Post weld heat treatment (PWHT) reduced the hardness in the heat affected zone (HAZ) to below 250 VHN, solving the HAZ hardness issue. However, PWHT caused carbon to diffuse to the fusion boundary, increasing the hardness there. Bead sequence one (BS1) welds had higher hardness values and were more susceptible to lack of fusion defects than bead sequence three (BS3) welds in all material combinations tested. The base steel 8630 also had higher hardness than F22 steel in all combinations, even after PWHT.
A review of effect of welding and post weld heat treatment on microstructure ...eSAT Journals
Abstract
Today getting high thermal efficiency in thermal and nuclear power plant is a big challenge. Many new material are developed. SA 335 grade 91 steel is modified high chrome-moly martenstitic steel. This material is having excellent toughness and high temperature creep strength. During welding, this material is having tremendous change in its microstructure and hence mechanical property. Many research works were done in this area. This paper discusses weld ability of P91 material. Effect of different welding process, type of filler wire, its chemical composition and type of flux is discussed in this paper. PWHT is necessary after welding of P91 steel. PWHT temperature and its duration affects phase transformation and mechanical properties of weld metal, HAZ and parent metal. Major focus is given on hardness, creep resistance and notch toughness.
Keywords - P91, Welding, Microstructure, Toughness, Creep, Hardness, PWHT
A review of effect of welding and post weld heat treatment on microstructure ...eSAT Journals
Abstract
Today getting high thermal efficiency in thermal and nuclear power plant is a big challenge. Many new material are developed. SA 335 grade 91 steel is modified high chrome-moly martenstitic steel. This material is having excellent toughness and high temperature creep strength. During welding, this material is having tremendous change in its microstructure and hence mechanical property. Many research works were done in this area. This paper discusses weld ability of P91 material. Effect of different welding process, type of filler wire, its chemical composition and type of flux is discussed in this paper. PWHT is necessary after welding of P91 steel. PWHT temperature and its duration affects phase transformation and mechanical properties of weld metal, HAZ and parent metal. Major focus is given on hardness, creep resistance and notch toughness.
Keywords - P91, Welding, Microstructure, Toughness, Creep, Hardness, PWHT
The Effect of Coating and Potting on the Reliability of QFN DevicesCheryl Tulkoff
The lack of a compliant lead structure makes QFN devices more susceptible to PCB warpage related failures:
oMechanical properties of the potting material
oGlass transition temperature (Tg)
oModulus should be specified above and below the Tg
oCTE should be specified above and below the Tg
The design of the housing:
oMay provide a surface to which the potting material can pull against when shrinking causing PCB warpage
oShould be designed to provide as close to a hydrostatic pressure as possible (equal pressure on all sides)
Hardening is a process of heating a metal above its upper critical temperature and quenched in water,oil,and salt solutions. In this material is heated because the heated materials are some of the precipitants to inside them
Project presentation on fixture design for eliminating key hole defectSubed Satyal
This project presentation includes the introduction of Friction stir welding along the pipe's circumference and the pipe is made of Aluminum alloy because it is suitable for friction stir welding. It also includes literature review regarding the key hole defect & its elimination. A brief methodology which is adopted for eliminating this defect is also mentioned. The final parts includes introduction, consequences & proposed method to eliminate key hole defect by using sacrificial material. A especially designed fixture is used to clamp the sacrificial material which is manually slides in a cross slide to connect pipe along the weld line with the sacrificial material's curved surface.
With pressures up to 6000 psig (413 bar), the new
Swagelok® FX Series 321 stainless steel braided hose is
suitable for a wide range of requirements. The convoluted
core allows for flexibility and limits kinking. Available with
a wide variety of end connections, it is commonly used in
a high-temperature vacuum or in cases where permeation
and corrosion are undesirable. The FX hose is specifically
designed for high-pressure applications in:
The Effect of Coating and Potting on the Reliability of QFN DevicesCheryl Tulkoff
The lack of a compliant lead structure makes QFN devices more susceptible to PCB warpage related failures:
oMechanical properties of the potting material
oGlass transition temperature (Tg)
oModulus should be specified above and below the Tg
oCTE should be specified above and below the Tg
The design of the housing:
oMay provide a surface to which the potting material can pull against when shrinking causing PCB warpage
oShould be designed to provide as close to a hydrostatic pressure as possible (equal pressure on all sides)
Hardening is a process of heating a metal above its upper critical temperature and quenched in water,oil,and salt solutions. In this material is heated because the heated materials are some of the precipitants to inside them
Project presentation on fixture design for eliminating key hole defectSubed Satyal
This project presentation includes the introduction of Friction stir welding along the pipe's circumference and the pipe is made of Aluminum alloy because it is suitable for friction stir welding. It also includes literature review regarding the key hole defect & its elimination. A brief methodology which is adopted for eliminating this defect is also mentioned. The final parts includes introduction, consequences & proposed method to eliminate key hole defect by using sacrificial material. A especially designed fixture is used to clamp the sacrificial material which is manually slides in a cross slide to connect pipe along the weld line with the sacrificial material's curved surface.
With pressures up to 6000 psig (413 bar), the new
Swagelok® FX Series 321 stainless steel braided hose is
suitable for a wide range of requirements. The convoluted
core allows for flexibility and limits kinking. Available with
a wide variety of end connections, it is commonly used in
a high-temperature vacuum or in cases where permeation
and corrosion are undesirable. The FX hose is specifically
designed for high-pressure applications in:
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International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
International Journal of Engineering Research and DevelopmentIJERD Editor
Electrical, Electronics and Computer Engineering,
Information Engineering and Technology,
Mechanical, Industrial and Manufacturing Engineering,
Automation and Mechatronics Engineering,
Material and Chemical Engineering,
Civil and Architecture Engineering,
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Aerospace Engineering.
The Certified Welding Inspector (CWI) plays an important role during any welded construction activities ensuring the required specifications and standards are followed. Due to the numerous materials and processes associated with metal joining (welding) THIS PRESENTATION SHALL SHOW ONLY THE BASIC WELDING PROCESSES AND EXAMINATION METHODS (NDE). National and International Codes and Specifications along with measuring devices are the Inspector’s tools. Hopefully the following presentation shall give an insight into basic welding inspection.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
1. IN625
Steel
PWHT F22 BS1
7
Objectives
• Verify the success of the post weld heat treatment (PWHT) at lowering
the hardness of the heat affected zone (HAZ) to meet NACE
requirements (< 250 VHN).
• Explore the effect of different substrates and weld bead sequences.
Results: Micro-Hardness Maps
Methods
• Eight hot-wire gas tungsten arc welded (GTAW) overlays were
prepared as they would be for subsea service.
• Samples were cut from the DMW interface (red boxes in 2 & 3),
mounted and prepared for optical microscopy.
• Chromic acid was used as the etchant for the 625 Nickel based alloy,
and 10% nital was used to etch the base steel forging.
• After pictures were taken and analyzed, the etchant was polished off
and Micro hardness maps were done over the interface.
• From the hardness data, hardness distribution by value graphs were
made to display the hardness trends across the DMW interface.
• PWHT
• Solved the HAZ hardness issue (from 370 VHN to 250 VHN)
• Caused carbon migration to the fusion boundary raising the hardness
(from 300 VHN to 450 VHN)
• The base metal hardness may have been lowered below an
expectable amount (from 270 VHN to 170 VHN)
• Substrate
• 8630 HAZ had higher hardness than F22 in all combinations (~25
VHN higher)
• BS (Bead sequence)
• BS1 has higher hardness values than BS3 in all material combinations
• BS1 was more susceptible to LOF defects
There have been several failures of Dissimilar metal welded
(DMW) pipes in subsea service. These DMW pipe joints are typically
done in three steps. First a multi-pass butter layer (of Inconel 625) is
added to both of the joint faces in one of two ways; in bead sequence
one (BS1) welds are layered normal to the fusion boundary, in bead
sequence three (BS3) welds are layered parallel to the fusion boundary.
The base forgings (either F22 or 8630 steel) are then post-weld heat
treated (PWHT) to temper the heat affected zone (HAZ). Finally a closure
weld is completed in the field using the same welding consumable as in
the buttering layer.
The butter layer applied is thick enough such that the HAZ of the
closure weld does not reach the base metal, and thus not critically
hardening the base forging.
Subsea pipes are cathodically protected to prevent corrosion. While
this keeps the pipes from rusting it also evolves atomic hydrogen at the
surface of the pipes and leads to hydrogen ingress into the pipes. The
failures mentioned earlier have been attributed to high hardness and this
buildup of hydrogen in the DMW fusion zone.
Acknowledgements
0%
1%
2%
3%
4%
5%
6%
7%
8%
150 250 350 450
PercentofIndents
Hardness (VHN)
8630 BS1
8630 BS3
0%
1%
2%
3%
4%
5%
6%
150 250 350 450
PercentofIndents
Hardness (VHN)
F22 BS1
F22 BS3
0%
1%
2%
3%
4%
5%
6%
7%
8%
150 250 350 450
PercentofIndents
Hardness (VHN)
PWHT 8630 BS1
PWHT 8630 BS3
0%
1%
2%
3%
4%
5%
6%
7%
8%
150 250 350 450
PercentofIndents
Hardness (VHN)
PWHT F22 BS1
PWHT F22 BS3
IN625
SteelF22 BS3
PWHT 8630 BS1 PWHT F22 BS1
Post weld heat treated (PWHT)
reduced the hardness in the heat
affected zone (HAZ) (4 & 5).
PWHT caused carbon to diffuse
to the fusion boundary which
increased the hardness there (6).
PWHT lowered
the hardness
of the base
metal to below
250 VHN (4 &
6). 8630 had
higher
hardness than
F22 in all
combinations
(4 & 6).
Schematic of a DMW joint
625
BS3
625
BS1
625
Steel
Steel
Step One
Final Step
IN625
SteelPWHT 8630 BS1
Results: Hardness Distribution by value Graphs
Bead sequence one (BS1) was harder and hence more brittle in all
material combinations than bead sequence three (BS3).
Results: Visual inspection
Bead sequence one (BS1)
produces lack of fusion (LOF)
defects at the dissimilar metal
weld (DMW) interface in all
material combinations.
Conclusion
Introduction