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1.
Trapping of hydrogen by sulfur-associated defects in steel 总被引:1,自引:0,他引:1
M. Iino 《Metallurgical and Materials Transactions A》1985,16(3):401-409
Reversible and irreversible trapping behaviors of sulfur-associated defects in steel were studied through electrochemical
hydrogen permeation experiments and the results were analyzed to obtain the follow-ing information: an apparent diffusion
constant of hydrogen influenced by reversible and irreversible trapping by sulfur-associated defects,D *, was shown to be given as a function of sulfur content, S, in wt ppm.byD * = 1.12·10−6(1 + 0.0933S0.548)−1cm2 s−1. Associated parameters of reversible and irreversible trapping, λ/μ and k, were also expressed as a function of sulfur content,
S. Both parameters, λ/μ, and k, are shown to increase with S, suggesting an increase of both reversible and irreversible trap
sites with increase in sulfur content in steel. 相似文献
2.
S. Yu. Nastich Yu. D. Morozov V. N. Marchenko A. M. Stepashin V. V. Zyryanov O. V. Sorokolet 《Metallurgist》2005,49(5-6):189-194
Ural'skaya Stal' has developed and introduced new grade of steel 12KhGN2MA. The steel is designed for use on the frames of
quarry trucks, mining machinery, and other metal structures used at low temperatures. The steel is distinguished by its excellent
cold resistance (KCV−70 ≥ 50 J/cm2) and good weldability, and it has satisfactorily high strength and ductility (σ0.2 ≥ 690 N/mm2, δu ≥ 790 N/mm2, and δ5 ≥ 16%) after quenching and tempering. The cold-shortness threshold — corresponding to 50% ductile component in the fracture
— is below −40°C for steel 12KhGN2MA (25-mm thick plate). Alloying the steel with elements that help stabilize austenite (chromium,
nickel, molybdenum, and magnesium) ensures the formation of a martensite-bainite structure. The technology used to make the
steel provides for its refining in electric-arc furnaces, rolling of the steel on a 2800 mill, and subsequent heat treatment
of the plates in high-productivity regimes. The weldability of the steel was studied by simulating the effects of the thermal
welding cycle on the structure and properties of the metal in the near-weld zone. This metal is given good cold resistance
down to −70°C by using cooling rates corresponding to the types and regimes of welding actually used. Ural'skaya Stal' has
successfully begun production of plates of the new steel in the 10–45-mm thickness range.
__________
Translated from Metallurg, No. 5, pp. 55–58, May, 2005. 相似文献
3.
The conditions of cathodic charging, gaseous hydrogen environment, and loading for which a TRIP steel may or may not be susceptible
to hydrogen embrittlement were investigated. In the austenitic state, the TRIP steel appeared to be relatively immune to hydrogen
embrittlement. It was shown that it is the strain-induced martensitic phase, α′, which is embrittled. In TRIP steel single-edge-notch specimens under fixed loads in gaseous hydrogen, slow crack growth
occurs when the stress intensity level exceeds a threshold level of about 25 ksi-in.1/2 and the growth rate varies approximately as the 2.5 power of the stress intensity level. The activation energy for this slow
crack growth was found to be about 10,000 cal/g-atom, the approximate activation for hydrogen diffusion in martensite. Thus
it was concluded that slow crack growth in TRIP steel loaded in gaseous hydrogen involves the diffusion of hydrogen through
the α′ phase.
Formerly with the Lawrence Berkeley Laboratory, Berkeley, Calif. 相似文献
4.
Hiroshi Majima Yasuhiro Awakura Keisuke Tsugui Ernest Peters 《Metallurgical and Materials Transactions B》1990,21(2):251-258
Measurements were made on the transport and equilibrium properties of dissolved chlorine in aqueous HC1, HCl-ZnCl2, HCl-MgCl2, and water. These measurements included solubility, absorption rates during bubbling, stripping rates during nitrogen bubbling,
and cathodic reduction rates. The solubility of chlorine was found to be affected by speciation into aqueous Cl2, HC1O, and C13
−. With increasing HCl concentration, the solubility of chlorine decreased to a minimum at 0.2 mol dm−3, followed by a slow and linear increase. Metal chloride salts depressed the chlorine solubility approximately in proportion
to concentration. Mass transfer of aqueous chlorine was found to support a current of about 100 A m−2 from a chlorine-saturated ZnCl2-HCl solution under typical zinc electrowinning conditions. Comparisons with published zinc electrowinning papers indicate
that air sparging would eliminate dissolved chlorine sufficiently to remove the need for diaphragm cell separation of dissolved
chlorine, insofar as current inefficiencies due to cathodic chlorine reduction are concerned. 相似文献
5.
Kensuke Miyahara Saburo Matsuoka Tohru Hayashi 《Metallurgical and Materials Transactions A》2001,32(13):761-768
A nanoindentation hardness testing system, including an atomic-force microscope (AFM)-based nanoindentation tester and a calibration
method using electrolytically polished single-crystal metals as references, was proposed. This was applied to a study of the
mechanical properties of fine-grained ferritic steel (grain size of 1.2 μm) and coarse-grained ferritic steel (30 μm). An
empirical function giving the macroscopic hardness for all four reference metals from the nanoindentation force curves was
established. The converted Vickers hardness (HV*) of the coarse-grained steel is almost independent of the indent size. The fine-grained steel shows only HV* 130 with an indent of only 100 nm, compared with a macroscopic hardness of HV 210. The difference, HV 80, is considered to
reflect the amount of grain-boundary strengthening. The critical indent size for the hardness transition seems to be around
1 μm, comparable to the grain size of the specimen. This result supports the explanation of grain-boundary strengthening.
It is also consistent with Pickering's work on low-carbon steel, as the estimated locking parameter (k of 2.6×105 N/m3/2) in the Hall-Petch relationship is in good agreement with his value of 2.4×105 N/m3/2.
TOHRU HAYASHI, Senior Researcher, formerly with the Strength and Life Evaluation Research Station, National Research Institute
for Metals. 相似文献
6.
C. Gupta J. K. Chakravartty S. Banerjee 《Metallurgical and Materials Transactions A》2010,41(13):3326-3339
A new generation nuclear reactor pressure vessel steel (CrMoV type) having compositional similarities with thick section 3Cr-Mo
class of low alloy steels and adapted for nuclear applications was investigated for various manifestations of dynamic strain
aging (DSA) using uniaxial tests. The steel investigated herein has undergone quenched and tempered treatment such that a
tempered bainite microstructure with Cr-rich carbides was formed. The scope of the uniaxial experiments included tensile tests
over a temperature range of 298 K to 873 K (25 °C to 600 °C) at two strain rates (10−3 and 10−4 s−1), as well as suitably designed transient strain rate change tests. The flow behavior displayed serrated flow, negative strain
rate sensitivity, plateau behavior of yield, negative temperature (T), and strain rate ( [(e)\dot] ) \left( {\dot{\varepsilon }} \right) dependence of flow stress over the temperature range of 523 K to 673 K (250 °C to 400 °C) and strain rate range of 5 × 10−3 s−1 to 3 × 10−6 s−1, respectively. While these trends attested to the presence of DSA, a lack of work hardening and near negligible impairment
of ductility point to the fact that manifestations of embrittling features of DSA were significantly enervated in the new
generation pressure vessel steel. In order to provide a mechanistic understanding of these unique combinations of manifestations
of DSA in the steel, a new approach for evaluation of responsible solutes from strain rate change tests was adopted. From
these experiments and calculation of activation energy by application of vacancy-based models, the solutes responsible for
DSA were identified as carbon/nitrogen. The lack of embrittling features of DSA in the steel was rationalized as being due
to the beneficial effects arising from the presence of dynamic recovery effects, presence of alloy carbides in the tempered
bainitic structure, and formation of solute clusters, all of which hinder the possibilities for strong aging of dislocations. 相似文献
7.
Xue-Min Yang Meng Zhang Cheng-Bin Shi Guo-Ming Chai Jian Zhang 《Metallurgical and Materials Transactions B》2012,43(2):241-266
A sulfide capacity prediction model of CaO-SiO2-MgO-FeO-MnO-Al2O3 ladle furnace (LF) refining slags has been developed based on the ion and molecule coexistence theory (IMCT). The predicted
sulfide capacity of the LF refining slags has better accuracy than the measured sulfide capacity of the slags at the middle
and final stages during the LF refining process. Increasing slag binary basicity, optical basicity, and the Mannesmann index
can lead to an increase of the predicted sulfide capacity for the LF refining slags as well as to an increase of the sulfur
distribution ratio between the slags and molten steel at the middle and final stages during the LF refining process. The calculated
equilibrium mole numbers, mass action concentrations of structural units or ion couples, rather than mass percentages of components,
are recommended to represent the slag composition for correlating with the sulfide capacity of the slags. The developed sulfide
capacity IMCT model can calculate not only the total sulfide capacity of the slags but also the respective sulfide capacity
of free CaO, MgO, FeO, and MnO in the slags. The comprehensive contribution of the combined ion couples (Ca2+ + O2−) and (Mn2+ + O2−) on the desulfurization reactions accounts for 96.23 pct; meanwhile, the average contribution of the ion couple (Fe2+ + O2−) and (Mg2+ + O2−) only has a negligible contribution as 3.13 pct and 0.25 pct during the LF refining process, respectively. The oxygen activity
of bulk molten steel in LF is controlled by the [Al]–[O] equilibrium, and the oxygen activity of molten steel at the slag–metal
interface is controlled by the (FeO)–[O] equilibrium. The ratio of the oxygen activity of molten steel at the slag–metal interface
to the oxygen activity of bulk molten steel will decrease from 37 to 5 at the initial stage, and further decrease from 28
to 4 at the middle stage, but will maintain at a reliable constant as 5 to 14 at the final stage during the LF refining process.
The proposed high-oxygen potential layer of molten steel beneath the slag–metal interface can be quantitatively verified. 相似文献
8.
In view of the potential of plain carbon dual phase (DP) steel as wear resistant material, the wear and friction characteristics
of this steel, which consists of hard martensite islands embedded in a ductile ferrite matrix, have been investigated and
compared with those observed in plain carbon normalized (N) steel that has the same composition of 0.14 wt pct carbon. Dry
sliding wear tests have been carried out using a pin-on-disk wear testing machine at normal loads of 14.7, 24.5, and 34.3
N and at a constant sliding velocity of 1.15 m/s. Weight loss in the samples has been measured over time on the same specimen,
and the variation of cumulative wear loss with sliding distance has been described by two linear segments, for both the DP
and the N steel. At these loads, the mechanism of wear is primarily oxidative, although subsurface cracking and delamination
wear could also be observed in a few places. The second linear segment could result from a dynamic steady state wear of the
transfer layer of compacted oxide wear debris on the sliding surfaces. The wear rate calculated on the basis of the first
linear segment varies linearly with normal load, which is indicative of Archard’s law, and it is significantly lower for the
DP steel than for the N steel. The wear rate calculated on the basis of the second linear segment, however, varies with load
linearly for the DP steel but nonlinearly in the N steel. In the first linear segment, the wear coefficient is about 0.39
× 10−4 for the DP steel and is 0.40 × 10−4 for the N steel. Higher hardness and, consequently, a lower real area of contact in the DP steel at all the loads have compensated
for the lower wear rates, and have resulted in a wear coefficient similar to that in the N steel. The steady state wear coefficient
from the second linear segment is 0.29 × 10−4 for the DP steel at all loads; for the N steel, these are 0.21 × 10−4 and 0.64 × 10−4, respectively, for lower and higher loads. 相似文献
9.
The diffusion current of hydrogen through palladium in an electrochemical cell initially rises linearly with the charging
current, reaches a steady “plateau” value, and then rises again. The diffusivity of hydrogen in palladium was measured using
standard transient techniques in the initial region of low current density. Combining this value with the measured value of
diffusion current at the plateau level gave a concentration of hydrogen at the entrance surface of the palladium that was
the same for three different palladium thicknesses, and was equal to the saturation value in α palladium. It is proposed that
this can be used as a known and reproducible effective hydrogen pressure (0.019 atm) if palladium is plated onto other metals
before measuring their permeability in an electrochemical cell. Experimental evidence for this was obtained from permeability
measurements made on several thicknesses of iron. Permeation studies were also made on AISI 410 stainless steel and tin plated
mild steel. The measured value for electrolytic tinplate was 107 times that expected from extrapolation of high temperature data. This could be attributed to grain boundaries or porosity
covering 0.003 pct of the area. The permeability values of iron and stainless steel are 8.4 x 1012 and 2.8 x 1013 H atom/cm • s • √atm, respectively.
Former Postdoctorate Fellow at McMaster University 相似文献
10.
Yoshiyuki Tomita 《Metallurgical and Materials Transactions A》1990,21(10):2739-2746
Commercial and low-sulfur 4340 steels have been studied to determine the effect of calcium treatment on modifying the morphology
of nonmetallic inclusions and plane-strain fracture toughness (K
IC
) of the ultrahigh-strength, low-alloy steels at commercial heat level. The significant conclusions are as follows: (1) for
the low-sulfur 4340 steel, the addition of calcium in the molten steel gave rise to the formation of finely distributed, spherical,
calcium-sulfide (CaS) inclusions with a mean diameter of 1.3 μm; (2) in comparing the calcium-modified 4340 steel with commercial
4340 steel, the calcium-modified steel not only had an improvedK
IC
by about 25 MPa•m1/2 in the longitudinal (L) orientation and by about 30 MPa • m1/2 in the transverse (T) orientation, but also had increased fracture ductility and Charpy impact energy at similar strength
levels; and (3) for the commercial 4340 steel, the calcium treatment was not very effective in modifying the morphology of
the inclusions on improving the mechanical properties of the steel. The beneficial effect of calcium modification coupled
with low sulfur content on theK
Ic
is briefly discussed in terms of a crack extension model involving the formation of voids at the inclusion sites and their
growth and eventual linking-up through the rupture of the intervening ligaments by localized shear. 相似文献
11.
Thermal effects during uniaxial straining of steels 总被引:3,自引:0,他引:3
When metals are deformed, most of the strain energy absorbed is converted to heat resulting in a temperature increase. Such
temperature increases could affect mechanical properties during forming operations and were studied during rapid uniaxial
tensile straining at strain rates of 3 x 103 and 10–2
s–1 in a dual phase steel, a high strength low alloy (HSLA) steel, and a plain carbon steel, using an infrared thermometer. The
maximum temperatures observed were directly related to the strain energy absorbed, as measured by the area under the stress-strain
curve. The dual phase steel absorbed the largest amount of strain energy and therefore registered the largest temperature
increase. However, the observed temperature increases were lower than those predicted by calculations assuming adiabatic heating,
indicating that such heating did not occur at the strain rates studied. 相似文献
12.
Large strain mechanical behavior of 1018 cold-rolled steel over a wide range of strain rates 总被引:1,自引:0,他引:1
M. Vural G. Ravichandran D. Rittel 《Metallurgical and Materials Transactions A》2003,34(12):2873-2885
The large-strain constitutive behavior of cold-rolled 1018 steel has been characterized at strain rates ranging from
to 5 × 104 s−1 using a newly developed shear compression specimen (SCS). The SCS technique allows for a seamless characterization of the
constitutive behavior of materials over a large range of strain rates. The comparison of results with those obtained by cylindrical
specimens shows an excellent correlation up to strain rates of 104 s−1. The study also shows a marked strain rate sensitivity of the steel at rates exceeding 100 s−1. With increasing strain rate, the apparent average strain hardening of the material decreases and becomes negative at rates
exceeding 5000 s−1. This observation corroborates recent results obtained in torsion tests, while the strain softening was not clearly observed
during dynamic compression of cylindrical specimens. A possible evolution scheme for shear localization is discussed, based
on the detailed characterization of deformed microstructures. The Johnson-Cook constitutive model has been modified to represent
the experimental data over a wide range of strain rates as well as to include heat-transfer effects, and model parameters
have been determined for 1018 cold-rolled steel. 相似文献
13.
Hideya Anzai Jiro Kuniya Isao Masaoka 《Metallurgical and Materials Transactions A》1992,23(4):1291-1298
In this report, hydrogen-assisted cracking (HAC) behavior of low-alloy steel was evaluated using a constant elongation rate
tensile test, and the temperature and crack tip strain rate effects were observed. It was found that temperature dependence
of the threshold condition (C
σm
c
) of HAC above about 100 °C followed the relation C
σm
c
= Kexp(−41,300/Rr) whereK is a constant andT is absolute temperature. The relationship between HAC growth rate and crack tip strain rate was established as almost linear,
irrespective of temperature and hydrogen concentration at the crack tip. Hydrogen heat release tests were also performed.
From these tests, formation and growth of microcracks which are trap sites of hydrogen were thought to be the mechanism of
HAC in the steel. From this mechanism, HAC behavior of the low-alloy steel could be qualitatively explained. 相似文献
14.
H. E. Biber R. C. Takacs A. E. Dickey 《Metallurgical and Materials Transactions B》1983,14(3):369-373
The way in which heating in hydrogen-nitrogen atmosphere affects the pyrolysis of the residual lubricant on cold-reduced steel
sheet was studied to discover the factors responsible for the formation of carbonaceous films on the steel surface. These
films, referred to as insoluble surface carbon, cannot be removed with the usual solvents or water-base cleaners and adversely
affect the paintability of the steel. A surprising result was the observation that the full-hard steel surface has a significant
amount of insoluble surface carbon; amounts in excess of 0.010 gm/m2 (1 mg/ft2) were observed. The origin of this “initial” insoluble carbon can be traced to the pickling operation after hot rolling.
During annealing much of the residual rolling lubricant on the surface is driven off by evaporation, but concurrently insoluble
pyrolysis products are formed. The amount of insoluble pyrolysis product formed is directly related to the amount of “initial”
insoluble carbon on the surface before annealing. The results show that at some point during annealing the total amount of
insoluble carbon on the surface is more than double the amount of “initial” insoluble carbon. These insoluble pyrolysis products
can also be driven from the surface at higher temperatures than are required for evaporation of the oil. The results suggest
that removal of the “initial” insoluble carbon prior to cold reduction might be very beneficial with respect to decreasing
the amount of insoluble carbon on the surface of steel sheet after annealing. 相似文献
15.
Modeling creep and fatigue of copper alloys 总被引:1,自引:0,他引:1
This article reviews expressions to quantify the thermal creep and fatigue lifetime for four copper alloys: Cu-Ag-P, Cu-Cr-Zr,
Cu-Ni-Be, and Cu-Al2O3. These property models are needed to simulate the mechanical behavior of structures with copper components, which are subjected
to high heat-flux and fatigue loading conditions, such as molds for the continuous casting of steel and the first wall in
a fusion reactor. Then, measurements of four-point bending fatigue tests were conducted on two-layered specimens of copper
alloy and stainless steel, and thermal ratchetting behavior was observed at 250 °C. The test specimens were modeled with a
two-dimensional elastic-plastic-creep finite-element model using the ABAQUS software. To match the measurements, a primary
thermal-creep law was developed for Cu-0.28 pct Al2O3 for stress levels up to 500 MPa and strain rates from 10−8 to 10−2 s−1. Specifically,
(s−1)=1.43×1010 exp (−197,000/8.31 T(K)) (σ(MPa))2.5 (t(s))−0.9. 相似文献
16.
The ductile-brittle transition temperature of a 2 1/4 pct Cr-1 pct Mo steel has been meas-ured using ‘V’ notch Izod impact
specimens for an unembrittled and embrittled 2 1/4 pct Cr-1 pct Mo steel with prior austenite grain sizes within the range
40 to 150 μm. The mi-crostructure of this steel was upper bainite. The variation of yield strength with grain size obeys a
Hall-Petch relationship. The ductile-brittle transition temperature was found to have a pronounced grain size dependence for
both unembrittled, 15 K mm1/2, and embrittled, 19 K mm1/2, specimens. The bainite colony size was found to vary as the prior austenite grain size. From the low temperature quasi-cleavage
facet size, together with metallographic observations of crack path, it has been concluded that bainite colony size rather
than prior austenite grain size is the effective grain size. 相似文献
17.
The rate of formation of intermetallic compounds between aluminum and three ferritic steels, one austenitic steel, and Inconel
has been determined by an electrolytic method. The steel was held at zero potential with respect to aluminum in a NaCl-AlCl3 melt, and the current measured. Comparison of measured thicknesses of intermetallic layers with those calculated from the
integrated current gives an average deposition efficiency of 95 pct. For the Type 304 austenitic steel thickness
(min), andk is given by logk= −6400/T(0K) +4.469. The ferritic steels show a linear rate of growth of Al5Fe2, with an initial higher rate such that extrapolation of the linear curve back to zero time gives an intercept of 16±7 μm.
The rate constants (mm min−1) may be represented by log (rate)=α/T+β, and the values of α and β are respectively −2650 and−0.788 for a plain carbon steel,−6580 and + 3.469 for a 1.3 pct Cr,
0.4 pct Mo steel, and−5950 and +2.466 for a 2.2 pct Cr, 0.9 pct Mo steel. The more highly alloyed steels are thus attacked,
more slowly. Results for Inconel could not be fitted to any simple equation. With the ferritic steels growth is by aluminum
diffusing inwards; with Inconel it is by nickel diffusing outward. 相似文献
18.
Local yielding attending fatigue crack growth 总被引:1,自引:0,他引:1
G. T. Hahn R. G. Hoagland A. R. Rosenfield 《Metallurgical and Materials Transactions B》1972,3(5):1189-1202
Fatigue crack growth rate measurements were performed at 100°C on an Fe-3Si steel in three thickness conditions and at different
ΔK-levels. The test pieces were subsequently sectioned and etched to reveal the plastic deformation attending crack growth both
on the surface and in the interior. Unlike preceding studies, the Fe-3Si steel displayed classical cyclic crack growth: well-defined
fatigue striations with a spacing close to the per-cycle growth rate, and essentially the same growth rates that have been
reported for low and medium strength steels. A highly strained region, approximately one-fifth the size of the monotonie plastic
zone, is identified as the cyclic plastic zone. On this basis three regions with distinct cyclic strain histories that precede
the crack are identified: a microstrain region wherein the material receives ∼103 to 104 strain cycles in the range 0 < Δε
P ≲ 10-3; a cyclic plastic zone corresponding to ∼200 cycles in the range 10-3 < Δ∈
P ≲ 10-1, and a COD-affected zone that receives ∼10 strain cycles in the range 10-1 ≲ Δ∈
P ≲ 1. It is suggested that the damage associated with the instabilities in the fatigue substructure to overstrain contribute
to the growth mechanism. 相似文献
19.
20.
I. I. Lube A. A. Pecheritsa I. V. Neklyudov I. G. Rodionova A. I. Zaitsev L. G. Marchenko A. V. Emel'yanov V. I. Stolyarov 《Metallurgist》2005,49(7-8):269-275
The main reason for the accelerated local corrosion of tubes is contamination of the steel by corrosion-active nonmetallic
inclusions (CANI), which determine the metallurgical properties of tube steel in terms of their corrosion resistance. Studies
have shown that there are two main types of corrosion-active nonmetallic inclusions: CANI1 — inclusions based on calcium aluminates; CANI2 — complex inclusions that contain calcium sulfide. In order to master to production of tubes of steel 20-PKS at the Volga
Pipe Plant (VTZ), a study was made of the effect of the parameters of out-of-furnace treatments on the contamination of steel
by CANI.
1. The mechanisms and main sources of formation of CANI in tube steels made by the VTZ were determined. The main reasons for
the formation of CANI1 in furnace slag containing thermodynamically active CaO are mixing of the metallic and slag phases during the argon blow
and the simultaneous introduction of additions to correct the chemical composition of the steel. Inclusions of the CANI2 type may be formed by deoxidation operations carried out with suboptimal proportions of added aluminum and calcium (lime).
2. The following measures are recommended to ensure that steel 20-PKS made by the VTZ is clean with respect to both types
of CANI:
• optimize the composition of the ladle slag (increase the average content of Al2O3, increase the average content of SiO2 as much as possible, and in any case decrease the average concentration of CaO);
• keep the mass ratio of added CaO to added Al within the range 1.5–2;
• continue the argon blow done after addition of the last batch of ferroalloys for at least 15–20 min;
• ensure that the intensity of the blow is at least 0.5–1.5 m3/min.
3. Vacuum-degassing steel in the ladle after treatment on a ladle-furnace unit makes it possible to distribute the CANI more
uniformly over the volume of the steel.
__________
Translated from Metallurg, No. 7, pp. 38–42, July, 2005. 相似文献