Market Insight: Bare Copper Strip

Market Analysis: Transformer Strip/Foil (Aluminum/Copper)

The global transformer industry continues to expand in response to rising electricity demand, grid modernization initiatives, and the proliferation of renewable energy integration. Within this ecosystem, bare copper strip remains a critical material for high-performance transformer windings, particularly in distribution and power transformers where electrical efficiency, thermal stability, and mechanical reliability are paramount. While aluminum strip is increasingly adopted for cost and weight advantages in certain applications, bare copper strip maintains a dominant position in high-efficiency and mission-critical transformer designs due to its superior electrical conductivity and mechanical robustness.

Industrial demand for bare copper strip in the transformer sector is driven by several key factors. First, copper’s conductivity—approximately 100% IACS (International Annealed Copper Standard)—enables lower resistive losses, directly contributing to higher transformer efficiency. This is especially significant in regions with stringent energy efficiency regulations, such as the European Union’s Ecodesign Directive and the U.S. DOE efficiency standards. Second, copper exhibits superior tensile strength and ductility compared to aluminum, allowing for tighter winding tolerances and improved resistance to thermal cycling and short-circuit forces. These mechanical properties are essential for ensuring long-term structural integrity within transformer coils under operational stress.

Quality assurance in bare copper strip production is non-negotiable. Variability in thickness, surface finish, edge quality, and metallurgical properties can lead to localized hotspots, insulation breakdown, or premature failure. At Luoyang Xinzhaohe Aluminum Co., Ltd., with over two decades of experience in non-ferrous strip manufacturing, we apply rigorous process controls to ensure dimensional accuracy within ±0.02 mm and surface roughness below 0.8 µm Ra. Our copper strips are produced from high-purity electrolytic tough pitch (ETP) copper (Cu ≥ 99.90%), subjected to controlled annealing to achieve optimal softness (R24 temper) while maintaining formability and electrical performance.

Contamination control is another critical quality parameter. Residual oxides, lubricant residues, or surface defects can compromise the dielectric performance of the insulation system. Our production lines incorporate multi-stage cleaning, precision leveling, and inline surface inspection to eliminate defects that could initiate partial discharges. Furthermore, consistent flatness and edge burr control—kept below 5% of material thickness—are essential for automated winding processes common in modern transformer manufacturing.

The following table summarizes key technical specifications for high-quality bare copper strip used in transformer applications:

Parameter	Typical Value	Importance
Purity (Cu)	≥ 99.90%	Ensures high conductivity
Conductivity	≥ 100% IACS	Minimizes resistive losses
Thickness Tolerance	±0.02 mm	Critical for winding consistency
Tensile Strength	200–240 MPa	Withstands winding and operational loads
Elongation	≥ 40%	Ensures formability and ductility
Surface Roughness	≤ 0.8 µm Ra	Prevents insulation damage
Edge Burr	≤ 5% of thickness	Avoids insulation puncture

In conclusion, while aluminum strip serves as a viable alternative in specific cost-sensitive applications, bare copper strip remains the material of choice for high-efficiency, high-reliability transformers. The consistent quality of the strip directly influences transformer performance, lifespan, and compliance with international standards. As global energy systems demand greater efficiency and resilience, the role of precision-manufactured copper strip will continue to be indispensable.

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Technical Specs: Bare Copper Strip

Technical Specifications: Bare Copper Strip for Precision Transformer Applications

Luoyang Xinzhaohe Aluminum Co., Ltd leverages 20+ years of metallurgical expertise in non-ferrous strip production to deliver bare copper strip meeting stringent transformer manufacturing requirements. Our technical specifications prioritize dimensional stability, electrical performance, and edge integrity to ensure seamless integration into high-speed winding operations and optimal end-product efficiency. Precision slitting to ±0.002 mm tolerance is non-negotiable for maintaining consistent coil geometry and preventing interlayer short circuits in transformer windings. This tolerance is achieved through servo-controlled tension systems and hardened tooling calibrated to sub-micron accuracy, validated via laser micrometry at 500 mm intervals across all coils.

Edge quality directly impacts winding stability and dielectric integrity. Our bare copper strip undergoes proprietary edge conditioning to eliminate burrs exceeding 1% of material thickness, verified through optical profilometry per ASTM B487. Micro-burr formation is suppressed through optimized shear clearance (3–5% of thickness) and tool rake angles, ensuring clean edges that prevent insulation damage during coil layering. Surface roughness (Ra) is maintained at ≤0.4 µm to minimize interfacial resistance and eddy current losses.

Electrical conductivity is certified at 100–101% IACS minimum per ASTM B193, utilizing high-purity electrolytic tough pitch (ETP) copper (Cu-ETP, C11000) with oxygen content held to 200–400 ppm. This guarantees minimal resistive heating and maximizes transformer energy efficiency. All coils undergo 100% eddy current testing to detect subsurface inhomogeneities that could compromise conductivity uniformity.

The following table details critical parameters for bare copper strip supply:

Parameter	Specification	Test Standard	Measurement Frequency
Material Grade	Cu-ETP (C11000)	ASTM B152	Lot certification
Thickness Range	0.10–3.00 mm	ASTM E3	Every 500 m
Width Range	10–300 mm	ASTM E3	Every coil
Thickness Tolerance	±0.002 mm (for widths ≤100 mm)	ISO 2178	Continuous monitoring
Width Tolerance	+0/-0.05 mm	ISO 7500-1	Every coil
Edge Burr	≤1% of thickness	ISO 4287	Every 1000 m
Surface Roughness (Ra)	≤0.4 µm	ISO 4287	Every coil
Conductivity	100–101% IACS	ASTM B193	Every melt
Flatness	≤5 I-Units	ISO 25178	Every coil
Tensile Strength	200–240 MPa	ASTM E8	Every melt

Consistency in these parameters reduces scrap rates in transformer assembly by up to 18% compared to industry averages, as validated by third-party production audits. Our slitting lines operate under ISO 9001-controlled environments with real-time statistical process control (SPC) tracking thickness deviation and edge deviation. Traceability is ensured via laser-etched batch codes linking to melt chemistry reports and conductivity certificates. For mission-critical applications, we offer optional helium leak testing to confirm edge integrity at 10⁻⁶ mbar·L/s sensitivity. Partnering with Xinzhaohe guarantees bare copper strip that meets the exacting demands of modern transformer design while optimizing your production throughput and electrical performance.

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Factory Tour: Manufacturing

Manufacturing Process for Bare Copper Strip

The production of high-performance bare copper strip at Luoyang Xinzhaohe Aluminum Co., Ltd. follows a tightly controlled, multi-stage manufacturing process designed to ensure dimensional accuracy, superior surface integrity, and consistent electrical conductivity. With over two decades of specialized experience in transformer-grade strip and foil production, our facility integrates advanced metallurgical practices with precision engineering to meet stringent international standards.

The process begins with cold rolling, where high-purity electrolytic tough pitch (ETP) copper ingots are first hot-rolled into intermediate thickness slabs and subsequently subjected to cold rolling. Cold rolling is performed on precision reversing mills under controlled temperature and tension conditions to achieve the target thickness, typically ranging from 0.05 mm to 3.0 mm, with tight tolerances as close as ±0.01 mm. This stage is critical for enhancing the mechanical properties of the copper, including tensile strength and elongation, while maintaining a uniform microstructure. Lubrication and roll surface finishing are meticulously managed to prevent surface defects such as scratches, roll marks, or edge waves.

Following cold rolling, the copper strip undergoes precision slitting. This operation involves longitudinal cutting of wide master rolls into narrow strips to meet customer-specific width requirements, typically ranging from 10 mm to 300 mm. Slitting is conducted on high-accuracy tension slitters equipped with tungsten carbide circular knives to ensure clean, burr-free cuts and minimal edge deformation. Strip edge tracking systems and automated width measurement devices are employed in real time to maintain consistent slit dimensions and minimize width variation across the coil.

Edge conditioning is the next critical phase, particularly for applications in transformers and electrical windings where sharp edges can compromise insulation systems or cause localized current concentration. The slit edges are subjected to mechanical edge rounding and deburring, using calibrated brushing or roller-based edge treatment systems. This process removes micro-burrs and creates a smooth, radius-formed edge profile, enhancing safety and performance in high-voltage environments.

Throughout the manufacturing sequence, comprehensive quality control (QC) protocols are enforced. In-process inspections include continuous surface defect monitoring via optical scanning systems, ultrasonic thickness gauging, and periodic mechanical and electrical testing. Finished coils are evaluated for dimensional conformity, surface cleanliness, flatness, and electrical resistivity, with each batch accompanied by a full material test report (FMTR) compliant with GB/T, ASTM, or IEC standards as required. All process parameters are logged in our traceability system, enabling full lot tracking from raw material to final shipment.

This integrated approach ensures that every coil of bare copper strip delivered meets the exacting demands of transformer and electrical equipment manufacturers worldwide.

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Packaging & Logistics

Export Packaging Specifications for Bare Copper Strip: Ensuring Integrity During Ocean Transit

Luoyang Xinzhaohe Aluminum CO., Ltd leverages over two decades of specialized experience in transformer conductor material production to implement rigorously engineered export packaging solutions. This is paramount for bare copper strip, a highly conductive yet hygroscopic material susceptible to oxidation and surface contamination during extended maritime exposure. Our packaging protocol is designed exclusively to mitigate the unique hazards of global sea freight, guaranteeing product integrity upon destination unloading.

All bare copper strip shipments depart our facility secured on custom-engineered wooden pallets compliant with ISPM-15 international phytosanitary standards. These pallets utilize kiln-dried, debarked softwood with precise load-bearing capacity calculations based on coil weight, dimensions, and stacking requirements. Each pallet undergoes structural validation to withstand dynamic forces encountered during vessel motion, crane handling, and multi-modal transfers without deformation. The strip coils are center-pinned and radially braced to the pallet deck using high-tensile steel strapping applied at manufacturer-specified tension levels, preventing axial shift or edge damage during transit.

The critical moisture barrier system employs a multi-layer co-extruded polyethylene film with integrated vapor corrosion inhibitors (VCI). This film is not a simple poly wrap; it features a minimum 125μm thickness with a scientifically formulated barrier layer providing a water vapor transmission rate (WVTR) of ≤0.5 g/m²/24hr at 38°C and 90% RH. The VCI technology actively releases corrosion-inhibiting molecules that form a molecular monolayer on the copper surface, neutralizing chloride ions and atmospheric moisture ingress. Film application occurs within our climate-controlled packaging hall under strict dew point monitoring, ensuring the strip surface is encapsulated below 40% relative humidity before sealing. Seams are hermetically welded using impulse sealers, creating a continuous, pinhole-free moisture barrier validated through ASTM D3078 vacuum decay testing.

Sea freight safety is non-negotiable. Our packaging system meets or exceeds ISO 11607-1:2019 requirements for terminally sterilized medical devices – a benchmark demonstrating exceptional environmental protection rigor. The palletized, film-sealed unit load is further secured within ISO shipping containers using cross-lashing with polyester webbing rated for 5,000 kg break strength, adhering to CTU (Cargo Transport Unit) Code lashing principles. This integrated approach prevents load migration during heavy weather, eliminating coil-to-coil impact and pallet collapse risks. Third-party accelerated corrosion testing per ASTM B117 confirms our packaged copper strip maintains pristine surface quality after simulated 60-day ocean voyages through tropical and temperate zones.

The table below summarizes key packaging performance metrics against industry baselines:

Parameter	Luoyang Xinzhaohe Specification	Typical Industry Baseline	Performance Impact
Film WVTR	≤0.5 g/m²/24hr	≤2.0 g/m²/24hr	75% reduction in moisture penetration
VCI Protection Duration	180+ days	30-60 days	Full coverage for global transit
Pallet Load Deflection	<1.5 mm under max load	<3.0 mm	Zero coil deformation risk
Seal Integrity Validation	ASTM D3078 Pass	Visual inspection only	Guaranteed hermetic seal

This systematic packaging methodology directly translates to reduced total landed costs for our clients. By eliminating oxidation-related rejections, surface cleaning requirements, and costly air freight contingencies, we ensure the bare copper strip arrives ready for immediate slitting or transformer winding operations. Partner with Luoyang Xinzhaohe for export solutions where metallurgical expertise converges with supply chain precision.

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Sourcing from Luoyang Xinzhaohe

Partner with Luoyang Xinzhaohe for High-Performance Bare Copper Strip

Luoyang Xinzhaohe Aluminum Co., Ltd brings over two decades of specialized expertise in the production of precision transformer strip and foil, serving global clients with engineered solutions in both aluminum and copper materials. As a trusted manufacturer of bare copper strip, our facility integrates advanced metallurgical processes, stringent quality assurance, and scalable production capacity to meet the demanding requirements of power transmission, electrical equipment, and industrial transformer applications.

Our manufacturing infrastructure is built around continuous rolling and annealing technologies, enabling tight control over dimensional tolerances, surface finish, and mechanical properties. We produce bare copper strip in a wide range of tempers—from soft (annealed) to hard tempers—with thicknesses from 0.05 mm to 3.0 mm and widths up to 600 mm, customizable to client specifications. All material is processed under oxygen-controlled environments to minimize oxidation, ensuring high electrical conductivity (exceeding 98% IACS) and superior weldability, formability, and fatigue resistance.

Quality is embedded at every stage of production. Our in-house laboratory is equipped with OES spectrometers, tensile testing machines, microhardness testers, and surface profilometers to validate material composition, mechanical performance, and surface integrity. Each coil undergoes 100% eddy current inspection and dimensional verification, with full traceability from raw material sourcing to final shipment. We maintain ISO 9001:2015 certification and comply with international standards including ASTM B187, GB/T 5584, and IEC 60464.

With an annual production capacity exceeding 15,000 metric tons, we support both high-volume OEM contracts and specialized low-volume orders. Our logistics network ensures on-time delivery to ports in Shanghai, Qingdao, and Ningbo, with options for FOB, CIF, and DDP terms. We also offer technical collaboration for custom alloys, slit-to-length services, and precision packaging to prevent transit damage.

Partnering with Luoyang Xinzhaohe means securing a stable, technically capable supply chain for mission-critical copper components. Our engineering team works directly with clients to optimize material selection, reduce scrap rates, and improve manufacturability in downstream processes such as stamping, winding, and brazing.

For reliable sourcing of high-purity bare copper strip with consistent quality and competitive lead times, contact us today.
Cathy Zhang | International Sales Manager
Email: cathy@transformerstrip.com
Luoyang Xinzhaohe Aluminum Co., Ltd
Established 2003 | ISO 9001 Certified | OEM & ODM Supported

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