ADVANCED VSR ADVANTAGES
The cost of thermal stress relief is generally based upon a work-piece weight or (if large) overall size. This cost has increased over the years. Although the cost of energy, which has varied, is the largest variable cost associated with thermal stress relief, other, so-called “fixed” costs associated with heat-treating, including capital investment, environmental regulations, labor, transport (included permit-loads) and insurance, have increased over time.
In other words, using the VSR Process is putting in to practice GREEN TECHNOLOGY.
Cycle time for thermal stress relief to process a typical welded structure varies, but is often 8 – 24 hours, with additional steps, such as sand or grit blasting, needed for cleanup / scale removal. A typical VSR Treatment will take one hour, although some components require two treatments.
Since the VSR Process can be done on a shop floor, the need for transport to and from a furnace, whether in-house or outside, is also saved, an added time consideration that is often overlooked.
Thermal stress relief consumes a significant amount of fossil fuel, typically natural gas. It has been estimated that thermal stress relief in the US alone consumes enough natural gas to heat 8 million homes. A typical thermal stress relief cycle of a 10 ton structure consumes more than the equivalent of 52 gallons of gasoline.
The VSR Process uses a modest amount of electric power to operate, often a fraction of 1 kWh per treatment.
CONTROL OF MANUFACTURE
Having a VSR System in-house keeps production moving, by minimizing time and handling associated with major components. It reduces reliance on outside vendors or transport, accelerating turn-around times by factors of 5 – 20.
MAINTENANCE OF PHYSICAL PROPERTIES
A significant number of alloys, including austenitic (300 series) and other stainless steels and low-carbon, high-strength (T-1, ASTM 514, 709, etc.) run significant risk of physical property loss / metallurgical damage, if thermally stress relieved. In recent years, research has shown that thermal stress relief / PWHT of certain titanium alloys degrades these materials fatigue properties. For more information, see PWHT risks.
- With stainless steels the risk of causing sigma-phase damage normally precludes thermal treatment. Yet, structures made of these materials often must satisfy stringent, stable dimensional properties.
- With low-carbon, high-strength steels, the degradation includes reduction in strength and toughness, properties of these alloys that justified their selection. Please consult plate-stock handbooks from your steel supplier for more detail.
In comparison, a VSR Treatment causes no change in metallurgy or physical properties.