JP2000167659A - Mig brazing method for plated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent brazing bead free from cracks in the MIG brazing method for a plate steel sheet. SOLUTION: In a method where a plated steel sheet is MIG-brazed using a brazing filler metal consisting mainly of Cu to which Si and Mn are added, and using Ar gas for the shielding gas, the heat input is set to be 450-1850 J/cm when the brazing speed is <60 cm/min, and the heat input is set to be 335-800 J/cm when the brazing speed is >=60 cm/min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MIG brazing method for a plated thin steel sheet used for automobile parts and the like.

[0002]

2. Description of the Related Art Plated thin steel sheets are
Due to its properties such as excellent corrosion resistance and decorativeness, it is expected to be applied to various mechanical parts. Examples of the type of plated thin steel sheet include an Al-based thin steel sheet, a Zn-based thin steel sheet, a Pb-based thin steel sheet, a Sn-based thin steel sheet, and a Ni-based thin steel sheet. Zn-based plated steel sheets are used for undercarriage of automobiles because of their excellent corrosion and rust resistance. Pb-based plated steel sheets and Sn-based plated steel sheets are already used as fuel tank materials for automobiles. Has been put to practical use. Also, recently, Al-based plated thin steel sheets have attracted attention as fuel tank materials for automobiles. Ni-based plated thin steel sheets can be plated even on complicated shapes, and have high hardness.
Because of its excellent corrosion resistance, it is used in precision parts of optical equipment and various parts such as watches.

[0003] Methods of joining these plated thin steel sheets include welding methods such as resistance welding and arc welding, brazing methods, and soldering methods. However, since the surface of a plated thin steel sheet is covered with various types of plating, there are cases where joining is difficult with a commonly used welding method.

For example, in the case of Al-based plated thin steel sheet, it is very difficult to join such as arc welding because the plated Al is easily oxidized in the air and a strong oxide film layer is formed on the plating surface. There are few industrial examples. Also, Z
In the arc welding of n-based, Sn-based, and Pb-based plated thin steel sheets, many pits and blowholes are generated in the bead, the arc becomes unstable, and in the case of Ni-based plated thin steel sheets, the strength of the weld decreases. Problems occur. Further, it is considered that the plated portion around the welded portion is removed by the arc welding, so that sufficient corrosion resistance may not be obtained, or the plated thin steel plate itself may be thermally deformed. Therefore, it is preferable to join by another method.

[0005] Brazing is a method in which a brazing material of a metal having a lower melting point than the base material is melted, and the brazing material is inserted between the base materials and joined. This method is easy to join complicated and precise shapes and dissimilar steel materials, and has little plating damage at the time of joining and small deformation of steel sheets. It is suitable for joining and has many practical examples in industry. For brazing material, pure Cu brazing, Cu-Z
Cu-based brazing materials such as n-alloy brazing, Cu-P alloy brazing, and Cu-Sn alloy brazing, and Ag-based brazing materials such as Ag-Cu alloy brazing are generally used.
No. 26486, 2) JP-A-8-206876, and 3) JP-A-10-102167, etc., as practical brazing materials.

[0006] However, it is known that the joining by the brazing method is difficult in the Al-based plated thin steel sheet represented by the Al-Si alloy plated thin steel sheet. this is,
This is because Al forms a strong oxide film layer on the surface, so that sufficient wettability cannot be obtained.

As a method for improving the brazing property of an Al-based plated thin steel sheet, there is an arc brazing method. In the arc brazing method, as shown in FIG. 1, an inert gas is caused to flow from between the contact tip 1 and the gas nozzle 2 to generate an arc between the base material 3 and the brazing wire 4, which is generated at that time. This is a method in which the brazing wire 4 is melted by the arc heat, and the melted brazing is caused to flow between the base materials 3 and joined. When brazing Al-based alloy plated thin steel sheet by arc brazing method, 5
The strong oxide film layer on the surface of the Al-coated steel sheet is removed by an arc having a high temperature of 000 ° C.
Brazing of the l-based alloy plated thin steel sheet is improved, and good brazing becomes possible. Because of these advantages, the arc brazing method is widely used as an effective joining method for a thin steel plate and the like. 4) JP-A-6-226486 also discloses an effective joining method for a thin steel plate and the like. It has been disclosed.

However, in the arc brazing method of a plated thin steel sheet, it is known that cracks occur in a brazed bead portion, which is a problem. Cracking of the brazing bead in various containers is a major cause of leakage, and also one of the causes of significantly lowering the joining strength and increasing the probability of breakage of the brazing portion.

[0009]

In the brazing of a plated thin steel sheet, there is a problem that a brazing bead is cracked, and its use is limited. An object of the present invention is to reduce brazing bead cracks and sufficiently secure joint strength and airtightness in MIG brazing of various plated thin steel sheets.

[0010]

According to the present invention, in order to solve the above-mentioned problems, a plated thin steel sheet is made of a brazing material mainly composed of Cu containing Si and Mn, and an inert gas is used as a shielding gas. When the brazing speed is less than 60 cm / min, the heat input is 4
50 to 1850 J / cm, brazing speed is 60 cm /
At min or more, the amount of heat input is limited to 335 to 800 J / cm, thereby reducing brazing bead cracks and obtaining a good brazing bead. Further, the plating of the thin steel sheet is one of Al-based, Zn-based, Pb-based, Sn-based, and Ni-based, and the basis weight is 5 to 300 g / cm ^{2 on} one side. 0.6 to 3.0 mm. Hereinafter, embodiments of the present invention will be specifically described.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventionally, there has been almost no study on cracking of a brazing bead in arc brazing of a plated steel sheet. Then, the present inventors investigated bead cracks in order to find out the cause of the cracks. Al-S, which is an Al-based plated thin steel sheet,
Using an i-alloy plated thin steel sheet, using a Cu-Si-Mn alloy brazing material,
G brazing was performed, and the cross section of the brazing bead was observed. The result is shown in FIG.

FIG. 2 is a cross-sectional macro view of a brazing bead portion, in which (a) shows a cross-section of a brazing bead when a crack occurs in the brazing portion, and (b) shows a cross-section of the brazing bead. FIG. 4 shows a cross section of a brazing bead when no brazing occurred. As can be seen from FIG. 2, the brazing bead in the case where a crack has occurred contains a large amount of Fe inside Cu, but the brazing bead in the case where no crack has occurred has a F
e content is low. The Fe content in the brazing bead is
Since the brazing arc state is largely caused, it is important to limit brazing conditions in order to reduce cracks in the brazing bead portion.

Usually, parameters for controlling the arc brazing include a brazing speed, a brazing current and a voltage, and a heat input amount which is a total value thereof. The brazing speed is the speed of the torch or the moving vehicle, and has a direct effect on bead formation and the like. The brazing current and voltage represent the arc state, the brazing current controls the strength of the arc, and the brazing voltage controls the arc length. These values are very effective as parameters representing the brazing state, but since they have different influences, it is difficult to evaluate them centrally.

The heat input is a parameter representing the amount of heat given per unit length by the moving heat source, and is a value obtained from the brazing current and voltage and the speed of the moving heat source, that is, a value obtained from the brazing speed. Desired.

Q = 60 · V · I / υ [J / cm] (1) V; arc voltage (V) I; brazing current (A) υ; brazing speed (cm / min)

[0016] The heat input indicates the metallurgical properties of the brazed portion and is widely used as a value that simply expresses the brazing conditions, and may affect mechanical properties such as joint strength and toughness. Are known. In addition, since the heat input is a value obtained from the brazing speed, the current, and the voltage, the influence of each parameter can be evaluated in a unified manner. As described above, the heat input is very effective as a value indicating the brazing state, but it is difficult to evaluate the entire brazing state only by the heat input. For example, the brazing speed is a very important value in terms of the work efficiency of brazing, but in the low-speed brazing in which the brazing speed is slow, and in the high-speed brazing in which the brazing speed is fast, the bead shape, even with the same heat input, Or, their characteristics are often different.

Therefore, according to the present invention, classification is performed based on the brazing speed, which is one of the parameters for obtaining the heat input, and the heat input is then limited. That is, brazing speed 60cm
/ Min, the heat input is 450-1850.
J / cm, on the high-speed side where the brazing speed is 60 cm / min or more, by limiting the heat input to 335 to 800 J / cm, the cracking of the brazing bead is reduced, and a good brazing bead is obtained. Made possible. The brazing speed and heat input were limited for the following reasons.

If the heat input is less than 450 J / cm in low-speed brazing at a brazing speed of less than 60 cm / min, the brazing current and voltage become very low, so that the wire feed rate is reduced, and The amount of welding cannot be obtained, the strength of the brazed portion is reduced, and a defective portion is generated. Therefore, a good brazing bead cannot be obtained.

In addition, when the brazing speed is lower than 60 cm / min and the heat input exceeds 1850 J / cm, the brazing current and the voltage increase, resulting in a very strong arc state and Fe inside the Cu. Contained in large quantities,
This causes cracking of the brazing bead, resulting in a brazing defect. For the above reasons, the brazing speed 60c
If it is less than m / min, the heat input is 450 to 1850 J / c.
m.

In high-speed brazing at a brazing speed of 60 cm / min or more, if the heat input is less than 335 J / cm, the brazing current and the voltage become low, so that the arc becomes unstable and sufficient welding to the brazing speed is performed. The amount cannot be secured, brazing failure occurs, and a good brazing bead cannot be obtained.

Also, in high-speed brazing at a brazing speed of 60 cm / min or more, if the heat input exceeds 800 J / cm, the brazing current and voltage become high, so that a large amount of Fe is contained in Cu of the brazing bead. This causes cracking of the brazing bead and a brazing defect occurs. For the reasons described above, the heat input was limited to 335 to 800 J / cm at a brazing speed of 60 cm / min or more.

In the present invention, the plated steel sheet is A
1-based, Zn-based, Pb-based, Sn-based, and Ni-based alloy-coated thin steel sheets. Among Al-based plated thin steel sheets, pure Al-coated thin steel sheets, Al-Si alloy-coated thin steel sheets, and Al-Mn alloy-coated thin steel sheets , Al-Zn alloy plated thin steel sheet
Pure Zn plated thin steel sheet, Zn-F
e-alloy-coated thin steel sheet, Zn-Al alloy-coated thin steel sheet, Pb-based plated thin steel sheet, Pb-Sn alloy-coated thin steel sheet, etc., Sn-based plated thin steel sheet, Sn-Zn alloy-plated thin steel sheet, Ni-based Examples of the plated thin steel sheet include a Ni—Zn alloy plated thin steel sheet. The weight per unit area of various types of plated thin steel sheets is within a range in which brazing bead cracks do not occur by applying the present invention.
² , Zn-based plated thin steel sheet is 5-300 g / m ^{2 on} one side, P
The upper and lower limits were limited to 5 to 300 g / m ² on one side for a b-based plated thin steel sheet, 5 to 300 g / m ^{2 for} a Sn-based plated thin steel sheet, and 5 to 300 g / m ^{2 for} a Ni-based plated thin steel sheet.
Further, as a range in which brazing bead cracks do not occur by applying the present invention, the thickness of the plated thin steel sheet is set to 0.6 mm to 3.0 mm.
mm.

As for the brazing material, since an arc is used as a heat source at the time of brazing, Cu having a high melting point of 1080 ° C.
And a Cu alloy brazing filler metal containing Si and Mn was used. Si has a function of improving the fluidity of the wax, stabilizing the arc, and improving the bead shape. However, 6.
If it exceeds 0%, the bead is hardened and the melting point is further increased. In addition, when the addition amount is less than 1.0%,
Since the effect cannot be obtained, the content of Si is set to 1.0
To 4.0%.

Mn has the function of increasing the fluidity of the wax without hardening the bead. However, if added excessively, the arc becomes unstable, and the bead shape deteriorates. Further, if the addition is less than 0.2%, the effect cannot be obtained, so that the content of Mn is set to 0.3 to 3.5.
%. Hereinafter, specific effects of the present invention will be described.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an embodiment of the present invention, first, as an embodiment of an Al-plated thin steel sheet, Al-S having a basis weight of 3 to 330 g / m ² was used.
JIS-K as shielding gas using i-alloy plated thin steel sheet
Using primary Ar gas specified in 1105, Si, Mn
Using a Cu-Si-Mn alloy brazing material containing, based on brazing conditions shown in Table 1, bead-on MIG brazing,
The shape and the number of cracks generated in the brazing bead were investigated.
Table 1 shows the results.

The number of cracks in the brazing bead is the number of cracks generated in the brazing bead with the bead length limited to 100 mm. Is not cracked and the shape is good, and x is when the brazing bead is cracked or the shape is not good.

[0027]

[Table 1]

In Table 1, the present invention example No. Nos. 1 to 4 have a brazing speed of less than 60 cm / min. 4 to 8 are brazing speeds 6
In the example of 0 cm / min or more, the heat input amount satisfies the conditions of the present invention, and it can be seen that a brazing bead having a good shape without cracks is obtained for each brazing bead. In addition, although the plate thickness was changed between 0.6 and 3.0 mm, it did not fall off.

On the other hand, in Comparative Example 1, the brazing speed was 4
Although the example is 0 cm / min, since the brazing current is as low as 30 A and the heat input is as small as 405 J / cm, the arc was not stable, and the amount of welding was insufficient, resulting in poor brazing. Comparative Example 2 is an example in which the brazing speed is 40 cm / min, the brazing current is as high as 95 A, and the heat input is as high as 1853 J / cm. The shape was good, but cracks occurred on the surface, resulting in poor brazing beads.

In Comparative Example 3, the brazing speed was 40 cm / mi.
n, brazing current and voltage are high together with 115A and 14V,
This is an example in which the heat input is as high as 2415 J / cm. In this comparative example, the shape was relatively good, but a number of cracks occurred on the surface, and brazing beads were defective.

In Comparative Example 4, the brazing speed was 80 cm / mi.
n, the brazing current and voltage were 35 A and 10 V, the heat input was as low as 263 J / cm, and the plating weight was 3 per side.
This is an extremely large example of 30 g / m ² . In this comparative example, the arc was not stable because the brazing current was low, and the brazing was poor because a sufficient amount of welding could not be secured.
Because of the large basis weight of the plating, the brazing property was poor and the shape was poor.

In Comparative Example 5, the brazing speed was 80 cm / m
In, the brazing current and voltage were 90 A and 13 V, and the heat input was 878 J / cm, which was out of the range of the present invention. The shape was good, but the surface had cracks, and the brazing beads were formed. It has become bad.

In Comparative Example 6, the brazing speed was 80 cm / mi.
n, brazing current and voltage are 120A, 14V,
This is the case where the basis weight is as small as 3 g / m ^{2 on} one side. In this comparative example, the basis weight of plating was very thin, and the heat input was 1260.
Due to the high J / cm, many cracks were generated on the surface, resulting in poor brazing bead.

Next, as an embodiment of the Zn-plated steel sheet,
A pure Zn-plated thin steel sheet having a basis weight of 5-330 g / m ² was used, a first-class Ar gas specified in JIS-K1105 was used as a shielding gas, and a Cu-Si-Mn alloy brazing material was used. Bead-on MI based on brazing conditions
G brazing was performed, and the shape and the number of cracks generated in the brazing bead were investigated. Table 2 shows the results.

[0035]

[Table 2]

In Table 2, the invention sample No. Nos. 1 to 4 have a brazing speed of less than 60 cm / min. 4 to 8 are brazing speeds 6
In the example of 0 cm / min or more, the heat input amount satisfies the conditions of the present invention, and it can be seen that a brazing bead having a good shape without cracks is obtained for each brazing bead. In addition, although the plate thickness was changed between 0.6 and 3.0 mm, it did not fall off.

On the other hand, in Comparative Example 1, the brazing speed was 4
Although the example is 0 cm / min, since the brazing current is as low as 30 A and the heat input is as small as 405 J / cm, the arc was not stable, and the amount of welding was insufficient, resulting in poor brazing. Comparative Example 2 is an example in which the brazing speed is 40 cm / min, the brazing current is as high as 90 A, and the heat input is as high as 1755 J / cm. The shape was good, but cracks occurred on the surface, resulting in poor brazing beads.

In Comparative Example 3, the brazing speed was 40 cm / mi.
n, brazing current and voltage are high together with 110A and 14V,
This is an example in which the heat input is as high as 2310 J / cm. In this comparative example, the shape was relatively good, but a number of cracks occurred on the surface, and brazing beads were defective.

In Comparative Example 4, the brazing speed was 80 cm / mi.
n, the brazing current and voltage were 30 A and 10 V, the heat input was as low as 225 J / cm, and the plating basis weight was 3 on one side.
This is an extremely large example of 30 g / m ² . In this comparative example, the arc was not stable because the brazing current was low, and the brazing was poor because a sufficient amount of welding could not be secured.
Because of the large basis weight of the plating, the brazing property was poor and the shape was poor.

In Comparative Example 5, the brazing speed was 80 cm / mi.
n, the brazing current and voltage were 100 A and 13 V, and the heat input was 975 J / cm, which was out of the range of the examples of the present invention. The shape was good, but the surface had cracks, and the brazing bead was used. It has become bad.

In Comparative Example 6, the brazing speed was 80 cm / mi.
n, brazing current and voltage are 115A, 14V,
This is the case where the basis weight is as small as 3 g / m ^{2 on} one side. In this comparative example, the basis weight of plating was very thin, and the heat input was 1208.
Due to the high J / cm, many cracks were generated on the surface, resulting in poor brazing bead.

Next, an example of a Pb-based plated steel sheet will be described.
And the basis weight of plating is 5 to 330 g / m^Two Pb-Sn alloy
Use JIS shielding gas as shielding gas using plated steel sheet
Use first-class Ar gas specified in JIS-K1105
Then, using a Cu-Si-Mn alloy brazing material, the filter shown in Table 3 was used.
Perform bead-on MIG brazing based on brazing conditions
The shape and the number of cracks generated in the brazing bead were investigated. So
Table 3 shows the results.

[0043]

[Table 3]

In Table 3, the invention sample No. Nos. 1 to 4 have a brazing speed of less than 60 cm / min. 4 to 8 are brazing speeds 6
In the example of 0 cm / min or more, the heat input amount satisfies the conditions of the present invention, and it can be seen that a brazing bead having a good shape without cracks is obtained for each brazing bead. In addition, although the plate thickness was changed between 0.6 and 3.0 mm, it did not fall off.

On the other hand, in Comparative Example 1, the brazing speed was 4
Although the example is 0 cm / min, since the brazing current is as low as 30 A and the heat input is as small as 405 J / cm, the arc was not stable, and the amount of welding was insufficient, resulting in poor brazing. Comparative Example 2 is an example in which the brazing speed is 40 cm / min, the brazing current is as high as 100 A, and the heat input is as high as 1950 J / cm. The shape was good, but cracks occurred on the surface, resulting in poor brazing beads.

In Comparative Example 3, the brazing speed was 40 cm / mi.
n, brazing current and voltage are high together with 115A and 14V,
This is an example in which the heat input is as high as 2415 J / cm. In this comparative example, the shape was relatively good, but a number of cracks occurred on the surface, and brazing beads were defective.

In Comparative Example 4, the brazing speed was 80 cm / mi.
n, the brazing current and voltage were 30 A and 10 V, the heat input was as low as 225 J / cm, and the plating basis weight was 3 on one side.
This is an extremely large example of 30 g / m ² . In this comparative example, the arc was not stable because the brazing current was low, and the brazing was poor because a sufficient amount of welding could not be secured.
Since the basis weight of the plating was out of the range of the present invention, the brazing property was deteriorated and the shape was poor.

In Comparative Example 5, the brazing speed was 80 cm / mi.
n, the brazing current and voltage were 95 A and 13 V, and the heat input was 926 J / cm, which was out of the range of the examples of the present invention. The shape was good, but the surface had cracks. It has become bad. In Comparative Example 6, the brazing speed was 80 cm / min, the brazing current and the voltage were 120 A,
14 V, and the basis weight is as small as 3 g / m ^{2 on} one side. In this comparative example, since the basis weight of plating was very thin and the heat input was as high as 1170 J / cm, many cracks were generated on the surface, and the brazing bead was defective.

FIG. 3 shows the result of the investigation in the embodiment. Fig. 3 shows Al-Si alloy plating, pure Zn plating, P
It shows the relationship between the amount of heat input and the number of cracks generated in the brazing bead during arc brazing of a b-Sn alloy plated thin steel sheet, where (a) shows a brazing speed of less than 60 cm / min, and (b)
Has a brazing speed of 60 cm / min or more.

In FIG. 3A, the heat input is 1850 J / c.
If the heat input amount is less than 450 J / cm, brazing failure occurs. In FIG. 3B, the heat input is 800 J / cm.
From the above, it can be seen that cracks have occurred in the brazing bead, and when the heat input is less than 335 J / cm, brazing failure has occurred. From the above results, it was confirmed that no crack occurred in the brazing bead at the heat input specified in the present invention.

[0051]

According to the present invention, a good brazing bead without cracking can be obtained in MIG brazing using a Cu alloy brazing material.

[Brief description of the drawings]

FIG. 1 is a diagram showing an arc brazing state;

FIG. 2 is a view showing a cross-sectional shape of a brazing bead part;
(A) is a brazed bead with cracks, and (b) is a brazed bead without cracks.

FIG. 3 is a diagram showing a relationship between a heat input amount and a bead crack;
Inspection results at a brazing speed of less than 60 cm / min, (b)
Investigation results with a brazing speed of 60 cm / min or more

[Explanation of symbols]

 A Cu (copper) B Fe (iron) 1 Contact tip 2 Gas nozzle 3 Base material 4 Brazing wire

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B23K 103: 16

Claims (3)

[Claims] In a method of brazing a plated thin steel sheet using a brazing material mainly containing Cu containing Si and Mn and using an inert gas as a shielding gas, a brazing speed is 60 cm / min. If less than 450 heat input
1850 J / cm, brazing speed 60 cm / min
In the above, the MIG brazing method of a plated thin steel sheet is performed by brazing with a heat input of 335 to 800 J / cm. 2. The thin steel sheet is plated with Al, Zn or Pb.
Type, Sn type, Ni type, with a basis weight of 5 to 5 per side
^{2. The} method according to claim 1, wherein the weight is 300 g / cm < ² >. 3. The MIG brazing method for a plated thin steel sheet according to claim 1, wherein the thickness of the thin steel sheet is 0.6 to 3.0 mm.