Effect of Heat Treatment and of Primary Austenite Grain Size on the Minimum Size of Detectable Defect on 26NiCrMoV11.5 High Strength Steel

2013 ◽  
Vol 16 (1) ◽  
pp. 103-111 ◽  
Author(s):  
Silvia Barella ◽  
Andrea Gruttadauria ◽  
Carlo Mapelli ◽  
Davide Mombelli ◽  
Claudia Lisiane Fanezi ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
High Strength Steel ◽  
High Strength ◽  
Minimum Size ◽  
Austenite Grain Size ◽  
Primary Austenite ◽  
Austenite Grain

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.

Influence of Austenite Grain Size on Martensite Start Temperature of Nb-V-Ti Microalloyed Ultra-High Strength Steel

2016 ◽  
Vol 848 ◽  
pp. 624-632 ◽  
Author(s):  
Ji Dong ◽  
Chen Xi Liu ◽  
Yong Chang Liu ◽  
Chong Li ◽  
Qian Ying Guo ◽  
...  
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
High Strength Steel ◽  
Volume Fraction ◽  
High Strength ◽  
Austenite Grain Size ◽  
Microstructure Observation ◽  
Austenite Grain ◽  
Ultra High Strength Steel ◽  
Start Temperature

In order to investigate the effect of austenite grain size on martensite start temperature of Nb-V-Ti micro-alloyed ultra-high strength steel, the phase transformation features of Nb-V-Ti micro-alloyed steel was investigated. It has been found that martensite start temperature increased with the increase of austenite grain size as a consequence of the increase of austenitizing temperature. Based on microstructure observation, two types of MX carbonitrides with different compositions and morphologies have been identified. With the increase of the austenite grain size, both the volume fraction of precipitates and the dislocation density decreased, which may be induced by the strengthening of the austenite matrix directly and increasing the resistance of austenite to plastic deformation. Hence, the increase of martensite start temperature could be attributed to a decrease in volume fraction of precipitates and dislocation density.

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.

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 Physical and Numerical Simulations of Closed Die Hot Forging and Heat Treatment of Forged Parts

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 15
Author(s):  
Łukasz Poloczek ◽  
Łukasz Rauch ◽  
Marek Wilkus ◽  
Daniel Bachniak ◽  
Władysław Zalecki ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Numerical Simulations ◽  
Phase Transformations ◽  
Hot Forging ◽  
Transformation Model ◽  
Controlled Cooling ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Conventional Heat Treatment

The paper describes physical and numerical simulations of a manufacturing process composed of hot forging and controlled cooling, which replace the conventional heat treatment technology. The objective was to investigate possibilities and limitations of the heat treatment with the use of the heat of forging. Three steels used to manufacture automotive parts were investigated. Experiments were composed of two sets of tests. The first were isothermal (TTT) and constant cooling rate (CCT) dilatometric tests, which supplied data for the identification of the numerical phase transformation model. The second was a physical simulation of the sequence forging-cooling on Gleeble 3800, which supplied data for the validation of the models. In the numerical part, a finite element (FE) thermal-mechanical code was combined with metallurgical models describing recrystallization and grain growth during forging and phase transformations during cooling. The FE model predicted distributions of the temperature and the austenite grain size in the forging, which were input data for further simulations of phase transformations during cooling. A modified JMAK equation was used to calculate the kinetics of transformation and volume fraction of microstructural constituents after cooling. Since the dilatometric tests were performed for various austenitization temperatures before cooling, it was possible to include austenite grain size as a variable in the model. An inverse algorithm developed by the authors was applied in the identification procedure. The model with optimal material parameters was used for simulations of hot forging and controlled cooling in one of the forging shops in Poland. Distributions of microstructural constituents in the forging after cooling were calculated. As a consequence, various cooling sequences during heat treatment could be analyzed and compared.

scholarly journals Effect of Heat Treatment on Mechanical Properties and Microstructure Morphology of Low-Alloy High-Strength Steel

2016 ◽  
Vol 61 (2) ◽  
pp. 475-480
Author(s):  
K. Bolanowski
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
High Strength Steel ◽  
High Strength ◽  
Strengthening Phase ◽  
Average Grain Size

Abstract The paper analyzes the influence of different heat treatment processes on the mechanical properties of low-alloy high-strength steel denoted by Polish Standard (PN) as 10MnVNb6. One of the findings is that, after aging, the mechanical properties of rolled steel are high: the yield strength may reach > 600 MPa, and the ultimate tensile strength is > 700 MPa. These properties are largely dependent on the grain size and dispersion of the strengthening phase in the ferrite matrix. Aging applied after hot rolling contributes to a considerable rise in the yield strength and ultimate tensile strength. The process of normalization causes a decrease in the average grain size and coalescence (reduction of dispersion) of the strengthening phase. When 10MnVNb6 steel was aged after normalization, there was not a complete recovery in its strength properties.

Investigation of the Austenite Grain Growth in HY-TUF Steel

2020 ◽  
Vol 299 ◽  
pp. 482-486
Author(s):  
Mikhail V. Maisuradze ◽  
Maksim A. Ryzhkov
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Heating Temperature ◽  
High Strength ◽  
Silicon Steel ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Austenite Grains ◽  
Austenite Grain Growth ◽  
Intensive Growth

The high strength silicon steel HY-TUF, applied for manufacturing of the heavy loaded aerospace and engineering parts, was investigated. The effect of the heating temperature in the range 900...1000 °C on the austenite grain size was studied. The steel under consideration had a significant scatter of the austenite grain size. The most intensive growth of the austenite grains was observed in the temperature range 975...1000 °C.

Tempering of Direct Quenched Low-Alloy Ultra-High-Strength Steel, Part I – Microstructure

2014 ◽  
Vol 922 ◽  
pp. 316-321 ◽  
Author(s):  
Antti J. Kaijalainen ◽  
Sakari Pallaspuro ◽  
David A. Porter
Keyword(s):  
Grain Size ◽  
Low Carbon Steel ◽  
High Strength ◽  
Steel Part ◽  
Grain Structure ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Direct Quenching ◽  
Austenite Grain ◽  
Effective Grain Size

The direct quenching of low-carbon steel has been shown to be an effective way of producing ultra-high-strength, tough structural steels in the as-quenched state without tempering. However, in the present study, the influence of tempering at 500 °C has been studied in order to evaluate the possibilities of widening the range of strengths that can be produced from a single base composition. The chosen composition was 0.1C-0.2Si-1.1Mn-0.15Mo-0.03Ti-0.002B. In order to compare direct quenching with conventional quenching, two pre-quench austenite states were studied: a thermomechanically rolled, non-recrystallized, pancaked austenite grain structure and a recrystallized, equiaxed grain structure. Quenched and quenched-and-tempered microstructures were studied using FESEM and FESEM-EBSD. The as-quenched microstructures of the reheated and quenched and direct quenched specimens were fully martensitic and martensitic-bainitic, respectively. In both cases, tempering made the needle-shaped auto-tempered carbides of the as-quenched materials more spherical. In the case of the direct quenched (DQ) material, tempering led to a notable increase in the size of the grain boundary carbides. Prior austenite grain size and effective grain size after quenching were larger in the case of reheated and quenched material (RQ). Tempering had no effect on effective grain size. The crystallographic texture of the DQ material showed strong {112}<131> and {554}<225> components. The RQ material also contained the same components, but it also contained an intense {110}<110> and {011}<100> components. The effects of these microstructural changes on tensile, impact toughness and fracture toughness are described in part II.

Control of Weld HAZ Properties in Modern High Strength Pipeline Steels

2014 ◽  
Author(s):  
Frank Barbaro ◽  
Lenka Kuzmikova ◽  
Zhixiong Zhu ◽  
Huijun Li
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
Weld Zone ◽  
High Strength ◽  
Alloy Design ◽  
Alternative Methods ◽  
Coarse Grained ◽  
Precipitate Size ◽  
Austenite Grain Size ◽  
Austenite Grain

Critical performance of modern high strength linepipe is related to the ability of the steel to maintain mechanical properties in the weld heat affected zone (HAZ). The region most susceptible to mechanical property degradation is the coarse grained HAZ, however in multipass welds, the intercritically reheated CGHAZ (ICCGHAZ) also presents challenges to maintain toughness. Currently Ti is employed to minimise austenite grain coarsening through the grain boundary pinning action of TiN precipitates. This is effective because of the high thermal stability of TiN but control of the precipitate size distribution is very much dependent on alloy design and processing conditions to ensure final weld HAZ properties, particularly toughness. This can be difficult to maintain and alternative methods are required to further improve performance of the weldments. It is now evident that increased additions of Nb in modern high temperature processed (HTP) steels have demonstrated increased control of HAZ microstructures with improved fracture toughness [1, 2]. The present paper details the microstructure - property relationship of two pipe steel grades with different alloy designs. Evaluation of the critical CGHAZ was achieved by simulation techniques, calibrated using real weld thermal cycles, to determine the influence of alloy design and specifically level of Nb on weld zone properties. The results reveal that the fracture toughness of the simulated CGHAZ in the HTP steel is superior to that of a conventional microalloyed pipeline steel grade. Toughness was related to the distribution of martensite-austenite (M-A) constituent and the effective grain size which appeared to correspond to prior austenite grain size as evidenced by examination of cleavage facet size (CFS) on fractured Charpy specimens.

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