Our expertise has been gained over 150 years (5 generations) working in Thiers, the cradle of French knife manufacturing. Today Rousselon uses this expertise to offer the best of contempory designs.
THE MANUFACTURING PROCESS
Different compositions determine quality of steel. We use 2 types of steel:
● Carbon steels containing mainly iron and carbon (0.6% to 1%).
● Stainless steel, alloyed in varying quantities to achieve desired quality : carbon (0,2% to 1%) ; chromium (12% to 17 %) ; molybdenum (0% to 1%) ; vanadium (0% to 2%).
Carbon provides hardness, chromium is unoxidizable, molybdenum and vanadium are anticorrosive. Quality depends on the mix and quantity of alloys used.
It must always be remembered that the lower alloy quantities used will mean lower price but also poorer quality. The mix selected is cast in ingots and then formed into the required shape depending on the final use of the knife. E.g. : round for fully forged blades or bevelled or flat for stamped blades.
Blades are heated up to a temperature of 2012 degrees Fahrenheit. This operation takes place in a controlled atmosphere with the introduction of a specific gas to avoid calamine deposits. Blades are then cooled down very quickly and then Tempered, to remove brittleness, by re-heating up to a temperatures of 240° and then cooling again until the requires hardness is achieved (from 52 to 58 HRC depending on intended final use). These delicate operations require rigorous analysis and constant checking of heating and cooling times, depending on the grade of steel to be produced. High-quality blades require high quality testing. For instance, if the heat treatment is completed too quickly, the steel’s structure may be altered in such a way that the blade will quickly lose its sharp edge during use, even if it is graded as being very hard.
Attention! Rapid heat treatment = surface only treatment = weak core steel = breakable or tender blade liable to corrosion.
Blades are ground on both sides to ensure that the cutting edge will be resistant to damage and easy to sharpen. Grinding can be done in different ways: flat, rounded or by wheel, which is more difficult and takes longer longer but results in a longer lasting edge.
Depending on the products range, these other operations contribute to quality and aesthetics. The most prestigious collections still require manual know-how and dexterity that even the best machines can’t equal.