As global powers lift the restrictions created by the COVID-19 pandemic in the last few years, the stainless-steel industry has begun to see a glimpse of hope for recovering its past production and consumption levels. Segments that are strong users of stainless, such as the Mobility, Energy Generation, and Capital Goods industries are showing signs of improvement in comparison to 2022 and are recovering the production of high-performance grades, such as Nb-stabilized ferritic, austenitic alloys, and duplex grades. However, these projected numbers are still not, mature and the second half of 2023 may result in weaker demand and production levels.
By Caio Pisano, Technical Market Development Manager, CBMM Europe
Returning to pre-pandemic levels of production continues to be a major challenge, as the consumption of stainless steel is still strongly dependent on the power of people’s consumption and macroeconomic indicators, such as interest rates, GDP, and consumer price index. For example, if interest rates are high, consumers will think twice before changing their cars or moving to a new house with a new kitchen.
Performance Driven
As the development of cost-effective solutions is never out of style, in any industry, Ferritic Stainless Steels and CrMn materials have been once again recovering space on the global mix of production. The combination of lower prices with very good corrosion resistance are major drivers for the application of these materials, however, there are still a few gaps. If these gaps are properly addressed, the consumption of these materials could be boosted further.
Over the last decade, austenitic stainless steels have been labeled as the best in class for all stamping operations. This is partially true, they indeed have amazing performance due to their low stacking fault energy (SFE), high efficiency of slipping systems on the face-centered cubic (FCC) structure, and in some cases partial transformation of austenite into martensite in cold operations which can increase the energy absorption potential.
To be considered the best in class, a material must be a reference in all its parameters, from the stamping performance to the final cost of components; this is why the statement above is only partially true. Ferritic stainless steel can be an interesting alternative to austenitic grades.
Two of the factors that can influence the consumption of these materials are formability and high-temperature performance.
The formability of stainless steel is an intricate topic; it has a direct influence over several elements involved in both its fabrication and its use. For example, it can impact the crystalline structure of the material in question and has a bearing on the type of lubricant one chose to use in a press shop.
The Move to Ferritic Stainless Steels
Ferritic stainless steels have a body-centered cubic (BCC) structure, with higher SFE, and even if they have more slipping systems than FCC structures, the FCC systems are less efficient.
However, if the crystallographic texture of these materials is properly worked during the steel-making process, the formability performance can be substantially enhanced. When combined with the correct stamping practices in the press shop, components can be easily shifted from austenitic steels (200 Series and 300 Series) to grades like the 430Nb (DDQ).
This process lowers the cost to the end users and promotes the development of fewer alloyed steels, ultimately bringing a more sustainable solution.
The best practice to optimize the crystallographic texture of ferritic stainless steels to enhance formability performance is to promote gamma fiber ({111}//ND)) and suppress the theta fiber ({100}//ND)) as much as possible. To achieve this, a combination of best practices needs to be implemented, such as the addition of Niobium (Nb) as an element to control recrystallization during hot rolling operations, or to increase the cold reductions during the cold rolling operations and promote proper annealing treatments afterward.
With improved uniform elongation values, adequate anisotropy, and better overall forming properties, ferritic stainless steels could be a cost-competitive and sustainable alternative to high Manganese (Mn), such as 200 Series. These Cr-Mn materials have gained a lot of market share in the last few years, capturing approximately 15% of the market from classical commodities, such as the AISI 304.
Final Thoughts
The concept of deep drawing quality (DDQ) ferritic grades is very mature and has been used for many years. With the increased demand for Nickel (Ni) in other markets, such as batteries, however, the industry could face another volatility of price in austenitic grades in the years to come.
The use of high-performance ferritic stainless steels is a way to safely guarantee the competitivity and market share of stainless steels versus other solutions in the white goods segment, the biggest consumer of stainless today. This idea is also a very nice way to integrate the supply chain into the development of applications.
The stamping performance of materials is never solely dependent on the material behavior, but also on the manufacturing process. It is therefore important to consider the benefits of developing cooperation between the supply chain players; it could result in important growth in the stainless steel industry.
