Steel for large-scale wind power fasteners and manufacturing method thereof

Abstract

The invention discloses a steel for large-scale wind power fasteners, the elemental composition of which is: C: 0.38-0.45%, Si: 0.20-0.35%, Mn: 0.60-0.80%, P≤0.015%, S≤0.010%, Cr: 0.95‑1.20%, Mo: 0.18‑0.30%, Ni: 0.10‑0.25%, Nb: 0.02‑0.08%, Al: 0.020‑0.050%, N≤0.008%, and the balance is Fe and Unavoidable impurities; after heat treatment, the core of the steel has more than 90% martensitic structure, the surface hardness difference of the core is small, especially the low temperature impact performance is relatively excellent, it has good mechanical properties, and the tensile properties meet the strength of 10.9 It can meet the user's processing and use requirements for 48mm-65mm large-scale wind power fastener steel.

Description

technical field [0001] The invention relates to a steel for fasteners and a manufacturing method thereof, in particular to a steel for large-scale wind power fasteners and a manufacturing method thereof. Background technique [0002] At present, wind power has made great progress in the context of building a resource-saving and environment-friendly society. With the high performance of wind turbines, the increase of material application stress, the reduction of the size of the main engine and the lightweight of the gearbox, higher design stress and weight reduction requirements for bolts are put forward, and the most effective measures to meet this requirement are Improve the service strength of steel for bolts. The service conditions of wind turbines are harsh, and they are subjected to extreme heat and cold and extreme temperature differences all year round. of toughness. [0003] The stability of mechanical properties of wind power bolts is mainly restricted by the har...

AI Technical Summary

Problems solved by technology

The hardening critical diameter of 42CrMo and B7 steel is Ф42-48mm. If these steel types are used to manufacture large-size bolts with a size of 48mm or more, the performance of the surface and the core will be very different, which will easily cause the area shrinkage of the finished product to be inconsistent and the low-temperature impact performance. Inferior problems, even lead to the occurrence of delayed fracture

Therefore, the use of traditional 42CrMo and B7 steel to manufacture large-scale wind power bolts will cause great safety hazards to wind turbines

At present, during the rolling production process of medium-carbon CrMo steel, bainite is likely to occur, resulting in the problem of steel bending. Rolled products with excessive bending (>0.4% L) need to be selected for straightening treatment, which increases the after-sales The pressure of road finishing has brought great difficulties to production, and the delivery date of orders will be delayed accordingly

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