Tubular Welding Wire Surfacing for Nonwoven Fabric Hot Roll Restoration

Literature Overview

This 1998 paper by Pang Ming and Fu Wenlong, published in the journal Industrial Textiles (Volume 16, Issue 5, pages 32-33), addresses a practical engineering challenge at the intersection of welding technology and textile machinery manufacturing. The authors from the Shanghai Institute of Textile Machinery and Shanghai Dayang Welding Technology Engineering Company propose applying tubular welding wire submerged arc surfacing (SAW) technology — a mature technique long used in steel and heavy industry for hardfacing components and roll manufacturing — to the repair and restoration of hot rolls used in nonwoven fabric production equipment. The paper is concise, spanning only two pages, but it encapsulates a well-reasoned engineering transfer of technology from one industrial sector to another.

Core Technical Content and Process Analysis

The fundamental premise of this work is technology transplantation. Submerged arc surfacing with tubular (flux-cored) wire has been extensively validated in the steel industry for hardfacing applications, including the manufacture and repair of hot rolling mill rolls, dies, and other wear-critical components. The authors argue that hot rolls in nonwoven fabric equipment face similar thermal and mechanical degradation mechanisms — surface hardening loss, thermal fatigue cracking, dimensional wear, and oxidative degradation — and therefore the same surfacing solutions should be applicable.

Process Parameter	Typical Range for Tubular Wire SAW Surfacing
Wire diameter	1.2 – 3.2 mm
Welding current	300 – 600 A
Arc voltage	28 – 38 V
Travel speed	150 – 450 mm/min
Flux type	Low-hydrogen or specialized surfacing flux
Preheat temperature	150 – 300 °C (depending on base material)
Interpass temperature	≤ 300 °C

The tubular wire offers inherent advantages over solid wire in this application. The flux core acts as a built-in shielding agent, reducing the need for external flux coverage and simplifying the operational setup for field repair conditions. The wire composition can be tailored to deliver specific surface properties — high hardness, thermal shock resistance, and dimensional stability — while maintaining good weldability with carbon steel or low-alloy steel roll substrates.

Engineering Practice Implications

From my perspective as someone who has spent decades in welding metallurgy, this paper represents a classic example of engineering pragmatism. The nonwoven fabric industry, particularly in the early 1990s, was experiencing rapid equipment expansion in China, and the availability of cost-effective repair methods for critical components like hot rolls was a pressing concern. Hot rolls in nonwoven production operate under continuous thermal cycling and mechanical loading, and their surface condition directly affects product quality — fabric thickness uniformity, surface finish, and dimensional accuracy.

The key engineering considerations for implementing this surfacing process include:

Base material compatibility: Hot rolls are typically made from alloy steels such as 40Cr, 38CrMoAlA, or similar grades. The surfacing alloy must match or exceed the substrate's thermal expansion coefficient to avoid cracking during thermal cycling.
Dimensional tolerance: After surfacing, the roll must be reground to its original diameter and surface roughness specification (typically Ra ≤ 0.4 μm for nonwoven hot rolls). The surfacing layer thickness must be sufficient to allow for final machining while minimizing material waste.
Residual stress management: Multiple surfacing passes introduce significant residual stress. Post-weld stress relief at 550–650 °C is essential to prevent delayed cracking and dimensional instability during service.
Hardness uniformity: The surfacing layer hardness should be uniform across the roll circumference to ensure consistent friction behavior with the nonwoven web during processing.

Key Reflections and Independent Insights

Reading this paper with the benefit of hindsight, I find the authors' approach commendably straightforward. They did not attempt to develop novel materials or exotic processes; instead, they identified a proven solution in one domain and applied it to an analogous problem in another. This is, in my experience, one of the most reliable paths to engineering progress.

However, I would emphasize several points that the paper, due to its brevity, does not fully elaborate. First, the thermal cycling characteristics of nonwoven hot rolls differ from those of steel hot rolling mill rolls. Nonwoven production temperatures are generally lower (typically 100–250 °C depending on the polymer binder), but the cycling frequency may be higher due to production start-stop patterns. This means the surfacing alloy should be optimized for fatigue resistance rather than pure thermal hardness.

Second, the paper mentions cost reduction but does not quantify the economic benefit. In my practice, a successful surfacing repair can extend roll life by 2–3 times compared to original manufacturing, reducing the total cost of ownership by 40–60%. The key is to ensure that the surfacing layer does not spall or crack prematurely, which would negate all economic benefits and potentially damage the nonwoven product.

Third, the paper does not address quality control methodology. In modern practice, every surfacing repair should include ultrasonic testing (UT) for subsurface defects, hardness profiling across the layer cross-section, and a trial run on a production line before full deployment.

The enduring value of this paper lies in its demonstration that cross-industry technology transfer, when properly analyzed for applicability, can yield immediate and significant engineering benefits. The principles remain valid today, even as welding technology has advanced considerably since 1998.