Metals are some of the most abundant substances globally, making them a viable resource pool for welders. Having the ability to twist and alter such unique pieces is thrilling. However, not all metals are as malleable as welders would like. What is the hardest metal to weld?
Aluminum and titanium often pop up in the industry as the hardest metals to weld. They have chemical and physical properties that make them difficult to manipulate into desired forms, unlike other metals like stainless steel.
This article delves into the characteristics of a strong weld and the hardest metal to weld. I also explain why welds fail and the strongest type of welds.
How Do I Know If My Weld Is Strong?
Many objects people rely on in the modern world are built on metal. From your cars to your stainless steel coffee pot to the skyscrapers and bridges you frequent, welding puts the pieces of the structure together.
Assessing the quality of your welds can be challenging, especially if you taught yourself. Another factor to consider in gauging your work is that different welding processes exist.
Each welding process produces a different kind of weld, and there are no rules across the board to tell apart good and bad welds. Regardless, strength and quality are two features to look out for in your weld. Here are some visual indicators of good and bad welds according to the welding processes:
- Stick weld characteristics
Good—consistent thickness, straight and uniform, no spatter drops, no cracks in the bead.
Bad—inconsistent bead width, visible spatter, undercutting, or breaks in the bead.
- MIG weld characteristics
Good—no slag, straight and uniform, no cracking or holes, smooth with no pattern.
Bad—lacks strength, thin bead, cracking along the weld, a lack of discoloration of the parent metal, lack of straightness and uniformity.
- TIG weld characteristics
Good—patterned, no slag or burnout, visually appealing, tiny welds neatly layered.
Bad—signs of burnout, erratic beads, wide with no distinct pattern.
Although there are visual tells of the quality of a weld, a weld that doesn’t look good is not necessarily a bad weld. Welding tests go past the appearance of a weld in ensuring its strength and quality. Some testing techniques are:
- Back Bend Test
- Physical Weld Testing
- Magnaflux Test
- Electromagnetic Tests
- X-Ray Testing
- Acoustic Emission Testing.
Welds are tested by putting them under conditions similar to or more than what structures in the field experience.
What Is the Hardest Metal to Weld?
While aluminum and titanium ate hard metals to weld, the welding procedure used also contributes to the difficulties you encounter when working with them. Each welding process has its unique challenges, and some metals flow better with some methods.
With that in mind, look at these factors that make these metals hard to weld:
- Aluminum has an oxide coat that is difficult to get through, and it gets hot very quickly (melting point). You must understand its chemical and physical properties in its alloy or ore form before using it.
- The melting point, ductility, and conductivity of aluminum make it unstable.
- Aluminum heats up without “glowing” or a significant color change, causing easy oxidation within the melting weld bead.
- Heated aluminum immediately sags, melts out, and drips to the floor, so building up a part to fill and join is difficult.
- Aluminum requires expensive wire feeders that cannot be used with other welding and more expensive gas and electrical setups.
Titanium requires a zero oxygen environment for welding, and it is costly too. However, it may be easier to handle than aluminum, and it is not as common as aluminum, so welders don’t encounter it often.
Why Do Welds Fail?
Welds fail due to weld defects and many other reasons. When assessing weld failures, it is important to know that a combination of many things rather than a single problem causes most failures.
Lost productivity, safety concerns, and the cost of reworking poor-quality welds are some incentives to prevent weld failures. Reasons for weld failure include:
- Poor weld design or part
Incorrect interpretation of the part design or design errors can cause welds to fail. A small weld cannot support its intended load in a structure, causing failure from compression, bending loads, or tension.
- Inadequate welding procedure
Temperature control, specifics about using the filler metal, and shielding gas properties are instructions to follow closely.
- Stress risers—appear as weld defects, including porosity, undercut, inclusions, hot and cold cracking.
- Poor welding techniques from a lack of training, experienced welders with bad habits, or new welding operators with low skill sets can cause weld failures.
- Incorrect testing or inspection.
Understanding and avoiding weld failures will lead to higher efficiency and product quality.
What Is the Strongest Type of Weld?
Because all welding processes can produce different welds, selecting one as the strongest can be tricky. However, some types of welding generally have stronger welds than others, depending on the materials being welded.
Among the welding processes, Tungsten Inert Gas (TIG) welding is the strongest welding. It is probably the most expensive arc welding process, and it produces the highest quality welds.
TIG welding was first used in 1959 when George Farcas invented it, and it is used mainly in the aerospace industry. It uses a special resistance wire (TIG welder), and it is a manual process that requires the welder to operate the machine with two hands while keeping a foot on the foot pedal.
These are some reasons it is the strongest welding:
- TIG welding has a slow travel speed, and the heat input can be relatively high, producing good metal fusion.
- There is no flux, so no micro-inclusions are present to lower the mechanical properties of the weld.
- Using pure argon as the shielding gas on carbon and stainless steel results in low oxygen content in the weld metal and enhances its mechanical properties.
- TIG welding melts the metal completely, preventing deformation and shrinking to ensure a strong joint.
- It requires a high skill level and is more time-consuming. Compared to the other arc welding methods, TIG welding produces more precise and cleaner welds – it doesn’t create splatter.
Choosing the strongest weld for your project ensures its quality, durability, and safety.