Zinc-induced crack-resistant steel sheet and manufacturing method thereof

Abstract

A zinc-induced-crack resistant steel plate and a manufacturing method therefor are disclosed. A low alloy steel with low C-ultralow Si-high Mn-low Als-(Ti+Nb) micro alloying treatment is taken as a basis, and the Als content in the steel is appropriately reduced; the content of the steel is controlled for Mn / C≥15, [(%Mn)+0.75(%Mo)]×(%C)≤0.16, Nb / Ti≥1.8 and Ti / N between 1.50-3.40, CEZ≤0.44% and B≤2ppm, Ni / Cu≥1.50; the Ca treatment is performed and the Ca / S ratio is controlled to be 1.0-3.0, and (%Ca)×(%S)0.28≤1.0×10-3. The TMCP process is optimized, so that the micro-structure of the finished steel plate is ferrite + fine bainite colonies dispersedly distributed, the average grain size is less than or equal to 10 μm, and excellent mechanical properties, good weldability and zinc-induced-crack resistance property are obtained. The steel plate is especially suitable for spraying zinc coating corrosion resistant steel plate for marine structures, spraying zinc corrosion resistant steel plate for extra-high voltage power transmission structures, spraying zinc coating corrosion resistant steel plate for coast bridge structures, and the like.

Description

technical field [0001] The present invention relates to steel for structural use and a manufacturing method thereof, in particular to a zinc-induced crack-resistant steel plate and a manufacturing method thereof. Cracks (CEZ≤0.44%), the microstructure of the finished steel plate is ferrite + finely dispersed and uniformly distributed bainite crystal clusters, the average grain size is controlled below 10 μm, and the microstructure of the welded heat-affected zone is fine and uniform Ferrite + a small amount of pearlite. Background technique [0002] As we all know, low-carbon (high-strength) low-alloy steel is one of the most important engineering structural materials, widely used in oil and gas pipelines, offshore platforms, shipbuilding, bridges, pressure vessels, building structures, automobile industry, railway transportation and machinery manufacturing . The properties of low-carbon (high-strength) low-alloy steel depend on its chemical composition and the process sys...

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Problems solved by technology

[0005] The above-mentioned large number of patent documents only explain how to realize the low-temperature toughness of the base metal steel plate, and explain less about how to obtain excellent low-temperature toughness of the heat-affected zone (HAZ) under welding conditions, especially how to ensure the low-temperature toughness of the heat-affected zone when welding with large heat input. The structure is uniform and fine ferrite + a small amount of pearlite, which makes ferrite nucleate and grow in the original austenite grain boundary, basically eliminates the original austenite grain boundary, and improves the zinc-induced crack resistance of the steel plate. Japanese patents Sho 63-93845, Sho 63-79921, Sho 60-258410, TK 4-285119, TK 4-308035, P 3-264614, P 2-250917, P 4-143246 and US Patent 4855106, USPatent5183198, USPatent4137104, etc.

[0006] At present, only Nippon Steel Corporation of Japan adopts oxide metallurgy technology to improve the low-temperature toughness of the heat-affected zone (HAZ) of welded steel plates with large heat input. This patent does not involve how to improve the zinc-induced crack resistance of steel plates.

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