JP2008074390A - Propeller for watercraft and outboard motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a propeller for watercraft having superior abrasion resistance and deformation resistance. <P>SOLUTION: The propeller for watercraft comprises a propeller body having a blade portion and a hub portion, the propeller body being made of an aluminum alloy and having Vickers hardness of 50-95 Hv, and an anodized coating of aluminum alloy provided so as to cover a surface of the propeller body. The anodized coating has a thickness of 20-100 μm, and preferably has a hardness of 300-450 Hv. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a marine propeller and an outboard motor.

  Outboard motors are widely used for small vessels such as pleasure boats and small fishing boats because they are attached to the hull just by hooking them to the stern of the vessel and do not occupy space in the vessel. Various outboard motors are used today depending on the size and application of the hull.

  Generally, an outboard motor having a propeller made of stainless steel and a high-power (for example, 100 horsepower or more) engine is used for a relatively large ship. On the other hand, an outboard motor equipped with a propeller made of aluminum or the like and an engine with a relatively small output is used for a relatively small ship. Propellers made of aluminum are lightweight and can be manufactured at a low cost. Therefore, propellers made of aluminum have the function and cost of propellers for outboard motors for small ships. This is because the request is satisfied.

  When the marine propeller is formed of aluminum, it is necessary to prevent the corrosion of aluminum by seawater. For this reason, in general, a propeller whose surface is coated with anti-corrosion on the surface of a propeller body made of aluminum is widely used.

In Patent Document 1, in order to solve the problem that the edge of the propeller becomes dull due to the coating film provided on the surface of the propeller and the water breakage when the propeller rotates, the hard anodized treatment is applied to the propeller made of aluminum. Ensuring sharpness is disclosed.
Utility Model Registration No. 3029215 Specification

  Conventional outboard motor propellers made of aluminum have the following problems.

  Specifically, small vessels are often used in the sea or rivers for purposes such as fishing, business, and leisure. In such places, driftwood and hard nuts may float near the surface of the water, and these suspended objects may collide with the outboard motor propellers. In addition, when traveling on a river, there is a possibility of contact with plants growing from the riverbank or riverbed. When it collides with such floating objects or comes into contact with plants, the propeller is deformed, and the propulsive force by the propeller is greatly reduced by the deformation.

  In addition, small ships equipped with outboard motors may be moored by being pulled up to the sandy coast or moored in shallow water on the riverbank. For this reason, when mooring a ship or sailing from a mooring place to a river or the sea, the surface of the propeller may be worn by rolling up the sand and rotating the propeller in the water containing sand. If the paint on the surface of the propeller is peeled off due to wear, the propeller body may be corroded or the propeller body may be further polished.

  Such problems have arisen not only in ships equipped with outboard motors, but also in small ships where the engine is installed in the ship.

  Patent Document 1 merely discloses the formation of an alumite layer known as an anticorrosive film for aluminum instead of a coating film for anticorrosion, and does not disclose or suggest any of the above problems. Absent. Moreover, in order to prevent the edge of a propeller from becoming dull, a hard alumite layer cannot be formed thickly. For this reason, the thickness of the hard alumite layer of the propeller of Patent Document 1 is about 15 μm at most, and it is considered that sufficient wear resistance and deformation resistance cannot be obtained.

  An object of the present invention is to solve such problems of the prior art and to provide a marine propeller and an outboard motor having excellent wear resistance and deformation resistance.

  A marine propeller according to the present invention is a propeller body having a blade portion and a hub portion, and is provided so as to cover a propeller body made of an aluminum alloy and having a Vickers hardness of 60 Hv or more and 95 Hv or less, and the surface of the propeller body. And an anodized film of the aluminum alloy, and the anodized film has a thickness of 20 μm to 100 μm.

  In a preferred embodiment, the anodic oxide film has a hardness of 300 Hv or more and 450 Hv or less.

  In a preferred embodiment, the propeller body is formed by die casting using the aluminum alloy.

  In a preferred embodiment, the aluminum alloy is an Al—Mg alloy containing 1.5 wt% or less of silicon.

  In a preferred embodiment, the Al—Mg-based alloy further contains at least one of iron and manganese of 0.5 wt% or more and 1.8 wt% or less.

  In a preferred embodiment, the aluminum alloy is an Al—Si based alloy and is subjected to an annealing treatment.

  The outboard motor of the present invention includes a marine propeller defined in any of the above.

  The ship of this invention is provided with the said outboard motor.

  The method for manufacturing a marine propeller according to the present invention includes a step of forming a propeller body having a Vickers hardness of 60 Hv or more and 95 Hv or less by die casting using an aluminum alloy, and the propeller. And anodizing the main body to form an anodized film having a thickness of 20 μm or more and 100 μm or less on the surface of the propeller body.

  In a preferred embodiment, the concentration and temperature of the electrolytic bath used for anodization are adjusted so that the anodized film has a hardness of 300 Hv to 450 Hv.

  In a preferred embodiment, the aluminum alloy is an Al—Mg alloy containing 1.5 wt% or less of silicon.

  In a preferred embodiment, the Al—Mg-based alloy further contains at least one of iron and manganese of 0.5 wt% or more and 1.8 wt% or less.

  In a preferred embodiment, the aluminum alloy is an Al—Si based alloy, and the step of forming the propeller body includes a step of performing an annealing process on the propeller body after forming by die casting.

  According to the present invention, the surface of the propeller is covered with a hard anodic oxide film, and the propeller body has an appropriate elastic deformation characteristic, so that even if a driftwood or the like collides, the blades are chipped or plastically deformed. Can be prevented. Moreover, it is excellent in abrasion resistance. Therefore, a marine propeller having excellent durability is realized.

  Hereinafter, embodiments of a marine propeller and an outboard motor according to the present invention will be described.

  FIG. 1A is a side view of a ship 50 provided with an outboard motor according to the present invention. The ship 50 includes a hull 51 and an outboard motor 52. The outboard motor 52 includes the clamp 16, the propeller 27, and the steering handle 22, and is attached to the stern 12 of the hull 51 by the clamp 16. The operator can adjust the direction of the outboard motor 52 with the steering handle 22 and change the traveling direction of the ship 50.

  FIG. 2 is a side view of the outboard motor 52. The outboard motor 52 includes an engine 48, and the rotational driving force of the engine 48 is transmitted to the drive shaft 21 to which the drive gear 23 is attached. The outboard motor 52 includes a switching mechanism 41 and a clutch device 25 in order to move the ship 50 forward or backward by changing the rotation direction of the propeller 27. The clutch device 25 includes a forward gear 31 and a reverse gear 33. By operating a shift lever 49 connected to the switching mechanism 41, one of the forward gear 31 and the reverse gear 33 is selectively meshed with the drive gear 23. Thereby, the propeller 27 fixed to the output shaft 29 rotates in the forward direction or the reverse direction. The engine 48 and these drive mechanisms are housed inside the casing 14 and the cowling 10.

  The marine propeller of the present invention is preferably used for an outboard motor, but is also suitable for a marine vessel in which an engine is mounted in a hull (also referred to as an inboard). FIG.1 (b) is a side view of the ship 150 provided with the propeller 27 for ships of this invention. An engine 152 is installed in the hull 151 of the ship 150, and the driving force of the engine 152 is transmitted via a shaft to the propeller 27 that is supported so as to be rotatable at the rear part of the ship bottom.

  FIG. 3 is a plan view showing the propeller 27. The propeller 27 includes a blade portion 61 and a hub portion 62 to which the blade portion 61 is connected. In this embodiment, the hub portion 62 includes an outer hub 70, an inner hub 71, and a rib 72 that connects the outer hub 70 and the inner hub 71. In the present embodiment, the outboard motor 52 employs a structure in which the exhaust gas of the engine 48 is ejected from the gap 72h between the inner hub 71 and the outer hub 70 to the rear of the propeller 27. In this way, the hub is doubled. However, when the outboard motor 52 emits exhaust gas from other places, the hub portion 62 may adopt a single structure. There is no restriction | limiting in particular in the number and shape of the blade | wing part 61, The propeller 27 may be provided with shapes other than the shape shown in FIG.

  An inner hub 71 of the hub portion 62 defines a cylindrical inner space, and a bush 73 is press-fitted into the inner space. The bush 73 is made of an elastic body such as rubber, and the bush 73 is fixed in the inner hub 71 by friction between the bush 73 and the inner hub 71. A hole 73c is provided in the center of the bush 73, and the output shaft 29 of the outboard motor 52 is inserted into the hole 73c.

  Since the bush 73 and the inner hub 71 are fixed by friction, when the propeller 27 collides with a driftwood or the like during rotation, the bush 73 slips with respect to the inner hub 71, so that the output shaft 29 rotates. The propeller 27 can be stopped. As a result, even if a foreign object collides with the propeller and the rotation of the propeller 27 stops, the rotation of the output shaft 29 and the engine 48 is stopped, the rotation of the clutch device 25 and the engine 48 is stopped, and various gears are damaged. Or the engine 48 is prevented from malfunctioning.

  The propeller 27 of the outboard motor 52 of the present invention is made of an aluminum alloy having a predetermined hardness so that the propeller 27 has excellent wear resistance and deformation resistance, and the entire surface of the propeller 27 is anodized. It is covered with a film. FIG. 4 shows a part of the cross section of the blade portion 61 of the propeller 27. The blade portion 61 includes a blade portion main body 61b and an anodized film 61c of aluminum alloy provided on the surface of the blade portion main body 61b. Although not shown, the hub portion similarly includes a hub body and an anodized film covering the surface of the hub body, and the propeller body is constituted by the blade body 61b and the hub body.

  The entire propeller 27 preferably absorbs energy due to collision by appropriately elastically deforming when foreign matter such as driftwood collides, thereby preventing plastic deformation of the entire propeller. For this reason, it is preferable that the propeller body has a Vickers hardness of 60 Hv to 95 Hv. When the hardness of the propeller body is smaller than 60 Hv, the strength of the entire propeller 27 cannot be obtained sufficiently. Moreover, when the hardness of the propeller body is greater than 95 Hv, the blade portion 61 is likely to be chipped due to a collision with a foreign object. If the blade portion 61 is chipped or deformed, the propulsive force of the outboard motor 52 is greatly reduced. In addition, the thickness of the outer periphery front-end | tip of the blade | wing part except an edge part is 1.0 mm-4.0 mm.

  The propeller body is formed of an aluminum alloy. In order to reduce the manufacturing cost and increase the joint strength between the blade portion 61 and the hub portion 62, it is preferable that the shape of the propeller 27 is integrally formed by casting, and more preferably, it is formed by die casting. preferable. For this reason, it is preferable that the propeller body is formed from an aluminum alloy having a composition that can be easily formed by die casting.

  Specifically, the aluminum alloy is preferably an Al—Mg alloy containing 1.5 wt% or less of silicon. When the content of silicon in the aluminum alloy is increased, the hot water flow during casting becomes good, and casting by the die casting method becomes easy. However, if the silicon content exceeds 1.5 wt%, the aluminum alloy becomes hard and brittle, and the Vickers hardness of the propeller body becomes greater than 95 Hv. For this reason, an appropriate deformability cannot be obtained.

  More preferably, the aluminum alloy further contains at least one of iron and manganese of 0.5 wt% or more and 1.8 wt% or less. By including at least one of iron and manganese in the above-described proportion, the releasability from the mold is improved during die casting, and seizure to the mold can be prevented.

  For example, Al-4Mg-0.8Fe-0.4Mn, Al-5Mg-1.3Si-0.8Fe-0.8Mn, Al-4.5Mg-1.1Fe-0.7Mn, Al-6.5Mg- An Al—Mg alloy having a composition such as 1.1Fe—0.7Mn can be used.

  As described above, the main reason for limiting the silicon content is that the Vickers hardness Hv of the propeller body becomes too high. Therefore, when heat treatment such as annealing is performed to reduce the Vickers hardness Hv of the propeller body, the silicon content can be increased to facilitate casting by the die casting method. Specifically, the propeller body is made of an Al-Si alloy, and may be annealed after being formed by a die casting method.

  For example, an Al-Si alloy having a composition such as Al-10Si-0.4Mg-0.5Mn, Al-9Si-0.7Fe-0.5Mn, or the like can be used. In this case, for example, by performing annealing under conditions of heating at 350 ° C. for 1.5 hours and then air cooling, the hardness of the propeller body is about 65 Hv even after the casting by the die casting method is about 106 Hv. Can be reduced.

  The anodized film of aluminum alloy covering the surface of the propeller body is formed by anodizing the surface of the propeller body. FIG. 5 shows a part of a cross section of the blade body 81 before forming the anodized film. By subjecting the blade body 81 to anodic oxidation, the surface region 81a is oxidized to form an anodized film 61c made of aluminum oxide. Further, the remaining portion 81b sandwiched between the surface regions 81a becomes the blade body 61b.

  In general, an anodized film of an aluminum alloy has a high hardness. For this reason, the propeller 27 on which the anodized film is formed has high wear resistance. More preferably, the anodized film has a hardness of 300 Hv or more and 450 Hv. When the hardness of the anodized film is smaller than 300 Hv, a sufficiently high wear resistance performance cannot be obtained. Further, the deformability is also lowered. On the other hand, the higher the hardness of the anodized film, the better. However, when an anodic oxide film having a hardness of 450 Hv is to be obtained, a special treatment solution must be used, which increases the manufacturing cost of the anodic oxide film.

  The anodized film preferably has a thickness of 20 μm to 100 μm. When the thickness of the anodized film is smaller than 20 μm, sufficient wear resistance and deformation resistance cannot be obtained. The thicker the anodic oxide film, the better the wear resistance, but it takes time to form the anodic oxide film and the productivity is lowered. In practice, if the anodized film has a thickness of 100 μm, the propeller 27 exhibits superior wear resistance as compared to conventional propellers.

  The hardness of the anodized film can be adjusted by changing the concentration and temperature of the electrolytic bath used for anodization. The thickness of the anodized film can be adjusted by the anodizing time. As an anodizing treatment method for forming the anodized film, a treatment method for forming a hard film is preferably used, and an electrolytic solution such as sulfuric acid or oxalic acid can be used.

  The propeller of the present invention is manufactured, for example, by the following procedure. As shown in FIG. 6, first, for example, an aluminum alloy having a composition of Al-4Mg-0.8Fe-0.4Mn is melted (step S101), and the molten metal is injected into a mold having the shape shown in FIG. 3 by die casting. (Step S102). After cooling, the gate for pouring molten metal is cut from the propeller body taken out from the mold, and cutting is performed so that the propeller body has a predetermined shape, such as adjustment of the thickness and shape of the blades (step S103). Further, the oxide film generated on the surface is removed.

Next, the surface of the propeller body is degreased and etched (step S104), and after the surface of the propeller is cleaned, anodization is performed (step S105). For example, a 17% sulfuric acid bath is used, and the propeller body is used as an anode, and oxidation is performed at a constant current of 4 A / dm ² for 30 minutes while maintaining a bath temperature of 4 ° C. As a result, an anodized film having a thickness of 40 μm and a hardness of 400 Hv is obtained.

  Next, dyeing is performed as necessary (step S106). Dyeing can be performed by coloring with a dye, electric field coloring, or the like, and is performed by depositing a dye or metal oxide in the fine pores of the anodized film. Thereafter, a micropore sealing process is performed so as not to cause decolorization or corrosion resistance (step S107).

  Thereafter, a bush is press-fitted into the hub of the propeller (S108), and after completion inspection (S109), the propeller is completed.

  In the propeller 27 having such a structure, the propeller body has appropriate elastic deformation characteristics, and the surface of the propeller 27 is covered with a hard anodic oxide film. Or the plastic deformation can be prevented and the propulsive force can be prevented from decreasing. In addition, it is possible to prevent the propeller from shifting its center of gravity due to deformation or chipping of the propeller and causing abnormal vibrations when the propeller rotates, thereby adversely affecting the main body of the outboard motor such as the engine or the clutch mechanism. Furthermore, since the surface of the propeller is covered with a hard anodic oxide film, the wear resistance is excellent. In particular, the propeller surface can be prevented from being worn even in water mixed with sand.

  Therefore, a ship equipped with the outboard motor of the present invention is less prone to deformation and chipping of the propeller even when it collides with driftwood, and can prevent propeller wear even when navigating in shallow sand. For this reason, when used in the near sea or rivers for the purpose of fishing, business, leisure, etc., the ship equipped with the outboard motor of the present invention exhibits excellent durability and is economical.

(Experimental example)
In order to confirm the effect of the present invention, an anodized film was formed on the surface of a propeller body formed from aluminum alloys having three compositions, and the physical characteristics and the like were examined. For comparison, a sample in which a film was formed on the propeller body by paint and plating was prepared and the characteristics were compared. The results are shown in Table 1 below.

  As aluminum alloys, Al-4Mg-0.8Fe-0.4Mn (hereinafter referred to as composition A), Al-10Si-0.4Mg-0.5Mn (hereinafter referred to as composition B), and Al-4.5Mg-0. An aluminum alloy having a composition of 7Fe-0.4Mn (hereinafter referred to as composition C) was prepared, and a propeller body was formed by a die casting method.

  Samples 1 to 13 having composition A, samples 14 to 16 having composition B, and samples 18 and 19 having composition C were not subjected to heat treatment. Sample 17 having composition B was annealed.

  Anodized films having different thicknesses and hardnesses are formed on samples 2 to 10 of the propeller body having the composition A, samples 15 to 17 of the propeller body having the composition B, and samples 18 and 19 of the propeller body having the composition C. did.

  For comparison, Samples 1, 14 and 11 to 13 were formed by coating and nickel-phosphorous plating.

  The characteristics of the prepared samples were evaluated as follows.

(appearance)
The quality of the appearance was visually determined at a position 300 mm away from the sample surface due to diffuse daylight. ○, Δ, and × indicate that the appearance was uniform, partially non-uniform and non-uniform, respectively.

(Corrosion resistance)
The sample was immersed in 5% salt water at room temperature for 100 hours, and the quality was judged by the appearance. ○ indicates that corrosion did not occur, Δ indicates that corrosion was partially observed, and × indicates that corrosion was observed throughout.

(Abrasion resistance)
A sand drop wear test specified in JIS H8501 was conducted for a certain period of time and judged by appearance. ○ indicates that the propeller body, which is the base material, is not exposed, and × indicates that the propeller body is exposed.

(Deformation resistance 1)
A sample was attached to an outboard motor of 40 horsepower, and hard wood pieces (rosewood) were continuously collided with the propeller for a fixed time at a rotation speed of 3000 rpm, and the blade deformation was examined. ○ indicates that no deformation of the blade was observed, and x indicates that the deformation of the blade was observed.

(Deformation resistance 2)
The sample was fixed, a static load was applied to the blade portion, and the maximum load value and the amount of deformation until cracking were determined. ○ indicates that the load value and the amount of deformation were not less than the specified values, and x indicates that the value was not more than the specified values.

(Judgment)
In the characteristic evaluation other than the appearance, a sample having one or more evaluation items determined as x was determined as x.

  As shown in Table 1, the appearances of Samples 1 to 14, 18, and 19 were all good, but the appearances of Samples 15 to 17 were partially uneven. This is because the composition of Samples 15 to 17 contains a large amount of silicon, so that during the molding by die casting, a large amount of silicon is precipitated in the portion where the molten metal cools quickly, and as a result, the film thickness and composition of the anodic oxide film are poor. It is thought that this is because it is uniform. As far as the appearance is concerned, some samples have poor uniformity, but there is no sample with a bad appearance so as to greatly impair the beauty.

  Regarding the corrosion resistance, in the case of an anodized film, it was found that the film had sufficient corrosion resistance if the film thickness was 20 μm or more. It was also found that the sample using the paint as a film also has sufficient corrosion resistance. On the other hand, it was found that the corrosion resistance is not sufficient in the film formed by nickel-phosphorous plating formed by electrolytic plating and electroless plating.

  As can be seen from Samples 1 and 14, regarding the wear resistance, the coating film does not have sufficient wear resistance. Of the samples having an anodized film, the abrasion resistance properties of Samples 2 and 15 were inferior. This is presumably because the thickness of the anodized film is 20 μm or less and the hardness of the anodized film is smaller than 300 Hv. From the results of Sample 3, it can be seen that even if the anodized film is 20 μm, sufficient wear resistance can be obtained if the hardness is 300 Hv.

  For the deformation resistance property 1, samples 1, 2, 14 and 15 do not show sufficient elastic deformation against the impact of wood. A coating film or an anodized film having a thickness of less than 20 μm and a hardness of less than 300 Hv has insufficient surface strength. Therefore, even if the propeller body has a high deformability, the blades may collide with driftwood, etc. It is thought that the part is deformed.

  Deformation resistance 2 indicates the deformability of the propeller body. As can be seen from Samples 18 and 19, the propeller body has sufficient deformability even when the hardness of the propeller body is 95 Hv. However, samples 14, 15 and 16 are not sufficiently deformable because the propeller body has a hardness of 102 Hv. This is considered to be caused by the fact that the aluminum alloy constituting the propeller body of Samples 14, 15 and 16 contains a large amount of silicon and is hard and brittle. On the other hand, as is apparent from the results of Sample 17, even the propeller made of the aluminum alloy having the same composition is annealed, the hardness of the propeller body is lowered and sufficient deformation characteristics are exhibited. For this reason, it is considered that the evaluation of the deformation resistance property 2 of the sample 17 is excellent. That is, the deformation resistance 2 is improved by the relatively soft propeller body and the hard anodic oxide film formed thicker than usual.

  From these results, samples 3 to 10 in which the propeller body has a Vickers hardness of 60 Hv to 95 Hv, a thickness of 20 μm to 100 μm, and an anodized film having a hardness of 300 Hv to 450 Hv formed on the surface, and It can be seen that Samples 17 to 19 are excellent in wear resistance and deformation resistance and are suitable as durable outboard propellers.

  INDUSTRIAL APPLICABILITY In the present invention, a marine propeller and an outboard motor are suitably used for various ships, and in particular, are suitably used for small ships used for various purposes such as fishing, business, and leisure.

(A) is a side view which shows the ship provided with the outboard motor by this invention, (b) is a side view which shows the ship provided with the propeller for ships by this invention. It is a side view which shows embodiment of the outboard motor of this invention. FIG. 3 is a plan view showing a propeller of the outboard motor shown in FIG. 2. It is a figure which shows the partial cross section in the blade | wing part of the propeller of FIG. It is sectional drawing explaining that an anodized film produces | generates by anodizing a propeller main body. It is a flowchart which shows the manufacturing process of the propeller shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cowling 12 Stern 14 Casing 16 Clamp 21 Drive shaft 22 Steering handle 25 Clutch device 27 Propeller 31 Forward gear 33 Reverse gear 50 Ship 51 Ship body 52 Outboard motor 61 Blade part 62 Hub part 73 Bush

Claims (13)

A propeller body having a blade portion and a hub portion, which is made of an aluminum alloy and has a Vickers hardness of 60 Hv to 95 Hv;
Anodized film of the aluminum alloy provided to cover the surface of the propeller body;
With
The anodized film is a marine propeller having a thickness of 20 μm to 100 μm.   2. The marine propeller according to claim 1, wherein the anodized film has a hardness of 300 Hv to 450 Hv.   The propeller body according to claim 2, wherein the propeller body is formed by die casting using the aluminum alloy.   The marine propeller according to claim 3, wherein the aluminum alloy is an Al—Mg alloy containing 1.5 wt% or less of silicon.   5. The marine propeller according to claim 4, wherein the Al—Mg alloy further includes at least one of iron and manganese of 0.5 wt% or more and 1.8 wt% or less. The marine propeller according to claim 3, wherein the aluminum alloy is an Al—Si based alloy and is subjected to an annealing treatment.   An outboard motor provided with a marine propeller defined in any one of claims 1 to 6.   A ship provided with an outboard motor as defined in claim 7. Using an aluminum alloy, a step of forming a propeller body having a vane part and a hub part and having a Vickers hardness of 60 Hv or more and 95 Hv or less by a die casting method;
Forming an anodized film having a thickness of 20 μm or more and 100 μm or less on the surface of the propeller body by anodizing the propeller body;
For manufacturing a marine propeller.   The method for manufacturing a marine propeller according to claim 9, wherein the concentration and temperature of the electrolytic bath used for anodization are adjusted so that the anodized film has a hardness of 300 Hv to 450 Hv.   The method for manufacturing a marine propeller according to claim 9, wherein the aluminum alloy is an Al—Mg alloy containing 1.5 wt% or less of silicon.   The method for producing a marine propeller according to claim 11, wherein the Al-Mg alloy further includes at least one of iron and manganese of 0.5 wt% or more and 1.8 wt% or less.   The method for manufacturing a marine propeller according to claim 9, wherein the aluminum alloy is an Al—Si based alloy, and the step of forming the propeller body includes a step of annealing the propeller body after forming by die casting.

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