Weldments
Table of Contents
- 1 What are Weldments?
- 2 Common Welding Methods
- 2.1 Arc Welding
- 2.1.1 MIG Welding:
- 2.1.2 TIG Welding:
- 2.1.3 Stick Welding:
- 2.1.4 Flux-cored arc welding:
- 2.2 Friction Welding
- 2.3 Electron Beam Welding
- 2.4 Resistance Welding
- 2.5 Forge Welding
- 2.1 Arc Welding
- 3 Brazing
- 4 Welding Equipment
- 5 Joint Configurations
- 6 Features of Completed Welds
- 7 Testing of Weldments
- 8 Welding Standards
- 9 Safety Considerations
- 10 SolidWorks: Weldments
- 11 References
- 11.1 Contributors:
Arc Welding [1] |
|---|
What are Weldments?
Welding is the process of joining metals by heating the surfaces to the point of melting by using a blowtorch, electric arch or many other methods [2]. After heating up the surfaces, the pieces are united through different methods, such as pressing or hammering [3]. The molten metal will then cool to form a joint, also known as a weldment. Carbon and low alloy steels are the most widely welded materials however, aluminium and its alloys are also weldable materials [4].
Common Welding Methods
There are various welding processes with unique techniques and applications which vary by industry. The primary processes include arc welding, friction welding, electron beam welding, laser welding and resistance welding, arc welding being the most popular [5]. The four most common methods of arc welding include Gas metal arc welding (MIG), Gas tungsten arc welding (TIG), Stick welding and Flux-cored arc welding [6].
Arc Welding
MIG Welding:
MIG welding is a very common method of welding. This method is used for a variety of different types of alloys and metals such as magnesium and copper [6]. In this process, a solid wire electrode is fed through a welding gun. An electric arc is formed between the base and the electrode, which heats the base and causes the material to melt and join [6]. A shielding gas is supplied, which protects the weld from nitrites and oxides, which could contaminant the weldments [6]. There are many advantages to using this method. It is the easiest welding technique, and can be used by entry level welders. There is a lower heat input requirement and the cleanup is quick and easy. MIG welding is commonly used for applications such as pipe welding, automotive production and maintenance, manufacturing, shipbuilding and construction [7].
TIG Welding:
In this method, a tungsten electrode, which is consumable, is used heat up the base of the metals and create a molten weld puddle on it [6]. An extra metal filter can be added to molten weld puddle to enhance the properties of the weldment. This method also needs an external gas supply to protect the puddle from contamination. Argon is the most common method for protecting the puddle [6]. There are also many different advantages to this welding method. TIG welding offers high quality weldments, and is clean without any splatters. Very thin materials can also be welded together using this method. The welder has tremendous control over the welding process, and this method is very accurate [6]. The weld beads produced in this process are highly aesthetic [6]. TIG welding is commonly used in the aerospace industry, automotive construction and repair, art, nuclear, pharmaceutical and ship fitting [7].
Stick Welding:
This type of welding is used for welding most ferrous metals and also other metal types by using a special electrode. A welding rod is sued to carry a current providing the majority of the metal weld. In this case, the metal and electrode are both being melted. This method is used for heavy equipment, construction and repairing [6]. One of greatest advantages of this method, is that it can used in rainy and windy conditions. The equipment required are also very affordable, and it requires no extra shielding supplies [6].
Flux-cored arc welding:
The process involves an electrode being continuously fed through a tubular wire filled with flux [6]. Flux-cored arc welding offers two processes, dual shield flux-cored welding and shielding flux-cored welding. Dual shield involves an externally supplied gas, which is used in conjunction with the electrode in shielding the molten welding puddle, whereas self shielding flux-cored welding requires no external gas to protect the weld [6]. Flux-cored arc welding is commonly used for pipeline welding, general repairs, shipbuilding, manufacturing and underwater welding [7].
Flux-cored arc welding [8] |
|---|
Friction Welding
Friction welding uses mechanical friction to heat and soften metals. The metals will then mix, and bond as they cool. Types of friction welding include rotary friction welding, linear friction welding, friction stir welding and friction stir spot welding [5]. Unlike other welding techniques, friction welding requires no filler metals, flux or shielding gas. Friction welding is used broadly across the industry and is even being explored as a technique to bond wood without adhesives [5].
Rotary Friction Welding [9] |
|---|
Electron Beam Welding
Electron beam welding is a fusion joining process in which a beam of high velocity electrons are used to join materials. The kinetic energy of the electrons is converted to heat as the electrons impact the workpieces, causing them to fuse together [5]. This technique has many common applications and it is used in various industries, including aerospace, nuclear, and automotive [5].
Resistance Welding
Resistance welding is split into two types, spot welding and seam welding. Spot welding is a process in which metal parts in contact are joined by heating them with an electric current [5]. Seam welding uses rotating wheels in place of electrodes to deliver heat to the metal surfaces. Resistance welding is commonly used in the assembly of bodies for automobiles and manufacturing of steel pipes [5].
Spot Welding [10] |
|---|
Forge Welding
Forge welding is a metal fusion technique that dates from the earliest uses of iron. This process was initially used to make small pieces of iron into larger pieces by joining them. The work pieces are first shaped, then heated in a forge and finally pressed or hammered together [4]. Forge welding has survived mainly as a blacksmith's craft and is used to some extend in chain making today [4].
Brazing
Brazing is also another process of joining metals where two or more metal items are joined by melting and flowing a filler metal into the joints. In brazing, the metal filler has a lower melting point then the metals being joined [11]. Brazing is different from welding in a few ways. This method does not require melting the work pieces [11]. One of the advantages of brazing is that it has the ability to join the same or different metals with great strength [11]. For high quality brazing, the parts must be closely fit and the base metals must be free of oxides [11]. Additionally, the brazing temperature should be above the the melting point of the filler metal. Some of the advantages of brazing include that it allows much tighter control over tolerances and produces a clean joint without the use of a secondary finish [11]. Brazing also produces less thermal distortion than welding since it uniformly heats the metals [11]. However, one of the disadvantages of brazing is the lack of joint strength compared to welding, since it uses a softer filler metal [11]. Additionally, the joint color may different from the metal color, which can create an aesthetic disadvantage.
Brazing [12] |
|---|
Welding Equipment
There are many different machines and equipment that can be used during the welding process. To start off, a welding station is a set of welding equipment that require participation from the welder [13]. A welding line combines many welding stations [13]. Welding stations include power supplies and equipment to regulate the arc during welding [13]. A welding transformer is used to match of the welding circuit and power supply, while also working as a voltage regulator [13]. A welding generator is another machine used during welding. This machine is a specifically designed electric machine, and is either a DC machine or a machine that operates at higher than standard frequencies [13]. There are also many different welding generators. Another piece of equipment is a welding rectifier, which converts alternating currents from a power supply to direct current [13]. Welding jigs and fixtures are used by welders to assemble parts before the welding process starts, to hold parts in place, and to weld previously assembled parts [13]. These parts can be held together with screws and magnetic clamps [13]. Finally, there are many different welding tools. Welders often use electrode holders, welding torches, cleaning tools like hammers, wire brushes, and many other tools [13].
Welding Torch [13] |
|---|
 |