Mechanical Fastening with Ultra-High-Strength Fail-Safe Bolts

2017 Fiscal Year Final Research Report

• Project/Area Number: 15H04150
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Structural/Functional materials
• Research Institution: National Institute for Materials Science
• Principal Investigator: Kimura Yuuji 国立研究開発法人物質・材料研究機構, 構造材料研究拠点, 主席研究員 (80253483)
• Co-Investigator(Kenkyū-buntansha): 佐藤 篤司 名古屋工業大学, 大学院工学研究科, 准教授 (00362319) ; 鈴木 康夫 京都大学, 大学院工学研究科, 助教 (50431698)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 低合金鋼 / 強度 / 靭性 / ボルト / メカニカルファスニング

Outline of Final Research Achievements

1.6-2.0 GPa-class ultra-high strength steel bars were fabricated through multi-pass warm caliber rolling for (0.2-0.6)%C-2%Si-1%Cr-1%Mo steels (mass%), and were warm formed into JIS M12 hexagon head bolts, and then their mechanical properties were investigated. The developed bolts consist of ultrafine grained structures and were demonstrated to be more ductile and tougher,compared to the conventionally quenched and tempered bolts at ultra-high tensile strength of 1.6-2.0 GPa. There was a linear relationship between shear strength and tensile strength. Friction tensile tests for joints using the developed bolts demonstrated that slip coefficient for the ultra-high-strength bolts were greater or equal to the ordinary high-strength bolts. No significant stress relaxation was observed in the bolted joints. Furthermore, the bolted joints using the ultra-high strength bolts were also observed to have high fracture resistance.

Free Research Field

鉄鋼材料