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Steel having improved toughness in welding heat-affected zone and its production

A technology for welding heat-affected zone and steel, which is applied in the field of steel with excellent toughness in the heat-affected zone of welding and its production method, which can solve the problems of steel toughness reduction, achieve the effect of improving toughness and preventing toughness deterioration

Inactive Publication Date: 2009-06-24
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the present inventors found that in order to further improve the toughness of the HAZ, the amount of oxides can be increased, but in the technology disclosed in the above-mentioned Patent Document 2, in order to increase the amount of oxides, it is necessary to add a large amount of Ti and Cr. Carbides such as Ti and Zr will be formed, and the toughness of the steel (base metal) will decrease instead.

Method used

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  • Steel having improved toughness in welding heat-affected zone and its production
  • Steel having improved toughness in welding heat-affected zone and its production
  • Steel having improved toughness in welding heat-affected zone and its production

Examples

Experimental program
Comparison scheme
Effect test

experiment example 1

[0068] After the molten iron is refined in a 240-ton converter, the steel is tapped from the converter to the ladle, and secondary refining is performed while adjusting the composition and temperature. Here, in the ladle, the amount of dissolved oxygen shown in Table 1 below was adjusted according to the deoxidation method shown in Table 1 below. Thereafter, elements were added in the order shown in Table 1 below. Then, other alloying elements were added as needed, and finally adjusted to the composition shown in Table 2 below. In addition, in the secondary refining, the RH degassing and refining device is used for dehydrogenation and desulfurization.

[0069] Table 1 below shows the order of component adjustment, the method of deoxidation, and the amount of dissolved oxygen, respectively. In addition, in the following Table 2, the component composition of the steel material after component adjustment is shown. In Table 1 below, La is added in the form of Fe-La alloy, Ce is...

experiment example 2

[0082] The slabs Nos. 6, 12, and 19 obtained in Experimental Example 1 above were hot-rolled to obtain steel plates with a thickness of 30 mm.

[0083] Using "EPMA-8705 (apparatus name)" manufactured by Shimadzu Corporation, a section perpendicular to the rolling direction of the obtained steel sheet was observed at 600 magnifications, and the composition of precipitates with a maximum diameter of 0.2 μm or more was quantitatively analyzed. The observation conditions are that the acceleration voltage is 20kV, the sample current is 0.01μA, and the observation field area is 3-5cm 2 , The number of samples to be analyzed was 100, and the composition of the central part of the precipitate was quantitatively analyzed by the wavelength dispersion spectroscopy of characteristic X-rays according to the same procedure as in the above-mentioned Experimental Example 1. Also, the observation position is the D / 4 position (where D is the thickness of the slab) of the steel plate.

[0084] ...

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Abstract

Provided is a steel having improved toughness in welding heat-affected zone and its producing method. The steel contains: carbon of 0.01-0.2% (wt., follows are the same), silicon less than 0.5% (exclusion of 0% ), manganese less than 2.5% (exclusion of 0% ), phosphor less than 0.02% (inclusion of 0% ), sulphur less than 0.015% (inclusion of 0% ), aluminum less than 0.01% (inclusion of 0% ), REM of 0.001-0.1% and / or calcium of 0.0003-0.02% and zirconium of 0.001-0.05%, and as oxides containing of REM oxide and / or CaO and ZrO2.

Description

technical field [0001] The present invention relates to a steel material having improved toughness at a portion affected by heat (hereinafter referred to as "welding heat-affected zone" or "HAZ") when welding steel materials used for bridges, high-rise buildings, ships, etc., and a method for producing the same . Background technique [0002] The properties required for steel materials used in bridges, high-rise buildings, ships, etc. have become increasingly stringent in recent years, and particularly excellent toughness is required. These steel materials are generally joined by welding, but there is a problem that especially HAZ is affected by heat at the time of welding and the toughness tends to deteriorate. This toughness deterioration appears more significantly as the heat input during welding increases, and the reason for this is considered to be that when the heat input during welding increases, the cooling rate of the HAZ decreases, the hardenability decreases, and...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/06C22C38/14C22C38/50C22C33/06
CPCC22C38/001C22C38/002C22C38/005C22C38/02C22C38/04C22C38/06C22C38/12C22C38/14C22C38/16
Inventor 出浦哲史杉村朋子水渡英昭
Owner KOBE STEEL LTD