What is Sheet Metal Welding: Process & Types
Once metal pieces are cut to the required sizes, joining them is the next step in the sheet metal fabrication process. Sheet metal joining allows product engineers to connect separate metal parts creating complex, functional structures. The main sheet metal joining techniques include riveting, adhesion, threaded components, and sheet metal welding. This article focuses on one of the most common and effective joining techniques: sheet metal welding.
Sheet metal welding is an essential process in industries like automotive, aerospace, construction, electrical appliances, and manufacturing. To achieve high-quality welds, you need to have a deep understanding of the different sheet metal welding methods. Electron beam welding, a high-precision technique suitable for tough metals like carbon steel, titanium, stainless steel, and aluminum, as well as thermoplastics, is one such method. Laser welding is another advanced technique used in sheet metal welding. During these processes, the molten metal solidifies to form a strong weld seam.
As an experienced engineer, I will guide you through the sheet metal welding process and various methods used in the industry. Discover useful welding tips for each technique and learn how to choose the right method for your project.
What Is Sheet Metal Welding?
Sheet metal welding is a joining technique that fuses two or more pieces of thin sheet metal using pressure, heat, or both. This allows manufacturers to fabricate the desired metal structures, components, and assemblies.
Sheet metal welding occurs at high temperatures. The workpieces are heated to their melting point creating a weld pool. As the molten metal cools down it solidifies as one unit forming a weld seam. One of the distinguishing features of sheet metal is its thinness compared to other commonly welded materials. Therefore sheet metal welding follows a unique approach.
5 Methods of Sheet Metal Welding
Sheet metal welding is classified into different categories based on the energy source used. During the welding process, a ‘weld puddle’ forms as the metal melts and fuses together. In this section, I’ll discuss five of the most common sheet metal welding methods, their operating principles, advantages, disadvantages, and applications.
One of the methods used in sheet metal welding is resistance welding, which involves the generation of heat by passing current through the resistance caused by the contact between two or more metal surfaces.
MIG Welding
Metal inert gas welding is a type of gas metal arc welding (GMAW) that uses electricity to create weld joints under an inert shielding gas. During the MIG welding process, a continuous solid wire electrode is fed through a welding gun allowing it to heat and join metal pieces. The metal wire serves as both the electrode and the filler metal that is melted into the weld.
MIG welding is conducted under the shielding of an inert gas to prevent a reaction between the molten metal and oxygen or other contaminants. Commonly used shielding gases include helium and argon. For the best results, the welder must maintain a steady hand and a suitable welding gun position. It’s generally recommended that the distance between the tip of the gun and the metal does not exceed 3/4”. This ensures that the inert gas adequately shields the weld puddle and helps form a clean weld bead.
MIG welding is a versatile process that is used for different metals ranging from aluminum and steel to copper and nickel alloys.
Advantages of MIG Welding
MIG welding is a simple process. It is suitable for both experienced welders and beginners.
It creates strong weld joints.
MIG welding is a fast and safe technique.
It is a cost-effective process that uses relatively inexpensive equipment.
Welded components only require light cleaning and finishing (if any).
Disadvantages of MIG Welding
MIG welding is less precise than other sheet metal welding techniques.
This welding method requires regular changing of the gas cylinder leading to machine downtime.
TIG Welding
Tungsten inert gas welding, also known as gas tungsten arc welding, is a welding technique that uses a non-consumable tungsten electrode and an inert gas to heat and fuse metal sheets. During this welding process, the electrode and workpiece generate a high-temperature arc that heats and melts the workpiece. The welder manually adds filler material into the molten pool to reinforce the weld. Upon cooling, this weld pool creates a strong bond. TIG welding is known for its exceptional precision even when welding thin metals and delicate components. It allows for greater control and, therefore, produces high-quality welds with excellent weld penetration.
TIG welding is similar to MIG welding in that it utilizes an inert gas to protect the weld zone from atmospheric contamination. One significant difference between these two processes is that TIG welding relies on a non-consumable tungsten electrode while MIG welding requires a consumable electrode. TIG welds are also typically stronger than MIG welds.
Advantages of TIG Welding
Creates precise, high-quality weld joints.
This process is ideal for a wide variety of metals including steel, aluminum, and nickel alloys.
Highly effective for thin materials due to its superior precision.
Clean welding process with minimal sparks and spatter.
Disadvantages of TIG Welding
Unlike MIG welding, TIG welding is a relatively slow process.
You need to have the relevant skills and expertise to successfully join metals using this technique.
Compared to MIG welding, this approach demands more expensive equipment.
Stick Welding
Stick welding is one of the earliest forms of electric arc welding. This manual process uses a consumable electrode that is covered in a layer of flux to weld metal pieces. Stick welding is also known as shielded metal arc welding (SMAW) or manual metal arc welding (MMA).
During this process, contact between the electrode and the metal workpiece ignites an electric arc. Electric current flows through the electrode melting the material and forming a weld puddle. The flux coating plays the same role as shielding gases in TIG and MIG welding. It forms a cloud of gases that protect the weld zone from contamination. However, this flux eventually becomes slag that needs to be removed from the welded part.
Stick welding is used for production and repair welding and has extensive applications in steel fabrication industries.
Advantages of Stick Welding
Creates strong welds with good mechanical properties.
Stick welding is not impacted by oxidation, paint, rust, mill scale, or grease at the welding point.
Supports efficient outdoor welding. Stick welding does not require shielding gases and is immune to unfavorable weather conditions.
It is can be used for the vast majority of metallic components.
Stick welding equipment is easy to handle, affordable, and portable.
Disadvantages of Stick Welding
Stick welding is a manual process that cannot be easily mechanized.
It is generally considered to be a slower welding technique.
Stick welding creates slag deposits that need to be chipped off once the welding action is complete. Increased cleanup time reduces the overall efficiency of this process.
Plasma Arc Welding
Plasma arc welding is another common process that uses a non-consumable tungsten electrode and a plasma torch to join metals. This arc-welding process requires four key components:
Plasma arc torch – This uniquely designed welding gun houses the tungsten electrode.
Shielding gas supply – Inert gases, such as argon and helium, envelope the weld zone preventing reactions with atmospheric gases.
Plasma gas supply – Inert gas is heated to extremely high temperatures inside the welding torch transforming it into plasma.
Power supply – Plasma arc welding relies on high-power direct current.
During the plasma arc welding process, direct current is supplied creating an arc between the tungsten electrode and the metal workpiece. This arc ionizes gas particles turning them into plasma. The hot plasma is responsible for heating, melting, and fusing sheet metal pieces. A welder will manually feed in filler metals where necessary.
Plasma arc welding is ideal for thin metals and applications that require deep, narrow welds. It can be used for welding stainless steel, aluminum, alloy steel, copper, carbon steel, and lead.
Advantages of Plasma Arc Welding
Plasma arc welding offers both speed and precision.
It is capable of welding tough metals.
This welding process can be automated thanks to modern plasma guns.
Unlike other sheet metal welding methods, this technique has no limitations on the viable welding positions.
Disadvantages of Plasma Arc Welding
Requires costly equipment.
Plasma arc welding demands highly skilled operators.
This process emits ultraviolet (UV) radiation.
Gas Welding
Gas welding is one of the most common techniques used to weld sheet metal, resulting in a strong weld joint. It involves burning gas fuels to generate heat. This heat is utilized in partially melting thin metal pieces to create a weld pool at the seam. As the molten pool cools and solidifies, it fuses the two metals forming a strong weld joint.
Gas welding can be classified into different categories based on the fuel gas involved. Common types of gas welding include;
Oxy-acetylene gas welding
Oxy-gasoline gas welding
Hydrogen gas welding
MAPP gas welding
Butane or propane welding
The ideal welding flame temperature will vary depending on the workpiece material. The speed at which you move the welder’s flame will also affect the weld quality. If you move it too fast, inadequate heating can lead to incomplete welding. Conversely, if the flame lingers too long, it may burn a hole through the workpiece.
Advantages of Gas Welding
Suitable for both ferrous and non-ferrous metal sheets.
Since gas welding doesn’t rely on electricity, it can be used in remote areas.
Simple process that is easy to master, even for newbies.
Gas welding equipment is portable.
Disadvantages of Gas Welding
Gas welding is slower than other welding techniques.
It may create weld defects due to the absence of flux shielding.
Author
Gavin Leo is a technical writer at Aria with 8 years of experience in Engineering, He proficient in machining characteristics and surface finish process of various materials. and participated in the development of more than 100complex injection molding and CNC machining projects. He is passionate about sharing his knowledge and experience.