Phase Transformations and Microstructure of the Alloyed Steels for Mining Application

2021 ◽  
Vol 410 ◽  
pp. 215-220
Author(s):  
Mikhail V. Maisuradze ◽  
Maxim A. Ryzhkov ◽  
Arkadiy Yu. Zhilyakov
Keyword(s):  
Chemical Composition ◽  
Ambient Temperature ◽  
Phase Transformations ◽  
Rock Drilling ◽  
Austenitization Temperature ◽  
Hardened Steels ◽  
Continuous Cooling ◽  
Drilling Equipment ◽  
Cct Diagrams

The dilatometer study of the austenite transformations in steels with different chemical composition was conducted. The studied steels were classified as the air hardened steels of different alloying systems (Cr-Ni-Mo, Cr-Mn-Si-Mo and Cr-Mo-V) designed for the mining applications (rock drilling equipment, drilling instrument). The microstructure of the steels was investigated after continuous cooling at the rates of 0.1...30 °C/s from the austenitization temperature down to the ambient temperature. The CCT diagrams of the studied steels were plotted showing that the alloying with different set of elements can provide the desired hardenability and microstructure.

scholarly journals Effects of Austenitization Temperature and Pre-Deformation on CCT Diagrams of 23MnNiCrMo5-3 Steel

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5116
Author(s):  
Ivo Schindler ◽  
Rostislav Kawulok ◽  
Petr Opěla ◽  
Petr Kawulok ◽  
Stanislav Rusz ◽  
...  
Keyword(s):  
Phase Transformations ◽  
Deformation Temperature ◽  
True Strain ◽  
Austenitization Temperature ◽  
Diffusion Controlled ◽  
Significant Acceleration ◽  
Wide Range ◽  
Mean Grain Size ◽  
Cct Diagrams ◽  
Kinetics Of

The combined effect of deformation temperature and strain value on the continuous cooling transformation (CCT) diagram of low-alloy steel with 0.23% C, 1.17% Mn, 0.79% Ni, 0.44% Cr, and 0.22% Mo was studied. The deformation temperature (identical to the austenitization temperature) was in the range suitable for the wire rolling mill. The applied compressive deformation corresponded to the true strain values in an unusually wide range. Based on the dilatometric tests and metallographic analyses, a total of five different CCT diagrams were constructed. Pre-deformation corresponding to the true strain of 0.35 or even 1.0 had no clear effect on the austenite decomposition kinetics at the austenitization temperature of 880 °C. During the long-lasting cooling, recrystallization and probably coarsening of the new austenitic grains occurred, which almost eliminated the influence of pre-deformation on the temperatures of the diffusion-controlled phase transformations. Decreasing the deformation temperature to 830 °C led to the significant acceleration of the austenite → ferrite and austenite → pearlite transformations due to the applied strain of 1.0 only in the region of the cooling rate between 3 and 35 °C·s−1. The kinetics of the bainitic or martensitic transformation remained practically unaffected by the pre-deformation. The acceleration of the diffusion-controlled phase transformations resulted from the formation of an austenitic microstructure with a mean grain size of about 4 µm. As the analysis of the stress–strain curves showed, the grain refinement was carried out by dynamic and metadynamic recrystallization. At low cooling rates, the effect of plastic deformation on the kinetics of phase transformations was indistinct.

scholarly journals The Phase Transformations in Hypoeutectoid Steels Mn-Cr-Ni

2015 ◽  
Vol 60 (1) ◽  
pp. 497-502 ◽  
Author(s):  
E. RoŻniata ◽  
R. Dziurka
Keyword(s):  
Chemical Composition ◽  
Phase Transformations ◽  
Critical Points ◽  
Light Microscope ◽  
Cooling Curves ◽  
Critical Temperatures ◽  
Martensitic Microstructure ◽  
Cct Diagrams ◽  
Kinetics Of ◽  
Undercooled Austenite

Abstract The results of a microstructure and hardness investigations of the hypoeutectoid steels Mn-Cr-Ni, imitating by its chemical composition toughening steels, are presented in the paper. The analysis of the kinetics of phase transformations of undercooled austenite of steels containing different amounts of alloying elements in their chemical composition, constitutes the aim of investigations. Metallographic examinations were carried out on a Axiovert 200 MAT light microscope. Sections were etched with a 3% HNO3 solution in C2H5OH. Dilatometric tests were performed using L78 R.I.T.A dilatometer. Using dilatometer the changes of elongation (Δl) of the samples with dimensions Ø 3×10 mm as a function of temperature (T) were registered. Obtained heating curves were used to precisely determine the critical temperatures (critical points) for the tested steels, while the differentiation of obtained cooling curves allowed to precisely define the temperatures of the beginning and the end of particular transition to draw CCT diagrams. Four CCT diagrams worked out for the tested hypoeutectoid steels (for quenching of steel) are - in the majority of steels - separated by the undercooled austenitic range and are of the letter „C” shape. However, for steels with Mn and Ni the separation of diffusive transformations from the bainitic transformation by the stable austenitic range is not observed. Hardenability of four investigated hypoeutectoid steels is similar, but still not high. To obtain martensite in the microstructure of these steels, it is necessary to apply the cooling rate higher than 25°C/s. The exception constitutes the Mn - Ni steel, in which only cooling with the rate higher than 50°C/s allows to achieve the martensitic microstructure and to avoid diffusive transformations (pearlitic and ferritic).

Phase Transformations in Novel Medium Carbon High Hardenability Steels

2017 ◽  
Vol 265 ◽  
pp. 717-722 ◽  
Author(s):  
Mikhail V. Maisuradze ◽  
Maksim Ryzhkov ◽  
O. Surnaeva
Keyword(s):  
Chemical Composition ◽  
Phase Transformations ◽  
High Hardenability ◽  
Medium Carbon ◽  
Continuous Cooling ◽  
Parts Manufacturing

Novel steels with high hardenability were proposed to replace the conventional HY-TUF steels for the large parts manufacturing. The chemical composition of the steels under consideration was, mass. %: C – 0.16...0.18; Cr – 2.35...2.55; Mn – 0.67...1.99; Si – 0.76...1.03; Ni – 1.17...2.31; Mo – 0.34...0.47; S. P < 0.025. The dilatometer experiments revealed that during the continuous cooling of the steels with the constant rates 0.1... 30 °C/s only martensite and bainite transformations occurred. for conventional HY-TUF steel ferrite and pearlite formed after cooling with the rates 0.1...0.3 °C/s.

Empirical formulas for calculating Continuous Cooling Transformation diagrams

2019 ◽  
Vol 1 (97) ◽  
pp. 21-30
Author(s):  
J. Trzaska
Keyword(s):  
Chemical Composition ◽  
Volume Fraction ◽  
Structural Steels ◽  
Austenitizing Temperature ◽  
Empirical Formulas ◽  
Continuous Cooling Transformation ◽  
Application Range ◽  
Continuous Cooling ◽  
Chemical Composition Of Steel ◽  
Cct Diagrams

Purpose: The paper presents empirical formulas for the calculation of Continuous Cooling Transformation (CCT) diagram basing on the chemical composition and austenitizing temperature. Design/methodology/approach: In the method of calculating CCT diagrams proposed in the paper, two types of tasks are solved. First task is classification and consists in determining the range of cooling rate for particular phase transformations. The second task is regression, which aims at calculating the transformations temperature, hardness and volume fraction of phases in steel. The model of CCT diagrams was developed using multiple regression and logistic regression methods. Research limitations/implications: CCT diagrams can be calculated according to the presented method, if the chemical composition of steel meets the criteria defined by the application range of the model. Practical implications: The formulas presented in the article can be used to determine the conditions for heat treatment of structural steels. Originality/value: The paper presents the method for calculating CCT diagrams of the structural steels and engineering steels, depending on their chemical composition as well as austenitizing temperature.

scholarly journals Continuous Cooling Transformation (CCT) Diagrams Of Carbidic Nodular Cast Iron

2015 ◽  
Vol 60 (2) ◽  
pp. 705-710 ◽  
Author(s):  
G. Gumienny ◽  
T. Giętka
Keyword(s):  
Cast Iron ◽  
Chemical Composition ◽  
Nodular Cast Iron ◽  
Lower Bainite ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Upper Bainite ◽  
Transformation Diagrams ◽  
Cct Diagrams ◽  
Kinetics Of

Abstract This work presents continuous cooling transformation diagrams for different kinds of carbidic nodular cast iron. We investigated the cast iron, chemical composition of which in nodular cast iron allows the obtainment of a metal matrix which consists of: pearlite, upper bainite and its mixture with lower bainite, ausferrite and martensite when the casts were cooled in the mold. The influence of the rate of cooling on the obtained microstructure and hardness of the casts was shown. The work describes the influence of the alloy additives on the curves of austenite decomposition in the carbidic nodular cast iron. Diagrams were plotted which enable an understanding of the kinetics of the transformations of austenite in carbidic nodular cast iron. The diagrams also indicate the possibility of obtaining pearlite, bainite, martensite and ausferrite with the established chemical composition and the wall thickness of the cast.

scholarly journals Optimization of the CCT Curves for Steels Containing Al, Cu and B

2021 ◽  
Author(s):  
Jyrki Miettinen ◽  
Sami Koskenniska ◽  
Mahesh Somani ◽  
Seppo Louhenkilpi ◽  
Aarne Pohjonen ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Austenite Decomposition ◽  
Final Phase ◽  
Cast Irons ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Final Optimization ◽  
Cct Diagrams

AbstractNew continuous cooling transformation (CCT) equations have been optimized to calculate the start temperatures and critical cooling rates of phase formations during austenite decomposition in low-alloyed steels. Experimental CCT data from the literature were used for applying the recently developed method of calculating the grain boundary soluble compositions of the steels for optimization. These compositions, which are influenced by solute microsegregation and precipitation depending on the heating/cooling/holding process, are expected to control the start of the austenite decomposition, if initiated at the grain boundaries. The current optimization was carried out rigorously for an extended set of steels than used previously, besides including three new solute elements, Al, Cu and B, in the CCT-equations. The validity of the equations was, therefore, boosted not only due to the inclusion of new elements, but also due to the addition of more low-alloyed steels in the optimization. The final optimization was made with a mini-tab tool, which discarded statistically insignificant parameters from the equations and made them prudently safer to use. Using a thermodynamic-kinetic software, IDS, the new equations were further validated using new experimental CCT data measured in this study. The agreement is good both for the phase transformation start temperatures as well as the final phase fractions. In addition, IDS simulations were carried out to construct the CCT diagrams and the final phase fraction diagrams for 17 steels and two cast irons, in order to outline the influence of solute elements on the calculations and their relationship with literature recommendations.

Hardenability of Medium Carbon Cr-Mn-Mo Alloyed Steels

2019 ◽  
Vol 946 ◽  
pp. 341-345
Author(s):  
Mikhail V. Maisuradze ◽  
Maksim A. Ryzhkov
Keyword(s):  
Cooling Rate ◽  
Structural Steels ◽  
Alloying Elements ◽  
Metallographic Analysis ◽  
Medium Carbon ◽  
Austenite Transformation ◽  
Continuous Cooling ◽  
Different Content ◽  
Cct Diagrams

Three medium carbon Cr-Mn-Mo structural steels with different content of alloying elements were studied. The austenite transformation during continuous cooling was investigated using dilatometer and metallographic analysis. The CCT diagrams were plotted showing the effect of the increased alloying elements content and B and Nb micro-alloying on the hardenability of the studied steels. The hardness dependences on the cooling rate were obtained.

Modeling Phase Transformation Kinetics and Their Effect on Hardness and Hardness Depth in Laser Hardening of Hypoeutectoid Steel

2015 ◽  
Author(s):  
Suhash Ghosh ◽  
Chittaranjan Sahay
Keyword(s):  
Thermal Analysis ◽  
Phase Transformation ◽  
Phase Transformations ◽  
Laser Hardening ◽  
Temperature History ◽  
Transformation Kinetics ◽  
Continuous Cooling ◽  
Phase Transformation Kinetics ◽  
Hardness Depth ◽  
Hypoeutectoid Steel

Much research has been done to model laser hardening phase transformation kinetics. In that research, assumptions are made about the austenization of the steel that does not translate into accurate hardness depth calculations. The purpose of this paper is to develop an analytical method to accurately model laser hardening phase transformation kinetics of hypoeutectoid steel, accounting for non-homogeneous austenization. The modeling is split into two sections. The first models the transient thermal analysis to obtain temperature time-histories for each point in the workpiece. The second models non-homogeneous austenization and utilizes continuous cooling curves to predict microstructure and hardness. Non-homogeneous austenization plays a significant role in the hardness and hardness depth in the steel. A finite element based three-dimensional thermal analysis in ANSYS is performed to obtain the temperature history on three steel workpieces for laser hardening process with no melting; AISI 1030, 1040 and 1045 steels. This is followed by the determination of microstructural changes due to ferrite and pearlite transformation to austenite during heating and the subsequent austenite to martensite and other diffusional transformations during cooling. Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation is used to track the phase transformations during heating, including the effects of non-homogenous austenitization. The solid state nodal phase transformations during cooling are monitored on the material’s digitized Continuous Cooling Transformation (CCT) curve through a user defined input file in ANSYS for all cooling rates within the Heat Affected Zone (HAZ). Material non-linearity is included in the model by including temperature dependent thermal properties for the material. The model predictions for hardness underneath the laser and the HAZ match well with the experimental results published in literature.

Effect of boron on the continuous cooling transformation kinetics in a low carbon advanced ultra-high strength steel (A-UHSS)

2012 ◽  
Vol 1485 ◽  
pp. 83-88 ◽  
Author(s):  
G. Altamirano ◽  
I. Mejía ◽  
A. Hernández-Expósito ◽  
J. M. Cabrera
Keyword(s):  
Research Work ◽  
High Strength Steels ◽  
High Strength ◽  
Microstructural Characterization ◽  
Low Carbon ◽  
Transformation Kinetics ◽  
Cooling Rates ◽  
Continuous Cooling Transformation ◽  
Continuous Cooling ◽  
Cct Diagrams

ABSTRACTThe aim of the present research work is to investigate the influence of B addition on the phase transformation kinetics under continuous cooling conditions. In order to perform this study, the behavior of two low carbon advanced ultra-high strength steels (A-UHSS) is analyzed during dilatometry tests over the cooling rate range of 0.1-200°C/s. The start and finish points of the austenite transformation are identified from the dilatation curves and then the continuous cooling transformation (CCT) diagrams are constructed. These diagrams are verified by microstructural characterization and Vickers micro-hardness. In general, results revealed that for slower cooling rates (0.1-0.5 °C/s) the present phases are mainly ferritic-pearlitic (F+P) structures. By contrast, a mixture of bainitic-martensitic structures predominates at higher cooling rates (50-200°C/s). On the other hand, CCT diagrams show that B addition delays the decomposition kinetics of austenite to ferrite, thereby promoting the formation of bainitic-martensitic structures. In the case of B microalloyed steel, the CCT curve is displaced to the right, increasing the hardenability. These results are associated with the ability of B atoms to segregate towards austenitic grain boundaries, which reduce the preferential sites for nucleation and development of F+P structures.

Microstructure and Mechanical Properties of High Strength Low Alloy Steel Q550D

2021 ◽  
Vol 1035 ◽  
pp. 424-429
Author(s):  
Fang Po Li ◽  
Ning Li ◽  
Xian Lin Wang ◽  
Ming Hua Liang
Keyword(s):  
Mechanical Properties ◽  
Chemical Composition ◽  
Oil And Gas ◽  
High Strength ◽  
Service Performance ◽  
Low Alloy Steel ◽  
Micro Structure ◽  
Gas Drilling ◽  
Drilling Equipment ◽  
Equipment Manufacture

Drilling equipment is the key of oil and gas drilling development. Its manufacturing quality and service performance have important influence on oil and gas drilling development safety. The application of high strength grade steel plays an important role in improving drilling equipment manufacturing level and service performance. In this paper, the chemical composition, microstructure, tensile properties, impact properties and hardness of TMCP Q550D and Q-T Q550D high-strength low-alloy steel were tested and compared, and the application feasibility for drilling equipment manufacture was analyzed comprehensively. The experimental results show that the mechanical properties of Q550D by two different methods were obviously higher than the requirement of national standard. Q550D steel had excellent plasticity and toughness, which meets the requirement of drilling equipment manufacture. The main difference between different steel lied in their chemical composition and micro-structure. Carbon content of TMCP Q550D steel plate was lower than that of QT Q550D, and TMCP Q550 was mainly depend on TMCP technology and micro-alloy elements, whose micro-structure was mainly granular bainite. Q-T Q550D was mainly depend on Q-T technology, and its microstructure was tempered sorbite with obvious banded structure and slightly low toughness.

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