What is stainless steel? A guide to stainless steel manufacturing
Infrastructure investment, electrification, and urbanization are driving global demand for stainless steel. At the same time, raw material quality and costs are fluctuating, while customer specifications are only getting tighter.
Stainless steel manufacturing leaders are under increasing pressure to maintain constant insight into material processes or risk costly waste, reprocessing, or even product rejection. With high sample volumes and fast-moving process lines, there is only a narrow margin for error.
In this blog, we break down what stainless steel is and how high-performance stainless steel analysis enables the optimization necessary for stainless steel manufacturing leaders to seize growing opportunities in the industry.
What is stainless steel?
Stainless steels are iron alloys that contain at least 10.5% chromium, making them highly resistant to rust and corrosion. This corrosion resistance makes them suitable for a variety of applications, from heavy industry to everyday items like silverware and household appliances.
What is stainless steel made out of?
In addition to chromium, stainless steel contains numerous additives that deliver particular performance characteristics. These other alloying elements depend on the desired material structure and properties, for instance:
- High concentrations of nickel help to stabilize crystal structure and improve durability and corrosion resistance.
- Manganese is a common, less expensive substitute for nickel in stainless steel, and helps to improve hot workability and enhance strength and toughness.
- Adding molybdenum helps to further increase stainless steel’s corrosion resistance, particularly pitting corrosion from saline solutions and acids.
- Using silicon as an alloying element augments resistance to oxidation at high temperatures and corrosion by strong acids, as well as boosting the metal’s strength.
- Carbon is commonly used as a hardening agent, improving tensile strength and heat resistance, but it can negatively impact corrosion resistance.
What are stainless steel grades?
Stainless steel grades are the classification systems that are used to refer to the specific chemical composition, properties, and applications of stainless steels.
The most common way of referring to stainless steel grades is with the numerical system developed by the Society of Automotive Engineers (SAE). This system assigns a three-digit number to each variant according to its composition and performance characteristics.
There are several series in the SAE grading system:
- 200 series (Austenitic)
These steels are chromium-nickel-manganese alloys that use manganese as a substitute for nickel, cutting costs but negatively impacting corrosion resistance. - 300 series (Austenitic)
These stainless steel grades are chromium-nickel alloys that are non-magnetic and highly resistant to rust. They are the most widely used stainless steel types around the world. - 400 series (Ferritic & Martensitic)
These are chromium alloys that are known for high strength and wear resistance; they are usually magnetic and lower in cost. - 500 & 600 series
These are specialized categories that include heat-resistant chromium alloys and precipitation-hardening alloys.
What is stainless steel 304?
Stainless steel 304 is the most common form of stainless steel used worldwide. It is primarily made of iron, with around 18–20% chromium and 8–12% nickel.
304 stainless steel is popular because it is highly resistant to oxidation and common chemicals, making it appropriate for food-grade applications such as pots and pans. It is also durable and easy to form and weld for many applications.
What is stainless steel used for?
Because of its extraordinary versatility, stainless steel has a wide variety of uses, from everyday household items to industrial machinery. Here are some examples from across the common stainless steel grades.
| Stainless steel series | Stainless steel grade | Applications |
| Austenitic (300 series) | Grade 304 | • Kitchenware • Food processing equipment • Piping |
| Ferritic (400 series) | Grade 430 | • Automotive trim • Washing machines • Indoor kitchen appliances |
| Martensitic (400 series) | Grade 410 | • Valve parts • Pump shafts • Turbine blades |
The stainless steel manufacturing process – in 5 steps
Precision stainless steel manufacturing is a multi-stage process in which diverse raw materials are progressively refined and transformed into final products with exacting performance requirements.
At every stage, elemental stainless steel analysis is essential to ensure final products arrive on-spec and on time to customers.
1. Melting
The first step of the stainless steel manufacturing process is putting raw materials such as iron ore, stainless steel scrap, and ferroalloys through an Electric Arc Furnace (EAF), where they are heated to over 1,500–1,600 °C.
This is the first point at which elemental analysis is necessary, as ensuring the right balance of alloys helps to avoid costly mistakes:
- Over-alloying wastes expensive raw materials
- Under-alloying can produce off-spec steel that doesn’t meet performance requirements
However, steel plants move fast: rapid, precise analysis is necessary to keep up with your materials stream and make data-driven interventions when you spot an imbalance.
Wavelength-dispersive XRF (WDXRF) instruments like Axios FAST help you deliver. Axios FAST measures up to 28 elements simultaneously in concentration ranges from parts per million to 100% and returns results in as little as 20 seconds – fast enough for real-time melt control.
This avoids cascading errors in your process stream and ensures your liquid steel has a broadly correct material composition before decarburization.
2. Removing impurities
Accurate stainless steel analysis can help ensure the first steel melt contains the correct balance of materials; however, it also contains excess carbon and sulfur that must be removed.
For most steels, this is achieved by transferring molten steel from the EAF to an Argon Oxygen Decarburization (AOD) converter. For ultra-low-carbon or high-purity steel grades, a Vacuum Oxygen Decarburization (VOD) vessel is used instead.
During the standard AOD process, oxygen and argon are pumped through the melt to oxidize and remove excess carbon by converting it into CO gas, while protecting chromium from oxidation through gas dilution.
This process produces chromium oxide-rich slag. As chromium is one of the most expensive inputs for stainless steel manufacturing, recovery at this stage can help maximize cost efficiency; ferrosilicon or aluminum are therefore used to recover it.
Axios FAST can be used to optimize the chromium recovery process by providing data on slag composition with a fast enough turnaround to avoid disrupting an active AOD cycle.
3. Secondary metallurgy
After the melt is decarburized, it is transferred to a ladle furnace for final chemistry adjustment, where alloying elements are added in precise quantities to meet the final grade specification.
During this process, the temperature is controlled and the melt is stirred with an inert gas, usually argon, to homogenize its composition. Further desulfurization, deoxidation, and degassing processes may also occur here.
This is the last opportunity to adjust the steel’s composition before it is cast; errors cannot be corrected downstream, so stainless steel analysis is especially important.
However, the time pressure is intense: the longer you wait for analysis results, the more the ladle cools, driving up energy costs and the risk of temperature-related defects. Multiple rapid analyses are often needed within a single heat as corrections are made to the mix.
This is where Axios FAST is designed to perform, with near-real-time turnaround that enables operators to receive, check, and act on results within the same heat cycle, minimizing corrections.
4. Forming
When the material is confirmed to be on-spec, it can be formed and further treated, ready for its final use. As well as being cast in molds, stainless steel can also be formed through other processes:
Hot rolling or cold rolling
Hot and cold rolling are the processes by which solidified steel slabs or billets are passed through rollers to achieve a desired thickness and shape.
Hot rolling takes place above the steel’s recrystallization temperature (around 1,100°C), whereas cold rolling occurs at room temperature, producing a harder, more precisely finished product.
Annealing or galvannealing
Heat treatment through annealing or galvannealing occurs after hot or cold rolling and can relieve the internal stress introduced during these processes. It also restores corrosion resistance, which is especially important for steel grades where cold rolling has reduced their ductility.
Galvannealed steel is made through precise heat treatment of hot-dip galvanized steel that drives a controlled diffusion reaction between iron and zinc, creating a protective surface over the steel.
Our On-line X-ray diffraction (XRD) technology, developed in partnership with a leading global steel manufacturer, monitors the phase evolution of galvannealed steel sheets as the strips exit the furnace, helping prevent under- or over-alloying and inconsistent intermetallic phase formation.
Descaling or pickling
The above processes, for instance hot rolling, can produce a surface oxide layer or scale that must be removed, either through:
- Descaling, which uses shot blasting or brushing to remove the layer
- Pickling, during which the steel is dipped in an acid bath to clean the surface and restore the passive chromium oxide layer that gives stainless steel its corrosion resistance.
Accurate stainless steel analysis during these processes helps verify that incoming slabs and coils are the correct grade before final processing and identify samples that require further adjustment to avoid off-spec production.
Axios FAST provides these rapid insights and can be complemented with the Aeris X-ray diffraction (XRD) instrument after annealing to generate added crystal structure insights for retained austenite QC.
5. Finishing and quality control
Finally, stainless steel coils or sheets are cut to length or shape and surface finishes and additional coatings are applied.
This final QC stage confirms that the product meets all compositional, mechanical, and regulatory requirements, with material test certificates (MTCs) generated for clients and non-conformances logged for investigation.
This is where measurement precision is especially critical: shipping the wrong grade can result in expensive product rejection, recalls, and even liability in safety-critical applications such as medical devices. Incomplete documentation also creates traceability gaps that are not tolerated in regulated industries.
For high-volume finishing lines, Axios FAST offers certified, high-accuracy results with a comprehensive data audit trail for full confidence in your final product.
Stainless steel analysis with Axios FAST: Summary table
Below is a short summary of where Axios FAST makes a difference in each stage of the stainless steel manufacturing process.
| Stainless steel manufacturing step | What is analyzed | Why Axios FAST makes a difference |
| 1. Melting | • Incoming scrap and ferroalloy identity • Cast melt sample chemistry | • Precision is paramount: incorrect melt composition wastes valuable raw materials • Slow results mean composition errors cannot be corrected before the melt is committed |
| 2. Removing impurities | • Slag composition for chromium recovery • Carbon and sulfur in cast samples | • Poor slag analysis means expensive chromium is lost to waste • Missing carbon targets requires expensive reprocessing |
| 3. Secondary metallurgy | • Final alloy composition | • Slow analysis drives reheat costs and alloy waste • Off-spec heats cannot be recovered |
| 4. Forming | • Grade of incoming slabs/coils | • Mixing up grades is an avoidable and costly production error |
| 5. Finishing and quality control | • Final elemental composition for certification | • Shipping the wrong grade triggers costly and reputation-damaging product rejection or recall • Traceability gaps are unacceptable to customers in regulated industries like healthcare and aerospace |
Precision stainless steel manufacturing requires precision analysis
At every stage of the stainless steel manufacturing process, precise monitoring makes the difference between on-spec production and a cascade of errors that costs your reputation and your bottom line.
For stainless steel manufacturing leaders, Axios FAST WDXRF analysis is the answer, helping you maintain control at every step.
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