Steel plate and manufacturing method thereof
A manufacturing method and technology for steel sheets, applied in manufacturing tools, furnaces, heat treatment equipment, etc., can solve problems such as stress increase and delayed failure resistance deterioration, and achieve the effect of improved component strength and excellent delayed failure resistance.
Active Publication Date: 2022-04-29
JFE STEEL CORP
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Problems solved by technology
[0003] However, when cold pressing is used to form high-strength steel sheets of TS: 1320 MPa class or higher into parts, the delayed fracture becomes worse due to the increase of residual stress in the part and the deterioration of the delayed fracture resistance characteristics caused by the raw material itself. significantly
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[0147] After melting the steels with the compositions shown in Table 1, they were cast into slabs. It should be noted that [%Ti]×[%Nb] in Table 1 2 The "E-number" in the item refers to 10 to the -number power. For example, E-07 refers to 10 -7 . In addition, "[%Ti] × [%Nb] of Table 1 2 "The unit is (mass%) 3 .
[0148] As shown in Table 2, the slabs were subjected to slab heating temperature (SRT): 1220°C or higher, holding time: 100 minutes or longer, finish rolling temperature (FT): 840 to 950°C, Coiling temperature (CT): Coiling is performed at 400-700°C. The obtained hot-rolled sheet (hot-rolled steel sheet) is pickled and then cold-rolled at a rolling reduction of 40% or more to obtain a cold-rolled sheet (cold-rolled steel sheet). The slab heating temperature of No. 41, the heating time of No. 42, and the reduction ratio of cold rolling in No. 43 were outside the above-mentioned ranges.
[0149] In the continuous annealing process, as shown in Table 2, except for...
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Abstract
The present invention provides the following steel plate and its manufacturing method. The steel plate is a steel plate with TS ≥ 1320 MPa, and cold pressing is carried out after rough processing by shearing, cutting, drilling by punching, or Excellent delayed fracture resistance properties can be imparted to parts subjected to cutting of parts by shearing and drilling by punching after cold pressing. A steel plate having a specific composition and a steel structure in which the total area ratio of martensite and bainite to the entire structure is 95% or more and 100% or less, and the balance is ferrite and one or two types of retained austenite, the specified inclusion clusters are 5 / mm 2 There exists a mode in which the average grain size of the prior-austenite grains is larger than 5 μm, and the tensile strength of the steel sheet is 1320 MPa or more.
Description
technical field [0001] The present invention relates to a steel plate and a manufacturing method thereof. The steel sheet of the present invention can be preferably used as a high-strength steel sheet for cold forming used in automobiles, home appliances, and the like through a cold forming process. Background technique [0002] In recent years, due to the further increase in the demand for lightweight automobile bodies, high-strength steel plates with tensile strength (TS): 1320-1470 MPa are used in car body frame parts such as center pillar R / F (reinforcement parts), bumpers, Applications in crash beam components and more continue to grow. In addition, from the viewpoint of further weight reduction, studies on increasing the strength of 1.8 GPa class or higher have also begun. In the past, high strength by hot pressing (pressing at high temperature) has been vigorously studied, and recently, application of high-strength steel by cold pressing has been re-examined from th...
Claims
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IPC IPC(8): C22C38/00C21D9/46C22C38/14C22C38/58
CPCC21D8/0226C21D8/0236C21D8/0247C23C2/06C21D1/18C22C38/001C22C38/002C22C38/005C22C38/02C22C38/04C22C38/06C22C38/08C22C38/12C22C38/14C22C38/16C22C38/18C22C38/22C22C38/26C22C38/28C21D2211/002C21D2211/008C23C2/02C23C2/28C23C2/40C21D9/46C21D8/0205C22C38/008C22C38/60C23C2/024C23C2/0224
Inventor 吉冈真平小野义彦飞鹰健太山口龙介
Owner JFE STEEL CORP