KR101435401B1 - An exhaust valve spindle for an internal combustion engine, and a method of manufacturing - Google Patents

Abstract

An exhaust valve spindle (1) for an internal combustion engine, which is a two-stroke crosshead engine, comprising: a valve head (3) having a base portion made of alloy steel; an outer surface (5). The outer surface 5 is formed from a particulate starting material of a nickel-based, chromium-based or cobalt-based hot-corrosion resistant alloy, the particulate starting material being integral with the coherent layer. In at least a transition region with respect to the base portion, the particles of the particulate matter on the outer surface are deformed into an egg-shaped or elongated shape by shear deformation generated by forging the outer surface 5 and the base portion, The side has a density of at least 98.0%.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an exhaust valve spindle for an internal combustion engine,

The present invention relates to an exhaust valve spindle for an internal combustion engine, more particularly to an exhaust valve spindle for a two-stroke crosshead engine, said valve spindle comprising a base portion of alloy steel and a valve spindle for forming a surface of the valve spindle towards the combustion chamber Wherein the outer surface is formed of a particulate starting material of a hot corrosion resistant alloy of a nickel, chromium, or cobalt series, wherein the particulate starting material is incorporated into a coherent layer.

U.S. Patent No. 6,173,702 describes a known exhaust valve spindle of the kind in which a corrosion-resistant outer surface is provided on the base portion by powder metallurgical treatment, wherein the particulate matter of the corrosion resistant alloy is disposed in the mold on the base portion and the HIP (Hot Isostatic Pressure) process. The mold is vacuumed to remove as much air or gas as possible. The HIP process is performed in a chamber that can be placed under constant pressure while being heated. In order to use the chamber efficiently, it is filled with as many base or other parts as possible, and these objects are subjected to the same HIP treatment in the chamber. When the process is started, the chamber is heated and pressurized under HIP conditions, and these conditions last for a required period of time, for example at least 8 hours to 12 hours.

During the HIP process, the pressure affects particulate matter as isostatic compression (fully uniform pressure in all directions), and the volume of particulate matter is uniformly reduced in all directions as it is compacted on the base portion. As a result of the microstructure of the outer surface, the particles are seen to be detected as spheres with a circular shape when viewed in a polished and polished sample taken with the finished valve spindle. Figures 1 and 10 are photographs of these samples.

The bottom valve head surface is large in area and thus exposed to significant thermal stresses, for example when the engine load changes, particularly when the engine starts or stops. This thermal shock is the most severe at the center of the surface, partly because the combustion gas is the highest temperature near the center of the combustion chamber, and for other partial reasons the valve head has a seat area on the top surface, Cooled below the outer rim that comes into contact with the water-cooling stop valve seat during the cooling operation. The cold perimeter material prevents thermal expansion of the hot center material, thus causing significant thermal stress. The slow, but large, thermal stresses caused by these thermal effects create high demands on the strength and quality of the outer surface.

Although HIP treatment is known to provide precise coherence of the outer surface and microstructures with high quality, the HIP treatment is very time consuming and the long treatment time at elevated temperature is due to the fact that the composition from one alloy to another Lt; RTI ID = 0.0 > diffusion < / RTI >

An object of the present invention is to secure a high rigidity of the outer surface and to form a microstructure on a strong structure, more specifically, on the outer surface adjacent to the transition section with respect to the base section.

Particles of particulate matter on the outer surface of the exhaust valve spindle according to the present invention are deformed into an egg shape or an elongated shape by a shear deformation caused by forging the outer side surface and the base portion, And the forged outer surface has a density of at least 98.0%.

The shear strain induced by forging causes displacement of the powder particles with respect to other powder particles such that the particles are rubbed together and penetrate the oxide film layer which is present on the surface of the particles. Any oxide film layer is thin, because particulate matter is created by atomization in an oxygen-free gas, but some oxygen is inevitably formed on the particle during storage. Shear deformation transforms particles into a non-circular shape characterized by an elliptical or elongated shape. During forging, particulate matter is pressurized into a dense layer, and the particles are incorporated with a coherent material bonded to an adjacent layer that is the base portion when the particulate matter is placed directly on the base portion. At least 98.0% of the density can be expressed with a porosity of at most 2%.

The shear deformation induced by forging causes the particulate matter to flow at least radially and this radial direction is perpendicular to the axial direction of the exhaust valve spindle so that this radial direction is parallel to the bottom surface of the valve head, Is substantially parallel to a substantially planar transition zone between the material of the outer surface. The shear deformation and thus the radial movement in the material adjacent to the transition zone creates an effective bond between the materials and, at the time of the deformation, rubbing the particles against one another to form bonds in an extremely effective manner, The number of inner breakage points in the microstructure is very small. Therefore, the coupling of the material in the transition region has a strong microstructure, and it becomes possible to completely eliminate the geometric fastening portion between the outer side surface and the base portion.

In a preferred embodiment, the transition section between the outer surface and the base section extends along at least one straight plane in the region extending from the rim region of the valve head to the central region of the valve head. In the rim region, the outer surface has an extension extending upwardly and surrounding the base portion along the periphery, and the outer surface itself is in the shape of a fan having walls upright at the periphery. At a certain distance from the rim, the transition section begins to extend along a plane extending straightly toward the middle of the valve head, which does not have a sudden change in the thickness or shape of the outer surface, There is no large local variation in how the process is processed. Adjacent to the transition section of the plane, the particulate matter is subjected to substantially the same treatment in the local region, and as more than one planar region extends from the rim region to the central region, the planar regions cover most of the region of the valve head .

And the outer side surface can be directly placed on the base portion. Optionally, at least one buffer layer of the alloy is disposed between the outer surface and the base portion. When such a buffer layer is used, the alloy of the buffer layer is formed of a third alloy different from the hot-corrosion-resistant alloy of the outer surface and having a different component from the alloy steel of the base portion. This difference in composition means that the analysis of the alloys of the buffer layer is different in terms of the sum (weight ratio) of one or more of the components of the alloying elements or in terms of alloy components. The buffer layer may be, for example, a different amount of carbon or an alloy steel having different amounts of other components such as chromium, iron or nickel. Thus, the term 'composition' refers to the analysis of alloys. The position of the buffer layer between the base portion and the other outer surface of the alloy shell exhibits the effect that the alloy steel is in direct contact only with the material of the buffer layer and not in contact with the corrosion resistant alloy of the outer layer. The buffer layer operates to prevent or reduce diffusion of alloy components from the outer side to the base and from the base to the outer side.

Preferably, the buffer layer is selected from the group comprising alloys of Fe or Ni, except for steel, austenitic steels, nickel based alloys and unavoidable impurities. Such an alloy is considered to correspond to both the alloy of the outer surface and the steel of the base portion.

In one embodiment, the alloy steel of the base portion is austenitic stainless steel. Over the years, it has been recognized that alloys NIMONIC 80 A (registered trademark for special materials) make the entire valve spindle. However, such a special alloy is not as readily available as austenitic stainless steel, and if the stainless steel has high strength and corrosion resistance is improved by overcoming the performance of the stainless steel on the surface facing the combustion chamber, It is considered to show performance. However, stainless steel has a relatively high carbon content. The buffer layer absorbs the diffused carbon and the advantage of using stainless steel for the main part of the exhaust valve is not compromised by the high requirements for long term toughness and corrosion resistance of the finished exhaust valve.

In a preferred embodiment, the buffer layer has a thickness of at least 2 mm. This thickness is sufficient to allow the buffer layer to diffuse across the buffer layer even if the buffer layer is an alloy that exhibits a carbide forming ability in which the carbon diffusion to the layer is converted to carbide but does not result in an increase in the carbon activity of the layer.

The present invention relates to a method of manufacturing an exhaust valve spindle for an internal combustion engine having an exhaust valve spindle having a valve head having a base portion of alloy steel and an outer surface defining a surface of a valve spindle toward the combustion chamber, Is formed from particles starting from a nickel-based, chromium-based or cobalt-based material of a hot-corrosion resistant alloy.

According to the present invention, the method is characterized in that the particulate matter of the hot-corrosion resistant alloy is contained in an enclosure of the base portion, the particulate matter is heated and forged to forging temperature and the particulate matter is deformed into an elongated shape or egg shape Shear deformation which compacts the particulate material to a density of at least 98.0% and integrates the base or base and buffer layers with the outer surface.

Forging occurs considerably quickly with respect to HIP treatment, and while the valve component is at the elevated forging temperature, the alloy component diffuses from one alloy to the adjacent alloy in only a short time. As described above, such forging presses the particulate matter against each other, and shear deformation moves the particles in a direction parallel to the transition section, and combines the particulate matter with each other. During this course of motion, the crushed and coalesced oxide film is initially present on the particle debris and the clean alloy material from the grain inside the grain is in direct contact with the clean alloy material obtained from the grains inside the other grain, Are effectively connected at the microstructure level.

In one embodiment, particulate matter in the vessel is provided in a layer of substantially uniform thickness in a region extending from within the rim region of the valve head to the central region of the valve head. When the layer of particulate matter is formed in the container to a substantially uniform thickness and substantially uniform forging conditions are applied, the outer surface will eventually have a substantially uniform base. The transition section between the outer surface and the base section extends along a plane which extends in a single direction in the radial direction of the valve head.

In another embodiment, particulate matter in the vessel is provided in a layer of increased thickness towards the longitudinal center axis of the valve in a region extending from within the rim region of the valve head to the central region of the valve head. The bottom surface of the valve head is generally a flat surface, and the bottom surface of the base portion may be formed with a central region that is thickened to allow the thickness of the outer surface to be thick. The transition section between the outer side surface and the base section may extend along a plurality of straightly extending planes, and the transition section may have a slightly curved shape. The increased thickness of the outer surface in the central region of the bottom surface of the valve head provides an exhaust valve with a longer service life than that consumed by the exhaust valve in relation to the amount of particulate matter, This is because the highest material loss in operation occurs in the central region of the bottom surface of the valve head. If the exhaust valve spindle is used in an engine in which the material loss is expected to be closest to the rim area or other local area, the outer surface can be either an increased thickness in the direction to the rim area or an increased thickness in the local area And may optionally have a thickness.

An additional method according to the present invention is a method in which the particulate material of a hot corrosion resistant alloy is hot sprayed in an inert atmosphere forming a preform and the preform and base are heated to forging temperature and forged so that the particulate material is in an elongated or oval shape The forging deforms the density of the particulate matter to at least 98.0%, and the outer surface is integrated with the base portion or integrated into the buffer layer and the base portion.

In this way, the particulate matter is first molded into a preform of sufficiently stable shape to allow particulate matter to be placed in the base portion as a monolith. The particulate matter may be sprayed on the base portion. When the particulate matter is connected without pores, it may be possible to avoid using the container. If the container is used, it must be machined after forging is completed. Even if the particulate matter of the preform has an irregular shape before forging, this forging results in the same effect as described in connection with the initially mentioned method, but the deformed particle has a highly irregular shape.

Whatever method is used, the material on the outer surface is vacuumed to a pressure of less than 1 X 10 ^-4 bar prior to forging. This vacuum treatment removes the gas from the pores in the particulate matter to be forged, and this vacuum treatment promotes the compression of the material. The gases present in the material of the outer surface are oxygen-free gases such as inert gases, but it is desirable to have as few gases as possible. As a result, the material on the outer side is vacuumed to a pressure of less than 1 X 10 < ^-7 > bar.

If a buffer layer of a third alloy is used, this third alloy is different from the alloy steel (first alloy) of the base portion and has a different composition from the hot-corrosion resistant alloy (second alloy) on the outer side. The third alloy is applied to the surface of the base portion before the material of the outer surface is disposed on the surface of the base portion. The third alloy may be selectively applied to the material on the outer surface. However, the surface of the base portion is a uniform and smooth surface in which the third alloy is controlled in a well controlled manner, in particular the amount is uniformly controlled and applied from the material in a uniform manner.

It is possible to perform forging in one or more steps in order to obtain the valve head having the outer surface. Following the forging step, which incorporates the base portion and the outer surface, the integrated base portion and the outer surface can be forged in at least one subsequent step to obtain the final shape. This is preferred if, for example, the base portion and the outer surface have a cylindrical shape at the time of incorporation in the first forging step followed by the operation in which the head portion of the valve is forged in a subsequent step.

In order to reduce diffusion across the transition section, the forging is preferably carried out in a time of less than 10 minutes, and the base part with the outer surface is immediately cooled after forging.

In a further less preferred embodiment, the valve shaft portion is friction welded onto the base portion after the forging is completed. One of the advantages of this is that the amount of material that must be heated to the forging temperature is smaller than when no valve shaft portion is present. Another advantage is that the base portion can be supported completely surrounded by the die on the side facing away from the outer surface instead of having the shaft portion extending laterally.

A left valve or a forged valve head with valve head and shaft is subjected to a final heat treatment such as temperature or annealing. This heat treatment causes the diffusion of the alloying elements in the transition region and enhances the metallic bonding between the materials.

Embodiments of the present invention will be described with reference to the accompanying drawings.
Figure 1 is a micrograph of a polished and polished sample taken from a valve spindle whose outer surface is provided by conventional HIP processing.
2 is a partial cross-sectional view of an exhaust valve spindle in the form of an exhaust valve according to the present invention.
3 and 4 are schematic views for forging a valve head according to the present invention.
5 is a schematic view of a valve shaft and valve head according to the present invention.
Figures 6 and 7 are photomicrographs of polished and polished samples taken from valve spindles provided with outer surfaces according to the present invention.
8 and 9 are a top view and a side view of a test sample, respectively.
10 is a micrograph of a polished and polished sample taken from a valve spindle on which an outer surface is provided by conventional HIP processing.
11 is a view showing particulate matter contained in a container prior to another forging in the method of the present invention.

Referring to Figures 1 and 10, a sample is obtained from HIP compacted particulate material and a circular shape from the cut through the particles is shown. This shows that the particles remain spherical during the compacting step. The spherical shape of the particles is typical of the HIP compacting process, which is the result of the isostatic pressure being applied during the compacting step. Due to the isobaric pressure, the particulate matter contracts in such a way that the particles do not migrate to the periphery in the material during the treatment process. This is a very straightforward treatment step, keeping the mutual position between the particles. Three cycles are added to the photograph of FIG. 10 to clearly distinguish the conventional microstructure, so that three contours of the particles appear in the photograph.

2 is a schematic view of an exhaust valve spindle 1 for an exhaust valve of a two stroke crosshead engine. The left half of the valve is visible from the outside and the right half of the valve is shown in cross section exemplarily showing the position and extent of the outer side 5. The valve spindle includes a valve head 3 having a valve shaft 2, a base portion 4 and an outer surface 5, the bottom section of which is shown in Fig. The axial direction of the exhaust valve is shown by the arrow A in the direction of the line C extending from the center of the shaft, and the arrow R indicates the radial direction perpendicular to the axial direction.

At the upper surface of the valve head 3, the valve seat 6 is made of a hot-corrosion resistant alloy suitable for counteracting the formation of a concave mark on the sealing surface of the seat. Such seat alloys are known and described, among others, in WO97 / 47862 of the applicant, WO97 / 47862 is incorporated herein by reference in the context of sheet alloys.

The outer surface 5 on the valve head is a layer of hot-corrosion resistant material that interacts to form a downward facing surface 7 towards the combustion chamber when the exhaust valve spindle is mounted to the engine and to sinter the material from the exhaust valve. The hot-corrosion resistant material is formed of particles starting from data of nickel-based, chromium-based or cobalt-based alloys. In operation in the engine, the exhaust valve spindle is in a closed position in which the valve seat 6 is in contact with the stationary valve seat in an exhaust valve housing (not shown) and in a closed position in which the exhaust valve spindle 1 is moved downward and the valve seat 6 ) Moves at an appropriate time in the engine cycle between an open position at a distance from the fixed valve seat. The exhaust valve spindle 1 together with the cylinder liner and the cylinder cover (not shown) forms a combustion chamber of the internal combustion engine and is exposed to a hot and harsh environment generated during combustion.

An internal combustion engine using an exhaust valve spindle is a four-stroke engine or a two-stroke crosshead engine. The two-stroke engine may be of the MC or ME type from MAN Diesel, RTA or RTA-flex type from Bert Suisse, or Mitsubishi's. In such a two-stroke crosshead engine, the diameter of the piston is in the range of 250 to 1100 mm, and the outer diameter of the valve head is in the range of 120 to 600 mm, generally 170 mm or more.

From these figures, the surface of the exhaust valve spindle facing the combustion chamber has a large area which causes a large thermal stress on the outer surface 5 and causes thermal stress in the boundary area between the outer surface and the base part, respectively. In an embodiment of the invention, the outer surface 5 is strongly connected to the base portion 4 in a flat area extending from the center of the exhaust valve spindle towards the rim region of the valve head.

The exhaust valve spindle 1 can be implemented in a small engine, such as a four-stroke engine of medium or high speed type, wherein the exhaust valve spindle is a two-stroke crosshead engine, which is a large engine, Lt; / RTI >

In one embodiment, the outer surface 5 is applied directly on the surface of the base portion 4. In another embodiment of the exhaust valve spindle, in one of the schematic photographs of the schematic photographs of FIGS. 6 and 7, the buffer layer 9 is disposed between the base portion 4 and the outer surface 5. The buffer layer 9 becomes a substantially pure layer of nickel applied to the surface of the base except for unavoidable impurities. The nickel layer is applied to the surface in a manner different from that provided as particulate matter located on top of the base portion. The nickel layer is provided in a separate process before disposing the particulate matter on the outer surface on the buffer layer. In a separate process, the base is placed in a galvanic bath, and nickel is deposited by nickel electroplating to form a layer having a thickness in the range of 30 to 150 micrometers, preferably 30 to 70 micrometers. The electroplated layer has the advantage of being pure nickel density. The electroplated layer is metal bonded to the base portion.

In another embodiment, the buffer layer is composed of Fe, except for unavoidable impurities. The advantage of making the buffer layer pure or substantially Fe or Ni is that the buffer layer is free of carbide or formed in small amounts. In this case, the formation of carbide in the buffer layer is suppressed, and the diffusion of carbon into the buffer layer increases the carbon activity in the buffer layer and is inhibited from further diffusion to the layer. Carbon has very low solubility in iron and nickel. For example, the solubility of nickel at a temperature of 500 < 0 > C is less than 0.1% by mass, and when a very small amount of carbon diffuses into the buffer layer, the buffer layer will have 100% Thereby virtually preventing additional diffusion of carbon.

As another example, the buffer layer 9 is formed of steel or austenitic steel. The buffer layer may be a steel plate. More specifically, base portion 4 is formed of forged valve steel (SNCrW-Alloy 1 in Table 1), outer surface 50 is formed of Alloy 671, and steel plate is selected from the alloys of Table 2 W.No. 1.4332. As another example, the buffer layer 9 may be provided as particulate matter of UNS S31603, and the outer surface 5 may be formed of Alloy 671 particulate matter. The base portion 4 is formed of forged steel. In this case, the particulate matter of the buffer layer and the particulate matter of the outer surface are integrated into the coherent material on the base portion 4 at the time of forging.

In an alternative embodiment, the buffer layer may be formed of a nickel-based alloy. This type of alloy is suitable for bonding to the outer side of the alloy and comprises an alloy IN 625 having a chromium content of less than 25%, that is, 20 to 23% chromium, an alloy INCOLOY 600 having 19 to 23 # chromium or An alloy IN718 having 10 to 25% chromium, an alloy NIMINIC Alloy 105 having about 15% chromium, and an alloy Rene 200 having 10 to 25% chromium. The buffer layer may be a nickel-rich alloy, such that a high capacity nickel tends to prevent carbon diffusion.

The particulate matter can be made in several different ways which are well known in the art. The particulate matter can be made, for example, by atomizing a liquid jet of a molten alloy of a desired component into a chamber at an inert atmosphere, which is quenched and solidified to a very precise dendritic structure. The particulate matter may be referred to as a powder.

The particulate matter may be made by atomizing a liquid jet of a molten alloy of a desired component into a chamber having an inert atmosphere, wherein the spray of atomized particles is oriented to be deposited and deposited on the solid portion. The solid portion is cooled and the instant particles form a preform separated from the solid portion. The particles may be bonded to the solid portion, and the base portion 4 is used so that the preform is directly bonded to the base portion.

Suitable materials for the base part 4 include stainless steel. Examples of such materials are given in Table 1 below. W.-No. Is the German standard number for alloys. The percentages mentioned are weight percentages.

W.-No. C Si Mn Cr Ni Etc balance Alloy 1 0.25% 1.4% 1.3% 20% 9% 3% W Fe - 0.35% 2.5% 0.8% 11.5% - 1% Mo Fe 1.4873 0.43% 2.3% 1.2% 18% 9% 1% W Fe 1.4718 0.45% 3.2% 0.4% 9% - - Fe 1.4871 0.52% - 9% 20.8% 3.9% 0.45% N Fe 1.4747 0.81% 2% - 19.5% 1.4% - Fe

Suitable materials for the optional buffer layer include the steels illustrated in Table 2 below. w.-nO. is the German standard number for the alloy. The percentages mentioned are weight percentages.

W.-No. C Si Mn Cr Ni Etc balance 1.4370 0.08% 0.8% 7% 18% 8% - Fe 1.4316 0.03% 0.5% 1.5% 20.5% 10.5% Nb > 12xC Fe 1.4551 0.04% 0.8% 1.8% 19.5% 10% - Fe 1.4430 0.025% 0.8% 1.8% 18.5% 12% 2.6% Mo Fe 1.4332 0.03% 0.5% One% 24.5% 13% - Fe - 0.08% 0.8% 1.8% 23.5% 13.5% - Fe

Other suitable materials for the buffer layer are: 0.5% -1.0% mN, 16.5-18% Cr, 11.5-14% Ni, 2.5-3.0% Mo, 0-0.1% N, 0-0.025% , And an alloy UNS S31603 containing balance Fe. If the buffer layer is made of a plate material, there is no general requirement for nitrogen and oxygen components. However, if the buffer layer is formed of particulate matter, it is preferable that the nitrogen component is at most 0.1%, and the oxygen component is at most 0.03%.

Suitable materials for the outer surface are known in the art as well known in the exhaust valve and include, for example, Stellite 6, an alloy of 50% Cr and 50% Ni type, 48-52% Cr, 1.4-1.7% Nb, , At most 0.16% Ti, at most 0.2% C + N, at most 0.5% Si, at most 1.0% Fe, at most 0.3% Mg and Ni balance. As another example, it is possible to use a ferritic stainless steel comprising 40 to 51% Cr, 0 to 0.1% C, less than 1.0% Si, 0 to 5.0% Mn, less than 1.0% Mo, 0.05 to 0.5% B, 0 to 1.0% , 0-0.2% Zr, 0.5-3.0% Nb, 5.0% Co and Fe, 0.2% max, 0.3% N, and Ni balance. Other Uses for External Use A suitable fasing alloy is described in a paper entitled "Review of Operational Experiments on Recent Valve Materials", 1990, published in 1990 by the Institute of Ocean Engineering, London, entitled "Diesel Engine Combustion Materials for Medium Fuel Operations" have.

The forging is prepared by placing the base portion (4) of the valve head in a forged position and, if necessary, applying the buffer layer (9) to the surface of the base portion. The particulate matter of the outer surface 5 is provided in various other ways. In the embodiment shown in Fig. 11, the outer side is provided as a particulate matter that is placed in the container 12 in the base portion 4, while the base portion and the particulate matter with the container are provided in the die portion . The placement of the particulate matter on the container 12 and the base portion is done in several different ways. The container is welded on the base and is provided with a pipe stud which is used to fill the container with particulate matter, connect the vacuum equipment and shut off prior to forging. Optionally, the vessel 12 is secured to the base portion 4 after the particulate matter is deposited in the vessel. This fixing operation is performed as another method by welding or vacuum brazing. As a further optional example, the vessel is fixed to the base portion, and subsequently the particulate matter is filled into the vessel, and finally brazing is performed. When vacuum brazing is used, the container is cup-shaped and provided with a rough threaded portion inside which the threaded portion is mated with the outer threaded portion on the base portion. The solder portion is provided in the thread portion. The heating and fixing operations are then performed in a vacuum oven. In another example, the particulate matter of the outer surface 8 is provided as a preform disposed in the base portion 4 shown in Fig. The formation of such preforms is described in more detail below.

Prior to forging, the base portion 4, possibly the buffer layer 9, and the container 12 with the particulate matter of the outer surface 5 are heated to a forging temperature which is preferably in the range of 950 캜 to 1100 캜 And heated. The heated parts are introduced into a forging press having a drive mechanism mechanically driven or hydraulically driven, a bottom die part 10 and an upper die part 11. The driving portion of the forging press displaces one die portion toward the other die portion, and the material placed in the die portion is mechanically deformed during this displacement. The force required to perform forging depends on the size of the valve head. An effective forging operation for a valve head diameter of about 490 mm is done with a forging press capable of achieving a compressive force in the range of about 250 to 400 MN. For smaller valve heads, the compressive force used is relatively small at 35 MN for an exhaust valve with a valve head diameter of 150 mm. The forging operation is preferably performed within 10 minutes, more preferably within 3 minutes. During the forging operation, the particulate matter of the outer surface 5 is compacted so that the thickness of the outer surface is reduced to 30 to 70% of the initial thickness of the particulate matter. If dense preforms are used, the density will be relatively high before forging, in which case the thickness of the outer surface will be reduced to 30 to 95% of the initial thickness of the particulate matter. The particulate matter is reduced in thickness so that the resulting density of the outer surface is at least 98.0%. When compacted to this level using forging, the particulate material will have an appropriate density. Of course, it is further preferred that particulate matter is further compacted to at least 99.0% or even at least 99.5% and most preferably 100% density.

During forging, the particulate matter undergoes shear deformation, placing the particles at the displaced position and deforming the material. Deformation is the geometric degree of deformation that represents the relative displacement between particles in a material. Due to the shear deformation, the particles are displaced, and when the particles come into contact, the particles deform. The shear deformation acts parallel to the surface to be affected by forging. This forging affects the surface 7 in the axial direction of the exhaust valve spindle where the axial direction is perpendicular to this surface and the shear deformation acts parallel to this surface and the surface is in the radial direction of the exhaust valve spindle Is set. During compacting of the outer layer, the shear displacement displaces the particles in the radial direction, and the particles are rubbed to be forced to displace non-spherically, such as oval, oval or atypical. When the forging is complete, the forged valve head is removed from the die and air is cooled by air cooling or otherwise.

The effective strain in the material of the outer surface is preferably at least 0.3. These valid variants are described in "Manufacturing Engineering and Technology ", 2006, Frances Hall, 5th ed., Carl Pakjan and Schmidt, or pages 222-223, Stockholm, Royal Swedish University of Technology, Quot; Formelsamgling I Hallfasthetslare ", which is described in the textbook entitled " Formelsamgling I Hallfasthetslare. &Quot; More preferably, the effective strain is at least 0.4. This enables effective and strong competition between the particles of the outer surface and the material of the base or buffer layer.

The first method of manufacturing an exhaust valve is described below. The exhaust valve spindle has a base portion made of alloy steel and a valve head having an outer surface formed by the surface of the valve seals facing the combustion chamber. The base portion of the alloy steel is prepared by forging the materials into a suitable shape. A particulate starting material forming the outer surface is prepared. These materials become hot-corrosion resistant alloys. The particulate starting material is contained in a container having the shape of the outer surface on the inner surface. The container is, in other words, ready to be removed after the valve head has been forged. The particulate material and the base portion are heated to the forging temperature and disposed within one of the die portions, such as the bottom die portion 10, while the particulate matter of the hot-corrosion resistant alloy lies within the container of the base portion. Next, when the material is forged, the particulate material undergoes shear deformation that deforms the particles into a long or oval shape. At the same time, the particulate matter is compacted at a density of at least 98.0% and integrated into the base portion or the buffer layer and the base portion.

A second method of manufacturing an exhaust valve is to hot spray particulate matter of a hot-corrosion resistant alloy to form a preform. The preform is formed directly on the base portion during the spraying operation, placed on the base portion or separately formed and heated to the forging temperature. Next, the preform and the base portion, and optionally the buffer layer, are forged with the exhaust valve portion. During forging, the particulate matter is subject to shear deformation that deforms the particles into a rough shape or an egg shape, which allows the particulate material to be compacted to a density of at least 98.0% ≪ / RTI >

Hot end spraying of particulate matter occurs by spraying the alloy as atomized particles on the base portion 4, which provides a spray dryer nozzle with the molten alloy and remains in a partially integrated but non-dense state of the particles . The base portion with the preforms applied with hot spray is heated to forging temperature and placed in one of the dies as described above for forging in a compact state.

The particulate matter prepared for the outer surface is vacuumed prior to forging to reduce the amount of oxygen present in the particles. In this manner, an oxide film is formed on the particles correspondingly.

In forging, the outer surface 5 is compressed to a small thickness, such as a thickness of less than about 25%, compared to the initial thickness. At the same time, the density of the material at the outer surface increases from about 65% to about 100%. As a result, the density is preferably at least 98.0%.

The valve head 3 manufactured by the above method is a valve head having an outer surface 5 at a surface oriented toward the combustion chamber. The valve head is provided with a valve shaft and if the base part 4 of the valve head 3 is integrally formed with the valve shaft 2, ). ≪ / RTI > In the latter case, the valve shaft must be mounted on the valve head after the valve head has been manufactured. Figure 5 shows the valve shaft 2 and the finished valve head. These two parts are joined by friction welding in a known manner. In such friction welding, one part, such as a valve head, is fixed and another part, such as a valve shaft, rotates once and then moves axially in contact with the valve head such that the two parts are connected to one exhaust valve spindle Are frictionally welded to each other.

Due to the strong microstructures obtained, the material is strongly bound in the transition region. According to the invention, this coupling can be tested. In order to measure the strength against breakage of the material at the shear load, special test specimens are prepared based on the incised samples of the exhaust valve. Such a test specimen has a shape as shown in Figs. 8 and 9. The test specimen has a width w = 9.0 mm, a length l = 40.0 mm, a distance d between centers of the pulling holes d = 52.4 mm, a thickness t = 3.5 mm of the base portion and a thickness T of the outer surface. The thickness of the outer surface is measured and set to T. The grooves g1 and g2 through the whole material are cut from both sides with a width of at least 2 mm and the overlapping portion of the mutual coupling portions of the layers is smaller than the measured thickness of the outer side in this manner in the longitudinal direction.

Six experiments were performed and the results are shown in Table 3. The obtained shear strength is high. This level is comparable to the shear strength of a solid material. The bond obtained according to the invention does not make the material weak.

width
(mm) thickness
(mm) Overlap
(mm) Overlap area
(mm ² ) Section
(mm ² ) Shear force (N)
Shear strength
(N / mm ² ) 8.91 1.30 1.39 12.38 11.58 6323.6 510.6 8.94 1.45 1.50 13.41 12.96 6088.6 454.0 8.91 1.46 1.52 13.54 13.01 6138.4 453.2 8.94 1.45 1.50 13.41 12.96 6424.8 479.1 8.90 1.62 1.77 15.75 14.42 7451.8 473.0 8.91 1.33 1.41 12.56 11.85 5527.3 440.0 8.91 1.20 1.24 11.05 10.69 5134.3 464.7 8.92 1.42 1.51 13.43 12.62 6314.4 469.8

In a further embodiment, the particulate material of the hot corrosion-resistant alloy is mixed with particles of a separating material such as zirconia (ZrO ₂ ) which is a ceramic material. It is preferable that the separating material has a higher concentration near the obverse surface of the outer surface and no separating material in the transition section between the outer surface and the base portion. The particulate matter on the outer surface includes 5 to 60% by mass of the separating material, but it is preferable that the amount of the separating material does not exceed 40% by mass of the outer surface.

The above-described embodiments may be combined with other embodiments within the scope of the claims. It is also possible to vary the above-described embodiments within the scope of the claims. The valve seat 6 may be formed of the same alloy as, for example, the valve head, and the buffer layer 9 is terminated at the valve seat 6 and has a range of inclination or vertical at the maximum diameter Lower region).

Any of the embodiments described above may be subject to a final heat treatment such as tempering or annealing. The heat treatment lasts for 2 to 6 hours and is performed at a temperature in the range of 800 to 1050 캜. It can be performed at different temperature ranges.

The exhaust valve valves are the main components of the engine, and information on the manufacturing specifications and recognition documentation of the specific exhaust valve spindle can be stored as a tag on the exhaust valve spindle. These tags are preferably RFID types that can be read and written remotely, preferably including separate authentication data for the traceability provided. A specific spindle is provided with one or more tags as needed. These tags are placed in position in the exhaust valve spindle and their position is properly blocked from heat or other parameters that hurt the tag.

1: exhaust valve spindle 3: valve head
4: Base portion 5: Outer side

Claims (15)

An exhaust valve spindle for an internal combustion engine, which is a two stroke, crosshead engine, comprising: a valve head having a base portion made of alloy steel; and an outer surface defining a surface of the valve spindle toward the combustion chamber, Wherein the side is formed from a particulate starting material of a hot-corrosion resistant alloy of nickel, chromium, or cobalt, the particulate starting material being integral with the coherent layer,
In at least the transition region relative to the base portion, the particles of particulate matter on the outer surface are deformed into an egg-shaped or longitudinally extending shape by shear deformation produced by forging the outer and base portions, Has a porosity of at most 2%. ≪ RTI ID = 0.0 > 11. < / RTI > The method according to claim 1,
Wherein in the region extending from the rim region of the valve head to the central region of the valve head, the transition region between the outer surface and the base portion extends along at least one straightened plane. The method according to claim 1,
At least one buffer layer of the alloy is disposed between the base portion and the outer side surface and the alloy of the buffer layer is different from the alloy steel of the base portion and is a third alloy having a different component from the hot- The exhaust valve spindle. The method of claim 3,
Wherein the buffer layer is selected from the group consisting of steel, austenitic steels, nickel-based alloys, and alloys formed of Fe or Ni except for unavoidable impurities. 5. The method according to any one of claims 1 to 4,
And the alloy steel of the base portion is an austenitic stainless steel. The method of claim 3,
Wherein the buffer layer has a thickness of at least 2 mm. A method for manufacturing an exhaust valve spindle for an internal combustion engine, the exhaust valve spindle comprising a valve head having a base portion made of alloy steel and an outer surface forming a surface of the valve spindle towards the combustion chamber, , Chromium-based, or cobalt-based hot-corrosion resistant alloy,
The particulate material of the hot-corrosion resistant alloy is contained in the container in the base portion, and the particulate material is heated and forged to a forging temperature so that the particulate material forms a shear deformation that deforms the particle into an egg- Wherein the forging operation compacts the particulate matter to a porosity of up to 2% and integrates the outer surface into the base portion or the buffer layer and the base portion. 8. The method of claim 7,
Wherein in the region extending from the rim region of the valve head to the central region of the valve head, particulate matter in the vessel is provided in a layer of substantially uniform thickness. 8. The method of claim 7,
Wherein particulate matter in said container is provided in a layer increasing in thickness towards the center of said valve, in an area extending from within the rim area of said valve head to the central area of said valve head. A method for manufacturing an exhaust valve spindle for an internal combustion engine, the exhaust valve spindle comprising a valve head having a base portion made of alloy steel and an outer surface forming a surface of the valve spindle towards the combustion chamber, , Chromium-based, or cobalt-based hot-corrosion resistant alloy,
The particulate material of the hot-corrosion resistant alloy is hot sprayed to form a preform, the preform and the base being forged by forging to a forging temperature such that the particulate material deforms the particles into an egg- Wherein the forging operation compacts the particulate matter to a porosity of at most 2% and integrates the outer surface into the base portion or the buffer layer and the base portion. 11. The method according to any one of claims 7 to 10,
Wherein the material of the outer surface is vacuumed to a pressure of less than 1 X 10 < ^-4 > bar prior to performing the forging operation. 11. The method according to any one of claims 7 to 10,
Characterized in that before the outer surface is disposed on the surface of the base portion, a third sum different from the alloy steel of the base portion and having a different component from the hot-corrosion resistant alloy of the outer surface is applied to the surface of the base portion A method for manufacturing an exhaust valve spindle. 11. The method according to any one of claims 7 to 10,
After the forging step which integrates the base part and the outer surface, the integrated base part and the outer surface are forged in at least one subsequent step to obtain the final shape. 11. The method according to any one of claims 7 to 10,
Wherein the forging operation is performed for a time less than 10 minutes, and the base portion having the outer surface is cooled immediately after forging. 11. The method according to any one of claims 7 to 10,
Wherein the valve shaft portion is frictionally welded onto the bicep after the forging operation is completed.

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