Canister Damascus or canned Damascus is a composite steel made by placing solid and powdered steels in an airtight environment inside a metal canister, and forge welding them together at high temperature and pressure. The welded bar is repeatedly reheated in the forge and pressed by a pressing machine (die mold) to produce a stout solid billet, then cut into cross-section pieces to be welded and turned into the final product. The process results in diverse mosaic patterns in the final product, such as a knife blade.
Materials for canister Damascus
A variety of steels is used for the canister Damascus, as in the case of ordinary Damascus. Powdered steel is poured in the can, between some elements of solid metal, such as ball-bearings or steel rods. Usually, a very fine granulated metal powder, like 1095 powdered steel, is used for making canister Damascus.
Another important element of forging canister Damascus is the white-out used to coat the can from inside. White-out is collodion with titanium dioxide white pigment in it. The purpose is to cover the canister walls with titanium dioxide coating that will not weld and will act as a resist on the inside of the can.
How to make canister Damascus?
First, you have to build a canister (a “can”) from metal walls. It is sometimes the most time-consuming part of the process, as you have to calculate the dimensions of the can and the thickness of the walls properly. During the process it is crucial to remove all the airspace out of the can and weld the final lid on correctly.
You’ll have to carefully estimate the time required for your can to soak in the forge, as every single grain of powdered steel must reach welding temperature to start fusing. Soak time largely depends on the mass of your canister. Although some smiths have been happy with as little as 15–20 minutes, often you will not get all the powdered steel completely fused until 30 to 45 minutes.
It is crucial to have your forge running and being properly heated before you weld a lid on the canister. Otherwise, if there is even a tiny hole in your weld, it will cool down and suck air into the can, which means you’re going to have a void inside. So, make sure you place the canister into the forge as soon as possible after adding the lid.
When passing the billet through the die mold, accuracy means much more than brute force. Make sure to execute every pass through the dies gently and not to press the can all at once, to prevent your billet from collapsing.
After thoroughly pressing the billet and letting it cool down, you can cut cross-section profiles to be further welded into a final product, for example, a canister Damascus blade with an aesthetic pretty pattern.
The production of a custom knife requires particular attention to the type and quality of steel to be used in the blade. Blade steel, as well as edge geometry and design, is the crucial element that determines knife performance. Steel quality depends on the alloy used – that is a mix of carbon and iron often enriched with other elements added for the purpose of a particular application. In the knife industry, not only the type of steel but also the finishing process matters: variation of types of additive elements and techniques of rolling and heating the blade results in different types of steel.
Blade heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve the desired result such as hardening or softening of a material.