Non-quenched acicular structure high strength low yield ratio weathering resistant steel and production method thereof

Abstract

The invention relates to a non-quenched acicular structure high strength low yield ratio weathering resistant steel and a production method thereof. The steel comprises components by weight percent: basic components: 0.03-0.08% of C, 0.30-0.60% of Si, 1.30-1.80% of Mn, less than or equal to 0.015% of P, less than or equal to 0.010% of S, 0.30-0.60% of Cu, 0.20-0.50% of Ni, 0.40-0.80% of Cr, 0.10-0.40% of Mo, 0.030-0.080% of Nb and less than or equal to 0.04% of Ti; optional components are two or more in less than or equal to 0.04% of AlS and less than or equal to 0.40kg/t steel of RE or less than or equal to 0.005% of Ca; and the rest of Fe and impurities. Welding cold crack is low in susceptibility coefficient and high in corrosion resisting index. The steel has simple components as wellas excellent moldability, weatherability, weldability and low temperature toughness; meanwhile, the preparation technique is simple, heat treatment is not needed, the production period is short, and the production cost is low.

Description

technical field [0001] The invention relates to a low-alloy steel and its production method, in particular to a non-quenched and tempered high-strength steel with excellent formability, excellent low-temperature toughness, excellent weldability and excellent atmospheric corrosion resistance and its production method, belonging to low-alloy steel manufacturing field. Background technique [0002] At present, the American Society for Testing and Materials standard ASTMA709 / A709M-01b has a steel grade HPS70W steel with a similar strength level, its carbon content is less than or equal to 0.11wt% (generally around 0.09wt%), and the welding cold crack sensitivity coefficient Pcm value Higher, more complicated process is required for welding, and this steel contains 0.04-0.08wt% vanadium, and vanadium carbonitrides will be precipitated during post-weld cooling, which will affect the welding toughness of the steel. In the production process of this kind of steel, quenching and tem...

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Problems solved by technology

In order to improve the performance of SMA570W, JFE Corporation of Japan has developed high-performance bridge steel BHS500W. This steel adopts non-tempered quality-controlled rolling and controlled-cooling process. The maximum thickness is 100mm. Preheating before welding is required. The welding performance is excellent, but its disadvantages The reason is that its low-temperature impact toughness is not much improved compared with SMA570W steel, and its Charpy V-type impact energy only requires greater than or equal to 100J at -5°C

[0004] In China, WISCO launched the fifth-generation bridge steel WNQ570 (Q420qE) in early 2007, and used this steel type for the construction of the Nanjing Dashengguan Yangtze River Bridge on the Beijing-Shanghai High-speed Railway. Its specific performance indicators are listed in the patent publication No. CN1609257A It is detailed that this steel adopts non-tempered quality controlled rolling and controlled cooling process, which has good low temperature toughness and weldability, but this steel has three shortcomings: 1. The maximum thickness is only 60mm

Calculated according to its strength level, it is not suitable for the construction of long-span bridges. In fact, in the manufacture of non-quenched and tempered steel of this strength level, no breakthrough has been made in thickness; 2. The yield ratio is too high, although this steel type It breaks through the bottleneck of the traditional high-strength non-quenched and tempered welded structural steel with a yield ratio of ≤0.93, but the yield ratio of this steel is still around 0.88, so the safety of the components is not enough; three, the weather resistance is insufficient, although the steel The corrosion resistance index I calculated according to the formula given in the American Society for Testing and Materials standard ASTM G101-01 reaches 6.0-6.1, which just meets the requirements of the weathering steel corrosion resistance index I>6.0, but it is used as a weathering bridge for high-speed railways The use of steel, the weather resistance of this steel is still insufficient

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