How to solve the various defects that may occur during heat treatment?
How to solve the various defects that may occur during heat treatment?
During industrial production, heat treatment is a key process, that can give specific properties and strength to workpieces. However, the heat treatment process is not always smooth sailing. Various defects often occur. These defects are like hidden “landmines”. If not taken seriously and solved, they will seriously affect the performance and service life of the workpiece. Today, let’s take a closer look at the various defects that may occur during heat treatment and how to control them. 1. Overheating and overburning
Defect manifestation: Overheating: During the heating process of the workpiece, the austenite grains are significantly coarsened due to too high temperature or too long holding time. This will lead to a reduction in the strength and toughness of the workpiece, especially the impact of toughness. Over-burning: The heating temperature is too high, which not only makes the austenite grains coarse but also causes local oxidation or melting of the grain boundaries. The performance of the over-burned workpiece has seriously deteriorated and cannot be saved, so it can only be scrapped. Control method: Strictly control the heating temperature and holding time, and operate according to the process requirements. Adopt advanced heating equipment and temperature control systems to ensure accurate and stable temperature. Provide training to operators to improve their attention to temperature control and operational skills. 2. Manifestations of oxidation and decarburization defects:
Oxidation: During the heating process, the workpiece reacts chemically with the oxidizing gas in the furnace gas, forming an oxide scale on the surface. The oxide scale will reduce the surface quality of the workpiece and affect subsequent processing and performance. Decarburization: The carbon element on the surface of the workpiece reacts with the oxidizing gas in the furnace gas, reducing the carbon content on the surface. Decarburization reduces the hardness, strength, and wear resistance of the workpiece. Control method: Pass in a protective atmosphere (such as nitrogen, argon, etc.) or use vacuum heating. Apply anti-oxidation paint to the surface of the workpiece. Control the atmosphere composition of the heating furnace to maintain a weakly reducing or neutral state. 3. Deformation and cracking defect manifestations:
Deformation: Due to the action of thermal stress and tissue stress, the workpiece changes in shape and size. Deformation will affect the assembly and performance of the workpiece. Cracking: Cracks appear in the workpiece due to excessive stress or poor structure. Cracks can cause the workpiece to be scrapped. Control method: Reasonably design the workpiece structure to avoid complex shapes and uneven thickness. Select appropriate heat treatment process parameters to reduce stress generation. Use preheating and slow cooling measures to reduce the temperature gradient. Perform stress relief annealing and other treatments to eliminate residual stress. 4. Defect manifestation of insufficient hardness:
After heat treatment, the hardness of the workpiece does not meet the process requirements. Insufficient hardness will affect the wear resistance, strength, and other properties of the workpiece. Control method: Check the quality of raw materials to ensure that the chemical composition and hardness meet the requirements. Strictly follow the heat treatment process to ensure that the parameters are correct. Perform regular maintenance and calibration of heat treatment equipment. Reheat treatment or other remedial measures for workpieces with insufficient hardness. 5. Manifestations of uneven tissue defects: After the workpiece is heat treated, the structure is uneven and there are coarse grains, undissolved carbides, and other undesirable structures. Uneven structure will affect the performance and service life of the workpiece. Control method: Optimize the heat treatment process and promote tissue uniformity. Preprocess raw materials to improve tissue uniformity. Strengthen the monitoring and inspection of the heat treatment process and deal with problems promptly.
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