Steel sheet

A steel plate and chemical composition technology, which is applied in the field of high-strength steel plate and its manufacturing, can solve the problems of low productivity and achieve the effect of high strength and hydrogen embrittlement resistance

Active Publication Date: 2021-06-15
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

In addition, in Patent Document 4, in order to improve delayed fracture characteristics, it is necessary to hold at 650°C or 700°C for 20 minutes or more in an atmosphere with a dew point of 15°C or higher, and there is a problem of low productivity.

Method used

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example 1

[0294] Steels having the chemical compositions shown in Table 1 were melted to cast billets. This steel slab was inserted into a furnace heated to 1220° C., held for 60 minutes for homogenization treatment, taken out into the air, and hot-rolled to obtain a steel plate with a plate thickness of 2.8 mm. In the hot rolling, the finish rolling was performed seven times in total, and among them, three rolling passes with a rolling reduction exceeding 20% ​​were given. In addition, the pass time between each rolling pass for which a rolling reduction of 20% or more is given in the finish rolling and the preceding rolling pass of each rolling pass was set to 0.6 seconds. The start temperature of finish rolling is 1070°C, and the end temperature is 890°C. After 2.2 seconds after finish rolling, it is cooled by water cooling, and cooled to 580°C at an average cooling rate of 35.0°C / s (it should be noted that after the start of cooling , and the average cooling rate from the finish ro...

example 2

[0311] Furthermore, in order to investigate the influence of the manufacturing conditions, in Table 2, the steel grades A to O, which exhibited excellent properties, were subjected to heat treatment under the manufacturing conditions described in Table 3 to produce hot-rolled steel sheets with a thickness of 2.3 mm. The properties of the steel sheet after cold rolling and annealing were evaluated. Here, the symbols GI and GA of the coating treatment indicate the method of galvanizing treatment. GI is a steel sheet obtained by immersing the steel sheet in a hot-dip galvanizing bath at 460° C. to give a galvanized layer to the surface of the steel sheet. A steel sheet in which an alloy layer of iron and zinc is given to the surface of the steel sheet by raising the temperature of the steel sheet to 485° C. after being immersed in a hot-dip galvanizing bath. In addition, while the steel sheet held at each retention temperature in the cold-rolled sheet annealing is cooled to room ...

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Abstract

Provided are: a steel sheet having high strength and excellent hydrogen embrittlement resistance; and a method for manufacturing the steel sheet. Provided is a steel sheet having a specified chemical composition and a specified structure, wherein the standard deviation sigma of the Mn concentration satisfies the formula: sigma >= 0.15 Mnave (wherein Mnave represents an average Mn concentration), and the equivalent circle diameter of a region having an Mn concentration of more than Mnave + 1.3 sigma is less than 10.0 microns. Also provided is a method for manufacturing a steel sheet, the method comprising: a hot rolling step including performing the finish rolling of a steel piece having a specified chemical composition under specific conditions; a step of winding up the hot-rolled steel sheet at a winding temperature of 450 to 700DEG C ; and a step of cold-rolling the hot-rolled steel sheet and then annealing the cold-rolled steel sheet at 800 to 900DEG C.

Description

technical field [0001] The present invention relates to a steel plate and a method for producing the same, and more specifically relates to a high-strength steel plate excellent in hydrogen embrittlement resistance (also referred to as delayed fracture resistance) and a method for producing the same. Background technique [0002] For ultra-high-strength steel plates with martensite as the main structure and a tensile strength above 1300 MPa, a fundamental solution to hydrogen embrittlement is strongly required. The so-called hydrogen embrittlement is a phenomenon in which hydrogen intruded into the steel segregates in the grain boundaries of martensite, embrittles the grain boundaries (decreases the strength of the grain boundaries), and causes cracks. Since the intrusion of hydrogen also occurs at room temperature, there is no method to perfectly suppress the intrusion of hydrogen. In order to fundamentally solve the problem, modification of the internal structure of steel ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C21D9/46C22C38/00C22C38/60
CPCC21D9/46C22C38/60C21D2211/008C21D8/005C21D8/0247C21D8/0263C21D8/0236C21D8/0231C21D8/0226C21D1/25C21D1/26C21D1/22C21D1/19C22C38/02C22C38/06C22C38/001C22C38/04C22C38/52C22C38/44C22C38/002C22C38/50C22C38/54C22C38/58C22C38/48C22C38/46C22C38/42C22C38/12C22C38/008C22C38/005C22C38/34C21D8/0273C21D2211/001C21D2211/002C21D2211/005C21D2211/009
Inventor 竹田健悟川田裕之横山卓史中野克哉
Owner NIPPON STEEL CORP
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