Search

US-20260126075-A1 - MATERIAL FOR ALUMINUM ALLOY SCREW, AND ALUMINUM ALLOY SCREW AND PRODUCTION METHOD THEREFOR

US20260126075A1US 20260126075 A1US20260126075 A1US 20260126075A1US-20260126075-A1

Abstract

The present invention provides an aluminum alloy screw that uses 6000 series aluminum suitable for recycling, that has sufficient mechanical properties, and that can be used for fastening, with respect to automobile parts or the like, which is subjected to loads and is required to be highly reliable. Also provided are: a simple and efficient method for producing this aluminum alloy screw; and an aluminum allow screw material that can be suitably used in said production. The aluminum alloy screw is characterized by containing 0.9-1.3 wt % Si, 0.8-1.5 wt % Cu, 0.8-1.2 wt % Mg, 0.2-0.4 wt % Cr, 0.15-0.45 wt % Mn, 0.005-0.05 wt % Ti, with the remainder including Al and unavoidable impurities, where the tensile properties of the screw shaft section is such that the tensile strength is 460 MPa or more, the 0.2% yield strength is 380 MPa or more, and the breaking elongation is 10% or more.

Inventors

  • Yuichiro TANAI
  • Kenji Niwa
  • Takeshi Handa
  • Seiji Ikeda

Assignees

  • NIPPON LIGHT METAL COMPANY, LTD.
  • YAMASHINA CORPORATION

Dates

Publication Date
20260507
Application Date
20230808
Priority Date
20221004

Claims (11)

  1. 1 . An aluminum alloy screw comprising: Si: 0.9 to 1.3 wt %, Cu: 0.8 to 1.5 wt %, Mg: 0.8 to 1.2 wt %, Cr: 0.2 to 0.4 wt %, Mn: 0.15 to 0.45 wt %, Ti: 0.005 to 0.05 wt %, with a balance being Al and inevitable impurities; and tensile properties of a screw shaft portion are a tensile strength of 460 MPa or more, a 0.2% yield strength of 380 MPa or more, and an elongation at break of 10% or more.
  2. 2 . The aluminum alloy screw according to claim 1 , wherein the Cu content is 1.1 to 1.5 wt %.
  3. 3 . The aluminum alloy screw according to claim 1 , wherein the Cr content is more than 0.25 wt % and 0.4 wt % or less.
  4. 4 . The aluminum alloy screw according to claim 1 , wherein a fine recrystallized structure is formed in the screw shaft portion, and that an average crystal grain size (equivalent circle diameter) of the fine recrystallized structure is 120 μm or less.
  5. 5 . A material for an aluminum alloy screw comprising: Si: 0.9 to 1.3 wt %, Cu: 0.8 to 1.5 wt %, Mg: 0.8 to 1.2 wt %, Cr: 0.2 to 0.4 wt %, Mn: 0.15 to 0.45 wt %, Ti: 0.005 to 0.05 wt %, with a balance being Al and inevitable impurities; wherein no cracks occur in a compression test in which a compression ratio is 60% or less.
  6. 6 . A material for an aluminum alloy screw comprising: Si: 0.9 to 1.3 wt %, Cu: 0.8 to 1.5 wt %, Mg: 0.8 to 1.2 wt %, Cr: 0.2 to 0.4 wt %, Mn: 0.15 to 0.45 wt %, Ti: 0.005 to 0.05 wt %, with a balance being Al and inevitable impurities; and having tensile properties of 430 MPa or more in tensile strength and 8% or more in elongation at break.
  7. 7 . The material for the aluminum alloy screw according to claim 5 , wherein the Cu content is 1.1 to 1.5 wt %.
  8. 8 . The material of the aluminum alloy screw according to claim 5 , wherein the Cr content is more than 0.25 wt % and 0.4 wt % or less.
  9. 9 . A method for producing an aluminum alloy screw, comprising the steps of: a heading process step of subjecting a material for an aluminum alloy screw containing Si: 0.9 to 1.3 wt %, Cu: 0.8 to 1.5 wt %, Mg: 0.8 to 1.2 wt %, Cr: 0.2 to 0.4 wt %, Mn: 0.15 to 0.45 wt %, Ti: 0.005 to 0.05 wt %, with a balance being Al and inevitable impurities to cold heading to form a screw head; a heat treatment step of subjecting the material for the aluminum alloy screw to T6 heat treatment; and a rolling process step of rolling the material for the aluminum alloy screw to form a screw shaft portion.
  10. 10 . The method for producing the aluminum alloy screw according to claim 9 , wherein as a pre-step of the heading process step, the material for the aluminum alloy screw is subjected to a heading process so that a cross-sectional area reduction rate is 30 to 85%.
  11. 11 . The method for producing the aluminum alloy screw according to claim 9 , wherein in the heat treatment step, a solution treatment is performed by holding at 500 to 570° C. for 1 to 5 hours and an aging treatment is performed by holding at 160 to 190° C. for 2 to 12 hours, and after the heat treatment step, the rolling process step is performed.

Description

TECHNICAL FIELD The present invention relates to an aluminum alloy screw, a material for the aluminum alloy used to manufacture the screw, and an efficient method for producing the aluminum alloy screw. The screws include bolts and nuts. PRIOR ARTS Conventionally, steel materials having excellent mechanical properties and stainless steel materials having good corrosion resistance have been used for bolts. However, in recent years, from the viewpoints of energy conservation and reduction of CO2 emissions, there is a strong demand for weight reduction in transportation equipment such as automobiles, and weight reduction is also being demanded for screws such as bolts used in such transportation equipment. In response to these demands, in order to achieve weight reduction of screws, bolts made of aluminum alloys and bolts made of magnesium alloys, which are lighter than aluminum, have been proposed. For example, in Patent Literature 1 (Japanese Patent Unexamined Publication No. 2017-202497), for solving the problem of “realizing a producing method of a high strength aluminum alloy bolt for realizing a high-quality bolt as a half-screw from a post-wire draw processing raw material provided by executing wire draw processing on an Al—Mg—Zn system aluminum alloy wire rod of including Zn of 8 mass % or more”, there is disclosed “a producing method of a bolt forms a head part intermediate element by executing header processing on a wire rod being a post-wire draw processing raw material formed by executing wire draw processing on an Al—Mg—Zn system aluminum alloy wire rod of including Zn of 8 mass % or more, and afterwards, heat treatment is executed, and next, rolling of a male screw is executed on the tip side among a shaft part intermediate element, and at least a part on the head part intermediate element side is formed as a non-screw part, and before executing the heat treatment on the post-wire draw processing raw material, first stage reduction is executed on a part for forming the male screw of the shaft part intermediate element and a part of becoming a non-screw part, and second stage reduction is executed on the part for forming the male screw except for the part of becoming the non-screw part among the shaft part intermediate element after the first stage reduction.” Further, in Patent Literature 2 (Japanese Patent Unexamined Publication No. 2015-124409), for solving the problem of “providing an aluminum alloy wire material suitable as a material of an aluminum alloy member which requires high intensity and heat resistance, a production method of it, and the aluminum alloy member”, there is disclosed “an aluminum alloy wire having a composition containing, by mass %, 0.7% or more of Si and Mg, 1.5% or less of Cu and Zn, and the balance being Al and inevitable impurities, which has a tensile strength of 400 MPa or more after being solution-treated at 550° C. and then aging-treated at 170° C.×8 hours, and which has a tensile strength of 370 MPa or more after being subjected to a heat resistance test at 150° C.×1000 hours after the heat resistance testing”. Furthermore, in Patent Literature 3 (Japanese Patent Unexamined Publication No. 2012-82474), for solving the problem of “providing a magnesium alloy filament excellent in heat resistance and plastic workability, and also providing bolts, nuts, and washers, obtained by using the same”, there is disclosed “a filament magnesium alloy of a filament configured from a magnesium alloy, the magnesium alloy containing 0.1 mass % or more and 6 mass % or less Zn, more than 0.4 mass % and 4 mass % or less Ca, with the balance being Mg and inevitable impurities, and characterized in that when a creep test is performed on the linear body under conditions of a temperature of 150° C., a stress of 75 MPa, and a holding time of 100 hours or less, the creep strain is 1.0% or less.” PRIOR LITERATURE Patent Literature Patent Literature 1: Japanese Patent Unexamined Publication No. 2017-202497Patent Literature 2: Japanese Patent Unexamined Publication No. 2015-124409Patent Literature 3: Japanese Patent Unexamined Publication No. 2012-82474 SUMMARY OF THE INVENTION Technical Problem Patent Literature 1 proposes the bolt made of the high-strength 7000 series aluminum alloy, and Patent Literature 2 proposes the bolt made of the 6000 series aluminum alloy whose strength has been increased by adding Zn or Zr. However, these aluminum alloys have problems in extrudability, corrosion resistance and electrical conductivity, and the 7000 series aluminum alloys also have problems in recyclability because of their high Zn content. Further, Patent Literature 3 proposes the bolt made of the magnesium alloy, but when the magnesium alloy bolt is mixed into steel scraps during recycling, it may cause a deterioration in the quality of the steel material. In view of the problems in the prior art as described above, an object of the present invention is to provide an aluminum alloy screw that us