Heat treatment is a set of measures that includes heating, holding and then cooling hard metal alloys. During the heat treatment process, the internal structure and crystal lattice of metals change, which makes it possible to achieve the required physical and mechanical characteristics.
Heat treatment of precision alloys, like other steels, is an integral part in the production of metal parts and tools, in particular hand tools, knives, springs, etc. It can significantly improve the strength of finished products, as well as reduce their brittleness, increase resistance to wear and restore other key characteristics.
The process of heat treatment of tool, stainless and other steels includes heating the workpiece to the temperature recommended by GOST, holding it for the time established by regulatory documents and then cooling it in a certain medium (in oil, water or air) at a regulated or unregulated rate.
Advantages of heat treatment of metal workpieces
Metal heat treatment is a key step in the production of durable and reliable structures. This process makes it possible to improve the physical and mechanical properties of alloys, including:
- increase the wear resistance of the metal and increase its resistance to mechanical stress;
- increase the service life of finished parts and structures, as well as minimize the number of defective workpieces;
- improve corrosion resistance by creating a protective layer on the metal surface, which is especially important if the structures are to be used in aggressive environments or outdoors;
- restore the original physical and mechanical characteristics, for example, for a precision alloy 79NM after the required part is formed, heat treatment is mandatory to impart the required magnetic qualities;
- increase the load capacity and make the finished structure more durable;
- make the metal softer and more supple to facilitate its subsequent deformation, cutting or drilling.
Heat treatment of steels is an integral part of the production of various tools and metal structures, ensuring high reliability and durability of finished products.
The main types of heat treatment of precision and other alloys
Each type of heat treatment is designed to give the finished structure certain characteristics.
- Normalization — relieves stress caused by casting, hardening or welding metal. It is carried out at a temperature of about 40°C above the maximum operating temperature. Due to normalization, steel becomes stronger and harder, and also acquires a uniform composition. It is recommended for products that require high impact strength and low tendency to deformation under maximum loads.
- Annealing — usually carried out at the maximum critical temperature. It increases viscosity, eliminates plastic deformations during recrystallization, relieves internal stress, and makes the alloy more malleable for subsequent molding. It can be of the first and second kind: it allows either to slightly change the crystal lattice or to achieve noticeable phase changes.
- Hardening — the most common type of heat treatment. During it, the metal is heated to a predetermined temperature and then cooled in water, oil or other liquid medium. This makes it possible to strengthen the outer layer of the finished product, leaving its inner part soft. This type of heat treatment is most often used in the manufacture of shafts. Hardening errors can lead to the formation of cracks, a decrease in the hardness of the steel, oxidation of the metal surface or its overheating and, consequently, an increase in grain size and increased brittleness.
- Vacation — reduces brittleness and restores the hardness of the alloy. It is usually carried out immediately after the hardening process. As the temperature rises during the tempering process, it increases the viscosity and softness of the metal workpiece. The temperature is determined visually by the color of the surfaces: dark red corresponds to approximately 630-730°C, light red — 800-900°C, dark yellow — 1050-1150°C, dazzling white — 1200-1300°C. Cooling high-carbon steel parts such as 65G, is produced in water or oil, made of stainless steel in oil. One of the most important factors when tempering is the trajectory of the workpiece immersing in a cooling medium: if the technology is broken, the part may bend.
Heat treatment is not always necessary and not for everyone precision alloys and steels. For example, to steel 50N it had the required magnetic properties; it must be annealed at temperatures from 1100°C to 1150°C and then cooled to 200°C. But for rafting 08KP heat treatment is not mandatory, although it may be recommended to improve the mechanical properties of the finished product or design.
St. Petersburg Precision Alloy Plant PZPS offers a number of formats of cooperation in the field of research and heat treatment of precision steels and alloys for engineers, technologists, designers and other specialists. For cooperation questions, please contact the following phones or leave a request on the site. Our specialists will contact you and answer all your questions in detail.
