Effect of Austenite Grain Size on Hardenability and Impact Toughness of SCM435H

2016 ◽  
Vol 867 ◽  
pp. 50-54
Author(s):  
Ji Lin Chen ◽  
Shi Peng Ruan ◽  
Li Jun Wang ◽  
Jin Po Zhai ◽  
Chao Liu
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Phase Region ◽  
Material Strength ◽  
Two Phase ◽  
Quenching Temperature ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Strength And Plasticity ◽  
The Impact

The effects of austenite grain size on hardenability and impact toughness were investigated. The results show that: Since the beginning of the two-phase region with quenching temperature, the austenite grain size from the initial 4+6 mixed crystal at 740°C, and gradually increased to 10 at 860°C; Austenite grain size and hardenability was directly proportional to the austenite grain size increased from 8μm to 36μm, the biggest change is the hardness 10HRC; Austenite grain size and impact toughness is linear, with the decrease of grain size, the impact energy increases linearly, and the austenite grain size and impact toughness curve fitting. Comprehensive analysis for ensuring the hardenability of cold heading steels should be considered optimal matching of material strength and plasticity.

scholarly journals Study on the Nucleation and Growth of Pearlite Colony and Impact Toughness of Eutectoid Steel

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1133 ◽  
Author(s):  
Zhang ◽  
Zhao ◽  
Tan ◽  
Ji ◽  
Xiang
Keyword(s):  
Grain Size ◽  
Impact Toughness ◽  
Colony Size ◽  
Eutectoid Steel ◽  
Austenitizing Temperature ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Nucleation Sites ◽  
Pearlite Colony ◽  
The Impact

The relationship between microstructure parameters and mechanical properties was studied in this paper. The steel was heat-treated at different austenitizing temperatures to acquire varying microstructure. The results showed that austenite grain size increases with austenitizing temperature, while the pearlite colony size was relatively constant. The strength followed a Hall–Petch relationship with the austenite grain size, but the austenite grain size has nothing to do with the impact toughness. The control unit for determining the impact toughness of pearlitic steel is the pearlite colony size using a comparison method. Further studies have found that, in the hypoeutectoid steel and hypereutectoid steel, the pearlite colony size changes with the austenitizing temperature. However, when the eutectoid steel with a carbon content of 0.81% undergoes the isothermal transformation, the number of grain boundary precipitates is very few. There are many nucleation sites at the grain boundary. The pearlite colonies randomly nucleate at the grain boundaries and grow into the interior of the grains. Simultaneously, new pearlite colonies nucleate by the side of the existing pearlite colony. The intragranular pearlite colonies are also randomly nucleated. These nucleation sites increase the chance of the growing pearlite colonies colliding with each other, eventually resulting in a constant pearlite colony size.

Application of the Betti Number to Prior Austenite Grain Size Analysis of Repeatedly Quenched Steel Based on the Homology Method

2015 ◽  
Vol 1102 ◽  
pp. 45-49
Author(s):  
Koshiro Mizobe ◽  
Katsuyuki Kida ◽  
Wakana Matsuda ◽  
Kazuaki Nakane
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Prior Austenite ◽  
Evaluation Method ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Material Strength ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Prior Austenite Grain

Grain refinement has a strong influence on material strength. Therefore, the automatic evaluation method of the grain refinement level is useful. In order to develop a grain size analysis system, we applied the homology theory to prior austenite grain analysis. We prepared repeatedly quenched high-carbon high-chromium steel samples (JIS-SUJ2) and evaluated their microstructures in order to investigate the relation between theBettinumbers (b0andb1) and prior austenite grains. We found that theBettinumber (b1) is strongly correlated to the number of grains.

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.

scholarly journals Overview of HSS Steel Grades Development and Study of Reheating Condition Effects on Austenite Grain Size Changes

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1988
Author(s):  
Tibor Kvackaj ◽  
Jana Bidulská ◽  
Róbert Bidulský
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
High Strength Steel ◽  
Single Phase ◽  
Hsla Steel ◽  
High Strength ◽  
Strength Properties ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Steel Grades

This review paper concerns the development of the chemical compositions and controlled processes of rolling and cooling steels to increase their mechanical properties and reduce weight and production costs. The paper analyzes the basic differences among high-strength steel (HSS), advanced high-strength steel (AHSS) and ultra-high-strength steel (UHSS) depending on differences in their final microstructural components, chemical composition, alloying elements and strengthening contributions to determine strength and mechanical properties. HSS is characterized by a final single-phase structure with reduced perlite content, while AHSS has a final structure of two-phase to multiphase. UHSS is characterized by a single-phase or multiphase structure. The yield strength of the steels have the following value intervals: HSS, 180–550 MPa; AHSS, 260–900 MPa; UHSS, 600–960 MPa. In addition to strength properties, the ductility of these steel grades is also an important parameter. AHSS steel has the best ductility, followed by HSS and UHSS. Within the HSS steel group, high-strength low-alloy (HSLA) steel represents a special subgroup characterized by the use of microalloying elements for special strength and plastic properties. An important parameter determining the strength properties of these steels is the grain-size diameter of the final structure, which depends on the processing conditions of the previous austenitic structure. The influence of reheating temperatures (TReh) and the holding time at the reheating temperature (tReh) of C–Mn–Nb–V HSLA steel was investigated in detail. Mathematical equations describing changes in the diameter of austenite grain size (dγ), depending on reheating temperature and holding time, were derived by the authors. The coordinates of the point where normal grain growth turned abnormal was determined. These coordinates for testing steel are the reheating conditions TReh = 1060 °C, tReh = 1800 s at the diameter of austenite grain size dγ = 100 μm.

The effect of austenite grain size on deformation mechanism of Fe–17Mn steel

2021 ◽  
Vol 809 ◽  
pp. 140972
Author(s):  
Jin-Young Lee ◽  
Jin-Sung Hong ◽  
Seok-Hyeon Kang ◽  
Young-Kook Lee
Keyword(s):  
Grain Size ◽  
Deformation Mechanism ◽  
Austenite Grain Size ◽  
Austenite Grain

Austenite Grain Evolution Mechanism of High Carbon Rail Based on Thermal Technology

2020 ◽  
Vol 837 ◽  
pp. 74-80
Author(s):  
Jun Yuan ◽  
Zhen Yu Han ◽  
Yong Deng ◽  
Da Wei Yang
Keyword(s):  
Grain Size ◽  
Tensile Strength ◽  
Rail Steel ◽  
Heating Temperature ◽  
Great Influence ◽  
Stable Operation ◽  
High Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Austenite Grains

In view of the special requirements of rails to ensure the safe and stable operation of Railways in China, the formation characteristics of austenite grains in high carbon rail are revealed through industrial exploration, the process of industrial rail heating and rolling is simulated, innovative experimental research methods such as different heating and heat treatment are carried out on the actual rails in the laboratory. Transfer characteristics of austenite grain size, microstructures and key properties of high carbon rail during the process are also revealed. The results show that the austenite grain size of industrial produced U75V rail is about 9.0 grade. When the holding temperature is increased from 800 C to 1300 C, the austenite grain size of high carbon rail steel decreases, the austenite grain are gradually coarsened, and the tensile strength increases slightly. The tensile strength is affected by the heating temperature. With the increase of heating temperature, the elongation and impact toughness of high carbon rail decrease. The heating temperature of high carbon rail combined with austenite grain size shows that the heating temperature has a great influence on austenite grain size, and has the most obvious influence on the toughness of high carbon rail.

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