High speed steel annealing process

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Why do high-speed steel workpieces be annealed, and what are the annealing processes?

After forging high-speed steel, in order to eliminate the forging stress and reduce the hardness, to facilitate the cutting process and prepare the structure for quenching, (final heat treatment), therefore, the high-speed steel forging must be annealed. In the actual production, the annealing process of high speed steel can be divided into ordinary annealing and isothermal annealing.

High speed steel annealing process

The annealing temperature of high speed steel should not be too high. Its Ac1 temperature is 820 ~ 840 ° C, the general heating temperature is slightly higher than Ac1, that is, 860 ~ 880 ° C. At this time, there are not many alloying elements dissolved in austenite, and the stability thereof is small, and it is easy to obtain a pearlite-like structure having a low hardness; if the heating temperature is too high, a large amount of carbon and alloying elements are dissolved in the austenite. The stability is increased, it is not easy to soften during annealing, and it takes a long time.

Annealing time should not be too long. The general holding time is 2 to 4 hours. If the time is too long, the easily soluble carbide Fe2 W2C in the steel will be converted into insoluble WC. When quenched and heated, WC is not easily dissolved in austenite, thereby reducing the quenching effect and lowering the hot hardness (red hardness) of the steel.

High-speed steel has a long annealing time, and care should be taken to prevent oxidative decarburization during operation. If annealing in an electric furnace, protection should be used. Our actual operation is to put the annealed workpiece into the iron box welded by iron plate (6~8mm thick) (the size of the iron box is determined according to the size and the number of the workpiece), and the top and bottom of the workpiece are protected with dry charcoal. It does not oxidize and does not decarburize, and the lid is sealed. Be careful not to protect with charcoal carburizing agent to prevent carbon on the surface of the workpiece.

Generally, the hardness of high speed steel after annealing is 207-255HB.

We use a common annealing process and the annealing results meet the technical requirements.

Learn More: Vacuum Annealing Furnace