Development of High-strength Low-Mo Fire-resistant Steel with Excellent Seismic Resistance

CHENG Tianle; WAN Rongchun; DAI Zhiyong; GONG Xun

doi:10.3969/j.issn.1674-6457.2026.06.017

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Journal of Netshape Forming Engineering ›› 2026, Vol. 18 ›› Issue (6) : 193-200. DOI: 10.3969/j.issn.1674-6457.2026.06.017

Iron and Steel Forming

Development of High-strength Low-Mo Fire-resistant Steel with Excellent Seismic Resistance

CHENG Tianle¹, WAN Rongchun², DAI Zhiyong^2,*, GONG Xun³

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Abstract

The work aims to design and melt two types of low-Mo experimental steels of Q355 grade (N1: base composition; N2: with approximately 0.021% Nb addition) to develop cost-effective, low-molybdenum (Mo) fire-resistant steel plates with excellent seismic performance and high-temperature strength. The microstructural evolution of the two experimental steels was characterized by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The comprehensive mechanical properties at room temperature and 600 ℃ were compared through tensile tests, obtaining key indicators including room-temperature and high-temperature tensile strength, yield strength, plasticity, and yield ratio. The results indicated that steel N1 primarily consisted of ferrite (F) + pearlite (P) with a small amount of bainite (B), exhibiting an average ferrite grain size of approximately 53.7 μm. In steel N2, the bainite content increased, and the ferrite grain size was significantly refined to an average of approximately 45.5 μm. At room temperature, the yield ratio of steel N1 was about 0.49-0.52, while that of steel N2 was about 0.59-0.60. The yield ratios of all experimental steels were far below the 0.8 required for building structural steels, indicating high seismic performance. At 600 ℃, the room-temperature to high-temperature yield strength ratio of steel N1 exceeded 0.69, meeting the mechanical property requirements for fire-resistant steel. In conclusion, both N1 and N2 experimental steels are successfully developed, demonstrating excellent seismic performance and good fire resistance. Notably, steel N2 exhibits significantly enhanced room-temperature strength, and its yield strength at 600 ℃ reaches approximately 240 MPa, achieving the standard for Q355 grade fire-resistant steel.

Key words

seismic performance / high-temperature strength / fire-resistant steel / microstructure / yield ratio

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CHENG Tianle, WAN Rongchun, DAI Zhiyong, GONG Xun. Development of High-strength Low-Mo Fire-resistant Steel with Excellent Seismic Resistance[J]. Journal of Netshape Forming Engineering. 2026, 18(6): 193-200 https://doi.org/10.3969/j.issn.1674-6457.2026.06.017

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