Instant Impact Quench (IIQ)
Contrary to popular belief, a faster quench rate DOES NOT increase the probability of cracking or distorting the part. Instant Impact Quench is “uniform and intensive” water quenching applied after Austenitize heating. Very high intensity quenchant flow is needed at the part surface shell to eliminate non-uniform film boiling.
The first step is very rapid and uniform cooling from the austenitizing temperature, usually in highly agitated water, until optimal compressive stresses are attained in the surface layer of the part. Once optimal compressive surface stresses are attained, the part is removed from the quench, and the final cooling step is done in air or inert gas. In contrast to conventional oil, polymer/water or gas quenching, IIQ methods provide higher as-quenched hardness, to a deeper level in the part, while maintaining high residual compressive surface stresses, and, at the same time yielding low distortion.
There are two types of IIQ. IQ-2™ is done in a tank with the hot parts presented in batches. IQ-3™ is single part quenching usually at a more intensive “high velocity” flow of 5 to 20 meters per second.