Do you know the great harm of oxide scale in forging plant?
Sep 22 , 2021

Oxide scale is a phenomenon in which the oxidizing gas in the furnace gas chemically reacts with the metal when the metal is heated, forming an oxide scale on the surface of the metal. When the iron on the surface of the steel diffuses from the inside to the outside surface in an ionic state, the oxygen in the oxidizing gas is adsorbed from the outer surface of the steel in an atomic state and diffuses to the inside. Because the expansion coefficient of the oxide scale is different from that of the steel, it is easier to fall off. The melting point of the oxide scale is lower at 1300-1350℃, and it is easy to melt at high temperatures. The fall off and melting of the oxide scale will cause the newly exposed steel surface to reoxidizes. Increase the loss of metal.

Let's look at the hazards of oxide skin below:

First of all, the oxide scale on the surface of the forging will cause metal loss, which will not only reduce the surface quality of the forging, but the oxide scale attached to the surface of the forging will cause unevenness in the structure and performance of the forging during heat treatment. The oxide scale has high hardness, which will accelerate the wear of the die forging cavity during die forging, and will accelerate the damage of the tool during machining. In addition, the oxide scale is alkaline and falls off in the furnace of the heating furnace to react chemically with acidic refractory materials, shortening the life of the heating furnace.

Therefore, scale on the surface of forgings has become a thorny problem in the forging industry. Sandblasting, shot blasting, heating and pickling, and mechanical descaling are usually used. Later, a descaling equipment using the principle of high-pressure water descaling was launched and won the favor of the majority of forging customers. Under the action of the high-pressure mouth, the fan-shaped surface formed is like a sharp blade of extremely fast water, which cuts the dense iron sheet and forms cracks.

It can be seen that the thin fan has a greater impact; the high-pressure water quickly vaporizes and evaporates when encountering the high-temperature base material through the cracks, forming an effect similar to blasting, peeling off the oxide scale and the base material; the oxide scale is impacted by water When cold shrinks, a transverse shear force is generated, which will peel off the oxide scale and the base material; the scouring action of the water jet with a forward inclination angle will wash away the loose iron sheet.

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