1. Barrel material

Just like the screw, in order to meet the working requirements of the barrel, it must be made of high-quality high-temperature resistant, wear-resistant, corrosion-resistant, and high-strength materials. These materials should also have good machining and heat treatment properties. In addition to 45 steel, 40Cr, and 38CrMoAL, the barrel can also be made of cast steel and ductile iron. The feeding section with a bushing can be made of high-quality cast iron.

In recent years. With the development of high-speed extrusion and engineering plastics, especially when extruding glass fiber reinforced plastics and plastics containing inorganic fillers, higher requirements are placed on the wear and corrosion resistance of the barrel.

The method of applying it to the barrel is as follows: the powdered Xaloy alloy is heated together with the barrel at high temperature. Due to its low melting point, it can melt into a flowing state at about 1200℃. At this time, the barrel is rotated at high speed, and the huge centrifugal force generated by the molten Xaloy causes it to be cast on the red-hot inner wall of the barrel. Its thickness is about 2 mm. After cooling, about 0.20 mm is ground off by grinding, which can meet the requirements of general barrels.

According to reports, a Xaloy alloy produced in Belgium has a hardness value of up to Rc58-64. At 482℃, the hardness does not drop significantly, and the corrosion resistance is 12 times greater than that of nitrided steel.

2. Determination of barrel wall thickness and strength calculation:

1) Determination of barrel wall thickness

Barrels are rarely scrapped due to insufficient strength, mainly due to corrosion and wear. In addition to considering strength, the determination of barrel wall thickness is more about considering the processability and thermal inertia of the barrel structure. The wall thickness determined by the latter two factors is often greater than the value calculated according to strength conditions. Since there is no mature method to calculate the barrel wall thickness according to the barrel heat transfer characteristics, most of the current methods determine the wall thickness based on empirical statistical analogy, and then perform strength verification.

2) Strength calculation

The strength calculation of the barrel is based on a thick-walled barrel.

Note: When the barrel is made of brittle material, the first strength theory can be used for calculation.

When the barrel is made of plastic material, the fourth strength theory is used for calculation.

When a bushing is inserted into the barrel, it is equivalent to the press-fit connection in the interference fit of the "mechanical parts". At this time, the stress state of the bushing and the barrel is relatively complex, and its strength calculation is also relatively complex.