A high-weather-resistant hot-rolled h-beam with a yield strength of 450mpa and its heat treatment process

Abstract

The invention discloses 450MPa-grade yield strength high-weather-resistance hot-rolled H-shaped steel and a heat treatment technology thereof. The 450MPa-grade yield strength high-weather-resistance hot-rolled H-shaped steel comprises the following chemical compositions of, by weight, 0.06-0.10% of C, 0.20-0.40% of Si, 0.40-0.70% of Mn, no more than 0.035% of P, no more than 0.010% of S, 2.00-3.50% of Cr, 0.30-0.50% of Ni, 0.30-0.50% of Cu, 0.015-0.035% of V, 0.020-0.040% of Alt, and the balance Fe and unavoidable impurities. The heat treatment tempering technology of the 450MPa-grade yield strength high-weather-resistance hot-rolled H-shaped steel comprises the following steps that heating is conducted to 600-700 DEG C at 5-20 DEG C / s, heat preservation is conducted for two hours, and then air cooling is conducted. The yield strength of the high-weather-resistance hot-rolled H-shaped steel obtained through the heat treatment technology exceeds 480 MPa, the tensile strength exceeds 600MPa, and the percentage elongation after fracture exceeds 20%, -40 DEG C KV<2> type impact work is larger than or equal to 65 J, and the good low-temperature impact toughness is achieved.

Description

technical field [0001] The invention belongs to the technical field of metal material production, and in particular relates to a high-weather-resistant hot-rolled H-shaped steel with a yield strength of 450 MPa and a heat treatment process thereof. Background technique [0002] Weather-resistant hot-rolled H-shaped steel is mainly used in railway freight car chassis and bridge structures. With the development of domestic rail transportation to high-speed, heavy-duty, and long-life, it operates in different climate regions, while bridges tend to be large-span and lightweight Development, construction and service environments also cover different climate regions in China. The manufacture of railway wagon chassis and bridge structures urgently needs hot-rolled H-shaped steel with high weather resistance, high strength and high toughness. [0003] In order to meet high weather resistance requirements (relative to Q345B corrosion rate ≤ 30%), hot-rolled H-beams have higher Cr, Ni...

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Problems solved by technology

[0004] Due to the current domestic hot-rolled H-shaped steel production process and equipment limitations, the austenite recrystallization zone and non-recrystallization zone rolling can not achieve large reduction, after rolling, air cooling or water spray cooling is used. After many verifications, only The current domestic hot-rolled H-beam tooling, hot-rolled high-weather-resistant hot-rolled H-beam, its microstructure is basically granular bainite or upper bainite, the product has high strength but poor plasticity and toughness, and the yield strength usually exceeds 800MPa, the tensile strength exceeds 900MPa, and its -40℃KV 2 The average impact energy of the model is only about 15J. When subjected to dynamic load or impact, it is prone to brittle fracture, which seriously affects the service safety of railway wagons and bridges, and is also very unfavorable to structural processing.

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