Niobium-containing R4 mooring cable steel and heat treatment technology and production method thereof

Abstract

The present invention relates to a niobium-containing R4 mooring cable steel and a heat treatment technology and a production method thereof, and the niobium-containing R4 mooring cable steel containing the following components by mass: 0.26-0.31 parts of C, 0.15-0.40 parts of Si, 0.60-0.90 parts of Mn, less than or equal to 0.010 parts of P, less than or equal to 0.005 parts of S, 1.00-1.20 parts of Cr, 0.20-0.30 parts of Mo, 0.50-0 .80 parts of Ni, 0.055-0.075 parts of Nb, 0.010-0.030 parts of Ti, 0.25-0.40 parts of Cu, 0.0008-0.0030 parts of B, 0.015-0 .050 parts of Als, and the balance of iron and trace impurities. The heat treatment technology comprises the steps of (1) quenching, to be more specific, the mooring chain steel is heated to a temperature of 900-950 DEG C, in the temperature section, the heating holding time is calculated by 1.5-2.0min / mm, and then the mooring chain steel is cooled; and (2) tempering, to be more specific, the mooring chain steel is heated to a temperature of 600-650DEG C, the heating holding time is calculated by 2-2.5min / mm, and then the mooring chain steel is cooled. The R4 mooring cable steel is developed, and the hardenability, corrosion resistance, fatigue resistance and low temperature toughness of the R4 mooring cable steel are significantly improved, and the overall performance uniformity.

Description

technical field [0001] The invention relates to steel for large-scale R4 mooring chains and a heat treatment process thereof, in particular to steel for R4 mooring chains containing niobium, a heat treatment process and a production method thereof. Background technique [0002] Mooring chain products are mainly used in floating production systems for offshore oil and natural gas development, semi-submersible drilling platforms, single-point mooring structures, floating production and storage ships, and other marine development facilities. The quality of its products is related to offshore operations. and safety of ships. Because the mooring chain has been immersed in seawater for a long time and the conditions are harsh, the steel used for the mooring chain is required not only to have high strength and good toughness, but also to be resistant to seawater corrosion, fatigue damage, and wear. According to different strength levels used, mooring chain products mainly include ...

AI Technical Summary

Problems solved by technology

[0004] (1) Due to the high content of alloying elements, the hot-rolled structure of the material is semi-martensitic. The material must be annealed before delivery, otherwise the material will undergo martensitic transformation during the placement process, resulting in structural stress. Leading to internal cracks in the material and scrapping

[0005] (2) Due to the high content of alloying elements such as Mn, Cr, Mo, etc., it will deteriorate the weldability of steel and increase the probability of welding cracks

[0007] (4) Increased production costs

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