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1.
Dae Jin Ha Hyo Kyung Sung Joon Wook Park Sunghak Lee 《Metallurgical and Materials Transactions A》2009,40(11):2568-2577
A study was made of the effects of carbon, tungsten, molybdenum, and vanadium on the wear resistance and surface roughness
of five high-speed steel (HSS) rolls manufactured by the centrifugal casting method. High-temperature wear tests were conducted
on these rolls to experimentally simulate the wear process during hot rolling. The HSS rolls contained a large amount (up
to 25 vol pct) of carbides, such as MC, M2C, and M7C3 carbides formed in the tempered martensite matrix. The matrix consisted mainly of tempered lath martensite when the carbon
content in the matrix was small, and contained a considerable amount of tempered plate martensite when the carbon content
increased. The high-temperature wear test results indicated that the wear resistance and surface roughness of the rolls were
enhanced when the amount of hard MC carbides formed inside solidification cells increased and their distribution was homogeneous.
The best wear resistance and surface roughness were obtained from a roll in which a large amount of MC carbides were homogeneously
distributed in the tempered lath martensite matrix. The appropriate contents of the carbon equivalent, tungsten equivalent,
and vanadium were 2.0 to 2.3, 9 to 10, and 5 to 6 pct, respectively. 相似文献
2.
Composition, microstructure, hardness, and wear properties of high-speed steel rolls 总被引:10,自引:0,他引:10
Joon Wook Park Huo Choon Lee Sunghak Lee 《Metallurgical and Materials Transactions A》1999,30(2):399-409
The effects of alloying elements on the microstructural factors, hardness, and wear properties of four high-speed steel (HSS)
rolls fabricated by centrifugal casting were investigated. A hot-rolling simulation test was carried out using a high-temperature
wear tester capable of controlling speed, load, and temperature. The test results revealed that the HSS roll containing a
larger amount of vanadium showed the best wear resistance because it contained a number of hard MC-type carbides. However,
it showed a very rough roll surface because of cracking along cell boundaries, the preferential removal of the matrix, and
the sticking of the rolled material onto the roll surface during the wear process, thereby leading to an increase in the friction
coefficient and rolling force. In order to improve wear resistance with consideration to surface roughness, it is suggested
that a reduction in the vanadium content, an increase in solid-solution hardening by adding alloying elements, an increase
in secondary hardening by precipitation of fine carbides in the matrix, and formation of refined prior austenite grains by
preaustenitization treatment be employed to strengthen the matrix, which can hold hard carbides in it. 相似文献
3.
Xiaodan Zhang Wei Liu Dale Sun Youguo Li 《Metallurgical and Materials Transactions A》2007,38(3):499-505
The transformation of carbides with austenization time of a high speed steel (HSS) roll material, manufactured by a centrifugal
casting method, has been studied. The correlation between wear resistance and the type, morphology, volume fraction, and distribution
of the carbides has also been investigated. Microstructural observations, X-ray diffraction (XRD) analysis, hardness measurements,
and energy dispersive spectroscopy (EDS) have been used to characterize the carbides. The type and volume fraction of carbides
were found to change with austenizing time. During austenization, the transformation of the M3C carbides can be postulated as M3C + γ-Fe → M2C, with much finer nodular and rodlike MC carbides also forming through a solid-state transformation. The M2C carbide decomposes as M2C + γ-Fe → MC + M7C3 + M6C. The decomposed carbide substantially maintains a platelike shape until the end of decomposition. The most important finding
of this study is that austenization results in changes in the type, morphology, volume fraction, and distribution of carbides
and that it can be controlled to produced a homogeneous distribution of hard carbides, resulting in an improvement in the
wear resistance of HSS rolls. This finding may be of great use for the industrial production of HSS rolls. 相似文献
4.
The effects of chromium and vanadium additions on the microstructure, hardness and wear resistance of high-vanadium alloy steel (containing 5–10 wt-% V and 2–10 wt-% Cr) were studied by means of optical microscopy, scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS), Vickers hardness and Rockwell-hardness tester & M-200 ring block wear tester. Researching results showed that the solidification structure of high-vanadium wear-resistant alloy steel was mainly consisted α-Fe (martensite), vanadium carbide (VC), M3C and M7C3. Vanadium is mainly distributed over VC, and certain amount of vanadium exists in the matrix and M7C3 type eutectic carbide. Chromium is mainly distributed over the M7C3, and the matrix also contains a small quantity of chromium. It is found that the content of VC increases with the increase of vanadium content when carbon and chromium contents are constant. The change of micro- and macro-hardness was not obvious with the increase of vanadium content. The content of M7C3 type eutectic carbides increases gradually with the increase of chromium content when carbon and vanadium contents are constant. The micro- and macro-hardness increases with the increase of chromium content. The increase of vanadium content brings to the increase of wear resistance of alloy steel when carbon and chromium contents are constant. The change of chromium content had no obvious effect on wear resistance of high-vanadium alloy steel when carbon and vanadium contents. The increase of vanadium content brings to the increase of wear resistance of alloy steel when carbon and chromium contents are constant. The wear resistance of as-cast high-vanadium alloy steel is the best when the content of vanadium and chromium is 10 wt-% and 5 wt-% respectively. 相似文献
5.
Chang Kyu Kim Sunghak Lee Jae-Young Jung 《Metallurgical and Materials Transactions A》2006,37(3):633-643
The objective of this study is to investigate effects of heat treatment on wear resistance and fracture toughness in duo-cast
materials composed of a high-chromium white cast iron and a low-chromium steel as a wear-resistant part and a ductile part,
respectively. Different size, volume fraction, and distribution of M7C3 carbides were employed in the wear-resistant part by changing the amount of chromium, and the volume fraction of martensite
in the austenitic matrix was varied by the heat treatment. In the alloys containing a small amount of chromium, an interdendritic
structure of eutectic M7C3 carbides was formed, and led to the improvement of wear resistance and fracture toughness. After the heat treatment, the
selective wear of the matrix and the cracking or spalled-off carbides were considerably reduced since the hardness difference
between carbides and matrix decreased by the increase in the matrix hardness, thereby leading to the improvement of the wear
resistance. However, the fracture toughness of the heat-treated alloys was lower than that of the as-cast alloys because the
matrix containing a considerable amount of martensite did not effectively prevent the crack propagation. 相似文献
6.
Hongsug Oh Sunghak Lee Jaeyoung Jung Sangho Ahn 《Metallurgical and Materials Transactions A》2001,32(3):515-524
The objective of this study is to investigate the correlation of microstructure with wear resistance and fracture toughness
in duocast materials that consisted of a high-chromium white cast iron and a low-chromium steel as the wear-resistant and
ductile parts, respectively. Different shapes, sizes, volume fractions, and distributions of M7C3 carbides were employed in the wear-resistant part by changing the amount of chromium and molybdenum. In the alloys containing
a large amount of chromium, a number of large hexagonal-shaped primary carbides and fine eutectic carbides were formed. These
large primary carbides were so hard and brittle that they easily fractured or fell off from the matrix, thereby deteriorating
the wear resistance and fracture toughness. In the alloys containing a smaller amount of chromium, however, a network structure
of eutectic carbides having a lower hardness than the primary carbides was developed well along solidification cell boundaries
and led to the improvement of both wear resistance and toughness. The addition of molybdenum also helped enhance the wear
resistance by forming additional M2C carbides without losing the fracture toughness. Under the duocasting conditions used in the present study, the appropriate
compositions for wear resistance and fracture toughness were 17 to 18 pct chromium and 2 to 3 pct molybdenum. 相似文献
7.
8.
During cold rolled production of steel,each change of rolls causes a halt in production and affects the roll’s grinding maintenance and consumption.Consequently,rolls are very critical to the costs of steel production. Besides the rolling accidents,surface quality problems,including inhomogeneous wear and a decrease of the surface roughness of the rolls are other main reasons for outage and a change of the rolls.Therefore,safe rolls,with superior wear resistance and roughness retentivity will be a future trend in the cold rolling steel industry.In this study,the property characteristics and in-service performance of high-speed steel(HSS)cold rolling work rolls at Baosteel are discussed.The results of this study indicate that in-service performance of HSS cold work rolls has an improvement over conventional rolls.Implementation of HSS work rolls will prolong the rolling campaign and improve the rolling stability,thus,the cost of cold rolling production can be better controlled. 相似文献
9.
Sunghak Lee Do Hyung Kim Jae Hwa Ryu Keesam Shin 《Metallurgical and Materials Transactions A》1997,28(12):2595-2608
This is a study of the thermal fatigue property in three centrifugally cast work rolls, i.e., a nickel-grain cast-iron roll (Ni-grain roll), a high-chromium cast-iron roll (Hi-Cr roll), and a high-speed steel roll
(HSS roll). The thermal fatigue mechanism was investigated with a focus on the roll microstructure and the increase in tensile
stress which led the specimen to fracture when it reached the tensile strength. The thermal fatigue test results indicated
that the thermal fatigue property was best in the HSS roll, followed by the Hi-Cr roll and the Ni-grain roll, respectively,
and that the thermal fatigue life of each roll decreased with the increase of the mean temperature or of the temperature range
of the thermal fatigue cycle. The results were then interpreted based on the amount of primary carbides and the cyclic softening
phenomenon associated with the exposed time to elevated temperatures. The coarse primary carbides on the specimen surface
acted as fatigue crack initiation sites, as they cleaved at a low stress level to form cracks. The HSS roll, having the highest
tensile strength and the smallest amount of primary carbides, thus showed better thermal fatigue property than the other rolls.
For the improvement of the thermal fatigue property of the rolls, this study suggests a homogeneous distribution of primary
carbides by reducing the carbide segregation formed along the solidification cell boundary and by optimizing of the roll-casting
process. 相似文献
10.
11.
E. Pagounis V. K. Lindroos M. Talvitie 《Metallurgical and Materials Transactions A》1996,27(12):4183-4191
The influence of the matrix structure on the mechanical properties of a hot isostatic pressed (hipped) white iron matrix composite
containing 10 vol pct TiC is investigated. The matrix structure was systematically varied by heat treating at different austenitizing
temperatures. Various subsequent treatments were also employed. It was found that an austenitizing treatment at higher temperatures
increases the hardness, wear resistance, and impact toughness of the composite. Although after every different heat treatment
procedure the matrix structure of the composite was predominantly martensitic, with very low contents of retained austenite,
some other microstructural features affected the mechanical properties to a great extent. Abrasion resistance and hardness
increased with the austenitizing temperature because of the higher carbon content in martensite in the structure of the composite.
Optimum impact energy values were obtained with structures containing a low amount of M (M7C3+M23C6) carbides in combination with a decreased carbon content martensite. Structure austenitized at higher temperatures showed
the best tempering response. A refrigerating treatment was proven beneficial after austenitizing the composite at the lower
temperature. The greatest portion in the increased martensitic transformation in comparison to the unreinforced alloy, which
was observed particularly after austenitizing the composite at higher temperatures,[1] was confirmed to be mechanically induced. The tempering cycle might have caused some additional chemically induced transformation.
The newly examined iron-based composite was found to have higher wear resistance than the most abrasion-resistant ferroalloy
material (white cast iron). 相似文献
12.
The precipitation strengthening of modified chromium steels is effected predominantly by M23C6 carbides. In molybdenum-modified 9% chromium steels, creep resistance depends on the dispersion of the M23C6 carbides and on the molybdenum content in the solid solution. There is no point in increasing molybdenum contents of molybdenum-modified steels above approximately 1 wt.%. In vanadium-modified steels precipitation strengthening is effected both by M23C6 carbides and by VCxNy carbonitrides. If the amount of nitrogen in solid solution is insufficient, this reduces the volume fraction of VCxNy in the structure and thus impairs the creep resistance of the steel. It is advisable to restrict the aluminium and titanium contents in the vanadium-modified chromium steels. 相似文献
13.
Yu. F. Ivanov A. A. Klopotov E. A. Petrikova Yu. A. Abzaev O. V. Ivanova 《Steel in Translation》2017,47(10):669-674
The formation of nanostructural multiphase surface layers in high-chromium 12Х18Н10Т and 20Х13 stainless steel under the action of an intense pulsed electron beam in a SOLO system is studied. The Fe–Cr–C system is thermodynamically analyzed. Alloying Fe–Cr alloys with carbon considerably changes their structural and phase state and determines the regions of existence of the carbides M23C6, M7C3, M3C2, and M3C with α and γ phases. The temperature field formed in the surface layer of the steel under the action of the electron beam is numerically calculated. When the energy density of the electron beam is 10 J/cm2, regardless of the pulse length of the electron beam (50–200 μs), the maximum temperature at the sample surface corresponding to the end of the pulse is less than the melting point of the steel. The structure and the mechanical and tribological properties of the surface layer of high-chromium 12Х18Н10Т and 20Х13 steel formed under the action of the intense pulsed electron beam are investigated. It is found that electron-beam treatment of the steel with melting and subsequent high-speed crystallization is accompanied by solution of the initial carbide particles of composition M23C6—specifically, (Cr, Fe)23C6—and hence saturation of the crystal lattice in the surface layer with carbon and chromium atoms. In addition, submicronic cells of dendritic crystallization are formed, and nanoparticles of titanium carbide and chromium carbide are deposited. Overall, electron-beam treatment improves the surface and tribological properties of the materials. For 12Х18Н10Т steel, the hardness of the surface layer is increased by a factor of 1.5 and the wear resistance by a factor of 1.5, while the frictional coefficient is decreased by a factor of 1.6. For 20Х13 steel, the microhardness is increased by a factor of 1.5 and the wear resistance by a factor of 3.2, while the frictional coefficient is decreased by a factor of 2.3. 相似文献
14.
High-carbon iron alloys containing carbide formers of chromium and molybdenum were rapidly solidified by means of a single
roller method. In the alloy containing a high level of both chromium and molybdenum (10Cr-5Mo) and a critical carbon content
of about 4 pct, the metastable phases,ε phase and austenite, are retained after solidification. Theε phase could contain a large amount of carbon in solid solution so that during tempering at about 900 K, it decomposes to
very fine ferrite and carbide, which bring about an enhanced hardness of 1300 DPN. Even after tempering at a high temperature
around 1100 K, the hardness hardly deteriorates due to a remarkable dispersion of fine M3C and M7C3 carbides. Thus, coaddition of chromium and molybdenum is effective in obtaining high hardness.
Formerly Graduate Student, Kyushu Institute of Technology 相似文献
15.
16.
Jette Oddershede Thomas L. Christiansen Kenny Ståhl Marcel A.J. Somers 《国际钢铁研究》2011,82(10):1248-1254
Low temperature carburized AISI 316 stainless steel ‐ carbon expanded austenite ‐ was investigated with EXAFS and synchrotron diffraction together with synthesized carbides of the type M3C2, M7C3 and M23C6. It was found that the chemical environment of carbon expanded austenite is not associated with any of the investigated carbides, that carbon has a strong affinity for chromium, i.e. short range order, and that carbon is in solid solution. 相似文献
17.
The surface hardness of powder injection molded (PIM) 316L is generally low due to the inherited austenitic structure and large grains induced during high-temperature sintering. To increase the surface hardness and the wear resistance, low-temperature carburization (LTC) was applied to PIM 316L. With carburization at 773 K (500 °C) for 24 hours, the resulting hardness at the surface increases from 160 to 810 HV due to the “colossal” supersaturation of interstitial carbon and M5C2 carbide, and the corrosion resistance is not deteriorated. The carburized depth is about 40 μm, and the carbon content in this layer is about 3.25 wt pct or 13.5 at. pct, which causes lattice expansion of the austenite. When the carburization temperature increases to 823 K (550 °C), or the carburization time increases to 72 hours, chromium carbides are observed and the corrosion resistance is impaired. One distinct advantage of applying LTC to PIM 316L is that no acid cleaning process is required, unlike for wrought counterparts, because of the clean surface of the sintered materials. 相似文献
18.
Correlation of microstructure and thermal-fatigue properties of centrifugally cast high-speed steel rolls 总被引:6,自引:0,他引:6
Chang Kyu Kim Jong Il Park Jae Hwa Ryu Sunghak Lee 《Metallurgical and Materials Transactions A》2004,35(2):481-492
This is a study of thermal-fatigue properties in centrifugally cast high-speed steel (HSS) rolls. The thermal-fatigue mechanism
was investigated, with special focus on the roll microstructure and the increase in tensile stress which led the specimens
to fracture when it reached the tensile strength. The thermal-fatigue test results indicated that the thermal-fatigue life
decreased with increasing maximum temperature of the thermal-fatigue cycle. The results were then interpreted based on the
amount of carbides and the cyclic-softening phenomenon associated with the exposed time to elevated temperatures. The coarse
intercellular carbides on the specimen surface acted as fatigue-crack initiation sites as they cleaved at a low stress level
to form cracks. The roll having the lowest matrix hardness and the smallest amount of intercellular carbides, thus, showed
better thermal fatigue properties than the other rolls. For the improvement of the thermal-fatigue properties of the rolls,
this study suggests a homogeneous distribution of carbides by reducing the carbide segregation formed along the solidification
cell boundary and by optimizing the roll compositions. 相似文献
19.
20.
Thermodynamic properties of carbides present in 2.25Cr-lMo steel were determined at 985 K by a gas flowing method with fixed
CH4/H2 gas mixtures and by a silica capsule method with reference alloys. The carbon activity range was from 0.06 to 0.5. Total
carbon content, carbide species, and Cr and Mo partitionings between the matrix and carbides were measured as a function of
the carbon activity. Both M6C and M23C6 carbides were present after 1000 to 3000 hours at the test temperature and in the carbon activity range studied. The amount
of M6C was greater in the low carbon activity range, while M23C6 carbide became the major carbide with increasing carbon activity. The M6C carbide contained Mo as a major element and Cr
and Si as minor elements; approximately 13 pct of the metal constituent was (Cr + Si). The stability of M6C carbide in this steel is significantly higher than M6C formed in the Fe-Mo-C system. The M23C6 carbide contained Cr as a major metal component and Mo as a minor. The M23C6 carbide is more stable in an extended range of the carbon activity in 2.25Cr-lMo steel than in the Fe-Cr-C system. The presence
of Si is apparently low in M23C6. Thermodynamic parameters were computed for M6C and M23C6 carbides using a regular solution model of component carbides, FeCx, CrCx, and MoCx. 相似文献