While it may be just a small piece of a much larger job, an effective method for preheating steel used to build structures is critically important. As it is required under the American Welding Society (AWS) D1.1: 2020 Structural Welding Code—Steel, preheating steel is a process that you’ll encounter when building all types of infrastructure from buildings to power plants to bridges, and everything else in between, so ensuring that you are managing this in the most efficient way for your project will alleviate issues later down the road.
Traditional Method for Preheating Steel
Flame heating is a traditional and commonly used method to preheat steel used in the welding process. Although flame heating is effective and beneficial in specific circumstances, it may not always be the best choice for your application. Compared to other methods, the operating costs are much higher due to fuel costs which can be unstable plus the ongoing use of consumable materials. It also poses some considerable safety risks related to using an open flame in high-traffic work areas as well as the inherent risks for burns, fires, and explosions associated with the process and the materials used. Additionally, there is an increased potential for destroying the base material as a result of the extremely high temperatures that are necessary to achieve the desired outcome.
Each project is different, so understanding the aspects that are important for the job at hand is crucial. While flame heating is a trusted and, perhaps even, a more comfortable process to use for welders who are more experienced with it, in many cases, other preheating methods can help increase your productivity while also protecting workers on the jobsite and maintaining compliance with code requirements.
Achieving Desired Temperatures with Modern Technology
Induction heating is a more modern approach to preheat and post-weld heat treatment (PWHT) and maintaining weld temperature. It is also useful for other industrial tasks such as coating removal, and placing or removing shrink-fit components. Although the conventional use of induction heating is limited to magnetic base materials, applications capable of using the process can reap significant operational savings and benefits compared to more conventional heating processes such as flame or torch heating.
In induction heating, a power source supplies alternating current (AC) through an induction heating cable which is coiled around a magnetic material (pipe, column, etc.). As a result, the coil generates an alternating magnetic field, reversing directions when the current switches direction (alternates). This creates an Electro-Magnetic Frequency (EMF) heating effect to occur to the coiled object (only in magnetic materials such as iron, nickel, cobalt, etc.). With induction heating, the part becomes its own heating element and heats from within. This makes induction very efficient since little heat is lost in the process.
One of the key reasons that induction heating technology is highly advantageous when managing preheating specifications for steel is because it decreases the risk of destroying the base material. As the number of skilled welders continues to be a persistent concern in the welding industry, it has been increasingly difficult to find welders who are able to use more traditional heating methods like flame heating without the risk of damaging the material. Using a more controlled process like induction heating allows welders with varying levels of skills to successfully heat parts to the desired temperature with a decreased risk of defects.
Induction heating equipment is also relatively easy to set up with the use of preheat blankets or flexible heating cables and reduces cycle times, heating materials in just a fraction of the time of other methods. Depending on the temperature requirements, in many cases, parts can reach the desired temperature in just 30 minutes or less. It also allows for uniformity and quality—providing the highest degree of temperature control across the heat affected zone and minimizing hotspots. However, it is important to be aware of the cable placement as that can impact the heating patterns. Finally, induction heating is a very reliable process since the heating system-components make cycle interruptions unlikely and the cabling fairly simple. This makes induction heating a much more efficient process when it comes to preheating steel.
Of course, safety is always a concern when using any type of equipment. Therefore, the proper precautions, such as use of Personal Protective Equipment (PPE) that is fit for purpose, is just as important when using induction heating on a job. However, safety is also greatly improved with this method of preheating. There are fewer fumes and the use of fuel gases is completely eliminated. This means there is no exposure to flame, gases, or hot elements when using this process. That is a huge help when it comes to creating a safer work environment for welders and others working on a jobsite as it provides another means for safety professionals who are responsible for assessing and minimizing safety risks.
Red-D-Arc Induction Heating Capabilities
Red-D-Arc offers a complete selection of induction heating solutions, including equipment and accessories, available for rental, lease and purchase. With more than 20 years of experience working with heat treating, our team of heat treating experts are ready to assist you. After learning more about your project, a Red-D-Arc heat treating expert will work with you to select the right equipment and customize a package for preheat and/or bakeout heat treating that is suitable for applications, including steel erection, bridge building, pressure vessels and ASME code work. Red-D-Arc carries both the Miller ProHeat 35 Induction Heater and the Miller ArcReach Induction Heater to cover a broad range of specifications. And with more than 70 service centers located throughout the US and Canada, induction heating equipment from Red-D-Arc is available when and where you need it.
Miller ArcReach Induction Heater
A small ultra-portable 8kW preheating unit designed for field use up to 600 ℉, that is powered off of a Miller ArcReach enabled welding power source like the EX360 Field Pro.
Miller ProHeat 35 Induction Heater
An all-in-one 35 kW system induction heater that can handle applications needing greater heating capability.
For more information about induction heating or to talk with a heat treating specialist about your specific project needs, contact us.
