800mpa grade high-strength steel with low composition and low pcm value and its production method

Abstract

The invention relates to 800MPa grade high-strength steel with low composition and low Pcm value and a production method thereof, belonging to the technical field of high-strength structural steel. A component system of the high-strength steel with low Pcm value is reasonably designed; under the premise of not adding alloys such as Ni, Mo and Cu, low C, appropriate Mn and Cr are adopted, and microalloy elements such as Nb, V and a trace element B are reasonably added; strict two-phase controlled rolling is adopted, after rolling, 'UFC+ACC' (ultra-fast cooling and accelerated control cooling) is used for combined cooling and subsequent tempering treatment, and various reinforcing effects of the alloy elements such as Mn, Cr, Nb and V in the processes of steel plate rolling, cooling and tempering are comprehensively utilized; therefore, the produced high-strength steel with low welding crack sensitivity and tensile strength of 800MPa grade has excellent mechanical performance, the surface quality of a steel plate is good, the alloy reduction production is realized, resources and energy are saved, and the production cost is greatly reduced.

Description

technical field [0001] The invention belongs to the technical field of high-strength structural steel, and in particular relates to an 800MPa-grade high-strength steel with low composition and low Pcm value (low welding crack sensitivity index) and a production method thereof, and a tensile strength 800MPa-grade high-strength steel. Background technique [0002] Construction machinery and coal mining machinery are basically composed of steel materials, and steel plays a pivotal role in their manufacturing process. Due to the special conditions of use of construction machinery, objects and environments, such as the main structural parts of excavators, cranes, and loaders, they generally bear complex and changeable loads. In addition to requiring high strength for steel, it is also required to have good Low temperature impact toughness, cold formability and welding performance. In order to improve work efficiency and service life, construction machinery is further developed i...

AI Technical Summary

Problems solved by technology

Compared with the patent "CN102260823A—an economical high-strength steel plate with a yield strength of 690MPa and its manufacturing method", more Mn elements are added, which increases the difficulty of smelting and at the same time makes it difficult to guarantee the internal quality of steel billets or steel plates (core segregation) At the same time, the design of this composition system has approached or exceeded the upper limit of the element Mn in national standards (GB / T1591-2008, YB / T4137-2005, GB / T16270-2009, etc.), and basically cannot meet the standard requirements; During the process, the final cooling temperature is low, which is similar to "offline quenching", and it is difficult to control the surface quality (shape) of the steel plate

The patent "CN101418418A—Steel plate with yield strength 690MPa and low crack sensitivity and its manufacturing method" adds a certain amount of Mo and Cr alloys, and adopts the "TMCP" process alone. It is difficult to overcome the defects of the process itself-the uniformity of the mechanical properties of the steel plate and Stability issues

Patents "CN101215624A - an online quenching production process for high-strength and tough thick steel plates", "CN103014539A - a high-strength and high-toughness steel plate with a yield strength of 700MPa and its manufacturing method" and "CN102851604A - a high-strength steel plate with a yield strength of 690MPa production method", using the "online quenching + tempering" process, in the cooling process, set a lower final cooling temperature, the shape of the steel plate is not easy to control; at the same time add a lot of alloys, such as Mo, Ni, Cu, etc., the alloy cost also higher

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