| This is an article to explain heat treating to a | | | | and then taking it out of the forge to cool in still |
| person who is not really interested in steel | | | | air.Why do we do this? We do this to help the |
| structure terms such as Martensite, Austensite | | | | steel adjust to it's new form after forging, |
| and Pearlite. They just want it explained in | | | | straightening or grinding. When we change the |
| everyday language.So here goes. | | | | form of the steel we create stresses that are |
| When we talk about "heat treating" steel for | | | | uneven in the steel. To use the rubber band |
| wood carving tools we are talking about the | | | | analogy, when you try to stretch them apart, |
| process of making a piece of steel as hard or | | | | some bands are very tight and some are still |
| soft as needed to perform a specific job. The | | | | relaxed. When we normalize we are trying to get |
| following is the series of events in order. | | | | all of the steel in the same state of |
| Heat treating can vary bladesmith to bladesmith | | | | tension.HardeningHardening is heating steel to a |
| and steel type to steel type. For example, one | | | | critical temperature where all of the molecules of |
| bladesmith may have a different process for heat | | | | the steel are at their best arrangement and |
| treating a high carbon steel for a carving blade | | | | stopping them abruptly using a coolant or |
| and yet another for heat treating a filet knife. The | | | | quench.Why do we do this?This is making steel as |
| bladesmith can equate to a chef, they all have | | | | hard as possible. A cutting edge is best when we |
| thier "special recipes" and methods to create their | | | | can form the hardest, finest, smoothest edge |
| individual product.For our purpose, critical | | | | possible. Back to the rubber band bundle. With the |
| temperature is when the molecules are moving | | | | bundles of rubber bands relaxed you can put |
| around without burning up or destroying each | | | | them across your leg and they don't make much |
| other. | | | | of a impression. Stretch them as far as you can |
| Annealing | | | | and push them into your leg and they make a |
| Annealing is heating steel to a critical temperature | | | | good impression. |
| (sometimes 2000º) and letting it cool down | | | | Tempering |
| very slowly to room temperature in an oven, | | | | Tempering is removing hardness from steel with |
| forge or insulating mediums such as woodstove | | | | heat to give it more toughness and flexibility.Why |
| ashes, vermiculite, or ceramic insulation. Why do | | | | do we do this?This process helps the blade |
| we do this?This is simply making steel as soft as | | | | become more stable. If left in its hardened state |
| possible. When we start to form our blade, | | | | the blade would be as hard and brittle as glass. |
| whether it is with a file, sandpaper or grinder, it is | | | | The blade will snap like a potato chip when we try |
| more easily formed when it is in a softer state. | | | | to carve with it. When we temper it we make it |
| For example, M2 steel is a high speed alloy steel | | | | relax to a more usable state. Rubber bands again. |
| that is used for planer and moulding blades. Very | | | | When we stretch the rubber bands to their limits |
| hard stuff. It is sharpened and cut with hard | | | | and push them against our leg some of them |
| ceramic stone. To try and file it in its hardened | | | | break. But if we can remove some of the |
| state is like trying to push a needle into glass. | | | | tension, and still make a dent in our leg without |
| When properly annealed, you can file it and sand it | | | | breaking them we've achieved a perfect |
| like a piece of copper.Picture in your mind a bundle | | | | hardness. |
| of rubber bands that you are grasping in both | | | | Heat treating can vary bladesmith to bladesmith |
| hands. We are taking the bundle of super | | | | and steel type to steel type. For example, one |
| stretched rubber bands and putting it in a totally | | | | bladesmith may have a different process for heat |
| relaxed state so that we are able to easily | | | | treating a high carbon steel for a carving blade |
| change its form and remove rubber bands from | | | | and yet another for heat treating a filet knife. The |
| the bundle. | | | | bladesmith can equate to a chef, they all have |
| Normalizing | | | | their "special recipes" and methods to create their |
| Normalizing is heating steel to a critical | | | | individual product. |
| temperature, holding it there for a few minutes, | | | | |