Enhanced Deep Drawing Performance of Ferritic Stainless Steel: A Cost-Effective and Sustainable Solution for Growth

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.

ABOUT THE AUTHOR: Caio is working with the technical development of Stainless Steels for the last 12 years of his career, he first started working in Aperam Stainless where he collaborated for 9 years in Brazil and in France. In 2020, he was invited by CBMM | Niobium, where he is currently leading the Stainless Steel Program of the company, supporting the technical development of Niobium (Nb) Bearing Stainless Steels in cooperation with the majority of Stainless Steel Producers and Final Users around the globe.
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