Steel plate for acicular ferrite/blocky ferrite ship and manufacturing method of steel plate

Abstract

The invention relates to an acicular ferrite / blocky ferrite marine steel plate and a manufacturing method thereof, the microstructure is acicular ferrite and blocky ferrite, the acicular ferrite accounts for 40 + / -5% by volume, and the average grain size of the ferrite is 3-6 [mu] m. The transverse tensile property of the yield strength ranges from 390 MPa to 420 MPa, the tensile strength ranges from 520 MPa to 550 MPa, the yield ratio ranges from 0.72 to 0.77, the ductility is larger than or equal to 29%, the longitudinal impact toughness values at the temperature of-40 DEG C and-60 DEG C are larger than or equal to 200 J, and after strain aging, the impact toughness values at the temperature of-40 DEG C and-60 DEG C are not obviously reduced. The low carbon content is adopted, and Si-Cr-Nb elements are added, so that ferrite phases are formed as many as possible, and formation of pearlite is inhibited. The high final cooling temperature is adopted, it is guaranteed that the matrix structure of the steel plate is still ferrite / acicular ferrite through the high final cooling temperature, and the situation that the toughness and the plastic structure of the steel plate are deteriorated although the strength can be improved through upper bainite or granular bainite is avoided.

Description

technical field [0001] The invention belongs to the field of iron and steel metallurgy, and in particular relates to an acicular ferrite / block ferrite marine steel plate and a preparation method thereof. The thickness of the steel plate is between 50-70mm, and it has good low-temperature impact toughness and strain aging performance. Background technique [0002] With the continuous development and utilization of marine resources in countries all over the world, the marine shipbuilding industry and equipment industry have achieved considerable development, which has driven the technological progress of steel plates for ships and marine engineering. The size of steel plates used in modern ships and marine engineering is developing towards greater thickness, and they need to have the characteristics of high strength, high toughness, easy welding, easy processing, and corrosion resistance. [0003] At present, the most orders are AH36, DH36, EH36 and other high-strength hull s...

AI Technical Summary

Problems solved by technology

The patent document CN106756543 relates to a high-strength ship plate steel for low-cost high-energy-input welding in TMCP state. There are many alloys added, and the cost of the alloy is too high, which does not meet the development trend of ship plate steel to reduce costs and increase efficiency.

Images