Method for improving low-temperature toughness of overall section of steel plate with strength larger than or equal to 690 MPa and thickness ranging from 60 mm to 100 mm

Abstract

The invention discloses a method for improving the low-temperature toughness of the overall section of a steel plate with the strength larger than or equal to 690 MPa and the thickness ranging from 60 mm to 100 mm. Low-temperature heating and large-reduction rolling are adopted, namely, the low-temperature heating temperature of a blank is Tnr + (100-150) DEG C, the heat preservation time is [(1.0-1.5) H] min, rough rolling is conducted at the temperature of Tnr + (30-80) DEG C in a recrystallization zone, the reduction of the first three passes is larger than or equal to 30 mm, finish rolling is conducted at the temperature of Tnr (50-100) DEG C in a non-recrystallization zone, and the accumulated reduction rate of the last three passes is larger than or equal to 30%; and through quenching and tempering heat treatment in a critical zone, the quenching temperature is Ac3 + (0-30) DEG C, the heat preservation time is [1.4 h + (15-45)] min, the tempering temperature is Ac1-(80-110) DEG C, the heat preservation time is [2.0 h + (40-100)] min, and the ultrahigh-strength large-thickness steel plate with the excellent low-temperature impact toughness of the section of the steel plate is obtained. Under the condition that the tensile property of the steel plate is ensured, the low-temperature toughness of the whole section of the super-thick steel plate is remarkably improved, so that the super-thick steel plate completely meets the use performance requirements of the super-thick steel plate with the thickness of 60-100 mm, and the super-thick steel plate can be widely applied to the fields of ship structures, ocean platforms, engineering machinery and the like.

Description

technical field [0001] The invention belongs to the technical field of steel plate rolling-heat treatment, in particular to a method for improving the low-temperature toughness of the overall cross-section of a steel plate with a strength ≥ 690 MPa and a thickness of 60-100 mm. Background technique [0002] Ocean engineering and construction machinery are the main fields of application of high-strength, ultra-high-strength, and large-thickness steel plates. High-strength or extra-thick steel plates must have excellent low-temperature toughness, and the thickness specifications must be 60 mm or above; in terms of steel for construction machinery, domestic Taiyuan Iron and Steel, Anshan Iron and Steel, etc. Research and development, involving thickness specification 6 ~ 100mm. Usually, extra-thick ultra-high-strength steel is quenched and tempered (quenched + tempered) to obtain a matrix structure dominated by tempered martensite, which contains high-density dislocation laths...

AI Technical Summary

Problems solved by technology

[0013] The technical problem to be solved by the present invention is: in view of the problem of uneven low-temperature toughness of the overall section of the steel plate with ultra-high strength (≥690MPa) and large thickness (60-100mm) in the prior art, and even low low-temperature impact toughness at the surface and core, the steel plate adopts Low-temperature heating and high-pressure rolling, through tempering heat treatment in the critical zone, can significantly improve the low-temperature toughness of the overall section of the ultra-high-strength large-thickness steel plate while ensuring the tensile properties of the steel plate (yield strength, tensile strength, elongation), and Provides a method for improving the low-temperature toughness of the overall cross-section of a steel plate with a strength ≥ 690 MPa and a thickness of 60-100 mm