EP0092683B1 - Method for forming a valve seat on an endothermic engine cylinder head, and the engine with valve seats formed by this method - Google Patents
Method for forming a valve seat on an endothermic engine cylinder head, and the engine with valve seats formed by this method Download PDFInfo
- Publication number
- EP0092683B1 EP0092683B1 EP83103005A EP83103005A EP0092683B1 EP 0092683 B1 EP0092683 B1 EP 0092683B1 EP 83103005 A EP83103005 A EP 83103005A EP 83103005 A EP83103005 A EP 83103005A EP 0092683 B1 EP0092683 B1 EP 0092683B1
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- EP
- European Patent Office
- Prior art keywords
- cylinder head
- compartment
- added material
- laser beam
- layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 238000000034 method Methods 0.000 title claims description 33
- 239000000463 material Substances 0.000 claims description 60
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 16
- 229910045601 alloy Inorganic materials 0.000 claims description 16
- 239000000956 alloy Substances 0.000 claims description 16
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 12
- 239000011248 coating agent Substances 0.000 claims description 12
- 238000000576 coating method Methods 0.000 claims description 12
- 229910001234 light alloy Inorganic materials 0.000 claims description 10
- 238000001816 cooling Methods 0.000 claims description 9
- 239000000843 powder Substances 0.000 claims description 9
- 239000004411 aluminium Substances 0.000 claims description 8
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- 238000010276 construction Methods 0.000 claims description 8
- 229910052742 iron Inorganic materials 0.000 claims description 8
- 239000010953 base metal Substances 0.000 claims description 6
- 238000002844 melting Methods 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 238000000151 deposition Methods 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 230000008018 melting Effects 0.000 claims description 4
- 239000007921 spray Substances 0.000 claims description 4
- 238000009792 diffusion process Methods 0.000 claims description 3
- 229910001092 metal group alloy Inorganic materials 0.000 claims description 3
- 238000007712 rapid solidification Methods 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- 239000002904 solvent Substances 0.000 claims description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 4
- 238000005275 alloying Methods 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 239000011651 chromium Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 238000001000 micrograph Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 239000011888 foil Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 230000008646 thermal stress Effects 0.000 description 2
- 230000003313 weakening effect Effects 0.000 description 2
- 229910001018 Cast iron Inorganic materials 0.000 description 1
- 229910001240 Maraging steel Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000004873 anchoring Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 238000004093 laser heating Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L3/00—Lift-valve, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces; Parts or accessories thereof
- F01L3/22—Valve-seats not provided for in preceding subgroups of this group; Fixing of valve-seats
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
- C23C26/02—Coating not provided for in groups C23C2/00 - C23C24/00 applying molten material to the substrate
Definitions
- This invention relates to a method for forming a valve seat on an endothermic engine cylinder head, and to a valve seat formed by this method.
- the present invention also relates to an endothermic engine comprising valve seats formed by this method.
- the seats for the engine intake and exhaust valves are formed in inserts constructed of alloys of high resistance to wear and oxidation, and driven into suitable compartments provided in the engine cylinder head.
- This constructional method is used particularly in engines of light alloy construction, in which said inserts are constructed of cast iron and are cold-driven into the cylinder head (FR-A-2.165.646).
- the described constructional method is not without drawbacks. Specifically, a notching effect is produced in the cylinder head at the edges of the insert carrying the valve seat. This drawback is serious, in that it produces high localised stresses in the cylinder head. Furthermore, because of the size of the inserts and their housing compartments formed in the cylinder head, the dimensions of the bridge (the cylinder head element lying between two adjacent valve seats) must be small, so weakening the cylinder head and requiring the cylinder head cooling ducts to be withdrawn from that head surface facing the engine cylinders, so increasing the thermal stresses acting on the cylinder head.
- the object of the present invention is to provide a method for forming valve seats in an endothermic engine cylinder head of light alloy construction, which disposes of the presence of said inserts therein and thus obviates the described drawbacks.
- a further object of the present invention is to provide an endothermic engine of light alloy construction provided with valve seats free from the described drawbacks.
- a method for forming a valve seat on a cylinder head of an endothermic engine of light alloy construction characterised by comprising the following stages:
- the reference numeral 1 indicates overall an endothermic engine which in the illustrated example is a compression ignition engine, or diesel engine.
- the engine 1 comprises a cylinder head 2 carrying a plurality of intake and exhaust valves 3 for the engine 1, and a cylinder block 4 comprising a plurality of cylinders 5 defining, together with the respective pistons 6 slidable therein, combustion chambers 7 which are closed towards the valves 3 by a base wall 8 of the cylinder head 2.
- This latter is provided with housings 9 for the valves 3, and seal seats 10 therefor provided in the wall 8.
- the housings 9 and the relative seal seats 10 of each pair of valves 3 disposed in any one cylinder 5 are divided by a portion 11 of the cylinder head 2 known technically as the bridge.
- the portion or bridge 11 is provided with a cooling duct 12 (Ricardo duct) for cooling the seats 10 of the valves 3.
- the cylinder head 2 is also provided with cooling ducts 13.
- the ducts 12 and 13 are disposed at predetermined distances from a surface 14 of the wall 8 which faces the chamber 7 and is thus exposed directly to the heat of combustion, and they serve to maintain the temperature of the cylinder head 2 within acceptable limits.
- the cylinder head 2 and base 4 are constructed of any suitable light alloy, for example an aluminium-based light alloy.
- the seats 10 must have a hardness and resistance to wear and oxidation which are superior to those of the constituent alloy of the cylinder head 2, because, together with the bridge 11, they represent the most highly stressed regions of the cylinder head 2.
- each seat 10 comprises a substantially circular compartment or bore 15 which passes through the wall 8 and is bounded by a flared edge 16 and an annular coating 18 of predetermined thickness which coats the edge 16 and is formed as a single piece with the cylinder head 2.
- the coating 18, which has hardness and strength characteristics superior to those of the base metal material of which the cylinder head 2 is constructed, is formed by alloying with said base material an added material able to form an alloy with the base material in the manner described hereinafter, using a laser beam produced by any power laser apparatus of known type.
- Said added material can be any metal, ceramic or metallo-ceramic material able to form with the base material an alloy having strength and hardness characteristics superior to those thereof.
- the base material is constituted substantially by aluminium, and the added material can be any of a whole series of metal or ceramic materials such as nickel powders, nickel-chrome powders, Eatonite powders (the commercial name of an alloy containing carbon, silicon, iron, chromium and mainly nickel), steel powders (of the molybdenum or maraging type), or nickel or chromium powders mixed with oxides.
- the powders can be deposited on the edge 16 in the form of paste, or by any other method. Alternatively, they can be applied in the form of sintered or prefused foils.
- valve seats 10 A method is described hereinafter by way of example for forming the aforesaid valve seats 10 in the particular case in which the cylinder head 2 is of light alloy construction, the base material being aluminium and the added material being in the form of iron-based alloys (maraging steels) and/or nickel.
- composition of these added alloys is substantially as follows. Iron-based alloys: chromium content 5-20%; molybdenum content 3-18%; carbon content 0.2-3% remainder iron and minimum percentages of other elements. Nickel- based alloys: chromium content 5-20%; iron content 1-5%; carbon content 0.2-1 %; remainder nickel and minimum percentages of other elements.
- FIG. 3 shows a micrograph of a portion of the cylinder head 3 surrounding the bore or compartment 15, in order to form a seat 10 such as that described on the cylinder head 2, an annular layer 19 of predetermined thickness of an added material 20, which in this case mainly contains iron, is firstly applied over the entire edge 16 of each compartment 15.
- the thickness of the layer 19 is substantially uniform and lies between 0.1 and 1 millimetre, and is preferably about 0.5 millimetres.
- the layer 19 can be applied to the edge 16 in various ways according to the composition and consistency of the material 20.
- the layer 19 is solid and compact, in that the material 20 has been deposited by a plasma spray depositing method. This method is well known and consists of atomising the added material 20, constituted by a powder or solid wire, into a jet of gas heated to high temperature, and projecting the plasma spray obtained in this manner onto the surface of the edge 16 via a suitable tube so as to deposit the material 20 in the fluid state onto the relatively cold edge 16, and consequently cause it to rapidly solidify to obtain the layer 19.
- the layer 19 can be deposited by extrusion, using a suitable device, or manually by means of a spatula.
- the added material 20 is in the form of a metal powder which is mixed with a solvent in order to obtain a paste, or a fluid substance of high viscosity having gel consistency. This paste is then deposited on the edge 16 to form the layer 1.9.
- the layer 19 is in the form of a metal foil of maraging steel, possibly obtained by sintering, and simply deposited in contact with the surface of the edge 16.
- the preferred is the first, i.e. plasma spray depositing, both because this method creates adhesion between the added material 20 and the base material of the cylinder head 2, and because it destroys the thin oxide layer (AI 2 0 3 ) present on the edge 16 of the aluminium cylinder head 2, and which is detrimental to the alloying.
- the cylinder head 2 After forming the layer 19, the cylinder head 2 is disposed in a working station, not shown, of a power laser apparatus, not shown.
- a laser beam of predetermined power preferably between 6 and 12 kilowatts, is focused onto the edge 16 of the compartment 15 in a position corresponding with the layer 19.
- the laser beam is projected onto the cylinder head 2 by a known scanning device, not shown, which moves at predeterminable speed so as to move said laser beam along the edge 16 of the compartment or bore 15 in an annular trajectory at a speed of between 10 and 50 cm/ minute.
- the laser beam power is also adjusted in accordance with the irradiated area so as to obtain on the cylinder head 2 a specific laser beam power of between 180 and 300 joules/mm 2 , i.e. the cylinder head 2 is irradiated in such a manner as to transmit to it a thermal energy of between 180 and 300 joules for each mm 2 of surface irradiated by the laser beam.
- the high-melting layer 19 (melting point between 1000 and 1400°C) can be melted together with part of the underlying base material, which is not directly irradiated but is low-melting (660°C).
- the laser beam on striking the layer 19, the laser beam rapidly heats the material 20 by radiation, and the heat is transmitted by conduction to the cylinder head 2, thus also heating a layer of determined thickness of the base material which immediately surrounds the compartment or bore 15.
- the laser heating is protracted for a time sufficient for melting all the material 20 of the layer 19 together with the said underlying layer of base material, and to allow diffusion of the former into the latter and vice-versa, so as to form a metal alloy in the substantially liquid state in the compartment or bore 15.
- the laser beam is suppressed, and the cylinder head 2 is allowed to cool in free air.
- the high thermal capacity of the cylinder head 2 produces rapid cooling of the metal alloy which has just been formed, so as to cause it to rapidly solidify within the compartment 15, to form the coating 18.
- Figure 4 which illustrates a micrograph of a portion of a valve seat 10 formed by the described method
- the metallo-graphic aspect of the darker coating 18 can be clearly seen, its composition corresponding approximately to that of the compound FeA1 3 (35-40% of iron in aluminium).
- a layer 21 of remelted base material (aluminium) is present immediately below the coating 18, and finally the base material of the cylinder head 2 which has not been altered by the surface thermal treatment undergone by the cylinder head 2 can be seen on the bottom right.
- the obtained Vickers hardness values are shown to the side of the micrograph.
- Figure 5 shows by way of example a diagram of the laser parameters, in which the shaded portion illustrates the optimum working region within which the point of intersection of the abscissa representing the laser beam scanning velocity and the ordinate representing the laser beam power must fall in order to obtain best results.
- valve seats By means of a simple and rapid surface alloying operation, it enables valve seats to be formed which are in one piece with the engine cylinder head but have superior mechanical characteristics (in the illustrated example, the hardness of the cylinder head base material was only 77 Vickers). This means that hard material inserts do not need to be mounted in the cylinder head, thus obviating the weakening of the cylinder head caused by the need to provide the insert seats therein, and by the notching effect produced by these on the cylinder head itself.
- valve seats formed by the method of the invention are of small overall size, and thus enable the bridge between one valve and the next to be of greater dimensions, and consequently stronger, so enabling the cooling ducts to be brought closer to the explosion chamber and reduce the thermal stresses on the valve seats and on the cylinder head.
Description
- This invention relates to a method for forming a valve seat on an endothermic engine cylinder head, and to a valve seat formed by this method. The present invention also relates to an endothermic engine comprising valve seats formed by this method.
- In most of the current endothermic engines, the seats for the engine intake and exhaust valves are formed in inserts constructed of alloys of high resistance to wear and oxidation, and driven into suitable compartments provided in the engine cylinder head. This constructional method is used particularly in engines of light alloy construction, in which said inserts are constructed of cast iron and are cold-driven into the cylinder head (FR-A-2.165.646).
- The described constructional method is not without drawbacks. Specifically, a notching effect is produced in the cylinder head at the edges of the insert carrying the valve seat. This drawback is serious, in that it produces high localised stresses in the cylinder head. Furthermore, because of the size of the inserts and their housing compartments formed in the cylinder head, the dimensions of the bridge (the cylinder head element lying between two adjacent valve seats) must be small, so weakening the cylinder head and requiring the cylinder head cooling ducts to be withdrawn from that head surface facing the engine cylinders, so increasing the thermal stresses acting on the cylinder head.
- The object of the present invention is to provide a method for forming valve seats in an endothermic engine cylinder head of light alloy construction, which disposes of the presence of said inserts therein and thus obviates the described drawbacks. A further object of the present invention is to provide an endothermic engine of light alloy construction provided with valve seats free from the described drawbacks.
- The aforesaid objects are attained according to the present invention by a method for forming a valve seat on a cylinder head of an endothermic engine of light alloy construction, characterised by comprising the following stages:
- - depositing an added material in a compartment provided in said cylinder head in the position which said valve seat is to occupy, said cylinder head being constructed of a base metal different from said added material and able to form therewith alloys capable of assuming strength and hardness characteristics superior to those of the base metal;
- - heating said added material by a laser beam of predetermined power focused onto said compartment until melting takes place of said added material in said compartment and of a layer of determined thickness of the base material which immediately surrounds this latter;
- - maintaining the molten state of said added material and said layer of base material by said laser beam for a time sufficient to form an alloy in the molten state in said compartment by diffusion of said added material into the base material and vice-versa, said laser beam being moved along said compartment at a speed of between 10 and 50 cm/minute; and
- - cooling said alloy in the molten state contained in said compartment in order to cause its rapid solidification therein.
- Further objects and advantages of the present invention will be apparent from the description given hereinafter of a non-limiting embodiment thereof, with reference to the accompanying drawings in which:
- Figure 1 is a diagrammatic cross-section through an endothermic engine, of which the cylinder head is provided with valve seats formed by the method of the present invention;
- Figure 2 is a diagrammatic plan view of an endothermic engine cylinder head constructed in accordance with the present invention;
- Figures 3 and 4 are two micrographs of an endothermic engine cylinder head after two different stages of the method of the invention; and
- Figure 5 is a schematic diagram relative to the method of the present invention.
- In Figures 1 and 2, the reference numeral 1 indicates overall an endothermic engine which in the illustrated example is a compression ignition engine, or diesel engine. The engine 1 comprises a
cylinder head 2 carrying a plurality of intake and exhaust valves 3 for the engine 1, and a cylinder block 4 comprising a plurality ofcylinders 5 defining, together with therespective pistons 6 slidable therein, combustion chambers 7 which are closed towards the valves 3 by abase wall 8 of thecylinder head 2. This latter is provided withhousings 9 for the valves 3, andseal seats 10 therefor provided in thewall 8. Thehousings 9 and therelative seal seats 10 of each pair of valves 3 disposed in any onecylinder 5 are divided by aportion 11 of thecylinder head 2 known technically as the bridge. The portion orbridge 11 is provided with a cooling duct 12 (Ricardo duct) for cooling theseats 10 of the valves 3. Thecylinder head 2 is also provided withcooling ducts 13. Theducts surface 14 of thewall 8 which faces the chamber 7 and is thus exposed directly to the heat of combustion, and they serve to maintain the temperature of thecylinder head 2 within acceptable limits. - The
cylinder head 2 and base 4 are constructed of any suitable light alloy, for example an aluminium-based light alloy. In all cases theseats 10 must have a hardness and resistance to wear and oxidation which are superior to those of the constituent alloy of thecylinder head 2, because, together with thebridge 11, they represent the most highly stressed regions of thecylinder head 2. - Consequently, each
seat 10 comprises a substantially circular compartment orbore 15 which passes through thewall 8 and is bounded by aflared edge 16 and anannular coating 18 of predetermined thickness which coats theedge 16 and is formed as a single piece with thecylinder head 2. In this respect, thecoating 18, which has hardness and strength characteristics superior to those of the base metal material of which thecylinder head 2 is constructed, is formed by alloying with said base material an added material able to form an alloy with the base material in the manner described hereinafter, using a laser beam produced by any power laser apparatus of known type. Said added material can be any metal, ceramic or metallo-ceramic material able to form with the base material an alloy having strength and hardness characteristics superior to those thereof. The base material is constituted substantially by aluminium, and the added material can be any of a whole series of metal or ceramic materials such as nickel powders, nickel-chrome powders, Eatonite powders (the commercial name of an alloy containing carbon, silicon, iron, chromium and mainly nickel), steel powders (of the molybdenum or maraging type), or nickel or chromium powders mixed with oxides. The powders can be deposited on theedge 16 in the form of paste, or by any other method. Alternatively, they can be applied in the form of sintered or prefused foils. - A method is described hereinafter by way of example for forming the
aforesaid valve seats 10 in the particular case in which thecylinder head 2 is of light alloy construction, the base material being aluminium and the added material being in the form of iron-based alloys (maraging steels) and/or nickel. - The composition of these added alloys is substantially as follows. Iron-based alloys: chromium content 5-20%; molybdenum content 3-18%; carbon content 0.2-3% remainder iron and minimum percentages of other elements. Nickel- based alloys: chromium content 5-20%; iron content 1-5%; carbon content 0.2-1 %; remainder nickel and minimum percentages of other elements.
- With reference to Figure 3, which shows a micrograph of a portion of the cylinder head 3 surrounding the bore or
compartment 15, in order to form aseat 10 such as that described on thecylinder head 2, anannular layer 19 of predetermined thickness of an addedmaterial 20, which in this case mainly contains iron, is firstly applied over theentire edge 16 of eachcompartment 15. - The thickness of the
layer 19 is substantially uniform and lies between 0.1 and 1 millimetre, and is preferably about 0.5 millimetres. Thelayer 19 can be applied to theedge 16 in various ways according to the composition and consistency of thematerial 20. In the case illustrated in Figure 3, thelayer 19 is solid and compact, in that thematerial 20 has been deposited by a plasma spray depositing method. This method is well known and consists of atomising the addedmaterial 20, constituted by a powder or solid wire, into a jet of gas heated to high temperature, and projecting the plasma spray obtained in this manner onto the surface of theedge 16 via a suitable tube so as to deposit thematerial 20 in the fluid state onto the relativelycold edge 16, and consequently cause it to rapidly solidify to obtain thelayer 19. - According to a modification, not illustrated, the
layer 19 can be deposited by extrusion, using a suitable device, or manually by means of a spatula. In this case, the addedmaterial 20 is in the form of a metal powder which is mixed with a solvent in order to obtain a paste, or a fluid substance of high viscosity having gel consistency. This paste is then deposited on theedge 16 to form the layer 1.9. - According to a further modification, not shown, the
layer 19 is in the form of a metal foil of maraging steel, possibly obtained by sintering, and simply deposited in contact with the surface of theedge 16. - Of the three described systems for forming the
layer 19, the preferred is the first, i.e. plasma spray depositing, both because this method creates adhesion between the addedmaterial 20 and the base material of thecylinder head 2, and because it destroys the thin oxide layer (AI203) present on theedge 16 of thealuminium cylinder head 2, and which is detrimental to the alloying. - After forming the
layer 19, thecylinder head 2 is disposed in a working station, not shown, of a power laser apparatus, not shown. In this, using known methods and systems, a laser beam of predetermined power, preferably between 6 and 12 kilowatts, is focused onto theedge 16 of thecompartment 15 in a position corresponding with thelayer 19. The laser beam is projected onto thecylinder head 2 by a known scanning device, not shown, which moves at predeterminable speed so as to move said laser beam along theedge 16 of the compartment or bore 15 in an annular trajectory at a speed of between 10 and 50 cm/ minute. - The laser beam power is also adjusted in accordance with the irradiated area so as to obtain on the cylinder head 2 a specific laser beam power of between 180 and 300 joules/mm2, i.e. the
cylinder head 2 is irradiated in such a manner as to transmit to it a thermal energy of between 180 and 300 joules for each mm2 of surface irradiated by the laser beam. In this manner, the high-melting layer 19 (melting point between 1000 and 1400°C) can be melted together with part of the underlying base material, which is not directly irradiated but is low-melting (660°C). - In this respect, on striking the
layer 19, the laser beam rapidly heats thematerial 20 by radiation, and the heat is transmitted by conduction to thecylinder head 2, thus also heating a layer of determined thickness of the base material which immediately surrounds the compartment or bore 15. The laser heating is protracted for a time sufficient for melting all thematerial 20 of thelayer 19 together with the said underlying layer of base material, and to allow diffusion of the former into the latter and vice-versa, so as to form a metal alloy in the substantially liquid state in the compartment or bore 15. Finally, the laser beam is suppressed, and thecylinder head 2 is allowed to cool in free air. The high thermal capacity of thecylinder head 2 produces rapid cooling of the metal alloy which has just been formed, so as to cause it to rapidly solidify within thecompartment 15, to form thecoating 18. In Figure 4, which illustrates a micrograph of a portion of avalve seat 10 formed by the described method, the metallo-graphic aspect of thedarker coating 18 can be clearly seen, its composition corresponding approximately to that of the compound FeA13 (35-40% of iron in aluminium). Alayer 21 of remelted base material (aluminium) is present immediately below thecoating 18, and finally the base material of thecylinder head 2 which has not been altered by the surface thermal treatment undergone by thecylinder head 2 can be seen on the bottom right. The obtained Vickers hardness values are shown to the side of the micrograph. As can be seen, immediately in front of the layer 21 (HV 115-121 kg/mm2) there is present a layer ofcoating 18 having a higher hardness (HV 482-413 kg/mm2) than the average hardness of the coating 18 (HV 378 kg/mm2). This is due to the fact that the addedmaterial 20, of higher density than the base material, melts into this latter when both are in the liquid state, and consequently thecoating 18 is richer in the addedmaterial 20 towards thelayer 21, whereas at the surface it is richer in aluminium (its base material) and thus more tender. This situation improves the anchoring of thecoating 18, which having been formed by direct alloying of thematerial 20 on thecylinder head 2, forms a single piece with this latter. - Figure 5 shows by way of example a diagram of the laser parameters, in which the shaded portion illustrates the optimum working region within which the point of intersection of the abscissa representing the laser beam scanning velocity and the ordinate representing the laser beam power must fall in order to obtain best results.
- The advantages of the present invention are apparent from the description. By means of a simple and rapid surface alloying operation, it enables valve seats to be formed which are in one piece with the engine cylinder head but have superior mechanical characteristics (in the illustrated example, the hardness of the cylinder head base material was only 77 Vickers). This means that hard material inserts do not need to be mounted in the cylinder head, thus obviating the weakening of the cylinder head caused by the need to provide the insert seats therein, and by the notching effect produced by these on the cylinder head itself. Furthermore, the valve seats formed by the method of the invention are of small overall size, and thus enable the bridge between one valve and the next to be of greater dimensions, and consequently stronger, so enabling the cooling ducts to be brought closer to the explosion chamber and reduce the thermal stresses on the valve seats and on the cylinder head.
Claims (12)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IT67531/82A IT1155320B (en) | 1982-04-22 | 1982-04-22 | METHOD FOR OBTAINING A VALVE SEAT ON AN ENDOTHERMAL MOTOR HEAD AND MOTOR WITH VALVE SEATS OBTAINED WITH SUCH METHOD |
IT6753182 | 1982-04-22 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0092683A1 EP0092683A1 (en) | 1983-11-02 |
EP0092683B1 true EP0092683B1 (en) | 1987-02-25 |
Family
ID=11303192
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP83103005A Expired EP0092683B1 (en) | 1982-04-22 | 1983-03-25 | Method for forming a valve seat on an endothermic engine cylinder head, and the engine with valve seats formed by this method |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0092683B1 (en) |
DE (1) | DE3369868D1 (en) |
IT (1) | IT1155320B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE10156196C1 (en) * | 2001-11-15 | 2003-01-02 | Daimler Chrysler Ag | Production of a valve seat used for a cylinder head of internal combustion engine comprises fusing an additive material made from an alloy or a mixture of an aluminum-lead alloy and a further component at a certain point on a cylinder head |
DE10353474B4 (en) * | 2003-11-15 | 2007-02-22 | Daimlerchrysler Ag | Component of an internal combustion engine and method for its production |
Families Citing this family (18)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3435460A1 (en) * | 1984-09-27 | 1986-04-10 | M.A.N. Maschinenfabrik Augsburg-Nürnberg AG, 8000 München | METHOD FOR PRODUCING WORKPIECES FROM LIGHT METAL |
GB2169318A (en) * | 1985-01-04 | 1986-07-09 | Rolls Royce | Metal surface hardening by carbide formation |
JPS62150014A (en) * | 1985-12-25 | 1987-07-04 | Toyota Motor Corp | Valve seatless cylinder head made of aluminum alloy |
US5742020A (en) * | 1995-01-23 | 1998-04-21 | Yamaha Hatsudoki Kabushiki Kaisha | Valve seat-bonded cylinder head and method for producing same |
JP3373317B2 (en) * | 1995-02-16 | 2003-02-04 | ヤマハ発動機株式会社 | Valve seat structure of cylinder head |
JP3380081B2 (en) * | 1995-03-13 | 2003-02-24 | ヤマハ発動機株式会社 | Valve seat |
DE69608434T2 (en) * | 1995-02-28 | 2000-09-14 | Yamaha Motor Co Ltd | Cylinder head and method for manufacturing a valve seat |
JPH08270500A (en) * | 1995-03-31 | 1996-10-15 | Yamaha Motor Co Ltd | Internal combustion engine |
JPH08312800A (en) * | 1995-05-15 | 1996-11-26 | Yamaha Motor Co Ltd | Joint type valve seat |
JP3394363B2 (en) * | 1995-06-28 | 2003-04-07 | ヤマハ発動機株式会社 | Engine cylinder head |
US5778531A (en) * | 1995-09-14 | 1998-07-14 | Yamaha Hatsudoki Kabushiki Kaisha | Method of manufacturing cylinder head for engine |
JPH0979014A (en) * | 1995-09-14 | 1997-03-25 | Yamaha Motor Co Ltd | Manufacture of cylinder head for engine |
US5705786A (en) * | 1995-12-29 | 1998-01-06 | General Electric Company | Underwater welding |
US5745993A (en) * | 1996-02-27 | 1998-05-05 | Yamaha Hatsudoki Kabushiki Kaisha | Valve seat |
FR2765915B1 (en) * | 1997-07-10 | 1999-08-27 | Renault | METHOD FOR MANUFACTURING CYLINDER HEAD WITH INTEGRATED VALVE SEATS AND CYLINDER HEAD WITH INTEGRATED VALVE SEATS |
DE19912889A1 (en) | 1999-03-23 | 2000-09-28 | Daimler Chrysler Ag | Production of a valve seat for a cylinder head of an I.C. engine comprises using an additional material made of an an alloy of aluminum, silicon and nickel |
FR2848245B1 (en) | 2002-12-10 | 2007-03-09 | Renault Sa | VALVE SEAT FOR INTERNAL COMBUSTION ENGINE CYLINDER HEAD |
DE10353473B4 (en) * | 2003-11-15 | 2007-02-22 | Daimlerchrysler Ag | Component of an internal combustion engine and method for its production |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB475585A (en) * | 1935-06-03 | 1937-11-23 | Wilcox Rich Corp | Improvements in or relating to valve parts and method of constructing the same |
FR1129024A (en) * | 1955-05-20 | 1957-01-15 | Automobiles Ind Latil | Method for improving the contact surfaces of valves and their seats |
US3505489A (en) * | 1965-12-10 | 1970-04-07 | Hitachi Metals Ltd | Method of depositing corrosion-resisting and wear-resisting alloy on contact parts between valve members and valve seats |
DE2164357B2 (en) * | 1971-12-23 | 1980-08-28 | Daimler-Benz Ag, 7000 Stuttgart | Valve seat insert with a thread for screwing into a cylinder head of an internal combustion engine |
IT1172891B (en) * | 1978-07-04 | 1987-06-18 | Fiat Spa | PROCEDURE FOR COATING A METALLIC SURFACE WITH ANTI-WEAR MATERIAL |
GB2052566B (en) * | 1979-03-30 | 1982-12-15 | Rolls Royce | Laser aplication of hard surface alloy |
-
1982
- 1982-04-22 IT IT67531/82A patent/IT1155320B/en active
-
1983
- 1983-03-25 EP EP83103005A patent/EP0092683B1/en not_active Expired
- 1983-03-25 DE DE8383103005T patent/DE3369868D1/en not_active Expired
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE10156196C1 (en) * | 2001-11-15 | 2003-01-02 | Daimler Chrysler Ag | Production of a valve seat used for a cylinder head of internal combustion engine comprises fusing an additive material made from an alloy or a mixture of an aluminum-lead alloy and a further component at a certain point on a cylinder head |
US7013858B2 (en) | 2001-11-15 | 2006-03-21 | Daimlerchrysler Ag | Method for the production of a valve seat |
DE10353474B4 (en) * | 2003-11-15 | 2007-02-22 | Daimlerchrysler Ag | Component of an internal combustion engine and method for its production |
Also Published As
Publication number | Publication date |
---|---|
EP0092683A1 (en) | 1983-11-02 |
IT1155320B (en) | 1987-01-28 |
IT8267531A0 (en) | 1982-04-22 |
DE3369868D1 (en) | 1987-04-02 |
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