SAF-FRO solutions for non alloyed steels welding and cutting applications
Unalloyed steels are in fact alloys of iron and carbon (proportion of 0.12% to 2.0%). The carbon steels are very widely used in large number industrial activities as transportation : automobile, trucks, railway cars and naval construction – pipe work and boiler making for chemical industries – offshore constructions – wind tower - building – mining… ).
Oxy flame and plasma cutting are the processes that can be used for thermal cutting of unalloyed steels as well in manual applications with the range of PRESTOJET/ PLASMAJET machines and in automatic applications on automatic cutting table (OPTITOME – ALPHATOME – OXYTOME and PLASMATOME) with MACH HP for oxy-fuel cutting and NERTAJET HP for plasma cutting.
The equipment is composed of a power source providing the welding current (from 10 A to ~500 A) by transformation of the primary main electrical network current (single phase or three phase 230 V to 440V). Modern arc power sources use "Inverter" technology providing cost effective solutions combined with increased ease of use (good striking, very stable welding current…).
The inverter power sources are also lighter than transformers for same welding current improving portability.
In SAF-FRO range the equipment for MMA welding are named PRESTO. In addition a MMA welding kit is necessary to connect the power to the piece to be welded and to the electrode holder maintaining the covered electrode.
The core metal composition of the electrode is generally similar to the base material while 2 main different coatings are possible rutile or basic (also named low hydrogen).
The equipment is composed of a power source providing a DC welding current (from 10 A to ~500 A ) by transformation of the primary main electrical network current (single phase or three phase 230 V to 440V). Modern TIG power sources use "Inverter" technology providing cost effective solutions combined with increased ease of use (good striking, very stable welding current…).
The inverter power sources are also lighter (up to 10 times) than transformers for same welding current improving portability.
In SAF-FRO range the equipment for TIG DC welding are named PRESTOTIG DC. In addition a TIG welding torch with a non-consumable electrode in Tungsten is required. Argon gas cylinder and a regulator-flowmeter is necessary to control the flow of the argon (Ar) shielding gas.
The choice of the filler metal will be done in accordance with base material to be weld. The SAF-FRO range covers most of the current applications. ALTIG is the commercial designation of this rods.
Plasma arc welding is similar to TIG welding with a key difference: in the welding torch the arc is mechanically constricted creating together with the plasma gas an ionized atmosphere of high temperature. At the impact point of the plasma base material is melted with a great energy concentration achieving a deep and narrow penetration. The plasma arc and the pool are protected by a shielding gas added from the torch.
Plasma arc welding process can be used manually for low welding intensity (~15 A - micro plasma) but is more often employed in automatic applications for high quality works in piping and in boiler making.
Filler metal is not mandatory especially for root pass but will improve productivity for large welds.
MIG/MAG welding equipment is composed of a power source providing the welding current, a wire feeder (built-in or separate), a welding torch or gun and a device for shielding gas supply.
Various technologies for the electrical power source are available step control transformers (DIGISTEP and PRESTOMIG) or inverters with digital control (DIGISTEEL, DIGIPULS and DIGIWAVE). Modern MIG-MAG power sources use digital controlled inverter technology providing cost effective solutions combined with increased ease of use (lower weight, very stable welding current…).
With these power sources, the current metal transfer modes (globular, short-circuit, spray and pulsed spray) are available but several evolution developed and patented by SAF-FRO are possible for example:
FILCORD is the commercial designations of the solid wire for welding unalloyed steels in the SAF-FRO range. Wire diameters are comprised between 0.6 mm and 1.6 mm. Wire is delivered in spools for most of the manual applications and in large bulk (drums) for automatic and robotic applications .The choice of the filler metal will be done in accordance with base material to be weld.
FCAW is a variant of MIG/MAG process where the wire electrode is replaced by a tubular wire containing a flux.
Main advantages are all position welding, higher deposition rate and higher versatility. Main drawback is the higher level of welding fumes.
Flux-cored wires are used in various industrial sectors: automotive and transport, manufacturing, pipe welding, steel buildings and structural steel works.
Equipment to weld with flux cored wires is the same that the one for MIG/MAG welding.
Filler material is flux cored wire and in the SAF-FRO range the commercial designation of these wires is SADUAL or STEELCORED according to the technology folded or tubular.
The Submerged Arc Welding (SAW) equipment is consisting in :
Filler material is a combination of :
MMA welding (Manual Metal Arc) or as per AWS SMAW (Shielded Metal Welding) use a consumable steel electrode covered with a flux.
An electric arc is generated between the plate to be joined and the stick electrode. With the heat generated in the arc, both (the piece and the electrode) are melting thus creating the weld pool. The coating of the electrode also melts and forms a shielding gas preventing the melted pool. As the welding operation is going on, the melted coating provides a slag that has to be removed. This process is one of the oldest methods of joining. Big drawbacks regarding this process are to be mentioned: it produces sparks and fumes, post-weld cleaning is important, it is a quite slow process and it requires a high level of skill from the welder. Low cost, flexibility portability and versatility are the main advantages of the process.
TIG welding (Tungsten Inert Gas) or as per AWS GTAW (Gas Tungsten Arc Welding)
In this process an arc is generated between the base material and a non meltable tungsten electrode part of the welding torch. At the point of contact of the arc the base material is melted and an additional filler material is provided into the pool. The pool is protected by a shielding gas (generally argon because tungsten is sensitive to oxygen) provided from the torch.
Advantages of the process are: the clean and high quality of the welds with high penetration, requiring little or no further works for post-welding clean. The main drawback is that TIG is the slower process in arc welding.
The process can easily be used in automation application.
MIG-MAG welding (Metal Inert Gas or Metal Active gas) or as per AWS GMAW (Gas Metal Arc Welding)
In MIG-MAG process an arc is generated between the base material and a continuous wire electrode that is consumed. The filler metal is the electrode wire fed throughout the torch.
Shielding gas is necessary to protect the arc and the molten pool. Various possibilities can be used: inert gas (a mixture of Argon + CO2) for MIG welding and CO2 for MAG welding. The shielding gas choice depends on various factors and on the required results.
MIG/MAG welding process is the most used method in all industrial applications as it is the fastest, economical and a high productivity process, requiring low skills from the welder. Disadvantages of the process were poor quality of weld appearance and spatters but modern power sources with advanced arc transfer modes provide much better results that in the past.
MIG/MAG process is used in manual applications but is more and more often used in automatic and robotic applications.
Submerged Arc Welding (SAW) is an arc welding process where an arc is generated between the base material and continuous wire electrode (solid or flux cored wires).
The arc and the molten pool are completely covered by a layer of flux, thus no sparks, no radiation and no fumes are produced. The SAW process is almost always operated in automatic application, flat butt or fillet positions for long welding beads or high thickness. Welding current is high (up to 1200 A in single wire and much more when used in multi-wire) and the deposition rate is very high. It is the arc welding process with the highest productivity.
Main advantages are very sound welds, productivity and important thickness weldable in one pass, no fumes and non-visible arc radiation. Main drawback is the heavy automatic equipment necessary to operate the process.
Submerged Arc Welding process is used in various industrial sectors: transportation industries (trucks and railway coaches..) pipe fabrication and heavy structural steel works.