Numerical Simulation of Local Post Weld Heat Treatment by Electric Heating Method of Pressure Equipment

2017 ◽  
Author(s):  
Liang Sun ◽  
Fang Ji ◽  
Xiaomei Wang ◽  
Guide Deng ◽  
Lei Cheng
Keyword(s):  
Numerical Simulation ◽  
Heat Treatment ◽  
Wall Temperature ◽  
Electric Heating ◽  
Post Weld Heat Treatment ◽  
Welding Residual Stress ◽  
Band Width ◽  
Butt Weld ◽  
Heating Method ◽  
Weld Heat

The local post weld heat treatment by electric heating method is widely used to eliminate welding residual stress in processes of manufacture and maintenance of pressure equipment. The key point of local post weld heat treatment is to choose a reasonable heated band width and insulated band width. But the criterions to determine the minimum heated band width and insulated band width are different according to Chinese, European and American standards, which are GB/T 30583-2014, EN 13445-4: 2009 and AWS D10.10/D10.10M :1999, respectively. Taking the local post weld heat treatment for the circumferential butt weld between two thick cylinders both with a 115 mm thickness as an example, numerical simulation is used to compare the wall temperature distribution of the cylinders during the heat preservation stage when the heated band width and insulated band width are chose according to the above three standards, and the numerical simulation was verified by the tested temperature from one field experiment. The results show that the numerical calculation method can accurately predict the wall temperature of the cylinders during the local heat treatment, and the wall temperature of the surfaces on which the heaters are arranged according to the three standards all well meets the requirement of the heat treatment, but the wall temperature of the surfaces without the heaters cannot meet the temperature requirement. So double-side heating and double-side insulating are suggested to be adopted during local post weld heat treatment.

Study on Key Process Parameters of the Local Post Weld Heat Treatment by Electric Heating for the Large Thick-Walled Pressure Vessel Cylinder Butt Weld

2019 ◽  
Author(s):  
Fang Ji ◽  
Guide Deng ◽  
Liang Sun ◽  
Cenfan Liu ◽  
Xiaonan Zhao
Keyword(s):  
Heat Treatment ◽  
Pressure Vessel ◽  
Electric Heating ◽  
Post Weld Heat Treatment ◽  
Cylinder Wall ◽  
Cylinder Pressure ◽  
Butt Weld ◽  
Exterior Surface ◽  
Butt Welds ◽  
Weld Heat

Abstract The local post weld heat treatment for pressure vessel cylinder butt circumferential weld performed by resistance heating a shielded band around the entire circumference. The width of heated band must be large enough to ensure that the temperature of the weld, heat-effect zone and a portion of base metal adjacent to the weld should meet the requirement given in the standards. When the diameter of pressure vessel cylinder is enough large to allow the installation of heater and thermal insulation on the inner surface of wall, the circumferential butt weld heated simultaneously on interior and exterior surface of cylinder wall is more energy economical. However, GB/T 30583-2014 don’t provide the recommended width of heated band for the local post weld heat treatment performed by heating simultaneously on the inner and outer surface of cylindrical wall when the wall thickness is large than 50mm. So numerical simulation was carried out to study the effect of the width of heated band on the soak band temperature distribution when the local post weld heat treatment for cylinder pressure vessel with the thickness rang of 60mm∼100mm performed by heating simultaneously on interior and exterior surface in this paper. The results show that the widths of heated band should be not less than six times thickness when post weld heat treatment for cylinder pressure vessel butt welds whose thickness is 60mm∼70mm with a diameter of 2000 mm performed by heating simultaneously on interior and exterior surface and the widths of heated band should be not less than five times thickness when post weld heat treatment for cylinder pressure vessel butt welds whose thickness is 70mm∼100mm.

Experimental and Numerical Investigation of Heated Band Width for Local Post Weld Heat Treatment of ASME P92 Steel Pipe

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Lianyong Xu ◽  
Yi Miao ◽  
Hongyang Jing ◽  
Yongdian Han ◽  
Yunjian Jiang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Parametric Design ◽  
Large Diameter ◽  
Post Weld Heat Treatment ◽  
Band Width ◽  
The Finite Element Method ◽  
P92 Steel ◽  
Gradient Control ◽  
Large Diameter Pipes ◽  
Weld Heat

Local post weld heat treatment (local PWHT) is usually carried out when it is impractical to place the entire component in a furnace or oven, which is an effective way to relax residual stress due to welding. However, there are various international codes or standards that define different criteria for local PWHT and it may bring confusion in engineering applications. In the present study, welding and local PWHT experiments on ASME SA-335 Grade P92 large-diameter pipes were conducted under field conditions. In order to simulate the temperature field distribution of welded joints during the process of local PWHT, a thermal tracking program has been successfully developed using the ansys parametric design language (APDL) and the numerical results agree well with experimental data. Furthermore, a series of pipe models were developed using the finite element method (FEM) and through repeated calculations, optimized numerical values for each pipe's heated band (HB) width and gradient control band (GCB) width were calculated. Through numerical analysis, recommended estimation of heated band width for local PWHT of P92 large-diameter pipes is obtained, which ensures the minimum temperature throughout the soak band.

Comparative Study on Different National Standards for Local Post Weld Heat Treatment of Pressure Vessels

2020 ◽  
Author(s):  
Fang Ji ◽  
Guide Deng ◽  
Linlin Duan ◽  
Cenfan Liu ◽  
Xiaonan Zhao
Keyword(s):  
Heat Treatment ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Temperature Difference ◽  
Pressure Vessel ◽  
Post Weld Heat Treatment ◽  
National Standards ◽  
Butt Weld ◽  
Axial Temperature ◽  
Weld Heat

Abstract In order to eliminate these welding residual stress which produced in the process of pressure vessel manufacturing and assembling, post-weld heat treatment is required for the weld structure. The Large size and complex structure pressure vessel which cannot integral post-welding heat treatment always implement local post-welding heat treatment. The reasonable heated band and insulated band are particularly important in the procedures of local post-welding heat treatment to meet the requirements of pressure vessel heat treatment. The recommended heated band and insulated band are given in different national standards. But the recommended width of heated band and insulated band are different in different national standards. In the paper, numerical simulation was carried out to compare and study the difference of temperature distribution in the holding temperature period when post-welding heat treatment of pressure vessel barrel butt weld. The result show that the temperature distribution on sock band is very closed when the barrel butt weld implements post weld heat treatment with the heated and insulated band recommended in ASME BPVC-VIII-2017 and EN 13445-4:2014. The axial temperature gradient on sock band is very small and the temperature difference almost comes from the temperature difference through the thickness. Compared with this, the axial temperature gradient is larger and the temperature difference through thickness is smaller when post weld heat treatment with the max recommended heated and insulated band given in GB/T 30583-2014.

scholarly journals Effect of Post-Weld Heat Treatment Conditions on Mechanical Properties, Microstructures and Nonductile Fracture Behavior of SA508 Gr.1a Thick Weldments

2021 ◽  
Author(s):  
Junsang Lee ◽  
Jong Sung Kim ◽  
Bongsang Lee ◽  
Sungwoo Cho ◽  
Dongil Kwon ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Residual Stress ◽  
Arc Welding ◽  
Post Weld Heat Treatment ◽  
Operating Conditions ◽  
Bend Test ◽  
Welding Residual Stress ◽  
Uniaxial Tensile ◽  
Weld Heat

AbstractThis study analyzes the effects of post-weld heat treatment (PWHT) on the mechanical properties and microstructures of SA-508 Gr.1a welds and proposes a new PWHT exemption criterion based on nonductile fracture evaluation considering welding residual stress. The welding coupons were prepared with submerged-arc welding, gas-tungsten arc welding, and shielded-metal arc welding, using ferritic steel, SA-508 Gr.1a. The microstructure of the heat-affected zone (HAZ) was analyzed using optical microscopy, electron-back-scatter diffraction and Vickers hardness testing. The mechanical properties of the welds were evaluated by uniaxial tensile test, transverse side bend test, Charpy V-notch impact test and side bend test. Bainite and ferrite structures formed mainly in the HAZ, and the grain size became coarser with proximity to the surface and fusion line. The mechanical properties did not depend strongly on PWHT, weldment thickness or welding techniques, and they satisfied the welding procedure qualification test specified in the ASME Boiler & Pressure Vessel code. Welding residual stresses were considered in assessing structural integrity using nonductile fracture evaluation. A margin of safety against nonductile fracture with residual stress was calculated for Korean Standard Nuclear Power Plant steam-generator welds, using its design parameters and operating conditions, and this safety margin is suggested as an acceptance criterion for residual stress for exemption from PWHT. Graphic abstract

scholarly journals An Economical and Mechanical Investigation on Local Post-Weld Heat Treatment for Stiffened Steel Plates in Bridge Structures

2021 ◽  
Vol 2 (4) ◽  
pp. 714-727
Author(s):  
Mikihito Hirohata ◽  
Shuhei Nozawa ◽  
Károly Jármai
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
High Energy ◽  
Post Weld Heat Treatment ◽  
Welding Residual Stress ◽  
Steel Plates ◽  
Bridge Structures ◽  
Long Time ◽  
Mechanical Investigation ◽  
Weld Heat

A heat treatment is effective for reducing the residual stress of the welded structures. A post-weld heat treatment (PWHT) requires a large heating apparatus (furnace). It requires a high energy, a long time, and a high cost. For examining the possibility of cost and energy saving in PWHT work, an economical and mechanical investigation of the local PWHT to stiffened plate members in steel bridges was conducted. The expense of apparatus for the furnace PWHT was 1.5 times higher than that of local PWHT by sheet-type ceramic heaters. When the number of heater units was reduced and were repeatedly used, the expense for the apparatus became lower. However, it took longer to complete the heat treatment than with the furnace PWHT or the local PWHT with full heater units. The thermal elastic-plastic finite element (FE) analysis examined the effect of local PWHT. The tendency of the stress distribution after the local PWHT differed from the welding residual stress or the stress after the furnace PWHT because of the temperature difference between the heated and the non-heated parts of the local PWHT. However, the effect of residual stress relief by the local PWHT could be almost the same as that of the furnace PWHT.

Relaxation of Exemption Requirement of PWHT for SA-508 Grade 1A, by Consideration Surface Welding Residual Stress As Evaluated by Instrumented Indentation Testing Method

2017 ◽  
Author(s):  
Jong-hyoung Kim ◽  
Jun Sang Lee ◽  
Sungki Choi ◽  
Jong-sung Kim ◽  
Dongil Kwon
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Residual Stress ◽  
Power Plants ◽  
Mechanical Tests ◽  
Pressure Vessels ◽  
Post Weld Heat Treatment ◽  
Welding Residual Stress ◽  
Acceptance Criterion ◽  
Weld Heat

Generally, post-weld heat treatment is applied to decrease welding residual stress and improve the mechanical properties and microstructure of weldment, and its performance has been recommended for many years [1, 2]. However, current steel-making technology has improved significantly and, steel toughness levels have generally improved substantially [1]. Additionally for several quenched and tempered steels, it is reported that in some cases, mechanical properties such as tensile strength and impact toughness are degraded after post-weld heat treatment [3]. In addition, for large steel assemblies, post-weld heat treatment can be expensive, so that there is an economic incentive to avoid post-weld heat treatment [2]. The research presented here suggests a way to exempt post-weld heat treatment for SA-508 Grade 1A material, which is used for pressure vessels in nuclear power plants, by considering both mechanical properties and residual stress to simplify the welding procedure. Weldments made of 120 mm thick SA-508 Grade 1A should be post-weld heat treated, according to current ASME BPV Code. In order to increase the PWHT exemption thickness to 120 mm, we performed mechanical tests using welding coupons without PWHT; the test results satisfied current mechanical property criteria. We present a residual stress acceptance criterion based on brittle fracture criteria in this research.

Evaluation of Cracking Behavior of SPV50Q High Strength Steel Weldment in Wet H2S Containing Environment

2005 ◽  
Vol 297-300 ◽  
pp. 951-957 ◽  
Author(s):  
Jian Ming Gong ◽  
Jian Qun Tang ◽  
Xian Chen Zhang ◽  
Shan Tung Tu
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
High Strength Steel ◽  
High Strength ◽  
Post Weld Heat Treatment ◽  
Welding Residual Stress ◽  
Cracking Behavior ◽  
Steel Weldment ◽  
Hydrogen Induced Cracking ◽  
Weld Heat

JIS-SPV50Q high strength steel is often employed in construction of liquid petroleum gas (LPG) spherical tanks due to its high strength and good ductility. In general, post weld heat treatment is not performed after welding of SPV50Q high strength steel and welding residual stress will be retained in weldment. Service experience and inspection indicate that higher H2S concentration and welding residual stress result in the environmental failure, such as blistering or hydrogen induced cracking (HIC), sulfide stress corrosion cracking (SSCC) and stress oriented hydrogen induced cracking (SOHIC). In the present paper, the cracking behavior of SPV50Q high strength steel weldment by manual electric arc welding has been investigated in various saturate solutions with different concentrations of H2S. The results of slow strain rate testing, performed at a strain of 1×10-6s-1, reveal the presence of SSCC and HIC in the base metal adjacent to HAZ. The ffects of the different temperatures of post weld heat treatment on cracking are discussed. The suitable post weld heat treatment could increase the resistance of SPV50Q weldment on SSCC or HIC and does not decrease the mechanical properties of SPV50Q weldment.

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