Have you heard of through hardening? It’s commonly used to increase the strength of metal fasteners, such as washers. Some fasteners are made of conventional stainless steel, whereas others are made of through-hardened stainless steel or other alloys. Through-hardened washers have a longer and more complex production process, but they are stronger than their conventional counterparts. Here are five facts about through hardening that you need to know.
#1) Involves Rapid Quenching
Through hardening involves rapid quenching. During this process, a metal fastener or object is heated to a critical temperature. The fastener or object is then quenched in oil or water. The rapid change of temperature — going from hot to cold — results in physical changes. The fastener or object will become harder, and its tensile strength will increase.
#2) Also Known as Neutral Hardening
You may through hardening described as “neutral hardening.” Both terms refer to the same process of rapidly quenching a piece of heat-treated metal for the purpose of making the metal stronger. Some people refer to it as “through hardening,” whereas others refer to the process as “neutral hardening.” Regardless, the terms are interchangeable, with both referring to the ame heat treatment process.
#3) High Carbon Content
The carbon content of through-hardened fasteners and other objects is typically greater than that of non-through-hardened fasteners and objects. Through hardening doesn’t necessarily add carbon. Rather, it has little or no effect on steel with a carbon content of less than 0.25%. Therefore, only steel with a higher carbon content is treated via through hardening.
#4) Not the Same as Case Hardening
In addition to through hardening, through’s case hardening. They are both heat treatment processes, and they can both increase the strength of metal fasteners and objects. With that said, through hardening isn’t the same as case hardening. Case hardening only affects the exterior or “case” of a fastener or object. It will create a stronger exterior while preserving the softer and more ductile interior. Through hardening, on the other hand, affects all of the fastener or object.
#5) May Involve Tempering
Through hardening may involve tempering. The first step is heating the metal fastener or object to a specific temperature. Once heated, the fastener or object is quickly quenched to lower its temperature. Next comes tempering. Tempering is done to remove brittle areas and increase the toughness. There are different ways to perform through hardening, but many o them involve these three steps: heating, quenching and then tempering.