KR102880816B1 - Manufacturing method for exhaust valve spindle of marine engin - Google Patents

Abstract

A method for manufacturing an exhaust valve spindle for a ship engine having a head portion and a stem portion is provided, comprising the steps of: manufacturing a billet in the shape of a round bar having a predetermined length and made of a nickel-containing alloy material; processing the billet with an electric upsetting device to expand the diameter of a tip portion of the billet; processing the tip portion of the billet, the diameter of which has been expanded, by a hot forging method to form a preliminary head portion; heat-treating the billet with the preliminary head portion formed thereon at a predetermined temperature for a predetermined time; and cutting the preliminary head portion to complete the head portion.

Description

Manufacturing method for exhaust valve spindle of marine engine

The embodiments disclosed herein relate to a method for manufacturing an exhaust valve spindle for a marine engine, and more particularly, to a method for manufacturing a spindle used as an exhaust valve of a marine engine requiring wear resistance and corrosion resistance.

Typically, exhaust valves, which are engine components used in large ships such as container ships, tankers, or bulk carriers, are designed to operate at high loads, but in recent years, they are being designed to operate at low loads to improve fuel efficiency.

The exhaust valve spindle of these marine diesel engines consists of a head that opens and closes the exhaust port of the engine, and a stem that guides the linear reciprocating movement of the head. When fuel explodes in the engine cylinder, it moves upward to maintain the cylinder's seal, and after the explosion, it moves downward to discharge the combustion gas through the exhaust port.

Since the exhaust valve spindles of these marine engines are exposed to high temperature and high pressure environments, they require high strength, corrosion resistance, and wear resistance at high temperatures.

The exhaust valve spindle of the prior art was manufactured by separately manufacturing the head part with a heat-resistant alloy material and welding it to the stem part, as disclosed in Korean Patent Publication No. 10-0543295.

However, the above-mentioned joining method has the problem that the manufacturing process is complicated and the strength of the joining part is weakened, resulting in reduced durability.

Meanwhile, exhaust valve spindles have recently been manufactured using Nimonic 80A, a nickel (Ni) alloy with excellent high-temperature properties, or Inconel (Inconel 625, Inconel 718), but the use of expensive nickel (Ni)-based superheat-resistant alloys has increased, limiting the reduction in manufacturing costs.

In addition, as disclosed in Korean Patent Publication No. 10-2016-0091833, a step-shaped round bar was formed through a rolling and forging process and then manufactured into a valve.

However, the conventional technology described above has the problem that continuous operation is impossible because the stepped round bar is manufactured by free forging or rotary forging, and thus the production speed is slow, making mass production difficult.

Accordingly, new technologies are required to overcome the limitations of the above prior art.

Meanwhile, the background technology described above is technical information that the inventor possessed for the purpose of deriving the present invention or acquired during the process of deriving the present invention, and cannot necessarily be said to be publicly known technology disclosed to the general public prior to the application for the present invention.

The embodiments disclosed herein are intended to provide a method for manufacturing an exhaust valve spindle for a marine engine having a head portion and a stem portion.

In particular, the embodiments disclosed in this specification aim to present a method for manufacturing an exhaust valve spindle for a marine engine, which can improve production speed through simplification of the manufacturing process by forming a head portion by electrically upsetting the leading end of a billet without joining the head portion and the stem portion.

In addition, the embodiments disclosed in this specification aim to present a method for manufacturing an exhaust valve spindle for a marine engine, which can improve the durability of the spindle as well as the corrosion resistance and wear resistance by manufacturing the spindle using a nickel-based alloy material having super heat resistance.

In addition, the embodiments disclosed in this specification aim to present a method for manufacturing a spindle for a marine engine, which can further improve the corrosion resistance and wear resistance of a head portion by processing by depositing a separate nickel alloy on the surface of a preliminary head portion formed by upsetting processing, and can partially improve the corrosion resistance and wear resistance of the head portion by forming a plurality of welded nickel alloy portions in the preliminary head portion and forming each portion with a different nickel content.

As a technical means for achieving the above-described technical task, one embodiment of a method for manufacturing an exhaust valve spindle for a marine engine comprises the steps of: manufacturing a billet in the form of a round bar having a predetermined length and made of a nickel-containing alloy material; processing the billet with an electric upsetting device to expand the diameter of a tip of the billet; processing the tip of the billet with the expanded diameter by a hot forging method to form a preliminary head portion; heat-treating the billet with the preliminary head portion formed thereon at a predetermined temperature for a predetermined time; and cutting the preliminary head portion to complete the head portion.

In addition, the alloy material may include 0.00 to 0.10 wt% of carbon, 0.00 to 1.00 wt% of silicon, 37.00 to 39.00 wt% of chromium, 0.00 to 0.05 wt% of copper, 3.00 to 4.00 wt% of aluminum, and a remainder of nickel.

In addition, the step of manufacturing the billet may include a step of cutting the round bar to a standard length; and a step of chamfering the edge of at least one of the longitudinal ends of the cut round bar.

The electrical upsetting device that performs the step of expanding the diameter of the tip of the billet may include a clamp electrode that forms one of the electrodes while movably supporting the billet, an anvil that forms the other of the electrodes while supporting the tip of the billet, a pressing cylinder that is arranged toward the rear end of the billet and presses the billet while moving in the direction of the anvil, and a retreat cylinder that movably supports the anvil and moves in the same direction as the pressing cylinder but moves at a different speed from the pressing cylinder.

In addition, the step of expanding the diameter of the tip of the billet may include the steps of: fixing the billet to the clamp electrode; heating the billet through electrical resistance heat generated by applying current to one of the clamp electrode and the anvil; and moving the pressing cylinder toward the anvil to pressurize the billet, and moving the retreat cylinder in the same direction as the pressing cylinder while moving it at a slower speed than the pressing cylinder.

In addition, the step of forming the preliminary head portion may include a step of preheating the tip of the billet with an expanded diameter at a temperature of 950 to 1100°C for 20 minutes or more; a step of forging the tip of the preheated billet into the preliminary head portion by inserting it into a mold and then applying pressure; and a step of cooling the forged preliminary head portion.

In addition, the manufacturing method may further include, after the step of forming the preliminary head portion, a step of forming a plurality of first welding grooves having a predetermined depth on the surface of the preliminary head portion; a step of forming a first weld portion on the surface of the preliminary head portion while depositing a nickel alloy in the first welding grooves; a step of forming a second welding groove having a predetermined depth around the preliminary head portion and the first welding portion; a step of forming a second welding portion around the preliminary head portion and the first welding portion while depositing a nickel alloy in the second welding groove; a step of forming a third welding groove having a predetermined depth on the seat surface of the preliminary head portion; and a step of forming a third welding portion on the seat surface of the preliminary head portion while depositing a nickel alloy in the third welding groove.

Additionally, the first weld portion may include a relatively larger amount of nickel than the second weld portion and the third weld portion, and the second weld portion may include a relatively larger amount of nickel than the third weld portion.

Additionally, an exhaust valve spindle for a ship engine according to one embodiment can be manufactured by any one of the above manufacturing methods.

According to any one of the above-described problem solving means, a method for manufacturing an exhaust valve spindle for a marine engine having a head portion and a stem portion can be proposed.

In particular, according to any one of the aforementioned problem solving means, a method for manufacturing an exhaust valve spindle for a marine engine can be proposed, which has a relatively fast production speed and enables mass production through continuous operation by processing the front end of a billet using an electric upsetting method and expanding the diameter rather than processing it using a free forging or rotary forging method.

In addition, by manufacturing a spindle using a nickel-based alloy material having super heat resistance according to any one of the aforementioned problem solving means, the durability of the spindle as well as its corrosion resistance and wear resistance can be improved.

In addition, according to any one of the aforementioned problem solving means, a method for manufacturing a spindle for a ship engine can be proposed that can further improve the corrosion resistance and wear resistance of the head portion when a separate nickel alloy is deposited and processed on the surface of the spare head portion.

The effects that can be obtained from the disclosed embodiments are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the disclosed embodiments belong from the description below.

FIG. 1 is a flowchart showing a method for manufacturing an exhaust valve spindle for a ship engine according to one embodiment.
Fig. 2 is a schematic diagram showing a method for manufacturing an exhaust valve spindle for a ship engine according to one embodiment.
FIG. 3 is a schematic diagram showing a step of expanding the diameter of a tip of a billet in a method for manufacturing an exhaust valve spindle for a ship engine according to one embodiment.
FIG. 4 is a flowchart showing a step of forming a spare head portion in a method for manufacturing an exhaust valve spindle for a ship engine according to one embodiment.
Fig. 5 is a flowchart showing a method for manufacturing an exhaust valve spindle for a ship engine according to another embodiment.
Fig. 6 is a schematic diagram showing a method for manufacturing an exhaust valve spindle for a ship engine according to another embodiment.

Below, various embodiments are described in detail with reference to the attached drawings. The embodiments described below may be modified and implemented in various different forms. To more clearly explain the features of the embodiments, detailed descriptions of matters widely known to those skilled in the art to which the embodiments pertain below have been omitted. In addition, parts of the drawings that are not related to the description of the embodiments have been omitted, and similar parts have been designated with similar drawing reference numerals throughout the specification.

Throughout the specification, when a component is said to be "connected" to another component, this includes not only the "direct connection" but also the "connection with other components in between." Furthermore, when a component is said to "include" another component, this does not exclude other components, but rather implies that other components may be included, unless otherwise specifically stated.

The embodiments will be described in detail with reference to the attached drawings below.

FIG. 1 is a flowchart showing a method for manufacturing an exhaust valve spindle for a marine engine according to one embodiment, FIG. 2 is a schematic diagram showing a method for manufacturing an exhaust valve spindle for a marine engine according to one embodiment, FIG. 3 is a schematic diagram showing a step of expanding the diameter of a tip of a billet in a method for manufacturing an exhaust valve spindle for a marine engine according to one embodiment, and FIG. 4 is a flowchart showing a step of forming a spare head portion in a method for manufacturing an exhaust valve spindle for a marine engine according to one embodiment.

An exhaust valve spindle (10) for a ship engine according to one embodiment is installed in an engine of a large ship such as a container ship, a tanker, or a bulk carrier to open and close an exhaust port according to the stroke of an engine piston, and may be configured to include a head portion (100) and a stem portion (200) as illustrated in FIG. 2.

This exhaust valve spindle (10) can shield the exhaust port through the seat surface (upper surface) when the head portion (100) in the shape of an umbrella rises during the engine's explosion stroke, and open the exhaust port when the head portion (100) descends after the explosion stroke, and the movement of the head portion (100) can be guided by the stem portion (200).

A method (S10) for manufacturing an exhaust valve spindle (10) for a ship engine according to one embodiment may be configured to include a step of manufacturing a billet (S100), a step of expanding the diameter of a tip of the billet (S200), a step of forming a preliminary head portion (S300), a step of heat-treating the billet (S400), and a step of cutting the billet (S500), as illustrated in FIG. 1.

The step of manufacturing the above billet (S100) is a step of manufacturing a billet (1) to be a base material for manufacturing a spindle (10) to a predetermined length.

Specifically, the step of manufacturing a billet (S100) may be performed by processing the received material to manufacture a round bar (S110), cutting the round bar to a standard length (S120), and including a step of chamfering the end of the cut round bar (s130).

The step (S110) of manufacturing the above-mentioned round bar can manufacture the round bar by processing an alloy material containing nickel (Ni).

Here, the step of manufacturing the above-mentioned ring (S110) can manufacture the ring by mixing the alloy materials described in [Table 1] below.

That is, the alloy material is composed of carbon (C), silicon (Si), chromium (Cr), copper (Cu), aluminum (Al), and nickel (Ni) and can be manufactured into a round bar.

It is preferable to contain C (carbon) in an amount of 0.2 wt% or more because it forms carbides, increases high-temperature strength, and improves wear resistance. However, if the content exceeds 0.2 wt%, toughness and ductility decrease, so the content can be limited to 0.10 wt% or less.

Si (silicon) is added as a deoxidizer, but if added in large amounts, strength and toughness decrease, so its content can be limited to 1.0 wt% or less.

Cr (chromium) can be mixed to secure high-temperature corrosion resistance, and its content can be limited to 37.00 to 39.00 wt%.

Copper (Cu) may be mixed to ensure corrosion resistance, and may be limited to 0.05 wt% or less.

Aluminum (Al) is intended to provide light weight and high strength, and its content can be limited to 3.00 to 4.00 wt%.

Nickel (Ni) improves high-temperature strength and corrosion resistance, and its content can reach 100% by weight together with the aforementioned components and other unavoidable impurities. This nickel (Ni) alloy has relatively high corrosion and wear resistance, thereby improving the durability of the spindle (10).

Meanwhile, the alloy material forming the ring can be made of a NiCr20TiAl alloy known as Nimonic 80A, a NiCr22Mo9Nb alloy known as Inconel 625, a NiCr19Fe18Nb alloy known as Inconel 718, or a NiCr38Al4 alloy known as DSA760.

Alternatively, the shaft may be made of a stainless steel alloy, for example, SNCrW, which has excellent heat resistance and corrosion resistance.

Here, the SNCrW may be composed of C: 0.2 to 0.3 parts by weight, Si: 1.0 to 2.0 parts by weight, Mn: 0.75 to 1.35 parts by weight, Cr: 18 to 20 parts by weight, Ni: 8 to 10 parts by weight, W: 1.6 to 2.5 parts by weight, the remainder being Fe and other unavoidable impurities.

In the step of manufacturing the round bar (S110), it can be manufactured to a length 2 to 3 times the length of the billet (1).

The step of cutting the above-mentioned bar into a standard length (S120) is a step of cutting the bar into a standard length. Specifically, in the step of cutting the bar into a standard length (S120), the bar can be cut into a standard length using a band saw.

The above chamfering step (S130) is a step of chamfering the edge circumference of at least one end of a round bar cut to a standard length.

Specifically, the chamfering process step (S130) can complete the production of a billet (1) by chamfering the edges of both ends of the cut round bar with a cutting machine to chamfer the edge perimeter.

This chamfering processing step (S130) can reduce the load on the anvil (51) constituting the upsetting device (50) and prevent surface cracking of the preformed product during the process of processing the billet (1) through the upsetting device (50) described later.

The step (S200) of expanding the diameter of the tip of the billet is a step of expanding the diameter of the tip of the billet (1) in order to form a head portion (100) at the tip of the billet (1).

The step (S200) of expanding the diameter of the tip of the billet can be performed by processing the tip of the billet (1) through an electric upsetting device (50) as illustrated in FIG. 3 to expand the diameter of the tip of the billet (1), thereby forming the tip of the billet (1) into a lump shape.

That is, the step (S200) of expanding the diameter of the tip of the billet is performed by electrical upset forming, rather than the existing method of processing by free forging or rotary forging, so that the production speed is relatively fast and mass production through continuous operation can be achieved.

Specifically, electric upsetting processing is a process that causes plastic deformation by heating and pressurizing at the recrystallization temperature, and it is a technology that utilizes the principle of bulging, which causes horizontal flow to increase the cross-sectional shape, and can ultimately be formed into a cylinder in the shape of an onion or a door handle. This electric upsetting processing is a forming method that enables continuous forming work by using a round bar, reduces scale generation due to heating, allows for precise control of the volume of the forming part, and maintains the continuity of the material's grain flow and makes the grains fine, so the fatigue strength and mechanical properties of the valve spindle are excellent.

Here, the step (S200) of expanding the diameter of the tip of the billet can be performed using an electric upsetting device (50) as shown in FIG. 3, and the electric upsetting device (50) can be configured to include a clamp electrode (51), an anvil (52), a pressure cylinder (53), and a retreat cylinder (54) as shown in FIG. 3.

The above clamp electrode (51) can perform the function of one of the electrodes for heating the billet (1) while movably supporting the billet (1) for an upset operation. Specifically, the clamp electrode (51) is formed in left and right divisions to guide the movement of the billet (1) while holding the billet (1) so that it comes into contact with an anvil (52) described later, and can be manufactured mainly using a copper alloy such as phosphor bronze and beryllium copper to secure high electrical conductivity and tensile strength.

The above anvil (52) is a component that supports the tip of the billet (1) while performing the function of an electrode together with the clamp electrode (51). This anvil (52) can be manufactured using tool steel SCM440, which has low thermal conductivity, excellent electrical conductivity, and little deformation at high temperatures and high pressures. Since the surface of the anvil subjected to high temperatures and high pressures is damaged, the damaged area can be reprocessed and used after a certain period of use.

The above-mentioned pressurizing cylinder (53) is a component that pressurizes the billet (1) toward the anvil (52), and is movably positioned toward the rear end of the billet (1) to support the rear end of the billet (1), and can pressurize the billet (1) while moving toward the anvil (52).

The above retreat cylinder (54) is a component that moves together with the pressure cylinder (53) while movably supporting the anvil (52) to process the front end of the billet (1). Specifically, the retreat cylinder (54) moves in the same direction as the pressure cylinder (53) while supporting the anvil (52), but moves at a relatively slower speed than the pressure cylinder (53), thereby allowing the diameter of the front end of the billet (1) to be expanded through the speed difference.

Specifically, the step (S200) of expanding the tip diameter of the billet can be performed by fixing the billet (1) to a clamp electrode (51) constituting an electrical upsetting device (50) as illustrated in FIG. 3 (S210).

At this time, in step S210, after fixing the billet (1) to the clamp electrode (51), the pressure cylinder (53) can be operated to press the tip of the billet (1) against the anvil (52), and the retreat cylinder (54) can be pressed against the anvil (52).

And after step S210 is performed, the billet (1) can be heated by applying current to the clamp electrode (51) and the anvil (52) respectively (S220).

Accordingly, the billet (1) can be heated to a high temperature in the area between the clamp electrode (51) and the anvil (52) by supplying current to the clamp electrode (51) and the anvil (52).

At this time, in step S220, the current can be controlled by providing current to the anvil (52) and the clamp electrode (51), and the current can be uniformly controlled by detecting the change in current according to the change in the distance between the clamp electrode (51) and the anvil (52).

And, after step S220 is performed, the pressurizing cylinder (53) can be operated to move the billet (1) toward the anvil (52) while pressing the billet (1) toward the anvil (52) and moving the retreat cylinder (54) (S230).

At this time, in step S230, the pressurizing cylinder (53) can pressurize the billet (1) while moving toward the anvil (52), and the retreating cylinder (54) can move the anvil (52) while moving in the same direction as the pressurizing cylinder (53) but at a slower speed than the pressurizing cylinder (53).

Accordingly, the billet (1) is continuously heated by the current of the anvil (52) and the clamp electrode (51) and is pressurized by the retreat cylinder (54), so that the diameter of the tip gradually increases and it can be lumped into a lump shape.

More specifically, the billet (1) is heated by the electrical resistance heat generated between the clamp electrode (51) and the anvil (52) forming the + and - electrodes. The heated billet (1) can expand to a diameter 1.8 to 2.2 times its original diameter as the end of the round bar is deformed into a round onion shape due to the speed difference between the pressurizing cylinder (53) and the retreating cylinder (54) while the flow stress of the material rapidly decreases.

The Ni-based alloy material forming the billet (1) has low resistance to plastic deformation at a temperature of 980 to 1090℃, so an appropriate current must be applied to enable forming in that temperature range. The current flows from the surface to the inner deep layer due to the surface effect, and the temperature of the surface is higher than that of the center of the round bar, and the deep layer is heated by heat conduction. Depending on the moving speed of the retraction cylinder (54), the temperature of the billet (1) in the part that contacts the anvil (52) drops, and the part that contacts the clamp electrode (51) maintains a high temperature. The shape is determined by the difference in speed between the pressurizing cylinder and the retraction cylinder. At this time, if the speed of the retraction cylinder (54) is relatively fast, the diameter of the tip of the billet (1) does not increase significantly compared to the original diameter, and the forming shape becomes a shape with an elongated length. If the speed of the retreat cylinder (54) is relatively slow, the diameter of the tip of the billet (1) increases and the length becomes shorter. In addition, if the speed of the pressure cylinder (53) is faster than the deformation speed of the tip of the billet (1), wrinkles may occur on the surface of the billet (1), and the wrinkles may remain on the surface of the product during hot forging. Therefore, the ratio of the pressure speed and the retreat speed is important in order to implement an appropriate shape for hot forging.

It is preferable that the billet (1) processed through the step (S200) of expanding the diameter of the tip of the billet as described above has a diameter of the tip expanded to more than twice.

The step (S300) of forming the above-described preliminary head part is a step of forming the preliminary head part (101) by first forming the tip of the billet (1) whose diameter has been expanded into a lump shape by the above-described upsetting processing step (S200) using a hot die forging method.

The step (S300) of forming such a preliminary head part can be performed by hot forging the tip of the billet (1) in a forging mold (30) to form the preliminary head part (101), as shown in FIG. 2.

Specifically, the step of forming a preliminary head portion (S300) can be performed including a preheating step (S310), a forging step (S320), and a cooling step (S330), as illustrated in FIG. 4.

In the above preheating step (S310), the tip of the billet (1) with an expanded diameter can be placed in a heating furnace and heated at 950 to 1100°C for 20 minutes or more. At this time, heating can be performed for a short time in a temperature range where the crystal grains of the alloy material of the billet (1) do not grow, and the crystal grain size of the valve spindle (10) is required to be ASTM Grain size NO. 4 or higher.

In the forging step (S320) above, the tip of the preheated billet (1) is processed into a preliminary head part (101), which is a preliminary forming step of the head part (100). As shown in FIG. 2, the billet (1) with the tip preheated can be forged by inserting it into a forging mold (30) to form the preliminary head part (101).

At this time, in step S320, forging may be performed by applying a hot forging release agent to the inside of the forging mold (30) or using an insulating material to reduce the temperature difference between the mold and the material.

The above cooling step (S330) is a step of cooling the billet (1) hot-forged by the above-described step S320. During hot forging, the surface of the billet (1) cools faster than the core, and the core cools relatively slowly, causing grain growth. Therefore, the billet (1) can be water-cooled or air-cooled at room temperature.

The above heat treatment step (S400) is a step of heat treating the billet (1) in which the preliminary head portion (101) is formed through the above-described S300 step so that age hardening occurs.

The alloy material forming the billet (1) is a material composed of a fine lamellar structure composed of a γ/γ'(Ni ₃ Al) layer formed by discontinuous precipitation and an α-Cr phase layered therein, which is generated by the grain boundary diffusion of Cr, and forms a γ phase at high temperatures, which provides good processability. In addition, the high Cr content exhibits high corrosion resistance in various corrosive environments, and the α-Cr phase causes high elastic deformation, enabling high hardness to be maintained. In addition, as the width between the lamellar structures of the α-Cr phase and the γ phase increases, the mechanical strength increases.

At this time, in the heat treatment step (S400), the billet (1) can be heat treated by putting it into a heating furnace and maintaining it at 800℃ for 24 hours.

The billet (1) that has undergone the S400 step can obtain mechanical properties as shown in [Table 2] below.

The step (S500) of completing the above head part is a step of completing the head part (100) of the spindle (10) by cutting the preliminary head part (101) formed by the above-described steps S300 and S400.

At this time, the step of completing the head part (S500) can be performed by first cutting the preliminary head part (101) by rough-cutting the preliminary head part (101) and then cutting the preliminary head part (101) through rolling processing and finishing processing to form the head part (100).

As shown in Fig. 2, the billet (1) in which the head portion (100) is formed can be processed into a shaft portion through step S600 to form the stem portion (200) of the spindle (10).

In step S600, the shaft portion of the billet (1) can be machined to have an outer diameter corresponding to the stem portion (200) to form the stem portion (200), and after coating a portion of the shaft with an alloy powder (201) having corrosion resistance and wear resistance, the coated shaft can be ground and lapped to complete the stem portion (200).

Meanwhile, a method for manufacturing an exhaust valve spindle for a ship engine according to one embodiment (S10) may be performed by further including a step of forming a plurality of nickel alloy welded portions in the aforementioned spare head portion (101) as illustrated in FIGS. 5 and 6.

That is, the method for manufacturing an exhaust valve spindle for a ship engine according to one embodiment (S10) may be performed by further including a step of forming a first welding groove (S710), a step of forming a first welding portion (S720), a step of forming a second welding groove (S730), a step of forming a second welding portion (S740), a step of forming a third welding groove (S750), and a step of forming a third welding portion (S760) after performing the step of forming the aforementioned preliminary head portion (S300) as illustrated in FIG. 5.

The step (S710) of forming the first welding groove is a step of forming a plurality of first welding grooves (71) having a predetermined depth on the surface of the preliminary head portion (101), i.e., the lower surface in the drawing, to form a welding portion of the first welding portion (72) of the nickel alloy.

At this time, the step of forming the first welding groove (S710) can form the first welding groove (71) to form a plurality of concentric circles on the surface (lower surface) of the preliminary head portion (101) that is approximately circular in shape.

The step (S720) of forming the first welding part is a step of forming the first welding part (72) on the surface of the preliminary head part (101) while depositing a nickel alloy into the first welding groove (71).

That is, the step (S720) of forming the first welded portion can form a first welded portion (72) of nickel alloy by forming a multi-layered welding bead of nickel alloy on the surface of the preliminary head portion (101), and at this time, the first welded portion (72) can be welded more firmly by being welded to a plurality of first welding grooves (71) formed on the surface of the preliminary head portion (101).

The step (S730) of forming the second welding groove is a step of forming a plurality of second welding grooves (73) having a predetermined depth around the preliminary head portion (101) and the first welding portion (72) to form a welding portion of the second welding portion (74) of the nickel alloy.

At this time, the step of forming the second welding groove (S730) can form the circumference of the preliminary head portion (101) and the first welding portion (72) into a roughly sawtooth shape by forming a plurality of second welding grooves (73) along the circumference of the preliminary head portion (101) and the first welding portion (72).

The step (S740) of forming the second welding portion is a step of forming the second welding portion (74) around the preliminary head portion (101) and the first welding portion (72) while depositing a nickel alloy into the second welding groove (73).

That is, the step (S740) of forming the second weld portion can form a second weld portion (74) of nickel alloy by forming a multi-layered welding bead of nickel alloy around the preliminary head portion (101) and the first weld portion (72), and at this time, the second weld portion (74) can be welded more firmly by being welded to a plurality of second welding grooves (73).

The step (S750) of forming the third welding groove is a step of forming a plurality of third welding grooves (75) having a predetermined depth on the sheet surface (upper surface) of the spare head portion (101), i.e., the surface that is in close contact with the exhaust port of the ship engine, thereby forming a welding portion of the third welding portion (76) of the nickel alloy.

At this time, the step of forming the third welding groove (S750) can form the third welding groove (75) to form a plurality of concentric circles on the sheet surface (upper surface) of the spare head portion (101).

The step (S760) of forming the third welding part is a step of forming the third welding part (76) on the sheet surface of the preliminary head part (101) while depositing a nickel alloy in the third welding groove (75).

That is, the step (S760) of forming the third weld portion can form a third weld portion (76) of nickel alloy by forming a multi-layered welding bead of nickel alloy on the sheet surface (upper surface) of the preliminary head portion (101), and at this time, the third weld portion (76) can be welded more firmly by being welded to a plurality of third welding grooves (75).

The first weld (72), the second weld (74) and the third weld (76) may be made of the same alloy material as the alloy material forming the billet (1), and may be made of a NiCr20TiAl nickel alloy known as Nimonic 80A, a NiCr22Mo9Nb nickel alloy known as Inconel 625 or a NiCr19Fe18Nb nickel alloy known as Inconel 718, or may be made of a NiCr38Al4 nickel alloy known as DSA760.

Meanwhile, the exhaust valve spindle (10) is subjected to relatively high temperature and pressure on the surface (lower surface) of the head portion (100) facing the cylinder of the ship engine, and relatively low temperature and pressure are applied on the seat surface (upper surface) facing the opposite side of the cylinder.

Here, the first welded portion (72) described above is composed of an alloy containing a relatively larger amount of nickel than the second welded portion (74) and the third welded portion (76), thereby providing relatively higher corrosion resistance and wear resistance than the second welded portion (74) and the third welded portion (76).

In addition, the second weld (74) is composed of an alloy containing a relatively larger amount of nickel than the third weld (76), thereby providing relatively higher corrosion resistance and wear resistance than the third weld (76).

After the first welded portion (72), the second welded portion (74), and the third welded portion (76) are formed as described above, the heat treatment step (S400) and the head portion completion step (S500) described above are performed, and the preliminary head portion (101) is cut together with the first welded portion (72), the second welded portion (74), and the third welded portion (76), thereby being formed into the head portion (100).

As described above, the exhaust valve spindle (10) for a marine engine manufactured through the above-described process is not manufactured by joining the head portion (100) and the stem portion (200) or by processing them using a free forging method, but by processing the tip portion of the billet (1) by expanding its diameter using an electric upsetting method, so that the manufacturing process is easy and mass production is possible while durability can be further improved. In particular, by manufacturing the spindle (10) using an alloy material containing nickel, the durability of the spindle (10) as well as corrosion resistance and wear resistance can be further improved.

The embodiments described above are provided for illustrative purposes only, and those skilled in the art will readily appreciate that the embodiments described above can be readily modified into other specific forms without altering the technical concepts or essential characteristics of the embodiments described above. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, components described as being single may be implemented in a distributed manner, and similarly, components described as being distributed may be implemented in a combined manner.

The scope of protection sought through this specification is indicated by the claims described below rather than the detailed description above, and should be interpreted to include all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts.

1: Billet
10: Spindle
30: Forging die
50: Electrical upsetting device
51: Electrode clamp
52: Anvil
53: Pressurized cylinder
54: Retractable cylinder
71: First welding groove
72: First weld
73: Second welding groove
74: Second weld
75: Third welding groove
76: Third weld
100: Head
101: Spare head section
200: Stem

Claims (9)

A method for manufacturing an exhaust valve spindle for a marine engine having a head portion and a stem portion,
A step of manufacturing a billet in the shape of a round bar having a predetermined length and made of an alloy material containing nickel;
A step of processing the billet with an electric upsetting device to expand the diameter of the tip of the billet;
A step of forming a preliminary head portion by processing the tip portion of the billet with an expanded diameter using a hot forging method;
A step of forming a plurality of first welding grooves having a predetermined depth on the surface of the preliminary head portion, which is performed after the step of forming the preliminary head portion;
A step of forming a first welding part on the surface of the preliminary head part while depositing a nickel alloy into the first welding groove;
A step of forming a second welding groove having a predetermined depth around the preliminary head portion and the first welding portion;
A step of forming a second welding part around the preliminary head part and the first welding part while depositing a nickel alloy in the second welding groove;
A step of forming a third welding groove having a predetermined depth on the seat surface of the above-mentioned spare head portion;
A step of forming a third welding part on the seat surface of the preliminary head part by depositing a nickel alloy in the third welding groove;
A step of heat-treating the billet on which the preliminary head portion is formed at a predetermined temperature for a predetermined period of time; and
It includes a step of completing the head part by cutting the above spare head part,
The above first welded portion,
Contains a relatively large amount of nickel compared to the second weld and the third weld,
The above second welded portion,
A method for manufacturing an exhaust valve spindle for a marine engine, comprising a relatively large amount of nickel compared to the third welded portion.
In the first paragraph,
The above alloy material is,
A method for manufacturing an exhaust valve spindle for a marine engine, comprising 0.00 to 0.10 wt% of carbon, 0.00 to 1.00 wt% of silicon, 37.00 to 39.00 wt% of chromium, 0.00 to 0.05 wt% of copper, 3.00 to 4.00 wt% of aluminum, and a remainder of nickel.
In the first paragraph,
The steps for making the above billet are:
A step of cutting the above-mentioned ring to a standard length; and
A method for manufacturing an exhaust valve spindle for a ship engine, comprising a step of chamfering by cutting the edge circumference of at least one of the longitudinal ends of the cut circular bar.
In the first paragraph,
The electric upsetting device that performs the step of expanding the diameter of the tip of the billet,
A method for manufacturing an exhaust valve spindle for a ship engine, comprising: a clamp electrode forming one of the electrodes while movably supporting the billet; an anvil forming the other of the electrodes while supporting the front end of the billet; a pressure cylinder positioned toward the rear end of the billet and moving in the direction of the anvil to pressurize the billet; and a retreat cylinder moving in the same direction as the pressure cylinder but at a different speed from the pressure cylinder while movably supporting the anvil.
In paragraph 4,
The step of expanding the tip diameter of the above billet is:
A step of fixing the billet to the clamp electrode;
A step of heating the billet through electric resistance heat generated by applying current to one of the clamp electrode and the anvil; and
A method for manufacturing an exhaust valve spindle for a ship engine, comprising the steps of moving the pressurizing cylinder toward the anvil to pressurize the billet, and moving the retreating cylinder in the same direction as the pressurizing cylinder while moving it at a slower speed than the pressurizing cylinder.
In the first paragraph,
The step of forming the above-mentioned spare head part is:
A step of preheating the tip of the billet with an expanded diameter at a temperature of 950 to 1100°C for 20 minutes or more;
A step of forging the tip of the preheated billet into the preliminary head portion by inserting it into a mold and applying pressure; and
A method for manufacturing an exhaust valve spindle for a marine engine, comprising a step of cooling the forged preliminary head portion.
delete delete An exhaust valve spindle for a marine engine, manufactured by any one of claims 1 to 6.