Harris TIG Rod 1/8" – 10 lb

Product Overview

What Is Harris Silicon Bronze TIG Welding Rod ERCuSi-A?

The Harris 3 Silicon Bronze GTAW TIG Welding Rod (part number 03SIB60) is a copper-silicon alloy filler metal classified ERCuSi-A per AWS A5.7/A5.7M. Available in a 1/8 in (3.18 mm) diameter, 36-inch cut length, 10 lb box, this rod is the primary filler metal for TIG welding of copper alloys, silicon bronze fabrications, and — uniquely — for braze-welding mild steel, galvanized steel, and thin-gauge carbon steel with minimal heat input and negligible base-metal distortion. Harris Products Group, a Lincoln Electric company, manufactures this rod with tightly controlled silicon (2.8–4.0%) and copper (balance) content. The 1/8 in diameter is suited for medium-to-heavy silicon bronze fabrication and braze-welding of sheet steel in the 14 gauge–3/16 in range.

Silicon bronze TIG rod occupies a unique position in welding: the ERCuSi-A alloy melts at approximately 1,880°F (1,027°C) — well below mild steel's 2,600°F melting point. When used to braze-weld steel, the silicon bronze wets and flows onto the cleaned steel surface without melting the steel itself. This "cold TIG" technique on steel produces joints with virtually zero distortion, no zinc fume from galvanized coatings (because the steel is not melted), and a distinctive bronze-colored bead. It is widely used in automotive body panel repair, automotive manufacturing, bicycle frame building, and art metal fabrication.

Specifications & AWS Classification — ERCuSi-A Silicon Bronze

Best Applications for ERCuSi-A Silicon Bronze TIG Rod

• Silicon Bronze Fabrication: Custom silicon bronze sculptures, art metal projects, architectural bronze cladding, decorative metalwork, and bronze gate fabrication. ERCuSi-A provides the matching chemistry for silicon bronze (Everdur, CDA 655) base metal in full-fusion TIG joints.
• Automotive Body Panel Braze-Welding: Joining galvanized steel body panels, door skins, and floor sections on modern automobiles. At ERCuSi-A brazing temperatures, zinc coatings are not vaporized (unlike fusion MIG welding of galvanized steel), eliminating zinc fume hazard. German, Japanese, and American OEM automotive manufacturers specify silicon bronze braze-welding for zinc-coated structural panels.
• Bicycle Frame Building: Custom steel bicycle frames (chromoly, mild steel) traditionally brazed with silicon bronze for aesthetic bead character and low-distortion joining of thin-wall tubing. Silicon bronze TIG on frames avoids the heat distortion of fusion MIG welding on thin chromoly tubes.
• Thin-Gauge Steel Fabrication: Joining 18–14 gauge mild steel with minimal distortion. Automotive body shops, fabricators of HVAC sheet metal components, and custom metal art studios use silicon bronze TIG to join thin steel parts that would warp severely under fusion MIG or TIG at steel melting temperatures.
• Copper Pipe & Fitting Welding: GTAW joining of 1/2 in and larger copper water pipe and fittings with ERCuSi-A rod — an alternative to torch brazing where high-integrity weld joints with verified penetration are needed (fire suppression systems, high-pressure water, medical gas).
• Restoration & Repair: Antique bronze castings, bell metal repair, and art bronze restoration. The silicon bronze filler chemistry matches historical bronze compositions closely enough for sympathetic repairs that take patina treatments similarly to the original metal.

How to Use Harris Silicon Bronze TIG Rod — Settings, Gas & Polarity

Silicon bronze TIG welding uses DCEN polarity (same as stainless), 100% argon, and standard GTAW technique with key differences in heat management:

Polarity — DCEN: Silicon bronze and copper alloys use DCEN polarity for TIG welding. Do not use AC — the cathodic cleaning function of AC is for aluminum only and is not needed for copper alloys. DCEN provides the focused, penetrating arc needed to wet and flow the ERCuSi-A alloy.

Preheating Copper Base Metal: Pure copper (C102, C110) and thick copper alloy sections are highly thermally conductive — the workpiece conducts heat away from the weld zone faster than the arc can supply it without preheating. For copper sections above 1/8 in thickness, preheat to 400–500°F (204–260°C) before welding. For silicon bronze base metal (lower conductivity than pure copper), preheat is usually not required below 1/4 in thickness.

Heat Input Control for Braze-Welding Steel: When silicon bronze TIG braze-welding steel, keep amperage conservative — just enough to melt the bronze rod and wet the steel surface. Melting the steel base metal defeats the purpose of braze-welding. Steel distortion increases dramatically if amperage is set too high. For 16–18 gauge steel: 50–80 A DCEN. For 14 gauge steel: 80–110 A.

Shielding Gas: 100% argon at 18–22 CFH for most silicon bronze TIG work. For copper (high thermal conductivity requires slightly more shielding coverage on the spreading weld pool): 20–25 CFH with a gas lens cup size #7–8.

Storage & Handling for Silicon Bronze TIG Rod

• Dry Storage: Store in original sealed box in a dry location (below 50% RH, 40–120°F). Copper alloys are not hydrogen-sensitive like aluminum, but moisture on the rod can cause porosity in the weld pool. Keep boxes sealed when not in use.
• Oxidation on Storage: Silicon bronze develops a green-brown tarnish (surface oxidation) when stored for long periods in humid conditions. Light surface tarnish is acceptable and does not significantly affect weld quality. Heavy scale or pitting should be cleaned with fine abrasive before use.
• Handling: Skin oils and cutting lubricants transferred to the rod can cause porosity in copper alloy TIG welds. Handle with clean gloves or a clean cloth. Wipe rods with acetone if contaminated before use.
• Separate from Steel Rods: Label silicon bronze boxes clearly to prevent confusion with mild steel TIG rods (which look similar in the 1/8 in diameter). Accidentally using ERCuSi-A on a structural steel joint produces a very low-strength braze joint — not a fusion weld.
• Ventilation During Use: Silicon bronze welding generates copper fume. Ensure adequate local exhaust ventilation (LEV) at the welding station. Copper fume fever is an industrial health concern with copper alloy welding — do not weld in enclosed spaces without forced ventilation or respiratory protection.

Compatible Machines & Base Metals for ERCuSi-A TIG Rod

Silicon bronze TIG rod uses the same DC TIG machines as stainless and mild steel TIG welding:

• Lincoln Electric Invertec V155-S: Compact DC TIG machine suitable for light silicon bronze fabrication and braze-welding thin steel. Easy portability for body shop or field repair work.
• Lincoln Electric Square Wave TIG 200 (K5126-1): Versatile AC/DC TIG with DC mode for silicon bronze; also covers aluminum TIG work in the same shop with one machine.
• Any DC GTAW/SMAW machine with DCEN output: ERCuSi-A rod requires only DC electrode negative — any DC TIG power source works.

Technical Reference — ERCuSi-A Silicon Bronze TIG Rod: AWS Classification, Metallurgy & Application Guide

Silicon bronze (Harris ERCuSi-A) is a fundamentally different TIG filler from steel or aluminum rods — it is a copper-base alloy used for braze-welding (brazing at welding amperage) rather than fusion welding in most applications. Understanding this distinction is essential for correct application and technique.

AWS A5.7 Classification & Chemistry

Harris ERCuSi-A is classified per AWS A5.7/A5.7M (Copper and Copper-Alloy Bare Welding Rods and Electrodes): Cu ≥94%, Si 2.8–4.0% (primary alloying element), Mn 1.0–1.5%, Sn ≤0.25%, Zn ≤1.0%, Fe ≤0.50%, Pb ≤0.02%. Silicon provides two functions: (1) solid-solution strengthening of the copper matrix, and (2) oxide film formation during welding that protects the melt pool from atmospheric oxygen without requiring flux.

Why 1/8 in Diameter — Production Applications

The 1/8 in (3.175 mm) diameter is the largest standard TIG rod size and is designed for production braze-welding applications requiring fast filler deposit rates:

• Heavy-gauge galvanized sheet braze-welding: 14–10 gauge (0.075–0.135 in) galvanized HVAC ductwork, rooftop unit frames, refrigeration panel corners. The 1/8 in rod provides deposition volume for production-rate corner and seam braze-welding.
• Architectural copper-to-steel joints: Copper cladding attachment to structural steel frames, copper gutter-to-iron gutter bracket joints, copper-to-steel braze-welded connections in building facades.
• Bronze sculpture repair: Large-scale bronze casting repair, museum conservation braze-welding, and bronze public art restoration where significant filler volume is needed to fill voids and rebuild lost sections.
• Copper plumbing to cast iron: Joining copper pipe to cast iron drain fittings (drain-waste-vent systems) in older building renovation where compatible flux-free joining is needed.

ERCuSi-A Braze-Welding vs Fusion Welding — The Technical Distinction

In most ERCuSi-A TIG applications, the base metal (steel, galvanized steel, cast iron) is NOT melted — the base metal is heated to brazing temperature (1500–1700°F / 815–927°C) and the silicon bronze filler flows into the joint by capillary action and wetting. This is braze-welding (not true fusion welding). Benefits of braze-welding over fusion welding:

• No zinc fuming on galvanized steel (base metal stays below zinc volatilization temperature)
• Less distortion — lower heat input to the steel base metal
• Can join dissimilar metals (copper to steel, steel to cast iron) without compatibility issues
• Cosmetically excellent on galvanized: smooth, flush braze bead with good cosmetics

Electrical and Thermal Conductivity of ERCuSi-A Deposits

ERCuSi-A deposits have significantly reduced electrical conductivity compared to pure copper ERCu rod: approximately 7–9% IACS (vs ≥85% IACS for ERCu). The silicon alloying that provides oxidation resistance and flow characteristics dramatically reduces conductivity. Do not use ERCuSi-A silicon bronze rod for electrical bus bar, conductor, or electrical connection welding — use Harris ERCu deoxidized copper rod for those applications.

Post-Braze Cleaning

ERCuSi-A braze welds on steel and galvanized steel require wire brushing and light grinding to remove the copper-oxide surface film that forms on the deposit exterior. The bulk bead metal underneath the surface film is sound; the surface film is cosmetically rough but not structurally significant. For painted or powder-coated finishes, grind flush and apply zinc-rich primer to any exposed steel areas adjacent to the braze bead before topcoating.

FAQs — Harris Silicon Bronze TIG Welding Rod ERCuSi-A

Q1: What is the difference between silicon bronze TIG welding and brazing?
Silicon bronze TIG welding uses an electric arc (GTAW process) to melt the silicon bronze filler rod and deposit it onto the base metal. Conventional brazing uses an oxy-fuel torch and flux without an electric arc. Both processes can join steel at below-steel-melting temperatures using copper-based filler. Silicon bronze TIG (braze-welding) provides more precise heat control, no flux, no post-weld flux removal, and better penetration at joints — particularly useful for production automotive work and artistic metalwork requiring clean, controllable deposits.

Q2: Why use silicon bronze TIG rod on galvanized steel instead of just welding it with ER70S-6?
When you fusion-weld galvanized steel with ER70S-6 (or any steel filler at steel melting temperatures), the zinc coating in the weld zone vaporizes at ~1,665°F — producing zinc oxide fumes that cause zinc fume fever (a temporary but unpleasant industrial illness) and burning off the protective coating. Silicon bronze TIG braze-welding runs cool enough that the zinc is not vaporized — the base steel does not melt, the zinc coating immediately around the bead is minimally affected, and zinc fume generation is greatly reduced. Modern automotive OEMs specify braze-welding for joining zinc-coated structural panels for exactly this reason.

Q3: Can silicon bronze TIG welding be used on structural steel joints?
Silicon bronze TIG (braze-welding) does not produce a fusion weld — it forms a metallurgical bond (braze bond) between the bronze deposit and the steel surface. The joint strength is limited by the bronze deposit's properties (55,000 psi tensile) and the braze interface. For structural steel joints subject to code compliance (AWS D1.1), braze-welding with ERCuSi-A is not a recognized pre-qualified procedure. Silicon bronze braze-welding on steel is appropriate for automotive, artistic, bicycle, and light fabrication applications where the structural load is not code-governed.

Q4: What filler should I use to TIG weld copper pipe?
ERCuSi-A (silicon bronze) is the most common TIG filler for copper pipe and fitting joints. For high-conductivity copper C110 at thickness above 3/16 in, preheating to 400–500°F before welding is required to prevent the copper's thermal conductivity from chilling the weld pool too quickly. For thin-wall copper tube (below 1/8 in), ERCuSi-A without preheat typically works at 80–120 A DCEN with careful arc length control. Alternative filler options include ERCu (deoxidized copper rod) and ERCuSn-A (phosphor bronze) for specific application requirements.

Q5: Does silicon bronze TIG welding require flux?
No. Silicon bronze TIG welding uses the argon shielding gas to prevent oxidation — flux is not required. This is a significant advantage over torch brazing with silver alloy or copper alloy brazing rods, which require flux and post-braze flux cleaning. The absence of flux also means no flux residue that can cause corrosion on copper plumbing or bronze art work.

Q6: What causes orange/red sparks when welding with silicon bronze TIG rod?
Orange sparks during silicon bronze TIG welding typically indicate either zinc contamination (from galvanized steel base metal) or excessive amperage causing the base metal steel to partially melt. If welding galvanized steel, some sparking is expected as the zinc coating near the bead edge volatilizes. Reduce amperage to minimize base metal heating. If sparking occurs on clean silicon bronze fabrication (non-galvanized), check for zinc-bearing base metal or clean the bronze for surface contaminants.

Q7: Can I braze-weld stainless steel with silicon bronze TIG rod?
Yes. Silicon bronze TIG can braze-weld stainless steel in thin-gauge applications where very low heat input is required — for example, joining thin stainless panels to mild steel frames with minimal distortion. The joint is a braze joint (not a fusion stainless weld), so for applications requiring stainless corrosion resistance in the weld zone, a stainless fusion TIG weld with ER308L or ER316L is preferred. Silicon bronze on stainless creates a copper-alloy deposit that will not match stainless corrosion resistance.