Evaluation of Fracture Toughness for P355NH Steel Subjected to Thermal Cycles Simulation

2015 ◽  
Vol 1111 ◽  
pp. 193-198
Author(s):  
Sergiu Valentin Galaţanu ◽  
Doru Romulus Pascu ◽  
Nicolae Faur
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Welded Joints ◽  
Thermal Cycle ◽  
Pressure Vessels ◽  
Thermal Cycles ◽  
Butt Welding ◽  
Cycle Simulation ◽  
Complex Equipment ◽  
The Impact

The thermal cycles simulator of welding is a complex equipment that reproduces in a specimen thermal cycles of the type caused in the HAZ by welding processes.In this paper, it is presented a comparison between the results obtained by welded joints and thermal cycle simulator specimens, from the material P355NH of 22 mm thickness for pressure vessels. Two types of thermal cycle simulator specimens were used: one specimen without post-simulation heat treatment and one specimen with post-simulation heat treatment.For the welded specimens Mn3Ni1CrMo filler material was used.This paper offers information about the impact energy of specific areas of the welded joints, both for butt welding and thermal cycle simulator specimens.A good correlation was observed between the results of thermal cycle simulation with post-simulation heat treatment and the results obtained by welding.

Analysis of Simulated Welding Thermal Cycles S700MC Using Thermal Imaging Camera

2013 ◽  
Vol 837 ◽  
pp. 375-380 ◽  
Author(s):  
Jacek Górka
Keyword(s):  
Impact Strength ◽  
Thermal Cycle ◽  
Carbon Equivalent ◽  
Aluminium Content ◽  
Thermal Cycles ◽  
Resistive Heating ◽  
Separation Processes ◽  
Cycle Simulation ◽  
Precise Knowledge ◽  
The Impact

In this paper an influence of simulated thermal cycle on properties and HAZ structure of 10 mm thick S700MC steel plates. The introduction of thermomechanically processed steels with high yield and relatively low carbon equivalent, will significantly reduce the time of welding works by reducing the preheating temperature, or even complete removal of this processing step, furthermore reduction of cross-sectional areas of structural elements, making welded structures with the same capacity will be more slender and lighter. The simulation of thermal cycles was carried out on a specially built test stand equipped with resistive heating source infrared camera VarioCam Head HR with 50 mm lens and a computer with software IRBIS 3 plus. Simulation was prepared for simple and complex thermal cycle. Simulation studies of thermal cycles consisted of resistive heating of samples prepared for the impact test. Single thermal cycles were simulated at temperatures ranging from 400 to 1300 oC, 100 oC and the cycle complex. For each temperature three repeats were carried out. Specimens were tested on impact, strength test and also hardness and metallographical tests. The study showed that there is a possibility to use a purpose built system to simulate simple and complex thermal cycles of S700 MC steel in specific ranges of the cooling time t8/5. Analysis of the results of the study showed that the welding thermal cycle strongly influences the structural changes and phase in the HAZ zone of S700 MC steel. Areas of HAZ heated to high temperatures above 1000 [°C], show a sudden drop of toughness to unacceptable levels of impact strength (27 [J/cm2]). This sharp decrease in toughness is associated with uncontrolled separation processes of MX phases and dissolution of carbides, niobium and vanadium carbonitrides in austenite during heating. The study also showed that the chemical composition of steel and especially titanium and aluminium content is sufficient to bind in the HAZ free nitrogen and reduce the aging process. The control of the amount of heat introduced into the joint area during welding will reduce the adverse separation processes in the weld and HAZ which will ensure adequate toughness of the connection. Precise knowledge of the phenomena occurring in the HAZ during the thermal cycle can impact the ability to control properties and structure of the welded joint.

Fracture Toughness After Long-Term Aging in 9Cr-1Mo-V Steel for Pressure Vessels

2014 ◽  
Author(s):  
Takeo Miyamura ◽  
Shigenobu Nanba ◽  
Tomoaki Nakanishi ◽  
Masato Yamada
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Aging Time ◽  
Charpy Impact ◽  
Pressure Vessels ◽  
High Temperature Strength ◽  
Boiler Tube ◽  
Treatment Conditions ◽  
The Impact

9Cr-1Mo-V steel with excellent high temperature strength is one of candidate materials for advanced pressure vessels in oil-refining plants, whose process temperature is expected to be around 500°C. Although 9Cr-1Mo-V steel has been applied as boiler tube material in power generation for a few decades, it was reported that embrittlement occurred after long-term aging around 600°C which is accelerated condition for pressure vessel operation. Since pressure vessels are more sensitive in stress-concentration around crack tip than boiler tube because of its large wall thickness, fracture toughness is an important property of concern when 9Cr-1Mo-V steel is applied to pressure vessels. In this research, 9Cr-1Mo-V steel with tempered-martensitic microstructure was aged up to max. 10000 hr at 500, 550 and 600°C, and fracture toughness was evaluated after the aging by Charpy impact test. The influence of heat treatment conditions such as austenitizing, tempering and PWHT were also investigated, because the heat treatment conditions used in pressure vessels are different from those of boiler tube. In case of samples treated under the conditions for pressure vessels, Charpy impact values at 0°C were sufficient around 200J before aging, and decreased after aging depending on its conditions, and longer time and higher temperature led to more severe degradation. When the aging time at 550°C and 600°C was converted to the equivalent aging time at 500°C by Larson-Miller-equation, the impact value was estimated to keep over 50J after several decades at the operating temperature for pressure vessels. In contrast to the conditions for pressure vessels, the heat treatment conditions used in boiler tube made initial impact value decreased significantly, because tempering and PWHT were shorter than those of pressure vessels. Therefore, the samples heat treated under boiler tube conditions showed lower impact values around 50J in the earlier stage of aging. Considering all obtained results, it was suggested that the serious degradation of fracture toughness in 9Cr-1Mo-V after long term aging would not occur in actual service time for pressure vessels.

Variations in Fracture Toughness for Alloy 718 Given a Modified Heat Treatment

1990 ◽  
Vol 112 (1) ◽  
pp. 116-123 ◽  
Author(s):  
W. J. Mills ◽  
L. D. Blackburn
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Fracture Mechanisms ◽  
Alloy 718 ◽  
Percent Confidence Level ◽  
Heat Treated ◽  
Curve Method ◽  
Heat Treated Condition ◽  
The Impact ◽  
Product Forms

Heat-to-heat and product-form variations in the JIC fracture toughness for Alloy 718 were characterized at 24, 427, and 538°C using the multiple-specimen JR-curve method. Six different material heats along with three product forms from one of the heats were tested in the modified heat treated condition. This heat treatment was developed at Idaho National Engineering Laboratory to improve the impact toughness for Alloy 718 weldments, but it has also been found to enhance the fracture resistance for the base metal. Statistical analysis of test results revealed four distinguishable JIC levels with mean toughness levels ranging from 87 to 190 kJ/m2 at 24°C. At 538°C, JIC values were 15 to 20 percent lower than room temperature toughness levels. Minimum expected values of JIC (ranging from 72 kJ/m2 at 24°C to 48 kJ/m2 at 538°C) and dJR/da (27 MPa at 24 to 538°C) were established based on tolerance intervals bracketing 90 percent of the lowest JIC and dJR/da populations at a 95 percent confidence level. Metallographic and fractographic examinations were performed to relate key microstructural features and operative fracture mechanisms to macroscopic properties.

scholarly journals Test of fatigue crack growth in welded specimens subjected to bending

2018 ◽  
Vol 67 (1) ◽  
pp. 185-196
Author(s):  
Janusz Lewandowski ◽  
Dariusz Rozumek ◽  
Maria Hepner
Keyword(s):  
Heat Treatment ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Welded Joints ◽  
Stress Ratio ◽  
Fatigue Cracks ◽  
Test Results ◽  
The Impact ◽  
Constant Moment

The paper presents the test results on the fatigue crack growth under cyclic bending specimens at constant moment amplitude made of S355 steel with fillet welds. Plane specimens with stress concentrators in form of the external two-sided blunt notches were tested. The tests were performed under constant value of the stress ratio R = –1 without and after heat treatment. The article also presents the test results of the microstructure of welded joints taking into account changes in the material after heat treatment and the impact of these changes on the fatigue life of specimens. Keywords: welded joints, fatigue cracks length, number of cycle, bending, microstructure

Effect of PWHT on the Mechanical Properties of P5 Steel Welded Joints

2010 ◽  
Vol 165 ◽  
pp. 104-109 ◽  
Author(s):  
Vigantas Kumšlytis ◽  
Algirdas Vaclovas Valiulis ◽  
Olegas Černašejus
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Welded Joints ◽  
Operational Reliability ◽  
Heat Treated ◽  
Molybdenum Steel ◽  
Key Issues ◽  
Optimum Heat ◽  
Property Changes ◽  
The Impact

Presented work analyses the impact of heat treatment parameters on the mechanical properties and operational reliability of P5 (5%Cr0.5%Mo) steel welded joints. The key objects of research are heat-treated chrome-molybdenum steel welded joints and piping elements operated at high temperature for an extensive period of time, where degradation of mechanical properties has been observed. The main objective is to investigate the causes of degradation of alloy steel mechanical properties during fabrication and operation of the equipment, and to develop a methodology for identification of optimum heat treatment parameters for chrome-molybdenum steel welded joints. A few key issues are addressed herein: identification of dependence of chrome-molybdenum (5%Cr-0.5%Mo) steel welded joint mechanical properties on heat treatment parameters, identification of the optimum value of temperature/time parameter, and identification of causes of mechanical property changes and degradation of the steel.

Applicability of the ASME Exemption Curve for Chinese Pressure Vessel Steel Q345R

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Qingfeng Cui ◽  
Hu Hui ◽  
PeiNing Li
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Impact Test ◽  
Pressure Vessels ◽  
Uniaxial Tensile ◽  
Assessment Procedure ◽  
Pressure Vessel Steel ◽  
Fracture Toughness Test ◽  
Vessel Steel ◽  
The Impact

Q345R steel is the most commonly used material in fabrication of the pressure vessels and boilers in China, due to its excellent properties. In 2010, ASME code case 2642 accepted Q345R steel for use in construction of pressure vessels. The code case specified impact test exemption curve A for the impact test requirements for Q345R. However, this provision severely limits the application of this material at low temperature, since most of the minimum design metal temperature (MDMT) of curve A is above the freezing point. In this paper, a series of tests (such as uniaxial tensile test, impact test, and fracture toughness test) were carried out at low temperature to investigate the mechanical properties of Q345R steel plates with thickness of 36–80 mm. This study of low temperature usage of Q345R steel was conducted using the fracture mechanics assessment procedure of API 579-1/ASME FFS-1. The fracture toughness is given by master curve (MC) method in the transition regime. The results show that Q345R can be used at lower temperature and that classifying Q345R steel into curve D is appropriate.

Brittle Fracture Prevention Model for Pressure Based on Master Curve Approach

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
QingFeng Cui ◽  
Hu Hui ◽  
PeiNing Li ◽  
Feng Wang
Keyword(s):  
Fracture Toughness ◽  
Brittle Fracture ◽  
Impact Toughness ◽  
Pressure Vessel ◽  
Master Curve ◽  
Fracture Prevention ◽  
Pressure Vessels ◽  
New Model ◽  
Prevention Model ◽  
The Impact

The brittle fracture prevention model is of great importance to the safety of pressure vessels. Compared to the semi-empirical approach adopted in various pressure vessel standards, a model based on Master Curve technique is developed in this paper. Referring to ASME nuclear code, the safety features including the lower bound fracture toughness and a margin factor equal to 2 for the stress intensity factor produced by primary stress are adopted in the new model. The technical background of the brittle fracture model in ASME VIII-2 has been analyzed and discussed, and then its inappropriate items have been modified in the new model. Minimum design temperature curves, impact toughness requirements, and temperature adjustment for low stress condition are established on the basis of new model. The comparison with the relevant curves in ASME VIII-2 is also made. The applicability of the new model is verified by the measured fracture toughness and impact toughness data of several kinds of pressure vessel steels. The results suggest that the minimum design temperature and the impact test requirements derived by the new model are compatible with each other. More testing data of different steels to check this model is necessary for further engineering application.

Impact of Heat Treatment on the Structure and Properties of the QE22 Alloy Welded Joints

2012 ◽  
Vol 191 ◽  
pp. 183-188
Author(s):  
Agata Kierzek ◽  
Janusz Adamiec
Keyword(s):  
Heat Treatment ◽  
Welded Joints ◽  
Creep Resistance ◽  
Welded Joint ◽  
Casting Process ◽  
Structure And Properties ◽  
Cast Magnesium Alloy ◽  
The One ◽  
Cast Magnesium ◽  
The Impact

The QE22 cast magnesium alloy containing silver, rare earth elements and zirconium is characterized by high mechanical properties and creep resistance of up to 200 ° C. It is cast gravitationally into sand moulds and permanent moulds. After the casting process any possible defects appearing in the cast are repaired with the application of welding techniques. The repaired cast should possess at least the same properties as the one which does not require any repairs. The aim of this thesis was to determine the impact of the heat treatment on the microstructure of the QE22 alloy welded joint. The creep resistance of the welded joints was also analyzed.

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