SAE 660 bronze, also known as leaded tin bronze, is a versatile and widely used material in various industries due to its excellent combination of mechanical properties, corrosion resistance, and machinability. As a trusted supplier of SAE 660 bronze products such as Lead Tin Bronze Hollow Bar, Leaded Tin Bronze Bar, and Bronze Hollow Bars, we understand the importance of proper welding techniques when working with this alloy. In this blog post, we will discuss the key welding considerations for SAE 660 bronze to help you achieve high-quality welds and ensure the integrity of your projects.
Understanding SAE 660 Bronze
SAE 660 bronze is a copper-based alloy that typically contains around 88% copper, 10% tin, and 2% lead. The addition of tin provides increased strength and hardness, while the lead improves machinability and lubricity. This alloy is known for its good corrosion resistance in a variety of environments, including freshwater, seawater, and many chemicals. It also has excellent wear resistance, making it suitable for applications such as bearings, bushings, gears, and valve components.
Welding Process Selection
When welding SAE 660 bronze, the choice of welding process is crucial to ensure a successful weld. Here are some commonly used welding processes for SAE 660 bronze and their considerations:
Gas Tungsten Arc Welding (GTAW/TIG)
GTAW, also known as TIG welding, is a popular choice for welding SAE 660 bronze due to its precise control and high-quality welds. This process uses a non-consumable tungsten electrode to create an arc between the electrode and the workpiece. A shielding gas, typically argon or a mixture of argon and helium, is used to protect the weld pool from oxidation.
Advantages:
- Precise control over heat input and weld bead shape
- Produces high-quality, clean welds with minimal spatter
- Suitable for thin and thick sections of SAE 660 bronze
- Can be used with or without filler metal
Considerations:
- Requires a high level of skill and experience
- Slower welding speed compared to other processes
- The presence of lead in SAE 660 bronze can cause some vaporization, which may require proper ventilation
Gas Metal Arc Welding (GMAW/MIG)
GMAW, or MIG welding, is a faster welding process compared to GTAW. It uses a consumable wire electrode that is fed continuously through a welding gun. A shielding gas, such as argon or a mixture of argon and carbon dioxide, is used to protect the weld pool.
Advantages:
- High welding speed, making it suitable for large-scale production
- Less skill required compared to GTAW
- Can be used with a variety of filler metals
Considerations:
- Higher heat input compared to GTAW, which may cause more distortion
- The presence of lead in SAE 660 bronze can cause some porosity in the weld if not properly controlled
- Requires a good understanding of process parameters to achieve high-quality welds
Shielded Metal Arc Welding (SMAW)
SMAW, also known as stick welding, is a simple and versatile welding process that uses a consumable electrode coated with a flux. The flux provides shielding gas and forms a slag that protects the weld pool from oxidation.
Advantages:
- Portable and suitable for field welding
- Can be used in various positions
- Relatively inexpensive equipment
Considerations:
- Slower welding speed compared to GMAW
- Requires more skill to control the arc and weld bead shape
- The slag must be removed after welding, which can be time-consuming
Filler Metal Selection
The choice of filler metal is an important factor in achieving a successful weld when working with SAE 660 bronze. The filler metal should have similar chemical composition and mechanical properties to the base metal to ensure good compatibility and strength. Here are some common filler metals used for welding SAE 660 bronze:
Copper-Tin Filler Metals
Copper-tin filler metals, such as AWS A5.7 ERCuSn-A or ERCuSn-C, are commonly used for welding SAE 660 bronze. These filler metals have a similar composition to the base metal and provide good strength and corrosion resistance.
Copper-Silicon Filler Metals
Copper-silicon filler metals, such as AWS A5.7 ERCuSi-A, are also suitable for welding SAE 660 bronze. They offer good fluidity and can be used for both fusion and braze welding applications.
Specialized Bronze Filler Metals
There are also specialized bronze filler metals available that are formulated specifically for welding SAE 660 bronze. These filler metals may contain additional elements to improve the weld properties, such as increased strength or better resistance to specific environments.
Welding Preparations
Proper welding preparations are essential to ensure the quality of the weld and the integrity of the joint. Here are some key preparations to consider when welding SAE 660 bronze:
Cleaning
The surface of the workpiece must be clean and free of any contaminants, such as oil, grease, dirt, or oxide layers. Use a suitable solvent or cleaning agent to degrease the surface, and then use a wire brush or grinder to remove any oxide layers.
Joint Design
The joint design plays a crucial role in the strength and quality of the weld. For SAE 660 bronze, common joint designs include butt joints, lap joints, and T-joints. The joint design should be selected based on the application requirements, such as the load capacity, the thickness of the materials, and the welding process.
Preheating
Preheating the workpiece before welding can help reduce the risk of cracking and improve the weld quality. The preheating temperature for SAE 660 bronze typically ranges from 150°C to 300°C (300°F to 600°F), depending on the thickness of the materials and the welding process. However, preheating should be carefully controlled to avoid overheating, which can cause the lead in the alloy to vaporize.
Welding Parameters
The welding parameters, such as the welding current, voltage, travel speed, and shielding gas flow rate, must be carefully selected to ensure a successful weld. The optimal welding parameters depend on the welding process, the thickness of the materials, the joint design, and the filler metal used. Here are some general guidelines for setting the welding parameters when welding SAE 660 bronze:
GTAW/TIG Welding
- Welding current: The welding current should be adjusted based on the thickness of the materials and the diameter of the tungsten electrode. For thin sections, a lower current may be used, while for thicker sections, a higher current may be required.
- Voltage: The voltage should be set to maintain a stable arc. A higher voltage may be used for longer arc lengths, but this can also increase the heat input and the risk of porosity.
- Travel speed: The travel speed should be adjusted to ensure proper fusion and penetration. A slower travel speed may be used for thicker sections, while a faster travel speed may be used for thinner sections.
- Shielding gas flow rate: The shielding gas flow rate should be set to provide adequate protection for the weld pool. A typical flow rate for argon shielding gas is 10 to 20 cubic feet per hour (CFH).
GMAW/MIG Welding
- Welding current: The welding current should be adjusted based on the thickness of the materials and the diameter of the wire electrode. A higher current may be required for thicker sections, while a lower current may be used for thinner sections.
- Voltage: The voltage should be set to maintain a stable arc and proper droplet transfer. The optimal voltage depends on the wire feed speed and the shielding gas used.
- Travel speed: The travel speed should be adjusted to ensure proper fusion and penetration. A faster travel speed may be used for thinner sections, while a slower travel speed may be required for thicker sections.
- Shielding gas flow rate: The shielding gas flow rate should be set to provide adequate protection for the weld pool. A typical flow rate for argon shielding gas is 20 to 30 CFH.
SMAW Welding
- Welding current: The welding current should be adjusted based on the thickness of the materials and the diameter of the electrode. A higher current may be required for thicker sections, while a lower current may be used for thinner sections.
- Arc length: The arc length should be maintained at a constant distance between the electrode and the workpiece. A longer arc length can increase the heat input and the risk of porosity, while a shorter arc length can cause the electrode to stick.
- Travel speed: The travel speed should be adjusted to ensure proper fusion and penetration. A slower travel speed may be used for thicker sections, while a faster travel speed may be used for thinner sections.
Post-Weld Treatment
After welding, it is important to perform post-weld treatment to ensure the quality and integrity of the weld. Here are some common post-weld treatments for SAE 660 bronze:
Stress Relieving
Stress relieving can help reduce the residual stresses in the weld and the base metal, which can improve the fatigue life and the corrosion resistance of the joint. The stress relieving temperature for SAE 660 bronze typically ranges from 200°C to 300°C (400°F to 600°F), depending on the thickness of the materials and the welding process.
Cleaning and Inspection
The weld should be cleaned to remove any slag, spatter, or other contaminants. A wire brush or grinder can be used to clean the surface of the weld. After cleaning, the weld should be inspected for any defects, such as cracks, porosity, or lack of fusion. Visual inspection, penetrant testing, or ultrasonic testing can be used to detect any defects in the weld.
Conclusion
Welding SAE 660 bronze requires careful consideration of the welding process, filler metal selection, welding preparations, welding parameters, and post-weld treatment. By following the guidelines and best practices outlined in this blog post, you can achieve high-quality welds and ensure the integrity of your projects. As a leading supplier of SAE 660 bronze products, we are committed to providing you with the highest quality materials and technical support to help you succeed in your welding applications. If you have any questions or need further assistance, please do not hesitate to contact us. We look forward to discussing your requirements and working with you to find the best solutions for your projects.
References
- Metals Handbook: Welding, Brazing, and Soldering, Volume 6, 9th Edition, American Society for Metals
- Welding Metallurgy and Weldability of Copper and Copper Alloys, John C. Lippold and Donald L. Kotecki
- AWS A5.7 Specification for Bare Copper and Copper - Alloy Welding Rods and Electrodes