What Is Crucible Steel?

Crucible steelmaking, a method of melting molten metal into molten steel in a graphite clay crucible. In 1742, the British B. Huntsman cut the carburized iron material into small pieces and placed it in a closed clay crucible, and heated outside the crucible. The iron material continued to absorb the carbon in the graphite and melted into high-carbon molten steel and cast. After forming into small ingots, it is forged into the desired shape.

Crucible steelmaking refers to the method of melting molten metal into molten steel in a graphite clay crucible. First applied by the British B. Huntsman in 1742, he cut the carburized iron material into small pieces and placed it in a closed clay crucible.

The continuous heating time ranges from 24 to 48 hours. When the temperature rises from 1000 degrees Celsius to 1200 degrees Celsius, the ore will transform into porous iron and stay at the bottom of the crucible. The crucible is closed, and the charcoal from the combustion and the leaves melt together Within the iron. Bamboo contains silicon oxide, which can help dissolve. In this process, iron does not reach its melting point. Through the solid diffusion process, carbon is absorbed, and the casting is continued for a long time, and then it is slowly cooled to 800 degrees Celsius for about 12 to 24 hours. These large crystals are in fact the main constituents of the Damascus steel pattern or water pattern. Cementite or carbide crystals are very hard and acid resistant. When the steel is polished, it will appear white or silver. In contrast, pearlite is made of bonded metal and eroded to black, which explains why different colors are produced.

After cooling, remove the crucible from the fire, break it, and remove the hemispherical steel ingot. Place it on an anvil and hammer it for hardness testing. Normally cast steel ingots are very hard and there are no dents after hammering. Therefore, it is necessary to cover with a clay mixture containing iron filings or powdered iron ore in order to strengthen the decarburization of the steel ingot. After reheating the steel ingot to a fire red temperature of about 700 degrees Celsius to 900 degrees Celsius, the hammer was tested for hardness. This heat treatment process is repeated until the metal is sufficiently soft to be forged. Steel ingot exercise: Slowly lower the temperature of the steel ingot and control it between 700 ° C and 900 ° C. This temperature is a very important key. The blacksmith can only rely on experience, see the color of fire with his eyes, and forge when it reaches dark red. Because if the temperature rises above 900 degrees Celsius, the process will be reversed. The higher the temperature, the carbon melts, causing the loss of crystals and wavy patterns. If the temperature is lower than 700 degrees Celsius, steel will not get enough exercise. Because European blacksmiths generally exercise metal at a high temperature of 1300 degrees Celsius, they cannot master the technique of exercising Damascus steel. Due to the controlled heat treatment and light exercise of the steel ingot, the covered clay, including iron filings or powdered iron ore, decarburizes the surface of the steel ingot. In addition, oxidation also produces the same effect. The carbon content of steel ingots gradually decreased from 2.2% or higher to 1.8%, that is, from white cast iron to carbon steel. This process can also be called annealing and spheroidizing. The steel bars have become malleable and flexible.