What is the difference between pure metal alloy resistance electron beam welding and non electron beam welding?

The welding quality of pure metal alloys (understood here as metal alloys used for resistance applications, such as nickel chromium alloys NiCr, constantan, manganese copper, etc.) is crucial to their resistance performance, stability, and reliability. There are significant differences between electron beam welding (EBW) and non electron beam welding (such as TIG welding, laser welding, resistance welding, etc.) when welding such materials, mainly reflected in the following aspects:

1. Energy density and heat input:
Electron beam welding: extremely high energy density (up to 10 ⁶ W/cm ² or even higher). This enables it to highly concentrate energy in a very small area, achieving a deep and narrow melt pool.
Non electron beam welding (such as TIG welding): The energy density is relatively low. Greater heat input and wider heat affected zone. The melt pool is usually wider and shallower (compared to EB).
influence:
Size of heat affected zone: The heat affected zone of EBW is very narrow, resulting in minimal thermal damage to the base material. The HAZ of non EBW is wider.
Thermal deformation: EBW has extremely small thermal deformation, making it particularly suitable for precision parts. The thermal deformation of non EBW is usually greater.
Melting efficiency: EBW can achieve high aspect ratio welds (with depth far greater than width), allowing for single pass penetration of thick materials. Non EBW typically requires multiple welds or bevels to weld thick plates.

2. Welding environment:
Electron beam welding: usually performed in a high vacuum environment (there are also low vacuum and non vacuum EBW, but high vacuum is the most common). This completely isolates the air.
Non electron beam welding:
TIG welding: usually carried out under inert gas protection (such as argon), with good protection effect, but it is difficult to achieve vacuum level purity.
Laser welding: It can be performed in air, inert gas, or vacuum, but high vacuum laser welding is less common.
Resistance welding: carried out in air, relying on the heat generated by pressure and current.
influence:
Oxidation and Pollution: Vacuum EBW completely avoids oxidation and nitriding, and the purity of the weld metal is extremely high, with almost no burn damage to the composition (especially important for alloying elements such as Cr, Al, etc.). Even with protective gas, there is a risk of trace air contamination or insufficient protection in non EBW, which may lead to oxidation of alloy elements, formation of inclusions, and affect the composition and resistance stability of the weld seam.
Pores: EBW vacuum environment can effectively eliminate dissolved gases such as hydrogen and oxygen, and the weld seam is dense with almost no pores. Non EBW (especially TIG, laser) is more prone to producing pores, especially when there is contamination or insufficient protection on the material surface.

3. Metallurgical effect:
Electron beam welding: The extremely high cooling rate (due to concentrated heat input) results in finer weld microstructure. Avoiding excessive grain growth. Small segregation tendency (rapid solidification inhibits element diffusion). The composition of the weld seam is close to that of the base metal.
Non electron beam welding: relatively slow cooling rate and wider HAZ may lead to grain coarsening. The greater the heat input, the higher the risk of grain growth and element segregation (such as enrichment of low melting point impurities at grain boundaries).
influence:
Mechanical properties: EBW welds typically have higher strength and better toughness (fine grain strengthening).
Resistance performance: For precision resistance alloys, the stability of composition and the uniformity of microstructure directly affect the resistivity and its temperature coefficient. The composition and microstructure changes of EBW welds are minimal, which is most conducive to maintaining the original electrical properties of the resistance alloy. Possible oxidation, burning, segregation, or coarse grain structure in non EBW welds may alter local resistivity, introduce non-uniformity, and affect the accuracy, stability, and long-term reliability of resistance elements.
Corrosion resistance: EBW welds have high purity, dense and fine structure, and usually have better corrosion resistance. If there is oxidation, inclusions, or compositional segregation in non EBW welds, the corrosion resistance may decrease.

4. Applicability and Cost:
Electron beam welding:
Advantages: Deep melting, narrow HAZ, minimal deformation, ultra-high cleanliness, excellent metallurgical quality. Specially suitable for high-precision, high reliability, difficult to weld materials, and thick plate single pass welding resistance alloy components.
Disadvantage: The equipment is extremely expensive. A vacuum chamber is required, and the size of the workpiece is limited. The clamping and positioning requirements are very precise. The operation and maintenance are complex. High cost.
Non electron beam welding:
Advantages: The equipment cost is relatively low (TIG is the cheapest, followed by laser). High flexibility, can be welded in various positions, with small workpiece size limitations (especially TIG). The operation is relatively simple. Low cost.
Disadvantages: Large heat affected zone and significant deformation. The protective effect is not as good as vacuum, and there is a risk of oxidation and porosity. Metallurgical quality (organization, uniformity of composition) is usually inferior to EBW. For precision resistance alloy welding with extremely high requirements, it may not be the most preferred option.

Summary of differences (for pure metal alloy resistor applications):

Characteristic electron beam welding (EBW) non electron beam welding (such as TIG, laser)
High energy density (deep narrow welds) and low energy density (wide shallow welds)
Extremely low heat input (highly concentrated) high
The heat affected zone is very narrow and wide
Extremely small and large thermal deformation
Environmental high vacuum (mainstream) inert gas protection/air
Complete avoidance of oxidation/contamination (high purity of welds) with risks (when protection is insufficient)
Very few pores (vacuum degassing) are common (strict control is required)
The metallurgical structure has small grain size and less segregation, and the composition is close to that of the base material. The grain size may be coarse, and the risk of segregation is high. The composition may change
The resistance performance is most conducive to maintaining the original resistivity and stability. Resistance performance may be changed due to oxidation, burning, segregation, and coarsening
The equipment cost is extremely expensive and relatively low (TIG<laser<EBW)
High operating costs (vacuum system, maintenance), low (TIG)/medium high (laser)
The size of the workpiece is limited by the vacuum chamber (especially TIG)
Low flexibility (requiring precise positioning inside the vacuum chamber) and high flexibility (especially TIG)
Main advantages include ultra-high quality, high precision, low deformation, high cleanliness, low cost, high flexibility, and relatively simple operation
Main disadvantages: high cost, limited size, complex operation, significant thermal impact, high quality control requirements, potential pollution/performance change risks

Conclusion:

For applications such as pure metal alloy resistors that require extremely high stability in composition, uniformity in microstructure, and consistency in resistance performance:

Electron beam welding (EBW) is the preferred process, especially when manufacturing high-precision, high stability, and high reliability precision resistance components or sensors. It can minimize thermal effects, avoid oxidation pollution, obtain small and uniform weld microstructure, and thus best maintain the original electrical properties of the resistance alloy (resistivity, temperature coefficient, etc.).
Non electron beam welding (such as TIG welding, laser welding) can be used in situations where cost is sensitive, precision requirements are relatively low, or the workpiece size is too large to enter the vacuum chamber. But it is necessary to strictly control the welding parameters and protective atmosphere to minimize oxidation, burning, porosity, and thermal effects, otherwise it may have adverse effects on the resistance performance (such as resistance drift, noise, long-term stability). The energy density of laser welding is between EBW and TIG, and good protection can achieve quality close to EBW (especially for thin plates), but the cost is also high.

The choice of welding method ultimately depends on the specific performance requirements of the resistance element, cost budget, production batch, as well as the geometric dimensions and complexity of the workpiece. For critical resistor applications that pursue the highest performance and reliability, the advantages of EBW are often irreplaceable.