One of the most innovative recent developments to take place in the South African welding and cutting industry must be the Lindoflamm® special torches and burners from Afrox’s parent company, The Linde Group.
A first for South Africa, Lindoflamm® special torches and burners provide optimal heat transfer to the work piece, reducing gas consumption, improving productivity, quality and therefore total cost — as well as enhancing safety on the factory floor.
Afrox’s Johan Pieterse, Business Manager, Process Development explains: “Our parent company’s research and development activities focus not only on improving existing customer processes, but also on completely new technologies. Lindoflamm is a perfect example of this, offering pre-heating, flame straightening and heat treatment solutions for manufacturers and fabricators working to the highest industry standards.”
Pre-heating with acetylene and compressed air
Pieterse says pre-heating is a critical requirement in the fabrication industry and plays a very important role in the integrity of the weld. It prevents failures such as hydrogen-induced cracking, as well as common failures in the heat-affected zone. An increasing number of fine-grained structural steels are being used for construction of structures, apparatus, and equipment – increasing the importance of pre-heating prior to welding.
Lindoflamm® technology offers the fabricator a number of advantages that improve quality, productivity, safety and reduced process costs. An important characteristic of acetylene is the high heat intensity in the primary flame. This results in a focused flame, pre-heating only in the weld area, increasing the speed at which the weld area is heated as much as a two thirds faster than other fuel gases, and could save as much as 32% on total process cost. Working conditions are also improved, since less heat is reflected, improving operator comfort. Due to this reduction in heat reflection, gas consumption is much lower.
Another important characteristic is lower water content (4%), compared to as much as 30% in other fuel gases, which reduces the risk of inducing hydrogen in the weld area and is an important factor in quality enhancement.
The mixture of compressed air and acetylene, coupled with the focused flame, reduces the risk of surface damage. Acetylene is also less dense than air, compared to other fuel gases that are denser than air, reducing the risk of accidents and incidents when working in confined spaces.
“This is the safest solution,” concludes Pieterse. “Lindoflamm torches, burners and nozzles are all application-specific designs, ensuring that particular needs are met.”
The heat of the welding in the heat affected zone causes steel structures to distort during the cooling period of the weld. This is a common defect in welding and although the weld sequence can be designed to minimise the effect of distortion, it still has an effect.
The Lindoflamm® flame straightening process uses oxygen and acetylene to heat localised areas of the work piece rapidly into the plastic temperature range. A restriction of heat expansion results in an upsetting in the heated zone. During the cooling down period, a shortening results around the heated zone, resulting in straightening of the work piece.
“The correct torch must always be used for flame straightening,” he says. “Work involving thick wall components can only be carried out successfully if high output torches are available. This often means special designs.
“The use of manually guided special high output torches is a standard application in steel construction and heavy machinery building.
“For mass production, mechanised flame-straightening torches have been developed. These torches are employed, for example, in the fully automated manufacture of thick-walled, longitudinal seam welded pipes for offshore oil drilling and production. Distortions in T and double T members, caused by longitudinal shrinking of fillet welds, can also be removed with mechanised torches during the welding process.”
In flame hardening, localised portions of the work piece are quickly heated to a temperature above the GOS line in the iron-carbon diagram. The heated region is immediately quenched, undergoing a transition to the structure present in hardened steel. The base material remains unaffected and unchanged in form.
Torch designs of proven value for flame hardening have a water spray integrated into the nozzle immediately behind the flame front in the direction of motion
Afrox is the leading supplier of welding consumables in southern Africa, offering an extensive product range covering most material that can be welded, from normal carbon steel to the more specialised type of material such as stainless steel, nickel based alloys and hardfacing alloys.
A team of local and global experts supports the Lindoflamm processes including trials, burner designs, installation and commissioning as well as training.