Method of Q345R steel for ultra-low temperature and manufacturing method thereof

Abstract

The invention provides a method of Q345R steel for ultra-low temperature and a manufacturing method thereof, and belongs to the technical field of steel manufacturing. According to the Q345R steel forultra-low temperature, scheme matching is conducted by optimizing the alloy elements, the low-cost alloy elements are adopted, the adding amount of the more expensive alloy elements is cancelled, thecontent of harmful impurities elements P and S is appropriately reduced, the purity of molten steel is ensured, and the influence of inducing of the impact toughness due to the harmful impurity elements is reduced; and on the one hand, the low temperature impact toughness of a steel plate is effectively reduced, and on the other hand, the production cost is also successfully reduced. By means ofthe manufacturing method, a rolling and cooling controlling + normalizing heat treatment process technology is adopted, the defects such as grain coarseness and uneven structure produced in the rolling process through the normalizing heat treatment process are eliminated, the carbide is fully dissolved, the pearlitic structure is refined, and the uniform ferrite + small pearlitic structure + carbide precipitation structure is obtained, so that the steel plate has the high strength and toughness performance, and the requirements of use in ultra-low temperature environments are met.

Description

technical field [0001] The invention belongs to the field of steel manufacturing, and in particular relates to a Q345R steel for ultra-low temperature and a manufacturing method thereof. Background technique [0002] Boiler steel plate Q345R was widely used to make reactors, heat exchangers, separators and other equipment in the early days. The application environment temperature of these equipments is generally 0 or -20 ℃. However, in recent years, with the rapid development of the national economy and the rapid rise of the petrochemical industry, Q345R steel plates have been endowed with new uses for manufacturing spherical tanks, oil and gas tanks, and liquefied gas tanks. The containers made by it are used to store propane, ethylene, etc., which need to be stored in an ultra-low temperature environment of -40~-50°C to ensure the stability of the gas. [0003] At present, the following problems generally exist in Q345R steel plates: 1. With the decrease of the applicatio...

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Problems solved by technology

[0003] At present, the following problems generally exist in Q345R steel plates: 1. With the decrease of the application environment temperature, the impact toughness of the steel plate drops sharply

The lowest detection temperature of the impact energy of Q345R stipulated in the standard GB713-2014 is -20°C. According to the current conventional production plan, it cannot meet the impact performance requirements of -40~-50°C.

2. In order to meet the impact toughness requirements in the ultra-low temperature environment of -40~-50℃, a large amount of alloying elements can be added, such as Ni (0.4-0.6%), V (0.04-0.06%), Cr (0.1-0.3 %), etc., or adding a tempering process after normalizing, has greatly increased production costs, resulting in almost no manufacturing profits for steel companies

However, the Q345R steel plate produced by it is also not suitable for the ultra-low temperature environment of -40~-50°C

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