In welding, like in many other manufacturing and fabrication processes, the process is not complete until the necessary post-processing has been carried out. Post-weld operations are usually performed for reasons such as improving mechanical properties, relieving stress, and improving aesthetics. The two most common Post-weld operations are Post-Weld Heat Treatment (PWHT) and Finishing.
Post-Weld Heat Treatment
During welding, the welded materials are exposed to very high temperatures that can cause micro-structural changes in them. Also, residual stresses build up in welded materials when they are allowed to cool naturally. If left unaddressed, these stresses and structural changes can severely compromise the mechanical properties of a material and can lead to failure during use. To prevent this, PWHT is required for welded parts. There are two major types of Post-weld heat treatment and they are as follows.
Post heating is usually carried out to prevent Hydrogen Induced Cracking (HIC). HIC results from the permeation of materials by high levels of ambient hydrogen during welding. In Post heating, the welded material is heated to a specified temperature and held at this temperature for a specified period. This process allows the hydrogen to diffuse out of the welded area, thus preventing HIC. Post heating is carried out immediately after welding before the material cools.
In this process, the welded material is first allowed to cool. After this, it is heated to a specified temperature and held at this temperature for a specified amount of time. The material is then cooled gradually at a specified rate. As its name implies, stress relieving is done to relieve stresses that may have built up during welding and natural cooling.
The heat required in both PWHT processes is usually provided by heating systems. While several heating systems can be used for this purpose, Induction heaters such as the Miller Induction Heating Systems are highly recommended. These systems provide uniform heating, precise temperature control, power efficiency, and many more.
It is important to note that most but not all materials require PWHT. The higher the content of carbon or any other alloying element in a material, the more likely it will need PWHT. Similarly, the thicker the material, the more PWHT is required. The required temperatures and time for different materials are covered by codes and standards.
Welding typically results in a visible weld seam along the areas that have been welded. Even machines as highly precise as the Miller TIG welder series produce visible, albeit very small, weld seams. These affect the appearance of the welded part.
Finishing operations are carried out to improve the aesthetic appearance of welded material. In some cases, they are done to improve the dimensional accuracy of a part.
Finishing involves two basic steps; grinding and polishing.
Grinding involves using an abrasive to level the welded area to be consistent with the surface of the material. This can be done using flap wheels, fibre discs, flap discs, or grinding wheels, depending on the type, shape, and size of the welded material, as well as the quality of finishing required.
Polishing typically takes place after grinding. For this process, gentler abrasives are used together with polishing compounds to produce a very neat surface finish. In some cases, it’s impossible to identify the welded joint after finishing.
Dear Valued Red-D-Arc Customer:
As we all continue to adjust to the global COVID-19 pandemic, we would like to take a moment to reach out to you to inform you that Red-D-Arc is continuing to vigilantly monitor the evolving developments and adjusting as necessary in order to safeguard our workforce and limit any potential impacts or disruptions to our commercial relationships.
At this time, Red-D-Arc operations are currently proceeding as usual, to the extent permitted by relevant governmental and federal authorities. While we are aware that various government-imposed shutdowns have been implemented for various industries in certain geographic locations, Red-D-Arc – like its parent company, Airgas – identifies itself as a business which provides essential services, including the supply of necessary equipment to various power plants, oil refineries, the petrochemical industry, government-led construction projects, and so forth.
Red-D-Arc prides itself on being a socially responsible corporate actor, and as such, the health and safety of Red-D-Arc’s employees, customers and suppliers have always been its top priority. To ensure our unwavering commitment to this position, we have implemented the following protocols designed to ensure the health and safety of our employees, customers and suppliers, while helping to curtail the spread of the COVID-19 virus:
- Implementation of a work-from-home policy for all applicable employees
- Postponement or cancelation of all in-person company meetings and events
- Automatic 14-day quarantine period for any employees who have left the country, prior to their return to work
- Limited visitor access to Red-D-Arc locations
- Enhanced cleaning and sanitization procedures at all Red-D-Arc locations
- Suspension of all air travel by Red-D-Arc
- Staggering work hours, wherever possible
- Encouragement of social distancing practices for all employees
As our welding-related product supply and distribution occurs domestically, our supply chain has not been materially impacted and, at this time, we remain in a position to meet your rental needs, subject to location-specific shutdowns. Where local issues have arose, we will seek to engage our integrated network of over 50 branches across the United States and Canada to seamlessly source products and ensure the continued delivery of essential products to our customers, as permitted by relevant authorities.
We plan to proactively communicate with our customers if we become aware of supply disruptions that will impact normal distribution, and will continue to update our contingency planning as the current situation evolves. While every emergency situation is different, we believe our commitment to emergency preparedness, extensive resources, strong national infrastructure, and experience during past emergency situations position us well to respond to your needs.
Customers should work with their Red-D-Arc sales or customer service representative(s) directly as this situation continues to evolve. Thank you for your current business and continued support.
President – Red-D-Arc Inc., Red-D-Arc Ltd.
How To Weld Aluminum To Steel: Is It Possible? What Are My Options?
If you’re new to welding, you may be wondering if it’s possible for you to weld aluminum to steel. Welding “like-to-like” metals like steel-to-steel and aluminum-to-aluminum is usually very straightforward. However, when you try to weld together two very different metals like aluminum and steel – such as two components manufactured by tube laser cutting – things can get a little bit more complicated. So, is it possible to weld aluminum to steel? What are your options for doing so? Let’s discuss everything you need to know.
Red-D-Arc’s dry ice blasting equipment was provided as part of the restoration effort for the prestigious Stephen F. Austin statue in Sugarland, Texas. Our team of dry ice blasting specialists delivered solutions to get the project completed with a package consisting of two Cold Jet dry ice blasting machines, two high volume after-cooled 375CFM air compressors, 2,500 lbs of blasting ice (CO2), and on-site operator/safety training. (more…)