Improving Strength of Structural Steels by Preheating in an Oxygen-Containing Medium

2019 ◽  
Vol 946 ◽  
pp. 58-62
Author(s):  
Vladimir Afanasyef ◽  
Marina Popova ◽  
Irina Zhibinova
Keyword(s):  
Heat Treatment ◽  
Structural Steels ◽  
Glass Mass ◽  
Preliminary Heat Treatment ◽  
Final Heat Treatment ◽  
High Oxygen Content ◽  
Granular Pearlite ◽  
Austenite Grain ◽  
Rapid Formation ◽  
Strength And Plasticity

The results of the preliminary heat treatment effecting in a medium with a high oxygen content on the microstructure and mechanical properties of structural steels are presented. It is shown that the usage of preheating in the glass mass in the range of (Ac130°C) – Ac1for steels of grades 50 and 40H leads to the formation of a structure with dispersed granular pearlite and crushed excess ferrite precipitates. Such a structure, when heated for quenching, provides rapid formation of a homogeneous austenite and a delay in the growth of austenite grain, which provides the best combination of strength and plasticity after the final heat treatment. It is established that the tensile strength increases 1.2-1.3 times while maintaining the plasticity characteristics. The reliability of the obtained estimates of the mechanical property characteristics is confirmed by the results of a statistical analysis.

Improving the Toughness of 3-1/2NiCrMoV Steam Turbine Disk Forgings

1989 ◽  
Vol 111 (1) ◽  
pp. 61-70 ◽  
Author(s):  
R. L. Bodnar ◽  
K. A. Taylor ◽  
K. S. Albano ◽  
S. A. Heim
Keyword(s):  
Heat Treatment ◽  
Stress Corrosion ◽  
Steam Turbine ◽  
Stress Corrosion Cracking ◽  
Turbine Disk ◽  
Notch Toughness ◽  
Preliminary Heat Treatment ◽  
Final Heat Treatment ◽  
Final Heat ◽  
Turbine Disks

Due to the in-service stress corrosion cracking of some 3-1/2NiCrMoV steam turbine disks, the Charpy V-notch toughness requirements for replacement forgings have dramatically increased in recent years. In response to the new requirements, several avenues for improving the toughness of 3-1/2NiCrMoV steel have been explored and are discussed in this paper. Improvements in forging practice, preliminary heat treatment, final heat treatment and composition are recommended which allow the new requirements to be met.

Effect of Chromium and Nickel Additions on the Transformation Characteristic and Ferrite Grain Size Refinement of Low Carbon Structural Steels Containing 0.13% C

2016 ◽  
Vol 860 ◽  
pp. 158-164
Author(s):  
Md Mohar Ali Bepari ◽  
Mohiuddin Ahmed
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Optical Microscopy ◽  
Chromium Carbide ◽  
Volume Fraction ◽  
Structural Steels ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Ferrite Grain Size

The effect of small addition of chromium and nickel alone or in combination on the transformation characteristic and ferrite grain size of low carbon (0.13%C) structural steels have been studied by cooling suitable steels at four different cooling rates ranging from 120°C/min to 3.6° C/min from temperatures giving a constant austenite grain size of 37 μm. Radio Frequency generator with control system was used for the heat treatment of the steel samples. Optical microscopy of the heat treated samples was carried out. Ferrite grain size was determined from the fictitious ferrite grain size measured by mean linear intercept method and the volume fraction of pearlite obtained by optical microscopy and point counting. It was found that although the heat treatment of the steels was started from a common austenite grain size, their subsequent ferrite grain size after cooling at the same cooling rate were not the same. Both chromium and nickel enhance the formation of Widmanstatten structure. But chromium is more effective than nickel in the formation of Widmanstatten structure. It was also found that the undissolved particles of chromium carbide (Cr2C) present during austenitizing have no role in determining the ferrite grain size. The precipitating particles of chromium carbide (Cr2C) are excellent ferrite grain size refiners. Nickel refines the ferrite grain size. In presence of nickel, Cr2C precipitates are less effective than Cr2C precipitates in absence of nickel in the refinement of ferrite grain size.

Effect of preliminary heat treatment on the size of inclusions and the stable austenite grain size

1966 ◽  
Vol 8 (11) ◽  
pp. 906-910
Author(s):  
V. D. Zelenova ◽  
G. A. Ostrovskii ◽  
K. Z. Shepelyakovskii ◽  
F. I. Shor
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Preliminary Heat Treatment ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Stable Austenite

scholarly journals A New Systematic Approach Based on Dilatometric Analysis to Track Bainite Transformation Kinetics and the Influence of the Prior Austenite Grain Size

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 324
Author(s):  
David San-Martin ◽  
Matthias Kuntz ◽  
Francisca G. Caballero ◽  
Carlos Garcia-Mateo
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Prior Austenite ◽  
Bainitic Transformation ◽  
Transformation Rate ◽  
Transformation Kinetics ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Prior Austenite Grain Size ◽  
Prior Austenite Grain

This investigation explores the influence of the austenitisation heat treatment and thus, of the prior austenite grain size (PAGS), on the kinetics of the bainitic transformation, using as A case study two high-carbon, high-silicon, bainitic steels isothermally transformed (TIso = 250, 300, 350 °C), after being austenised at different temperatures (γTγ = 925–1125 °C). A methodology, based on the three defining dilatometric parameters extracted from the derivative of the relative change in length, was proposed to analyse the transformation kinetics. These parameters are related to the time to start bainitic transformation, the time lapse for most of the transformation to take place and the transformation rate at the end of the transformation. The results show that increasing the PAGS up to 70 µm leads to an increase in the bainite nucleation rate, this effect being more pronounced for the lowest TIso. However, the overall transformation kinetics seems to be weakly affected by the applied heat treatment (γTγ and TIso). In one of the steels, PAGS > 70 µm (γTγ > 1050 °C), which weakly affects the progress of the transformation, except for TIso = 250 °C, for which the enhancement of the autocatalytic effect could be the reason behind an acceleration of the overall transformation.

Substantiation into Parameters of Carbon Fuel Production Technology from Brown Coal

2021 ◽  
Vol 1045 ◽  
pp. 90-101
Author(s):  
Oleksandr Shustov ◽  
Artem Pavlychenko ◽  
Andrii Bondarenko ◽  
Oleksandr Bielov ◽  
Olena Borysovska ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Brown Coal ◽  
Vacuum Drying ◽  
Preliminary Heat Treatment ◽  
Fuel Production ◽  
Thermal Coal ◽  
Heat Treated ◽  
Thermal Influence ◽  
Coking Products ◽  
Qualitative And Quantitative Characteristics

Technological solutions for brown coal processing, thermal influence on it at temperature change, thermo vacuum drying are analysed and qualitative and quantitative characteristics of semi – coking products are studied. The parameters of crushing and thermo vacuum drying of brown coal, heat treatment and cascade separation (electrostatic and magnetic) are substantiated. Studies on the manufacture of a pilot batch of carbon fuel with high quality characteristics are performed. Cascade treatment of heat-treated brown coal on electric and magnetic separators allowed to obtain a concentrate with ash content from 17.72 to 22.8%, volatile yield ≤ 35%, higher heat of combustion from 7256.1 to 7523.6 kcal/kg. It is determined that favourable modes of preliminary heat treatment of brown coal samples are in the temperature range of 200-400°С. The established characteristics of the obtained solid fuel correspond to the gas group of thermal coal. The obtained technological solutions for the processing of brown coal can be the basis for the manufacture of an industrial line, taking into account the thermo vacuum installation for further implementation in enterprises using carbon fuel.

scholarly journals RESEARCH OF THE PROCESS OF EXTRACTION OF BLACK CUMIN OIL WITH PRELIMINARY HEAT TREATMENT

2021 ◽  
pp. 66-69
Keyword(s):  
Heat Treatment ◽  
Treatment Process ◽  
Acid Number ◽  
Oil Yield ◽  
Preliminary Heat Treatment ◽  
Heat Treatment Process ◽  
Drying Process ◽  
Technological Parameters ◽  
Variable Parameters ◽  
Black Cumin

The aim of the study is to increase the yield of oil from black cumin seeds. The results of studies of the influence of technological parameters - temperature and duration of drying of black cumin seeds on indicators of the yield of oil, cake and moisture removal from seeds are presented. The optimal technological parameters of the influence of the preliminary heat treatment process on the indicators of the maximum oil yield, acid number, color, and oil moisture have been established. The variable parameters were the temperature from 80 to 130 °C and the duration of the heat treatment process from 5 to 60 minutes. The possibility of increasing the oil yield by 6,11% has been shown. For this, the drying process must be carried out at a temperature of 100 °C and a process duration of 15 minutes. At the same time, the degree of oil extraction increases from 59,13% to 75,24%, the acid number decreases to 2,98, humidity to 0,12%, and color to 40.

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