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Without good “heat treatment”, no matter how good-looking the screws are, they are all good looking!

Without good “heat treatment”, no matter how good-looking the screws are, they are all good looking!

As a key technology to control the performance of fasteners and ensure long life, safety and reliability, heat treatment is the core element of the competitiveness of advanced materials and high-end machinery and equipment. After all, without good “heat treatment”, no matter how good-looking the screws are, they are all good looking!

What is heat treatment?

Heat treatment is a general term for a process in which solid metals are subjected to specific heating and cooling methods to obtain the properties required in engineering. It includes three stages of heating, heat preservation and cooling.

As one of the important processes in the manufacturing process of fasteners, mechanical parts and tools, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but changes the microstructure inside the workpiece or changes the chemical composition of the workpiece surface. , Endow or improve the performance of the workpiece, it can control various properties of the workpiece, such as wear resistance, corrosion resistance, magnetic properties, etc., and can also improve the structure and stress state of the blank to facilitate various cold and hot processing.

Several fires in the heat treatment of fasteners

>>annealing

Annealing is a process of heating to an appropriate temperature-holding-slow cooling.

Purpose of annealing:

  1. Reduce hardness and facilitate cutting. 2. Eliminate the structural defects of forging, casting and welding parts. 3. Refine the grain and improve the structure, as a preliminary heat treatment to prepare for the final heat treatment. 4. Eliminate stress and prevent deformation and cracking.

The second and third fires are used in conjunction. Generally, it is usually called quenching and tempering in the fastener industry. Quenching and tempering treatment is a heat treatment process of quenching and tempering to obtain a tempered sorbite structure, in which the cementite is uniformly distributed in granular form. In order to obtain good comprehensive mechanical properties.

>>quenching

Heating to proper temperature – holding – cooling rapidly in oil quenching medium.

The purpose of quenching:

  1. Obtain martensite structure, improve hardness, strength and wear resistance; 2. Reduce internal stress, avoid deformation and cracking; 3. Combine with the subsequent tempering process to obtain good comprehensive mechanical properties of parts; parts after quenching microstructure (martensite)

>>Tempering

Heating to an appropriate temperature higher than room temperature but lower than 650°C – holding for a long time – cooling

Purpose: Increase toughness, increase dimensional stability, reduce quenching stress