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What is the purpose of heat treatment of brass? Will it harden?

November 17, 2023

What is the purpose of heat treating brass?

 

1. The purpose of quenching is to make brass obtain high hardness and wear resistance. The hardness of brass through quenching can generally reach HRC60~65. However, internal stress is generated inside the brass after quenching, making the brass brittle, so , to be eliminated through tempering treatment.

 

2. The purpose of tempering is to eliminate the internal stress generated during quenching of brass and stabilize the brass structure; reduce the brittleness during quenching and increase plasticity and toughness. Tempering is a heat treatment process performed after quenching and is also the final process of heat treatment. It has a decisive impact on the final performance and structure of the product. It is believed that after quenching, although the hardness and strength are greatly improved, the plasticity and toughness are significantly reduced. This is quenching brittleness.

 

3. The purpose of annealing is to reduce hardness, improve plasticity, improve cutting performance, eliminate internal stress, such as eliminating internal stress in forging and casting, prevent deformation after processing, refine grains, uniform structure, and improve mechanical properties. The annealing purposes pointed out above are not achieved by all brass, but can only meet one or several purposes.

 

What is the brass heat treatment process?

 

(1) Low temperature annealing

This process is to eliminate cold deformation processing stress and prevent cracking. The heat treatment specification is: (260~300)℃×(1~3)h, and air cooling after the heat preservation is completed. This process is used for brass with a zinc content greater than 20%. When it is cold deformed, the residual internal stress will accelerate intergranular corrosion, especially in humid air or in gases containing trace amounts of ammonia or ammonium salts. , after staying for a period of time, cracking will occur, that is, "seasonal cracking". Its temperature is lower than the recrystallization temperature. Generally, the heating temperature is 200~350℃ and the heating time is 1~5h to eliminate cracking defects.

 

(2) Recrystallization annealing

The purpose of recrystallization annealing of brass is to eliminate cold work hardening and restore plasticity. The process is to insulate the pit furnace at 500 to 700°C for 1 to 2 hours, and then air cooling or water cooling can be selected according to requirements. The advantage of water cooling is that parts can be removed surface oxide scale for a clean appearance. Generally, after the copper strips used in salt furnaces are used for a period of time, the surface is oxidized or deformed, resulting in poor contact with the electrodes. They are heated in the salt furnace for a certain period of time, and then water-cooled to obtain a good surface, which is also convenient for alignment. Ensure the normal operation of the salt furnace.

 

The process of brass heat treatment includes quenching and annealing. After heat treatment, the toughness of brass can be greatly improved, which will extend the service life of brass products.