Control method of inclusions in thick steel plate used for high heat input welding

Abstract

The invention relates to a control method of inclusions in a thick steel plate used for high heat input welding, which is characterized by adding a deoxidizing agent during steel liquid pouring, wherein the components and adding order of the deoxidizing agent are as follows: Mn and Si, Al, Ti, Ca and Mg; the Mg content is 0.0005-0.007%, when Mg is added for deoxidizing, the oxygen content in steel liquid needs to be adjusted and precisely controlled through adding Fe2O3 powder to a casting ingot mold, and the adding amount of the Fe2O3 powder is such that the oxygen content in the steel liquid is maintained at 0.001-0.008%; the Al content in steel is lower than 0.006%; the ratio of the inclusions with size smaller than 3mu m in the steel liquid is not lower than 80%, and the surface density of the inclusions is not smaller than 300 inclusions / mm<2>; the main components in the center of the inclusions are MgO or MgO and Ti2O3, and the main component on the external surface of the inclusions is MnS. The inclusions formed by using the method provided by the invention can favorably inhibit the growth of austenite crystal in a welding heat-affected zone and promote the growth of intracrystalline ferrite, thus improving the high heat input welding performance of the thick plate.

Description

technical field [0001] The invention belongs to the field of iron and steel metallurgy, and particularly relates to a method for controlling inclusions of thick steel plates for high-energy-input welding. During the smelting process of thick steel plates for high-energy-input welding, the oxygen position during Mg deoxidation is precisely controlled, and a suitable deoxidation method is adopted. Depending on the type of agent and the method of addition, a large number of inclusions with fine dispersion and certain components are formed. This inclusion can meet the requirements of thick steel plate to improve the welding performance of large heat input. Background technique [0002] In many fields such as shipbuilding, construction, pressure vessels, oil and gas pipelines, and offshore platforms, it has become an increasingly urgent requirement to improve the toughness of the heat-affected zone of thick steel plate welding. For example, welding is one of the key links in the...

AI Technical Summary

Problems solved by technology

Fe 3 Although carbide particles such as C, VC, TiC, and NbC, and nitride particles such as AlN and TiN can be finely dispersed in steel, solid solution or growth, cannot well inhibit the growth of austenite grains

al 2 o 3 、Ti 2 o 3 Oxide particles such as oxides, although they can exist stably under the high temperature of the welding thermal cycle without solid solution, but the particle size of these particles is relatively large, and the growth of austenite grains cannot be well inhibited.

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