scholarly journals Acicular Ferrite Formation and Its Influencing Factors-A Review

2016 ◽  
Vol 6 (1) ◽  
pp. 24 ◽  
Author(s):  
Denise Loder ◽  
Susanne K. Michelic ◽  
Christian Bernhard
Keyword(s):  
Acicular Ferrite ◽  
Steel Composition ◽  
Titanium Addition ◽  
Austenite Grain Size ◽  
Ferrite Formation ◽  
Austenite Grain ◽  
Size Number ◽  
Metallic Inclusions ◽  
The Impact ◽  
Steel Properties

Acicular ferrite is a microstructure nucleating intergranularly on non-metallic inclusions and forming an arrangement of fine, interlocking grains. This structure is known to improve steel properties, especially steel toughness, essentially. The formation of acicular ferrite is mainly affected by steel composition, cooling rate, inclusion landscape and austenite grain size. In recent decades, extensive research has been conducted to investigate these factors. The present paper provides an overview of the impact of published results and the state of knowledge regarding acicular ferrite formation. Special attention is paid to the effect of carbon, manganese and titanium addition to steel, as well as the optimum size, number and composition of non-metallic inclusions. In addition, the reactions during the nucleation and growth of acicular ferrite needles are briefly addressed. Further, characteristics of acicular ferrite and bainite are summarized, which should help to distinguish these similar structures.

The Influence of Oxide Inclusion on Austenite Grain Size and Heat Affected Zone Toughness for Low Carbon Steels

2012 ◽  
Vol 715-716 ◽  
pp. 617-622 ◽  
Author(s):  
Wei Shu ◽  
Xue Min Wang ◽  
Cheng Jia Shang ◽  
Xin Lai He
Keyword(s):  
Grain Size ◽  
Heat Affected Zone ◽  
Acicular Ferrite ◽  
Oxide Inclusion ◽  
Thermal Simulation ◽  
Carbon Steels ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Low Carbon Steels ◽  
Austenite Grain

The low carbon steels were smelted with special oxide introduction technique and the HAZ properties has been studied with thermal simulation. The optical microscope, SEM and TEM were used to analyze the composition, size and distribution of the inclusions, and the mechanical properties after thermal simulation were also investigated. The influence of oxide inclusions on the austenite grain size was also studied. The results show that after the smelting the inclusion is complex, in the core is Ti oxides about 1-3 micron and around it is MnS. When the reheat temperature is below 1000, the size of austenite grain is the same for experimental steel and base steel. However, when the reheat temperature is over than 1100, the size of austenite grains in experimental steel is one third of that in base steels. After thermal simulation, with thet8/5increasing the toughness of HAZ decreased. The austnite grain size also increased. The microstructure is composed of intergranular ferrite and intragranular acicular ferrite. Therefore by introducing the fine oxide inclusion to the steel the austenite grain was refined and during the phase transformation the acicular ferrite formed at inclusions at first. These two factors are the main causes to improve the toughness of heat affected zone for steels produced by oxide metallurgy technique.

The calculation of stress intensity factor steel of railway wheels

2020 ◽  
Vol 109 ◽  
pp. 187-193
Author(s):  
Igor VAKULENKO ◽  
Svetlana PROYDAK ◽  
Hangardas ASKEROV
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Impact Strength ◽  
Structural Parameters ◽  
Critical Stress Intensity Factor ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Railway Wheels ◽  
Steel Properties

From an analysis of the dependence complex of carbon steel properties on structural parameters, it was found that for an isostructural state, the influence of austenite grain size on impact strength exceeds the dependence on carbon content. As a result of explaining correlation relationships between individual mechanical characteristics, to evaluate critical stress intensity factor, a relationship is proposed based on the use of impact strength. The proportionality coefficient in proposed dependence is determined by ratio of elongation to narrowing at tensile test.

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.

A New Free-Machining Steel Containing Bismuth and Calcium

2016 ◽  
Vol 857 ◽  
pp. 251-255 ◽  
Author(s):  
A.V. Ryabov ◽  
Aleksandr A. Dyakonov ◽  
M.G. Vakhitov
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Surface Quality ◽  
Quality Characteristics ◽  
Austenite Grain Size ◽  
Bismuth Content ◽  
Austenite Grain ◽  
Metallic Inclusions ◽  
Bottom To Top

The paper presents a new environmentally friendly lead-free free-machining structural steel AVTs19KhGN containing bismuth and calcium. The following quality characteristics of the new steel (in as-cast and forged condition) are determined: mechanical properties; austenite grain size; amount of non-metallic inclusions; surface quality. In forged rods (square 20 mm) a tendency towards an increase of bismuth content is observed from bottom to top of the ingot. Calcium distribution along the billet is uniform. Surface quality of billets in heats following the test heats is comparable to that of analog steels. Austenite grain size does not exceed ASTM number 6. Austenite grain is refined with increasing bismuth content. Mechanical properties are at the same level as for the steel without bismuth and calcium.

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.

scholarly journals Grain Size Evolution and Mechanical Properties of Nb, V–Nb, and Ti–Nb Boron Type S1100QL Steels

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 492
Author(s):  
Jan Foder ◽  
Jaka Burja ◽  
Grega Klančnik
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Hot Forging ◽  
Size Control ◽  
High Strength ◽  
Fatigue Properties ◽  
Titanium Addition ◽  
Austenite Grain Size ◽  
Size Evolution

Titanium additions are often used for boron factor and primary austenite grain size control in boron high- and ultra-high-strength alloys. Due to the risk of formation of coarse TiN during solidification the addition of titanium is limited in respect to nitrogen. The risk of coarse nitrides working as non-metallic inclusions formed in the last solidification front can degrade fatigue properties and weldability of the final product. In the presented study three microalloying systems with minor additions were tested, two without any titanium addition, to evaluate grain size evolution and mechanical properties with pre-defined as-cast, hot forging, hot rolling, and off-line heat-treatment strategy to meet demands for S1100QL steel. Microstructure evolution from hot-forged to final martensitic microstructure was observed, continuous cooling transformation diagrams of non-deformed austenite were constructed for off-line heat treatment, and the mechanical properties of Nb and V–Nb were compared to Ti–Nb microalloying system with a limited titanium addition. Using the parameters in the laboratory environment all three micro-alloying systems can provide needed mechanical properties, especially the Ti–Nb system can be successfully replaced with V–Nb having the highest response in tensile properties and still obtaining satisfying toughness of 27 J at –40 °C using Charpy V-notch samples.

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