JP5802114B2 - Aluminum alloy wire for bolt, bolt and method for producing aluminum alloy wire for bolt - Google Patents

Description

  The present invention relates to aluminum alloy wires and bolts for bolts, and methods for producing them. In particular, the present invention relates to an aluminum alloy wire for bolts that is excellent in workability at the time of bolt manufacture and from which a bolt having sufficient strength can be obtained.

  A6056 is known as a material for aluminum alloy bolts. In addition, an aluminum alloy wire rod described in Patent Document 1 is also known. This alloy wire rod has a rolled structure with a composition of 6000 series, and has a predetermined fine average crystal grain size. And this aluminum alloy wire rod material is excellent in bolt moldability, and can give predetermined tensile strength by performing a further appropriate heat treatment and processing.

JP 2011-1602

  However, A6056 is inferior in formability and is caused by flaws generated during casting and rolling, causing cracks during bolt processing and intergranular corrosion due to minute cracks. Also, the bolt made of A6056 cannot obtain sufficient strength even after artificial age hardening.

  On the other hand, the aluminum alloy wire rod described in Patent Document 1 can improve the formability of A6056, and it is said that strength is also obtained when it is used as a bolt, but after forming into a bolt while ensuring formability. Therefore, it is desired to develop an aluminum alloy wire that can obtain higher strength. In particular, when a bolt is used in a high-temperature environment, the development of an aluminum alloy wire for a bolt that is small in strength reduction and can maintain high strength is expected.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide an aluminum alloy wire for bolts having sufficient formability when being formed into a bolt and having high strength as a bolt and its manufacture. It is to provide a method.

  Another object of the present invention is to provide an aluminum alloy wire for bolts that is further excellent in heat resistance and a method for producing the same.

  Furthermore, another object of the present invention is to provide a bolt obtained by using the aluminum alloy wire and a method for producing the same.

  Based on the composition of the 6000 series aluminum alloy, the present inventors have made extensive studies aiming to further improve the formability and strength, and as a result, have found that it is effective to contain a predetermined amount of Sr. As a result, the present invention has been completed.

  The aluminum alloy wire for bolts of the present invention is, by mass, Si: 0.60 to 1.5%, Fe: 0.02 to 0.40%, Cu: 0.50 to 1.2%, Mn: 0.50 to 1.1%, Mg: 0.70 to 1.3%, Cr : 0.30% or less (including 0%), Zn: 0.005 to 0.50%, Ti: 0.01 to 0.20%, Zr: 0.05 to 0.20%, Sr: 0.005 to 0.05%, with the balance being Al and inevitable impurities . This composition is sometimes referred to as the first composition.

  By using an alloy wire having this composition, it is excellent in formability when forming into a bolt, and a bolt having sufficient strength can be obtained after forming. In particular, by containing a predetermined amount of Sr, generation of flaws during casting and rolling can be suppressed, and generation of cracks and the like during molding can be reduced. With this alloy wire, a bolt having a tensile strength of 380 MPa or more, 0.2% proof stress: 350 MPa or more, and elongation: 6% or more can be obtained.

  As one form of the aluminum alloy wire for bolts of the present invention, Sr: 0.005 to 0.03% is contained by mass%, and the ratio Zr / Sr of the Zr content to the Sr content is 3 to 50. It is done.

  By limiting the Sr content from the first composition and further containing Zr and Sr in a predetermined ratio, sufficient formability can be secured while maintaining the heat resistance of the aluminum alloy wire. Zr is an element necessary for improving the heat resistance of the aluminum alloy wire. However, if Zr is contained, the casting temperature becomes high and it is difficult to refine the crystal grains. On the other hand, if Sr is contained at a predetermined ratio with respect to Zr, the coarsening of crystal grains can be effectively suppressed. Further, when Sr is contained in an aluminum alloy wire, it tends to be brittle although the strength is improved. However, when Sr is contained in the presence of a predetermined amount of Zr, embrittlement is suppressed and formability is ensured. The

  As one form of the aluminum alloy wire for bolts of the present invention, in mass%, Si: 0.80 to 1.4%, Fe: 0.05 to 0.30%, Cu: 0.50 to 1.2%, Mn: 0.50 to 1.1%, Mg: 0.80 to 1.3 %, Cr: 0.01 to 0.30%, Zn: 0.05 to 0.25%, Ti: 0.01 to 0.10%, Zr: 0.10 to 0.20%, Sr: 0.005 to 0.03%. This composition is sometimes referred to as a second composition.

  By limiting the content of the above elements with respect to the first composition, a bolt having further excellent mechanical properties can be obtained. Specifically, a bolt having a tensile strength of 400 MPa or more, 0.2% proof stress: 360 MPa or more, and elongation: 6% or more can be obtained.

  As one form of the aluminum alloy wire for bolts of this invention which has a 2nd composition, it is mentioned that Cu: 0.80-1.2%, Mn: 0.70-1.1%, Cr: 0.05-0.30% is contained by the mass%. This composition is sometimes referred to as a third composition.

  By further limiting the content of the above elements with respect to the second composition, it is possible to obtain a bolt having further excellent mechanical characteristics. Specifically, a bolt having excellent heat resistance can be obtained with tensile strength: 430 MPa or more, 0.2% proof stress: 370 MPa or more, and elongation: 6% or more.

As a form of bolt aluminum alloy wire of the present invention, include Mg ₂ Si, and the content of Mg ₂ Si, the ratio _{Mg 2 Si / (Mn + Cr} ) between the total content of Mn and Cr is at 1.0-2.1 Can be mentioned.

Depending on the Si and Mg contents, there is a difference in the strength of the bolts obtained. In the aluminum alloy, at least part of Si and Mg is precipitated as Mg ₂ Si by solution treatment and aging treatment, and the strength of the bolt is improved. By defining the ratio between the Mg ₂ Si content and the total amount of Cr and Mn, a bolt having high mechanical properties and heat resistance can be obtained. This ratio Mg ₂ Si / ( Mn + Cr ) is 1.0 to 2.1 at the stage of the cast material, and then each stage of the bolt formed from the drawn or rolled wire or the drawn material. Is substantially maintained.

The manufacturing method of the aluminum alloy wire for bolts of this invention comprises the following process.
Casting process:% by mass, Si: 0.60 to 1.5%, Fe: 0.02 to 0.40%, Cu: 0.50 to 1.2%, Mn: 0.50 to 1.1%, Mg: 0.70 to 1.3%, Cr: 0.30% or less (0% Zn: 0.005 to 0.50%, Ti: 0.01 to 0.20%, Zr: 0.05 to 0.20%, Sr: 0.005 to 0.05%, with the balance being Al and inevitable impurities.
Rolling process: The cast material is rolled into a rolled material.
Wire drawing step: The rolled material is drawn into a wire drawing material having a predetermined wire diameter.
Intermediate softening step: The wire rod in the middle of the wire drawing step is subjected to a softening treatment at 250 to 500 ° C for 0.5 to 40 hours.

  According to this method, an aluminum alloy wire suitable for the manufacture of bolts can be obtained. In particular, it is possible to obtain an aluminum alloy wire that is a bolt material excellent in productivity and mechanical properties.

  The bolt of the present invention is a bolt made of an aluminum alloy, and the aluminum alloy is, in mass%, Si: 0.60 to 1.5%, Fe: 0.02 to 0.40%, Cu: 0.50 to 1.2%, Mn: 0.50 to 1.1. %, Mg: 0.70 to 1.3%, Cr: 0.30% or less (including 0%), Zn: 0.005 to 0.50%, Ti: 0.01 to 0.20%, Zr: 0.05 to 0.20%, Sr: 0.005 to 0.05% The balance consists of Al and inevitable impurities. And, tensile strength: 380 MPa or more, 0.2% proof stress: 350 MPa or more, elongation: 6% or more.

  By using a material having the above composition as a bolt, a bolt having excellent mechanical properties such as tensile strength, 0.2% proof stress, and elongation can be obtained.

The bolt manufacturing method of the present invention includes the following steps.
Cutting step: The above-described aluminum alloy wire of the present invention is cut into a predetermined length.
Header process: The aluminum alloy wire for the cut bolt is subjected to header processing to form the head of the bolt.
Rolling step: The cut aluminum alloy wire for the bolt is rolled to form a thread portion of the bolt.
Heat treatment step: Solution treatment and aging treatment are performed on the object in the process from the manufacture of bolts to the bolt aluminum alloy wire.

  According to this method, it is difficult for cracks to occur during the molding of the bolt, and the bolt can be manufactured with high productivity. Further, the obtained bolt is excellent in mechanical strength such as tensile strength. Furthermore, depending on the composition of the aluminum alloy wire of the present invention, a bolt having excellent heat resistance can be obtained.

  The aluminum alloy wire of the present invention having the predetermined first composition described above, the method of manufacturing the alloy wire, the bolt, and the method of manufacturing the bolt are bolts excellent in workability at the time of bolt forming and excellent in mechanical properties. Can be obtained.

  Embodiments of the present invention will be described below. In the following description, the composition of the aluminum alloy wire is shown by mass%.

[Aluminum alloy wire]
〔composition〕
(Si: 0.60-1.5%)
Si partially dissolves in the matrix together with Mg, strengthening the aluminum alloy wire. Moreover, Si is an element necessary for improving the strength by forming an aging precipitate or the like during artificial aging of the alloy wire and obtaining predetermined mechanical characteristics required for the bolt. By setting the lower limit of the Si content to 0.60%, the effects of solid solution strengthening and age hardening can be appropriately expressed, and a bolt having a predetermined strength can be obtained. In addition, by setting the upper limit to 1.5%, the workability from casting to wire and formability to bolts are not hindered, and the formation of coarse crystals and precipitates that become the starting point of cracking is suppressed. , Can contribute to increasing the strength of the bolt. A more preferable Si content is 0.80 to 1.4%. By setting it within this range, it is easy to obtain a bolt having further excellent mechanical strength.

(Fe: 0.02-0.40%)
Fe is necessary to promote the effect of the crystal refining agent containing Ti during casting in the presence of an alkaline earth metal element (for example, Mg or Sr). By making the lower limit of the Fe content 0.02%, it contributes effectively to the refinement of crystal grains in the alloy. On the other hand, by setting the upper limit value to 0.40%, it is possible to suppress the formation of Fe-based crystallized grains at the grain boundaries in the alloy structure and the deterioration of the plastic workability of the alloy. A more preferable Fe content is 0.05 to 0.30%, and a still more preferable content is 0.05 to 0.25%. By setting it within this range, it is easy to obtain a bolt having further excellent mechanical strength.

(Cu: 0.50-1.2%)
Cu contributes to strength improvement together with Mg and Si. By setting the lower limit of the Cu content to 0.50%, the effect can be easily obtained. On the other hand, by setting the upper limit value to 1.2%, it is easy to ensure the formability to the bolt. A more preferable Cu content is 0.80 to 1.2%. By setting it as this range, it is easy to obtain a bolt having further excellent mechanical strength and good heat resistance.

(Mn: 0.50-1.1%)
Mn partially dissolves in the matrix and strengthens the aluminum alloy wire by solid solution. Further, Mn forms Al-Mn-based dispersed particles, the crystal grains of the wire structure can be refined, and the strength, formability, corrosion resistance, and the like can be improved. By setting the lower limit of the Mn content to 0.50%, the aluminum alloy wire is strengthened by solid solution, and sufficient strength as a bolt can be easily obtained. Further, by setting the upper limit value to 1.1%, it is possible to suppress the formation of coarse crystallized substances and precipitates that are the starting points of cracks, and to contribute to increasing the strength of the bolt. A more preferable content of Mn is 0.70 to 1.1%. By setting it as this range, it is easy to obtain a bolt having further excellent mechanical strength and good heat resistance.

(Mg: 0.70 to 1.3%)
Mg is an element necessary for satisfying the mechanical properties required for bolts by solid solution strengthening of aluminum alloy wires and forming aging precipitates that contribute to strength improvement together with Si during artificial aging. By setting the lower limit of the Mg content to 0.70%, a sufficient solid solution strengthening function and age hardening function can be exhibited. By setting the upper limit to 1.3%, it is possible to suppress the formation of coarse crystallized substances and precipitates that are the starting points of cracks, and to contribute to increasing the strength of the bolt. A more preferable Mg content is 0.80 to 1.3%. By setting it as this range, it is easy to obtain a bolt having further excellent mechanical strength and good heat resistance.

(Cr: 0.30% or less (including 0%))
Since Cr forms dispersed particles in the same manner as Mn and Zr, it has the effect of preventing the crystal grains from becoming coarse during the heat treatment of the aluminum alloy wire and miniaturizing the crystal grains. By making the crystal grains finer, it contributes to improving the strength of the bolt and the formability to the bolt. Cr also has the effect of improving corrosion resistance. By setting the upper limit of the Cr content to 0.30%, the coarsening of the crystal grains is suppressed and the effect of refining the crystal grains is appropriately expressed. Cr may not be contained, but the lower limit of the preferable content is 0.01%, and more preferably 0.05%. By containing 0.01% or more of Cr, it is easy to obtain strength when used as a bolt. Further, by containing 0.05% or more of Cr, a bolt excellent in not only strength but also heat resistance can be obtained.

(Zn: 0.005-0.50%)
Zn has a function of improving the strength of the alloy by dissolving in the aluminum matrix. By setting the lower limit of the Zn content to 0.005%, the effect of improving the strength can be appropriately exhibited. Moreover, appropriate corrosion resistance can be ensured by setting the upper limit to 0.50%. A more preferable Zn content is 0.05 to 0.25%. By setting it within this range, it is easy to ensure the toughness necessary for forming the bolt, and it is easy to obtain a bolt having further excellent mechanical strength, excellent workability, heat resistance, and corrosion resistance.

(Ti: 0.01-0.20%)
Ti has the effect of making the crystal structure of the cast material fine, suppressing the ratio of columnar crystals in the cast material, and increasing the ratio of equiaxed crystals. Therefore, by containing Ti, it is possible to improve the rolling workability and wire drawing workability of the cast material, and further the formability to the bolt. In addition, since the crystal structure is made finer, it is difficult for wrinkles to occur during plastic processing, so that a plastic working material with less wrinkles and an excellent surface state can be obtained. By making the lower limit of the Ti content 0.01%, the effect of crystal grain refinement can be easily obtained. The higher the Ti content, the more effective the refinement of crystal grains and the reduction of wrinkles associated with the refinement, but this effect tends to saturate at about 0.20%, and the formation of coarse intermetallic compounds can also be suppressed. . Therefore, the upper limit of Ti content is 0.20%. A more preferable Ti content is 0.01 to 0.10%. By setting it within this range, it is easy to obtain a bolt having further excellent mechanical strength. Further, Ti may be mixed in the molten metal as TiB ₂ , and B also has the effect of improving the strength by making the crystal structure finer like Ti. Therefore, the content of B is allowed to be about 50 ppm (mass ratio) or less.

(Zr: 0.05-0.20%)
Zr, like Mn, forms dispersed particles containing the respective elements, and has the effect of preventing the crystal grains from becoming coarse during the heat treatment of the aluminum alloy wire and making the crystal grains finer. Along with this, it contributes to the improvement of bolt strength and formability to bolts. Zr is an element necessary for improving the heat resistance of the aluminum alloy wire. By setting the lower limit of the Zr content to 0.05%, it is possible to appropriately obtain the effect of improving the strength and the formability to the bolt. By setting the upper limit to 0.20%, it is possible to effectively suppress the coarsening of crystal grains. A preferable Zr content is 0.10 to 0.20%. By setting it as this range, it is easy to obtain a bolt having further excellent mechanical strength and good heat resistance.

(Sr: 0.005-0.05%)
Sr also has the function of refining the crystal structure of the cast material and contributes to improving the strength of the obtained bolt. In particular, when Sr is contained in the presence of Zr, the strength can be improved without the aluminum alloy wire becoming brittle. By setting the lower limit of the Sr content to 0.005%, it is easy to obtain an effect of improving the bolt strength. By setting the upper limit to 0.05%, embrittlement of the aluminum alloy wire can be effectively suppressed and sufficient strength can be obtained. A more preferable content of Sr is 0.005 to 0.03%. By setting it as this range, it is easy to obtain a bolt having further excellent mechanical strength and good heat resistance.

(Zr / Sr: 3-50)
As described above, Zr is an element necessary for improving the heat resistance, but if it is contained, the melting point of the alloy increases, the casting temperature becomes high, and solidification becomes difficult. Although it is not a problem in billet casting or the like, in the case of continuous casting, a phenomenon in which the outer surface of the cast material is deformed easily occurs when an outer shrinkage occurs during solidification of the molten metal. This deformed part is slow to cool because the cast material does not come into contact with the mold, re-raises to a temperature higher than the melting point due to the heat inside the cast material, a remelt phenomenon occurs, the crystal grains become coarse, the cast material The surface properties of the resin are deteriorated. As a result, the coarsened portion of the crystal grains and the deteriorated portion of the surface properties are the starting points, and are easily wrinkled by rolling or wire drawing after casting. On the other hand, Sr has a function of improving the strength of the aluminum alloy, but easily causes embrittlement. By defining the ratio of Zr and Sr within a predetermined range, occurrence of remelting due to the inclusion of Zr and embrittlement due to the inclusion of Sr can be effectively suppressed. By setting the lower limit of this ratio to 3, it can be said that an appropriate amount of Zn is contained with respect to Sr, which can effectively suppress embrittlement and contribute to the improvement of strength. By setting the upper limit of the ratio to 50, it can be said that an appropriate amount of Sr is contained with respect to Zn, and it is easy to eliminate the problems associated with remelting. A more preferable range of the ratio is about 5 to 20. By setting it as this range, it is easy to obtain a bolt having further excellent mechanical strength and good heat resistance. This limitation of the ratio is not essential in the present invention.

(Mg ₂ Si / ( Mn + Cr ) : 1.0 to 2.1)
A part of Si and Mg is dissolved in the matrix of the aluminum alloy and contributes to strength improvement, and the remainder is contained as Mg ₂ Si. On the other hand, both Cr and Mn have the function of forming dispersed particles and suppressing the coarsening of the structure to contribute to the improvement of strength. By defining the ratio between the Mg ₂ Si content and the total amount of Cr and Mn, a bolt having high mechanical properties and heat resistance can be obtained. The reason is not clear, but the interaction between Mg ₂ Si and Mn, Cr seems to suppress the decrease in strength due to the progress of aging during high temperature holding, and Mn, Cr commensurate with the amount of Mg ₂ Si. It seems that heat resistance is improved by adding. This ratio is preferably about 1.4 to 2.0, particularly about 1.5 to 1.8. In addition, when aluminum alloy is processed after artificial aging, Mn and Cr suppress the movement of dislocations, and may suppress the strength reduction of the part where the strength is improved by work hardening. Conceivable. As the content of Mg ₂ Si, a value calculated from the added amounts of Mg and Si is used. Specifically, the content of Mg ₂ Si is obtained by the following formula 1. The calculated value indicates the content of Mg ₂ Si of solution treated and aged to precipitate Mg ₂ Si material. The total amount of Cr and Mn is preferably about 0.55 to 1.5%, more preferably about 0.70 to 1.4%, and particularly preferably about 0.75 to 1.3%. This limitation of the ratio is not essential in the present invention.
{Mg content [mass%] / (Mg atomic weight x 2)} x (Mg ₂ Si molecular weight)

〔Wire diameter〕
Although the wire diameter of the aluminum alloy wire of the present invention is not particularly limited, for example, about 12 mm to 3 mm can be selected. By using an aluminum alloy wire having such a wire diameter, a bolt having a size suitable for fastening automobile parts can be manufactured.

[Method of manufacturing aluminum alloy wire]
An aluminum alloy wire is typically manufactured through casting, rolling, wire drawing, and intermediate softening. Details of each step are as follows.

〔casting〕
A cast material having the composition described above is cast. Casting is preferably continuous casting. In the production method of the present invention, by making the aluminum alloy have a predetermined composition, it is possible to obtain a cast material having excellent surface properties and less wrinkles even by continuous casting. By using such a cast material, it is possible to reduce the occurrence of cracks and wrinkles during rolling or wire drawing, and it is possible to obtain a rolled material or wire drawing material having excellent surface properties. In particular, in the production method of the present invention, a wire drawing material having an excellent surface state can be obtained without increasing the number of peeling during drawing, increasing the amount of peeling, or increasing the sensitivity of the flaw detector as in the prior art. Can be obtained. Therefore, the production method of the present invention can produce an aluminum alloy wire having a good yield and an excellent surface state with high productivity. As the continuous casting method, a belt and wheel method is preferable.

  Cooling during casting is preferably performed at 5 ° C./sec or more, more preferably 8 ° C./sec or more, and further preferably 20 ° C./sec or more. By setting the cooling rate to 5 ° C / sec or more, the crystal grains are prevented from coarsening, so that the casting material has a fine structure or the ratio of equiaxed crystals per unit cross-sectional area is high. be able to. Further, it is preferable that the cooling rate is 5 ° C./sec or more at any position of the molten metal in the cooling process, that is, the whole is cooled uniformly. For example, when a continuous casting machine having a water-cooled copper mold or a forced water cooling mechanism is used, rapid solidification at the cooling rate as described above can be realized.

〔rolling〕
The cast material is rolled into a rolled material. This rolling is preferably performed hot or warm. Moreover, it is preferable to perform rolling continuously with casting. When rolling is continuously performed for casting, heat rolling can be easily performed using heat accumulated in the casting material, and energy efficiency is good. Excellent productivity. For example, a casting machine combining a belt and a wheel and a rolling mill connected to the casting machine are used. An example of such an apparatus is a Properti type continuous casting and rolling mill.

[Drawing]
The rolled material is drawn and processed into a predetermined wire diameter. This wire drawing is preferably performed cold. Depending on the surface state of the rolled material before drawing, stripping may be performed.

[Intermediate softening]
A softening process is performed on the wire in the middle of the wire drawing. This intermediate softening treatment is performed under conditions such that the elongation of the wire after the treatment is 10% or more. This intermediate softening treatment is performed in order to increase the toughness of the wire by softening without extremely reducing the strength of the wire that has been increased by refinement of the crystal structure and work hardening.

As the softening treatment, a batch treatment can be suitably used. The atmosphere during the softening treatment is preferably a non-oxidizing atmosphere in order to suppress the formation of an oxide film on the surface of the wire due to the heat during the treatment. For example, a vacuum atmosphere (reduced pressure atmosphere), an inert gas atmosphere such as nitrogen (N ₂ ) or argon (Ar), a hydrogen-containing gas (for example, hydrogen (H ₂ ) only, an inert gas such as N ₂ , Ar, helium (He), etc. A reducing gas atmosphere such as a mixed gas of active gas and hydrogen (H ₂ ) and a carbon dioxide-containing gas (for example, a mixed gas of carbon monoxide (CO) and carbon dioxide (CO ₂ )).

  The softening treatment can increase the elongation of the wire to 10% or more by setting the heating temperature to 250 ° C. or higher. In the case of batch processing, preferable conditions are heating temperature: 250 ° C. or higher and 500 ° C. or lower, holding time: 0.5 hour or longer, more preferably 1 hour or longer. When the heating temperature is less than 250 ° C. and the holding time is less than 0.5 hour, the effect of the softening treatment is poor, and when the heating temperature exceeds 500 ° C., the crystal grains and crystal precipitates are coarsened and the workability is liable to be lowered. In particular, the heating temperature is preferably 300 ° C. or higher and 450 ° C. or lower, and the holding time is preferably 2 hours or longer and 40 hours or shorter. A more preferable heating temperature is 380 to 420 ° C., and the holding time is 24 hours or less, particularly the holding time is 15 hours or less.

[Others]
Further, a softening process (final softening process) may be performed after the final wire drawing. This final softening treatment is also preferably performed at 300 ° C. or higher for 1 hour or longer. The final softening treatment can improve the formability during bolt processing.
[bolt]
〔composition〕
The composition of the bolt is the same as that of the aluminum alloy wire described above.

(Mechanical properties)
According to the aluminum alloy wire of the first composition, the tensile strength: 380 MPa or more, 0.2% proof stress: 350 MPa or more, and elongation: 6% or more can be obtained as the characteristics after bolt forming. Moreover, according to the aluminum alloy wire of the second composition, the tensile strength: 400 MPa or more, 0.2% proof stress: 360 MPa or more, and elongation: 6% or more can be obtained as the characteristics after bolt forming. Furthermore, according to the aluminum alloy wire of the third composition, the tensile strength: 430 MPa or more, 0.2% proof stress: 370 MPa or more, and elongation: 6% or more can be obtained after the bolt forming.

  These characteristics are characteristics after performing bolt processing on the aluminum alloy wire after the final wire drawing, and performing solution treatment and aging treatment at the time of the processing. All of the characteristics can be measured by a tensile test using a bolt as a product according to JIS B1051.

[Bolt manufacturing method]
The bolt is typically manufactured through cutting of the aluminum alloy wire, header processing, rolling, solution treatment, and aging treatment. Details of each step are as follows.

[Cut]
The cutting is performed by cutting the aluminum alloy wire into a length suitable for processing the bolt. What is necessary is just to select the length of the cut piece obtained suitably according to the size of the volt | bolt to manufacture.

[Header processing]
In the header processing, the end of the cut piece obtained in the cutting process is forged to form the head of the bolt. Known conditions can be applied to the processing conditions.

[Rolling]
In the rolling process, a thread portion is formed on the cut piece obtained in the cutting step. Known conditions can be applied to the processing conditions. Usually, rolling is performed after header processing.

[Solution + Aging]
The solution treatment and the aging treatment are performed on the workpiece to be bolted, thereby generating precipitates in the alloy and improving the strength of the workpiece. The procedure for solution and aging has the following pattern.
(1) Cutting → Header processing → Solution + Aging → Rolling (2) Cutting → Intermediate forging → Solution + Aging → Header processing → Rolling (3) Cutting → Header processing → Rolling → Solution + Aging

  Among the above, the pattern (1) has high dimensional accuracy of the threaded portion by rolling in the final process. In addition, by applying plastic working to a portion that becomes a screw portion by rolling, the material can be work-hardened and the strength of the bolt can be slightly increased.

  The pattern (2) can work and harden the material and increase the strength by performing plastic working after aging.

  Since the pattern (3) is subjected to plastic working before aging, a material having relatively low workability can be processed into a screw.

In any pattern, the solution treatment conditions are preferably 520 to 560 ° C. for 1 to 5 hours, and the aging treatment conditions are preferably 160 to 180 ° C. and about 4 to 30 hours. The mechanical properties can also be adjusted by controlling the precipitation state of Mg ₂ Si by this solution treatment and aging treatment.

<Test Example 1>
An aluminum alloy wire is produced by a process of casting → rolling → drawing → intermediate softening → drawing. During the production process, the surface properties of the cast material and wire drawing material are evaluated, and the resulting aluminum alloy wire is processed into bolts to evaluate cracking and heat resistance during molding, and the mechanical properties of the bolts are also evaluated. evaluated. The composition of the sample is shown in Table 1, and the evaluation results are shown in Table 2. In Tables 1 and 2, Comparative Example 2 is an A6056 equivalent material.

<Production of alloy wire>
First, pure aluminum as a base is melted, and an additive element is introduced into the molten metal so as to have a predetermined concentration. The molten aluminum alloy whose components are adjusted is appropriately subjected to a hydrogen gas removal treatment or a foreign matter removal treatment. This aluminum alloy melt is cast and hot-rolled by a belt-wheel type continuous casting and rolling machine to produce a φ9.5 mm wire rod. The cooling rate during casting is 5 ° C / sec or more. In addition, a water-cooled copper mold was used so that the cooling rate was 5 ° C./sec or more at any position of the molten metal in the cooling process. Ti and B for microstructure refinement are added by preparing Al-3% Ti-1% B (mass%) wire and casting so that the molten metal and wire are simultaneously supplied into the mold. did. Subsequently, the wire rod is cold-drawn to φ8.3 mm, followed by batch softening at 400 ° C. for 5 hours, and the softened material is drawn to φ7.05 mm. And the final softening process of 350 degreeC x 5 hours is performed by batch processing to the obtained alloy wire, and it is set as an aluminum alloy wire. In each sample, since Si was added in excess of the stoichiometric composition, the content of Mg ₂ Si in Table 1 was calculated by the following formula 1.
{Mg content [% by mass] / (Mg atomic weight x 2)} x (Mg ₂ Si molecular weight)

<< Evaluation of remelted part >>
The obtained cast material is appropriately sampled and the appearance is observed, and the number of remelted portions generated along with remelting during solidification is examined. The evaluation of the remelted portion was based on Comparative Example 2, with the sample having the number of remelted portions decreased, ◯ for an equivalent sample, and × for the increased sample.

<< Evaluation of the number of flaw detection >>
The rolled material obtained by continuous casting and rolling is stripped to a thickness of 11.7 mm and stripped to a thickness of 0.2 mm with a stripping die. Note that skinning may not be performed. By this skinning, it is possible to remove causes other than remelting, for example, relatively small wrinkles generated in hot rolling and subsequent wire drawing. Evaluation of the number of flaw detection is performed by first observing the number of wrinkles on the surface of the above stripping material using an on-line eddy current flaw detector provided in a wire drawing machine and marking the flaw detection count section. Then, assuming that the number of flaw detection in Comparative Example 1 is 100, the relative number is used for evaluation.

<Production of bolt>
A bolt is produced from the obtained aluminum alloy wire. In this example, an M8 bolt T6 treated material and a T9 treated material obtained by adding cold working (intermediate forging) to the T6 treated material were produced. The manufacturing process of each bolt is as follows. In either case, the solution treatment was 550 ° C. × 2 hours, and the aging treatment was 175 ° C. × 8 hours. In Comparative Examples 1 to 7, no T9 treatment material was produced.

T6 treatment material Cutting → Header processing → Solution treatment → Aging treatment → Rolling
T9 treated material Cutting → Intermediate forging → Solution treatment → Aging treatment → Header processing → Rolling

<Evaluation of bolt cracking>
Evaluation is based on the occurrence rate of cracks in 500 bolts obtained. The presence or absence of this crack is judged by visually observing a crack generated during header processing or rolling. This evaluation is based on the comparative example 2 as △, if it is equivalent to the comparative example 2, △ if it is improved by 20% or more, ◯ if it is inferior by 20% or more. For example, if the number of occurrences of cracks in Comparative Example 2 was 10, if the number of occurrences of cracks in the sample was 8 or less, it was improved by 20% or more. % Is inferior.

<Heat resistance test>
The produced bolt was held at 150 ° C. for 1000 hours and then subjected to a tensile test at room temperature. The heat resistance was evaluated by the rate of decrease in tensile strength after heat treatment relative to the tensile strength before heat treatment. On the basis of Comparative Example 2, it was rated as ○ if the above-mentioned decrease rate was the same, and ◎ if improved by 20% or more. The improvement of 20% or more means that, for example, when the decrease rate of Comparative Example 2 is 10%, the decrease rate of the sample is 8% or less.

<< Evaluation of mechanical properties >>
Tensile tests were conducted at room temperature using bolts as samples to evaluate tensile strength, 0.2% proof stress, and elongation. This tensile test is performed in accordance with JIS B1051. However, only the tensile strength and 0.2% proof stress are shown in Table 2 for the T9 treated material described above.

<Discussion>
As shown in Tables 1 and 2, the present inventions 1 to 14 containing 0.005% by mass or more of Sr are good in any evaluation of remelting, flaw detection number, and cracking. These T6 treated materials have tensile strength: 380 MPa or more, 0.2% proof stress: 350 MPa or more, elongation: 6% or more, and T9 treated materials have tensile strength: 460 MPa or more, 0.2% proof stress: 440 MPa. As described above, it also has heat resistance. In addition, the present inventions 2 and 9 having the second composition are provided with tensile strength: 400 MPa or more, 0.2% proof stress: 360 MPa or more, and elongation: 6% or more. Further, the T6 treated material of the present invention 4, 6-8, 10, 12 having the third composition has a tensile strength: 430 MPa or more, 0.2% proof stress: 370 MPa or more, and elongation: 6% or more. In particular, the T9 treatment material of the present invention 4, 6, 7, 8, 10, 12 having a third composition, Zr / Sr of 3 to 50, and Mg ₂ Si / ( Mn + Cr ) of 1.0 to 2.1, Tensile strength: 510MPa or more, 0.2% proof stress: 500MPa or more, and good heat resistance. Among them, the present invention 4, 6, 7, 8, 12 wherein Zr / Sr is 3 or more and less than 40, especially the T9 treatment material of the present invention 4, 6, 7, 12 wherein Zr / Sr is 5 or more and 15 or less, It also has high heat resistance. On the other hand, none of the comparative examples not satisfying the first composition has an insufficient or inferior improvement effect in terms of remelting, the number of flaw detections or formability to bolts, and no heat resistance is improved by 20% or more. .

  Note that the present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the gist of the present invention.

  The aluminum alloy wire of the present invention and the method for manufacturing the same can be used for a bolt wire or the manufacturing thereof, and the bolt of the present invention and the method for manufacturing the same can be suitably used for a bolt for tightening automobile parts or the manufacturing thereof.

Claims (6)

% By mass
Si: 0.60 to 1.5%
Fe: 0.02-0.40%
Cu: 0.50-1.2%
Mn: 0.50 to 1.1%
Mg: 0.70 to 1.3%
Cr: 0.30% or less (including 0%)
Zn: 0.005-0.50%
Ti: 0.01-0.20%
Zr: 0.05-0.20%
Sr: 0.005-0.05%
Hints, Rubo aluminum alloy wire belt, such a balance is Al and inevitable impurities. In mass%, Sr: 0.005-0.03%
Zr content and bolt aluminum alloy wire according ratio Zr / Sr content is 3 to 50 der Ru請 Motomeko 1 Sr. % By mass
Si: 0.80 to 1.4%
Fe: 0.05-0.30%
Cu: 0.50-1.2%
Mn: 0.50 to 1.1%
Mg: 0.80 to 1.3%
Cr: 0.01-0.30%
Zn: 0.05-0.25%
Ti: 0.01-0.10%
Zr: 0.10 to 0.20%
Sr: 0.005-0.03%
The including請 Motomeko 1 or claim 2 volts for aluminum alloy wire according to. % By mass
Cu: 0.80-1.2%
Mn: 0.70 to 1.1%
Cr: 0.05-0.30%
Bolt aluminum alloy wire according to including請 Motomeko 3. % By mass
Si: 0.60 to 1.5%
Fe: 0.02-0.40%
Cu: 0.50-1.2%
Mn: 0.50 to 1.1%
Mg: 0.70 to 1.3%
Cr: 0.30% or less (including 0%)
Zn: 0.005-0.50%
Ti: 0.01-0.20%
Zr: 0.05-0.20%
Sr: 0.005-0.05%
A step of obtaining a cast material, the balance of which is made of Al and inevitable impurities,
Rolling the cast material into a rolled material;
Drawing the rolled material into a drawn material having a predetermined wire diameter;
Method for producing Rubo belt for aluminum alloy wire and a step of performing a softening treatment from 0.5 to 40 hours at 250 to 500 ° C. relative to the middle of the wire of the wire drawing step. A bolt made of an aluminum alloy,
The aluminum alloy contains the following elements in mass%, the balance consists of Al and inevitable impurities,
Si: 0.60 to 1.5%
Fe: 0.02-0.40%
Cu: 0.50-1.2%
Mn: 0.50 to 1.1%
Mg: 0.70 to 1.3%
Cr: 0.30% or less (including 0%)
Zn: 0.005-0.50%
Ti: 0.01-0.20%
Zr: 0.05-0.20%
Sr: 0.005-0.05%
Tensile strength: 380MPa or more,
0.2% proof stress: 350MPa or more,
Growth: 6% or more der Rubo belt.