Investigation of the Mechanical Properties of Intercritically Treated Ultra High Strength Steel

Intercritically treated ultra high strength steel was investigated using a continuous annealing simulator of the laboratory. The results have shown that the microstructure consists of a ferrite matrix with martensite. A satisfactory mechanical property was obtained by intercritical annealing and subsequent overaging. The specimen exhibited optimum Rm (1360MPa) and At (20%), a relatively low Rp0.2/Rm (0.72) and an ideal product of Rm and At (27200MPa%). Satisfactory mechanical properties of the present steel are attributed to the fact that the effect of dispersion strengthening of martensite islands as well as the contribution to strength by the softer phase, such as ferrite (retained austenite).

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Effect of Overaging Temperature on the Mechanical Properties of Ultra-High Strength Multiphase Steel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.556-562.249 ◽

2014 ◽

Vol 556-562 ◽

pp. 249-252

Author(s):

Zhuang Li ◽

Zhen Zheng ◽

Da Tong Qiu ◽

Li Zhe Guo ◽

Xin Gao ◽

...

Keyword(s):

Mechanical Properties ◽

High Strength Steel ◽

Intercritical Annealing ◽

High Strength ◽

Total Elongation ◽

Good Combination ◽

Continuous Annealing ◽

Steel Microstructure ◽

Ultra High Strength Steel ◽

Multiphase Steel

Overaging after intercritical annealing of ultra-high strength multiphase steel was conducted in a continuous annealing simulator of the laboratory. The effect of overaging temperature on the mechanical properties of multiphase steel has been studied by observing the microstructural evolution during overaging. The results have shown that multiphase microstructures containing ferrite, martensite, bainite and retained austenite were obtained by overaging treatments after intercritical annealing in ultra-high strength steel, and overaging temperatures affected all constituents of the microstructure. UTS and YS dereased with increasing overaging temperature, and TEL decreased after overaging at 350°C. A good combination of ultimate tensile strength (1400MPa), yield strength (795MPa), and total elongation (15%) was exhibited for the specimen overaged at 250°C. This was attributed to synthetic action of all constituents of ultra-high strength steel microstructure.

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Development of high strength steel sheet with improved strainhardenability for automotive application

Izvestiya Ferrous Metallurgy ◽

10.17073/0368-0797-2019-11-827-832 ◽

2019 ◽

Vol 62 (11) ◽

pp. 827-832

Author(s):

Madhawan Chandrawanshi ◽

Rajan Kumar Singh ◽

R. Sudharshan

Keyword(s):

High Strength Steel ◽

Retained Austenite ◽

High Strength ◽

Xrd Analysis ◽

Ferrite Matrix ◽

Granular Bainite ◽

Automotive Application ◽

Continuous Annealing ◽

Microstructure And Mechanical Property ◽

Hardening Coefficient

Advance high strength steel with minimum UTS of 780 MPa is industrially developed utilizing continuous annealing line (CAL) and Gleeble thermo mechanical simulation. An outline of superior elongation, improved strain hardenability, enhanced strength of developed Fe – C – Mn – Si TRIP assisted steel is described. Correlation amid Simulated result and industrially annealed steel are stabilized for microstructure and mechanical property. Annealing condition is optimized for best combination of strength and formability accordingly. CCT diagram for the selected composition from JMatPro is utilized to optimize rapid cooling rate and over aging section temperature. Final microstructure of developed steel comprises tempered martensite, granular bainite with retained austenite distributed in polygonal ferrite matrix. An evaluation of developed TRIP steel is carried out with the help of microstructure and XRD analysis. It was concluded that strain hardening coeﬃcient of new steel is comparable to that of drawing grades attributable to about 13 % retained austenite in microstructure.

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