JP4622305B2 - Method of lap fusion welding of Zn-plated steel sheet and Fe-based filler material - Google Patents

Description

  The present invention relates to a lap-melt welding method for Zn-plated steel sheets and an Fe-based filler material that can be used for the lap-melt welding method for Zn-plated steel sheets. The present invention relates to a lap fusion welding method and an Fe-based filler material for Zn-plated steel sheets that integrally join plated steel sheets.

  When laminating and welding Zn-plated steel sheets, superimpose two Zn-plated steel sheets with a Zn-plated layer formed on the surface of the base material, and apply laser heat, arc heat, etc. to a predetermined part of the overlapped portion. Thus, both the base materials are melted to form a molten pool, and the molten pool is cooled and solidified to integrally bond the two base materials.

  By the way, in the Zn plating steel plate, the boiling point of Zn of the Zn plating layer is lower than the melting point of the steel plate as the base material. For this reason, when the base material of the Zn-plated steel sheet is melted during welding, Zn in the Zn-plated layer is gasified to become Zn vapor. Therefore, in the lap fusion welding of Zn plated steel sheets, Zn vapor obtained by gasification of Zn between the stacked Zn plated steel sheets remains trapped in the molten pool or becomes high pressure in the molten pool and becomes high pressure from the molten pool. A welding defect such as a blow hole due to scattering of the spouted molten base material becomes a problem.

  For such welding defects such as blowholes caused by Zn vapor, it is effective to form an appropriate minute gap between the two Zn-plated steel sheets that are overlapped, and escape the Zn vapor from this minute gap for deaeration. There is known a technique for forming a minute gap for gas escape between the two Zn-plated steel plates that are overlapped (see, for example, Patent Document 1).

  In the technique disclosed in Patent Document 1, a convex portion is provided on one surface of a Zn-plated steel sheet by press forming to form a minute gap for gas escape between the two Zn-plated steel sheets that are overlapped. For this reason, it is possible to suppress high-pressure gas ejection through the molten pool by allowing Zn vapor generated between both Zn-plated steel plates during laser welding to escape from a minute gap between both Zn-plated steel plates.

  In addition, the technique which prevents generation | occurrence | production itself of Zn vapor | steam causing a welding defect, such as a blowhole, is also known (for example, refer patent document 2).

In the technique disclosed in Patent Document 2, laser welding is performed while supplying Mn oxide powder (MnO powder), which is a material having a standard free energy of formation of oxide smaller than Fe and larger than Zn, to a weld. is doing. And in this patent document 2, MnO which is more active than Fe but inactive than Zn reacts with Zn without reacting with Fe in the molten pool to produce ZnO, and this ZnO has a high boiling point. Therefore, since gasification is not performed during laser welding, the generation of Zn vapor itself can be prevented and welding defects such as blow holes due to Zn vapor can be prevented.
JP 2001-162387 A (page 3-5, FIG. 2) JP-A-8-215882 (page 3-4)

  However, it is difficult and difficult to manage the size of the minute gap in the conventional technique in which the minute gap for gas escape is formed by providing a convex portion on one surface of the Zn-plated steel sheet by press forming.

  That is, if the minute gap is too large, the molten base materials are not connected to each other and separated, whereas if the minute gap is too small, the degassing of the Zn vapor is insufficient and a welding defect such as the blow hole occurs. Therefore, it is necessary to manage the size of the minute gap within the range of about 0.1 to 0.4 mm. However, considering the mold wear and molding accuracy of the press molding machine, the size of the minute gap is increased. It is cumbersome and difficult to manage accurately.

  The technique disclosed in Patent Document 2 prevents generation of Zn vapor itself by laser welding while supplying MnO powder, and is different in technical idea from the present invention. In the technique disclosed in Patent Document 2, since ZnO generated by the reaction between MnO and Zn remains in the welded portion, the remaining ZnO may reduce the strength of the welded portion.

  The present invention has been made in view of the above circumstances, and suppresses welding defects such as blow holes due to Zn vapor by successfully escaping Zn vapor generated between Zn-plated steel sheets without troublesome and difficult gap management. This is a technical problem to be solved.

  The present inventor has paid attention to the fact that troublesome and difficult gap management is not required if Zn vapor generated between Zn-plated steel plates during welding can be successfully escaped from the molten pool, and a novel that allows Zn vapor to escape through the molten pool. The present invention was completed based on the idea.

That is, the method for lap-melting welding of Zn-plated steel sheets according to the present invention that solves the above problems includes a superimposing step of superimposing Zn-plated steel sheets formed with a Zn-plated layer on the surface of a base material, The part is irradiated with laser light from a direction substantially perpendicular to the surface of the Zn-plated steel sheet to heat both the base materials by laser heat to form a molten pool in which both the base materials are melted, and the molten pool is cooled. A joining step of integrally joining the base materials of both the Zn-plated steel sheets by solidification, wherein in the joining step, at least selected from the group of viscosity-decreasing metals consisting of Fe, Al, Si, and Mn One type of Fe-based filler material is mixed in the molten pool, and the Fe-based filler material is expressed by the following formula (a) when the entire Fe-based filler material is 100%. To include in the content to satisfy It is an butterfly.
0.27 Al (%) + 0.044 Si (%) + 0.035 Mn (%) ≧ 0.32
... (a)
Here, “%” in the formula (a) means “mass%”. Moreover, in the following description, what is simply described as “%” means “mass%”.

  In addition, the “both base metals are melted” means that the entire base material of one of the Zn-plated steel plates superposed on the heated portion is melted and the entire base material of the other Zn-plated steel plate or one of the base materials is one. It means that the part is melted.

  In a preferred aspect, the Fe-based filler material comprises a cored wire composed of an Fe-based outer shell and a metal powder and / or an alloy powder filled in the Fe-based outer shell, and the metal powder is made of the viscosity-reducing metal. It is at least one metal powder selected from the group, and the alloy powder is at least one alloy powder consisting of at least two kinds selected from the group of the viscosity reducing metals.

  In a preferred aspect, the lap fusion welding method of the Zn-plated steel sheet according to the present invention is such that, in the joining step, a laser beam is irradiated to a predetermined portion of the overlapped portion, and both the base material and the Fe-based filler are heated by laser heat. Melt the material.

  In a preferred embodiment, the method for lap melting welding of a Zn-plated steel sheet according to the present invention is a method in which, in the joining step, a predetermined portion of the overlapped portion is irradiated with laser light to melt both the base materials mainly by laser heat. The Fe-based filler material is melted by arc heat.

  In a preferred embodiment, the method for lap melting welding of a Zn-plated steel sheet according to the present invention is a method in which, in the joining step, a predetermined portion of the overlapped portion is irradiated with laser light to melt both the base materials mainly by laser heat. Then, an arc is generated using the cored wire as a consumable electrode, and the cored wire is melted by arc heat.

The Fe-based filler material of the present invention that solves the above problems is substantially the same as the plate surface of the Zn-plated steel sheet at a predetermined portion of the overlapping portion of the Zn-plated steel sheets formed by forming a Zn-plated layer on the surface of the base material. Laser beam is irradiated from the vertical direction and both the base materials are heated by laser heat to form a molten pool in which both the base materials are melted, and the molten metal is cooled and solidified to form the base materials of both the Zn-plated steel sheets. An Fe-based filler material used in a lap-melt welding method of Zn-plated steel plates that integrally join each other, wherein the Fe-based filler material is a group of viscosity-reducing metals consisting of Fe, Al, Si, and Mn The Fe-based filler material has a content satisfying the following formula (a) when the Fe-based outer shell and the Fe-based filler material as a whole are 100%. Metal powder filled in the Fe-based outer shell so as to include And and / or alloy powder, characterized in that consisting of cored wire made of.
0.27 Al (%) + 0.044 Si (%) + 0.035 Mn (%) ≧ 0.32
... (a)

  The lap fusion welding method for Zn-plated steel sheets according to the present invention is a lap fusion welding method for Zn-plated steel sheets in which a Zn plating layer is formed on the surface of a base material, and includes a superposition step and a joining step.

  In the superimposing step, Zn plated steel plates formed by forming a Zn plating layer on the surface of the base material are overlapped. At this time, it is not necessary to strictly manage the gap between both Zn-plated steel sheets, and the gap can be about 0 to 0.8 mm. The kind of the steel plate in the Zn plated steel plate and the basis weight of the Zn plated layer are not particularly limited. The plating method for the Zn-plated steel sheet may be either hot dipping or electroplating.

  In the joining step, a predetermined portion of the overlapped portion of the Zn-plated steel plates is heated to form a molten pool in which both base materials are melted, and the base materials of both Zn-plated steel plates are integrated by cooling and solidifying the molten pool. To join.

In this joining process, as a means for heating a predetermined portion of the overlapped portion (portion that becomes a welded portion after welding) to melt both base materials, the entire base material of one of the Zn-plated steel plates overlapped in the heated portion was melted, and state, and are not capable of melting a part of the base material overall or base material of the other Zn-plated steel sheets, the degree of freedom of the weld line shape is high, excellent operability and controllability of the welding and have to use the laser heat.

That is, the method of lap fusion welding of a Zn-plated steel sheet according to the present invention includes irradiating a predetermined portion of the overlap portion with a laser beam in the joining step to melt both the base materials by laser heat , It is preferable to melt the filler material.

The type of the laser beam and the laser welding conditions are not particularly limited, and can be set as appropriate according to the type and thickness of the Zn-plated steel sheet. A YAG laser, a CO ₂ laser, or the like can be preferably used. However, in consideration of ease of operation and the like, it is more preferable to use a YAG laser than a CO ₂ laser.

  In the joining process using laser welding, the laser light source is moved in a substantially horizontal direction at a predetermined speed with respect to the plate surface of the overlapped portion of the Zn-plated steel plate, while being substantially perpendicular to the plate surface (the overlap direction). ) Is irradiated with a predetermined output laser beam. In the portion irradiated with the laser beam, both base materials of the superimposed Zn-plated steel sheets are melted by laser heat to form a molten pool.

  And in the lap fusion welding method of the Zn plating steel plate of this invention, a predetermined Fe-type filler material is mixed in the said molten pool by which the both base materials fuse | melted by the laser heat etc. by the said joining process.

  The aspect in which the Fe-based filler material is mixed into the molten pool is not particularly limited, and the Fe-based filler material in a solid state (solid phase) is added to the molten pool as it is, and the Fe-based filler material is melted by the heat of the molten pool. Or the Fe-based filler material may be added to the molten pool after being previously melted (liquid phase) by arc heat or the like. The base material may be melted almost simultaneously to mix them.

Further, when the base metal is melted using laser heat, the Fe-based filler material is welded to a predetermined position of the Zn-plated steel sheet (laser light is irradiated to become a welded portion) prior to laser light irradiation. May be preliminarily arranged on the line), or supplied to the laser beam irradiation point (welding point) or its vicinity (near the front or rear side of the laser beam moving direction) almost simultaneously with the laser beam irradiation. May be. The direction from which the Fe-based filler metal is supplied to the laser beam irradiation point (welding point) or the molten pool in the vicinity of the laser beam is also behind (laser beam moving direction) and forward (laser beam moving direction). Any of the front side and the side of the light moving direction may be used.

The Fe-based filler material is composed of Fe and at least one selected from the group of viscosity-decreasing metals consisting of Al, Si, and Mn , and the viscosity-reducing metal when the entire Fe-based filler material is 100%. In a content satisfying the above-mentioned formula (a). Al, Si, and Mn as viscosity-reducing metals are mixed into the molten pool of the base material of the Zn-plated steel sheet, thereby acting to lower the viscosity of the molten pool. The Fe-based filler material according to the present invention contains at least one of Al, Si, and Mn as the viscosity reducing metals. There are no particular limitations on the combination of the viscosity-reducing metals contained in this Fe-based filler material, and one of Al, Si, or Mn may be included alone, or two of Al and Si, Al and Mn, and These may be included, or two types of Si and Mn may be included, or all three types of Al, Si and Mn may be included.

  Here, as shown in FIG. 1, the relationship between the concentration of the additive metal added to the Fe alloy and the viscosity at 1550 ° C. of the molten binary Fe alloy to which the additive metal is added is Al, Mn, Si. It can be seen that the four kinds of Ni and Ni decrease the viscosity of the molten Fe alloy. Of these four types, Ni has a small effect on reducing the viscosity, so a considerable amount of addition is necessary, but this raises the melting point of the filler metal, so it cannot be melted in an appropriate amount. It was.

  In addition, the Fe-based filler material includes at least one selected from the group of viscosity-decreasing metals made of Al, Si, and Mn in a content that satisfies the formula (a). If the content of at least one of Al, Si, and Mn is too small to satisfy the above formula (a), the effect of reducing the viscosity of the molten pool becomes insufficient, such as blowholes caused by Zn vapor. It becomes difficult to effectively suppress welding defects.

  In such a lap fusion welding method of the Zn-plated steel sheet of the present invention, this molten metal is mixed with an Fe-based filler material containing at least one selected from the group of viscosity-reducing metals in a specific ratio. The properties of the pond change and the viscosity of the molten pool decreases. When the viscosity of the molten pool is lowered, Zn vapor easily moves in the molten pool. For this reason, Zn vapor generated by gasification of Zn in the Zn plating layer between the Zn plated steel sheets easily escapes from the plate surface through the molten pool. Therefore, it is possible to prevent the Zn vapor from being confined in the molten pool, or to be prevented from being blown out from the molten pool while the Zn vapor becomes high pressure in the molten pool and the base material is scattered. Defects can be effectively suppressed.

  Furthermore, since the fusion welding is performed while supplying the Fe-based filler material to the molten pool, it is not necessary to strictly manage the gap between both Zn-plated steel sheets in order to suppress welding defects such as blow holes due to Zn vapor. Work becomes easy. That is, according to the method of the present invention, even if the gap between both Zn-plated steel sheets is zero, welding defects such as blow holes due to Zn vapor can be effectively suppressed. Moreover, since the said molten pool can be replenished by supply of the said Fe type filler material, the clearance gap between both Zn plating steel plates will be over about 0.4 mm (for example, about 0.4-0.8 mm). Even when the size is increased, the gap can be filled by the replenishment with the Fe-based filler material, and welding failure due to melting or separation of the molten pools can be prevented.

The Fe-based filler material is composed of Fe and at least one selected from the group of viscosity-decreasing metals consisting of Al, Si, and Mn , and the viscosity-reducing metal when the entire Fe-based filler material is 100%. Is not particularly limited, for example, a mixed powder composed of Fe powder and at least one of Al powder, Si powder and Mn powder. It may be a powdered alloy material made of Fe alloy formed by alloying at least one of Al, Si and Mn with Fe, or a wire-like alloy material made of the same Fe alloy. Also good.

  However, when supplying the mixed powder consisting of Fe powder and at least one of Al powder, Si powder and Mn powder to the molten pool, the width of the molten pool is narrow or the powder is scattered during the supply. As a result, the material yield decreases, and it is not always easy to reliably supply the metal powder of the viscosity-reduced metal and the Fe-based powder to the molten pool at a specific ratio. On the other hand, in an alloy material made of the Fe alloy formed by alloying at least one of Al, Si and Mn with Fe, the Fe and the viscosity-reducing metal are reliably supplied to the molten pool at a specific ratio. However, there are the following drawbacks. That is, when the powdered alloy material made of the Fe alloy is supplied to the molten pool, the material yield decreases due to powder scattering during the supply, and when the powder is made from the Fe alloy ingot. There is a risk of cracking in the ingot or powdering process. Also, in the case of the wire-like alloy material made of the Fe alloy, it is not always easy to produce a thin wire shape from an ingot by drawing or the like, and there is a risk that it will break in the ingot state or break in the middle of the drawing process There is.

  Therefore, the form of the Fe-based filler material is preferably a cored wire made of an Fe-based outer shell and metal powder and / or alloy powder filled in the Fe-based outer shell. At this time, in the Fe-based outer shell, when the entire Fe-based filler material (cored wire) is 100%, at least one selected from the group of viscosity-decreasing metals consisting of Al, Si, and Mn is expressed by the formula (a). It may be filled with at least one metal powder selected from the group of viscosity-reducing metals (that is, at least one of Al powder, Si powder, and Mn powder) so as to include a content that satisfies, At least one of at least two alloy powders selected from the group of metals (that is, Al and Si alloy powder, Al and Mn alloy powder, Si and Mn alloy powder, and Al, Si and Mn Or at least one of these alloy powders, or both of these metal powders and alloy powders.

  As described above, the use of the cored wire formed by wrapping the metal powder or alloy powder of the viscosity-reducing metal with the Fe-based outer shell as the Fe-based filler material makes it easier to handle than the powder. The cored wire can be reliably and easily supplied to the molten pool or the laser beam irradiation section, and the supply amount can be easily controlled. For this reason, the material yield does not decrease. In addition, it is possible to reliably mix the Fe-based filler material containing the viscosity-reducing metal with a specific content represented by the formula (a) into the molten pool. Therefore, the viscosity of the molten pool can be surely lowered by this cored wire, and welding defects such as blow holes can be effectively suppressed.

  The outer diameter and thickness of the Fe-based outer sheath in the cored wire, and the average particle diameter of the metal powder and alloy powder can be set as appropriate.

Here, when using laser welding in which the base material is melted by laser heat, in the joining step, laser light is irradiated to a predetermined portion of the overlapping portion to melt both the base materials mainly by laser heat. At the same time, it is preferable to melt the Fe-based filler material by arc heat.

  In particular, when adopting the cored wire as the Fe-based filler material, in the joining step, a laser beam is irradiated to a predetermined portion of the overlapping portion to melt both the base materials mainly by laser heat, It is preferable that an arc is generated using the cored wire as a consumable electrode and the cored wire is melted by arc heat.

  The laser beam irradiation point (welding point) in laser welding is extremely small and the molten pool is narrow, so the Fe-based filler metal can be heated or melted due to misalignment of the Fe-based filler material such as cored wire. It becomes difficult to melt reliably by the heat of the pond. In this regard, both the base metal is melted mainly by laser heat by irradiating a predetermined portion of the overlapping portion with laser light, and the Fe-based filler material is melted by arc heat in combination with so-called arc welding. Then, even if there is a deviation or the like in the supply position of the Fe-based filler material, the Fe-based filler material can be reliably melted and mixed into the molten pool. In particular, arc welding using the cored wire as a consumable electrode also facilitates the operation, and can be reliably and easily supplied to the molten pool. Therefore, the viscosity of the molten pool can be reliably lowered by the Fe-based filler material, and welding defects such as blow holes can be effectively suppressed. In addition, if the Fe-based filler metal is melted by arc heat, part of the laser heat is not used for melting the Fe-based filler material, so that the laser output can be reduced and the cost can be reduced. It becomes possible to weld with.

  The type and conditions of the arc in the arc welding are not particularly limited as long as the Fe filler metal can be melted, and a MIG arc, a plasma arc, a TIG arc, or the like can be appropriately used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

[First embodiment]
In this embodiment, the Zn-plated steel sheet is laminated and welded using laser welding in which the base metal of the Zn-plated steel sheet and the Fe filler metal are melted by laser heat.

Example 1
As a Zn-plated steel sheet, a zinc-plated layer is formed on both the front and back surfaces of the base material (Zn basis weight is 45 g / m ² per side), and a hot-dip galvanized steel sheet having a thickness t = 0.8 mm (SCGA270-45 / 45 ) Was prepared.

  On the other hand, as an Fe-based filler material, as shown in the schematic cross-sectional view of FIG. 2, a cored wire 10 comprising a substantially cylindrical Fe-based outer shell 1 and a metal powder 2 filled in the Fe-based outer shell is prepared. did. The Fe-based outer skin 1 is made of pure Fe and has an outer diameter φ = 1.2 mm and a thickness t = 0.4 mm. The metal powder 2 is Al powder.

  The cored wire 10 contains Fe as a main component, and the cored wire 10 as a whole contains 100% of Al as a viscosity-reducing metal, and satisfies the formula (a). ing.

  The cored wire 10 was manufactured by bending an iron plate into a substantially cylindrical shape so as to wrap a predetermined amount of the metal powder 2.

<Overlay process>
Two pieces of the Zn-plated steel plates were superposed. At this time, the gap between both Zn-plated steel sheets was zero.

<Joint process>
A laser with a predetermined output from a substantially vertical direction (overlapping direction) with respect to the plate surface while moving the light source of the laser beam at a predetermined speed in a substantially horizontal direction with respect to the plate surface of the overlapped portion of the Zn-plated steel sheet. Light was irradiated onto a predetermined welding line that became a welded portion after laser welding, and a molten pool was formed in which the entire base materials of both of the Zn-plated steel sheets superimposed were melted in the heated portion irradiated with the laser light. At this time, the cored wire 10 was continuously supplied to the formed molten pool at a predetermined supply amount from the rear in the moving direction of the laser beam. Thus, laser welding was performed while continuously supplying the cored wire 10 in a solid state to the molten pool formed by laser light irradiation, thereby laminating both Zn-plated steel sheets and performing laser welding. The welding conditions at this time are as follows.

Laser light: YAG laser Laser output: 3.0 kW
Welding speed: 2.0 m / min
Supply rate of cored wire: 3.0 m / min
In this joining step, the cored wire 10 is supplied to the molten pool in a solid state, the cored wire 10 is melted by the heat of the molten pool, and the base metal molten metal of the molten pool and the molten metal of the cored wire 10 are mixed. did.

  Moreover, sufficient practical strength was ensured in the welded portion thus overlapped by laser welding.

(Example 2)
In this example, the cored wire 10 was manufactured using Al powder and Si powder as the metal powder 2.

  This cored wire 10 contains Fe as a main component, and when the entire cored wire 10 is 100%, it contains Al as a viscosity-reducing metal in a content of 0.5%, and contains Si as a viscosity-reducing metal at 5%. It is included in an amount and satisfies the formula (a).

  Other configurations were the same as in Example 1, and two Zn-plated steel plates were stacked and laser welded.

(Example 3)
In this example, the cored wire 10 was manufactured using Si powder and Mn powder as the metal powder 2.

  This cored wire 10 contains Fe as a main component and the cored wire 10 as a whole has a content of 5% of Si as a viscosity reducing metal and a content of 5% of Mn as a viscosity reducing metal. It is included and satisfies the formula (a).

  Other configurations were the same as in Example 1, and two Zn-plated steel plates were stacked and laser welded.

(Comparative Example 1)
Two bare steel plates (SPC270D, plate thickness t = 0.8 mm) on which no Zn plating layer was formed on the surface were prepared and overlapped. At this time, the gap between the two bare steel plates was zero.

Then, two bare steel plates were overlapped and laser welded in the same manner as in Example 1 except that the cored wire 10 was not supplied to the molten pool.

(Comparative Example 2)
Two Zn-plated steel sheets similar to those in Example 1 were prepared and overlapped. At this time, the gap between both Zn-plated steel sheets was zero.

  Then, two Zn-plated steel sheets were overlapped and laser-welded in the same manner as in Example 1 except that the cored wire 10 was not supplied to the molten pool.

(Comparative Example 3)
A cored wire was manufactured using Al powder as the metal powder 2.

  This cored wire contains Fe as a main component and 100% of the entire cored wire and contains Al as a viscosity-reducing metal in a content of 0.5%, and does not satisfy the formula (a).

  Other configurations were the same as in Example 1, and two Zn-plated steel plates were stacked and laser welded.

(Comparative Example 4)
A cored wire was manufactured using Al powder as the metal powder 2.

  This cored wire contains Fe as a main component and the entire cored wire as 100% and contains Al as a viscosity-reducing metal in a content of 1.0%, and does not satisfy the formula (a).

  Other configurations were the same as in Example 1, and two Zn-plated steel plates were stacked and laser welded.

(Comparative Example 5)
A cored wire was manufactured using Si powder as the metal powder 2.

  This cored wire contains Fe as a main component and the entire cored wire as 100%, and contains Si as a viscosity-reducing metal in a content of 5.0%, and does not satisfy the formula (a).

  Other configurations were the same as in Example 1, and two Zn-plated steel plates were stacked and laser welded.

(Comparative Example 6)
A cored wire was manufactured using Mn powder as the metal powder 2.

  This cored wire contains Fe as a main component and the whole cored wire is 100%, and contains Mn as a viscosity-reducing metal in a content of 5.0%, and does not satisfy the formula (a).

  Other configurations were the same as in Example 1, and two Zn-plated steel plates were stacked and laser welded.

(Evaluation based on weight loss)
In Examples 1 to 3 and Comparative Examples 1 to 6, the weight reduction amount (per 100 mm weld length) obtained by subtracting the post-weld weight from the pre-weld weight is obtained by the following equation (b), and the quality of the lap laser welding is determined. Evaluated. The results are shown in Table 1.

Weight reduction (g / 100 mm) = {weight before welding (g) + added weight of cored wire (g) −weight after welding (g)} × 100 (mm) / welding length (mm) (b)
The weight before welding is the total weight of the two steel plates before lap laser welding, and the weight after welding is the total weight after the two steel plates are overlapped and laser welded. The added weight of the cored wire is the weight of the cored wire added to the molten pool during the lap laser welding.

  Here, the smaller the value of the weight reduction amount, the smaller the amount of base metal scattered from the molten pool as spatter or the like, which means that good welding with fewer welding defects such as blow holes was performed.

  In Table 1, Examples 1, 2, and 3 are No. The comparative examples 1, 2, 3, 4, 5, 6 correspond to No. 5, 8, 9 respectively. 1, 2, 3, 4, 6, and 7 respectively.

表１から明らかなように、Ｎｏ．５の前記実施例１、Ｎｏ．８の前記実施例２及びＮｏ．９の前記実施例３では、いずれも重量減少量が０．１２ｇ／１００ｍｍ以下で、ブローホール等の溶接欠陥の少ない良好な溶接が行われていた。特に、Ｎｏ．５の前記実施例１及びＮｏ．８の前記実施例２では、いずれも重量減少量が０．１ｇ／１００ｍｍ以下で、ブローホール等の溶接欠陥が極少ない極めて良好な溶接が行われていた。なお、本発明者の調査により、この重量減少量が０．１２ｇ／１００ｍｍ以下であれば、少量のブローホール等の欠陥が多少認められるが、実用上問題ないことがわかっている。

As is apparent from Table 1, No. 5 in Example 1, No. 5; No. 8 in Example 2 and No. 8 above. In Example 3 of No. 9, good welding was performed with a weight loss of 0.12 g / 100 mm or less and few welding defects such as blow holes. In particular, no. 5 in Example 1 and No. 5 above. In Example 2 of No. 8, the weight loss was 0.1 g / 100 mm or less, and extremely good welding was performed with very few welding defects such as blow holes. According to the investigation by the present inventor, it is known that if the weight loss is 0.12 g / 100 mm or less, a small amount of defects such as blowholes are recognized, but there is no practical problem.

  On the other hand, No. 1 in which laser welding was performed without supplying the cored wire 10. In Comparative Example 2 of 2, the amount of weight reduction was as large as 0.55 g / 100 mm, and welding defects such as blow holes were extremely generated.

  In addition, No. 1 using a cored wire containing one of Al, Si and Mn as a viscosity-reducing metal in a range not satisfying the formula (a). In all of Comparative Examples 3, 4, 5, and 6 of 3, 4, 6, and 7, the weight loss amount was as large as 0.13 g / 100 mm or more, and many welding defects such as blow holes were generated.

  In addition, No. 1 was obtained by laser welding the bare steel plates without supplying a cored wire. In Comparative Example 1 of 1, almost no spatter was generated, but a weight reduction amount of 0.05 g / 100 mm was recognized by the amount of the evaporated metal and the molten metal that escaped to the back side.

(Correlation between content of viscosity-reducing metal and weight loss in Fe filler metal)
No. 1 obtained by laser welding the Zn-plated steel sheets shown in Table 1 above. As for the results of Nos. 2 to 9, laser welding was performed without adding a cored wire as an Fe-based filler material. The correlation between the content of the viscosity-reducing metal and the weight loss in the Fe filler metal was investigated by performing multivariate analysis by multiple regression analysis with the content of each viscosity-reducing metal in 2 as 0%.

In this multiple regression analysis, no. For 8 specimens (n = 8) of 2 to 9, the Al content, the Si content, and the Mn content are set as explanatory variables x ₁ , x _2, and x ₃ , respectively, and the weight loss is set as a target variable y. Then, a multiple regression prediction formula of the following formula (c) representing the correlation between the explanatory variables (x ₁ , x ₂ , x ₃ ) and the objective variable (y) is considered, and the actual sample data and the multiple regression prediction formula (c) Let the difference from the value represented by the following equation be the residual ε, and the multiple regression equation is the following equation (d). When attention is paid to the residual ε in the following formula (c) and the following formula (d), the residual ε is expressed by the following formula (e). Therefore, the residual sum of squares Σ (ε _i is expressed by the following formula (f). ² )

Y _i = b ₁ · x _1i + b ₂ · x _2i + b ₃ · x _3i + b ₀ (c)
_{y i = b 1 · x 1i} + b 2 · x 2i + b 3 · x 3i + b 0 + ε i ... (d)
ε _i = y _i −Y _{i
= Y i - (b 1 ·} x 1i + b 2 · x 2i + b 3 · x 3i + b 0) ... (e)
^{_{Σ (ε i) 2 = Σ}} (y i -b 1 · x 1i -b 2 · x 2i -b 3 · x 3i -b 0) 2 ... (f)
Then, by calculating b ₀ , b ₁ , b ₂ , and b ₃ that minimize the residual sum of squares Σ (ε _i ) ² of the above equation (f), multiple regression shown by the above equation (d) is obtained. The formula can be obtained.

That is,
_{f = Σ (y i -b 1} · x 1i -b 2 · x 2i -b 3 · x 3i -b 0) 2 ... (g)
Then, 上 記 f / ∂b ₀ , ∂f / ∂b ₁ , ∂f / ∂b ₂ , ∂f / ∂ obtained by partial differentiation of the above equation (g) with b ₀ , b ₁ , b ₂ , and b _3. By setting b ₃ and ∂f / ∂b ₀ to 0, four normal equations represented by the following equations (h) to (k) can be obtained.

_{Σ (y i -b 1 · x} 1i -b 2 · x 2i -b 3 · x 3i -b 0) = 0 ... (h)
_{Σx 1i (y i -b 1 ·} x 1i -b 2 · x 2i -b 3 · x 3i -b 0) = 0 ... (i)
_{Σx 2i (y i -b 1 ·} x 1i -b 2 · x 2i -b 3 · x 3i -b 0) = 0 ... (j)
_{Σx 3i (y i -b 1 ·} x 1i -b 2 · x 2i -b 3 · x 3i -b 0) = 0 ... (k)
Therefore, by solving these simultaneous equations, b ₀ , b ₁ , b ₂ , b ₃ that minimize the residual sum of squares Σ (ε _i ) ² expressed by the above equation (g), that is, the above equation (f). And the multiple regression equation represented by the above equation (d) can be obtained.

  And by the multivariate analysis by such multiple regression analysis, the multiple regression formula shown by the following (1) formula was able to be obtained.

y _i = −0.27x _1i −0.044x _2i −0.035x _3i +0.44 (l)
Therefore, it was found that there is a correlation represented by the following equation (m) between the Al content, the Si content, the Mn content, and the weight loss in the cored wire.

Weight reduction = −0.27Al−0.044Si−0.035Mn + 0.44 (m)
Here, as described above, there is no practical problem if the weight reduction amount is 0.12 g / 100 mm or less, and if the weight reduction amount is 0.10 g / 100 mm or less, there are very few welding defects such as blow holes. Can be welded. For this reason, it has been confirmed that welding defects such as blow holes can be effectively prevented as long as the following expression (a) is satisfied.
0.27 Al (%) + 0.044 Si (%) + 0.035 Mn (%) ≧ 0.32 (a)
(Comparative Example 7)
An Fe-based wire made of an Fe alloy having an outer diameter of φ = 1.2 mm and an alloy composition of Fe-0.35Si-1.5Mn was prepared.

  Note that this Fe-based wire does not satisfy the formula (a).

  Then, two Zn-plated steel plates were overlapped and laser-welded in the same manner as in Example 1 except that the Fe-based wire was used instead of the cored wire 10.

(Evaluation of appearance after welding)
For the Example 3, Comparative Example 2 and Comparative Example 7, external appearance photographs of the welded part after lap laser welding as seen from the laser irradiation side are shown in FIG. 3, FIG. 4 and FIG.

  The welded part of Example 3 in which the laser welding was performed while supplying the cored wire 10 was good without any appearance defect. On the other hand, the welded portion of Comparative Example 2 in which the lap laser welding was performed without supplying the cored wire 10 and the Comparative Example 7 in which the lap laser welding was performed while supplying the Fe-based wire was made by a blow hole or the like. The rough bead was terrible.

[Second Embodiment]
Example 4
In this embodiment, laser welding in which a base material of a Zn-plated steel sheet is mainly melted by laser heat, an arc is generated using the cored wire 10 as an Fe-based filler material as a consumable electrode, and the cored wire 10 is melted by arc heat. This is a combination of arc welding.

  A Zn-plated steel plate and a cored wire 10 similar to those in Example 1 were prepared.

<Overlay process>
Two pieces of the Zn-plated steel plates were superposed. At this time, the gap between both Zn-plated steel sheets was zero.

<Joint process>
A laser with a predetermined output from a substantially vertical direction (overlapping direction) with respect to the plate surface while moving the light source of the laser beam at a predetermined speed in a substantially horizontal direction with respect to the plate surface of the overlapped portion of the Zn-plated steel sheet. Light was irradiated onto a predetermined welding line that became a welded portion after laser welding, and a molten pool was formed in which the entire base materials of both of the Zn-plated steel sheets superimposed were melted in the heated portion irradiated with the laser light. At this time, both the Zn-plated steel plates were overlapped and laser-welded by a MIG arc while the cored wire 10 was continuously supplied from the rear of the laser beam moving direction to the formed molten pool at a predetermined supply amount. The welding conditions at this time are as follows.

Laser light: YAG laser Laser output: 2.0 kW
Welding speed: 2.0 m / min
Supply rate of cored wire: 3.0 m / min
Arc current: 100A
Arc voltage: 20V
In this joining step, the cored wire 10 is completely melted by the arc heat and the base material surface of one of the Zn-plated steel plates is partially melted, and both the base materials of the two Zn-plated steel plates are laser-heated. When the core wire 10 is completely melted, the cored wire 10 is mixed in a molten pool in which both base materials are melted.

  For this reason, even if the supply position of the cored wire 10 is misaligned, the cored wire 10 can be reliably melted and mixed into the molten pool, and the molten pool can be reliably reduced in viscosity by the cored wire 10. Is possible. Therefore, also according to the present embodiment, weld defects such as blow holes can be effectively suppressed to the same extent as in the first embodiment or more.

  Further, since the cored wire 10 is melted by the arc heat, the laser output can be suppressed and the welding can be performed at a lower cost because a part of the laser heat is not used for melting the cored wire. .

(Other examples)
In the above-described embodiment, an example of so-called keyhole welding (back wave welding) in which a molten pool is formed by melting the entire base materials of both of the Zn-plated steel plates stacked in the heating unit has been described. When melting the entire base material of one of the two Zn-plated steel sheets and partially melting the other base material (part of the overlapping surface side) to form a molten pool In addition, the present invention can be applied.

It is a diagram which shows the relationship between the density | concentration of the addition metal added to Fe alloy, and the viscosity in 1550 degreeC of the fusion | melting binary Fe alloy to which the addition metal was added. It is sectional drawing which shows typically the cored wire as Fe-type filler material which concerns on Example 1. FIG. 6 is a photograph showing an appearance of a welded part of Example 3. 6 is a photograph showing an appearance of a welded portion of Comparative Example 2. 10 is a photograph showing the appearance of a welded portion of Comparative Example 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fe-type outer skin 2 ... Metal powder 10 ... Cored wire (Fe-type filler material)

Claims (6)

A superposition process for superimposing Zn-plated steel sheets formed by forming a Zn-plated layer on the surface of the base material, and irradiating a laser beam from a direction substantially perpendicular to the surface of the Zn-plated steel sheet to a predetermined portion of the superposed portion. Then, both the base materials are heated by laser heat to form a molten pool in which both the base materials are melted, and the base materials of both the Zn-plated steel sheets are integrally joined by cooling and solidifying the molten pool. A joining process,
In the joining step, an Fe-based filler material consisting of Fe and at least one selected from the group of viscosity-decreasing metals consisting of Al, Si and Mn is mixed in the molten pool,
The Fe-based filler material includes the viscosity-reducing metal in a content satisfying the following formula (a) when the entire Fe-based filler material is taken as 100%. .
0.27 Al (%) + 0.044 Si (%) + 0.035 Mn (%) ≧ 0.32
... (a) The Fe-based filler material is composed of a Fe-based outer sheath and a cored wire composed of a metal powder and / or an alloy powder filled in the Fe-based outer shell,
The metal powder is at least one metal powder selected from the group of viscosity reducing metals, and the alloy powder is at least one of alloy powders of at least two selected from the group of viscosity reducing metals. The lap fusion welding method for Zn-plated steel sheet according to claim 1.   3. The Zn plating according to claim 1, wherein in the joining step, a laser beam is irradiated to a predetermined portion of the overlapping portion, and both the base material and the Fe-based filler material are melted by laser heat. Steel sheet lap fusion welding method.   In the joining step, a laser beam is irradiated to a predetermined portion of the overlapping portion to melt both the base materials mainly by laser heat, and the Fe-based filler material is melted by arc heat. The lap fusion welding method for Zn-plated steel sheets according to claim 1.   In the joining process, a laser beam is irradiated to a predetermined portion of the overlapping portion to melt both the base materials mainly by laser heat, and an arc is generated using the cored wire as a consumable electrode, and the cored wire is melted by arc heat. The lap fusion welding method for Zn-plated steel sheet according to claim 2, wherein: A laser beam is irradiated from a direction substantially perpendicular to the plate surface of the Zn-plated steel sheet to a predetermined portion of the overlapped portion of the Zn-plated steel sheets formed by forming a Zn-plated layer on the surface of the base material, and both the mothers are irradiated by laser heat. A lap-melt welding method for Zn-plated steel sheets, in which the base materials of both Zn-plated steel sheets are joined together by heating the material to form a molten pool in which both the base materials are melted and cooling and solidifying the molten pool Fe-based filler material used for
The Fe-based filler material comprises Fe and at least one selected from the group of viscosity-decreasing metals consisting of Al, Si and Mn,
The Fe-based filler material includes the Fe-based outer shell and the Fe-based outer shell so that the viscosity-reducing metal is contained in a content satisfying the following formula (a) when the entire Fe-based filler material is 100%. An Fe-based filler material comprising a cored wire made of metal powder and / or alloy powder filled in a metal.
0.27 Al (%) + 0.044 Si (%) + 0.035 Mn (%) ≧ 0.32
... (a)

Images