Influence of Cooling Rate on Free Interstitial Concentration in Type 430 Ferritic Stainless Steel

2014 ◽  
Vol 611-612 ◽  
pp. 111-116 ◽  
Author(s):  
Timo J. Juuti ◽  
Timo Manninen ◽  
David Porter
Keyword(s):  
Stainless Steel ◽  
Cooling Rate ◽  
Ferritic Stainless Steel ◽  
Volume Fraction ◽  
Post Annealing ◽  
The Matrix ◽  
Free Interstitial ◽  
C And N ◽  
Kinetic Calculations ◽  
Lüders Bands

In ferritic steels, the amount of free C and N should be as low as possible to avoid the formation of Cottrell atmospheres and their associated discontinuous yielding and Lüders bands during forming. During the post-annealing cooling of ferritic stainless steel, carbides and nitrides of the type MX and M23C6precipitate. The volume fraction of the precipitates is determined by chemical composition, microstructure and the cooling path. In some cases, precipitation might not be sufficient to remove all free interstitials from the matrix, in which case, the process parameters or composition of the steel should be reconsidered. Here, thermodynamic and kinetic calculations using Thermo-calc and TC Prisma software have been made to investigate the precipitation of C and N as a function of total interstitial content and cooling rate. According to the calculations, decreasing the cooling rate would result in a more efficient precipitation and hence, less free C and N in the matrix, but the amount is not sufficient to remove the upper yield point. Furthermore, changing the C and N content of the steel was found to have insignificant influence. However, the free C and N could possible be bound through a more complex cooling.

scholarly journals Effect of Cooling Rate on AlN Precipitation in FeCrAl Stainless Steel During Solidification

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1091 ◽  
Author(s):  
Zhenqiang Deng ◽  
Yang He ◽  
Jianhua Liu ◽  
Baijun Yan ◽  
Yindong Yang ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Nitrogen Content ◽  
Cooling Rate ◽  
Molten Steel ◽  
Volume Fraction ◽  
Particle Growth ◽  
Growth Time ◽  
Model Combining ◽  
Set Up ◽  
Kinetic Calculations

The effect of cooling rate on the evolution of AlN inclusions precipitated during solidification in FeCrAl stainless steel was investigated using an experimental study and thermodynamic and kinetic calculations. The number and size of AlN inclusions precipitated under different cooling rates were examined with the feature function of the field-emission scanning electron microscope. A model combining micro-segregation and the diffusion-controlled growth model was set up to determine the mechanism of AlN particle growth. The results showed that AlN precipitates in the mushy zone. The size of AlN particles decreases and the number of AlN particles increases with increasing cooling rate, whereas the volume fraction is essentially unchanged. The AlN particles grow during solidification after the content of solutes in molten steel has exceeded the concentration in equilibrium with AlN. The nitrogen content varies significantly with the cooling rate during solidification. Increasing the cooling rate and reducing the nitrogen content in the molten steel can reduce the AlN particle size in FeCrAl alloys as the growth time decreases.

Preparation of Electron Transparent Metal-Matrix Composites

1968 ◽  
Vol 26 ◽  
pp. 334-335 ◽  
Author(s):  
M. R. Pinnel ◽  
A. Lawley
Keyword(s):  
Stainless Steel ◽  
Load Transfer ◽  
Volume Fraction ◽  
Steel Wire ◽  
Initial Step ◽  
Interfacial Region ◽  
Matrix Composites ◽  
Specific Test ◽  
The Matrix ◽  
The One

Numerous phenomenological descriptions of the mechanical behavior of composite materials have been developed. There is now an urgent need to study and interpret deformation behavior, load transfer, and strain distribution, in terms of micromechanisms at the atomic level. One approach is to characterize dislocation substructure resulting from specific test conditions by the various techniques of transmission electron microscopy. The present paper describes a technique for the preparation of electron transparent composites of aluminum-stainless steel, such that examination of the matrix-fiber (wire), or interfacial region is possible. Dislocation substructures are currently under examination following tensile, compressive, and creep loading. The technique complements and extends the one other study in this area by Hancock.The composite examined was hot-pressed (argon atmosphere) 99.99% aluminum reinforced with 15% volume fraction stainless steel wire (0.006″ dia.).Foils were prepared so that the stainless steel wires run longitudinally in the plane of the specimen i.e. the electron beam is perpendicular to the axes of the wires. The initial step involves cutting slices ∼0.040″ in thickness on a diamond slitting wheel.

Simple Estimation of Deformation-Induced Martensite in Stainless Steel

2005 ◽  
Vol 297-300 ◽  
pp. 500-506 ◽  
Author(s):  
Hidefumi Date
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Magnetic Force ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Electric Resistivity ◽  
Electric Resistance ◽  
The Matrix ◽  
Simple Estimation ◽  
Measured Resistivity

To estimate the volume fraction of martensite induced in 304ss type austenitic stainless steel during tensile deformation, the electric resistance of the specimen was measured using the four-point-probes method at the temperatures of 77, 196 and 293K during the deformation. The magnetic force of the deformed specimen was also measured using a permanent magnet to determine the strain at which the martensite was induced initially in the specimen. The parallelepiped model was suggested to separate the effects of the deformation and transformation on the electric resistivity because the resistivity was influenced by the evolution of the martensite and the growth of the defect in the matrix at a constant temperature. The parallelepiped model consisted of m columns with n pieces of the cubic element and was assumed to be a group of small electric resistors. The volume fraction of the martensite estimated using the measured resistivity and the model was compared with the experimental results reported by other researchers and then it was clarified that the volume fraction of the martensite estimated by the model was in agreement with the volume fraction measured by the experiment.

Microstructural evolution and properties of tungsten inert gas and fiber laser welded SUS445 ferritic stainless steel

2021 ◽  
Vol 112 (9) ◽  
pp. 687-694
Author(s):  
Ching-Wen Lu ◽  
Huei-Sen Wang ◽  
Chih-Chun Hsieh ◽  
Jie-Jyun Wu
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Fiber Laser ◽  
Ferritic Stainless Steel ◽  
Heat Affected Zone ◽  
Volume Fraction ◽  
Inert Gas ◽  
Laves Phases ◽  
Welding Processes

Abstract To determine the weldability of SUS445 ferritic stainless steel, two welding approaches, tungsten inert gas and fiber laser welding processes, were used and compared. After the welding processes, the microstructure, mechanical properties, and corrosion resistance of the welds were investigated. In the weld fusion zones of these two welding approaches, different morphologies of the grains were obtained. No obvious precipitation formed in these zones. In the heat affected zone of the tungsten inert gas welds, more volume fraction and larger grain sizes of the Laves phase and larger matrix grains were observed, which significantly affected its corrosion resistance and mechanical properties. However, in the heat affected zone of the fiber laser welds, only small amounts Laves phases and a relatively narrow matrix grain growth area were observed, which offers better corrosion resistance and mechanical properties.

Effect of Cooling Rate below Ms Temperature on Hydrogen Embrittlement of TRIP-Aided Martensitic Steels

2021 ◽  
Vol 1016 ◽  
pp. 654-659
Author(s):  
Naoya Kakefuda ◽  
Shintaro Aizawa ◽  
Ryo Sakata ◽  
Junya Kobayashi ◽  
Goroh Itoh ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
Cooling Rate ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
High Strength ◽  
Martensitic Steels ◽  
The Matrix ◽  
Embrittlement Resistance ◽  
Hydrogen Embrittlement Resistance

Low alloy TRIP steel is expected to be applied to automobile bodies because of its high strength, high ductility, and excellent impact properties and press formability. It has been reported that the low alloy TRIP steel of hydrogen embrittlement resistance is improved by utilizing the hydrogen storage characteristics of highly stable retained austenite. Therefore, for the purpose of increasing the volume fraction of retained austenite, it was produced at various cooling rates below the martensite transformation start temperature. As a result, the volume fraction of retained austenite increased, and then the effect of hydrogen embrittlement decreased. The matrix phase and retained austenite is refined with decrees of the cooling rate. It is considered that the size and surface area of the retained austenite also affected the improvement of hydrogen embrittlement resistance.

scholarly journals New Ferritic Stainless Steel for Service Temperatures up to 1050 °C Utilizing Intermetallic Phase Transformation

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 664 ◽  
Author(s):  
Timo Juuti ◽  
Timo Manninen ◽  
Sampo Uusikallio ◽  
Jukka Kömi ◽  
David Porter
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Stainless Steels ◽  
Creep Resistance ◽  
Volume Fraction ◽  
Intermetallic Phase ◽  
Precipitation Strengthening ◽  
Ferritic Stainless Steels ◽  
Thermodynamic Simulations ◽  
Grain Boundary Pinning

A large number of thermodynamic simulations has been used to design a new Nb-Ti dual stabilized ferritic stainless steel with excellent creep resistance at 1050 °C through an optimal volume fraction of Laves (η) phase stabilized by the alloying elements Nb, Si and Mo. By raising the dissolution temperature of the phase, which also corresponds to the onset of rapid grain growth, the steel will better maintain the mechanical properties at higher service temperature. Laves phase precipitates can also improve creep resistance through precipitation strengthening and grain boundary pinning depending on the dominant creep mechanism. Sag tests at high temperatures for the designed steel showed significantly better results compared to other ferritic stainless steels typically used in high temperature applications at present.

The Effect of Niobium Carbides and Laves Phase on the Yielding Behaviour of a Stabilized Ferritic Stainless Steel

2014 ◽  
Vol 783-786 ◽  
pp. 807-812 ◽  
Author(s):  
Timo J. Juuti ◽  
Timo Manninen ◽  
L. Pentti Karjalainen ◽  
David A. Porter
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Yield Point ◽  
Ferritic Stainless Steel ◽  
Stainless Steels ◽  
Laves Phase ◽  
Temper Rolling ◽  
Ferritic Stainless Steels ◽  
High Chromium ◽  
The Matrix

High-chromium ferritic stainless steels have been developed for applications such as exhaust systems that require good formability. To improve formability, continuous yielding is preferred. However, in high-chromium ferritic stainless steels an upper yield point is often present as a result of free interstitials and Cottrell atmospheres. The upper yield point can be removed by temper rolling but it would be better to avoid it via a suitable heat treatment. This paper describes how this can be done in the case of a ferritic stainless steel containing 0.011%C, 0.012%N, 18%Cr, 2,1%Mo, 0.33%Nb, 0.15Ti%. Despite the presence of Nb and Ti, which should bind the free carbon and nitrogen as carbides and nitrides, an upper yield point was still observed. Previously it has been suspected that this is due to an intermetallic Laves phase present in this steel depleting the Nb in the matrix so that some carbon remains free. A series of short-term annealing experiments showed that the upper yield point diminishes, when the annealing temperature increases above 550 °C, finally disappearing after a heat treatment at 750 °C. On the basis of Thermo-Calc calculations and EDS analyses, free interstitials in the matrix could be related to depletion of MX or insufficient time to reach the equilibrium state.

scholarly journals Radiation damage and phase instability in irradiated stainless steel

1983 ◽  
Vol 41 ◽  
pp. 234-235
Author(s):  
Edward A. Kenik ◽  
Eal H. Lee
Keyword(s):  
Stainless Steel ◽  
Low Dose ◽  
Volume Fraction ◽  
Ion Irradiation ◽  
Dislocation Loops ◽  
Nickel Ion ◽  
Phase Instability ◽  
Void Swelling ◽  
Damage Structure ◽  
The Matrix

The radiation response of metallic alloys can be strongly dependent on specific solute elements. Void swelling and phase instability of the matrix are two primary concerns in the design of nuclear reactors. A 316 stainless steel, LS1A, with greater than nominal levels of silicon and titanium has been developed which exhibits high resistance to swelling under ion irradiation. The origin of this swelling resistance and the roles of silicon and titanium have been investigated in the current study.Figure 1 illustrates the evolution of the damage structure in LS1A under nickel ion irradiation at 625°C. At low dose [∽1 dpa, Fig. 1(a)], faulted interstitial dislocation loops (43-nm-av diam) are observed. We have previously reported that significant solute silicon segregation (approaching 7.0 at. %) in the vicinity of the loop fault plane occurs at such doses in LS1A. Below 10 dpa, precipitates appear to replace the loops in similar sizes and densities. At 70 dpa [Fig. 1(b)] there is no swelling and the matrix phase instability has produced ∽5% volume fraction precipitate.

Study of Cooling Rate Influence on SAF 2205 Duplex Stainless Steel Solution Annealed

2014 ◽  
Vol 802 ◽  
pp. 398-403 ◽  
Author(s):  
Maria Eurenice Rocha Cronemberger ◽  
Neide Aparecida Mariano ◽  
Mariny F.C. Coelho ◽  
Juliete N. Pereira ◽  
Érika C.T. Ramos ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Cooling Rate ◽  
Volume Fraction ◽  
Annealing Treatment ◽  
Rate Variation ◽  
Slow Cooling ◽  
Steel Microstructure ◽  
Constituent Elements ◽  
Saf 2205

In this work was investigated the microstructural evolution process of the duplex stainless steel SAF 2205 as-cast after solution annealing treatment. The aim was to detect the effects on the material microstructure by the cooling rate variation. The studied material were submitted to solution anneal at 1100 °C for 240 min, followed by cooling in water, air and furnace. The results evaluation was based on micrographic analysis, energy dispersive spectrometry measurements (EDS), X-ray diffraction and hardness tests. The ferrite volume fraction obtained in the microstructure increased with the cooling rate, because it causes diffusion inhibition of the steel constituent elements, promoting retention of the ferrite. The volume fraction of austenite phase increased with a lower cooling rate. The cooling rate is an important factor in defining the steel microstructure, particularly about intermetallic phases precipitation, which occurred by the slow cooling rate. Additionally, it was observed the precipitation of sigma phase.

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