Large, Custom Heat Treat Furnace Fabrication

The video below demonstrates the erection of a 16' x 16' x 62' heat treat furnace built out of a 6x6 I-Beam skeletal structure with 11 gauge steel skin. Full size doors, two per end, will allow the furnace to heat loads using it's full volume. The furnace is equipped with eight 3-Million BTU burners, one at either end and 3 down each side, to circulate the air. Four dampers are included, two at each end. It will move back and forth on a rail system by (16) 10" crane wheels. A hydraulic system will act to lift the furnace 3" in the air off the hearth. This will allow the furnace to move freely and without damaging the insulation on the bottom seals. It will be controlled via a remote HMI screen with full SCADA capabilities.

For more information, visit http://www.hotfoilehs.com or call 609.588.0900.

Welding Heat Treatment Products from Hotfoil-EHS

Here's a little shameless, self-promotion from your friends at Hotfoil-EHS.

New Product: The ISG Wireless Heat Treatment Controller

The ISG heat treat controller.

The ISG heat treatment controller is a panel-mounted controller which can easily be connected to thyristor, electrical contactor, or induction/inverter driven power sources. The controller has 2 analog outputs, 5 digital outputs, 2 analog inputs and 2 digital inputs.

The ISG is capable of controlling two measurement points and monitoring two measurement points. If more measuring points are required, up to 14 controllers can be daisy-chained to the same heating process via cables or wireless, while all being managed from a single computer. The ISG communicates with PC's via Zigbee radio or with an RS485 Serial port.

All routines or process plans are created with ISPort software. After the process is started, the routine and the process data is saved to the PC, and also to the controller's memory. This enables the controller to work independently should the connection between ISG and computer be lost. The ISG includes a convenient LED process display and additional process status and alarm LED's.

For more information on the ISG heat treatment controller, visit http://www.hotfoilehs.com or call 609.588.0900.

Hotfoil-EHS Products

Weld Heat Treatment is Critical to Structure Integrity

Welding pre-heat is critical to the quality of the weld and
and the integrity of the structure.

In any large scale welding operation (such as pipeline welding, shipbuilding, boiler fabrication) heat treatment is critical to the quality of a weld, and therefore critical to the performance of a structure, and never should not be taken lightly.

When in doubt, review of industry code or a consultation with a welding expert is imperative. Welding code is the first determinant to whether pre-heating is needed. Welding code carefully specifies the minimum preheat temperature, the soak time, and the welding process. Many criteria are considered by welding codes, all gathered from years of rigorously tested data. This data is accumulated from many sources, including metallurgical science, chemical properties of materials, and radiographic analysis.

In its simplest form, weld heat treatment is the process of heating the base metal (parts to be welded) to a desired temperature prior to welding, and then allowing it to cool at a given rate under controlled conditions. The specific temperature to which the part needs to be heated (before welding) is referred to as the “preheat temperature”.

There are several key reasons why it's important to preheat before welding. 

• A preheated part cools more slowly, which slows the overall cooling rate of the welded part. This improves the metallurgical (crystalline) structure and makes it less prone to cracking. 
• Hydrogen that may be present immediately after a weld is also released more efficiently, which further reduces the possibility cracking. Preheating also mitigates stress from the shrinkage at the weld joint and nearby metal. 
• Pre-heating reduces the possibility of fracture during fabrication due to brittleness.

Electric welding preheaters, known as "ceramic mat heaters", are rugged and flexible heating elements designed so that they conform uniformly around the weld and surrounding area.  Ceramic mat heaters are normally controlled by a power console that uses thermocouples and electronic controllers to regulate, monitor, and many times record, the preheat temperature profile.

Another less preferred method to heat the target piece is with a torch, or open flame, but this method carries safety concerns as well as controllability issues. Furnaces are also used, but these typically require the transport of the target piece off-site.

Induction heaters offer an attractive alternative for safety, portability and controllability. Induction heating is unique because it uses molecular excitation as its source of heat, as opposed to open flames or external electric elements. Induction heating works very quickly, and since there is no contact with the target piece, there are far less concerns about part contamination.  Many industrial processes use induction heating when very high temperatures and uniform control is desired.

Each welding application has it's own unique set of circumstances which dictate the optimal heat treating method.  It is always best to contact an expert and solicit their opinion on your best available option.