Morphology, Nature and Formation Mechanism of Packet Plate Martensite in Medium and High Carbon Steels

2011 ◽  
Vol 121-126 ◽  
pp. 231-238 ◽  
Author(s):  
Yue Xin Ma ◽  
Yue Jun Liu ◽  
Long Wang ◽  
De Chang Zeng ◽  
Yu Hua Tan
Keyword(s):  
Twin Boundary ◽  
Misorientation Angle ◽  
Martensite Transformation ◽  
Lath Martensite ◽  
Carbon Steels ◽  
Plate Martensite ◽  
Low Carbon ◽  
High Carbon ◽  
Boundary Misorientation ◽  
Carbon Martensite

The microstructures of 11 kinds of commercial steels quenched from high temperature were deeply studied by optical microscope and canning election microscope. It was proved that packet martensite in medium and high carbon steels is not lath martensite, but rather packet plate martensite. Through the analysis of crystallography，it was found that four change rules of crystal orientation may arise during the process of martensite transformation. Two inner interfaces spontaneously formed were only discovered in martensite transformation process: small-angel boundary (misorientation angle is 0 ~ 10º) and twin boundary (misorientation angle is 70º32’). The former mainly appeared in low carbon martensite, and the latter principally formed in medium and high carbon martensite. The twin boundary packet mechanism in medium and high carbon steels has made in detail in this paper.

Investigation of Lath and Plate Martensite in a Carbon Steel

2011 ◽  
Vol 172-174 ◽  
pp. 61-66 ◽  
Author(s):  
Albin Stormvinter ◽  
Annika Borgenstam ◽  
Peter Hedström
Keyword(s):  
Carbon Steel ◽  
Carbon Content ◽  
Morphological Change ◽  
Retained Austenite ◽  
Alloy Composition ◽  
Lath Martensite ◽  
Carbon Steels ◽  
Plate Martensite ◽  
High Carbon ◽  
Martensite Microstructure

Martensite in carbon steels forms in different morphologies, often referred to as lath andplate martensite. The alloy composition has a strong effect on the morphology, for instance in car-bon steels there is a morphological change of the martensite microstructure from lath martensite atlow carbon contents to plate martensite at high carbon contents. In the present work a decarburizedhigh-carbon steel, enabling the isolation of carbons' influence alone, has been studied in order to in-vestigate the changes in morphology and hardness. From the results it is concluded that there is acontinuous change of hardness with increased carbon content. The increasing hardness slows down atabout 0.6 wt%C before decreasing at higher carbon contents. This is in accordance with the change inmorphology since it was found that lath martensite dominates below 0.6 wt%C and the first units ofgrain boundary martensite and plate martensite appear above 0.6 wt%C. At high carbon contents thedominating morphology is plate martensite, but retained austenite is also present.

The martensite transformation in carbon steels

1960 ◽  
Vol 259 (1296) ◽  
pp. 45-58 ◽  
Keyword(s):  
Experimental Data ◽  
Martensite Transformation ◽  
Carbon Steels ◽  
Fine Scale ◽  
Low Carbon ◽  
High Carbon ◽  
Transformation Mechanism ◽  
Direct Examination ◽  
Low Carbon Steels ◽  
Thin Foils

Martensite formed in plain carbon steels containing less than 1·4% carbon has been studied by direct examination of thin foils in the electron microscope. It was found that the martensite in low-carbon steels forms predominantly as long needles parallel to <111> M while in the high-carbon steels it forms as plates internally twinned on a fine scale. The existence of these narrow twins in the high-carbon martensites enables the transformation mechanism to be derived uniquely. This mechanism, which is largely in agreement with those previously proposed, explains all the observed experimental data. The observed change in the morphology of the martensite from needles to plates as the carbon content increases suggests an explanation of the change in hardness of quenched steels with change in the percentage carbon.

Martensitic Transformation in a Low-Alloy Ultra-High-Strength Steel

2011 ◽  
Vol 295-297 ◽  
pp. 1470-1473 ◽  
Author(s):  
Zhi Xia Qiao ◽  
Dan Tian Zhang ◽  
Yong Chang Liu ◽  
Ze Sheng Yan
Keyword(s):  
Martensitic Transformation ◽  
High Strength Steel ◽  
Lath Martensite ◽  
High Strength ◽  
Transformation Rate ◽  
Low Carbon ◽  
High Carbon ◽  
Process Characteristics ◽  
Ultra High Strength Steel ◽  
Carbon Martensite

Martensitic transformation is the most important phase transformation strengthening the 30CrNi3MoV ultra-high-strength steel during heat treatment process. Characteristics of the martensitic transformation in the 30CrNi3MoV steel were investigated by means of dilatometric measurements and microstructural observations. The results showed that the starting and finishing martensitic transformation temperatures of the 30CrNi3MoV explored steel are 317°C and 167°C respectively, which are hardly influenced by the cooling rate from austenite region. Such a wide temperature range of martensitic transformation in the 30CrNi3MoV steel results into the diversity of martensite microstructures. The microstructures in all the quenched 30CrNi3MoV samples are composed of mixture of lath and acicular martensite, corresponding to low-carbon and high-carbon martensite respectively. The transformation rate of acicular martensite is much slower than that of lath martensite, which can be attributed to the stabilization of the rest high-carbon austenite after the formation of lath martensite.

Precipitation at the transformation interface of pearlite in steel

1990 ◽  
Vol 48 (4) ◽  
pp. 912-913
Author(s):  
F. A. Khalid ◽  
D. V. Edmonds
Keyword(s):  
Thin Foil ◽  
Carbon Steels ◽  
Model Alloy ◽  
Low Carbon ◽  
High Carbon ◽  
Growth Interface ◽  
Medium Carbon ◽  
Interphase Precipitation ◽  
Solution Treated ◽  
Wide Range

The austenite/pearlite growth interface in a model alloy steel (Fe-1lMn-0.8C-0.5V nominal wt%) is being studied in an attempt to characterise the morphology and mechanism of VC precipitation at the growth interface. In this alloy pearlite nodules can be grown isothermally in austenite that remains stable at room temperature thus facilitating examination of the transformation interfaces. This study presents preliminary results of thin foil TEM of the precipitation of VC at the austenite/ferrite interface, which reaction, termed interphase precipitation, occurs in a number of low- carbon HSLA and microalloyed medium- and high- carbon steels. Some observations of interphase precipitation in microalloyed low- and medium- carbon commercial steels are also reported for comparison as this reaction can be responsible for a significant increase in strength in a wide range of commercial steels.The experimental alloy was made as 50 g argon arc melts using high purity materials and homogenised. Samples were solution treated at 1300 °C for 1 hr and WQ. Specimens were then solutionised at 1300 °C for 15 min. and isothermally transformed at 620 °C for 10-18hrs. and WQ. Specimens of microalloyed commercial steels were studied in either as-rolled or as- forged conditions. Detailed procedures of thin foil preparation for TEM are given elsewhere.

Effects of Microstructure Transformation on Strengthening and Toughening for Heat-Treated Low Carbon Martensite Stainless Bearing Steel

2015 ◽  
Vol 817 ◽  
pp. 667-674 ◽  
Author(s):  
Xiao Hong Yuan ◽  
Mao Sheng Yang ◽  
Kun Yu Zhao
Keyword(s):  
Electron Microscope ◽  
Cryogenic Treatment ◽  
Lath Martensite ◽  
Optical Microscope ◽  
Bearing Steel ◽  
Strength Increase ◽  
Low Carbon ◽  
Packet Size ◽  
Block Width ◽  
Carbon Martensite

Microstructural transformations and mechanical properties of a low carbon martensite stainless bearing steel treated with different heat treatment parameters and cryogenic treatment (-82°C) were investigated. The function of microstructural transformations on strengthening and toughening process was quantitatively characterized as well. These analyses were performed by the optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and electron back scattering diffraction (EBSD) technique. The obtained results show that with execution of cryogenic treatment and tempering, the tensile strength increase owing to the reduction of retained austenite and fine carbides precipitating respectively. The effect of martensitic microstructure on yield strength increment can be regarded as packet size and block width which conform to Hall-Petch relationship. Meanwhile, the results suggest that the block width is the key structural controlling unit when analyzing the strength-structure relationship of lath martensite in low carbon martensite stainless bearing steel. In addition, packet size can be related to toughness controlling as well because of the same size as cleavage plane.

scholarly journals Mechanism of the Microstructural Evolution of 18Cr2Ni4WA Steel during Vacuum Low-Pressure Carburizing Heat Treatment and Its Effect on Case Hardness

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2352
Author(s):  
Bin Wang ◽  
Yanping He ◽  
Ye Liu ◽  
Yong Tian ◽  
Jinglin You ◽  
...  
Keyword(s):  
Low Temperature ◽  
Carbon Content ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
Lath Martensite ◽  
Low Pressure ◽  
Low Carbon ◽  
High Carbon ◽  
Carburized Layer ◽  
Martensite Matrix

In this study, vacuum low-pressure carburizing heat treatments were carried out on 18Cr2Ni4WA case-carburized alloy steel. The evolution and phase transformation mechanism of the microstructure of the carburized layer during low-temperature tempering and its effect on the surface hardness were studied. The results showed that the carburized layer of the 18Cr2Ni4WA steel was composed of a large quantity of martensite and retained austenite. The type of martensite matrix changed from acicular martensite to lath martensite from the surface to the core. The hardness of the carburized layer gradually decreased as the carbon content decreased. A thermodynamic model was used to show that the low-carbon retained austenite was easier to transform into martensite at lower temperatures, since the high-carbon retained austenite was more thermally stable than the low-carbon retained austenite. The mechanical stability—not the thermal stability—of the retained austenite in the carburized layer dominated after carburizing and quenching, and cryogenic treatment had a limited effect on promoting the martensite formation. During low-temperature tempering, the solid-solution carbon content of the martensite decreased, the compressive stress on the retained austenite was reduced and the mechanical stability of the retained austenite decreased. Therefore, during cooling after low-temperature tempering, the low-carbon retained austenite transformed into martensite, whereas the high-carbon retained austenite still remained in the microstructure. The changes in the martensite matrix hardness had a far greater effect than the transformation of the retained austenite to martensite on the case hardness of the carburized layer.

Deformation and Structure Difference of Steel Droplets during Initial Solidification

2017 ◽  
Vol 36 (4) ◽  
pp. 347-357 ◽  
Author(s):  
Yang Li ◽  
Jing Wang ◽  
Jiaquan Zhang ◽  
Changgui Cheng ◽  
Zhi Zeng
Keyword(s):  
Carbon Steel ◽  
Continuous Casting ◽  
High Carbon Steel ◽  
Low Carbon Steel ◽  
Carbon Steels ◽  
Solidification Structure ◽  
Low Carbon ◽  
High Carbon ◽  
Peritectic Steel ◽  
Initial Solidification

AbstractThe surface quality of slabs is closely related with the initial solidification at very first seconds of molten steel near meniscus in mold during continuous casting. The solidification, structure, and free deformation for given steels have been investigated in droplet experiments by aid of Laser Scanning Confocal Microscope. It is observed that the appearances of solidified shells for high carbon steels and some hyper-peritectic steels with high carbon content show lamellar, while that for other steels show spherical. Convex is formed along the chilling direction for most steels, besides some occasions that concave is formed for high carbon steel at times. The deformation degree decreases gradually in order of hypo-peritectic steel, ultra-low carbon steel, hyper-peritectic steel, low carbon steel, and high carbon steel, which is consistent with the solidification shrinkage in macroscope during continuous casting. Additionally, the microstructure of solidified shell of hypo-peritectic steel is bainite, while that of hyper-peritectic steel is martensite.

Crucible Steel in South India-Preliminary Investigations on Crucibles from Some Newly Identified Sites

1996 ◽  
Vol 462 ◽  
Author(s):  
Sharada Srinivasan
Keyword(s):  
Carbon Steel ◽  
Tamil Nadu ◽  
High Carbon Steel ◽  
Carbon Steels ◽  
Low Carbon ◽  
High Carbon ◽  
Metal Mining ◽  
Hypereutectoid Steel ◽  
Iron And Steel ◽  
Crucible Steel

ABSTRACTEuropean accounts from the 17th century onwards have referred to the repute and manufacture of “wootz’, a traditional crucible steel made especially in parts of southern India in the former provinces of Golconda, Mysore and Salem. Pliny's Natural History mentions the import of iron and steel from the Seres which have been thought to refer to the ancient southern Indian kingdom of the Cheras. As yet the scale of excavations and surface surveys is too limited to link the literary accounts to archaeometallurgical evidence, although pioneering exploratory investigations have been made by scholars, especially on the pre-industrial production sites of Konasamudram and Gatihosahalli discussed in 18th-19th century European accounts. In 1991–2 during preliminary surveys of ancient base metal mining sites, Srinivasan came across unreported dumps with crucible fragments at Mel-Siruvalur in Tamil Nadu, and Tintini and Machnur in Karnataka and she collected surface specimens from these sites as well as from the known site of Gatihosahalli. She was also given crucible fragments by the Tamil University, Tanjavur, from an excavated megalithic site at Kodumanal, dated to ca 2nd c. Bc, mentioned in Tamil Sangam literature (ca 3rd c. BC-3rd c. AD), and very near Karur, the ancient capital of the Sangam Cheras. Analyses of crucible fragments from the surface collection at Mel-Siruvalur showed several iron prills with a uniform pearlitic structure of high-carbon hypereutectoid steel (∼1–1.5% C) suggesting that the end product was uniformly a high-carbon steel of a structure consistent with those of high-carbon steels used successfully to experimentally replicate the watered steel patterns on ‘Damascus’ swords. Investigations indicate that the process was of carburisation of molten low carbon iron (m.p. 1400° C) in crucibles packed with carbonaceous matter. The fabric of crucibles from all the above mentioned sites appears similar. Preliminary investigations on these crucibles are thus reported to establish their relationship to crucible production of carbon steel and to thereby extend the known horizons of this technology further.

scholarly journals Heat Treatment Effect on Lath Martensite

2018 ◽  
Vol 1 (1) ◽  
pp. 26-30
Author(s):  
Enikő Réka Fábián ◽  
Áron Kótai
Keyword(s):  
Heat Treatment ◽  
Lath Martensite ◽  
Carbon Steels ◽  
Low Carbon ◽  
Low Carbon Steels ◽  
Heat Treated ◽  
Different Temperatures ◽  
Cold Rolled ◽  
Ice Water ◽  
Martensite Microstructure

Abstract During our investigation lath martensite was produced in low carbon steels by austenitization at 1200 °C/20 min, and the cooling of samples in ice water. The samples were tempered at a range of temperatures. The tempering effects on microstructure and on mechanical proprieties were investigated. Some samples with lath martensite microstructure were cold rolled and heat treated at different temperatures. Recrystallization was observed after heat treatment at 600-700 °C.

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