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1.
Metallurgist - Results are presented from an analysis of the mechanical properties of forgings made of low-alloy structural steels cast in a vacuum. These forgings sometimes have substandard... 相似文献
2.
The appearance of sulfide inclusions and their position with respect to the grain boundaries in cast 38KhN3MFA and 45 steel are considered as a function of the type of reducing agents employed and the quantities introduced. In the reduction of steel by aluminum, sulfides are seen at the grain boundaries. When using silicocalcium, the sulfides are concentrated within the grains on account of the modifying effect. In selecting the reducing agent, attention must be paid not only to its oxygen affinity but also to its influence on the position of sulfides within the grain. 相似文献
3.
4.
Sulfur content and sulfide shape are known to have a marked influence on the tensile ductility and notch toughness of plate
steels. To investigate the initiation and growth of fractures at inclusions during plastic straining, a detailed study was
conducted with a series of 0.1 and 0.2 pct carbon, 1.0 pct manganese steels containing either 0.004 or 0.013 pct sulfur with
and without rare-earth additions. This paper describes the results of this study and evaluates the influence of sulfur content
and sulfide shape on the anisotropy in tensile ductility and notch toughness in the steels and assesses the influence of other
factors, such as pearlite content, affecting the ductility and toughness. Both globular and stringered sulfide inclusions
had a detrimental effect on reduction of area, shelf energy, and transition temperature, which was particularly evident in
deterioration of through-thickness properties and which was much more severe for stringered inclusions than for globular inclusions.
Increased pearlite content was more detrimental to reduction of area and transition temperature when stringered inclusions
were also present, whereas its effect on shelf energy appeared to be about the same regardless of the presence of inclusions
or their morphology. 相似文献
5.
Effect of decreased hot-rolling reduction treatment on fracture toughness of low-alloy structural steels 总被引:2,自引:0,他引:2
Yoshiyuki Tomita 《Metallurgical and Materials Transactions A》1990,21(9):2555-2563
Commercial low-alloy structural steels, 0.45 pct C (AISI 1045 grade), 0.40 pct C-Cr-Mo (AISI 4140 grade), and 0.40 pct C-Ni-Cr-Mo
(AISI 4340 grade), have been studied to determine the effect of the decreased hot-rolling reduction treatment (DHRRT) from
98 to 80 pct on fracture toughness of quenched and highly tempered low-alloy structural steels. The significant conclusions
are as follows: (1) the sulfide inclusions were modified through the DHRRT from a stringer (mean aspect ratio: 16.5 to 17.6)
to an ellipse (mean aspect ratio: 3.8 to 4.5), independent of the steels studied; (2) the DHRRT significantly improvedJ
Ic
in the long-transverse and shorttransverse orientations, independent of the steels studied; and (3) the shelf energy in the
Charpy V-notch impact test is also greatly improved by the DHRRT, independent of testing orientation and steels studied; however,
(4) the ductile-to-brittle transition temperature was only slightly affected by the DHRRT. The beneficial effect on theJ
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 local shear. 相似文献
6.
针状铁素体是一种具有大角度晶界、高位错密度的板条状中温转变组织,该组织能有效细化晶粒并具有良好的强韧性匹配.因此,通常在低合金高强度钢焊缝和粗晶区中,利用细小的夹杂物来诱导针状铁素体形成,形成有效晶粒尺寸细小的针状铁素体联锁组织或者针状铁素体和贝氏体的复合组织,使其具有良好的韧性.然而,相关研究对针状铁素体组织的形成机理和控制原理的解释并不十分清楚,对于针状铁素体的定义和理解也存在差异.总结了针状铁素体的本质、相变、形核、形态、晶体学取向关系、长大行为、细化机理和力学性能等方面的特征,归纳了奥氏体晶粒尺寸、转变温度、冷却速度、夹杂物类型和尺寸等对针状铁素体形成的影响,提出了针状铁素体组织形态和转变机理方面几个仍需深入研究的问题和方向. 相似文献
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8.
S. Sivaprasad S. Tarafder V. R. Ranganath S. K. Das K. K. Ray 《Metallurgical and Materials Transactions A》2002,33(12):3731-3740
The effects of prestrain on the ductile fracture behavior of two varieties of Cu-strengthened high-strength low-alloy (HSLA)
steels have been investigated through stretch-zone geometry measurements. It is noted that the ductile fracture-initiation
toughness of both the steels remained unaltered up to prestrains of ∼2 pct, beyond which the toughness decreased sharply.
A methodology for estimating the stretch-zone dimensions is proposed. Fracture-toughness estimations through stretch-zone
width (SZW) and stretch-zone depth (SZD) measurements revealed that the nature of the variation of ductile fracture toughness
with prestrain can be better predicted through SZD rather than the SZW measurements. However, for the specimen geometries
and prestrain levels that were investigated, none of these methods were found suitable for quantifying the initiation fracture
toughness. 相似文献
9.
Hitoshi Asahi Akira Yagi Masakatsu Ueno 《Metallurgical and Materials Transactions A》1998,29(5):1375-1381
Abnormal coarsening of austenite (γ) grains occurred in low-alloy steels during a seamless pipe hotrolling process. Often,
the grains became several hundred micrometers in diameter. This made it difficult to apply direct quenching to produce high-performance
pipes. The phenomenon of grain coarsening was successfully reproduced using a thermomechanical simulator, and the factors
which affected grain coarsening were clarified. The mechanism was found to be basically strain-induced grain rowth which occurred
during reheating at around 930 °C. Furthermore, once a pipe temperature decreased to the dual-phase region after the minimal
hot working and prior to the reheating process, the grain coarsening was more pronounced. It was understood that the formation
of ferrite along grain boundaries had the role of reducing the migration of grain boundaries into neighboring grains, leaving
a strain-free, recrystallized region behind. This abnormal grain coarsening was found to be effectively prevented by an addition
of Nb, the content of which varied depending on the C content. The effect of the Nb addition was confirmed by an in-line test. 相似文献
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11.
Deformation dilatometry is used to simulate the hot rolling of 0.20 pct C-1.10 pct Mn steels over a product thickness range
of 6 to 170 mm. In addition to a base steel, steels with additions of 0.02 pct Ti, 0.06 pct V, or 0.02 pct Nb are included
in the study. The transformation behavior of each steel is explored for three different austenite grain sizes, nominally 30,
55, and 100 μm. In general, the volume fraction of Widmanst?tten ferrite increases in all four steels with increasing austenite
grain size and cooling rate, with austenite grain size having the more significant effect. The Nb steel has the lowest transformation
temperature range and the greatest propensity for Widmanst?tten ferrite formation, while the amount of Widmanst?tten ferrite
is minimized in the Ti steel (as a result of intragranular nucleation of polygonal ferrite on coarse TiN particles). The data
emphasize the importance of a refined austenite grain size in minimizing the formation of a coarse Widmanst?tten structure.
With a sufficiently fine prior austenite grain size (e.g., ≤30 μm), significant amounts of Widmanst?tten structure can be avoided, even in a Nb-alloyed steel. 相似文献
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13.
《Canadian Metallurgical Quarterly》2013,52(3):219-226
AbstractLaboratory experiments have been conducted on a series of vanadium and vanadium-nitrogen steels. The results indicate that the combination of vanadium plus nitrogen gives an excellent notch toughness in the normalized plates (EA TT < ?80°C). Controlled rolling gives about 100 MPa higher yield strength with somewhat reduced notch toughness (EATT? ?50°C). Aluminum does not improve the properties of a normalized or controlled-rolled vanadium-nitrogen plate. Vanadium is able to combine with nitrogen so effectively that the steel can be considered. to be unsusceptible to strain ageing. Résumé Les auteurs ont fait des essais de laboratoire sur une série d'aciers au vanadium et au vanadium-azote. Les résultats indiquent que la combinaison vanadium-azote donne d'excellentes propriétés de résilience pour des tôles fortes normalisées (EA TT < ?80 °C). Le laminage contrôlé conduit à une limite d'élasticité plus élevée d'environ 100 MPa et a une résilience quelque peu réduite (EATT ? -50°C). L'aluminium n'améliore pas les propriétés d'une tôle forte d'acier au vanadium-azote après normalisation ou après laminage contrôlé. L'efficacit;amp;#x00E9; de la réaction entre Ie vanadium et l'azote est telle que l'acier peut être consideéré comme n'étant pas susceptible au vieillissement après écrouissage. 相似文献
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The state of melt before solidification is of great importance for the properties of metal products made from low-alloy steels. It depends on the melting method, the type of charge materials, the temperature-time parameters of melting, the intensity of mixing during out-furnace treatment, and other technological parameters. The improvement of the physical properties of liquid steel as a result of various actions demonstrates the formation of a more equilibrium and homogeneous state of melt, which substantially influences the structure, properties, and quality of metal products. 相似文献
16.
W. A. Spitzig 《Metallurgical and Materials Transactions A》1984,15(6):1259-1264
The effects of sulfur content (0.004 or 0.013 pct) and sulfide morphology (stringered or globular) on anisotropy of tensile
ductility and Charpy shelf energy were investigated in a series of 0.1 and 0.2 pct carbon, 1.0 pct manganese steels. The effect
of sulfide inclusions on fracture strain or Charpy shelf energy correlated with the projected area of inclusions per unit
volume,A
v
, on a plane perpendicular to the tensile direction and the mean free distance between inclusions, λ, in a direction parallel
to the tensile direction regardless of the amount or the shape of the inclusions or the test direction: longitudinal, transverse,
or through-thickness. The magnitude ofA
v
is directly proportional to the volume fraction of inclusions and inversely proportional to the inclusion dimension parallel
to the tensile direction. The mean free distance, λ, is inversely proportional toA
v
. Approximate relations were obtained for the nearest-neighbor distances between inclusions on the longitudinal, transverse,
and through-thickness planes. These distances were incorporated into a model for ductile fracture based on an adaptation of
a previously proposed criterion for the linkage of voids nucleated at second-phase particles. The agreement between the observed
and predicted fracture strains for longitudinal, transverse, and through-thickness specimens of the steels studied is encouraging.
Formerly with United States Steel Corporation, Research Laboratory, Monroeville, PA 15146 相似文献
17.
Hardness of tempered martensite in carbon and low-alloy steels 总被引:3,自引:0,他引:3
R. A. Grange C. R. Hribal L. F. Porter 《Metallurgical and Materials Transactions A》1977,8(11):1775-1785
This paper presents the results of a systematic study of the effect of carbon, manganese, phosphorus, silicon, nickel, chromium,
molybdenum, and vanadium on the hardness of martensite in low to medium carbon steels tempered for one hour at 100°F (56°C)
intervals in the range 400 to 1300°F (204 to 704°C). Results show that the as-quenched hardness depends solely on carbon content.
On tempering, the effect of carbon on hardness decreases markedly with increasing tempering temperature. Studies of carbon-0.5
manganese steels showed that the incremental increase in hardness from 0.5 pct manganese after a given tempering treatment
was independent of carbon content. Based on this result, studies of the effects of the other alloying elements were made using
a 0.2 or 0.3 pct carbon, 0.3 to 0.5 pct manganese steel base composition. The hardness of the resulting tempered martensite
was assumed to be due to a given alloy addition, and when two or more alloying elements were added, their effects were assumed
to be additive.
Each of the seven alloying elements increased the hardness of tempered martensite by varying amounts, the increase being greater
as more of each element was present. Nickel and phosphorus have substantially the same effect at all tempering temperatures.
Manganese has essentially the same hardening effect at any temperature in the range 700 (371°C) to 1300°F; silicon is most
effective at 600°F (316°C), chromium at 800°F (427°C), molybdenum at 1000 to 1100°F (538 to 592°C), and vanadium at 1200°F
(649°C).
Using the data obtained, a procedure is established for calculating the hardness of tempered martensite for carbon and alloy
steel compositions in the range studied and for any combination of tempering time and temperature.
R. A. GRANGE was formerly with U. S. Steel Corporation (retired) 相似文献
18.
19.
分析了稀土处理钢中夹杂物的特征(夹杂物种类、尺寸分布和体积分数)对微观组织中针状铁素体形成的影响.结果表明,钢中夹杂物种类和体积分数对针状铁素体组织的形成非常重要.稀土氧化物(包含稀土氧硫化物)与铁素体具有低至1.9%的错配度降低针状铁素体在夹杂物表面的形核能垒,从而促使它在稀土氧化物上形核.反之,稀土硫化物与铁素体具有高达42.5%的错配度不能诱导生成针状铁素体组织.此外,微观组织中针状铁素体的体积分数随着夹杂物体积分数的增加而增大,当钢中夹杂物体积分数是9.5×10-4时其体积分数达到53%. 相似文献
20.
Effect of volume fraction and shape of sulfide inclusions on through-thickness ductility and impact energy of high-strength 4340 plate steels 总被引:4,自引:0,他引:4
The effect of volume fraction and shape of sulfide inclusions on the tensile ductility and impact energy of high-strength
AISI 4340 plate steels in the transverse and through-thickness testing directions was investigated for four tensile-strength
levels of 930, 1210, 1410, and 1960 MPa (135, 175, 205, and 285 ksi). The volume fraction of sulfide inclusions was changed
by varying the sulfur content from 0.002 to 0.022 pct. The shape of the sulfide inclusions was changed from lenticular MnS
to spheroidal RE2O2S (RExSy) by rare-earth treatment. Axisymmetric tensile ductility and charpy impact energy [22 °C (72 °F)] decreased much more rapidly
in the through-thickness testing direction than in the transverse testing direction when the volume fraction of sulfide inclusions
was increased. Changing the shape of the sulfide inclusions from lenticular MnS to spheroidal RE2O2S (RExSy) by rare-earth treatment increased axisymmetric tensile ductility and impact energy in the through-thickness testing direction
for tensile-strength levels at or below 1410 MPa (205 ksi), but not at 1960 MPa (285 ksi). Impact energy was also improved
in the transverse testing direction but only for tensile strength levels at or below 1210 MPa (175 ksi). Changes in the volume
fraction or shape of the sulfide inclusions had little or no effect on transition temperature. Plane-strain tensile ductility
was much less affected than either axisymmetric tensile ductility or impact energy by changes in inclusion morphology or in
testing direction because of the formation of macroscopic shear bands inclined at about 45 deg to the tensile axis. As a result
impact energy correlated better with axisymmetric tensile ductility than with plane-strain tensile ductility. The results
are discussed in terms of various models involving the formation of voids at inclusion sites and their growth and eventual
coalescence by localized shear during plastic straining. 相似文献