Steel for large-sized wind power fastener and manufacturing method of steel

Abstract

The invention discloses steel for a large-sized wind power fastener. The steel is prepared from the element components in percentage by mass: 0.38-0.45% of C, 0.20-0.35% of Si, 0.60-0.80% of Mn, lessthan or equal to 0.015% of P, less than or equal to 0.010% of S, 0.95-1.20% of Cr, 0.18-0.30% of Mo, 0.10-0.25% of Ni, 0.02-0.08% of Nb, 0.020-0.050% of Al, less than or equal to 0.008% of N, and thebalance of Fe and inevitable impurities. After heat treatment, the core part of the steel is provided with 90% or above of a martensitic structure, the surface hardness difference of the core part isless, especially the low-temperature impact property is excellent, the good mechanical properties are achieved, the tensile property meets the 10.9-grade strength requirements, and the machining usingrequirements for the steel for 48-65 mm of the large-sized wind power fastener by a user can be met.

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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