JP4351609B2 - Aluminum alloy, heat-resistant and high-strength aluminum alloy part, and manufacturing method thereof - Google Patents

Description

  The present invention relates to an aluminum alloy, a heat-resistant and high-strength aluminum alloy component that can be suitably used for engine parts, frame parts, and the like used in a high-temperature environment of 100 to 150 ° C., and a method for producing the same.

  Conventionally, from the viewpoint of protecting the global environment, for example, for the purpose of improving the fuel efficiency of vehicles, etc., it has been considered to replace materials constituting engine parts and frame parts with light alloy materials such as aluminum and magnesium from steel materials, It has been implemented. And when applying a light alloy material, in order to make the whole rigidity of a part equivalent to a steel material, expanding the cross-sectional area of each part of a part was performed.

  However, when conventional light alloy materials are applied to engine parts, etc., the operating temperature atmosphere of the parts cannot be ignored. Depending on the temperature atmosphere in which the parts are used, the cross-sectional area may be increased as described above. Even if the rigidity of the entire part is equal to or higher than that of the steel material, there is a problem that the strength of the part is greatly reduced with respect to the required strength of the part.

  This is due to the following reasons. For example, in a part exposed to a cooling oil temperature atmosphere (100 to 150 ° C.) inside the engine, when the part is made of a steel material, the melting point of the steel material is as high as 1000 ° C. or higher, so that the temperature is about 100 to 150 ° C. In a relatively low temperature range, the strength characteristics of the material hardly deteriorate. However, when the parts are made of a conventional light alloy material, the melting point of the conventional light alloy material is as low as about 660 ° C., so the strength characteristics of the material are significantly reduced in the temperature range of 100 to 150 ° C. It is because it ends. Therefore, there has been a demand for the development of a light alloy material that replaces the steel material that does not deteriorate the strength characteristics of the material even in the use temperature atmosphere (100 to 150 ° C.) of the component.

By the way, in order to prevent a decrease in strength characteristics at 100 to 150 ° C. of a material made of such a light alloy material, it is widely known that a material made of a light alloy material is subjected to a heat treatment, most of which are in solution. It involves treatment (maintained isothermally at 450 ° C. to 530 ° C. for several hours). For example, in Patent Documents 1 and 2, an aluminum alloy plate (casting) as a material is composed of an aluminum alloy containing a predetermined amount of Cu, Si, Mg, and Ag, and solution treatment and tempering (artificial) are performed under predetermined conditions. It is described that a product having high creep resistance or high strength can be obtained by aging treatment.
JP-A-9-165640 (paragraph numbers 0018, 0039, 0040, 0045, 0046, 0055) JP 2004-91822 A (paragraph numbers 0006, 0009, 0019 to 0021)

  However, when the conventional light alloy material is applied to manufacture of engine parts and the like, the following problems occur. First, when the above-mentioned solution treatment is performed after molding such as casting, the casting cavity and shrinkage cavity that existed as casting defects inside the material undergo thermal expansion, appearing as blisters and blisters in the material, Not only is the appearance significantly worsened, but the strength properties are also significantly reduced. And when the material is an extruded member, a stretched member, or a forged member, the presence of the above-mentioned cast or shrinkage is negligibly small, but when the material is a cast member or a die-cast member The above-mentioned casting cavity and shrinkage cavity are prominent, and the material appearance and strength characteristics are adversely affected.

  Secondly, if an artificial aging treatment is performed after the solution treatment, the following problems occur. That is, in the solution treatment process, the precipitated element is dissolved in the matrix matrix serving as a solvent, and the solid solution concentration is maintained even at room temperature by the subsequent rapid cooling treatment. Then, in the subsequent artificial aging treatment, a necessary amount of elements is precipitated in the matrix. During this artificial aging treatment, a large strain is generated in the matrix due to the coarsening of precipitates, and the strength characteristics can be improved by maintaining this strain. However, on the other hand, dimensional growth of the material occurs due to distortion accompanying the coarsening of the precipitate.

  From these viewpoints, it is very difficult to optimally perform the solution treatment and the artificial aging treatment in the production of an engine part having a complicated shape and extremely strict requirements for material strength and dimensional accuracy. For this reason, when manufacturing engine parts using light alloy materials, they are manufactured by casting or die casting, and combined with non-heat treatment or artificial aging treatment without solution treatment. The strength characteristics are often forced to be moderate.

  The present invention has been made in view of the above problems, and the present invention has both strength characteristics (yield strength, fatigue strength, elongation) at 100 to 150 ° C. corresponding to the oil temperature in the engine, and dimensional stability. An object of the present invention is to provide an aluminum alloy excellent in wear resistance and a heat-resistant high-strength aluminum alloy part.

In order to solve the above problems, the aluminum alloy of the present invention has Cu: 1.5 mass% or more and less than 3.8 mass%, Si: 7.5 to 12.0 mass%, Mg: 0.7 to 1 0.5% by mass, Ag: 0.1 to 0.5% by mass , Zn : 0.5 to 4.0% by mass, Ca: 50 to 200 ppm , the balance being made of Al and inevitable impurities To do.

If comprised in this way, while aluminum alloy contains predetermined amount Cu, Si, Mg, and Ag, while the castability and workability of aluminum alloy will improve, the crystallization of primary Si will be suppressed, Al A precipitation strengthening phase (Ω phase) composed of Cu, Mg, and Ag is formed. Thereby, the strength characteristics (proof strength, fatigue strength, elongation) and wear resistance of the aluminum alloy in a high temperature environment are improved only by artificial aging treatment without solution treatment. Further, dimensional growth due to strain generated in the Al matrix of the aluminum alloy is suppressed. Moreover, if it comprises so that Zn may be included further, the intensity | strength of an aluminum alloy will become still higher. Furthermore, if it is configured to further contain Ca, the eutectic Si becomes finer and the elongation of the aluminum alloy becomes even larger.

  Moreover, the aluminum alloy of this invention is characterized by further including Ti: 0.02-0.2 mass% in the aluminum alloy of the said composition. If comprised in this way, the excessive growth of Al matrix will be suppressed, a crystal grain will refine | miniaturize, and the yield strength of an aluminum alloy will become high.

  The aluminum alloy of the present invention is characterized in that the aluminum alloy having the above composition is subjected to T5 heat treatment as defined in JIS. If comprised in this way, the thermal expansion of the casting defect resulting from a solution treatment does not generate | occur | produce by performing the heat treatment (T5 heat treatment) only of an artificial aging treatment without solution treatment to an aluminum alloy, Strength characteristics of aluminum alloy are improved.

  Moreover, the heat-resistant and high-strength aluminum alloy part of the present invention is characterized by being formed from the aluminum alloy. If comprised in this way, while the intensity | strength characteristic and abrasion resistance in the high temperature environment of an aluminum alloy component will improve, dimensional growth will be suppressed.

  Furthermore, the method for producing a heat-resistant and high-strength aluminum alloy part according to the present invention is characterized in that die-casting is performed with the above-described aluminum alloy, and then T5 heat treatment specified by JIS is performed. If comprised in this way, the said aluminum alloy will improve the intensity | strength characteristic and abrasion resistance in the high temperature environment of aluminum alloy components, and a dimension growth will be suppressed. In addition, die casting and T5 heat treatment shorten the solidification time and eliminate the time-consuming solution treatment.

  The aluminum alloy of the present invention can improve both the strength and elongation, which are generally in conflict with each other, and has a high strength and high strength under a moderate high temperature environment of 100 ° C to 150 ° C. It has toughness and excellent dimensional stability and wear resistance. And it can be used as a material for a structural part, for example, a structural part for a high-speed moving body, an internal combustion engine part and a supercharger part, especially a rocker arm material inside the engine.

  Similarly, the heat-resistant and high-strength aluminum alloy part of the present invention has high strength and high toughness in a high-temperature environment, and is excellent in dimensional stability and wear resistance. And it can be used as a structural part, for example, a structural part of a high-speed moving body, an internal combustion engine part and a supercharger part, particularly a rocker arm inside the engine.

  Furthermore, the method for producing a heat-resistant and high-strength aluminum alloy part of the present invention can similarly produce a product having high strength and high toughness and excellent dimensional stability and wear resistance in a high-temperature environment. At the same time, productivity can be improved and manufacturing costs can be reduced.

Next, an embodiment of the present invention will be described in detail.
First, in order to improve the strength characteristics (proof stress, fatigue strength, elongation) and dimensional stability at 100 to 150 ° C., which is the purpose of the aluminum alloy of the present invention, the aluminum alloy takes any fracture form in the temperature atmosphere. It is necessary to know whether it is.

  As a generally known result, in an aluminum alloy, the base metal is separated from a temperature of about one-half (about 460 K, that is, about 190 ° C.) of the melting point of the alloy (most of which is about 920 K). In the present invention, the intragranular fracture is suppressed because there is an experimental fact that the fracture mode shifts from the intragranular fracture mode where the fracture occurs from the inside of the crystal to the grain boundary fracture mode where the fracture occurs from the crystal grain boundary. It came to examine the material composition. And it was set as the material composition which reinforces the inside of a crystal grain.

  That is, the aluminum alloy of the present invention has Cu: 1.5 mass% or more and less than 3.8 mass%, Si: 7.5-12.0 mass%, Mg: 0.3-1.5 mass%, Ag: It contains 0.1 to 0.5% by mass, and the balance consists of Al and inevitable impurities. Moreover, the aluminum alloy of the present invention is obtained by adding Zn: 0.5 to 4.0% by mass, at least one element of Ca, Na, Sr, and Sb (Ca is desirable) to the aluminum alloy having the above composition: It is desirable to further contain at least one element of 30 to 300 ppm and Ti: 0.02 to 0.2 mass%. The action and component range of each element will be described below.

1. Action and component range of Cu Cu affects solidification shrinkage, dimensional growth, and strength. When Cu is contained in an amount of 3.8% by mass or more, solidification shrinkage during casting is remarkable and dimensional growth during heat treatment is also large. If Cu is less than 1.5% by mass, the contribution of precipitation hardening during heat treatment is small. That is, the component range of Cu of the present invention is 1.5% by mass or more and less than 3.8% by mass. Further, Cu is desirably 2.0 to 3.0% by mass (here, “to” means the following, and is 2.0% by mass or more and 3.0% by mass or less). "~" Is also synonymous.)

2. Action and component range of Si Si has an effect on castability, wear resistance, and workability and is known to have the best castability in the vicinity of the eutectic composition. When Si is contained up to the composition, primary Si is crystallized sparsely. This primary crystal Si is poor in bondability with the Al matrix side and easily cracks at the interface, so that it tends to cause a decrease in elongation. Therefore, the upper limit of the Si content in the present invention is set to 12.0 mass% as a composition in which primary Si does not crystallize at all. Also, if the Si content is low, the uniform dispersibility of the structure deteriorates this time, resulting in a decrease in wear resistance, and the strength also decreases. The lower limit of the amount was 7.5% by mass. That is, the Si component range of the present invention is 7.5 to 12.0 mass%. In consideration of wear resistance, Si is desirably 10.5 to 11.5% by mass.

3. Action of Mg and component range Mg affects casting cracking and strength, and if it exceeds 1.5 mass%, cracking during casting is remarkable and it becomes difficult to obtain a sound product. If Mg is less than 0.3% by mass, the precipitation strengthening phase (Ω phase) with Al, Cu, and Ag becomes insufficient, and sufficient strengthening cannot be expected. That is, the component range of Mg of the present invention is 0.3 to 1.5% by mass. Moreover, it is desirable that Mg is 0.7 to 1.5% by mass which is most effective.

4). Action of Ag and Component Range Ag forms a precipitation strengthening phase (Ω phase) with Al, Cu, and Mg among the alloy components of the present invention, and has a high contribution to strength. However, for the purpose of precipitating Ag as an Ω phase, even if it contains more than 0.5% by mass, the effect is small and only the alloy cost is increased. On the other hand, when Ag is less than 0.1% by mass, the Ω phase becomes insufficient and sufficient strengthening cannot be expected. Further, if Ag is not added, Al—Cu-based θ phase precipitation occurs due to heat treatment, and lattice distortion increases at that time, resulting in dimensional growth. However, the addition of Ag precipitates an Ω phase, and this Ω phase has less lattice distortion and is a thermally stable phase, and therefore, dimensional growth is less likely to occur than when Ag is not added. That is, the component range of Ag of the present invention is 0.1 to 0.5% by mass. In consideration of cost, Ag is preferably 0.1 to 0.3% by mass.

5. Action of Zn and component range Zn affects the flowability and strength of the molten metal, and does not affect the castability up to about 5.0% by mass, but if it exceeds 4.0% by mass, the strength decreases, Even if it is less than 0.5% by mass, the strength is lowered. That is, the component range of Zn of the present invention is 0.5 to 4.0% by mass. Further, Zn is desirably 2.0 to 3.5% by mass which is most effective in strength.

6). Actions and component ranges of Ca, Na, Sr, and Sb Ca, Na, Sr, and Sb are elements that make eutectic Si fine. When these elements do not contain at least one element, eutectic Si crystallizes in a needle shape (three-dimensionally plate-like) and tends to cause cracking and elongation reduction. However, when at least one of these elements is contained, these elements are present in a concentrated form at the eutectic Si growth interface (three-dimensionally surrounding the growth interface), and are plate-like. It has the function of suppressing the growth of silicon into eutectic Si having a fine resinous (network-like) structure. Since eutectic Si becomes a resinous structure in this manner, interfacial cracking is less likely to occur, and an improvement in elongation can be expected, while the structure is uniformly dispersed and wear resistance is improved.

  If at least one of these elements exceeds 300 ppm, it becomes excessive, and a brittle compound with Mg or Zn is crystallized, leading to a decrease in strength. Further, if at least one of these elements is less than 30 ppm, a sufficient eutectic Si refinement effect cannot be obtained. That is, the component range of at least one element among Ca, Na, Sr, and Sb of the present invention is 30 to 300 ppm. Moreover, it is desirable that at least one element of Ca, Na, Sr, and Sb is 50 to 200 ppm.

  In addition, among Ca, Na, Sr, and Sb, Na is a very active element, so that it is difficult to handle, and Sr is easy to form a compound at the grain boundary, and thus easily causes a decrease in elongation. Sb may be designated as a hazardous substance in the future. Therefore, it is most desirable to use Ca.

7). Action and component range of Ti Ti is a peritectic element with respect to Al, and becomes an effective heterogeneous nucleus when Al solidifies. Therefore, when Ti is contained, a large number of crystal nuclei exist, and excessive growth of the Al matrix is suppressed. As a result, crystal grains are refined and yield strength is improved. However, even if Ti is contained in an amount exceeding 0.2% by mass, the solubility of Ti in Al is very small, so that the effect of improving the miniaturization cannot be obtained. On the contrary, since it crystallizes out as a Ti compound at the grain boundary, it causes a decrease in elongation. Further, when Ti is less than 0.02% by mass, a sufficient fine effect cannot be obtained. That is, the component range of Ti of the present invention is 0.02 to 0.2% by mass. Further, Ti is desirably 0.05 to 0.15 mass%.

8). Inevitable impurities In the aluminum alloy of the present invention, Fe is 1.3% by mass or less, Mn is 0.5% by mass or less, Ni is 0.5% by mass or less, and Sn is 0.3% by mass or less as inevitable impurities. Even if it contains, the effect of this invention is not prevented, and inclusion of such an unavoidable impurity is accept | permitted.

  Next, the heat-resistant and high-strength aluminum alloy part of the present invention is formed from the aluminum alloy, and requires high strength and high toughness in a high temperature environment of 100 to 150 ° C., and dimensional stability is emphasized. Specifically, it is used for structural parts (for example, frame parts), internal combustion engine parts (rocker arms inside the engine) and supercharger parts of high-speed moving bodies such as vehicles. As a forming method, a conventionally known forming method can be used. For example, extrusion, rolling, forging, casting, die casting are performed in consideration of the shape of the heat-resistant and high-strength aluminum alloy component, the strength of the component, and the like. It is suitably selected from the above, and die casting is preferred because the solidification time of the aluminum alloy is short and the productivity is high.

  In addition, the heat-resistant and high-strength aluminum alloy part of the present invention is preferably one that has been heat-treated after the molding. Further, the heat treatment is preferably T5 heat treatment that performs only artificial aging treatment as defined in JISH001. And the conditions of an artificial aging treatment are suitably adjusted with the thickness, size, etc. of a heat-resistant high-strength aluminum alloy part, for example, 200-250 degreeC and 1 to 5 hours are preferable.

  Furthermore, in the heat-resistant and high-strength aluminum alloy part of the present invention, the heat-resistant and high-strength aluminum alloy part is manufactured from the above-mentioned aluminum alloy. It is possible to manufacture heat-resistant and high-strength aluminum alloy parts by the above-described T5 heat treatment that only performs artificial aging treatment, not T6 treatment that performs solution treatment and artificial aging treatment. It is possible to omit the solution treatment that is liable to cause blistering or blistering. As a result, a heat-resistant and high-strength aluminum alloy part having high strength, high toughness and dimensional stability in a high-temperature environment can be obtained.

Next, examples in which the effects of the present invention have been confirmed will be described.
( Reference Examples 1-11, Examples 1-3 )
Fourteen types of Al alloy melts having the composition shown in Table 1 were melted and held at about 700 ° C., injected into a round bar test piece mold by die casting, and the resulting die cast material was subjected to T5 heat treatment (230 ° C x 3 hours).

(Comparative Examples 1-14)
As a comparative control of Reference Examples 1 to 11 and Examples 1 to 3 , shown in Table 2, as a comparative example 1, the most frequently used alloy for Al-Si die casting, a JIS-regulated molten ADC12 alloy, comparative example 2 14 using 13 types of molten Al alloy having a component composition outside the component range of the present invention, a die-cast material was prepared in the same manner as in Reference Examples 1 to 11 and Examples 1 to 3, and the obtained die-cast material was T5. Heat treatment (230 ° C. × 3 hours) was performed.

Using the die cast materials after the T5 heat treatment of Reference Examples 1 to 11, Examples 1 to 3 and Comparative Examples 1 to 14, the internal quality, strength characteristics in an atmosphere at 150 ° C., and 0 to 400 hours are as follows. The size growth and wear resistance of the test piece in the longitudinal direction were confirmed.

(Internal quality)
About the die-cast material after T5 heat processing, the solidification shrinkage | contraction and generation | occurrence | production of a crack were confirmed visually, and the result is shown in Table 1, Table 2. In addition, “○” indicates that no solidification shrinkage or cracking occurs, “Good” indicates that solidification shrinkage or cracking is observed. Defective.

(150 ° C strength characteristics)
The die-cast material after the T5 heat treatment was turned to obtain tensile test pieces and fatigue test pieces. These test pieces were soaked at 150 ° C. for 100 hours, and then subjected to a tensile test specified in JISZ2241 and a rotating bending fatigue test specified in JISZ2286 at 150 ° C., respectively. The results are shown in Tables 1 and 2. In Table 2, the average value was set for 0.2% proof stress and elongation, and the fatigue strength was P = 0.5 (50% fracture probability) fatigue strength at a test repetition number of 1 × 10 ⁷ . And about 0.2% yield strength, 190 MPa or more was made favorable and less than 190 MPa was made bad. Moreover, about fatigue strength, 96 MPa or more was made favorable and less than 96 MPa was made bad. Furthermore, about elongation, 0.4% or more was made favorable and less than 0.4% was made defective.

(Abrasion resistance)
The die-cast material after the T5 heat treatment of Example 2 , Comparative Example 1 and Comparative Example 2 was turned into a plate shape of 8 mm × 10 mm × 50 mm, and the wear resistance was verified with a reciprocating sliding tester. Specifically, the die-cast material after the T5 heat treatment is reciprocated 150, 300, or 600 times on a JIS-specified S58C steel material while applying a measurement temperature of 150 ° C. and a load of 5 N or 30 N. The amount of wear was measured. The result is shown in FIG.

(Dimensional growth)
Example 2 A round bar test piece of φ10 mm × 25 mm was cut out from the die-cast material of Comparative Example 1, and dimensional growth in the longitudinal direction of the test piece in a 150 ° C. atmosphere was confirmed from 0 to 400 hours. The result is shown in FIG.

From the results of Tables 1 and 2, the aluminum alloys of the present invention of Reference Examples 1 to 11 and Examples 1 to 3 have all of internal quality and 150 ° C. strength characteristics (0.2% proof stress, fatigue strength, elongation). It was good. In addition, the aluminum alloys of Comparative Examples 1 to 13 have poor internal quality and 150 ° C. strength characteristics (0.2% proof stress, fatigue strength, elongation), and Comparative Example 14 has a high Ag content. The cost of the aluminum alloy was high and lacked practicality. Further, from the results of FIG. 1, the aluminum alloy of the present invention (Example 2 ) had a smaller dimensional growth than the aluminum alloy of the comparative example (Comparative Example 1). Furthermore, from the results shown in FIG. 2, the aluminum alloy of the present invention (Example 2 ) was less worn than the aluminum alloys of Comparative Examples (Comparative Examples 1 and 2).

  Therefore, it was confirmed that the aluminum alloy of the present invention has high strength and toughness in a high temperature environment, and is excellent in wear resistance and dimensional stability.

It is a graph which shows transition of the dimension growth in 150 degreeC. Abrasion resistance at 150 ° C. is shown, (a) is a graph showing the measurement results of the wear amount at a load of 5 N, and (b) at a load of 30 N.

Claims (5)

Cu: 1.5% by mass or more and less than 3.8% by mass, Si: 7.5 to 12.0% by mass, Mg: 0.7 to 1.5% by mass, Ag: 0.1 to 0.5% by mass , Zn: 0.5-4.0 mass%, Ca: 50-200 ppm , the balance consisting of Al and unavoidable impurities. The aluminum alloy according to claim 1, further comprising Ti: 0.02 to 0.2% by mass. An aluminum alloy characterized in that the aluminum alloy according to claim 1 or 2 is subjected to T5 heat treatment as defined in JIS. A heat-resistant and high-strength aluminum alloy part formed from the aluminum alloy according to any one of claims 1 to 3 . A method for producing a heat-resistant and high-strength aluminum alloy part, wherein the aluminum alloy according to any one of claims 1 to 3 is die-cast and then subjected to JIS-defined T5 heat treatment.

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