Hot and Cold Precision Straightening: What Are The Differences?17 October 2016
High tolerances rule hot and cold precision straightening work. The factory floor is filled with high-tonnage presses and industrial grinding stations, the larger-than-life tools that enable expert material engineers to meet any deadline. But why is a straightening service essential in a heat treatment shop? In order to answer this question, we need to know why treated parts manifest physical deformations.
Quantifying Mechanical Deformations
There’s no way around the fact that some heat treatment work does cause an observable deformation effect. This is due to the stress placed on the alloyed part during its passage through the tempering and quenching process. Machining and cold working stations also introduce distortion zones, but a recovery annealing procedure offsets this undesirable result. Otherwise, a warping component could crack or split while clamped. This abrupt deformation becomes even more likely when complex profiles are part of the part’s design.
Rectifying Warpage by Employing Cold Straightening Processes
If the microcrystalline grain of the metal part hasn’t assumed an overly hardened form, then it can be loaded into a powerful mechanical press and straightened. High tolerance straightening is further refined by passing the part through a grinding machine. The plasticity quotient of the metal’s structure is key here, for a low elasticity limit locks the metal in its twisted form unless further thermal processing is applied. Any attempt to cold straighten a part that’s this hard will likely result in cracking and stress fracturing, thus rendering the part useless.
Using Controlled Thermal Straightening
If cold type precision straightening is voided, a thermal technique is called upon, which makes sense since we’re working under the constraints of a heat treatment facility. Thermal methodologies clamp the part and restore its profile to acceptable tolerances by controlling the direction of the linear-restorative vector, all so that the final part is ready for application. Of course, further annealing may be required to offset the strain introduced by any straightening, but this is an executive decision, one best left to the head engineer.
Linear corrections are as simple as loading the part into a 20-Tonee press until it’s dimensionally stable, but new straightening techniques use proprietary technologies to assure a dead-level profile. These computer-aided scanners use mathematical analysis to correct flaws that are invisible to the eye. Hot and cold precision work is currently meshing the finest attributes of mechanical processing and electronic scanning to create a perfectly repeatable corrective mechanism, one that straightens based on material hardness and any deformations introduced by the heat treatment workflow.
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