Effect of Mg–Ti Treatment on Nucleation Mechanism of TiN Inclusions and Ferrite

Large sizes of columnar crystals and TiN particles have a great influence on the surface quality of ferritic stainless steel. In the present paper, this study proposed to obtain fine-grained equiaxed structures by Mg–Ti treatment. Through the experiment happened in resistance furnace with argon protection, the refining effect of Mg–Ti addition on the microstructure and TiN particles were investigated, and the refinement mechanism was discussed from interface coherence theory. It was found that due to adding Mg and Ti into molten ferritic stainless steel, the equiaxed crystal ratio increased from 37% to 50%, and the size of TiN particles reduced at the same time. The lattice matching characteristics of MgAl2O4/TiN and TiN/δ-Fe were investigated by FIB-HRTEM. According to Bramfitt’s equation, the lattice misfit for (400)MgAl2O4∥(200)TiN and (200)TiN∥(110)δ-Fe was 5.02% and 4.41%, respectively, which were all belong to the effective nucleation range. It could be considered that MgO and MgAl2O4 formed in the molten steel promoted TiN nucleation easier to precipitate out with large quantities in the liquid phase. The TiN particles with more uniform distribution significantly enhanced the heterogenous nucleation of ferritic phase during initial solidification process base on the good lattice fitting condition. Finally the equiaxed crystal ratio of δ-Fe phase increased dramatically.

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Numerical Simulation of Temperature and Fluid Fields in Solidification Process of Ferritic Stainless Steel under Vibration Conditions

Crystals ◽

10.3390/cryst9030174 ◽

2019 ◽

Vol 9 (3) ◽

pp. 174

Author(s):

Wenli Wang ◽

Jing Chen ◽

Miaomiao Li ◽

Along Wang ◽

Mengyao Su

Keyword(s):

Stainless Steel ◽

Temperature Field ◽

Flow Field ◽

Ferritic Stainless Steel ◽

Stokes Equations ◽

Solidification Process ◽

Crystal Formation ◽

Positive Temperature ◽

Vibration Direction ◽

Casting Mold

A three-dimensional model of a circular casting mold with a vibrating nucleus generator was established, and the characteristics of temperature and flow fields during the solidification process of ferritic stainless steel Cr17 in the casting mold were analyzed using finite element and finite difference methods. A standard k-ε turbulent current model was adopted to simulate the temperature field, and a standard k-ε model in Reynolds-averaged Navier–Stokes equations (RANS) was employed to deal with the flow field. The temperature field diffuses outward with a positive temperature gradient. Low degrees of undercooling can prevent solidified shells from forming rapidly on the surface of the nucleus generator. The temperature perpendicular to the direction of vibration is lower than that in the direction of vibration. The flow field exhibits a heart-shaped distribution and spreads gradually outward. The uniform distribution of grains can be achieved at three different frequencies of vibration. The results show that the degree of undercooling affects the distribution of the temperature field while the frequency of vibration affects the flow field significantly. Under the conditions of undercooling of 540 K and vibration frequency of 1000 Hz, the region perpendicular to the vibration direction of the nucleus generator is the optimum area for equiaxed crystal formation.

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Effects of Initial Equiaxed Crystal Ratio in As-Cast Slab on Texture Evolution and Formability of Ferritic Stainless Steel

Journal of Materials Engineering and Performance ◽

10.1007/s11665-020-05441-1 ◽

2021 ◽

Author(s):

Maojun Li ◽

Zhuoling Wang ◽

Xu Chen

Keyword(s):

Stainless Steel ◽

Ferritic Stainless Steel ◽

Texture Evolution ◽

Equiaxed Crystal ◽

Cast Slab

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Comparison of electrochemical behavior between coarse-grained and fine-grained AISI 430 ferritic stainless steel by Mott–Schottky analysis and EIS measurements

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2015.03.142 ◽

2015 ◽

Vol 639 ◽

pp. 301-307 ◽

Cited By ~ 94

Author(s):

A. Fattah-alhosseini ◽

S. Vafaeian

Keyword(s):

Stainless Steel ◽

Ferritic Stainless Steel ◽

Electrochemical Behavior ◽

Coarse Grained ◽

Fine Grained ◽

Eis Measurements ◽

Aisi 430

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Titanium Nitride and Niobium Carbide in the Ferritic Stainless Steel and the Influence to Casting Macrostructure

Materials Science Forum ◽

10.4028/www.scientific.net/msf.944.322 ◽

2019 ◽

Vol 944 ◽

pp. 322-328

Author(s):

Heng Ke Du ◽

Dian Xiu Xia ◽

Cheng Jia Shang ◽

Kun Chen

Keyword(s):

Grain Size ◽

Stainless Steel ◽

Titanium Nitride ◽

Ferritic Stainless Steel ◽

Niobium Carbide ◽

Equiaxed Crystal ◽

Corrosion Performance ◽

Solidification Processing ◽

Different Content

Titanium and niobium were applied to stable the carbon or nitrogen which dissolved ferritic stainless steel for improving the anti-corrosion performance. The titanium nitride and niobium carbide had been formed during solidification processing. For understanding those precipitates how to influence the casting macrostructure, three steels that had different content of niobium and the fixed content of titanium had been designed. The result showed the casting macrostructure of ingot and the grain size of the centre-equiaxed crystal zones had different tendency. And the titanium nitride and niobium carbide had interacted.

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Interfacial structures of dissimilar materials joined by capacitor-discharge welding

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100170402 ◽

1994 ◽

Vol 52 ◽

pp. 534-535

Author(s):

C. P. Doğan ◽

R. D. Wilson ◽

J. A. Hawk

Keyword(s):

Rapid Solidification ◽

Fusion Zone ◽

Dissimilar Materials ◽

Solidification Process ◽

Weld Interface ◽

Capacitor Discharge ◽

Fine Grained ◽

Iron Aluminum ◽

Conductive Ceramics ◽

Capacitor Discharge Welding

Capacitor Discharge Welding is a rapid solidification technique for joining conductive materials that results in a narrow fusion zone and almost no heat affected zone. As a result, the microstructures and properties of the bulk materials are essentially continuous across the weld interface. During the joining process, one of the materials to be joined acts as the anode and the other acts as the cathode. The anode and cathode are brought together with a concomitant discharge of a capacitor bank, creating an arc which melts the materials at the joining surfaces and welds them together (Fig. 1). As the electrodes impact, the arc is extinguished, and the molten interface cools at rates that can exceed 106 K/s. This process results in reduced porosity in the fusion zone, a fine-grained weldment, and a reduced tendency for hot cracking.At the U.S. Bureau of Mines, we are currently examining the possibilities of using capacitor discharge welding to join dissimilar metals, metals to intermetallics, and metals to conductive ceramics. In this particular study, we will examine the microstructural characteristics of iron-aluminum welds in detail, focussing our attention primarily on interfaces produced during the rapid solidification process.

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Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177775 ◽

1990 ◽

Vol 48 (4) ◽

pp. 928-929

Author(s):

Wang Zheng-fang ◽

Z.F. Wang

Keyword(s):

Stainless Steel ◽

Thermal Cycle ◽

Secondary Phase ◽

Corrosion Cracking ◽

Coarse Grained ◽

Test Environment ◽

Fine Grained ◽

Evaluation Test ◽

Welding Thermal Cycle ◽

Micro Analysis

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.

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