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In steel production, there are numerous specialized processes used to enhance both quality and efficiency. One of the most critical among them—especially in secondary metallurgy—is vacuum degassing, a process used to remove unwanted gases from steel. But what exactly is this process, and why is it so important?
Vacuum degassing is more than just a technical step in steelmaking; it directly influences the mechanical properties, durability, and overall quality of the steel.
In this article, we’ll take a deep dive into the vacuum degassing process, examining its role in ladle metallurgy, the different types of vacuum degassing, and the advantages it offers to metallurgy. We’ll also explore the differences between vacuum and non-vacuum steels, the types of gases removed from steel, and the types of steel produced using vacuum metallurgy at Hasçelik.
This article is designed for professionals specialized in steelmaking, those seeking in-depth knowledge of vacuum metallurgy, and anyone interested in innovations within the industry.
Ready? Let’s step into the world of vacuum degassing!
Vacuum degassing is a highly precise and crucial metallurgical process used in steel production. But what does this process actually involve, and why does it play such a vital role? In answering these questions, we’ll thoroughly examine what vacuum degassing is, how it works, and why it's widely used.
Gases are considered unwanted foreign elements in steelmaking. These gases can negatively affect the chemical composition of steel and degrade its mechanical properties. For example, gases such as oxygen, nitrogen, and especially hydrogen can harm the toughness, strength, and hardness of steel. This is where vacuum degassing comes in—it’s a process applied to eliminate these harmful gases from the steel.
The process effectively removes gases from the steel under vacuum conditions, resulting in a purer and higher-quality metal. The vacuum casting environment allows gases to escape more quickly and efficiently from the molten steel. As a result, the steel becomes more homogeneous and achieves the desired properties.
Vacuum degassing is typically carried out in the advanced stages of steel production. These stages are intended to enhance steel quality, minimize the oxygen content in the metal, and produce a final product that is stronger and more durable. The low-pressure environment created by the vacuum makes it harder for gases to remain dissolved in the metal, allowing them to separate more easily.
This process can be conducted in vacuum furnaces as well as other vacuum metallurgical equipment. The result? Higher-quality steels! These types of steels are preferred in the production of high-performance products used in industries such as automotive, aerospace, and energy.
Vacuum degassing is not only essential for purifying steel, but it also plays a critical role in other processing techniques in steel production. It improves the quality of steel, making it more durable, longer-lasting, and reliable—creating a significant impact at every stage of the production process.
While the primary goal of vacuum degassing is to remove unwanted gases from steel in their gaseous form, it also improves the steel’s properties, enhances its mechanical strength, and ultimately allows for more efficient use of the material.
Vacuum degassing is one of the most critical stages of steel production and plays a fundamental role in the manufacturing of high-quality steels. So why exactly is this process necessary? What are the intended outcomes and benefits? Let’s take a closer look at the key reasons for implementing vacuum degassing:
In steel production, gases present within the metal’s internal structure can pose significant problems. Gases like oxygen (O), nitrogen (N), and hydrogen (H) can create undesirable effects in the chemical makeup of steel. These gases may reduce the durability and hardness of the steel. Vacuum degassing eliminates these gases from the steel, producing a purer and more homogeneous final product. This improves the overall quality of the steel, ensures a smoother internal structure, and enhances material performance.
This process significantly reduces harmful gases such as oxygen, hydrogen, and nitrogen within the steel when performed in a vacuum environment. If left inside the steel, these gases can lead to:
• Porosity,
• Microcracks,
• Premature fatigue,
• Brittleness.
Vacuum treatment effectively reduces these risks to near-zero levels.
The presence of gases in steel can weaken its mechanical properties, especially toughness, hardness, and tensile strength. Vacuum degassing removes these harmful gases, enhancing the mechanical performance of the steel. The result is a stronger, more durable, and longer-lasting material. This is especially critical in industries like automotive, aerospace, and other high-safety-demanding fields.
The accumulation of gases within steel can cause weak spots in the material. Vacuum degassing allows for the even removal of gases from the metal, increasing the homogeneity of the steel. As a result, the steel becomes more stable, and error rates during production are reduced.
Since the steel must exhibit consistent properties throughout, uneven gas distribution disrupts this homogeneity.
Thanks to vacuum degassing:
• The microstructure after casting becomes more uniform,
• Undesirable segregation during solidification is reduced,
• The grain structure becomes more stable and controlled.
Vacuum degassing is especially used for manufacturing high-performance steels. These steels must exhibit excellent durability, resistance to high temperatures, and outstanding mechanical characteristics. Vacuum degassing enables the steel to withstand such demanding conditions. For this reason, it’s indispensable for steels used in aerospace, energy, and automotive sectors.
One of the greatest challenges in steel production is accurately controlling the levels of hydrogen and nitrogen in the material. Vacuum degassing lowers these gases to the desired levels, ensuring the final quality of the steel. Excessive oxygen can make the steel brittle, while nitrogen can reduce its hardness. Vacuum treatment eliminates these negative effects, achieving the ideal chemical composition.
In Conclusion
Vacuum degassing is carried out to ensure quality control in steel, to purify the metal, and to produce a more durable final product. By enhancing the steel’s quality, it becomes stronger, longer-lasting, and more reliable. For both manufacturers and industrial users, this process is an indispensable part of modern steelmaking.
Hydrogen, in particular, is one of steel's greatest enemies. Even in small amounts, it can cause serious problems such as hydrogen embrittlement.
With vacuum degassing:
• Fracture toughness is improved,
• Cold forming processes become safer,
• The risk of post-weld cracking is reduced.
Good steel lies in the details. And one of those details is the vacuum degassing process!
There’s no room for chance when it comes to quality in steel production. The homogeneity, purity, and structural integrity of the material depend on the measures taken at every step of the manufacturing process. One of those steps—vacuum degassing—offers numerous metallurgical advantages to steel.
But why is it so important?
Let’s take a closer look…
Processes carried out in a vacuum environment enable alloying elements to be integrated into steel more effectively and with better control.
The result?
• Alloy waste is minimized,
• Targeted mechanical and chemical properties are achieved more consistently.
Uncontrolled gas presence can cause rough textures and defect zones on the steel’s surface.
Thanks to vacuum degassing:
• A smoother and brighter surface is achieved,
• Subsequent processes (such as heat treatment, coating, or forming) benefit from improved quality and efficiency.
Steel produced through vacuum degassing:
• Has fewer micro-defects,
• Is more resistant to fatigue,
• Endures longer—even under demanding conditions.
“If two steels look the same, pay attention if one is vacuum-treated.”
Two steel plates may look identical at first glance. But to understand what’s really going on inside, you have to dig deeper.
That’s where the differences between vacuum and non-vacuum steel come into play.
Ready to go beneath the surface?
• Vacuum steel undergoes a degassing process under vacuum conditions during production. Harmful gases such as hydrogen, nitrogen, and oxygen are significantly reduced.
• Non-vacuum steel skips this step, retaining more gas that can lead to microcracks, porosity, and internal stress.
The result?
Vacuum steel is purer, more reliable, and behaves more predictably.
• Lower gas levels in vacuum steel lead to a finer and more homogeneous grain structure.
• Non-vacuum steels are at higher risk of segregation, which can cause inconsistent behavior across different parts of the material.
What does this mean?
Vacuum steel offers consistent quality in every centimeter. With non-vacuum steel, you're lucky if you get a good batch.
• Vacuum steel provides more stable and predictable values in tensile strength, yield strength, elongation, and impact resistance.
• In non-vacuum steel, these properties show greater variability.
This difference is critical, especially in high-safety industries such as automotive, aerospace, and energy.
• Vacuum steel’s low hydrogen content reduces the risk of cracking during welding and results in higher-quality welds.
• In non-vacuum steel, gas residues can create pores in the weld zone.
The same applies to heat treatment—vacuum steel ensures more consistent outcomes.
• Vacuum steels not only have refined internal structures but also cleaner, more flawless surfaces.
• Non-vacuum steels are more prone to surface defects, scaling, and inclusion (solid foreign particles).
This gives vacuum steel a clear advantage in final processes such as turning, milling, or coating.
Vacuum steels are preferred in high-performance applications such as:
• Automotive components
• Bearings
• Aircraft
• Pressure-resistant equipment
Non-vacuum steels are used in general-purpose applications with lower precision requirements.
“The most valuable form of steel is brought to life through proper processing.”
Steel production is a complex art. One of the most delicate aspects of this art is ladle metallurgy. These processes improve the internal structure of steel, regulate gas content, and achieve desired mechanical properties.
This is where VD, VOD, and RH processes come into play—specialized techniques tailored to different needs. Let’s take a closer look at each one.
“Discover quality under vacuum!”
VD (Vacuum Degassing) is one of the most essential and widely used techniques in steel production. This process removes harmful gases (especially oxygen, nitrogen, and hydrogen) from the steel under vacuum.
Vacuum degassing improves the purity and durability of steel. During the process, the steel is liquefied under vacuum, and the gases are extracted.
Characteristics:
• Hydrogen and oxygen levels are reduced, resulting in fewer cracks and a more homogeneous microstructure.
• Steel can be produced with lower carbon content, enhancing formability.
• The vacuum environment ensures excellent surface quality.
Advantages:
Vacuum degassing is indispensable for producing high-performance steel. It is particularly preferred for critical applications in the automotive, aerospace, and energy industries.
“Manage carbon and oxygen with perfect balance!”
VOD (Vacuum Oxygen Decarburization) is used primarily to control carbon content. In this process, excess carbon is removed by reacting it with oxygen under vacuum conditions.
VOD plays a critical role in producing low-carbon and ultra-low-carbon steels.
Characteristics:
• Carbon content is precisely reduced under vacuum.
• Oxygen injection removes carbon effectively.
• The resulting steel is highly durable and formable with excellent mechanical properties.
Advantages:
VOD is the preferred method for producing high-quality, low-carbon steels. These steels are ideal for industries that demand extreme precision, such as automotive.
“Shape steel perfectly with precise gas control.”
The RH process (Ruhrstahl-Heraeus) is a technique used to reduce gas content and achieve a more homogeneous structure in steel.
This process enhances steel purity by removing gases under vacuum during production.
Characteristics:
• Conducted under vacuum, it removes gases such as hydrogen, oxygen, and nitrogen.
• Used in the production of high-quality steels.
• Results in a more homogeneous and controlled internal structure.
Advantages:
The RH process plays a key role in producing premium alloys and specialized steels. It is indispensable in industries like automotive and aerospace, where precision is critical.
“Steel shaped in a vacuum is not only durable but also possesses a unique character.”
Vacuum metallurgy is one of the most advanced technologies used to purify steel and impart desired properties. Through this process, steel becomes more homogeneous, stronger, and more durable. So, what types of steel are produced using vacuum metallurgy? Let’s explore the transformation of steel in a vacuum.
“Not just for durability, but for those in pursuit of excellence…”
Vacuum metallurgy homogenizes the internal structure of steel, removes harmful gases, and enhances its mechanical properties. This process is critical for producing high-performance steels, which typically feature:
• High durability
• Low carbon content
• Excellent surface quality
Applications:
• Automotive industry: High-strength components, engine parts
• Aerospace: Jet engines, aircraft fuselages, landing gears
• Energy: High-pressure systems and equipment
“Corrosion-resistant and long-lasting steels…”
Vacuum metallurgy also plays a critical role in the production of stainless steels. The process significantly reduces harmful gases and oxygen levels within the steel, resulting in increased durability and enhanced corrosion resistance.
Applications:
• Food processing industry: Long-lasting equipment compliant with hygienic standards
• Chemical industry: High corrosion-resistant pipes and tanks
“Perfect steels for specialized alloys…”
Vacuum metallurgy is used in the production of alloy steels, which are created by adding various elements to optimize specific properties. The vacuum environment ensures a homogeneous structure, allowing the steel to meet precise performance criteria.
Applications:
• Defense industry: Materials resistant to harsh conditions
• Automotive industry: Components that withstand high temperatures and pressure
“In a world where flame and heat shape steel…”
These steels are preferred for equipment operating under high temperature and pressure. Vacuum metallurgy controls gas and carbon levels, making the steel more resistant and stable.
Applications:
• Furnaces and reaction chambers
• Equipment in the energy sector exposed to high temperatures
Hasçelik manufactures high-quality steel products using vacuum metallurgy technology. This advanced method plays a key role in purifying steel, adding alloy elements, and optimizing its microstructure. Vacuum steel production is ideal for industrial applications requiring high performance and precision.
Types of Steel Produced:Key steel types produced through vacuum metallurgy include heat-treatable steels that gain strength through thermal processing (e.g., 42CrMo4, 41Cr4), case-hardening steels used to enhance surface hardness (e.g., 16MnCr5, 20MnCr5, 21NiCrMo2, 17NiCrMo6), and specially alloyed steels. These steels can be custom-produced based on customer requirements, offering tailored solutions for diverse industrial needs.
Production Dimensions:Vacuum steel production is typically performed in section sizes of 160x160 mm, 200x200 mm, and 240x240 mm blooms. These products fall under the SBQ (Special Bar Quality) class, offering high quality and strength characteristics.
Dual Vacuum Degassing System (VD)Hasçelik’s new steel plant utilizes a Dual Vacuum Degassing System (VD) that enhances efficiency in steel production. This system provides precise control to achieve the desired steel properties. Comprising one 62-ton Vacuum Degassing (VD) unit and two fixed ladles, the system ensures excellent quality throughout all production stages.
Vacuum Alloying and EfficiencyBefore the VD process begins, most alloying elements have already been added to the steel, requiring only minor adjustments. Vacuum conditions prevent significant burn-off of alloying elements. This minimizes material loss and increases efficiency. Alloying in a vacuum not only enhances steel quality but also reduces production costs.
Hydrogen Degassing MechanismAn important stage in vacuum steel production is the hydrogen degassing process. This step removes unwanted hydrogen from the steel. As hydrogen diffuses into the refining gas, it rises from the ladle lining to the ladle surface. As it moves toward the surface, hydrogen escapes from the molten steel in the form of bubbles, thereby reducing its concentration. This process helps achieve a uniform microstructure and improves steel performance.
Why Do Customers Prefer Hasçelik’s Vacuum Degassed Steel?At Hasçelik, we know that for high-performance applications, steel must be more than just strong—it must also be exceptionally clean and homogeneous internally. That’s why vacuum degassing is a critical phase of our production process. Performed just before the steel solidifies, this process removes dissolved gases that directly affect final product quality.
Hydrogen, in particular, can lead to microstructural issues in steel. If retained, it may cause serious problems such as hydrogen embrittlement or delayed cracking. Hasçelik’s modern vacuum degassing technology ensures the controlled removal of harmful gases like hydrogen from molten steel. As a result, ductility and tensile strength are preserved, preventing unexpected fractures during use.
Reducing oxygen and nitrogen is also a key part of this process. These gases can cause cracks and voids in the steel, weakening mechanical properties—especially fatigue strength. Hasçelik minimizes such defects through vacuum degassing, providing more predictable, higher-performing, and longer-lasting steel products.
The core reason for making vacuum technology a cornerstone of our steelmaking process is our commitment to delivering not just steel, but a trustworthy engineering material in its purest form.
