Thermomechanical Treatments of Ultrahigh Carbon Steels and Optimal Microstructures to Improve Toughness

2007 ◽  
Vol 539-543 ◽  
pp. 4826-4831 ◽  
Author(s):  
Manuel Carsí ◽  
A. Fernández-Vicente ◽  
Oleg D. Sherby ◽  
Félix Peñalba ◽  
Oscar A. Ruano
Keyword(s):  
Particle Size ◽  
Carbide Particle ◽  
Thermomechanical Processing ◽  
Ferrite Matrix ◽  
Carbon Steels ◽  
Processing Route ◽  
Austenitizing Temperature ◽  
Fine Grained ◽  
Carbide Size ◽  
Carbide Particles

Thermomechanical processing allows the attainment of spheroidized microstructures that show improved mechanical properties. In this work, a thermomechanical processing route consisting of two steps was developed for two ultrahigh carbon steels (UHCS) containing 1.3 and 1.5%C. This route develops structures of fine spheroidized cementite particles in a fine-grained ferrite matrix. Spheroidized microstructures are formed by eutectoid carbide particles in the UHCS- 1.3C and by proeutectoid and eutectoid carbide particles in the UHCS-1.5C. In the latter steel, the proeutectoid carbide particle size is larger than the eutectoid carbide particle size. The carbide size distribution remains basically constant with austenitizing temperature for both steels. Plane-strain fracture toughness of spheroidized UHCS-1.3C is higher than for UHCS-1.5C, about 80 vs 40 MPa m1/2. These values do not vary significantly with austenitizing temperature which is attributed to the constancy of the mean proeutectoid and eutectoid carbide size.

Microstructure and Mechanical Properties of A Ultra-High Carbon Steel

2006 ◽  
Vol 324-325 ◽  
pp. 907-910 ◽  
Author(s):  
Wei Ping Lin ◽  
Ya Jun Fan ◽  
Zhan Ling Zhang ◽  
Jie Wu Zhu ◽  
Yong Ning Liu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
High Carbon Steel ◽  
Ferrite Matrix ◽  
Carbon Steels ◽  
Eutectoid Transformation ◽  
High Carbon ◽  
Fine Carbide ◽  
Carbide Particles

A ultrahigh carbon steels (UHCS) containing 1.6 wt pct carbon was studied. Through spheroidizing process by divorced-eutectoid transformation (DET), the forged microstructure was spheroidized and the microstructure was fine carbide particles distributed in ferrite matrix. Second-time heat treatment included two kinds of technologies: normalizing and quenching + tempering. Finally, the UHCS obtained ideal mechanical properties. The yield strength and tensile strength of the UHCS were higher than that of 40CrNiMo, moreover plasticity of the UHCS was equal to that of 40CrNiMo. So the UHCS was an excellent structural material.

Lattice Imaging of Twin, Lath and α/Martensite Boundaries in Duplex Low Carbon Steels

1977 ◽  
Vol 35 ◽  
pp. 118-119
Author(s):  
J. Y. Koo ◽  
G. Thomas
Keyword(s):  
High Resolution Electron Microscopy ◽  
Ferrite Matrix ◽  
Carbon Steels ◽  
Bright Field Image ◽  
Low Carbon ◽  
Lattice Imaging ◽  
Bright Field ◽  
Lattice Image ◽  
New Information ◽  
Resolution Electron

High resolution electron microscopy has been shown to give new information on defects(1) and phase transformations in solids (2,3). In a continuing program of lattice fringe imaging of alloys, we have applied this technique to the martensitic transformation in steels in order to characterize the atomic environments near twin, lath and αmartensite boundaries. This paper describes current progress in this program.Figures A and B show lattice image and conventional bright field image of the same area of a duplex Fe/2Si/0.1C steel described elsewhere(4). The microstructure consists of internally twinned martensite (M) embedded in a ferrite matrix (F). Use of the 2-beam tilted illumination technique incorporating a twin reflection produced {110} fringes across the microtwins.

High-resolution x-ray imaging of small copper-rich precipitates in steels

1988 ◽  
Vol 46 ◽  
pp. 528-529
Author(s):  
J. R. Michael ◽  
K. A. Taylor
Keyword(s):  
Electron Microscopy ◽  
Thermomechanical Processing ◽  
Atom Probe ◽  
Ferrite Matrix ◽  
Scanning Transmission Electron Microscope ◽  
Probe Field ◽  
X Ray ◽  
Subsequent Transformation ◽  
Transmission Electron ◽  
Scanning Transmission

Although copper is considered an incidental or trace element in many commercial steels, some grades contain up to 1-2 wt.% Cu for precipitation strengthening. Previous electron microscopy and atom-probe/field-ion microscopy (AP/FIM) studies indicate that the precipitation of copper from ferrite proceeds with the formation of Cu-rich bcc zones and the subsequent transformation of these zones to fcc copper particles. However, the similarity between the atomic scattering amplitudes for iron and copper and the small misfit between between Cu-rich particles and the ferrite matrix preclude the detection of small (<5 nm) Cu-rich particles by conventional transmission electron microscopy; such particles have been imaged directly only by FIM. Here results are presented whereby the Cu Kα x-ray signal was used in a dedicated scanning transmission electron microscope (STEM) to image small Cu-rich particles in a steel. The capability to detect these small particles is expected to be helpful in understanding the behavior of copper in steels during thermomechanical processing and heat treatment.

TEM study on fine carbide precipitates and dislocation cell structure

1990 ◽  
Vol 48 (4) ◽  
pp. 904-905
Author(s):  
Mengzhe Chen ◽  
Siqin Wang ◽  
Jun Ke
Keyword(s):  
Carbide Particle ◽  
Cell Structure ◽  
Ferrite Matrix ◽  
Dislocation Cell ◽  
Isothermal Treatment ◽  
Particle Sizes ◽  
Dislocation Cell Structure ◽  
Thin Foils ◽  
Hsla Steels ◽  
Fine Carbide

A series of investigations have been conducted into the nature and origin of the dislocation cell structure. R.J.Klassen calculated that the dislocation cell limiting size in pure ferrite matrix is about 0.4 μm. M.N.Bassion estimated the size of dislocation cell in deformed ferrite of HSLA steels to be of the same order.In this paper, TEM observation has been concentrated on the interaction of fine carbide precipitates with dislocation cell structure in deformed Fe-C-V (0.05%C, 0.13% and 0.57%V) and Fe-C-Nb (0.07 %C and 0.04%Nb) alloys and compared with that in Fe-C (0.05%). Specimens were austenitized at 1500 “C/20 min and followed by isothermal treatment at 750 °C and 800 “C for 20, 40 and 120 minutes . The carbide particle sizes in these steels are from 9 to 86nm measured from carbon extraction replicas. Specimens for TEM were cut from differently deformed areas of tensile specimens deformed at room temperture. The thin foils were jet electropolished at -20 C in a solution of 10% perchloric acid and 90% ethanol. The TEM observation was carried out in JEM 100CX , EM420 at 100kv and JEM 2000FX at 200kv.

Microstructure Evolution of Undercooled Austenite during Deformation for Medium-Carbon Si-Mn Steel

2011 ◽  
Vol 704-705 ◽  
pp. 903-906
Author(s):  
Yun Li Feng ◽  
Shao Qiang Yuan ◽  
Meng Song
Keyword(s):  
Microstructure Evolution ◽  
Ferrite Matrix ◽  
Eutectoid Reaction ◽  
Deformation Bands ◽  
Degree Of Deformation ◽  
Medium Carbon ◽  
Transmission Electron ◽  
Mn Steel ◽  
Carbide Particles ◽  
Undercooled Austenite

The microstructure evolution of a medium-carbon Si-Mn steel during deformation of undercooled austenite at different degree of deformation, temperatures and strain rates has been investigated by means of a hot compression simulation test, metallographic microscope, scanning electron microscope and transmission electron microscopy. Also, the mechanism of carbide spheroidized during deformed process has been discussed. The experiment results demonstrate that the process of evolution experienced three stages: that is, strain-induced transformation, austenite eutectoid decomposed to carbides and ferrite matrix, and spheroidization of pearlite at the range of A3-Ar3. The austenitic grains would be refined for the extra-product of ferrite above the Ar3. The eutectoid reaction was induced on the grain boundaries of ferrite and non-transformed austenite and deformation bands with the increasing volume of deformation. An optimum combination of deformation temperature and strain rate is important to obtian the dulplex microstructure consisting of ultrafine ferrites and dispersed carbide particles. The fine spheroidized microstructures are obtained while the deformed temperature reaches 650°C with ≥1.0, meanwhile, The carbides precipate in globular and shot-rod shapes. Keywords: Medium-carbon Si-Mn steel, Undercooled austentite, Microstructure evolution, Deformation induced transformation, Carbide spheroidization

scholarly journals Flotation and Tailing Discarding of Copper Cobalt Sulfide Ores Based on the Process Mineralogy Characteristics

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1078
Author(s):  
Wentao Hu ◽  
Kai Tian ◽  
Zhengyang Zhang ◽  
Jiuchuan Guo ◽  
Xinwei Liu ◽  
...  
Keyword(s):  
Particle Size ◽  
Sulfide Mineral ◽  
Cobalt Sulfide ◽  
Sulfide Concentration ◽  
Total Recovery ◽  
Copper Sulfides ◽  
Fine Grained ◽  
Mineralogical Characteristics ◽  
Process Mineralogy ◽  
Mineralogical Characteristic

The mineral composition of copper–cobalt ores is more complex than that of copper sulfides, and it is also difficult to discard tailing efficiently in primary flotation for the fine-grained disseminated of ore. In this work, a mineral liberation analyzer (MLA) was employed to study the characteristics of minerals. As a significant mineralogical characteristic, the liberation degree of useful mineral aggregates was determined after grinding, and a correlation was established between the ore grinding size and mineralogical characteristics. The results showed that the adopted ore occurred in sulfide form. However, the particle size of the mineral’s monomer was fine grained, whereas its aggregate was coarse. The sulfide mineral aggregate obtained after primary grinding was selected as the recovery object, and its mineralogical characteristics, such as liberation degree and particle size, were investigated to promote total recovery in primary flotation. The copper–cobalt sulfide concentration was obtained at the following optimal conditions: the grinding size of −0.074 mm (65%), the aggregate’s liberation degree of 67%, a collector dosage of 50 g·t−1, a collector combination of 35% aerofloat + 65% butyl xanthate, a pH of 8.5, and 2# oil (a terpineol type foaming agent) dosage of 60 g·t−1. The recovered rough Cu and Co concentrates were 89.45% and 88.03%, respectively. Moreover, the grades of Cu and Co were 13.4% and 4.81%, respectively, with 85.07% of the ore weight discarded as tailing. The consideration of sulfide aggregates instead of singeral minerals mineralogy characters in primary grinding and primary flotation provides an effective theoretical guide for the sorting of sulfide minerals and reduction in the power consumption of grinding.

scholarly journals PRELIMINARY INVESTIGATION OF BILLET PROCESSING ROUTE ON MICROSTRUCTURE, TEXTURE AND FATIGUE RESPONSE OF Ti834 FORGED DISC PRODUCTS

2020 ◽  
Vol 321 ◽  
pp. 11031
Author(s):  
B. Fernandez-Silva ◽  
B. P. Wynne ◽  
M. Jackson ◽  
M. Bodie ◽  
K. Fox
Keyword(s):  
Fatigue Life ◽  
Texture Analysis ◽  
Fatigue Fracture ◽  
Thermomechanical Processing ◽  
Preliminary Investigation ◽  
Processing Route ◽  
Bimodal Microstructure ◽  
Primary Alpha ◽  
Dwell Fatigue ◽  
Beta Matrix

Non-standard processing routes for the manufacture of industrial scale Ti834 billet have been undertaken to investigate their effect on macrozones in final forged product. Microstructure, texture and dwell fatigue fracture surfaces were characterised from forged disc samples fabricated from these new billets. All processing routes showed a bimodal microstructure consisting of 25pct of primary alpha grains in a transformed beta matrix. Texture analysis has revealed variations in the presence and size of macrozones with relatively weak textures. Quasi-cleavage facets were present in all dwell fatigue samples although the fatigue life was doubled for the sample whose thermomechanical processing has the highest imposed strain.

Microstructure and Mechanical Properties of a 1.6C (pct) Ultra-Fine Grained Ultra-High Carbon Steel

2011 ◽  
Vol 682 ◽  
pp. 131-137
Author(s):  
Ya Jun Fan ◽  
Ji Min Cao ◽  
Wei Min Wang ◽  
Yong Ning Liu
Keyword(s):  
Carbon Steel ◽  
Lower Cost ◽  
High Carbon Steel ◽  
Ferrite Matrix ◽  
Grain Boundary Sliding ◽  
High Carbon ◽  
Fine Grained ◽  
Engineering Steel ◽  
Deformation Mechanics ◽  
Boundary Sliding

With massive trials, spheroidized by austeniting at 810°C and cooling by 1°C/min, a 1.6C (pct) Ultra-high Carbon Steel shows a microstructure of uniformly distributed fine carbides in the ultra-fine ferrite matrix. The grain size of ferrite matrix and spheroidized carbides are about 5um and 0.1～2um, respectively. Further investigation by TEM shows that much dislocation together with twins is obtained for the UHCS, and generally finer grains have higher dislocation density. The spheroidized steel exhibits high tensile strength of 910 MPa and high yielding strength of 653 MPa at room temperature, together with excellent elongation of 18.3%, which shows the UHCS can entirely satisfy certain grades of engineering materials and means the steel may substitute present engineering steel considering lower cost. Furthermore, the steel owns good high-temperature superplasticity, the elongation of 216% obtained at 800°C under a strain rate of 2.5×10-4. Initial analysis suggests that the superplastic deformation mechanics of the steel is grain boundary sliding and grain rotating (GBSR), coordinated by migration of dislocation.

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