What causes case hardening in timber?
Case hardening describes lumber or timber that has been dried too rapidly. Wood initially dries from the shell (surface), shrinking the shell and putting the core under compression. When this shell is at a low moisture content it will ‘set’ and resist shrinkage.
What causes case hardening?
Case hardening is the result of produce that has been dehydrated at too high of a heat, causing the outer portion of the fruit or vegetable to become hard, making it hard for moisture to escape the piece. Thus, you get a hard, dry outside, and moist inside, even after drying for an appropriate amount of time.
What happens if timber is dried unevenly?
If timber is dried unevenly one side may shrink, twist, bow or split. The end result is that timber will respond to the external conditions it is exposed to and will constantly adapt to the prevailing conditions whether whilst installed or whilst being stored.
What is case hardening on wood?
Case hardening is a feature of dried wood that causes the wood to deform (cup) after re-sawing and equalising the moisture content. With effective conditioning at the drying temperature, or with steaming after cooling, it is possible to reduce or remove the case hardening.
What type of defect is case hardening?
Severe case hardening can cause another serious defect known as Honeycombing. This defect is only visible after resawing when checks are seen in the interior of the boards.
What causes twisting in timber?
Wood acts as a sponge, expanding as it takes in moisture from an environment with high humidity. And then it shrinks and hardens as it drys out while acclimating to a lower humidity. This causes twisting and warping to varying degrees.
What causes springing in timber?
Spring – Occurs when the board remains flat in width, but curves in length like a river going around a bend. Case hardening – When lumber or timber is dried too quickly, wood shrinks much at the surface, compressing its damp interior. Extreme cases of case hardening leads to honeycombing.
How does case hardening work?
Case-hardening involves packing the low-carbon iron within a substance high in carbon, then heating this pack to encourage carbon migration into the surface of the iron. This forms a thin surface layer of higher carbon steel, with the carbon content gradually decreasing deeper from the surface.
What is the difference between case hardening and induction hardening?
Case hardening technology marries heat with chemistry to create a thermochemical process. Conversely, an induction hardened metal part uses pure electromagnetic energy to “induce” an alternating current within the part.
