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Microstructure Transformation in the Welding Heat Affected Zone of 800MPa Grade Ultra Fine Structured Steel

J.B. Liu , L.J. Hu , Y.T. Wang , Z.Q. Liu , K. Miao , Z.L. Tian

金属学报(英文版)

The transformation behavior and microstructure development in the heat affected zone (HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found that the HAZ has intermediate temperature transformation characteristics in a wide range of cooling rates, with the bainite sheaves consisting of bainite ferrite plates without carbide precipitation and retained austenite in the fast cooling regime. At relatively high cooling rates, which corresponded to low heat inputs, the hardness of the simulated HAZ was above that of the base metal. When the cooling rate was below 9±C/s, the welding HAZ would have an obvious softening. The analysis of transformation rates in continuous cooling processes was completed by numerical differential method. The result indicated that the microstructure transformation rate of the HAZ in 800MPa grade ultra fine structured steel changed sharply to slow speeds when the cooling time t8=5 is longer than 7s.

关键词: ultra fine structured steel , null , null , null , null

STUDY ON PTA CLAD (Cr,Fe)7C3 /γ-Fe CERAMAL COMPOSITE COATING

J.B. Liu , J.H. Huang , L.M. Wang

金属学报(英文版)

A wear resistant (Cr,Fe)7C3 /γ-Fe ceramal composite coating was fabricated on substrate of a 0.45%C carbon steel by plasma transferred arc (PTA) cladding process using the Fe-Cr-C elemental powder blends. The microstructure, microhardness and dry sliding wear resistance of the coating were evaluated. Results indicate that the plasma transferred arc clad ceramal composite coating has a rapidly solidified microstructure consisting of blocky primary (Cr,Fe)7C3 and the inter- blocky (Cr,Fe)7C3 /γ-Fe eutectics and is metallurgically bonded to the 0.45%C carbon steel substrate. The ceramal composite coating has high hardness and excellent wear resistance under dry sliding wear test condition.

关键词: plasma transferred arc (PTA) cladding , null , null , null

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