Frequently Asked Questions

GB/T 8320-2025 is the current Chinese national standard for copper-tungsten and silver-tungsten electrical contacts, effective from 2026-05-01. It defines minimum requirements for chemical composition, density, hardness, electrical conductivity, bending strength, and several other properties for both CuW and AgW grades. Material we supply is produced to meet or exceed GB/T 8320-2025 minimums for the specified grade; certified material documentation per lot is available on request.

Yes. Send the sample part and we can scan, measure, and produce to a drawing we generate. This is common for refurbishment of installed switchgear or contactors where the original OEM documentation isn't available. We treat customer-supplied parts as confidential; IP terms are discussed during quoting.

Contact resistance depends on more than just material, surface finish, contact force, and operating temperature all matter. For the bulk material, CuW70 has roughly 18% lower resistivity than CuW80 (corresponding to the conductivity ratio of 42% vs 34% IACS minimums per GB/T 8320-2025). In a specific contact assembly, the resistance difference is usually smaller because joint and interface resistance dominate over bulk resistance. For your specific application, send the assembly drawing and we can provide guidance.

For CuW contacts, common surface treatments are: as machined (default), silver plating on non-arcing surfaces, or nickel plating for corrosion resistance. The contact (arc) face is typically left bare CuW. For AgW contacts, the default is as machined, the silver matrix already provides a low-resistance contact surface. Plating on AgW is uncommon but available for specialty applications. Specify plating zones and thickness in your drawing.

Higher tungsten content increases density, hardness, bending strength, and arc-erosion resistance, but decreases electrical conductivity. CuW70 has ≥42% IACS conductivity and ≥175 HB hardness per GB/T 8320-2025; CuW80 has ≥34% IACS and ≥220 HB. The trade-off drives grade selection, CuW70 for standard MV duty where conductivity matters, CuW80 for severe arc duty where erosion resistance matters more.

Standard grades (CuW70 / 75 / 80 / 85 / 90 and AgW30 to AgW80) cover most applications. Non-standard compositions, different tungsten content, Ni-containing CuW, or specialty material additions, are available on request for specific applications. Per GB/T 8320-2025 Appendix A, Ni-containing CuW has documented conductivity-vs-Ni relationships if your application needs that specifically. Send your specification with the inquiry.

AgW70 is the typical specification for AC-3 motor duty (squirrel-cage motor starting per IEC 60947-4-1). The 70 wt% tungsten content balances arc-erosion resistance for motor inrush currents with adequate conductivity for continuous load. For AC-4 / reversing duty or higher cycle counts, AgW70 or AgW80, discuss your duty cycle. For lighter-duty general contactors, AgW40 or AgW50 is more typical. See our AgW grade selection guide for the full mapping.

When a vacuum interrupter opens or closes under load, an arc forms briefly between the contacts. The arc heats the contact surface locally, vaporizing material. Over thousands of operations, this material loss is called arc erosion. CuW contacts handle vacuum arc erosion much better than pure copper, the tungsten skeleton retains structural integrity even when local copper vaporizes. The arc-erosion rate scales inversely with tungsten content; this is why CuW80 lasts longer than CuW70 in severe arc duty, at the cost of lower conductivity.

CuW is CNC-friendly with carbide tooling. It cuts more like a brass-tungsten composite than pure copper, slower feed rates, conservative depth of cut, and more tool wear than equivalent volume in copper. CuW80 is harder to machine than CuW70 due to higher tungsten content. For machine shops new to CuW, we can share tooling and feed-rate recommendations based on the specific grade and part geometry.

Both are tungsten-composite contact materials, but with different matrix metals. CuW (copper tungsten) is the standard for medium-voltage applications like vacuum interrupters and MV switchgear, cost-effective with adequate arc-erosion resistance. AgW (silver tungsten) is the standard for low-voltage applications like AC contactors and relays, higher conductivity at the cost of significantly higher material price. The choice usually follows the application: LV → AgW, MV → CuW. See our AgW vs CuW guide for detailed comparison.

Standard production goes through ISO 9001:2015 certified facilities in our supply network. Additional certifications beyond ISO 9001 are confirmed per specific project requirements during quoting; please specify your documentation needs when inquiring and we will confirm what can be provided for your order.

Yes. CuW contacts brazed onto copper or copper-alloy carriers, and AgW contacts brazed onto copper alloy carriers, are routine. We braze in our supply network using silver-based fillers (BAg-7 or BAg-8 typical) under controlled atmosphere. Per GB/T 8320-2025, bonded joint strength meets ≥185 MPa for Cu conductive ends and ≥226 MPa for CuCrZr alloy ends. Specify both the contact and the carrier drawing in your order.

Yes, evaluation samples are typically available for serious sourcing programs. The sample quantity, cost, and lead time depend on the part complexity and grade. For complex custom parts, single-piece prototypes are relatively expensive per piece; ordering a small batch (10–20 pieces) is often more cost-effective. Discuss your evaluation needs when inquiring.

Yes. Submit your drawing in DXF / PDF / STEP format and we'll review for features that affect cost, yield, or feasibility: thin walls, tight tolerances on non-critical features, and complex geometries that could be simplified. There's no obligation to change the design; the feedback is a free first step before quoting. We can review CuW, AgW, bronze, and copper component drawings.

A whole contact is a CuW or AgW arc-resistant face bonded (typically brazed) to a copper or copper-alloy conductive end as a single assembly. It's specified when the apparatus design needs an arc-resistant contact face but the assembly only needs current-carrying conductor behavior elsewhere. Most MV switchgear and many LV contactor contact assemblies are whole contacts. Per GB/T 8320-2025, whole contact bonding strength must meet minimum tensile values (≥185 MPa for Cu end, ≥226 MPa for CuCrZr end).

TungArc operates as a B2B brand serving international customers, with production through a network of qualified manufacturing facilities. This model lets us match the right factory to your specific application, different grades, geometries, and order volumes have different optimal manufacturers, while presenting a single point of contact to our customers. For quality assurance, all production goes through ISO 9001:2015 facilities; material certification per lot is available on request.

We support common B2B Incoterms including EXW, FOB, CIF, and DDP depending on the destination market and order specifics. Each has trade-offs between buyer convenience and total cost, DDP simplifies the buyer experience but typically costs more; EXW gives the buyer most control but requires the buyer to arrange international freight. Discuss your preferred Incoterm during quoting.

Standard silver plating thickness on CuW contact carriers is typically in the range of a few micrometers, sufficient for low contact resistance over normal MV switchgear service life. For high-cycle applications or severe environments, thicker plating extends service life. Exact thickness depends on your duty cycle and joint design, for new applications, specifying the application duty helps us recommend; for refurbishment, match the original plating spec.

Yes, CuW85 and CuW90 are covered by GB/T 8320-2025 and we can supply both grades. They're specialty grades, primarily used for 40.5 kV and above apparatus, or high-cycle severe-duty applications where standard CuW70–80 erodes too fast. For most MV applications, CuW70 to CuW80 is the practical range. Discuss your application when sourcing.

Materials are sourced from suppliers providing RoHS and REACH declarations of conformity on request. Certain alloy variants (cadmium-containing braze fillers, for example) are inherently non-compliant for some markets. These are avoided in our standard production. For specific compliance documentation requirements with your order, specify when inquiring; we can confirm whether the materials and processes meet your market's requirements.