In addition to the working medium, working temperature and external environment, the selection of the bellow expansion joint of the heating pipe network should also consider the possibility of stress corrosion, the influence of water treatment agents and pipeline cleaning agents on materials. On this basis, combined with the welding forming of the bellows material and the cost performance of the material, the economical and practical materials for the production of bellows are optimized.

In general, the material of the bellow expansion joint should meet the following conditions:

(1) Good plasticity, easy processing, forming a bellows, after subsequent treatment (cold work hardening, heat treatment, etc.), sufficient hardness and strength can be obtained.

(2) High elastic limit, high tensile strength and fatigue strength can achieve a larger displacement range in a unit pipe section, withstand higher pressure values, and have good adaptability to various complex environments.

(3) Good welding performance, meeting the welding process requirements of the bellows in the production process. Good welding performance can make the connection between the bellows and the flange form a high-strength connection, and can also increase the service life of the compensator.

(4) Good corrosion resistance, meeting the requirements of bellows in different environments. The pipeline transportation medium of modern industry is becoming more and more complex. Media with different properties will have different degrees of corrosion on the inner wall of the pipeline. In order to improve the corrosion resistance of the bellows, in the heating pipe network, most of the bellows are 316 or 316L. These two materials are materials with better performance and price when used in heat pipe networks.