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