The bimetallic barrel cylinder is a kind of cylinder with a 2-3 mm-thick alloy coat on the cylinder inner wall which has the ability toundergo abrasion,erosion and high-temperature.And its useful service life is greatly improved contrast to common nitrationg barrel.Bimetalhas more obvious advantages when processing special plastics such asengineering plastics,fluoride plastic,PPO,etc.The company uses special alloy powders being sprayed and welded on the screw's ridge,and uses different alloys and welding methods for the Screws of different functions.