CLADDING TECHNOLOGY SHANXI CO., LTDTIG Spot Welding Application in Pulsating Net Manufacturing
Literature Overview
This 1995 technical report from Zhengzhou Textile Machinery Factory documents the application of TIG (Gas Tungsten Arc Welding) spot welding in the manufacturing of pulsating nets, a component used in textile machinery for fabric feeding and tension control. The work by Li Wenli represents an early industrial application of TIG welding beyond conventional butt and fillet joints, extending the process into the domain of spot welding for thin-walled, precision components. The reference to "pulsating net" likely refers to a mesh or grid structure used in textile machinery that undergoes cyclic deformation during operation, requiring joints that can withstand repeated mechanical loading without fatigue failure.
Core Technical Points
The fundamental challenge in applying TIG spot welding to pulsating nets lies in the combination of thin base materials, small weld dimensions, and the requirement for fatigue-resistant joints. Unlike resistance spot welding, which relies on electrical resistance to generate localized heat, TIG spot welding provides precise thermal input control through argon shielding, tungsten electrode geometry, and current modulation. For textile machinery components, the base materials are typically mild steel or spring steel with thicknesses ranging from 0.3 mm to 1.5 mm, where the heat-affected zone (HAZ) must be minimized to preserve the mechanical properties of the surrounding material.
Key process parameters for TIG spot welding in this application include:
| Parameter | Typical Range | Rationale |
|---|---|---|
| Current | 15–45 A | Low current for thin sheet penetration |
| Arc Length | 1.5–3.0 mm | Ensures stable arc and minimal spatter |
| Shielding Gas | Argon (99.99%) | Prevents oxidation of weld pool |
| Gas Flow Rate | 8–12 L/min | Adequate coverage for small weld pool |
| Travel Speed | Manual or 0–5 mm/s | Controlled for spot weld formation |
| Tungsten Electrode | WC-20 or LaB6 | Fine tip for precise energy delivery |
Process Analysis and Engineering Considerations
The selection of TIG over resistance spot welding for pulsating net manufacturing is driven by several engineering requirements. First, the pulsating net undergoes cyclic deformation, meaning that any weld defect such as porosity, incomplete fusion, or microcracking could serve as a fatigue crack initiation site. TIG welding provides a clean, controlled weld pool that minimizes such defects when properly executed. Second, the geometric complexity of the net structure—with intersecting wires or strips at various angles—makes resistance spot welding equipment difficult to adapt, whereas the flexibility of a TIG torch allows access to tight geometries.
A critical concern in this application is the post-weld residual stress distribution. Spot welds introduce localized plastic deformation, and in a component subjected to cyclic loading, these residual stresses can accelerate fatigue crack growth. The report likely addresses this through process optimization, including current ramping, pulse parameters, and possibly post-weld stress relief procedures such as low-temperature annealing.
Defect Analysis and Countermeasures
| Defect Type | Root Cause | Countermeasure |
|---|---|---|
| Porosity | Inadequate gas shielding or base material contamination | Increase gas flow, clean base material, use trailing shield |
| Burn-through | Excessive current or arc length | Reduce current, maintain consistent arc distance |
| Incomplete Fusion | Insufficient heat input or poor joint fit-up | Increase current, improve fit-up tolerance |
| Tungsten Inclusion | Arc striking on tungsten or excessive arc length | Use high-frequency arc starting, maintain short arc |
| Undercut | Excessive current with rapid travel | Reduce current, adjust travel speed |
Integration with Engineering Practice
From a pressure vessel and cladding engineering perspective, the principles demonstrated in this report—precise thermal input control, minimal HAZ, and fatigue-resistant joint design—are directly transferable to overlay welding applications. In weld overlay cladding, particularly for hydrogenation reactors and high-pressure hydrogen service, the fatigue life of the overlay layer is critical. The TIG spot welding approach documented here reinforces the importance of controlling heat input to avoid grain coarsening and microstructural degradation in the base material, a principle equally applicable to thin overlay layers of nickel-based alloys on carbon steel substrates.
Study Insights and Reflections
This early 1995 report represents a pragmatic application of TIG welding technology in a non-traditional setting. The move from butt welding to spot welding within the TIG process demonstrates the versatility of the method when process parameters are appropriately adapted. For engineers working in bimetal product manufacturing, this work serves as a reminder that the fundamental principles of arc stability, shielding gas effectiveness, and heat input control remain constant regardless of the specific joint configuration. The fatigue considerations raised in this context are particularly relevant to modern applications where overlay layers must withstand cyclic thermal and mechanical loading in high-pressure equipment.