The modern stainless steel manufacturing processes reduce production costs while ensuring high-quality material.
In this guide, you are going to learn how to make stainless steel. From choosing the right raw material, heating, melting, removing impurities, and forming to various finishing operations – you will learn everything about stainless steel production.
Let’s dive right in:
Step 1: Choose Raw Material for Making Stainless Steel
Stainless steel contains various chemical elements such as iron, carbon, chromium, silicon, manganese, nickel, and nitrogen, among others.
Usually, during the production process, you will mix these stainless steel materials in different proportions. As a result, there will be different stainless steel grades such as 430, 304, 316, etc.
So, even as you choose suitable raw materials, it is important to know the stainless steel material composition.
Remember, each raw material in stainless steel production plays a unique and important role. Take for example:
|Stainless Steel Raw Material Composition
|Role in Stainless Steel
|· Improves stainless steel ductility, yield strength, and resistance to pitting corrosion.
|· There is no viable alternative for this in stainless steel production
· Responsible for unmatched corrosion resistance in stainless steel.
|· High hardness and strength in stainless steel
|· Improves corrosion, heat, and oxidation resistance
· Contributes to stainless steel strength and toughness
|· For better crack resistance, toughness, hardenability, and de-oxidation
|· Prevents intergranular corrosion and stabilizes carbide
|· Improves pitting and crevice corrosion
|· Better machining properties and strength
|· Improves machining properties and may work as a deoxidizing agent
Remember, all these materials exist in different proportions (% by weight).
For example, when you are planning how to make stainless steel grade 430 (Ferritic stainless steel), the material composition should be:
- Carbon – 0.12%
- Chromium – 17%
- Nickel – 0.5%
- Phosphorous – < 0.04%
- Manganese – > 1%
- Iron – forms the remaining percentage
Although most of these stainless steel raw materials occur naturally, you can use the scrap metal. You can recycle old stainless steel parts to make new products.
A reason the availability of scrap metal determines the latest stainless steel prices.
Once you have the right material during the manufacturing process for stainless steel – you will melt the raw material.
Step 2: Melt Materials Ready for Stainless Steel Processing
Once you have all stainless steel raw materials in the right proportion, it is now time for melting.
Using an electric arc furnace, melt the stainless steel material. On average, the melting process can take between 8 and 12 hours.
The final product should be a molten material with different stainless steel alloying elements.
Step 3: Remove Carbon during Stainless Steel Manufacturing Process
Although carbon is also an alloying element during stainless steel production, it is important to limit the composition. It may have negative effects on the properties of stainless steel.
For instance, a high quantity of carbon in Ferritic and austenitic stainless steel makes welding problematic. At the same time, carbon improves stainless steel strength and hardness.
Of course, this is up to a certain limit. It will ensure stainless steel does not become brittle.
On average, the amount of carbon in stainless steel should be 1.2% max. Some stainless steels have 0% carbon content.
To improve the properties of stainless steel, you will reduce the carbon content to acceptable levels. There are two cost-effective techniques here:
Argon Oxygen Decarburization Converter (AOD Converter)
As you process molten stainless steel material, the converter will inject a gas mixture. This gas mixture contains oxygen and argon.
Depending on the assessment and stainless steel grade requirements, you can add molybdenum or nickel.
Vacuum Oxygen Decarburization (VOD)
In the manufacturing of stainless steel process, you may need very low carbon content. Consequently, you will use the VOD technique.
Step 4: Tuning Molten Stainless Steel Material
During the stainless steel production process in stages 1 to 3, many factors may affect the material’s final composition. Remember, every stainless steel grade has specific chemical elements.
Therefore, the tuning process will ensure stainless steel has the required chemical composition. You can carefully adjust the stainless steel composition by stirring the molten metal.
While stirring molten stainless steel, you will remove any impurities. The impurities can be unwanted elements.
Step 5: Forming Stainless Steel
At this stage, you will form molten stainless steel into various convenient shapes. In most cases, stainless steel may come as:
- Stainless steel blooms – the shape may be square or rectangular
- Stainless steel billets – the billets may be square or round shapes
- Stainless steel slabs, rods, or tubes
Step 6: Secondary Processes after Stainless Steel Production
After manufacturing stainless steel blooms, billets, or slabs, they require other secondary operations. Remember, after forming process, stainless may not have superior mechanical or physical properties.
A reason these secondary operations are critical. Let’s look at some critical processes.
Hot Rolling Stainless Steel
Hot rolling stainless steel process is a metal forming technique involving:
- Heating stainless steel products in stage 5 above the recrystallization temperature
- Pass the heated stainless steel through one or a series of rollers
- The process produces stainless steel with uniform thickness
During the hot rolling stainless process, stainless steel will acquire desirable mechanical properties. You can transform stainless steel into strips, plates, or sheets.
Cold Rolling Stainless Steel
The process is similar to the hot rolling stainless steel. However, in this case, you will transform stainless steel into different shapes below the recrystallization temperature.
Cold-rolling stainless steel guarantees precise dimensions. You can make a stainless steel sheet. At the same time, the process produces many stainless steel finishes.
Usually, rollers with small diameters are a perfect choice for the stainless steel cold rolling process.
Annealing Stainless Steel
During the annealing process, you will use reasonable heat to treat stainless steel. As a result, the process will:
- Improve stainless steel ductility
- Ensure the final stainless steel structure has a refined grain structure
- Relieve internal stresses which could be due to the stainless steel manufacturing process
Ideally, annealing stainless steel involves heating and cooling stainless steel under strictly controlled conditions.
Descaling Stainless Steel
As you anneal stainless steel, the final material may form some scales. Remember, the scaling on stainless steel will compromise the corrosion resistance properties.
Therefore, pickling stainless steel is necessary. You will use about 10% to 15% nitric acid alongside 1% to 3% hydrofluoric acid. When pickling stainless steel, the temperature should range between 50°C and 60°C.
Alternatively, you can use electrocleaning. Here, instead of using electrical current, you will use electrical current.
Cutting Stainless Steel
Of course, cutting is a critical stage during stainless steel production. There are many techniques you can use to cut stainless steel such as a saw, laser cutter, Waterjet cutting machine, plasma cutting machine, etc.
Surface Finishing on Stainless Steel
There are many surface finishing options available you can apply on stainless steel. Depending on the specific applications, you can apply:
- Stainless steel mill finish – here we have the No. 1, No. 2B, No. 2D, BA, or TR stainless steel finish
- Stainless steel brushed finish
- Polishing stainless steel
- Colored stainless steel
- Patterned stainless steel
Ideally, you can opt for custom stainless steel finishing. It will depend on the specific application requirements you want to achieve.
Stainless Steel Quality Inspection
Quality inspection is critical when manufacturing stainless steel products. After forming stainless steel into billets, rods, pipes, etc. you should ensure they meet the desired quality criteria.
That is, you must test and verify:
- Mechanical properties – the quality tests may range from tensile, toughness, Brinell, and loading to stress tests
- Chemical properties – you will analyze the stainless steel chemical composition of various alloying elements for classification. Quality tests such as spectrochemical analysis, and salt spray testing play an important role here. Of significance, stainless steel must meet the recommended corrosion resistance threshold.
The global stainless steel manufacturing process mainly uses scrap metals. Again, over the years, the production of stainless steel has witnessed innovation to reduce costs and improve efficiency. In fact, as of January 31, 2023, the stainless steel production was 58.3 million metric tons.
At Tuolian Metal we help you get high-quality and reliable stainless steel parts that meet your unique application requirements – contact us now.
Stainless Steel Production Process – Source: Made How
How Stainless Steel is made – Source: Discovery
Manufacturing Stainless Steel Products – Source: CMP
Stainless Steel Production – Source: Reliance Foundry
How Stainless Steel is Made – Source: Metal Supermarket
Stainless Steel Standards – Source: Engineering Tool Box