Thick steel board

A thick steel plate and steel plate technology, which is applied in the field of low yield ratio and high toughness thick steel plate, can solve the problems of low yield ratio and high toughness, and achieve the effect of low yield ratio

CN101665887AInactive Publication Date: 2010-03-10KOBE STEEL LTD
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Patent Information

Authority / Receiving Office
CN · China
Current Assignee / Owner
Publication Date
2010-03-10
Estimated Expiration
Not applicable · inactive patent

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Abstract

The invention provides a thick steel board exhibiting low tensile ratio and high toughness, which contains following elements: 0.03-0.15 weight percent of C, less than 1.0 weight percent of Si (0 weight percent not included), 1.0-2.0 weight percent of Mn, less than 0.015 weight percent of P (0 weight percent not included), less than 0.010 weight percent of S (0 weight percent not included); 0.005-0.060 weight percent of Al, 0.008-0.030 weight percent of Ti; 0.0020-0.010 weight percent of N, and less than 0.010 weight percent of O (0 weight percent not included). The microscopic constitution at the t / 4 position of the steel board comprises mixed constitution of ferrite and bainite, wherein t represents thickness of the steel board. Island martensite is dispersed in the bainite, the average particle diameter of the ferrite is 10-50 mu m, and the island martesite in the bainite is 1-20 area percent of the total area.
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Description

technical field

[0001] The invention relates to a thick steel plate suitable for construction, marine structures, line pipes, shipbuilding, civil engineering, construction machinery and the like, especially relates to a thick steel plate with low yield ratio and high toughness. Background technique

[0002] In recent years, among various steel materials for welded structures, in addition to high strength and high toughness, it is also required to reduce the yield strength ratio YR (YR = YS / TS). In general, it is known that the yield ratio of the steel material can be reduced by making the metal structure of the steel material into a hard phase in which bainite, martensite, etc. are moderately dispersed in a soft phase such as ferrite.

[0003] As a production method for obtaining the above-mentioned structure in which the hard phase is moderately dispersed in the soft phase, for example, in Patent Document 1, there is known a heat treatment method in which quenching (Q) and...

Examples

experiment example 1

[0074] Various molten steels with the chemical composition shown in the following Tables 1 to 3 are smelted by the usual smelting method, and after cooling the molten steel to form a slab, hot rolling and cooling are performed under the conditions shown in the following Tables 4 and 5. , to obtain various steel plates (thickness: 50mm). In addition, in the following Tables 1 and 3, REM is added in the form of misch metal containing about 50% of La and about 25% of Ce. In addition, "-" in following Tables 1-3 shows that an element was not added.

[0075]

[0076]

[0077]

[0078] 【Table 4】

[0079]

[0080] 【table 5】

[0081]

[0082]

[0083] For each of the obtained steel sheets, the base metal structure (ferrite grain size, MA fraction), mechanical properties (tensile properties of the base material, impact properties of the base material) were measured by the following method, and the HAZ toughness was also measured. evaluate. The measurement results ...