Do you know The difference between Annealing and Tempering?

Annealing and Tempering are production process for steel pipes. Do you know the difference between Annealing and Tempering?

Annealing is applied to a variety of metal processing, the main effect of annealing is to soften the metal and strengthen toughness. Annealing of steel is used in the production of preliminary heat treatment process. Most of machine parts or metal pieces, after rough mold annealed, it can eliminate casting, tissue inhomogeneity stress and forging components and weldments. Beiseds, annealing can improve and adjust the mechanical properties of steel, it make sure the metal piece is ready for the next process organization and preparation. For those less important parts, less demanding performance, some ordinary castings, weldments, annealing can be used as the final heat treatment. Annealed steel is the steel which is heated to a suitable temperature, and holding a certain time, and then slowly cooled to get close to equilibrium tissue heat treatment process. Annealing aims to uniform chemical composition, mechanical properties and improved process performance, eliminate or reduce stress and prepare the organization for the part to prepare the final heat treatment.


However, tempering is mainly used in steel hardening after reducing brittleness. Steel Tempering is to heated the steel to a certain temperature for certain time, and then cool the steel to room temperature by appropriate manner. In general, it will be applied after hardening heat treatment process. Tempering will decide the steel micro structure and properties during the application. Also, it is a key step to decide the using time of the work piece. The main purpose of tempering is to reduce or eliminate quenching stress, and ensure appropriate organizational changes. Moreover, tempering will improve thermal resistance and ductility of the steel. In order to meet the performance requirements of different metal parts, it is necessary to choose a different tempering temperature to obtain a good hardness, strength, ductility and toughness combination.

What is Quenching?

Quenching is the heat treatment process applied on metal. Heated the metal to a suitable temperature and hold for a certain time, then immersed in quenching medium and cooled immediately. In general, saline, water, mineral oil, air can be used as quenching medium. Quenching process is widely used in various engineering, mold, measuring tools and requirements of surface wear of parts ( such as gears, rollers, carburizing parts ect.). Because quenching can increase the hardness and wear resistance of metal parts. Quenching process has been widely used in modern machinery manufacturing industry. For those important mechanical parts, especially the metal parts applied on automotive, aircraft, rockets.

Generally, quenching and tempering will be applied together on the metal, by quenching and tempering with different temperatures can greatly improve the strength of the metal, fell toughness and fatigue strength, and to get fit ( mechanical properties) between the performance of these to meet different requirements. Further hardening can also make some special properties of steel to obtain certain physical and chemical properties, such as hardened steel reinforcing its permanent magnet ferromagnetic stainless steel to improve its corrosion resistance.

Quenching process is mainly used for steel parts, when steel heated to above the critical temperature, the original organization of steel turned into austenite ( all or most of). Then the steel will be immersed in water or oil rapidly cooling, and the austenite turned into martensite. Compared with other organizations in steel, martensite has highest hardness. Rapid quenching cooling causes internal stress generated. When it to a certain extent, the steel might be distortion or cracking. Therefore, the right method of cooling is significant.

For more manufacturing news, please read What is Annealing?, What is Tempering?, The difference between Annealing and Tempering