At Lilleker Engineering we are committed to giving our customers a fabrication that will meet their requirements.
Part of that commitment is that the fabrication is manufactured to a high standard and having coded welders helps us to do that. Our welders go through stringent examinations every two years which include x-ray and mechanical tests that show the welds they produce are of a sound quality. Our welders are qualified to EN287 – 1 2004 and Asme IX standards in Mig and Tig welding and as this is an ongoing process you can be assured that all our welding is always produced to the most recent standards.
Manual Metal arc process
The first recorded use of manual metal arc welding was just a bare metal rod with no flux coating goes back to 1888 in Russia. Coated electrodes were not developed until the early 1900s when a process was invented in Sweden called Kjellberg also the Quasi-arc method was introduced in the UK around that time. The use of coated electrodes was slow to be adopted because of their high cost but as the demand for sound welds grew, manual metal arc became synonymous with coated electrodes.
The arc is produced when a metal rod (electrode) it is struck onto the work piece, both the rod and work piece surface melt to form a weld pool. Simultaneous melting of the flux coating on the rod forms gas and slag which protects the weld pool from the surrounding atmosphere. The slag then solidifies and cools and must be chipped off the weld bead once the weld run is complete. The process allows only short lengths of weld to be produced before a new electrode needs to be inserted in the holder. Weld penetration is low and the quality of the weld deposit is highly dependent on the skill of the welder.
MIG Welding Process
In the 1940s Metal Inert Gas (MIG) Welding, also sometimes called Gas Metal Arc Welding (GMAW) was developed for welding aluminium and other non-ferrous metals. MIG welding is a process that uses a wire connected to a source of direct current that can be fed either automatically or semi-automatically, as the wire continuously passes through the welding gun it acts as an electrode to join two pieces of metal together. An inert gas also passes through the welding gun at the same time as the wire electrode, this gas which was originally argon and is now a mixture of various gasses acts as a shield, keeping airborne contaminants away from the weld zone.
The main advantage of MIG welding is that it allows metal to be welded much more quickly than older traditional methods. This makes it ideal for welding softer metals such as aluminium. When this method was first developed, the cost of the inert gas made the process too expensive for welding steel. Over the years, the process has evolved, and semi-inert gases such as carbon dioxide can now be used to provide the shielding function. The use of these cheaper gasses now makes MIG welding a cost-effective process for welding steel.
TIG Welding Process
TIG welding was developed in the 1930s and was used during World War 2 as the preferred way to weld many aircraft parts. Previously, some alloy steels and aluminium had to be welded with a torch, something that required considerable skill and time. Tungsten Inert Gas (TIG) welding uses the heat generated by an electrode to produce a molten weld pool. The arc is made between a non-consumable tungsten electrode and the work piece, once the weld pool is established the joint area is fused together. The arc area is shrouded in an inert or reducing gas shield such as pure Argon to protect the weld pool and the non-consumable electrode. The process may be operated with or without a consumable filler wire that is fed into the established weld pool. The TIG process produces very high quality welds across a wide range of materials with thicknesses up to about 8 or 10mm and is particularly well suited to sheet material.
Gas Welding Process
Gas welding, is also known as oxy-fuel welding is a system of welding that uses one of various gases and oxygen to ignite a torch, the intense focussed flame burns at approximately 3,500 degrees centigrade. When the flame comes in contact with steel, it melts the surface forming a molten pool, allowing welding to take place. A Filler wire is added into this molten material to produce the weld
A variety of metals can be joined using gas welding techniques, although a skilled torch operator is necessary in order to ensure a smooth weld. Not all metals melt at the same temperature, so the welder must know how long to heat varying types of materials. There is also a certain level of skill required for gas welding, to ensure that the weld is flawlessly done. Less experienced welders may end up with a joint that is lumpy or uneven.
Resistance spot welding uses a thermo-electric process where heat is generated at the weld point of the parts to be joined by passing an electrical current through them for a precisely controlled time and under a controlled pressure. The name “resistance” spot welding is derived from the fact that the resistance of the work pieces and electrodes are used in combination to generate the heat at their weld point.
Resistance spot welding is a fairly simple heat generation process: the passage of current through a resistance generates heat. This is the same principle used in the operation of heating coils. In addition to the bulk resistances, the contact resistances also play a major role. The contact resistances are influenced by the surface condition (surface roughness, cleanliness, oxidation, and coatings).