Surface Electric Arc Hardening of Low-Carbon Steels

Examined geometric characteristics, microhardness and features of structure formation in the heat affected zone of steels 09G2, 20L, 20FL. These studies were carried out after surface quenching by a magnetically controlled (scanning) DC electric arc in a protective argon atmosphere. It is shown that electric arc hardening forms on the treated surface of the steel a thin layer of martensitic-austenitic structure with varying composition and hardness. A ferrite-austenitic structure is formed in the region of transition from the base metal to the heat-strengthened metal. This structure contains crushed ferrite grain and winding boundaries between the structural components. On the periphery of austenitic grains martensitic layer is observed. Repeated heating, occurring during heat treatment of the adjacent surface area, is accompanied by a partial decay of martensite and austenite of a pre-hardened structure with the formation of bainite-and sorbitol-like tempering structures. On the surface, experienced repeated heating, the volume fraction of austenite increases. The dependences allowing to control the structural state and depth of the hardening zone are established.

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Study of the effect of nano-sized precipitates on the mechanical properties of boron-added low-carbon steels by neutron scattering techniques

Journal of Applied Crystallography ◽

10.1107/s0021889808020943 ◽

2008 ◽

Vol 41 (5) ◽

pp. 906-912 ◽

Cited By ~ 6

Author(s):

B. S. Seong ◽

Y. R. Cho ◽

E. J. Shin ◽

S. I. Kim ◽

S.-H. Choi ◽

...

Keyword(s):

Mechanical Properties ◽

Neutron Scattering ◽

Volume Fraction ◽

Weight Fraction ◽

Ferrite Matrix ◽

Carbon Steels ◽

Average Radius ◽

Boron Addition ◽

Low Carbon ◽

Low Carbon Steels

Small-angle neutron scattering (SANS) and neutron powder diffraction (ND) techniques were used to study quantitatively the effect of nano-sized precipitates and boron addition on the mechanical properties of low-carbon steels. SANS was used to evaluate nano-sized precipitates, smaller than about 600 Å in diameter, and ND was used to determine the weight fraction of the cementite precipitates. Fine core–shell structured spherical precipitates with an average radius of ~50 Å, such as MnS and/or CuS, surrounded by BN layers were observed in the boron-added (BA) low-carbon steels; fine spherical precipitates with an average radius of ~48 Å were mainly observed in the boron-free (BF) low-carbon steels. In the BA steels, the number of boron precipitates, such as BN, Fe3(C,B) and MnS, surrounded by BN layers increased drastically at higher hot-rolling temperatures. The volume fraction of the fine precipitates of the BA steels was higher than that of the BF steels; this difference is related to the rapid growth of the BN layers on the MnS and CuS precipitates. Boron addition to low-carbon steels resulted in a reduction in strength and an improvement in elongation; this behaviour is related to the reduction of the solute carbon and the nitrogen contents in the ferrite matrix caused by the precipitation of BN, as well by the increase in the volume fraction of the cementites.

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Relationship between Microstructure and Texture Development during the Early Stages of Annealing in Warm Rolled Low Carbon Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.500-501.795 ◽

2005 ◽

Vol 500-501 ◽

pp. 795-802

Author(s):

Ilana B. Timokhina ◽

John J. Jonas ◽

Simon P. Ringer ◽

S. Bulcock ◽

Elena V. Pereloma

Keyword(s):

Volume Fraction ◽

Shear Bands ◽

Low Carbon Steel ◽

Warm Rolling ◽

Carbon Steels ◽

Texture Development ◽

Low Carbon ◽

Phosphorus Addition ◽

Low Carbon Steels ◽

Early Stages

The influence of chromium and phosphorus addition on the microstructure and on texture development was studied during the early stages of the annealing of warm rolled, low carbon steels. The addition of alloying elements led to an increase in the volume fraction of grains containing both shear bands and microbands. Moreover, the alloyed steels displayed lower stored energies and dislocation densities compared with an unalloyed low carbon steel. Two types of carbides were present after warm rolling in the steels containing the alloying additions: (i) coarse carbides; and (ii) fine strain-induced particles. These microstructural differences affected the development of texture during annealing.

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