12.9-grade delayed-fracture-resistant weather-proof bolting steel and production method

Abstract

The invention discloses 12.9-grade delayed-fracture-resistant weather-proof bolting steel and a production method. The steel comprises the following components according to the mass percentages: 0.35-0.45% of C, 0.10-0.40% of Si, 0.50-0.90% of Mn, less than or equal to 0.012% of P, less than or equal to 0.005% of S, 0.80-1.20% of Cr, 0.20-0.50% of Cu, 0.80-1.20% of Ni, 0.10-0.50% of V, Nb and Ti, 0.10-0.50% of Mo, 0.015-0.045% of Alt and the balance Fe and inevitable impurities. By designing the components and production technology parameters, the strength of the steel reaches a 12.9 grade, and meanwhile, the steel has excellent atmospheric corrosion resistance performance and delayed fracture resistance performance.

Description

technical field [0001] The invention relates to a bolt steel and a preparation method thereof, in particular to a 12.9-grade delayed-fracture-resistant and weather-resistant bolt steel and a preparation method thereof. Background technique [0002] In the process of manufacturing and installing steel structure bridges and buildings, high-strength bolts are widely used in bridges and buildings because of their technical characteristics such as simple construction technology, convenient installation and disassembly, large bearing capacity, and not easy to loosen. The consumption of buildings has reached hundreds of thousands to millions of sets. Therefore, the design of high-strength bolts, the production of raw materials and the manufacture of high-strength bolt products have all received great attention worldwide. [0003] Highway bridges at home and abroad use up to 8.8 grade bolts, and railway bridges use up to 10.9 grade bolts. In the last century, Japan used 11.9 and 13...

AI Technical Summary

Problems solved by technology

The delayed fracture of high-strength bolts is mainly caused by the hydrogen existing in the raw material itself, the hydrogen entering during the bolt manufacturing process, and the hydrogen intruding during the bolt service process. It is easy to produce sudden brittle fracture at the root of the thread or the transition between the screw and the head, which will bring serious safety hazards

At present, since there are no industrial dehydrogenation standards and testing standards, the development of high-strength bolts resistant to delayed fracture at home and abroad is mainly concentrated in the field of material research. Studies have shown that adding an appropriate amount of microalloying elements V, Ti, Nb, etc. , forming fine carbonitrides, in addition to refining the austenite grains before expediting, it can also serve as a hydrogen trap, inhibiting the diffusion of hydrogen and making hydrogen evenly distributed. This composition is designed in 10.9 grade delayed fracture resistant bolt steel However, with the requirement of bridge lightweight, the bolt strength increases, and the risk of delayed fracture increases. It is necessary to carry out a series of research on materials to improve the delayed fracture resistance of high-strength bolt steel.

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