Comparison of up ladder type and terraced type normalizing heat treatments of heavy cylinder

Abstract

Because of the mixed grain and coarse grain structure, the long heat treatment cycle and large energy conservation in the heavy cylinder heat treatment process, the up ladder type and terraced type normalizing heat treatment of heavy cylinder after rolling were put forward. The microstructure and mechanical properties of 2.25Cr1Mo0.25V steel after the up ladder type normalizing, terraced type normalizing and isothermal type normalizing were studied. Experimental results show that: 1) For the grain refinement, the twice terraced type normalizing is better than the up ladder type and isothermal type normalizing, and the average grain size is 18 μm; 2) The yield strength, tensile strength and -30 °C charpy impact energy after twice terraced type normalizing are 681 MPa, 768 MPa and 181 J, respectively, and the mechanical properties are better than those of the up ladder type and isothermal type normalizing; 3) Compared with the isothermal type normalizing, the holding time of terraced type normalizing can be shortened by 30%, which greatly reduces the energy consumption.

Keywords

heavy cylinder / terraced type normalizing / up ladder type normalizing / mechanical properties

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