After the alloy steel tube is cold drawn, the tensile strength, yield strength, elongation, reduction of area, as well as the impact and hardness indicators in the cold working hardened state are far from reaching the technical requirements required for making cylinder barrels. The only solution is to adopt appropriate heat treatment process.

Through repeated practice tests and analysis and demonstration, the alloy steel contains alloying elements and has strong hardenability characteristics, and adopts low temperature and long-term heat preservation to achieve the aging treatment process for the purpose of precipitation hardening.

When the steel tube is cold-worked, the metal crystal grains are longitudinally slipped and elongated to produce dislocation. On the basis of cold work hardening, during aging heat treatment, the deformed grains form a polygonal substructure. When the grains are precipitation hardened, the mechanical properties and process performance of the steel tube are improved in an all-round way, which fully meets the technical conditions of high strength, high hardness, good wear resistance, strong plasticity, and high pressure resistance required by the hydraulic cylinder.

In addition, due to the low heating temperature during the aging heat treatment, the alloy steel tube surface has no oxide scale and decarburization phenomenon, which effectively guarantees the surface finish and carbon content of the steel tube; at the same time, due to the low heating temperature and uniform heating, there is no deformation. This phenomenon can effectively guarantee the geometric dimensional accuracy of steel tubes.