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56
Corrosion resistance. Cast irons will corrode readily under atmospheric
conditions. This corrosion, however, forms a protective surface that offers resistance
to firther atmospheric corrosion as well as soil corrosion. Widespread use of cast iron
for water-main and soil pipe is a good indication of its generally favorable corrosion
resistance. Gray-cast-iron water mains and gas lines have been in service in some
areas for more than 100 years.
Vibration damping. Damping capacity is an inverse finction of the modulus
of elasticity. Gray cast iron has good damping qualities, making it a valuable
engineering material in the design of parts subject to vibration due to dynamic
forces.
One way of demonstrating damping capacity is to strike the casitng: steel will
ring, while cast iron will thud. The energy absorbed per cycle in gray iron is about
10 times that of steel, but damping capacity decreases with applied load.
Wear resistance. In sliding friction, gray iron is outstanding in its wear
resistance. This is amply demonstrated by the fact that practically all engine
cylinders or liners are made of gray iron. The ways of many machine tools are made
of gray iron for the same reason.
Weldability. Two methods lend themserves most readily to the welding of
gray-iron castings. These are oxyacetylene welding with cast-iron filler and metal
arc with nickel or copper-nickel welding electrodes. Oxiacetylene welding is the
fastest method of depositing metal and offers sound deposits and identical color
match. When properly executed, the welds are readily machinable and free from
defects. The items to be joined must be preheated.
Shinkage rules and machining allowances. Unlike most metals, gray iron
shrinks very little when it solidifies. The amount of material necessary to provide for
machine finish will vary with the casting size and the materials’ tendency to warp, as
well as the analysis of cast iron itself.
Glossary
№ English word Translation
1. castability жидкотекучесть
2. cast iron чугун
3. fluid текучая среда
4. alloy сплав
5. steel сталь
6. aluminum алюминий
7. automobile автомобиль
8. engine двигатель
9. block блок
10. head головка
11. ferrous «черный»
12. machinability обрабатываемость
