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High strength thin steel sheet having high hydrogen embrittlement resisting property and high workability

A technology with excellent processability and ultra-high strength, applied in metal processing equipment, manufacturing tools, rolling mill control devices, etc., can solve the problems of reduced hydrogen embrittlement resistance and poor mechanical production efficiency, and achieve excellent hydrogen embrittlement resistance Effect

Inactive Publication Date: 2006-07-05
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the delayed fracture characteristic of TBF steel disclosed in this document takes only about 1,000 seconds until cracks are generated in the cathode filling test, and it is difficult to say that it is not sufficient to take into account the harsh use environment such as automotive parts for a long time. after the result
In addition, since the heat treatment conditions of the above-mentioned documents are set at a high heating temperature, there are cases where the production efficiency of the actual machine is poor, and there is an urgent need to develop a new TBF steel that is also excellent in production efficiency.
In addition, there is also a problem that the hydrogen embrittlement resistance is lowered due to press forming, etc.

Method used

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  • High strength thin steel sheet having high hydrogen embrittlement resisting property and high workability
  • High strength thin steel sheet having high hydrogen embrittlement resisting property and high workability
  • High strength thin steel sheet having high hydrogen embrittlement resisting property and high workability

Examples

Experimental program
Comparison scheme
Effect test

Embodiment approach 1

[0063] The first ultra-high-strength steel sheet of the present invention satisfies: C: more than 0.25 to 0.60% (mass%, the following composition is the same), Si: 1.0 to 3.0%, Mn: 1.0 to 3.5%, P: 0.15% or less, S: 0.02% or less, Al: 1.5% or less (excluding 0%), Mo: 1.0% or less (excluding 0%), Nb: 1.0% or less (excluding 0%), and the rest is iron and unavoidable impurity composition,

[0064] (1) The metal structure after stretching with a processing rate of 3% satisfies the area ratio of the entire structure:

[0065] Retained austenite: more than 1%;

[0066] Bainitic ferrite and martensite: more than 80% in total;

[0067] ・Ferrite and pearlite: 9% or less in total (including 0%); also meet

[0068] The average axis ratio (major axis / short axis) of the retained austenite grains: 5 or more,

[0069] (2) A steel plate containing a predetermined amount of Mo and / or Nb in the steel.

[0070] Each of the necessary conditions has the following meanings.

[0071] (Metal str...

Embodiment approach 2

[0124] The second ultra-high-strength steel sheet of the present invention satisfies: C: more than 0.25 to 0.60% (mass%, the following composition is the same), Si: 1.0 to 3.0%, Mn: 1.0 to 3.5%, P: 0.15% or less, S: 0.02% or less, Al: 1.5% or less (excluding 0%), the remainder is composed of iron and unavoidable impurities,

[0125] (1) The structure after forming and processing shall meet the following requirements:

[0126] Retained austenite: more than 1%;

[0127] The average axis ratio (major axis / short axis) of the retained austenite grains: 5 or more;

[0128] Bainitic ferrite and martensite: more than 80% in total;

[0129] ・Ferrite and pearlite: 9% or less in total (including 0%); and,

[0130] (2) A predetermined amount of Cu and / or Ni is contained in the steel.

[0131] The reason for specifying (1) is as described above.

[0132] Next, the reason for specifying (2) will be described in detail.

[0133] As mentioned above, it is necessary to ensure the residua...

Embodiment approach 3

[0159] The third ultra-high-strength steel sheet of the present invention satisfies: C: more than 0.25% to 0.60% (mass%, the following composition is the same), Si: 1.0 to 3.0%, Mn: 1.0 to 3.5%, P: 0.15% or less , S: 0.02% or less, Al: 1.5% or less (excluding 0%), and the remainder is composed of iron and unavoidable impurities,

[0160] (3) The tissues after forming process all meet:

[0161] Retained austenite: more than 1%;

[0162] The average axis ratio (major axis / short axis) of the retained austenite grains: 5 or more;

[0163] The average minor axis length of the retained austenite grains: 1 μm or less; and

[0164] · The nearest-neighbor distance between the retained austenite grains: 1 μm or less.

[0165] By controlling the structure in this way, the hydrogen embrittlement resistance of the ultra-high-strength steel sheet can be sufficiently improved without excessive addition of alloy elements.

[0166] In addition, the above-mentioned "after forming processing...

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Abstract

The present invention provides an ultrahigh strength steel sheet that has high hydrogen embrittlement resisting property and high workability. The ultrahigh strength steel sheet comprises: C: more than 0.25-0.60 wt%, si: 1.0-3.0 wt%, Mn: 1.0-3.5 wt%, P: less than 0.15 wt%, S: less than 0.02 wt%, Al: less than 1.5 wt% (excluding 0%), the residual consists of Fe and unavoidable impurity, has a metallurgical structure after stretch forming process with 3% working rate, which comprises: 1% or more residual austenite; 80% or more in total of bainitic ferrite and martensite; and 9% or less (may be 0%) in total of ferrite and pearlite in terms of proportion of area to the entire structure, wherein the mean axis ratio (major axis / minor axis) of the residual austenite grains is 5 or higher; and the steel sheet has tensile strength of 1180 MPa or higher.

Description

technical field [0001] The present invention relates to an ultra-high-strength thin steel sheet with excellent hydrogen embrittlement resistance (especially after forming) and workability, and particularly relates to a steel sheet capable of suppressing the An ultra-high-strength thin steel sheet with excellent workability due to cracking and hydrogen embrittlement that delays failure due to problems. Background technique [0002] When high-strength parts constituting automobiles or industrial machinery are obtained by press forming or bending, steel sheets used for the processing are required to have both excellent strength and ductility. In recent years, demand for ultra-high-strength steel sheets of 1,180 MPa or higher has been increasing as automobiles become lighter in weight, and TRIP (Transformation Induced Plasticity) steel sheets in particular have attracted attention as steel sheets that meet such needs. [0003] TRIP steel plate is processed and deformed at a tem...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/04C21D8/02C21D11/00B21B37/00
Inventor 汤濑文雄池田周之向井阳一赤水宏衣笠润一郎齐藤贤司杉本公一北条智彦
Owner KOBE STEEL LTD
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