JP3516566B2 - Aluminum alloy for cold forging and its manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for cold forging, which is used as a raw material for parts to be cold forged, a method for producing the same, and a method for producing a cold forged product.

[0002]

2. Description of the Related Art Aluminum alloys have a specific gravity of about 1/3 that of iron and are lighter in weight. Therefore, there are many examples in which iron is replaced with aluminum alloys to reduce the weight. Forging methods include hot forging in which the material is forged in a softened state at high temperature and cold forging in which the material is forged at room temperature. In cold forging, it is necessary to soften the material so that it can be easily forged at the time of working. Therefore, a material that has been annealed in advance is used as the material. For example, in the case of JIS6061 alloy, which is a typical heat-treatable aluminum alloy, since the strength after extrusion (T1) is high and it is hard,
After annealing (O material treatment) at about 20 ° C. × 2 hr, it is subjected to cold forging (for example, JP-A-3-170636).
(See Japanese Patent Publication).

[0003]

As described above, since the conventional material is annealed before cold forging, it is necessary to go through the steps of solution hardening and aging in order to obtain high strength after cold forging. (See FIG. 2 (a)). However, if the cold forging can be performed without performing the annealing process, not only the annealing process but also the subsequent quenching process becomes unnecessary, and a large cost reduction is expected by omitting the process. Further, by not quenching, the processing strain due to cold forging can be used for increasing the strength.

On the other hand, in order to omit the annealing step and the solution hardening step, for example, the extruded material in a high temperature state immediately after extrusion, that is, so-called press quenching is carried out, and the strength and hardness immediately after the press quenching are low while the material is cooled. It is conceivable that forging is carried out for a while, followed by aging treatment. However, the above 60
Conventional Al-Mg-Si alloys such as 61 alloy have a large deformation resistance during cold working and are difficult to cold work. Even when a large press is used to forcibly perform cold forging, the deformation resistance gradually increases and the dimensional accuracy varies greatly. From the perspective of, it is not realistic.

The present invention has been made from this point of view, and does not require an annealing treatment before cold forging, and high strength can be obtained without solution hardening after cold forging.
Furthermore, it is to provide an aluminum alloy for cold forging in which the mechanical properties do not fluctuate much and the cold forgeability does not deteriorate even if it is left at room temperature for a long time after press quenching and before cold forging (that is, it has slow-acting properties). To aim.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have conducted various studies to develop an aluminum alloy for cold forging having the above-mentioned characteristics, and as a result, in order to obtain the required cold forgeability. Indicates that it is necessary to limit the amount of addition of Mg and Si to a predetermined value or less, and that the Mg / Si ratio has a great influence on the retardation effect that prevents the change in cold forgeability over time.
It was also found that the progress of room temperature aging is suppressed in a specific composition region on the Si-rich side from the stoichiometric ratio of Mg ₂ Si. Also, in order to improve the strength after cold forging,
It was found that the addition of Cu, which has the effect of making the distribution of precipitates (Mg ₂ Si) after heat treatment uniform and fine, is effective,
The present invention has been completed.

The aluminum alloy for cold forging according to the present invention contains 0.4 to 0.8 wt% of Mg, 0.4 to 1.0 wt% of Si, 0.15 to 0.5 wt% of Cu, and 0.005 to Ti of 0.005.
When 0.2% by weight is contained and the balance is Al and unavoidable impurities, and further, Mg content weight% is X and Si content weight% is Y, the relation of Y ≧ (1 / 1.73) X + 0.15 It is characterized by satisfying. This alloy contains Mn 0.05 to 0.6% by weight and Cr 0.05 to 0.
3 wt% and one or more of 0.05 to 0.3 wt% Zr are contained in a total amount of 0.9 wt% or less. In addition, it is preferable that the amount of unavoidable impurities is small, but Fe 0.35% by weight or less,
0.05% by weight or less (0.15% or less in total) of other impurities is allowed as a simple substance.

Further, the method for producing an aluminum alloy for cold forging according to the present invention uses the aluminum alloy having the above-mentioned composition.
It is characterized in that it is extruded at 40 to 560 ° C. and press-hardened immediately after extrusion. Then, this press-quenched extruded material is used as a material for cold forging, which is cold forged,
Then, a normal forging treatment or a short-time heat treatment is performed to obtain a high-strength cold forged product.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The reasons for adding components and limiting the composition of the aluminum alloy for cold forging according to the present invention will be described below.

Mg, Si As described above, S relative to the stoichiometric ratio of Mg ₂ Si
When i is added in an excessive amount, the room temperature aging is suppressed and the delayed effect is exhibited. When the Mg content weight% is X and the Si content weight% is Y, the ratio of Mg and Si is Y ≧ (1/1.
73) A range satisfying X + 0.15. Than Mg
Rich side, that is, Y <(1 / 1.73) X + 0.15
In the range, the effect of suppressing the room temperature aging by Si is insufficient, and the room temperature aging will proceed.

On the other hand, Mg combines with Si to form Mg ₂ Si, thereby improving the alloy strength. In order to exert this effect, the addition amount of Mg needs to be 0.4% by weight or more. However, if the content of Mg exceeds 0.8% by weight, even if the above range is satisfied, room temperature aging will proceed due to the diffusion of Mg, and the deformation resistance at room temperature will increase, resulting in cold forging. Reduce sex. Therefore, the content of Mg is 0.4% by weight or more and 0.8% by weight or less. Further, Si has the effect of forming Mg ₂ Si and improving the alloy strength as described above. However, if the amount of Si added is less than 0.4% by weight, the strength of the material cannot be improved, and if it is 1.0% by weight or more, the ductility of the material is impaired and the deformation resistance at room temperature rises, causing a decrease in cooling. Forgeability is reduced. Furthermore, Si becomes nuclei for precipitation of Mg ₂ Si, but as the amount of addition of Si increases, the nuclei for precipitation increase, and as a result, precipitation easily progresses and the delayed effect is lost. Therefore, the Si content is 0.4% by weight or more and 1.0% by weight or less.

Within the above range, the Mg-reduced region has a better slow-acting property, the cold forgeability is improved, and a member having a complicated shape can be formed. The range of application expands. Therefore, the Mg content is preferably 0.65% by weight or less, and within this range, a markedly superior slow-release effect is exhibited. More preferably, the Mg content is 0.6% by weight or less, and by simultaneously setting Si in the range of 0.5 to 0.7% by weight, a cold forging material exhibiting excellent cold forgeability and delayed effect. Can be obtained. FIG. 1 illustrates the composition ranges of Mg and Si according to the present invention. Note that Y = (1 /
The 1.73) X line is the line of the stoichiometric ratio of Mg ₂ Si.

Cu Cu improves the alloy strength and the ductility of the material by precipitation hardening. In addition, the addition of Cu has the effect of uniformly and finely distributing the precipitate Mg ₂ Si produced by Mg and Si. However, if the added amount of Cu is less than 0.15% by weight, the above effect cannot be exhibited. On the other hand, if it exceeds 0.5% by weight, press hardenability is deteriorated and deformation resistance is increased. Therefore, C
The content of u is 0.15% by weight or more and 0.5% by weight or less.

Mn, Cr, and Zr Mn, Cr, and Zr are precipitated as fine intermetallic compounds during homogenization treatment of the billet, and crystal grains are refined to improve strength and ductility. However, these elements have the effect of sharpening the quenching sensitivity and decreasing the press hardenability as the added amount increases. Mn, C
If the addition amounts of r and Zr are each less than 0.05% by weight, the above effect cannot be exhibited. On the other hand, if the addition amounts of Mn, Cr, and Zr exceed 0.6% by weight, 0.3% by weight, and 0.3% by weight, respectively, or if the total amount of these exceeds 0.9% by weight, coarse intermetallic compounds are present. As the compound crystallizes out, the quenching sensitivity becomes sharp, and the predetermined alloy strength cannot be improved.
Therefore, the content of Mn, Cr, and Zr is Mn0.05 to
0.6 wt%, Cr 0.05 to 0.3 wt%, Zr0.
0.9% by weight in total of at least one of 05 to 0.3% by weight
Below.

Ti Ti improves the alloy strength by refining the crystal grains during casting. In order to exert this effect, the Ti addition amount must be 0.005% by weight or more.
On the other hand, if the amount of addition of Ti exceeds 0.2% by weight, the above effect is saturated, and coarse intermetallic compounds are crystallized, so that a predetermined alloy strength cannot be obtained. Therefore, the content of Ti is 0.0
It is set to 05 to 0.2% by weight.

Inevitable Impurity Fe Fe is the most abundant impurity in aluminum ingot,
If it is present in the alloy in an amount of more than 0.35% by weight, coarse intermetallic compounds crystallize during casting and impair the mechanical properties of the alloy. Therefore, the Fe content is 0.35% by weight or less.

When casting aluminum alloys, impurities are mixed in through various routes such as a base metal and an intermediate alloy of additive elements. Further, although various elements are mixed in, if the impurities other than Fe are 0.05 wt% or less for each element and 0.15% or less for the total amount, the characteristics of the alloy are hardly affected. Therefore, these impurities should be 0.05 wt% or less (total amount is 0.15% or less).

The aluminum alloy ingot having the above composition was added to 5
It is possible to obtain a material for cold forging by performing homogenization treatment under the condition of 0 to 600 ° C. × 2 to 10 hours, then extruding at 440 to 560 ° C., and immediately after extrusion, press quenching with water cooling or fan air cooling. it can. It should be noted that the homogenization treatment temperature set as described above is insufficient to diffuse segregation generated during casting into the matrix at less than 500 ° C, and local melting occurs at more than 600 ° C, resulting in extrusion. This is because it sometimes becomes a defect. Further, if the temperature of the extrusion process is set as described above, if it is lower than 440 ° C., it is insufficient to decompose the precipitate generated in the cooling process after the homogenization treatment into a solid solution state, and it exceeds 560 ° C. This is because the processing heat generated during extrusion causes local melting.

This material is cut into a predetermined length and subjected to cold forging, and after cold forging, it is subjected to normal conditions (for example, 180 to 19).
Aging treatment is performed at 0 ° C. × 3 to 8 hours (FIG. 2B).
reference). The aluminum alloy for cold forging can obtain high strength reaching almost 90% or more after the above-mentioned aging treatment only by performing heating for a short time after cold forging. This is because the work strain due to cold forging is applied, so that precipitation is promoted and aging proceeds in a short time.
Therefore, instead of the above aging treatment, 190 to 250 ° C.
You may make it heat this short time on the condition of 5 to 30 minutes.

Next, the fact that the aluminum alloy extruded material having the composition specified in the present invention has an excellent slow-acting property will be specifically described with reference to examples. First, 16 of the composition shown in Table 1
580 ℃ for 0φ × 150h aluminum alloy billet
A homogenization treatment of × 2 hr was performed. The billet was reheated and extruded at a billet temperature of 500 ° C. and an extrusion speed of 5 m / min. At this time, press quenching was performed using No. 18 (J
Only IS6061) was water-cooled, and others were air-cooled with a fan. Cross-sectional shape of extruded material is 40 × 40 × 2
It was extruded with a square pipe of t.

[0021]

[Table 1]

A JIS No. 5 tensile test piece was sampled from the extruded material, and a tensile test was conducted immediately after extrusion (within 3 days) and after 120 days of standing at room temperature to investigate the mechanical properties of the test material. The results are shown in Table 2. Further, Table 3 shows the results of similarly examining mechanical properties by JIS No. 5 tensile test pieces after artificial aging (T5 tempering) was performed on the extruded material immediately after extrusion at 190 ° C. for 3 hours.

[0023]

[Table 2]

[0024]

[Table 3]

No. 1 to 7 are conventional product Nos. Compared with 18, the change in mechanical properties is small even when left at room temperature for a long time,
No. containing no Mn, etc. Except for 7, the strength in the T5 state is the same as the conventional product. On the other hand, comparative alloy No. 8,
Looking at the results of No. 9, the Ti content was less than 0.005% by weight. No. 9 has a low strength in the T5 state, on the contrary, 0.20
No. more than weight%. Since No. 8 is a coarse intermetallic compound, both strength and elongation are low.

Comparative alloy No. 3 in which the contents of Mn, Cr and Zr exceeded 0.90% by weight. Looking at the result of No. 10, it was found that T5 was not found due to the coarse intermetallic compound and the deterioration of press hardenability.
Both strength and elongation in the state are low. Comparative alloy No. 11,
Looking at the results of No. 12, No. 12 with a Mg content of less than 0.40% by weight. No. 12 has a low strength in the T5 state, on the contrary 0.8
No. over 0% by weight. It can be seen that No. 11 has a large change in mechanical properties after 120 days, and that aging at room temperature is progressing.

Comparative alloy No. Looking at the results of Nos. 13 and 14, No. 3 having a Cu content of less than 0.15% by weight. No. 14 has a low strength in the T5 state, and conversely exceeds 0.50% by weight. In No. 13, both strength and elongation are low, and room temperature aging is progressing. Comparative alloy No. Looking at the results of 15 and 16, S
No. in which the content of i is less than 0.40% by weight. 16 is T
Strength in 5 states is low, conversely N exceeding 0.80% by weight
o. No. 15 has low elongation. Comparative alloy No. 17 is Y ≧
(1 / 1.73) X + 0.15, not within the range of 120
It can be seen that the change in mechanical properties after a lapse of days is large, the effect of suppressing room temperature aging by Si is insufficient, and room temperature aging is progressing.

As described above, the extruded material of the alloy of the present invention that has been press-quenched is excellent in retardation. The present invention intends to use the extruded material of this composition as a material for cold forging,
This cold forging material does not have large deformation resistance, and its mechanical properties do not change even when left at room temperature for a long time, so it has excellent cold forgeability, and it is possible to obtain high strength by subsequent aging treatment. I have

[0029]

[Examples] In the following, according to the examples of the present invention, JIS60
61 will be described as a comparative example.

An aluminum alloy billet having a composition of 160φ × 150 hours shown in Table 4 was cast and homogenized at 580 ° C. for 2 hours. The billet was reheated and extruded at a billet temperature of 500 ° C. and an extrusion speed of 5 m / min. At this time, press quenching was performed with water cooling. The cross-sectional shape of the extruded material was extruded with a φ20 round bar. The bent round bar was removed by tension straightening. JIS606
Part of 1 alloy is straightened and then 420 ° C in an air furnace
After holding for 2 hours, the furnace was cooled to 100 ° C. and annealed.

[0031]

[Table 4]

After 30 days from press quenching , the above test material was cut into 20 mm, the deformation resistance was measured by a room temperature hammer test, and the processing rate was 6 by a 30 ton compression tester.
Upset up to 5% was forged, and it was visually judged whether or not cracks had occurred on the surface, and those with no cracks were evaluated as ◯. Next, some of the upset forged test materials were subjected to an aging treatment at 180 ° C for 8 hours in an air furnace, and the other were heated at 220 ° C for 15 minutes for a short time, and the Vickers hardness was measured for each. did. In addition, about a part of JIS6061 alloy which performed upset forging, before performing an aging treatment or a short time heating, it is 530 degreeC x 2h in an air furnace.
Immediately after holding r, it was immersed in a water tank and water-quenched.
The above manufacturing conditions are shown in Table 5, and the test results are shown in Table 6.

[0033]

[Table 5]

[0034]

[Table 6]

As shown in Table 6, if the JIS6061 alloy was not annealed, the deformation resistance was too high and the force of the compression tester was exceeded, and only 40% upsetting was possible. From this, it can be seen that the JIS6061 alloy has undergone room temperature aging and the forgeability is remarkably inferior unless annealing is performed. On the other hand, the example of the present invention is JIS without the annealing process.
It can be seen that it has the same deformation resistance and cold forgeability as the 6061 annealed material.

Further, in the case of the JIS6061 alloy, if the solution hardening is not performed, the predetermined strength is not exhibited even if the subsequent aging treatment is performed, whereas in the example of the present invention, only the aging treatment without the quenching step is equivalent to JIS6061 alloy T6. You can see that it exerts its strength. Further, in the example of the present invention, 22
It can be seen that even after heating for a short time of 0 ° C. × 15 min, the strength after the aging treatment is 90% or more.

[0037]

According to the present invention, a high strength cold forging material can be obtained by using an aluminum alloy having a predetermined composition. Further, by using the aluminum alloy for cold forging, it is possible to omit the annealing treatment before forging and the quenching treatment after forging, and it is possible to reduce the cost of the manufacturing process.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a conventional process of cold forging and a process of the present invention.

FIG. 2 is a diagram showing Mg and Si ranges of the alloy of the present invention.

Continuation of front page (56) Reference JP-A-63-199841 (JP, A) JP-A-3-180453 (JP, A) JP-A-1-225756 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) C22C 21/00-21/18 C22F 1/04-1/057

Claims (8)

(57) [Claims] 1. Mg 0.4 to 0.65% by weight, Si0.
5 to 0.7% by weight, Cu 0.15 to 0.5% by weight, Ti
0.005 to 0.2% by weight, Mn 0.05 to
0.6 wt%, Cr 0.05 to 0.3 wt%, Zr0.
0.9% by weight in total of at least one of 05 to 0.3% by weight
Below (total content of Mn and Cr is 0.45 wt% or more
Other than Al ) and the balance Al and inevitable impurities, and further, Mg content weight% is X, Si content weight% is Y.
The aluminum alloy for cold forging having excellent slow-acting properties, which satisfies the relation of Y ≧ (1 / 1.73) X + 0.15. 2. Mg 0.4-0.65% by weight, Si0.
5 to 0.7% by weight, Cu 0.15 to 0.5% by weight, Ti
0.005 to 0.2% by weight, Mn 0.05 to
0.6 wt% (excluding 0.4 wt% or more) , Cr0.0
1 to 5 to 0.3% by weight and 0.05 to 0.3% by weight of Zr
When the total content of the seeds is 0.9 wt% or less, the balance is Al and inevitable impurities, and the Mg content wt% is X and the Si content wt% is Y, Y ≧ (1 / 1.7
3) An aluminum alloy for cold forging having excellent slow-acting properties, which satisfies the relationship of X + 0.15. 3. Mg 0.4 to 0.65% by weight (0.6 % by weight)
(Excluding amount% or more) , Si 0.5 to 0.7% by weight, Cu
0.15 to 0.5% by weight, Ti 0.005 to 0.2% by weight, Mn 0.05 to 0.6% by weight, Cr 0.0
1 to 5 to 0.3% by weight and 0.05 to 0.3% by weight of Zr
When the total content of the seeds is 0.9 wt% or less, the balance is Al and inevitable impurities, and the Mg content wt% is X and the Si content wt% is Y, Y ≧ (1 / 1.7
3) An aluminum alloy for cold forging having excellent slow-acting properties, which satisfies the relationship of X + 0.15. 4. The aluminum alloy for cold forging having excellent slow-acting property according to any one of claims 1 to 3, which is an extruded material that is press-quenched. 5. The set according to claim 1.
Made of an aluminum alloy
Aluminum alloy extruded material for cold forging having slow-acting properties. 6. An aluminum alloy having the composition according to any one of claims 1 to 3 is extruded at 440 to 560 ° C. and press-quenched immediately after extrusion, which is a cold alloy having excellent slow-acting properties. Method for producing aluminum alloy for hot forging. 7. An aluminum alloy having the composition according to any one of claims 1 to 3 is extruded at 440 to 560 ° C., press-quenched immediately after extrusion, and cold forged by using this as a raw material. A method for manufacturing a cold forged product, characterized by performing an aging treatment. 8. Mg 0.4-0.65% by weight, Si0.
5 to 0.7% by weight, Cu 0.15 to 0.5% by weight, Ti
0.005 to 0.2% by weight, Mn 0.05 to
0.6 wt%, Cr 0.05 to 0.3 wt%, Zr0.
0.9% by weight in total of at least one of 05 to 0.3% by weight
Contains the following, consisting of the balance Al and unavoidable impurities,
In addition, the Mg-containing weight% was X and the Si-containing weight% was Y.
Then satisfy the relation of Y ≧ (1 / 1.73) X + 0.15
Aluminum alloys having to composition extruded at four hundred forty to five hundred sixty ° C., and placed pressing baked immediately after extrusion, which then cold forging the as a material, followed by 190~250 ℃ × 5~30min
A method for manufacturing a cold forged product, which comprises performing heat treatment for a short time.