How to deal with the phenomenon of burning and oxidative decarburization during heating in a box furnace?
Time：2020-12-25 16:43
The material is easily oxidized and decarburized in the heating process of the box furnace, which will deplete the metal elements on the surface of the workpiece, which will affect the surface quality, and the mechanical properties and corrosion resistance of the metal will also be reduced.
The convex and concave molds of the mold generally need to be quenched. After quenching, they are lightly ground before assembly. If the mold is heated, the mold produces severe oxidative decarburization, and the oxidative decarburization layer is often not completely eliminated during assembly, which affects the use of accessories.
To avoid the formation of overburning and oxidative decarburization, we must first understand how overburning and oxidative decarburization are formed.
First, we need to understand a few phenomena, which can help everyone understand better.
Overburning phenomenon: The so-called overburning refers to the phenomenon that the heating temperature of industrial electric furnace is too high, which causes the austenite grains to be coarse, and the grain boundaries are locally oxidized or melted, which leads to the weakening of the grain boundaries. The performance of steel will deteriorate severely after overburning, and even tortoise cracks will be formed during quenching. The overburned structure of the tube furnace cannot be recovered and must be scrapped. Therefore, we must avoid overburning during actual operation.
Decarburization: Generally, when an industrial electric furnace heats steel, the carbon on the surface reacts with oxygen, hydrogen, carbon dioxide and water vapor in the medium to reduce the carbon concentration on the surface. This is called decarburization. After decarburization steel is quenched, not only the surface hardness and fatigue strength will be greatly reduced, but also its wear resistance will be weakened, and the residual tensile stress formed on the surface will also easily form surface network cracks.
Oxidation phenomenon: Oxidation is usually called oxidation when iron and alloys and elements on the surface of steel react with oxygen, carbon dioxide, and water vapor in the medium when heated in a box-type electric furnace. For such problems, the surface coating of the workpiece is generally used, the stainless steel foil is used for sealing and heating, and the salt bath furnace is used for heating to prevent the oxidation and decarburization of the workpiece. Ordinary workpieces will be oxidized above 570 degrees. After oxidation, not only the dimensional accuracy and surface brightness of the oxidized workpiece will be extremely deteriorated, but also the steel parts with poor hardenability when they have an oxide film will be prone to quenching soft spots. occur.
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