface (the laser light irradiation surface), e is the melting width of the flange steel back surface (non-laser light irradiation surface), and Tw is the thickness of the sheet material of the web steel; Is mm. The laser welded steel according to claim 1 or 2, wherein the flanged steel melting area of the welded portion is represented by Sf, and the web steel melting area is represented by Su, and the ratio Sf/Su is Sf/ Su <0.75.