Metal Wire Mesh Belts in the Fastener Industry

Metal wire mesh belts (metal conveyor belts) are integral to fastener manufacturing, used across multiple stages from cold forming to final packaging. Their high heat resistance, large open area for airflow/liquid flow, dimensional stability, corrosion resistance, and load capacity make them ideal for continuous processes like heat treatment, washing/cleaning, plating/coating, drying, and conveying. 

1. Fastener Types and Where Wire Mesh Belts Fit In

Category	Examples	Typical Heat Treatment
Bolts & Screws	Hex bolts, machine screws, flange bolts	Quench & temper, case hardening
Nuts	Hex nuts, lock nuts, flange nuts	Often just stress relief anneal
Studs	Double-ended studs, fully threaded rods	Normalize or anneal
Self-tapping Screws	Thread-forming, thread-cutting screws	Case harden, zinc plating
Sheet-metal Screws	Phillips, hex washer head	Surface hardening
Rivets	Solid rivets, semi-tubular rivets	Anneal (for forming)
Pins	Cotter pins, dowel pins, Taper pins	Quench & temper
Hose Clamps	Worm-drive clamps, spring clamps	Passivation, plating
Specialty Fasteners	Automotive clips, plastic clips, retainer rings	Varies

Regardless of type, most fasteners follow a similar production sequence: Cold Heading → Thread Rolling → Heat Treatment → Surface Finishing → Cleaning → Inspection → Packaging. Metal mesh belts are present at nearly every stage from heat treatment through final packaging.

2. Production Stages Using Metal Mesh Belts

2.1 Heat Treatment (Continuous Belt Furnaces)

This is the single largest application of metal mesh belts in fastener manufacturing. Fasteners require precise thermal cycling to achieve target hardness, tensile strength, and case depth — and mesh belts are the only practical conveyor choice inside high-temperature furnaces.

How It Works

A vibratory feeder or magnetic conveyor evenly spreads individual fasteners onto the mesh belt as it enters the furnace. The belt carries parts through multiple temperature zones (preheat, austenitizing, soak), then through the quench zone (oil, gas, or liquid nitrogen), and finally through the tempering zone. The process is fully automated and continuous.

Key Advantages Over Batch Furnaces

● Uniform heating: multi-zone control keeps temperature within ±3°C across the load
● Consistent case depth and hardness from part to part
● Continuous throughput eliminates batch handling delays
● ~25–30% energy savings per piece vs. box furnaces
● Inert-gas quenching eliminates oil mist and VOC emissions — no fire hazard from hot oil

Temperature and Atmosphere

Parameter	Typical Value
Quench temperature	840–900°C (austenitizing)
Tempering temperature	250–620°C
Oil quench temperature	~70°C
Atmosphere	N₂, NH₃, or inert gas (reduces oxidation)
Belt speed	0.5–3 m/min (process-dependent)
Throughput	100–1,000 kg/h (line-dependent)

Belt Material Requirement

At 840–900°C, only high-grade stainless steels (304, 316, 314 310S) or nickel alloys (Inconel 600, Hastelloy) can maintain structural integrity. Carbon steel belts oxidize rapidly above ~300°C and are unsuitable for furnace applications.

2.2 Quenching & Annealing

Oil Quench

After heating, fasteners enter an oil quench tank. The mesh belt carries parts through the oil — mesh open area ensures rapid, uniform cooling from all sides. Belt must resist 70°C oil splash and thermal shock.

Gas / Liquid Nitrogen Quench

Inert-gas (N₂) or cryogenic quenching is increasingly used to eliminate fire risk and VOC emissions. The mesh belt still functions as the conveyor, but the quench medium flows through the mesh rather than submerging parts in liquid.

Annealing (Batch or Continuous)

For large-batch annealing (stress relief or grain refinement), mesh belts carry parts through long low-temperature sections with slow cooling. Belt speed is reduced to allow proper thermal cycles.

2.3 Ultrasonic Degreasing & Acid Pickling

Before plating or coating, fasteners must be completely free of cutting fluids, oils, and scale.

Ultrasonic Degreasing Mesh Conveyor

Parts are dropped onto an ultrasonic mesh-belt conveyor, which carries them through multiple ultrasonic cleaning stations, each containing alkaline cleaning solution. The open mesh structure allows ultrasonic waves to reach all surfaces and allows cleaning fluid to circulate freely — achieving better cleaning than static racks.

Acid Pickling

After degreasing, fasteners go through acid pickling (typically HCl or H₂SO₄) to remove oxide scale. Mesh belts carry parts through acid baths and multiple water rinse stages. The mesh allows acid and rinse water to flow through continuously.
Key Requirement: Belt material must resist strong acids. 316L stainless or Hastelloy C is commonly specified for acid pickling lines.

2.4 Coating & Plating Lines

Hot-Dip Galvanizing

An automated galvanizing line operates as follows:
1. Vibratory feed → ultrasonic degreasing on mesh belt
2. Acid pickling in tilting baskets
3. Water rinse
4. Flux treatment (parts dumped via tilting bucket)
5. Drying on mesh belt — removes moisture before zinc immersion (critical)
6. Hot-dip zinc (zinc bath ~460°C)
7. Cooling on mesh belt → inspection
The drying mesh belt before the zinc kettle must resist zinc vapor and chromate exposure.

Electroplating

For electroplated fasteners (zinc, zinc-nickel, trivalent chromium), mesh belts convey parts through plating tanks, rinse tanks, and passivation baths. The open mesh allows plating solution to contact all surfaces and ensures even current distribution.

Phosphate Coating & Drying

Mesh belts carry fasteners through phosphating baths (for corrosion resistance and lubricity) and then through convection drying ovens. The high open area of mesh belts allows hot air to circulate freely around every part, ensuring uniform drying.

2.5 Drying Ovens

Mesh belts are ideal for drying because:

● Open area (60–86%) allows hot air to flow through and around parts freely
● No pooling of water or cleaning agents
● Fast drying cycles compared to solid conveyors
● Used after cleaning, plating, phosphating, or any wet process
Typical drying temperatures: 80–200°C. Belt speed: 1–3 m/min.

2.6 Material Handling & Conveying

Throughout the production line, mesh-belt conveyors handle bulk parts between machines:

● Thread rolling → heat treat line
● Heat treat line → cleaning / plating line
● Plating line → drying → inspection
● Inspection → packaging
Mesh belts handle vibratory feeder loads, high part density, and bulk weight without degradation.

2.7 Inspection & Packaging

Mesh belts provide a stable, flat, single-layer surface — ideal for integration with automated inspection:
● Optical sorting — cameras detect surface defects as parts move on the belt
● Eddy-current inspection — for case depth or hardness verification
● Weight sorting — integrated weigh cells on the belt path
After inspection, fasteners continue on mesh belts to automated packaging or counting systems.

3. Functions and Benefits of Metal Mesh Belts

Function	Benefit in Fastener Industry
High-Temperature Resistance	Survives 800–1,150°C furnace environments (304SS to Inconel)
Large Open Area (60–86%)	Allows hot air, cleaning solutions, and quench media to flow through freely — ensures uniform heating, cooling, and cleaning
Corrosion Resistance	Resists acid pickling, alkaline cleaning, zinc vapor, chromate — 316L and Hastelloy for harsh environments
High Strength & Load Capacity	Supports bulk fasteners (bolts, nuts) at high throughput — tensile strength ≥515 MPa for 304SS
Dimensional Stability	Minimal stretch under load and heat — maintains belt geometry and tracking
Easy Cleanability	Smooth stainless surface — no residue retention, complies with hygiene standards
Versatile Weave Types	Balanced Spiral Woven, Compound Woven — each optimized for different loads, flex requirements, and equipment

4. Technical Requirements and Selection

4.1 Temperature Capability

Material	Maximum Operating Temperature °C
304 Stainless Steel	750
316 Stainless Steel	800
314 Stainless Steel	1120
310S Stainless Steel	1150
80/20 Nickel Chrome	1150
Inconel 600	1150
Inconel 601	1150

4.2 Mesh Aperture and Open Area

Aperture Size	Application
<1 mm (fine mesh)	Small screws, fasteners <2 mm dia.
1–3 mm	General fasteners: bolts M4–M12, nuts, studs
3–5 mm	Large bolts, heavy parts, bulk handling

Open area of 50–86% is typical. Higher open area = better airflow/drainage but less part support.

4.3 Weave Type Selection

In the fastener industry, the two most common types of metal conveyor belts are Balanced Spiral Woven Belts and Compound Woven Belts. These are essential for handling high-volume production and extreme thermal environments.

Below is a detailed breakdown of these two belt types and their specific roles in fastener manufacturing:

Balanced Spiral Woven Belt

This is the most widely used "workhorse" belt in the industry due to its stability and cost-effectiveness.

Design: It consists of alternating left-hand and right-hand spirals joined by a straight cross-rod.

Best For: Medium to large fasteners such as structural bolts, nuts, and washers.

Key Applications:

Washing & Degreasing: The large open area allows high-pressure sprays and chemicals to easily remove drawing oils and debris.

Drying: High airflow ensures fasteners are moisture-free before entering the furnace.

Advantage: It resists "tracking" issues (running to one side) and provides excellent fluid drainage.

Compound Woven Belt (Cordweave)

When dealing with heavy loads or tiny precision parts, the Compound Woven belt is the preferred choice.

Design: It features multiple spirals and cross-rods nested together to create a very dense, smooth, and flat mesh surface.

Best For: Micro-screws, small rivets, and heavy-duty bulk loading.

Key Applications:

Heat Treatment & Hardening: The dense surface prevents small screws from falling through or getting caught in the mesh during high-temperature cycles (850°C–950°C).

Quenching: Its high tensile strength allows it to carry heavy, dense loads of steel out of oil or polymer quench tanks.

Advantage: It provides the highest surface stability and can handle the extreme "pounds per square foot" requirements of bulk fastener processing.

4.4 Methods of Drive for Wire Mesh Belts

Different fastener production processes require different drive systems depending on temperature, load, furnace atmosphere, product size, and conveyor length.

Friction Drive (Smooth End Drum)

A driven drum at the furnace exit transmits force to the belt through surface friction. Simple and low-cost, but unreliable when belt surfaces are contaminated with quench oil or scale — a common condition in fastener hardening lines. Suitable only for short, light-duty furnaces such as tempering or black oxide lines.

Positive Sprocket Drive

Toothed sprockets engage the belt's transverse drive rods directly, eliminating slip. This is the standard method for fastener hardening and carbonitriding furnaces. It ensures consistent belt speed regardless of load variation — critical when operators batch-charge large quantities of fasteners. Belt elongation over time changes the effective rod pitch, so periodic tension adjustment is necessary.

Dual End-Drive (Push-Pull)

Two sprocket drive stations — one at the exit end (pull) and one at the entry end or intermediate position (push) — share the load and reduce peak belt tension. Essential for longer furnaces exceeding 10–12 m. Both drives are synchronized via variable frequency drives (VFDs); if the push drive overspeeds relative to the pull drive, belt buckling results.

Intermediate In-Furnace Drive

For furnaces exceeding 15–20 m, a drive station is installed inside the furnace body. The motor is mounted externally, with a sealed shaft penetrating the furnace wall to maintain atmosphere integrity. In-furnace bearings must withstand continuous temperatures of 850–950°C, requiring high-temperature or ceramic-type bearing solutions.

Selection Guide

Process	Furnace Length	Recommended Drive
Tempering / black oxide	≤ 6 m	Friction drum
Mesh belt hardening	6 – 12 m	Single positive sprocket
Carbonitriding	12 – 20 m	Dual end-drive with VFD sync
Heavy structural bolt lines	> 20 m	Dual drive + intermediate in-furnace drive

5. Case Studies

Case 1: Arnold Fastening Systems (China)

Arnold's continuous mesh-belt furnace line for fasteners:
● Parts are distributed by vibratory feeder onto the mesh belt entering an inert-gas furnace
● Heated up to ~900°C
● Quenched in oil (mesh belt carries parts through quench zone)
● Washed to remove oil residue on downstream conveyors
● Finally tempered at 340–620°C
This single continuous line handles heat, quench, wash, and temper — demonstrating how mesh belts seamlessly bridge multiple process stages in one automated system.

Case 2: Automated Hot-Dip Galvanizing Line (Patent CN112301302A)

A Chinese patent discloses a fully automated galvanizing line:
1. Vibratory feed
2. Ultrasonic degreasing on mesh belt conveyor (through multiple cleaning stations)
3. Acid pickling in tilting baskets
4. Water rinse
5. Flux treatment (parts dumped via tilting bucket onto flux bath)
6. Drying on mesh belt — removes moisture before zinc immersion
7. Hot-dip zinc immersion (~460°C)
8. Cooling on mesh belt → inspection
The mesh belt is explicitly used in ultrasonic cleaning and drying stages, enabling fully automated multi-stage processing without manual handling.

Case 3: High-Capacity Quench/Temper Lines

Equipment suppliers publish automated lines for screws and bolts with throughputs of 150 kg/hr and higher:
● Automatic feeder → pre-washer → induction hardening furnace → oil quench → tempering furnace
● Mesh belts handle the transition between each stage
● Energy savings and yield improvement cited as key benefits vs. batch processing

Case 4: Dongyu/Dong'an Heat Treat Technology (China)

A technical paper documents mesh-belt continuous furnaces achieving:
● Nitrogen or ammonium atmosphere (eliminates oil quench VOC)
● Tight hardness consistency: ±0.15 mm case variation across the load
● ~30% energy savings vs. conventional batch furnaces
● Compliance with environmental regulations (no oil fume emissions)