High requirements for physical-mechanical properties of precision steels place special responsibility on the production stages of the presented materials.
Elevated requirements for purity of chemical composition and accuracy of physical-mechanical characteristics of precision alloys hinder development of a single technological melting algorithm. In some cases introduction of additional production stages is required, such as:
- selecting the optimal charge composition;
- choosing the correct working environment;
- applying specific remelting methods (electroslag, plasma, electron-beam, etc.).
Among special melting technologies the most widespread is vacuum-induction. It provides for induction heating of the prepared charge in vacuum-induction furnaces. It is predominantly used in producing blanks that will later be remelted. In steel marking it is denoted by the letters VI, for example alloy 49K2FA-VI.
Special melting methods
Besides vacuum-induction blank melting technology, there are other special methods:
- plasma-arc melting method — metal melting occurs in special plasma furnaces where the energy source is an inert gas ionized and heated to a certain temperature, mainly argon; this method is recommended for melting heat-resistant precision alloys and steels with high nitrogen content;
- electron-beam melting — metal is heated by a stream of accelerated electrons created by special electron guns;
- electroslag melting method — makes it possible to raise quality of the material produced; melting is performed in a bath of electrically conductive slag heated by electric current;
- vacuum-arc method — makes it possible to obtain blanks with dense and homogeneous macrostructure and a minimal amount of harmful impurities.
Chemical composition of precision alloys is regulated by GOST 10994-74. This document defines maximum allowable quantitative indicators of alloying elements and harmful impurities.
Precision casting technologies
Within production of precision alloys application of various melting technologies is provided. In particular:
- Refractory castings. The process includes pouring molten metal into special molds made from a mixture of cleaned sand and specialized refractory resins. Makes it possible to create parts with high accuracy and stable chemical composition.
- Centrifugal casting method. Helps ensure uniform distribution of material composition under centrifugal force. Molten metal is poured into the cavity of a rotating plate and uniformly distributed in casting molds through special channels.
- Using silicate molds for melting blanks. This method makes it possible to obtain products from precision alloys of specified sizes and precise geometric shapes. Silicate molds ensure excellent surface quality and minimize deformations.
GOST 10994-74 also contains recommendations on choosing certain steel grades for producing products of various shapes, in particular thin wire or cold-rolled strip.
Methods of raising service qualities of metals
Failures to which products from precision alloys are subjected in service may be caused by various factors. One of the main ones is metal corrosion and surface oxidation. Such failures may lead to deterioration of physical-mechanical characteristics of steels and loss of operability of complex units and assemblies.
To prevent corrosion and protect metal the following methods are applied:
- Hot processing in vacuum or an inert gas environment. This method makes it possible to process melted blanks under conditions excluding contact with air and moisture, which substantially reduces the risk of corrosion and oxidation. Such processing ensures preservation of metal quality and its durability.
- Directed crystallization technology. This process contributes to more uniform and ordered growth of the metal crystal structure, which improves its mechanical properties and corrosion resistance.
- Thermomagnetic, thermomechanical, or heat treatment in vacuum or a hydrogen environment. These processing methods make it possible to improve metal structure and properties, making it stronger and more resistant to aggressive effects.
Petersburg Plant of Precision Alloys produces cold-rolled strip from various steel grades with precise chemical composition in accordance with GOSTs or customer technical specifications. For cooperation, call the listed phones or leave requests on the website. Our engineers will contact you and provide full information on products released.
