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Induction Heating

Induction heat treatment equipment has greatly improved the speed and ease of the heating of large scale metal pieces for construction, weld preheating/post-heating and the maintenance of industrial equipment.  Red-D-Arc has become known for our expertise in the application of induction heat using induction heat blankets, coils and ovens in a diverse variety of applications.

Post-Processing Welded Parts

20 March, 20 4:52 pm · Leave a comment · Geoff Campbell
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miller proheat 35 liquid cooled on pipe

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

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.

Stress relieving

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.
induction heating plate with miller proheat - infrared image

Finishing

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.

Supporting Maintenance at the Grand Coulee Dam

04 June, 19 2:09 pm · Leave a comment · reddarc
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Grand Coulee Dam interio

Originally built in the 1930s, the Grand Coulee Dam in Washington State has been undergoing a series of maintenance projects to ensure that it will continue to produce safe and reliable power into the future. One stage of the project required the heating of a 40-ft wide, 7-ft tall outer headcover of the turbine shaft to specific core temperature.  In order to achieve this temperature, the engineers applied induction heating to one side of the workpiece.

Only when the opposite side of the workpiece reached target temperature could the maintenance engineers be certain that the required core temperature had been achieved.  The team from Red-D-Arc provided induction heating systems and assistance with training and set up during this essential part of the maintenance process.
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Construction Firm Beats Competition With Fast Induction Heating

31 May, 19 5:22 am · Leave a comment · Colin Brown
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pipeline welding project using induction heat

19 Hours Faster Than the Competition

Texas – One of our customers was trying to heat 42” diameter pipe using pear burners so that welders could weld out the joints. Our team saw an opportunity to create a solution that would help our customer get the job done much more quickly. To make this in-the-field heating job go faster, we put together a package including a Miller ProHeat 35 induction heating system, a 60kVA generator and a DP25 power distribution panel.

Red-D-Arc provided a reliable RDA Induction heating solution to a pipeline construction and maintenance company in Houston who needed to maintain consistent temperatures for their welders to weld out joints from pipes. Our induction heating specialist supplied our customer with a portable induction heating package consisting of a 60 KVA generator, a Miller Pro-Heat 35 induction heating system, and a DP25 power distribution panel. As a cost-effective alternative to their existing propane burners, induction heaters allowed them a secure heating, consistent temperature control, increased weld time, and improved safety.

With this setup we were able to get the pipe up to 250 degrees in about 5 minutes. Our customer was able to beat the competition’s target time by over 19 hours and has been asked to quote on other pipeline work for their client. Needless to say they were pleased with the solution and the opportunity for extra work it created.
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Induction Heating vs Other Methods

29 April, 19 4:48 am · Leave a comment · Colin Brown
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Pre-weld and post-weld heat treating is critical for many welding operations. Without proper thermal manipulation, welds and heat affected zones can have mechanical properties that are undesirable. Worse yet, inadequate heat treatment can result in cracks and devastating weld failures. While temperature and time are the primary concerns when heat treating a weld, the heating method should also be considered diligently when selecting a process. Induction heating is one of the most popular types of heat treating methods, and rightfully so. The benefits of induction heating are many, and Red-D-Arc has the equipment you need to successfully implement an induction heat treating operation for your projects.
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92% Improvement – Turning Problems into Possibilities with a Custom Welding Package

31 August, 18 11:30 am · Leave a comment · reddarc
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Induction Heating with Submerged Arc Welding

When one of our customers was tasked with an electrical motor shaft rebuild that required them to weld new fins onto a 7” diameter shaft, they called on Red-D-Arc’s team of experts for assistance. The job required the shaft to be preheated to a temperature of 400°F and welded using a submerged-arc process (SAW). Using the Miller Proheat 35 and Lincoln’s LT7 sub arc package, a job that was originally bid at 40 hours took just 3 hours to complete.
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Airgas, an Air Liquide company, is the nation's leading single-source supplier of gases, welding and safety products. Known locally nationwide, our distribution network serves more than one million customers of all sizes with a broad offering of top-quality products and unmatched expertise.