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.

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.

scholarly journals Characterization of Microstructure in High-Hardness Surface Layer of Low-Carbon Steel

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 995
Author(s):  
Haitao Xiao ◽  
Shaobo Zheng ◽  
Yan Xin ◽  
Jiali Xu ◽  
Ke Han ◽  
...  
Keyword(s):  
Surface Layer ◽  
Carbon Steel ◽  
Yield Strength ◽  
Carbon Content ◽  
Acicular Ferrite ◽  
Lath Martensite ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Upper Bainite ◽  
Mixed Microstructure

Surface hardening improves the strength of low-carbon steel without interfering with the toughness of its core. In this study, we focused on the microstructure in the surface layer (0–200 μm) of our low-carbon steel, where we discovered an unexpectedly high level of hardness. We confirmed the presence of not only upper bainite and acicular ferrite but also lath martensite in the hard surface layer. In area of 0–50 μm, a mixed microstructure of lath martensite and B1 upper bainite was formed as a result of high cooling rate (about 50–100 K/s). In area of 50–200 μm, a mixed microstructure of acicular ferrite and B2 upper bainite was formed. The average nanohardness of the martensite was as high as 9.87 ± 0.51 GPa, which was equivalent to the level reported for steel with twenty times the carbon content. The ultrafine laths with an average width of 128 nm was considered to be a key cause of high nanohardness. The average nanohardness of the ferrites was much lower than for martensite: 4.18 ± 0.39 GPa for upper bainite and 2.93 ± 0.30 GPa for acicular ferrite. Yield strength, likewise, was much higher for martensite (2378 ± 123 MPa) than for upper bainite (1007 ± 94 MPa) or acicular ferrite (706 ± 72 MPa). The high yield strength value of martensite gave the surface layer an exceptional resistance to abrasion to a degree that would be unachievable without additional heat treatment in other steels with similar carbon content.

Thermal and mechanical stability of retained austenite in high carbon steel: An in - situ investigation

2016 ◽  
Vol 163 ◽  
pp. 209-213 ◽  
Author(s):  
Abhilash Molkeri ◽  
Farshid Pahlevani ◽  
Irene Emmanuelawati ◽  
Veena Sahajwalla
Keyword(s):  
Carbon Steel ◽  
Retained Austenite ◽  
Mechanical Stability ◽  
High Carbon Steel ◽  
High Carbon ◽  
In Situ Investigation

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.

Effect of Ausforming Temperature on Bainite Transformation of High Carbon Low Alloy Steel

2015 ◽  
Vol 817 ◽  
pp. 454-459 ◽  
Author(s):  
Jian Guo He ◽  
Ai Min Zhao ◽  
Huang Yao ◽  
Chao Zhi ◽  
Fu Qing Zhao
Keyword(s):  
Low Temperature ◽  
Alloy Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Transformation Rate ◽  
Low Alloy Steel ◽  
High Carbon ◽  
Bainite Transformation ◽  
Electron Backscattered Diffraction ◽  
In Situ Experiments

The effect of ausforming temperature on bainite transformation of high carbon low alloy steel was studied by in situ experiments using a Gleeble 3500 thermal and mechanical testing system. Morphology and crystallography of ausforming bainite were examined by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It has been found that deformation at all temperatures range from 230°C to 600°C can accelerate low temperature bainite transformation, and transformation rate increased with deformation temperature reduced. Quantitative X-ray analysis shows that the volume fraction of retained austenite was about 35.84% after deformation and isothermal transformation for 20 hours, it was approximately the same amount with austempering bainite transformation process (no strain) which austenite volume fraction was about 32.01%. Low temperature bainite formation can be accelerated with a smaller increase amount of retained austenite by deformation at a low temperature range of 230~600 oC.

Effects of Starting Carbon Sources on the Carbothermal Synthesis of SiC Powders

2010 ◽  
Vol 105-106 ◽  
pp. 754-757 ◽  
Author(s):  
Jun Hua Cheng ◽  
Di Jiang Wen
Keyword(s):  
Carbon Content ◽  
Rice Husk ◽  
Carbon Sources ◽  
External Source ◽  
Laser Diffraction ◽  
Low Carbon ◽  
High Carbon ◽  
High Carbon Content ◽  
Carbothermal Synthesis ◽  
The Difference

Silicon carbide (SiC) powders have been prepared at 1200–1500°C by carbothermal reduction of two kind precursors of carbonl/silica mixtures: coked rice husk with high-carbon content, and gasified rice husk with low-carbon content mixed with carbon powders as an external carbon sources. The differences in nature of carbon matter in the external source and coked rice husk, and their effect on SiC synthesis have been studied by TG-DSC, TEM, XRD and laser diffraction technique. Experimental results show that the difference in nature of carbon source may affect the formation of SiC powders. The characteristics of the synthesized SiC particles strongly depend on the characteristics of the carbon sources.

scholarly journals Fracture Toughness Properties of Savannah River Site Storage Tank ASTM A285 Low Carbon Steel

2002 ◽  
Author(s):  
K. H. Subramanian ◽  
A. J. Duncan ◽  
R. L. Sindelar
Keyword(s):  
Fracture Toughness ◽  
Carbon Steel ◽  
Carbon Content ◽  
Storage Tank ◽  
Low Carbon Steel ◽  
Savannah River Site ◽  
Low Carbon ◽  
Savannah River ◽  
High Carbon ◽  
River Site

A materials test program was developed to measure mechanical properties of ASTM A285 Grade B low carbon steel for application to structural and flaw stability analysis of storage tanks at the Department of Energy (DOE) Savannah River Site (SRS). Under this plan, fracture toughness and tensile testing are being performed at conditions that are representative of storage tank conditions on steels that span compositions within ASTM A285 specifications. The testing is being done within the framework of a statistical test matrix and the data collected will be used to develop a predictive model for materials properties. The results presented herein are limited to a subset of data comparing for comparison of a recent vintage steel versus an older steel for fracture resistance behavior. These preliminary results indicate that dynamic loading rates result in a greater increase in the fracture toughness response in the case of the recent vintage steels of lower carbon content when compared to the archival heat of high carbon content. In addition, ductile tearing in the archival, high carbon steel was more likely to be interrupted by cleavage fracture at lower fracture energies than the modern, low carbon steel.

scholarly journals Characteristics and agrarian properties of biochar derived from pyrolysis and co-pyrolysis of rubberwood sawdust and sewage sludge for further application to soil improvement

2021 ◽  
Author(s):  
Liaqat Ali ◽  
Arkom Palamanit ◽  
Kuaanan Techato ◽  
Md. Shahariar Chowdhury ◽  
Khamphe Phoungthong
Keyword(s):  
Sewage Sludge ◽  
Carbon Content ◽  
Soil Improvement ◽  
Nonpoint Source ◽  
Low Carbon ◽  
High Carbon ◽  
High Carbon Content ◽  
Surface Areas ◽  
Weight Losses ◽  
Water Holding

Abstract This study investigated the characteristics of biochars derived from pyrolysis of rubberwood sawdust and sewage sludge, and co-pyrolysis of these feedstocks at the ratios of 50:50 and 75:25. All feedstocks were pyrolyzed at 550°C in slow pyrolysis with a moving bed pyrolysis reactor. Then, the investigated characteristics of biochar samples were determined and are reported. The rubberwood sawdust biochar (RWSB) had a higher in carbon content (86.70 wt%) and was lower in oxygen content (7.89 wt%), while sewage sludge biochar (SSB) had a higher ash content (65.61 w%) and a low carbon content (24.27 wt%). The weight losses of biochars were observed in TGA while the DTG graphs show degradation rate of biochar produced in pyrolysis specific conditions. RWSB had a lower content of Si, Fe, K, Na and P than SSB as observed by XRF. The pH of RWSB, SSB and the blends (50:50, 75:25) of biochars was in the range 8.41–10.02. High carbon content of the biochar confirms potential for its use in carbon sequestration. The large pore volumes and specific surface areas of biochars were found by SEM and BET. The available functional groups in biochars were C–O, C = C, and C–H as confirmed by FTIR. Water holding capacity (WHC) and water releasing ability (WRA) of RWSB, SSB, and the blends (50:50 and 75:25) of biochars were 1.01–3.08 (mL/g) and 1.19–52.42 (wt%), respectively. In this study, our results show that blending woody and non-woody based biochars can help address nonpoint source contaminants in environment. So, these all findings should develop as tune to parameters of thermal degradation of biomass and bio-biowaste with sustain and eco-friendly biochar production.

UDDEHOLM STAINLESS 24 and 24L

Alloy Digest ◽  
1978 ◽  
Vol 27 (5) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Low Temperature ◽  
Physical Properties ◽  
Carbon Content ◽  
Chemical Industry ◽  
Heat Treating ◽  
Low Carbon ◽  
Temperature Performance ◽  
Wide Usage

Abstract UDDEHOLM Stainless 24 and 24L are essentially similar except for the extra-low carbon content of 24L for use where forming and welding result in relatively long heating within the range 930-1650 F (500-900 C). They are acid-resistant, non-hardenable and nonmagnetic steels. Their wide usage includes process vessels and containers in the chemical industry, steam superheaters and pickling vats. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness and creep. It also includes information on low temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SS-350. Producer or source: Uddeholm Aktiebolag.

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