MIG Brazing Overlay of Copper Strip Technology for Steel Substrates

Literature Overview

This paper by Ma Wangzhe and colleagues from the Harbin Welding Research Institute, published in 2006, presents a novel application of MIG brazing (GMAW brazing) technology for depositing copper strip overlays on steel substrates. The work addresses the limitations of mechanically formed copper strips and demonstrates that MIG brazing can produce copper overlays with sound metallurgical bonding and acceptable mechanical properties.

Core Technical Content

Process Principles

MIG brazing, also known as GMAW brazing or solid wire brazing, uses a solid copper wire as the filler material while maintaining the base metal temperature below its melting point. The process relies on wetting and capillary action to achieve bonding between the molten copper filler and the solid steel substrate. Key process parameters include:

Parameter	Typical Range	Effect on Bond Quality
Shielding gas flow	15–25 L/min	Prevents oxidation of molten copper
Wire feed speed	3–8 m/min	Controls deposition rate and heat input
Travel speed	200–600 mm/min	Affects bond thickness and dilution
Current	150–300 A	Determines wetting and penetration
Voltage	18–28 V	Controls arc stability and heat input

Metallurgical Bonding Characteristics

The study confirms that MIG brazing achieves true metallurgical bonding between copper and steel, with no defects observed at the interface. The bonding mechanism involves:

Wetting: Molten copper wets the clean steel surface through capillary action
Interdiffusion: Limited interdiffusion of Fe and Cu at the interface forms a thin reaction layer
Solidification: The copper solidifies in direct contact with the steel, creating a metallurgical bond
Microstructure: The interface typically shows a thin Fe-Cu intermetallic layer (Fe₃Cu, FeCu) with good adhesion

Mechanical Properties of the Overlay

The deposited copper overlay exhibits:

Tensile strength: 200–350 MPa (depending on process parameters)
Bond strength: Sufficient for most industrial applications
Conductivity: Maintains high electrical and thermal conductivity characteristic of copper
Weldability: The overlay can be further processed without significant degradation

Engineering Practice Applications

The MIG brazing overlay of copper strips finds applications in:

Electrical contact surfaces: Providing conductive surfaces on steel components
Thermal management: Creating heat transfer interfaces in heat exchangers
Wear-resistant linings: Copper's softness provides conformability against mating surfaces
Corrosion protection: Copper overlays can protect steel in specific environments
Repair applications: Restoring worn copper surfaces on industrial components

Comparison with Alternative Methods

Method	Advantages	Limitations
MIG brazing	Low dilution, good bonding, controllable thickness	Requires surface preparation, limited to thin overlays
Mechanical attachment	Simple, no heat input	Poor contact, risk of delamination
Electroplating	Uniform thickness, good adhesion	Expensive, limited to small areas
Hot dipping	Thick coatings possible	High temperature, poor dimensional control
Laser cladding	Excellent bonding, minimal dilution	High equipment cost, limited to small areas

Key Technical Challenges

Surface preparation: Oxide removal and surface cleaning are critical for achieving reliable wetting and bonding
Heat input control: Excessive heat can cause base metal melting, while insufficient heat prevents proper wetting
Porosity prevention: Gas entrapment during solidification can create voids in the overlay
Dimensional control: Achieving uniform thickness across large areas requires careful process parameter optimization

Study Insights

The MIG brazing approach for copper overlay deposition represents a practical solution to the challenges of creating conductive or wear-resistant copper surfaces on steel components. The key advantage over conventional mechanical attachment methods is the achievement of true metallurgical bonding, which provides superior adhesion and long-term reliability.

For piping and fitting applications, where copper overlays may be used for electrical grounding, thermal management, or wear protection, the MIG brazing technology offers a viable manufacturing solution. The process is particularly well-suited for localized overlay applications where precision control of thickness and position is required.

Concluding Remarks

The MIG brazing overlay of copper strip technology presented in this paper demonstrates a practical and effective method for creating metallurgically bonded copper overlays on steel substrates. The process offers advantages in terms of bonding quality, process control, and applicability to industrial manufacturing settings. For engineering practitioners, this technology provides a valuable option for creating copper-functional surfaces on steel components where traditional mechanical attachment methods are inadequate. The demonstrated capability to achieve sound metallurgical bonds with no interface defects confirms the technical maturity of this approach for industrial applications.