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1.
Creep Rupture Strength and Microstructure of Low C-10Cr-2Mo Heat-Resisting Steels with V and Nb 总被引:1,自引:0,他引:1
T. Fujita K. Asakura T. Sawada T. Takamatsu Y. Otoguro 《Metallurgical and Materials Transactions A》1981,12(6):1071-1079
The new ferritic heat-resisting steels of 0.05C-10Cr-2Mo-0.10V-0.05Nb (Cb) composition with high creep rupture strength and
good ductility have already been reported. The optimum amounts of V and Nb that can be added to the 0.05C-10Cr-2Mo steels
and their effects on the creep rupture strength and microstructure of the steels have been studied in this experiment. The
optimum amounts of V and Nb are about 0.10 pct V and 0.05 pct Nb at 600 °C for 10,000 h, but shift to 0.18 pct V and 0.05
pct Nb at 650 °C. Nb-bearing steels are preferred to other grades on the short-time side, because NbC precipitation during
initial tempering stages delays recovery of martensite. On the long-time side, however, V-bearing steels have higher creep
rupture strength. By adding V to the steels, electron microscopic examination reveals a stable microstructure, retardation
during creep of the softening of tempered martensite, fine and uniform distribution of precipitates, and promotion of the
precipitation of Fe2Mo. 相似文献
2.
The creep resistance of advanced chromium steels can be significantly increased due to precipitation of very small particles of vanadium nitride VN. The solubility and precipitation of VN, Nb(C,N) and AIN in austenite and ferrite was analysed using relevant solubility products. The calculated values of nitrogen in solid solution were used for assessment of creep rupture strength of chromium steel (mean considered chemical composition, mass contents in %: 0.18 C; 10.5 Cr; 1.0 Mo; 0.2 V; 0.07 Nb; 0.05 N; 0.01 Al). Increasing N mass contents from 0.03 to 0.07 % leads to increasing creep rupture strength in 100 000 h at 600°C of about 60 %. Lowering AI mass contents from 0.045 to 0.005 % produces higher creep rupture strength of about 30 %. 相似文献
3.
Y. Fukui R. Sasaki F. Hataya T. Kashimura 《Metallurgical and Materials Transactions A》1981,12(6):1033-1039
An attempt has been made to develop a cobalt base casting superalloy (30Cr-10Ni-7W-Co) having high creep rupture strength
and ductility for first stage nozzles of gas turbines. In cobalt base superalloys, there was found to exist a close correlation
between the creep rupture strength and MC type carbide forming elements such as Ti, Nb and Zr. In cobalt base alloys with
0.25 wt pct C, precipitation and coarsening of carbides can be reduced by addition of Ti, Nb and Zr. Therefore, by adding
the optimum amount of Ti, Nb and Zr, precipitation of carbides in the alloy reaches such an amount as to give the highest
creep rupture strength. Excess addition of Ti, Nb and Zr does not improve the creep rupture strength. By adding C, creep rupture
strength of the cobalt alloy with Ti, Nb and Zr can be improved and becomes the highest at 0.40 wt pct. C. According to the
experimental results, the creep rupture strength becomes the highest at a value of (Ti + Nb + Zr)/C (atomic ratio) of about
0.3. Contrary to the expectation, it was found in this experiment that the ductility in creep rupture tests increases with
increasing carbon content up to 0.6 wt pct. 相似文献
4.
Induction melting and electron beam melting techniques were employed in the production of unidirectionally solidified eutectic composites of Ti-1.7 wt pct B and Ti-8.5 wt pct Si. The grown eutectics were reinforced by 7.7 volume pct of TiB fibers and 31 volume pct of Ti5Si3 fibers respectively. Controlled dendritic solidification of a hypereutectic composition of Ti-12 wt pct Si was also accomplished. Tensile, compressive, creep, and stress rupture specimens were cut from the eutectic composites and tested with reinforcing fibers parallel to the load axis. Ti?TiB eutectic was found to have less than the critical volume fraction of fibers necessary for reinforcement, while Ti?Ti5Si3 composite attained a compressive yield strength of 275,000 psi and a compressive Young's modulus of 30×108 psi after heat treatment. The 500 and 4000 hr stress rupture properties of Ti?Si eutectic were superior to commercial titanium alloys at 1000° and 1200°F. The minimum creep rate of Ti?Ti5Si3 eutectic composite was lower than all other titanium alloys at 1000°F. Tensile, compressive, and creep properties of the Ti-8.5 wt pct Si eutectic are discussed in terms of the current theories of composite behavior. 相似文献
5.
The article reports the creep behavior, at 565 °C, of 1Cr1Mo0.75V (Ti, B) (Durehete D1055) steel, in each of two grain sizes
and doped with individual trace elements such as P, As, and Sn, in comparison to a reference cast of the base material containing
0.08 wt pct Ti. The addition of the trace elements P, As, or Sn (each <0.045 wt pct) appears to produce no significant effect
on creep strength or creep crack-growth resistance at 565 °C. The fine-grained material shows low creep strength but notch
strengthening, while the coarse-grained material shows higher creep strength and exhibits notch weakening for test times up
to 2750 hours. From creep crack-growth tests, it appears that the C* parameter is not appropriate for correlating the creep crack-growth rate under the present test conditions. The parameters
K
I
or σ
net are found to correlate better, but, from the present data, it is not possible to judge which of these parameters is more
appropriate for general use. It is suggested that the presence of Ti in CrMoV steels has an inhibiting effect on trace-element
embrittlement. 相似文献
6.
M. J. Crooks A. J. Garratt-Reed J. B. Vander Sande W. S. Owen 《Metallurgical and Materials Transactions A》1981,12(12):1999-2013
Static precipitation and recrystallization following hot compression of austenite and the interactions between the two processes
have been studied in a set of aluminum-killed HSLA steels containing 0.1 pct carbon, [0.016 - 0.026] pct nitrogen and 0.1
or 0.2 pct vanadium. Two steels containing both vanadium (0.1 and 0.2 pct) and niobium (0.03 pct) were included for purposes
of comparison. The compression and the static tests were all carried out isothermally at temperatures between 800 and 900
°C. The course of recrystallization was followed by measurements of the rate of softening and by optical metallography of
specimens quenched from the test temperature after different times. Precipitation was studied by measurements of the rate
of hardening, by transmission electron microscopy of thin foils, carbon and aluminum extraction replicas, and by X-ray dispersion
and energy-loss spectroscopy from individual precipitates.
The temperature of the nose of theC-curve for precipitation in vanadium steels is much lower than that in niobium steels, as is the temperature, TR, below which no recrystallization occurs in short times. Precipitation occurs both at austenite grain boundaries and in the
grains (matrix precipitation). The former starts early and the precipitates grow rapidly to an approximately constant size;
the matrix precipitates grow more slowly and are responsible for the observed hardening of the austenite. The relevance of
various models proposed for the retardation and arrest of recrystallization of austenite are discussed.
In the steels containing vanadium and niobium the precipitates contain both heavy elements: (V,Nb) (C,N). The Nb/V ratio in
the matrix precipitates is different than in the parent austenite. The grain-boundary precipitates, however, contain the same
Nb/V ratio as the parent austenite. The rate of hardening exhibits a reverseC-curve behavior, being more rapid than in the corresponding vanadium steels at higher temperatures and about the same at lower
temperatures.
Formerly Research Associate at MIT 相似文献
7.
S. Yu. Nastich E. V. Shul’ga I. V. Lyasotskii D. L. D’yakonov 《Steel in Translation》2012,41(12):1040-1046
Deposits of the carbonitrides (Ti, Nb)(C, N), Nb(C, N), and (Nb, V)(C, N) in the austenite and ferrite phases of X70 steel
sheet after thermomechanical treatment are investigated. Nb(C, N) particles measuring up to 10 nm are seen in austenite in
the final stage of rolling and after its conclusion prior to accelerated cooling of thick sheet. After intense accelerated
cooling, most of the niobium and vanadium is retained in the solid solution, as confirmed by the vigorous deposition of (Nb,
V)(C, N) particles measuring ∼2–4 nm in ferrite after tempering at 600°C. In coil production, the particles observed may be
the result of general deposition or interphase deposition, depending on the cooling of the strip on the output roller conveyer
of the continuous broad-strip mill. Carbonitride particles measuring 2–8 nm are deposited at winding temperatures of 550–570°C
in steel with niobium and vanadium and at 590°C in steel without vanadium. 相似文献
8.
P. J. Grobner V. Bišs D. L. Sponseller 《Metallurgical and Materials Transactions A》1980,11(6):909-917
Nine experimental delta-ferritic steels have been examined as potential low expansion heat-resistant steels for use in fossil
fuel power generation, nuclear power generation, nuclear process heat plants and coal gasification plants. The steels contain
10 to 14 pct Cr and 2 to 6 pct Mo, with additions of columbium, titanium, vanadium, aluminum and boron. Room-temperature tensile
properties and oxidation resistance of all steels were determined. Selected steels were aged for 1000 h at 760 °C (1400 °F)
and subjected to elevated temperature tensile tests at the aging temperature. Creep-rupture properties of selected steels
were determined at 760 and 815 °C (1400 and 1500 °F). Extensive metallographic and phase identification studies were conducted.
Of the two steels tested for creep-rupture strength, the 10Cr-6Mo-0.5Cb steel, with good room-temperature ductility, has rupture
strength exceeding that of martensitic 12Cr-1Mo-V steel. The 14Cr-3Mo-0.5Cb-lTi-2Al steel exhibits an even higher rupture
strength, but has only marginal ductility at room temperature. 相似文献
9.
The effect of a low level of titanium on the microstructure and creep properties of 2.25 pct Cr-1 pct Mo steels has been examined as a function of carbon content and austenitizing temperature. The addition of 0.04 wt pct titanium resulted in a dramatic increase in creep strength at 565 °C, and this was found to be associated with the presence in the microstructure of very small (50 to 100 Å) titanium-bearing precipitates based upon both TiC and Mo2C. The variation of the minimum creep rate with carbon content and austenitizing treatment was explained in terms of the solubility of TiC in austenite. The titanium-bearing carbides have an important effect on microstructural stability and on the maintenance of creep strength, but it is also apparent that solid solution strengthening by molybdenum can make a significant contribution to creep strength at low carbon levels (0.02 wt pct). 相似文献
10.
R. Viswanathan 《Metallurgical and Materials Transactions A》1975,6(7):1135-1141
A program to study the effect of Sb, P, Sn and B on creep properties of four normalized and tempered 1.25 Cr-0.5 Mo steels
at 538°C (1000°F) has been completed. Results show that even a combined addition of large amounts of Sb, P and Sn does not
affect short time creep strength or ductility of the steel at 538°C (1000°F). Addition of B resulted in an increase or decrease
of creep strength depending on the nature of the impurity species present, presumably due to B-impurity interactions. Regardless
of the effect on creep strength, B additions caused sharp reductions in rupture ductility in all cases. Comparison of the
present results on the four laboratory steels (100 pct bainite) with results of a previous study on a commercial steel (60
pct bainite + 40 pct ferrite) show that the effect of microstructure becomes negligible and rupture strength values of the
various steels at 538°C (1000°F) approach each other at rupture times in excess of 104 h. 相似文献
11.
R. Viswanathan 《Metallurgical and Materials Transactions A》1975,6(6):1135-1141
A program to study the effect of Sb, P, Sn and B on creep properties of four normalized and tempered 1.25 Cr−0.5 Mo steels
at 538°C (1000°F) has been completed. Results show that even a combined addition of large amounts of Sb, P and Sn does not
affect short time creep strength or ductility of the steel at 538°C (1000°F). Addition of B resulted in an increase or decrease
of creep strength depending on the nature of the impurity species present, presumably due to B-impurity interactions. Regardless
of the effect on creep strength, B additions caused sharp reductions in rupture ductility in all cases. Comparison of the
present results on the four laboratory steels (100 pct bainite) with results of a previous study on a commercial steel (60
pct bainite + 40 pct ferrite) show that the effect of microstructure becomes negligible and rupture strength values of the
various steels at 538°C (1000°F) approach each other at rupture times in excess of 104 h. 相似文献
12.
The effects of vanadium/nitrogen additions on dynamic and static recovery and recrystallization have been studied in a set
of aluminum-killed HSLA steels containing 0.1 pct carbon, 0.01 to 0.02 pct nitrogen, and either vanadium (0.1 or 0.2 pct),
niobium (Cb) (0.03 pct), or vanadium and niobium together. Most, but not all, of the tests were carried out at 1173 K (900°C),
a temperature at which precipitation of VN might be expected under some conditions. The net effect of dynamic recovery, recrystallization,
and precipitation was monitored by measuring the change in compressive flow stress with strain at a constant temperature.
Static changes were followed by measuring the change in compressive flow stress on isothermally holding unloaded specimens
after a hot precompression. These kinetic data were supplemented by metallographic and electron-microscopic examinations of
quenched specimens and of carbon extraction replicas taken from them. Evidence is presented which indicates that, at a holding
temperature of 1173 K (900°C), static recrystallization occurs in vanadium steels containing 0.1 pct vanadium before any precipitation
is detected. The progress of this recrystallization is arrested by the precipitation of vanadium nitride. At a higher vanadium
concentration, 0.2 pct, recrystallization does not start. The effects of V/N ratio, austenitizing temperature (between 1373
K (1100°C) and 1523 K (1250°C), and isothermal holding temperature (between 1173 K (900°C) and 1273 K (1000°C)) on the kinetics
of static softening and hardening are compared in some vanadium steels and plain-carbon and niobium steels of similar base-composition. 相似文献
13.
M. Dilip Bhandarkar M. Shanthidas Bhat Victor F. Zackay Earl R. Parker 《Metallurgical and Materials Transactions A》1975,6(6):1281-1289
A Laves phase, Fe2Ta, was utilized to obtain good elevated temperature properties in a carbon-free iron alloy containing 1 at. pct Ta and 7
at. pct Cr. Room temperature embrittlement resulting from the precipitation of the Laves phase at grain boundaries was overcome
by spheroidizing the precipitate. This was accomplished by thermally cycling the alloys through theα →γ transformation. The short-time yield strength of the alloys decreased very slowly with increase in test temperature up to
600°C, but above this temperature, the strength decreased rapidly. Results of constant load creep and stress rupture tests
conducted at several temperatures and stresses indicated that the rupture and creep strengths of spheroidized 1 Ta−7 Cr alloy
were higher than those of several commercial steels containing chromium and/or molybdenum carbides but lower than those of
steels containing substantial amounts of tungsten and vanadium. When molybdenum was added to the base FeTa-Cr alloy, the rupture
and creep strengths were considerably increased.
Formerly with Lawrence Berkeley Laboratory. 相似文献
14.
M. Dilip Bhandarkar M. Shanthidas Bhat Victor F. Zackay Earl R. Parker 《Metallurgical and Materials Transactions A》1975,6(7):1281-1289
A Laves phase, Fe2Ta, was utilized to obtain good elevated temperature properties in a carbon-free iron alloy containing 1 at. pct Ta and 7
at. pct Cr. Room temperature embrittlement resulting from the precipitation of the Laves phase at grain boundaries was overcome
by spheroidizing the precipitate. This was accomplished by thermally cycling the alloys through the α→γ transformation. The short-time yield strength of the alloys decreased very slowly with increase in test temperature up to
600°C, but above this temperature, the strength decreased rapidly. Results of constant load creep and stress rupture tests
conducted at several temperatures and stresses indicated that the rupture and creep strengths of spheroidized 1 Ta-7 Cr alloy
were higher than those of several commercial steels containing chromium and/or molybdenum carbides but lower than those of
steels containing substantial amounts of tungsten and vanadium. When molybdenum was added to the base Fe-Ta-Cr alloy, the
rupture and creep strengths were considerably increased.
M. Dilip Bhandarkar, formerly with Lawrence Berkeley Laboratory. 相似文献
15.
Effect of molybdenum,niobium, and vanadium on static recovery and recrystallization and on solute strengthening in microalloyed steels 总被引:4,自引:0,他引:4
H. L. Andrade M. G. Akben J. J. Jonas 《Metallurgical and Materials Transactions A》1983,14(10):1967-1977
The effect of molybdenum, niobium, and vanadium on the occurrence of static recovery and recrystallization after high temperature
deformation was investigated in a series of microalloyed steels. The steels had a base composition of 0.05 pct C and 1.40
pct Mn. To this, single additions of 0.30 pct Mo, 0.035 pct Nb, and 0.115 pct V were made. Interrupted hot compression tests
were performed at 900 and 1000 °C, and at a constant true strain rate of 2 s-1. The load-free time was decreased from 5000 s to 50 ms, and the degree of static softening during this period was determined.
Both graphite and glass were used as lubricants. Percent softeningvs delay time curves are presented and the retarding effect of molybdenum, niobium, and vanadium addition on the rate of static
recovery and recrystallization is discussed. The greatest solute retardation of static recovery and recrystallization is produced
by niobium addition, followed by that of molybdenum, vanadium leading to the smallest delay. Although the rank order of this
effect is the same as found under dynamic softening conditions, the relative contribution of niobium is more profound for
the static condition. The solute strengthening attributable to each element was also assessed, and found to follow the same
order as for the recovery and recrystallization results. At 900 °C, the onset of the static precipitation of Nb (CN) was detected
at approximately 10 seconds, somewhat earlier than previously reported.
Formerly Graduate Student at McGill University, Montreal, Quebec. 相似文献
16.
Effects of micro-alloying elements and production process on microstructure,mechanical properties and precipitates of 600 MPa grade rebars were studied by using pilot test,metallographic observation,tensile test,thermodynamic calculation and transmission electron microscopy. The results show that the tested steels are composed of ferrite and pearlite,in which the content range of pearlite is 33%-45%. For vanadium microalloyed steel,interphase precipitation strengthening effect of V can be promoted and the yield strength of tested steels can be increased with increasing V content and decreasing finishing rolling temperature. The temperature of terminated cooling should be more than 700 °C when the water cooling is used. When niobium is added to the steel,more coarse( Nb,V) C,N precipitates are generated at high temperature,so that the solid solubility of precipitated phases of vanadium is reduced and the precipitation strengthening effect of vanadium is weakened. 相似文献
17.
Liqing Chen Zhouyu Zeng Yang Zhao Fuxian Zhu Xianghua Liu 《Metallurgical and Materials Transactions A》2014,45(3):1498-1507
Thermo-mechanical treatments (TMT) at different rolling deformation temperatures were utilized to process a martensitic heat-resistant stainless steel 403Nb containing 12 wt pct Cr and small additions of Nb and V. Microstructures and mechanical properties at room and elevated temperatures were characterized by scanning electron microscopy, transmission electron microscopy, and hardness, tensile, and creep tests. The results showed that high-temperature mechanical behavior after TMT can be greatly improved and microstructures with refined martensitic lath and finely dispersed nanosized MX carbides could be produced. The particle sizes of M23C6 and MX carbides in 403Nb steel after conventional normalizing and tempering (NT) treatments are about 50 to 160 and 10 to 20 nm, respectively, while those after TMT at 1123 K (850 °C) and subsequent tempering at 923 K (650 °C) for 2 hours reach about 25 to 85 and 5 to 10 nm, respectively. Under the condition of 260 MPa and 873 K (600 °C), the tensile creep rupture life of 403Nb steel after TMT at 1123 K (850 °C) is 455 hours, more than 3 times that after conventional NT processes. The mechanisms for improving mechanical properties at elevated temperature were analyzed in association with the existence of finely dispersed nanosized MX particles within martensitic lath. It is the nanosized MX particles having the higher stability at elevated temperature that assist both dislocation hardening and sub-grain hardening for longer duration by pinning the movement of dislocations and sub-grain boundary migration. 相似文献
18.
The results of a recent study of the effects of ternary alloying with Ti on the fatigue and fracture behavior of a new class
of forged damage-tolerant niobium aluminide (Nb3Al-xTi) intermetallics are presented in this article. The alloys studied have the following nominal compositions: Nb-15Al-10Ti
(10Ti alloy), Nb-15Al-25Ti (25Ti alloy), and Nb-15Al-40Ti (40Ti alloy). All compositions are quoted in atomic percentages
unless stated otherwise. The 10Ti and 25Ti alloys exhibit fracture toughness levels between 10 and 20 MPa√m at room temperature.
Fracture in these alloys occurs by brittle cleavage fracture modes. In contrast, a ductile dimpled fracture mode is observed
at room-temperature for the alloy containing 40 at. pct Ti. The 40Ti alloy also exhibits exceptional combinations of room-temperature
strength (695 to 904 MPa), ductility (4 to 30 pct), fracture toughness (40 to 100 MPa√m), and fatigue crack growth resistance
(comparable to Ti-6Al-4V, monolithic Nb, and inconnel 718). The implications of the results are discussed for potential structural
applications of the 40Ti alloy in the intermediate-temperature (∼700 °C to 750 °C) regime. 相似文献
19.
Vu The Ha Woo Sang Jung Jin Yoo Suh 《Metallurgical and Materials Transactions A》2011,42(11):3378-3385
Austenitic stainless steels are expected to be a major material for boiler tubes and steam turbines in future ultra-supercritical
(USC) fossil power plants. It is of great interest to maximize the creep strength of the materials without increasing the
cost. Precipitation strengthening was found to be the best and cheapest way for increasing the creep strength of such steels.
This study is concerned with improving creep properties of a high nitrogen Nb-stabilized 15Cr-15Ni austenitic alloy through
introducing a high number of nanosized particles into the austenitic matrix. The addition of around 4 wt pct Mn and 0.236 wt
pct N into the 15Cr-15Ni-0.46Si-0.7Nb-1.25Mo-3Cu-Al-B-C matrix in combination with a special multicycled aging-quenching heat
treatment resulted in the fine dispersion of abundant quantities of thermally stable (Nb,Cr,Fe)(C,N) precipitates with sizes
of 10 to 20 nm. Apart from the carbonitrides, it was found that a high number of coherent copper precipitates with size 40
to 60 nm exist in the microstructure. Results of creep tests at 973 K and 1023 K (700 °C and 750 °C) showed that the creep
properties of the investigated steel are superior compared to that of the commercial NF709 alloy. The improved creep properties
are attributed to the improved morphology and thermal stability of the carbonitrides as well as to the presence of the coherent
copper precipitates inside the austenitic matrix. 相似文献
20.
K. S. Chandravathi Kinkar Laha C. S. Sasmal P. Parameswaran M. Nandagopal H. M. Tailor M. D. Mathew T. Jayakumar E. Rajendra Kumar 《Metallurgical and Materials Transactions A》2014,45(10):4280-4292
Microstructure and mechanical properties of 9Cr-W-0.06Ta Reduced Activation Ferritic-Martensitic (RAFM) steels having various tungsten contents ranging from 1 to 2 wt pct have been investigated on subjecting the steels to isothermal heat treatments for 5 minutes at temperatures ranging from 973 K to 1473 K (700 °C to 1200 °C) (below Ac1 to above Ac3) followed by oil quenching and tempering at 1033 K (760 °C) for 60 minutes. The steels possessed tempered martensite structure at all the heat-treated conditions. Prior-austenitic grain size of the steels was found to decrease on heating in the intercritical temperature range (between Ac1 and Ac3) and at temperatures just above the Ac3 followed by increase at higher heating temperatures. All the steels suffered significant reduction in hardness, tensile, and creep strength on heating in the intercritical temperature range, and the reduction was less for steel having higher tungsten content. Strength of the steels increased on heating above Ac3 and was higher for higher tungsten content. Transmission Electron Microscopy (TEM) investigations of the steels revealed coarsening of martensitic substructure and precipitates on heating in the intercritical temperature range, and the coarsening was relatively less for higher tungsten content steel, resulting in less reduction in tensile and creep strength on intercritical heating. Tensile and creep strengths of the steels at different microstructural conditions have been rationalized based on the estimated inter-barrier spacing to dislocation motion. The study revealed the uniqueness of inter-barrier spacing to dislocation motion in determining the strength of tempered martensitic steels subjected to different heat treatments. 相似文献