Effect of 580 °C (20 h) Heat Treatment on Mechanical Properties of 25Cr2NiMo1V Rotor-Welded Joints of Oscillating Arc (MAG) Narrow Gap Thick Steel.

Xiaoyan Qian,Zhishui Yu,Xiaoqi Hou,Fuxin Wang,Xin Ye,Chen Huang,Chunxiang Zhu,Shanglei Yang,Jinpeng Cui,Shaowei Li

doi:10.3390/ma14164498

Abstract

The thick plate narrow gap welding of 25Cr2NiMo1V rotor steel is achieved by metal active gas arc welding, in which the weld gap was 18.04–19.9 mm. After welding, the weldment was heat treated at 580 °C (20 h). The impact and tensile properties in the as-welded and heat-treated were studied. The results show that after heat treatment, the coarse carbides in the center of the weld were transformed into fine granular carbides distributed along the grain boundaries, and the quantity of carbide precipitates in the weld near the fusion line was reduced. The tensile fracture mode changed from a ductile fracture to a combination of brittle and ductile fractures, and the tensile strength of the weld metal changed from 605 MPa to 543 MPa. After heat-treated, the radiation zone of the weld center changed from a brittle fracture to a combination of brittle and ductile fractures, and the impact energy changed from 141 J to 183 J; the characteristics of the brittle fracture in the radial zone of the fusion line were more obvious, and the impact energy changed from 113 J to 95 J. Therefore, after heat treatment, the toughness of the welded metal was improved, without reducing the strength and hardness of the welded metal to a large extent.

Highlights

Due to the rapid development of society, the demand for electricity is steadily increasing, resulting in a large quantity of emissions of carbon dioxide and other gases, and worsening environmental pollution
To study the mechanical properties of the welded metal after heat treatment, the tensile and impact properties were measured at room temperature to evaluate the tensile
Treatment, study the effect of tensile heat treatment the tensile properties, the temperature tensile properties ofthe the and impact on properties were measured at room to evaluate tensile strength and toughness of the welded metal

Summary

Introduction

Due to the rapid development of society, the demand for electricity is steadily increasing, resulting in a large quantity of emissions of carbon dioxide and other gases, and worsening environmental pollution. Power generation technology needs to be improved to increase energy utilization and reduce environmental pollution. Improving its performance is an important requirement for enabling supercritical power generation technology. Chu et al [8] studied the welded joints of NiCrMoV steel and found that the small grains in WM can withstand the crack driving force, reduce stress concentration, and increase the resistance to transgranular crack propagation. To further increase the productivity of rotor steel welding and improve its mechanical properties, arc narrow gap welding is widely used. Narrow gap arc welding uses fewer consumables and reduces deformation. It has been widely used in medium and thick steel plates. It is an effective method for welding rotor steel [15,16]

Methods

Results

Conclusion