On site pre-heating, hydrogen de-gassification and post weld heat treatment of pipework, welded fabrication and pressure vessels. Flexible electrical resistance heating elements are manufactured in a range of sizes to suit a wide range of applications and are connected to either low Voltage (65 Volt) or high Voltage (240 Volt) power sources.
Temperature control is via pre-programmable microprocessor based modules and temperature measurement by pre calibrated temperature recorders. All temperature measuring equipment is calibrated in accordance with national standards.
Preheating is the application of heat to the base metal prior to welding or cutting operations. It does not change the properties of the steel, but it is advisable under certain conditions to drive off moisture and helps to ensure even expansion to eliminate undesirable stresses. Concurrent heating during welding (also referred to as preheating) retards the cooling thus preventing the formulation of an under bead crack.
Stress Relieving (Post Weld Heat Treatment)
Stress Relieving is the heating of steel to a relatively high temperature and maintaining that temperature for a specific period of time. The purpose is to reduce internal stresses, caused by welding, quench hardening or by cold working. It also has an advantageous effect on the elasticity, ductility and strength of the metal. This process involves heating the steel to a temperature below the materialsí transformation point.
Annealing is essentially the softening of a metal to make it more malleable. The process involves a controlled heating and slow cooling which induces softness and ductility. Additionally, the process removes gasses, relieves stresses and enhances the mechanical properties in alloyed steels. This is generally performed at temperatures above the materialsí re-crystallisation point.
Normalising is much like annealing, but the cooling process is much faster. This results in increased strength but less ductility in the metal. It also produces a higher yield strength with greater tensile strength, and in most instances, a higher impact resistance. This process involves heating the steel to just above the upper critical limit.
Solution Heat Treatment
Solution Heat Treatment is performed on certain types of austenitic stainless steel to prevent decay in weldment. This is done at a very high temperatures (e.g) 1200C and the cooling is very rapid.