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Weldable super-strength steel with excellent low-temperature flexibility and method for manufacturing the same

A technology of ultra-high-strength steel and low-temperature toughness, which is applied in the field of ultra-high-strength steel and its manufacturing to achieve high impact energy and high yield strength

Inactive Publication Date: 2010-03-24
KOREA INST OF MASCH & MATERIALS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0009] 【Problem solution】

Method used

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  • Weldable super-strength steel with excellent low-temperature flexibility and method for manufacturing the same
  • Weldable super-strength steel with excellent low-temperature flexibility and method for manufacturing the same
  • Weldable super-strength steel with excellent low-temperature flexibility and method for manufacturing the same

Examples

Experimental program
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preparation example Construction

[0021] The preparation of the ultra-high-strength steel of the present invention is as follows. After reheating a slab containing 0.5-2.0% by weight of copper and a very small amount of boron, it is subjected to controlled rolling, rapid cooling, and tempering. It is a weldable ultra-high-strength steel with excellent low-temperature toughness and a mixed structure of fire martensite and bainite whose volume fraction is more than 90%.

[0022]

[0023] The steel material of the present invention has the following compositions, and here, the reasons for limiting the numerical values ​​based on each composition will be described together. Here, % represents % by weight, and ECO alloy index, Ceq (carbon content), and Pcm (welding crack susceptibility index) are defined as follows.

[0024] ECO alloy index = Mn% + 2Ni% + 0.5Cu% + 4Mo%

[0025] Ceq=C%+Mn% / 6+(Cr%+Mo%+V%) / 5+(Ni%+Cu%) / 15

[0026] Pcm=C%+Si% / 30+(Mn%+Cu%+Cr%) / 20+Ni% / 60+Mo% / 15+V% / 10+5B%.

[0027] The ECO alloy index...

Embodiment

[0065] Table 1 shows the chemical composition, ECO alloy index, cooling rate, and cooling end temperature of the tempered material used in the examples of the present invention and the non-tempered material that can be compared with the above-mentioned tempered material. Among them, the untempered material refers to steel that has not been tempered.

[0066] According to Table 1, the 100mm-thick steel materials composed of Steel 1 to Steel 3 as described are reheated at 1,150°C for about 2 hours, and then 50 - About 60% stress load, hot rolled to 15mm thickness. Next, the above-mentioned hot-rolled sheet was subjected to Ar 3 At the above temperature, cool down to below 300°C at a rate of 20°C / s or more to produce untempered materials, or temper the above-mentioned untempered materials at temperatures of 450°C, 550°C, and 650°C for 30 minutes respectively Fire to create 3 tempered materials.

[0067] 【Table 1】

[0068]

[0069] On the other hand, yield strength, tensile...

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Abstract

The present invention discloses weldable super-strength steel with excellent low-temperature flexibility produced by adding environmental protection and cheap cuprum (Cu) and boron (B) into low-carbonlow-alloy steel, and a method for manufacturing the super-strength steel. According to the invention, the weldable super-strength steel with excellent low-temperature flexibility contains 0.5-2.0 wt%of cuprum and infinitesimal boron, also contains part elements of C, Si, Mn, Ni, Cr, Mo, Nb, V, Ti and Al, and whole element Fe, characterized in that a mixed tissue of tempered martensite and bainite is more than 90% of the whole tissue in a microscopic tissue of steel. According to the invention, it is possible to manufacture the super-strength steel economically, where an ECO alloy index (by wt%, Mn%+2Ni%+0.5Cu%+4Mo%) is less than 4.5, a yield strength is more than 1.1GPa (more than 150 of API standard), and low-temperature impact energy is more than 200J. Key words: low-temperature flexibility, weldability, super-strength steel, flash-back fire, tempered martensite.

Description

technical field [0001] The present invention relates to weldable ultra-high strength steel (ultra-high strength) with excellent low-temperature toughness (low-temperature toughness) and its manufacturing method. More specifically, it is to add environmentally friendly and cheap element copper (Cu) to low-carbon low-alloy steel The ultra-high-strength steel made of boron (B) has a yield strength of more than 1.1GPa and a low-temperature impact energy of more than 200J, and a manufacturing method thereof. Background technique [0002] Structural steel materials currently used in construction, shipbuilding, marine structures, pressure vessels, steel pipes, or industrial machinery are being replaced by ultra-high-strength change. In addition, as the service environment of shipbuilding steel, marine structural steel, and steel pipe steel becomes more and more harsh, in order to ensure structural stability at low temperatures below -20°C, excellent low-temperature toughness is re...

Claims

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Application Information

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IPC IPC(8): C22C38/58C22C38/54C21D8/02
CPCC21D8/005C22C38/06C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50C22C38/54C22C38/58C22C2200/00
Inventor 黄昞哲李昌吉李泰昊
Owner KOREA INST OF MASCH & MATERIALS