JPH02277751A - Manufacture of aluminum powder alloy connecting rod - Google Patents

Abstract

PURPOSE:To provide the connecting rod with high strength and to improve its fatigue resistance by forming a connecting rod from an Al powder alloy having specified compsn. and subjecting it to shot peening under selected conditions. CONSTITUTION:An extruded material obtd. from a powder Al alloy material contg., by weight, 15 to 18% Si, 5 to 7% Fe and 4 to 6% Cu is formed into a connecting rod by hot forging at 400 to 500 deg.C, which is subjected to T6 treatment and is thereafter subjected to shot peening in the range of 0.05 to 0.20mmA2. As the result, the fatigue resistance of the Al powder alloy connecting rod can be improved, by which the lightweight connecting rod instead of the one made of steel can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing an aluminum powder alloy connecting rod.

[Prior Art] There is a high demand for reducing the weight of automobiles, motorcycles, etc. as a measure to save energy. In particular, reducing the weight of internal combustion engine parts, especially connecting rods, can greatly improve engine performance, so there is a strong desire to make these connecting rods and other parts aluminum.

By the way, connecting rods are used at temperatures ranging from room temperature to 200°C. For this reason, the Hunrod material is required to have tensile strength and fatigue strength at room temperature to 200°C, and it is also important that it has a high modulus of longitudinal elasticity and a low coefficient of linear expansion.

Conventionally, A is an aluminum alloy with excellent high-temperature strength.
221g, A2818, etc. are known.

In addition, an aluminum alloy material formed by molding rapidly solidified powder has been proposed, and the present applicant also previously filed Japanese Patent Application No. 82-26385.
No. 7, Patent Application No. 82-283658 was proposed.

[Problems to be Solved by the Invention] Even with the above-mentioned conventional aluminum alloys that are considered to have excellent high-temperature strength, their tensile strength, fatigue strength, and notch fatigue strength are still insufficient at temperatures of 150° C. or higher.

In particular, there is a demand for further improvement in fatigue strength in aluminum and nickel alloys for connecting rods.

Under these circumstances, the present invention aims to provide a method for manufacturing an aluminum powder alloy connecting rod that has high strength and improved fatigue strength.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the inventors of the present invention have conducted extensive research, and have formed a connecting rod from an aluminum powder alloy with a specific composition, and formed a connecting rod under selected conditions. It has been discovered that shot peening is effective, leading to the present invention.

That is, the present invention provides Si: 15 to 1 in weight %.
8%, Fe: 5-7%, Cu: 4-1I%.
After forming into a connecting rod by hot forging at 0°C and subjecting it to T6 treatment, the IgvA
This is a method for manufacturing an aluminum powder alloy connecting rod, which is characterized by performing shot peening in a range of 2.

The reasons for limiting the composition of the alloy material in the present invention are as follows.

Si: Coexists with Fe and disperses as an Al-8i-Fe-based compound, increasing fatigue strength and notch fatigue strength. It also increases the elastic modulus and lowers the linear expansion coefficient. If the amount is less than 15%, the fatigue strength and notch fatigue strength will decrease and the linear expansion coefficient will increase. If it exceeds 18%, the toughness will deteriorate.

Fe: Coexists with Sl and is dispersed as an Al-5i-Fe-based compound, and also makes Si particles fine. These increase tensile strength, fatigue strength, and notch fatigue strength. It also increases the elastic modulus and lowers the linear expansion coefficient. If the amount is less than 5%, tensile strength, fatigue strength, and notch fatigue strength will be insufficient. If it exceeds 7%, the toughness will decrease significantly. Furthermore, forgeability is also deteriorated.

Cu: Coexists with Mg and imparts age hardenability.

Age hardening improves tensile strength, fatigue strength, and notch fatigue strength. If the amount is less than 4%, the effect is not sufficient, and 6%
If it exceeds this, the toughness will be poor.

In addition to the above essential components, the powdered aluminum alloy used in the present invention contains less than 1% Mn and less than 1% Mg.
, less than 0.2% Cr.

Less than 0.3%Zns Less than 0.2%'ri%0.2
% of NL may be included.

Next, the manufacturing process will be explained. The aluminum alloy powder is prepared using a rapid solidification method such as gas atomization, single roll method, twin roll method, or spray roll method. Manufacture. It is necessary to set the average cooling rate to 103° C./sec or more in order to improve strength and toughness. The alloy powder is then subjected to a degassing step. This degassing step
It was carried out at 0°C. This is important for improving toughness. If the degassing temperature is less than 400°C, the degassing effect will be insufficient and the toughness will decrease, and if it exceeds 520°C, compound particles will grow and the strength will decrease. Degassing can be done by packing the powder into cans or in a vacuum furnace. The atmosphere during degassing may be vacuum, N2 gas, inert gas, etc., or in some cases, evacuation may be performed for a short time after heating in air.

Next, it is subjected to an extrusion process. Providing metal flow through extrusion is important for improving toughness. Extrusion is 30
It is carried out at a temperature of 0 to 500°C and an extrusion ratio of 4 or more. If the extrusion ratio is less than 4, the bonding between the powders will be insufficient and the toughness will be insufficient. If the extrusion temperature is less than 800°C, the deformation resistance is large and extrusion becomes difficult, and if the extrusion temperature exceeds 500°C,
Extrusion cracking occurs. The extruded material thus obtained is subjected to a hot forging process in order to form a connecting rod.

Hot forging is performed at 400°C to 500°C. If the forging temperature is less than 400°C, the deformability is insufficient and cracks occur.

Furthermore, forging cracks occur even when the temperature exceeds 500°C. The formed connecting rod is then subjected to a T6 treatment step.

The T6 treatment process causes age hardening through solution treatment, quenching, and tempering to improve strength. Normally, quenching is performed by water cooling, and tempering is performed under conditions that provide maximum strength. However, hot water quenching and over-aging tempering at relatively high temperatures are also performed to alleviate quenching distortion and residual stress.

In the shot peening process, shot peening is performed on the connecting rod surface after the T6 treatment. In this process, the connecting rod is rotated on a roller conveyor, and shot material is projected by the rotation of the impeller to process the connecting rod surface. This shot peening process is performed at an arc height of 0.05 to 0.20 svA2. The surface roughness (Ra) at this time is 1.5 to 4.
, 5μI, which is the maximum value of compressive residual stress due to processing! ;
L 17-25kgr/as 2 te.

This shot peening process increases the fatigue strength [σw(
107)] can be improved by about 10%. If the processing range is smaller than the above, the compressive residual stress will be too small and no improvement in fatigue strength will be observed.

Furthermore, if the processing range exceeds the above range, the surface roughness will be excessive and the fatigue strength will decrease.

In the present invention, in addition to the above steps, further steps can be added as necessary. For example, a process may be employed in which the powder is preliminarily compressed before the degassing process, or after degassing, the powder is densified by hot pressing while maintaining a vacuum, and then extrusion is performed. Furthermore,
Crushing and classification of powder, flakes, and ribbons can also be carried out as appropriate.

[Example] Example I S L: ty% by weight, Fe: 8% by weight, Cu:
After melting an aluminum alloy consisting of 4.5% by weight, Mn: 0.5% by weight, and Mg: 0.5% by weight, powder was produced by air atomization. Then, it was classified to 149μ or less. The average particle size of the powder thus obtained was BOμ-, and the average cooling rate was 8XLO3''C/sec.

This powder was mixed with CI P (Cold l5ostatic).
The material was pre-compressed using a vacuum cleaner (Pressing), and then placed in an aluminum can for vacuum degassing. The degassing temperature is 4
The temperature was 90°C. Thereafter, the aluminum can was sealed to form a billet for extrusion. Thereafter, extrusion was performed at 400° C. to obtain a square bar with a cross-sectional shape of 30×110 am.

At this time, the extrusion ratio was 15. This extruded rod was used as a forging material and was forged into a connecting rod shape. Forging temperature is 450
It was ℃. After this, 490℃XLhr → water cooling → 175
T6 treatment was performed at ℃ for 6 hours.

Next, as described above, the surface of the connecting rod was subjected to shot peening to finish it as a connecting rod product.

The results are shown in the table below.

Table Arc Height and Fatigue Strength As explained above, according to the structure of the present invention, the fatigue strength of an aluminum powder alloy connecting rod can be improved, and a lightweight connecting rod that can replace a steel connecting rod can be obtained.

Claims (1)

[Claims] (1) In weight%, Si: 15-18%, Fe: 5-7%
, an extruded material obtained from a powdered aluminum alloy material containing 4 to 6% Cu and the remainder Al, was heated at 400 to 500°C.
It is formed into a connecting rod by hot forging at
6. A method for producing an aluminum powder alloy connecting rod, which comprises subjecting the connecting rod to shot peening in a range of 0.05 to 0.20 mmA_2 after subjecting the rod to 6 treatments.