High-strength part and process for producing the same

A manufacturing method and high-strength technology, applied in the field of components, can solve the problems of unfavorable economy, complex mold structure, and inability to deny hydrogen embrittlement.

Active Publication Date: 2007-08-15
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, when this method is used, the structure of the mold becomes complicated, which is generally considered to be economically disadvantageous.
Moreover, this method does not involve hydrogen embrittlement at all. Even if the strength of the steel plate is reduced by this method and the residual stress after post-processing is reduced to some extent, if it is the state where hydrogen remains in the steel, it cannot be denied that it has occurred. Possibility of hydrogen embrittlement

Method used

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  • High-strength part and process for producing the same
  • High-strength part and process for producing the same
  • High-strength part and process for producing the same

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0137] Slabs having the chemical compositions shown in Table 1 were cast. These slabs are heated to 1050-1350° C., hot-rolled to a finish rolling temperature of 800-900° C., and rolled at a coiling temperature of 450-680° C. to produce hot-rolled steel sheets with a thickness of 4 mm. Next, after pickling, cold rolling was performed to form a cold-rolled steel sheet having a thickness of 1.6 mm. Then heated to Ac 3 After the austenite zone above 950°C, hot forming processing is carried out. Regarding the atmosphere of the heating furnace, the hydrogen content and dew point were changed. The conditions are shown in Table 2 and Table 3. The tensile strengths are 1523MPa and 1751MPa respectively.

[0138] When evaluating the punched and pierced parts, these molded products were cut out to a size of 100mm×100mm to prepare test pieces, and the center was punched with a Φ10mm punch with a gap of 15%, and then tested under various conditions. 2 processing. In addition, when eva...

Embodiment 2

[0147] Slabs having the chemical compositions shown in Table 4 were cast. These slabs are heated to 1050-1350° C., hot-rolled to a finish rolling temperature of 800-900° C., and rolled at a coiling temperature of 450-680° C. to produce hot-rolled steel sheets with a thickness of 4 mm. Then, after pickling, cold rolling was performed to form a cold-rolled steel sheet having a thickness of 1.6 mm. In addition, a part of the cold-rolled sheet was subjected to hot-dip aluminum plating, hot-dip aluminum-zinc plating, alloying hot-dip galvanizing, and hot-dip galvanizing. Table 5 shows examples of plating types. Then those cold-rolled steel sheets and surface-treated steel sheets are heated through a furnace until they are heated at Ac 3 After the austenite zone above 950°C, hot forming is performed. Regarding the atmosphere of the heating furnace, the hydrogen content and dew point were changed. The conditions are shown in Table 6.

[0148] Figure 14 shows a cross-section of t...

Embodiment 3

[0167] Slabs having the chemical compositions shown in Table 4 were cast. These slabs are heated to 1050-1350° C., hot-rolled to a finish rolling temperature of 800-900° C., and rolled at a coiling temperature of 450-680° C. to produce hot-rolled steel sheets with a thickness of 4 mm. Then, after pickling, cold rolling was performed to form a cold-rolled steel sheet having a thickness of 1.6 mm. In addition, a part of the cold-rolled sheet was subjected to hot-dip aluminum plating, hot-dip aluminum-zinc plating, alloying hot-dip galvanizing, and hot-dip galvanizing. Table 5 shows examples of plating types. Then those cold-rolled steel sheets and surface-treated steel sheets are heated through a furnace until they are heated at Ac 3 After the austenite zone above 950°C, hot forming is performed. Regarding the atmosphere of the heating furnace, the hydrogen content and dew point were changed. The conditions are shown in Table 7.

[0168] Figure 14 shows a cross-section of t...

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Abstract

A high-strength part that excels in hydrogen embrittlement resistance and strength after high-temperature forming; and a process for producing the same. The atmosphere in a heating furnace before forming is regulated to one of <= 10% hydrogen volume fraction and = 30 DEG C dew point. As a result, the amount of hydrogen penetrating in a steel sheet during heating is reduced. After forming, there are sequentially carried out quench hardening in die assembly and post-working. As the method of post-working, there can be mentioned shearing followed by re-shearing or compression forming of sheared edge portion; punching with a cutting blade having a gradient portion at which the width of blade base is continuously reduced; punching with a punching tool having a curved blade with a protrudent configuration at the tip of cutting blade part, the curved blade having a shoulder portion of given curvature radius and / or given angle; fusion cutting; etc. Consequently, the tensile residual stress after punching is reduced and the performance of hydrogen embrittlement resistance is improved.

Description

technical field [0001] The present invention relates to members requiring strength, such as structural members and reinforcing members used in automobiles, and in particular, to a member having excellent strength after high-temperature forming and a method for producing the same. Background technique [0002] Due to the weight reduction of automobiles due to global environmental issues, it is necessary to increase the strength of steel sheets used in automobiles as much as possible. However, generally, when the strength of steel sheets is increased, the elongation and r-value decrease, and the formability deteriorates. In order to solve such a problem, JP-A-2000-234153 discloses a technique of forming at an intermediate temperature and utilizing the heat at this time to improve the strength. The purpose of this technology is to properly control the composition of the steel, heat it in the ferrite temperature zone, and use the precipitation strengthening in the temperature zo...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B21D28/00C22C38/00B21D28/14C22C38/04C21D9/46C22C38/38C21D1/74
CPCC22C38/04C21D8/0205C21D1/673C21D2211/008C22C38/06C22C38/02C21D9/48C21D9/0068C21D1/74C22C38/28C22C38/18C22C38/38
Inventor 楠见和久佐藤宽哲阿部雅之藤田展弘铃木规之林邦夫中岛信也真木纯大神正浩神田俊之高桥学高桥雄三
Owner NIPPON STEEL CORP
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