Stabilization of retained austenite by the two-step intercritical heat treatment and its effect on the toughness of a low alloyed steel

There is a currently desirable demand for high strength steels with good ductility reduce the weight of steel parts for automobile and train applications. Retained austenite in steels can improve the toughness and plasticity. The austenite reverse transformation + quenching and partitioning (ART + Q&P) process was treated on a 0.2C-Mn-Si-Cr low alloyed steel, a multiphase microstructure composed of intercritical ferrite (IF), martensite, bainite and retained austenite (RA) can be obtained in the low carbon steel. Microstructures of the steel treated by different heat treatments were characterized by SEM and XRD. Results show that the formation of RA in low alloy steel depends on the following: (1) the enrichment of the carbon and manganese in the reversed austenite during the ART step; (2) the secondary enrichment of carbon in retained austenite during the following Q&P step. High fraction of RA (14vol.%) was obtained through the two-step element enrichment treatment (ART + Q&P). Due to continuous TRIP effect of RA during the deformation, a good combination of strength and plasticity was achieved in our works: the product of strength and elongation is greater than 35 GPa•%, the tensile strength is more than 1230 MPa, the yield strength greater than 890 MPa, the total elongation is about 28.6%.

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Using Electron Beam to the Surface Heat Treatment of the Carbon Steels

Advanced Engineering Forum ◽

10.4028/www.scientific.net/aef.34.10 ◽

2019 ◽

Vol 34 ◽

pp. 10-17

Author(s):

Adriana Zara ◽

Maria Stoicănescu ◽

I. Giacomelli

Keyword(s):

Heat Treatment ◽

Electron Beam ◽

Carbon Steel ◽

Superficial Layer ◽

Carbon Steels ◽

Surface Heat ◽

Alloyed Steel ◽

Mechanical Products ◽

Low Alloyed Steel ◽

Working Parameters

Usage of electron beam shows the possibility of using its energy in different thermic processes. Among these, it is found the heating of mechanical products for the surface heat treatment. During the effectuated practical attempts, two types of construction steels were analyzed, namely carbon steel (OLC 45) and a low alloyed steel (41 Cr 4). The electron beam was applied on samples that were previous subjected to the heat treatment of improvement. The working parameters were chosen in order to obtain the heating of the superficial layer without melting. The samples treated as above were subjected to studies regarding the metallographic structures and the resulted hardness; also there were effectuated wear attempts. It was concluded that the use of electron beam in superficial heat treatment may also fit in practical terms.

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Effect of Vanadium on Microstructure and Mechanical Properties of Air Cooled Medium Carbon High Silicon Bainite Steels

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.311-313.931 ◽

2011 ◽

Vol 311-313 ◽

pp. 931-935

Author(s):

Jun Miao ◽

Li Jun Wang ◽

Chun Ming Liu

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Retained Austenite ◽

Silicon Steel ◽

Alloyed Steel ◽

Air Cooling ◽

Medium Carbon ◽

Transmission Electron ◽

High Silicon Steel ◽

High Silicon

The effect of vanadium on the bainite transformation of medium carbon high silicon steel during air cooling was studied by using Optical Microscopy (OM) and Transmission Electron Microscopy (TEM). The mechanical properties of the test steels subjected to heat treatment were measured by tensile, hardness and impact tests. The results showed that, through the same heat treatment process, the microstructure of the V-alloyed steel was comprised of Carbide-Free Bainite (CFB, bainite + retained austenite) and martensite while the microstructure of the V-free steel was composed of ferrite/pearlite, which made the V-alloyed steels exhibit superior combination of strength, hardness and toughness to the V-free steel, but the elongation of the V-alloyed steel was worse than that of the V-free steel somewhat. Vanadium was helpful for the transformation of bainite in the tested medium carbon high silicon steel under air cooling condition. The carbon-enriched retained austenite films in the CFB enhanced the toughness of the V-alloyed steel.

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Two-Step Quenching & Partitioning of 42SiCrB Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.783-786.738 ◽

2014 ◽

Vol 783-786 ◽

pp. 738-743 ◽

Cited By ~ 1

Author(s):

Niko Grosse-Heilmann ◽

Isabella Maria Zylla ◽

Ernst Kozeschnik ◽

Andreas Peters

Keyword(s):

Heat Treatment ◽

Retained Austenite ◽

Thermal Process ◽

Treatment Process ◽

Volume Fraction ◽

High Strength ◽

Carbon Diffusion ◽

Process Route ◽

Low Alloyed Steel ◽

Step Quenching

In recent years, Quenching and Partitioning (Q&P) became an interesting thermal process route for semi-finished high strength low alloyed steel components. Recent publications demonstrate promising mechanical properties with considerable ductility enhancement. To assess the potential of the two-step Q&P heat treatment in seamless tube production, corresponding tests are carried out on 42SiCrB steel (0.42wt% C, 2.0wt% Si, 1.3wt.% Cr, 0.6wt.% Mn, 0.002wt.% B). Feasible Q&P heat treatment process parameters are identified using the Constrained-Carbon-Equilibrium (CCE) model, carbon diffusion calculations and isothermal TTT curves with previous quenching. Furthermore achieved volume fraction of retained austenite is analyzed by XRD experiments.

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