JP6452042B2 - Method for producing magnesium alloy - Google Patents

Description

The present invention relates to a method for producing a magnesium alloy capable of high-speed extrusion.

  Magnesium alloys are lightweight and have high specific strength, so their application to various fields such as portable equipment and transportation equipment is expanding. However, since the magnesium alloy has poor plastic workability as compared with, for example, a 6000 series aluminum alloy used for an aluminum sash or the like, it cannot be extruded at the same speed as the aluminum alloy. The 6000 series aluminum alloy can be extruded at an outlet speed of usually 20 to 30 m / min, but the most general-purpose magnesium alloy AZ31 alloy is usually an outlet speed of about 5 m / min, which is slower than that. Extrusion can only be performed at AZX611 alloy with Ca added as a flame retardant alloy, and the extrusion speed is further limited to 1.5 m / min.

An object of the present invention is to provide a method for producing a magnesium alloy with good extrudability capable of increasing the extrusion speed and reducing the extrusion load in view of the circumstances described above.

The manufacturing method of the magnesium alloy of the present invention includes 0.1 to 3.0 wt% of Al, 0.1 to 0.43 wt% of Ca, 0.15 to 1.2 wt% of Mn, the balance being Mg and inevitable It consists of impurities, and the billet after casting is subjected to a homogenization treatment at 450 to 500 ° C. for 1 to 4 hours.

The manufacturing method of the magnesium alloy of the present invention includes 0.1 to 0.34 wt% Al, 0.1 to 0.35 wt% Ca, 0.15 to 1.2 wt% Mn, and 0.15 wt% or less Zn. And the balance is made of Mg and inevitable impurities, and the billet after casting is subjected to a homogenization treatment at 450 to 500 ° C. for 1 to 4 hours.

  It contains 0.1 to 3.0 wt% Al, 0.1 to 0.43 wt% Ca, 0.15 to 1.2 wt% Mn, and the balance consists of Mg and inevitable impurities. The magnesium alloy of the present invention subjected to a homogenization treatment at ˜500 ° C. × 1 to 4 hours can increase the extrusion speed of 15 m / min or more and can reduce the extrusion load.

  0.1 to 0.34 wt% of Al, 0.1 to 0.35 wt% of Ca, 0.15 to 1.2 wt% of Mn, 0.15 wt% or less of Zn, and the balance from Mg and inevitable impurities The magnesium alloy of the present invention in which the billet after casting is subjected to a homogenization treatment at 450 to 500 ° C. for 1 to 4 hours can increase the extrusion speed of 15 m / min or more and can reduce the extrusion load. .

It is an external appearance photograph of the extruded shape material of Examples 1-9. It is an external appearance photograph of the extruded shape material of Comparative Examples 1-4. It is an external appearance photograph of the extruded material which changed the quantity of Mn. It is an EBSD reverse pole figure map of the as-extruded material which changed the quantity of Mn. It is the external appearance photograph of the shape material extruded after giving the homogenization process in the state as cast, and various conditions. It is a graph which shows the influence of the homogenization process conditions on an extrusion load. It is a figure which shows the relationship between content of Al and Ca, extrusion achievement speed, and extrusion load. (A) is a microstructure photograph of a billet subjected to a homogenization treatment at 500 ° C. × 1 hour, (b) is a microstructure photograph of a billet subjected to a homogenization treatment at 500 ° C. × 64 hours, (c ) Is a micrograph of a billet subjected to a homogenization treatment at 350 ° C. for 1 hour, and (d) is a micrograph of a billet of a billet as cast. It is a graph which shows the relationship between the temperature and time of a homogenization process, and the crystal grain size of an extruded material.

Embodiments of the present invention will be described below. The magnesium alloy according to the present invention contains 0.1 to 3.0 wt% of Al, 0.1 to 0.43 wt% of Ca, 0.15 to 1.2 wt% of Mn, and the balance is composed of Mg and inevitable impurities. It is characterized by becoming.
Al has the effect of improving mechanical properties such as the tensile strength of the alloy, but if added in excess, the extrudability decreases. Therefore, Al was made 0.1 to 3.0 wt% so that good mechanical properties were obtained and extrudability was good.
Ca has a function of suppressing the ignition of magnesium during melting and casting, but if added in excess, the extrudability deteriorates. Therefore, Ca is made 0.1 to 0.43 wt% so that flame retardancy is obtained and extrudability is good.
Mn functions to suppress the coarsening of recrystallized grains and improve extrudability. If Mn is less than 0.15 wt%, this effect is not exhibited, so Mn is set to 0.15 to 1.2 wt%. In addition, 1.2 wt% of an upper limit is a value which cannot be added any more on operation.

  The magnesium alloy according to the present invention may contain 0.15 wt% or less of Zn. In this case, the Al content is 0.1 to 0.34 wt%, the Ca content is 0.1 to 0.35 wt%, and the Mn content is 0.15 to 1.2 wt%. High-speed extrusion at / min or higher becomes possible.

  The magnesium alloy according to the present invention is obtained by melting and casting raw materials blended so as to have a predetermined composition. The casting method is not particularly limited, but a die casting method or a continuous casting method can be used.

The magnesium alloy according to the present invention is characterized by subjecting a billet after casting to a homogenization treatment at 450 to 500 ° C. for 1 to 4 hours. As a result, the extrudability is further improved, and an extrusion speed of 15 m / min or more can be increased. Also, the extrusion load can be reduced.
When an Mg-Al-based magnesium alloy is subjected to extrusion processing, a low melting point compound (Mg-Al-based intermetallic compound) is melted by billet heating or processing heat generation during extrusion processing, and defects such as cracks are generated on the surface of the extruded material. Sometimes. In addition, when extruding a hollow shape such as a pipe shape, poor welding may occur in the extruded material, and it may be difficult to obtain a sound extruded material. Therefore, for the purpose of preventing the above-mentioned defects during the extrusion process, conventionally, a homogenization treatment in which the low melting point compound is solid-dissolved in the magnesium matrix is performed on the billet before the extrusion process. 410 ° C. × 24 hours is common.
The present invention is characterized in that the homogenization treatment is performed at a high temperature in a short time, and by performing the homogenization treatment under these conditions, Al and Mn dissolved in the magnesium matrix are Al—Mn-based metals. Since it precipitates as an intermetallic compound and the amount of Al and Mn in the magnesium matrix decreases, the deformation resistance during processing decreases, and the extrusion load decreases. As the amount of the precipitated compound increases, the extrudability improves.
Moreover, since the Al-Mn intermetallic compound is finely and densely dispersed by applying a homogenization treatment at 450 to 500 ° C. for 1 to 4 hours, the recrystallized grain boundary of the extruded material is pinned and crystallized. Grain coarsening can be suppressed. Therefore, the strength characteristics of the extruded material are improved.
The homogenization treatment time is 1 hour, which is sufficiently effective for improving the extrudability. Even if the time is longer, the effect is not so different. When the homogenization time is 4 hours or longer, the effect is the same as when the homogenization is performed at 350 ° C. Further, if the homogenization treatment is performed for longer than 4 hours, the recrystallized grains of the extruded material are coarsened and the strength characteristics are deteriorated. Therefore, the time for the homogenization treatment is 4 hours at the longest.
Cooling after the homogenization treatment may be under any conditions such as furnace cooling, air cooling, water cooling, etc., but a coarse compound precipitates when the cooling rate is slow, and a fine compound precipitates when the cooling rate is fast.

  The billet subjected to the homogenization treatment can be processed into shapes having various cross-sectional shapes by extrusion. The extrusion method is not particularly limited, and for example, a direct extrusion method or an indirect extrusion method can be used.

An experiment to find the fastest extrusion speed (extrusion achievement speed) that can be extruded without causing defects such as cracks for billets cast from magnesium alloy billets with the composition shown in Table 1 and homogenized with the cast material. went. In Examples 1 to 7 and 9, the contents of Al, Ca, and Mn are within the scope of claim 1, and in Example 8, the contents of Al, Ca, Mn, and Zn are in the scope of Claim 2. It is in. In Comparative Examples 1 and 4, the contents of Al, Zn and Ca exceed the range of Claim 2, and in Comparative Examples 2 and 3, the content of Ca exceeds the range of Claim 1. Components other than the main components shown in the table are Mg and inevitable impurities. The billet was cast by a continuous casting method using a heat insulating mold. The diameter of the billet was 76 mm. The homogenization treatment was performed at 500 ° C. for 1 hour. Cooling after the homogenization treatment was performed by cooling the fan with the billet out of the furnace. The cooling rate at this time was 300 ° C./h. Extrusion is performed by a direct extrusion method. The billet temperature is 350 ° C., the mold temperature is 350 ° C., the extrusion shape is a plate shape with a width of 30 mm and a thickness of 2 mm, and the extrusion ratio is 47.
Table 1 shows the composition of each billet, the speed at which extrusion was achieved, and the extrusion load (maximum load). FIG. 1 is an appearance photograph of the extruded shapes of Examples 1 to 9, and FIG. 2 is an appearance photograph of the extruded shapes of Comparative Examples 1 to 4.

As is clear from Table 1 and FIGS. 1 and 2, Examples 1 to 9 can be extruded at 10 m / min or more even if extrusion is performed in the as-cast state. Except for Examples 5, 6, and 9, extrusion at a high speed of 28 m / min was possible. Further, it was confirmed that when the homogenization treatment was performed, the extrusion speed could be increased and the extrusion load was reduced. By performing the homogenization treatment, the extrusion load was reduced by approximately 10 to 20%, and in Example 7, where the Al content was as high as 2.69 wt%, the load reduction ratio was increased to 23%.
Examples 2 and 3 having an Al content of 0.4 wt% or less and an Mn content of 0.4 wt% or more could be extruded at 28 m / min even when cast.
On the other hand, in Comparative Example 1 containing more than 0.15 wt% of Zn and Comparative Examples 2 to 4 containing more than 0.43 wt% of Ca, it was impossible to increase the extrusion speed of 15 m / min or more. It was.

  FIG. 7 is a diagram showing the relationship between the content of Al and Ca, the speed of achieving extrusion, and the extrusion load. As is clear from the figure, extrudability is clearly lowered when Ca is 0.4 wt% or more. In the region where Ca is 0.35 wt% or less and Al is 0.35 wt% or less, it is possible to increase the extrusion speed of 20 m / min or more even when cast. In the region where Ca is 0.35 wt% or less and Al is 0.35 to 0.63 wt%, it is possible to increase the extrusion speed of 20 m / min or more by performing a homogenization treatment. In the region where Ca is 0.35 wt% or less and Al is 0.63 to 2.6 wt%, it is possible to increase the extrusion speed by 15 m / min or more by applying a homogenization treatment.

  A tensile test was performed on the extruded shapes of Examples 1, 2, 3, 4, 6, and 7 treated with T5, and mechanical properties were measured. In addition, the microstructure of these shapes was observed and the crystal grain size was measured. The measurement results are shown in Table 2.

  In Example 1, where the Mn content is as low as 0.2 wt%, the crystal grain size is as coarse as about 50 μm, but Examples 2, 3, 4, 6, and 7 containing Mn in an amount of 0.4 wt% or more are crystals. Grain coarsening is suppressed, and mechanical properties are also improved. As the Al content increases, the tensile strength improves.

  As shown in Table 3, three types of magnesium alloy billets with different Mn contents were cast, each billet was subjected to a homogenization treatment at 450 ° C. for 1 hour, the billet was extruded, and the appearance of the extruded material and The microstructure was observed. Extrusion was performed by the indirect extrusion method, the extrusion temperature was 400 ° C., and the extrusion speed was 60 m / min.

FIG. 3 is an appearance photograph of the extruded material of each of the above magnesium alloys. As is clear from the figure, as the Mn content increases, the surface properties of the extruded material improve.
FIG. 4 is a photograph of the microstructure of each extruded material. As is clear from the figure, as the Mn content increases, the crystal grain size tends to become finer and the texture becomes stronger.

  About 0.4Mn magnesium alloy in Table 3, indirect extrusion of billet as cast and homogenized under conditions of 500 ° C. × 1 hour, 450 ° C. × 1 hour, 400 ° C. × 1 hour Extrusion processing was carried out, and the extrudability of each material was evaluated. The extrusion speed was 60 m / min.

  FIG. 5 is a photograph of the appearance of the extruded material. As shown in the figure, in the case of the as-cast material, a large crack was generated on the surface, and when the homogenization treatment was performed at 400 ° C. × 1 hour, the crack was generated on the surface although not as much as the as-cast material. When the homogenization treatment was performed at 500 ° C. × 1 hour and 450 ° C. × 1 hour, an extruded material having a good appearance with no defects such as cracks on the surface was obtained.

  A magnesium alloy billet having the composition shown in Table 4 below is cast, and extrusion processing is performed on the as-cast material and billets homogenized at 350 ° C, 400 ° C, 450 ° C, and 500 ° C for 1, 4, 16, and 64 hours, respectively. The effect of the homogenization treatment conditions on the extrudability was investigated. Cooling after the homogenization treatment was performed by water cooling. Extrusion was performed by indirect extrusion, the extrusion temperature was 350 ° C., the extrusion speed was 60 m / min, and the extrusion ratio was 20.

  FIG. 6 is a graph of the results of this experiment. As is clear from the figure, by performing the homogenization treatment at 450 ° C. × 1 hour and 500 ° C. × 1 hour, the extrusion load is greatly reduced and the extrudability is also dramatically improved.

  Fig. 8 shows a homogenized treatment at 500 ° C for 1 hour, a homogenized treatment at 500 ° C for 64 hours, a homogenized treatment at 350 ° C for 1 hour, and a micro of each billet as cast. It is an organization photograph. In the spherical compound having a white color of about 60 nm or less as seen in the photograph (lower photograph) of the homogenized treatment at 500 ° C. × 1 hour shown in FIG. 8A, an Al—Mn intermetallic compound was precipitated. It can be seen that this intermetallic compound is dispersed and deposited in a high density at a volume ratio of 1% or more. This feature can be seen only in the case of homogenization treatment at 500 ° C. × 1 hour, and not in the case of homogenization treatment under other conditions or as-cast. As the Al-Mn intermetallic compound is precipitated at a high density in this way, the solid solution amount of Al and Mn in the magnesium matrix decreases, so the deformation resistance during processing decreases and the extrusion load decreases. It is considered a thing.

  FIG. 9 is a graph showing the relationship between the temperature and time of the homogenization treatment and the crystal grain size of the extruded material. As is clear from the figure, when the homogenization treatment is performed at 450 ° C. or 500 ° C., the crystal grains of the extruded material increase as the treatment time increases. Due to the stopping effect, coarsening of crystal grains is suppressed, and within 4 hours, the crystal grains can be suppressed to 150% or less of the crystal grains of the extruded material obtained by extruding the material as cast.

  As described above, a magnesium alloy containing 0.1 to 3.0 wt% Al, 0.1 to 0.43 wt% Ca, and 0.15 to 1.2 wt% Mn is extruded at 10 m / min or more. The speed can be increased. A magnesium alloy containing 0.1 to 0.34 wt% of Al, 0.1 to 0.35 wt% of Ca, 0.15 to 1.2 wt% of Mn, and 0.15 wt% or less of Zn is also 10 m / It is possible to increase the extrusion speed at least min. By subjecting the cast billet to a homogenization treatment at 450 to 500 ° C. for 1 to 4 hours, extrusion at a higher speed (15 m / min or more) becomes possible, and the extrusion load can be reduced. By containing a predetermined amount of Al, mechanical properties equivalent to or higher than those of a general aluminum alloy 6063 for stretching can be obtained. Moreover, flame retardance can be provided by containing a predetermined amount of Ca.

  The present invention is not limited to the embodiments described above. The magnesium alloy of the present invention is not limited to the one for extrusion, and can also be used for rolling, press molding, and forging.

Claims (2)

It contains 0.1 to 3.0 wt% Al, 0.1 to 0.43 wt% Ca, 0.15 to 1.2 wt% Mn, and the balance consists of Mg and inevitable impurities. A method for producing a magnesium alloy , characterized by performing a homogenization treatment at ˜500 ° C. × 1 to 4 hours. 0.1 to 0.34 wt% of Al, 0.1 to 0.35 wt% of Ca, 0.15 to 1.2 wt% of Mn, 0.15 wt% or less of Zn, and the balance from Mg and inevitable impurities It becomes method for producing a magnesium alloy, characterized in that performing a homogenization treatment of 450 to 500 ° C. × 1 to 4 hours billet after casting.