共查询到20条相似文献,搜索用时 31 毫秒
1.
Guang-Jun Cai Hans-Olof Andrén Lars-Erik Svensson 《Metallurgical and Materials Transactions A》1997,28(7):1417-1428
The microstructure of three 12 pct cr steel weld metals with different nickel and nitrogen contents was studied in as-welded
condition and after postweld heat treatment with and without intercooling. Tensile strength and impact toughness of the weld
metals were investigated in different postweld heat treatment conditions. In weld metals heat treated without intercooling,
austenite decomposed by a eutectoid reaction that resulted in M23C6 aggregates around retained δ-ferrite. Two morphologies of M2N and MN precipitates were found in a low-dislocation α-ferrite. It was concluded that these phases were also transformed from austenite. In weld metals heat treated with intercooling,
M23C6 precipitates were smaller and more homogeneously distributed. Different MN precipitates were found in the tempered martensite.
The fracture mode of the weld metals at room temperature was mainly transgranular cleavage with some fibrous fracture. Intercooling
treatment improved Charpy impact toughness of the 12 pct Cr steel weld metals substantially. It was found that the important
microstructural factors affecting the impact toughness of the weld metals which were heat treated without intercooling were
the sizes of the α-ferrite grains, nonmetallic inclusions, and M23C6 aggregates. For the weld metals heat treated with intercooling, the factors which affect the toughness of the weld metals
were the sizes of martensite packets and nonmetallic inclusions. 相似文献
2.
V. Maduraimuthu M. Vasudevan V. Muthupandi A. K. Bhaduri T. Jayakumar 《Metallurgical and Materials Transactions B》2012,43(1):123-132
A novel variant of tungsten inert gas (TIG) welding called activated-TIG (A-TIG) welding, which uses a thin layer of activated
flux coating applied on the joint area prior to welding, is known to enhance the depth of penetration during autogenous TIG
welding and overcomes the limitation associated with TIG welding of modified 9Cr-1Mo steels. Therefore, it is necessary to
develop a specific activated flux for enhancing the depth of penetration during autogeneous TIG welding of modified 9Cr-1Mo
steel. In the current work, activated flux composition is optimized to achieve 6 mm depth of penetration in single-pass TIG
welding at minimum heat input possible. Then square butt weld joints are made for 6-mm-thick and 10-mm-thick plates using
the optimized flux. The effect of flux on the microstructure, mechanical properties, and residual stresses of the A-TIG weld
joint is studied by comparing it with that of the weld joints made by conventional multipass TIG welding process using matching
filler wire. Welded microstructure in the A-TIG weld joint is coarser because of the higher peak temperature in A-TIG welding
process compared with that of multipass TIG weld joint made by a conventional TIG welding process. Transverse strength properties
of the modified 9Cr-1Mo steel weld produced by A-TIG welding exceeded the minimum specified strength values of the base materials.
The average toughness values of A-TIG weld joints are lower compared with that of the base metal and multipass weld joints
due to the presence of δ-ferrite and inclusions in the weld metal caused by the flux. Compressive residual stresses are observed in the fusion zone
of A-TIG weld joint, whereas tensile residual stresses are observed in the multipass TIG weld joint. 相似文献
3.
P. Vasantharaja M. Vasudevan V. Maduraimuthu 《Transactions of the Indian Institute of Metals》2018,71(1):127-137
The present study aims at understanding the effect of various arc welding processes on the evolution of microstructure, mechanical properties, residual stresses and distortion in 9 mm thick type 316LN austenitic stainless steel weld joints. Weld joints of type 316LN stainless steel were fabricated by three different arc welding processes which were commonly employed in the nuclear industry. All the weld joints passed radiographic examination. Microstructural characterization was done using optical and scanning electron microscope. Volume fraction of δ-ferrite was lowest in the A-TIG weld joint. The A-TIG welded joint exhibited adequate strength and maximum impact toughness values in comparison to that of weld joints made by SMAW and FCAW processes. The A-TIG weld joint was found to exhibit lowest residual stresses and distortion compared to that of other welding processes. This was attributed to lower weld metal volume and hence reduced shrinkage in the A-TIG weld joint compared to that of weld joints made by FCAW and SMAW processes which involved v-groove with filler metal addition. Therefore, type 316LN stainless steel A-TIG weld joint consisting of lower δ-ferrite, adequate strength, high impact toughness, lower residual stresses and distortion was suited better for elevated temperature service compared to that of SMAW and FCAW weld joints. 相似文献
4.
P. K. Ghosh S. R. Gupta H. S. Randhawa 《Metallurgical and Materials Transactions A》2000,31(9):2247-2259
The performance of the pulsed-current gas metal arc welding (GMAW) process for vertical-up weld deposition of steel has been
found to be superior over the use of the short-circuiting arc GMAW process with respect to the tensile, impact, and fatigue
properties of the weld joint. The microstructure, weld geometry, and mechanical properties of a pulsed-current weld joint
are largely governed by the pulse parameters, and correlate well to the factor φ, defined as a summarized influence of pulse parameters such as peak current, base current, pulse-off time, and pulse frequency.
The increase of φ has been found favorable to refine the microstructure and enhance the tensile strength, C
v
toughness, and fatigue life of a weld joint. The fatigue life of a short-circuiting arc weld joint has been found to be markedly
reduced due to the presence of an undercut at the weld toe and incomplete side-wall fusion of the base material. 相似文献
5.
The grain structure of the weld metal can significantly affect its resistance to solidification cracking during welding and
its mechanical properties after welding. An experimental study was conducted to investigate the effect of two basic welding
parameters,i.e., the heat input and the welding speed, on the grain structure of aluminum-alloy welds. Gas-tungsten arc welding was performed
under various heat inputs and welding speeds, with thermal measurements in the weld pool being carried out during welding
and the amounts and nuclei of equiaxed grains in the resultant welds being examined using optical and electron microscopy.
The experimentally measuredG/R ratios and the clearly revealed heterogeneous nuclei together demonstrated the thermodynamic effect of the heat input and
welding speed on the weld metal grain structure. 相似文献
6.
7.
M. J. Perricone J. N. Dupont T. D. Anderson C. V. Robino J. R. Michael 《Metallurgical and Materials Transactions A》2011,42(3):700-716
A series of 31 Mo-bearing stainless steel compositions with Mo contents ranging from 0 to 10 wt pct and exhibiting primary
δ-ferrite solidification were analyzed over a range of laser welding conditions to evaluate the effect of composition and cooling
rate on the solid-state transformation to γ-austenite. Alloys exhibiting this microstructural development sequence are of particular interest to the welding community
because of their reduced susceptibility to solidification cracking and the potential reduction of microsegregation (which
can affect corrosion resistance), all while harnessing the high toughness of γ-austenite. Alloys were created using the arc button melting process, and laser welds were prepared on each alloy at constant
power and travel speeds ranging from 4.2 to 42 mm/s. The cooling rates of these processes were estimated to range from 10 K
(°C)/s for arc buttons to 105 K (°C)/s for the fastest laser welds. No shift in solidification mode from primary δ-ferrite to primary γ-austenite was observed in the range of compositions or welding conditions studied. Metastable microstructural features were
observed in many laser weld fusion zones, as well as a massive transformation from δ-ferrite to γ-austenite. Evidence of epitaxial massive growth without nucleation was also found when intercellular γ-austenite was already present from a solidification reaction. The resulting single-phase γ-austenite in both cases exhibited a homogenous distribution of Mo, Cr, Ni, and Fe at nominal levels. 相似文献
8.
Laser beam welding generally does without the use of filler metal, in contrast to conventional welding processes. The use of filler metal in laser beam welding or in the combined GMA (g as-m etal-a rc) - laser beam - hybrid welding process widens the field of application for laser beam welding. The main advantages worthy of mention include, primarily, a greater weld gap bridging ability and a metallurgical influence on the weld metal. Based on the current state of knowledge, this article gives a few examples of different materials and material combinations the limited weldability of which is broadened when filler metal is used with laser beam welding. Listed as examples are low-alloy steels with partly elevated carbon contents, duplex steels, and the material combinations of steel/cast iron and austenite-ferrite joints. Besides laser beam welding with filler metal wire, examples of the combined GMA-laser hybrid welding process are also described. 相似文献
9.
Wei Dong Hiroyuki Kokawa Yutaka S. Sato Susumu Tsukamoto 《Metallurgical and Materials Transactions B》2005,36(5):677-681
Nitrogen desorption by high-nitrogen steels (HNSs) containing 0.32 and 0.53 pct nitrogen during CO2 laser welding in an Ar-N2 gas mixture was investigated and the obtained data were compared with those for arc welding and at the equilibrium state
predicted by Sieverts’ Law. Although the nitrogen content in the weld metal during CO2 laser welding was lower than that in the as-received base material in all conditions, the nitrogen desorption was larger
in the top part of the weld metal than in the keyhole region. The nitrogen desorption in the Ar atmosphere was less during
CO2 laser welding than during arc welding. With the increase in nitrogen partial pressure, the nitrogen content in the weld metal
sharply increased during arc welding, but only slightly increased during CO2 laser welding. The nitrogen absorption and desorption of the HNS weld metal were much smaller during CO2 laser welding than during arc welding. 相似文献
10.
Liangyun Lan Xiangwei Kong Zhiyuan Chang Chunlin Qiu Dewen Zhao 《Metallurgical and Materials Transactions A》2017,48(9):4140-4153
This paper analyzed the evolution of microstructure, composition, and impact toughness across the fusion line of high-strength bainitic steel weldments with different heat inputs. The main purpose was to develop a convenient method to evaluate the HAZ toughness quickly. The compositions of HAZ were insensitive to higher contents of alloy elements (e.g., Ni, Mo) in the weld metal because their diffusion distance is very short into the HAZ. The weld metal contained predominantly acicular ferrite at any a heat input, whereas the main microstructures in the HAZ changed from lath martensite/bainite to upper bainite with the increasing heat input. The evolution of HAZ toughness in relation to microstructural changes can be revealed clearly combined with the impact load curve and fracture morphology, although the results of impact tests do not show an obvious change with heat input because the position of Charpy V notch contains the weld metal, HAZ as well as a part of base metal. As a result, based on the bead-on-plate welding tests, the welding parameter affecting the HAZ toughness can be evaluated rapidly. 相似文献
11.
Mathematical models capable of accurate prediction of the weld bead and weld pool geometry in gas metal arc (GMA) welding
processes would be valuable for rapid development of welding procedures and empirical equations for control algorithms in
automated welding applications. This article introduces a three-dimensional (3-D) model for heat and fluid flow in a moving
GMA weld pool. The model takes the mass, momentum, and heat transfer of filler metal droplets into consideration and quantitatively
analyzes their effects on the weld bead shape and weld pool geometry. The algorithm for calculating the weld reinforcement
and weld pool surface deformation has been proved to be effective. Difficulties associated with the irregular shape of the
weld bead and weld pool surface have been successfully overcome by adopting a boundary-fitted nonorthogonal coordinate system.
It is found that the size and profile of the weld pool are strongly influenced by the volume of molten wire, impact of droplets,
and heat content of droplets. Good agreement is demonstrated between predicted weld dimensions and experimently measured ones
for bead-on-plate GMA welds on mild steel plate. 相似文献
12.
The effect of oxygen content on the susceptibility of high-strength weld metal to hydrogen cracking is examined. Increasing
oxygen content had a detrimental effect on the cracking susceptibility of weld metal containing a dψusible hydrogen content
of 4.7 ppm. In weld metal containing a much lower dψusible hydrogen content (0.87 ppm), increasing weld metal oxygen content
had no detrimental effect on hydrogen cracking susceptibility. These results are explained by a model which proposes that
hydrogen cracking occurs when a critical oxide inclusion density promotes intergranular fracture at prior austenite grain
boundaries and when a critical level of hydrogen is present in the weld metal. For the same level of hydrogen (moisture) contamination,
high-strength weld metals containing oxygen contents greater than 200 ppm will be much more susceptible to hydrogen cracking
than deposits made using inert gas-shielded or vacuum-operated welding processes.
Formerly Visiting Scientist, Department of Metallurgy and Materials Science, University of Toronto 相似文献
13.
The effect of oxygen content on the susceptibility of high-strength weld metal to hydrogen cracking is examined. Increasing
oxygen content had a detrimental effect on the cracking susceptibility of weld metal containing a dψusible hydrogen content
of 4.7 ppm. In weld metal containing a much lower dψusible hydrogen content (0.87 ppm), increasing weld metal oxygen content
had no detrimental effect on hydrogen cracking susceptibility. These results are explained by a model which proposes that
hydrogen cracking occurs when a critical oxide inclusion density promotes intergranular fracture at prior austenite grain
boundaries and when a critical level of hydrogen is present in the weld metal. For the same level of hydrogen (moisture) contamination,
high-strength weld metals containing oxygen contents greater than 200 ppm will be much more susceptible to hydrogen cracking
than deposits made using inert gas-shielded or vacuum-operated welding processes.
Formerly Visiting Scientist, Department of Metallurgy and Materials Science, University of Toronto 相似文献
14.
John W. Elmer Joe Wong Thorsten Ressler 《Metallurgical and Materials Transactions A》2001,32(5):1175-1187
Phase transformations that occur in the heat-affected zone (HAZ) of gas tungsten arc welds in AISI 1005 carbon-manganese steel
were investigated using spatially resolved X-ray diffraction (SRXRD) at the Stanford Synchrotron Radiation Laboratory. In situ SRXRD experiments were performed to probe the phases present in the HAZ during welding of cylindrical steel bars. These real-time
observations of the phases present in the HAZ were used to construct a phase transformation map that identifies five principal
phase regions between the liquid weld pool and the unaffected base metal: (1) α-ferrite that is undergoing annealing, recrystallization, and/or grain growth at subcritical temperatures, (2) partially transformed
α-ferrite co-existing with γ-austenite at intercritical temperatures, (3) single-phase γ-austenite at austenitizing temperatures, (4) δ-ferrite at temperatures near the liquidus temperature, and (5) back transformed α-ferrite co-existing with residual austenite at subcritical temperatures behind the weld. The SRXRD experimental results were
combined with a heat flow model of the weld to investigate transformation kinetics under both positive and negative temperature
gradients in the HAZ. Results show that the transformation from ferrite to austenite on heating requires 3 seconds and 158°C
of superheat to attain completion under a heating rate of 102°C/s. The reverse transformation from austenite to ferrite on
cooling was shown to require 3.3 seconds at a cooling rate of 45 °C/s to transform the majority of the austenite back to ferrite;
however, some residual austenite was observed in the microstructure as far as 17 mm behind the weld. 相似文献
15.
Manidipto Mukherjee Tapan Kumar Pal 《Metallurgical and Materials Transactions A》2012,43(6):1791-1808
This article describes in detail the effect of the modes of metal transfer on the microstructure and mechanical properties
of gas metal arc-welded modified ferritic stainless steel (SSP 409M) sheets (as received) of 4 mm thickness. The welded joints
were prepared under three modes of metal transfer, i.e., short-circuit (SC), spray (S), transfer, and mix (M) mode transfer using two different austenitic filler wires (308L and
316L) and shielding gas composition of Ar + 5 pct CO2. The welded joints were evaluated by means of microstructural, hardness, notched tensile strength, Charpy impact toughness,
and high cycle fatigue. The dependence of weld metal microstructure on modes of metal transfer and filler wires has been determined
by dilution calculation, WRC-1992 diagram, Creq/Nieq ratio, stacking fault energy (SFE), optical microscopy (OM), and transmission electron microscopy (TEM). It was observed
that the microstructure as well as the tensile, Charpy impact, and high cycle fatigue of weld metal is significantly affected
by the mode of metal transfer and filler wire used. However, the heat-affected zone (HAZ) is affected only by the modes of
metal transfer. The results have been correlated with the microstructures of weld and HAZ developed under different modes
of metal transfer. 相似文献
16.
The use of high-power density laser beam for welding of many important alloys often leads to appreciable changes in the composition
and properties of the weld metal. The main difficulties in the estimation of laser-induced vaporization rates and the resulting
composition changes are the determination of the vapor condensation rates and the incorporation of the effect of the welding
plasma in suppressing vaporization rates. In this article, a model is presented to predict the weld metal composition change
during laser welding. The velocity and temperature fields in the weld pool are simulated through numerical solution of the
Navier-Stokes equation and the equation of conservation of energy. The computed temperature fields are coupled with ve-locity
distribution functions of the vapor molecules and the equations of conservation of mass, momentum, and the translational kinetic
energy in the gas phase for the calculation of the evap-oration and the condensation rates. Results of carefully controlled
physical modeling experi-ments are utilized to include the effect of plasma on the metal vaporization rate. The predicted
area of cross section and the rates of vaporization are then used to compute the resulting com-position change. The calculated
vaporization rates and the weld metal composition change for the welding of high-manganese 201 stainless steels are found
to be in fair agreement with the corresponding experimental results. 相似文献
17.
The effect of heat input and hydrogen partial pressure of the TIG process without filler wire and of restraining conditions in the IRC test on hydrogen induced cracking have been investigated for weld metals of StE 380, 15 NiCrMo 10 6 (HY 80) and 12 Ni 19. The weld metals are fused from the roots of the plate materials exclusively. The continuously measured combined nominal stresses transverse to the welds are strongly dependent on transformation stress release prior to cold cracking of the respective weld metals. Higher restraints are increasing nominal stresses. Critical heat inputs for prevention of hydrogen weld metal cracking are increased with restraint, hydrogen potentials and carbon contents of the weld metal, 12 Ni 19 revealing no fracture. 相似文献
18.
Abdel-Monem El-Batahgy 《国际钢铁研究》1994,65(12):551-555
Controlled thermal severity (CTS) test which simulates the conditions in a single-pass fillet welding was carried out to determine the suitable minimum preheating temperature for the cold-crack-free welding of high strength steel ASTM A 516-70. The dependence of this minimum preheating temperature on diffusible hydrogen contents in weld metal was clarified. Then, the effect of climatic conditions on cold cracking susceptibility as a function of diffusible hydrogen contents in weld metal was studied. It is found that the cold cracking susceptibility of high strength steel is primarily related to the microsturcture of the HAZ which, in turn, is related to the preheating temperature. A lower preheating level, which resulted in harder microstructure, led to increased susceptibility. Suitable minimum preheating temperature required to prevent cold cracking increased with the increase in diffusible hydrogen contents of weld metal as a function of climatic conditions. 相似文献
19.
R. W. Davies G. J. Grant M. A. Khaleel M. T. Smith H. Eddie Oliver 《Metallurgical and Materials Transactions A》2001,32(2):275-283
The current work develops forming-limit diagrams (FLDs) for weld materials in aluminum tailorwelded blanks (TWBs) under biaxial
stretching conditions. Aluminum TWBs consist of multiple-thickness and alloy sheet materials welded together into a single,
variable-thickness blank. The manufacture of TWBs and their application in automotive body panels requires their constituent
weld material to deform under biaxial loading during sheet-metal stamping. The weld geometry is typically nonuniform and relatively
small, causing difficulty if one attempts to determine the weld metal FLDs via traditional experimental methods. The subject work primarily relies on theoretical FLD calculation techniques using the Marciniak
and Kuczynski (M-K) method. This numerical technique requires the use of material constants and levels of initial material
imperfection that have been experimentally determined using unique miniature tensile specimens to isolate and characterize
the weld metal. The experimental and numerical work, together with statistical analysis of the level of initial imperfection,
allows generation of both an average and safe FLD. The weld metals studied in this work were produced via autogeneous gas tungsten arc welding of a 1- to 2-mm-thick 5000 series aluminum alloy sheet. 相似文献
20.
Microstructural Evolution of Inconel 625 and Inconel 686CPT Weld Metal for Clad Carbon Steel Linepipe Joints: A Comparator Study 总被引:1,自引:0,他引:1
Charles A. Maltin Alexander M. Galloway Martin Mweemba 《Metallurgical and Materials Transactions A》2014,45(8):3519-3532
Microstructural evolution of Inconel 625 and Inconel 686CPT filler metals, used for the fusion welding of clad carbon steel linepipe, has been investigated and compared. The effects of iron dilution from the linepipe parent material on the elemental segregation potential of the filler metal chemistry have been considered. The results obtained provide significant evidence to support the view that, in Inconel 686CPT weld metal, the segregation of tungsten is a function of the level of iron dilution from the parent material. The data presented indicate that the incoherent phase precipitated in the Inconel 686CPT weld metal has a morphology that is dependent on tungsten enrichment and, therefore, iron dilution. Furthermore, in the same weld metal, a continuous network of finer precipitates was observed. The Charpy impact toughness of each filler metal was evaluated, and the results highlighted the superior impact toughness of the Inconel 625 weld metal over that of Inconel 686CPT. 相似文献