Different types of remelting in metallurgy: from technology to quality

In modern metallurgy, the quality of steels and alloys directly depends on the accuracy and cleanliness of their production. One of the key stages in this process is remelting, due to which the metal is cleaned of impurities, acquires a more uniform structure and improved physical and chemical properties. Let's figure out what types of remelting are used today in metallurgy and what role they play in the production of modern materials.

What is remelting and why is it needed?

Remelting is the process of re-melting a metal or alloy followed by crystallization. Its goal is to improve the properties of the material: remove unwanted impurities, change the chemical composition, increase the homogeneity of the structure and improve the physical and mechanical properties.

The role of remelting in metallurgy:

• remove harmful impurities and non-metallic inclusions that can deteriorate the quality of the material;
• change the chemical composition of steel or alloy by adding or removing certain elements;
• improve the structure of the material, making it more uniform;
• increase the strength, hardness and other mechanical properties of steel or alloy.

Remelting can significantly improve the performance characteristics of steels and alloys - strength, hardness, heat resistance and corrosion resistance. This is especially important for materials that will be used in conditions of high temperatures, pressures or aggressive environments. Remelting also reduces the likelihood of defects in the metal, such as cracks, pores and structural inhomogeneity, which increases the reliability and durability of finished products.

Types of remelting: technologies, features, advantages

Electric arc remelting (EAM)

EAF is one of the classical technologies in which a metal or alloy is melted using an electric arc. In the EAF process, an electrode (usually graphite or metal) is connected to an electrical current source. A high-temperature electric arc is created between the electrode and the metal to be melted, melting the metal. The molten metal is collected in a special mold or mold, where it then crystallizes and solidifies.

Advantages of EAF:

• High melting point: The electric arc allows one to reach very high temperatures, which makes it possible to remelt refractory and alloyed alloys.
• Control accuracy: Process parameters such as current, voltage and electrode feed rate can be precisely controlled, allowing remelting conditions to be optimized for different materials.
• Possibility of obtaining high-quality metal: EDP allows you to delete unwanted impurities and non-metallic inclusions, which improves the quality and properties of the remelted metal.
• Versatility: The method is suitable for remelting various metals and alloys, including high-alloy steels, nickel, titanium, etc.

Flaws:

• High energy consumption: creating and maintaining an electric arc requires a significant amount of electricity.
• Process complexity: operating an EAF requires certain skills and knowledge, especially when working with refractory or high-alloy alloys.
• Possibility of defect formation: If the technological process is disrupted, defects may occur: pores, cracks or inhomogeneity of the metal structure.

The electric arc remelting method is used for tungsten, titanium, tantalum, molybdenum metals, as well as to improve the properties of special steels and precision alloys. EAF is suitable for the production of electrodes, tool steels and other products requiring increased strength and wear resistance.

Vacuum arc remelting (VAR)

This method is an improved version of EAF, but is carried out in a vacuum. Under low pressure conditions, contact of the melt with oxygen and other gases is eliminated, which increases the purity of the metal.

In the VAR process, a consumable electrode (made from the alloy being remelted) is connected to a source of electrical current. An electric arc is created between the electrode and the workpiece, which causes the metal to melt. The molten steel is collected in a special mold or mold, where it then crystallizes and solidifies. 

Advantages of VDP:

• Improvement of metal quality: vacuum helps remove gases and non-metallic inclusions from the melt, which improves the mechanical and physical properties of the material.
• Obtaining a homogeneous composition: Thanks to controlled remelting conditions, a more uniform metal structure is achieved, which is important for products requiring high strength and reliability.
• Ability to work with high-alloy alloys: VAR allows you to effectively remelt complex alloys that are difficult to process by other methods.
• Reduction of impurity content: the process helps reduce unwanted impurities, which improves the quality of the final product.

Flaws:

• High energy consumption: To create and maintain an electric arc, as well as to provide a vacuum, a significant amount of electricity is required.
• Limited performance: Compared to some other remelting methods, VAR, due to the need to create and maintain a vacuum, has lower productivity.

VDPs are used in the aviation and space industries, as well as in the production of medical equipment. Vacuum arc remelting is used to produce steels and alloys with special properties, such as resistance to atmospheric and chemical corrosion, heat resistance, etc., as well as in the production of precision alloys, for example, 50NP And 42N.

Electroslag remelting (ESR)

In ESR, melting occurs due to the passage of current through an electrically conductive slag. In the ESR process, a consumable electrode, made from a remelted metal or alloy, is dipped into molten slag, which serves as a conductor of electric current. Under the influence of the heat generated when current passes through the slag, the electrode melts and drops drop by drop into the crystallizer, where an ingot is formed.

The process takes place in a special furnace with a controlled atmosphere, often in a vacuum or protective gas environment, which minimizes the interaction of the melt with the environment and improves the quality of the metal.

Advantages of ESR:

• High quality metal: ESR makes it possible to obtain metal with a high degree of purification from non-metallic inclusions and gases, which improves its mechanical and physical properties.
• Uniformity of structure: thanks to the peculiarities of the process, a more uniform metal structure is achieved, which is important for products requiring high strength and reliability.
• Energy efficiency: Compared to some other remelting methods, ESR can be more energy efficient because it uses the heat generated when current passes through the slag.

Flaws:

• High requirements for the purity of raw materials: for successful ESR, high quality raw materials are required, which increases the cost of production.

Electroslag remelting is widely used in mechanical engineering and energy - for example, for the production of large shafts, rotors and supports. With its help, high-quality steels and alloys are produced with a minimum content of impurities and gases, which ensures high purity of the metal and uniformity of its properties. 

Vacuum induction remelting (VIP)

In VIP, the metal is melted in a vacuum using induction heating. This method is widely used in the metallurgical industry to obtain high-quality materials with improved physical and chemical properties, as it allows obtaining exceptional purity and precision of the chemical composition.

VIP benefits:

• High quality metal: VIP allows you to obtain metal with a minimum content of gases, non-metallic inclusions and other impurities, which improves its mechanical and physical properties.
• Precise control of process parameters: Thanks to the ability to strictly control the technological process, you can obtain the most suitable conditions to achieve the desired result.
• Environmental friendliness: working in a vacuum reduces emissions of harmful substances into the atmosphere, which makes the process more environmentally friendly.

Flaws:

• Complexity of technology: Highly qualified personnel are required to control the process and maintain the equipment.
• Limitations on the size and shape of ingots: The method may not be effective for producing large or irregular ingots.

Vacuum induction remelting is used to produce pure metals and alloys with a high degree of homogeneity. VIP is used in the production of a number of steels, including alloys 29NK And 36N and other materials with a given coefficient of linear thermal expansion, which are used in electronic devices and satellite systems, as well as other materials for aviation, space and the nuclear industry. This method makes it possible to minimize the content of gases and non-metallic inclusions, as well as to ensure high physical and mechanical properties of special steels and precision alloys.

How to choose a remelting method

The choice of remelting technology is determined by a number of factors:

• Required metal quality: For high purity, vacuum remelting methods (VAR, VIP) are preferred.
• Product purpose: ESR is suitable for large-sized parts, while VDP is suitable for parts with special strength requirements.
• Chemical composition of the alloy: Some alloying elements are sensitive to oxidation and require remelting in an inert atmosphere or vacuum.
• Economic forces: Remelting methods vary in energy, equipment and personnel costs.
• Industry specifics: aviation and space have more stringent cleanliness requirements than, say, the construction industry.

Modern remelting methods make it possible not only to improve the properties of metals, but also to give them the necessary characteristics in advance. For enterprises such as PZPS, this is the basis creating alloys, capable of operating in a wide variety of operating conditions.

The role of remelting at PZPS

Our factory uses induction smelting methods and, where necessary, a variety of remelting methods to produce precision alloys and specialty steels that meet stringent industry standards. 

Particular attention is paid to materials with high stability and precise characteristics:

• soft magnetic alloys: 49K2FA-VI, 50N, 79NM, 81NMA etc.;
• thermostable alloys: 33NK, 42N and others;
• heat-resistant alloys: ХН78Т and others.

Each melt at PZPS is the result of many years of experience, precise engineering calculations and modern technologies aimed at ensuring the reliability and durability of the product. Order high quality alloys and take advantage production services PZPS today! Contact us — and get materials that fully meet the requirements of your industry.

‍