A movable wall member in form of an exhaust valve spindle or a piston for an internal combustion engine, and a method of manufacturing such a member
A technology for exhaust valves, internal combustion engines, applied to pistons, engine components, machines/engines, etc., to solve problems such as erosion, exhaust valve failure, star cracking, etc.
Active Publication Date: 2011-02-09
MAN DIESEL & TURBO FILIAL AF MAN DIESEL & TURBO SE TYSKLAND
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Problems solved by technology
It is well known that slowly varying but large thermal stresses resulting from said thermal influences can lead to a star-shaped crack starting at the middle of the lower surface of the valve head
These star cracks can become so deep that they penetrate the heat-corrosion-resistant material, leaving the underlying material vulnerable to corrosive impact and being eroded, causing the exhaust valve to fail
Method used
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[0034] figure 1 A schematic diagram showing a wall member in the form of a valve stem 1 for an exhaust valve of a two-stroke crosshead engine. The valve stem comprises a base portion generally indicated at 20 comprising a valve head 2 and a valve shaft 3, only the bottom part of which is shown. The valve seat 4 at the upper surface of the valve head is manufactured from a heat-corrosion-resistant alloy suitable for counteracting the formation of dimple marks on the sealing surface of the valve seat. The lower surface of the valve head has an outer portion 5 of a layer of heat-corrosion-resistant material that counteracts the burn-off of the outer surface 6 facing downwards towards the disk. A buffer layer 21 is arranged between the base part 20 and the outer part 5 . When the engine is running, the exhaust valves move at appropriate times in the engine cycle between a closed position in which the valve seat abuts a fixed valve seat (not shown) and an open position in which ...
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Abstract
A movable wall member, in form of an exhaust valve spindle (1) or a piston (7) for an internal combustion engine, comprises a base portion (17, 20) of an alloyed steel having a carbon-content in the range from 0.15 to 0.35 % by weight, and an outer portion (14, 5) forming the surface of the wall member facing a combustion chamber. The outer portion is of a hot-corrosion-resistant alloy, which is nickel-based, chromium-based or cobalt-based. At least one buffer layer (18, 21) of an alloy is located in between the base portion and the outer portion. The alloy of the buffer layer is different from the alloyed steel of the base portion and different from the hot-corrosion-resistant alloy of the outer portion. The alloy of the buffer layer comprises from 0% to at the most 0.09% C in percent byweight of the buffer layer, and that the buffer layer has a thickness of at least 1.5 mm.
Description
technical field [0001] The invention relates to a movable wall member in the form of an exhaust valve stem or piston for an internal combustion engine, in particular a two-stroke crosshead engine, said movable wall member comprising: a base part of alloy steel, The alloy steel has a carbon content in the range from 0.15% to 0.35% by weight; and an outer portion forming the combustion chamber-facing surface of the wall member, the outer portion being nickel-based, chromium Based or cobalt based hot corrosion resistant alloys. Background technique [0002] US Patent 6,173,702 describes a known movable wall member of this type, wherein a corrosion-resistant outer part is provided onto a base part by powder metallurgy processing, wherein granular material of a corrosion-resistant alloy is provided in a mold on the base part, And it is integrated with the base portion in a HIP (Hot Isostatic Pressing) process. Due to the use of powder metallurgy and HIP treatment, the resulting...
Claims
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IPC IPC(8): B22F5/00C22C38/00F01L3/22F01L3/04F02F3/12
CPCC22C30/00C22C38/34C22C19/05B22F5/008F01L3/12C22C38/04C22C38/40B22F3/15F02F3/12C22C38/44C22C19/058C22C38/02C22C38/30F01L3/04F01L3/02C22C38/58F01L2820/01F05C2201/0448B22F7/08Y10T29/49426Y10T29/49298F01L3/22B22F5/00
Inventor H·A·赫格
Owner MAN DIESEL & TURBO FILIAL AF MAN DIESEL & TURBO SE TYSKLAND