The specification of ot rolled round bar is 5.5-250mm. Among them, the small round steel of 5.5-25mm is mostly supplied in bundles of straight bars, which is often used as reinforcement, bolts and various mechanical parts: the ot rolled round bar greater than 25mm is mainly used for manufacturing mechanical parts or Seamless steel tube billets.
Hot rolled round bar has the advantages of good hardenability, high hardness, good wear resistance and small heat treatment deformation. It is often used to make cold working dies with heavy load, large production batch and complex shape.
However, Q345B low alloy round bar is prone to brittleness and other problems in the process of use. The results show that improving the morphology and distribution of carbides in Q345B low alloy round bar can effectively improve the toughness of the material.
The common processes of hot rolled round bar include forging preheating quenching, solid solution double refining process, cooling quenching, isothermal quenching and so on.
The solution double refining treatment is to refine carbides, round edges and corners and super refine austenite grains by heat treatment. The main measures of the process are high-temperature solid solution and cyclic refinement. High temperature solid solution can improve the morphology and particle size of carbides; The purpose of cyclic refinement is to make austenite grain super fine.
Compared with ordinary heat treatment, vacuum heat treatment has many outstanding characteristics, such as preventing oxidation and decarburization on the surface of Q345B low alloy round bar; Small quenching deformation; The stability and repeatability of the process are good; Safe operation, high degree of automation, good working environment, etc. With the increasing requirements, the vacuum heat treatment of Q345B low alloy round bar has attracted more and more attention.
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