How to Weld Brass to Brass: 3 Methods and 5 Tips Explained

Welding brass to brass can be a tricky endeavor, especially for the DIY enthusiast. TIG weld brass with AC, 70% EN, 30% EP, argon@15-25 CFH. Clean, bevel >3mm@70-90°. Preheat 200-400°F. Use ERCuSi-A filler. 50-80A, small puddle, push technique. Backstep >1/4″. Tack every 2-3″. Cool slowly. Clean flux, restore color. Tensile: 70-80 ksi. Elongation: 25-35%.

In this comprehensive guide, we’ll dive into the nitty-gritty details of brass welding, providing you with a step-by-step playbook for your DIY welding projects.

Choosing the Right Welding Method

There are three primary welding methods suitable for brass:

TIG (GTAW) Welding:

• Use AC current with a pure tungsten electrode (2% thoriated or lanthanated).
• AC current helps to break up the oxide layer on the brass surface, promoting better weld penetration.
• Employ a gas lens and a large gas cup (up to #12) for optimal shielding gas coverage.
• Argon or a 75/25 argon/helium mix shielding gas is recommended, flowing at 15-25 CFH.
• Set the AC balance to 70% electrode negative (EN) and 30% electrode positive (EP) for proper oxide cleaning action.
• Maintain a short arc length (0.5-1mm) and use a slight weaving motion.

MIG (GMAW) Welding:

• Use 100% argon shielding gas at 25-30 CFH for improved weld pool fluidity and reduced spatter.
• Select a silicon bronze filler wire (ERCuSi-A) with a diameter between 0.8-1.2mm.
• Set the wire feed speed to 200-300 inches per minute (IPM) and the voltage to 16-18V for a stable arc.
• Pulsed MIG can help control heat input and minimize distortion, with a peak current of 200A and a background current of 50A.

Oxyacetylene Welding:

• Use a #2 or #3 tip size for most brass thicknesses.
• Adjust the flame to be slightly oxidizing (1/16″ feather of excess acetylene) to compensate for the zinc content.
• Select a silicon bronze or copper-silicon filler rod with a diameter of 1.6-2.4mm.
• Apply a suitable brazing flux to the joint and heat evenly until the flux melts and the brass reaches a dull red color.
• Maintain a consistent travel speed and add filler rod to the leading edge of the puddle.

Preparing the Brass

Proper preparation is crucial for successful brass welding:

1. Identify the zinc content of your brass using a handheld XRF analyzer or by consulting the supplier. Brasses with higher zinc content (up to 45%) are more susceptible to zinc fuming and cracking during welding.
2. Clean the brass thoroughly using a stainless steel wire brush, 120-grit sandpaper, or a chemical cleaner like acetone. Remove all surface oxides, oils, and contaminants to ensure proper weld fusion.
3. For brass thicknesses greater than 3mm (1/8″), bevel the joint edges to a 70-90° included angle using a grinder or file. This ensures complete penetration and reduces the risk of lack of fusion defects.
4. Preheat the brass to 200-400°F (93-204°C) using an oxy-fuel torch or induction heating system. Use temperature indicating crayons or a contact thermocouple to monitor the preheat temperature accurately. Preheating reduces thermal stress and minimizes zinc vaporization during welding.

Filler Metal Selection

Choosing the right filler metal is essential for achieving a strong, crack-free brass weld:

• Silicon bronze (ERCuSi-A) is the most commonly used filler for brass welding. It offers good wetting properties, high tensile strength (up to 80,000 psi), and a close color match to brass.
• Copper-tin filler metals like ECuSn-C (phosphor bronze) can also be used for welding brass. They provide even higher tensile strength (up to 100,000 psi) but may be more prone to cracking in restrained joints.
• For oxyacetylene welding, use a bare silicon bronze or copper-silicon filler rod with a diameter between 1.6-2.4mm.

Filler Metal	AWS Classification	Composition	Tensile Strength (psi)	Elongation (%)
Silicon Bronze	ERCuSi-A	Cu: 94-96%, Si: 2.8-4%, Mn: 0.5-1.5%, Fe: 0.5% max	70,000-80,000	25-35
Phosphor Bronze	ECuSn-C	Cu: 92-94%, Sn: 4-6%, P: 0.15-0.35%	80,000-100,000	10-20

Welding Technique Tips

Mastering brass welding technique is key to avoiding defects and achieving strong, ductile joints:

• Use the lowest heat input possible to minimize zinc fuming and distortion. This may require using lower amperage settings (50-80A for TIG, 80-120A for MIG) and multiple passes on thicker brass sections.
• Maintain a short arc length (0.5-1mm) and a small weld puddle. Use a push technique and add filler metal frequently to keep the puddle cool and control the weld bead shape.
• On brass thicknesses greater than 6mm (1/4″), use a backstep or skip welding technique to control heat input and minimize distortion. Weld in 1-2″ segments, allowing each segment to cool before welding the next.
• Due to brass’s high thermal expansion and contraction rate, it’s crucial to use tack welds and fixturing to maintain joint alignment during welding. Space tack welds every 2-3″ along the joint.
• After welding, allow the brass to cool slowly by covering it with an insulating blanket or burying it in sand. Slow cooling helps to reduce residual stress and prevent cracking.

Post-Weld Cleaning and Finishing

To restore the appearance and corrosion resistance of your brass weld, follow these post-weld cleaning steps:

1. Remove any slag, spatter, or oxide residue from the weld using a stainless steel wire brush or a glass bead blaster.
2. If flux was used during oxyacetylene welding, remove the flux residue using warm water and a soft brush. Rinse thoroughly and dry the weld with compressed air.
3. To restore the original brass color, apply a brass-tone chemical cleaner (like Brasso) to the weld using a soft cloth. Rub the cleaner in a circular motion until the desired color match is achieved.
4. For a polished finish, sand the weld using progressively finer grit sandpaper (120, 240, 400, 600 grit) and then buff with a polishing wheel and compound.

References:

Welding With Brass

Brass Welding Techniques