JP7356116B2 - Method of manufacturing aircraft parts - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a method of manufacturing an aircraft component, and particularly to a method of manufacturing a secondary structural component of an aircraft.

Due to recent demands for improved fuel efficiency, commercial aircraft are increasingly required to reduce their weight. Aluminum alloys are used in the main structural components of conventional commercial aircraft (fuselage skins, etc.), but the strength of aluminum alloy components has reached its limit, and materials with even higher specific strength need to be applied. The situation is necessary.

Under these circumstances, in recent years, composite materials have been applied to the main structure of the aircraft, but currently there are issues such as high manufacturing costs, long manufacturing lead times, and high assembly costs. be.

In order to solve these problems, research is being carried out on magnesium alloys that have a manufacturing cost comparable to that of aluminum alloys and have a specific strength equal to or higher than that of aluminum alloys (see Patent Documents 1 and 2).

Magnesium alloy is an active metal and requires anti-corrosion treatment. In Patent Document 1, a non-chromate conversion coating is formed on the surface of a magnesium alloy to improve corrosion resistance. On the other hand, Patent Document 2 discloses a highly corrosion-resistant magnesium alloy member that does not require anti-corrosion treatment by defining the number and size of fine precipitates containing both Mg and Al present in the surface layer region. ing.

Special Publication No. 2008-536013 Japanese Patent Application Publication No. 2010-209452

In addition to corrosion resistance, materials used for aircraft components are required to have both strength (tensile strength) and ductility (elongation). Magnesium alloys have lower strength than aluminum alloys. Therefore, it is necessary to improve the strength, but the strength of magnesium alloys is in a trade-off relationship with ductility, and it is difficult to achieve both.

Furthermore, in order to apply magnesium alloys to aircraft components, it is necessary to improve flame retardancy and raise the ignition temperature.

As described in Patent Document 2, a magnesium alloy member is manufactured using a billet cast using an ingot made of a magnesium alloy.

For manufacturing large aircraft parts, it is desirable to use billets that are somewhat large. However, as the diameter of the billet increases, the quality of the billet as a whole tends to become uneven. Unevenness in quality can be a factor that affects the strength and ductility of a magnesium alloy member.

Magnesium alloys change grain size and microstructure depending on processing conditions, and their strength and ductility change.

FIG. 5 illustrates a photograph of the metal structure of a Mg-Al-Ca-Si alloy. As shown in Figure 5, the metal structure contains α-Mg (solid solution with Al and Ca), Mg-Si-Ca compound, (Mg,Al) ₂ Ca compound (C36), etc. . FIG. 6 shows a photograph of the metallographic structure of (Mg-Si-Ca compound). FIG. 7 shows a photograph of the metallographic structure of the (Mg, Al) ₂ Ca compound.

According to the studies conducted by the present inventors, it has been found that when intermetallic compounds such as Mg-Si-Ca compounds and (Mg,Al) ₂ Ca compounds become coarser, the ductility tends to decrease. There is. As the billet becomes larger, the (Mg, Al) ₂ Ca compound tends to become coarser.

In small billets, the addition of Si to magnesium alloys may improve ductility. However, according to studies conducted by the present inventors, it has been found that billets that are large to a certain extent have low ductility.

The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a manufacturing method that can stably obtain a magnesium alloy member having both strength and ductility, regardless of the size of the billet. do.

In order to solve the above problems, the method for manufacturing an aircraft component of the present disclosure employs the following means.

The present disclosure is a method for producing an aircraft component by extrusion processing using an Mg-Al-Ca alloy containing a (Mg, Al) ₂ Ca compound, wherein Al: 6 atomic % or more and 8 atoms based on the total amount. % or less , Ca : 3 atomic % or more and 4 atomic % or less, Mn: more than 0 atomic % and 0.3 atomic % or less , and the balance is Mg and unavoidable impurities. The present invention provides a method for manufacturing an aircraft component, in which the billet is extruded under conditions in which the temperature of the billet is maintained below the melting temperature of the (Mg, Al) ₂ Ca.

According to the manufacturing method of the present disclosure, by using a billet with Al and Ca contents in the above range and optimizing the extrusion processing conditions, an aircraft member with both strength and ductility can be produced compared to conventional methods. Stably obtained. Further, according to the manufacturing method of the present disclosure, an aircraft member that satisfies the required flame retardancy can be obtained.

It is a figure showing the relationship between extrusion conditions, tensile strength (FTY), and ductility (elongation/EL). It is a figure showing the range of preferable extrusion processing conditions. FIG. 2 is a diagram showing the relationship between Al and Ca contents, extrusion conditions, tensile strength (FTY), and ductility (elongation/EL). FIG. 3 is a diagram showing the results of a corrosion test. This is a photograph of the metal structure of a Mg-Al-Ca-Si alloy as an example. This is a photograph of the metallographic structure of a Mg-Si-Ca compound. It is a metal structure photograph of a (Mg, Al) ₂ Ca compound.

The manufacturing method according to the present disclosure is suitable for manufacturing secondary structural members for aircraft. A secondary structural member is a member that is attached to a primary structural member such as a stringer. Secondary structural members include clips, brackets, fittings for securing piping, and seat frames. The secondary structural member is a member to which a large load is not applied compared to the primary structural member.

An embodiment of the method for manufacturing an aircraft component according to the present disclosure will be described below with reference to the drawings.

In this embodiment, an aircraft member is extruded using a billet of an Mg-Al-Ca alloy containing a (Mg, Al) ₂ Ca compound (hereinafter referred to as (Mg, Al) ₂ Ca). The extrusion process is carried out under conditions in which the temperature of the billet is maintained below the melting temperature of the (Mg,Al) ₂ Ca compound. In extruded aircraft parts (extruded materials), (Mg, Al) ₂ Ca is dispersed in the metal structure.

The above-mentioned Mg-Al-Ca alloy (billet) is a cast product manufactured by melting and casting. The cooling rate during billet casting is 1000 K/sec or less, preferably 100 K/sec or less.

The diameter of the billet is 29 mm or more and 180 mm or less. The diameter of the billet may be 69 mm or more.

The billet is selected from a Mg-Al-Ca alloy containing Al in an amount of 6 atomic % to 8 atomic %, and Ca in an amount of 3 atomic % to 4 atomic %, based on the total amount.

The Mg-Al-Ca alloy (billet) may contain more than 0 atomic % and 0.3 atomic % or less of Mn, preferably 0.01 or more and 0.05 or less.

The remainder of the Mg-Al-Ca alloy (billet) consists of Mg.
The phrase "the remainder" is "consisting of Mg" means not only that the remainder is entirely composed of Mg, but also that the remainder may contain impurities or other elements to the extent that they do not affect the alloy properties.

The Mg-Al-Ca alloy (billet) does not contain Si. Here, "not containing" means not only when the Si content is 0 atomic %, but also when Si is unavoidably contained (for example, 0.1 atomic % or less).

The Mg-Al-Ca alloy (billet) contains a (Mg, Al) ₂ Ca compound. In the Mg-Al-Ca alloy, (Mg,Al) ₂ Ca may be contained in an amount of preferably 10% by volume or more and 35% by volume or less, more preferably 10% by volume or more and 30% by volume or less.

The melting temperature of (Mg, Al) ₂ Ca is 490°C. The melting temperature is derived from the phase diagram.

The temperature of the billet during extrusion can be maintained below the melt temperature by setting the extrusion temperature and exit speed. "Extrusion exit speed" is the speed at which material is extruded from an extrusion mold (die) during extrusion molding.

The extrusion ratio is preferably 10 or more and 80 or less.

The cross section of the extruded material may be, for example, L-shaped, T-shaped, or Z-shaped.

The Mg-Al-Ca based alloy billet may be heat treated at 400° C. or more and 500° C. or less for 1 hour or more and 6 hours or less before extrusion processing. The treatment temperature is preferably 450°C or higher and 500°C or lower. It is more desirable that the processing time be as short as about one hour.

(Extrusion temperature and extrusion exit speed)
The billet was extruded under predetermined conditions, and the tensile yield strength (FTY) and ductility (elongation/EL) of the obtained extruded material were measured.

For the billet, an Mg-Al-Ca alloy (φ69 mm) containing 8 at% of Al, 4 at% of Ca, and 0.015 at% of Mn was used. The extrusion ratio was 15.

The measurement results are shown in FIG. 1 and Table 1. In Figure 1, the horizontal axis (x-axis) is the extrusion temperature (℃), the vertical axis (y-axis) is the extrusion exit speed Ve (m/min), and the solid line is the 〇 plot (x: 375℃, y: 3.6m/min). min) and the 〇 plot (x: 450°C, y: 0.9 m/min) (y=-0.036x+17.1). In the graph of the xy coordinate system in FIG. 1, the colored part on the right side of the paper as viewed from the above straight line is a region where the temperature at the time of extrusion (temperature of the billet) exceeds 490°C.

According to Figure 1 and Table 1, the extruded material (x plot/extruded material No. 8) that was extruded under conditions where the billet temperature exceeds 490°C (the billet melts) has a tensile strength of 264 MPa and a ductility of 264 MPa. It was 1.6%. On the other hand, the extruded materials (〇 plot/extruded materials No. 1 to 7, 9) that were extruded under conditions where the billet temperature does not melt (maintained below the melting temperature of the billet) have a tensile strength of 270 MPa. The ductility was 3% or more.

The above results suggested that an extruded material having both tensile strength and ductility could be obtained by extruding under conditions (extrusion temperature and extrusion exit speed) in which the billet does not melt.

FIG. 2 shows the range of preferable extrusion processing conditions suggested from the results of FIG. 1. In Figure 2, the horizontal axis (x-axis) is the extrusion temperature (°C), the vertical axis (y-axis) is the extrusion exit speed Ve (m/min), and the solid line is the 〇 plot (x: 375°C, y: 3.6 m/min). straight line (y=-0.036x+17.1) connecting the plot (x: 450°C, y: 0.9 m/min), the two-dot chain line indicates the preferred range, and the one-dot chain line is more preferable. This is a line indicating a range. In the graph of the xy coordinate system in FIG. 2, the colored part on the right side of the paper as viewed from the above straight line is a region where the temperature at the time of extrusion (temperature of the billet) exceeds 490°C.

The extrusion temperature and extrusion exit speed are plotted in the first plot (x: 375°C, y: 3.6 m/min) and the second plot (x: 450° C., y: 0.9 m/min), or from a range where x and y are smaller than the straight line.

It is practical to set the extrusion temperature to 350° C. or higher and the extrusion exit speed to 0.3 m/min or higher. If the extrusion temperature is lower than 350°C, the fluidity of the billet will deteriorate, making extrusion difficult. When the extrusion exit speed is slower than 0.3 m/min, it becomes difficult to control the speed of the extrusion device.

Considering the limitations of the extrusion device capacity, the extrusion temperature and extrusion exit speed are preferably selected from within the range surrounded by the three straight lines of formulas (1) to (3) (including on the straight line).
Formula (1): y=-0.036x+17.1
Formula (2): x=350
Formula (3): y=0.3

According to FIG. 2, it has been confirmed that if the extrusion exit speed is in the range of 0.9 m/min or more and 3.6 m/min or less, the extruded material can more reliably have both tensile strength and ductility. From this, it is more desirable to select the extrusion temperature and extrusion exit speed from within the range surrounded by the four straight lines (including those on the straight lines) of formulas (1) to (4).
Formula (1): y=-0.036x+17.1
Formula (2): x=350
Formula (3'): y=0.9
Formula (4): y=3.6

For reference, FIG. 3 and Table 2 show the tensile strength (FTY) and ductility ( The results of measuring elongation/EL) are shown.

The billet used was an Mg--Al--Ca alloy (69 mm in diameter) containing 10 atomic % of Al, 5 atomic % of Ca, and 0.05 atomic % of Mn. The extrusion ratio was 15.

It has been confirmed that in an extruded material using a billet in which Al and Ca are outside the ranges of the above embodiments, there are cases where the ductility is significantly reduced even if the extrusion processing conditions are within the ranges disclosed above.

From the above results, it is necessary to select a Mg-Al-Ca based alloy billet containing Al: 6 at% or more and 8 at% or less, and Ca: 3 at% or more and 4 at% or less, based on the total amount. was suggested.

(ignition temperature)
Extruded material No. Nos. 12 to 23 were heated with a heater and the temperature at the time of ignition was measured.
The extrusion ratio during extrusion processing was 15. The measurement results are shown in Table 3.

The ignition temperatures of extruded materials No. 12 to 23 were all 1000°C or higher. On the other hand, the ignition temperature of a commercially available magnesium alloy (Elektron 43) was lower than 900°C. This result suggested that the method according to the above embodiment can produce an extruded material (aircraft member) with better flame retardancy than conventional ones.

(corrosive)
The billet was extruded under predetermined conditions, and the resulting extruded material (test plate, n=3) was subjected to a corrosion test in accordance with ATSM B117. More specifically, a rectangular test plate was propped up in a chamber, and salt water (5% NaCl) was continuously sprayed for 96 hours.The weight change of the test plate before and after spraying was measured, and the amount of wall loss (corrosion rate) was measured. ) was calculated.

The billet (φ69mm) contains Mg-10Al-5Ca, Mg-10Al-5Ca-0.015Mn, Mg-8Al-4Ca-0.015Mn, Elektron 43 (commercially available magnesium alloy), 7075-T6 (commercially available aluminum alloy). ) was used. The extrusion ratio was 15.

Figure 4 shows the results of the corrosion test. In the figure, the vertical axis is the corrosion rate (mm/year), and the bar for each test piece is the average value.

The corrosion rate (average) of Mg-10Al-5Ca was 0.75 mm/year. On the other hand, the corrosion rate (average) of Mg-10Al-5Ca-0.015Mn was 0.125 mm/year. This confirmed that the presence of Mn affected the corrosion rate. Similarly, the corrosion rate (average) of Mg-8Al-4Ca-0.015Mn containing Mn was as low as 0.175 mm/year.

The corrosion rate (average) of Elektron 43 was 0.425 mm/year. It was confirmed that the Mg-Al-Ca based alloy containing Mn has a lower corrosion rate than Elektron 43.

The corrosion rate (average) of 7075-T6 was 0.15 mm/year. It was confirmed that the Mg-Al-Ca alloy containing Mn has a corrosion rate equivalent to that of 7075-T6.

〈Additional notes〉
The refrigerant, its design method, and the refrigerator filled with the refrigerant described in the embodiments described above can be understood, for example, as follows.

The present disclosure relates to a method for manufacturing an aircraft component by extrusion processing using an Mg-Al-Ca based alloy containing (Mg, Al) ₂ Ca. In the present disclosure, a Mg-Al-Ca based alloy billet containing Al: 6 at % or more and 8 at % or less and Ca: 3 at % or more and 4 at % or less is selected, and the billet is The billet is extruded under conditions such that the temperature is maintained below the melting temperature of the (Mg,Al) ₂ Ca.
The melting temperature of (Mg, Al) ₂ Ca is 490°C.

The Mg-Al-Ca alloy has a lighter specific gravity than the aluminum alloys conventionally used in the aircraft field. Therefore, by processing such a Mg-Al-Ca alloy into an aircraft component, it is possible to reduce the weight by 10% or more compared to an aluminum alloy component.

According to intensive studies by the present inventors, when extrusion processing is performed using an Mg-Al-Ca alloy containing (Mg, Al) ₂ Ca, elongation occurs due to the start of melting of (Mg, Al) ₂ Ca. It has been found that (ductility) decreases.

In the above disclosure, by performing extrusion processing under conditions where (Mg, Al) ₂ Ca does not melt, it is possible to prevent a decrease in ductility due to melting of (Mg, Al) ₂ Ca.

(Mg,Al) ₂ Ca, which is a C36 type compound, is a hard compound. When (Mg, Al) ₂ Ca is dispersed in the metal structure, high strength and relatively large ductility are obtained. The degree of dispersion of (Mg, Al) ₂ Ca is preferably 1 piece/μm ² or more. (Mg, Al) ₂ Ca is preferably fine (for example, 2 μm or less).

Addition of Ca can improve the flame retardancy and mechanical properties of extruded materials (aircraft parts). If the Ca content is too high, it will be difficult to make the magnesium alloy into a solidified state, making extrusion processing difficult. If the Ca content is too low, sufficient flame retardancy cannot be obtained.

Addition of Al can improve the mechanical properties and corrosion resistance of the extruded material. If the Al content is too high, sufficient strength cannot be obtained. If the Al content is too low, sufficient ductility cannot be obtained.

If the amount of Al and Ca contained in the Mg-Al-Ca alloy increases, it may become a factor in coarsening of (Mg, Al) ₂ Ca in the metal structure. When (Mg, Al) ₂ Ca becomes coarse, the ductility of the extruded material tends to decrease. By setting the contents of Al and Ca within the above ranges, the extruded material can have desired ductility.

In one aspect of the above disclosure, the conditions are set by an extrusion temperature and an extrusion exit speed, and the extrusion temperature and the extrusion exit speed are such that the x-axis is the extrusion temperature (°C) and the y-axis is the extrusion exit speed (m /min), the first plot (x: 375°C, y: 3.6m/min) and the second plot (x: 450°C, y: 0.9m/min) , or from a range where x and y are smaller than the straight line.

In one aspect of the above disclosure, the straight line is represented by equation (1): y=-0.036x+17.1.

According to intensive studies by the present inventors, by selecting the extrusion temperature and extrusion exit speed from the above ranges, the temperature of the billet can be maintained at less than the melting temperature of (Mg,Al) ₂ Ca during extrusion processing. The coordinates of the first plot and the second plot were obtained through actual measurements and are highly reliable. Therefore, an extruded material having both tensile strength and ductility can be produced more stably than before.

In one aspect of the above disclosure, the extrusion temperature under the conditions is preferably 350° C. or higher. If the extrusion temperature is too low, the fluidity of the billet will decrease, making extrusion difficult.

Considering the extrusion device capacity, in one aspect of the disclosure, the extrusion exit speed under the conditions is preferably 0.3 m/min or more.

In one aspect of the above disclosure, the extrusion temperature and extrusion exit speed are within a range surrounded by the three straight lines of the above equation (1), equation (2): x=350, and equation (3): y=0.3. can be selected from among the following.

In one aspect of the disclosure, the extrusion temperature and extrusion exit speed are determined by the formula (1), the formula (2): x=350, the formula (3'): y=0.9, and the formula (4): y= 3.6 may be selected from within the range surrounded by the four straight lines.

According to the inventors' intensive studies, (1): x and y are smaller than the straight line of y = -0.036x + 17.1, the extrusion temperature is 350°C or higher, and the extrusion exit speed is 0.9 m/min or higher. By extruding at 3.6 m/min or less, an extruded material having both tensile strength and ductility can be obtained more reliably.

In one aspect of the above disclosure, the Mg-Al-Ca based alloy may contain Mn in an amount of more than 0 atomic % and 0.3 atomic % or less.

Mn has the effect of improving corrosion resistance even when added in a small amount. On the other hand, as the amount added increases, the ductility of the extruded material decreases. In order to achieve both corrosion resistance and ductility, it is desirable to suppress the amount of Mn added.

Claims (7)

(Mg, Al) ₂ A method for manufacturing an aircraft component by extrusion using a Mg-Al-Ca alloy containing a Ca compound, the method comprising:
Based on the total amount, Al: 6 at % or more and 8 at % or less , Ca : 3 at % or more and 4 at % or less , and Mn: more than 0 at % and 0.3 at % or less , and the remainder is Mg and unavoidable elements. Select a billet of Mg-Al-Ca based alloy consisting of impurities ,
A method for manufacturing an aircraft component, comprising extruding the billet under conditions in which the temperature of the billet is maintained below the melting temperature of the (Mg,Al) ₂ Ca. The conditions are set by extrusion temperature and extrusion exit speed,
The extrusion temperature and the extrusion exit speed are
In a graph of an xy coordinate system in which the x axis is the extrusion temperature (° C.) and the y axis is the extrusion exit speed (m/min), the first plot (x: 375° C., y: 3.6 m/min) and the second plot (x: 450° C., y: 0.9 m/min), and is selected from a range where x and y are smaller than the straight line or the straight line. Method. The method for manufacturing an aircraft member according to claim 2, wherein the extrusion temperature under the conditions is 350°C or higher. The method for manufacturing an aircraft member according to claim 2 or 3, wherein the extrusion exit speed under the conditions is 0.3 m/min or more. 3. The method for manufacturing an aircraft member according to claim 2, wherein the straight line is expressed by equation (1): y=-0.036x+17.1. The extrusion temperature and extrusion exit speed are:
The method for manufacturing an aircraft member according to claim 5, wherein the method is selected from within a range surrounded by three straight lines: the formula (1), the formula (2): x = 350, and the formula (3): y = 0.3. . The extrusion temperature and extrusion exit speed are:
Selected from within the range surrounded by the four straight lines of formula (1), formula (2): x = 350, formula (3'): y = 0.9, formula (4): y = 3.6. The method for manufacturing an aircraft component according to claim 6.