At the top of the A-frames there is a strong cast iron frame called （）.
举一反三
- （） of the A-frames there is a strong cast iron frame called the scavenging air box.
- On top of scavenging air box is mounted a strong cast iron frame for each cylinder known as（）
- The cast iron guide-ways for （） are attached to the top section and seal off the crankcase.
- Frames to which the tank top and bottom shell are fastened are called（）.
- In addition to iron and carbon, list the other elements that may be found in a grey cast iron and describe their effect on the properties of a grey cast iron.