Zhuojin Pipe Fitting Co., LtdTIG Electric Rivet Welding Technology for Stainless Steel Rail Vehicle Underframe Corrugated Plate Assembly
Literature Overview
This paper, published in Urban Mass Transit Research (2025, Vol. 28, No. 12, pp. 68-73) by Kong Lizhi and colleagues from CRRC Changchun Railway Vehicles Co., Ltd., addresses a highly specific manufacturing challenge in stainless steel rail vehicle fabrication. The core problem is that the corrugated plate troughs of the underframe require rubber seat adhesion, which demands a flush weld surface without any weld reinforcement. Conventional arc welding processes inevitably produce weld bead protrusion, making them unsuitable for this application. The authors propose and validate a TIG electric rivet welding process that achieves a flush, defect-free joint on thin stainless steel sheets of 0.6-0.8 mm thickness, using the Xi'an Metro Line 4 vehicle structure as a practical verification case.
Core Technical Challenge and Process Principle
The fundamental engineering constraint here is geometric rather than metallurgical. Unlike butt joints where weld reinforcement is acceptable or even desirable for load-bearing capacity, the corrugated plate trough application requires the weld to sit perfectly flush with the base metal surface to allow proper rubber seat bonding. The authors adapt the TIG electric rivet welding principle, which operates by positioning the non-consumable tungsten electrode above the workpiece surface and allowing the arc to form a molten pool that solidifies into a flat, rivet-like nugget. The key innovation lies in the design of the clamping device and torch protection structure tailored to the actual flatness characteristics of the corrugated plate in production.
Process Configuration and Equipment Design
The TIG electric rivet welding process differs significantly from conventional TIG butt welding in its equipment requirements. The clamping device must maintain precise, uniform pressure across the joint interface while accommodating the inherent flatness variations of the corrugated plate. The torch protection structure serves a dual purpose: it shields the arc from convective disturbances and prevents spatter from contaminating the torch components. Based on the paper's findings, the following process parameters were optimized:
| Parameter | Specification | Notes |
|---|---|---|
| Base metal thickness | 0.6-0.8 mm | Upper plate of corrugated structure |
| Welding process | TIG electric rivet welding | Non-consumable tungsten electrode |
| Shielding gas | Argon (implied by TIG) | Inert atmosphere protection |
| Weld reinforcement | Zero (flush) | Required for rubber seat adhesion |
| Verification standard | Resistance spot welding standard | Internal defect criteria |
Verification Methodology and Results
The authors conducted a rigorous verification program comprising four test methods: visual inspection, tensile-shear testing, fracture surface analysis, and chiseling tests. Each test method targets a different quality attribute of the weld joint.
Test Results Analysis
The chiseling test revealed that the weld nugget diameter was consistent and well-defined, indicating stable arc transfer and proper molten pool formation. The metallographic examination confirmed that the weld nugget diameter and penetration depth were within acceptable ranges for the material thickness. Most critically, the internal weld zone showed no defects such as porosity, cracks, or incomplete fusion. The tensile-shear force measurements demonstrated that the joint strength was adequate for the structural requirements of the rail vehicle underframe.
The key finding is that the TIG electric rivet welding process, when properly parameterized and equipped with appropriate clamping and torch protection, can produce joints that meet resistance spot welding quality standards. This cross-process equivalence is significant because it means existing quality assurance frameworks for resistance welding can be applied to validate this novel TIG-based approach.
Engineering Practice Integration and Reflections
From a manufacturing engineering perspective, this work addresses a genuine gap in stainless steel rail vehicle fabrication. The corrugated plate underframe is a common structural solution in lightweight rail vehicle design, but the flatness requirement for rubber seat bonding has historically limited process options. The TIG electric rivet welding approach offers several practical advantages:
- The process is inherently clean and produces no spatter, which is critical for stainless steel surfaces that must remain free of contamination.
- The equipment footprint is smaller than resistance spot welding stations, offering flexibility in production line layout.
- The process is amenable to automation, as demonstrated by the use of dedicated clamping fixtures and torch protection structures.
However, several questions remain for practical implementation. The paper does not extensively discuss the effect of welding sequence on accumulated distortion in the corrugated plate, which is a critical concern in thin-sheet welding. Additionally, the long-term durability of the rubber seat bond under cyclic thermal and mechanical loading warrants further investigation. The transition from the Xi'an Metro Line 4 prototype to high-volume production will require additional qualification of parameter windows and defect tolerance criteria.
This study exemplifies how a fundamental understanding of welding process physics can be applied to solve application-specific problems that conventional processes cannot address. The adaptation of TIG welding principles to achieve a rivet-like joint without reinforcement demonstrates the flexibility of arc welding technology when process parameters and equipment design are carefully tailored to the application requirements.
Study Insights and Implications
The most valuable insight from this paper is the demonstration that process selection should be driven by the functional requirement of the final assembly rather than by conventional categorization of welding methods. The TIG electric rivet welding approach bridges the gap between arc welding and resistance welding, offering the cleanliness and controllability of TIG with the geometric precision required for surface-adhesive applications. For engineers working in rail vehicle manufacturing, this work opens a new process option for thin-sheet stainless steel joints where flush weld geometry is mandatory. The methodology of validating a novel welding process against established quality standards (in this case, resistance spot welding criteria) provides a practical framework for process qualification that can be replicated in other application contexts.