Kute tłoki

he forged piston is made very differently. The metal is not molten, but heated somewhat. A blob of this hot aluminun alloy called an ingot is placed in a female mold, and a male ram is pounded into it. The result is not a piston, but a piston blank, which must then undergo many machining operations before it resembles a piston.

Forging Alloys
The earliest forged pistons were also made with poor alloys. In many cases however they were even worse than the alloys the cast pistons used, because when the cast piston finally got silicon, the forged piston did not. The same brittleness that makes the cast piston crack when bumped hard would have resulted in even larger defects had it been used in a forging. Consequently, during the time that the cast piston defined a piston's normal expansion rate, the forged piston was far behind the technology. The forged piston had to be fitted loose, which made it noisy and wasted power. Recently however, silicon has been introduced to the forged piston. A mixture of alloys has been found that together with silicon do not result in defective forgings. For example, nickel has been found to offset the silicon's tendency toward brittleness. However, not very much nickel can be used, as it is a heavy metal, and it affects the mixture in other ways. The result is that the modern forged piston is much more dimensionally stable than was true in the past.

The result is that the modern forged piston is much more dimensionally stable than was true in the past.

2008-12-26 15:10:28, 3zeR_MDS pisze:
tłoki kute wykonuje się ze stopów 4032 bądz tez 2618 w zaleznosci od zastosowania i wymagan stawianych tłokowi. 4032 to aluminium z domieszka 11% silikonu dla zapewnienia wytrzymalosci scian tloka i zminimalizowania zmian ksztaltu. Zeby zminimalizowac skutki dodania silikonu (kruchosc) dodaje sie domieszki miedzi, jednak w niewielkiej ilosci. 4032 jest stosowane do silnikow seryjnych. do sportu stosuja 2618 dzieki lepszej wytrzymalosci na wysokie temperatury. 2618 praktycznie nie zawiera silikonu przez co jest bardziej podatny na zmiane ksztaltu, wymaga przez to wiekszych luzow w cylindrach. jesli doda sie do tego to, ze odkuwka jest prasowana z sila kilku tysiecy ton, mozemy sie domyslic o ile lepsza i bardziej jednolita bedzie wewnetrzna struktura materialu niz w przypadku odlewu. Zdecydowanie zageszczona bedzie siec krystaliczna. i jeszcze podstawowe dane tych stopow, bo w tabeli, ktora pavlus wkleil ich nie ma: 4032: Aluminum Balance Chromium 0.1 max Copper 0.5 - 1.3 Iron 1 max Magnesium 0.8 - 1.3 Nickel 0.5 - 1.3 Remainder Each 0.05 max Remainder Total 0.15 max Silicon 11 - 13.5 Zinc 0.25 max 2618: Aluminum Balance Copper 1.9 - 2.7 Iron 0.9 - 1.3 Magnesium 1.3 - 1.8 Nickel 0.9 - 1.2 Remainder Each 0.05 max Remainder Total 0.15 max Silicon 0.25 max Titanium 0.04 - 0.1 wartosci w % zawartosci [ wiadomość edytowana przez: 3zeR_MDS dnia 2008-12-26 15:19:10 ]