JP7271980B2 - Manufacturing method for aluminum alloy continuous cast material - Google Patents

Description

The present invention relates to an aluminum alloy casting material used as a forging material.

In aluminum forgings, since the mechanical properties and structure of the forging material tend to remain in the areas with low workability, cast materials of aluminum alloys with excellent mechanical properties have been developed (Patent Document 1).

JP 2007-92125 A

However, with conventional aluminum alloy castings, if the cast material is not a small-diameter continuous cast material, the ingot structure becomes coarse at the center of the cast material where the cooling rate is slow, and the mechanical strength such as tensile strength and 0.2% proof stress is reduced. However, there was a problem that the characteristics of the product deteriorated.

SUMMARY OF THE INVENTION An object of the present invention is to provide an aluminum alloy cast material which has a finer ingot structure, thereby improving mechanical properties and having a high electric conductivity, and which can be used as a material for alloy forging.

In order to solve the above problems, the present invention has the following means.

[1] Si: 9 to 11 mass%, Fe: 0.5 mass% or less, Cu: 0.7 to 1.1 mass%, Mn: 0.09 mass% or less, Mg: 0.3 to 0.7 % by mass, Cr: 0.05 mass % or less, Ni: 0.05 mass % or less, Zn: 0.25 mass % or less, Ti: 0.005 to 0.06 mass %,
Furthermore, any one of Sr, Sb, Ca, and Na is added to Sr: 0.01 to 0.1 mass%, Sb: 0.03 to 0.2 mass%, Ca: 0.003 to 0.02 mass%, Contains Na: 0.003 to 0.02% by mass,
The remainder consists of Al and inevitable impurities,
Tensile strength is 330 N/mm ² or more, 0.2% yield strength is 250 N/mm ² or more, elongation is 4% or more, Rockwell hardness (HRB) is 65 or more and 82 or less, and electrical conductivity is 40% IACS or more. An aluminum alloy casting material characterized by:

[2] B: The cast aluminum alloy material according to the above item 1, containing 0.0002 to 0.01% by mass.

[3] The aluminum alloy casting material according to the preceding item 1 or 2, which is produced by simultaneously adding Ti and any one of Sr, Sb, Ca and Na to the molten metal.

[4] A forging material made of the cast aluminum alloy material according to any one of 1 to 3 above.

[5] A forged material obtained by forging the cast aluminum alloy material according to any one of 1 to 3 above.

According to the above [1], the composition contains predetermined amounts of Si, Cu, and Mg, and the content of Fe, Mn, Cr, Ni, and Zn is set to a predetermined amount or less, a predetermined amount of Ti, and further Sr, Sb, It has a composition in which a predetermined amount of either Ca or Na is added, and mechanical properties such as tensile strength, 0.2% yield strength, and elongation are achieved by making the ingot structure fine even at the center of the cast material with a slow cooling rate. It is possible to obtain an aluminum alloy cast material that is excellent in hardness and has an appropriate hardness and can be used as a material for aluminum alloy forging. In addition, by having a high electrical conductivity, the heat dissipation is also improved, so it can be used as a member in a place where the operating environment temperature is high, or as a conductive material that requires mechanical properties.

According to the above [2], since it is a composition in which a predetermined amount of B is added, an aluminum alloy cast material having an even finer ingot structure and improved mechanical properties can be obtained.

According to the above [3], Ti and any one of Sr, Sb, Ca and Na are added to the molten metal at the same time, so that the ingot is more effective than the aluminum alloy cast material manufactured by the conventional manufacturing method. An aluminum alloy cast material having a finer structure and improved mechanical properties can be obtained.

According to [4] and [5] above, it is possible to obtain an aluminum forged product with good characteristics even in a portion with a low forging workability.

A mode for carrying out the aluminum alloy cast material of the present invention will be described in detail.

The cast aluminum alloy material of the present invention contains predetermined amounts of Si, Cu, Mg, and Ti, contains less than a predetermined amount of Fe, Mn, Cr, Ni, and Zn, and further contains any one of Sr, Sb, Ca, and Na. or 1 type, and the balance consists of Al and unavoidable impurities.

Moreover, it is preferable that the cast aluminum alloy material of the present invention further contains B in a predetermined amount.

Each element constituting the cast aluminum alloy material of the present invention will be described.

The Si content is 9-11% by mass. Si has the effect of improving wear resistance. If the amount of Si is less than the lower limit, the effect of improving wear resistance is weak. If the amount of Si exceeds the upper limit, the forgeability and moldability are degraded.

The content of Fe is 0.5% by mass or less. Fe improves the heat resistance without lowering the mechanical strength. When the amount of Fe exceeds the upper limit, a large amount of Fe-containing crystallized substances are generated, resulting in a decrease in mechanical strength.

The Cu content is 0.7 to 1.1% by mass. Cu can achieve both corrosion resistance and mechanical strength. Mechanical strength falls that the amount of Cu is less than a lower limit. When the amount of Cu exceeds the upper limit, it leads to deterioration of corrosion resistance.

The Mn content is 0.09% by mass or less, the Cr content is 0.05% by mass or less, and the Ni content is 0.05% by mass or less. If the content of any of these elements exceeds the upper limit, the mechanical properties (especially forgeability) will be degraded.

The content of Mg is 0.3-0.7% by mass. Mg improves mechanical strength. Mechanical strength falls that Mg is less than a lower limit. When the amount of Mg exceeds the upper limit, the amount of crystallization of intermetallic compounds increases, resulting in brittleness.

The Zn content is 0.25% by mass or less. Zn improves mechanical strength. When the amount of Zn exceeds the upper limit, the corrosion resistance deteriorates.

The content of Ti is 0.005 to 0.06% by mass. Ti improves forgeability through refinement of the ingot structure or refinement of Al--Si eutectic grains. If the amount of Ti is less than the lower limit, the above effect cannot be expected. When the amount of Ti exceeds the upper limit, the toughness is lowered due to the formation of coarse Al--Si--Ti compounds. Also, by adding one of Sr, Sb, Ca, and Na to the molten metal at the same time, the ingot structure can be made finer and the mechanical properties can be improved.

B is an optional additive element, and its additive amount is 0.0002 to 0.01% by mass. B refines the ingot structure. If the amount of B is less than the lower limit, the above effects cannot be sufficiently obtained. If the amount of B exceeds the upper limit, TiB2 is generated, which leads to deterioration of working tool life. Also, by simultaneously adding Ti and any one of Sr, Sb, Ca, and Na to the molten metal, the ingot structure can be made finer and the mechanical properties can be improved.

Sr, Sb, Ca, and Na are selective additive elements, and one of them is added. The respective contents are 0.01 to 0.1 mass % for Sr, 0.03 to 0.2 mass % for Sb, 0.003 to 0.02 mass % for Ca, and 0.003 to 0.02 mass % for Na. 02% by mass. Each element has an effect of improving the Al--Si alloy, and in particular, an effect of improving such as refinement of eutectic Si can be obtained. If the amount of any element added is less than the lower limit, the above effect cannot be sufficiently obtained. If the amount added exceeds the upper limit, the fluidity of the molten metal is lowered and shrinkage cavities are generated accordingly. In addition, by simultaneously adding Ti or Ti and B to the molten metal, the ingot structure is refined, and in addition to improving the mechanical properties, the electrical conductivity improvement is achieved.

Among these selective additive elements Sr, Sb, Ca and Na, Sr is most preferable. This is because Sb has a weaker refining effect than Sr. This is because Ca may cause a decrease in degassing properties, a deterioration in corrosion resistance, and the generation of pores. This is because Na shortens the life of the furnace material and melts it more severely than Sr, and the effect of addition does not last for a long time, resulting in poor mass productivity.

In an Al-Si alloy containing 9 to 12% Si, which is usually near the eutectic point, the addition of Ti and B improves the mechanical properties and electrical conductivity associated with the refinement of the ingot structure. is difficult to obtain. However, the addition of any one of Sr, Sb, Ca, and Na causes compositional supercooling, and a phenomenon occurs in which the eutectic point shifts to the hypereutectic side. Due to this phenomenon, the eutectic structure becomes a hypo-eutectic structure, so that the effect of Ti and B added simultaneously becomes greater. Therefore, by simultaneously adding Ti and one of the elements Sr, Sb, Ca, and Na, the effect of improving the mechanical properties and improving the electrical conductivity becomes greater.

For this reason, it is preferable to add Ti and any one of Sr, Sb, Ca, and Na to the molten metal at the same time, and the simultaneous addition of B makes it easier to obtain the above effects. In addition, simultaneous addition to the molten metal immediately before casting can bring out the best performance of the refining material. Since the refining performance of the above refining agents deteriorates with the lapse of time after addition, if either one of them is added first, it will not contribute sufficiently to refining the ingot structure.

As a method of simultaneously adding the refining agent of Ti, B, Sr, Sb, Ca, and Na to the molten metal, it is most preferable to add a rod material using a rod feeder. Two rod feeders are required for simultaneous addition, but by using the rod feeders, it is possible to accurately set the addition speed and add the targeted mass % of the fine grains.

Moreover, the location for simultaneous addition is most preferably a GBF furnace (gas bubbling filter). By adding it to the GBF furnace, there is also the effect of removing inclusions contained in the rod material, and since the molten metal can be stirred by the rotation effect of the GBF rotor, the finely divided metal compound existing in the rod material is finely divided. This is because they are uniformly dispersed. Further, as an advantage of adding in the form of rods, the size of finely refined intermetallic compounds such as Al3Ti and TiB2 is smaller than that of bare metal due to rapid solidification during production of rods, so fineness performance is further improved.

Next, the aluminum alloy casting material of the present invention and the method for producing a forged product using the same will be described.

First, by melting, an aluminum alloy molten metal whose components are adjusted as described above is produced.

At this time, any one of Ti, B, Sr, Sb, Ca, and Na, which are additive elements for the refining effect, should be added at a molten metal temperature of 740 ° C. ± 30 ° C. in order to obtain a sufficient refining effect. is desirable. If the molten metal temperature exceeds 770° C., the above addition effect cannot be obtained. Moreover, even if it is added at a temperature lower than 710° C., the above-mentioned effect of addition cannot be obtained.

Also, since it is preferable to add Ti and B at the same time, it is desirable to add them in the Al--Ti--B master alloy.

It is preferable to add Sr, Sb, Ca and Na as a master alloy with Al.

In addition, since the effect of addition of each refiner decreases as time elapses after addition, it is preferable to add it in the process immediately before casting.

An aluminum alloy casting material is obtained by continuously casting the aluminum alloy molten metal whose composition has been adjusted in this way.

As for specific casting conditions, the cooling rate is important, and various conditions such as the casting rate are set so that the cooling rate is 0.1° C./s or more, although it varies depending on the casting diameter. If the cooling rate is slower than this condition, the various additives will not be sufficiently solid-dissolved, and the effects of the additives will not be obtained sufficiently. As a result, the effect of improving the mechanical properties due to the refinement of the ingot structure cannot be sufficiently obtained.

The casting diameter is preferably φ100 to φ203.

At this time, the ingot quality is enhanced by casting by the gas pressurized hot top casting method. This is because the ingot can be solidified and cooled only by water cooling without contact with the mold by supplying gas from between the header and the mold.

The continuously cast material of this embodiment is used as a forging material. An extruded material obtained by extruding a continuously cast material may be used as the forging material.

The continuously cast material may be subjected to a homogenization treatment in order to remove non-uniform structure due to segregation of crystallized substances during casting.

The continuously cast material is cut into a predetermined length to form a forging material, and forged to obtain a forged material.

The aluminum alloy cast material of the present invention has a tensile strength of 330 N/mm ² , a 0.2% proof stress of 250 N/mm ² , an elongation of 4% or more, a Rockwell hardness (HRB) of 65 or more and 82 or less, and an electrical conductivity. provided that the rate is greater than or equal to 40% IACS.

The high conductivity of 40% IACS or more improves heat dissipation, so it can be used for members with high ambient temperature. It can also be used as a conductive material because of its good conductivity. In particular, busbars are required to have electrical conductivity and high mechanical properties. Therefore, bus bars are generally made of copper, but aluminum alloys can also be used. In particular, the material of the present invention has higher mechanical properties and electrical conductivity than aluminum alloy cast materials manufactured by conventional methods, and is expected to be lighter and significantly lower in cost than copper materials.

EXAMPLES The present invention will now be described with reference to examples and comparative examples.

Table 1 shows the composition of each example and comparative example.

In each example and comparative example, first, raw materials of Si, Cu, and Mg, which are main elements, were melted in a melting furnace.

After that, the molten metal is transferred to a holding furnace, and after the molten metal is held for a certain period of time, the refining agents Ti, Sr, and B are added. The master alloy was simultaneously added to the melt in the GBF furnace using a rod feeder.

The GBF treatment was performed in the same GBF furnace, the molten metal subjected to the GBF treatment was transferred to a gutter, and casting was performed by the gas pressurized hot top casting method. This molten metal treatment device is for removing aluminum oxides and hydrogen gas present in the molten metal. It moves to the upper part of the furnace and is transferred to the casting machine.

The diameter of the casting rod was φ203 mm, and the other casting conditions were a casting temperature of 710° C. and a casting speed of 100 mm/min.

From the cast material thus obtained, a test piece was taken from the central portion of the cross section of the cast material, and the mechanical properties, hardness, and electrical conductivity of each test piece were measured.

The mechanical properties were measured by setting the TP shape to ASTM No. 3, performing T6 refining on each test piece, and measuring the tensile strength (N/mm ² ), 0.2% proof stress (N/mm ² ) and elongation (%) were measured. n=3 measurements were performed for each example, and the average value was calculated. Hardness measurement is Rockwell hardness (hardness symbol: HRB) measured in accordance with JIS Z2245:2005 "Rockwell hardness test - test method", and the scale used for the measurement is "B". , the indenter is a steel ball of 1.5875 mm, and the test load is 980.7 N. Conductivity measurement is performed on aluminum alloy castings after homogenization treatment, and the unit at that time is %IACS (International Annealed Copper Standard).

Table 2 shows the results.

As described above, by manufacturing under appropriate casting conditions with the composition specified in the present invention, the cast material has a tensile strength of 330 N/mm ² or more, a 0.2% proof stress of 250 N/mm ² or more, an elongation of 4% or more, It can be seen that an aluminum alloy cast material having good mechanical properties such as a hardness (HRB) of 65 or more and 82 or less and a good conductivity of 40% IACS or more can be obtained.

The cast aluminum alloy material of the present invention can be suitably used as a material for various forging materials.

Claims (5)

Si: 9 to 11% by mass, Fe: 0.5% by mass or less, Cu: 0.7 to 1.1% by mass, Mn: 0.09% by mass or less, Mg: 0.3 to 0.7% by mass, Cr: 0.05% by mass or less, Ni: 0.05% by mass or less, Zn: 0.25% by mass or less, Ti: 0.005 to 0.06% by mass,
Furthermore, any one of Sr, Sb, Ca, and Na is added to Sr: 0.01 to 0.1 mass%, Sb: 0.03 to 0.2 mass%, Ca: 0.003 to 0.02 mass%, Contains Na: 0.003 to 0.02% by mass,
The remainder consists of Al and inevitable impurities,
Tensile strength when tempered to T6 is 330 N/mm ² or more, 0.2% yield strength is 250 N/mm ² or more, elongation is 4% or more, Rockwell hardness (HRB) is 65 or more and 82 or less. A method for producing an aluminum alloy continuously cast material having an electrical conductivity of 40% IACS or more when homogenized ,
A method for producing an aluminum alloy continuous cast material, characterized in that Ti and any one of Sr, Sb, Ca and Na are simultaneously added to a molten metal. The method for producing an aluminum alloy continuously cast material according to claim 1, further comprising B: 0.0002 to 0.01% by mass. 3. A method for producing an extruded aluminum alloy material, further comprising extruding the continuously cast aluminum alloy material produced by the method for producing a continuously cast aluminum alloy material according to claim 1 or 2. A method for producing an aluminum alloy, wherein the continuously cast aluminum alloy material produced by the method for producing a continuously cast aluminum alloy material according to claim 1 or 2 is further subjected to a homogenization treatment. A method for producing an aluminum alloy forged material, wherein the continuously cast aluminum alloy material produced by the method for producing a continuously cast aluminum alloy material according to claim 1 is further forged.