JP2006150439A - Steel material-aluminum material welded joint, and welding method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steel material-aluminum material welded joint whose fabrication is easy, and which has high joint strength, and to provide an arc welding method capable of easily producing the same. <P>SOLUTION: Voids 4 are formed beforehand on the side of a steel material 2 along a weld line, said voids 4 are filled with molten aluminum welding material, so as to form a solidified aluminum weld 7. The lower end portion of the aluminum weld 7 melts in the surface layer of said aluminum material 3, and the upper end portion thereof melts and is joined to a weld bead 5 formed over the surface of said steel material 2. When the thickness of said aluminum material 3 is defined as Ta, the maximum melt-in depth of said aluminum material as D, the average thickness of said weld bead 5 on said weld line as Tb, and the circle-equivalent radius of said voids 4 as R, the value D/Ta is not less than 0.10 and the value Tb/R is not less than 0.50. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention mainly welds steel materials and aluminum materials in structures such as roofs, interiors, curtain walls, etc., equipment, electrical parts, optical equipment, transportation equipment such as automobiles, railway vehicles and aircraft, and general machine parts. The present invention relates to a welded joint and a welding method thereof.

In order to reduce the weight of various structures, it may be necessary to join a steel plate and a plate material of pure aluminum or various aluminum alloys (hereinafter simply referred to as “aluminum plate” in the present invention). .
When such joining is performed, brittle intermetallic compounds that deteriorate joint strength are likely to be generated at the joint, so that vacuum rolling joining or between steel sheets and aluminum plates should be avoided so as not to generate such intermetallic compounds. Although a method of seam welding with a two-layer clad plate joined with these materials is proposed, the work is generally complicated, new equipment needs to be introduced, and there is a lack of versatility. is there.

On the other hand, in order to use a versatile welding method, in the following Non-Patent Documents 1 and 2, one through hole is provided in advance on the side of the steel plate to be joined, and this hole is filled with a molten aluminum material. Has proposed a method of joining a steel plate and an aluminum plate. Patent Document 1 below proposes a method of directly MIG brazing a steel plate and an aluminum plate using a Cu alloy, Ni alloy, or Si bronze Cu alloy wire.
JP 2003-33865 A WELDING JOURNAL, (1963), p. 302 Light metal welding: Vol.16 (1978) No.12, p.8

The technologies of Non-Patent Documents 1 and 2 and Patent Document 1 are excellent in workability and do not require special equipment, and are therefore versatile. However, Non-Patent Documents 1 and 2 are technically established. However, it is difficult to say that this is the case, and sufficient bonding strength is not obtained with any of the techniques, and there is still room for improvement.
The present invention has been made in view of such problems, and an object thereof is to provide a steel-aluminum weld joint that is easy to construct and has high joint strength, and an arc welding method for manufacturing the weld joint.

  As a result of closely observing the portion where the aluminum welding material is melt-filled in the through hole of the steel plate and the solidified aluminum joint is melt-joined to the aluminum plate, the inventor simply welded the aluminum joint to the aluminum plate. In some cases, sufficient bonding strength may not be exhibited, and when the thickness of the weld bead coated on the surface of the steel plate is too small compared to the diameter of the through hole, it may be melt bonded to the aluminum bonded portion. It was found that the weld bead fractured in the thickness direction (plate thickness direction), and sufficient bonding strength could not be obtained. Based on these findings, the present inventor has a maximum penetration depth D in which the aluminum joint has melted into the surface of the aluminum plate so that the aluminum joint filled in the through hole can function as an original rivet. The relationship between the average thickness Tb of the weld bead coated on the surface of the steel plate, the thickness Ta of the aluminum plate, and the circle equivalent radius R of the through hole is clarified, and the aluminum joint has a sufficient rivet function. In this way, excellent bonding strength is realized.

  That is, the steel-aluminum welded joint of the present invention is a welded joint having an overlapped portion in which a steel plate and an aluminum plate are overlapped, and the overlapped portion is joined by arc welding along a weld line, The steel plate is provided with a plurality of through-holes along a weld line, and an aluminum joint is formed by melting and filling aluminum welding material in the through-hole, and the lower end of the aluminum joint has a through-hole. It melts into the surface of the aluminum plate exposed in the hole, and its upper end is melt-bonded to a weld bead coated on the surface of the steel plate, the thickness of the aluminum plate is Ta, and the aluminum joint is the surface of the aluminum plate When the maximum penetration depth dissolved in D is D, the average thickness at the weld line of the weld bead is Tb, and the equivalent circle radius of the through hole is R, / Ta of 0.10 or more, in which the Tb / R is 0.50 or more.

  As the steel sheet, a hot dip galvanized steel sheet may be used. In this case, the aluminum welding material preferably contains 2.0 to 6.0 mass% of Mg. When a hot dip galvanized steel sheet is used as a counterpart material for an aluminum plate, zinc vapor is generated during welding and is ejected from the opening of the through hole, so that it is difficult to fill and form the aluminum joint. By using the aluminum welding material containing a predetermined amount of Mg, not only the strength of the aluminum welding material is improved, but also the arc is shortened and stabilized, and the adverse effect of the zinc vapor can be prevented. For this reason, the filling formation of the aluminum joint portion in the through hole is facilitated, and the joining strength is easily secured.

In the steel-aluminum welding method of the present invention, an aluminum plate is overlaid on a steel plate in which a plurality of through holes are formed along a weld line so as to close the through hole, and aluminum welding is performed on the through hole along the weld line. A steel-aluminum welding method in which a weld bead is coated on the surface of the steel plate along the weld line by arc welding with an AC power source or a DC power source while melting and filling a wire, and the heat input of arc welding is expressed by the following equation: The welding is performed so as to satisfy the following formula, where Q (kJ / cm) and the thickness of the aluminum plate are Ta (mm) as defined in the above.
Q (kJ / cm) = 60 (s / min) x welding current (A) x welding voltage (V) / welding speed (cm / min) / 1000
Ta / 3.5 ≦ Q ≦ Ta / 1.4 (for AC power supply)
Ta / 1.5 ≦ Q ≦ Ta / 0.7 (DC power supply)

  By this welding method, the steel-aluminum weld joint can be easily manufactured. In this welding method, when a hot dip galvanized steel sheet is used as the steel sheet, the aluminum welding wire preferably contains 2.0 to 6.0 mass% Mg. Thereby, the arc is short and stable, the arc disturbance due to the zinc vapor blown from the opening of the through hole can be suppressed, and the aluminum joint can be easily filled and formed in the through hole.

  According to the steel-aluminum welded joint of the present invention, the maximum penetration depth D of the aluminum joint formed by melting and filling the through hole of the steel sheet into the aluminum plate, and melt-joined to the aluminum joint, The average thickness Tb of the weld bead formed on the surface of the plate is D / Ta of 0.10 or more and Tb / R of 0.50 or more with respect to the plate thickness Ta of the aluminum plate and the equivalent circle radius R of the through hole. As a result, the aluminum bonded portion performs the original rivet function, and an excellent bonding strength can be obtained. Moreover, according to the welding method of the present invention, the weld joint can be easily manufactured.

  FIGS. 1A and 1B are a plan view of a steel-aluminum welded joint (hereinafter, simply referred to as “welded joint”) 1 showing an embodiment of the present invention and a cross-sectional side view taken along a weld line. Indicates. In this welded joint, the steel plate 2 that is the upper plate and the aluminum plate 3 that is the lower plate are overlapped and joined by arc welding along the weld line 6. A weld bead 5 formed by melting and solidifying an aluminum welding material supplied from an aluminum welding wire or the like along the welding line 6 is formed on the surface of the joint portion of the steel plate 2.

  The steel plate 2 is provided with a plurality of through holes 4 at predetermined intervals along the weld line 6. The through holes 4 are supplied from an aluminum welding wire or the like at the time of welding joining. The aluminum joint 7 is formed by melting and filling the aluminum welding material.

  As the steel plate 2, a steel plate or a steel plate such as plain steel or high-tensile steel (high ten) can be used, and a hot-dip galvanized steel plate obtained by subjecting these steel plates to hot dip galvanization can also be used. The steel plate is not limited to a flat shape, but may be a curved shape having an appropriate round shape. The aluminum plate 3 is a plate material formed of pure aluminum or an aluminum alloy, and is not limited to a flat shape, but may be a curved shape, like the steel plate shape.

  Moreover, as an aluminum welding wire used as the origin which forms the said aluminum junction part and a weld bead, a well-known Al-Si type | system | group wire and an Al-Mg type | system | group wire can be used. Specifically, various types defined by JIS can be used. For example, A4043-WY and A4047-WY can be used as the Al—Si-based wire, and A5554-WY, A5356-WY, and A5183-WY can be used as the Al—Mg-based wire.

However, the Al—Mg-based wire is preferable because the strength of the aluminum material is higher than that of the Al—Si-based wire, and the arc is short and has a strong stabilizing effect. For this reason, even when using a hot dip galvanized steel plate as a steel plate, it can be used conveniently. When welding is performed using a hot dip galvanized steel sheet, zinc vapor is ejected from the opening of the through hole 4 during welding, and when an Al—Si based wire is used, the arc is likely to become unstable, and aluminum is formed in the through hole 4. Although it is difficult to fill and form the joint 7, the Al—Mg-based wire containing Mg is preferable because it has a short arc and stabilizes, and does not have the above-described disadvantages.
The Al—Mg-based wire is preferable because the weld bead 5 hardly breaks. Since aluminum and steel have different heat shrinkage during welding and cooling, tensile stress is generated in the weld bead during welding. For this reason, the strength of the aluminum welding material forming the weld bead is lower, and the larger the amount of thermal shrinkage, the easier the bead cracking occurs. Since the Al—Mg-based wire has higher material strength than the Al—Si-based wire, it is difficult for the weld bead 5 to crack. For this reason, there exists an advantage that the fall of the fatigue strength of the welded joint by bead cracking can be prevented, without impairing the external appearance of a welded joint.
If the amount of Mg in the Al—Mg-based wire is less than 2.0%, the above actions are insufficient. On the other hand, if it exceeds 6.0%, the weldability of the wire is deteriorated (smut is generated) and the corrosion resistance is also lowered. To come. For this reason, the lower limit of the Mg content should be 2.0%, preferably 2.5%, and the upper limit should be 6.0%, preferably 5.5%.

  As shown in FIG. 2, the through hole 4 of the steel plate 2 is filled with an aluminum joint 7, but the lower end of the aluminum plate 3 is melted into the surface exposed to the through hole 4. The melt-bonded portion is formed from the lower end edge of the inner surface of the through hole 4 to the maximum depth portion of the center portion (the maximum melt depth is D). The upper end of the aluminum joint 7 is welded and integrated with a weld bead 5 that is coated on the surface of the steel plate 2 along the weld line. The distance from the upper surface of the steel plate 1 to the upper surface of the weld bead 5 along the weld line 6 is called bead thickness, and the average thickness is represented by Tb. The weld bead 5, the aluminum joint portion 7 and the penetration portion are portions integrally formed by the supplied aluminum welding material by melting the welding wire.

  In the present invention, when the thickness of the aluminum plate 3 is Ta, D / Ta is set to 0.10 or more. As will be apparent from the examples described later, when the ratio is less than 0.10, the aluminum weld material is less likely to be melted into the aluminum plate 3, and the aluminum joint portion 7 is easily broken along the interface of the melted portion, thereby obtaining sufficient joint strength. I can't. For this reason, the lower limit of D / Ta is set to 0.10, preferably 0.40.

The planar shape of the through hole 4 is circular in the illustrated example, but is not particularly limited. However, a polygon with an obtuse angle is preferable to a triangle or quadrangle having an acute angle or a right angle that tends to be a stress concentration end, and a rounded shape such as a circle or an ellipse with no corners is most preferable. preferable. In order to uniformly represent the inner diameter sizes of these hole shapes, a circular radius having an area equal to the area of the cross section of the through hole is referred to as “circle equivalent radius” R.
In the present invention, Tb / R is 0.50 or more. If it is less than 0.50, the weld bead 5 is broken, and the weld bead 5 and the aluminum joint 7 do not function as rivets. For this reason, the lower limit of Tb / R is set to 0.50, preferably 0.70. In addition, when a penetration part becomes large, the molten aluminum welding material will penetrate the aluminum plate 3, will spread on a back surface, and a welding bead 5 will not be formed. For this reason, it is not necessary to specifically define the upper limit of D / Ta, and it is sufficient to define the lower limit of Tb / R.

  In addition, regarding the arrangement of the through holes 4, when the length of the steel plate portion between the through holes 4 along the weld line 6 is L (see FIG. 2), the value of 2R / L is 0. It is good to arrange so that it may become 5-7, preferably about 1-5. Thereby, the penetration of Fe from the steel sheet into the aluminum welding material can be suppressed, and the ductility deterioration of the aluminum joint and the weld bead can be prevented. The weld line 6 may be a straight line or a curved line.

Next, the manufacturing method of the said welded joint is demonstrated with reference to FIG.
The weld joint moves the welding torch 11 together with the aluminum welding wire 10 in the direction of the arrow along the weld line 6 at the portion where the steel plate 2 as the upper plate and the aluminum plate 3 as the lower plate are overlapped. However, it is manufactured by arc welding while forming the weld bead 5.

  Through holes 4 are provided in the steel plate 2 along the weld line 6 at a predetermined interval. In FIG. 2, the left two through holes 4 are not melt-filled with aluminum welding material. On the right side, the aluminum welded material supplied from the aluminum welding wire is melt-filled to form a solidified aluminum joint 7. In order to melt and solidify the aluminum welding material in the through-hole 4, it is necessary to perform arc welding with the steel plate 2 as the upper side and the aluminum plate as the lower side.

The welding conditions for producing the above welded joint satisfy the following formula when the heat input of arc welding is defined as Q (kJ / cm) defined by the following formula and the thickness of the aluminum plate is Ta (mm). The welding current, welding voltage, and welding speed may be controlled.
Q (kJ / cm) = 60 (s / min) x welding current (A) x welding voltage (V) / welding speed (cm / min) / 1000
Ta / 3.5 ≦ Q ≦ Ta / 1.4 (for AC power supply)
Ta / 1.5 ≦ Q ≦ Ta / 0.7 (DC power supply)
As will be apparent from the examples described later, when Q is less than Ta / 3.5 (in the case of an AC power supply) or less than Ta / 1.5 (in the case of a DC power supply), the aluminum joint does not melt into the aluminum plate. Necessary, and if Ta / 1.4 (in the case of AC power supply) or Ta / 0.7 (in the case of DC power supply) is exceeded, the penetration becomes excessive, and if it is remarkable, it will flow through the aluminum plate. The bead thickness cannot be secured. By controlling the amount of heat input within the above range, the conditions that the D / Ta is 0.10 or more and the Tb / R is 0.50 or more are satisfied, and the aluminum joint has the original rivet function. It will come out and an excellent bonding strength can be obtained.

Preferable arc welding conditions for carrying out the present invention are as follows on the premise that the above heat input requirements are satisfied.
Welding current: In the case of an AC power supply, it is 60 A or more, more preferably 70 A or more, 100 A or less, more preferably 90 A or less. On the other hand, in the case of a DC power supply, it is 60 A or more, more preferably 70 A or more, 140 A or less, more preferably 130 A or less.
Welding voltage: In the case of an AC power supply, it is 10 V or higher, more preferably 11 V or higher, 15 V or lower, more preferably 14 V or lower. On the other hand, in the case of a DC power supply, it is 13 V or higher, more preferably 14 V or higher, 19 V or lower, more preferably 18 V or lower.
Welding speed: 20 cm / min or more, more preferably 30 cm / min or more, 120 cm / min or less, more preferably 100 cm / min or less in either case of AC power supply or DC power supply.
Shielding gas: General-purpose gas such as Ar can be used as appropriate, and a general-purpose flow rate can be selected as the gas flow rate, and there is no particular limitation.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated more concretely, this invention is not limitedly interpreted by this Example.

Steel sheets shown in Table 1 below ("GA" in the type means hot-dip galvanized steel sheets), aluminum plates, and various aluminum welding wires, and arcs from AC power sources under various heat input conditions Welding was performed to produce a welded joint. The steel plate used was a circular hole having a diameter (2R, R: equivalent circle radius) shown in the same table, which was previously opened at intervals shown in the same table (hole center interval). Further, Ar (flow rate: 20 to 25 L / min) was used as a shielding gas for arc welding. The angle of the welding torch was 80 °.
In addition, the amount of Mg of the used aluminum welding wire is as follows.
A4043WY: 0.05% or less, A5183WY: 4.3-5.2%, A5356WY: 4.5-5.5%, A5554WY: 2.4-3.2%

The obtained welded joint was visually observed for the presence or absence of bead cracks, and the joint strength was examined. The evaluation of bead cracking was evaluated as “A” when there was no crack at all, “B” when the number of cracks per 100 mm of the weld line was 2 or less, and “B” when 3 or more. When the number of cracks is 2 or less, there is no practical problem.
The joint strength was obtained by counting the number of rivets (aluminum joints) of the fractured pieces after the tensile test of each sample (test piece), calculating the joint area for each sample, and dividing the fracture load by that value. The results are shown in Table 2. Table 2 also shows the objects to be joined.

  As is apparent from Tables 1 and 2, in the case of an AC power supply, the welding conditions (heat input Q) satisfy Ta / 3.5 ≦ Q ≦ Ta / 1.4 (Ta: thickness of aluminum plate mm). Sample Nos. 1 to 20 (invention examples) all have Tb / R of 0.50 or more, D / Ta of 0.10 or more, excellent bonding strength of 90 MPa or more, and bead cracking. There is almost no, and an excellent welded joint is obtained.

  On the other hand, sample Nos. 21 to 26, 29 and 30 in which the heat input Q does not satisfy the predetermined condition are such that Tb / R or D / Ta is outside the conditions of the present invention, and the bonding strength is at most 80 MPa. It stopped to the extent. Sample Nos. 27 and 28 using a hot dip galvanized steel sheet as the target steel sheet used Al-Si A4043WY containing almost no Mg as the welding wire. Steam was blown out, filling the through holes with aluminum welding material and forming weld beads was insufficient, and the bonding strength was also low.

  Steel sheets shown in Table 3 below ("GA" in the type means hot-dip galvanized steel sheets), aluminum plates, and various aluminum welding wires, and various types of arc welding with a DC power source under various heat input conditions. Welding was performed to produce a welded joint. The steel plate used was a circular hole having a diameter (2R, R: equivalent circle radius) shown in the same table, which was previously opened at intervals shown in the same table (hole center interval). Further, Ar (flow rate: 20 to 25 L / min) was used as a shielding gas for arc welding. The angle of the welding torch was 80 °.

  As in Example 1, the obtained welded joint was evaluated by visually observing and evaluating the presence or absence of bead cracks, and the bonding strength was examined. The results are shown in Table 4.

  As is clear from Tables 3 and 4, in the case of a DC power supply, the welding conditions (heat input Q) satisfy Ta / 1.5 ≦ Q ≦ Ta / 0.7 (Ta: thickness of aluminum plate mm). Samples Nos. 31 to 41 (invention examples) all have Tb / R of 0.50 or more, D / Ta of 0.10 or more, excellent bonding strength of 90 MPa or more, and bead cracking. Excellent weld joints are obtained.

  On the other hand, Sample Nos. 42 to 47 whose heat input Q does not satisfy the predetermined condition are such that Tb / R or D / Ta is outside the conditions of the present invention, and the bonding strength is at most about 74 MPa, Some cracks were also observed in the weld bead.

It is the (A) top view and (B) cross-sectional side view of the steel-aluminum weld joint concerning embodiment of this invention. It is a principal part cross-sectional enlarged view in the cross section along the weld line of FIG. It is sectional explanatory drawing which shows the arc welding point of the welded joint of this invention.

Explanation of symbols

1: Steel-aluminum welded joint 2: Steel plate 3: Aluminum plate 4: Through hole 5: Weld bead 6: Weld line 7: Aluminum joint

Claims (5)

A steel-aluminum welded joint having a superposed portion obtained by superimposing a steel plate and an aluminum plate, and joining the superposed portion by arc welding along a weld line,
The steel sheet is provided with a plurality of through holes along the weld line,
In the through hole, an aluminum joint is formed by melting and filling the aluminum welding material,
The aluminum joint is melted and joined to a weld bead whose upper end is coated on the surface of the steel sheet, the lower end melts into the surface of the aluminum plate exposed in the through-hole,
The thickness of the aluminum plate is Ta, the maximum penetration depth at which the aluminum joint has melted into the surface of the aluminum plate is D, the average thickness at the weld line of the weld bead is Tb, and the equivalent circle radius of the through hole is R. Steel / aluminum welded joint in which D / Ta is 0.10 or more and Tb / R is 0.50 or more.   The steel-aluminum welded joint according to claim 1, wherein the steel plate is a hot-dip galvanized steel plate, and the aluminum welding material contains 2.0 to 6.0 mass% of Mg. An aluminum plate is overlaid on a steel plate in which a plurality of through holes are formed along the weld line so as to block the through hole, and an aluminum welding wire is melt-filled into the through hole along the weld line while the steel plate is melted and filled. A steel-aluminum welding method for forming a weld bead on the surface along the weld line by arc welding with an AC power source,
Satisfying Ta / 3.5 ≦ Q ≦ Ta / 1.4, where Q (kJ / cm) is the heat input for arc welding and Ta (mm) is the aluminum plate thickness. Steel-aluminum welding method for welding.
Q (kJ / cm) = 60 (s / min) x welding current (A) x welding voltage (V) / welding speed (cm / min) / 1000 An aluminum plate is overlaid on a steel plate in which a plurality of through holes are formed along the weld line so as to block the through hole, and an aluminum welding wire is melt-filled into the through hole along the weld line while the steel plate is melted and filled. A steel-aluminum welding method in which a weld bead is formed on a surface along the weld line by arc welding with a DC power source,
Satisfying Ta / 1.5 ≦ Q ≦ Ta / 0.7, where Q (kJ / cm) is the heat input for arc welding and Ta (mm) is the aluminum plate thickness. Steel-aluminum welding method for welding.
Q (kJ / cm) = 60 (s / min) x welding current (A) x welding voltage (V) / welding speed (cm / min) / 1000   The steel-aluminum welding method according to claim 3 or 4, wherein the steel sheet is a hot-dip galvanized steel sheet, and the aluminum welding wire contains 2.0 to 6.0 mass% of Mg.

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