Weld ability is the most crucial factor to consider when choosing metal for welding. Although it is possible to weld all metals, some specialized metals require more advanced welding techniques. Additionally, the weldability of a metal depends on using the correct type of welder. The goal of any welder is to achieve clean welds that are free of cracks and don’t break under stress. So, you need to know the importance of what is weldability and how does it affect the type of metals you want to weld together.
Are you starting a career in welding or thinking about taking up welding as a hobby? If so, this article is for you. This article answers questions about what is weldability and how you can determine the weldability of metals. Additionally, you will learn how to identify a good weld from a bad one.
Definition of Weldability
Weld-ability is defined as the ability of two metals to be joined together using the welding process. Good weldability is when minimal effort produces a sound weld that won’t crack or break under pressure. Poor weld-ability refers to metal that requires careful preparation and specialized welding techniques to create a strong weld.
Before attempting to weld two metals, a welder must consider their join-ability. For example, certain types of metal require MIG or TIG welding. Additionally, the number of processes used to create a weld can impact the weld’s strength and quality. Therefore, the definition of weldability depends on several things.
How to Determine What is Weldability of the Metal you are Using
Several factors determine the weldability of a material. These factors can be the composition of the material, the heat treatment applied to the material, and the welding process used. A standard method for determining the weldability of a material is to use tension testing. This test measures the strength of the material after welding.
To determine a material’s weldability, the welder would create a test piece. Then to determine if the weld was successful, the welder would use one or more tests that measure different aspects of weldability.
Weldability tests include the following:
- Hydrogen-induced cold cracking — Many alloys and metals can become weaker when hydrogen atoms start to land in their crystalline structures. However, some metals are more susceptible to hydrogen-induced cracking (HIC) than others.
- Lamellar tearing — This type of failure mode has been virtually eliminated with cleaner steels and innovative manufacturing techniques.
- Spot-weld peeling — The excessive hardenability that can occur when spot welding high-strength, low-alloy steel can be an issue. This happens when using the equivalent carbon content as a parameter to evaluate the propensity for failure.
The main factors determining the weldability of metal are the electrode material, cooling rate, shielding gas supply, weld preparation, and welding speed.
Here is an overview of how to determine what is weldability of certain materials.
Type of material: Only certain welding types are appropriate for specific materials. For example, arc welding using a stick, MIG, or TIG welder is suitable for steel, stainless steel, or cast iron. However, if you plan to weld copper or brass, you must use TIG welding.
Welding process: There are 67 different welding processes. Factors affecting weldability include how the heat is applied, how much pressure is necessary, the type of welding equipment used, and the welding speed.
Weld preparation: A metal’s weldability also depends on how much preparation is necessary before joining the metals. For example, it’s essential to thoroughly clean rusted, painted, greasy, or dirty metal to remove contaminants from the base material. Clean surfaces result in good join-ability and a quality weld
Joint analysis and structure: Before welding any material, it is vital to determine its weldability by analyzing the joints. The metal’s thickness, size, and position can affect the welding process. You should also check the arc visibility to decide on the correct welding procedure.
Melting point: Good weldability relies on using metals having a medium melting point. Certain types of metals or thin metals are more challenging to weld. This is because it requires greater skill and usually more expensive equipment to achieve a consistent weld.
How to Identify Weldable Metals
Excellent weldability is usually possible when joining two similar pieces of metal. However, with the correct welding technique and equipment, it is possible to weld almost all types of metal together. The three most common metals used in welding are steel, aluminum, and cast iron.
Steel has excellent weldability
Steel is the most common metal used in welding projects and is relatively cheap, strong, and has high weldability. Additionally, steel has a tensile strength, meaning it withstands a lot of stress before it cracks and breaks.
Most types of welders work well with steel, stainless steel, carbon steel, and low-carbon mild steel. For example, you can use gas arc welding, stick welding, flux wire welding, and resistance spot welding. Also, MIG and TIG welders are suitable for welding all types of alloy steel.
Welding cast iron is challenging
Cast iron typically has low weld-ability characteristics because of its high carbon content. Typically, welding iron results in hard, brittle welds that are prone to cracking. However, cast iron is a durable metal that is resistant to wear. You must use the correct heating and cooling techniques and welding rods to weld with iron.
The best type of welding technique for cast iron is stick welding.
Welding aluminum is challenging
Aluminum is widely used in many industries because it resists corrosion, is lightweight and is versatile. However, the weld-ability of aluminum depends on its grade. Thicker aluminum is easier to weld than thin aluminum sheet metal. The best welders for aluminum welding are stick welding, AC-TIG welding, and gas metal arc welding.
How to Identify a Good Weld
Two major factors help tell a good weld apart from a bad weld — quality and strength. First, the weld-ability of any material significantly affects weld quality. However, because different metals result in various types of welds, there aren’t hard and fast rules for defining a good weld or lousy weld.
Let’s look in detail at various types of welding processes and how to recognize a clean, strong weld apart from a bad weld.
Stick weld — How to identify a good weld
Stick welding is a highly versatile welding process, and it’s the easiest type of welding to learn. You can use stick welding on a range of weldable materials, including alloy steel, stainless steel, carbon steel, iron, nickel, copper, and even aluminum. A good stick weld will be straight without any visible spatter.
How to recognize a quality stick weld:
- Straight and uniform
- No drops of spatter
- The bead should be consistent with no holes, cracks, or breaks.
MIG weld — How to identify a quality weld
A MIG weld is easy to spot because It will be straight and uniform with no cracking, slag, holes, breaks, or craters in the bead. Conversely, a poor MIG weld will look bad because there will be no uniformity and contain dips in the bead. Typically, metal inert gas (MIG) welding is considered the easiest because it’s like working with a glue gun.
Even though MIG welding is suitable for various metals, it’s best suited for thin materials, such as stainless steel, mild steel, or aluminum.
How to recognize a quality MIG weld:
- Uniform bead with no craters or dips
- The weld should look and feel smooth without a visible pattern
- Straight bead without spatter
- No cracking along the weld bead
- A thin bead lacks proper strength and breaks easily
TIG Weld — How to identify a good weld vs. bad weld
A good quality, clean TIG weld should consist of many tiny, neatly layered welds, creating an attractive pattern in the weld. A sign of a good TIG weld is that there shouldn’t be any slag or burnout. It takes skill and precision to great a strong, nice-looking weld with a tungsten inert gas (TIG) welder.
The patterning is the difference between a quality TIG weld and a MIG weld. If there is no distinct pattern and the weld bead is flat, it’s a poor TIG weld. However, a smooth, pattern-less bead is what you look for in a MIG weld.
How to recognize a quality TIG weld:
- A pretty pattern of overlaid welds neatly layered on each other
- Uniform pattern with no erratic beads
- No spatter, slag, or signs of burnout
- Relatively thin yet strong weld
What is Weldability — In Conclusion
The weld-ability of a material affects the type of welding technique and process you must use. In addition, some types of metal, like steel, are easier to weld than other metals with lower weldability. However, with the right equipment, preparation, and skill, it is possible to create beautiful, solid, and long-lasting welds you can be proud of.