Annealing furnace oxidation and decarburization

Annealing furnace oxidation and decarburization

 

1. Oxidation is because when steel is heated in an oxidizing gas, it will oxidize and form an oxide scale on the surface. At high temperatures, even grain boundaries will oxidize.

 

2. When steel is heated in certain media, these media will reduce the carbon content of the steel surface. We call this phenomenon "decarburization". Methods to reduce or prevent oxidation and decarburization of steel during quenching include:

 

1). Use a salt furnace with good deoxidation for heating;

 

2). Heating in a controllable protective atmosphere furnace;

 

3). Heating in a vacuum furnace;

 

4). Reserve enough machining allowance.

Annealing furnace recrystallization annealing

 

It is applied to alloys that undergo solid phase transformation (recrystallization) during balanced heating and cooling. The annealing temperature is a temperature above or within the phase transformation temperature range of each alloy. Both heating and cooling are slow. The alloy undergoes a phase change and recrystallization during the heating and cooling process, so it is called recrystallization annealing, often referred to as annealing for short.

Deformation and cracking measures of annealing furnace:

 

1. Use reasonable forging and pre-heat treatment;

 

2. Use a reasonable heat treatment process;

 

3. Adopt the correct method of operation;

 

4. For the parts that are easy to crack during quenching, such as keyways, holes, etc., block them with asbestos.

The latter is mainly used for forging and rolling parts of medium carbon and high carbon steel and low alloy structural steel. If the cooling rate after forging and rolling of this forging and rolling is high, the pearlite formed is finer and the hardness is higher; if the forging and rolling stop temperature is too low, there will be large internal stress in the steel. At this time, annealing can be used instead of annealing to recrystallize the pearlite, reduce the grain size, reduce the hardness, eliminate the internal stress, and improve the machinability. In addition, the spheroidizing annealing of hypereutectoid steel whose annealing temperature is between Ac1 and Acm is also annealing.

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