JP2007296564A - Friction welding method of steel pipe and aluminum alloy hollow member - Google Patents

Abstract

[Objective] Friction welding method of steel pipe and aluminum alloy hollow member capable of obtaining excellent joint strength in friction welding of a steel pipe having a diameter of 50 mm or more and a wall thickness of less than 5 mm and an aluminum alloy hollow member containing less than 2% Mg I will provide a.
[Configuration] A friction process in which the end faces of the steel pipe and the aluminum alloy hollow member are brought into contact with each other, and a relative rotational friction is applied with the friction pressure (P1), and an upset pressure (P2) higher than P1 is applied while the rotary brake is applied after the completion of the friction process. When the pressure is switched from P1 to P2 and the pressure is switched from P1 to P2 after the friction process is completed, the P2 arrival time t is set to 1.2 ≦ 1 / (t / t ₀ ) ≦ 2 (t ₀ : rotary brake It is characterized by the range of the time from stop to stop.
[Selection figure] None

Description

  The present invention relates to a friction welding method for a steel pipe and an aluminum alloy hollow member, particularly an aluminum alloy hollow member having a diameter of 50 mm or more and a wall thickness of less than 5 mm and an aluminum alloy hollow member containing less than 2% Mg.

  Conventionally, in order to realize a structure in which members made of steel hollow members are partially replaced with aluminum alloy hollow members in automobile propeller shafts, axle housings, torsion bars, etc., it is necessary to join them together. However, if steel and an aluminum alloy are to be joined by fusion welding such as MIG welding, TIG welding, or electron beam welding, joining becomes impossible because iron and aluminum form a brittle intermetallic compound.

On the other hand, since friction welding does not form a liquid phase at the time of joining, it is one of the few methods that can join steel and aluminum alloy, but in reality, friction welding between steel and aluminum alloy is not easy and is close to the strength of the aluminum alloy base material. Currently, joint strength has not been obtained, and many proposals have been made to improve the joint strength (see, for example, Patent Document 1). Further improvement is desired.
Japanese Patent Application No. 2004-08664

  The inventors have less than 2% of steel pipes having a diameter of 50 mm or more and a wall thickness of less than 5 mm, and Al-Cu (2000), Al-Mn (3000), Al-Si-Mg (6000), etc. In the research process on the friction welding method of the aluminum alloy hollow member containing Mg, the conditions in the process of switching from P1 to P2 together with the friction pressure (P1), the friction time (T1), and the upset pressure (P2) are joined. It was found to affect the strength.

  The present invention has been made as a result of repeated testing and examination based on the above knowledge, and its purpose is a hollow aluminum alloy containing a steel pipe having a diameter of 50 mm or more and a wall thickness of less than 5 mm and Mg of less than 2%. An object of the present invention is to provide a method for friction welding of a steel pipe and an aluminum alloy hollow member, which has excellent joint strength in friction welding of members and can be suitably applied to the joining of automobile members.

In order to achieve the above object, the friction welding method of a steel pipe and an aluminum alloy hollow member according to claim 1 is a carbon steel pipe or alloy steel pipe having a diameter of 50 mm or more and a wall thickness of less than 5 mm and an aluminum alloy hollow containing less than 2% Mg. A method of friction-welding members, wherein the end faces of the steel pipe and the aluminum alloy hollow member are butted against each other, and a relative rotational friction is performed with the friction pressure (P1). An upset process for applying an upset pressure (P2), and when applying the rotary brake after the end of the friction process and when the pressure is switched from P1 to P2, the P2 arrival time t is set to 1.2 ≦ 1 / (t / t ₀ ) ≦ 2 (t ₀ : time from applying the rotation brake to stopping) is a characteristic.

The friction welding method of a steel pipe and an aluminum alloy hollow member according to claim 2 is a method of friction welding a carbon steel pipe or alloy steel pipe having a diameter of 50 mm or more and a thickness of less than 5 mm and an aluminum alloy hollow member containing less than 2% Mg. A friction process of performing relative rotational friction with the end faces of the steel pipe and the aluminum alloy hollow member butting the friction pressure (P1) of 10 to 80 MPa and the friction time (T2) of 0.02 to 0.2 s; An upset process in which an upset pressure (P2) of 80 to 160 MPa is applied while the rotation brake is applied after the process is completed, and one peripheral speed in the relative rotational friction is in a range of 1.5 to 3.5 m / s, when the pressure with applying a rotational braking after the process is completed is switched from P1 to P2, the P2 arrival time t 1.2 ≦ 1 / (t / t 0) ≦ Characterized in that the range _of: (t 0 time to stop from over the rotating brake).

  According to the present invention, an excellent joint strength can be obtained in friction welding of a steel pipe having a diameter of 50 mm or more and a wall thickness of less than 5 mm and an aluminum alloy hollow member containing Mg of less than 2%, and suitable for joining automobile members. An applicable method of friction welding of a steel pipe and an aluminum alloy hollow member is provided.

  The present invention relates to a steel pipe having a diameter of 50 mm or more and a wall thickness of less than 5 mm, and less than 2% Mg such as Al—Cu (2000), Al—Mn (3000), Al—Si—Mg (6000). Is a friction welding method with a hollow member of an aluminum alloy containing Normally, when steel and an aluminum alloy are in close contact with each other and exposed to a high temperature, a Fe-Al intermetallic compound that is brittle at the interface is generated, and intermetallic compounds are easily generated even in friction welding that is exposed to a high temperature for a very short time. In an aluminum alloy having an Mg content of less than 2%, it was confirmed that the generation and growth of Fe—Al intermetallic compounds harmful to bondability were suppressed.

  In the present invention, it is not necessary to discharge the intermetallic compound in the upset process, and the amount of burrs generated in the upset process is reduced in spite of increasing the upset pressure P2, and the flow of burrs is reduced between the inner diameter side and the outer diameter of the pipe The joint can be made uniform on the side and has high tensile strength.

(Friction pressure P1)
In the friction process, the purpose is to heat the end surfaces of the butted materials to be joined, and the amount of heat input is controlled by the friction time T1, so the size of P1 is not strongly limited and has a wide range of values. Can be taken. Practically, a range of 10 MPa ≦ P1 ≦ 80 MPa is preferable. If it is less than 10 MPa, it takes time to obtain the heating necessary for metal bonding, so that the aluminum alloy at the interface is likely to be oxidized, and the heating region is likely to spread to a distance away from the interface, causing a reduction in bonding strength. . If it exceeds 80 MPa, there is a condition of P1 ≦ P2, which limits the use range of P2 and is not practical. However, since the interface tends to become high temperature when P1 increases, the range of 20 MPa ≦ P1 ≦ 60 MPa is more preferable.

(Friction time T1)
The end faces to be joined are heated by rotationally rubbing the end faces (joint faces) of the butted materials at a pressure of P1 for a time T1. It is desirable to locally heat only the end face, and T1 is the minimum necessary. Therefore, T1 is performed in the range of 0.02 to 0.2 s. As a control method for heating the joint surface, there is a U1 control method (Patent Document 1) that continues rotational friction with the pressure of P1 until the set frictional margin U1 is generated, and a T1 control method in which the above T1 is in a specific range. However, the T1 control method is preferable for controlling the minimum required amount of heat input. This is because if the heat input corresponding to T1 of 0.02 to 0.2 s is controlled by the U1 control method, U1 becomes about 0.5 mm or less and the detection accuracy of U1 is deteriorated.

  When T1 is less than 0.02 s, it is difficult to obtain heating necessary for bonding. When T1 exceeds 0.2 s, heating becomes excessive, softening in the vicinity of the interface becomes remarkable, and the softening area widens, causing the generation of an oxide layer at the interface. Adverse effects such as inducing non-uniform metal flow.

(Upset pressure P2)
The upset pressure P2 is a factor that strongly influences the strength of the bond between the steel pipe and the aluminum alloy hollow member. In order to strengthen the metal bond at the interface between steel and aluminum alloy, it is desirable that P2 is high. However, when P2 becomes excessive, the total margin becomes large, and the non-uniformity of the flow of burrs generated inside and outside the hollow member such as an aluminum alloy tube increases, resulting in residual shearing force in the radial direction at the interface, resulting in increased bonding strength. descend. Furthermore, the vicinity of the interface of the aluminum alloy hollow member is deformed and the roundness is disturbed. The upper limit of P2 is related to the deformation resistance of the material in such a size that the non-uniformity of the flow of burrs does not appear remarkably.

  After the friction process, the process shifts to the upset process, and the rotation brake is applied. However, the load on P2 is maintained after P1 is maintained for a short time without immediately starting the load on P2, and the load on P2 is immediately applied. There is a method (P2 slope) that starts slowly but slows down to reach P2 (see FIG. 1). For an aluminum alloy having an Mg content of 2% or less, when the latter P2 slope is applied, the upper limit of P2 is further increased, which is effective in increasing the bonding force. Under the condition where the P2 slope is set, P2 at which a high bonding force is obtained is 80 to 160 MPa. If it is lower than 80 MPa, the bonding strength tends to be insufficient, and if it is higher than 160 MPa, the unevenness of the flow of burrs tends to increase with an increase in the margin of allowance and the strength decreases.

(P2 slope)
As described above, the P2 slope is set to slow down the speed required to reach P2. By setting the P2 slope, the shift margin during the upset process can be reduced. Further, P2 can be increased when the shift margin is determined. The P2 slope is defined by 1 / (t / t ₀ ). This means the magnitude of the gradient of the pressure is intended (see FIG. 2), t is usually 0.4 by P1 time reaches P2, t ₀ is device capability by the time required for the rotation is stopped It is about 0.6 s. If the P2 slope is not set, the pressure is increased at the maximum speed allowed by the hydraulic system of the apparatus, approximately P2 slope is about 3.

The lower limit of the P2 slope value is a slope that reaches P2 shortly before the rotation stops, and is 1 / (t / t ₀ ) = 1.2. At this time, a small amount of rotation is performed with P2 applied, and the motor stops. When the inclination is smaller than 1.2, the amount of rotation in the state where P2 is applied is reduced and the joining force is reduced. When the inclination is smaller than 1, the rotation is stopped before reaching P2, so that the strength is remarkably reduced. If it exceeds 1.2, the amount of rotation in the state where P2 is applied increases and the joining force also increases, but after reaching the maximum value of about 1.5 to 1.7, the total margin becomes excessive and the joining force is increased. Begins to decrease. When 1 / (t / t ₀ ) exceeds 2, the effect of setting the P2 slope is lost.

(Rotational speed)
The peripheral speed of rotation greatly affects the rate of heat generation and the size of the margin for friction. By setting one peripheral speed in the relative rotational friction to be in the range of 1.5 to 3.5 m / s, the joining force can be further increased. When the peripheral speed is less than 1.5 m / s, it is difficult to obtain the heating necessary for metal bonding, and when the peripheral speed exceeds 3.5 m / s, the shift margin becomes large during the upset process, resulting in uneven deformation. It tends to happen.

  Examples of the present invention will be described below in comparison with comparative examples to demonstrate the effects. These examples show one embodiment of the present invention, and the present invention is not limited to these examples.

Example 1
Brake-type rotary friction welding machine is used in combination with steel pipe STKM13A (outer diameter 60mm, thickness 3.1mm, length 150mm) and aluminum alloy pipe 6061-T6 (outer diameter 60mm, thickness 3.1mm, length 150mm) Then, the end faces of both materials were friction welded. Table 1 shows the pressure contact conditions. The aluminum pipe was rubbed against the rotating steel pipe at the friction pressure P1 for T1 hours, and then the rotary brake was applied and simultaneously switched from P1 to the upset pressure P2. Here, the pressure change gradient when changing from P1 to P2, that is, the P2 slope was variously changed. The time t ₀ from when the rotation brake was applied until the rotation completely stopped was 0.5 seconds. The actual pressure does not change linearly from P1 to P2, but after the set P2 is exceeded, the vibration waveform is drawn and settles to P2, so the definition of the P2 slope is the slope until the first peak pressure occurs (See FIG. 3).

  After joining, the tube was cut vertically to cut out a strip-shaped test piece, and a tensile test of the joining material was performed. Table 1 shows the tensile test results. As shown in Table 1, the test material No. 1 to 8 change only the P2 slope, but the test material No. The tensile strength becomes maximum at 5, and the tensile strength is reduced regardless of whether the P2 slope value is larger or smaller than 1.5.

  Those whose P2 slope values are outside the conditions of the present invention are underlined. The test material No. whose P2 slope value deviated from the condition of the present invention. 1-3 and 7-8 are inferior in tensile strength. No. Nos. 9 to 11 change the rotation speed (rotation speed), but even if the P2 slope is within the conditions of the present invention, the tensile strength is inferior when the rotation speed is out of the conditions of the present invention (No. 11).

  The steel alloy STKM13A (outer diameter 60 mm, thickness 3.1 mm, length 150 mm) and the aluminum alloy pipe (outer diameter 60 mm, thickness 3.1 mm, length 150 mm) of Table 2 with different alloy types are the same as in Example 1. Friction welding was performed using a brake type rotary friction welding machine. The pressure contact conditions were P1: 40 MPa, T1: 0.04 s, rotation speed: 1000 rpm, P2 slope: 1.3, P2: test material No. 1 to 4 and 7, 120 MPa, No. In 5-6, it was set to 80 MPa. No. The reason why P2 of 5 and 6 is reduced is that the strength of the material is so small that it is excessive at the same P2 (120 MPa) as other materials. The definition of the P2 slope is the same as in the first embodiment.

  After joining, the tube was cut vertically to cut out a strip-shaped test piece, and a tensile test of the joining material was performed. Table 2 shows the tensile test results. As shown in Table 2, the test material No. 1-4 have high tensile strength of the bonding material. No. The tensile strength of the bonding material 5 is 176 MPa, but the ratio to the tensile strength of the base material, that is, the joint efficiency is as high as 85%. In contrast, test material No. Since Nos. 6 and 7 are alloys containing 2% or more of Mg (No. 6: 2.8%, No. 7: 2.5%), the tensile strength of the bonding material and the joint efficiency are extremely inferior.

Example 3
A steel pipe STKM13A (outer diameter 50 mm, thickness 2.4 mm) was used as the rotation side, and a 6082 alloy forged material having a hollow portion having the same shape as the steel pipe at the end face was friction welded (cross section: FIG. 4). The conditions are P1: 25 MPa, P2: 110 MPa, T1: 0.05 s, N: 900 rpm, brake timing P2L: _{0 s} , P2 slope value 1 / (t / t ₀ ): 1.5 (t _0: 0.55 s) , T2: 10 s. After the pressure welding, a torsion test was carried out, and the joint did not break even under a torque load of 5000 N · m. Further, when a test piece was cut out and subjected to a tensile test, the tensile strength was a high value of 283 MPa.

It is a figure for demonstrating the P2 slope and P2 delay in friction welding. It is a figure for demonstrating the definition of P2 slope in friction welding. It is a figure for demonstrating the definition of P2 slope in Example 1. FIG. It is a figure which shows the longitudinal cross-section after the friction welding of Example 3. FIG.

Claims (2)

A method of friction welding a carbon steel pipe or alloy steel pipe having a diameter of 50 mm or more and a wall thickness of less than 5 mm to an aluminum alloy hollow member containing less than 2% (mass%, the same shall apply hereinafter) Mg, The friction process is completed, including a friction process in which end faces are brought into contact with each other and a relative rotational friction is caused by the friction pressure (P1), and an upset process in which an upset pressure (P2) higher than P1 is applied while the rotary brake is applied after the completion of the friction process. When the rotation brake is applied later and the pressure is switched from P1 to P2, the P2 arrival time t is set to 1.2 ≦ 1 / (t / t ₀ ) ≦ 2 (t ₀ : time from applying the rotation brake to stopping) A friction welding method of a steel pipe and an aluminum alloy hollow member, characterized in that A method of friction-welding a carbon steel pipe or alloy steel pipe having a diameter of 50 mm or more and a wall thickness of less than 5 mm and an aluminum alloy hollow member containing less than 2% Mg, with the end faces of the steel pipe and the aluminum alloy hollow member being brought into contact with each other and subjected to friction A friction process in which relative rotational friction is performed with a pressure (P1) of 10 to 80 MPa and a friction time (T2) of 0.02 to 0.2 s, and an upset pressure (P2 of 80 to 160 MPa while the rotary brake is applied after completion of the friction process. ), The one peripheral speed in the relative rotational friction is in the range of 1.5 to 3.5 m / s, and after the friction process is finished, the rotary brake is applied and the pressure is switched from P1 to P2. At this time, the P2 arrival time t is set to a range of 1.2 ≦ 1 / (t / t ₀ ) ≦ 2 (t ₀ : time from applying the rotation brake to stopping). A friction welding method for a steel pipe and an aluminum alloy hollow member.

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