Environment-friendly, Free-cutting Aluminum Alloys “KS Series”

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For parts used in precision instruments, electrical equipment
and other items conform to RoHS or ELV directives

In the past, alloys with Pb-Bi additives (KS21, KS62) have been used as free-cutting aluminum alloys with excellent chip splitting performance. However, global environmental initiatives such as the EU RoHS directive*1 and the ELV directive*2 have prompted the need to develop more environment-friendly alloys. Accordingly, we have developed a lineup comprising five types of free-cutting alloys "KS Series" (KS21L, KS26, KS28S, KS62L & KS69S) that address environmental problems.

  • *1 RoHS directive: EU regulations limiting the use of specified hazardous substances in electrical and electronic equipment.
  • *2 ELV directive: EU regulations related to the recycling and disposal of end-of-life vehicles.

Picture of Environment-friendly, Free-cutting Aluminum Alloys “KS Series”

Features

  • Depending on the application, alloys can be selected that are made up mainly of Al-Cu (KS2 series) or Al-Mg-Si (KS6 series) and that are either lead-free(lead content ≦ 0.05% by weight) or that fall lead threshold of RoHS and ELV directives(lead ≦ 0.4% by weight).
  • The newly developed five types of alloys have essentially the same chip splitting performance during cutting and corrosion resistance as conventional KS21 and KS62 materials.
  • Elevated temperatures must be avoided when working with Type 2000 free-cutting alloys, which contain elements with low melting points and is brittle at high temperatures above 120° C or higher. However, this high-temperature embrittlement can be avoided with KS26. Type 6000 free-cutting alloys do not exhibit the same sudden embrittlement as with Type 2000, but KS67 and KS69 show the trend to be somewhat brittle at temperature above 160 °C.
  • Contact with alcohol-containing fluids has been confirmed to prompt dissolution of free-cutting alloys containing Sn . KS21L, KS26 and KS62L offer superior resistance to the dissolution.

Product Characteristics

Alloy characteristics

KS2 Series

○:excellent, △:fair, ×:poor

Alloy Additive elements Chip splitting performance*1 Corrosion resistance*2 Hot embrittlement resistance Dissolution resistance*3
KS21 Conventional Pb + Bi
KS21L Fall under RoHS and ELV directives Pb < 0.4% Pb + Bi
KS26 Lead-free Pb free
(Pb ≦ 0.05%)
Bi ○–△
KS28S Lead-free Sn + Bi ○–△

KS6 Series

Alloy Additive elements Chip splitting performance*1 Corrosion resistance*2 Hot embrittlement resistance Dissolution resistance*3
KS62 Conventional Pb + Bi
KS67 Sn + Pb ×
KS62L Fall under RoHS and ELV directives Pb < 0.4% Pb + Bi
KS69S Pb free (Pb ≦ 0.05%) Sn + Bi ○–△
  • *1 Chip splitting performance: Shapes of chips shapes differ, depending on cutting conditions
  • *2 Corrosion resistance: Determined by maximum pitting corrosion depth after salt spray test for 200 hours.
  • *3 Dissolution resistance: Determined by the amount of dissolution resulting from contact with brake fluid and other alcohol-containing liquids ( e.g., certain types of brake fluids).

Characteristics of KS2 Series alloy (Type 2000)

Alloy characteristics and mechanical properties (tempered T8)

Alloy Additive elements Restriction for usage conditions (metal temperature) Mechanical properties
(Typical values)
TS[MPa] YS[MPa] El.[%] Hv
KS21 Conventional Pb + Bi Not exceeding 120°C 425 355 17 130
KS21L Fall under RoHS and ELV directives Pb < 0.4% Pb + Bi 425 325 28 125
KS26 Lead-free Pb free (≦ 0.05%) Bi - 430 340 25 125
KS28S Lead-free   Sn + Bi Not exceeding 120°C 420 330 23 128

Chip splitting performance (tempered T8)

Conventional free-cutting alloy Newly developed free-cutting alloys General alloy
KS21 (Pb + Bi) KS21L (Pb + Bi) KS26 (Bi) KS28S (Sn + Bi) 2017-T4
Picture of KS21 (Pb + Bi) Picture of KS21L (Pb + Bi) Picture of KS26 (Bi) Picture of KS28S (Sn + Bi) Picture of 2017-T4

Hot embrittlement resistance

Charpy impact test values, compliant with JIS Z2242

Graph of Hot embrittlement resistance

Corrosion resistance (tempered T8)

Maximum pitting corrosion depth after salt spray test for 200 hours, compliant with JISZ2371

Graph of Corrosion resistance (tempered T8)

Characteristics of Type 6000 free-cutting alloy

Alloy characteristics and mechanical properties (tempered T8)

Alloy Additive elements Restriction for usage conditions (contact liquids) Mechanical properties
(Typical values)
TS[MPa] YS[MPa] El.[%] Hv
KS62 Conventional Pb + Bi - 325 305 19 118
KS67 Sn + Pb Prevent contact with alcohol-containing liquids 305 280 13 105
KS62L Fall under RoHS and ELV directives Pb < 0.4% Pb + Bi - 325 305 17 113
KS69S Pb free (≦ 0.05%) Sn + Bi Prevent contact with alcohol-containing liquids 345 330 18 119

Chip splitting performance (tempered T8)

Traverse cutting, rotating speed: 2,000 rpm, cutting depth: 1mm, feed rate: 0.04 mm/rev, lubricant: non

Conventional free-cutting alloy Newly developed free-cutting alloys General alloy
KS62 (Pb + Bi) KS67 (Pb + Sn) KS62L (Pb + Bi) KS69S (Sn + Bi) 6061-T9
Picture of KS62 (Pb + Bi) Picture of KS67 (Pb + Sn) Picture of KS62L (Pb + Bi) Picture of KS69S (Sn + Bi) Picture of 6061-T9

Hot embrittlement resistance

Charpy impact test values, compliant with JIS Z2242

Graph of Hot embrittlement resistance

Corrosion resistance (tempered T8)

Maximum pitting corrosion depth after salt spray test for 200 hours, compliant with JISZ2371

Graph of Corrosion resistance (tempered T8)