JP2007092125A - Aluminum alloy, aluminum alloy bar, method for manufacturing aluminum alloy ingot for forging, and forged and formed article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy which has eutectic Si refined, has pro-eutectic Si less formed, inhibits a harmful intermetallic compound from forming, makes the DAS of an α crystal lowered, and has macro crystal grains all finely granulated. <P>SOLUTION: The aluminum alloy includes 8-18 mass% Si, 2.5-6.0 mass% of Cu, 0.3-1.2 mass% of Mg, 0.010-0.020 mass% of B, and Ti in such an amount by mass% that a value of (B-0.45 Ti) is 0.010 or more; and has pro-eutectic Si with the maximum size of 50 μm or less, eutectic Si with an average size of 10 μm or less, and the DAS of the aluminum α crystal with a size of 15 μm or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an aluminum alloy used for a product that requires wear resistance and a forged product using the same, and is particularly used for sliding parts such as automobile parts such as engines and compressors or guides such as magnetic tape. The present invention relates to an aluminum alloy, an aluminum alloy rod, a method for producing an aluminum alloy ingot for forging, and a forged product.

  As a sliding part for automobiles such as an engine piston and a compressor piston, or a sliding member for electric appliances such as a guide for a magnetic tape, an aluminum alloy is used in order to reduce the weight. In addition, since sliding parts for automobiles or sliding members for electric appliances are particularly required to have wear resistance during sliding and have little thermal expansion, eutectic Si is crystallized out. A relatively large amount of eutectic Al-Si alloy with wear resistance is used.

In recent years, as the demand for higher performance and higher quality of these parts increases, various Al-Si alloys to which elements aiming at high strength are added have been proposed. At present, an alloy based on Al—Si—Cu—Mg that aims at the precipitation effect of Mg ₂ Si, CuAl _2, etc. by solution heat treatment is used most in large quantities. In order to provide wear resistance, there are comparatively many eutectic-based materials in the vicinity of 10% by mass with Si as high as possible. This is because fine Si that is eutectic and exists at the grain boundaries is effective in wear resistance. Furthermore, in order to improve the reliability and strength of the internal quality, the manufacturing method is changing from castings to forgings and changing to parts having a fine structure and no casting defects.

The forging material is usually a horizontal forging in which a round bar is cut to a certain length and placed sideways and forged in the diametrical direction, or cut into slices and placed in a die forging into a die shape. There are die forging. The characteristics and quality of these forged products are highly dependent on the underlying material and material structure. Specifically, continuous casting products that increase the cooling rate and finely control the structure improve forgeability, Improvements in the mechanical properties of the final product are expected, making it the mainstream material.
As the round bar, there are used an extruded bar obtained by extruding a billet having a diameter of about 4 inches to several tens of inches to form a round bar, and recently, a continuous cast bar obtained by directly continuously casting a small diameter bar of less than 4 inches. .
As an example of such an alloy material, wear resistance and strength are improved by continuously casting a eutectic Al-Si-Cu-Mg alloy having Si of about 10% by weight, plastic working, and precipitation hardening. (For example, refer to Patent Document 1, Patent Document 2, and Patent Document 3.)
Japanese Patent Publication No.55-12095 Japanese Patent Publication No. 58-36668 Japanese Examined Patent Publication No. 56-38666

On the other hand, in recent years, complex shapes have been formed, and forging processability has become important as a new issue. However, forgeability has not been sufficiently evaluated in conventional studies.
In general, these conventional wear-resistant alloys are often forged by heating to a temperature close to 400 ° C., so-called hot forging, or cold forging forged at room temperature. From the composition, the macrocrystal tends to be a coarse crystal such as a columnar crystal or a feather crystal on the composition, cracks occur along the grain boundary during forging, or from non-uniformity in which crystal grains are mixed, Problems such as non-uniform deformation have occurred.

  In order to solve this problem, the internal structure is usually refined uniformly. As a means for making the macro structure fine at the time of casting, what is usually performed in 2000 series, 6000 series, and 7000 series alloys is that Al-Ti-B master alloy is added before casting, and Ti is added. It promotes the generation of crystal grains as nuclei and makes them finer. Similarly, miniaturization by addition of Al-Ti is performed in the same manner, but Al-Ti-B is said to have a higher miniaturization capacity than Al-Ti.

However, the refinement of the structure by the addition of Al-Ti-B or Al-Ti has a low effect in Al-Si alloys, and can only obtain the effect of coarse granular crystals in which columnar crystals disappear at most. In the case of a fine structure, a rough structure appears on the surface as it is on the free forging surface, orange peel-like surface roughness is observed, and the commercial value may be lost.
In addition, problems caused by these coarse macro-grains also affect the smoothness of the end face during shear cutting before forging the material, and a flat cut surface cannot be obtained. It leads to.

Fe, Mn, Ti, and B are added to the eutectic Al—Si—Cu—Mg alloy described above, and shear cutting performance is improved by making 80% or more of the macrostructure equiaxed (for example, Patent Document 4). reference.).
However, the random addition of Fe and Mn makes it easy to crystallize Al-Fe-Mn (-Si) -based coarse and hard crystallized materials, which causes a deterioration in mechanical properties.
Japanese Patent No. 2506115

In particular, when the composition of Si is 10% by mass or more, since the effect of adding the Al—Ti—B master alloy in the equiaxed crystallization of the macro structure is small, it is necessary to add a large amount of Ti and B. . As a result, the ingot becomes an equiaxed crystal, but the effect of improving forgeability is small because the grain size of the macrocrystal is a coarse granular crystal of several mm or more. Furthermore, unfortunately, excessively added Ti and B are aggregated as hard TiB ₂ particles in the molten metal, staying inside the material in a hard spot shape, and wear and mechanical properties of the cutting tool Degradation may occur.

In order to improve the forgeability, B is added to refine the macro structure (for example, refer to Patent Document 5).
However, by simply adding B, impurities Ti in Al metal as a melting raw material are easily bonded in the molten metal, and TiB ₂ particles are generated. It cannot be said that there is no possibility. Al-B aims for a finer effect, but Ti and B in the metal react with each other as described above to cause aggregation of TiB ₂ compound, or when B is added excessively, Al The crystallization of other crystallized substances such as -Fe-Mn type and Al-Mg type is promoted, and the possibility of hindering mechanical properties and forgeability is increased, resulting in a problem.
Japanese Examined Patent Publication No. 6-78580

Further, high Si containing B in an amount of 0.005 wt% to 0.03 wt%, Fe in an amount of 0.2 wt% to 0.5 wt%, and Mn in an amount of 0.2 wt% to 0.5 wt%. A system alloy has been proposed (see, for example, Patent Document 6).
However, in the coexistence of Fe and Mn, when B is added excessively, not only the problem of TiB ₂ particle generation, but also the aforementioned Al—Fe—Mn (—Si) -based crystals and Al—Mg-based crystals The product is more likely to crystallize between α-dendrites than usual. And it turned out that a structure | tissue becomes weak in this part and causes deterioration of a mechanical characteristic.
Furthermore, when Ti is added in an excessive amount such as 0.01 wt% to 0.25 wt% and B is added 0.05 wt% to 0.25 wt%, even when Fe and Mn do not enter, only TiB ₂ is added. In other words, it was found that AlB ₂ or AlB ₁₂ compounds promote accumulation between α-crystal dendrites and greatly deteriorate the characteristics.
Japanese Patent Laid-Open No. 1-104741

The present invention is as follows.
(1) Si is 8% by mass to 18% by mass, Cu is 2.5% by mass to 6.0% by mass, Mg is 0.3% by mass to 1.2% by mass, and B is 0.010% by mass to 0% by mass. 0.020% by mass and Ti (B-0.45Ti) containing 0.0% or more by mass%, primary Si is at most 50 μm or less, eutectic Si is an average of 10 μm or less, aluminum An aluminum alloy having an α-crystal DAS of 15 μm or less.
(2) The aluminum alloy according to (1), wherein the macro crystal grains of the cross section are granular crystals over the entire surface.
(3) The aluminum alloy according to (1) or (2), wherein the average grain size of the macro crystal grains in the cross section is 300 μm or less.
(4) The aluminum alloy according to any one of (1) to (3), which contains Fe and / or Mn less than 0.2% by mass.
(5) A uniform macro structure is exhibited in the longitudinal direction and an orthogonal direction orthogonal to the longitudinal direction, and the difference in elongation between the longitudinal direction and the orthogonal direction orthogonal to the longitudinal direction is within 10% (1) to ( An aluminum alloy rod comprising the aluminum alloy according to any one of 4).
(6) At least 8% by mass to 18% by mass of Si, 2.5% by mass to 6.0% by mass of Cu, 0.3% by mass to 1.2% by mass of Mg, and Ti as impurities Forging in which Al-B master alloy is added to Al-Si-based aluminum alloy molten metal so that the value of (B-0.45Ti) is 0.010 or more in mass% in the ingot after casting, and then casting is performed. For producing aluminum alloy ingots for use.
(7) The method for producing an aluminum alloy ingot for forging according to (6), wherein the casting is performed by a direct cooling type casting apparatus.
(8) The method for producing an aluminum ingot for forging according to (6) or (7), wherein the production is performed by casting at a cooling rate of 4 ° C./second or more.
(9) A forged molded product produced using the ingot produced by the method for producing an aluminum ingot for forging described in any one of (6) to (8) as a forging material.

According to the aluminum alloy of the present invention of (1), a sufficient effect of refining the structure can be obtained by making the lower limit of addition of B in this way. Crystallization and aggregation can be suppressed.
Furthermore, by making Ti and B in such a relationship, Ti and B become hard particles of TiB ₂ and do not stay inside the material in the form of hard spots, so that wear of the cutting tool can be suppressed, and forging The mechanical properties of the molded product are not deteriorated.
The occurrence of problems due to coarse macro-crystal grains can be suppressed, and the smoothness of the end face during shear cutting to obtain a forging material will be good, thus suppressing the occurrence of missing parts in the product after forging. Can do.
A rough structure does not appear on the free forging surface, and a forged molded product having no orange peel-like surface roughness can be obtained.
(B) Eutectic Si can be refined, (b) Primary crystal Si can be suppressed, (c) Harmful intermetallic compounds can be suppressed, (d) α-crystal DAS can be reduced, and (e) Macro. The crystal grains are finely grained on the entire surface. As a result, it is possible to improve forgeability, obtain hot and cold forgeability that could not be obtained with conventional wear-resistant aluminum alloys, and have excellent mechanical properties with isotropic properties. is there.
According to the aluminum alloy of the present invention of (2), since the macro crystal grains in the cross section are granular crystals over the entire surface, the crystal grains are fine and the distribution is uniform, so that they are generated along the grain boundaries. It is possible to suppress cracks that occur and to prevent the problem of non-uniform molding direction during forging.
Furthermore, according to the aluminum alloy of the present invention of (3), since the average grain size of the macro crystal grains in the cross section is 300 μm or less, the effect obtained by the aluminum alloy of (2) becomes more reliable.
According to the aluminum alloy of the present invention of (4), Fe and / or Mn is contained in an amount of less than 0.2% by mass, so that an Al—Fe—Mn (—Si) based crystallization product, an Al—Mg based crystallization Crystallization of an object between α-crystal dendrites can be suppressed, and it is possible to suppress the structure from becoming brittle or from deteriorating mechanical properties in this portion.
Further, according to the aluminum alloy rod of the present invention of (5), a uniform macro structure is exhibited in the longitudinal direction and the orthogonal direction orthogonal to the longitudinal direction, and the elongation in the longitudinal direction and the orthogonal direction orthogonal to the longitudinal direction is exhibited. Is within 10%, it is possible to suppress the problem of non-uniformity in the molding direction during forging.
Moreover, according to the manufacturing method of the aluminum alloy ingot for forging of this invention of (6), Si is 8 mass%-18 mass%, Cu is 2.5 mass%-6.0 mass%, Mg is at least. The Al—Si based aluminum alloy melt containing 0.3% by mass to 1.2% by mass and containing Ti as an impurity has a value of (B−0.45Ti) of 0.010% by mass in the ingot after casting. Since the casting is performed after the Al—B master alloy is added as described above, the aluminum alloy described in (1) can be easily manufactured.
And according to the manufacturing method of the aluminum alloy ingot for forging of this invention of (7), since it casts with a direct cooling type casting apparatus, the aluminum alloy rod as described in (5) can be manufactured easily.
Furthermore, according to the method for producing an aluminum alloy ingot for forging according to the present invention of (8), since the aluminum alloy is produced by casting at a cooling rate of 4 ° C./second or more, the aluminum according to (1) to (3) Alloys can be easily manufactured.
Moreover, according to the forged molded product of the present invention of (9), a forged molded product having no surface roughness, good molding accuracy, and excellent mechanical properties can be obtained.

Since the alloy of the present invention is used for a sliding member, wear resistance is required. For that purpose, Si is contained in an amount of 8% by mass to 18% by mass.
Furthermore, in this invention, B was limited to 0.010 mass%-0.020 mass%. By setting the B content in this range, even in the alloy of the present invention having a large Si content, a uniform and fine macro structure is obtained over the entire cross section.
Si is present as eutectic particles having an average particle size of 2 μm to 10 μm (preferably 2 μm to 3 μm) depending on the cooling rate, and is dispersed in the grain boundaries of the α-crystal dendrites. As a result, this is effective for wear resistance. For example, a mold casting may be needle-shaped, but by using a continuous casting method, the cooling rate can be increased and the shape can be made finer. When Si is less than 8% by mass, the amount of eutectic particles is small and the effect of wear resistance is reduced.
In a so-called hypereutectic alloy state in which Si is an eutectic point of 11% by mass or more, macromolecules as primary crystal grains having a maximum grain size of 15 μm to 50 μm (preferably 15 μm to 25 μm) together with eutectic grains. Crystallized by being dispersed throughout the crystal grains.
It should be noted that if the primary crystal particles become too large, they may fall off during cutting or cause breakage of the cutting tool. Therefore, it is desirable that the primary crystal particles do not exceed 50 μm.

This primary crystal is larger than the eutectic, and if it is uniformly dispersed, the wear resistance is further increased. When wear resistance is required, it is preferable to use a hypereutectic alloy of 11% by mass or more in order to produce this primary crystal.
However, if Si exceeds 18% by mass, the melting temperature becomes high, gas absorption increases, casting temperature becomes high and casting becomes difficult, and dispersion of primary crystal particles in the cross section Is not uniform, and segregation in the cross section increases, resulting in deterioration of mechanical properties. Therefore, as a hypereutectic alloy, the upper limit of Si is 18% by mass.

In order to keep the particle size of Si eutectic particles and primary crystal particles within the above-mentioned range, it is better that the cooling rate at the time of casting is large, and the production method is a direct cooling casting method, for example, vertical semi-continuous casting. It is preferable to use a method or a horizontal continuous casting method. In particular, when obtaining a bar-shaped ingot, the smaller diameter of the cast bar diameter is preferably 100 mmφ or less (preferably 25 mmφ to 50 mmφ). This is because the ingot having a small diameter can increase the cooling rate and further reduce the difference between the surface and the central portion.
The cooling rate is preferably 4 ° C./second or more. When this cooling rate is exceeded, DAS (secondary dendrite arm space) also becomes finer (for example, an average of 15 μm or less, preferably 10 μm or less). As a result, the metal generated between the dendrites is reduced by reducing the dendrite size. Since the intermetallic compound is also small, it is preferable.
The size of DAS is described in, for example, “Light Metals (1998), Vol. 38, no. 1, p. 45 ”can be measured according to the“ Dendrite arm spacing measurement method ”.

Conventional thin-diameter materials produced by extrusion have thick billets used for extrusion, so the cooling rate for obtaining billets is slow, so the ingot structure, especially eutectic, primary crystal Si becomes coarse, for example The primary crystal exceeds 100 μm and remains in the small-diameter material even after extrusion, and the characteristic deterioration occurs in this primary crystal portion. In some cases, Al—Fe—Mn compounds exceeding 100 μm may crystallize coarsely, which also causes deterioration of mechanical properties. Extrusion rods are strong in the longitudinal direction (extrusion direction), but generally weak in the orthogonal direction perpendicular to the longitudinal direction (extrusion direction). Not preferred for free forging.
On the other hand, the alloy of the present invention is a small diameter material obtained by a production method in which a direct thin diameter material is cast as a continuous casting rod by a direct cooling casting method and then the surface is peeled off. Since the cooling rate is faster than that of the small-diameter material produced by extrusion, the primary crystal and eutectic Si can be made finer, which is preferable.

  When the eutectic particles of Si are coarse, they are likely to fall off during cutting, and the uniformity of the structure is poor as in the case of primary Si. Accordingly, the average value is preferably 10 μm or less. For this purpose, the above-described small-diameter continuous casting method is more desirable. Further, by performing a homogenization heat treatment (for example, 490 ° C. to 500 ° C., maintained for several hours) after casting, the Si eutectic particles are in the form of spheroids, and the temperature is changed. By increasing the temperature and the time for a long time, supersaturated Si in the α crystal can be aggregated into the primary crystal, and control to increase the size of the crystal grains is also possible. Therefore, it is preferable to apply a homogenization heat treatment.

  This alloy material is intended to be used for forging after being cast into a round bar. Forging may be either hot forging or cold forging. In the alloy of the present invention, since the macro crystal grains of the material are made fine and uniform, the forgeability is improved, the deformability is improved, and in particular, the maximum working rate can be increased.

  In order to obtain such an alloy, what is conventionally performed is addition of a finer agent of Al—Ti or Al—Ti—B to the molten alloy. The addition of a finer agent is a common method for high-strength alloys of the 2000 series, 6000 series, and 7000 series, making the macrocrystal grains fine and preventing cracks during forging.

  On the other hand, this alloy is an Al—Si based alloy with excellent wear resistance, and refinement of macrocrystals by adding Al—Ti and Al—Ti—B to this type of alloy has been conventionally performed. Not. This is because when the amount of Si increases, especially when the eutectic composition is exceeded, the effect of miniaturization due to the addition of Al—Ti or Al—Ti—B cannot be expected. For example, in Patent Document 4 (Patent No. 2506115 specification), Al—Ti—B is added, but the macro structure becomes a granular crystal, but the state of the structure is the above 2000 series, 6000 series. It is a coarse structure that cannot be said to be a fine structure as obtained with an alloy.

  The range of the alloy composition of the present invention will be described with reference to FIG.

  In this invention, B was limited to 0.01 mass%-0.02 mass%. This is because even the alloy of the present invention having a large Si content has a uniform and fine macro structure over the entire cross section. When B is less than 0.01% by mass (region E in FIG. 1), the effect of miniaturization is lost, and when viewed in cross section, the entire surface does not have a uniform and fine macrostructure, and partly columnar crystals or feathery crystals. Is not preferable because it is mixed.

Further, B is 0.01% by mass or more, and the mass% of B and Ti is set such that the value of (B-0.45Ti) is 0.010 or more. Otherwise (area in FIG 1 B, C.), TiB 2 are agglomerated occur during casting, TiB ₂ settles with casting time. As described above, the generation of TiB ₂ only has a small influence on the deterioration of the mechanical characteristics. However, when TiB ₂ aggregates, the influence on the deterioration of the mechanical characteristics becomes large, and a substantial effect of B is substantially obtained. It cannot be obtained.
This composition is obtained by directly analyzing the ingot of the alloy, or by analyzing a sampling sample from the molten metal immediately before casting as disclosed in the chemical component inspection method of JIS H 0321. It can be defined as an alloy composition.

  Here, Ti combined with B is present in the molten metal before addition of B, and is not only added but also included as an unavoidable component in the molten metal from the aluminum metal, other return materials ( Mixed products).

  The cast structure under the above conditions becomes granular and fine macrocrystals over the entire surface. For coarse granular crystals, forgeability is reduced, and the average macrocrystal grain size is preferably 300 μm or less (preferably 50 μm to 100 μm). Above this, for example, the upsetting rate at the time of upsetting does not increase, the free forging surface is wrinkled, and if it is severe, fine cracks may occur.

Here, the “fine granular crystals” are those in a state where the state can be visually confirmed when observed by a macroscopic method that is usually performed, but the particle size cannot be measured at the visual level. After polishing the sample, it is of a level that can be measured with a polarizing microscope after being subjected to polarization etching treatment.
Here, “over the entire surface” is a state in which mixing of columnar crystals or feather crystals is not observed in the field of view of 98% or more in the cross-sectional observation of the cast product.

  If the entire surface is not a granular crystal, for example, if a granular crystal and a columnar crystal are mixed, or if a feather crystal is mixed, there is a partial difference in deformability when molding such as upsetting by using it as a raw material. Therefore, uniform deformation cannot be obtained. For example, when upsetting forging is performed, the molded product may not be a perfect circle even if a circular material is used.

Next, when B exceeds 0.020% by mass (region A in FIG. 1), Al-Mg based crystals are easily crystallized between the α crystals, the crystal grains become brittle, and the mechanical properties are increased. Drop.
Further, even when B is 0.020% by mass or more, Ti is present in a large amount, and the range of (B-0.45Ti) exceeds 0.010 (on the right side of region A in FIG. 1). As a result, the effect of miniaturization is reduced. Further, the accumulation of TiB ₂ described above occurs with time, and becomes a harmful foreign matter, which deteriorates mechanical properties and deteriorates forgeability.

Here, the forgeability can be compared by the limit at which cracking occurs when the upsetting ratio between hot and cold is changed. As the upsetting rate is higher, cracking is less likely to occur, so forgeability is better. Alternatively, it is evaluated that the forgeability is so good that there is no crack on the free surface, defects such as holes, and surface skin defects such as orange peel at the same upsetting rate.
This relationship is illustrated in FIG. 1, and the region D according to the present invention has an optimum composition.

Cu aims to improve the strength by precipitation hardening by solution treatment after forging, strengthens the alloy matrix, holds the eutectic crystal grains of Si and the primary crystal grains of Si in the macro crystal grains, and Prevent dropping out.
As a result, it contributes to wear resistance, which is preferable. If the Cu content is less than 2.5% by mass, the effect is small and the effect increases as the amount added increases. However, if the Cu content exceeds 6.0% by mass, the effect does not increase any more, and cracking occurs during forging. The problem at the time of manufacture etc. comes out.

  Similarly, Mg contributes to improvement of mechanical properties by precipitation age hardening by solution, but if it is less than 0.3% by mass, the effect is poor, and if it exceeds 1.2% by mass, the oxide during casting increases. In addition, mechanical properties are deteriorated or cracking during forging is likely to occur.

In addition, although forgeability is good even if Fe and Mn are not added, when addition is necessary, less than 0.2% by mass is preferable in terms of suppressing generation of coarse intermetallic compounds.
Fe and Mn are used as solid solution strengthening and recrystallization suppression, but mainly crystallize an intermetallic compound coarser than Si eutectic when the casting diameter is large and the solidification rate is slow, for example. Since there is a possibility, it becomes a factor that hinders and lowers the mechanical properties. Therefore, it is preferable that both be suppressed to less than 0.2% by mass as necessary.

  As for the state of the micro crystal grains of the alloy of the present invention, the α crystal is 15 μm or less in terms of DAS (secondary dendrite arm interval). When the DAS exceeds 15 μm, the dendritic shape becomes a petal shape. Are likely to accumulate between the petal-like α-crystal dendrites, the crystal grain boundaries between α-crystals become brittle, and even if the macrostructure is fine, good mechanical properties cannot be obtained and forgeability is reduced. It becomes.

  Next, a manufacturing method will be described.

FIG. 2 is a process diagram showing an example of production equipment for an aluminum alloy and a bar-shaped ingot according to the present invention.
In FIG. 2, a melting and holding furnace (melting step) is for melting a raw material for an aluminum alloy to obtain a molten aluminum alloy.
The molten metal treatment apparatus (molten metal treatment step) is for removing in-line the aluminum oxide and hydrogen gas in the molten aluminum alloy from the melting and holding furnace.
The continuous casting apparatus (continuous casting process) is a horizontal continuous casting apparatus that casts an aluminum alloy continuous casting rod from the molten aluminum alloy supplied from the molten metal processing apparatus, as will be described later. .
The synchronized cutting device (cutting step) is for cutting an aluminum alloy continuous cast bar cast by a continuous casting device into a fixed length.
The heat treatment device (heat treatment step) is for homogenizing heat treatment of a fixed aluminum alloy continuous cast bar cut by a synchronous cutting device.
The peeling device [periphery removing device (periphery removing step)] removes the outer peripheral portion of the aluminum alloy continuous cast bar heat-treated by the heat treatment device.
The straightening device [bending straightening device (rectifying process)] is capable of accurately inspecting the inside of an aluminum alloy continuous cast bar when the inside of the aluminum alloy continuous cast bar heat treated by the heat treatment device is inspected by the following nondestructive inspection device. Therefore, the bending of the aluminum alloy continuous casting rod is corrected.
The nondestructive inspection device (nondestructive inspection step) is for inspecting whether or not there is a defect inside the aluminum alloy continuous cast bar whose curvature has been corrected by a correction device.

Depending on the product specifications of the aluminum alloy rod, the straightening device and the nondestructive inspection device are omitted, and the melting and holding furnace → the molten metal processing device → the continuous casting device → the synchronized cutting device → the peeling device → the heat treatment device (also serving as homogenization and homogenization processing). ).
In FIG. 3, a melting and holding furnace, a continuous casting apparatus, and a heat treatment apparatus (homo) are arranged as a minimum production system, so that continuous casting of cast material in the continuous casting apparatus and heat treatment by the heat treatment apparatus (homo) are continuously performed. The bar can be manufactured continuously.

  Here, when B is not included as a raw material of the molten aluminum alloy, the Al—B master alloy is added to the molten alloy immediately before the continuous casting apparatus from the melting holding furnace. The added amount of the Al—B master alloy is an amount obtained in advance by a preliminary experiment so that the value of (B−0.45Ti) in mass% is 0.010 or more in the final ingot.

By the way, Ti existing in the molten metal before addition of B becomes TiB ₂ by addition of B, becomes finer particles heavier than the molten Al, and agglomerates and mostly settles. Since this agglomeration and sedimentation phenomenon requires a certain amount of time for standing for several minutes to several tens of minutes, when casting in a short time, TiB ₂ is left in the furnace bottom to leave TiB ₂ in the cast product. However, when B is added in the middle, it is preferable to attach a mechanical filter device before casting to remove excess TiB ₂ that has not settled to avoid aggregation of TiB ₂ . Thus, those in mass% the value of (B-0.45Ti) was in the range of 0 to 0.010 it is, since it is possible to suppress the generation and aggregation of unnecessary TiB ₂ preferred. If this is a negative value, Ti will be excessive, and if more B is present, the generation of TiB ₂ will increase. When this is 0.010 or more, crystallization of harmful and coarse Al—Mg compounds, Al—Mn—Fe (—Si) compounds, etc. is promoted as a result of excess B.

<Continuous casting equipment>
FIG. 3 is an explanatory view showing an example of a horizontal continuous casting apparatus.
In FIG. 3, 202 indicates a tundish for storing the molten aluminum alloy 1, and an opening 203 is provided on the side wall.
Reference numeral 204 denotes a refractory plate-like body, which is attached to the outside of the tundish 202 so as to surround the opening 203, and a pouring hole 205 communicating with the opening 203 is provided.
Reference numeral 302 denotes a cylindrical mold constituting the horizontal continuous casting apparatus 301, which is attached to the refractory plate 204 so that the central axis is substantially horizontal, and the circumference between the mold 302 and the molten aluminum alloy 1. Lubricating oil for supplying a lubricating oil on the circumference between the gas supply path 303 for supplying gas from between the refractory plate-like body 204 and the mold 302 and the circumference between the mold 302 and the aluminum alloy continuous casting rod 2 A supply path 304 and a cooling water supply path 305 for supplying cooling water to the periphery of the aluminum alloy continuous casting rod 2 at the outlet are provided.

Next, casting of the aluminum alloy continuous casting rod 2 will be described.
The molten aluminum alloy 1 supplied into the tundish 202 from the molten metal treatment apparatus (not shown) is contained in the mold 302 held from the pouring hole 205 of the refractory plate-like body 204 so that the central axis is substantially horizontal. And is forcibly cooled at the outlet of the mold 302 to form the aluminum alloy continuous casting rod 2.
Here, the composition of the molten aluminum alloy 1 stored in the tundish 202 will be described.
In particular, the molten aluminum alloy contains Si in an amount of 8% by mass to 18% by mass (preferably 9% by mass to 11% by mass). Since a layered structure called a crystal is formed, it is preferable because the mechanical properties are excellent and the wear resistance is improved by hard Si.
The composition ratio of the alloy components of the aluminum alloy continuous casting rod can be confirmed by a photoelectric photometric emission spectroscopic analyzer as described in JIS H 1305, for example.

The horizontal continuous casting apparatus has been described. However, a vertical continuous casting apparatus, vertical semi-continuous casting, and DC continuous casting can be used as long as the cooling rate can be increased and a direct cooling type casting apparatus capable of casting a rod shape. An apparatus, a hot top casting apparatus, a gas pressure hot top casting apparatus, an electromagnetic field casting apparatus, or the like can be used.
In the gas pressure type hot top casting device, by supplying gas from between the header and the mold in the hot top casting system, the ingot can be cooled and solidified only by water cooling without contact with the mold. Rise.
In the electromagnetic field casting apparatus, an electromagnetic coil is placed in place of the mold, the molten metal is held by the electromagnetic coil, and the surface thereof is controlled so as not to come into contact with the mold, and water is directly applied in this state. That is, since the ingot can be cooled and solidified only by water cooling without contacting with the mold, there is no heat from the mold and no surface segregation, as in the case of the gas pressure hot top casting apparatus.

In order to obtain the microstructure described above, it is preferable to perform continuous casting with a small diameter of 100 mmφ or less as much as possible. In particular, a cooling rate of casting of 30 mmφ or less is most preferable, and the cooling rate is improved to about 15 ° C./second, and an α crystal having a desirable DAS can be obtained.
In addition, crystallization of coarse primary crystal Si and other crystallized substances can be suppressed by increasing supercooling.
In particular, by performing continuous casting with a small diameter of 50 mmφ or less, the casting speed can be increased and the cooling speed can be greatly improved. This can be done by casting horizontally.

The aluminum alloy rod manufactured by such an apparatus and method exhibits a uniform macro structure in the longitudinal direction and the orthogonal direction orthogonal to the longitudinal direction, and the difference in elongation between the longitudinal direction and the orthogonal direction orthogonal to the longitudinal direction. Is an aluminum alloy rod having a content of 10% or less.
In the case of using a rod by extrusion from billet casting as in the past, the mechanical characteristics in the longitudinal direction (extrusion direction) are good due to the processed structure in the extrusion direction, but the characteristics in the orthogonal direction perpendicular to the longitudinal direction (extrusion direction). Falls.
Since the material according to the present invention does not have such anisotropy and is homogeneous in any direction, the degree of freedom in forging is high. For example, when a tensile test is performed, almost uniform elongation is exhibited in the longitudinal direction of the bar and the orthogonal direction perpendicular to the longitudinal direction.
Note that almost uniform is within 10% in the numerical comparison.

  The rod-shaped forging aluminum alloy ingot produced as described above is further cut into a predetermined length and subjected to surface cutting treatment as necessary to produce hot forging materials and cold forging materials. can do.

<Description of forging materials>
The forging material used in the present invention is manufactured by the aforementioned method for manufacturing an aluminum ingot for forging according to the present invention.
The rod-shaped material is further cut into a predetermined length by shear cutting, and is subjected to a face grinding process if necessary, and is sent to the next step.

<Forging process>
Forging in the present invention is die forging, and an example of the configuration of a forging device used in the present invention will be described with reference to FIG.
The forging device 601 includes a forging machine 611, a lower die 622 attached to the lower die set plate 612, and an upper die 625 attached to the upper die set plate 613.
The upper die set plate 613 is guided by the guide post 614 and comes into contact with and separates from the lower die set plate 612.
Next, FIG. 5 shows a cross-sectional view of an example of a mold used in the present invention.
The forging die 621 includes a lower die 622 and an upper die 625 for forging a forged molded product from a metal material, and a knockout pin 627 for taking out the molded product from the lower die 622. ing.
The lower die 622 is provided with a forging hole 623 in the center. If necessary, a lubricant spray nozzle (not shown) including a spray front / rear transfer device (not shown) and a spray rotation device (not shown) attached to the spray before / after device via a shaft (not shown). It is possible to install a lubricant application device having an illustration omitted.

  The present invention can be applied regardless of whether it is hot, warm or cold. Generally, the fluidity of the forging material changes depending on the forging temperature conditions (mold, material), and the die is designed according to it.

The prepared forging material 3 is pushed into a space (forged molding hole 623) formed by the upper mold 625 and the lower mold 632, and the molded product is forged. Further, the molded material is taken out from the lower mold 632 by the knockout pin 637.
Note that forging is preferably performed after applying a lubricant to the inner periphery of the mold.
The forging material 3 is preferably subjected to a lubricant treatment as necessary.

<Features of molded products>
(B) Eutectic Si can be refined, (b) Primary crystal Si can be suppressed, (c) Harmful intermetallic compounds can be suppressed, (d) α-crystal DAS can be reduced, and (e) Macro. Since the crystal grain is made by forging a material with features that make the entire surface finely granulated, as a result, the forgeability is improved, so it could not be obtained with conventional wear resistant aluminum alloys Good hot and cold forgeability is obtained, and a molded product having isotropic mechanical properties is obtained.
In particular, the processing rate can be increased and a molded product having a complicated shape can be obtained.

[Example 1] to [Example 4]

An alloy having the composition shown in Table 1 (Si: 8% by mass to 17% by mass, Cu: 2% by mass to 5% by mass, B / Ti changed) was prepared.
For casting, a horizontal continuous casting apparatus and a vertical continuous casting apparatus were used, and the diameter of the casting rod was 35 mm to 100 mm.
Samples were sampled from each cast bar and subjected to macro observation and micro observation to evaluate the structure state, crystal grain size, and the like.
The macro crystal state is confirmed by visual inspection and a 10 × magnifier after the entire cross section of the cast product is etched. The macrocrystal grain size is calculated from the number of cross-sections that are polarized and etched with a polarizing microscope.
The microcrystal grain size was measured by image analysis of primary and eutectic crystals with a 400x microscope after polishing the cross section.
DAS measured the space | interval of the secondary dendrite arm of (alpha) crystal | crystallization of a microstructure.
As a result, according to the present invention (Example 1: No2, Example 2: No3, Example 3: No11, Example 4: No13), the entire surface of the macro is fine depending on the cooling rate by the casting diameter and the B / Ti ratio. The organization was obtained.
No1 is Comparative Example 1, No4 to No10 are Comparative Example 2 to Comparative Example 8, and No12 is Comparative Example 9.

<Forgeability evaluation>
A cylinder of 15 mmφ × 20 mmL was cut out from the center of each cast product (billet) and hot upset was performed at 400 ° C. The thickness before installation is L1, and the thickness after installation is L2.

As a result, it was set up to 80%, evaluation was made with no appearance defects such as surface cracks at the outer peripheral portion, and evaluation was made with x for appearance defects.
In the present invention (Example 1: No2, Example 2: No3, Example 3: No11, Example 4: No13), cracks did not occur even with hot deformation of 80% or more.

[Example 5], [Example 6]

An alloy having the composition shown in Table 2 (Cu: 2.8% by mass and 4.4% by mass, with B / Ti changed) was prepared.
As conventional methods (Comparative Example 10 to Comparative Example 17 are No14 to No21, Comparative Example 18 to Comparative Example 20 are No23 to No25), DAS is increased by die casting, and extruded material is a granular crystal + Some recrystallized materials were included.

<Forgeability evaluation>
Each material was homogenized at 490 ° C., held at 370 ° C. for 4 hours and cooled in a furnace, and then a 15 mmφ × 20 mm L cylinder was cut out from the center as a sample and placed at room temperature for compression. The upsetting rate when cracks appear on the surface was determined by the above formula and used as an evaluation index for cold forgeability.
Further, after T6 (aging at 490 ° C. water quenching and 180 ° C. × 7 hours), the material was cut out and processed in two types of tensile test pieces: a longitudinal direction and an orthogonal direction perpendicular to the longitudinal direction. A tensile test was conducted.
In the present invention [Example 5 (No. 22) and Example 6 (No. 26)], the mechanical characteristics were good, and there was no significant difference in characteristics between the longitudinal direction and the orthogonal direction perpendicular to the longitudinal direction.
The mold casting material has poor mechanical characteristics, and the extruded material has a large difference in characteristics between the longitudinal direction and the orthogonal direction perpendicular to the longitudinal direction.

It is explanatory drawing which shows the range of the alloy composition of this invention. It is process drawing which shows an example of the manufacturing equipment of the aluminum alloy and rod-shaped ingot of this invention. It is explanatory drawing which shows an example of a horizontal type continuous casting apparatus. It is explanatory drawing which shows an example of a structure of the forging apparatus used for this invention. It is sectional drawing which shows an example of the metal mold | die used for this invention.

Explanation of symbols

AE region 1 Aluminum alloy melt 2 Aluminum alloy continuous casting rod 3 Forging material 202 Tundish 203 Opening 204 Refractory plate 205 Pouring hole 301 Horizontal continuous casting apparatus 302 Mold 303 Gas supply path 304 Lubricating oil supply path 305 Cooling water supply path 601 Forging device 611 Forging machine 612 Lower die set plate 613 Upper die set plate 614 Guide post 621 Forging die 622 Lower die 623 Forging hole 625 Upper die 627 Knockout pin

Claims (9)

  8 mass% to 18 mass% of Si, 2.5 mass% to 6.0 mass% of Cu, 0.3 mass% to 1.2 mass% of Mg, 0.010 mass% to 0.020 mass of B % And Ti (B-0.45Ti) value of 0.010 or more is included, primary Si is 50 μm or less at maximum, eutectic Si is 10 μm or less on average, aluminum α crystal An aluminum alloy having a DAS of 15 μm or less.   The aluminum alloy according to claim 1, wherein the macro crystal grains of the cross section are granular crystals over the entire surface.   The aluminum alloy according to claim 1 or 2, wherein the average grain size of the macro crystal grains in the cross section is 300 µm or less.   The aluminum alloy according to any one of claims 1 to 3, comprising Fe and / or Mn in an amount of less than 0.2% by mass.   5. A uniform macro structure is exhibited in the longitudinal direction and an orthogonal direction orthogonal to the longitudinal direction, and a difference in elongation between the longitudinal direction and the orthogonal direction orthogonal to the longitudinal direction is within 10%. An aluminum alloy rod made of the aluminum alloy according to any one of the above items.   Al—Si containing at least 8% by mass to 18% by mass of Si, 2.5% by mass to 6.0% by mass of Cu, 0.3% by mass to 1.2% by mass of Mg, and Ti as an impurity Aluminum alloy for forging in which Al-B master alloy is added to molten aluminum alloy so that the value of (B-0.45Ti) is 0.010 or more in mass% in the ingot after casting. Ingot manufacturing method.   The method for producing an aluminum ingot for forging according to claim 6, wherein the casting is performed by a direct cooling casting apparatus.   The method for producing an aluminum ingot for forging according to claim 6 or 7, wherein the production is performed by casting at a cooling rate of 4 ° C / second or more.   A forged product manufactured by using the ingot manufactured by the method for manufacturing an aluminum alloy ingot for forging described in any one of claims 6 to 8 as a forging material.

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