Secondary Austenite Morphologies in Fusion Zone of Welded Joint after Postweld Heat Treatment with a Continuous Wave Laser

Characteristics and forming causes of the cracks in welded joint of 15Cr1Mo1V steel serviced 70000h are investigated by mechanical and chemical testing and crack morphology observation. Results show that the cracks initiate from welded metal or coarse grain heat affect zone (CGHAZ) near fusion line, and there are three kinds of defects observed in the crack region, which are macrocracks, microcracks and voids. According to the forming position, process and morphology of the cracks, it is estimated that the cracks are a kind of stress relief crack (SRC). The main reasons of the cracking are because of residual stress caused by improper temperature field during post welding heat treatment, strong stress concentration caused by welding structure, additional stress caused by abnormal hangers & supports and decreased ductility of welded joint in service. The SRC in welded joint can be avoided through optimizing the welding process and postweld heat treatment(PWHT) process to ensure enough critical ductility deformation ability εc and avoiding and reducing stress concentration and additional stress to decrease ductility deformation εP of welded joint which make εc>εp consistently.

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Surface quality, microstructure, mechanical properties and tribological results of the SKD 61 tool steel with prior heat treatment affected by the deposited energy of continuous wave laser micro-polishing

Journal of Materials Processing Technology ◽

10.1016/j.jmatprotec.2016.03.024 ◽

2016 ◽

Vol 234 ◽

pp. 177-194 ◽

Cited By ~ 7

Author(s):

Chang-Shuo Chang ◽

Chen-Kuei Chung ◽

Jen-Fin Lin

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Surface Quality ◽

Tool Steel ◽

Continuous Wave ◽

Continuous Wave Laser ◽

Prior Heat Treatment ◽

Deposited Energy ◽

Wave Laser

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Surface quality, microstructure, and mechanical properties of the SKD 61 tool steel with prior heat treatment affected by single- and double-pass continuous wave laser polishing

The International Journal of Advanced Manufacturing Technology ◽

10.1007/s00170-017-0264-7 ◽

2017 ◽

Vol 92 (5-8) ◽

pp. 1643-1658 ◽

Cited By ~ 4

Author(s):

Chang-Shuo Chang ◽

Kai-Shiang Yang ◽

Chen-Kuei Chung ◽

Jen-Fin Lin

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Surface Quality ◽

Tool Steel ◽

Continuous Wave ◽

Continuous Wave Laser ◽

Double Pass ◽

Laser Polishing ◽

Prior Heat Treatment ◽

Wave Laser

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Local Postweld Heat Treatment of Heterogeneous Welded Joint

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.730.259 ◽

2017 ◽

Vol 730 ◽

pp. 259-264

Author(s):

Zhong Bing Chen ◽

Zhi Qiang Sun ◽

Yi Shi Lv

Keyword(s):

Thermal Conductivity ◽

Heat Treatment ◽

Temperature Field ◽

Welded Joint ◽

Postweld Heat Treatment ◽

Compensation Method ◽

Longitudinal Temperature ◽

Postweld Heat ◽

Longitudinal Thermal Conductivity ◽

Temperature Area

A concept of heterogeneous welded joint is proposed for researching and describing the characteristics of local postweld heat treatment (PWHT) temperature field for asymmetric thermal conductivity welded joint. Its three types have been classified according to thermal conductivity direction around the weld, separately, welded joint with transverse unidirectional thermal conductivity, transverse bidirectional thermal conductivity, transverse and longitudinal thermal conductivity. Compared with the temperature field of symmetric thermal conductivity welded joint, the highest temperature point of heterogeneous welded joint deviates from the heat device center, and uniform temperature area shrinks. In addition, longitudinal temperature difference and dramatic temperature change zone have arisen for the third type heterogeneous welded joint. In order to improve the temperature distribution, two PWHT methods called temperature compensation method and power compensation method have been put forward and developed. Several engineering applications of two methods are illustrated as examples.

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