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RWMA / AWS Standards Est. 1998 | Monterrey, N.L.
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RWMA Class 3

Copper Class 3 – Copper Nickel Beryllium (C17510)

High hardness + balanced conductivity. The choice for AHSS, stainless steels and nut projection. Specifications per AWS J1.3.

AWS J1.3 Technical Specifications

Property Value Unit
UNS Designation C17510 -
Composition Cu + 0.2-0.6% Be + 1.4-2.2% Ni % wt
Electrical Conductivity ≥45 % IACS (AWS J1.3 min)
Hardness ≥90 HRB (AWS J1.3 min)
Thermal Conductivity 208 W/m·K
Softening Temperature 550 °C
Tensile Strength 760-900 MPa

Recommended Applications

AHSS / UHSS Steels Dual Phase, TRIP, Boron Steel
Nut Projection Welding Massive contact electrodes
Stainless Steels 304, 316, 400 series
High Welding Pressure High resistivity materials

The Thermal Balance Principle

The formula Q = I²Rt (Joule's Law) governs resistance welding. When the material being welded has high resistivity (like AHSS or stainless), we need an electrode with lower conductivity to balance the heat generated.

Class 2 (75% IACS) → Low resistivity materials
Class 3 (45-60% IACS) → High resistivity materials
  • Higher hardness (96-102 HRB) resists deformation under high pressure
  • 550°C softening temperature for high energy cycles
  • Superior tensile strength for projection applications
  • Less electrode "mushrooming" in intensive production
Technical Note: Class 3 (CuNiBe) offers the best conductivity/hardness balance for projection welding and spot welding of AHSS/UHSS steels. For extreme applications with M10+ nuts on ultra-high strength steels, consider Elkonite (CuW) which offers greater wear resistance while maintaining acceptable conductivity.
Safe Handling Note: Beryllium alloys in solid bar or plate form are completely safe to handle. Potential risk exists only during machining if dusts are generated. ALCAVIL complies with OSHA 1910.1024 protocols.

Frequently Asked Questions about Copper Class 3

What is RWMA Class 3 Copper?

Class 3 Copper is an RWMA classification for copper alloys with high hardness and moderate conductivity. According to AWS J1.3, it must have minimum electrical conductivity of 45% IACS and minimum hardness of 90 HRB. The most common alloys are:

  • C17510 (CuNiBe): Copper-Nickel-Beryllium - the most widely used
  • C17500 (CuCoBe): Copper-Cobalt-Beryllium - higher hardness
  • C18000 (CuCrNiSi): Beryllium-free - Be-free alternative
When should I use Class 3 instead of Class 2?

Use Class 3 Copper when:

  • Welding high strength steels (AHSS/UHSS with >590 MPa)
  • Working with nut and stud projection welding
  • Need to resist high welding pressure without deformation
  • Welding stainless steels that generate more heat

The thermal balance (Q=I²Rt) is the reason: high resistivity materials require electrodes with lower conductivity and higher hardness.

Is it safe to work with beryllium alloys?

Beryllium alloys in solid bar or plate form are completely safe to handle. Potential risk exists only during machining if fine dusts are generated. At ALCAVIL:

  • We comply with OSHA 1910.1024 protocols
  • We provide machined material ready to use
  • We offer a beryllium-free alternative (C18000) for customers who require it
What is the difference between C17510, C17500 and C18000?

All are Class 3 Copper per AWS J1.3, but with differences:

  • C17510 (CuNiBe): Best conductivity/hardness balance. The industry standard.
  • C17500 (CuCoBe): Higher hardness (up to 102 HRB). For extreme wear.
  • C18000 (CuCrNiSi): Beryllium-free. Ideal where 0% Be is required.

See C17500 and C18000 (beryllium-free) for more details.