Welding aluminum alloys

The question often comes up 'Isn't there one filler metal I can use for all my aluminum welding?' The answer, unfortunately, is no. However, there are basic rules for filler metal selection. First, know which aluminum alloys will be welded (Fig. 1). If all you know is that you have aluminum, that is not enough information to choose a filler metal.


Key Concepts
  • You must know the composition of both base metals to be joined when selecting a filler metal.

  • Two alloys satisfy 80% of filler metal requirements.

  • Improper filler metals can cause brittle welds.

80% of applications
20% of applications

The question often comes up "Isn't there one filler metal I can use for all my aluminum welding?" The answer, unfortunately, is no. However, there are basic rules for filler metal selection.

First, know which aluminum alloys will be welded (Fig. 1). If all you know is that you have aluminum, that is not enough information to choose a filler metal. Once the aluminum alloys are known, that you will be joining alloy A to alloy B, there are a number of good tables for selecting filler metals (see table).

Filler metal selection can be simplified somewhat. Almost all of the aluminum filler metals fall into either the aluminum-silicon 4XXX series or the aluminum-magnesium 5XXX series.

Overall in North America, 80% of the aluminum filler metal sold is made from just two alloys, 4043 and 5356. Also, one of these two alloys is the right choice for 80% of applications.

80% of applications

Alloy 4043 works very well for joining any of the 6XXX extrusion/sheet/plate alloys, such as 6061 or 6063. It also works well for welding most casting alloys and for welding 6XXX alloys to castings. However, 4043 should not, with one exception, be used to weld the 5XXX alloys.

Alloy 4043 has a 5% silicon (Si) content, while the 5XXX alloys contain as much as 6% magnesium (Mg). If welding 5XXX alloys with 4043, a lot of the intermetallic compound Mg 2 Si is formed, which is very brittle and can adversely affect the toughness and ductility of the weld.

What about exceptions? The common alloy 5052 contains only 21/2% magnesium. Because of its low magnesium content, it is acceptable and common to weld it using 4043.

One time 4043 should not be used to weld 6XXX alloys is when the material will be anodized after welding. If 4043 is used, the weld will anodize with a very dark, unpleasant color. In this case 5356, should be used.

Alloy 5356 works very well for joining 5XXX alloys, 6XXX alloys, and 5XXX alloys to 6XXX alloys. However, it should never be used to weld any of the 2XXX alloys or other alloys containing copper, such as 6013 or 6111 because the weld will very likely crack.

Both 4043 and 5356 work well when welding 6XXX alloys. Which one should be chosen? 5356 will provide welds that have higher shear strength and better ductility, although the welds will show more black weld smut (Fig. 2). 4043 will be easier for the welder to use, will deposit a better looking weld, and will be less crack sensitive.

20% of applications

Filler alloy 2319 is specifically designed to weld alloys 2219 and 2319.

Filler alloy 4643 has been specifically designed to be heat treatable. When welding a component which will be completely heat treated (solution treated, quenched, and aged) after welding to re-establish T6 properties, consider using 4643. It will result in welds of 40 ksi after heat treating.

The 5XXX alloys with magnesium content above 3% (5356 falls into this category) can become susceptible to stress corrosion cracking if they are exposed to temperatures above 150 F for long periods of time. In this case, a filler alloy of lower magnesium content than 5356 should be used.

Filler alloy 5554 was developed specifically for this purpose.

Many welding codes require welds in higher strength 5XXX alloys, such as 5083 or 5456, to have a minimum tensile strength of 40 ksi. While welding these alloys using 5356 will sometimes meet this requirement, tensile samples will often fail to meet it, failing at 38 ksi or 39 ksi. If there are such tensile failures, consider changing to filler alloy 5556 or 5183.

When welding the 6XXX alloys and/or castings and there are cracking problems, including crater cracking, consider changing to 4047. Filler alloy 4047 is similar to 4043 but contains 12% silicon, has a narrower melting range than 4043, and is more resistant to cracking.

Portion of a filler metal guide table

Notes: Filler metals shown in table.
Guidelines in this table apply to gas-shielded arc welding processes.
%%POINT%% Welding not recommended
Base metal 607069515456545452545086508356525050

Top Plant
The Top Plant program honors outstanding manufacturing facilities in North America.
Product of the Year
The Product of the Year program recognizes products newly released in the manufacturing industries.
System Integrator of the Year
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
October 2018
Tools vs. sensors, functional safety, compressor rental, an operational network of maintenance and safety
September 2018
2018 Engineering Leaders under 40, Women in Engineering, Six ways to reduce waste in manufacturing, and Four robot implementation challenges.
GAMS preview, 2018 Mid-Year Report, EAM and Safety
October 2018
2018 Product of the Year; Subsurface data methodologies; Digital twins; Well lifecycle data
August 2018
SCADA standardization, capital expenditures, data-driven drilling and execution
June 2018
Machine learning, produced water benefits, programming cavity pumps
Spring 2018
Burners for heat-treating furnaces, CHP, dryers, gas humidification, and more
October 2018
Complex upgrades for system integrators; Process control safety and compliance
September 2018
Effective process analytics; Four reasons why LTE networks are not IIoT ready

Annual Salary Survey

After two years of economic concerns, manufacturing leaders once again have homed in on the single biggest issue facing their operations:

It's the workers—or more specifically, the lack of workers.

The 2017 Plant Engineering Salary Survey looks at not just what plant managers make, but what they think. As they look across their plants today, plant managers say they don’t have the operational depth to take on the new technologies and new challenges of global manufacturing.

Read more: 2017 Salary Survey

The Maintenance and Reliability Coach's blog
Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
One Voice for Manufacturing
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Maintenance and Reliability Professionals Blog
The Society for Maintenance and Reliability Professionals an organization devoted...
Machine Safety
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
Research Analyst Blog
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Marshall on Maintenance
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
Lachance on CMMS
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
Material Handling
This digital report explains how everything from conveyors and robots to automatic picking systems and digital orders have evolved to keep pace with the speed of change in the supply chain.
Electrical Safety Update
This digital report explains how plant engineers need to take greater care when it comes to electrical safety incidents on the plant floor.
IIoT: Machines, Equipment, & Asset Management
Articles in this digital report highlight technologies that enable Industrial Internet of Things, IIoT-related products and strategies.
Randy Steele
Maintenance Manager; California Oils Corp.
Matthew J. Woo, PE, RCDD, LEED AP BD+C
Associate, Electrical Engineering; Wood Harbinger
Randy Oliver
Control Systems Engineer; Robert Bosch Corp.
Data Centers: Impacts of Climate and Cooling Technology
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
Safety First: Arc Flash 101
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
Critical Power: Hospital Electrical Systems
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
Design of Safe and Reliable Hydraulic Systems for Subsea Applications
This eGuide explains how the operation of hydraulic systems for subsea applications requires the user to consider additional aspects because of the unique conditions that apply to the setting
click me