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Steel material and method for producing same

A steel quality technology, applied in temperature control, metal rolling, gas emission reduction, etc., can solve problems such as crack arrest, and achieve excellent crack arrest and excellent toughness

Pending Publication Date: 2021-11-05
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0015] However, none of Patent Documents 1 to 5 considered crack arrestability.

Method used

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  • Steel material and method for producing same
  • Steel material and method for producing same
  • Steel material and method for producing same

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0281] The molten iron coming out of the blast furnace is subjected to desulfurization treatment through molten iron pretreatment, and after de-P and de-C treatment in a converter-type refining vessel, it is loaded into a ladle. When tapping, alloying elements are added and mold slag for heat preservation is added.

[0282] In the refining process, the molten steel in the ladle is decompressed using the RH vacuum degassing device. During smelting, samples of molten steel are properly taken for analysis to obtain components of molten steel. The temperature of molten steel changes between 1560°C and 1610°C. In the first half of the RH treatment, alloys other than Zr and B were added to adjust the composition, and vacuum degassing was performed to adjust the dissolved oxygen concentration. The dissolved oxygen concentration was measured using an oxygen concentration probe. Then, Zr was added, and B was further added when 0.7 to 5.4 minutes passed. Then, reflux treatment was p...

Embodiment 2

[0312] The molten iron coming out of the blast furnace is subjected to desulfurization treatment through molten iron pretreatment, and after de-P and de-C treatment in a converter-type refining vessel, it is loaded into a ladle. When tapping, alloying elements are added and mold slag for heat preservation is added.

[0313] In the refining process, the molten steel in the ladle is decompressed using the RH vacuum degassing device. During smelting, samples of molten steel are properly taken for analysis to obtain components of molten steel. The temperature of molten steel changes between 1560°C and 1610°C. In the first half of the RH treatment, alloys other than Zr and B were added to adjust the composition, and vacuum degassing was performed to adjust the dissolved oxygen concentration. The dissolved oxygen concentration was measured using an oxygen concentration probe. Then, Zr is added, and B is further added when 0.8 to 5.3 minutes pass. Then, reflux treatment was perfo...

Embodiment 3

[0345] Using the same slab as in Example 2, it was processed to a thickness of 50 to 100 mm by a hot rolling process to produce a steel material. That is, the chemical composition and carbon equivalent of the steel materials are as shown in Table 4A to Table 4D.

[0346] Conditions of the heating process, the rough rolling process, the primary cooling process, the finish rolling process, the secondary cooling process, and the tempering process are shown in Table 7A - Table 7C. Moreover, Insol.Zr content, Sol.Zr content, B F , evaluation results of microstructure, evaluation results of texture, number density of (Zr, B) oxide particles, Charpy impact absorption energy, tensile strength TS, yield stress YP, Fracture toughness value Kca, NDT temperature and vTrs. The underlined parts in Table 7A to Table 8C indicate that they are outside the scope of the present invention.

[0347] The circle-equivalent diameter and number density of the oxide particles containing (Zr, B) were...

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Abstract

The steel material according to the present invention has a prescribed chemical composition, and is, from among (Zr, B)-containing oxide particles comprising 5.0 mass% or more of Zr, 0.1 mass% or more of B, and 1.0 mass% or more of O, (Zr, B)-containing oxide particles having a circle-equivalent diameter of 0.5 um or greater with Insol. Zr: 0.0007-0.0040%, Sol. Zr: 0.0010% or less, and BF expressed by the prescribed formulas (1) and (2) being 0.0030% or less. The number density of (Zr, B)-containing oxide particles for which a composition of Al2O3 accounts for 50 mass% or less is 5-300 particles / mm2.

Description

technical field [0001] The present invention relates to steel and its manufacturing method. [0002] This application is based on the patent application No. 2019-119789 filed with Japan on June 27, 2019, the patent application No. 2019-184528 filed with Japan on October 7, 2019, and the patent application 2020 filed with Japan on April 1, 2020 -065648 claims priority, the contents of which are hereby incorporated by reference. Background technique [0003] Examples of uses of steel materials include welded structures such as ships, high-rise buildings and other buildings, bridges, marine structures, LNG storage tanks, other large tanks, and line pipes. In recent years, due to the increase in the loading weight of container ships, etc., the size of welded structures is advancing. Along with this, thicker plate thickness and higher strength are required for steel materials. In addition, in the above-mentioned welded structure, it is also necessary to further ensure safety a...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/04C22C38/06C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50C22C38/54C22C38/58C21D8/02C22C33/04
CPCC22C38/02C22C38/04C22C38/06C22C38/58C22C38/50C22C38/54C22C38/42C22C38/44C22C38/48C22C38/46C22C38/008C22C38/001C22C38/002C22C33/04C21D8/0205C21D8/0226C22C38/14C22C38/16C22C38/12C22C38/08C22C38/28C22C38/32C22C38/20C22C38/22C22C38/26C22C38/24C22C38/38B22D11/001C21D8/0247C21D6/001C21D6/002C21D6/004C21D6/005C21D6/008C21D1/18C21D2211/005C21D2211/002C21D2211/009C21D2211/008C21D2211/001B21B1/26B21B3/00B21B37/74B22D1/00B22D11/00B22D11/124B22D11/22C21C7/10C21C7/04C21D8/02C22C38/00Y02P10/143
Inventor 今城大贵新宅祥晃中井启介中村真吾
Owner NIPPON STEEL CORP