High-strength steel having superior brittle crack arrestability, and production method therefor

A technology of crack propagation and manufacturing method, which is applied in the field of high-strength steel and its manufacturing, can solve the problems of low impact toughness, lower productivity, and resistance to brittle crack growth, and achieve excellent resistance to brittle crack growth and high yield strength. Effect

Inactive Publication Date: 2017-08-29
POHANG IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] However, although this technology contributes to the microstructure of the surface layer, it cannot solve the problem of low impact toughness due to the coarsening of the structure other than the surface layer, so it cannot be said to be a fundamental measure to solve the brittle crack growth resistance.
[0008] Moreover, it is expected that the productivity will drop significantly when the technology itself is applied to a general mass production system, so it can be said that the technology is not suitable for commercial application

Method used

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  • High-strength steel having superior brittle crack arrestability, and production method therefor
  • High-strength steel having superior brittle crack arrestability, and production method therefor
  • High-strength steel having superior brittle crack arrestability, and production method therefor

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0130] A slab having a thickness of 400 mm and having the composition in Table 1 below was reheated to a temperature of 1045° C., and then rough rolled at a temperature of 1015° C. to produce a bar. The cumulative rolling reduction during rough rolling was 50%, and the same rolling reduction was used.

[0131] The thickness of the rough-rolled bar is 180 mm, and the grain size of the 1 / 4t portion after rough rolling and before finish rolling is 95 μm.

[0132] After the rough rolling, finish rolling was performed at a temperature difference between the finish rolling temperature shown in Table 2 and the Ar3 temperature to obtain a steel sheet having a thickness shown in Table 2 below, and then cooled at a rate of 4° C. / sec. Cool to a temperature below 700°C.

[0133] Know the microstructure, yield strength, average grain size of the 1 / 4t part of the thickness of the steel plate produced as above, and the 15-degree angle from the surface layer to the 1 / 4 part of the plate thic...

Embodiment 2

[0150] As shown in Table 3, except that the Cu / Ni weight ratio of the slab was changed, steel plates were produced with the same composition and production conditions as Invention Steel 2 in Example 1, and the surface properties of the produced steel plates were known. And the results are shown in Table 3.

[0151] The surface properties of the steel sheets in Table 3 below were measured to determine whether or not star cracks occurred in the surface portion due to hot shortness.

[0152] table 3

[0153]

[0154] As shown in Table 3, it can be seen that when the Cu / Ni weight ratio is properly controlled, the surface characteristics of the steel sheet are improved.

Embodiment 3

[0156] As shown in Fig. 4, except that the grain size (μm) after rough rolling and before finish rolling was changed, steel sheets were produced with the same composition and production conditions as Invention Steel 1 of Example 1, and it was understood that the produced The impact transition temperature characteristics of the 1 / 4 part of the steel plate, and the results are shown in Table 4.

[0157] Table 4

[0158] steel type

[0159] As shown in Table 4, it can be seen that the smaller the 1 / 4t grain size of the bar after rough rolling becomes, the lower the impact transition temperature is, and thus it is expected that the brittle crack growth resistance is improved.

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Abstract

The present invention provides high-strength steel having superior brittle crack arrestability and a production method therefor. Provided according to the present invention are: high-strength steel, which has superior brittle crack arrestability, comprises 0.05-0.1 wt% of C, 1.5-2.2 wt% of Mn, 0.3-1.2 wt% of Ni, 0.005-0.1 wt% of Nb, 0.005-0.1 wt% of Ti, 0.1-0.5 wt% of Cu, 0.1-0.3 wt% of Si, at most 100 ppm of P, and at most 40 ppm of S with the remainder being Fe and other inevitable impurities, has microstructures including one structure selected from the group consisting of a single-phase structure of ferrite, a single-phase structure of bainite, a complex-phase structure of ferrite and bainite, a complex-phase structure of ferrite and pearlite, and a complex-phase structure of ferrite, bainite, and pearlite, and has a thickness of at least 50 mm; and a production method therefor. According to the present invention, high-strength steel having high yield strength and superior brittle crack arrestability can be obtained.

Description

technical field [0001] The present invention relates to a high-strength steel excellent in brittle crack growth resistance and a manufacturing method thereof. Background technique [0002] Recently, in the design of structures used in domestic and foreign ships, marine, construction, and civil engineering fields, the development of an ultra-thick plate steel with high strength characteristics is required. [0003] In the case of using high-strength steel when designing a structure, the shape of the structure can be reduced in weight, so not only can economic benefits be obtained, but also the thickness of the steel plate can be thinned, so that processing and welding operations can be ensured at the same time convenience. [0004] For high-strength steel, in general, when producing ultra-thick plates, due to the low total reduction ratio, sufficient deformation cannot be achieved compared with thin plate materials, so the microstructure of ultra-thick plate materials become...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/04C22C38/08C22C38/12C22C38/14C22C38/16C22C38/02C21D8/02
CPCC21D8/0226C22C38/02C22C38/04C22C38/08C22C38/12C22C38/14C22C38/16C21D2211/002C21D2211/005C21D2211/009C21D8/021C21D8/0247C21D8/0263C21D9/46C21D2201/05
Inventor 李学哲张成豪
Owner POHANG IRON & STEEL CO LTD
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