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.