Cause Analysis and Preventive Measures against Cracks in 15Cr1Mo1V Steel Welded Joint in Service

2017 ◽  
Vol 863 ◽  
pp. 328-333
Author(s):  
Wei Shi ◽  
Yi Shi Lv ◽  
Zhong Bing Chen ◽  
Ling Hui Meng ◽  
Li Jun Zhang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Stress Concentration ◽  
Welded Joint ◽  
Welding Process ◽  
Postweld Heat Treatment ◽  
Additional Stress ◽  
Heat Affect Zone ◽  
Crack Morphology ◽  
Deformation Ability ◽  
Postweld Heat

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.

Finite Element Analysis of Effects of Preheating and Postweld Heat Treatment on Residual Stress in Pipe Welding

2011 ◽  
Vol 314-316 ◽  
pp. 428-431 ◽  
Author(s):  
Hui Du ◽  
Dong Po Wang ◽  
Chun Xiu Liu ◽  
Hai Zhang
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Finite Element ◽  
Stress Distribution ◽  
Welding Process ◽  
Postweld Heat Treatment ◽  
Element Model ◽  
Element Analysis ◽  
Pipe Welding ◽  
Postweld Heat

To simulate preheating and postweld heat treatment of Q345 steel pipe welding, the finite element model was established. The welding process was simulated by method of the ANSYS element birth and death technique. In this paper, to obtain the distribution of the temperature field and stress field in different situations, preheating processes with two different values of temperature and postweld heat treatment process were simulated respectively. The results show that preheating can homogenize residual stress distribution of the weldment and decrease the residual stress. The heat treatment reduces the residual stress in inner and outer walls by 24% and 70% respectively and the stress distribution is more even and stress concentration is reduced.

A Study of Temper Bead Technique on A508 Steel Welds

2011 ◽  
Vol 295-297 ◽  
pp. 1938-1942
Author(s):  
Wei Chih Chung ◽  
Leu Wen Tsay ◽  
Chun Chen
Keyword(s):  
Heat Treatment ◽  
Heat Affected Zone ◽  
Filler Metal ◽  
Welding Process ◽  
Postweld Heat Treatment ◽  
Weld Interface ◽  
Structural Components ◽  
Time Saving ◽  
Steel Welds ◽  
Postweld Heat

The use of temper bead technique in an attempt to eliminate the conventional postweld heat treatment (PWHT) in welding of A508 steel with Alloy 52 filler metal was evaluated. A PWHT at 621°C for 24 h reduced hardness in the heat-affected zone (HAZ) of the conventional welds but led to forming a carbon-denuded zone near the weld interface. The temper bead welding process not only softened the hardness in the HAZ but also diminished the carbon-denuded zone of A508-Alloy 52 welds. Apparently, the temper bead technique provides a convenient and time- saving process for welding/repairing large structural components.

Influences of Overall and Local PWHT on Residual Stresses in the Under-Matching Welded Joints

2015 ◽  
Author(s):  
Yuwen Qian ◽  
Jianping Zhao
Keyword(s):  
Residual Stress ◽  
Welded Joint ◽  
Welding Process ◽  
Postweld Heat Treatment ◽  
Engineering Practice ◽  
Transverse Stress ◽  
Longitudinal Stress ◽  
Finite Element Software ◽  
The Common ◽  
Postweld Heat

The under-matching welded joint is commonly used in engineering practice and the postweld heat treatment (PWHT) is the common method to reduce the residual stress in the welded joint, while the research on the under-matching welded joint after PWHT is few. The finite element software-ABAQUS is used to simulate the welding process and PWHT process of the under-matching welded joint which is the combination of CF62 (base metal) and 316L (weld) in this paper. The discussion of the influences of both overall and local PWHT on the residual stress in the under-matching welded joint is based on the experimental verification. And the influences of the two methods are compared to propose the better PWHT method to the under-matching welded joint. The results show that both overall and local PWHT can reduce the residual stress in the under-matching welded joint significantly, especially the lower transverse stress than the longitudinal stress. The distribution of the residual stress in the under-matching welded joint after the local PWHT is a little more uniform than that after the overall PWHT. The local PWHT is recommended to the under-matching welded joint in this paper.

Local Postweld Heat Treatment of Heterogeneous Welded Joint

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.

scholarly journals Influence of Heat Treatment in the Microstructure of a Joint of Nodular Graphite Cast Iron when Using the Tungsten Inert Gas Welding Process with Perlitic Grey Cast Iron Rods as Filler Material

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 48
Author(s):  
Francisco-Javier Cárcel-Carrasco ◽  
Manuel Pascual-Guillamón ◽  
Fidel Salas-Vicente ◽  
Vicente Donderis-Quiles
Keyword(s):  
Heat Treatment ◽  
Cast Iron ◽  
Welding Process ◽  
Postweld Heat Treatment ◽  
Inert Gas ◽  
Graphite Cast Iron ◽  
Grey Cast ◽  
Hard Structures ◽  
Nodular Graphite ◽  
Postweld Heat

The present article analyses the influence of preheating and a postweld heat treatment in the microstructure, mechanical properties and wear behaviour of a joint of nodular graphite cast iron when using the tungsten inert gas (TIG) welding process with perlitic grey cast iron rods as filler material. Data obtained from the tests and the microstructural study of the samples show that the absence of a postweld heat treatment and of preheating leads to the apparition of hard structures and a notable reduction in elongation. Preheating or annealing the weld avoid the presence of these hard structures and increase the ductile behaviour of the joint although at the cost of a further loss of mechanical strength. Wear rate was found to be higher at the weld bead than at the base metal, even when the hardness of both areas is the same.

Effect of postweld heat treatment on interface microstructure and metallurgical properties of explosively welded bronze—carbon steel

2018 ◽  
Vol 25 (8) ◽  
pp. 1849-1861 ◽  
Author(s):  
Mohammad Reza Khanzadeh Gharahshiran ◽  
Ali Khoshakhlagh ◽  
Gholamreza Khalaj ◽  
Hamid Bakhtiari ◽  
Ali Reza Banihashemi
Keyword(s):  
Heat Treatment ◽  
Carbon Steel ◽  
Postweld Heat Treatment ◽  
Interface Microstructure ◽  
Metallurgical Properties ◽  
Postweld Heat

scholarly journals Examining Stress Relaxation in a Dissimilar Metal Weld Subjected to Postweld Heat Treatment

2018 ◽  
Vol 7 (4) ◽  
pp. 20180018
Author(s):  
K. Abburi Venkata ◽  
S. Khayatzadeh ◽  
A. Achouri ◽  
J. Araujo de Oliveira ◽  
A. N. Forsey ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Stress Relaxation ◽  
Postweld Heat Treatment ◽  
Dissimilar Metal ◽  
Dissimilar Metal Weld ◽  
Postweld Heat ◽  
Metal Weld

A Method for Applying Automatic Temperature Control to the Transient Finite Element Analysis of a Pressure Vessel Undergoing Postweld Heat Treatment

2004 ◽  
Author(s):  
Michael Sciascia
Keyword(s):  
Heat Treatment ◽  
Finite Element ◽  
Boundary Conditions ◽  
Temperature Profile ◽  
Pressure Vessel ◽  
Postweld Heat Treatment ◽  
Transient Temperature ◽  
Element Analysis ◽  
Heater Power ◽  
Postweld Heat

For complex finite element problems it is often desirable to prescribe boundary conditions that are difficult to quantify. The analysis of a pressure vessel undergoing postweld heat treatment (PWHT) is an example of such a problem. The PWHT process is governed by Code rules, but the temperature and gradient requirements they impose are not sufficient to precisely describe the complete vessel temperature profile. The imposition of such a profile in the analysis results in uncertainty and errors. A suitable but difficult approach is to specify heater power instead of temperatures, letting the solver determine the temperature profile. Unfortunately, the individual heater power levels necessary to meet the Code requirements are usually not known in advance. Determining the power levels necessary is particularly difficult if a transient solution is required. A means of actively controlling the heaters during the FEA solution is requirement for this approach. A simple and adaptive control algorithm was incorporated into the FEA solver via its scripting capability. Heat flux boundary conditions (heater power) were applied instead of transient temperature boundary conditions. Heater power levels were optimized to achieve predetermined time/temperature goals as the solution proceeded. The algorithm described was successfully applied to a pressure vessel PWHT with 14 zones of control. The approach may be adapted to other problems and boundary conditions.

Sign in / Sign up

Export Citation Format

Share Document