JP2000288747A - Friction welded member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction welded member which is cut at the position away from a welded part by at least a specified value in the case of being subjected to a tensile test across the welded part, and which is excellent in tensile strength of the welded part, reduced in weight and high in function. SOLUTION: A steel member 2 and a spheroidal graphite cast iron member 3 are friction welded to each other to form a friction welded member 1. The friction welded member 1 is allowed to be cut in the tensile test at the position away from a welded part 4 by at least 0.1 mm. Regarding the shape of the welded part 4, a groove 3b is of V-shaped section in the axial direction, and a projection 2b is of L-shape. At least one of the steel 2 and the spheroidal graphite cast iron member 3 is hollow. A heat affected zone of the spheroidal graphite cast iron member 3 is preferably <=10% in martensitic area ratio of a base matrix except graphite, and more preferably, <=1%. The friction welded member 1 is suitable for a lower arm, a torque rod, a propeller shaft, and an axle housing. The welded part 4 is cooled in the temperature range of 780-680 deg.C at the cooling speed of 4 deg.C/second.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a friction welding member, and more particularly, to a friction welding member for joining a steel material and a spheroidal graphite cast iron by friction welding.

[0002]

2. Description of the Related Art For example, a lower arm, a torque rod or the like, which is a component such as a truck, has a structure in which a rod-shaped or pipe-shaped shaft portion is provided with a connection portion with another U-shaped or U-shaped member. Generally, the shaft portion and the connecting portion are integrally formed by forging.

In recent years, there has been a demand for weight reduction of trucks and truck parts due to the problem of overloading regulations. Also, in the case of strength members such as lower arms and torque rods, propeller shafts similar in shape to these lower arms and torque rods, and axle housings with more complex shapes, the shaft is made of hollow pipes such as carbon steel for mechanical structures. After forming the connecting part from carbon steel to forged carbon steel product by forging method,
Friction welding has been performed between the end surface of the shaft portion and the end surface of the connecting portion. However, the forging method requires a draft angle due to the ease of die removal during forging, and it is difficult to form this in the case of a joint with a complicated shape. is there.

Therefore, the shaft portion is a hollow pipe made of a steel material such as carbon steel for mechanical structures, and the connecting portion having a complicated shape is replaced with the above-mentioned carbon steel forged steel (specific gravity 7.8) to replace the spheroidal graphite cast iron material (specific gravity 7). It is conceivable that the strength member is made lighter and more functional by friction-welding the end faces with each other by producing by a casting method. For example, Japanese Patent Application Laid-Open No. Hei 4-231183 discloses a method of friction-welding a hollow end pipe made of carbon steel applied to an axle housing of an automobile to a housing body made of spheroidal graphite cast iron, with a friction pressure of 20 to 40 MPa and a friction time of 60 mm. After relative motion while rubbing for ~ 120 seconds, upset pressure 80 ~ 140MPa, upset time 6 ~
There is a description of upsetting in 10 seconds. This Japanese Patent Laid-Open No. 4-2
According to Japanese Patent No. 31183, a frictional rotation is performed by a small friction pressure and a long friction time to moderate a temperature gradient around a joint of a material, thereby preventing precipitation of martensite and cementite in a structure of the joint and graphite. Are melted in a good condition by disappearing from the joint, and the material is joined with a large strength because the upset is performed with a large upset and a short upset time.

[0005] Japanese Patent No. 268033 (Japanese Unexamined Patent Application Publication No.
Japanese Patent Application Laid-Open No. 16605) discloses a method of manufacturing an axle housing as a strength member, in which an axle housing body is formed of a spheroidal graphite cast iron material. In addition, there is a description that an axle end pipe is formed of carbon steel, and when the axle housing main body is cast, a joint thereof is rapidly cooled and chilled and then frictionally welded to a joint casting of the axle end pipe.
Japanese Patent No. 268033 (JP-A-5-16605)
According to Japanese Patent Application Laid-Open Publication No. H11-157, friction welding is performed in a state where the structure of the joint casting part of the axle housing is cementite, graphite precipitation is prevented, and inhibition of friction welding by graphite is prevented. The company says that it can be friction-welded with sufficient strength even if it is abutted in a cut state. Also, Japanese Patent No. 268033 (JP-A-5-166)
Japanese Patent Publication No. 05-2005), one of the joint castings of the axle housing main body and the axle end pipe is formed with a convex tapered surface, and the other is formed with the same concave tapered surface as the convex tapered surface. It is described that the friction welding can be performed with more sufficient strength by increasing the area of both joining surfaces.

[0006]

In the friction welding, since oxides and the like on the abutting surfaces of the base material are destroyed and extruded during the friction process, pores such as carbon dioxide gas and welds such as welds are formed in the welded portion. Since there are few inclusions and the heating temperature is lower than that of fusion welding, there are few heat affected zones, and by controlling the pressure welding conditions, the process is automated and stable quality is obtained.
It has features such as high economic efficiency.

However, the above effect can be obtained with respect to friction welding between steel materials such as carbon steel. However, when at least one of the materials is a spheroidal graphite cast iron material, the graphite performs a lubricating action and hardly generates frictional heat. Also, since the melting point is low and the temperature of the solid phase surface of friction welding is low, it is considerably difficult compared with friction welding between steel materials.

[0008] The friction rotation with a small friction pressure and a long friction time described in JP-A-4-231183,
When the upset pressure and the upset time are controlled, the matrix structure of the spheroidal graphite cast iron material is recrystallized into a hard structure such as a pearlite matrix by frictional heat, and apparently the strength increases. However, when joining members having a large difference in heat capacity, such as a solid round bar and a pipe having a hollow portion, the tensile strength of the joint is
It may be lower than the tensile strength of the steel material or the spheroidal graphite cast iron material to be pressed, and may be broken at the joint, and it is difficult to apply to a strength member.

Also, Japanese Patent No. 268033 (Japanese Patent Laid-Open No.
JP-A-16605) discloses a manufacturing method in which an axle housing body made of a spheroidal graphite cast iron material is chilled by quenching at the time of casting and then frictionally welded to an axle end pipe formed of carbon steel. Chilling of the axle housing body during casting may impair the toughness of the spheroidal graphite cast iron base material. Chill can be eliminated by a heat treatment at about 700 ° C. for 1 hour, but if this heat treatment is performed, the fatigue strength may be reduced by about 15 to 20%, and it is difficult to apply to a strength member.

[0010] Japanese Patent No. 268033 (Japanese Unexamined Patent Application Publication No.
As described in paragraph No. 0011 of JP-A-16605), when the convex and concave tapered surfaces are joined to each other, the graphite present in the spheroidal graphite cast iron material plays a role of lubrication during friction in friction welding to generate heat. However, it takes a long time to obtain good bonding. In addition, when the tapered surfaces are joined together, the thickness of the edge portions becomes extremely thin, which may cause deformation. Then, the tensile strength of the joint may be lower than the tensile strength of the steel material or the spheroidal graphite cast iron material to be pressed.

Normally, in friction welding, the joints of the materials to be joined have the same shape in order to equalize the heat balance during frictional heating. However, when the shapes cannot be the same, that is, when the heat capacities of the joining materials are largely different, the joined portions are easily cooled, and are likely to have high hardness and low toughness. In addition, spheroidal graphite cast iron material tends to generate martensite because it contains more carbon than steel material, and even in the case of a similar shape, martensite is likely to be generated when the heat capacity is small. For these reasons, it has been difficult to frictionally weld steel and spheroidal graphite cast iron to form a strength member.

SUMMARY OF THE INVENTION An object of the present invention is to provide a friction welding member for joining steel and spheroidal graphite cast iron by friction welding, which has an excellent tensile strength at a joint and is suitable for a strength member such as a lower arm, a propeller shaft, a torque rod, or an axle housing. An object of the present invention is to provide a friction welding member that can be applied to reduce the weight and enhance the function.

[0013]

Means for Solving the Problems The present inventors have proposed a friction welding method for joining steel material and spheroidal graphite cast iron material by friction welding.
We studied the joint shape and the structure of the joint to improve the tensile strength of the joint. If the shape of the joint after friction welding is V-shaped, L-shaped, or a combination of V-shaped and L-shaped in a sectional view in the axial direction, it is possible to improve the tensile strength of the joint by firmly joining. I found it. Here, the joint refers to a portion where the composition or the structure changes rapidly.

Further, in order to further improve the tensile strength, it is only necessary to reduce or eliminate martensite due to the thermal influence of the joint of the spheroidal graphite cast iron, and a predetermined cooling rate during or after the friction heating step. Found that it can be achieved by passing through. And even if the dimensions and the volume of the steel material and the spheroidal graphite cast iron material are different, the martensite generation of the spheroidal graphite cast iron material is suppressed, and when a tensile test is performed across the joint, at a position 0.1 mm or more away from the joint The inventors of the present invention have found that the friction welding member that can be broken can be applied to strength members such as a lower arm, a propeller shaft, a torque rod, and an axle housing, and can be reduced in weight and made functional.

That is, the friction welding member of the present invention is a friction welding member for joining steel material and spheroidal graphite cast iron by friction welding. It is characterized in that it breaks at the position where it is bent.

[0016] The shape of the joint portion is characterized in that it has one of a V-shape and an L-shape or a combination of the V-shape and the L-shape in a sectional view in the axial center direction.

Further, the joint portion has a substantially hollow portion.

In the heat affected zone of the spheroidal graphite cast iron material, the matrix structure is characterized in that the martensite area ratio excluding graphite is 10% or less, preferably 1% or less.

The friction welding member is a lower arm, a torque rod, a propeller shaft, and an axle housing.

Next, the configuration of the friction welding member of the present invention will be explained.
Explain why.(1) When a tensile test is performed across the joint,
Break at a distance of 0.1 mm or more 0.1m from the joint when the tensile test is performed across the joint
m or more when broken at a distance of more than
Strength members can be designed with the weaker tensile strength of iron.
You. For example, structural carbon steel pipe with a hollow part (JIS)
STKM13A and spheroidal graphite cast iron (JIS) FCD4
If it is a friction welding member that friction welds 00
Tensile strength of carbon steel pipe (JIS) STKM13A is 37
0N / mm ^Two And spheroidal graphite cast iron (JIS)
The tensile strength of FCD400 is 400 N / mm^Two Is over
So, the weaker structural carbon steel pipe (JIS) STKM1
The shape can be designed based on the tensile strength of 3A.

(2) Shape of Joint of Steel and Spheroidal Graphite Cast Iron
The joint between the steel- like material and the spheroidal graphite cast iron material is V
If the shape is V-shaped, the V-shaped slope and the end surface are firmly joined, and the joining area is increased, so that the tensile strength of the joint is improved. If it is L-shaped when viewed in the axial direction cross section, the cylindrical surface and the end surface are firmly joined, and the joining area is increased, so that the tensile strength of the joint is improved. In the case of the combination of the V shape and the L shape, the V-shaped slope, the cylindrical surface, and the end surface are firmly joined, and the joining area is increased to improve the tensile strength of the joint. Here, the V-shape excludes a shape formed by simple butt friction welding, but is an open V-shape, a V-shape having an R at the bottom of the V-shape, a U-shape, and a W-shape.
Includes shapes such as shapes.

(3) Less steel or spheroidal graphite cast iron
If one side is formed of a steel material such as a steel pipe for piping, a steel pipe for heat transfer, a steel pipe for structure, or a steel pipe for special use and an alloy pipe having a hollow part substantially defined by JIS (Japanese Industrial Standards) , And can be manufactured at low cost. Even if a steel material having a hollow portion or a spheroidal graphite cast iron material is manufactured by forging, casting, machining from a solid material, etc., the weight can be reduced. Here, the substantially hollow portion indicates that the entire steel material or spheroidal graphite cast iron material is hollow, both end portions are hollow, or only one end surface is hollow. According to the spheroidal graphite cast iron material, a connection portion with another member can be formed as a complicated shape. And
As a friction welding member between steel and spheroidal graphite cast iron, it can be reduced in weight and improved in function.

(4) The heat affected zone of the spheroidal graphite cast iron material is
Martensite area ratio excluding graphite in the structure is 10% or less
Bottom, preferably 1% or less The heat-affected zone of the joint of the spheroidal graphite cast iron material has a martensite area ratio excluding graphite of the base structure of 10% or less, preferably 1% or less, with the joint being sandwiched. When subjected to a tensile test, it breaks at a distance of 0.1 mm or more from the joint, so that it can be applied to a strength member.

(5) The friction welding member has a lower arm and a torque
Friction welding of rod, propeller shaft, or axle housing steel to spheroidal graphite cast iron using the above means, friction welding member such as lower arm, torque rod, propeller shaft, or axle housing, especially steel or spheroidal graphite cast iron The weight can be reduced by forming the hollow portion in the material, and the function can be enhanced by forming the material from multiple materials.

In the case of spheroidal graphite cast iron, the microstructure is determined by the cooling rate when passing through the A1 transformation point after the friction step. When passing through the temperature range of 780 ° C. to 680 ° C. including the A1 transformation point at a cooling rate lower than 4.0 ° C./sec, the generation of martensite is small. Control of the cooling rate after the friction step can be easily performed by a high-frequency induction heating device combined with the friction welding device.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG.
FIG. 6 is a cross-sectional view of a principal part of one side of a friction welding member 1 in which a joint 4 is formed in a V-shape in a sectional view in the axial direction, and FIG. ) Shows the state after friction welding. As shown in FIG. 1 (a), the joined portion of the steel material 2 before the pressure welding has an outer diameter 2e and an inner diameter 2f, and a projection 2b having a convex cross section is formed at the end 2a. On the other hand, the joint portion of the spheroidal graphite cast iron material 3 before the pressure welding has an outer diameter 3e and an inner diameter 3f, and forms a V-shaped groove 3b in the end face 3c of the end 3a. The projection 2b and the groove 3b may be formed of any of the steel material 2 and the spheroidal graphite cast iron material 3. In addition, outer diameter 3e, inner diameter 3
If f is appropriate, the projection 2b does not need to be formed in a convex shape. FIG. 6 is a side view of a main part of the friction welding device 5 provided with the high-frequency induction heating device 6, in which reference numeral 7 denotes a heating element arranged with a gap around the outer periphery of the joint 4, reference numeral 8 denotes a main shaft, and reference numeral 9 denotes a slide. The friction welding is performed as follows. First, the steel 2 is attached to the main shaft 8, and the spheroidal graphite cast iron 3 is attached to the slide 9. By moving the slide 9 while rotating the main shaft 8, the convex protrusion 2b comes into contact with the V-shaped groove 3b to generate frictional heat. Then, the convex protrusion 2b and the V-shaped groove 3b fill each other. Further metallic bonding is performed in an upset process following the friction heating process.

After the frictional heating, the high-frequency induction heating device 6 is energized to cause the heating element 7 to generate heat.
Cooling control for passing the temperature range of ° C at a cooling rate lower than 4.0 ° C / sec is performed. Here, if the cooling conditions are prepared, the cooling control need not be performed. After the friction welding, the pressure welding member 1 is removed from the friction welding device 5.

By the friction welding and the cooling control, as shown in FIG. 1B, the joining portion 4 is joined in a V shape. The heat-affected zone 3h of the joint 4 of the spheroidal graphite cast iron material 3 becomes almost 100% pearlite when the martensite area ratio excluding graphite of the base structure is 0.1% or less, and the graphite shape does not collapse. , Remains almost spherical. When the tensile test is performed with the joint 4 interposed therebetween, the steel material 2 or the spheroidal graphite cast iron material 3
0.1 mm from the joint 4 at the weaker one of the tensile strengths
It breaks at a distance more than that.

(Embodiment 2) FIG. 2 shows an essential part of one side of a friction welding member 1 in which a steel material 2 and a spheroidal graphite cast iron material 3 are joined and a joint 4 is formed in an L-shape in a sectional view in the axial direction. It is sectional drawing, (a) shows before friction welding and (b) shows after friction welding. As shown in FIG. 2 (a), the joined portion of the steel material 2 before the pressure welding has an outer diameter 2e and an inner diameter 2f, and the end 2a has an I-shaped cross section of the end face 2c while being cut. On the other hand, the joint portion of the spheroidal graphite cast iron material 3 before pressure welding has an end face 3c, an outer diameter 3e and an inner diameter 3f, and the end 3a has an outer diameter 3d and an inner diameter 2f of the steel material 2.
Are made to fit together in a radial gap 3g to form an L-shaped cross section. The I-shaped or L-shaped formation may be made of either the steel material 2 or the spheroidal graphite cast iron material 3. Also in the second embodiment, the friction welding device 5 provided with the high-frequency induction heating device 6 shown in FIG.
To perform friction welding. First, the steel 2 is attached to the main shaft 8, and the spheroidal graphite cast iron 3 is attached to the slide 9. By moving the slide 9 while rotating the main shaft 8, the steel 2
And the end face 3c of the spheroidal graphite cast iron material 3 generates frictional heat. Under the influence of the frictional heat, a gap 3 g between the inner diameter 2 f of the steel material 2 and the stepped outer diameter 3 d of the spheroidal graphite cast iron material 3.
Is buried. In the upset process following the friction heating process,
The end face direction and the cylindrical direction are further metallically connected.

After the frictional heating, the high-frequency induction heating device 6 is energized to cause the heating element 7 to generate heat.
Cooling control for passing the temperature range of ° C at a cooling rate lower than 4.0 ° C / sec is performed. Here, if the cooling conditions are prepared, the cooling control need not be performed. After the friction welding, the pressure welding member 1 is removed from the friction welding device 5.

By the friction welding and the cooling control, as shown in FIG. 2B, the joining portion 4 is joined in an L shape. The heat-affected zone 3h of the joint 4 of the spheroidal graphite cast iron material 3 becomes almost 100% pearlite when the martensite area ratio excluding graphite of the base structure is 0.1% or less, and the graphite shape does not collapse. , Remains almost spherical. When the tensile test is performed with the joint 4 interposed therebetween, the steel material 2 or the spheroidal graphite cast iron material 3
0.1 mm from the joint 4 at the weaker one of the tensile strengths
It breaks at a distance more than that.

(Embodiment 3) FIG. 3 shows a friction welding member in which a steel material 2 and a spheroidal graphite cast iron material are joined, and a joint 4 is formed by combining a V shape and an L shape in a sectional view in the axial direction. 1
3A is a cross-sectional view of a main part of one side of FIG.
Indicates the state after friction welding. As shown in FIG.
Has an outer diameter 2e and an inner diameter 2f, and a projection 2b having a convex cross section is formed at the end 2a. on the other hand,
The joint portion of the spheroidal graphite cast iron material 3 before the pressure welding has an outer diameter 3e and an inner diameter 3f. The stepped outer diameter 3d is made to protrude and fit in the radial gap 3g to form an L-shaped cross section. Projection 2b and groove 3b
May be formed on any of the steel material 2 and the spheroidal graphite cast iron material 3.
If the outer diameter 2e and the inner diameter 2f are appropriate, the projection 2b does not need to be intentionally formed in a convex shape. The L-shaped formation may be made of either the steel material 2 or the spheroidal graphite cast iron material 3. Also in the third embodiment, friction welding is performed by the friction welding device 5 provided with the high-frequency induction heating device 6 shown in FIG. First, the steel 2 is attached to the main shaft 8, and the spheroidal graphite cast iron 3 is attached to the slide 9. By moving the slide 9 while rotating the main shaft 8, the convex protrusion 2c comes into contact with the V-shaped groove 3c to generate frictional heat. Then, the convex protrusion 2c and the V-shaped groove 3c fill each other. Under the influence of the frictional heat, the steel material 2
The gap 3g between the inner diameter 2f and the stepped outer diameter 3d of the spheroidal graphite cast iron material 3 is filled. Then, in the upset process following the friction heating process, the end face direction and the cylindrical direction are further metallically connected.

After the frictional heating, the high-frequency induction heating device 6 is energized to cause the heating element 7 to generate heat.
Cooling control for passing the temperature range of ° C at a cooling rate lower than 4.0 ° C / sec is performed. Here, if the cooling conditions are prepared, the cooling control need not be performed. After the friction welding, the pressure welding member 1 is removed from the friction welding device 5.

By the friction welding and the cooling control, as shown in FIG. 3 (b), the joining portion 4 is joined in a shape combining V and L shapes. The heat-affected zone 3h of the joint 4 of the spheroidal graphite cast iron material becomes almost 100% pearlite when the martensite area ratio of the base structure excluding graphite is 0.1% or less, and the graphite shape does not collapse. It remains almost spherical. Then, when a tensile test is performed with the joint 4 interposed therebetween, the joint 4 breaks at a position 0.1 mm or more away from the joint 4 at the weaker of the tensile strengths of the steel material 2 and the spheroidal graphite cast iron material 3.

[0035]

Example (Example 1)

As the steel material, (JIS) STKM13A,
Outer diameter 34.0mm, thickness 2.3mm [tensile strength 370N
/ Mm ² or more, yield strength 215 N / mm ² or more, elongation (12
No. 30% or more in the longitudinal direction of the test piece)], and as a spheroidal graphite cast iron material (JIS) FCD400
[Tensile strength of 370 N / mm ² or more] and outer diameter of 34.0 m
The friction welding was performed by changing the shape of the pressure contact portion shown in Table 1 and the cooling rate after frictional heating in various ways using m and thickness of 5.0 mm.

(Table 1) Time from the start to the end of the joining part at the end of the temperature holding time to the end Temperature cooling rate (° C.) (second) (second) (° C.) (° C./second) Example 01 V 800 0 120 600 1.67 Example 02 V 800 0 60 600 3.34 Example 03 L 800 0 200 600 1.00 Example 04 V + L 750 5 15 700 3.33 Comparative Example 01 V 800 5 25 600 8.00 Comparative Example 02 Butt 750 0 33 650 3.03 Comparative Example 03 Butt 750 10 10 700 5.00

In Table 1, in Example 01, in Example 01, a steel material and a spheroidal graphite cast iron material were joined in the end face direction, and the joined portion was formed into a V shape in a sectional view in the axial center direction shown in FIG. 800 ° C
To 600 ° C for 120 seconds and a cooling rate of 1.67 ° C / second. In Example 02, the shape of the joining portion was the same as that of Example 01, and the steel material and the spheroidal graphite cast iron material were joined in the end face direction, and the joining portion was V-shaped in the axial center cross-sectional view shown in FIG. After the heat generation, cooling is performed from 800 ° C. to 600 ° C. at a cooling rate of 60 seconds and 3.34 ° C./second. Example 0
3 is joined in the end face direction and the radial direction, and the joined portion is formed into an L shape in an axial cross-sectional view shown in FIG.
Cooling from 0 ° C. to 600 ° C. is performed at a cooling rate of 200 seconds and 1.00 ° C./second. In Example 04, joining was performed in the end face direction and the radial direction, and the joined portion was formed into a shape combining V-shape and L-shape in the axial direction sectional view shown in FIG. Then, after holding to 700 ° C, 1
The cooling is performed at a cooling rate of 5 seconds and a cooling rate of 3.33 ° C./second.

On the other hand, in Comparative Example 01, a steel material and a spheroidal graphite cast iron material were joined in the end face direction, and the joined portion was formed into a V shape in a sectional view in the axial direction shown in FIG. After the second holding, cooling was performed at a cooling rate of 25 seconds and 8.00 ° C./second from the holding to 600 ° C. Comparative Example 02 is a conventional friction welding by butt welding, in which a steel material and a spheroidal graphite cast iron material are joined in an end face direction, and the joined portion is formed into an I shape in an axial sectional view. Up to 650 ° C
It is cooled at a cooling rate of 3 seconds and 3.03 ° C./second. Comparative Example 03 is friction welding by conventional butting,
A steel material and a spheroidal graphite cast iron material are joined in the end face direction, and the joined portion is formed into an I-shape in a sectional view in the axial direction.
After holding for 10 seconds at 700 ° C., 10 seconds and 5.
Cooling is performed at a cooling rate of 00 ° C./sec.

Examples 01 to 04 in Table 1 and Comparative Example 0
With respect to Nos. 1 to 03, (1) the martensite area ratio of the heat-affected zone of the spheroidal graphite cast iron material, (2) the tensile strength by a tensile test using a test piece sandwiching the joint, and (3) the fracture site were examined. Table 2 shows the results. FIG. 4 is a metallographic micrograph of the joint of Example 01, FIG. 5 is a metallographic micrograph of the joint of Example 03, and FIG. 12 is a metallographic micrograph of Comparative Example 01.

(Table 2) Martensite area ratio joint tensile strength fracture site (%) (N / mm ² ) Example 01 0.9 420 (JIS) STKM13A 5 mm away from joint Example 02 9.2 395 From joint (JIS) STKM13A Example 3 0.8 415 3mm away from the joint (JIS) STKM13A Example 04 8.7 400 3mm away from the joint (JIS) STKM13A Comparative Example 01 12.0 360 Joint Part Comparative Example 02 15.5 365 Joint Part Comparative Example 03 20.0 350 Joint

As can be seen from Table 2, in Examples 01 to 04, the martensite area ratio of the heat-affected zone of the spheroidal graphite cast iron material was 10% or less, the tensile strength of the fractured portion was secured, and 0.1 m from the joint.
It is broken by a carbon steel pipe for machine structure of (JIS) STKM13A at a position separated by m or more. From this, (JI
S) A strength member can be designed by the tensile strength of the carbon steel pipe for machine structure of STKM13A.

On the other hand, in Comparative Examples 01 to 03, the martensite area ratio of the heat-affected zone of the spheroidal graphite cast iron material exceeded 10%,
The tensile strength of the joint is lower than that of the carbon steel pipe for machine structure (JIS) STKM13A or the spheroidal graphite cast iron material of (JIS) FCD400, and the joint breaks. In this case, it becomes difficult to design a strength member with a weaker tensile strength of (JIS) STKM13A carbon steel pipe for machine structural use or (JIS) FCD400 spheroidal graphite cast iron material.

(Embodiment 2) FIG. 8 is a side view of a lower arm 21, which is a component of a truck, after friction welding, in which both ends of a steel material 22 are friction welded with spheroidal graphite cast irons 23A and 23B. are doing. And the steel material 22 is (J
IS) STKM13A, outer diameter 34.0 mm, thickness 2.3
mm [tensile strength 370 N / mm ² or more, yield strength 215 N /
mm ² or more, elongation (30% or more in the longitudinal direction of No. 12 test piece)]
Is composed of a carbon steel pipe for mechanical structure, a spheroidal graphite cast iron material 23A and a spheroidal graphite cast iron material 23B (JIS) FCD400 [tensile strength of 370 N / mm ² or more].

Before the friction welding, the steel material 22 is formed with the end faces of both ends being cut, and the end faces of the spheroidal graphite cast iron material 23A and the spheroidal graphite cast iron material 23B are formed in a V-shaped cross section. The steel material 22 and the spheroidal graphite cast iron material 23A are friction-welded by the friction welding device 5 provided with the high-frequency induction heating device 6 and the heating element 7 shown in FIG. A steel material 22 is attached to the main shaft 8 of the friction welding device 5.
Is attached to the slide 9, and the slide 9 is moved in accordance with the rotation of the main shaft 8. The friction heating step includes a friction pressure of 50 to 75 MPa and a friction time of 1
Heat is generated by friction at a friction speed of 1.0 to 3.8 m / s for 5 to 40 seconds, and then the upset step is performed at an upset pressure of 75 to 90 MPa and an upset time of 5 to 10 seconds. Simultaneously with the upset process, the high-frequency induction heating device 6 is energized to cause the heating element 7 to generate heat and pass through the joint 24A through the temperature range of 780 ° C. to 680 ° C. at a cooling rate lower than 4.0 ° C./sec. Perform cooling control.

After being removed from the friction welding device 5 after the friction welding, the axial section of the joining portion 24A is joined in a V-shape.
Then, the heat-affected zone of the joint 24A of the spheroidal graphite cast iron material 23A becomes almost 100% pearlite when the martensite area ratio excluding the graphite of the base structure is 0.1% or less, and the graphite shape does not collapse. It remains spherical.

Similarly to the above, by friction welding the steel material 22 to which the spheroidal graphite cast iron material 23A has been friction-welded and the spheroidal graphite cast iron material 23B, the joint portions 24A and 24B have excellent tensile strength and light weight. A highly functional lower arm 21 can be obtained.

(Embodiment 3) FIG. 9 shows components of a truck.
FIG. 3 is a side view of a certain torque rod 31 after friction welding.
Each end of the material 32 has a spheroidal graphite cast iron material 33A,
It is in frictional pressure contact with iron 33B. And the steel material 32 is (J
IS) STKM17C, outer diameter 76.3 mm, thickness 4.0
mm [tensile strength 650 N / mm^Two Above, proof stress 480N /
mm^Two Elongation (10% or more in the longitudinal direction of No. 12 test piece)]
Carbon steel pipe for machine structural use, spheroidal graphite cast iron material 33A and
33B is (JIS) FCD700 [tensile strength 650 N /
mm ^Two Or more].

Before the friction welding, the steel material 32 is formed with both ends being cut, and the spheroidal graphite cast iron material 33A and the spheroidal graphite cast iron material 33B form a stepped outer diameter 33d at the ends thereof.
A gap of 0.2 mm is formed in the inner diameter 32d of the steel material 32 in the radial direction. This gap is 0.04 to 0.3 in the radial direction when the stepped outer diameter 33d has a diameter of 30 to 150 mm.
mm. The thickness of the joint in the radial direction was 4.0 mm for the steel material 32, and the spheroidal graphite cast iron material 33.
A and 33B are 20 mm.

The steel material 32 and the spheroidal graphite cast iron material 33A are friction-welded by a friction welding device 5 provided with a high-frequency induction heating device 6 and a heating element 7 shown in FIG. The steel material 32 is attached to the main shaft 8 of the friction welding device 5 and the spheroidal graphite cast iron material 33A is attached to the slide 9, and the slide 9 is moved in accordance with the rotation of the main shaft 8. Then, the friction heat generation step includes a friction pressure of 50 to 75MP.
a, friction time 15 to 40 seconds, friction speed 1.0 to 3.8 m
/ S to generate frictional heat.
Upset pressure 75 ~ 90MPa, upset time 5 ~
Upset in 10 seconds. At the same time as moving to this upset process, the high-frequency induction heating device is used to perform heating at 780 ° C.
Cooling control for passing the temperature range of ° C at a cooling rate lower than 4.0 ° C / sec is performed.

After being removed from the friction welding device 5 after the friction welding, the axial section of the joining portion 34A is joined in an L-shape.
The heat-affected zone of the joint 34A of the spheroidal graphite cast iron material 33A becomes almost 100% pearlite when the martensite area ratio excluding the graphite of the base structure is 0.1% or less, and the graphite shape is not collapsed. It remains spherical.

Similarly to the above, by friction welding the steel material 32 to which the spheroidal graphite cast iron material 33A has been friction-welded and the spheroidal graphite cast iron material 33B, the joining parts 34A and 34B have excellent tensile strength and light weight. Highly functional propeller shaft 3
1 can be obtained.

(Embodiment 4) FIG. 10 is a side view of a propeller shaft 41 which is a component of a truck after friction welding, in which both ends of a steel material 42A are frictionally welded to a spheroidal graphite cast iron material 43 and a steel material 42B. I have. And the steel material 42A is (J
IS) STKM14B [tensile strength 500 N / mm ² or more] carbon steel tube for machine structure, spheroidal graphite cast iron 43 (JIS) FCD700 [tensile strength 700 N / mm ² or more], steel 42B (JIS) SFCM690S [ Chromium molybdenum steel forging having a tensile strength of 690 to 830 N / mm ² ].

Before the friction welding, the steel material 42A is formed by cutting both ends, and the spheroidal graphite cast iron material 43 and the steel material 42A are formed.
B has a V-shaped cross section at its end and a stepped outer diameter 42e.
And 43d, and a gap of 0.04 to 0.3 mm is formed in the radial direction with the inner diameter 42d of the steel material 42A.

First, friction welding between the steel material 42A and the steel material 42B is performed by a normal friction welding device. Next, the friction welding between the steel material 42A and the steel material 42B and the spheroidal graphite cast iron material 43 using the friction welding device 5 combining the high frequency induction heating device 6 and the heating element 7 shown in FIG. I do.
The main shaft 8 of the friction welding device 5 is friction-welded with a steel material 42A and a steel material 42B.
The slide 9 is moved in accordance with the attachment and rotation of the main shaft 8. Then, frictional heat is generated at a friction pressure of 40 MPa, a friction time of 30 seconds, and a friction speed of 3 m / s, and thereafter, an upset is performed at an upset pressure of 70 MPa and an upset time of 10 seconds. Simultaneously with the upset process, the high-frequency induction heating device 6 is energized to generate heat in the heating element 7, and cooling control is performed from 800 ° C. to 600 ° C. in 200 seconds.

After being removed from the friction welding device 5 after the friction welding, the joining portion 44A is joined in a combined shape of a V shape and an L shape in a sectional view in the axial direction. The heat-affected zone of the joint 44A of the spheroidal graphite cast iron material 43 has a martensite area ratio of 0.1% or less excluding graphite of the base structure and is almost 100%.
%, And the graphite shape is not collapsed, remains substantially spherical, and the joint portions 44A and 44B have excellent tensile strength, so that a lightweight and highly functional propeller shaft 41 can be obtained.

(Embodiment 5) FIG. 11 is a front view of an axle housing 51, which is a component of a truck, after friction welding, and shows an axle housing main body 53A made of spheroidal graphite cast iron.
Are friction-welded on one side of the carbon steel pipe 52 at the joint 54A, and one side of the carbon steel pipe 52 is
The joint 54B is friction-welded to the axle end pipe 53B made of spheroidal graphite cast iron. In FIG. 11, the left side of the cutting line at the left end is omitted, but is substantially symmetric with the right side with respect to the axle housing main body 53A.

Before the friction welding, both ends of the pipe 52 are cut as they are, and the ends of the axle housing main body 53A and the axle end pipe 53B have a V-shaped cross section to form a stepped outer diameter. A gap of 0.04 to 0.3 mm is formed in the radial direction with the inner diameter 42d of 52 in the radial direction.

First, the friction welding of the pipe 52 and the axle end pipe 53B is performed by using the friction welding device 5 in which the high frequency induction heating device 6 and the heating element 7 shown in FIG. 5 are combined.
A pipe 52 is attached to the main shaft 8 of the friction welding apparatus 5 and an axle end pipe 53B is attached to the slide 9, and the slide 9 is moved in accordance with the rotation of the main shaft 8. And friction pressure 4
Heat is generated by friction at 0 MPa, friction time of 30 seconds and friction speed of 3 m / s, and then upset at an upset pressure of 70 MPa and an upset time of 10 seconds. Simultaneously with the upset process, the high-frequency induction heating device 6 is energized to cause the heating element 7 to generate heat.
Perform cooling control in seconds.

When the joint 54B is removed from the friction welding device 5 after the friction welding, the joining portion 54B is joined in a V-shaped and L-shaped combined shape in a sectional view in the axial direction. The joint portion 54B of the axle end pipe 53B has a martensite area ratio of the base structure other than graphite of 0.1% or less and almost 100%.
And the graphite shape does not collapse and remains almost spherical.

Next, the pipe 52 and the axle end pipe 53B are friction-welded with the axle housing main body 53A using the friction welding apparatus 5 in which the high-frequency induction heating device 6 and the heating element 7 shown in FIG. Are friction-welded at the joint 54A.

The main shaft 8 of the friction welding device 5 is frictionally pressed between the pipe 52 and the axle end pipe 53B, and the axle housing main body 53A is attached to the slide 9, and the slide 9 is moved in accordance with the rotation of the main shaft 8. And
Friction pressure 40MPa, friction time 30 seconds, friction speed 3m /
s to generate frictional heat and then upset pressure 70M
Pa is upset at an upset time of 10 seconds. Simultaneously with the upset process, the high-frequency induction heating device 6 is energized to generate heat in the heating element 7, and cooling control is performed from 800 ° C. to 600 ° C. in 200 seconds.

After being removed from the friction welding device 5 after the friction welding, the joining portion 54A is joined in a combined shape of a V shape and an L shape in a sectional view in the axial direction. The joining portion 54A of the axle housing main body 53A has a martensite area ratio of the base structure excluding graphite of 0.1% or less and almost 100%.
% Pearlite, and the graphite shape does not collapse and remains almost spherical.

The opposite pipe 52 and the axle end pipe 53B are also friction-welded in the same manner as described above. And
Friction welding between the pipe 52 and the axle end pipe 53B on the opposite side and friction welding between the axle housing body 53A and the axle end pipe 53B are performed in the same manner, so that the joining portions 54A,
An axle housing 51 having excellent tensile strength of 4B, light weight, and high functionality can be obtained.

[0065]

The friction welding member of the present invention has the following excellent effects. (1) The area of the joint is increased, and the joint becomes a joint where the formation of martensite is prevented. When a tensile test is performed across the joint, the joint breaks at a position 0.1 mm or more away from the joint. . (2) The strength member can be designed based on the weaker tensile strength of the steel material or the spheroidal graphite cast iron material before the friction welding. (3) Lower arm, propeller shaft, torque rod,
Alternatively, the present invention can be applied to a strength member such as an axle housing to achieve weight reduction and high functionality.

[Brief description of the drawings]

Fig. 1 Steel and spheroidal graphite cast iron are joined in the end face direction,
FIG. 5 is a cross-sectional view of a principal part of one side of a friction welding member whose joint is formed in a V-shape in a sectional view in the axial direction.

Fig. 2 Steel and spheroidal graphite cast iron are joined in the end face direction.
FIG. 5 is a cross-sectional view of a main part on one side of a friction welding member whose joint is formed in an L-shape in a direction cross-sectional view.

FIG. 3 is a cross-sectional view of a principal part of one side of a friction welding member in which a steel material and a spheroidal graphite cast iron material are joined in an end face direction and a radial direction, and the joining portion is formed in a V-shape and an L-shape in a sectional view in the axial direction.

FIG. 4 is a metallographic micrograph of the joint of Example 1.

FIG. 5 is a metallographic micrograph of a joint of Example 3.

FIG. 6 is a side view of a friction welding device provided with a high-frequency induction heating device.

FIG. 7 is a view showing the shape of a test piece subjected to a tensile test.

FIG. 8 is a side view of a lower arm which is one of the friction welding members.

FIG. 9 is a side view of a torque rod which is one of the friction welding members.

FIG. 10 is a side view of a propeller shaft which is one of the friction welding members.

FIG. 11 is an overall front view of an axle housing which is one of the friction welding members.

FIG. 12 is a metallographic micrograph of Comparative Example 1.

[Explanation of symbols]

1: friction welding member, 2: steel material, 2a: end, 2b: projection, 2c: end surface, 2e: outer diameter, 2f: inner diameter, 3: spheroidal graphite cast iron material, 3a: end, 3b: groove, 3d: Stepped outer diameter,
3h: heat affected zone, 4: joint, 5: friction welding device, 6:
High frequency induction heating device, 7: heating element, 8: spindle, 9: slide, 10: tensile test piece, 21: lower arm, 31: torque rod, 41: propeller shaft, 51: axle housing.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B23K 103: 06

Claims (11)

[Claims] 1. A friction welding member for joining a steel material and a spheroidal graphite cast iron by friction welding, wherein when subjected to a tensile test across the joint portion, the member breaks at a position 0.1 mm or more away from the joint portion. Friction welding member. 2. The friction welding member according to claim 1, wherein the shape of the joining portion has a V shape in a sectional view in the axial direction. 3. The friction welding member according to claim 1, wherein the shape of the joining portion has an L-shape as viewed in a sectional view in the axial center direction. 4. The friction welding member according to claim 1, wherein the shape of the joining portion is a combination of a V shape and an L shape in a sectional view in the axial direction. 5. The friction welding member according to claim 1, wherein at least one of the steel material and the spheroidal graphite cast iron material has a substantially hollow portion. 6. The heat-affected zone of the spheroidal graphite cast iron material has a martensite area ratio excluding graphite of a base structure of 10% or less.
Item 8. The friction welding member according to Item 1. 7. The friction welding member according to claim 6, wherein the martensite area ratio is preferably 1% or less. 8. The friction welding member according to claim 1, wherein the friction welding member is a lower arm. 9. The friction welding member according to claim 1, wherein the friction welding member is a torque rod. 10. The friction welding member according to claim 1, wherein the friction welding member is a propeller shaft.
Item 8. The friction welding member according to Item 1. 11. The friction welding member according to claim 1, wherein the friction welding member is an axle housing.