Heat treatment of steel is an important process for the production of an alloy of iron, which can improve its useful properties. Today, such a procedure is used to transform the natural characteristics of most metal products.
Heat treatment of steel involves the sequential implementation of three stages:
- Heating the iron alloy to the desired temperature.
- Exposure to steel over time.
- Cooling.
What happens to the iron alloy with this procedure?
Heat treatment consists of the following steps:
1. Annealing. This process is mainly used for casting, rolling and forging. This procedure is necessary to reduce hardness or reduce internal stresses that are created in welded products. In addition, annealing is used to prepare the metal structure for subsequent processing of a thermal nature in order to improve its heterogeneity. This method includes heat treatment of steel 45, 45X, 40XC, 40XH and other grades of iron alloy.
2. Normalization. This procedure differs from the previous process in the nature of the passage of the cooling stage. The last step is carried out after exposure of the parts. In this case, special attention is paid to the set temperature. In this case, the steel is obtained with a slight, but higher hardness. The structure of these products is fine-grained. Thus, the normalization of steel is necessary to correct the composition of the weld, as well as to obtain the desired configuration.
3. Hardening. This step related to steel processing is used for forgings, castings, stampings, as well as parts machined in order to increase strength, hardness, corrosion resistance, wear resistance and other important characteristics. This process is the heating of an iron alloy to a temperature above, or within its transformation. Exposure to steel at such a thermal indicator, as well as subsequent cooling, is carried out, as a rule, at a slightly higher speed. For this, aqueous solutions of NaOH salts, oils, and also air are most often used. So, for example, heat treatment of 40x steel at this stage is carried out in oil. Quite rarely, large parts are quenched in water with immediate subsequent low tempering. Often, products from this brand of iron alloy pass this stage by heating high-frequency currents. The result is a high hard surface.
4. Vacation. This procedure involves heating the hardened steel to a specific temperature. Next, the metal passes the exposure, as well as cooling. The last step is usually carried out in air.
5. Aging. This step consists in maintaining the alloy of iron with a metastable structure for some long time. The temperature should not be lower than room temperature. This procedure allows the metal structure to partially transition to a more stable state by changing its mechanical and physical properties.
6. Cold treatment. This step is a continuation of quenching cooling, which was interrupted at room temperature. This indicator for metal is not a critical level.
Scopes of an alloy of iron
Since the steel heat treatment procedure can significantly improve the characteristics of parts made of various types of iron alloys, it is in great demand in all areas of industry. Machine building, aircraft building, tank building, and concrete products are no exception. Heat-treated products can be operated under conditions of dynamic increased load and vibration. In addition, such iron alloys are used in the construction of skyscrapers, factories and bridges.