Normalizing is a process that makes the grain size normal. This process is usually carried out after forging, extrusion, drawing or heavy bending operations.
When steel is heated to elevated temperatures to complete the above operations, the grain of the steel will grow. In other words, the steel experiences a phenomenon called “grain growth.”
This leaves the steel with a very coarse and erratic grain structure. Furthermore, when the steel is mechanically deformed by the aforementioned operations, the grain becomes elongated.
There are mechanical property changes that take place as a result of normalizing – inasmuch as the normalized steel is soft, but not as soft as a fully annealed steel. Its grain structure is not as coarse as an annealed steel, simply because the cooling rate is faster than that of annealing.
Usually the steel is cooled in still air and free from air drafts. The process temperature is virtually the same as for annealing, but the results are different due to the cooling rate.
The process is designed to:
Give improved machining characteristics.
Ensure a homogenous structure.
Reduce residual stresses from rolling and forging.
Reduce the risk of “banding.”
Help to give a more even response to the steel when hardening.
Normalizing regularizes the grain structure of the material, resulting in smaller and more uniform grains throughout and improved anisotropy. This alters mechanical properties, increasing strength and toughness while reducing hardness. Normalizing helps relieve internal stresses that develop during previous manufacturing processes, particularly bending, forging, and welding. This reduces the risk of distortion or cracking in the material, in the “worked” zone which will have become relatively harder and more brittle.
Normalized materials are often easier to machine, making them more efficient and cost-effective for subsequent manufacturing processes. In particular, the hardness variations that result from local work hardening can be a barrier to consistent machining processes. Such hardness can also greatly reduce machined part quality and tool life. The process improves the homogenization of the material’s composition. It ensures a more consistent distribution of alloying elements throughout the structure and reduces the uneven distribution of precipitates that can badly affect regional properties. Normalizing can return the materials to which it’s applied to a more native ductility level, making subsequent processes easier and lowering the risk of fracture. Once normalized, materials are often more receptive to subsequent heat-treatment processes, allowing for more precise control over their final properties.
Why Is Normalizing Important in Manufacturing?
Normalizing is important in manufacturing because it improves the mechanical properties of materials, reduces internal stresses, and refines the microstructure. This enhances the material’s strength, toughness, and machinability, making it suitable for various manufacturing processes. Normalizing also promotes consistency and quality control in production.
Does Normalizing Materials Increase Ductility?
Yes, normalizing materials can increase ductility. Normalizing refines the microstructure of materials, leading to smaller and more uniform grain sizes. This finer grain structure enhances ductility, making the material more malleable and easier to deform without fracturing.
What Are the Different Types of Normalizing?
There are several variations and techniques of normalizing, each tailored to specific materials and desired outcomes. These types are listed below:
Full Normalizing: The material is heated to a temperature slightly above its upper critical temperature. It is then soaked for a period that is often derived by trial, and then allowed to cool naturally, in still, ambient air. This process alters and refines the grain structure and relieves internal stresses, most commonly for low-carbon steels.
Process Normalizing: A variation in which the cooling stage is accelerated by immersing the material in a medium like water or oil. This results in a finer grain structure and increased hardness compared to full normalizing. Note the difference between this and heat/quench hardening is that the peak temperature of the part is generally lower when the process normalizes.
Isothermal Normalizing: This involves cooling the material to a specific intermediate temperature range, typically targeting the pearlite transformation range. The material is then held at this temperature before being cooled further. It is used to achieve a finer grain and higher strength.
Air Normalizing: This process is essentially a common terminology used to identify a process that is identical to full normalizing.
How Does Normalizing Work?
Normalizing is used to refine the microstructure and improve the mechanical properties of materials, particularly steel and its alloys.
The diverse, coarse, and often anisotropic grain structure of a material that resulted from prior manufacturing processes (particularly cold working) is refined to a moderately controllable degree. Internal stresses are relieved, reducing the risk of post-machining deformation or fracture. The mechanical properties are improved, increasing strength, toughness, and ductility. The material is prepared for subsequent manufacturing processes or heat treatments, either reducing the stress and effort of further forming or returning the structure to a known and consistent quality that existed prior to heat treatment/hardening.
When To Normalize Materials?
Materials are normalized for a spectrum of reasons that are highly dependent on the specific material, its pre-existing condition, and the properties for the intended application or subsequent processes. Materials that have been heat/quenched for hardening will exhibit high internal stresses and brittleness. Normalizing can relieve these stresses and enhance toughness, at the cost of reduced hardness. Forged or welded materials often have irregular and highly regionalized grain structures and internal stresses, due to non-uniform heating. Where that irregularity/anisotropy is not a target of the production (as it can be in forgings), normalizing can revert the grain structure to the natural state and relieve stresses. Materials with uneven composition or inconsistent properties may benefit from normalizing to achieve a more uniform distribution of alloying elements and mechanical properties. This can be because of thermal, work, or other processes creating uneven condensates in some regions, dramatically altering local properties. Normalizing can improve the machinability of materials by essentially softening them, rendering them easier to machine, shape, or fabricate, easing manufacturability. Normalizing is often used as an intermediate step before other heat treatment processes such as hardening. It prepares the material for these subsequent treatments, improving the uniformity of the final treatment. Normalizing is often used to ensure consistent material properties in production, promoting better quality control and minimizing inter- and intra-batch variations in properties.
What Are the Applications of Normalizing?
Normalizing is a widely used heat-treatment process with applications across various industries. It is employed in the production of steel to refine grain structures, relieve internal stresses, and optimize uniformity and mechanical properties. It is crucial for manufacturing components in automotive, construction, and machinery. Forged materials often undergo normalizing after one or more forging steps to eliminate irregular grain structures and internal stresses, enhance strength, and restore toughness. Normalizing is used to relieve stresses and refine the microstructure of welded materials, ensuring weld integrity, uniformity of properties across the weld zone, and prevention of fracture.
Aerospace components, such as landing gear and engine parts, undergo normalizing to meet stringent strength and durability requirements. Durability is restored after forming, by normalizing. Normalizing is applied to automotive components like crankshafts and axles to enhance their toughness and performance. Tools and dies are often normalized to improve durability and wear resistance. Steel beams, rods, and structural components are normalized to meet safety and durability standards in construction. Components for the oil & gas industry, such as drill-string components and valves are normalized for improved toughness performance and longevity.
Normalizing and annealing are both heat treatment methods which alter the properties of the treated material. Both processes involve heating steel and other metals to an elevated temperature which is at or above the recrystallization temperature. Then, the metal is allowed to cool down slowly.
The cooling process is the difference between both heat treatment techniques. While the metal gets cooled at a controlled rate in a furnace during the annealing process, normalizing allows to cool the material at room temperature. Typically, this is simply done by exposing the material to air.
Due to the different methods, the metal cools faster in the normalizing process. Normally, this leads to a less ductile and harder material in comparison to annealing. Because of the shortened time in the furnace, normalizing is less expensive than annealing.
Compared to annealing, normalizing is less expensive. Therefore, the procedure is one of the most widely used industrialization process of metals.
Further, normalizing produces harder and stronger metals in contrast to annealing. Thus, it is used for hot-rolled products such as bars, railroad wheels and forged steel products.
How is normalizing different to annealing?
Normalizing and annealing are both heat treatment methods which alter the properties of the treated material. Both processes involve heating steel and other metals to an elevated temperature which is at or above the recrystallization temperature. Then, the metal is allowed to cool down slowly.
The cooling process is the difference between both heat treatment techniques. While the metal gets cooled at a controlled rate in a furnace during the annealing process, normalizing allows to cool the material at room temperature. Typically, this is simply done by exposing the material to air.
Due to the different methods, the metal cools faster in the normalizing process. Normally, this leads to a less ductile and harder material in comparison to annealing. Because of the shortened time in the furnace, normalizing is less expensive than annealing.
Normalizing is a heat treatment process that is akin to annealing but with lower standards of control and a somewhat lesser effect on the microstructure of the metals. It involves raising the temperature of a metal component that has either undergone heat/quench hardening or work hardening. It is held at that temperature for a prescribed and approximate period and then naturally cooled back to ambient in open air, room temperature. The temperature required for normalizing is above the critical and glass transition temperatures, but well below the melting point. This article will discuss normalizing, its purpose, how it works, its applications, and the stages.
What Is Normalizing?
Normalizing is a simple heat treatment process applied to metals, particularly steel and its alloys but also various others. It helps to improve their mechanical properties, reduce internal stresses, and achieve a more uniform and refined microstructure. Normalizing involves three main stages, each performed in a moderately controlled manner: heating, soaking (in a maintained, elevated temperature), and cooling.
Specific parameters of the normalizing process, including heating temperature and soaking time, are dependent on: the material type, its initial hardness condition, and the desired degree of change in its properties. Normalizing is widely employed in automotive, aerospace, construction, and manufacturing to prepare materials for further processing and to achieve desired mechanical characteristics.
Normalizing is often named interchangeably with annealing. Though the processes use the same basic mechanisms, normalizing has a generally lesser effect on the resultant properties. Its intervention is less controlled, particularly in the cooling phase, during which normalizing involves the natural pace of convective/radiative cooling in an ambient atmosphere, without any effort to restrain or reduce that rate.
The Purpose of Normalizing
Normalizing regularizes the grain structure of the material, resulting in smaller and more uniform grains throughout and improved anisotropy. This alters mechanical properties, increasing strength and toughness while reducing hardness. Normalizing helps relieve internal stresses that develop during previous manufacturing processes, particularly bending, forging, and welding. This reduces the risk of distortion or cracking in the material in the “worked” zone, which will have become relatively harder and more brittle.
Normalized materials are often easier to machine, making them more efficient and cost-effective for subsequent manufacturing processes. In particular, the hardness variations that result from local work hardening can be a barrier to consistent machining processes. Such hardness can also greatly reduce machined part quality and tool life. The process improves the homogenization of the material’s composition. It ensures a more consistent distribution of alloying elements throughout the structure and reduces the uneven distribution of precipitates that can badly affect regional properties. Normalizing can return the materials to which it’s applied to a more native ductility level, making subsequent processes easier and lowering the risk of fracture. Once normalized, materials are often more receptive to subsequent heat-treatment processes, allowing for more precise control over their final properties.
Normalizing is important in manufacturing because it improves the mechanical properties of materials, reduces internal stresses, and refines the microstructure. This enhances the material’s strength, toughness, and machinability, making it suitable for various manufacturing processes. Normalizing also promotes consistency and quality control in production.
Normalizing materials can increase ductility. Normalizing refines the microstructure of materials, leading to smaller and more uniform grain sizes. This finer grain structure enhances ductility, making the material more malleable and easier to deform without fracturing.
To learn more, see our guide on the Definition of Ductility.
The Different Types of Normalizing
There are several variations and techniques of normalizing, each tailored to specific materials and desired outcomes. These types are listed below:
Full Normalizing: The material is heated to a temperature slightly above its upper critical temperature. It is then soaked for a period that is often derived by trial, and then allowed to cool naturally, in still, ambient air. This process alters and refines the grain structure and relieves internal stresses, most commonly for low-carbon steels.
Process Normalizing: A variation in which the cooling stage is accelerated by immersing the material in a medium like water or oil. This results in a finer grain structure and increased hardness compared to full normalizing. Note the difference between this and heat/quench hardening is that the peak temperature of the part is generally lower when the process normalizes.
Isothermal Normalizing: This involves cooling the material to a specific intermediate temperature range, typically targeting the pearlite transformation range. The material is then held at this temperature before being cooled further. It is used to achieve a finer grain and higher strength.
Air Normalizing: This process is essentially a common terminology used to identify a process that is identical to full normalizing.
How Normalizing Works
Normalizing is used to refine the microstructure and improve the mechanical properties of materials, particularly steel and its alloys.
The diverse, coarse, and often anisotropic grain structure of a material that resulted from prior manufacturing processes (particularly cold working) is refined to a moderately controllable degree. Internal stresses are relieved, reducing the risk of post-machining deformation or fracture. The mechanical properties are improved, increasing strength, toughness, and ductility. The material is prepared for subsequent manufacturing processes or heat treatments, either reducing the stress and effort of further forming or returning the structure to a known and consistent quality that existed prior to heat treatment/hardening.
When To Normalize Materials
Materials are normalized for a spectrum of reasons that are highly dependent on the specific material, its pre-existing condition, and the properties for the intended application or subsequent processes. Materials that have been heat/quenched for hardening will exhibit high internal stresses and brittleness. Normalizing can relieve these stresses and enhance toughness, at the cost of reduced hardness. Forged or welded materials often have irregular and highly regionalized grain structures and internal stresses due to non-uniform heating. Where that irregularity/anisotropy is not a target of the production (as it can be in forgings), normalizing can revert the grain structure to the natural state and relieve stresses. Materials with uneven composition or inconsistent properties may benefit from normalizing to achieve a more uniform distribution of alloying elements and mechanical properties. This can be because of thermal, work, or other processes creating uneven condensates in some regions, dramatically altering local properties. Normalizing can improve the machinability of materials by essentially softening them, rendering them easier to machine, shape, or fabricate, easing manufacturability. Normalizing is often used as an intermediate step before other heat treatment processes such as hardening. It prepares the material for these subsequent treatments, improving the uniformity of the final treatment. Normalizing is often used to ensure consistent material properties in production, promoting better quality control and minimizing inter- and intra-batch variations in properties.
The Applications of Normalizing
Normalizing is a widely used heat-treatment process with applications across various industries. It is employed in the production of steel to refine grain structures, relieve internal stresses, and optimize uniformity and mechanical properties. It is crucial for manufacturing components in automotive, construction, and machinery. Forged materials often undergo normalizing after one or more forging steps to eliminate irregular grain structures and internal stresses, enhance strength, and restore toughness. Normalizing is used to relieve stresses and refine the microstructure of welded materials, ensuring weld integrity, uniformity of properties across the weld zone, and prevention of fracture.
Aerospace components, such as landing gear and engine parts, undergo normalizing to meet stringent strength and durability requirements. Durability is restored after forming by normalizing. Normalizing is applied to automotive components like crankshafts and axles to enhance their toughness and performance. Tools and dies are often normalized to improve durability and wear resistance. Steel beams, rods, and structural components are normalized to meet safety and durability standards in construction. Components for the oil & gas industry, such as drill-string components and valves, are normalized for improved toughness performance and longevity.
Typically, the heating and soaking stages of normalizing may take anywhere from a few minutes to several hours, depending on: the degree of lattice adjustment required, the thickness of the section, and the properties of the material. The cooling stage is considerably slower than quenching but still relatively fast.
The heat-up time will vary depending on the material’s thickness and the heating method used. It may take anywhere from a few minutes to a few hours. Soaking times can range from a few minutes to several hours, again depending on the desired properties, the material, and its section thickness. The cooling stage, which is typically done in still air, can take several hours to return the material to room temperature.
The total duration of the normalizing process, from heating to cooling, can vary from a few minutes for small parts, up to several hours for larger parts and thicker sections.
In mechanical manufacturing, Normalizing is just a very common heat treatment method