Importance of Preheating in Welding – Equipment Options
Preheating reduces the risk of cracking in weld metal and heat-affected zone (HAZ) by:
- Lowering the cooling rate of the weld – prevents formation of brittle weld metal/HAZ, allows more time for hydrogen to escape the molten weld.
- Removing moisture (hydrogen source) from the part.
- Reducing shrinkage by lowering the temperature differential.
Preheat or not?
The requirement and level of preheating for steel is determined by the relevant welding code and is dependent on the weld heat input, chemical composition of steel (carbon equivalent), thicknesses, diffusible hydrogen etc. Non-ferrous materials generally require preheat because of their high thermal conductivity.
Preheating can be carried out using the following methods:
- Applying direct flame – surface of the part heated and then heat conducted through the part, open flame.
- Placing the part in a furnace – uniform heating of complete part if sufficient time provided in furnace, limitations of use due to the size of the furnace.
- Electric blankets – surface of the part heated and then heat conducted through the part.
- Induction heating using blankets – heat generated by electromagnetic currents within the material.
Out of the above methods, induction heating delivers the most consistent and fastest results and allows for the precise temperature control. It is also the safest and most energy efficient method.
The temperature is measured on the workpiece using thermocouples, temperature crayons or infrared pyrometers. The measuring positions are specified by the relevant welding code and are typically dependent on the thickness and geometry of the joint.
Red-D-Arc’s range of induction heating equipment includes air cooled and water cooled induction heating systems with heat applied via blankets and rolling inductors (for moving parts). These systems feature the ability to accurately monitor, control and record temperature. The required accessories including blankets, cables, thermocouples and recorders are also available for rental.
Visit our induction heating equipment page to find out more.
Red-D-Arc supplied three 125 kVA power generators and one 70 kVA power generator to the recent Stars and Thunder music festival. The generators were used for lighting and backstage power throughout the entire 8 day festival.
Stars and Thunder music festival took place in Timmins, Ontario June 24th-July 1st 2017 to celebrate Canada’s 150th birthday. The festival spotlighted Canadian groups such as Michel Pagliaro, David Wilcox, Sass Jordan, Tom Cochrane, April Wine, as well as some international acts like Keith Urban.
Red-D-Arc offers a full line of engine-driven, parallel ready generators including diesel generators, natural gas/LPG bi-fuel gaseous generators and diesel/natural gas dual fuel generators for rent, lease and sale. Learn more about Red-D-Arc power generators.
By guest blogger David H.
How important is it to remove welding smoke from the work area? Ask a welder, or ask someone who has to work in the vicinity of welders working in enclosed or semi-enclosed areas.
I recall some years ago working on a Navy general cargo ship. The ship was was undergoing extensive renovations and the hold of the had four or five levels. My employer, a small repair yard in San Francisco, unfortunately did not take air quality in the work area seriously. There were more than 20 of us working in the hold, and some number of us were welders. From a distance you could see where the work was being done — smoke and fumes drifting up out of the hold! In those days, safety requirements weren’t always top of mind. OSHA and other regulations aside, taking care of your workers by providing a safe work environment is simply the right thing to do. Without them your business can never be profitable. By failing to provide a safe workplace, you may lose workers due to health issues and employee turnover or face consequences for not complying with standards.
“respirators are hot and uncomfortable, and many welders simply refuse to use them”
There are a number of ways to deal with welding fume issues. One approach is the use of respirators. I often wore one, but they are hot and uncomfortable, and many welders simply refuse to use them. They can be remarkably expensive, over the long haul, given that filters must be replaced daily. If the mask is a disposable type, the entire mask must be replaced daily.
Portable smoke extractors – sometimes referred to as smoke eaters – are a far better solution. They extract a higher percentage of the fumes than respirator masks and protect everyone in the work area, not just the welders. They can be moved around the job site and from one job site to another, but can also be set up at permanent work stations. These machines can help make sure that your work space is a place where people can get their work done safely. Your employees will thank you.
To view the smoke extractors Red-D-Arc offers for rent head over to our smoke extractor rental page.
We also have used smoke extractors for sale on our used equipment page.
Red-D-Arc was featured in the December/January issue of Tank Storage Magazine in an editorial titled “Rental welding equipment for storage tank fabricators”. Tank Storage Magazine is an industry leading publication, reporting exclusively on the bulk liquid tank storage and terminal sector.
The storage tank construction industry is highly competitive and fabricators gain a significant advantage by leveraging Red-D-Arc’s rental fleet of automatic tank welding equipment. Red-D-Arc supplies specialized automatic storage tank welding equipment to companies in the tank fabrication industry for projects all over the world.
Along with our specialized tank welding equipment comes a highly knowledgeable and experienced team of Red-D-Arc technicians. Sayer Hendricks – storage tank welding equipment specialist at Red-D-Arc is quoted in the article: “A fabrication company without prior knowledge of the equipment, is able to rent a turn-key tank welding automation system and increase their welding productivity by 40-50%. With on-site training, service and support, our customers are up and running quickly and making 100% x-ray quality welds without fail”
The full article is available here: Rental welding equipment for storage tank fabricators
By guest blogger David H.
Some years back I was working in a shipyard in San Francisco. The yard had several small repair jobs going, plus a fairly large project building six ocean-going barges. The supervisor who was in charge of the barge-building project was looking for volunteers to operate semi-automatic wire feeders, using flux-cored wire, to weld stiffeners to the skin of the barges. I had never used a wire feeder before, so I volunteered out of curiosity.
After a very short training period, possibly all of 30 minutes but I think a bit less, I was off and running. I was impressed by the quality of the welds and the speed at which they were deposited. Without question I was outpacing anything that could be done by stick welding, and I felt it was easier to maintain a uniform weld size too. The machine itself was light enough and small enough to move without difficulty, and the spools of wire lasted long and were quick and easy to replace when the spool of welding wire was finished.
Red-D-Arc has nearly a dozen semi-automatic wire feeders available for almost any application. We also carry fully automatic wire feeders, which are faster still and appropriate in certain circumstances – like building storage tanks – especially for large-deposition welds.