JPH0913137A - Torque rod and its production - Google Patents

Abstract

PURPOSE: To lighten a torque rod by welding or pressure-welding ends and the connected part made of aluminum. CONSTITUTION: This torque rod is the one in which ends 1 and 2 made of an Al alloy are welded or pressure-welded to both end parts of a connecting rod 3 produced from an extruded pipe made of an Al alloy, and an aluminum alloy having a compsn. contg. 1.0 to 1.5% Si, 0.4 to 0.9% Cu, 0.2 to 0.6% Mn, 0.8 to 1.5% Mg and 0.3 to 0.9% Cr, and in which the content of Fe is regulated to <=0.25%, and also, the total content of Mn+Cu is regulated to <=1.2% is used. This aluminum alloy may furthermore contain one or >=two kinds among 0.005 to 0.05% Ti, 0.0001 to 0.01% B and 0.1 to 0.2%. Zr. The ends are prepd. by forging the cast material or extruded material of the Al alloy and next executing heat treatment by heating at 510 to 555 deg.C, thereafter executing water cooling and holding at 155 to 190 deg.C for 5 to 20hr.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque rod used as a torque rod or the like mounted on a truck suspension and provided with ring-shaped end members at both ends and a method of manufacturing the same.

[0002]

2. Description of the Related Art A torque rod, which is one of the components of a rear suspension such as a truck, has a structure in which rod-shaped or pipe-shaped ends are provided with ring-shaped ends. As the torque rod, an iron-based material integrally formed by forging has been conventionally used. However, due to the recent problem of overloading regulations, it is required to reduce the weight of trucks and truck parts, and torque rods are no exception. Therefore, as shown in FIGS. 1 and 2, a light weight structure in which the torque rod is divided into two ends 1 and 2 and a connecting rod 3 has been studied. In this structure, the connecting rod 3 is made of a thin pipe made of iron in order to reduce the weight, and the ends 1 and 2 are welded or pressure-welded to the connecting rod 3.

[0003]

The torque rod shown in FIGS. 1 and 2 uses a thin-walled iron pipe for the connecting rod 3, so that it can be compared with a conventional solid torque rod made by casting and forging. It is getting lighter. However, since iron is used as a material, there is a limit to weight reduction. In order to achieve further weight reduction, it is necessary to use a material having strength comparable to iron and lighter than iron. In addition, since the suspension is a part having a function of holding the axle with respect to the vehicle body, the required characteristics of the torque rod, which is one of the components thereof, cannot be satisfied only with a light material. That is, it is necessary for a product having a predetermined size and shape to satisfy required characteristics such as strength, elongation, and stress corrosion cracking resistance. Specifically, the iron torque rod currently used has a center-to-center distance between the ends 1 and 2 of 522 mm, and has a tensile strength and a compressive strength of 32,000 kgf or more, and a repetitive load of ± 6,000 kgf. Tensile and compressive fatigue strength to withstand 2 × 10 ⁶ times or more and 1
It is required to have an elongation of 0% or more. An object of the present invention is to reduce the weight of a torque rod by producing a torque rod using an Al material satisfying such required characteristics.

[0004]

In order to achieve the object, the torque rod of the present invention is a torque in which an Al alloy end is welded or pressure welded to both ends of a connecting rod made of an Al alloy extruded pipe. Rod, the Al alloy is Si: 1.0 to 1.5 wt%, Cu: 0.4 to 0.9
% By weight, Mn: 0.2-0.6% by weight, Mg: 0.8-
1.5 wt%, Cr: 0.3 to 0.9 wt% inclusive, F
e content is regulated to 0.25% by weight or less, and Mn
The composition is characterized in that the total content of + Cr is regulated to 1.2% by weight or less. As an Al alloy used for the end and the connecting rod, Ti: 0.005 to 0.0
5% by weight, B: 0.0001 to 0.01% by weight and Z
r: 0.1 to 0.2% by weight of one kind or two or more kinds may be contained. This torque rod is obtained by forging a cast material or an extruded material of an Al alloy having the above-mentioned composition, and then 510
After heating to ~ 555 ℃, water-cooling to 155 ~ 190 ℃
It is manufactured by performing a heat treatment of holding for 20 hours, and welding or pressure-welding an extruded pipe connecting rod having the same composition and subjected to the same heat treatment to the end made from the Al alloy after the heat treatment.

[0005]

In the present invention, an Al-Mg-Si based Al alloy is used as the material of the end and the connecting rod. This Al alloy secures the required strength by the fine precipitation of Mg ₂ Si. When Cu, Cr, Mn, etc. are added to this type of Al alloy, the strength is improved by solid solution of the matrix, crystallization and structure control. Therefore, in order to obtain a higher Al alloy depending on the application as the torque rod, first, Si
It is conceivable to increase the amount of Mg and Mg to increase the amount of precipitation of Mg ₂ Si. However, simply increasing the contents of Si and Mg not only lowers elongation, toughness, etc., but also fails to achieve the desired strength. The present inventors
The effects of the Mg ₂ Si-based precipitates on the mechanical properties and the effects of heat treatment on the crystal growth of the macrostructure of the forged and extruded materials were investigated from various viewpoints. As a result, Mg ₂ Si
In order to effectively utilize the action of the system precipitates and suppress the crystal growth of the macrostructure, it is concluded that the alloy components, their contents, and the heat treatment conditions must be determined in consideration of their mutual relationships. It was

In order to achieve the required action of the Mg ₂ Si based precipitates and the refinement of the macrostructure, the experiments by the present inventors show that the Si and Mg contents are 1.0 to 1.5% by weight, respectively. And 0.8 to 1.5% by weight have to be specified. However, even if the contents of Si and Mg are in this range, when the Al alloy after hot extrusion is subjected to T ₆ treatment or the hot or cold forged Al alloy is subjected to T ₆ treatment, abrupt crystal formation occurs. There is a phenomenon in which the macrostructure becomes coarse due to the growth of grains, and mechanical properties such as strength and elongation deteriorate. The coarsening of the recrystallized grains of the processed structure due to the heat treatment is suppressed by adding Cr and Mn in combination and optimizing the heat treatment conditions. As a result, the obtained Al alloy is
The structure has fine crystal grains, and the strength and elongation are remarkably improved. It is presumed that the property improvement due to the combined addition of Cr and Mn is due to the effect of suppressing the coarse growth of recrystallization when the solution treatment is performed after hot or cold working. In addition to the combined addition of Cr and Mn, Zr
When added together, the elongation is further improved and the crystal structure becomes finer. This is because Mn and Cr have the effect of suppressing the coarsening of the recrystallized grains, whereas Mn and Cr
This is because Zr promotes the refinement of the recrystallized grains when recrystallized in a high working region that exceeds the effect of suppressing the crystal grain growth.

The alloy components and contents of the Al alloy used in the present invention will be described below. Si: 1.0 to 1.5 wt% It is an alloying element that improves the strength of the Al alloy by the precipitation effect. In the alloy system of the present invention, since it is added in combination with Mg, the Mg ₂ Si-based compound precipitates and the strength is improved. The effect of such Si addition becomes significant when 1.0 wt% or more is added. However, excess Si over 1.5% by weight
The addition raises the liquidus temperature of the Al alloy and makes melting and casting difficult. Further, if the Si content is excessive, extrudability, forgeability and the like deteriorate. Cu: 0.4 to 0.9% by weight Mg ₂ S effective for strengthening the matrix by solid solution strengthening and improving the strength
It is an effective alloying element that promotes the precipitation of i. The effect of Cu becomes significant when added at 0.4% by weight or more. But,
A large amount of Cu exceeding 0.9% by weight deteriorates quenching sensitivity, corrosion resistance and the like.

Mn: 0.2 to 0.6% by weight An alloying element effective in suppressing the growth of crystal grains and maintaining a fine structure after heat treatment. The effect of becomes remarkable. However, if a large amount of Mn exceeding 0.6% by weight is contained, the workability during forging deteriorates. Mg: 0.8-1.5 wt% Reacts with Si to form a Mg ₂ Si-based compound that precipitates in the matrix and improves the strength of the Al alloy. In order to obtain this precipitation effect, a Mg content of 0.8% by weight or more is required. However, a large amount of Mg exceeding 1.5% by weight
In addition to saturation of precipitation effect, quenching sensitivity decreases. Cr: 0.3 to 0.9% by weight and Mn + Cr ≦ 1.2% by weight or less It is an alloying element that acts in cooperation with Mn to suppress the coarsening of crystal grains. The effect of adding Cr becomes remarkable at a content of 0.3% by weight or more. However, addition of a large amount exceeding 0.9% by weight deteriorates processability. Further, the Cr content needs to be regulated to 1.2% by weight or less in total with the Mn content. When the total content of Cr + Mn is maintained at 1.2% by weight, the above-described effect of the combined addition of Cr and Mn can be obtained without adversely affecting other components. On the other hand, if the Cr + Mn content exceeds 1.2% by weight, a huge Al-Mn-Cr-based compound is likely to crystallize, and the elongation of the Al alloy is significantly reduced.

Fe: 0.25% by weight or less Fe mixed in the Al alloy as an impurity is dispersed in the matrix as an Al-Fe-Si type compound that adversely affects elongation, corrosion resistance and the like. In this respect, the Fe content is preferably as small as possible, but excessively reducing the Fe content makes it difficult to melt the alloy. Therefore, in the present invention, the upper limit of the Fe content is set to 0.25% by weight where no substantial adverse effect is observed. Ti: 0.005 to 0.05% by weight An alloying element that is added as necessary, and has the effect of stabilizing the structure and improving the mechanical properties of the welded portion or the pressed portion. Such an effect is 0.005% by weight.
It becomes remarkable with the above Ti addition. However, 0.05% by weight
If a large amount of Ti exceeding the range is added, the toughness of the Al alloy deteriorates.

B: 0.0001 to 0.01 wt% Like Ti, it is an alloying element effective for stabilizing the structure,
The effect becomes remarkable when 0.0001% by weight or more of B is added. However, if a large amount of B exceeding 0.01% by weight is added, the toughness of the Al alloy deteriorates. Zr: 0.1-0.2% by weight Alloying element added as necessary, such as Mn and Cr
In cooperation with the above, an effect of suppressing the coarsening of crystal grains is exhibited. Z
The r also acts to improve the tensile strength by allowing the fiber structure formed by extrusion to remain in the forged product that has undergone the extrusion process. Such an addition effect becomes significant when Zr is added in an amount of 0.1% by weight or more. However, if a large amount of Zr is contained, the workability is adversely affected.
When adding r, the upper limit is 0.2% by weight.

Conditions for solution treatment and quenching: In order to improve the strength of the Al alloy having the above-mentioned composition, it is first necessary to completely dissolve the strength improving element into a solid solution. For that purpose, it is necessary to heat the Al alloy to a temperature of at least 510 ° C. or higher. However, at a temperature above 555 ° C, partial melting occurs and defects occur. After the solution treatment, the Al alloy is required to be water-quenched so that coarse MgSi-based precipitates are not generated. If A after solution treatment
When the 1-alloy is gradually cooled, the precipitated Mg ₂ Si-based precipitate grows coarsely and the target strength cannot be obtained. Aging treatment conditions: The water-quenched Al alloy is in a state where the alloying elements are supersaturated and solid-solved. This Al alloy is 155-
When the temperature is maintained at 190 ° C. for 5 to 20 hours, fine Mg ₂ Si-based compound is precipitated in the entire structure and the target strength is obtained. However, the temperature condition or the holding time is 155 to 190 ° C.
Otherwise, if it is out of the range of 5 to 20 hours, the deposited Mg ₂ Si grows large, or sufficient Mg ₂ Si does not precipitate, and the target strength cannot be obtained. The heat-treated Al alloy, whose components and compositions have been adjusted in this way, is 38 kgf / c
It exhibits a tensile strength of m ² or more and an elongation of 13% or more, and sufficiently satisfies the required characteristics as a connecting rod or end of a torque rod.

[0012]

EXAMPLES Various Al alloys having the compositions shown in Table 1 were heat treated to give an outer diameter φ ₁ = 1 as shown in FIGS. 3 (a) and 3 (b).
Ends 1 and 2 having a diameter of 30 mm, an inner diameter φ _{2 of} 105 mm and a width W of 51 mm were produced. One end of the annular part 4 of the ends 1 and 2 with a radius of curvature of 50 mm and a tip diameter of 60 mm
The joining protrusion 5 was formed. On the other hand, as the connecting rod 3, a pipe having an outer diameter of 60 mm made of the same heat-treated Al alloy extruded material was used. The connecting rod 3 was pressed against the end face of the joining projection 5, and the joining portion 6 was formed by MIG welding or friction welding, and the ends 1 and 2 were integrated with the joining rod 3. The connecting rod 3 has an inner diameter of 35 mm in the case of MIG welding, and an inner diameter of 40 mm in the case of friction welding.
I used a pipe. MIG welding conditions are welding rod A53
56, voltage 28V, current 280A, welding speed 1
It was set to m / min. Heating pressure of 500 kg for friction welding
f / cm ² , heating time 5 seconds, upset pressure 1000k
A gf / cm ² and upset amount of 10 mm were adopted.

[0013]

[Table 1]

Example 1 A casting rod of Alloy No. 1 was hot forged to prepare an end, which was then heated to 510 ° C. and cooled with water.
A heat treatment of holding at 150 ° C. for 20 hours was performed. The connecting rod was also manufactured by the same process. The torque rod obtained by MIG welding these ends and connecting rods has a tensile strength of 41,000 kgf and a compressive strength of 35,000 kg.
f, end portion elongation 14.5%, connecting rod portion elongation 15.
± 6,000 kgf at 5% and joint elongation 13.0%
It had never be damaged by the fatigue of repeated load, even after giving 2 × 0 ⁶ times. Further, a test piece was cut out from the joined torque rod and subjected to a stress corrosion cracking test in accordance with JIS H8711. That is, with 75% of the proof stress added, it was dipped in a 3.5% NaCl solution, and soaked for 10 minutes and dried for 50 minutes was repeated for 30 days. And
When the torque rod after the test was observed, no stress corrosion cracking was detected in the end portion, the connecting rod portion, and the joint portion.
On the other hand, the torque rod in which the end is joined to the connecting rod by friction welding has a tensile strength of 40,000 kgf, a compressive strength of 34,000 kgf, an end portion elongation of 14.5%, a connecting rod portion elongation of 15.5%, and a joint portion. Elongation of 11.0%, ±
The repeated load of 6,000kgf even after giving 2 × 0 ⁶ times had never damaged by fatigue. Further, in the results of the similar stress corrosion cracking test, no stress corrosion cracking was detected in any of the end portion, the connecting rod portion, and the joint portion.

Example 2 An extruded rod of Alloy No. 1 was hot forged to form an end, which was then heated to 555 ° C., cooled with water, and heat-treated at 190 ° C. for 5 hours. The connecting rod was manufactured by the same process as in Example 1. The torque rod obtained by MIG welding these ends and the connecting rod has a tensile strength of 39,000 kgf and a compressive strength of 34.5.
+/- 600 at 00 kgf, end part elongation 18.0%, connecting rod part elongation 15.5%, and joint part elongation 13.0%.
The repeated load of 0kgf even after giving 2 × 0 ⁶ times had never damaged by fatigue. When the same stress corrosion cracking test as in Example 1 was performed, the end portion, the connecting rod portion,
No stress corrosion cracking was detected at the joints. On the other hand, the torque rod whose end is joined to the connecting rod by friction welding has a tensile strength of 38,000 kgf and a compressive strength of 34.0.
00 kgf, end part elongation 18.0%, connecting rod part elongation 15.5%, joint part elongation 11.0%, ± 6.00
The repeated load of 0kgf even after giving 2 × 0 ⁶ times had never damaged by fatigue. Further, in the results of the similar stress corrosion cracking test, no stress corrosion cracking was detected in any of the end portion, the connecting rod portion, and the joint portion.

Example 3 An extruded rod of Alloy No. 2 was hot forged to form an end, which was then heated to 530 ° C., water cooled, and then heat-treated at 175 ° C. for 8 hours. The connecting rod was also manufactured by the same process. The torque rod obtained by MIG welding these ends and connecting rods has a tensile strength of 41,000 kgf and a compressive strength of 35,000 kg.
f, end portion elongation 16.3%, connecting rod portion elongation 17.
± 6,000 kgf at 2% and joint elongation of 13.0%
It had never be damaged by the fatigue of repeated load, even after giving 2 × 0 ⁶ times. When subjected to the same stress corrosion cracking test as in Example 1, no stress corrosion cracking was detected in any of the end portion, the connecting rod portion, and the joint portion. On the other hand, the torque rod whose end is joined to the connecting rod by friction welding has a tensile strength of 40,000 kgf and a compressive strength of 34,000 kg.
f, end portion elongation 16.2%, connecting rod portion elongation 17.
± 6,000 kgf at 3% and 11.1% elongation of the joint
It had never be damaged by the fatigue of repeated load, even after giving 2 × 0 ⁶ times. Further, in the results of the similar stress corrosion cracking test, no stress corrosion cracking was detected in any of the end portion, the connecting rod portion, and the joint portion.

Example 4 An extruded rod of Alloy No. 1 was hot forged to prepare an end, which was then heated to 530 ° C., cooled with water, and heat-treated at 180 ° C. for 8 hours. The connecting rod was manufactured by subjecting an extruded pipe of alloy No. 2 to the same heat treatment. The torque rod obtained by MIG welding these ends and connecting rods has a tensile strength of 41,500.
kgf, compressive strength 35,000 kgf, end portion elongation 15.0%, connecting rod portion elongation 17.1%, joint portion elongation 13.0%, and repeated load of ± 6,000 kgf 2 ×.
Even after giving 0 ⁶ times had never damaged by fatigue. When subjected to the same stress corrosion cracking test as in Example 1, no stress corrosion cracking was detected in any of the end portion, the connecting rod portion, and the joint portion. On the other hand, the torque rod whose end is joined to the connecting rod by friction welding has a tensile strength of 40,50.
0kgf, compressive strength 34,000kgf, end part elongation 14.9%, connecting rod part elongation 17.0%, joint part elongation 10.9%, with a repeated load of ± 6,000kgf 2
× 06 Even after being given ^six times, there was no breakage due to fatigue. Further, in the results of the similar stress corrosion cracking test, no stress corrosion cracking was detected in any of the end portion, the connecting rod portion, and the joint portion.

Comparative Example 1: An extruded rod of Alloy No. 3 was hot forged to prepare an end, which was then heated to 530 ° C., cooled with water, and heat-treated at 180 ° C. for 8 hours. The connecting rod was also manufactured using the same material and the same heat treatment. The torque rod obtained by MIG welding these end and connecting rod is
Tensile strength 38,500kgf, Compressive strength 34,000
Repeated load of ± 6,000 kgf at 2 x 0 ^{6 in} kgf
It was not damaged due to fatigue even after repeated application. However, the elongation was 6.0% at the end and 6.0 at the connecting rod.
%, A low value of 10.0% at the joint portion, which was unsuitable as a torque rod. On the other hand, the torque rod whose end is joined to the connecting rod by friction welding has a tensile strength of 37,
± 6 at 500 kgf, compressive strength 33,500 kgf
Even after a repeated load of 000 kgf was applied 2 × 0 ⁶ times, it did not break due to fatigue. However, also in this case, the elongation was low at 5.9% at the end portion, 6.1% at the connecting rod portion, and 9.5% at the joint portion, which was unsuitable as a torque rod.

Comparative Example 2: An extruded rod of Alloy No. 4 was hot forged to form an end, which was then heated to 530 ° C., water cooled, and heat treated at 180 ° C. for 8 hours. The connecting rod was also manufactured using the same material and the same heat treatment. The torque rod obtained by MIG welding these end and connecting rod is
The elongation is 19.8% at the end and 20.9% at the connecting rod.
Although the bonding portion showed a value of 11.5%, the tensile strength was 31,000 kgf and the compressive strength was 27,000 kgf, which were insufficient. Further, after giving 2 × 0 ⁶ times repeated load of ± 6,000Kgf it is damaged by fatigue occurs. Therefore, it was unsuitable as a torque rod. On the other hand, the torque rod in which the end is joined to the connecting rod by friction welding has an elongation of 19.9% at the end and 2 at the connecting rod.
0.6% and 11.0% at the joint, but the tensile strength was 31,000 kgf and the compressive strength was 27,000.
There was a shortage of 0 kgf. Further, after giving 2 × 0 ⁶ times repeated load of ± 6,000Kgf it is damaged by fatigue occurs. Therefore, it was unsuitable as a torque rod.

Comparative Example 3: An extruded rod of Alloy No. 5 was hot forged to form an end, which was then heated to 530 ° C., cooled with water, and heat-treated at 180 ° C. for 8 hours. The connecting rod was also manufactured using the same material and the same heat treatment. The torque rod obtained by MIG welding these end and connecting rod is
Tensile strength of 34,000 kgf, ± 6,000 kg
No damage due to fatigue occurred even after the repeated load of f was applied 2 × 0 ⁶ times. However, the elongation is 10.2 at the end.
%, 11.8% at the connecting rod portion and 10.2% at the joint portion, and the compressive strength was insufficient at 29,500 kgf. Therefore, it was unsuitable as a torque rod. The torque rod with the end joined to the connecting rod by friction welding also has a tensile strength of 34,000 kgf, ± 6,000.
damage due to fatigue the kgf repeated load of even after giving 2 × 0 ⁶ times did not occur. However, the growth is 1 at the end
0.0%, 11.9% at the connecting rod, 10.0% at the joint
And the compressive strength was insufficient at 29,000 kgf. Therefore, it was unsuitable as a torque rod.

[0021]

INDUSTRIAL APPLICABILITY As described above, in the present invention, the components are regulated and the heat treatment is performed under a specific condition A.
By making an end member and a connecting rod member from an alloy and welding or pressure welding the end member and the connecting rod member, the torque rod made of iron, which has been conventionally used, has substantially the same size and shape, and has characteristics comparable to those of iron. We have obtained a torque rod made of aluminum alloy with. This aluminum alloy torque rod is 55 to 60% lighter than that made of iron, and there is no need to change the design of the bushing that is press-fitted into the end portion or the parts that fix the torque rod. Used in the same way as an iron torque rod, it contributes to weight reduction of trucks.

[Brief description of the drawings]

FIG. 1 is a side view of a conventional iron torque rod divided into three parts, an end and a connecting rod.

FIG. 2 is a plan view of the iron torque rod.

FIG. 3 is a part (b) of a torque rod in which an aluminum end (a) is welded or pressure welded to an aluminum connecting rod in the embodiment of the present invention.

[Explanation of symbols]

1,2: end 3: connecting rod 4: annular part
5: Connecting protrusion 6: MIG welded or friction welded joint

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsu Yamada 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Inside the Nippon Light Metal Co., Ltd. Group Technology Center (72) Inventor Kenji Tsuchiya 1 Kambara-cho, Kambara-cho, Abara-gun, Shizuoka Chome 34-1, Nippon Light Metal Co., Ltd. Group Technology Center (72) Inventor Jindo Hino 1-34-1, Kambara-cho, Kambara-cho, Anbara-gun, Shizuoka Prefecture Nippon Light Metal Co., Ltd. Group Technology Center (72) Inventor Motoji Hotta Shizuoka 1-34-1 Kambara, Kambara-cho, Abara-gun Nippon Light Metal Co., Ltd. Group Technology Center

Claims (3)

[Claims] 1. A torque rod in which ends of an Al alloy are welded or pressure welded to both ends of a connecting rod made of an extruded pipe of the Al alloy, and the Al alloy is Si: 1.0.
~ 1.5 wt%, Cu: 0.4-0.9 wt%, Mn:
0.2-0.6% by weight, Mg: 0.8-1.5% by weight,
Cr: 0.3-0.9 wt% and Fe content of 0.
A torque rod having a composition in which the total content of Mn + Cr is regulated to 1.2 wt% or less while being regulated to 25 wt% or less. 2. The Al alloy according to claim 1 further comprises Ti:
0.005 to 0.05% by weight, B: 0.0001 to 0.
A torque rod containing one or more of 01 wt% and Zr: 0.1 to 0.2 wt%. 3. A cast or extruded material of an Al alloy having the composition according to claim 1 or 2 is forged, and then 510 to 55.
After being heated to 5 ° C., water-cooled and subjected to a heat treatment of holding at 155 to 190 ° C. for 5 to 20 hours, and an end made from the Al alloy after the heat treatment is made of an extruded pipe having the same composition and the same heat treatment. A method for manufacturing a torque rod, which comprises welding or pressure-welding a connecting rod.