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High yield ratio high tension steel plate with excellent inhibition of fatigue craze progression and toughness of welding heat affected zone

A kind of steel plate and proportioning technology, applied in the field of high yield ratio and high tension steel plate, it can solve the problems that are not established, the crack progress speed and the state of grain boundaries are not considered, and the effect of good HAZ toughness and excellent inhibition of fatigue crack progress can be achieved.

Inactive Publication Date: 2009-09-09
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the speed of crack progression and the state of the grain boundary are not taken into account, especially in steel sheets regarding the influence of the state of the grain boundary on the characteristics, and the actual situation is that no established conclusions have been obtained

Method used

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  • High yield ratio high tension steel plate with excellent inhibition of fatigue craze progression and toughness of welding heat affected zone
  • High yield ratio high tension steel plate with excellent inhibition of fatigue craze progression and toughness of welding heat affected zone
  • High yield ratio high tension steel plate with excellent inhibition of fatigue craze progression and toughness of welding heat affected zone

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0122] The steel (steel types A to R) having the chemical composition shown in Table 2 below was used to manufacture steel sheets under the production conditions shown in Table 3 below. In addition, Table 2 also shows the PM value stipulated in the present invention. In addition, the steel types A to M in Table 2 satisfy the chemical composition composition specified in the present invention, and the steel types N to R deviate from the necessary conditions (chemical composition composition, PM value) specified in the present invention.

[0123] 【Table 2】

[0124]

[0125] 【table 3】

[0126]

[0127] For each steel plate obtained, the bainite fraction and the tensile properties of the steel material (base material) [0.2% yield point (YS), tensile strength (TS), yield ratio (YR: YS / TS)], impact characteristics (fracture transition temperature vTrs), welding low-temperature cracking resistance, HAZ toughness, etc., and the large-angle grain boundary diameter (average equivalent ...

Embodiment 2

[0157] Using the steel type A shown in Table 2 above, the same HAZ reproduction test as in Example 1 except for changing the heat energy was performed. Heat energy input at this time: equivalent to 1-20KJ, change the cooling time to 800-500℃ to conduct the thermal cycle test. In addition, the cooling time is 10 seconds when the heat input is 1KJ / mm, the cooling time is 20 seconds when the heat input is 2KJ / mm, the cooling time is 40 seconds when the heat input is 5KJ / mm, the cooling time is 60 seconds when the heat input is 7KJ / mm, and the heat input is 15KJ. The cooling time is 120 seconds when / mm, and the cooling time is 160 seconds when the heat input is 20KJ / mm.

[0158] After that, two pendulum impact test pieces (JIS Z 2202V notched test pieces) were extracted from each test piece, and 10 pieces for each steel plate were calculated to obtain the average impact absorption energy vE at -15°C -15 .

[0159] The results are shown in Table 5 below. However, in the high-tensile s...

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Abstract

The high-yield-ratio high-tensile steel sheet of the present invention has a chemical composition appropriately defined, satisfies the PM value specified by the following formula (1) of less than 0.27%, and is composed of a structure in which the bainite phase accounts for 90% or more of the area. In addition, when the region where the orientation difference of two crystals is surrounded by a high-angle grain boundary of 15° or more is regarded as a crystal grain, the average circle-equivalent diameter of the crystal grain is 15 μm or less, and the orientation difference between adjacent crystal grains is 55 to 60°. The ratio of ° is 0.3 or more, or the ratio of Σ3 superimposed grain boundaries is 0.065 or more among the high-angle grain boundaries where the orientation difference of two crystals is 15° or more. PM=[C]+[Mn] / 30+[Cr] / 23+[Mo] / 5+[Si] / 5+[Cu] / 50+[Ni] / 50...(1) Among them, [C ], [Mn], [Cr], [Mo], [Si], [Cu], and [Ni] represent the contents (mass %) of C, Mn, Cr, Mo, Si, Cu, and Ni, respectively.

Description

Technical field [0001] The present invention relates to high-yield-ratio high-tensile steel plates used in various applications such as civil engineering, construction, bridges, marine structures, pipelines, ships, storage, construction machinery, etc., and particularly relates to suppressing the progress rate of cracks and ensuring good fatigue life, In addition, the toughness of the heat-affected zone (HAZ) is also excellent for welding high-yield-ratio high-tensile steel plates mainly composed of bainite phase. Background technique [0002] In the structural materials used in the above-mentioned various applications, there are many cases of applying repeated stress. Therefore, in order to ensure the safety of the structural materials, it is extremely important to design the steel plate used as the raw material to have good fatigue characteristics. [0003] The fatigue process of a steel plate is considered to be roughly divided into two processes: the occurrence of cracks in t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/54C22C38/58
Inventor 高桥祐二大垣诚一大西宏道
Owner KOBE STEEL LTD
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