Ultrahigh tough steel with tensile strength of 1100 Mpa and manufacturing method thereof

Abstract

The invention discloses ultrahigh tough steel with tensile strength of 1100 Mpa and a manufacturing method thereof. Chemical components of the tough steel comprises, by weight, 0.245-0.350% of C, 0.10-0.50% of Si, 0.20-1.20% of Mn, P less than or equal to 0.015%, S less than or equal to 0.003%, 0.30-1.20% of Cr, 0.20-0.80% of Mo, 2.00-3.70% of Ni, 0-0.30% of Cu, 0-0.08% of Nb, 0-0.12% of V, 0.01-0.08% of Al, 0.003-0.06% of Ti, Ca less than or equal to 0.005%, H less than or equal to 0.002%, N less than or equal to 0.0120%, O less than or equal to 0.0030%, Fe and inevitable impurities. The preparation method adopts quenching plus tempering heat treatment, and tempered martensites plus tempered bainites and residual austenite tissue are obtained. The yield strength of steel is greater than or equal to 900 Mpa, the tensile strength is greater than or equal to 1100 Mpa, the charpy impact energy Akv (-20 DEG C) is greater than or equal to 70 J, the elongation rate is greater than or equal to 15%, the shrinkage rate of a fracture surface is greater than or equal to 50%, good strength, low-temperature toughness and plasticity are achieved, and the ultrahigh tough steel can be used for manufacturing high-performance ocean platform mooring cables of R6 grade and the like.

Description

technical field [0001] The invention relates to an ultra-high-strength steel material with good low-temperature toughness, in particular to an ultra-high-strength tough steel with a tensile strength of 1100 MPa and a manufacturing method thereof. Background technique [0002] High-strength and tough steel bars are used in the production of mooring chains on offshore platforms and high-safety mechanical and structural components. With the development of marine resources in the deep sea, the scale of the offshore platform, the complexity of the structure and function, the requirements for the mooring chain of the offshore platform are also increasing. Offshore platform mooring chains are used in harsh environments and are subjected to high tensile loads, seawater impacts during wave motion, seawater erosion and microbial corrosion. The steel used for mooring chains on offshore platforms mainly includes R3, R3S, R4, R4S, R5, etc. The corresponding tensile strengths are 690MPa...

AI Technical Summary

Problems solved by technology

High-strength steel mainly composed of martensite, due to the strain storage energy reaching 1000J / mol, the dislocation density is high, resulting in poor low-temperature impact energy

There are high-density dislocations and sub-grain boundaries inside the martensitic high-strength steel, and it will break and fail rapidly when tiny defects such as microcracks appear during the stretching process, and the elongation is low

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