Normalizing
Austenitizing and air cooling of suitable steels, with starting-condition, section-size, delivery-route and acceptance boundaries.
Tags: processes, heat-treatment, normalizing
On this page
Ovako's 20NiCrMo7 guidance lists 860–890°C with air cooling for normalizing. Its +N delivery designation covers normalized or normalized-rolled condition. Confirm the grade variant, prior condition and actual section cooling. The delivery designation alone leaves the full thermal history open. Ovako 20NiCrMo7, heat-treatment recommendations
Process and purpose
Normalizing austenitizes suitable carbon or low-alloy steel and cools it in air to refine and even out the structure after casting, forging or rolling. Bodycote normalizing
Specify the material, starting condition, intended output and acceptance together. A note reading “normalize” does not establish final hardness, tensile properties, grain size, dimensional stability or a complete temperature cycle. The same treatment can change different incoming structures in different ways.
What distinguishes the route
| Route | Important distinction | Handoff implication |
|---|---|---|
| Furnace normalizing | Austenitizing followed by the specified air-cooling route | Define the alloy, thermal history, load and output requirements |
| Full annealing of suitable steel | Commonly uses slower furnace cooling | Do not assume the same structure or hardness as normalizing |
| Subcritical stress relief | Intended below the relevant transformation range | Not equivalent to forming a new austenitic structure |
| Quenching and tempering | A separately controlled hardening and tempering sequence | A similar final hardness does not establish an identical condition |
| Normalized rolling | A controlled thermomechanical production route | Check whether the material standard permits this delivery route |
ASM's 2015 Subject Guide: Heat Treating distinguishes furnace-cooled annealing from air-cooled normalizing for carbon and low-alloy steels. Cooling affects the resulting structure; its typical-property explanations are not final-design or procurement values. Select the required route from the material/product specification rather than substituting treatments based on a shared word such as “softening.” ASM subject guide, printed page 4
Starting material and transformation
ASM's March 2023 heat-treatment article explains that normalizing requires a homogeneous austenitic phase before cooling. It also states that normalizing can increase or decrease hardness and strength depending on the product's previous thermal and mechanical history. Thus “normalized is harder than annealed” describes a particular comparison, not an unconditional change from every incoming condition. ASM, March 2023, printed page 53
Record the producer grade, heat/lot, product form, section dimensions, prior cold or hot work, welds and previous heat treatment. An already quenched-and-tempered part may lose the condition on which its drawing relies. A normalized microstructure is also not evidence that casting defects, inclusions or all chemical segregation have been eliminated; specify the required product quality separately.
Material selection matters. The same ASM article notes that stainless steels and most tool steels are generally not normalized: their hardenability or transformation behavior can make air cooling inappropriate for the intended result. A generic normalizing temperature should therefore not be transferred to an unidentified alloy, nor should air cooling automatically be treated as a softening operation. ASM material limitations
For a bounded producer example, Ovako's 20NiCrMo7 page, revised 10 September 2026, lists 860–890°C with air cooling under normalizing. It labels +N as “normalised or normalised rolled.” Those entries belong to that producer's identified steel variants and delivery descriptions; they do not supply a cycle or an acceptance guarantee for another grade or an arbitrary finished part. Ovako 20NiCrMo7, heat-treatment recommendations
Air cooling and section response
Air cooling is a process description, not one numerical cooling rate. Establish part spacing, support, load arrangement and cooling conditions for the actual geometry. Surface and interior regions need not follow the same temperature history. ASM's guide emphasizes cooling rate as a determinant of final structure and identifies nonuniform cooling as a source of residual stress. Retain dimensional and property inspection even when the aim is a more uniform condition. ASM subject guide, printed pages 1 and 4
HTA's service guidance makes the route conditional on material and initial state. It also notes that some air-hardening engineering steels can require a subsequent subcritical treatment to soften the structure or aid machining. That is a defined combination of operations, not permission to improvise an extra temper after an unsuccessful normalizing cycle. HTA normalizing guidance
Original bounded cooling comparison
Assume two monitored locations in a hypothetical trial each cool from 800°C to 600°C. Location A takes 40 seconds and location B takes 160 seconds over that same interval. Their mean cooling rates over the interval are:
A: (800 − 600) / 40 = 5.00°C/s
B: (800 − 600) / 160 = 1.25°C/s.
Both could be described as air cooled while their interval averages differ by a factor of four. These are invented observations, not alloy-specific cooling requirements. The averages do not reveal the full cooling curves, establish a transformation product or prove acceptance. Use representative part-temperature evidence and applicable transformation/property information when qualifying the actual route.
Surface condition, dimensions and subsequent work
HTA explains that normalizing is often performed in air on semi-finished products, with scale and decarburized material removed afterward. Protective conditions may be needed for some final-size products. State the required surface condition and subsequent removal before processing; a dimension that passes before cleaning or machining does not establish final compliance. HTA atmosphere and surface limitations
Review fixture support, thin/thick transitions, permitted straightening and finishing allowance with the processor. Establish which dimensions are accepted before treatment and which after the complete route. If normalizing prepares the part for later hardening, keep its intermediate acceptance distinct from the final hardened condition. A treatment record alone cannot demonstrate that either set of outputs was achieved.
Normalized rolling and delivery condition
Voestalpine distinguishes conventional hot rolling, normalizing rolling and thermomechanical rolling. Its normalized-rolling description uses high-temperature forming followed by cooling and lower-temperature final forming to refine the structure, producing properties similar to normalized-annealed plate. This is a producer explanation of its manufacturing route, not evidence that every rolled product received a separate furnace normalizing operation. Voestalpine normalizing rolling
Resolve the permitted delivery condition in the applicable product standard and purchase order. Preserve the distinction between the producer's certified condition and an additional heat treatment of a machined component. Do not replace a specifically required furnace operation merely because another material certificate carries a broadly similar suffix.
Acceptance and production handoff
Choose tests that establish the ordered output: hardness with method/location, mechanical properties where required, structure, grain size, surface condition and dimensions. Hardness alone cannot identify every phase or prove the specified grain structure.
ISO 643:2024, edition 5, August 2024, covers micrographic determination of apparent ferritic or austenitic grain size in steels. Its scope addresses revealing boundaries and estimating mean grain size for unimodal distributions, and explains the effects of viewing three-dimensional grains in a two-dimensional section. Specify the relevant structure, location, preparation and criterion; the public scope does not create a universal grain-size limit for normalizing. ISO 643:2024
Provide the drawing revision, alloy/starting condition, product standard and permitted delivery route, treatment objective, qualified thermal/cooling controls, significant test locations, sampling and traceability. Agree the final surface and dimensional condition, subsequent operations and approved disposition of deviations. Keep process records and measured output requirements connected to the actual lot.
Source versions are stated where verified: ASM's guide prints ©2015, its magazine article is March 2023, Ovako's page gives 10 September 2026, and ISO identifies August 2024. No technical issue date is assigned to the undated supplier web guidance. The cooling-rate example is original and separate from all producer recommendations.